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SDLRC - Scientific Articles all years by Author - X


The Sheahan Diamond Literature Reference Compilation
The Sheahan Diamond Literature Reference Compilation is compiled by Patricia Sheahan who publishes on a monthly basis a list of new scientific articles related to diamonds as well as media coverage and corporate announcementscalled the Sheahan Diamond Literature Service that is distributed as a free pdf to a list of followers. Pat has kindly agreed to allow her work to be made available as an online digital resource at Kaiser Research Online so that a broader community interested in diamonds and related geology can benefit. The references are for personal use information purposes only; when available a link is provided to an online location where the full article can be accessed or purchased directly. Reproduction of this compilation in part or in whole without permission from the Sheahan Diamond Literature Service is strictly prohibited. Return to Diamond Resource Center
Sheahan Diamond Literature Reference Compilation - Scientific Articles by Author for all years
A-An Ao+ B-Bd Be-Bk Bl-Bq Br+ C-Cg Ch-Ck Cl+ D-Dd De-Dn Do+ E F-Fn Fo+ G-Gh Gi-Gq Gr+ H-Hd He-Hn Ho+ I J K-Kg Kh-Kn Ko-Kq Kr+ L-Lh
Li+ M-Maq Mar-Mc Md-Mn Mo+ N O P-Pd Pe-Pn Po+ Q R-Rh Ri-Rn Ro+ S-Sd Se-Sh Si-Sm Sn-Ss St+ T-Th Ti+ U V W-Wg Wh+ X Y Z
Sheahan Diamond Literature Reference Compilation - Media/Corporate References by Name for all years
A B C D-Diam Diamonds Diamr+ E F G H I J K L M N O P Q R S T U V W X Y Z
Tips for Users
Posted/Published Reference CodesThe SDLRC provides 3 types of references identified in the reference code. DS for scientific article, DM for a media article, and DC for a corporate announcement. Consider DS0512-0001. The DS stands for "diamond scientific". 05 stands for 2005, the year the reference was posted. 12 represents the month the reference was posted. For all years prior to 2015 the default month is 12. -0001 is the reference's identifier and it does not mean anything. The number below the refence code, ie 2015, is the year the article was published. Note that the posted year may sometimes be later than the published year.
Sort OrderReferences are sorted by the "author" name and when the reference was posted to the compilation.
Most RecentIf the reference code is highlighted yellow, the reference was made available through the most recent monthly compilation of new literature. Use this to check out new references. When new references are posted, we make it our priority to track down an online link and obtain an abstract. With regard to older references, tracking down an abstract and an online link is a work in progress.
Link to external location of article: If the title has a link, it means we have found a location online where you can either retrieve the full article free, or purchase access to it. The Sheahan Diamond Literature Service is not a technical article procurement service; if you want a restricted article, you must deal directly with the vendor who controls the copyright to the article.
Searching this page for a specific term or authorIn your Firefox browser click Edit in the menu bar and then Find. In the Find box that shows up at the bottom of the web page enter your search term. Firefox will highlight all occurrences. This is particularly helpful when the author you are seeking was not the lead author by whom the compilation is sorted.
Sending or sharing a referenceThe left column (Posted/Published) has an embedded hyperlink for each reference. In Firefox, if you right click on it, you can obtain the link url for that reference's location within the page, which you can copy and paste into an email or any other document. You can also use the "share this link" option to tweet, facebook etc the link.
Author Index
A-An Ao+ B-Bd Be-Bk Bl-Bq Br+ C-Cg Ch-Ck Cl+ D-Dd De-Dn Do+ E F-Fn Fo+ G-Gh Gi-Gq Gr+ H-Hd He-Hn Ho+ I J K-Kg Kh-Kn Ko-Kq Kr+ L-Lh
Li+ M-Maq Mar-Mc Md-Mn Mo+ N O P-Pd Pe-Pn Po+ Q R-Rh Ri-Rn Ro+ S-Sd Se-Sh Si-Sm Sn-Ss St+ T-Th Ti+ U V W-Wg Wh+ X Y Z
Sheahan Diamond Literature Reference Compilation - Scientific Articles by Author for all years - X
Posted/
Published
AuthorTitleSourceRegionKeywords
DS201901-0083
2018
XSun, N., Wei, W., Han, S., Song, J., Li, X, Duan, Y., Prakapenka, V.B., Mao, Z.Phase transition and thermal equations of state of ( Fe, Al) - bridgmanite and post-perovskite: implication for the chemical heterogeneity at the lowermost mantle.Earth and Planetary Science Letters, Vol. 490, 1, pp. 161-169.Mantlegeothermometry

Abstract: In this study, we have determined the phase boundary between Mg0.735Fe0.21Al0.07Si0.965O3-Bm and PPv and the thermal equations of state of both phases up to 202 GPa and 2600 K using synchrotron X-ray diffraction in laser heated diamond anvil cells. Our experimental results have shown that the combined effect of Fe and Al produces a wide two-phase coexistence region with a thickness of 26 GPa (410 km) at 2200 K, and addition of Fe lowers the onset transition pressure to 98 GPa at 2000 K, consistent with previous experimental results. Furthermore, addition of Fe was noted to reduce the density (?) and bulk sound velocity () contrasts across the Bm-PPv phase transition, which is in contrast to the effect of Al. Using the obtained phase diagram and thermal equations of state of Bm and PPv, we have also examined the effect of composition variations on the ? and profiles of the lowermost mantle. Our modeling results have shown that the pyrolitic lowermost mantle should be highly heterogeneous in composition and temperature laterally to match the observed variations in the depth and seismic signatures of the D? discontinuity. Normal mantle in a pyrolitic composition with ~10% Fe and Al in Bm and PPv will lack clear seismic signature of the D? discontinuity because the broad phase boundary could smooth the velocity contrast between Bm and PPv. On the other hand, Fe-enriched regions close to the cold slabs may show a seismic signature with a change in the velocity slope of the D? discontinuity, consistent with recent seismic observations beneath the eastern Alaska. Only regions depleted in Fe and Al near the cold slabs would show a sharp change in velocity. Fe in such regions could be removed to the outer core by strong core-mantle interactions or partitions together with Al to the high-pressure phases in the subduction mid ocean ridge basalts. Our results thus have profound implication for the composition of the lowermost mantle.
DS201905-1086
2019
X=Zheng, J.Wu, W., Yang, J., Wirth, R., X=Zheng, J., Lian, D., Qiu, T., Milushi, I.Carbon and nitrogen isotopes and mineral inclusions in diamonds from chromitites of the Mirdita ophiolite ( Albania) demonstrate recycling of oceanic crust into the mantle.American Mineralogist, Vol. 104, pp. 485-500.Europe, Albaniadiamond inclusions

Abstract: Geophysical investigations and laboratory experiments provide strong evidence for subduction of ancient oceanic crust, and geological and mineralogical observations suggest that subducted oceanic crust is recycled into the upper mantle. This model is supported by some direct petrologic and miner-alogical evidence, principally the recovery of super-deep diamonds from kimberlites and the presence of crustal materials in ophiolitic chromitites and peridotites, but many details are still unclear. Here we report the discovery of ophiolite-hosted diamonds in the podiform chromitites of the Skenderbeu massif of the Mirdita ophiolite in the western part of Neo-Tethys. The diamonds are characterized by exceedingly light C isotopes (d13CPDB ~ -25‰), which we interpret as evidence for subduction of organic carbon from Earth's surface. They are also characterized by an exceptionally large range in d 15Nair (-12.9‰ to +25.5‰), accompanied by a low N aggregation state. Materials sparsely included in diamonds include amorphous material, Ni-Mn-Co alloy, nanocrystals (20 × 20 nm) of calcium silicate with an orthorhombic perovskite structure (Ca-Pv), and fluids. The fluids coexisting with the alloy and Ca-Pv provide clear evidence that the diamonds are natural rather than synthetic. We suggest that the Skenderbeu diamonds nucleated and grew from a C-saturated, NiMnCo-rich melt derived from a subducted slab of ocean crust and lithosphere in the deep mantle, at least in the diamond stability field, perhaps near the top of the mantle transition zone. The subsequent rapid upward transport in channeled networks related to slab rollback during subduction initiation may explain the formation and preservation of Skenderbeu diamonds. The discovery of diamonds from the Mirdita ophiolite not only provides new evidence of diamonds in these settings but also provides a valuable opportunity to understand deep cycling of subducted oceanic crust and mantle composition.
DS201112-0596
2011
Xaio, Y.Li, W-Y., Teng, F-Z., Xaio, Y., Huang, J.High temperature inter-mineral magnesium isotope fractionation in eclogite from the Dabie orogen, China.Earth and Planetary Science Letters, Vol. 304, 1-2, pp. 224-230.ChinaEclogite UHP
DS201412-0877
2014
Xarlamova, E.I.Spetsius, Z.V., Polyanichko, V.V., Xarlamova, E.I.,Tarskix, O.V., Ivanov, A.S.Geology, petrography and mineralogy of the Zarya pipe kimberlites.Deep Seated Magmatism, its sources and plumes, Ed. Vladykin, N.V., pp. 160-177.RussiaDeposit - Zarya
DS201510-1807
2014
Xarlamova, E.I.Spetsius, Z.V., Polyanichko, V.V., Xarlamova, E.I., Tarskix, O.V., Ivanov, A.S.Geology, petrography and mineralogy of the Zarya pipe kimberlites.Deep-seated magmatism, its sources and plumes, Proceedings of XIII International Workshop held 2014., Vol. 2014, pp. 160-177.RussiaDeposit - Zarya
DS202002-0220
2019
X-CXu, R., Liu, Y., Wang, X-C, Foley, S.F., Zhang, Y., Yuan, H.Generation of continental intraplate alkali basalts and deep carbon cycle.Earth Science Reviews, in press available, 38p. Doi.org/1010.1016 /jearsciev.2019.103073Globalcarbon

Abstract: Although the deep recycling of carbon has been proposed to play a key role in producing intraplate magmatism, the question of how it controls or triggers mantle melting remains poorly understood. In addition, generation of incipient carbonated melts in the mantle and their subsequent reaction with the mantle are critical processes that can influence the geochemistry of intraplate basalts, but the details of such processes are also unclear. Here we present geochemical evidence for the existence of pervasive carbonate melt in the mantle source of Cenozoic continental intraplate highly alkali basalts (SiO2 < 45 wt%), which are volumetrically minor but widespread in eastern China. The primary magma compositions of these basalts cannot be explained by either partial melting of a single mantle source lithology or mixing of magmas derived from distinct mantle sources, but can be adequately explained by carbonate-fluxed melting of eclogite and subsequent reaction between silica-rich melts and peridotite that ultimately transformed the initial carbonated silica-rich melts into silica-undersaturated alkalic magmas. The source of the carbonate is in subducted eclogites associated with the Pacific plate, which stagnated in the mantle transition zone (MTZ). The spatial distribution of the alkali basalts is in accord with large-scale seismic low-velocity anomalies in the upper mantle above the MTZ. Similar scenarios in central-western Europe and eastern Australia lead us to propose that reaction between carbonated silica-rich melt and peridotite may be a pivotal mechanism for the generation of continental intraplate alkali basalts elsewhere in the world.
DS200512-1203
2005
XceldiamXceldiamXceldiam - if you missed the Petra boat. Luangue concession.Mineweb, July 12, 1p.Africa, AngolaNews item - Xceldiam
DS1990-0977
1990
Xenophontos, C.Malpas, J., Moores, E.M., Pantayiotou, A., Xenophontos, C.Ophiolites- oceanic crustal analoguesCyprus Geological Survey, 733p. $ 65.00Japan, Indonesia, California, Oregon, Mid-Atlantic Ridge, ScotlandOphiolites, Book -ad
DS201709-2021
2017
Xhu, F.Li, J., Xhu, F., Dong, J., Liu, J., LaI, X., Chen, B., Meng, Y.Experimental investigations into the fate of subducted carbonates and origin of super deep diamonds.Goldschmidt Conference, abstract 1p.Mantlepetrology

Abstract: Carbonates are common rock-forming minerals in the Earth’s crust and act as sinks of atmospheric carbon dioxide. Subduction of hydrothermally altered oceanic lithosphere returns carbon to the interior, where more than three quarters of Earth’s carbon is stored. The contribution of subducted carbonates to the Earth's long-term deep carbon cycle is uncertain and has recently emerged as a topic of intense debate [1]. Moreover, mantle-slab interaction has been proposed as a mechanism to produce super-deep diamonds, thus questioning the use of certain mineral inclusions to infer lower-mantle origin [2]. Here we report new data on the chemical stability and reaction kinetics of carbonates in the mantle from multianvil and diamond-anvil-cell experiments. Our results suggest that carbon can be sequestered into deep Earth through reaction freezing and that the index minerals for super-deep diamonds are not reliable indicators for their formation depths.
DS201910-2281
2019
Xhu, F.Liu, J., Dorfman, S.M., Lv, M., Li, J., Xhu, F., Kono, Y.Loss of immiscible nitrogen from metallic melt explains Earth's missing nitrogen.Geochemical Perspectives Letters, Vol. 11, pp. 18-22.Mantlenitrogen

Abstract: Nitrogen and carbon are essential elements for life, and their relative abundances in planetary bodies are important for understanding planetary evolution and habitability. The high C/N ratio in the bulk silicate Earth (BSE) relative to chondrites has been difficult to explain through partitioning during core formation and outgassing from molten silicate. Here we propose a new model that may have released nitrogen from the metallic cores of accreting bodies during impacts with the early Earth. Experimental observations of melting in the Fe-N-C system via synchrotron X-ray radiography of samples in a Paris-Edinburgh press reveal that above the liquidus, iron-rich melt and nitrogen-rich liquid coexist at pressures up to at least 6 GPa. The combined effects of N-rich supercritical fluid lost to Earth’s atmosphere and/or space as well as N-depleted alloy equilibrating with the magma ocean on its way to the core would increase the BSE C/N ratio to match current estimates.
DS201508-0365
2015
XiLiu, Xi, Zhong, ShijieThe long wave length geoid from three dimensional spherical models of thermal and thermochemical mantle convection.Journal of Geophysical Research, Vol. 120, 6, pp. 4572-4596.MantleGeothermometry
DS202105-0795
2021
Xi, B.Tang, Li., Wagner, T.,Fusswinkel, T., Zhang, S-T., Xi, B., Jia, L-H., Hu, X-K. Magmatic-hydrothermal evolution of an unusual Mo-rich carbonatite: a case study using LA-ICP-MS fluid inclusion microanalysis and He-Ar isotopes from the Huangshuian deposit, Qinling, China.Mineralium Deposita, 10.1007/s00126 -021-01055-2 18p. PdfChinacarbonatites

Abstract: The Huangshui'an deposit located in East Qinling (China) is an unusual case of a Si-rich carbonatite hosting economic Mo and minor Pb and REE mineralization. The role of mantle-sourced carbonatite melts and fluids in the formation of the Mo mineralization remains poorly understood. Our integrated study based on field geology, petrography, microthermometry, and LA-ICP-MS analysis of single fluid inclusions, and noble gas isotopes of pyrite permits to reconstruct the source characteristics, the magmatic-hydrothermal evolution of the carbonatitic fluids, and their controls on Mo mineralization. Fluid inclusions hosted in calcite in the carbonatite dikes have the highest concentrations of Mo (9.9-62 ppm), Ce (820-9700 ppm), Pb (1800-19500 ppm), and Zn (570-5800 ppm) and represent the least modified hydrothermal fluid derived from the carbonatite melt. Fluid inclusions hosted in calcite (Cal) and quartz (Qz2 and Qz3) of the stage I carbonatite dikes have different metal concentrations, suggesting that they formed from two distinct end member fluids. The FIA in calcite represent fluid A evolved from carbonatite melt with relatively high-ore metal concentrations, and those in quartz characterize fluid B having a crustal signature due to metasomatic reactions with the wall rocks. The FIA in quartz (Qz1) within the altered wall rock have overlapping elemental concentrations with those of massive quartz (Qz2) and vuggy quartz (Qz3) in carbonatite. This suggests that the volumetrically significant quartz in the Huangshui'an carbonatite has been formed by the introduction of Si by fluid B. The positive correlations between Rb, B, Al, Cl, and Sr in stage II fluid inclusions in late fluorite + quartz + calcite veins indicate that this late mineralization formed from the mixing of primary hydrothermal fluid B with meteoric water. The He-Ar isotope data, in combination with available C-O-Sr-Nd-Pb isotope data, constrain the carbonatite source as an enriched mantle source modified by contributions from crustal material which was probably the fertile lower crust in the region. This distinct source facilitated the enrichment in Mo, REE, and Pb in the primary carbonatite magma. The carbonatite magmatism and Mo mineralization at 209.5-207 Ma occurred in the regional-scale extensional setting at the postcollision stage of the Qinling Orogenic Belt.
DS201805-0979
2018
Xi, C.Song, W., Xi, C., Smith, M.P., Chakhmouradian, A.R., Brenna, M., Kynicky, J., Chen, W., Yang, Y., Tang, H.Genesis of the world's largest rare earth element deposit, Bayan Obo, China: protracted mineralization evolution over ~ 1.b.y.Geology, Vol. 48, 4, pp. 323-326.Chinadeposit - Bayan Obo

Abstract: The unique, giant, rare earth element (REE) deposit at Bayan Obo, northern China, is the world’s largest REE deposit. It is geologically complex, and its genesis is still debated. Here, we report in situ Th-Pb dating and Nd isotope ratios for monazite and Sr isotope ratios for dolomite and apatite from fresh drill cores. The measured monazite ages (361-913 Ma) and previously reported whole-rock Sm-Nd data show a linear relationship with the initial Nd isotope ratio, suggesting a single-stage evolution from a Sm-Nd source that was formed before 913 Ma. All monazites show consistent eNd(1.3Ga) values (0.3 ± 0.6) close to those of the adjacent 1.3 Ga carbonatite and mafic dikes. The primary dolomite and apatite show lower 87Sr/86Sr ratios (0.7024-0.7030) than the recrystallized dolomite (0.7038-0.7097). The REE ores at Bayan Obo are interpreted to have originally formed as products of ca. 1.3 Ga carbonatitic magmatism and to have undergone subsequent thermal perturbations induced by Sr-rich, but REE-poor, metamorphic fluids derived from nearby sedimentary rocks.
DS1995-2090
1995
XiaXia, Jinghai, Sprowl, D.R.Moho depths in Kansas from gravity inversion assuming exponential densitycontrast.Computers and Geosciences, Vol. 21, No. 2, pp. 237-244.GlobalBasement, Geophysics - gravity
DS201412-0381
2014
XiaHuang, J-X., Li, P., Griffin, W.L., Xia, Q-K, Greau, Y., Pearson, N.J., O'Reilly, S.Y.Water contents of Roberts Victor xenolithic eclogites: primary and metasomatic controls.Contributions to Mineralogy and Petrology, Vol. 168, pp. 1092-1095Africa, South AfricaDeposit - Roberts Victor
DS201502-0063
2014
XiaHuang, J-X., Li, P., Griffin, W.L., Xia, Q-K, Greau, Y., Pearson, N.J., O'Reilly, S.Y.Water contents of Roberts Victor xenolithic eclogites: primary and metasomatic controls.Contributions to Mineralogy and Petrology, Vol. 168, pp. 1092-1105.Africa, South AfricaDeposit - Roberts Victor
DS2002-1789
2002
Xia, B.Zhao, T.P., Zhou, M.F., Zhai, M., Xia, B.Paleoproterozoic rift related volcanism of the Xiong'er group, north Chin a Craton: implications for the breakup of Columbia.International Geology Review, Vol. 44, 4, pp. 336-51.ChinaTectonics - rifting
DS2003-0656
2003
Xia, B.Ji, S., Saruwateri, K., Mainproce, D., Wirth, R., Xu, Z., Xia, B.Microstructures, petrofabrics and seismic properties of ultra high pressure eclogitesTectonophysics, Vol. 370, 1-4, pp. 49-76.ChinaGeophysics - seismics, UHP, subduction
DS200412-0915
2003
Xia, B.Ji, S., Saruwateri, K., Mainproce, D., Wirth, R., Xu, Z., Xia, B.Microstructures, petrofabrics and seismic properties of ultra high pressure eclogites from Sulu region, China: implications forTectonophysics, Vol. 370, 1-4, pp. 49-76.ChinaGeophysics - seismics UHP, subduction
DS200512-1164
2005
Xia, B.Wang, Q., Ji, S., Salisbury, M.H., Xia, B., Pan, M., Xu, Z.Pressure dependence and anisotropy of P wave velocities in ultrahigh pressure metamorphic rocks from the Dabie Sulu orogenic belt: implications for seismic propertiesTectonophysics, Vol. 398, 1-2, pp. 67-99.ChinaMantle reflections, subduction slabs
DS200512-1165
2005
Xia, B.Wang, Q., Shaocheng, J., Salisbury, M.H., Xia, B., Pan, M., Xu, Z.Shear wave properties and Poisson's ratios of ultrahigh pressure metamorphic rocks from the Dabie Sulu orogenic belt, China: implications for crustal composition.Journal of Geophysical Research, Vol. 110, B8, pp. B08411 10.1029/2004 JB003435Asia, ChinaUHP
DS200612-1506
2005
Xia, B.Wang, Q., Ji, S., Salisbury, M.H., Xia, B., Pan, M., Xu, Z.Shear wave properties and Poisson's ratios of ultrahigh pressure metamorphic rocks from Dabie Sulu orogenic belt.Journal of Geophysical Research, Vol. 110, B8, BO8208.ChinaUHP
DS200612-1555
2006
Xia, B.Xiong, X.L., Xia, B., Hu, J.F., Niu, H.C., Xiao, W.S.Na depletion in modern adakites via melt/rock reaction within the subarc mantle.Chemical Geology, Vol. 229, 4, May 30, pp. 273-292.MantleSlab, subduction, melting
DS201501-0034
2015
Xia, B.Zheng, J.P., Lee, C.T.A., Lu, J.G., Zhao, J.H., Wu, Y.B., Xia, B., Li, X.Y., Zhang, J.F., Liu, Y.S.Refertilization driven destabilization of subcontinental mantle and the importance of initial lithospheric thickness for the fate of continents. Earth and Planetary Science Letters, Vol. 409, pp. 225-229.ChinaPeridotite
DS201812-2844
2018
Xia, B.Ma, Q., Xu, Y-G., Deng, Y,m Zhengm J-P., Sur, M., Griffin, W.L., Xia, B., Yan Wang, C.Similar crust beneath disrupted and intact cratons: arguments against lower crust delamination as a decratonization trigger. North China cratonTectonophysics, in press available 31p.Chinacraton

Abstract: The continental lithosphere is not forever; some cratons have lost their original roots during the course of their evolution. Yet, it is not clear whether gravitational instability of dense lower crust is the primary driver of decratonization. This is addressed here with emphasis being placed on the North China Craton (NCC), because it represents one of the best examples of craton-root disruption in the world, and a place where models can be tested. If lower-crustal delamination was the trigger for decratonization, we would expect a clear contrast in crustal structure and composition between disturbed (rootless) and intact cratons. However, the eastern (disturbed) and western (intact) parts of the NCC show virtually identical physical structure and composition (a thin mafic lower crust and a predominantly intermediate composition overall) although the crust in the disturbed part is thinner than in the intact craton. This suggests that delamination of the lower crust was not a viable mechanism of craton-root disruption in the NCC case. Indeed, the crust beneath the NCC largely resembles those of stable Archean cratons worldwide. Therefore the delamination, if it occurred, may have taken place much earlier (Archean) than previously thought, rather than in the Mesozoic. Delamination may have been a common phenomenon in the early evolution of cratons, probably due to relatively higher mantle temperatures in the Archean Eon.
DS201212-0822
2012
Xia, G.Zhao, S., Jin, Z., Zhang, J., Xu, H., Xia, G., Green, H.W.II.Does subducting lithosphere weaken as it enters the lower mantle?Geophysical Research Letters, Vol. 39, L10311 5p.MantleSubduction
DS202006-0944
2020
Xia, G.O'Bannon, E., Xia, G., Shi, F., Wirth, R., King, R.A., Dobrzhinetskaya, L.The transformation of diamond to graphite: experiments reveal the presence of an intermediate linear carbon phase. Diamonds & Related Materials, in press available, 31p. PdfGlobalcarbon

Abstract: Natural diamonds that have been partially replaced by graphite have been observed to occur in natural rocks. While the graphite-to-diamond phase transition has been extensively studied the opposite of this (diamond to graphite) remains poorly understood. We performed high-pressure and temperature hydrous and anhydrous experiments up to 1.0?GPa and 1300?°C using Amplex premium virgin synthetic diamonds (20-40?µm size) as the starting material mixed with Mg (OH)2 as a source of H2O for the hydrous experiments. The experiments revealed that the diamond-to-graphite transformation at P?=?1GPa and T?=?1300?°C was triggered by the presence of H2O and was accomplished through a three-stage process. Stage 1: diamond reacts with a supercritical H2O producing an intermediate 200-500?nm size “globular carbon” phase. This phase is a linear carbon chain; i.e. a polyyne or carbyne. Stage 2: the linear carbon chains are unstable and highly reactive, and they decompose by zigzagging and cross-linking to form sp2-bonded structures. Stage 3: normal, disordered, and onion-like graphite is produced by the decomposition of the sp-hybridized carbon chains which are re-organized into sp2 bonds. Our experiments show that there is no direct transformation from sp3 C-bonds into sp2 C-bonds. Our hydrous high-pressure and high-temperature experiments show that the diamond-to-graphite transformation requires an intermediate metastable phase of a linear hydrocarbon. This process provides a simple mechanism for the substitution of other elements into the graphite structure (e.g. H, S, O).
DS201503-0178
2015
Xia, H.H.Wang, T., Song, X., Xia, H.H.Earth's core has a core.Nature Geoscience, Feb. 10, 3p. OnlineEarth, MantleGeophysics - seismic
DS1996-1568
1996
Xia, J.Xia, J., Sprowl, D.R., Steeples, D.W.A model of Precambrian geology of Kansas derived from gravity and magneticdata.Computers and Geosciences, Vol. 22, No. 8, pp. 883-895.KansasGeophysics - magnetics, Precambrian
DS201704-0653
2017
Xia, J.Xia, J., Qin, L., Shen, J., Carlson, R.W., Ionov, D.A., Mock, T.D.Chromium isotope heterogeneity in the mantle.Earth and Planetary Science Letters, Vol. 464, pp. 103-115.MantleGeochronology

Abstract: To better constrain the Cr isotopic composition of the silicate Earth and to investigate potential Cr isotopic fractionation during high temperature geological processes, we analyzed the Cr isotopic composition of different types of mantle xenoliths from diverse geologic settings: fertile to refractory off-craton spinel and garnet peridotites, pyroxenite veins, metasomatised spinel lherzolites and associated basalts from central Mongolia, spinel lherzolites and harzburgites from North China, as well as cratonic spinel and garnet peridotites from Siberia and southern Africa. The d53CrNIST 979 values of the peridotites range from -0.51±0.04‰-0.51±0.04‰ (2SD) to +0.75±0.05‰+0.75±0.05‰ (2SD). The results show a slight negative correlation between d53Cr and Al2O3 and CaO contents for most mantle peridotites, which may imply Cr isotopic fractionation during partial melting of mantle peridotites. However, highly variable Cr isotopic compositions measured in Mongolian peridotites cannot be caused by partial melting alone. Instead, the wide range in Cr isotopic composition of these samples most likely reflects kinetic fractionation during melt percolation. Chemical diffusion during melt percolation resulted in light Cr isotopes preferably entering into the melt. Two spinel websterite veins from Mongolia have extremely light d53Cr values of -1.36±0.04‰-1.36±0.04‰ and -0.77±0.06‰-0.77±0.06‰, respectively, which are the most negative Cr isotopic compositions yet reported for mantle-derived rocks. These two websterite veins may represent crystallization products from the isotopically light melt that may also metasomatize some peridotites in the area. The d53Cr values of highly altered garnet peridotites from southern Africa vary from -0.35±0.04‰-0.35±0.04‰ (2SD) to +0.12±0.04‰+0.12±0.04‰ (2SD) and increase with increasing LOI (Loss on Ignition), reflecting a shift of d53Cr to more positive values by secondary alteration.
DS1989-0712
1989
Xia, M.Jing, Y., Pan, G., Xia, M., Liang, W., Liou, J.G.Occurrences of abundant eclogites in the DabieMountains, Central SOURCE[ EOSEos, Vol. 70, No. 15, April 11, p. 505. (abstract.)ChinaEclogite
DS1990-0765
1990
Xia, M.Jing, Y., Pan, G., Xia, M., Wang, X., Liou, J.G., Maruyama, S.Petrology of coesite bearing eclogites from the Dabie Mountains CentralChinaInternational Mineralogical Association Meeting Held June, 1990 Beijing China, Vol. 2, extended abstract p. 864-865ChinaEclogites, Coesite
DS1990-1537
1990
Xia, M.Wang Xiaomin, Jing, Y., Liou, J.G., Pan, G., Liang, W., Xia, M.Field occurrences and petrology of eclogites from the Dabie Mountains, Anhui, central ChinaLithos, Vol. 25, No. 1-3, November pp. 119-130ChinaEclogites, Dabie Mountains
DS200912-0063
2009
Xia, Q.Bonadiman, C., Yantao, H., Coltorti, M., Dallai, L., Faccini, B., Huang, YU., Xia, Q.Water content of pyroxenes in intraplate lithospheric mantle.European Journal of Mineralogy, Vol. 21, 3, June pp. 637-647.MantleWater
DS201802-0240
2018
Xia, Q.Gu, X., Ingrin, J., Deloule, E., France, L., Xia, Q.Metasomatism in the sub-continental lithospheric mantle beneath the south French Massif Central: constraints from trace elements, Li and H in peridotite minerals.Chemical Geology, Vol. 478, pp. 2-17.Europe, Franceperidotite

Abstract: Mantle metasomatism by percolating melts/fluids can significantly modify the geochemical and mineralogical compositions of the sub-continental lithospheric mantle (SCLM). We present a detailed study of water contents and Li concentrations and isotopic compositions in mantle minerals from a suite of peridotite xenoliths entrained by a Cenozoic Strombolian volcano in the southern French Massif Central (FMC). Wide ranging clinopyroxene trace element distributions (e.g., (La/Yb)N from 0.25 to 22.21; Ti/Eu ratios from 453 to 4892) suggest that the SCLM has undergone metasomatism by carbonatitic melts/fluids or melts/fluids related to subducted materials. Two amphibole-bearing samples exhibit depletion of light rare earth elements (LREE; (La/Yb)N = 0.26 and 0.30, respectively) in amphiboles, similar to that in co-existing clinopyroxenes; these samples indicate that amphiboles grew during a separate modally metasomatic event predating the cryptic metasomatism accounting for LREE enrichment and negative HFSE anomalies in other samples. Mineral Li concentrations are similar to those in the normal mantle, with inter-mineral Li partitioning nearly equilibrated and intragranular Li distributions nearly homogeneous. However, negative d7Li values of pyroxenes in some samples (as low as - 8.8‰ in clinopyroxene of sample MC38) can be attributed to diffusive exchange with a small-volume melt of moderate Li concentration and light Li isotopic composition, originally associated with a recycled component. Preservation of the currently observed large inter-mineral Li isotopic variations indicates that melt percolation occurred shortly before entrainment of the peridotite xenoliths by the host magma. Mineral water contents vary from 41 to 428 ppm in clinopyroxenes and from 28 to 152 ppm in orthopyroxenes, and their roughly negative co-variation with coexisting olivine Fo contents imply that partial melting was the main control over mineral water content variations in most samples. Varied water contents in LREE-enriched metasomatized samples indicate the involvement of metasomatic agents of different origins. The aqueous agent responsible for generation of amphiboles in two samples did not produce a notable increase in the water contents of coexisting nominally anhydrous minerals.
DS200612-1552
2005
Xia, Q-K.Xia, Q-K., Sheng, Y-M., Yang, X-Z., Yu, H-M.Heterogeneity of water in garnets from UHP eclogites, eastern Dabie Shan, China.Chemical Geology, Vol. 224, 4, Dec. 20, pp. 237-246.ChinaUHP, Bixiling
DS201702-0243
2017
Xia, Q-K.Tian, Z-Z., Liu, J., Xia, Q-K., Ingrin, J., Hao, Y-T., Depecker, C.Water concentraion profiles in natural mantle orthopyroxenes: a geochronometer for long annealing of xenoliths within magma.Geology, Vol. 45, 1, pp. 87-90.ChinaBasanites, Foidites

Abstract: Both mantle-derived clinopyroxene and orthopyroxene are generally homogeneous in water concentration, while water content in the coexisting olivine is affected by partial or complete loss during the ascent of the hosting magma. Here, we report the first record of water content profiles (higher water in the cores than in the rims) in natural orthopyroxene grains in peridotite xenoliths hosted by Cenozoic alkali basalts in Tianchang volcano, eastern China. The water contents of the coexisting clinopyroxene grains are homogeneous and are twice that measured in the cores of orthopyroxene grains, confirming previous chemical equilibrium between the two pyroxenes. The olivines (ol) are nearly dry (~0 ppm). These observations demonstrate that H diffusion in mantle orthopyroxene (opx) is faster than in clinopyroxene (cpx), and the relative mobility of H in each mineral phase could be quantified as: Graphic (where is the chemical diffusion coefficient of hydrogen). Combining this with experimental diffusion coefficients from the literature, we infer that (1) the xenoliths remained in contact with the magma below 900 °C for several months, and (2) clinopyroxene remains the more reliable recorder of water from depth, and orthopyroxene should be used more cautiously but can be considered with olivine for tracing slow transport and cooling of magma.
DS201112-1126
2011
Xia, Q-X.Xia, Q-X., Zheng, Y-F., Lu, X-N.Multistage growth of garnet in UHP metagranite in the Dabie orogen.Goldschmidt Conference 2011, abstract p.2188.ChinaUHP
DS201112-1172
2011
Xia, Q-X.Zhou, L-G., Xia, Q-X., Zheng, Y-F., Chen, R-X.Multistage growth of garnet in ultrahigh pressure eclogite during continental collision in the Dabie Orogen: constrained by trace elements and U Pb ages.Lithos, Vol. 127, 1-2, pp. 101-127.ChinaUHP
DS1987-0818
1987
XIA, W.XIA, W., Feng, ZhiwenRock forming analysis of carbonatites and their metallogenic prognosis In central Shandong (China).*CHIDiqiu Kexue, *CHI, Vol. 12, No. 3, pp. 285-292ChinaBlank
DS201812-2899
2018
Xia, X.Xia, X.Mineral inclusions in diamonds from Chidliak ( Nunavut, Canada): constraining the diamond substrates.Thesis, Msc. University of Alberta, 112p. Pdf availableCanada, Nunavutdeposit - Chidliak
DS201903-0517
2019
Xia, X-P.Huang, D-L., Wanf, X-L., Xia, X-P., Wan, Y-S., Zhang, F-F., Li, J-Y., Du, D-H.Neoproterozoic low delta 180 zircons revisited: implications for Rodinia configuration.Geophysical Research Letters, Vol. 46, 2, pp. 678-688.Globalcraton

Abstract: Low-d18O magma has received great attention and it has profound implications on geological and climate evolution. Neoproterozoic era is a unique period to breed low-d18O magmas and snowball Earth. This manuscript first report Neoproterozoic moderately 18O-depleted zircons from the central part of the Cathaysia Block in South China, and it builds a four end-member Hf-O isotopic mixing model to explain the global low-d18O magmas at Neoproterozoic era. Our compilation of low-d18O zircon data and our new data confirms that globally Neoproterozoic 18O-depleted magmatic activities generally began after 800 Ma and reached a peak at 780-760 Ma. This provides new information on the rifting of Rodinia supercontinent and suggests close connections between northwest India, Madagascar, and South China in the Rodinia supercontinent. This manuscript deals with the hot-debated topics on oxygen isotopes and supercontinent cycle. We believe that this manuscript will attract international readers from a wide scope of geosciences.
DS201904-0800
2019
Xia, Y.Xia, Y., Xu, X.A fragment of Columbia Supercontinent: insight for Cathayasia block basement from tectono-magmatic evolution and mantle heterogeneity.Geophysical Research Letters, Vol. 46, 4, pp. 2012-2024.South America, Colombia, Australiacraton

Abstract: Significant amounts of landmasses are brought together in a hemispheric supercontinent, then breaks up, disperse, and reform in a new supercontinent in every 400-450 Myrs. During the supercontinent cycle, global-scale continental magmatism and orogenic activity increased. The assembly and breakup of Pangaea, the latest supercontinent, are well understood today. However, the evidence becomes more sparse further back in geological history. The geological and paleomagnetic data are insufficient to determine the exact geometries of Rodinia and Columbia supercontinents. Hence, we trace the position of Cathaysia block in the Columbia supercontinent and its relationship with other continental blocks, based on its Paleoproterozoic magmatisms, metamorphisms, and sedimentations, especially ultradepleted mantle-derived rocks. This work has important implications for the mantle heterogeneity in supercontinent reconstruction.
DS1990-1595
1990
Xia LingiXia Lingi, Cao RonglongDetermination of nature of fuids and melts in upper mantle of Xilong area from Zhejiang province, ChinaInternational Mineralogical Association Meeting Held June, 1990 Beijing China, Vol. 1, extended abstract p. 577-578ChinaMantle, Geochemistry
DS201212-0795
2012
Xiabo, T.Xiaoyu, G., Encarnacion, J., Xiao, X., Deino, A., Li, Z., Xiabo, T.Collision and rotation of the South Chin a block and their role in the formation and exhumation of ultrahigh pressure rocks in the Dabie Shan orogen.Terra Nova, Vol. 24, 5, pp. 339-350.ChinaUHP
DS200612-0815
2006
Xian, H.Liang, X-Q, Fan, W-M., Wang, Y-J., Xian, H.Early Mesozoic post collisional shoshonitic lamprophyres along the western margin of the South Chin a orogen; geochemical characteristics and tectonicInternational Geology Review, Vol. 48, 4, pp. 311-328.ChinaGeochemistry - shoshonites
DS1987-0408
1987
Xiang, K.W.Leung, I.S., Xiang, K.W.chromium diopside macrocrysts from the Mengyin kimberlite pipe, ChinaEos, Vol. 68, No. 44, November 3, p. 1537. abstract onlyChinaBlank
DS202004-0546
2020
Xiang, L.Xiang, L., Zheng, J., Zhai, M., Siebel, W.Geochemical and Sr-Nd-Pb isotopic constraints on the origin and petrogenesis of Paleozoic lamproites in the southern Yangtze Block, south China.Contributions to Mineralogy and Petrology, Vol. 175, 18p. PdfChinalamproites

Abstract: Lamproites and kimberlites are natural probes of the subcontinental lithospheric mantle providing insights into the Earth’s continental lithosphere. Whole-rock major-, trace-element and Sr-Nd-Pb isotopic compositions of the Paleozoic (~?253 Ma) lamproite dikes from the Baifen zone of the Zhenyuan area in southeastern Guizhou Province (in the southern Yangtze Block, South China) are presented. The Baifen lamproites are characterized by high MgO (7.84-14.1 wt%), K2O (3.94-5.07 wt%) and TiO2 (2.69-3.23 wt%) contents, low SiO2 (41.3-45.7 wt%), Na2O (0.21-0.28 wt%) and Al2O3 (6.10-7.20 wt%) contents. All lamproites have elevated Cr (452-599 ppm) and Ni (485-549 ppm) abundances, as well as high Ba (1884-3589 ppm), La (160-186 ppm), Sr (898-1152 ppm) and Zr (532-632 ppm) concentrations. They show uniform REE distribution patterns that are strongly enriched in light REEs relative to heavy REEs [(La/Yb)N?=?71.1-87.6], and exhibit OIB-like geochemical features with obvious enrichment of both LILEs and HFSEs in the primitive mantle-normalized multi-element distribution diagram. Moderately radiogenic Sr (87Sr/86Sri?=?0.706336-0.707439), unradiogenic Nd (143Nd/144Ndi?=?0.511687-0.511704 and eNd(t)?=??-?12.2 to?-?11.9), and low initial Pb (206Pb/204Pbi?=?16.80-16.90, 207Pb/204Pbi?=?15.34-15.35 and 208Pb/204Pbi?=?37.43-37.70) isotopic compositions are obtained from the rocks. They yield old model ages of TDM(Nd)?=?1.48-1.54 Ga. These signatures suggest that the Baifen lamproite magmas are alkaline, ultrapotassic and ultramafic in character and mainly represent mantle-derived primary melts, which have undergone insignificant crustal contamination and negligible fractional crystallization. The Baifen lamproites originated from a veined metasomatized lithospheric mantle source. We envisage that they were derived by partial melting of old, mineralogically complex metasomatic vein assemblages in the subcontinental lithospheric mantle beneath the southern Yangtze Block. The source region experienced ancient mantle metasomatism with complex modification by enriched fluids and melts. The metasomatic agents are most likely to originate from pre-existing slab subduction beneath the southeastern margin of the Yangtze Block. Tectonically, the Baifen lamproites were emplaced at the southern margin of the Yangtze Block, and they formed in an intraplate extensional setting, showing an anorogenic affinity. In terms of time and space, the genesis of Baifen lamproites is presumably related to the Emeishan large igneous province. The Emeishan mantle plume is suggested as an effective mechanism for rapid extension and thinning of the lithosphere, followed by decompression melting of the subcontinental lithospheric mantle. Combined with the thermal perturbation from asthenospheric upwelling induced by the Emeishan mantle plume, the lamproite magmas, representing small volume and limited partial melts of ancient enriched mantle lithosphere, arose. We propose that the generation of the Baifen lamproite dikes probably was a consequence of the far-field effects of the Emeishan mantle plume.
DS201610-1872
2016
Xiang, Y.Huang, J-X., Xiang, Y., An, Y., Griffin, W.L., Greau, Y., Xie, L., Pearson, N.J., Yu, H., O'Reilly, S.Y.Magnesium and oxygen isotopes in Roberts Victor eclogites.Chemical Geology, Vol. 438, pp. 73-83.Africa, South AfricaDeposit - Roberts Victor

Abstract: Magnesium and oxygen are critical elements in the solid Earth and hydrosphere. A better understanding of the combined behavior of Mg and O isotopes will refine their use as a tracer of geochemical processes and Earth evolution. In this study, the Mg-isotope compositions of garnet and omphacite separated from well-characterized xenolithic eclogites from the Roberts Victor kimberlite pipe (South Africa) have been measured by solution multi-collector ICP-MS. The reconstructed whole-rock d26Mg values of Type I (metasomatized) eclogites range from - 0.61‰ to - 0.20‰ (Type IA) and from - 0.60‰ to - 0.30‰ (Type IB) (mean - 0.43‰ ± 0.12‰), while d26Mg of Type IIA (fresh, least metasomatized) eclogites ranges from - 1.09‰ to - 0.17‰ (mean - 0.69‰ ± 0.41‰); a Type IIB (fresh, least metasomatized) has d26Mg of - 0.37‰. Oxygen-isotope compositions of garnet were analyzed in situ by SIMS (CAMECA 1280) and cross-checked by laser fluorination. Garnets have d18O of 6.53‰ to 9.08‰ in Type IA, 6.14‰ to 6.65‰ in Type IB, and 2.34‰ to 2.91‰ in Type IIB. The variation of d26Mg and d18O in Type IA and IB eclogites is consistent with the previously proposed model for the evolution of these samples, based on major and trace elements and radiogenic isotopes. In this model, the protoliths (Type II eclogites) were metasomatized by carbonatitic to kimberlitic melts/fluids to produce first Type IA eclogites and then Type IB. Metasomatism has changed the O-isotope compositions, but the Mg-isotope compositions of Type IA are mainly controlled by the protoliths; those of Type IB eclogites reflect mixing between the protoliths and the kimberlitic melt/fluid. The combination of a large range of d26Mg and low d18O in Type II eclogites cannot be explained easily by seawater alteration of oceanic crust, interaction of carbonate/silicate sediments with oceanic crust, or partial melting of mafic rocks.
DS200712-1245
2007
Xiang Li, Z.Zhong, S., Zhang, N., Xiang Li, Z., Roberts, J.H.Supercontinent cycles, true polar wander, and very long wavelength mantle convection.Earth and Planetary Science Letters, Vol. 261, 3-4, pp. 551-564.MantleConvection
DS1990-0199
1990
Xiang XinBi, Xiang Xin, Eklund, P.C., et al.Optical properties of chemical vapour deposited diamond filmsJournal of Material Research, Vol. 5, No. 4, pp. 811-817GlobalDiamond synthesis, CVD.
DS200512-1258
2005
Xiangiun, L.Zheng Fu, G., Hertogen, J., Liu, J., Pasteels, A., Boven, L., Punzalan, H., Xiangiun, L., Zhang, W.Potassic magmatism in western Sichuan and Yunnan Provinces, SE Tibet, China: petrological and geochemical constraints on petrogenesis.Journal of Petrology, Vol. 46, 1, pp. 33-78.China, TibetMagmatism
DS201707-1332
2016
Xiangkun, G.Guowu, L., Guangming, Y., Fude, L., Ming, X., Xiangkun, G., Baoming, P., Fourestier, J.Fluorcalciopyrochlore, a new mineral species from Bayan Obo, inner Mongolia, P.R. China.The Canadian Mineralogist, Vol. 54, pp. 1285-1291.China, Mongoliacarbonatite - Bayan Obo

Abstract: Fluorcalciopyrochlore, ideally (Ca,Na)2Nb2O6F, cubic, is a new mineral species (IMA2013-055) occurring in the Bayan Obo Fe-Nb-REE deposit, Inner Mongolia, People's Republic of China. The mineral is found in a dolomite-type niobium rare-earth ore deposit. Associated minerals are dolomite, aegirine, riebeckite, diopside, fluorite, baryte, phlogopite, britholite-(Ce), bastnäsite-(Ce), zircon, magnetite, pyrite, fersmite, columbite-(Fe), monazite-(Ce), rutile, and others. Crystals mostly form as octahedra {111}, dodecahedra {110}, and cubes {100}, or combinations thereof, and generally range in size from 0.01 to 0.3 mm. It is brownish-yellow to reddish-orange in color with a light yellow streak. Crystals of fluorcalciopyrochlore are translucent to transparent with an adamantine to greasy luster on fractured surfaces. It has a conchoidal fracture. No parting or cleavage was observed. The Mohs hardness is 5, and the calculated density is 4.34(1) g/cm3. The empirical formula is (Ca1.14Na0.74Ce0.06Sr0.03Th0.01Fe0.01Y0.01La0.01Nd0.01)S2.02(Nb1.68Ti0.29Zr0.02Sn0.01)S2.00O6.00(F0.92O0.08)S1.00 on the basis of 7(O,F) anions pfu. The simplified formula is (Ca,Na)2Nb2O6F. The strongest four reflections in the X-ray powder-diffraction pattern [d in Å (I) hkl] are: 6.040 (9) 1 1 1, 3.017 (100) 2 2 2, 2.613 (17) 0 0 4, 1.843 (29) 0 4 4, and 1.571 (15) 2 2 6. The unit-cell parameters are a 10.4164(9) Å, V 1130.2(2) Å3, Z = 8. The structure was solved and refined in space group FdEmbedded Image m with R = 0.05. The type material is deposited in the Geological Museum of China, Beijing, People's Republic of China, catalogue number M12182.
DS1991-1350
1991
Xianhua LiPhilpotts, J., Tatsumoto, M., Xianhua Li, Kaiyi WangSome neodymium and Strontium isotopic systematics for the rare earth elements (REE) enriched deposit at Bayan Obo, ChinaChemical Geology, Vol. 90, pp. 177-188ChinaGeochronology, rare earth elements (REE)., Carbonatite
DS201312-0990
2012
Xianhzhen, X.Yang, J., Wirth, R., Xianhzhen, X., Robinson, P.T., Rong, H.Mineral inclusions in diamonds from ophiolitic peridotite and chromities.Geological Society of America Annual Meeting abstract, Paper 74-4, 1/2p. AbstractTechnologyDiamond inclusions
DS1996-1569
1996
Xianjie, S.Xianjie, S.Plate kinematic origin of the N S heterogeneity of the Tibetan Crust Mantle thermal structure and its synamic implications.Continental Dynamics, Vol. 1, No.1, pp. 38-48.MantleGeodynamics
DS200612-0644
2006
Xianren, Y.Jinlong, M., Mingxin, T., Xianren, Y.Characteristics and origins of primary fluids and noble gases in mantle derived minerals from the Yishu area, Shandong Province, China.Science China Earth Sciences, Vol. 49, 1, Jan. pp. 77-87.ChinaMineral chemistry
DS200612-1553
2006
Xianwu, B.Xianwu, B., Ruizhong, H., Jiantang, P., Li, L., Kaixing, W., Wenchao, S.Geochemical characteristics of the Yaoan and Machangqing alkaline rich intrusions in the Ailaoshan Jinshajiang belt, western Yunnan, China.Geochimica et Cosmochimica Acta, Vol. 70, 18, p. 1, abstract only.ChinaAlkalic
DS1990-1596
1990
Xianyu XueXianyu Xue, Baadsgaard, H., Irving, A.J., Scarfe, C.M.Geochemical and isotopic characteristics of lithospheric mantle beneath West Kettle River, British Columbia: evidence from ultramafic xenoliths #2Journal of Geophysical Research, Vol. 95, No. B 10, September 10, pp. 15, 879-15, 891British ColumbiaGeochemistry, Mantle xenoliths
DS1990-1597
1990
Xianyu XueXianyu Xue, Baadsgard, H., Irvingm A.J., Scarfe, C.S.Geochemical and isotopic characteristics of lithospheric mantle beneath West Kettle River British Columbia: evidence from ultramafic xenoliths #1Eos, Vol. 71, No. 28, July 10, p. 824. AbstractBritish ColumbiaMantle, Xenolith
DS201506-0300
2015
XiaoWu, Xiao, Xu, Santosh, Li, Huang, Hou.Geochronology and geochemistry of felsic xenoliths in lamprophyre dikes from the southeastern margin of the North Chin a Craton: implications for the interleaving of the Dabie Sulu orogenic crust.International Geology Review, Vol. 57, 9-10, pp. 1305-1325.ChinaDabie Sulu
DS1998-0982
1998
Xiao, G.McLennan, S.M., Xiao, G.Composition of the upper continental crust revisited: insights from sedimentary rocks.Mineralogical Magazine, Goldschmidt abstract, Vol. 62A, p. 983-4.Northwest TerritoriesSediments - geochemistry, Trace elements
DS200512-1231
2005
Xiao, H.Y.Zang, C.Y., Jia, X.P., Ma, H.A., Tian, Y., Xiao, H.Y.Effect of regrown graphite on the growth of large gem diamonds by temperature gradient method.Chinese Physics Letters , Vol. 22, 9, pp. 2415-2417.TechnologyDiamond morphology
DS201811-2621
2018
Xiao, J.Yang, H., Xiao, J., Yao, Z., Zhang, X., Younus, F., Melnik, R., Wen, B.Homogeneous and heterogenous dislocation nucleation in diamond.Diamond & Related Materials, Vol. 88, pp. 110-117.Mantlediamond morphology

Abstract: Dislocation nucleation plays a key role in plastic deformation of diamond crystal. In this paper, homogeneous and heterogeneous nucleation nature for diamond glide set dislocation and shuffle set dislocation is studied by combining molecular dynamics method and continuum mechanics models. Our results show that although heterogeneous dislocation nucleation can decrease its activation energy, the activation energy at 0?GPa for diamond heterogeneous nucleation is still in the range of 100?eV. For glide set and shuffle set homogeneous nucleation, their critical nucleation shear stress approaches to diamond's ideal shear strength which implies that those dislocations do not nucleate before diamond structural instability only by a purely shearing manner. While for glide set and shuffle set heterogeneous nucleation, their critical nucleation shear stresses are 28.9?GPa and 48.2?GPa, these values are less than diamond's ideal shear strength which implies that these dislocations may be nucleated heterogeneously under certain shear stress condition. In addition, our results also indicate there exists a deformation mode transformation for diamond deformation behavior at strain rate of 10-3/s. Our results provide a new insight into diamond dislocation nucleation and deformation.
DS2003-0566
2003
Xiao, L.He, B., Xu, Y.G., Chung, S.L., Xiao, L., Wang, Y.Sedimentary evidence for a rapid kilometer scale crustal doming prior to eruption of theEarth and Planetary Science Letters, Vol. 213, 3-4, pp. 391-405.GlobalBasalts - not specific to diamonds, tectonics
DS200412-0808
2003
Xiao, L.He, B., Xu, Y.G., Chung, S.L., Xiao, L., Wang, Y.Sedimentary evidence for a rapid kilometer scale crustal doming prior to eruption of the Emeishan flood basalts.Earth and Planetary Science Letters, Vol. 213, 3-4, pp. 391-405.TechnologyBasalts - not specific to diamonds Tectonics
DS200512-1204
2004
Xiao, L.Xiao, L., Xu, Y.G., Mei, H.J., Zheng, Y.F., He, B., Pirajno, F.Distinct mantle sources of low Ti and high Ti basalts from the western Emeishan large igneous province, SW China: implications for plume?? lithosphere interactionEarth and Planetary Science Letters, Vol. 228, 3-4, pp. 525-546.ChinaMantle mineralogy, titanium
DS200712-1187
2006
Xiao, L.Xiao, L., Clemens, J.Origin of potassic (C type) adakite magmas: experimental and field constraints.Lithos, In press, availableChinaPetrogenesis, adakite
DS200712-1188
2006
Xiao, L.Xiao, L., Clemens, J.D.Origin of potassic (C-type) adakite magmas: experimental and field constraints.Lithos, In press availableChinaTectonic, geochemistry
DS201012-0894
2010
Xiao, L.Zhong, J.P., Griffin, W.L., Sun, M., O'Reilly, S.Y., Zhang, H.F., Zhou, J., Xiao, L., Tang, H.Y., Zhang, Z.Tectonic affinity of the west Qingling terrane ( central Chin a): North Chin a or Yangtze?Tectonics, Vol. 29, 2, TC2009ChinaTectonics
DS201511-1889
2015
Xiao, S.Yap, C.M., Tarum, A., Xiao, S., Misra, D.S.MPCVD growth of 13 C-enriched diamond single crystals with nitrogen addition.Diamond and Related Materials, in press available, 29p.TechnologySynthetics - nitrogen

Abstract: This study describes the growth of 13C-enriched (100)-oriented diamond single crystals by the MPCVD (microwave plasma chemical vapour deposition) process. All crystals are at least 6 × 6 mm2 in area and 0.5-1.0 mm in thickness. The samples with nominal 13C percentages (R = [13C] / [13C + 12C]) of 0.011 (natural abundance), 0.10, 0.21, 0.24 and 0.34 were obtained by controlling the flow of the carbon-13 and carbon-12 methane feed gases. To obtain thicker and near-colourless quality 13C-enriched diamond, 190 ppm of nitrogen was added into the gas mixture. The shift towards lower frequency in the Raman peak positions and decrease in the thermal conductivities of the near-colourless crystals with increasing 13C percentages are similar to previous studies of isotopically-controlled diamond grown with no nitrogen additive. The images of the structural defects associated with 13C-enrichment obtained by spatially-resolved X-ray rocking curve measurement show distinct patterned structures that runs parallel to the < 100 > direction. Moreover, the broadening in the line width of the nuclear magnetic resonance (NMR) peak from sp313C correlates with increasing R. We also expand the study by injecting 500 ppm of nitrogen. Higher nitrogen concentration leads to the formation of brown crystals. The brown crystals show far greater 13C NMR peak intensity than the near-colourless. This suggests that paramagnetic nitrogen impurities in the brown crystals hasten the spin-lattice relaxation time of the 13C nuclear spin that resulted in higher intensity. The isotopic splitting observed for the localized vibrational mode of the NVH0 defect in brown crystals is attributed to the co-existence of both the 13C (3114.2 cm- 1) and 12C (3123.5 cm- 1). Unlike the isotopic splitting observed for NVH0 defect, the peak position of the Ns+ defect shifts towards lower frequency as R increases. Not only have we demonstrate the growth of bigger isotopically-controlled diamond single crystals, the results shown here have provided a framework to further investigate the interplay between 13C atoms and nitrogen impurity.
DS200512-1207
2005
Xiao, W.Xu, S., Liu, Y., Chen, G., Ji, S., Ni, P., Xiao, W.Microdiamonds, their classification and tectonic implications for the host eclogites from the Dabie and Su-Lu regions in central eastern China.Mineralogical Magazine, Vol. 69, 4, Aug. pp. 509-520.ChinaUHP, microdiamonds
DS200912-0827
2008
Xiao, W.Xu, S., Wu, W., Xiao, W., Yang, J., Chen, J., Ji, S., Liu, Y.Moissanite in serpentine from the Dabie Mountains in China.Mineralogical Magazine, Vol. 72, 4, pp. 899-908.ChinaUHP
DS201510-1815
2015
Xiao, W.Xu, S., Liu, Y., Chen, G., Ji, S., Ni, P., Xiao, W.Microdiamonds, their classification and tectonic implications for the host eclogites from the Dabie and Su-Lu regions in central eastern China.Mineralogical Magazine, Vol. 69, 4, pp. 590-520.ChinaUHP

Abstract: We have found >10 in situ microdiamonds in thin sections of eclogites from the Dabie and Su-Lu regions of central eastern China since the first occurrence of microdiamond in eclogites from the Dabie Mountains (DMT) reported in 1992. The microdiamonds are found not only in the central part but also in the northern part of the DMT. Several free crystals have been recovered from the crushed eclogites from the central DMT. Most in situ microdiamonds are inclusions in garnets but a few larger ones are intergranular. Most of the diamondiferous eclogites in the central part of the DMT are associated with coesite. Most importantly, the observation of microdiamonds in northern Dabie lead us to question the supposition that this is a low-P metamorphic terrane. All the diamondiferous eclogites from both the north and central DMT are of continental affinity as demonstrated by their negative eNd values. Therefore, both the north and central eclogite belts in the DMT are considered to be from the deep subducted terrane. Five in situ microdiamonds and two free crystals are first reported in this paper. The dimensions of the in situ microdiamonds are 30-80 µm and the free crystals are up to 400–-00 µm across. All the microdiamonds are confirmed as such by Raman spectroscopy. The results of an infrared spectroscopic investigation on two larger free crystals and two in situ microdiamonds show that all the microdiamonds from both the Dabie and Su-Lu regions are mixed types IaA and IaB diamonds and there is no indication of any synthetic microdiamonds in our samples because such synthetic microdiamonds are always rich in type Ib.
DS2002-1745
2002
Xiao, W.J.Xiao, W.J., Windley, B.F., Chen, H.L.,Zhang, G.C., LiCarboniferous Triassic subduction and accretion in the western Kunln: implications for collisional tectonics..Geology, Vol. 30,4,Apr.pp.295-8.China, TibetTectonics - accretionary
DS201312-1015
2013
Xiao, W.J.Zheng, Y.F., Xiao, W.J., Zhao, G.C.Introductions to tectonics of China.Gondwana Research, Vol. 23, 4, pp. 1189-1206.ChinaOverview of cratons and belts
DS200612-1555
2006
Xiao, W.S.Xiong, X.L., Xia, B., Hu, J.F., Niu, H.C., Xiao, W.S.Na depletion in modern adakites via melt/rock reaction within the subarc mantle.Chemical Geology, Vol. 229, 4, May 30, pp. 273-292.MantleSlab, subduction, melting
DS2000-0593
2000
Xiao, X.Luo, Z., Xiao, X., Cao, Y.The Cenozoic mantle magmatism and motion of lithosphere on the north margin of the Tibetan Plateau.Science in China Series d. Earth, *CHINESE, Vol.44,pp.10-17.ChinaMagmatism
DS201212-0795
2012
Xiao, X.Xiaoyu, G., Encarnacion, J., Xiao, X., Deino, A., Li, Z., Xiabo, T.Collision and rotation of the South Chin a block and their role in the formation and exhumation of ultrahigh pressure rocks in the Dabie Shan orogen.Terra Nova, Vol. 24, 5, pp. 339-350.ChinaUHP
DS2000-1030
2000
Xiao, Y.Xiao, Y., Hoefs, J., Zheng, Y.Fluid history of ultra high pressure (UHP) metamorphism in Dabie Shan: a fluid inclusion and oxygen isotope coesite-bearing....Contrib. Min. Pet., Vol. 139, No. 1, pp. 1-16.ChinaEclogite, Bixiling area
DS2002-1746
2002
Xiao, Y.Xiao, Y., Hoefs, J., Van den Kerkof, A.M., Simon, K., Fiebig, J., Zheng, Y.F.Fluid evolution in the Baia Mare epithermal gold/polymetallic district, Inner Carpathians, RomaniaJournal of Petrology, Vol. 43, No. 8, pp. 1505-28.ChinaGeochemistry, UHP
DS200512-1205
2005
Xiao, Y.Xiao, Y., Hoefs, J., Kronz, A.Compositionally zoned Cl rich amphiboles from North Dabie Shan, China: monitor of high pressure metamorphic fluid rock interaction processes.Lithos, Vol. 81, 1-4, April pp. 279-295.ChinaUHP
DS200512-1251
2005
Xiao, Y.Zhang, Z., Xiao, Y., Liu, F., Liou, J.G., Hoefs, J.Petrogenesis of UHP metamorphic rocks from Qinglongshan, southern Sulu east central China.Lithos, Vol. 81, 1-4, April pp. 189-207.ChinaUHP
DS200612-1554
2006
Xiao, Y.Xiao, Y., Sun, W., Hoefs, J., Simon, K., Zhang, Z., Li, S., Hofmann, A.W.Making continental crust through slab melting: constraints from niobium tantalum fractionation in UHP metamorphic rutile.Geochimica et Cosmochimica Acta, Vol. 70, 18, Sept. 15, pp. 4770-47082.ChinaDabie Sulu - eclogites - UHP
DS200612-1596
2005
Xiao, Y.Zhang, Z., Xiao, Y., Hoefs, J., Xu, Z., Liou, J.G.Petrogenesis of UHP metamorphic crustal and mantle rocks from the Chinese continent in the main hole pre-pilot hole 1 Sulu Basin.International Geology Review, Vol. 47, 11, pp. 1160-1177.Asia, ChinaUHP
DS200712-0952
2007
Xiao, Y.Schmidt, A., Weyer, S., Xiao, Y., Hoefs, J., Brey, G.P.Lu Hf geochronology of eclogites from the Dabie Sulu terrain: constraints on the timing of eclogite facies metamorphism.Plates, Plumes, and Paradigms, 1p. abstract p. A894.ChinaUHP
DS200812-1020
2008
Xiao, Y.Schmidt, A., Weyer, S., Mezger, K., Scherer, E.E., Xiao, Y., Hoefs, J., Brey, G.P.Rapid eclogization of the Dabie Sulu UHP terrane: constraints from Lu Hf garnet geochronology.Earth and Planetary Science Letters, Vol. 273, 1-2, Aug. 30, pp. 203-213.ChinaUHP
DS200812-1021
2008
Xiao, Y.Schmidt, A., Weyer, S., Mezger, K., Scherer, E.E., Xiao, Y., Hoefs, J., Brey, G.P.Rapid eclogitization of the Dabie Sulu UHP terrane: constraints from Lu Hf garnet geochronology.Earth and Planetary Science Letters, In press available, 49p.ChinaUHP
DS200812-1136
2008
Xiao, Y.Su, B-X., Zhang, H-F., Ying, J-F., Xiao, Y., Zhao, X-M.Nature and processes of the lithospheric mantle beneath the western Qinling: evidence from deformed peridotitic xenoliths in Cenozoic kamafugite from Haoiti, Gansu ProJournal of Asian Earth Sciences, Vol. 34, 3, pp. 258-274.ChinaKamafugite
DS200912-0738
2009
Xiao, Y.Su, B-X., Zhang, H-F., Ying, J-F., Xiao, Y., Zhao, X-M.Nature and processes of the lithospheric mantle beneath the western Qinling: evidence from deformed peridotitic xenoliths in Cenozoic kamafugite from Haoti Province.Journal of Asian Earth Sciences, Vol. 34, pp. 258-274.ChinaKamafugite
DS201012-0441
2010
Xiao, Y.Li, W-Y., Teng, F-Z., Xiao, Y., Huang, J.Mantle like magnesium isotopic composition of orogenic eclogites from the Dabie Sulu UHPM belt, China.Goldschmidt 2010 abstracts, abstractChinaUHP
DS201012-0765
2010
Xiao, Y.Su, B-X., Zhang, H-F., Sakyi, P.A., Yang, Y-H., Ying, J-F., Tang, Y-J., Qin, K-Z., Xiao, Y., Zhao, Mao, MaThe origin of spongy texture in minerals of mantle xenoliths from the western Qinling, central China.Contributions to Mineralogy and Petrology, in press available, 18p.ChinaXenoliths
DS201012-0766
2010
Xiao, Y.Su, B-X., Zhang, H-F., Sakyi, P.A., Ying, J-F., Tang, Y-J., Yang, Y-H., Qin, K-Z., Xiao, Y., Zhao, X-M.Compositionally stratified lithosphere and carbonatite metasomatism recorded in mantle xenoliths from the Western Qinling (Central China).Lithos, Vol. 116, pp. 111-128.ChinaCarbonatite
DS201112-0154
2011
Xiao, Y.Catalli, K., Shim, S-H., Dera, P., Prakapenka, V.B., Zhao, J., Sturhahn, W., Chow, P., Xiao, Y., Cynn, H., Evans, W.J.Effects of the Fe3 +spin transition on the properties of aluminous perovskite - new insights for lower mantle seismic heterogeneities.Earth and Planetary Science Letters, Vol. 310, 3-4, pp. 293-302.MantlePerovskite
DS201112-0456
2011
Xiao, Y.Huang, J., Xiao, Y., Worner, G.Element mobility across the boundary between UHP eclogite and gneiss: insights into supercritical fluids in continental subduction zones.Goldschmidt Conference 2011, abstract p.1062.ChinaDabie UHP
DS201212-0716
2013
Xiao, Y.Tang, Y-L., Zhang, H-F., Ying, J-F., Su, B-X., Chu, Z.Y., Xiao, Y., Zhao, X-M.Highly heterogeneous lithospheric mantle beneath the Central Zone of the North Chin a Craton evolved from Archean mantle through diverse melt refertilization.Gondwana Research, Vol. 23, 1, pp. 130-140.ChinaMelting
DS201212-0812
2012
Xiao, Y.Zhang, H-F., Yang,Y-H., Santosh, M., Zhao, X-M., Ying, J-F., Xiao, Y.Evolution of the Archean and Paleoproterozoic lower crust beneath the Trans-North Chin a Orogen and the western block of the north Chin a craton.Gondwana Research, Vol. 22, 1, pp. 73-85.ChinaGeochronology, tectonics, cratons
DS201212-0815
2012
Xiao, Y.Zhang, P.-F., Tang, Y-J., Hu, Y., Zhang, H-F., Su, B-X., Xiao, Y., Santosh, M.Review of melting experiments on carbonated eclogite and peridotite: insights into mantle metasomatism.International Geology Review, in press availableMantleMetasomatism
DS201212-0816
2012
Xiao, Y.Zhang, P=F., Tang, Y-J., Hu, Y., Zhang, H-F., Su, B-X., Xiao, Y., Santosh, M.Review of melting experiments on carbonated eclogite and peridotite: insights into mantle metasomatism.International Geology Review, In press availableMantleMetasmatism
DS201312-0147
2013
Xiao, Y.Chang, Y-Y., Jacobsen, S.D., Lin, J-F., Bina, C.R., Thomas, S-M., Wu, J., Shen, G., Xiao, Y., Chow, P., Frost, D.J., McCammon, C.A., Dera, P.Spin transition off F23+ in Al bearing phase D: an alternative explanation for small scale seismic scatterers in the mid-lower mantle.Earth and Planetary Science Letters, Vol. 382, pp. 1-9.MantleGeophysics, seismics
DS201412-0519
2014
Xiao, Y.Liu, L., Xiao, Y., Worner, G., Kronz, A., Hou, Z.Detrital rutile geochemistry and theromometry from the Dabie orogen: implications for source - sediment links in a UHPM terrane.Journal of Asian Earth Sciences, Vol. 89, pp. 123-140.ChinaUHP
DS201412-0547
2014
Xiao, Y.Mao, Z., Lin, J-F., Yang, J., Bian, H., Liu, J., Watson, H.C., Huang, S., Chen, J., Prakapenka, V.B., Xiao, Y., Chow, P.Fe, Al bearing post-perovskite in the Earth's lower mantle.Earth and Planetary Science Letters, Vol. 403, pp. 157-163.MantlePerovskite
DS201412-0889
2014
Xiao, Y.Su, B-X., Zhang, H-F., Deloule, E., Vigier, N., Hu, Y., Tang, H-J., Xiao, Y., Sakyi, P.A.Distinguishing silicate and carbonatite mantle metasomatism by using lithium and its isotopes.Chemical Geology, Vol. 381, pp. 67-77.ChinaXenoliths - Hannuoba
DS201607-1306
2016
Xiao, Y.Li, W-Y., Teng, F-Z., Xiao, Y., Gu, H-O., Zha, X-P.Empirical calibration of the clinopyroene-garnet magnesium isotope geothermometer and implications. DabieContributions to Mineralogy and Petrology, Vol. 171, 7, 14p.ChinaGeothermometry

Abstract: The large equilibrium Mg isotope fractionation between clinopyroxene and garnet observed in eclogites makes it a potential high-precision geothermometer, but calibration of this thermometer by natural samples is still limited. Here, we report Mg isotopic compositions of eclogite whole rocks as well as Mg and O isotopic compositions of clinopyroxene and garnet separates from 16 eclogites that formed at different temperatures from the Dabie orogen, China. The whole-rock d26Mg values vary from -1.20 to +0.10 ‰. Among them, 11 samples display limited d26Mg variations from -0.36 to -0.17 ‰, similar to those of their protoliths. The mineral separates exhibit very different d26Mg values, from -0.39 to +0.39 ‰ for clinopyroxenes and from -1.94 to -0.81 ‰ for garnets. The clinopyroxene -garnet Mg isotope fractionation (?26Mgclinopyroxene -garnet = d26Mgclinopyroxene -d26Mggarnet) varies from 1.05 to 2.15 ‰. The clinopyroxene -garnet O isotope fractionation (?18Oclinopyroxene -garnet = d18Oclinopyroxene -d18Ogarnet) varies from -1.01 to +0.98 ‰. Equilibrium Mg isotope fractionation between clinopyroxene and garnet in the investigated samples is selected based on both the d26Mgclinopyroxene versus d26Mggarnet plot and the state of O isotope equilibrium between clinopyroxene and garnet. The equilibrium ?26Mgclinopyroxene -garnet and corresponding temperature data obtained in this study, together with those available so far in literatures for natural eclogites, are used to calibrate the clinopyroxene -garnet Mg isotope thermometer. This yields a function of ?26Mgclinopyroxene -garnet = (0.99 ± 0.06) × 106/T 2, where T is temperature in Kelvin. The refined function not only provides the best empirically calibrated clinopyroxene -garnet Mg isotope thermometer for precise constraints of temperatures of clinopyroxene- and garnet-bearing rocks, but also has potential applications in high-temperature Mg isotope geochemistry.
DS201907-1553
2019
Xiao, Y.Jing, J-J., Su, B-X., Xiao, Y., Zhang, H-F., Uysal, I., Chen, C., Lin, W., Chu, Y., Saka, S.Reactive origin of mantle harzburgite: evidence from orthopyroxene-spinel association.Lithos, Vol. 342-343, pp. 175-186.Europe, Turkeymelting

Abstract: Harzburgites with high modal orthopyroxene (generally >23?vol%) in Archean craton, mantle wedge and oceanic lithospheric mantle are considered to be produced by the interaction between Si-rich liquids and rocks. However, the absence of samples from continental margin hinders the recognition whether this process is prevalent. Mantle xenoliths entrained in Miocene basalts from the Thrace Basin, the margin of Eurasian continent, are dominated by harzburgites with anomalously high orthopyroxene modes. These orthopyroxene grains closely associate with spinel and occasionally with clinopyroxene. In these orthopyroxene-spinel associations, orthopyroxene grains can be up to 1?cm in diameter and display high Al2O3 contents (1.41-4.61?wt%) and Mg# values (89.6-92.4), while spinel crystals are anhedral and bud-shaped and are commonly foliated, with a wide variation in Cr# values ranging from 7.8 to 52.7. The Fe2+/Fe3+ vs. TiO2 diagram shows lots of these spinels are “magmatic” (i.e. spinel crystallized from melts). The orthopyroxene grains have LREE diverging from the modelled melting trends, indicating possible metasomatism following partial melting. They are present in elongated shape, cutting across olivine grains and also replacing olivine as surrounding rims. Fine-grained olivine is occasionally enclosed in the orthopyroxene-spinel association. We, therefore, propose that the association of orthopyroxene and spinel developed from the melt/fluid-rock interaction. These features indicate mineral phase transformation from olivine to orthopyroxene, which can be expressed by the equation: ‘Mg2SiO4 (Ol)?+?SiO2?=?Mg2Si2O6 (Opx)’. The observed Al-rich rim of spinel and bud-shaped Al-spinel, suggest sufficient amount of Al in the Si-rich liquids. The mechanism involved here is the consumption of olivine to produce orthopyroxene and spinel as in the equation: ‘Mg2SiO4 (Ol)?+?Al2O3?=?MgSiO3 (Opx)?+?MgAl2O4 (Sp)’. The Si and Al were enriched in the percolating liquids. Both the high-Cr# and low-Cr# spinels with ‘magmatic’ features imply the percolating liquids were multi-staged or inhomogeneous Cr contents in the liquids. This melt/fluid-rock interaction may account for the formation of abundant harzburgites with high orthopyroxene modes in the Eurasian continental margin. Thus, it indicates the reacting harzburgites are prevalent in the lithospheric mantle beneath oceanic crust, Archean craton and mantle wedge, as well as in the continental margin.
DS201909-2051
2019
Xiao, Y.Jing, J-J., Su, B-X., Xiao, Y., Zhang, H-F., Uysal, I., Chen, C., Lin, W., Chu, Y., Saka, S.Reactive origin of mantle harzburgite: evidence from orthopyroxene-spinel association.Lithos, Vol. 342-343, pp. 175-186.Mantleharzburgite

Abstract: Harzburgites with high modal orthopyroxene (generally >23?vol%) in Archean craton, mantle wedge and oceanic lithospheric mantle are considered to be produced by the interaction between Si-rich liquids and rocks. However, the absence of samples from continental margin hinders the recognition whether this process is prevalent. Mantle xenoliths entrained in Miocene basalts from the Thrace Basin, the margin of Eurasian continent, are dominated by harzburgites with anomalously high orthopyroxene modes. These orthopyroxene grains closely associate with spinel and occasionally with clinopyroxene. In these orthopyroxene-spinel associations, orthopyroxene grains can be up to 1?cm in diameter and display high Al2O3 contents (1.41-4.61?wt%) and Mg# values (89.6-92.4), while spinel crystals are anhedral and bud-shaped and are commonly foliated, with a wide variation in Cr# values ranging from 7.8 to 52.7. The Fe2+/Fe3+ vs. TiO2 diagram shows lots of these spinels are “magmatic” (i.e. spinel crystallized from melts). The orthopyroxene grains have LREE diverging from the modelled melting trends, indicating possible metasomatism following partial melting. They are present in elongated shape, cutting across olivine grains and also replacing olivine as surrounding rims. Fine-grained olivine is occasionally enclosed in the orthopyroxene-spinel association. We, therefore, propose that the association of orthopyroxene and spinel developed from the melt/fluid-rock interaction. These features indicate mineral phase transformation from olivine to orthopyroxene, which can be expressed by the equation: ‘Mg2SiO4 (Ol)?+?SiO2?=?Mg2Si2O6 (Opx)’. The observed Al-rich rim of spinel and bud-shaped Al-spinel, suggest sufficient amount of Al in the Si-rich liquids. The mechanism involved here is the consumption of olivine to produce orthopyroxene and spinel as in the equation: ‘Mg2SiO4 (Ol)?+?Al2O3?=?MgSiO3 (Opx)?+?MgAl2O4 (Sp)’. The Si and Al were enriched in the percolating liquids. Both the high-Cr# and low-Cr# spinels with ‘magmatic’ features imply the percolating liquids were multi-staged or inhomogeneous Cr contents in the liquids. This melt/fluid-rock interaction may account for the formation of abundant harzburgites with high orthopyroxene modes in the Eurasian continental margin. Thus, it indicates the reacting harzburgites are prevalent in the lithospheric mantle beneath oceanic crust, Archean craton and mantle wedge, as well as in the continental margin.
DS201912-2799
2019
Xiao, Y.Liu, J., Hu, Q., Bi, W., Yang, L., Xiao, Y., Chow, P., Meng, Y., Prakapenka, V.B., Mao, H-K., Mao, W.L.Altered chemistry of oxygen and iron under deep Earth conditionsNature Communications, 8p. PdfMantlegeochemistry

Abstract: A drastically altered chemistry was recently discovered in the Fe-O-H system under deep Earth conditions, involving the formation of iron superoxide (FeO2Hx with x?=?0 to 1), but the puzzling crystal chemistry of this system at high pressures is largely unknown. Here we present evidence that despite the high O/Fe ratio in FeO2Hx, iron remains in the ferrous, spin-paired and non-magnetic state at 60-133?GPa, while the presence of hydrogen has minimal effects on the valence of iron. The reduced iron is accompanied by oxidized oxygen due to oxygen-oxygen interactions. The valence of oxygen is not -2 as in all other major mantle minerals, instead it varies around -1. This result indicates that like iron, oxygen may have multiple valence states in our planet’s interior. Our study suggests a possible change in the chemical paradigm of how oxygen, iron, and hydrogen behave under deep Earth conditions.
DS202001-0047
2020
Xiao, Y.Wang, X., Xiao, Y., Sun, Y., Wang, Y., Liu, J., Yang, K., Gu, H., Hou, Z., Tian, Y., Wu, W., Ma, Y.Initiation of the North China craton destruction: constraints from the diamond bearing alkaline basalts from Langan, China.Gondwana Research, Vol. 80, pp. 228-243.Chinacraton

Abstract: The North China Craton (NCC) is an atypical ancient landmass that suffered lithospheric destruction. Previous studies suggest that the eastern part of the lithospheric mantle of the NCC has been thinned and modified in the Mesozoic. However, the initiation time and mechanism of the destruction remain controversial. Mafic magmatismcould provide a unique windowinto deciphering the lithospheric mantle composition and its evolution. Here we present geochemical and geochronological data of the diamond-bearing alkaline basalts from Lan'gan, located in the southeastern margin of the NCC. Zircon U-Pb dating yielded an average age of 174 ± 14 Ma, representing the first reported Jurassic basalts in the eastern NCC. The Lan'gan basalts are enriched in light rare earth elements (LREE) and large ion lithosphile elements (LILE). Sr-Nd-Pb-Hf isotopic compositions (87Sr/86Sr(t) = 0.70646-0.70925, eNd(t) = -2.1 to -4.9, 206Pb/204Pb(t) = 17.14-18.12, 207Pb/204Pb(t) = 15.28-15.61, 208Pb/204Pb(t) = 37.82-38.67, and zircon eHf(t) = -17 to -21) are enriched compared to depleted mantle. The presence of primary amphibole indicates that the magma source of the basalts was water enriched. These observations suggest that, the lithospheric mantle of the eastern NCC were significantly refertilized, likely by slab derived fluids/melts fromthe Paleo-Pacific subduction. Owing to the Paleo-Pacific subduction, the lithosphericmantle of the eastern NCCwere reduced in viscosity and intensity, and finally promoted partialmelting in a limited scale to generate the investigated alkaline basalts. Hence, the discovery of diamond in the Lan'gan basalts demonstrates that the lithosphere of the NCC remained thick, and that large-scale destruction had not initiated in the early Jurassic beneath this region.
DS202004-0542
2020
Xiao, Y.Wang, X., Xiao, Y., Wang, Y., Liu, J., Yang, K., Gu, H., Hou, Z., Tian, Y., Wu, W., Ma, Y.Initiation of the North China Craton destruction: constraints from the diamond bearing alkaline basalts from Langan China.Gondwana Research, Vol. 80, pp. 228-243.Chinadeposit - Langan

Abstract: The North China Craton (NCC) is an atypical ancient landmass that suffered lithospheric destruction. Previous studies suggest that the eastern part of the lithospheric mantle of the NCC has been thinned and refertilized in the Mesozoic. However, the initiation time and mechanism of the destruction remain controversial. Mafic magmatism could provide a unique window into deciphering the lithospheric mantle composition and its evolution. Here we present geochemical and geochronological data of the diamond-bearing alkaline basalts from Lan'gan, located in the southeastern margin of the NCC. Zircon UPb dating yielded an average age of 174?±?14?Ma, representing the first reported Jurassic basalts in the eastern NCC. The Lan'gan basalts are enriched in light rare earth elements (LREE) and large ion lithosphile elements (LILE). Sr-Nd-Pb-Hf isotopic compositions (87Sr/86Sr(t)?=?0.70646-0.70925, eNd(t)?=?-2.1 to -4.9, 206Pb/204Pb(t)?=?17.14-18.12, 207Pb/204Pb(t)?=?15.28-15.61, 208Pb/204Pb(t)?=?37.82-38.67, and zircon eHf(t)?=?-17 to -21) are slightly enriched compared to depleted mantle. The presence of primary amphibole indicates that the magma source of the basalts was water enriched. These observations suggest that, the lithospheric mantle of the eastern NCC were significantly refertilized, likely by slab derived fluids/melts from the Paleo-Pacific subduction. Owing to the Paleo-Pacific subduction, the lithospheric mantle of the eastern NCC were reduced in viscosity and intensity, and finally promoted partial melting in a limited scale to generate the investigated alkaline basalts. Hence, the discovery of diamond in the Lan'gan basalts demonstrates that the lithosphere of the NCC remained thick, and that large-scale destruction had not initiated in the early Jurassic beneath this region.
DS202104-0614
2021
Xiao, Y.Wang, W.,Liu, J., Yang, H., Dorfman, S.M., Lv, M., Li, J., Zhao, J., Hu, M.Y., bi, W., Alp, E.E., Xiao, Y., Wu, Z., Lin, J-F.Iron force constants of bridgmanite at high pressure: implications for iron isotope fractionation in the deep mantle.Geochimica et Cosmochimica Acta, Vol. 294, pp. 215-231. pdfMantlebridgmanite

Abstract: The isotopic compositions of iron in major mantle minerals may record chemical exchange between deep-Earth reservoirs as a result of early differentiation and ongoing plate tectonics processes. Bridgmanite (Bdg), the most abundant mineral in the Earth’s lower mantle, can incorporate not only Al but also Fe with different oxidation states and spin states, which in turn can influence the distribution of Fe isotopes between Bdg and ferropericlase (Fp) and between the lower mantle and the core. In this study, we combined first-principles calculations with high-pressure nuclear resonant inelastic X-ray scattering measurements to evaluate the effects of Fe site occupancy, valence, and spin states at lower-mantle conditions on the reduced Fe partition function ratio (ß-factor) of Bdg. Our results show that the spin transition of octahedral-site (B-site) Fe3+ in Bdg under mid-lower-mantle conditions generates a +0.09‰ increase in its ß-factor, which is the most significant effect compared to Fe site occupancy and valence. Fe2+-bearing Bdg varieties have smaller ß-factors relative to Fe3+-bearing varieties, especially those containing B-site Fe3+. Our models suggest that Fe isotopic fractionation between Bdg and Fp is only significant in the lowermost mantle due to the occurrence of low-spin Fe2+ in Fp. Assuming early segregation of an iron core from a deep magma ocean, we find that neither core formation nor magma ocean crystallization would have resulted in resolvable Fe isotope fractionation. In contrast, Fe isotopic fractionation between low-spin Fe3+-bearing Bdg/Fe2+-bearing Fp and metallic iron at the core-mantle boundary may have enriched the lowermost mantle in heavy Fe isotopes by up to +0.20‰.
DS1998-1605
1998
Xiao, Y.L.Xiao, Y.L., Hoefs, J., Van der Kerkof, A.M., Zheng, Y.Fluid inclusions in ultra high pressure eclogites from the Dabie Shan, eastern China.Mineralogical Magazine, Goldschmidt abstract, Vol. 62A, p. 1667-8.ChinaEclogites, metamorphic, Deposit - Dabie Shan
DS2001-1267
2001
Xiao, Y.L.Xiao, Y.L., Hoefs, J., Li, S.G.Geochemical constraints of the eclogite and granulite facies metamorphism as recognized in Raobazhai Complex.Journal of Metamorphic Geology, Vol. 19, No. 1, Jan. pp. 3-20.ChinaGeochemistry, Dabie Shan
DS1990-1598
1990
Xiao XugangXiao Xugang, Liu GangElectron microscopic study of inclusions in small diamonds occurred inLiaokingInternational Mineralogical Association Meeting Held June, 1990 Beijing China, Vol. 1, extended abstract p. 361-363ChinaMineralogy, Microdiamonds
DS1983-0649
1983
XIAO ZHENGYUE, Wang yitem.Zhao dasheng, XIAO ZHENGYUE, Wang yitem.Petrologic characteristics and genesis of Cenozoic volcanic rocks of the Tacheng Luijang fault belt and neighbouringregions.*CHIActa Geol. Sinica, *CHI, Vol. 57, No. 2, pp. 128-141ChinaBlank
DS1990-1599
1990
Xiaomin WangXiaomin Wang, Liou, J.G., Maryuama, S.Regional ultrahigh pressure metamorphic terrane in central ChinaEos, Vol. 71, No. 43, October 23, p. 1708 AbstractChinaEclogites, Metamorphic
DS1991-1899
1991
Xiaomin WangXiaomin Wang, Liou, J.G.Regional ultrahigh pressure coesite bearing eclogite terrane in centralChina: evidence form country rocks, gneiss, marble and metapeliteGeology, Vol. 19, No. 9, September pp. 933-936ChinaCoesite, Eclogite
DS1993-1782
1993
Xiaomin WangXiaomin Wang, Liou, J.G.Ultra high pressure metamorphism of carbonate rocks in the Dabie central China.Journal of Metamorphic Geology, Vol. 11, pp. 575-588.ChinaCoesite, metamorphism
DS1997-1274
1997
Xiaondon SongXiaondon SongAnisotropy of the earth's inner coreReviews of Geophysics, Vol. 35, No. 3, August pp. 297-314MantleGeophysics - seismics, Core rotation
DS200612-0207
2006
Xiaopeng, H.Cai, L., Qingguo, Z., Yonsheng, D., Xiaopeng, H.Discovery of eclogite and its geological significance in Qiantang central Tibet.Chinese Science Bulletin, Vol. 51, 9, May pp. 1095-1100.China, TibetEclogite, tectonics
DS200712-1189
2007
Xiaoying, G.Xiaoying, G., Meihua, C.Garnets from diamond deposits in Chin a and the Arkangelsk Diamondiferous province.Moscow University Geology Bulletin, Vol. 62, 5, pp. 342-346.China, Russia, Kola PeninsulaMineralogy - garnets
DS200812-0914
2008
Xiaoying, G.Posukhova, T.V., Xiaoying, G.Mineralogical features of the Chin a kimberlites - comparison with Arkangelsk Diamondiferous province.9IKC.com, 3p. extended abstractChina, RussiaCraton, Hua Bei, Fu Xian
DS201012-0864
2010
Xiaoying, G.Xiaoying, G., Posukkhova, T.V.Chromium spinels in north Chinese kimberlites , Huabei platform.Moscow University Geology Bulletin, Vol. 65, 4, pp. 234-243.China, RussiaMengyin, Fuxian, Arkangel
DS201212-0795
2012
Xiaoyu, G.Xiaoyu, G., Encarnacion, J., Xiao, X., Deino, A., Li, Z., Xiabo, T.Collision and rotation of the South Chin a block and their role in the formation and exhumation of ultrahigh pressure rocks in the Dabie Shan orogen.Terra Nova, Vol. 24, 5, pp. 339-350.ChinaUHP
DS1990-1600
1990
Xiaoyuan LiXiaoyuan Li, Jeanloz, R.Laboratory studies of the electrical conductivity of silicate perovskites at high pressures and temperaturesJournal of Geophysical Research, Vol. 95, B4, April 10, pp. 5067-5078GlobalExperimental petrology, Perovskites
DS1991-1900
1991
Xiaoyuan LiXiaoyuan Li, Jeanloz, R.Phases and electrical conductivity of a hydrous silicate assemblage at lower mantle conditionsNature, Vol. 350, No. 6316, March 28, pp. 332-334GlobalSilicates -experimental, Mantle
DS1992-0937
1992
XieLeung, I.S., Wang, M., Xie, JiuwuSIC microphenocrysts found in newly discovered lamproites in Sichuan, ChinaGeological Society of America (GSA) Abstracts with programs, 1992 Annual, Vol. 24, No. 7, abstract p. A258ChinaLamproites
DS200812-1172
2008
XieTian, S., Hou, Ding, Yang, Yang, Yuan, Xie, Liu, Li.Ages of carbonatite and syenite from the Mianning Dechang REE belt in eastern Indo-Asian collision zone, SW Chin a and their geological significance.Goldschmidt Conference 2008, Abstract p.A947.ChinaCarbonatite
DS201112-1169
2011
XieZhao, Z., Niu, Y., Christensen, N.I., Zhou, Hou, Zhang, Xie, Zhang, LiuDelamination and ultra deep subduction of continental crust: constraints from elastic wave velocity and density measurement in ultra high pressure metamorphic rocksJournal of Metamorphic Geology, Vol. 29, 7, pp. 781-801.ChinaUHP - Dabie
DS200412-2096
2003
Xie, G.Wei, Q., Wang, J., Xie, G.The chemical composition characteristics of clinopyroxenes from spinel lherzolite xenoliths in Maguan area, Eastern Tibet and itEarth Science Frontiers, Vol. 10, 3, pp. 87-92. Ingenta 1035303170China, TibetXenoliths - not specific to diamonds
DS202107-1139
2021
Xie, G.Sun, W-D., Zhang, L., Li, R., Xie, G., Liu, L., Li, C-y., Zhang, L. Origin of kimberlite from the base of the upper mantle.Research Square, doi.org/10.21203/rs-532988/v1 19p. PdfMantlemagmatism
DS2001-1273
2001
Xie, G.H.Xu, Y.G., Menzies, M.A., Thirwall, M.F., Xie, G.H.Exotic lithosphere mantle beneath the western Yangtze craton: petrogenetic links to Tibet using ultrapotassicGeology, Vol. 29, No. 9, Sept. pp. 863-866.China, Tibet, Asiaultra high pressure (UHP), ultrapotassic highly magnesian, Metasomatism
DS1993-0901
1993
Xie, G.O.Lee, K.H., Xie, G.O.A new approach to imaging with low frequency electromagnetic fieldsGeophysics, Vol. 58, No. 6, June pp. 780-796GlobalGeophysics, Imaging
DS202008-1451
2020
Xie, G-z.Sun, W-D., Zhang, L-p., Xie, G-z., Hawkesworth. C., Zartmam, R.Carbonatite formed through diamond oxidation.Goldschmidt 2020, 1p. AbstractMantlecarbonatite

Abstract: Carbonatite is a magmatic rock with high carbonate and low silicate contents, which mostly originate in the mantle. It is therefore of critical importance to understand the behavior of carbon in the mantle, and consequently deep carbon recycling. However, the formation of carbonatite is largely unresolved. In particular, the source of carbonatite the carbonate remains obscure. Previous studies showed that the solidus of carbonated mantle peridotite was lower than the Earth’s geotherm in the Archean and the Early Proterozoic era, before ~1.4 Ga ago. Therefore, the mantle should have been severely decarbonated early in Earth’s history. This is consistent with the low carbon abundance in the asthenospheric mantle (~100 ppm), as indicated by low carbonate concentrations in mid-ocean ridge basalts. Consequently, carbonate in young mantle must have been mostly obtained in the post-Archean era by two processes. These are either oxidation of diamond in the mantle or recycling of sedimentary carbonates through plate subduction. Here we show that the Sr and Nd isotope variations in carbonatite may be plausibly explained by mixing of three endmembers, (1) recycled sedimentary carbonates, (2) depleted mantle, and (3) a low Sr and Nd isotopes endmember. The low Sr, Nd carbonate reservoirs for carbonatites of different ages plot roughly on the evolution line of the primitive mantle, suggesting that they were successively released from a well-preserved, non-carbonate mantle source. The preferred candidate for this endmember is carbonate formed through oxidation of diamond by ferric ion released through decomposition of bridgmanite, which is carried up from the lower mantle via background upwelling, compensational to the volume of oceanic slabs penetrating into the lower mantle1.
DS202106-0927
2021
Xie, G-Z.Chen, Q., Liu, S-g., Qiu L., Liao, R-q., Xie, G-Z., Sun, W-d.Enhanced deep carbon cycle marked by the upsurge of silica-undersaturated nephelinitic magmatism at the Proterozoic-Phanerozoic boundary.Journal of Asian Earth Sciences, Vol. 214, 104772, 8p. PdfMantlecarbon

Abstract: The temperature of the upper mantle was a principal factor controlling the style of plate tectonics and influencing magmatism and metamorphism on Earth over geological history. Recent studies emphasized that Earth’s tectonic style has transited into the modern plate tectonics since the late Neoproterozoic, which is characterized by a global network of plate boundaries with deep and cold oceanic plate subduction. However, the consequence of the establishment of modern plate tectonics to Earth’s mantle temperature and deep carbon cycle has not been fully understood. Here we apply statistical analysis on the geochemical data of continental igneous rocks and identify an increased magnitude of nephelinitic volcanism at the end of the Ediacaran. Nephelinitic rocks, a silica-undersaturated high-alkaline rock group, are mostly formed by low-degree melting of carbonated mantle sources. We link their widespread emergence with an enhanced mantle cooling event and a dramatically increased flux of crustal carbonates transporting to the mantle. The rapid cooling of the mantle was ascribed to the onset of modern-style plate tectonics with global-scale cold oceanic and continental subduction since the late Neoproterozoic. The declined upper-mantle temperature could not only favor the low-degree melting but also allow the subduction of carbonates into the deep mantle without decarbonation at shallow depth. Considering the high oxygen fugacity feature of the nephelinitic rocks and some other high-alkaline volcanism, the establishment of modern plate tectonics and thereafter enhanced mantle cooling and deep carbon cycle might contribute to the high-level atmospheric oxygen content during the Phanerozoic.
DS201112-1170
2011
Xie, H.Zhao, Z., Niu, Y., Christensen, N.I., Zhou, W., Hou, Q., Zhang, Z.M., Xie, H., Zhang, Z.C., Liu, J.Delamination and ultradeep subduction of continental crust: constraints from elastic wave velocity and density measurement in ultrahigh pressure met. rocksJournal of Metamorphic Geology, Vol. 29, 7, pp. 781-801.MantleUHP
DS201412-0870
2013
Xie, H.Sommer, H., Wan,Y., Kroner, A., Xie, H., Jacob, D.E.Shrimp zircon ages and petrology of lower crustal granulite xenoliths from the Letseng-La-Terae kimberlite, Lesotho: further evidence for a Namaquanatal connection.South Africa Journal of Geology, Vol. 116, 2, pp. 183-198.Africa, LesothoDeposit - Letseng
DS201811-2586
2018
Xie, H.Kroner, A., Nagel, T.J., Hoffmann, J.E., Liu, X., Wong, J., Hegner, E., Xie, H., Kasper, U., Hofmann, A., Liu, D.High temperature metamorphism and crustal melting at ca. 3.2 Ga in the eastern Kaapvaal craton.Precambrian Research, Vol. 317, pp. 101-116.Africa, South Africacraton

Abstract: The question of whether high-grade metamorphism and crustal melting in the early Archaean were associated with modern-style plate tectonics is a major issue in unravelling early Earth crustal evolution, and the eastern Kaapvaal craton has featured prominently in this debate. We discuss a major ca. 3.2?Ga tectono-magmatic-metamorphic event in the Ancient Gneiss Complex (AGC) of Swaziland, a multiply deformed medium- to high-grade terrane in the eastern Kaapvaal craton consisting of 3.66-3.20?Ga granitoid gneisses and infolded greenstone remnants, metasedimentary assemblages and mafic dykes. We report on a 3.2?Ga granulite-facies assemblage in a metagabbro of the AGC of central Swaziland and relate this to a major thermo-magmatic event that not only affected the AGC but also the neighbouring Barberton granitoid-greenstone terrane. Some previous models have related the 3.2?Ga event in the eastern Kaapvaal craton to subduction processes, but we see no evidence for long, narrow belts and metamorphic facies changes reflecting lithospheric suture zones, and there is no unidirectional asymmetry in the thermal structure across the entire region from Swaziland to the southern Barberton granite-greenstone terrane as is typical of Phanerozoic and Proterozoic belts. Instead, we consider an underplating event at ca. 3.2?Ga, giving rise to melting in the lower crust and mixing with mantle-derived under- and intraplated mafic magma to generate the voluminous granitoid assemblages now observed in the AGC and the southern Barberton terrane. This is compatible with large-scale crustal reworking during a major thermo-magmatic event and the apparent lack of a mafic lower crust in the Kaapvaal craton as shown by seismic data.
DS1997-1275
1997
Xie, J.Xie, J., Liu, Z., Chiu, J.M.Rupture properties of clustered microearthquakes near intersecting intraplate faults of New Madrid Seismic..Journal of Geophysical Research, Vol. 102, No. 4, April 10, pp. 8187-02.MidcontinentGeophysics - seismics, Faulting
DS2001-1268
2001
Xie, J.Xie, J.Rupture characteristics of clustered microearthquakes and variations in fault properties New Madrid seismic..Journal of Geophysical Research, Vol. 106, No. 11, pp.26,495-510.Appalachia, ArkansasTectonics, Geophysics - seismics
DS201610-1872
2016
Xie, L.Huang, J-X., Xiang, Y., An, Y., Griffin, W.L., Greau, Y., Xie, L., Pearson, N.J., Yu, H., O'Reilly, S.Y.Magnesium and oxygen isotopes in Roberts Victor eclogites.Chemical Geology, Vol. 438, pp. 73-83.Africa, South AfricaDeposit - Roberts Victor

Abstract: Magnesium and oxygen are critical elements in the solid Earth and hydrosphere. A better understanding of the combined behavior of Mg and O isotopes will refine their use as a tracer of geochemical processes and Earth evolution. In this study, the Mg-isotope compositions of garnet and omphacite separated from well-characterized xenolithic eclogites from the Roberts Victor kimberlite pipe (South Africa) have been measured by solution multi-collector ICP-MS. The reconstructed whole-rock d26Mg values of Type I (metasomatized) eclogites range from - 0.61‰ to - 0.20‰ (Type IA) and from - 0.60‰ to - 0.30‰ (Type IB) (mean - 0.43‰ ± 0.12‰), while d26Mg of Type IIA (fresh, least metasomatized) eclogites ranges from - 1.09‰ to - 0.17‰ (mean - 0.69‰ ± 0.41‰); a Type IIB (fresh, least metasomatized) has d26Mg of - 0.37‰. Oxygen-isotope compositions of garnet were analyzed in situ by SIMS (CAMECA 1280) and cross-checked by laser fluorination. Garnets have d18O of 6.53‰ to 9.08‰ in Type IA, 6.14‰ to 6.65‰ in Type IB, and 2.34‰ to 2.91‰ in Type IIB. The variation of d26Mg and d18O in Type IA and IB eclogites is consistent with the previously proposed model for the evolution of these samples, based on major and trace elements and radiogenic isotopes. In this model, the protoliths (Type II eclogites) were metasomatized by carbonatitic to kimberlitic melts/fluids to produce first Type IA eclogites and then Type IB. Metasomatism has changed the O-isotope compositions, but the Mg-isotope compositions of Type IA are mainly controlled by the protoliths; those of Type IB eclogites reflect mixing between the protoliths and the kimberlitic melt/fluid. The combination of a large range of d26Mg and low d18O in Type II eclogites cannot be explained easily by seawater alteration of oceanic crust, interaction of carbonate/silicate sediments with oceanic crust, or partial melting of mafic rocks.
DS202003-0371
2020
Xie, L.Xie, L. , Yoneda, A., Andraught, D.Formation of bridgmanite-enriched layer at the top lower-mantle during magma ocean solificiation.Nature Communications, Vol. 11, pp. 1-10.Mantlebridgmanite

Abstract: Thermochemical heterogeneities detected today in the Earth’s mantle could arise from ongoing partial melting in different mantle regions. A major open question, however, is the level of chemical stratification inherited from an early magma-ocean (MO) solidification. Here we show that the MO crystallized homogeneously in the deep mantle, but with chemical fractionation at depths around 1000?km and in the upper mantle. Our arguments are based on accurate measurements of the viscosity of melts with forsterite, enstatite and diopside compositions up to ~30?GPa and more than 3000?K at synchrotron X-ray facilities. Fractional solidification would induce the formation of a bridgmanite-enriched layer at ~1000?km depth. This layer may have resisted to mantle mixing by convection and cause the reported viscosity peak and anomalous dynamic impedance. On the other hand, fractional solidification in the upper mantle would have favored the formation of the first crust.
DS200612-1548
2006
Xie, L-W.Wu, F-Y., Yang, Y-H., Xie, L-W., Yang, J-H., Xu, P.Hf isotopic compositions of the standard zircons and baddeleyites used in U Pb geochronology.Chemical Geology, Vol. 234, 1-2, Oct 30, pp. 105-126.ChinaUHP, geochronology
DS200712-0173
2007
Xie, L-W.Chen, L-H., Jiang, S-Y., Hofmann, A.W., Jovanovic, Z., Xie, L-W., Zhou, X-H.Are peridotite xenoliths in Mesozoic plutons inherited from Paleozoic kimberlites?Plates, Plumes, and Paradigms, 1p. abstract p. A166.ChinaNorth China Craton
DS200912-0836
2009
Xie, L-W.Yang, Y-H., Wu, F-Y., Wilde, S.A., Liu, X-M., Zhang, Y-B., Xie, L-W., Yang, J-H.In in situ perovskite Sr Nd isotopic constraints on the petrogenesis of the Ordovician Mengyin kimberlites in North Chin a craton.Chemical Geology, Vol. 264, 1-4, pp. 24-42.ChinaDeposit - Mengyin
DS201803-0488
2018
Xie, L-W.Yang, Y-H., Wu, F-Y., Yang, J-H., Mitchell, R.H., Zhao, Z-F., Xie, L-W., Huang, C., Ma, Q., Yang, M., Zhao, H.U-Pb age determination of schorlomite garnet by laser ablation inductively coupled plasma mass spectrometry. Magnet Cove, Fanshan, Ozernaya, Alno, Prairie LakeJournal of Analytical At. Spectrometry, Vol. 33, pp. 231-239.United States, Arkansas, China, Hebei, Russia, Kola Peninsula, Europe, Sweden, Canada, Ontariogeochronology

Abstract: We report the first U-Pb geochronological investigation of schorlomite garnet from carbonatite and alkaline complexes and demonstrate its applicability for U-Pb age determination using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) due to its relatively high U and Th abundances and negligible common Pb content. The comparative matrix effects of laser ablation of zircon and schorlomite are investigated and demonstrate the necessity of a suitable matrix-matched reference material for schorlomite geochronology. Laser-induced elemental fractional and instrumental mass discrimination were externally-corrected using an in house schorlomite reference material (WS20) for U-Pb geochronology. In order to validate the effectiveness and robustness of our analytical protocol, we demonstrate the veracity of U-Pb age determination for five schorlomite samples from: the Magnet Cove complex, Arkansas (USA); the Fanshan ultrapotassic complex, Hebei (China); the Ozernaya alkaline ultramafic complex, Kola Peninsula (Russia); the Alnö alkaline-rock carbonatite complex (Sweden); and the Prairie Lake carbonatite complex, Ontario (Canada). The schorlomite U-Pb ages range from 96 Ma to 1160 Ma, and are almost identical to ages determined from other accessory minerals in these complexes and support the reliability of our analytical protocol. Schorlomite garnet U-Pb geochronology is considered to be a promising new technique for understanding the genesis of carbonatites, alkaline rocks, and related rare-metal deposits.
DS201912-2835
2019
Xie, L-W.Yang, Y-H., Wu, F-Y., Qiu-Li, L., Rojas-Agramonte, Y., Yang, J-H., Yang, L., Ma, Q., Xie, L-W., Huang, C., Fan, H-R., Zhao, Z-F., Xu, C.In situ U-Th-Pb dating and Sr-Nd isotope analysis of bastnasite by LA-(MC)-ICP-MS.Geostandards and Geoanalltical Research, Vol. 43, 3, pp. 543-565.China, Europe, Sweden, Asia, Mongolia, United States, Africa, Malawi, MadagascarREE

Abstract: Bastnäsite is the end member of a large group of carbonate-fluoride minerals with the common formula (REE) CO3F•CaCO3. This group is generally widespread and, despite never occurring in large quantities, represents the major economic light rare earth element (LREE) mineral in deposits related to carbonatite and alkaline intrusions. Since bastnäsite is easily altered and commonly contains inclusions of earlier-crystallised minerals, in situ analysis is considered the most suitable method to measure its U-Th-Pb and Sr-Nd isotopic compositions. Electron probe microanalysis and laser ablation (multi-collector) inductively coupled plasma-mass spectrometry of forty-six bastnäsite samples from LREE deposits in China, Pakistan, Sweden, Mongolia, USA, Malawi and Madagascar indicate that this mineral typically has high Th and LREE and moderate U and Sr contents. Analysis of an in-house bastnäsite reference material (K-9) demonstrated that precise and accurate U-Th-Pb ages could be obtained after common Pb correction. Moreover, the Th-Pb age with its high precision is preferable to the U-Pb age because most bastnäsites have relatively high Th rather than U contents. These results will have significant implications for understanding the genesis of endogenous ore deposits and formation processes related to metallogenic geochronology research.
DS1995-2091
1995
Xie, Q.Xie, Q., McCuaig, T.C., Kerrich, R.Secular trends in the melting depths of mantle plumes: evidence systematics of Archean high magnesium lavasChemical Geology, Vol. 126, No. 1, Nov. 20, pp. 29-42MantleBasalts, Geochemistry
DS2002-0832
2002
Xie, Q.Kerrich, R., Xie, Q.Compositional recycling structure of an Archean super plume: Nb Th U LREE systematics of Archean komatiites..Contributions to Mineralogy and Petrology, Vol. 142, No. 4, pp. 476-84.GlobalKomatiites, basalts revisited, niobium, thorium, uranium, light rare earth
DS202108-1313
2021
Xie, Q.Wang, C., Zhang, Z., Xie, Q., Cheng, Z., Kong, W., Liu, B., Santosh, M., Jin, S.Olivine from aillikites in the Tarim large igneous province as a window into mantle metasomatism and multi-stage magma evolution.American Mineralogist, Vol. 106, pp. 1064-1076.Chinametasomatism

Abstract: Aillikites are carbonate-rich ultramafic lamprophyres, and although they are volumetrically minor components of large igneous province (LIP), these rocks provide important clues to melting and meta-somatism in the deep mantle domain during the initial stages of LIPs. In this study, we investigate the Wajilitag “kimberlites” in the northwestern part of the Tarim LIP that we redefine as hypabyssal aillikites based on the following features: (1) micro-phenocrystic clinopyroxene and Ti-rich andradite garnet occurring in abundance in the carbonate-rich matrix; (2) Cr-spinel exhibiting typical Fe-Ti enrichment trend also known as titanomagnetite trend; and (3) olivine showing dominantly low Mg values (Fo < 90). To constrain the magma source and evolution, the major, minor, and trace element abundance in olivine grains from these rocks were analyzed using electron microprobe and laser ablation-inductively coupled plasma-mass spectrometry. Olivine in the aillikites occurs as two textural types: (1) groundmass olivines, as sub-rounded grains in matrix, and (2) macrocrysts, as euhedral-anhedral crystals in nodules. The groundmass olivines show varying Mg (Fo89-80) with high-Ni (1606-3418 ppm) and Mn (1424-2860 ppm) and low-Ca (571-896 ppm) contents. In contrast, the macrocrysts exhibit a restricted Fo range but a wide range in Ni and Mn. The former occurs as phenocrysts, whereas the latter are cognate cumulates that formed from earlier, evolved aillikite melt. The two olivine populations can be further divided into sub-groups, indicating a multi-stage crystallization history of the aillikite melt. The crystallization temperatures of groundmass olivines and macrocrysts in dunite nodules as computed from the spinel-olivine thermometers are 1005-1136 and 906-1041 °C, respectively. The coupled enrichment of Ca and Ti and lack of correlation between Ni and Sc and Co in the olivine grains suggest a carbonate-silicate metasomatized mantle source. Moreover, the high 100•Mn/Fe (average 1.67) at high Ni (up to 3418 ppm), overlapping with OIB olivine, and the 100•Ni/Mg (~1) of primitive Mg-Ni-rich groundmass olivines suggest a mixed source that involved phlogopite- and carbonate-rich metasomatic veins within mantle peridotite.
DS202106-0952
2021
Xie, R.Li, W., Xie, X., Song, J., Xie, R., Wang, J., Li, G.,Hou, H., Lu, J.Assessment and source identification of toxic metals in an abandoned synthetic diamond production plant from Anhui Province, China.Environmental Forensics, Vol. 22, 3-4, pp. 340-350. abstract onlyChinasynthetics

Abstract: In this study, soil and sediment samples along with groundwater samples were collected and analyzed from an abandoned synthetic diamond production plant in Anhui Province, South China. Chemical analysis, pollution characteristics analysis, and correlation analysis were conducted to assess and to determine the source(s) of the toxic metal and organic pollutions in the study sites. The Co and Ni concentrations of soil samples collected from the production area exceed the risk screening value for contaminated development land in Soil Environment Quality Standards for soil pollution risk control on construction land (Trial) of China, while the concentrations of other toxic elements such as Cr, Cu, and Zn are lower than the screening value. The PCA and HCA results are consistent with the correlation coefficient analysis and indicate that industrial activities are the main sources of Co and Ni. The chemical composition and source analysis results of soil and groundwater show that toxic metals originating from catalyst and low pH value from acid waste water should be the main point of concern in the synthetic diamond production plant.
DS2002-1574
2002
Xie, S.Tackley, P.J., Xie, S.The thermochemical structure and evolution of Earth's mantle: constraints and numerical models.Philosophical Transactions, Royal Society of London Series A Mathematical, Vol.1800, pp. 2593-2610.MantleGeochemistry - model, geothermometry
DS200412-2154
2004
Xie, S.Xie, S., Tackley, P.J.Evolution of helium and argon isotopes in a convecting mantle.Physics of the Earth and Planetary Interiors, Vol. 146, 3-4, pp. 417-439.MantleGeochronology, convection, radiogenic isotopes
DS200512-1206
2004
Xie, S.Xie, S., Tackley, P.J.Evolution of U-Pb and Sm-Nd systems in numerical modles of mantle convection and plate tectonics.Journal of Geophysical Research, Vol. 109, 11, DOI 10:1029/2004 JB003176MantleTectonics, geochronology
DS200612-1405
2005
Xie, S.Tackley, P.J., Xie, S., Nakagawa, T., Hernlund, J.W.Numerical and laboratory studies of mantle convection: philosphy, accomplishments and thermochemical structure and evolution.American Geophysical Union, Geophysical Monograph, Ed. Van der Hilst, Earth's Deep Mantle, structure ...., No. 160, pp. 83-100.MantleConvection
DS2002-0235
2002
Xie, X.Byerly, G.R., Lowe, D.R., Wooden, J.L., Xie, X.An Archean impact layer from the Pilbara and Kaapvaal cratonsScience, No. 5586,Aug. 30, pp. 1325-6.Australia, South AfricaGeodynamices
DS200812-0389
2008
Xie, X.Garrett, R.G., Reiman, C., Smith, D.B., Xie, X.From geochemical prospecting to international geochemical mapping: a historical overview.Geochemistry, Exploration Environment Analysis, Vol. 8, 3-4, pp. 205-217.TechnologyGeochemistry
DS201901-0017
2018
Xie, X.Chen, M., Shu, J., Xie, X., Tan, D.Maohokite, a post-spinel polymorph of MgFe2O4 in shocked gneiss from the Xiuyan crater in China.Meteoritics & Planetary Science, doi.10.1111/ maps.13222 8p.Chinamineralogy

Abstract: Maohokite, a post-spinel polymorph of MgFe2O4, was found in shocked gneiss from the Xiuyan crater in China. Maohokite in shocked gneiss coexists with diamond, reidite, TiO2-II, as well as diaplectic glasses of quartz and feldspar. Maohokite occurs as nano-sized crystallites. The empirical formula is (Mg0.62Fe0.35Mn0.03)2+Fe3+2O4. In situ synchrotron X-ray microdiffraction established maohokite to be orthorhombic with the CaFe2O4-type structure. The cell parameters are a = 8.907 (1) Å, b = 9.937(8) Å, c = 2.981(1) Å; V = 263.8 (3) Å3; space group Pnma. The calculated density of maohokite is 5.33 g cm-3. Maohokite was formed from subsolidus decomposition of ankerite Ca(Fe2+,Mg)(CO3)2 via a self-oxidation-reduction reaction at impact pressure and temperature of 25-45 GPa and 800-900 °C. The formation of maohokite provides a unique example for decomposition of Fe-Mg carbonate under shock-induced high pressure and high temperature. The mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA 2017-047). The mineral was named maohokite after Hokwang Mao, a staff scientist at the Geophysical Laboratory, Carnegie Institution of Washington, for his great contribution to high pressure research.
DS202106-0952
2021
Xie, X.Li, W., Xie, X., Song, J., Xie, R., Wang, J., Li, G.,Hou, H., Lu, J.Assessment and source identification of toxic metals in an abandoned synthetic diamond production plant from Anhui Province, China.Environmental Forensics, Vol. 22, 3-4, pp. 340-350. abstract onlyChinasynthetics

Abstract: In this study, soil and sediment samples along with groundwater samples were collected and analyzed from an abandoned synthetic diamond production plant in Anhui Province, South China. Chemical analysis, pollution characteristics analysis, and correlation analysis were conducted to assess and to determine the source(s) of the toxic metal and organic pollutions in the study sites. The Co and Ni concentrations of soil samples collected from the production area exceed the risk screening value for contaminated development land in Soil Environment Quality Standards for soil pollution risk control on construction land (Trial) of China, while the concentrations of other toxic elements such as Cr, Cu, and Zn are lower than the screening value. The PCA and HCA results are consistent with the correlation coefficient analysis and indicate that industrial activities are the main sources of Co and Ni. The chemical composition and source analysis results of soil and groundwater show that toxic metals originating from catalyst and low pH value from acid waste water should be the main point of concern in the synthetic diamond production plant.
DS202109-1454
2021
Xie, X.Bindi, L., Sinmyo, R., Bykova, E., Ovsyannikov, S.V., McCammon, C., Kupenko, I., Ismailova, L., Dubrovinsky, L., Xie, X.Discovery of Elgoresyite ( Mg,FE)5Si2O9: implications for novel iron magnesium silicates in rocky planetery interiors. Mentions Earth's magmatismACS Earth Space Chemistry, Vol. 5, pp. 2124-2130.Mantlebridgmanite

Abstract: As the most abundant material of rocky planets, high-pressure polymorphs of iron- and aluminum-bearing magnesium silicates have long been sought by both observations and experiments. Meanwhile, it was recently revealed that iron oxides form (FeO)m(Fe2O3)n homologous series above ~10 GPa according to laboratory high-pressure experiments. Here, we report a new high-pressure iron-magnesium silicate, recently approved by the International Mineralogical Association as a new mineral (No. 2020-086) and named elgoresyite, in a shock-induced melt vein of the Suizhou L6 chondrite with a chemistry of (Mg,Fe)5Si2O9. The crystal structure of this new silicate is the same as the iron oxide Fe7O9, strongly suggesting that silicates also form ((Mg,Fe)O)m + n(SiO2)n series that are isostructural to iron oxides via (Mg2+,Fe2+) + Si4+ = 2Fe3+ substitution. To test this hypothesis, the phase relationships of the silicates and iron oxides should be further investigated at higher temperature conditions. Newly found iron-magnesium silicate is a potential constituent mineral in rocky planets with relatively high MgO + FeO content.
DS200612-0603
2006
Xie, Y.Hou, Z., Tian, S., Yuan, Z., Xie, Y., Yin, S., Yi, L., Fei, H., Yang, Z.The Himalayan collision zone carbonatites in western Sichuan, SW China: petrogenesis, mantle source and tectonic implication.Earth and Planetary Science Letters, in pressAsia, ChinaCarbonatite
DS200712-1190
2007
Xie, Y.Xie, Y., et al.Carbonatitic melt fluids evolution: evidence from inclusions in the Maoniuping REE deposit in the western Sichuan, China.9th Biennial SGA Meeting held Dublin August 20-23, abstracts, Session 21b.ChinaCarbonatite
DS200912-0313
2009
Xie, Y.Hou, Z., Tian, S., Xie, Y., Yang, Z., Yuan, Z., Yin, S., Yi, L., Fei, H., Zou, T., Bai, G., Li, X.The Himalayan Mianning Dechang REE belt associated with carbonatite alkaline complexes eastern Indo Asian collision zone, SW China.Ore Geology Reviews, Vol. 36, 1-3, pp. 65-89.ChinaCarbonatite
DS201508-0382
2015
Xie, Y.Xie, Y., Li, Y., Hou, Z., Cooke, D.R., Danyushevsky, L., Dominy, S.C., Yin, S.A model for carbonatite hosted REE mineralization - the Mianning-Dechang REE belt, western Sichuan Province, China.Ore Geology Reviews, Vol. 70, pp. 595-612.ChinaCarbonatite
DS201605-0921
2016
Xie, Y.Xie, Y., Hou, Z., Goldfarb, R.J., Guo, X., Wang, L.Rare earth element deposits in China.SEG Reviews in Economic Geology, editors Verplanck, P.L., Hitzman, M.W., No. 18, pp. 115-136.ChinaBayan Obo, Maoniuping
DS201702-0253
2016
Xie, Y.Xie, Y., Hou, Z., Goldfarb, R.J., Guo, X., Wang, L.Rare earth element deposits in China.Reviews in Economic Geology, Vol. 18, pp. 115-136.ChinaREE deposits

Abstract: China is the world’s leading rare earth element (REE) producer and hosts a variety of deposit types. Carbonatite-related REE deposits, the most significant deposit type, include two giant deposits presently being mined in China, Bayan Obo and Maoniuping, the first and third largest deposits of this type in the world, respectively. The carbonatite-related deposits host the majority of China’s REE resource and are the primary supplier of the world’s light REE. The REE-bearing clay deposits, or ion adsorption-type deposits, are second in importance and are the main source in China for heavy REE resources. Other REE resources include those within monazite or xenotime placers, beach placers, alkaline granites, pegmatites, and hydrothermal veins, as well as some additional deposit types in which REE are recovered as by-products. Carbonatite-related REE deposits in China occur along craton margins, both in rifts (e.g., Bayan Obo) and in reactivated transpressional margins (e.g., Maoniuping). They comprise those along the northern, eastern, and southern margins of the North China block, and along the western margin of the Yangtze block. Major structural features along the craton margins provide first-order controls for REE-related Proterozoic to Cenozoic carbonatite alkaline complexes; these are emplaced in continental margin rifts or strike-slip faults. The ion adsorption-type REE deposits, mainly situated in the South China block, are genetically linked to the weathering of granite and, less commonly, volcanic rocks and lamprophyres. Indosinian (early Mesozoic) and Yanshanian (late Mesozoic) granites are the most important parent rocks for these REE deposits, although Caledonian (early Paleozoic) granites are also of local importance. The primary REE enrichment is hosted in various mineral phases in the igneous rocks and, during the weathering process, the REE are released and adsorbed by clay minerals in the weathering profile. Currently, these REE-rich clays are primarily mined from open-pit operations in southern China. The complex geologic evolution of China’s Precambrian blocks, particularly the long-term subduction of ocean crust below the North and South China blocks, enabled recycling of REE-rich pelagic sediments into mantle lithosphere. This resulted in the REE-enriched nature of the mantle below the Precambrian cratons, which were reactivated and thus essentially decratonized during various tectonic episodes throughout the Proterozoic and Phanerozoic. Deep fault zones within and along the edges of the blocks, including continental rifts and strike-slip faults, provided pathways for upwelling of mantle material.
DS201811-2618
2019
Xie, Y.Xie, Y., Qu, Y., Zhong, R., Verplanck, P.L., Meffre, S., Xu, D.The ~1.85 Ga carbonatite in north China and its implications on the evolution of the Columbia supercontinent.Gondwana Research, Vol. 65, pp. 125-141.Chinacarbonatite

Abstract: Mantle-derived carbonatites provide a unique window in the understanding of mantle characteristics and dynamics, as well as insight into the assembly and breakup of supercontinents. As a petrological indicator of extensional tectonic regimes, Archean/Proterozoic carbonatites provide important constraints on the timing of the breakup of ancient supercontinents. The majority of the carbonatites reported worldwide are Phanerozoic, in part because of the difficulty in recognizing Archean/Proterozoic carbonatites, which are characterized by strong foliation and recrystallization, and share broad petrologic similarities with metamorphosed sedimentary lithologies. Here, we report the recognition of a ~1.85?Ga carbonatite in Chaihulanzi area of Chifeng in north China based on systematic geological, petrological, geochemical, and baddeleyite U-Pb geochronological results. The carbonatite occurs as dikes or sills emplaced in Archean metasedimentary rocks and underwent intense deformation. Petrological and SEM/EDS results show that calcite and dolomite are the dominant carbonate minerals along with minor and varied amounts of Mg-rich mafic minerals, including forsterite (with Fo?>?98), phlogopite, diopside, and an accessory amount of apatite, baddeleyite, spinel, monazite, and ilmenite. The relatively high silica content together with the non-arc and OIB-like trace element signatures of the carbonatite indicates a hot mantle plume as the likely magma source. The depleted Nd isotopic signatures suggest that plume upwelling might be triggered by the accumulation of recycled crust in the deep mantle. As a part of the global-scale Columbia supercontinent, the Proterozoic tectonic evolution of the North China Craton (NCC) provides important insights into the geodynamics governing amalgamation and fragmentation of the supercontinent. The Paleo-Mesoproterozoic boundary is the key point of tectonic transition from compressional to extensional settings in the NCC. The newly identified ~1.85?Ga carbonatite provides a direct link between the long-lasting supercontinental breakup and plume activity, which might be sourced from the “slab graveyard,” continental crustal slabs subducted into asthenosphere, beneath the supercontinent. The carbonatite provides a precise constraint of the initiation of the continental breakup at ~1.85?Ga.
DS201812-2900
2019
Xie, Y.Xie, Y., Qu, Y., Zhong, R., Verplanck, P.L., Meffre, S., Xu, D.The ~1/85 carbonatite in north China and its implications on the evolution of the Columbia supercontinent.Gondwana Research, Vol. 65, pp. 125-141.Chinacarbonatite

Abstract: Mantle-derived carbonatites provide a unique window in the understanding of mantle characteristics and dynamics, as well as insight into the assembly and breakup of supercontinents. As a petrological indicator of extensional tectonic regimes, Precambrian carbonatites provide important constraints on the timing of the breakup of ancient supercontinents. The majority of the carbonatites reported worldwide are Phanerozoic, in part because of the difficulty in recognizing Precambrian carbonatites, which are characterized by strong foliation and recrystallization, and share broad petrologic similarities with metamorphosed sedimentary lithologies. Here we report the recognition of a ~1.85?Ga carbonatite in Chaihulanzi area of Chifeng in north China based on systematic geological, petrological, geochemical, and baddeleyite U-Pb geochronological results. The carbonatite occurs as dikes or sills emplaced in Archean metasedimentary rocks and underwent intense deformation. Petrological and SEM/EDS results show that calcite and dolomite are the dominant carbonate minerals along with minor and varied amounts of Mg-rich mafic minerals, including forsterite (with Fo?>?98), phlogopite, diopside, and an accessory amount of apatite, baddeleyite, spinel, monazite, and ilmenite. The relatively high silica content together with the non-arc and OIB-like trace element signatures of the carbonatite indicates a hot mantle plume as the likely magma source. The depleted Nd isotopic signatures suggest that plume upwelling might be triggered by the accumulation of recycled crust in the deep mantle. As a part of the global-scale Columbia supercontinent, the Proteozoic tectonic evolution of the North China Craton (NCC) provides important insights into the geodynamics governing amalgamation and fragmentation of the supercontinent. The Paleo-Mesoproterozoic boundary is the key point of tectonic transition from compressional to extensional settings in the NCC. The newly-identified ~1.85?Ga carbonatite provides a direct link between the long-lasting supercontinental breakup and plume activity, which might be sourced from the “slab graveyard”, continental crustal slabs subducted into asthenosphere, beneath the supercontinent. The carbonatite provides a precise constraint of the initiation of the continental breakup at ~1.85?Ga.
DS201901-0092
2018
Xie, Y.Xie, Y., Qu, Y., Zhong, R., Verplanck, P.L., Meffre, S., Xu, D.The ~1.85 GA carbonatite in north China and its implications on the evolution of the Columbia supercontinent. Chaitulanzi, ChifengGondwana Research, Vol. 65, pp. 135-141.Chinacarbonatite

Abstract: Mantle-derived carbonatites provide a unique window in the understanding of mantle characteristics and dynamics, as well as insight into the assembly and breakup of supercontinents. As a petrological indicator of extensional tectonic regimes, Precambrian carbonatites provide important constraints on the timing of the breakup of ancient supercontinents. The majority of the carbonatites reported worldwide are Phanerozoic, in part because of the difficulty in recognizing Precambrian carbonatites, which are characterized by strong foliation and recrystallization, and share broad petrologic similarities with metamorphosed sedimentary lithologies. Here we report the recognition of a ~1.85?Ga carbonatite in Chaihulanzi area of Chifeng in north China based on systematic geological, petrological, geochemical, and baddeleyite U-Pb geochronological results. The carbonatite occurs as dikes or sills emplaced in Archean metasedimentary rocks and underwent intense deformation. Petrological and SEM/EDS results show that calcite and dolomite are the dominant carbonate minerals along with minor and varied amounts of Mg-rich mafic minerals, including forsterite (with Fo?>?98), phlogopite, diopside, and an accessory amount of apatite, baddeleyite, spinel, monazite, and ilmenite. The relatively high silica content together with the non-arc and OIB-like trace element signatures of the carbonatite indicates a hot mantle plume as the likely magma source. The depleted Nd isotopic signatures suggest that plume upwelling might be triggered by the accumulation of recycled crust in the deep mantle. As a part of the global-scale Columbia supercontinent, the Proteozoic tectonic evolution of the North China Craton (NCC) provides important insights into the geodynamics governing amalgamation and fragmentation of the supercontinent. The Paleo-Mesoproterozoic boundary is the key point of tectonic transition from compressional to extensional settings in the NCC. The newly-identified ~1.85?Ga carbonatite provides a direct link between the long-lasting supercontinental breakup and plume activity, which might be sourced from the “slab graveyard”, continental crustal slabs subducted into asthenosphere, beneath the supercontinent. The carbonatite provides a precise constraint of the initiation of the continental breakup at ~1.85?Ga.
DS202006-0957
2016
Xie, Y.Xie, Y., Hou, Z., Goldfarb, R.J., Guo, X., Wang, L.Rare Earth element deposits in China.SEG Reviews In Economic Geology Chapter 6, Vol. 18, pp. 115-136.ChinaREE

Abstract: China is the world’s leading rare earth element (REE) producer and hosts a variety of deposit types. Carbonatite- related REE deposits, the most significant deposit type, include two giant deposits presently being mined in China, Bayan Obo and Maoniuping, the first and third largest deposits of this type in the world, respectively. The carbonatite-related deposits host the majority of China’s REE resource and are the primary supplier of the world’s light REE. The REE-bearing clay deposits, or ion adsorption-type deposits, are second in importance and are the main source in China for heavy REE resources. Other REE resources include those within monazite or xenotime placers, beach placers, alkaline granites, pegmatites, and hydrothermal veins, as well as some additional deposit types in which REE are recovered as by-products. Carbonatite-related REE deposits in China occur along craton margins, both in rifts (e.g., Bayan Obo) and in reactivated transpressional margins (e.g., Maoniuping). They comprise those along the northern, eastern, and southern margins of the North China block, and along the western margin of the Yangtze block. Major structural features along the craton margins provide first-order controls for REE-related Proterozoic to Cenozoic carbonatite alkaline complexes; these are emplaced in continental margin rifts or strike-slip faults. The ion adsorption-type REE deposits, mainly situated in the South China block, are genetically linked to the weathering of granite and, less commonly, volcanic rocks and lamprophyres. Indosinian (early Mesozoic) and Yanshanian (late Mesozoic) granites are the most important parent rocks for these REE deposits, although Caledonian (early Paleozoic) granites are also of local importance. The primary REE enrichment is hosted in various mineral phases in the igneous rocks and, during the weathering process, the REE are released and adsorbed by clay minerals in the weathering profile. Currently, these REE-rich clays are primarily mined from open-pit operations in southern China. The complex geologic evolution of China’s Precambrian blocks, particularly the long-term subduction of ocean crust below the North and South China blocks, enabled recycling of REE-rich pelagic sediments into mantle lithosphere. This resulted in the REE-enriched nature of the mantle below the Precambrian cratons, which were reactivated and thus essentially decratonized during various tectonic episodes throughout the Proterozoic and Phanerozoic. Deep fault zones within and along the edges of the blocks, including continental rifts and strike-slip faults, provided pathways for upwelling of mantle material.
DS202006-0958
2019
Xie, Y.Xie, Y., Verplanck, P.L., Hou, Z., Zhong, R.Rare Earth element deposits in China: a review and new understandings.SEG Special Publication , No. 22, pp. 500-552.ChinaREE

Abstract: The rare earth elements (REEs) consist of the 15 lantha-nide elements (La to Lu). Because of the increasing application of REEs and yttrium (REY) in high-and green-tech industries, the demand for the REY is projected to increase in the future. Rare earth elements are relatively abundant in the Earth's crust, but discovered, minable concentrations are less common than for most other ore types. Bastnaesite and monazite are the main mineral source of REEs in the world. Bastnaesite-hosted deposits in China and the United States Abstract China has been the world's leading rare earth element (REE) and yttrium producer for more than 20 years and hosts a variety of deposit types. Carbonatite-related REE deposits are the most significant REE deposit type, with REY (REE and yttrium)-bearing clay deposits, or ion adsorption-type deposits, being the primary source of the world's heavy REEs. Other REY resources in China include those hosted in placers, alkaline granites, pegmatites, and hydrothermal veins, as well as in additional deposit types in which REEs may be recovered as by-product commodities. Carbonatite-related REE deposits in China provide nearly all the light REE production in the world. Two giant deposits are currently being mined in China: Bayan Obo and Maoniuping. The carbonatite-related REE deposits in China occur along the margins of Archean-Paleoproterozoic blocks, including the northern , southern, and eastern margins of the North China craton, and the western margin of the Yangtze craton. The carbonatites were emplaced in continental rifts (e.g., Bayan Obo) or translithospheric strike-slip faults (e.g., Maoniuping) along reactivated craton margins. The craton margins provide the first-order control for carbonatite-related REE resources. Four REE metallogenic belts, including the Proterozoic Langshan-Bayan Obo, late Paleozoic-early Mesozoic eastern Qinling-Dabie, late Mesozoic Chishan-Laiwu-Zibo, and Cenozoic Mianning-Dechang belts, occur along cratonic margins. Geologic and geochemical data demonstrate that the carbonatites in these belts originated from mantle sources that had been previously enriched, most likely by recycled marine sediments through subduction zones during the assembly of continental blocks. Although the generation of carbonatite magma is debated, a plausible mechanism is by liquid immiscibility between silicate and carbonate melts. This process would further enrich REEs in the carbonatite end member during the evolution of mantle-derived magma. The emplacement of carbonatite magma in the upper crust, channeled by translithospheric faults in extensional environments, leads to a rapid decompression of the magma and consequently exsolution of a hydrothermal fluid phase. The fluid is characterized by high temperature (600°-850°C), high pressure (up to 350 MPa), and enrichment in sulfate, CO2, K, Na, Ca, Sr, Ba, and REEs. Immiscibility of sulfate melts from the aqueous fluid, and phase separation between CO2 and water may take place upon fluid cooling. Although both sulfate and chloride have been called upon as important ligands in hydrothermal REE transport, results of our studies suggest that sulfate is more important. The exsolution of a sulfate melt from the primary carbonatite fluid would lead to a significant decrease of the sulfate activity in the fluid and trigger REE precipitation. The subsequent unmixing between CO2 and water may also play an important role in REE precipitation. Because of the substantial ability of the primary carbonatite fluid to contain REEs, a large-volume magma chamber or huge fluid flux are not necessary for the formation of a giant REE deposit. A dense carbonatite fluid and rapid evolution hinder long distance fluid transportation and distal mineralization. Thus, carbonatite-related alteration and mineralization occur in or proximal to carbonatite dikes and sills, and this is observed in all carbonatite-related REE deposits in China. Ion adsorption-type REE deposits are primarily located in the South China block and are genetically linked to the weathering of granite and, less commonly, volcanic rocks and lamprophyres. Indosinian (early Mesozoic) and Yanshanian (late Mesozoic) granites are the most important parent rocks for these REE deposits. Hydro-thermal alteration by fluids exsolved from late Mesozoic granites or related alkaline rocks (e.g., syenite) may have enriched the parent rocks in REEs, particularly the heavy REEs. Furthermore, this alteration process led to the transformation of some primary REE minerals to secondary REE minerals that are more readily broken down during subsequent weathering. During the weathering process, the REEs are released from parent rocks and adsorbed onto kaolinite and halloysite in the weathering profile, and further enriched by the loss of other material to form the ion adsorption-type REE deposits. A warm and humid climate and a low-relief landscape are important characteristics for development of ion adsorption REE deposits.
DS202011-2069
2019
Xie, Y.Xie, Y., Verplank, P.L., Hou, Z., Zhong, R.IN: An overview of mineral deposits of China. Rare earth element deposits in China.SEG Special Publication, No. 22, pp. 509-552.ChinaREE

Abstract: China is the world’s leading rare earth element (REE) producer and hosts a variety of deposit types. Carbonatite- related REE deposits, the most significant deposit type, include two giant deposits presently being mined in China, Bayan Obo and Maoniuping, the first and third largest deposits of this type in the world, respectively. The carbonatite-related deposits host the majority of China’s REE resource and are the primary supplier of the world’s light REE. The REE-bearing clay deposits, or ion adsorption-type deposits, are second in importance and are the main source in China for heavy REE resources. Other REE resources include those within monazite or xenotime placers, beach placers, alkaline granites, pegmatites, and hydrothermal veins, as well as some additional deposit types in which REE are recovered as by-products. Carbonatite-related REE deposits in China occur along craton margins, both in rifts (e.g., Bayan Obo) and in reactivated transpressional margins (e.g., Maoniuping). They comprise those along the northern, eastern, and southern margins of the North China block, and along the western margin of the Yangtze block. Major structural features along the craton margins provide first-order controls for REE-related Proterozoic to Cenozoic carbonatite alkaline complexes; these are emplaced in continental margin rifts or strike-slip faults. The ion adsorption-type REE deposits, mainly situated in the South China block, are genetically linked to the weathering of granite and, less commonly, volcanic rocks and lamprophyres. Indosinian (early Mesozoic) and Yanshanian (late Mesozoic) granites are the most important parent rocks for these REE deposits, although Caledonian (early Paleozoic) granites are also of local importance. The primary REE enrichment is hosted in various mineral phases in the igneous rocks and, during the weathering process, the REE are released and adsorbed by clay minerals in the weathering profile. Currently, these REE-rich clays are primarily mined from open-pit operations in southern China. The complex geologic evolution of China’s Precambrian blocks, particularly the long-term subduction of ocean crust below the North and South China blocks, enabled recycling of REE-rich pelagic sediments into mantle lithosphere. This resulted in the REE-enriched nature of the mantle below the Precambrian cratons, which were reactivated and thus essentially decratonized during various tectonic episodes throughout the Proterozoic and Phanerozoic. Deep fault zones within and along the edges of the blocks, including continental rifts and strike-slip faults, provided pathways for upwelling of mantle material.
DS200412-0533
2004
Xie, Yi-H.Fan, H-R., Xie, Yi-H., Wang, K-Y., Tao, K-J.REE daughter minerals trapped in fluid inclusions in the Giant Bayan Obo REE Nb Fe deposit, inner Mongolia, China.International Geology Review, Vol. 46, 8, pp. 638-645.China, MongoliaCarbonatite
DS201412-0092
2014
Xie, Y-W.Campbell, I., Stepanov, A., Liang, H-Y., Allen, C., Norman, M., Zhang, Y-Q, Xie, Y-W.The origin of shoshonites: new insights from the Tertiary high-potassium intrusions of eastern Tibet.Contributions to Mineralogy and Petrology, Vol. 167, 3, pp. 1-22.Asia, TibetShoshonite
DS2003-0248
2003
Xie, Z.Chen, J.F., Xie, Z., Li, H.M., Zhang, X.D., Zhou, T.X., Park, Ahn, Chen, ZhangU Pb zircon ages for a collision related K rich complex at Shidao in the Sulu ultrahighGeochemical Journal, Vol. 37, pp. 35-46.ChinaBlank
DS200412-0319
2003
Xie, Z.Chen, J.F., Xie, Z., Li, H.M., Zhang, X.D., Zhou, T.X., Park, Ahn, Chen, ZhangU Pb zircon ages for a collision related K rich complex at Shidao in the Sulu ultrahigh pressure terrane, China.Geochemical Journal, Vol. 37, pp. 35-46.ChinaUHP, shoshonites
DS200412-2155
2004
Xie, Z.Xie, Z., Zheng, Y-F., Jahn, B-M., Ballevre, M., Chen, J., Gautier, P., Gao, T., Gong, B., Zhou, J.Sm Nd and Rb Sr dating of pyroxene garnetite from North Dabie in east centra China: problem of isotope disequilibrium due to retChemical Geology, Vol. 206, 1-2, May 28, pp. 137-158.ChinaUHP, eclogite, geochronology
DS200512-1262
2005
Xie, Z.Zheng, Y-F., Zhou, J-B, Wu, Y-B., Xie, Z.Low grade metamorphic rocks in the Dabie Sulu orogenic belt: a passive margin accretionary wedge deformed during continent subduction.International Geology Review, Vol. 47, 7, pp. 851-871.Asia, ChinaSubduction
DS201012-0865
2010
Xie, Z.Xie, Z., Chen, J-F., Cui, Y-R.Episodic growth of zircon in UHP orthogneisses from the North Dabie Terrane of east central China: implications for crustal architecture of a collisional orogen.Journal of Metamorphic Geology, In press available,ChinaUHP
DS201312-0950
2013
Xie, Z.Wang, J., Hattori, K., Xie, Z.Oxidation state of lithospheric mantle along the northeastern margin of the North Chin a craton: implications for geodynamic processes.International Geology Review, Vol. 55, no. 11, pp. 1418-1444.ChinaGeodynamics
DS201312-0987
2013
Xie, Z.Xie, Z., Hattori, K., Wang, J.Origins of ultramafic rocks in the Sulu ultrahigh pressure terrane, eastern China.Lithos, Vol. 178, pp. 158-170.ChinaUHP
DS201112-1168
2011
Xie, Z.C.Zhao, Z., Niu, N.I., Christensen, W., Zhou, Q., Zhang, Z.M., Xie, Z.C., Zhang, J.L.Delamination and ultradeep subduction of continental crust: constraints from elastic wave velocity and density measurement in ultrahigh pressure metamorphic rocksJournal of Metamorphic Geology, Vol. 29, 7, pp. 781-801.MantleSubduction, UHP
DS1990-0496
1990
Xie HongsenFu Pingqiu, Xie Hongsen, Zhang LimingA structure mineralogical study of ringwooditeInternational Mineralogical Association Meeting Held June, 1990 Beijing China, Vol. 1, extended abstract p. 490-491ChinaMineralogy, Ringwoodite
DS1990-0497
1990
Xie HongsenFu Pingqui, Xie Hongsen, Zhang LimingA structure -mineralogical study of ringwooditeChinese Journal of Geochemistry, Vol. 9, No. 2, pp. 99-103ChinaMineralogy, Ringwoodite
DS1990-1601
1990
Xie HongsenXie Xianbde, Liu Junsuo, Xie HongsenStudies on the defect structures and metasomatism of olivine and pryoxenein lherzolite xenoliths from basalts in Fujian and Zhejiang Provinces, southeastern ChinaInternational Mineralogical Association Meeting Held June, 1990 Beijing China, Vol. 1, extended abstract p. 363-364ChinaLherzolite, Xenoliths
DS1990-1602
1990
Xie HongsenXie Xiande, Liu Junsuo, Xie HongsenMicromineralogical investigations on the metasomatism in mantle xenoliths from basalts in southeasternChinaChinese Journal of Geochemistry, Vol. 9, No. 2, pp. 93-98ChinaGeochemistry, Lherzolites
DS1990-1601
1990
Xie XianbdeXie Xianbde, Liu Junsuo, Xie HongsenStudies on the defect structures and metasomatism of olivine and pryoxenein lherzolite xenoliths from basalts in Fujian and Zhejiang Provinces, southeastern ChinaInternational Mineralogical Association Meeting Held June, 1990 Beijing China, Vol. 1, extended abstract p. 363-364ChinaLherzolite, Xenoliths
DS1990-1602
1990
Xie XiandeXie Xiande, Liu Junsuo, Xie HongsenMicromineralogical investigations on the metasomatism in mantle xenoliths from basalts in southeasternChinaChinese Journal of Geochemistry, Vol. 9, No. 2, pp. 93-98ChinaGeochemistry, Lherzolites
DS1991-1925
1991
Xie XiingZhang Andi, Xu Dehuan, Xie Xiing, Guo Lihe, Zhou Jianzong, Wang WuyiThe status and future of diamond exploration in ChinaProceedings of Fifth International Kimberlite Conference held Araxa June 1991, Servico Geologico do Brasil (CPRM) Special, pp. 10-12China, Russia, Australia, South AfricaSinokorean, Yangtze, Tarim, Fuxiam, Tieling, Huanren, Mengyi, Lamproites
DS1990-1624
1990
Xie XilinZhang Andi, Meyer, H.O.A., Guo Lihe, Zhou Jianxiong, Xie Xilin, Wang Alian, XuComparative study of inclusions in diamonds with macrocrysts From kimberlites in north Chin a cratonInternational Mineralogical Association Meeting Held June, 1990 Beijing China, Vol. 1, extended abstract p. 504-505ChinaDiamond inclusions, Macrocrysts
DS1991-1931
1991
Xie XilinZhou Jianxiong, Zhang Andi, Wang Wuyi, Xie Xilin, Guo LiheSpinel - as indicator for diamondProceedings of Fifth International Kimberlite Conference held Araxa June 1991, Servico Geologico do Brasil (CPRM) Special, pp. 208-211ChinaSpinel -compositional range table, Geochemistry
DS1987-0419
1987
XiguangLiu, XiguangCharacteristics of typomorphic minerals of kimberlite in Mengyin and their relationship to orepotentiality. *CHIZhongguo Dizhi Kexueyuan Kuangchan Dizhi Yanjiuso Sokan, *CHI, Vol. 19, pp. 74-88ChinaKimberlite, Mineralogy
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2010
Xihuan, Z.Zhonghua, S., Taijin, L., Mendong, S., Jun, S., Jing, D., Xihuan, Z.2010 coated and fracture filled coloured diamond.The Australian Gemmologist, Vol. 24, 1,TechnologyDiamond filling
DS201511-1894
2014
Xikuan, Z.Zhonghua, S., Taijin, L., Meidong, S., Jun, S., Jing, D., Xikuan, Z.Coated and fracture filled coloured diamond.Australian Gemmologist, Vol. 24, 2, pp. 41-43.TechnologyDiamond morphology
DS1994-1982
1994
Xiling, X.Zhang Andi, Dehuan, X., Xiling, X., Lihe, G., Jianzong Z., Wuyi W.The status and future of diamond exploration in ChinaProceedings of Fifth International Kimberlite Conference, Vol. 2, pp. 268-284.ChinaDiamond exploration, Review
DS2002-0360
2002
Xin, M.Dawer, M., Xiuling, W., Yujing, H., Xin, M.Ultra structure of coesite - retrogressive metamorphic quartz and their interface transition belt from ultra high pressure metamorphic rocks.18th. International Mineralogical Association Sept. 1-6, Edinburgh, abstract p.72.MantleUHP, mineralogy, coesite
DS1993-0192
1993
Xin HuaBuseck, P.R., Xin HuaMatrices of carbonaceous chondrite meteoritesAnnual Review of Earth and Planetary Sciences, Vol. 21, pp. 255-306GlobalMeteorites
DS1990-0933
1990
XingLiebermann, R.C., Wang, Y., Liu, Xing, Guyot, F.What is the stable phase of MgSiO3 in the lower mantleV.m. Goldschmidt Conference Held May 2-4, 1990, Program And Abstract, p. 61. Abstract onlyGlobalMantle, Experimental petrology
DS201112-0593
2011
Xing, G.Li, L-M., Sun, M., Wang, Y., Xing, G., Zhao, G., Cai, K., Zhang, Y.Geochronological and geochemical study of Paleproterozoic gneissic granites and clinopyroxenite xenolths from NW Fujian: implications for crustal evol.Journal of Asian Earth Sciences, Vol. 41, 2, pp. 204-212.ChinaMagmatism - not specific to diamonds
DS1991-0262
1991
Xing FengmingChen Jiangfeng, Foland, K.A., Xing Fengming, Xu Xiang, Zhou TaixiMagmatism along the southeast margin of the Yangtse block: Precambrian collision of the Yangtse and Cathysia blocks of ChinaGeology, Vol. 19, No. 8, August, pp. 815-818ChinaTectonics, Ophiolites
DS1992-0243
1992
XingzhiChen, Xingzhi, Giglierano, J.The extraction of structural lineaments using Land sat multispectral imagery and geophysical dat a for northeast IowaGeological Society of America (GSA) Abstract Volume, Vol. 24, No. 4, April p. 9. abstract onlyIowaGeophysics, Lineaments
DS200412-2175
2004
Xinlong, Q.Yangsong, D., Hyunkoo, L., Xinlong, Q.Underplating of Mesozoic mantle derived magmas in Tongling, Anhui Province: evidence from megacrysts and xenoliths.Acta Geologica Sinica, Vol. 78, 1, pp. 131-136.China, AnhuiMagmatism
DS1994-1422
1994
Xinming ZhouQu Qi, Taylor, L.A., Xinming ZhouGeochemistry and petrogenesis of three series of Cenozoic basalts from southeastern China.International Geology Review, Vol. 36, No. 4, pp. 435-451.ChinaPicrite, nephelinite
DS201809-2016
2018
XinyangDuan, Yunfei, Sun, Ningyu, Wang, Siheng, Li, Xinyang, Guo, Xuan, Ni.Phase stability and thermal equation of state of delta -AIOOH: implication for water transportation in the deep lower mantle.Earth and Planetary Science Letters, Vol. 494, 1, pp. 92-98.Mantlewater

Abstract: In this study, we present new experimental constraints on the phase stability and thermal equation of state of an important hydrous phase, d-AlOOH, using synchrotron X-ray diffraction up to 142 GPa and 2500 K. Our experimental results have shown that d-AlOOH remains stable at the whole mantle pressure-temperature conditions above the D? layer yet will decompose at the core-mantle boundary because of a dramatic increase in temperature from the silicate mantle to the metallic outer core. At the bottom transition zone and top lower mantle, the formation of d-AlOOH by the decomposition of phase Egg is associated with a ~2.1-2.5% increase in density (?) and a ~19.7-20.4% increase in bulk sound velocity (VF). The increase in ? across the phase Egg to d-AlOOH phase transition can facilitate the subduction of d-AlOOH to the lower mantle. Compared to major lower-mantle phases, d-AlOOH has the lowest ? but greatest VF, leading to an anomalous low ? /VF ratio which can help to identify the potential presence of d-AlOOH in the region. More importantly, water released from the breakdown of d-AlOOH at the core-mantle boundary could lower the solidus of the pyrolitic mantle to cause partial melting and/or react with Fe in the region to form the low-velocity FeO2Hx phase. The presence of partial melting and/or the accumulation of FeO2Hx phase at the CMB could be the cause for the ultra-low velocity zone. d-AlOOH is thus an important phase to transport water to the lowermost mantle and helps to understand the origin of the ultra-low velocity zone.
DS2002-0445
2002
XioFang, W., Hu, Su, Xio, Ji, JiangOn emplacment ages of lamproite in Zhenyuan County, Guizhon Province, ChinaChina Sciences Bulletin, Vol.47, 10,pp. 874-80.China, GuizhonGeochronology, Lamproites
DS200712-1191
2007
Xio, L.Xio, L., Wang, C., Pirajno, F.Is the underthrust Indian lithosphere split beneath the Tibetan Plateau?International Geology Review, Vol. 49, 1, pp. 90-98.IndiaTectonics
DS201908-1822
2019
Xion, X.Wang, J., Xion, X., Takahashi, E., Zhang, L., Li, L., Liu, X.Oxidation state of arc mantle revealed by partitioning of V, Sc, Ti between mantle minerals and basaltic melts.Journal of Geophysical Research , Vol. 124, 5, pp. 4617-4638.Mantlemelting

Abstract: The oxidation state of the Earth`s mantle, often expressed as oxygen fugacity (fO2), could control the behavior of multivalent elements and thus exert a significant influence on the formation of magmatic ore deposits and the secular evolution of Earth`s atmosphere. Whether arc mantle is more oxidized than oceanic mantle remains a controversial topic. As a multivalent element, partitioning behavior of vanadium is fO2 sensitive and is capable of tracking mantle redox state. However, except fO2, other factors (temperature, pressure, and phase composition) that may affect vanadium partitioning behavior have not been clearly evaluated. Here we conducted high temperature and pressure experiments to determine partition coefficients of vanadium during mantle melting under various fO2 conditions. Combining our and published data, we evaluated the effects of fO2, T, P, and compositions of mineral and melt on the vanadium partitioning using multiple linear regressions. The results indicate that, in addition to fO2, temperature exerts a significant control on the vanadium partitioning. Additionally, we estimated fO2 of the arc mantle via numerical modelling using appropriate partition coefficients for vanadium. Our results clarify and reconcile the discrepancies between previous studies and reveal that arc mantle is generally ~10 times more oxidized than oceanic mantle.
DS1996-0023
1996
XiongAmes, L., Zhou, XiongGeochronology and isotopic character of ultrahigh pressure metamorphism with implications for collision of the Sino Korean and Yangtze Cratons, centralChina.Tectonics, Vol. 15, No. 2, Apr. pp. 472-89.Chinametamorphism
DS1985-0745
1985
Xiong, D.Xiong, D., Lu, ZT.Experimental Studies of Calcium Carbonate As a Carbon Source for Synthesizing Diamonds.Sci. Geol. Sinica., No. 3, PP. 259-ChinaBlank
DS201502-0093
2014
Xiong, F.Robinson, P.T., Trumbull, R.B., Schmitt, A., Yang, J-S., Li, J-W., Zhou, M-F., Erzinger, J., Dare, S., Xiong, F.The origin and significance of crustal minerals in ophiolitic chromitites and peridotites.Gondwana Research, Vol. 27 2, pp. 486-506.Peridotite
DS201506-0297
2015
Xiong, F.Tian, Y., Yang, J., Robinson, P.T., Xiong, F., Li, Y., Zhang, Z., Liu, Z., Liu, F., Niu, X.Diamond discovered in high Al chromitites of the Sartohay ophiolite, Xinjiang province China.Acta Geologica Sinica, Vol. 89, 2, pp. 332-340.ChinaChromitite
DS201601-0019
2015
Xiong, F.Huang, Yang, J., Zhu, Y., Xiong, F., Liu, Z., Zhang, Z., Xu, W.The discovery of diamonds in chromitite of the Hegenshan ophiolite, Inner Mongolia.Acta Geologica Sinica, Vol. 89, 2, p. 32.Asia, MongoliaOphiolite

Abstract: Diamond, moissanite and a variety of other minerals, similar to those reported from ophiolites in Tibet and northern Russia, have recently been discovered in chromitites of the Hegenshan ophiolite of the Central Asian Orogenic Belt, north China. The chromitites are small, podiform and vein-like bodies hosted in dunite, clinopyroxene-bearing peridotite, troctolite and gabbro. All of the analysed chromite grains are relatively Al-rich, with Cr# [100Cr/(Cr+Al)] of about 47-53. Preliminary studies of mainly disseminated chromitite from ore body No. 3756 have identified more than 30 mineral species in addition to diamond and moissanite. These include oxides (mostly hematite, magnetite, rutile, anatase, cassiterite, and quartz), sulfides (pyrite, marcasite and others), silicates (magnesian olivine, enstatite, augite, diopside, uvarovite, pyrope, orthoclase, zircon, sphene, vesuvianite, chlorite and serpentine) and others (e.g., calcite, monazite, glauberite, iowaite and a range of metallic alloys). This study demonstrates that diamond, moissanite and other exotic minerals can occur in high-Al, as well as high-Cr chromites, and significantly extends the geographic and age range of known diamond-bearing ophiolites.
DS201601-0049
2015
Xiong, F.Xiong, F., et al.Diamond discovered in Dangqiong ophiolite, western Yarlung-Zangbu suture zone, Tibet.Acta Geologica Sinica, Vol. 89, 2, pp. 99-100.Asia, TibetOphiolite
DS201601-0050
2015
Xiong, F.Yang, J., Wirth, R., Xiong, F., Tian, Y., Huang, Z., Robinson, P.T., Dilek, Y.The lower mantle minerals in ophiolite hosted diamond.Acta Geologica Sinica, Vol. 89, 2, pp. 108-109.MantleMineralogy
DS201605-0922
2016
Xiong, F.Xiong, F., Yang, J., Robinson, P.T., Xu, X., Ba, D., Li, Y., Zhang, Z., Rong, H.Diamonds ad other exotic minerals recovered from peridotites of the Dangqiong ophiolite, western Yarlung-Zangbo suture zone, Tibet.Acta Geologica Sinica, Vol. 90, 2, pp. 425-439.Asia, TibetPeridotite

Abstract: Various combinations of diamond, moissanite, zircon, quartz, corundum, rutile, titanite, almandine garnet, kyanite, and andalusite have been recovered from the Dangqiong peridotites. More than 80 grains of diamond have been recovered, most of which are pale yellow to reddish-orange to colorless. The grains are all 100-200 µm in size and mostly anhedral, but with a range of morphologies including elongated, octahedral and subhedral varieties. Their identification was confirmed by a characteristic shift in the Raman spectra between 1325 cm-1 and 1333 cm-1, mostly at 1331.51 cm-1 or 1326.96 cm-1. Integration of the mineralogical, petrological and geochemical data for the Dongqiong peridotites suggests a multi-stage formation for this body and similar ophiolites in the Yarlung-Zangbo suture zone. Chromian spinel grains and perhaps small bodies of chromitite crystallized at various depths in the upper mantle, and encapsulated the UHP, highly reduced and crustal minerals. Some oceanic crustal slabs containing the chromian spinel and their inclusion were later trapped in suprasubduction zones (SSZ), where they were modified by island arc tholeiitic and boninitic magmas, thus changing the chromian spinel compositions and depositing chromitite ores in melt channels.
DS201709-2076
2017
Xiong, F.Xiong, F., Yang, J., Robinson, P.T., Dilek, Y., Milushi, I., Xu, X., Zhou, W., Zhang, Z., Rong, H.Diamonds discovered from high-Cr podiform chromitites from Bulqiza, eastern Mirdita ophiolite, Albania.Acta Geologica Sinica, Vol. 91, 2, pp. 455-468.Europe, Albaniadiamonds in chromitites

Abstract: Various combinations of diamond, moissanite, zircon, corundum, rutile and titanitehave been recovered from the Bulqiza chromitites. More than 10 grains of diamond have been recovered, most of which are pale yellow to reddish–orange to colorless. The grains are all 100–300 µm in size and mostly anhedral, but with a range of morphologies including elongated, octahedral and subhedral varieties. Their identification was confirmed by a characteristic shift in the Raman spectra between 1325 cm-1 and 1333 cm-1, mostly at 1331.51 cm-1 or 1326.96 cm-1. This investigation extends the occurrence of diamond and moissanite to the Bulqiza chromitites in the Eastern Mirdita Ophiolite. Integration of the mineralogical, petrological and geochemical data of the Bulqiza chromitites suggests their multi–stage formation. Magnesiochromite grains and perhaps small bodies of chromitite formed at various depths in the upper mantle, and encapsulated the ultra–high pressure, highly reduced and crustal minerals. Some oceanic crustal slabs containing the magnesiochromite and their inclusion were later trapped in suprasubduction zones, where they were modified by tholeiitic and boninitic arc magmas, thus changing the magnesiochromite compositions and depositing chromitite ores in melt channels.
DS201710-2240
2017
Xiong, F.Lian, D., Yang, J., Dilek, Y., Wu, W., Zhang, Z., Xiong, F., Liu, F., Zhou, W.Deep mantle origin and ultra-reducing conditions in podiform chromitite: diamonds, moissanite, and other unusual minerals in podiform chromitites from the Pozanti-Karsanti ophiolite, southern Turkey.Americam Mineralogist, Vol. 103, 5p.Europe, Turkeymoissanites

Abstract: The Pozanti-Karsanti ophiolite situated in the eastern Tauride belt, southern Turkey, is a well-preserved oceanic lithosphere remnant comprising, in ascending order, mantle peridotite, ultramafic and mafic cumulates, isotropic gabbros, sheeted dikes, and basaltic pillow lavas. Two types of chromitites are observed in the Pozanti-Karsanti ophiolite. One type of chromitites occurs in the cumulate dunites around the Moho, and the other type of chromitites is hosted by the mantle harzburgites below the Moho. The second type of chromitites has massive, nodular, and disseminated textures. We have conducted the mineral separation work on the podiform chromitites hosted by harzburgites. So far, more than 100 grains of microdiamond and moissanite (SiC) have been recovered from the podiform chromitite. The diamonds and moissanite are accompanied by large amounts of rutile. Besides zircon, monazite and sulfide are also very common phases within the separated minerals. The discovery of diamond, moissanite, and the other unusual minerals from podiform chromitite of the Pozanti-Karsanti ophiolite provides new evidences for the common occurrences of these unusual minerals in ophiolitic peridotites and chromitites. This discovery also suggests that deep mantle processes and materials have been involved in the formation of podiform chromitite.
DS201805-0993
2018
Xiong, F.Xiong, F., Yang, J., Xu, X., Kapsiotis, A., Hao, X., Liu, Z.Compositional and isotopic heterogeneities in the Neo-Tethyan upper mantle recorded by coexisting Al rich and Cr rich chromitites in the Purang massif, SW Tibet (China).Journal of Asian Earth Sciences, Vol. 159, pp. 109-129.China, Tibetchromitites

Abstract: The Purang harzburgite massif in SW Tibet (China) hosts abundant chrome ore deposits. Ores consist of 20 to >95% modal chromian spinel (Cr-spinel) with mylonitic fabric in imbricate shaped pods. The composition of Cr-spinel in these ores ranges from Al-rich [Cr#Sp or Cr/(Cr?+?Al)?×?100?=?47.60-57.56] to Cr-rich (Cr#Sp: 62.55-79.57). Bulk platinum-group element (PGE) contents of chromitites are also highly variable ranging from 17.5?ppb to ~2.5?ppm. Both metallurgical and refractory chromitites show a general enrichment in the IPGE (Os, Ir and Ru) with respect to the PPGE (Rh, Pt and Pd), resulting mostly in right-sloping primitive mantle (PM)-normalized PGE profiles. The platinum-group mineral (PGM) assemblages of both chromitite types are dominated by heterogeneously distributed, euhedral Os-bearing laurite inclusions in Cr-spinel. The Purang chromitites have quite inhomogeneous 187Os/188Os ratios (0.12289-0.13194) that are within the range of those reported for mantle-hosted chromitites from other peridotite massifs. Geochemical calculations demonstrate that the parental melts of high-Cr chromitites were boninitic, whereas those of high-Al chromitites had an arc-type tholeiitic affinity. Chromite crystallization was most likely stimulated by changes in magma compositions due to melt-peridotite interaction, leading to the establishment of a heterogeneous physicochemical environment during the early crystallization of the PGM. The highly variable PGE contents, inhomogeneous Os-isotopic compositions and varying Cr#Sp ratios of these chromitites imply a polygenetic origin for them from spatially distinct melt inputs. The generally low ?Os values (<1) of chromitites indicate that their parental melts originated within different sections of a heterogeneously depleted mantle source region. These melts were most likely produced in the mantle wedge above a downgoing lithospheric slab.
DS201907-1586
2019
Xiong, F.Xu, X., Cartigny, P., Yang, J., Dilek, Y., Xiong, F., Guo, G.FTIR spectroscopy data and carbon isotope characteristics of the ophiolite hosted diamonds.Acta Geologica Sinica, Vol. 93, 1, p.38.Asia, Russiamicrodiamonds

Abstract: We report new d13C -values data and N-content and N-aggregation state values for microdiamonds recovered from peridotites and chromitites of the Luobusa ophiolite (Tibet) and chromitites of the Ray-Iz ophiolite in the Polar Urals (Russia). All analyzed microdiamonds contain significant nitrogen contents (from 108 up to 589 ± 20% atomic ppm) with a consistently low aggregation state, show identical IR spectra dominated by strong absorption between 1130 cm-1 and 1344 cm-1, and hence characterize Type Ib diamond. Microdiamonds from the Luobusa peridotites have d13C -PDB-values ranging from -28.7‰ to -16.9‰, and N-contents from 151 to 589 atomic ppm. The d13C and N-content values for diamonds from the Luobusa chromitites are -29‰ to -15.5‰ and 152 to 428 atomic ppm, respectively. Microdiamonds from the Ray-Iz chromitites show values varying from -27.6 ‰ to -21.6 ‰ in d13C and from 108 to 499 atomic ppm in N. The carbon isotopes values bear similar features with previously analyzed metamorphic diamonds from other worldwide localities, but the samples are characterized by lower N-contents. In every respect, they are different from diamonds occurring in kimberlites and impact craters. Our samples also differ from the few synthetic diamonds; we also analyzed showing enhanced d13C -variability and less advanced aggregation state than synthetic diamonds. Our newly obtained N-aggregation state and N-content data are consistent with diamond formation over a narrow and rather cold temperature range (i.e. <950°C), and in a short residence time (i.e. within several million years) at high temperatures in the deep mantle.
DS201907-1587
2019
Xiong, F.Yang, J., Robinson, P., Xu, X., Xiong, F., Lian, D.Diamond in oceanic peridotites and chromitites: evidence for deep recycled mantle in the global ophiolite record.Acta Geologica Sinica, Vol. 93, 2, p.42.Europe, Turkey, Albania, Russia, Chinamicrodiamonds

Abstract: Diamonds have been discovered in mantle peridotites and chromitites of six ophiolitic massifs along the 1300 km-long Yarlung-Zangbo suture (Bai et al., 1993; Yang et al., 2014; Xu et al., 2015), and in the Dongqiao and Dingqing mantle peridotites of the Bangong-Nujiang suture in the eastern Tethyan zone (Robinson et al., 2004; Xiong et al., 2018). Recently, in-situ diamond, coesite and other UHP mineral have also been reported in the Nidar ophiolite of the western Yarlung-Zangbo suture (Das et al., 2015, 2017). The above-mentioned diamond-bearing ophiolites represent remnants of the eastern Mesozoic Tethyan oceanic lithosphere. New publications show that diamonds also occur in chromitites in the Pozanti-Karsanti ophiolite of Turkey, and in the Mirdita ophiolite of Albania in the western Tethyan zone (Lian et al., 2017; Xiong et al., 2017; Wu et al., 2018). Similar diamonds and associated minerals have also reported from Paleozoic ophiolitic chromitites of Central Asian Orogenic Belt of China and the Ray-Iz ophiolite in the Polar Urals, Russia (Yang et al., 2015a, b; Tian et al., 2015; Huang et al, 2015). Importantly, in-situ diamonds have been recovered in chromitites of both the Luobusa ophiolite in Tbet and the Ray-Iz ophiolite in Russia (Yang et al., 2014, 2015a). The extensive occurrences of such ultra-high pressure (UHP) minerals in many ophiolites suggest formation by similar geological events in different oceans and orogenic belts of different ages. Compared to diamonds from kimberlites and UHP metamorphic belts, micro-diamonds from ophiolites present a new occurrence of diamond that requires significantly different physical and chemical conditions of formation in Earth's mantle. The forms of chromite and qingsongites (BN) indicate that ophiolitic chromitite may form at depths of >150-380 km or even deeper in the mantle (Yang et al., 2007; Dobrthinetskaya et al., 2009). The very light C isotope composition (d13C -18 to -28‰) of these ophiolitic diamonds and their Mn-bearing mineral inclusions, as well as coesite and clinopyroxene lamallae in chromite grains all indicate recycling of ancient continental or oceanic crustal materials into the deep mantle (>300 km) or down to the mantle transition zone via subduction (Yang et al., 2014, 2015a; Robinson et al., 2015; Moe et al., 2018). These new observations and new data strongly suggest that micro-diamonds and their host podiform chromitite may have formed near the transition zone in the deep mantle, and that they were then transported upward into shallow mantle depths by convection processes. The in-situ occurrence of micro-diamonds has been well-demonstrated by different groups of international researchers, along with other UHP minerals in podiform chromitites and ophiolitic peridotites clearly indicate their deep mantle origin and effectively address questions of possible contamination during sample processing and analytical work. The widespread occurrence of ophiolite-hosted diamonds and associated UHP mineral groups suggests that they may be a common feature of in-situ oceanic mantle. The fundamental scientific question to address here is how and where these micro-diamonds and UHP minerals first crystallized, how they were incorporated into ophiolitic chromitites and peridotites and how they were preserved during transport to the surface. Thus, diamonds and UHP minerals in ophiolites have raised new scientific problems and opened a new window for geologists to study recycling from crust to deep mantle and back to the surface.
DS201908-1827
2018
Xiong, F.Yang, J., Robinson, P.T., Xu, X., Xiong, F., Lian, D.Diamond in oceanic peridotites and chromitites: evidence for deep recycled mantle in the global ophiolite record.International Symposium on Deep Earth Exploration and Practices, Beijing Oct. 24-26. 1 p. abstractChinadiamond genesis

Abstract: Diamonds have been discovered in mantle peridotites and chromitites of six ophiolitic massifs along the 1300 km-long Yarlung-Zangbo suture (Bai et al., 1993; Yang et al., 2014; Xu et al., 2015), and in the Dongqiao and Dingqing mantle peridotites of the Bangong-Nujiang suture in the eastern Tethyan zone (Robinson et al., 2004; Xiong et al., 2018). Recently, in-situ diamond, coesite and other UHP mineral have also been reported in the Nidar ophiolite of the western Yarlung-Zangbo suture (Das et al., 2015, 2017). The above-mentioned diamond-bearing ophiolites represent remnants of the eastern Mesozoic Tethyan oceanic lithosphere. New publications show that diamonds also occur in chromitites in the Pozanti-Karsanti ophiolite of Turkey, and in the Mirdita ophiolite of Albania in the western Tethyan zone (Lian et al., 2017; Xiong et al., 2017; Wu et al., 2018). Similar diamonds and associated minerals have also reported from Paleozoic ophiolitic chromitites of Central Asian Orogenic Belt of China and the Ray-Iz ophiolite in the Polar Urals, Russia (Yang et al., 2015a, b; Tian et al., 2015; Huang et al, 2015). Importantly, in-situ diamonds have been recovered in chromitites of both the Luobusa ophiolite in Tbet and the Ray-Iz ophiolite in Russia (Yang et al., 2014, 2015a). The extensive occurrences of such ultra-high pressure (UHP) minerals in many ophiolites suggest formation by similar geological events in different oceans and orogenic belts of different ages. Compared to diamonds from kimberlites and UHP metamorphic belts, micro-diamonds from ophiolites present a new occurrence of diamond that requires significantly different physical and chemical conditions of formation in Earth's mantle. The forms of chromite and qingsongites (BN) indicate that ophiolitic chromitite may form at depths of >150-380 km or even deeper in the mantle (Yang et al., 2007; Dobrthinetskaya et al., 2009). The very light C isotope composition (d13C -18 to -28‰) of these ophiolitic diamonds and their Mn-bearing mineral inclusions, as well as coesite and clinopyroxene lamallae in chromite grains all indicate recycling of ancient continental or oceanic crustal materials into the deep mantle (>300 km) or down to the mantle transition zone via subduction (Yang et al., 2014, 2015a; Robinson et al., 2015; Moe et al., 2018). These new observations and new data strongly suggest that micro-diamonds and their host podiform chromitite may have formed near the transition zone in the deep mantle, and that they were then transported upward into shallow mantle depths by convection processes. The in-situ occurrence of micro-diamonds has been well-demonstrated by different groups of international researchers, along with other UHP minerals in podiform chromitites and ophiolitic peridotites clearly indicate their deep mantle origin and effectively address questions of possible contamination during sample processing and analytical work. The widespread occurrence of ophiolite-hosted diamonds and associated UHP mineral groups suggests that they may be a common feature of in-situ oceanic mantle. The fundamental scientific question to address here is how and where these micro-diamonds and UHP minerals first crystallized, how they were incorporated into ophiolitic chromitites and peridotites and how they were preserved during transport to the surface. Thus, diamonds and UHP minerals in ophiolites have raised new scientific problems and opened a new window for geologists to study recycling from crust to deep mantle and back to the surface.
DS201909-2109
2019
Xiong, F.Yang, J., Lian, D., Robinson, P.T., Qiu, T., Xiong, F., Wu, W.A shallow origin for diamonds in ophiolitic chromitites. Geology, Vol. 47, pp. e475.North America, Mexicomicrodiamonds
DS202105-0800
2020
Xiong, F.Yang, J.. Dongyang. L., Robinson, P.T., Qiu, T. , Xiong, F., Wu, W.Geological evidence does not support a shallow origin for diamonds in ophiolite.Acta Geologica Sinica, Vol. 94, 1, pp. 70-72.Europe, Albaniaophiolite

Abstract: Farré-de-Pablo et al. (2018) report a new occurrence of in situ microdiamonds enclosed in chromite from ophiolitic chromitite pods hosted in the Tehuitzingo serpentinite of southern Mexico. The discovery enlarges the number of occurrence of the ophiolite-hosted microdiamonds to 7 countries in the world, including India (Das, 2015, 2017), Albania (Xiong et al., 2017; Wu et al., 2017), Turkey (Lian et al., 2017), Myanmar (Chen et al., 2018), Russia (Yang et al., 2015), and China (Bai et al., 1993; Xu et al., 2009). The microdiamonds occur in ophiolitic podiform chromitites and peridotites, and are generally interpreted as UHP phases formed at pressures > 4 GPa (Yang et al., 2014; Griffin et al., 2016; Das et al., 2017). However, Farré-de-Pablo et al. (2018) conclude that the Tehuitzingo diamonds were formed under low-temperature and low-pressure conditions during serpentinization, which challenges the current knowledge of diamond formation. Here, we discuss several lines of evidence that do not support the authors' conclusion.
DS201810-2390
2018
Xiong, F.H.Yang, J.S., Trumball, R.B., Robinson, P.T., Xiong, F.H., Lian, D.Y.Comment: Ultra high pressure and ultra reduced minerals in ophiolites may form by lightning strikes. Super Reduced Minerals SURGeochemical Perspectives Letters, Vol. 8, pp. 6-7.Mantlemoissanite
DS1989-1665
1989
Xiong, G.C.Xiong, G.C.Success of geophysics for nonferrous metal ore deposits in South ChinaZhao, J.X., Wang, X.X. editors.Overview of exploration geophysics in, pp. 487-500ChinaGeophysics
DS1997-0803
1997
Xiong, J.Mitchell, R.H., Xiong, J., Mariano, A.N., Fleet, M.E.Rare earth element activated cathodluminescence in apatiteCanadian Mineralogist, Vol. 35, No. 4 Aug. p. 979-998.GlobalCarbonatite, Alkaline rocks
DS201212-0826
2012
Xiong, Q.Zheng, J.P., Griffin, W.L., Ma, Q., O'Reilly, S.Y., Xiong, Q., Tang, H.Y., Zhao, J.H., Yu, C.M., Su, Y.P.Accretion and reworking beneath the North Chin a craton.Lithos, Vol. 149, pp. 61-78.ChinaAccretion
DS201504-0231
2015
Xiong, Q.Xiong, Q., Griffin, W.L., Zheng, J-P., O'Reilly, S.Y., Pearson, N.J.Episodic refertilization and metasomatism of Archean mantle: evidence from an orogenic peridotite in North Qaidam ( NE Tibet) China.Contributions to Mineralogy and Petrology, Vol. 169, 24p.China, TibetPeridotite
DS201606-1090
2016
Xiong, Q.Griffin, W.L., Afonso, J.C., Belousova, E.A., Gain, S.E., Gong, X-H., Gonzalez-Jiminez, J.M., Howell, D., Huang, J-X., McGowan, N., Pearson, N.J., Satsukawa, T., Shi R., Williams, P., Xiong, Q., Yang, J-S., Zhang, M., O'Reilly, S.Y.Mantle recycling: transition zone metamorphism of Tibetan ophiolitic peridotites and its tectonic implications.Journal of Petrology, in press available, 30p.Asia, China, TibetPeridotite

Abstract: Large peridotite massifs are scattered along the 1500?km length of the Yarlung-Zangbo Suture Zone (southern Tibet, China), the major suture between Asia and Greater India. Diamonds occur in the peridotites and chromitites of several massifs, together with an extensive suite of trace phases that indicate extremely low fO2 (SiC, nitrides, carbides, native elements) and/or ultrahigh pressures (UHP) (diamond, TiO2 II, coesite, possible stishovite). New physical and isotopic (C, N) studies of the diamonds indicate that they are natural, crystallized in a disequilibrium, high-T environment, and spent only a short time at mantle temperatures before exhumation and cooling. These constraints are difficult to reconcile with previous models for the history of the diamond-bearing rocks. Possible evidence for metamorphism in or near the upper part of the Transition Zone includes the following: (1) chromite (in disseminated, nodular and massive chromitites) containing exsolved pyroxenes and coesite, suggesting inversion from a high-P polymorph of chromite; (2) microstructural studies suggesting that the chromitites recrystallized from fine-grained, highly deformed mixtures of wadsleyite and an octahedral polymorph of chromite; (3) a new cubic Mg-silicate, with the space group of ringwoodite but an inverse-spinel structure (all Si in octahedral coordination); (4) harzburgites with coarsely vermicular symplectites of opx + Cr-Al spinel ± cpx; reconstructions suggest that these are the breakdown products of majoritic garnets, with estimated minimum pressures to?>?13?GPa. Evidence for a shallow pre-metamorphic origin for the chromitites and peridotites includes the following: (1) trace-element data showing that the chromitites are typical of suprasubduction-zone (SSZ) chromitites formed by magma mixing or mingling, consistent with Hf-isotope data from magmatic (375?Ma) zircons in the chromitites; (2) the composition of the new cubic Mg-silicate, which suggests a low-P origin as antigorite, subsequently dehydrated; (3) the peridotites themselves, which carry the trace element signature of metasomatism in an SSZ environment, a signature that must have been imposed before the incorporation of the UHP and low-fO2 phases. A proposed P-T-t path involves the original formation of chromitites in mantle-wedge harzburgites, subduction of these harzburgites at c. 375?Ma, residence in the upper Transition Zone for >200 Myr, and rapid exhumation at c. 170-150?Ma or 130-120?Ma. Os-isotope data suggest that the subducted mantle consisted of previously depleted subcontinental lithosphere, dragged down by a subducting oceanic slab. Thermomechanical modeling shows that roll-back of a (much later) subducting slab would produce a high-velocity channelized upwelling that could exhume the buoyant harzburgites (and their chromitites) from the Transition Zone in?
DS201702-0254
2017
Xiong, Q.Xu, B., Griffin, W.L., Xiong, Q., Hou, Z-Q, O'Reilly, S.Y., Guo, Z., Pearson, N.J., Greau, Y., Yang, Z-M., Zheng, Y-C.Ultrapotassic rocks and xenoliths from South Tibet: contrasting styles of interaction between lithospheric mantle and asthenosphere during continental collision.Geology, Vol. 45, 1, pp. 51-54.China, TibetUPR - metasomatism

Abstract: Widespread Miocene (24-8 Ma) ultrapotassic rocks and their entrained xenoliths provide information on the composition, structure, and thermal state of the sub-continental lithospheric mantle in southern Tibet during the India-Asia continental collision. The ultrapotassic rocks along the Lhasa block delineate two distinct lithospheric domains with different histories of depletion and enrichment. The eastern ultrapotassic rocks (89°E-92°E) reveal a depleted, young, and fertile lithospheric mantle (87Sr/86Srt = 0.704-0.707 [t is eruption time]; Hf depleted-mantle model age [TDM] = 377-653 Ma). The western ultrapotassic rocks (79°E-89°E) and their peridotite xenoliths (81°E) reflect a refractory harzburgitic mantle refertilized by ancient metasomatism (lavas: 87Sr/86Srt = 0.714-0.734; peridotites: 87Sr/86Srt = 0.709-0.716). These data integrated with seismic tomography suggest that upwelling asthenosphere was diverted away from the deep continental root beneath the western Lhasa block, but rose to shallower depths beneath a thinner lithosphere in the eastern part. Heating of the lithospheric mantle by the rising asthenosphere ultimately generated the ultrapotassic rocks with regionally distinct geochemical signatures reflecting the different nature of the lithospheric mantle.
DS201706-1094
2017
Xiong, Q.Lu, J-G, Xiong, Q., Griffin, W.L., Zheng, J-P., Huang, J-X., O'Reilly, S.Y., Satsuskawa, T., Pearson, N.J.Uplift of the southeastern Australian lithosphere: thermal tectonic evolution of garnet pyroxenite xenoliths from western Victoria.Geological Society of America, SPE 526 pp. 27-48.Australiageothermometry

Abstract: Detailed petrography, microstructure, and geochemistry of garnet pyroxenite xenoliths in Holocene basanite tuffs from maars at Lakes Bullenmerri and Gnotuk (western Victoria, southeastern Australia) have been used to track their igneous and metamorphic history, enabling the reconstruction of the thermal-tectonic evolution of the lithospheric mantle. The exsolution of orthopyroxene and garnet and rare spinel, plagioclase, and ilmenite from complex clinopyroxene megacrysts suggests that the xenoliths originally were clinopyroxene-dominant cumulates associated with minor garnet, orthopyroxene, or spinel. The compositions of exsolved phases and their host clinopyroxene were reintegrated using measured modal proportions to show that the primary clinopyroxene was enriched in Al2O3 (5.53-13.63 wt%) and crystallized at ~1300-1500 °C and 16-30 kbar. These cumulates then underwent extensive exsolution, recrystallization, and reaction during cooling, and finally equilibrated at ~950-1100 °C and 12-18 kbar before entrainment in the basanites. Rare earth element (REE) thermobarometry of garnets and coexisting clinopyroxenes preserves evidence of an intermediate stage (1032 °C and 21 kbar). These results imply that the protoliths of the garnet pyroxenite formed at a range of depths from ~50 to 100 km, and then during or shortly after cooling, they were tectonically emplaced to higher levels (~40-60 km; i.e., uplifted by at least 10-20 km) along the prevailing geotherm. This uplift may have been connected with lithosphere-scale faulting during the Paleozoic orogeny, or during Mesozoic-Cenozoic rifting of eastern Australia.
DS201708-1576
2017
Xiong, Q.Lu, J-G., Xiong, Q., Griffin, W.L., Zheng, J-P., Huang, J-X., O'Reilly, S.Y., Satsukawa, T., Pearson, N.J.Uplift of southeastern Australian lithosphere: thermal tectonic evolution of garnet pyroxenite xenoliths from western Victoria.Geological Society of London, Chapter 2, pp. 27-48.Australia, Victoriaxenoliths

Abstract: Detailed petrography, microstructure, and geochemistry of garnet pyroxenite xenoliths in Holocene basanite tuffs from maars at Lakes Bullenmerri and Gnotuk (western Victoria, southeastern Australia) have been used to track their igneous and metamorphic history, enabling the reconstruction of the thermal-tectonic evolution of the lithospheric mantle. The exsolution of orthopyroxene and garnet and rare spinel, plagioclase, and ilmenite from complex clinopyroxene megacrysts suggests that the xenoliths originally were clinopyroxene-dominant cumulates associated with minor garnet, orthopyroxene, or spinel. The compositions of exsolved phases and their host clinopyroxene were reintegrated using measured modal proportions to show that the primary clinopyroxene was enriched in Al2O3 (5.53–13.63 wt%) and crystallized at ~1300–1500 °C and 16–30 kbar. These cumulates then underwent extensive exsolution, recrystallization, and reaction during cooling, and finally equilibrated at ~950–1100 °C and 12–18 kba
DS201709-1999
2017
Xiong, Q.Huang, J-X., Xiong, Q., Griffin, W.L., Martin, L., Toledo, V., O'Reilly, S.Y.Moissanite in volcanic systems: super reduced conditions in the mantle.Goldschmidt Conference, abstract 1p.Mantlemoissanite

Abstract: Moissanite (SiC) occurs in mantle and mantle-generated rocks from different tectonic settings. SiC is stable only at low oxygen fugacity (ƒO2) ?IW. Israeli SiC is assiociated with corundum, Fe globules, native V and other phases in Cretaceous pyroclastic rocks from Mt Carmel and associated alluvial deposits[1]. The SiC grains contain inclusions of Si metal, FeSi2, FeTiSi2, FeAlSi2 and CaSi2+xSi2-x, which were liquids before being trapped during SiC crystallization. SiC has been found included in corundum, associated with Fe-Ti silicides, connecting the formation of SiC, reduced melts in corundum and conrundum itself. All grains are of the 6H polytype. d13C ranges from - 32.1 to -24.5‰ and d30Si from -0.68 to +1.42‰. These SiC grains are one product of the interaction of basaltic magma and mantle methane in a volcanic plumbing system. SiC crystallized from metallic melts that became immiscible during the reduction of the magma. Its low d13C may reflect Rayleigh fractionation under reduced conditions; the variation in Si isotopes may reflect fractionation between SiC and immiscible metallic melts. SiC samples from the Udachnaya and Mir kimberlite pipes contain inclusions of Si metal, FeSi2, FeSi, FeTiSi2, Si(N,O). The SiC has d13C ranging from -28.5 to -24.8‰, and d30Si from -1.72 to +1.42‰. SiC from harzburgites, chromitites and pyroxenites of the Tibetan Zedang ophiolites have inclusions of Si metal and unmixed Fe-Ni-Ti-Si alloy. Their d13C ranges from -30.6 to -24.7‰ and d30Si from -0.85 to +1.26‰. SiC samples from these different settings show very similar characteristics, implying that they may be formed in similar mantle conditions, where the flux of mantle methane gradually reduces magmas and interacts with them to produce different reduced phases at different stages.
DS201710-2280
2017
Xiong, Q.Xiong, Q., Griffin, W.L., Huang, J-X., Gain, S.E.M., Toledo, V., Pearson, N.J., O'Reilly, S.Y.Super reduced assemblages in "ophiolitic" chromitites and peridotites: the view from Mount Carmel.European Journal of Mineralogy, Vol. 29, 4, pp. 557-570.Europe, Israelmineralogy

Abstract: Ultrahigh-pressure (UHP) materials (e.g., diamond, high-pressure polymorph of chromite) and super-reduced (SuR) phases (e.g., carbides, nitrides, silicides and native metals) have been identified in chromitites and peridotites of the Tibetan and Polar-Urals ophiolites. These unusual assemblages suggest previously unrecognized fluid- or melt-related processes in the Earth’s mantle. However, the origin of the SuR phases, and in particular their relationships with the UHP materials in the ophiolites, are still enigmatic. Studies of a recently recognized SuR mineral system from Cretaceous volcanics on Mt Carmel, Israel, suggest an alternative genesis for the ophiolitic SuR phases. The Mt Carmel SuR mineral system (associated with Ti-rich corundum xenocrysts) appears to reflect the local interaction of mantle-derived CH4 ± H2 fluids with basaltic magmas in the shallow lithosphere (depths of ~30-100 km). These interactions produced desilication of the magma, supersaturation in Al2O3 leading to rapid growth of corundum, and phase assemblages requiring local oxygen fugacity (fO2) gradually dropping to ~11 log units below the iron-wüstite (IW) buffer. The strong similarities between this system and the SuR phases and associated Ti-rich corundum in the Tibetan and Polar-Urals ophiolites suggest that the ophiolitic SuR suite probably formed by local influx of CH4 ± H2 fluids within previously subducted peridotites (and included chromitites) during their rapid exhumation from the deep upper mantle to lithospheric levels. In the final stages of their ascent, the recycled peridotites and chromitites were overprinted by a shallow magmatic system similar to that observed at Mt Carmel, producing most of the SuR phases and eventually preserving them within the Tibetan and Polar-Urals ophiolites.
DS201810-2349
2018
Xiong, Q.Lu, J., Griffin, W.L., Tilhac, R., Xiong, Q., Zheng, J., O'Reilly, S.Y.Tracking deep lithospheric events with garnet-websterite xenoliths from southeastern Australia.Journal of Petrology, Vol. 59, 5, pp. 901-903.Australiabasanite

Abstract: Pyroxenites provide important information on mantle heterogeneity and can be used to trace mantle evolution. New major and trace element and Sr-, Nd-, and Hf-isotope analyses of minerals and whole-rock samples of garnet websterites entrained in basanite tuffs in Bullenmerri and Gnotuk maars, southeastern Australia, are here combined with detailed petrographic observations to constrain the sources and genesis of the pyroxenites, and to trace the dynamic evolution of the lithospheric mantle. Most garnet websterites have high MgO and Cr2O3 contents, relatively flat light rare earth element (LREE) patterns ([La/Nd]CN?=?0•77-2•22) and ocean island basalt-like Sr-, Nd-, and Hf-isotope compositions [87Sr/86Sr?=?0•70412-0•70657; eNd(t)?=?-0•32 to +4•46; eHf(t)=+1•69 to +18•6] in clinopyroxenes. Some samples show subduction-related signatures with strong enrichments in large ion lithophile elements and LREE, and negative anomalies in high field strength elements, as well as high 87Sr/86Sr (up to 0•709), and decoupled Hf- and Nd-isotope compositions [eNd(t)?=?-3•28; eHf(t) =?+11•6). These data suggest that the garnet pyroxenites represent early crystallization products of mafic melts derived from a convective mantle wedge. Hf model ages and Sm-Nd mineral isochrons suggest that these pyroxenites record at least two stages of evolution. The initial formation stage corresponds to the Paleozoic subduction of the proto-Pacific plate beneath southeastern Australia, which generated hydrous tholeiitic melts that crystallized clinopyroxene-dominated pyroxenites at ~1420-1450°C and ~75?km depth in the mantle wedge. The second stage corresponds to Eocene (c. 40?Ma) back-arc lithospheric extension, which led to uplift of the former mantle-wedge domain to 40-60?km depths, and subsequent cooling to the ambient geotherm (~950-1100°C). Extensive exsolution and recrystallization of garnet and orthopyroxene (±?ilmenite) from clinopyroxene megacrysts accompanied this stage. The timing of these mantle events coincides with vertical tectonism in the overlying crust.
DS202007-1161
2020
Xiong, Q.Lu, J., Tilhac, R., Griffin, W.L., Zheng, J.P., Xiong, Q., Oliveira, B., O'Reilly, S.Y.Lithospheric memory of subduction in mantle pyroxenite xenoliths from rift related basalts.Earth and Planetary Science Letters, Vol. 544, 116365 14p. PdfAustraliacarbonatite

Abstract: Petrological and geochemical studies have revealed the contribution of garnet pyroxenites in basalt petrogenesis. However, whether primary mantle melts are produced with such signature or acquired it subsequently remains somewhat controversial. We here integrate new major-, trace-element and Sr-Nd-Hf isotopic compositions of garnet pyroxenite xenoliths in Holocene alkali basalts from Lakes Bullenmerri and Gnotuk, Southeastern Australia, to relate their petrogenesis to mantle-wedge melt circulation and subsequent lithospheric evolution. Results show that the clinopyroxenites have lower MgO and Cr2O3 contents than the associated websterites, and range in compositions from depleted LREE patterns and highly radiogenic Nd and Hf isotopic signatures in relatively low-MgO samples (Type 1), to enriched REE patterns with negative HFSE anomalies, unradiogenic Nd and Hf isotopes, and extremely radiogenic Sr-isotopic ratios in samples with higher MgO (Type 2). Such compositional variabilities suggest that these pyroxenites represent segregates from melts derived from a recycled oceanic lithosphere with a potential contribution from pelagic sediments. Variable LREE contents and isotopic compositions between those of Type 1 and 2 clinopyroxenites are observed in amphibole-bearing samples (Type 3), which are interpreted as Type 1-like protoliths metasomatized by the basaltic and carbonatitic melts, possibly parental to Type 2 clinopyroxenites. The lithosphere beneath Southeastern Australia thus has received variable melt contributions from a heterogeneous mantle-wedge source, which notably includes a subducted oceanic slab package that has retained its integrity during subduction. On this basis, we suggest that the compositional heterogeneity and temporal evolution of the subsequent Southeastern Australian basaltic magmatism were probably affected by the presence of pyroxenite fragments in the basalt source and formed by the tectonic reactivation of this lithosphere during Cenozoic rifting. This interpretation is notably consistent with a trend of Nd-Pb isotopes towards EMII in Older Volcanic Provinces (OVP basalts) and limited Sr-Nd-Pb isotopic variations towards HIMU in the Newer Volcanic Provinces (NVP basalts, including the host lavas), which also exhibit low SiO2, high FeO and high CaO/Al2O3 commonly interpreted as due to pyroxenite contributions. Therefore, the identification of a subduction signature in these rift-related lavas attests to a "lithospheric memory" of earlier subduction episodes (as documented by the xenoliths), rather than a reflection of contemporaneous subduction tectonics.
DS202009-1622
2020
Xiong, Q.Dai, H-K., Zheng, J.P., Griffin, W.L., O'Reilly, S.Y., Xiong, Q., Ping, X., Chen, F-K., Lu, J.Pyroxenite xenoliths record complex melt impregnation in the deep lithosphere of the northwestern North China Craton.Journal of Petrology, 10.1093/petrology/egaa079 110p. PdfChinaxenoliths

Abstract: Transformation of refractory cratonic mantle into more fertile lithologies is the key to the fate of cratonic lithosphere. This process has been extensively studied in the eastern North China Craton (NCC) while that of its western part is still poorly constrained. A comprehensive study of newly-found pyroxenite xenoliths from the Langshan area, in the northwestern part of this craton is integrated with a regional synthesis of pyroxenite and peridotite xenoliths to constrain the petrogenesis of the pyroxenites and provide an overview of the processes involved in the modification of the deep lithosphere. The Langshan pyroxenites are of two types, high-Mg# [Mg2+/(Mg2++Fe2+)*100 = ~ 90, atomic ratios] olivine-bearing websterites with high equilibration temperatures (880 ~ 970 oC), and low-Mg# (70 ~ 80) plagioclase-bearing websterites with low equilibration temperatures (550 ~ 835 oC). The high-Mg# pyroxenites show trade-off abundances of olivine and orthopyroxene, highly depleted bulk Sr-Nd (?Nd?=?+11.41, 87Sr/86Sr = ~0.7034) and low clinopyroxene Sr isotopic ratios (mean 87Sr/86Sr = ~0.703). They are considered to reflect the reaction of mantle peridotites with silica-rich silicate melts derived from the convective mantle. Their depletion in fusible components (e.g., FeO, TiO2 and Na2O) and progressive exhaustion of incompatible elements suggest melt extraction after their formation. The low-Mg# pyroxenites display layered structures, convex-upward rare earth element patterns, moderately enriched bulk Sr-Nd isotopic ratios (?Nd = -14.20 ~ -16.74, 87Sr/86Sr?=?0.7070 ~ 0.7078) and variable clinopyroxene Sr-isotope ratios (87Sr/86Sr?=?0.706-0.711). They are interpreted to be crustal cumulates from hypersthene-normative melts generated by interaction between the asthenosphere and heterogeneous lithospheric mantle. Combined with studies on regional peridotite xenoliths, it is shown that the thinning and refertilization of the lithospheric mantle was accompanied by crustal rejuvenation and that such processes occurred ubiquitously in the northwestern part of the NCC. A geodynamic model is proposed for the evolution of the deep lithosphere, which includes long-term mass transfer through a mantle wedge into the deep crust from the Paleozoic to the Cenozoic, triggered by subduction of the Paleo-Asian ocean and the Late Mesozoic lithospheric extension of eastern Asia.
DS202105-0759
2021
Xiong, Q.Dai, H-K., Zheng, J-P., Griffin, W.L., O'Reilly, S.Y., Xiong, Q., Ping, X-Q., Chen, F-K., Lu, J-G.Pyroxenite xenoliths record complex melt impregnation in the deep lithosphere of the northwestern North China craton.Journal of Petrology, Vol. 62, 2, pp. 1-32. pdf.ChinaCraton

Abstract: Transformation of refractory cratonic mantle into more fertile lithologies is the key to the fate of cratonic lithosphere. This process has been extensively studied in the eastern North China Craton (NCC) while that of its western part is still poorly constrained. A comprehensive study of newly-found pyroxenite xenoliths from the Langshan area, in the northwestern part of this craton is integrated with a regional synthesis of pyroxenite and peridotite xenoliths to constrain the petrogenesis of the pyroxenites and provide an overview of the processes involved in the modification of the deep lithosphere. The Langshan pyroxenites are of two types, high-Mg# [Mg2+/(Mg2++Fe2+)*100 = ~90, atomic ratios] olivine-bearing websterites with high equilibration temperatures (880-970 oC), and low-Mg# (70-80) plagioclase-bearing websterites with low equilibration temperatures (550-835 oC). The high-Mg# pyroxenites show trade-off abundances of olivine and orthopyroxene, highly depleted bulk Sr-Nd (eNd = +11•41, 87Sr/86Sr = ~0•7034) and low clinopyroxene Sr isotopic ratios (mean 87Sr/86Sr = ~0•703). They are considered to reflect the reaction of mantle peridotites with silica-rich silicate melts derived from the convective mantle. Their depletion in fusible components (e.g., FeO, TiO2 and Na2O) and progressive exhaustion of incompatible elements suggest melt extraction after their formation. The low-Mg# pyroxenites display layered structures, convex-upward rare earth element patterns, moderately enriched bulk Sr-Nd isotopic ratios (eNd = -14•20- -16•74, 87Sr/86Sr = 0•7070-0•7078) and variable clinopyroxene Sr-isotope ratios (87Sr/86Sr = 0•706-0•711). They are interpreted to be crustal cumulates from hypersthene-normative melts generated by interaction between the asthenosphere and heterogeneous lithospheric mantle. Combined with studies on regional peridotite xenoliths, it is shown that the thinning and refertilization of the lithospheric mantle was accompanied by crustal rejuvenation and that such processes occurred ubiquitously in the northwestern part of the NCC. A geodynamic model is proposed for the evolution of the deep lithosphere, which includes long-term mass transfer through a mantle wedge into the deep crust from the Paleozoic to the Cenozoic, triggered by subduction of the Paleo-Asian Ocean and the Late Mesozoic lithospheric extension of eastern Asia.
DS201810-2324
2018
Xiong, Q..Griffin, W.L., Howell, D., Gonzalez-Jimenez, J.M., Xiong, Q.., O'Reilly, S.Y.Comment: Ultra high pressure and ultra reduced minerals in ophiolites may form by lightning strikes. Super Reduced Minerals SURGeochemical Perspectives Letters, Vol. 7, pp. 1-2.Mantlemoissanite

Abstract: Ballhaus et al. (2017) use electric-discharge experiments to argue that lightning strikes could produce ultra-high pressure (UHP) and super-reduced (SuR) phases "identical to those found in 'high-pressure' ophiolites" and that thus there is "not sufficient evidence to challenge long-established models of ophiolite genesis", specifically for the UHP processing of Tibetan ophiolites. However, the authors produced no evidence for UHP phases in their experiments. There are pertinent observations, relevant to the authors’ assertions, in the literature regarding the relationship between the UHP and SuR assemblages in the Tibetan peridotites. Their conclusions are not consistent with this evidence.
DS200912-0858
2009
Xiong, X.Zhao, Z., Xiong, X., Wang, Q., Bai, Z., Qiao, Y.Late Paleozoic underplating in North Xinjiang: evidence from shoshonites and adakites.Gondwana Research, Vol. 18, 2, pp. 216-226.ChinaShoshonite
DS201412-0520
2014
Xiong, X.Liu, X., Xiong, X., Audetat, A., Li, Y., Song, M., Li, L., Sun, W., Ding, X.Partitioning of copper between olivine, orthopyroxene, clinopyroxene, spinel, garnet, and silicate melts at upper mantle conditions.Geochimica et Cosmochimica Acta, Vol. 125, pp. 1-22.MantleMineral chemistry
DS200612-1555
2006
Xiong, X.L.Xiong, X.L., Xia, B., Hu, J.F., Niu, H.C., Xiao, W.S.Na depletion in modern adakites via melt/rock reaction within the subarc mantle.Chemical Geology, Vol. 229, 4, May 30, pp. 273-292.MantleSlab, subduction, melting
DS2003-1120
2003
Xiong, X.M.Qian, Q., Chu, M.F., Chung, S.L., Lee, T.Y., Xiong, X.M.Was Triassic continental subduction solely responsible for the generation of MesozoicInternational Geology Review, Vol. 45, 7, July pp. 659-70.ChinaMagmatism - UHP
DS2003-1121
2003
Xiong, X.M.Qian, Q., Chu, M.-F., Chung, S.L., Tung, Y.L., Xiong, X.M.Was Triassic continental subduction soley responsible for the generation of MesozoicInternational Geology Review, Vol. 45, 7, July pp. 659-ChinaMagmatism, UHP
DS200412-1604
2003
Xiong, X.M.Qian, Q., Chu, M.F., Chung, S.L., Lee, T.Y., Xiong, X.M.Was Triassic continental subduction solely responsible for the generation of Mesozoic mafic magmas and mantle source enrichmentInternational Geology Review, Vol. 45, 7, July pp. 659-70.ChinaMagmatism - UHP
DS200612-1507
2006
Xiong, X-L.Wang, Q., Wyman, D.A., Xu, J-F., Zhao, Z-H., Jian, P., Xiong, X-L., Bao, Z-W., Li, C-F., Bai, Z-H.Petrogenesis of Cretaceous adakitic and shoshonitic igneous rocks in the Luzong area, Anhui Province: implications for geodynamics and Cu-Au mineralization.Lithos, In pressChinaShoshonites - not specific to diamond
DS200712-1192
2006
Xiong, X-L.Xiong, X-L.Trace element evidence for growth of early continental crust by melting of rutile eclogite.Geology, Vol. 37, 11, pp. 945-948.MantleMelting - not specific to diamonds
DS202105-0768
2020
Xiong, Y.Jiang, S. Su, H., Xiong, Y., Liu, T., Zhu, K., Zhang, L.Spatial temporal distribution, geological characteristics and ore formation controlling factors of major types of rare metal mineral deposits in China.Acta Geologica Sinica, Vol. 94, 6, pp. 1757-1773.ChinaREE

Abstract: Rare metals including Lithium (Li), Beryllium (Be), Rubidium (Rb), Cesium (Cs), Zirconium (Zr), Hafnium (Hf), Niobium (Nb), Tantalum (Ta), Tungsten (W) and Tin (Sn) are important critical mineral resources. In China, rare metal mineral deposits are spatially distributed mainly in the Altay and Southern Great Xingán Range regions in the Central Asian orogenic belt; in the Middle Qilian, South Qinling and East Qinling mountains regions in the Qilian-Qinling-Dabie orogenic belt; in the Western Sichuan and Bailongshan-Dahongliutan regions in the Kunlun-Songpan-Garze orogenic belt, and in the Northeastern Jiangxi, Northwestern Jiangxi, and Southern Hunan regions in South China. Major ore-forming epochs include Indosinian (mostly 200-240 Ma, in particular in western China) and the Yanshanian (mostly 120-160 Ma, in particular in South China). In addition, Bayan Obo, Inner Mongolia, northeastern China, with a complex formation history, hosts the largest REE and Nb deposits in China. There are six major rare metal mineral deposit types in China: Highly fractionated granite; Pegmatite; Alkaline granite; Carbonatite and alkaline rock; Volcanic; and Hydrothermal types. Two further types, namely the Leptynite type and Breccia pipe type, have recently been discovered in China, and are represented by the Yushishan Nb-Ta- (Zr-Hf-REE) and the Weilasituo Li-Rb-Sn-W-Zn-Pb deposits. Several most important controlling factors for rare metal mineral deposits are discussed, including geochemical behaviors and sources of the rare metals, highly evolved magmatic fractionation, and structural controls such as the metamorphic core complex setting, with a revised conceptual model for the latter.
DS1990-1633
1990
Xiong BaochengZhou Gaozhi, Xiong Baocheng, Liou, J.G., et al.Occurrence and mineral parageneses of abundant eclogitic rocks from northern Hubei, Central ChinaEos, Vol. 71, No. 43, October 23, p. 1708 AbstractChinaEclogite, Paragenesis
DS1985-0744
1985
Xiong dahe, LU ZHAOTIAN.Xiong dahe, LU ZHAOTIAN.Experimental studies using calcium carbonate as a carbon source for synthesizing diamonds.*CHIScientia Sinica Ser. B., *CHI, 1985 No. 3, pp. 259-265ChinaDiamond Morphology
DS1993-1783
1993
Xiping WuXiping Wu, Yingxin ZhouReserve estimation using neural network techniquesComputers and Geosciences, Vol. 19, No. 4, pp. 567-576GlobalOre reserve estimation, Geostatistics
DS2001-1269
2001
Xirouchakis, D.Xirouchakis, D., Hirschmann, M.M., Simpson, J.A.The effect of titanium on the silica content and on mineral liquid partitioning mantle equilibrated melts.Geochimica et Cosmochimica Acta, Vol. 65, No. 14, pp. 2201-2217.MantleMelting - not specific to kimberlites, Olivine, orthopyroxene saturated mafic
DS2003-1568
2003
Xisheng XuZou, H.,Reid, M.R., Yongshun Liu, Yupeng Yao, Xisheng Xu, Qicheng FanConstraints on the origin of historic potassic basalts from northeast Chin a by U ThChemical Geology, Vol. 200, 1-2, Oct. 16, pp. 189-201.ChinaPhlogopite garnet bearing peridotite, melting, metasoma
DS200412-2239
2003
Xisheng XuZou, H.,Reid, M.R., Yongshun Liu, Yupeng Yao, Xisheng Xu, Qicheng FanConstraints on the origin of historic potassic basalts from northeast Chin a by U Th disequilibrium data.Chemical Geology, Vol. 200, 1-2, Oct. 16, pp. 189-201.ChinaPhlogopite garnet bearing peridotite, melting, metasoma
DS2002-0360
2002
Xiuling, W.Dawer, M., Xiuling, W., Yujing, H., Xin, M.Ultra structure of coesite - retrogressive metamorphic quartz and their interface transition belt from ultra high pressure metamorphic rocks.18th. International Mineralogical Association Sept. 1-6, Edinburgh, abstract p.72.MantleUHP, mineralogy, coesite
DS1988-0780
1988
XiuyingZhao, XiuyingRelation between pyrope and diamond in kimberlites,Liaoning province, China. *CHIKuangwu Xuebao, *CHI, Vol. 8, No. 1, pp. 31-38ChinaDiamond morphology, Pyrope
DS1990-1630
1990
XixiZhao, Xixi, Coe, R.S., Zhou Yaoxiu, Wu Haoruo, Wang, JieNew paleomagnetic results from northern China: collision and suturing with Siberia and KazakhstanTectonophysics, Vol. 181, pp. 43-81China, RussiaGeophysics, Paleomagnetics
DS201802-0268
2018
X-LSun, W-d., Hawkesworth, C.J., Yao, C., Zhang, C-C., Huang, R.f., Liu, X., Sun, X-L, Ireland, T., Song, M-s., Ling, M-x., Ding, X., Zhang, Z-f., Fan, W-m., Wu, Z-q.Carbonated mantle domains at the base of the Earth's transition zone.Chemical Geology, Vol. 478, pp. 69-75.Mantlecarbonatite

Abstract: The oxygen fugacity of the upper mantle is 3-4 orders of magnitude higher than that of the lower mantle and this has been attributed to Fe2 + disproportionating into Fe3 + plus Fe0 at pressures > 24 GPa. The upper mantle might therefore have been expected to have evolved to more oxidizing compositions through geological time, but it appears that the oxygen fugacity of the upper mantle has remained constant for the last 3.5 billion years. Thus, it indicates that the mantle has been actively buffered from the accumulation of Fe3 +, and that this is linked to oxidation of diamond to carbonate coupled with reduction of Fe3 + to Fe2 +. When subducted plates penetrate into the lower mantle, compensational upwelling transports bridgmanite into the transition zone, where it breaks down to ringwoodite and majorite, releasing the ferric iron. The system returns to equilibrium through oxidation of diamond. Early in Earth history, diamond may have been enriched at the base of the transition zone in the Magma Ocean, because it is denser than peridotite melts at depths shallower than 660 km, and it is more buoyant below. Ongoing oxidation of diamond forms carbonate, leading to relatively high carbonate concentrations in the source of ocean island basalts.
DS200612-0838
2006
XoLu, X.P., Wu, F.Y., Guo, J.H., Wilde, S.A., Yang, J.H., Liu, X.M., Zhang, XoZircon U Pb geochronological constraints on the Paleoproterozoic crustal evolution of the Eastern Block in the North Chin a Craton.Precambrian Research, Vol. 146, 3-4, pp. 138-164.ChinaGeochronology
DS200612-0815
2006
X-QLiang, X-Q, Fan, W-M., Wang, Y-J., Xian, H.Early Mesozoic post collisional shoshonitic lamprophyres along the western margin of the South Chin a orogen; geochemical characteristics and tectonicInternational Geology Review, Vol. 48, 4, pp. 311-328.ChinaGeochemistry - shoshonites
DS1990-1624
1990
XuZhang Andi, Meyer, H.O.A., Guo Lihe, Zhou Jianxiong, Xie Xilin, Wang Alian, XuComparative study of inclusions in diamonds with macrocrysts From kimberlites in north Chin a cratonInternational Mineralogical Association Meeting Held June, 1990 Beijing China, Vol. 1, extended abstract p. 504-505ChinaDiamond inclusions, Macrocrysts
DS1992-0468
1992
XuFitches, W.R., Fletcher, C.J.N., Jiawei, XuGeotectonic relationships between cratonic blocks in E. Chin a and KoreaJournal of Southeast Asian Earth Science, Vol. 6, No. 3-4, pp. 185-199China, KoreaTectonics, Craton
DS1992-1706
1992
XuXu, Shutong, Okay, A.I., Ji, S.Y., Sengor, A.H.C., Wen, S., LiuDiamond from the Dabie-Shaw metamorphic rocks and its implication for tectonic settingScience, Vol. 256, No. 5053, April 3, pp. 80-82ChinaMetamorphic rocks, Diamonds
DS1992-1707
1992
XuXu, Shutong, Su W., Liu, YC, Jiang, LLDiamonds from high-pressure metamorphic rocks in eastern Dabie Mountains.*CHIChin. Sci. B., *CHI, Vol. 37, No. 2, January pp. 140-145. # H331ChinaMetamorphic rocks, Dabie Mountains
DS1994-1959
1994
XuXu, AnshunGeochemistry of the Elk Creek carbonatite, Johnson County, NebraskaEos, Annual Meeting November 1, Vol. 75, No. 44, p.709. abstractNebraskaCarbonatite
DS1995-2092
1995
XuXu, Anshun, Goble, R.J., Treves, S.B.Distribution of rare earth elements in the rocks and minerals of the ElkCreek carbonatite.Geological Society of America (GSA) Abstracts, Vol. 27, No. 3, p. 98.NebraskaCarbonatite, Rare earths
DS1996-1526
1996
XuWen, Su, Shutong, Xu, Laili, J., Yican, LiuCoesite from quartz jadeitite in the Dabie Mountains, eastern ChinaMineralogical Magazine, Vol. 60, pp. 659-662.ChinaCoesite
DS1996-1570
1996
XuXu, AnshunMineralogy, petrology, geochemistry and origin of the Elk Creekcarbonatite, Nebraska.Thesis, Ph.d. University of Nebraska, 299p. avail. University of Microfilms96-82130-B.NebraskaCarbonatite, Elk Creek
DS2002-0614
2002
XuGriffin, W.L., Wang, X., Jackson, Pearson, O'Reilly, XuZircon chemistry and magma mixing, SE China: in situ analysis of Hf isotopes, Tonglu and Pingtan complexes.Lithos, Vol.61, No.1-4, pp. 237-69., Vol.61, No.1-4, pp. 237-69.China, SoutheastGeochemistry - magma mixing, Geochronology
DS2002-0615
2002
XuGriffin, W.L., Wang, X., Jackson, Pearson, O'Reilly, XuZircon chemistry and magma mixing, SE China: in situ analysis of Hf isotopes, Tonglu and Pingtan complexes.Lithos, Vol.61, No.1-4, pp. 237-69., Vol.61, No.1-4, pp. 237-69.China, SoutheastGeochemistry - magma mixing, Geochronology
DS2002-1685
2002
XuWang, X., Griffin, O'Reilly, Zhou, Xu, Jackson, PearsonMorphology and geochemistry of zircons from late Mesozoic igneous complexes in coastal SE China:Mineralogical Magazine, Vol.66,2,pp. 235-52., Vol.66,2,pp. 235-52.China, southeastPetrogenesis
DS2002-1686
2002
XuWang, X., Griffin, O'Reilly, Zhou, Xu, Jackson, PearsonMorphology and geochemistry of zircons from late Mesozoic igneous complexes in coastal SE China:Mineralogical Magazine, Vol.66,2,pp. 235-52., Vol.66,2,pp. 235-52.China, southeastPetrogenesis
DS2003-1314
2003
XuSong, S.G., Yang, J.S., Xu, ZQ, Shi, R.D.Metamorphic evolution of the coesite bearing ultrahigh pressure terrane in the NorthJournal of Metamorphic Geology, Vol. 21, 6, pp. 631-44.ChinaUHP
DS200412-1880
2003
XuSong, S.G., Yang, J.S., Xu, ZQ, Shi, R.D.Metamorphic evolution of the coesite bearing ultrahigh pressure terrane in the North Qaidam northern Tibet, NW China.Journal of Metamorphic Geology, Vol. 21, 6, pp. 631-44.ChinaUHP
DS200412-2174
2003
XuYang, Y.S., Wooden, J.L., Wu,C.L., Liu, F.L., Xu,ZQ, Shi, R.D., Katayama, I., Liou, J.G., Maruyama, S.SHRIMP U Pb dating of coesite bearing zircon from the ultrahigh pressure metamorphic rocks, Sulu terrane, east China.Journal of Metamorphic Geology, Vol. 21, 6, pp. 551-60.ChinaUHP
DS200712-0204
2007
XuCourtier, A.M., Jackson, Lawrence, Wang, Lee, Halama, Warren, Workman, Xu, Hirschmann, Larson, Hart, Lithgo-Bertelloni, Stixrude, ChenCorrelation of seismic and petrologic thermometers suggests deep thermal anomalies beneath hotspots.Earth and Planetary Science Letters, Vol. 264, 1-2, pp. 308-316.MantleGeothermometry
DS200812-0385
2008
XuGao, S., Rudnick, R.L., Xu, Yuan, Liu, Walker, Puchtel, Liu, Huang, Wang, WangRecycling deep cratonic lithosphere and generation of intraplate magmatism in the North Chin a Craton.Earth and Planetary Science Letters, Vol. 270, 1-2, June 15, pp. 41-53.ChinaTectonics - delamination, picrites
DS201012-0421
2010
XuKynicky, J., Chakhmouradian, A.R., Cheng, Xu, Krmicek, L., Krmickova, M., Davis, B.Evolution of rare earth mineralization in carbonatites of the Lugiin Gol complex southern Mongolia.International Mineralogical Association meeting August Budapest, abstract p. 573.Asia, MongoliaCarbonatite
DS201506-0300
2015
XuWu, Xiao, Xu, Santosh, Li, Huang, Hou.Geochronology and geochemistry of felsic xenoliths in lamprophyre dikes from the southeastern margin of the North Chin a Craton: implications for the interleaving of the Dabie Sulu orogenic crust.International Geology Review, Vol. 57, 9-10, pp. 1305-1325.ChinaDabie Sulu
DS201605-0863
2016
XuMa, L., Jiang, S-Y., Hofmann, A.W., Xu, Y-G, Dai, B-Z., Hou, M-L.Rapid lithospheric thinning of North Chin a craton: new evidence from Cretaceous mafic dikes in the Jiaodong Peninsula.Chemical Geology, Vol. 432, pp. 1-15.ChinaDikes

Abstract: The North China Craton is a classic case for the destruction of an ancient craton, in that it records the loss of more than 100 km of ancient refractory lithospheric mantle during the late Mesozoic and early Cenozoic. However, the mechanisms for this lithospheric thinning remain controversial in large part due to the lack of any systematic investigations of the Mesozoic asthenospheric mantle via its derived mafic rocks, which are key to understand the thinning processes. In this paper, we present detailed zircon U-Pb geochronology, elemental geochemistry, and Sr-Nd-Hf isotopic data for lamprophyres and diabase-porphyries of the Jiaodong Peninsula, in the eastern North China Craton in order to place constraints on models for lithospheric thinning. Our results show that the lamprophyres and diabase-porphyries are derived from the convective asthenospheric mantle via different degrees of partial melting, and that this mantle source was previously modified by carbonatitic liquids. Zircon LA-ICP-MS U-Pb dating suggests an emplacement age for these rocks of 123-121 Ma, the earliest evidence for asthenospherically-derived melts in the Jiaodong Peninsula so far. This emplacement age indicates that the thickness of the lithosphere in the Jiaodong Peninsula was relatively thin at that time. Co-occurrence of the asthenospheric and lithospheric mantle-derived mafic rocks as well as high-Mg adakites record a rapid transition from lithospheric to asthenospheric mantle sources, indicating that the lithosphere beneath the Jiaodong Peninsula was rapidly detached just prior to ca. 120 Ma. Lithospheric thinning of the North China Craton may have been initiated from the Jiaodong Peninsula and Bohai Sea and then propagated towards the interior of the craton.
DS2000-1031
2000
Xu, B.Xu, B., Grove, M., Liu, S.40 Ar-39 Ar thermochronology from the northwestern Dabie Shan: constraints on evolution of Qinling-DabieTectonophysics, Vol. 322, No. 3-4, July 30, pp. 279-301.China, East CentralTectonics, geothermal, geochronology, Argon, Dabie Shan orogenic belt
DS200812-0657
2008
Xu, B.Li, L., Xu, B., li, M.Analysis of the carbon source for diamond crystal growth.Chinese Science Bulletin, Vol. 53, 6, pp. 937-942.TechnologyDiamond synthesis
DS201412-0383
2014
Xu, B.Huang, Q., Yu, D., Xu, B., Hu, W., Ma, Y., Wang, Y., Zhao, Z., Wen, B., He, J., Liu, Z., Tian, Y.Nanotwinned diamond with unprecedented hardness and stability.Nature, Vol. 510, June 12, pp. 250-253.TechnologyDiamond synthetic
DS201702-0254
2017
Xu, B.Xu, B., Griffin, W.L., Xiong, Q., Hou, Z-Q, O'Reilly, S.Y., Guo, Z., Pearson, N.J., Greau, Y., Yang, Z-M., Zheng, Y-C.Ultrapotassic rocks and xenoliths from South Tibet: contrasting styles of interaction between lithospheric mantle and asthenosphere during continental collision.Geology, Vol. 45, 1, pp. 51-54.China, TibetUPR - metasomatism

Abstract: Widespread Miocene (24-8 Ma) ultrapotassic rocks and their entrained xenoliths provide information on the composition, structure, and thermal state of the sub-continental lithospheric mantle in southern Tibet during the India-Asia continental collision. The ultrapotassic rocks along the Lhasa block delineate two distinct lithospheric domains with different histories of depletion and enrichment. The eastern ultrapotassic rocks (89°E-92°E) reveal a depleted, young, and fertile lithospheric mantle (87Sr/86Srt = 0.704-0.707 [t is eruption time]; Hf depleted-mantle model age [TDM] = 377-653 Ma). The western ultrapotassic rocks (79°E-89°E) and their peridotite xenoliths (81°E) reflect a refractory harzburgitic mantle refertilized by ancient metasomatism (lavas: 87Sr/86Srt = 0.714-0.734; peridotites: 87Sr/86Srt = 0.709-0.716). These data integrated with seismic tomography suggest that upwelling asthenosphere was diverted away from the deep continental root beneath the western Lhasa block, but rose to shallower depths beneath a thinner lithosphere in the eastern part. Heating of the lithospheric mantle by the rising asthenosphere ultimately generated the ultrapotassic rocks with regionally distinct geochemical signatures reflecting the different nature of the lithospheric mantle.
DS202002-0185
2020
Xu, B.Forster, M.W., Buhre, S., Xu, B., Prelevic, D., Mertz-Kraus, R., Foley, S.F.Two stage origin of K-enrichment in ultrapotassic magmatism simulated by melting of experimentally metasomatized mantle.MDPI Minerals, Vol. 10, 41;doe.10.3390/min10010041 21p. PdfMantlemetasomatism

Abstract: The generation of strongly potassic melts in the mantle requires the presence of phlogopite in the melting assemblage, while isotopic and trace element analyses of ultrapotassic rocks frequently indicate the involvement of subducted crustal lithologies in the source. However, phlogopite-free experiments that focus on melting of sedimentary rocks and subsequent hybridization with mantle rocks at pressures of 1-3 GPa have not successfully produced melts with K2O >5 wt%-6 wt%, while ultrapotassic igneous rocks reach up to 12 wt% K2O. Accordingly, a two-stage process that enriches K2O and increases K/Na in intermediary assemblages in the source prior to ultrapotassic magmatism seems likely. Here, we simulate this two-stage formation of ultrapotassic magmas using an experimental approach that involves re-melting of parts of an experimental product in a second experiment. In the first stage, reaction experiments containing layered sediment and dunite produced a modally metasomatized reaction zone at the border of a depleted peridotite. For the second-stage experiment, the metasomatized dunite was separated from the residue of the sedimentary rock and transferred to a smaller capsule, and melts were produced with 8 wt%-8.5 wt% K2O and K/Na of 6-7. This is the first time that extremely K-enriched ultrapotassic melts have been generated experimentally from sediments at low pressure applicable to a post-collisional setting.
DS202108-1310
2021
Xu, B.Tang, L., Wagner, T., Fusswinkel, T., Zhang, S-T., Xu, B., Jia, L-H.Magmatic-hydrothermal evolution of an unusual Mo-rich carbonatite: a case study using LA-ICP-MS fluid inclusion microanalysis and He-Ar isotopes from the Huanshuiian deposit, Qinling, China.Mineralium Deposita, 18p. PdfChinadeposit - Huanshuian

Abstract: The Huangshui'an deposit located in East Qinling (China) is an unusual case of a Si-rich carbonatite hosting economic Mo and minor Pb and REE mineralization. The role of mantle-sourced carbonatite melts and fluids in the formation of the Mo mineralization remains poorly understood. Our integrated study based on field geology, petrography, microthermometry, and LA-ICP-MS analysis of single fluid inclusions, and noble gas isotopes of pyrite permits to reconstruct the source characteristics, the magmatic-hydrothermal evolution of the carbonatitic fluids, and their controls on Mo mineralization. Fluid inclusions hosted in calcite in the carbonatite dikes have the highest concentrations of Mo (9.9-62 ppm), Ce (820-9700 ppm), Pb (1800-19500 ppm), and Zn (570-5800 ppm) and represent the least modified hydrothermal fluid derived from the carbonatite melt. Fluid inclusions hosted in calcite (Cal) and quartz (Qz2 and Qz3) of the stage I carbonatite dikes have different metal concentrations, suggesting that they formed from two distinct end member fluids. The FIA in calcite represent fluid A evolved from carbonatite melt with relatively high-ore metal concentrations, and those in quartz characterize fluid B having a crustal signature due to metasomatic reactions with the wall rocks. The FIA in quartz (Qz1) within the altered wall rock have overlapping elemental concentrations with those of massive quartz (Qz2) and vuggy quartz (Qz3) in carbonatite. This suggests that the volumetrically significant quartz in the Huangshui'an carbonatite has been formed by the introduction of Si by fluid B. The positive correlations between Rb, B, Al, Cl, and Sr in stage II fluid inclusions in late fluorite + quartz + calcite veins indicate that this late mineralization formed from the mixing of primary hydrothermal fluid B with meteoric water. The He-Ar isotope data, in combination with available C-O-Sr-Nd-Pb isotope data, constrain the carbonatite source as an enriched mantle source modified by contributions from crustal material which was probably the fertile lower crust in the region. This distinct source facilitated the enrichment in Mo, REE, and Pb in the primary carbonatite magma. The carbonatite magmatism and Mo mineralization at 209.5-207 Ma occurred in the regional-scale extensional setting at the postcollision stage of the Qinling Orogenic Belt.
DS1996-1601
1996
Xu, C.Zhang, Y., Wan, H., Xu, C.The characteristics of the extrusive carbonatite in Guantian area WudingCounty, Yunnan Province.International Geological Congress 30th Session Beijing, Abstracts, Vol. 2, p. 398.ChinaCarbonatite
DS2000-0602
2000
Xu, C.Ma, C., Ehlers, C., Xu, C., Li, Z., Yang, K.The roots of the Dabie Shan ultrahigh pressure metamorphic terrane: constraints from geochemistry ...Precambrian Research, Vol. 102, No. 3-4, Aug.pp. 279-301.Chinaultra high pressure (UHP), geochronology, Dabie Shan region
DS2000-1043
2000
Xu, C.Yongbei, Zhang, Zhao, C., Xu, C.The characteristics of apatitic carbonatite of Proterozoic Kunyang Rift, Yunnan China.Igc 30th. Brasil, Aug. abstract only 1p.ChinaCarbonatititic tuff
DS2003-1155
2003
Xu, C.Reiners, P.W., Zhou, Z., Ehlers, T.A., Xu, C., Brandon, M.T., Donelick, R.A.Post orogenic evolution of the Dabie Shan, eastern Chin a ( U Th) He and fission trackAmerican Journal of Science, Vol. 303, 6, pp. 489-518.ChinaGeothermometry, UHP
DS2003-1508
2003
Xu, C.Xu, C.The cause of formation of the upper mantle and crust high conductive layers in ChineseEarth Science Frontiers, Vol. 10, supp. pp. 101-111.ChinaTectonics - seismics
DS200412-1652
2003
Xu, C.Reiners, P.W., Zhou, Z., Ehlers, T.A., Xu, C., Brandon, M.T., Donelick, R.A., Nicolescu, S.Post orogenic evolution of the Dabie Shan, eastern Chin a ( U Th) He and fission track thermochronology.American Journal of Science, Vol. 303, 6, pp. 489-518.ChinaGeothermometry UHP
DS200412-2156
2003
Xu, C.Xu, C.The cause of formation of the upper mantle and crust high conductive layers in Chinese maIn land and the study of Tangshan earthqEarth Science Frontiers, Vol. 10, supp. pp. 101-111.ChinaTectonics - seismics
DS200412-2157
2004
Xu, C.Xu, C., Zhang, H., Huang, Z., Liu, C., Qi, L.Li.W., Guan, T.Genesis of the carbonatite syenite complex and REE deposit at Maoniuping, Sichuan Province, China: evidence from Pb isotope geocGeochemical Journal, Vol. 38, pp. 67-76.China, SichuanGeochronology, carbonatite
DS200712-1193
2007
Xu, C.Xu, C.Why carbonatites in the Lesser Qinling have high HREE compositions?Plates, Plumes, and Paradigms, 1p. abstract p. A1133.ChinaCarbonatite
DS200712-1194
2006
Xu, C.Xu, C., Campbell, I.H., Allen, C.M., Huang, Z., Qi, L., Zhang, H., Zhang, G.Flat rare earth element patterns as an indicator of cumulate processes in the Lesser Qinlin carbonatites, China.Geochimica et Cosmochimica Acta, In press availableChinaCarbonatite, REE geochemistry
DS200812-1280
2008
Xu, C.Xu, C., Qi, L., Huang, Z., Chen, Y., Yu, X., Wang, L., Li, E.Abundances and significance of platinum group elements in carbonatites from China.Lithos, in press available, 7p.ChinaCarbonatite
DS200812-1314
2008
Xu, C.Zhang, Y., Bi, H., Yu, L., Sun, S., Qui, J., Xu, C., Wang, H., Wang, R.Evidence for metasomatic mantle carbonatitic magma extrusion in Mesoproterozoic ore hosting dolomite rocks in the middle Kunyang rift, central Yunnan China.Progress in Natural Science, Vol. 18, 8, pp. 965-974.ChinaCarbonatite
DS201012-0618
2010
Xu, C.Reguir, E., Chakhmouradian, A., Xu, C., Kynicky, J.An overview of geology, mineralogy and genesis of the giant REE-Fe-Nb deposit Bayan Obo, Inner Mongolia, China.International Workshop Geology of Rare Metals, held Nov9-10, Victoria BC, Open file 2010-10, extended abstract pp. 15-18.China, MongoliaCarbonatite
DS201012-0866
2010
Xu, C.Xu, C., Kynicky, J., ChakmourTrace element modeling of the magmatic evolution of rare earth rich carbonatite from the Miaoya deposit, central China.Lithos, in press available not formatted 32p.ChinaCarbonatite
DS201012-0867
2010
Xu, C.Xu, C., Kynicky, J., Chamouradian, A.R., Qi, L., Wenlei, SongA unique Mo deposit associated with carbonatites in the Qinling orogenic belt, central China.Lithos, In press unformatted 46p. availableChinaCarbonatite
DS201112-0852
2011
Xu, C.Reguir, E.P., Xu, C., Kynicky, J., Coueslan, C.G.Amphibole in carbonatites: an equivocal petrogenetic indicator.Peralk-Carb 2011... workshop June 16-18, Tubingen, Germany, Abstract p.126-128.MantleCarbonatite
DS201112-0853
2011
Xu, C.Reguir, E.P., Xu, C., Kynicky, J., Coueslan, C.G.Amphibole in carbonatites: an equivocal petrogenetic indicator.Peralk-Carb 2011... workshop June 16-18, Tubingen, Germany, Abstract p.126-128.MantleCarbonatite
DS201112-1127
2011
Xu, C.Xu, C., Kynicky, J., Chakhmouradian, A.R.REE deposits in China.Goldschmidt Conference 2011, abstract p.2196.ChinaCarbonatite
DS201112-1128
2011
Xu, C.Xu, C., Taylor, R.N., Kynicky, J., Chakhmouradiam, A.R., Song, W., Wang, L.The origin of enriched mantle beneath North Chin a block: evidence from young carbonatites.Lithos, Vol. 127, 1-2, pp. 1-9.ChinaCarbonatite
DS201212-0391
2012
Xu, C.Kynicky, J., Smith, M.P., Xu, C.Diversity of rare earth deposits: the key example of China.Elements, Vol. 8, 5, Oct. pp. 361-367.ChinaDeposit - Bayan Obo, carbonatite
DS201412-0995
2014
Xu, C.Xu, C., Chakhmouradian, A.R., Taylor, R.N., Kynicky, J., Li, W., Song, W., Fletcher, I.R.Origin of carbonatites in the South Qinling orogen: implications for crustal recycling and timing of collision between south and north Chin a blocks.Geochimica et Cosmochimica Acta, Vol. 143, pp. 189-206.ChinaCarbonatite
DS201602-0242
2016
Xu, C.Song, WL., Xu, C., Veksler, H.V., Kynicky, J.Experimental study of REE, Ba, Sr, Mo and W partitioning between carbonatitic melt and aqueous fluid with implications for rare metal mineralization.Contributions to Mineralogy and Petrology, Vol. 171, 12p.MantleCarbonatite

Abstract: Carbonatites host some unique ore deposits, especially rare earth elements (REE). Hydrothermal fluids have been proposed to play a significant role in the concentration and transport of REE and other rare metals in carbonatites, but experimental constraints on fluid-melt equilibria in carbonatitic systems are sparse. Here we present an experimental study of trace element (REE, Ba, Sr, Mo and W) partitioning between hydrous fluids and carbonatitic melts, bearing on potential hydrothermal activity associated with carbonatite ore-forming systems. The experiments were performed on mixtures of synthetic carbonate melts and aqueous fluids at 700-800 °C and 100-200 MPa using rapid-quench cold-seal pressure vessels and double-capsule assemblages with diamond traps for analyzing fluid precipitates in the outer capsule. Starting mixtures were composed of Ca, Mg and Na carbonates spiked with trace elements. Small amounts of F or Cl were added to some of the mixtures to study the effects of halogens on the element distribution. The results show that REE, Ba, Sr, Mo and W all preferentially partition into carbonatite melt and have fluid-melt distribution coefficients (D f/m) below unity. The REE partitioning is slightly dependent on the major element (Ca, Mg and Na) composition of the starting mixtures, and it is influenced by temperature, pressure, and the presence of halogens. The fluid-melt D values of individual REE vary from 0.02 to 0.15 with Df/mLu being larger than Df/mLa by a factor of 1.1-2. The halogens F and Cl have strong and opposite effects on the REE partitioning. Fluid-melt D REE are about three times higher in F-bearing compositions and ten times lower in Cl-bearing compositions than in halogen-free systems. Df/mW and Df/mMo are the highest among the studied elements and vary between 0.6 and 0.7; Df/mBa is between 0.05 and 0.09, whereas Df/mSr is at about 0.01-0.02. The results imply that carbonatite-related REE deposits were probably formed by fractional crystallization of carbonatitic melts rather than from exsolved hydrothermal fluids. The same appears to be true for a carbonatite-related Mo deposit recently discovered in China.
DS201702-0201
2017
Xu, C.Chakhmouradian, A.R., Rehuir, E.P., Zaitsev, A.N., Coueslan, C., Xu, C., Kynicky, J., Hamid Mumin, A., Yang, P.Apatite in carbonatitic rocks: compositional variation, zoning, element partitioning and petrogeneitic significance.Lithos, in press available, 138p.TechnologyCarbonatite

Abstract: The Late Cretaceous (ca. 100 Ma) diamondiferous Fort à la Corne (FALC) kimberlite field in the Saskatchewan (Sask) craton, Canada, is one of the largest known kimberlite fields on Earth comprising essentially pyroclastic kimberlites. Despite its discovery more than two decades ago, petrological, geochemical and petrogenetic aspects of the kimberlites in this field are largely unknown. We present here the first detailed petrological and geochemical data combined with reconnaissance Nd isotope data on drill-hole samples of five major kimberlite bodies. Petrography of the studied samples reveals that they are loosely packed, clast-supported and variably sorted, and characterised by the presence of juvenile lapilli, crystals of olivine, xenocrystal garnet (peridotitic as well as eclogitic paragenesis) and Mg-ilmenite. Interclast material is made of serpentine, phlogopite, spinel, carbonate, perovskite and rutile. The mineral compositions, whole-rock geochemistry and Nd isotopic composition (Nd: + 0.62 to - 0.37) are indistinguishable from those known from archetypal hypabyssal kimberlites. Appreciably lower bulk-rock CaO (mostly < 5 wt%) and higher La/Sm ratios (12-15; resembling those of orangeites) are a characteristic feature of these rocks. Their geochemical composition excludes any effects of significant crustal and mantle contamination/assimilation. The fractionation trends displayed suggest a primary kimberlite melt composition indistinguishable from global estimates of primary kimberlite melt, and highlight the dominance of a kimberlite magma component in the pyroclastic variants. The lack of Nb-Ta-Ti anomalies precludes any significant role of subduction-related melts/fluids in the metasomatism of the FALC kimberlite mantle source region. Their incompatible trace elements (e.g., Nb/U) have OIB-type affinities whereas the Nd isotope composition indicates a near-chondritic to slightly depleted Nd isotope composition. The Neoproterozoic (~ 0.6-0.7 Ga) depleted mantle (TDM) Nd model ages coincide with the emplacement age (ca. 673 Ma) of the Amon kimberlite sills (Baffin Island, Rae craton, Canada) and have been related to upwelling protokimberlite melts during the break-up of the Rodinia supercontinent and its separation from Laurentia (North American cratonic shield). REE inversion modelling for the FALC kimberlites as well as for the Jericho (ca. 173 Ma) and Snap Lake (ca. 537 Ma) kimberlites from the neighbouring Slave craton, Canada, indicate all of their source regions to have been extensively depleted (~ 24%) before being subjected to metasomatic enrichment (1.3-2.2%) and subsequent small-degree partial melting. These findings are similar to those previously obtained on Mesozoic kimberlites (Kaapvaal craton, southern Africa) and Mesoproterozoic kimberlites (Dharwar craton, southern India). The striking similarity in the genesis of kimberlites emplaced over broad geological time and across different supercontinents of Laurentia, Gondwanaland and Rodinia, highlights the dominant petrogenetic role of the sub-continental lithosphere. The emplacement of the FALC kimberlites can be explained both by the extensive subduction system in western North America that was established at ca. 150 Ma as well as by far-field effects of the opening of the North Atlantic ocean during the Late Cretaceous.
DS201705-0878
2017
Xu, C.Song, WL, Xu, C., Chakhmouradian, A.R., Kynicky, J., Huang, K., Zhang, ZL.Carbonatites of Tarim ( NW China): first evidence of crustal contribution in carbonatites from a large igneous province.Lithos, Vol. 282-283, pp. 1-9.ChinaCarbonatite, subduction

Abstract: Many carbonatites are associated both spatially and temporally with large igneous provinces (LIPs), and considered to originate from a mantle plume source lacking any contribution from recycled crustal materials. Here, we report an occurrence of carbonatite enriched in rare-earth elements (REE) and associated with the Tarim LIP in northwestern China. The Tarim LIP comprises intrusive and volcanic products of mantle plume activity spanning from ~ 300 to 280 Ma. The carbonatites at Wajilitage in the northwestern part of Tarim are dominated by calcite and dolomite varieties, and contain abundant REE minerals (principally, monazite and REE-fluorcarbonates). Th-Pb age determination of monazite yielded an emplacement age of 266 ± 5.3 Ma, i.e. appreciably younger than the eruption age of flood basalts at ~ 290 Ma. The carbonatites show low initial 87Sr/86Sr (0.7037-0.7041) and high eNd(t) (1.2-4) values, which depart from the isotopic characteristics of plume-derived basalts and high-Mg picrites from the same area. This indicates that the Wajilitage carbonatites derived from a mantle source isotopically distinct from the one responsible for the voluminous (ultra)mafic volcanism at Tarim. The carbonatites show d26MgDSM3 values (- 0.99 to - 0.65‰) that are significantly lower than those in typical mantle-derived rocks and rift carbonatites, but close to marine sediments and orogenic carbonatites. We propose that the carbonatites in the Tarim LIP formed by decompressional melting of recycled sediments mixed with the ambient mantle peridotite. The enriched components in the Tarim plume could be accounted for by the presence of recycled sedimentary components in the subcontinental mantle.
DS201705-0890
2017
Xu, C.Xu, C., Kynicky, J., Tao, R., Liu, X., Zhang, L., Pohanka, M., Song, W., Fei, Y.Recovery of an oxidized majorite inclusion from Earth's deep asthenosphere.Science Advances, Vol. 3, 4, e1601589MantleEclogite

Abstract: Minerals recovered from the deep mantle provide a rare glimpse into deep Earth processes. We report the first discovery of ferric iron-rich majoritic garnet found as inclusions in a host garnet within an eclogite xenolith originating in the deep mantle. The composition of the host garnet indicates an ultrahigh-pressure metamorphic origin, probably at a depth of ~200 km. More importantly, the ferric iron-rich majoritic garnet inclusions show a much deeper origin, at least at a depth of 380 km. The majoritic nature of the inclusions is confirmed by mineral chemistry, x-ray diffraction, and Raman spectroscopy, and their depth of origin is constrained by a new experimental calibration. The unique relationship between the majoritic inclusions and their host garnet has important implications for mantle dynamics within the deep asthenosphere. The high ferric iron content of the inclusions provides insights into the oxidation state of the deep upper mantle.
DS201707-1370
2017
Xu, C.Song, W., Xu, C., Chakhmouradian, A.R., Kynicky, J., Huang, K., Zhang, Z.Carbonatites of Tarim ( NW China): first evidence of crustal contribution in carbonatites from large igneous province.Lithos, Vol. 282-283, pp. 1-9.China, Mongoliacarbonatite - Tarim

Abstract: Many carbonatites are associated both spatially and temporally with large igneous provinces (LIPs), and considered to originate from a mantle plume source lacking any contribution from recycled crustal materials. Here, we report an occurrence of carbonatite enriched in rare-earth elements (REE) and associated with the Tarim LIP in northwestern China. The Tarim LIP comprises intrusive and volcanic products of mantle plume activity spanning from ~ 300 to 280 Ma. The carbonatites at Wajilitage in the northwestern part of Tarim are dominated by calcite and dolomite varieties, and contain abundant REE minerals (principally, monazite and REE-fluorcarbonates). Th–Pb age determination of monazite yielded an emplacement age of 266 ± 5.3 Ma, i.e. appreciably younger than the eruption age of flood basalts at ~ 290 Ma. The carbonatites show low initial 87Sr/86Sr (0.7037–0.7041) and high eNd(t) (1.2–4) values, which depart from the isotopic characteristics of plume-derived basalts and high-Mg picrites from the same area. This indicates that the Wajilitage carbonatites derived from a mantle source isotopically distinct from the one responsible for the voluminous (ultra)mafic volcanism at Tarim. The carbonatites show d26MgDSM3 values (- 0.99 to - 0.65‰) that are significantly lower than those in typical mantle-derived rocks and rift carbonatites, but close to marine sediments and orogenic carbonatites. We propose that the carbonatites in the Tarim LIP formed by decompressional melting of recycled sediments mixed with the ambient mantle peridotite. The enriched components in the Tarim plume could be accounted for by the presence of recycled sedimentary components in the subcontinental mantle.
DS201712-2683
2017
Xu, C.Deng, M., Xu, C., Song, W., Tang, H., Liu, Y., Zang, Q., Zhou, Y., Feng, M., Wei, C.REE mineralization in the Bayan Obo deposit, China: evidence from mineral paragenesis.Ore Geology Reviews, in press available, 10p.Chinadeposit - Bayan Obo

Abstract: Preliminary mineralogical and geochemical studies have been carried out on dolomite marble drill cores from the Bayan Obo REE deposit in China. Three types of apatites and four types of monazites have been identified based on textural features: Type 1 apatite occurs as grains with minor monazite (Type 1 monazite) on its border; Type 2 apatite veinlet shows clusters of assemblages with abundant bastnäsite and parisite at the rim; Type 3 apatite has a linear array associated with fluorite and bastnäsite veinlets. Type 2 monazite occurs as clusters intergrowing with parisite and fluorite. Type 3 and 4 monazites occur as polymineralic (fluorite and bastnäsite) and monomineralic veinlets, respectively. These four types of monazites have similar LREE composition but variable Y content (Y2O3 ranging from below determination limits to 0.7?wt%). The three types of apatites also show different REE content and distribution patterns, ranging from high REE abundance (?REE?+?Y: 27243-251789?ppm) and strong LREE enrichment [(La/Yb)CN ~101] in Type 1, less LREE enrichment [(La/Yb)CN ~8] in Type 2 to relatively low REE abundance (?REE?+?Y: 4323-11175?ppm) but high REE fractionation [(La/Yb)CN ~58] in Type 3. The primary apatite has high Sr (5461-6892?ppm) and REE content, implying a carbonatite origin. The late-stage apatites (Types 2 and 3) show different Sr and REE abundances. Significant differences in their Sr composition (6189?±?573, 6041?±?549 and 3492?±?802 for Types 1-3 samples, respectively) and Y/Ho ratio (20.9?±?0.11, 19.5?±?0.17 and 17.4?±?0.37, respectively) indicate that the three types of apatites may have crystallized from different metasomatic fluids. Multi-stage metasomatism resulted in remobilization and redeposition of primary REE minerals to form the Bayan Obo REE deposit.
DS201803-0481
2018
Xu, C.Tao, R., Fei, Y., Bullock, E.S., Xu, C., Zhang, L.Experimental investigation of Fe3+ rich majoritic garnet and its effect on majorite geobarometer.Geochimica et Cosmochimica Acta, Vol. 225, pp. 1-16.Technologygeobarometry

Abstract: Majoritic garnet [(Ca, Mg, Fe2+)3(Fe3+, Al, Si)2(SiO4)3] is one of the predominant and important constituents of upper mantle peridotite and ultra-deep subducted slabs. Majoritic substitution in garnet depends on pressure, and it has been used to estimate the formation pressure of natural majoritic garnet. Ferric iron (Fe3+) substitution occurs in natural majoritic garnets from mantle diamonds and shocked meteorites. However, available majorite geobarometers were developed without considering the effect of Fe3+ substitution in the structure. In this study, we systematically synthesized Fe3+- bearing majoritic garnets from 6.5?GPa to 15?GPa to evaluate the effect of Fe3+ on the majorite geobarometer. The Fe3+ contents of synthetic majoritic garnets were analyzed using the "Flank method" with the electron probe microanalyzer (EPMA). The results were compared with those based on the charge balance calculations. From the known synthesis pressures and measured Fe3+ contents, we developed a new majorite geobarometer for Fe3+-bearing majoritic garnets. Our results show that the existing majorite geobarometer, which does not take into account the Fe3+ substitution, could underestimate the formation pressure of majoritic garnets, especially for samples with a high majoritic component.
DS201805-0977
2018
Xu, C.Smith, M., Kynicky, J., Xu, C., Song, W., Spratt, J., Jeffries, T., Brtnicky, M., Kopriva, A., Cangelosi, D.The origin of secondary heavy rare earth element enrichment in carbonatites: constraints from the evolution of the Huanglongpu district, China.Lithos, Vol. 308-309, pp. 65-82.Chinacarbonatite

Abstract: The silico-carbonatite dykes of the Huanglongpu area, Lesser Qinling, China, are unusual in that they are quartz-bearing, Mo-mineralised and enriched in the heavy rare earth elements (HREE) relative to typical carbonatites. The textures of REE minerals indicate crystallisation of monazite-(Ce), bastnäsite-(Ce), parisite-(Ce) and aeschynite-(Ce) as magmatic phases. Burbankite was also potentially an early crystallising phase. Monazite-(Ce) was subsequently altered to produce a second generation of apatite, which was in turn replaced and overgrown by britholite-(Ce), accompanied by the formation of allanite-(Ce). Bastnäsite and parisite where replaced by synchysite-(Ce) and röntgenite-(Ce). Aeschynite-(Ce) was altered to uranopyrochlore and then pyrochlore with uraninite inclusions. The mineralogical evolution reflects the evolution from magmatic carbonatite, to more silica-rich conditions during early hydrothermal processes, to fully hydrothermal conditions accompanied by the formation of sulphate minerals. Each alteration stage resulted in the preferential leaching of the LREE and enrichment in the HREE. Mass balance considerations indicate hydrothermal fluids must have contributed HREE to the mineralisation. The evolution of the fluorcarbonate mineral assemblage requires an increase in aCa2+ and aCO32- in the metasomatic fluid (where a is activity), and breakdown of HREE-enriched calcite may have been the HREE source. Leaching in the presence of strong, LREE-selective ligands (Cl-) may account for the depletion in late stage minerals in the LREE, but cannot account for subsequent preferential HREE addition. Fluid inclusion data indicate the presence of sulphate-rich brines during alteration, and hence sulphate complexation may have been important for preferential HREE transport. Alongside HREE-enriched magmatic sources, and enrichment during magmatic processes, late stage alteration with non-LREE-selective ligands may be critical in forming HREE-enriched carbonatites.
DS201906-1351
2019
Xu, C.Smith, M.P., Estrade, G., Marquis, E., Goodenough, K., Nason, P., Xu, C., Kynicky, J., Borst, A.M., Finch, A.A., Villanova de Benevent, C.Ion adsorption deposits: a comparison of deposits in Madagascar and China.3rd International Critical Metals Meeting held Edinburgh, 1p.abstract p. 53.Africa, Madagascar, ChinaREE

Abstract: Link to presentation pdf.
DS201906-1363
2019
Xu, C.Wei, C.W., Xu, C., Chakhmouradian, A.R., Brenna, M., Kynicky, J., Song, W.L.Petrogenesi of dolomite and calcite carbonatites in orogenic belts.GAC/MAC annual Meeting, 1p. Abstract p. 194.Chinadeposit - Caotan

Abstract: Subduction zones are an important way for crustal materials to enter deep parts of the Earth. Therefore, carbonatites in orogenic belt are of great significance in revealing deep carbon cycling pathways. To date, mantle-derived carbonatites have been identified in many orogenic belts, and their origin is considered to be related to subducted sediments. However, almost all orogenic carbonatites are composed of calcite, and their C isotopic compositions show typical mantle values, lacking any evidence of sedimentary origin. Here, we report decoupling of C and Sr isotopes between intimately associated dolomite and forsterite-calcite carbonatites from Caotan in the Qinling orogen, central China. The dolomite carbonatite is mainly composed of dolomite (plus minor apatite and magnetite), which has elevated d13CPDB values (-3.1 to -3.6 ‰) and low 87Sr/86Sr ratios (0.7026-0.7042). The forsterite-calcite carbonatite consists of calcite (60-65 vol. %), forsterite and its replacement products (30-35 vol. %), and magnetite. The calcite shows mantle-like d13CPDB (-6.2 to -7.2 ‰) but high initial 87Sr/86Sr values (0.7053-0.7076). Neodymium and Pb isotopic compositions are comparable in the two carbonatite types. The forsterite-calcite carbonatite is interpreted to have formed by metasomatic interaction of primary dolomitic melts with eclogite in thickened lower crust during collision of the North and South China cratons. The reaction resulted in decarbonation and depletion of the carbonatitic magma in 13C. Because of its initially low REE and Pb contents, the Nd-Pb isotopic signature of the primary dolomitic melt was preserved in the forsterite-calcite carbonatite. We propose that some orogenic calcite carbonatites may not be primary mantle-derived rocks and their mantle-like d13CPDB values may be misleading.
DS201907-1532
2019
Xu, C.Chen, W., Liu, H-Y,m Jiang, S-Y., Simonetti, A., Xu, C., Zhang, W.The formation of the ore-bearing dolomite marble from the giant Bayan Obo REE-Nb-Fe deposit, Inner Mongolia: insights from micron-scale geochemical data.Mineralium Deposita, in press available, 16p.Asia, Mongoliadeposit - Bayan Obo

Abstract: The genesis of Earth’s largest rare earth element (REE) deposit, Bayan Obo (China), has been intensely debated, in particular whether the host dolomite marble is of sedimentary or igneous origin. The protracted (Mesoproterozoic to Paleozoic) and intricate (magmatic to metasomatic) geological processes complicate geochemical interpretations. In this study, we present a comprehensive petrographic and in situ, high-spatial resolution Sr-Pb isotopic and geochemical investigation of the host dolomite from the Bayan Obo marble. Based on petrographic evidence, the dolomite marble is divided into three facies including coarse-grained (CM), fine-grained (FM), and heterogeneous marble (HM). All carbonates are ferroan dolomite with high SrO and MnO contents (>?0.15 wt.%), consistent with an igneous origin. Trace element compositions of these dolomites are highly variable both among and within individual samples, with CM dolomite displaying the strongest LREE enrichment. In situ 206Pb/204Pb and 207Pb/204Pb ratios of the dolomite are generally consistent with mantle values. However, initial 208Pb/204Pb ratios define a large range from 35.45 to 39.75, which may result from the incorporation of radiogenic Pb released from decomposition of monazite and/or bastnäsite during Early Paleozoic metasomatism. Moreover, in situ Sr isotope compositions of dolomite indicate a large range (87Sr/86Sr?=?0.70292-0.71363). CM dolomite is characterized by a relatively consistent, unradiogenic Sr isotope composition (87Sr/86Sr?=?0.70295-0.70314), which is typical for Mesoproterozoic mantle. The variation of 87Sr/86Sr ratios together with radiogenic 206Pb/204Pb signatures for dolomite within FM and HM possibly represents recrystallization during Early Paleozoic metasomatism with the contribution of radiogenic Sr and Pb from surrounding host rocks. Therefore, our in situ geochemical data support a Mesoproterozoic igneous origin for the ore-bearing dolomite marble in the Bayan Obo deposit, which subsequently underwent intensive metasomatism during the Early Paleozoic.
DS201911-2577
2019
Xu, C.Xu, C., Inoue, T.Melting of Al-rich phase D up to the uppermost lower mantle and transportation of H2O to the deep Earth.Geochemistry, Geophysics, Geosystems, Vol. 20, 9, pp. 4382-4389.Mantlewater

Abstract: We investigated the stability of the Al-rich dense hydrous magnesium silicate Phase D (PhD) in a MgO-Al2O3-SiO2-H2O system between 14 and 25 GPa at 900-1,500 °C. Al-rich PhD has a very wide stability region from 900 °C and 14 GPa to at least 1,500 °C and 25 GPa, showing strong temperature stability with increasing pressure. Al-rich PhD decomposes to Phase Egg at pressure of the mantle transition zone, whereas it decomposes to d-AlOOH phase with a temperature increase at pressure of the uppermost lower mantle. X-ray diffraction and Raman spectroscopy measurements of Al-rich PhD show that the unit-cell volume is slightly larger, but the Raman spectra resemble that of Al-free PhD. The wide stability region of Al-bearing PhD would contribute an important storage site for water in the mantle transition zone, suggesting that it can deliver a certain amount of water into the lower mantle along hot subduction and even at the normal mantle geothermal P-T condition. Furthermore, the dehydration of Al-bearing PhD might be responsible for a series of observed seismic discontinuities from the transition zone to the uppermost lower mantle and even for deep earthquakes in some typical locations.
DS201912-2835
2019
Xu, C.Yang, Y-H., Wu, F-Y., Qiu-Li, L., Rojas-Agramonte, Y., Yang, J-H., Yang, L., Ma, Q., Xie, L-W., Huang, C., Fan, H-R., Zhao, Z-F., Xu, C.In situ U-Th-Pb dating and Sr-Nd isotope analysis of bastnasite by LA-(MC)-ICP-MS.Geostandards and Geoanalltical Research, Vol. 43, 3, pp. 543-565.China, Europe, Sweden, Asia, Mongolia, United States, Africa, Malawi, MadagascarREE

Abstract: Bastnäsite is the end member of a large group of carbonate-fluoride minerals with the common formula (REE) CO3F•CaCO3. This group is generally widespread and, despite never occurring in large quantities, represents the major economic light rare earth element (LREE) mineral in deposits related to carbonatite and alkaline intrusions. Since bastnäsite is easily altered and commonly contains inclusions of earlier-crystallised minerals, in situ analysis is considered the most suitable method to measure its U-Th-Pb and Sr-Nd isotopic compositions. Electron probe microanalysis and laser ablation (multi-collector) inductively coupled plasma-mass spectrometry of forty-six bastnäsite samples from LREE deposits in China, Pakistan, Sweden, Mongolia, USA, Malawi and Madagascar indicate that this mineral typically has high Th and LREE and moderate U and Sr contents. Analysis of an in-house bastnäsite reference material (K-9) demonstrated that precise and accurate U-Th-Pb ages could be obtained after common Pb correction. Moreover, the Th-Pb age with its high precision is preferable to the U-Pb age because most bastnäsites have relatively high Th rather than U contents. These results will have significant implications for understanding the genesis of endogenous ore deposits and formation processes related to metallogenic geochronology research.
DS202104-0616
2021
Xu, C.Wu, B., Hu, Y-Q., Bonnetti, C., Xu, C., Wang, R-C., Zhang, Z-S., Li, Z-Y., Yin, R.Hydrothermal alteration of pyrochlore group minerals from the Miaoya carbonatite complex, central China and its implications for Nb mineralization.Ore Geology Reviews, Vol. 132, 1040459, 16p. PdfChinadeposit - Miaoya

Abstract: Carbonatite represents a major host rock for niobium (Nb) resources worldwide. Both magmatic and post-magmatic metasomatic processes are crucial for Nb mineralization in carbonatites. However, the roles of these metasomatic processes are difficult to be evaluated due to their multiple origins and complexity of the physico-chemical conditions. In this study, we present detailed mineralogical investigations of pyrochlore group minerals and chemical U-Th-Pb geochronology of uraninite within the Miaoya carbonatite complex, aiming to better characterize the role of post-magmatic metasomatic events. The Miaoya complex (ca. 420-440?Ma) hosts the second largest carbonatite-related Nb deposit in China, mainly in the form of pyrochlore group minerals, ferrocolumbite and Nb-bearing rutile. Primary pyrochlore group minerals evolved from pyrochlore to uranpyrochlore, and ultimately reaching the betafite end-member during the magmatic stage. They have then experienced an episode of metasomatic events at 235.4?±?4.1?Ma, as determined by U-Th-Pb chemical ages of secondary uraninite. Fluids activity for uranpyrochlore alteration was concomitant with the hydrothermal reworking of REE mineralization, which was probably related to tectono-thermal events that occurred during the Triassic closure of the ancient Mianlue Ocean. During this process, hydration and decomposition of uranpyrochlore were characterized by the leaching of Na, Ca and F from its structure, the incorporation of Fe, Si, Sr and Ba from the fluids, and the final in situ replacement by secondary ferrocolumbite, uraninite and Nb-bearing rutile. In addition, parts of Nb and U liberated from uranpyrochlore by metamictization were then transported over distances of several hundreds of microns in relatively reducing (Fe, Si, S, CO2)-bearing fluids under high temperature, and were ultimately re-precipitated in amorphous Fe-Si-U-Nb-bearing oxide veins and poorly crystallized Nb-Ti-Ca-Fe-rich oxides. The relatively weak fluids activity failed to efficiently promote the Nb re-enrichment.
DS202109-1495
2021
Xu, C.Xu, C., Inoue, T., Kakizawa, S., Noda, M., Gao, J.Effect of Al on the stability of dense hydrous magnesium silicate phases to the uppermost lower mantle: implications for water transportation into the deep mantle.Physics and Chemistry of Minerals, Vol. 48, 31, 10p. PdfMantlewater

Abstract: We have systematically investigated the high-pressure and high-temperature stability of Al-bearing dense hydrous magnesium silicate phases (DHMSs) in natural chlorite compositions containing?~?16 wt% H2O and?~?14 wt% Al2O3 between 14 and 25 GPa at 800-1600 °C by an MA8-type multi-anvil apparatus. A chemical mixture similar to Fe-free chlorite was also investigated for comparison. Following the pressure-temperature (P-T) path of cold subduction, the phase assemblage of phase E?+?phase D is stable at 14-25 GPa. Superhydrous phase B is observed between 16 and 22 GPa coexisting with phase E?+?phase D. Following the P-T path of hot subduction, the phase assemblage of phase E?+?garnet is identified at 14-18 GPa coexisting with the melt. The phase assemblage of superhydrous phase B?+?phase D was found at 18-25 GPa, which is expected to survive at higher P-T conditions. We have confirmed that the presence of Al could enhance the stability of DHMSs. Our results indicate that, after chlorite decomposition at the shallow region of the subduction zone, the wide stability field of Al-bearing DHMSs can increase the possibility of water transportation into the deep lower mantle.
DS1984-0780
1984
Xu, CHANGYU.Xu, CHANGYU.A Study of Stope Parameters During Changing from Open Pit To Underground at the Meng-yin Diamond Mine in China.Mining Science And Technology, Vol. 1, PP. 179-188.ChinaKimberlite, Mining Methods, Mengyin
DS1996-1593
1996
Xu, D.Zhang, A., Griffin, W.L., Win, T.T., Xu, D.Lithosphere mapping in eastern Chin a garnets and spinels from kimberlitic and lamproitic rocks.International Geological Congress 30th Session Beijing, Abstracts, Vol. 2, p. 398.ChinaGeothermometry, Kimberlites, lamproites
DS201811-2618
2019
Xu, D.Xie, Y., Qu, Y., Zhong, R., Verplanck, P.L., Meffre, S., Xu, D.The ~1.85 Ga carbonatite in north China and its implications on the evolution of the Columbia supercontinent.Gondwana Research, Vol. 65, pp. 125-141.Chinacarbonatite

Abstract: Mantle-derived carbonatites provide a unique window in the understanding of mantle characteristics and dynamics, as well as insight into the assembly and breakup of supercontinents. As a petrological indicator of extensional tectonic regimes, Archean/Proterozoic carbonatites provide important constraints on the timing of the breakup of ancient supercontinents. The majority of the carbonatites reported worldwide are Phanerozoic, in part because of the difficulty in recognizing Archean/Proterozoic carbonatites, which are characterized by strong foliation and recrystallization, and share broad petrologic similarities with metamorphosed sedimentary lithologies. Here, we report the recognition of a ~1.85?Ga carbonatite in Chaihulanzi area of Chifeng in north China based on systematic geological, petrological, geochemical, and baddeleyite U-Pb geochronological results. The carbonatite occurs as dikes or sills emplaced in Archean metasedimentary rocks and underwent intense deformation. Petrological and SEM/EDS results show that calcite and dolomite are the dominant carbonate minerals along with minor and varied amounts of Mg-rich mafic minerals, including forsterite (with Fo?>?98), phlogopite, diopside, and an accessory amount of apatite, baddeleyite, spinel, monazite, and ilmenite. The relatively high silica content together with the non-arc and OIB-like trace element signatures of the carbonatite indicates a hot mantle plume as the likely magma source. The depleted Nd isotopic signatures suggest that plume upwelling might be triggered by the accumulation of recycled crust in the deep mantle. As a part of the global-scale Columbia supercontinent, the Proterozoic tectonic evolution of the North China Craton (NCC) provides important insights into the geodynamics governing amalgamation and fragmentation of the supercontinent. The Paleo-Mesoproterozoic boundary is the key point of tectonic transition from compressional to extensional settings in the NCC. The newly identified ~1.85?Ga carbonatite provides a direct link between the long-lasting supercontinental breakup and plume activity, which might be sourced from the “slab graveyard,” continental crustal slabs subducted into asthenosphere, beneath the supercontinent. The carbonatite provides a precise constraint of the initiation of the continental breakup at ~1.85?Ga.
DS201812-2900
2019
Xu, D.Xie, Y., Qu, Y., Zhong, R., Verplanck, P.L., Meffre, S., Xu, D.The ~1/85 carbonatite in north China and its implications on the evolution of the Columbia supercontinent.Gondwana Research, Vol. 65, pp. 125-141.Chinacarbonatite

Abstract: Mantle-derived carbonatites provide a unique window in the understanding of mantle characteristics and dynamics, as well as insight into the assembly and breakup of supercontinents. As a petrological indicator of extensional tectonic regimes, Precambrian carbonatites provide important constraints on the timing of the breakup of ancient supercontinents. The majority of the carbonatites reported worldwide are Phanerozoic, in part because of the difficulty in recognizing Precambrian carbonatites, which are characterized by strong foliation and recrystallization, and share broad petrologic similarities with metamorphosed sedimentary lithologies. Here we report the recognition of a ~1.85?Ga carbonatite in Chaihulanzi area of Chifeng in north China based on systematic geological, petrological, geochemical, and baddeleyite U-Pb geochronological results. The carbonatite occurs as dikes or sills emplaced in Archean metasedimentary rocks and underwent intense deformation. Petrological and SEM/EDS results show that calcite and dolomite are the dominant carbonate minerals along with minor and varied amounts of Mg-rich mafic minerals, including forsterite (with Fo?>?98), phlogopite, diopside, and an accessory amount of apatite, baddeleyite, spinel, monazite, and ilmenite. The relatively high silica content together with the non-arc and OIB-like trace element signatures of the carbonatite indicates a hot mantle plume as the likely magma source. The depleted Nd isotopic signatures suggest that plume upwelling might be triggered by the accumulation of recycled crust in the deep mantle. As a part of the global-scale Columbia supercontinent, the Proteozoic tectonic evolution of the North China Craton (NCC) provides important insights into the geodynamics governing amalgamation and fragmentation of the supercontinent. The Paleo-Mesoproterozoic boundary is the key point of tectonic transition from compressional to extensional settings in the NCC. The newly-identified ~1.85?Ga carbonatite provides a direct link between the long-lasting supercontinental breakup and plume activity, which might be sourced from the “slab graveyard”, continental crustal slabs subducted into asthenosphere, beneath the supercontinent. The carbonatite provides a precise constraint of the initiation of the continental breakup at ~1.85?Ga.
DS201901-0092
2018
Xu, D.Xie, Y., Qu, Y., Zhong, R., Verplanck, P.L., Meffre, S., Xu, D.The ~1.85 GA carbonatite in north China and its implications on the evolution of the Columbia supercontinent. Chaitulanzi, ChifengGondwana Research, Vol. 65, pp. 135-141.Chinacarbonatite

Abstract: Mantle-derived carbonatites provide a unique window in the understanding of mantle characteristics and dynamics, as well as insight into the assembly and breakup of supercontinents. As a petrological indicator of extensional tectonic regimes, Precambrian carbonatites provide important constraints on the timing of the breakup of ancient supercontinents. The majority of the carbonatites reported worldwide are Phanerozoic, in part because of the difficulty in recognizing Precambrian carbonatites, which are characterized by strong foliation and recrystallization, and share broad petrologic similarities with metamorphosed sedimentary lithologies. Here we report the recognition of a ~1.85?Ga carbonatite in Chaihulanzi area of Chifeng in north China based on systematic geological, petrological, geochemical, and baddeleyite U-Pb geochronological results. The carbonatite occurs as dikes or sills emplaced in Archean metasedimentary rocks and underwent intense deformation. Petrological and SEM/EDS results show that calcite and dolomite are the dominant carbonate minerals along with minor and varied amounts of Mg-rich mafic minerals, including forsterite (with Fo?>?98), phlogopite, diopside, and an accessory amount of apatite, baddeleyite, spinel, monazite, and ilmenite. The relatively high silica content together with the non-arc and OIB-like trace element signatures of the carbonatite indicates a hot mantle plume as the likely magma source. The depleted Nd isotopic signatures suggest that plume upwelling might be triggered by the accumulation of recycled crust in the deep mantle. As a part of the global-scale Columbia supercontinent, the Proteozoic tectonic evolution of the North China Craton (NCC) provides important insights into the geodynamics governing amalgamation and fragmentation of the supercontinent. The Paleo-Mesoproterozoic boundary is the key point of tectonic transition from compressional to extensional settings in the NCC. The newly-identified ~1.85?Ga carbonatite provides a direct link between the long-lasting supercontinental breakup and plume activity, which might be sourced from the “slab graveyard”, continental crustal slabs subducted into asthenosphere, beneath the supercontinent. The carbonatite provides a precise constraint of the initiation of the continental breakup at ~1.85?Ga.
DS1998-1606
1998
Xu, F.Xu, F., Vidale, J.E., Benz, H.M.Mantle discontinuities under southern Africa from precursors to P'P'dfGeophysical Research. Letters, Vol. 25, No. 4, Feb. 15, pp. 571-574.South Africa, southern AfricaGeophysics - discontinuity, Mantle
DS2003-1509
2003
Xu, F.Xu, F., Vidale, J.E., Earle, P.S.Survey of precursors to P'P': fine structure of mantle discontinuitiesJournal of Geophysical Research, Vol. 08, 2, 10.1029/2001JB000817.MantleGeophysics - seismics, Discontinuity
DS200412-1961
2004
Xu, F.Takafuji, N., Hirose, K., Ono, S., Xu, F., Mitome, M., Bando, Y.Segregation of core melts by permeable flow in the lower mantle.Earth and Planetary Science Letters, Vol. 224, 3-4, pp. 249-257.MantleGeothermometry - boundary
DS200412-2158
2003
Xu, F.Xu, F., Vidale, J.E., Earle, P.S.Survey of precursors to P'P': fine structure of mantle discontinuities.Journal of Geophysical Research, Vol. 08, 2, 10.1029/2001 JB000817.MantleGeophysics - seismics Discontinuity
DS200812-0584
2008
Xu, H.Konish, H., Xu, H., Spicuzza, M.,Valley, J.W.Polycrystalline diamond inclusions in Jack Hills zircon: carbonado?Goldschmidt Conference 2008, Abstract p.A489.AustraliaDiamond inclusions
DS200912-0446
2009
Xu, H.Liu, Q., Yang, T., Zeng, Q., Zheng, J., Luo, Y., Qui, N., Xu, H., Jin, Z.Magnetic study of the UHP eclogites from the Chinese Continental Scientific drilling project.Journal of Geophysical Research, Vol. 114, B02106.ChinaUHP
DS201212-0822
2012
Xu, H.Zhao, S., Jin, Z., Zhang, J., Xu, H., Xia, G., Green, H.W.II.Does subducting lithosphere weaken as it enters the lower mantle?Geophysical Research Letters, Vol. 39, L10311 5p.MantleSubduction
DS201012-0829
2010
Xu, H.J.Wang, L., Jin, Z.M., Kusky, T., Xu, H.J., Liu, X.W.Microfabric characteristics and rheological significance of ultra high pressure metamorphosed jadeite quartzite and eclogite Shuanghe, Dabie Mtns.Journal of Metamorphic Geology, Vol. 28, 2, pp. 163-182.ChinaUHP
DS201112-1161
2011
Xu, H.J.Zhang, J.F., Xu, H.J., Liu, Q., Green, H.W., Dobrzhinetskaya, L.F.Pyroxene exsolution topotaxy in majoritic garnet from 250 to 300 km depth.Journal of Metamorphic Geology, Vol. 29, 7, pp. 741-751.TechnologyGarnet mineralogy
DS201112-1162
2011
Xu, H.J.Zhang, J.F., Xu, H.J., Liu, Q., Green, H.W., Dobrzhinetskaya, L.F.Pyroxene evolution topotaxy in majorite garnet from 250 to 300 km depth.Journal of Metamorphic Geology, In press available,MantleGarnet
DS202101-0041
2020
Xu, H-J.Wang, Y-F., Qin, J-Y., Soustelle, V., Zhang, J-F., Xu, H-J.Pyroxene does not always preserve its source hydrogen concentration: clues from peridotite xenoliths. Geochimica et Cosmochimica Acta, in press availabe 38p. PdfChinametasomatism

Abstract: Water is key to many geodynamical processes in the Earth's upper mantle, yet its preservation in mantle minerals is still debated. To throw some light on this problem, we here carried out an integrated study of whole-rock and mineral chemistry, and hydrogen concentrations in olivine, orthopyroxene, and clinopyroxene within 18 spinel lherzolite samples from three localities (Lianshan, Panshishan, and Tashan) in the Nanjing area, eastern China. Whole-rock and mineral compositions suggest that the studied peridotite samples interacted with melt at different melt/rock ratios following various degrees of partial melting (up to 11%). Fourier transform infrared (FTIR) measurements show that olivine is almost dry (<1 wt ppm H2O) while the cores of orthopyroxene and clinopyroxene contain 14-151 wt ppm H2O and 41-218 wt ppm H2O, respectively. Profile analyses of >70 orthopyroxene grains, which are homogeneous in major-element compositions, covering all the studied samples show hydrogen-depleted rims, indicative of hydrogen diffusional loss. This hydrogen zonation is probably caused by hydrogen chemical diffusion controlled by the mobility of trivalent cations (most likely Al3+) in response to magma degassing or partial melting of peridotite during ascent, or interactions of peridotite with melt, or a combination of these processes. By contrast, no hydrogen zonation is observed in clinopyroxene. Based upon the comparison of chemical compositions (especially Fe and AlIV contents) of clinopyroxene within our samples with those in diffusion experiments, it is inferred that the hydrogen diffusivity in clinopyroxene should be larger than that in orthopyroxene from our samples. This inference points to that clinopyroxene within the studied samples must have experienced diffusional loss of hydrogen as well, suggesting that water concentrations in the lithospheric mantle beneath the study area are probably underestimated. Furthermore, it also implies that orthopyroxene instead of clinopyroxene most likely preserves the in-situ water concentrations at depth, at least at its core. The absence of hydrogen zonation in clinopyroxene can be attributed to its fine-grained nature and fast hydrogen diffusivity. Our FTIR data also show that Lianshan and Tashan samples have water concentration ratio between clinopyroxene and orthopyroxene (RCpx/Opx) of ~2, similar to mantle xenoliths from eastern China and other localities worldwide, yet Panshishan samples have higher RCpx/Opx values (2.3-5.9). Since hydrogen loss is suggested for both pyroxenes, RCpx/Opx of ~2 thus cannot be taken as a reliable indicator of preservation of original water concentration of mantle source and equilibrium partitioning of hydrogen between pyroxene, as opposed to previous suggestions.
DS2000-1032
2000
Xu, J.Xu, J., Mao, H.Moissanite: a window for high pressure experimentsScience, Vol. 290, No. 5492, Oct. 27, pp. 783-4.GlobalMoissanite
DS200512-1263
2005
Xu, J.Zhenyu, C., Yuchuan, C., Denghong, W., Xu, J., Zhou, J.Rutiles in eclogite from the Sulu UHPM terrane: a preliminary study.Mineral deposit Research: Meeting the Global Challenge. 8th Biennial SGA Beijing, Aug. 18-22, 2005. Springer, Chapter 7-3, pp. 731-734.ChinaUHP
DS200712-1133
2007
Xu, J.Wang, Q., Wyman, D.A., Xu, J., Jian, P., Zhao, Z., Li, C., Xu, W., Ma, J., He, B.Early Cretaceous adakitic granites in the northern Dabie Complex, central China: implications for partial melting and delamination of thickened lower crust.Geochimica et Cosmochimica Acta, Vol. 71, 10, May 15, pp. 2609-2636.ChinaUHP - Dabie Shon
DS201708-1792
2017
Xu, J.Xu, J.Ilmenite as a recorder of the kimberlite history from mantle to surface: examples from Indian kimberlites.11th. International Kimberlite Conference, PosterIndiailmenite
DS201708-1793
2017
Xu, J.Xu, J.Magma mingling at the Menominee pipe, USA? Contributions from texture and chemistry.11th. International Kimberlite Conference, PosterUnited States, Michigandeposit - Menominee
DS201710-2239
2017
Xu, J.Li, W-Y., Huang, F., Yu, H-M., Xu, J., Halama, R., Teng, F-Z.Barium isotopic composition of the mantle constrained by carbonatites.Goldschmidt Conference, 1p. AbstractAfrica, Tanzania, east Africa, Canada, Europe, Germany, Greenlandcarbonatite

Abstract: Deep mantle origin and ultra-reducing conditions in podiform chromitite: diamonds, moissanite, and other unusual minerals in podiform chromitites from the Pozanti-Karsanti ophiolite, southern Turkey
DS201808-1797
2018
Xu, J.Xu, J., Melgarejo, J.C., Castillo-Oliver, M.Styles of alteration of Ti oxides of the kimberlite groundmass: implications on the petrogenesis and classification of kimberlites and similar rocks.Minerals, Vol. 8, 2, pp. 51-66.Indiaperovskite

Abstract: The sequence of replacement in groundmass perovskite and spinel from SK-1 and SK-2 kimberlites (Eastern Dharwar craton, India) has been established. Two types of perovskite occur in the studied Indian kimberlites. Type 1 perovskite is found in the groundmass, crystallized directly from the kimberlite magma, it is light rare-earth elements (LREE)-rich and Fe-poor and its ?NNO calculated value is from -3.82 to -0.73. The second generation of perovskite (type 2 perovskite) is found replacing groundmass atoll spinel, it was formed from hydrothermal fluids, it is LREE-free and Fe-rich and has very high ?NNO value (from 1.03 to 10.52). Type 1 groundmass perovskite may be either replaced by anatase or kassite along with aeschynite-(Ce). These differences in the alteration are related to different f(CO2) and f(H2O) conditions. Furthermore, primary perovskite may be strongly altered to secondary minerals, resulting in redistribution of rare-earth elements (REE) and, potentially, U, Pb and Th. Therefore, accurate petrographic and chemical analyses are necessary in order to demonstrate that perovskite is magmatic before proceeding to sort geochronological data by using perovskite. Ti-rich hydrogarnets (12.9 wt %-26.3 wt % TiO2) were produced during spinel replacement by late hydrothermal processes. Therefore, attention must be paid to the position of Ca-Ti-garnets in the mineral sequence and their water content before using them to classify the rock based on their occurrence.
DS201808-1798
2018
Xu, J.Xu, J., Melgarejo, J.C., Castillo-Oliver, M.Ilmenite as a recorder of kimberlite history from mantle to surface: examples from Indian kimberlites. Bastar, Dharwar cratonsMineralogy and Petrology, 10.1007/s00710-018-0616-5 13p.Indiailmentite

Abstract: Indian kimberlites occur in the Bastar craton (Central India) and in the Eastern Dharwar craton (EDC) Southern India. Nearly 100 kimberlite pipes have been discovered in the Eastern Dharwar craton of southern India, and they are distributed in three distinct fields: 1) the southern Wajrakarur kimberlite field (WKF); 2) the northern Narayanpet kimberlite field (NKF); and 3) the Raichur kimberlite field (RKF) (Chalapathi Rao et al, 2013). Nine kimberlites have been selected for this study: three came from the Siddanpalli cluster of RKF (SK-1, SK-2 and SK-3); other six kimberlites came from WKF, from Chigicherla (CC-4 and CC-5), Kalyandurg (KL-3 and KL-4), Lattavaram (P-3) and Mulligripally (P-5). The kimberlite emplacement took place during the Mesoproterozoic, around 1.1 Ga (Chalapathi Rao et al., 2013). Ilmenite is one of the classic diamond indicator minerals (DIMs) and for long it has been used as a guide for kimberlite exploration. The aim of this study is to evaluate the petrogenetic information that can be provided from the textural and geochemical study of the different ilmenite generations present in the Indian kimberlites studied in this work.
DS201811-2619
2018
Xu, J.Xu, J., Melgarejo, J.C., Castillo, O., Montgarri, A., Laia, S., Santamaria, J.Ilmenite generations in kimberlite from Banankoro, Guinea. ConakryNeues Jahrbuch fur Mineralogie, doi:.org/10.1127/njma/2018/0096Africa, Guineadeposit - Banakoro

Abstract: A complex mineral sequence in a kimberlite from the Banankoro Cluster (Guinea Conakry) has been interpreted as the result of magma mixing processes. The composition of the early generations of phlogopite and spinel suggest direct crystallisation of a kimberlitic magma. However, the compositional trends found in the late generations of phlogopite and spinels could suggest magma mixing. In this context, four ilmenite generations formed. The first generations (types 1 and 2) are geikielitic and are associated with spinel and phlogopite which follow the kimberlitic compositional trends. They are interpreted as produced by crystallization from the kimberlite magma. A third generation of euhedral tabular Mg-rich ilmenite (type 3) formed during the interval between two generations of serpentine. Finally, a late generation of Mn-rich ilmenite (type 4) replaces all the Ti-rich minerals and is contemporaneous with the last generation of serpophitic non-replacing serpentine. Therefore, the formation of type 3 and type 4 ilmenite took place after the crystallization of the groundmass, during late hydrothermal process. Our results suggest a detailed textural study is necessary when use Mg-rich and Mn-rich ilmenites as KIMs.
DS201901-0093
2018
Xu, J.Xu, J., Melgarejo, C.M., Castillo-Oliver, M., Arques, L., Santamaria, J.Ilmenite generations in kimberlite from Banankoro, Guinea Conakry.Neues Jhabuch fur Mineralogie, Vol. 195, 3, pp. 191-204.Africa, Guineadeposit - Banankoro

Abstract: A complex mineral sequence in a kimberlite from the Banankoro Cluster (Guinea Conakry) has been interpreted as the result of magma mixing processes. The composition of the early generations of phlogopite and spinel suggest direct crystallisation of a kimberlitic magma. However, the compositional trends found in the late generations of phlogopite and spinels could suggest magma mixing. In this context, four ilmenite generations formed. The first generations (types 1 and 2) are geikielitic and are associated with spinel and phlogopite which follow the kimberlitic compositional trends. They are interpreted as produced by crystallization from the kimberlite magma. A third generation of euhedral tabular Mg-rich ilmenite (type 3) formed during the interval between two generations of serpentine. Finally, a late generation of Mn-rich ilmenite (type 4) replaces all the Ti-rich minerals and is contemporaneous with the last generation of serpophitic non-replacing serpentine. Therefore, the formation of type 3 and type 4 ilmenite took place after the crystallization of the groundmass, during late hydrothermal process. Our results suggest a detailed textural study is necessary when use Mg-rich and Mn-rich ilmenites as KIMs. © 2018 E. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, Germany.
DS201902-0334
2019
Xu, J.Xu, J., Zhang, D., Fan, D., Dera, P.K., Shi, F., Zhou, W.Thermoeleastic properties of eclogitic garnets and omphacites: implications for deep subduction of oceanic crust and density anomalies in the upper mantle.Geophysical Research Letters, Vol. 46, 1, pp. 179-188.Mantlesubduction

Abstract: Eclogite mainly consists of pyrope-almandine-grossular garnet and sodium-rich pyroxene (omphacite) and is a key component of the Earth's upper mantle and oceanic crust. It plays an important role in the mantle convection. The lack of thermoelastic parameters of eclogitic garnets and omphacites hampers accurate modeling of eclogite density at deep-Earth pressure-temperature conditions. In this study, we obtained the thermoelastic parameters of natural eclogitic garnets and omphacites and then modeled the densities of high-Fe and low-Fe eclogites in the subducted oceanic crust and the normal upper mantle. In the upper mantle, eclogite enhances the slab subduction into the transition zone; however, the presence of the metastable low-Fe eclogite would promote the slab stagnation within the upper range of the transition zone. Additionally, eclogite can explain positive density anomalies at depths of 100-200 km of the upper mantle of Asia identified by seismic observations.
DS201908-1786
2019
Xu, J.Li, W-Y., Yu, H-M., Xu, J., Halama, R., Bell, K., Nan, X-Y., Huang, F.Barium isotopic composition of the mantle: constraints from carbonatites.Geochimica et Cosmochimica Acta, in press available doi.org/10.1016 / j.gca.2019.06.041 36p.Africa, Tanzania, Canada, East Africa, Europe, Germany, Greenlanddeposit - Oldoinyo Lengai

Abstract: To investigate the behaviour of Ba isotopes during carbonatite petrogenesis and to explore the possibility of using carbonatites to constrain the Ba isotopic composition of the mantle, we report high-precision Ba isotopic analyses of: (1) carbonatites and associated silicate rocks from the only active carbonatite volcano, Oldoinyo Lengai, Tanzania, and (2) Archean to Cenozoic carbonatites from Canada, East Africa, Germany and Greenland. Carbonatites and associated phonolites and nephelinites from Oldoinyo Lengai have similar d137/134Ba values that range from +0.01 to +0.03‰, indicating that Ba isotope fractionation during carbonatite petrogenesis is negligible. The limited variation in d137/134Ba values from -0.03 to +0.09‰ for most carbonatite samples suggests that their mantle sources have a relatively homogeneous Ba isotopic composition. Based on the carbonatites investigated in this work, the average d137/134Ba value of their mantle sources is estimated to be +0.04?±?0.06‰ (2SD, n?=?16), which is similar to the average value of +0.05?±?0.06‰ for mid-ocean ridge basalts. The lower d137/134Ba value of -0.08‰ in a Canadian sample and higher d137/134Ba values of +0.14‰ and?+?0.23‰ in two Greenland samples suggest local mantle isotopic heterogeneity that may reflect the incorporation of recycled crustal materials in their sources.
DS202006-0931
2020
Xu, J.Li, W-Ye., Yu, H-M., Xu, J., Halama, R., Bell, K., Nan, X-Y., Huang, F.Barium isotopic composition of the mantle: constraints from carbonatites.Geochimica et Cosmochimica Acta, Vol. 278, pp. 235-243. pdfAfrica, Tanzania, Canada, Europe, Germany, Greenlanddeposit - Oldoinyo Lengai

Abstract: To investigate the behaviour of Ba isotopes during carbonatite petrogenesis and to explore the possibility of using carbonatites to constrain the Ba isotopic composition of the mantle, we report high-precision Ba isotopic analyses of: (1) carbonatites and associated silicate rocks from the only active carbonatite volcano, Oldoinyo Lengai, Tanzania, and (2) Archean to Cenozoic carbonatites from Canada, East Africa, Germany and Greenland. Carbonatites and associated phonolites and nephelinites from Oldoinyo Lengai have similar d137/134Ba values that range from +0.01 to +0.03‰, indicating that Ba isotope fractionation during carbonatite petrogenesis is negligible. The limited variation in d137/134Ba values from -0.03 to +0.09‰ for most carbonatite samples suggests that their mantle sources have a relatively homogeneous Ba isotopic composition. Based on the carbonatites investigated in this work, the average d137/134Ba value of their mantle sources is estimated to be +0.04?±?0.06‰ (2SD, n?=?16), which is similar to the average value of +0.05?±?0.06‰ for mid-ocean ridge basalts. The lower d137/134Ba value of -0.08‰ in a Canadian sample and higher d137/134Ba values of +0.14‰ and?+?0.23‰ in two Greenland samples suggest local mantle isotopic heterogeneity that may reflect the incorporation of recycled crustal materials in their sources.
DS202007-1160
2020
Xu, J.Li, W-Y., Yu, H-M., Xu, J., Halama, R., Bell, K., Nan, X-Y., Huang, F.Barium isotopic composition of the mantle: constraints from carbonatites.Geochimica et Cosmochimica Acta, Vol. 278, pp. 235-243.Mantlecarbonatite

Abstract: To investigate the behaviour of Ba isotopes during carbonatite petrogenesis and to explore the possibility of using carbonatites to constrain the Ba isotopic composition of the mantle, we report high-precision Ba isotopic analyses of: (1) carbonatites and associated silicate rocks from the only active carbonatite volcano, Oldoinyo Lengai, Tanzania, and (2) Archean to Cenozoic carbonatites from Canada, East Africa, Germany and Greenland. Carbonatites and associated phonolites and nephelinites from Oldoinyo Lengai have similar d137/134Ba values that range from +0.01 to +0.03‰, indicating that Ba isotope fractionation during carbonatite petrogenesis is negligible. The limited variation in d137/134Ba values from -0.03 to +0.09‰ for most carbonatite samples suggests that their mantle sources have a relatively homogeneous Ba isotopic composition. Based on the carbonatites investigated in this work, the average d137/134Ba value of their mantle sources is estimated to be +0.04?±?0.06‰ (2SD, n?=?16), which is similar to the average value of +0.05?±?0.06‰ for mid-ocean ridge basalts. The lower d137/134Ba value of -0.08‰ in a Canadian sample and higher d137/134Ba values of +0.14‰ and?+?0.23‰ in two Greenland samples suggest local mantle isotopic heterogeneity that may reflect the incorporation of recycled crustal materials in their sources.
DS1986-0881
1986
Xu, J.A.Xu, J.A., Mao, H.K., Bell, P.M.high pressure ruby and diamond fluoresence: observations at 0.21 and 0.55terapascalScience, Vol. 232, June 13, pp. 1404-1406. also reviewed in EOSGlobalDiamond, Crystallography
DS2003-1510
2003
Xu, J.F.Xu, J.F., Shinjo, R., Defant, M.J., Wang, Q., Rapp, R.P.Origin of Mesozoic adakitic intrusive rocks in the Nigzhen area of east China: partialGeology, Vol. 30, 12, Dec.pp. 111-1114.ChinaMelting, mantle, slab
DS200412-2163
2004
Xu, J.F.Xu, Y.G., Huang, X.L., Wang, Y.B., Iizuka, Y., Xu, J.F., Wang, Q., Wu, X.Y.Crust mantle interaction during the tectono-thermal reactivation of the North Chin a Craton: constraints from SHRIMP zircon U PbContributions to Mineralogy and Petrology, Vol. 147, 6, pp. 750-767.China, ShandongGeothermometry, geochronology
DS2002-1776
2002
Xu, J-A.Zhang, J., Wang, L., Weidner, D.J., Uchida, T., Xu, J-A.The strength of moissaniteAmerican Mineralogist, Vol. 87, pp. 1005-8.GlobalMoissanite, Petrology - experimental
DS200612-1507
2006
Xu, J-F.Wang, Q., Wyman, D.A., Xu, J-F., Zhao, Z-H., Jian, P., Xiong, X-L., Bao, Z-W., Li, C-F., Bai, Z-H.Petrogenesis of Cretaceous adakitic and shoshonitic igneous rocks in the Luzong area, Anhui Province: implications for geodynamics and Cu-Au mineralization.Lithos, In pressChinaShoshonites - not specific to diamond
DS201012-0440
2010
Xu, J-F.Li, J.,Xu, J-F., Suzuki, K., He, B., Xu, Y-G., Ren, Z-Y.Os, Nd and Sr isotope and trace element geochemistry of the Muli picrites: insights into the mantle source of the Emeishan large igneous province.Lithos, in press available, 15p.ChinaGeochronology
DS201312-0536
2014
Xu, J-F.Li, J., Wang,-C., Ren, Z-Y., Xu, J-F., He, B., Xu, Y-G.Chemical heterogeneity of the Emeishan mantle plume: evidence from highly siderophile element abundances in picrites.Journal of Asian Earth Studies, Vol. 79, A, pp. 191-205.ChinaPicrite
DS201112-1129
2011
Xu, L.Xu,L., Zhou, Q.J., Pei, F.P., Yang, D.B., Gao, S., Wang, W., Feng, H.Recycling lower continental crust in an intra continental setting: mineral chemistry and oxygen isotope insights from websterite xenoliths.Goldschmidt Conference 2011, abstract p.2197.ChinaNorth China craton
DS201703-0439
2016
Xu, L.Wang, H., Li, J., Zhang, H., Xu, L., Li, W.The absolute paleoposition of the North Chin a block during the middle Ordovician.Science China Earth Sciences, Vol. 59, 3, pp. 573-582.ChinaCraton, North China

Abstract: Present-day hot spots and Phanerozoic large igneous provinces (LIPs) and kimberlites mainly occur at the edges of the projections of Large Low Shear Wave Velocity Provinces (LLSVPs) on the earth’s surface. If a plate contains accurately dated LIPs or kimberlites, it is possible to obtain the absolute paleoposition of the plate from the LIP/kimberlite and paleomagnetic data. The presence of Middle Ordovician kimberlites in the North China Block provides an opportunity to determine the absolute paleoposition of the block during the Middle Ordovician. In addition to paleobiogeographical information and the results of previous work on global plate reconstruction for the Ordovician Period, we selected published paleomagnetic data for the North China Block during the Middle Ordovician and determined the most reasonable absolute paleoposition of the North China Block during the Middle Ordovician: paleolatitude of approximately 16.6°S to 19.1°S and paleolongitude of approximately 10°W. The block was located between the Siberian Plate and Gondwana, close to the Siberian Plate. During the Cambrian and Ordovician periods, the North China Block may have moved toward the Siberian Plate and away from the Australian Plate.
DS2000-1033
2000
Xu, M.Xu, M., Midleton, M.F., Xue, L.F., Wang, D.P.Structure of the lithosphere and Mesozoic sedimentary basins in western Liaoning Northern Liaoning.International Geology Review, Vol. 42, No. 3, March pp. 269-78.China, northeastTectonics
DS200812-1315
2007
Xu, M.Zhang, Y., Xu, M., Zhu, M., Wang, H.Silicate melt properties and volcanic eruptions.Reviews of Geophysics, Vol. 45, RG 4004MantleMagmatism
DS201112-0457
2011
Xu, M.Huang, Z., Wang, L., Zhao, D., Mi, N., Xu, M.Seismic anisotropy and mantle dynamics beneath China.Earth and Planetary Science Letters, Vol. 306, 1-2, pp. 105-117.ChinaGeophysics - seismics
DS202104-0618
2020
Xu, M.Xu, M., Jing, Z., Bajgain, S.K., Mookherjee, M., Van Orman, J.A., Yu, T., Wang, Y.High pressure elastic properties of dolomite melt supporting carbonate-induced melting in deep upper mantle.Proceedings of the National Academy of Sciences PNAS, Vol. 117, 31, pp. 18285-18291. pdfMantlemelting

Abstract: Deeply subducted carbonates likely cause low-degree melting of the upper mantle and thus play an important role in the deep carbon cycle. However, direct seismic detection of carbonate-induced partial melts in the Earth’s interior is hindered by our poor knowledge on the elastic properties of carbonate melts. Here we report the first experimentally determined sound velocity and density data on dolomite melt up to 5.9 GPa and 2046 K by in-situ ultrasonic and sink-float techniques, respectively, as well as first-principles molecular dynamics simulations of dolomite melt up to 16 GPa and 3000 K. Using our new elasticity data, the calculated VP/VS ratio of the deep upper mantle (~180-330 km) with a small amount of carbonate-rich melt provides a natural explanation for the elevated VP/VS ratio of the upper mantle from global seismic observations, supporting the pervasive presence of a low-degree carbonate-rich partial melt (~0.05%) that is consistent with the volatile-induced or redox-regulated initial melting in the upper mantle as argued by petrologic studies. This carbonate-rich partial melt region implies a global average carbon (C) concentration of 80-140 ppm. by weight in the deep upper mantle source region, consistent with the mantle carbon content determined from geochemical studies.
DS202106-0939
2021
Xu, M.Guan, H., Geoffroy, L., Xu, M.Magma-assisted fragmentation of Pangea: continental breakup initiation and propagation.Gondwana Research, Vol. 96, pp. 56-75. pdfMantlemagmatism

Abstract: Pre-magmatic continental extension often precedes the major magmatic expulsion of large igneous provinces (LIPs). However, the cause-and-effect relationship between pre-magmatic rifting and the extrusion of large amount of magma is controversial. It remains unclear whether magmatism arises as a consequence of passive rifting or whether it is related to active upwelling of the mantle. In addition, the relationship between the pre-magmatic stages and the final breakup, with the onset of conjugate passive margins, is ambiguous. In this study, we compiled available data from six LIPs (Central Atlantic, Karoo, Parana-Etendeka, Deccan, North Atlantic, and Afar igneous provinces) that successively occurred during the fragmentation of Pangea and found that pre-magmatic rift trends may show a high obliquity or even be orthogonal with respect to the future passive margins. We conclude that syn-magmatic rifts should not be directly correlated, both structurally and dynamically, to the ancient pre-magmatic rift phase. Furthermore, following the breakup of a supercontinent, seafloor spreading usually initiates within volcanic passive margins (VPMs) and then propagates away to create non-volcanic passive margins (NVPMs) as a consequence of the consumption and cooling of a sub-lithospheric positive thermal anomaly. Major transform faults often exist between VPMs and NVPMs, acting as a mechanical barrier to mantle melting and magmatism transportation.
DS2001-1270
2001
Xu, P.Xu, P., Liu, F., Chen, F.Slab like high velocity anomaly in the uppermost mantle beneath the Dabie Sulu orogen.Geophysical Research Letters, Vol. 28, No. 9, May 1, pp. 1847-50.Chinaultra high pressure (UHP), subduction, Geophysics - seismics
DS2002-1747
2002
Xu, P.Xu, P., Liu, F., Ye, K., Wang, Q., Cong, B., Chen, H.Flake tectonics in the Sulu Orogen in eastern Chin a as revealed by seismic tomographyGeophysical Research Letters, Vol. 29,10,May15,pp.23-ChinaGeophysics - seismics
DS2002-1761
2002
Xu, P.Ye, K., Liu, J-B., Cong, B-L., Ye, D-N., Xu, P., Omori, S., Maruyama, S.Ultrahigh pressure (UHP) low Al titanites from carbonate bearing rocks in the Dabie shan Sulu UHP terrane, eastern China.American Mineralogist, Vol. 87, pp. 875-881.ChinaUHP - mineralogy, Dabie Shan area
DS200612-1548
2006
Xu, P.Wu, F-Y., Yang, Y-H., Xie, L-W., Yang, J-H., Xu, P.Hf isotopic compositions of the standard zircons and baddeleyites used in U Pb geochronology.Chemical Geology, Vol. 234, 1-2, Oct 30, pp. 105-126.ChinaUHP, geochronology
DS200912-0826
2009
Xu, P.Xu, P., Zhao, D.Upper mantle velocity structure beneath the North Chin a Craton: implications for lithospheric thinning.Geophysical Journal International, Vol. 177, 3, pp. 1279-1283.ChinaGeophysics - seismics
DS201412-1024
2014
Xu, R.Zhang, L., Meng, Y., Yang, W.,Wang, L., Mao, W.L., Zeng, Q-S., Jeong, J.S., Wagner, A.J., Mkhoyan, K.A., Liu, W., Xu, R., Mao, H-K.Disproportionation of (Mg,Fe) SiO3 perovskite in Earth's deep lower mantle.Science, Vol. 344, no. 6186, pp. 877-882.MantlePerovskite
DS202002-0220
2019
Xu, R.Xu, R., Liu, Y., Wang, X-C, Foley, S.F., Zhang, Y., Yuan, H.Generation of continental intraplate alkali basalts and deep carbon cycle.Earth Science Reviews, in press available, 38p. Doi.org/1010.1016 /jearsciev.2019.103073Globalcarbon

Abstract: Although the deep recycling of carbon has been proposed to play a key role in producing intraplate magmatism, the question of how it controls or triggers mantle melting remains poorly understood. In addition, generation of incipient carbonated melts in the mantle and their subsequent reaction with the mantle are critical processes that can influence the geochemistry of intraplate basalts, but the details of such processes are also unclear. Here we present geochemical evidence for the existence of pervasive carbonate melt in the mantle source of Cenozoic continental intraplate highly alkali basalts (SiO2 < 45 wt%), which are volumetrically minor but widespread in eastern China. The primary magma compositions of these basalts cannot be explained by either partial melting of a single mantle source lithology or mixing of magmas derived from distinct mantle sources, but can be adequately explained by carbonate-fluxed melting of eclogite and subsequent reaction between silica-rich melts and peridotite that ultimately transformed the initial carbonated silica-rich melts into silica-undersaturated alkalic magmas. The source of the carbonate is in subducted eclogites associated with the Pacific plate, which stagnated in the mantle transition zone (MTZ). The spatial distribution of the alkali basalts is in accord with large-scale seismic low-velocity anomalies in the upper mantle above the MTZ. Similar scenarios in central-western Europe and eastern Australia lead us to propose that reaction between carbonated silica-rich melt and peridotite may be a pivotal mechanism for the generation of continental intraplate alkali basalts elsewhere in the world.
DS202007-1185
2020
Xu, R.Xu, R., Liu, Y., Lambert, S.Melting of a hydrous peridotite mantle source under the Emeishan large igneous province.Earth Science Reviews, in press available 30p. PdfChinapicrites

Abstract: Large igneous provinces on Earth result from anomalously enormous volcanic eruptions at high melt production rates. These eruptions are often linked to catastrophic events such as mass extinctions, global climate changes, or continental break-up. Decoding their petrogenesis is therefore of great importance for our comprehensive understanding of the evolution and geodynamics of our planet. The ~260 Ma Emeishan large igneous province is an important geological feature of SW China with world-class ore deposits and is also suggested to be linked with the Capitanian mass extinction. However, fundamental aspects of the genesis of Emeishan province's most primitive lavas (picrites), such as the source lithology (pyroxenite or peridotite), the origin of compositional variations of olivines and the melting temperature and pressure conditions, remain poorly constrained. Here, we compile information on melt inclusion and host olivine, and whole-rock compositions from the ELIP picrites and show that these data are consistent with decompression melting of a relatively homogeneous peridotitic mantle plume, with a potential temperature higher than 1560 °C. The compositional variability of the olivines and picrites can be explained by varying the equilibrium depth of primary magma segregation and does not require the contribution of a pyroxenite component as previously suggested. Our results favor a scenario for the origin of the Emeishan large igneous province in which the decompression melting during upwelling of a hot hydrous and oxidized mantle plume is accompanied by catastrophic lithospheric thinning. In combination with the now extensive multi-element geochemical data, our findings provide a starting point for re-evaluation of the petrogenesis models for large igneous provinces.
DS2003-1511
2003
Xu, S.Xu, S., Liu, Y., Chen, G., Compagnoni, R., Rolfo, F., He, M., Liu, H.New finding of microdiamonds in eclogites from Dabie Sulu region in central easternChinese Science Bulletin, Science Press, Vol. 48, 10, May, pp. 988-994.ChinaUHP, Deposit - Dabie Shan area
DS200412-1684
2004
Xu, S.Rolfo, F., Compagnoni, R., Wu, W., Xu, S.A coherent lithostratigraphic unit in the coesite eclogite complex of Dabie Shan China: geologic and petrologic evidence.Lithos, Vol. 73, 1-2, March pp. 71-94.ChinaUHP, metamorphism
DS200412-2159
2003
Xu, S.Xu, S., Liu, Y., Chen, G., Compagnoni, R., Rolfo, F., He, M., Liu, H.New finding of microdiamonds in eclogites from Dabie Sulu region in central eastern China.Chinese Science Bulletin, Vol. 48, 10, May, pp. 988-994.ChinaUHP Deposit - Dabie Shan area
DS200512-1207
2005
Xu, S.Xu, S., Liu, Y., Chen, G., Ji, S., Ni, P., Xiao, W.Microdiamonds, their classification and tectonic implications for the host eclogites from the Dabie and Su-Lu regions in central eastern China.Mineralogical Magazine, Vol. 69, 4, Aug. pp. 509-520.ChinaUHP, microdiamonds
DS200712-0635
2006
Xu, S.Liu, D., Jian, P., Kroner, A., Xu, S.Dating of prograde metamorphic events deciphered from episodic zircon growth in rocks of the Dabie Sulu UHP complex, China.Earth and Planetary Science Letters, Vol. 250, 3-4, Oct. 30, pp. 650-666.ChinaUHP
DS200912-0827
2008
Xu, S.Xu, S., Wu, W., Xiao, W., Yang, J., Chen, J., Ji, S., Liu, Y.Moissanite in serpentine from the Dabie Mountains in China.Mineralogical Magazine, Vol. 72, 4, pp. 899-908.ChinaUHP
DS201212-0796
2012
Xu, S.Xu, S., Wu, W., Lu, Y., Wang, D.Tectonic setting of the low grade metamorphic rocks of the Dabie Orogen, central eastern China.Journal of Structural Geology, Vol. 37, pp. 134-149.ChinaUHP
DS201510-1815
2015
Xu, S.Xu, S., Liu, Y., Chen, G., Ji, S., Ni, P., Xiao, W.Microdiamonds, their classification and tectonic implications for the host eclogites from the Dabie and Su-Lu regions in central eastern China.Mineralogical Magazine, Vol. 69, 4, pp. 590-520.ChinaUHP

Abstract: We have found >10 in situ microdiamonds in thin sections of eclogites from the Dabie and Su-Lu regions of central eastern China since the first occurrence of microdiamond in eclogites from the Dabie Mountains (DMT) reported in 1992. The microdiamonds are found not only in the central part but also in the northern part of the DMT. Several free crystals have been recovered from the crushed eclogites from the central DMT. Most in situ microdiamonds are inclusions in garnets but a few larger ones are intergranular. Most of the diamondiferous eclogites in the central part of the DMT are associated with coesite. Most importantly, the observation of microdiamonds in northern Dabie lead us to question the supposition that this is a low-P metamorphic terrane. All the diamondiferous eclogites from both the north and central DMT are of continental affinity as demonstrated by their negative eNd values. Therefore, both the north and central eclogite belts in the DMT are considered to be from the deep subducted terrane. Five in situ microdiamonds and two free crystals are first reported in this paper. The dimensions of the in situ microdiamonds are 30-80 µm and the free crystals are up to 400–-00 µm across. All the microdiamonds are confirmed as such by Raman spectroscopy. The results of an infrared spectroscopic investigation on two larger free crystals and two in situ microdiamonds show that all the microdiamonds from both the Dabie and Su-Lu regions are mixed types IaA and IaB diamonds and there is no indication of any synthetic microdiamonds in our samples because such synthetic microdiamonds are always rich in type Ib.
DS2003-0004
2003
Xu, W.Ai, Y., Zheng, T., Xu, W., He, Y., Dong, D.A complex 660 km discontinuity beneath northeast ChinaEarth and Planetary Science Letters, Vol. 212, 1-2, pp. 63-71.ChinaTectonics
DS200412-0009
2003
Xu, W.Ai, Y., Zheng, T., Xu, W., He, Y., Dong, D.A complex 660 km discontinuity beneath northeast China.Earth and Planetary Science Letters, Vol. 212, 1-2, pp. 63-71.ChinaGeophysics - seismics Tectonics
DS200412-2160
2004
Xu, W.Xu, W., Liu, X., Wang, Q., Lin, J., Wang, D.Garnet exsolution in garnet clinopyroxenite and clinopyroxenite xenoliths in early Cretaceous intrusions from the Xuzhou region,Mineralogical Magazine, Vol. 68, 3, June 1, pp. 443-453.ChinaXenolith - geochemistry
DS200512-1208
2004
Xu, W.Xu, W., Wang, Q., Wang, D.Processes and mechanism of Mesozoic lithospheric thinning in eastern North Chin a Craton: evidence from Mesozoic igneous rocks and deep seated xenoliths.Earth Science Frontiers, Vol. 11, 4, pp. 309-318. Ingenta 1045384777ChinaXenoliths
DS200612-1378
2006
Xu, W.Stixrude, L., Lithgow-Bertelloni, Xu, W.Physical properties of multi-phase mantle assemblages.International Mineralogical Association 19th. General Meeting, held Kobe, Japan July 23-28 2006, Abstract p.102.MantleMineralogy
DS200612-1608
2006
Xu, W.Zheng, T., Chen, L., Zhao, L., Xu, W., Zhu, R.Crust mantle structure difference across the gravity gradient zone in North Chin a Craton: seismic image of the thinned continental crust.Physics of the Earth and Planetary Interiors, Vol. 159, 1-2, pp. 43-58.ChinaGeophysics - seismics
DS200712-1133
2007
Xu, W.Wang, Q., Wyman, D.A., Xu, J., Jian, P., Zhao, Z., Li, C., Xu, W., Ma, J., He, B.Early Cretaceous adakitic granites in the northern Dabie Complex, central China: implications for partial melting and delamination of thickened lower crust.Geochimica et Cosmochimica Acta, Vol. 71, 10, May 15, pp. 2609-2636.ChinaUHP - Dabie Shon
DS200812-1281
2008
Xu, W.Xu, W., Lithgow Bertelloni, C., Stixrude, L., Ritsema, J.The effect of bulk composition and temperature on mantle seismic structure.Earth and Planetary Science Letters, Vol. 275, 1-2, pp. 70-79.MantleGeophysics - seismics, geochemistry
DS200912-0096
2009
Xu, W.Cammarano, F., Romanowicz, B., Stixrude, L., Lithgow-Bertelloni, C., Xu, W.Inferring the thermochemical structure of the upper mantle from seismic data.Geophysical Journal International, Vol. 179, 2, Nov. pp. 1169-1185.MantleGeothermometry
DS200912-0629
2009
Xu, W.Ritsema, J., Cupillard, P., Tauzin, B., Xu, W., Stixrude, L., Lithgow-Bertelloni, C.Joint mineral physics and seismic wave traveltime analysis of upper mantle temperature.Geology, Vol. 37, 4, April pp. 363-366.MantleGeophysics - seismics, thermodynamics
DS200912-0631
2009
Xu, W.Ritsema, J., Xu, W., Stixrude, L., Lithgow Bertelloni, C.Estimates of the transition zone temperature in mechanically mixed upper mantle.Earth and Planetary Science Letters, Vol. 277, 1-2, pp. 244-252.MantleGeothermometry
DS201012-0453
2010
Xu, W.Liu, J., Rudnick, R., Walker, R., Gao, S., Wu, F., Xu, W., Xu, Y.OS isotope evidence for diachronous formation of lithospheric mantle beneath the Trans-North Chin a oorgen, north Chin a, craton.Goldschmidt 2010 abstracts, abstractChinaGeochronology
DS201112-1108
2011
Xu, W.Wei, Z., Chen, L., Xu, W.Crustal thickness and Vp/Vs ratio of the central and western North Chin a craton and its tectonic implications.Geophysical Journal International, Vol. 186, 2, pp. 385-389.ChinaTectonics
DS201506-0302
2015
Xu, W.Zhu, H., Yang, J., Robinson, P.T., Zhu, Y., Zhu, F., Zhao, X., Liu, Z., Zhang, W., Xu, W.The discovery of diamonds in chromitites of the Hegenshan ophiolite, Inner Mongolia, China.Acta Geologica Sinica, Vol. 89, 2, pp. 341-350.China, MongoliaChromitite
DS201601-0019
2015
Xu, W.Huang, Yang, J., Zhu, Y., Xiong, F., Liu, Z., Zhang, Z., Xu, W.The discovery of diamonds in chromitite of the Hegenshan ophiolite, Inner Mongolia.Acta Geologica Sinica, Vol. 89, 2, p. 32.Asia, MongoliaOphiolite

Abstract: Diamond, moissanite and a variety of other minerals, similar to those reported from ophiolites in Tibet and northern Russia, have recently been discovered in chromitites of the Hegenshan ophiolite of the Central Asian Orogenic Belt, north China. The chromitites are small, podiform and vein-like bodies hosted in dunite, clinopyroxene-bearing peridotite, troctolite and gabbro. All of the analysed chromite grains are relatively Al-rich, with Cr# [100Cr/(Cr+Al)] of about 47-53. Preliminary studies of mainly disseminated chromitite from ore body No. 3756 have identified more than 30 mineral species in addition to diamond and moissanite. These include oxides (mostly hematite, magnetite, rutile, anatase, cassiterite, and quartz), sulfides (pyrite, marcasite and others), silicates (magnesian olivine, enstatite, augite, diopside, uvarovite, pyrope, orthoclase, zircon, sphene, vesuvianite, chlorite and serpentine) and others (e.g., calcite, monazite, glauberite, iowaite and a range of metallic alloys). This study demonstrates that diamond, moissanite and other exotic minerals can occur in high-Al, as well as high-Cr chromites, and significantly extends the geographic and age range of known diamond-bearing ophiolites.
DS200512-0313
2004
Xu, W.L.Gao, S., Rudnick, R.L., Yuan, H.L., Liu, X.M., Liu, Y.S., Xu, W.L., Ling, W.L., Ayers, K., Wang, X.C.,Wang, Q.H.Recycling lower continental crust in the North Chin a Craton.Nature, No. 7019, Dec. 16, pp. 892-896.ChinaSubduction
DS200612-0428
2006
Xu, W.L.Gao, S., Rudnick, R.L., Xu, W.L., Yuan, H.L., Hu, Z.C., Liu, X.M.Lithospheric evolution of the North Chin a Craton: evidence from high Mg adakitic rocks and their entrained xenoliths.Geochimica et Cosmochimica Acta, Vol. 70, 18, p. 193, abstract only.ChinaGeochemistry
DS200712-0347
2007
Xu, W-L.Gao, S., Rudnick, R.L., Xu, W-L., Yuan, Liu, Puchtel, Liu, Huang, WangRecycling deep cratonic lithosphere and generation of intraplate magmatism.Plates, Plumes, and Paradigms, 1p. abstract p. A307.ChinaAlkaline rocks, picrites
DS200812-1282
2008
Xu, W-L.Xu, W-L., Yang, D.B., Gao, S., Yu, Y., Pei, F.P.Mesozoic lithospheric mantle of the Central North Chin a craton: evidence from peridotite xenoliths.Goldschmidt Conference 2008, Abstract p.A1047.ChinaXenoliths
DS201112-0611
2011
Xu, W-l.Liu, J., Rudnick, R.L., Walker, R.J., Gao, S., Wu, F-y., Piccoli, P.M., Yuan, H., Xu, W-l., Xu, Yi-G.Mapping lithospheric boundaries using Os isotopes of mantle xenoliths: an example from the North Chin a Craton.Geochimica et Cosmochimica Acta, Vol. 75, 13, pp. 3881-3902.ChinaGeochronology
DS201212-0797
2013
Xu, W-L.Xu, W-L., Zhou, Q-J., Pei, F-P., Gao, S., Li, Q-L., Yang, Y-H.Destructive of the North Chin a craton: delamin ation or thermal/chemical erosion? Mineral chemistry and oxygen isotope insights from websterite xenoliths.Gondwana Research, Vol. 23, 1, pp. 119-129.ChinaCraton, destruction
DS1996-1571
1996
Xu, X.Xu, X., O'Reilly, S.Y., Griffin, W.L.Thermal and redox states of subcontinental lithospheric mantle: constraints from basalt-borne mantle xenolithsInternational Geological Congress 30th Session Beijing, Abstracts, Vol. 1, p. 118.ChinaXenoliths
DS1996-1572
1996
Xu, X.Xu, X., O'Reilly, S.Y., Griffin, W.L.A xenolith derived geotherm and the crust mantle boundary at Qilin southeastern China.Lithos, Vol. 38, No. 1/2, pp. 41-62.ChinaXenoliths, Geothermometry
DS1999-0814
1999
Xu, X.Xu, X., O'Reilly, S.Y., Griffin, W.L.Reply: the geotherms of the lithosphere beneath Qilin, southeast China: are-appraisal and implications for P-T ...Lithos, Vol. 47, No. 3-4, July pp. 195-200.ChinaPyroxenites - iron rich, Lithosphere
DS2003-1512
2003
Xu, X.Xu, X., O'Reilly, S.Y., Griffin, W.L., Zhou, X.Enrichment of upper mantle peridotite: petrological, trace element and isotopic evidenceChemical Geology, Vol. 198, 3-4, pp. 163-188.ChinaPetrology, Geochronology
DS2003-1513
2003
Xu, X.Xu, X., O'Reilly, S.Y., Griffin, W.L., Zhou, X.Enrichment of upper mantle peridotite: petrological, trace element and isotopic evidenceChemical Geology, Vol. 198, 3-4, August 15, pp. 163-188.China, southeastBasalts, Nushan, Mingxi, Geochronology
DS2003-1535
2003
Xu, X.Yu, J.H., O'Reilly, S.Y., Griffin, W.L., Xu, X., Zhang, M., Zhou, X.The thermal state and composition of the lithospheric mantle beneath the LeizhouJournal of Volcanology and Geothermal Research, Vol. 122, 3-4, pp. 165-89.China, southGeothermometry
DS2003-1536
2003
Xu, X.Yu, J-H., O'Reilly, S.Y., Griffin, W.L., Xu, X., Zhang, M., Zhou, X.The thermal state and composition of the lithospheric mantle beneath the LeizhouJournal of Volcanology and Geothermal Research, Vol. April 1, pp. 165-189.ChinaMetapyroxenites, xenoliths
DS2003-1537
2003
Xu, X.Yu, J-H., Xu, X., O'Reilly, S.Y., Griffin, W.L., Zhang, M.Granulite xenoliths from Cenozoic basalts in SE Chin a provide geochemical fingerprintsLithos, Vol. 67, 1-2, March pp. 77-102.China, southeastXenoliths, Geochemistry
DS200412-2161
2003
Xu, X.Xu, X., O'Reilly, S.Y., Griffin, W.L., Zhou, X.Enrichment of upper mantle peridotite: petrological, trace element and isotopic evidence in xenoliths from SE China.Chemical Geology, Vol. 198, 3-4, August 15, pp. 163-188.ChinaBasalts, Nushan, Mingxi, geochronology
DS200412-2190
2003
Xu, X.Yu, J-H., O'Reilly, S.Y., Griffin, W.L., Xu, X., Zhang, M., Zhou, X.The thermal state and composition of the lithospheric mantle beneath the Leizhou Peninsula, south China.Journal of Volcanology and Geothermal Research, Vol. April 1, pp. 165-189.ChinaMetapyroxenites, xenoliths
DS200412-2191
2004
Xu, X.Yu, J-H., Xu, X., O'Reilly, S.Y., Griffin, W.L., Zhang, M.Granulite xenoliths from Cenozoic basalts in SE Chin a provide geochemical fingerprints to distinguish lower crust terranes fromLithos, Vol. 73, 1-2, March, pp. 135-144.ChinaTectonics, geochemistry
DS200512-1209
2005
Xu, X.Xu, X., O'Reilly, S.Y., Griffin, W.L., Deng, P., Pearson, N.J.Relict Proterozoic basement in the Nanling Mountains (SE China) and its tectonothermal.Tectonics, Vol. 24, 2, TC2003001652ChinaGeothermometry
DS200612-1556
2006
Xu, X.Xu, X.Re-Os isotopes in mantle xenoliths from eastern China: age and evolution of the lithospheric mantle.GEMOC Annual Report, 2005, p. 46-47.ChinaGeochronology - sulphides
DS200612-1577
2006
Xu, X.Yu, J-H., O'Reilly, S.Y., Zhang Ming, Griffin, W.L., Xu, X.Roles of melting and metasomatism in the formation of the lithospheric mantle beneath the Leizhou Peninsula, South China.Journal of Petrology, Vol. 47, 2, Feb. pp. 355-383.ChinaMetasomatism
DS200812-1283
2008
Xu, X.Xu, X., Griffin, W.L., O'Reilly, S.Y., Pearson, N.J., Geng, H., Zheng, J.Re-Os isotopes of sulfides in mantle xenoliths from eastern China: progressive modifications of lithospheric mantle.Lithos, Vol. 102, 3-4, pp.43-64.ChinaGeochronology
DS201012-0872
2010
Xu, X.Yang, J., Zhang, Z., Xu, X., Li, Y., Li, J., Jia, Y., Liu, Z., Ba, D.Diamond in the Purang peridotite Massif, west of the Yarlung Zangbu Suture, Tibet: a new discovery.Goldschmidt 2010 abstracts, abstractAsia, TibetPurang Massif
DS201112-1131
2011
Xu, X.Yang, J., Xu, X., Li, Y., Liu, Z., Li, J., Ba, D., Robinson, P.T.Diamond discovered from six different ultramafic massifs along the Yarlung Zangbu suture between the Indian and Eurasian plates.Geological Society of America, Annual Meeting, Minneapolis, Oct. 9-12, abstractAsia, IndiaMantle harzburgites
DS201212-0271
2012
Xu, X.Guo, X., Encarnacion, J., Deino, A., Xu, X., Li, Z., Tian, X.Collision and rotation of the South Chin a block and their role in the formation and exhumation of ultrahigh pressure rocks in the Dabie Shan orogen.Terra Nova, in press availableChinaUHP
DS201212-0272
2012
Xu, X.Guo, X., Encarnacion, J., Xu, X., Deino, A., Li, Z.,Tian, X.Collision and rotation of the South Chin a block and their role in the formation and exhumation of ultrahigh pressure rocks in the Dabie Shan orogen.Terra Nova, Vol. 24, 5, pp. 339-350.ChinaUHP
DS201212-0801
2012
Xu, X.Yang, J., Wirth, R., Xu, X., Robinson, P.T., Rong, H.Mineral inclusions in diamonds from ophiolitic peridotite and chromites.GSA Annual Meeting, Paper no. 74-4, abstractChina, TibetDiamond inclusions
DS201312-0991
2013
Xu, X.Yang, J., Xu, X., Robinson, P.T.Ophiolite type diamond.Geological Society of America Annual Meeting, Vol. 45, 7, p. 451 abstractTechnologyDiamond genesis
DS201412-0999
2014
Xu, X.Yang, J., Meng, F., Xu, X., Robinson, P.T., Dilek, Y., Makeyev, A.B., Wirth, R., Wiedenbeck, M., Cliff, J.Diamonds, native elements and metal alloys from chromitites of the Ray-Iz ophiolite of the Polar Urals.Gondwana Research, Vol. 27, 2, pp. 459-485.Asia, TibetUHP ophiolite diamonds
DS201502-0126
2014
Xu, X.Yang, J., Meng, F., Xu, X., Robinson, P.T., Dilek, Y., Makeyev, A.B., Wirth, R., Wiedenbeck, M., Cliff, J.Diamonds, native elements and metal alloys from chromitites of the Ray-Iz ophiolite of the Polar Urals.Gondwana Research, Vol. 27, 2, pp. 459-485.Russia, UralsChromitite
DS201510-1789
2015
Xu, X.Moe, K.S., Yang, J-S, Johnson, P., Xu, X., Wang, W.Microdiamonds in chromitite and peridotite. Type 1aB and 1bGSA Annual Meeting, Paper 300-5, 1p. Abstract only BoothRussiaSpectroscopy
DS201510-1816
2015
Xu, X.Yang, J-S., Wirth, R., Xu, X., Tian, Y., Huang, Z., Robinson, P.T., Dilek, Y.Formation of ophiolite hosted diamonds by deep subduction of oceanic lithosphere: evidence from mineral inclusions.GSA Annual Meeting, Paper 81-2, 1p. Abstract onlyMantleMineral inclusions

Abstract: In recent years we have confirmed the existence of ophiolite-hosted diamonds on Earth, which occur in mantle peridotites and podiform chromitites of many ophiolites. These diamonds differ significantly from most kimberlite varieties, particularly in their inclusions. The typical inclusions in the diamonds are Mn-rich phases, i.e., NiMnCo alloy, native Mn, MnO, galaxite, Mn olivine and Mn garnet. Ca-silicate perovskite, a typical lower mantle mineral, was identified as mineral inclusions in diamond. One occurs as a 60-nanometer, euhedral grain associated with NiMnCo alloy and graphite, while another one occurs as a 50-nanometer grain within a large inclusion containing both NiMnCo alloy and Nd-Se-Cu-S phase. By EDS the perovskite has Ca 48.3%, Si 37.7% and Mn 14.1% with oxygen. TEM diffraction data show that the inclusion has d-spacings and angles between adjacent lattice planes are consistent to the Ca-silicate perovskite with an orthorhombic structure. The only known source of such light carbon is organic material in surface sediments and the best known sources of abundant manganese are Fe-Mn-rich sediments and Mn nodules, both of which are common on the seafloor. Many parts of the modern seafloor are also covered by sediments with a continental provenance. Phases such as SiO2 and Al2O3 are not expected in mantle peridotites and must have been introduced from shallow levels. We propose that subduction of oceanic lithosphere carries C, Mn, Si, Al and REE to the transition zone or lower mantle where the material is mixed with highly reduced material, perhaps derived from greater depths. Crystallization of diamond from a C-rich fluid encapsulates the observed inclusions. The diamonds and associated minerals are incorporated into chromite grains during chromite crystallization at depth of mantle transition zone, and are carried to shallower levels by mantle convection. Accumulation of chromite grains produces podiform chromitites containing a range of exotic minerals. However, the presence of diamonds and other UHP minerals in ophiolitic peridotites indicates that such phases can persist far outside their normal stability fields.
DS201605-0922
2016
Xu, X.Xiong, F., Yang, J., Robinson, P.T., Xu, X., Ba, D., Li, Y., Zhang, Z., Rong, H.Diamonds ad other exotic minerals recovered from peridotites of the Dangqiong ophiolite, western Yarlung-Zangbo suture zone, Tibet.Acta Geologica Sinica, Vol. 90, 2, pp. 425-439.Asia, TibetPeridotite

Abstract: Various combinations of diamond, moissanite, zircon, quartz, corundum, rutile, titanite, almandine garnet, kyanite, and andalusite have been recovered from the Dangqiong peridotites. More than 80 grains of diamond have been recovered, most of which are pale yellow to reddish-orange to colorless. The grains are all 100-200 µm in size and mostly anhedral, but with a range of morphologies including elongated, octahedral and subhedral varieties. Their identification was confirmed by a characteristic shift in the Raman spectra between 1325 cm-1 and 1333 cm-1, mostly at 1331.51 cm-1 or 1326.96 cm-1. Integration of the mineralogical, petrological and geochemical data for the Dongqiong peridotites suggests a multi-stage formation for this body and similar ophiolites in the Yarlung-Zangbo suture zone. Chromian spinel grains and perhaps small bodies of chromitite crystallized at various depths in the upper mantle, and encapsulated the UHP, highly reduced and crustal minerals. Some oceanic crustal slabs containing the chromian spinel and their inclusion were later trapped in suprasubduction zones (SSZ), where they were modified by island arc tholeiitic and boninitic magmas, thus changing the chromian spinel compositions and depositing chromitite ores in melt channels.
DS201606-1093
2015
Xu, X.Howell, D., Griffin, W.L., Yang, J., Gain, S., Stern, R.A., Huang, J-X., Jacob, D.E., Xu, X., Stokes, A.J., O'Reilly, S.Y., Pearson, N.J.Diamonds in ophiolites: contamination or a new diamond growth environment?Earth and Planetary Science Letters, Vol. 430, pp. 284-295.Asia, TibetLuobusa Massif Type Iib

Abstract: For more than 20 years, the reported occurrence of diamonds in the chromites and peridotites of the Luobusa massif in Tibet (a complex described as an ophiolite) has been widely ignored by the diamond research community. This skepticism has persisted because the diamonds are similar in many respects to high-pressure high-temperature (HPHT) synthetic/industrial diamonds (grown from metal solvents), and the finding previously has not been independently replicated. We present a detailed examination of the Luobusa diamonds (recovered from both peridotites and chromitites), including morphology, size, color, impurity characteristics (by infrared spectroscopy), internal growth structures, trace-element patterns, and C and N isotopes. A detailed comparison with synthetic industrial diamonds shows many similarities. Cubo-octahedral morphology, yellow color due to unaggregated nitrogen (C centres only, Type Ib), metal-alloy inclusions and highly negative View the MathML sourcedC13 values are present in both sets of diamonds. The Tibetan diamonds (n=3n=3) show an exceptionally large range in View the MathML sourcedN15 (-5.6 to +28.7‰+28.7‰) within individual crystals, and inconsistent fractionation between {111} and {100} growth sectors. This in contrast to large synthetic HPHT diamonds grown by the temperature gradient method, which have with View the MathML sourcedN15=0‰ in {111} sectors and +30‰+30‰ in {100} sectors, as reported in the literature. This comparison is limited by the small sample set combined with the fact the diamonds probably grew by different processes. However, the Tibetan diamonds do have generally higher concentrations and different ratios of trace elements; most inclusions are a NiMnCo alloy, but there are also some small REE-rich phases never seen in HPHT synthetics. These characteristics indicate that the Tibetan diamonds grew in contact with a C-saturated Ni-Mn-Co-rich melt in a highly reduced environment. The stable isotopes indicate a major subduction-related contribution to the chemical environment. The unaggregated nitrogen, combined with the lack of evidence for resorption or plastic deformation, suggests a short (geologically speaking) residence in the mantle. Previously published models to explain the occurrence of the diamonds, and other phases indicative of highly reduced conditions and very high pressures, have failed to take into account the characteristics of the diamonds and the implications for their formation. For these diamonds to be seriously considered as the result of a natural growth environment requires a new understanding of mantle conditions that could produce them.
DS201709-2076
2017
Xu, X.Xiong, F., Yang, J., Robinson, P.T., Dilek, Y., Milushi, I., Xu, X., Zhou, W., Zhang, Z., Rong, H.Diamonds discovered from high-Cr podiform chromitites from Bulqiza, eastern Mirdita ophiolite, Albania.Acta Geologica Sinica, Vol. 91, 2, pp. 455-468.Europe, Albaniadiamonds in chromitites

Abstract: Various combinations of diamond, moissanite, zircon, corundum, rutile and titanitehave been recovered from the Bulqiza chromitites. More than 10 grains of diamond have been recovered, most of which are pale yellow to reddish–orange to colorless. The grains are all 100–300 µm in size and mostly anhedral, but with a range of morphologies including elongated, octahedral and subhedral varieties. Their identification was confirmed by a characteristic shift in the Raman spectra between 1325 cm-1 and 1333 cm-1, mostly at 1331.51 cm-1 or 1326.96 cm-1. This investigation extends the occurrence of diamond and moissanite to the Bulqiza chromitites in the Eastern Mirdita Ophiolite. Integration of the mineralogical, petrological and geochemical data of the Bulqiza chromitites suggests their multi–stage formation. Magnesiochromite grains and perhaps small bodies of chromitite formed at various depths in the upper mantle, and encapsulated the ultra–high pressure, highly reduced and crustal minerals. Some oceanic crustal slabs containing the magnesiochromite and their inclusion were later trapped in suprasubduction zones, where they were modified by tholeiitic and boninitic arc magmas, thus changing the magnesiochromite compositions and depositing chromitite ores in melt channels.
DS201805-0993
2018
Xu, X.Xiong, F., Yang, J., Xu, X., Kapsiotis, A., Hao, X., Liu, Z.Compositional and isotopic heterogeneities in the Neo-Tethyan upper mantle recorded by coexisting Al rich and Cr rich chromitites in the Purang massif, SW Tibet (China).Journal of Asian Earth Sciences, Vol. 159, pp. 109-129.China, Tibetchromitites

Abstract: The Purang harzburgite massif in SW Tibet (China) hosts abundant chrome ore deposits. Ores consist of 20 to >95% modal chromian spinel (Cr-spinel) with mylonitic fabric in imbricate shaped pods. The composition of Cr-spinel in these ores ranges from Al-rich [Cr#Sp or Cr/(Cr?+?Al)?×?100?=?47.60-57.56] to Cr-rich (Cr#Sp: 62.55-79.57). Bulk platinum-group element (PGE) contents of chromitites are also highly variable ranging from 17.5?ppb to ~2.5?ppm. Both metallurgical and refractory chromitites show a general enrichment in the IPGE (Os, Ir and Ru) with respect to the PPGE (Rh, Pt and Pd), resulting mostly in right-sloping primitive mantle (PM)-normalized PGE profiles. The platinum-group mineral (PGM) assemblages of both chromitite types are dominated by heterogeneously distributed, euhedral Os-bearing laurite inclusions in Cr-spinel. The Purang chromitites have quite inhomogeneous 187Os/188Os ratios (0.12289-0.13194) that are within the range of those reported for mantle-hosted chromitites from other peridotite massifs. Geochemical calculations demonstrate that the parental melts of high-Cr chromitites were boninitic, whereas those of high-Al chromitites had an arc-type tholeiitic affinity. Chromite crystallization was most likely stimulated by changes in magma compositions due to melt-peridotite interaction, leading to the establishment of a heterogeneous physicochemical environment during the early crystallization of the PGM. The highly variable PGE contents, inhomogeneous Os-isotopic compositions and varying Cr#Sp ratios of these chromitites imply a polygenetic origin for them from spatially distinct melt inputs. The generally low ?Os values (<1) of chromitites indicate that their parental melts originated within different sections of a heterogeneously depleted mantle source region. These melts were most likely produced in the mantle wedge above a downgoing lithospheric slab.
DS201809-2028
2018
Xu, X.Gong, Z., Xu, X., Evans, D.A.D., Hoffman, P.F., Mitchell, R.N., Bleeker, W.Paleomagnetism and rock magnetism of the ca. 1.87 Ga Pearson Formation, Northwest Territories, Canada: a test of vertical axis rotation within the Great Slave Basin.Precambrian Research , Vol. 305C, pp. 295-309.Canada, Northwest Territoriesgeophysics

Abstract: A geometrically quantitative plate-kinematic model, based on paleomagnetism, for the initial assembly of Laurentia has taken form in the past few decades. Within this framework, there remains but one problematic interval of data predominantly from the Slave craton, which is the 1.96-1.87?Ga Coronation apparent polar wander path (APWP). The Coronation APWP shows large (~110°) back-and-forth oscillations that are difficult to explain in terms of plate motion. Nonetheless, poles from the Coronation APWP have been incorporated in various paleogeographic reconstructions of Laurentia and the supercontinent Nuna, pointing to the importance of testing its veracity. In this study, we conducted a detailed paleomagnetic and rock magnetic study of the ca. 1.87?Ga Pearson Formation, East Arm of Great Slave Lake, Northwest Territories, Canada. Our results show that Pearson Formation yields a characteristic remanent magnetization carried by single-domain or small pseudo-single-domain magnetite. The age of the magnetization is constrained to be older than Paleoproterozoic deformation and is interpreted as primary. Paleomagnetic declinations reveal a one-to-one correlation with local structural attitudes, indicating that some small blocks in the fold belt likely experienced significant (~60°) vertical-axis rotations, presumably related to large dextral displacements along the McDonald Fault system. Alternative explanations, such as true polar wander or a non-dipole magnetic field, are considered less parsimonious for the data presented here. It is suspected that some existing Christie Bay Group poles (the Stark and Tochatwi Formations), which were sampled in areas with anomalous structural attitudes and differ from time-equivalent poles obtained from areas of the Slave craton far from major transcurrent faults, may similarly suffer from vertical-axis rotation. We suggest further study before using possibly rotated Christie Bay Group poles for paleogeographic reconstructions.
DS201904-0800
2019
Xu, X.Xia, Y., Xu, X.A fragment of Columbia Supercontinent: insight for Cathayasia block basement from tectono-magmatic evolution and mantle heterogeneity.Geophysical Research Letters, Vol. 46, 4, pp. 2012-2024.South America, Colombia, Australiacraton

Abstract: Significant amounts of landmasses are brought together in a hemispheric supercontinent, then breaks up, disperse, and reform in a new supercontinent in every 400-450 Myrs. During the supercontinent cycle, global-scale continental magmatism and orogenic activity increased. The assembly and breakup of Pangaea, the latest supercontinent, are well understood today. However, the evidence becomes more sparse further back in geological history. The geological and paleomagnetic data are insufficient to determine the exact geometries of Rodinia and Columbia supercontinents. Hence, we trace the position of Cathaysia block in the Columbia supercontinent and its relationship with other continental blocks, based on its Paleoproterozoic magmatisms, metamorphisms, and sedimentations, especially ultradepleted mantle-derived rocks. This work has important implications for the mantle heterogeneity in supercontinent reconstruction.
DS201907-1586
2019
Xu, X.Xu, X., Cartigny, P., Yang, J., Dilek, Y., Xiong, F., Guo, G.FTIR spectroscopy data and carbon isotope characteristics of the ophiolite hosted diamonds.Acta Geologica Sinica, Vol. 93, 1, p.38.Asia, Russiamicrodiamonds

Abstract: We report new d13C -values data and N-content and N-aggregation state values for microdiamonds recovered from peridotites and chromitites of the Luobusa ophiolite (Tibet) and chromitites of the Ray-Iz ophiolite in the Polar Urals (Russia). All analyzed microdiamonds contain significant nitrogen contents (from 108 up to 589 ± 20% atomic ppm) with a consistently low aggregation state, show identical IR spectra dominated by strong absorption between 1130 cm-1 and 1344 cm-1, and hence characterize Type Ib diamond. Microdiamonds from the Luobusa peridotites have d13C -PDB-values ranging from -28.7‰ to -16.9‰, and N-contents from 151 to 589 atomic ppm. The d13C and N-content values for diamonds from the Luobusa chromitites are -29‰ to -15.5‰ and 152 to 428 atomic ppm, respectively. Microdiamonds from the Ray-Iz chromitites show values varying from -27.6 ‰ to -21.6 ‰ in d13C and from 108 to 499 atomic ppm in N. The carbon isotopes values bear similar features with previously analyzed metamorphic diamonds from other worldwide localities, but the samples are characterized by lower N-contents. In every respect, they are different from diamonds occurring in kimberlites and impact craters. Our samples also differ from the few synthetic diamonds; we also analyzed showing enhanced d13C -variability and less advanced aggregation state than synthetic diamonds. Our newly obtained N-aggregation state and N-content data are consistent with diamond formation over a narrow and rather cold temperature range (i.e. <950°C), and in a short residence time (i.e. within several million years) at high temperatures in the deep mantle.
DS201907-1587
2019
Xu, X.Yang, J., Robinson, P., Xu, X., Xiong, F., Lian, D.Diamond in oceanic peridotites and chromitites: evidence for deep recycled mantle in the global ophiolite record.Acta Geologica Sinica, Vol. 93, 2, p.42.Europe, Turkey, Albania, Russia, Chinamicrodiamonds

Abstract: Diamonds have been discovered in mantle peridotites and chromitites of six ophiolitic massifs along the 1300 km-long Yarlung-Zangbo suture (Bai et al., 1993; Yang et al., 2014; Xu et al., 2015), and in the Dongqiao and Dingqing mantle peridotites of the Bangong-Nujiang suture in the eastern Tethyan zone (Robinson et al., 2004; Xiong et al., 2018). Recently, in-situ diamond, coesite and other UHP mineral have also been reported in the Nidar ophiolite of the western Yarlung-Zangbo suture (Das et al., 2015, 2017). The above-mentioned diamond-bearing ophiolites represent remnants of the eastern Mesozoic Tethyan oceanic lithosphere. New publications show that diamonds also occur in chromitites in the Pozanti-Karsanti ophiolite of Turkey, and in the Mirdita ophiolite of Albania in the western Tethyan zone (Lian et al., 2017; Xiong et al., 2017; Wu et al., 2018). Similar diamonds and associated minerals have also reported from Paleozoic ophiolitic chromitites of Central Asian Orogenic Belt of China and the Ray-Iz ophiolite in the Polar Urals, Russia (Yang et al., 2015a, b; Tian et al., 2015; Huang et al, 2015). Importantly, in-situ diamonds have been recovered in chromitites of both the Luobusa ophiolite in Tbet and the Ray-Iz ophiolite in Russia (Yang et al., 2014, 2015a). The extensive occurrences of such ultra-high pressure (UHP) minerals in many ophiolites suggest formation by similar geological events in different oceans and orogenic belts of different ages. Compared to diamonds from kimberlites and UHP metamorphic belts, micro-diamonds from ophiolites present a new occurrence of diamond that requires significantly different physical and chemical conditions of formation in Earth's mantle. The forms of chromite and qingsongites (BN) indicate that ophiolitic chromitite may form at depths of >150-380 km or even deeper in the mantle (Yang et al., 2007; Dobrthinetskaya et al., 2009). The very light C isotope composition (d13C -18 to -28‰) of these ophiolitic diamonds and their Mn-bearing mineral inclusions, as well as coesite and clinopyroxene lamallae in chromite grains all indicate recycling of ancient continental or oceanic crustal materials into the deep mantle (>300 km) or down to the mantle transition zone via subduction (Yang et al., 2014, 2015a; Robinson et al., 2015; Moe et al., 2018). These new observations and new data strongly suggest that micro-diamonds and their host podiform chromitite may have formed near the transition zone in the deep mantle, and that they were then transported upward into shallow mantle depths by convection processes. The in-situ occurrence of micro-diamonds has been well-demonstrated by different groups of international researchers, along with other UHP minerals in podiform chromitites and ophiolitic peridotites clearly indicate their deep mantle origin and effectively address questions of possible contamination during sample processing and analytical work. The widespread occurrence of ophiolite-hosted diamonds and associated UHP mineral groups suggests that they may be a common feature of in-situ oceanic mantle. The fundamental scientific question to address here is how and where these micro-diamonds and UHP minerals first crystallized, how they were incorporated into ophiolitic chromitites and peridotites and how they were preserved during transport to the surface. Thus, diamonds and UHP minerals in ophiolites have raised new scientific problems and opened a new window for geologists to study recycling from crust to deep mantle and back to the surface.
DS201908-1827
2018
Xu, X.Yang, J., Robinson, P.T., Xu, X., Xiong, F., Lian, D.Diamond in oceanic peridotites and chromitites: evidence for deep recycled mantle in the global ophiolite record.International Symposium on Deep Earth Exploration and Practices, Beijing Oct. 24-26. 1 p. abstractChinadiamond genesis

Abstract: Diamonds have been discovered in mantle peridotites and chromitites of six ophiolitic massifs along the 1300 km-long Yarlung-Zangbo suture (Bai et al., 1993; Yang et al., 2014; Xu et al., 2015), and in the Dongqiao and Dingqing mantle peridotites of the Bangong-Nujiang suture in the eastern Tethyan zone (Robinson et al., 2004; Xiong et al., 2018). Recently, in-situ diamond, coesite and other UHP mineral have also been reported in the Nidar ophiolite of the western Yarlung-Zangbo suture (Das et al., 2015, 2017). The above-mentioned diamond-bearing ophiolites represent remnants of the eastern Mesozoic Tethyan oceanic lithosphere. New publications show that diamonds also occur in chromitites in the Pozanti-Karsanti ophiolite of Turkey, and in the Mirdita ophiolite of Albania in the western Tethyan zone (Lian et al., 2017; Xiong et al., 2017; Wu et al., 2018). Similar diamonds and associated minerals have also reported from Paleozoic ophiolitic chromitites of Central Asian Orogenic Belt of China and the Ray-Iz ophiolite in the Polar Urals, Russia (Yang et al., 2015a, b; Tian et al., 2015; Huang et al, 2015). Importantly, in-situ diamonds have been recovered in chromitites of both the Luobusa ophiolite in Tbet and the Ray-Iz ophiolite in Russia (Yang et al., 2014, 2015a). The extensive occurrences of such ultra-high pressure (UHP) minerals in many ophiolites suggest formation by similar geological events in different oceans and orogenic belts of different ages. Compared to diamonds from kimberlites and UHP metamorphic belts, micro-diamonds from ophiolites present a new occurrence of diamond that requires significantly different physical and chemical conditions of formation in Earth's mantle. The forms of chromite and qingsongites (BN) indicate that ophiolitic chromitite may form at depths of >150-380 km or even deeper in the mantle (Yang et al., 2007; Dobrthinetskaya et al., 2009). The very light C isotope composition (d13C -18 to -28‰) of these ophiolitic diamonds and their Mn-bearing mineral inclusions, as well as coesite and clinopyroxene lamallae in chromite grains all indicate recycling of ancient continental or oceanic crustal materials into the deep mantle (>300 km) or down to the mantle transition zone via subduction (Yang et al., 2014, 2015a; Robinson et al., 2015; Moe et al., 2018). These new observations and new data strongly suggest that micro-diamonds and their host podiform chromitite may have formed near the transition zone in the deep mantle, and that they were then transported upward into shallow mantle depths by convection processes. The in-situ occurrence of micro-diamonds has been well-demonstrated by different groups of international researchers, along with other UHP minerals in podiform chromitites and ophiolitic peridotites clearly indicate their deep mantle origin and effectively address questions of possible contamination during sample processing and analytical work. The widespread occurrence of ophiolite-hosted diamonds and associated UHP mineral groups suggests that they may be a common feature of in-situ oceanic mantle. The fundamental scientific question to address here is how and where these micro-diamonds and UHP minerals first crystallized, how they were incorporated into ophiolitic chromitites and peridotites and how they were preserved during transport to the surface. Thus, diamonds and UHP minerals in ophiolites have raised new scientific problems and opened a new window for geologists to study recycling from crust to deep mantle and back to the surface.
DS202003-0365
2019
Xu, X.Tang, S., Liu, H., Yan, S., Xu, X., Wu, W., Fan, J., Liu, J., Hu, C., Tu, L.A high sensitivity MEMS gravimeter with a large dynamic range. ( not specific to diamonds)Nature.com Microsystems & Nanoengineering, Vol. 5, doi:org/10.1038/ s41378-019-0089-7Globalgeophysics - gravity

Abstract: Precise measurement of variations in the local gravitational acceleration is valuable for natural hazard forecasting, prospecting, and geophysical studies. Common issues of the present gravimetry technologies include their high cost, high mass, and large volume, which can potentially be solved by micro-electromechanical-system (MEMS) technology. However, the reported MEMS gravimeter does not have a high sensitivity and a large dynamic range comparable with those of the present commercial gravimeters, lowering its practicability and ruling out worldwide deployment. In this paper, we introduce a more practical MEMS gravimeter that has a higher sensitivity of 8?µGal/vHz and a larger dynamic range of 8000 mGal by using an advanced suspension design and a customized optical displacement transducer. The proposed MEMS gravimeter has performed the co-site earth tides measurement with a commercial superconducting gravimeter GWR iGrav with the results showing a correlation coefficient of 0.91.
DS201601-0051
2015
Xu, X.X.Yang, J.S., Wirth, R., Wiedenbeck, M., Griffin, W.L., Meng, F.C., Chen, S.Y., Bai, W.J., Xu, X.X., Makeeyev, A.B., Bryanchaniniova, N.I.Diamonds and highly reduced minerals from chromitite of the Ray-Iz ophiolite of the Polar Urals: deep origin of podiform chromitites and ophiolitic diamonds.Acta Geologica Sinica, Vol. 89, 2, p. 107.Russia, Polar UralsOphiolite
DS200812-1289
2008
Xu, X-S.Yan, J., Chen, J-F., Xu, X-S.Geochemistry of Cretaceous mafic rocks from the Lower Yangtze region, eastern China: characteristics and evolution of the lithospheric mantle.Journal of Asian Earth Sciences, Vol. 33, 3-4, July 15, pp. 177-193.ChinaGeochemistry
DS1996-1573
1996
Xu, Y.Xu, Y., Mercier, J.C-C., Shi, L.Potassium rich glass bearing wehrlite xenoliths from Yitong: petrological and chemical evidence mantle MetasomatismContributions to Mineralogy and Petrology, Vol. 125, No. 4, pp. 406-17.ChinaMantle Metasomatism, Xenoliths
DS1999-0815
1999
Xu, Y.Xu, Y., Lin, C., Shi., L.The geotherms of the lithosphere beneath Qilin, southeast China: a re-appraisaland implications for P-T ...Lithos, Vol. 47, No. 3-4, July pp. 181-94.ChinaPyroxenites - iron rich, Lithosphere
DS1999-0816
1999
Xu, Y.Xu, Y., Shankland, T.J.Electrical conductivity of orthopyroxene and its high pressure phasesGeophysical Research Letters, Vol. 26, No. 17, Sept. 1, pp. 2645-48.GlobalGeophysics - electrical, Mineralogy
DS2000-1034
2000
Xu, Y.Xu, Y., Shankland, T.J., Duba, A.G.Pressure effect on electrical conductivity of mantle olivinePhysical Earth and Planetary Interiors, Vol. 118, No.1-2, pp. 149-61.MantleGeophysics, Olivine
DS2002-1748
2002
Xu, Y.Xu, Y.Evidence for crustal components in the mantle and constraints on crustal recycling mechanism: pyroxeniteChemical Geology, Vol.182, 2-4, Feb.15, pp. 301-22.China, northXenoliths, Deposit - Hannuoba
DS2002-1749
2002
Xu, Y.Xu, Y., Liu, F., Jianhua, C.H.Crust and upper mantle structure beneath western Chin a from P wave travel time tomography.Journal of Geophysical Research, Oct. 29, 10.1029/2001JB000402.ChinaGeophysics - seismics
DS2002-1750
2002
Xu, Y.Xu, Y., Liu, F., Liu, J., Chen, X.Crust and upper mantle structure beneath western Chin a from P wave travel time tomography.Journal of Geophysical Research, Vol. 107, 10, ETE 4 DOI 10.1029/2001JB000402ChinaGeophysics - seismics, Tomography
DS2002-1751
2002
Xu, Y.Xu, Y., McCammon, C.Evidence for ionic conductivity in lower mantle. ( Mg Fe Si Al O3) perovskiteJournal of Geophysical Research, Vol. 107, 10, ECV 11 DOI 10.1029/2001JB000677MantleGeophysics - seismics
DS2002-1752
2002
Xu, Y.Xu, Y., McCammon, C.Evidence for ionic conductivity in lower mantle perovskiteJournal of Geophysical Research, Oct. 29, 10.1029/2001JB000677.MantlePerovskite
DS200412-2162
2003
Xu, Y.Xu, Y., Huang, X., Menzies, M.A., Wang, R.Highly magnesian olivines and green core clinopyroxenes in ultrapotassic lavas from western Yunnan China: evidence for a complexEuropean Journal of Mineralogy, Vol. 15, 6, pp. 965-75.ChinaAlkalic
DS200512-0450
2005
Xu, Y.Huang, X., Xu, Y., Karota, S.Water content in the transition zone from electrical conductivity of wadsleyite and ringwoodite.Nature, Vol. 434, pp. 746-749.MantleWater content
DS201012-0453
2010
Xu, Y.Liu, J., Rudnick, R., Walker, R., Gao, S., Wu, F., Xu, W., Xu, Y.OS isotope evidence for diachronous formation of lithospheric mantle beneath the Trans-North Chin a oorgen, north Chin a, craton.Goldschmidt 2010 abstracts, abstractChinaGeochronology
DS201012-0868
2010
Xu, Y.Xu, Y., Song, S., Zheng, Y-F.Evidence from pyroxenite xenoliths for subducted lower oceanic crust in subcontinental lithospheric mante,Goldschmidt 2010 abstracts, abstractMantleSubduction
DS201312-0132
2013
Xu, Y.Cawood, P.A., Wang, Y., Xu, Y., Zhao, G.Locating South Chin a in Rodinia and Gondwana: a fragment of greater India lithosphere?Geology, Vol. 41, 8, pp. 903-906.IndiaGondwana
DS201412-0996
2014
Xu, Y.Xu, Y., Cawood, P., Du, Y., Yu, L., Yu, W., Zhu, Y., Li, W.Linking south Chin a to northern Australia and India on the margin of Gondwana: constraints from detrital zircon U-Pb isotopes in Cambrian strata.Tectonics, Vol. 32, 6, pp. 1547-1558.ChinaGeochronology
DS201502-0124
2014
Xu, Y.Wu, F.Y., Xu, Y., Zhu, X., Zhang, G.W.Thinning and destruction of the cratonic lithosphere: a global perspective.Science China Earth Sciences, Vol. 57, no. 12, pp. 2878-2890.China, GlobalPlume, subduction
DS201802-0242
2018
Xu, Y.Ionov, D.A., Doucet, L.S., Xu, Y., Golovin, A.V., Oleinikov, O.B.Reworking of Archean mantle in the NE Siberian craton by carbonatite and silicate melt metasomatism: evidence from a carbonate bearing, dunite to web sterite xenolith suite from the Obnazhennaya kimberlite.Geochimica et Cosmochimica Acta, in press available, 46p.Russia, Siberiadeposit - Obnazhennaya

Abstract: The Obnazhennaya kimberlite in the NE Siberian craton hosts a most unusual cratonic xenolith suite, with common rocks rich in pyroxenes and garnet, and no sheared peridotites. We report petrographic and chemical data for whole rocks (WR) and minerals of 20 spinel and garnet peridotites from Obnazhennaya with Re-depletion Os isotope ages of 1.8-2.9 Ga (Ionov et al., 2015a) as well as 2 pyroxenites. The garnet-bearing rocks equilibrated at 1.6-2.8 GPa and 710-1050°C. Some xenoliths contain vermicular spinel-pyroxene aggregates with REE patterns in clinopyroxene mimicking those of garnet. The peridotites show significant scatter of Mg# (0.888-0.924), Cr2O3 (0.2-1.4 wt.%) and high NiO (0.3-0.4 wt.%). None are pristine melting residues. Low-CaO-Al2O3 (=0.9 wt.%) dunites and harzburgites are melt-channel materials. Peridotites with low to moderate Al2O3 (0.4-1.8 wt.%) usually have CaO > Al2O3, and some have pockets of calcite texturally equilibrated with olivine and garnet. Such carbonates, exceptional in mantle xenoliths and reported here for the first time for the Siberian mantle, provide direct evidence for modal makeover and Ca and LREE enrichments by ephemeral carbonate-rich melts. Peridotites rich in CaO and Al2O3 (2.7-8.0 wt.%) formed by reaction with silicate melts. We infer that the mantle lithosphere beneath Obnazhennaya, initially formed in the Mesoarchean, has been profoundly modified. Pervasive inter-granular percolation of highly mobile and reactive carbonate-rich liquids may have reduced the strength of the mantle lithosphere leading the way for reworking by silicate melts. The latest events before the kimberlite eruption were the formation of the carbonate-phlogopite pockets, fine-grained pyroxenite veins and spinel-pyroxene symplectites. The reworked lithospheric sections are preserved at Obnazhennaya, but similar processes could erode lithospheric roots in the SE Siberian craton (Tok) and the North China craton, where ancient melting residues and reworked garnet-bearing peridotites are absent.The modal, chemical and Os-isotope compositions of the Obnazhennaya xenoliths produced by reaction of refractory peridotites with melts are very particular (high Ca/Al, no Mg#-Al correlations, highly variable Cr, low 187Os/188Os, continuous modal range from olivine-rich to low-olivine peridotites, wehrlites and websterites) and distinct from those of fertile lherzolites in off-craton xenoliths and peridotite massifs. These features argue against the concept of ‘refertilization’ of cratonic and other refractory peridotites by mantle-derived melts as a major mechanism to form fertile to moderately depleted lherzolites in continental lithosphere. The Obnazhennaya xenoliths represent a natural rock series produced by ‘refertilization’, but include no rocks equivalent in modal, major and trace element to the fertile lherzolites. This study shows that ‘refertilization’ yields broad, continuous ranges of modal and chemical compositions with common wehrlites and websterites that are rare among off-craton xenoliths.
DS201902-0279
2018
Xu, Y.Ionov, D.A., Doucet, L.S., Xu, Y., Golovin, A.V., Oleinikov, O.B.Reworking of Archean mantle in the NE Siberian craton by carbonatite and silicate melt metasomatism: evidence from a carbonate bearing, dunite to websterite xenolith suite from the Obnazhennaya kimberlite.Geochimica et Cosmochimica Acta, Vol. 224, pp. 132-153.Russia, Siberiadeposit - Obnazhennaya

Abstract: The Obnazhennaya kimberlite in the NE Siberian craton hosts a most unusual cratonic xenolith suite, with common rocks rich in pyroxenes and garnet, and no sheared peridotites. We report petrographic and chemical data for whole rocks (WR) and minerals of 20 spinel and garnet peridotites from Obnazhennaya with Re-depletion Os isotope ages of 1.8-2.9?Ga (Ionov et al., 2015a) as well as 2 pyroxenites. The garnet-bearing rocks equilibrated at 1.6-2.8?GPa and 710-1050?°C. Some xenoliths contain vermicular spinel-pyroxene aggregates with REE patterns in clinopyroxene mimicking those of garnet. The peridotites show significant scatter of Mg# (0.888-0.924), Cr2O3 (0.2-1.4?wt.%) and high NiO (0.3-0.4?wt.%). None are pristine melting residues. Low-CaO-Al2O3 (=0.9?wt.%) dunites and harzburgites are melt-channel materials. Peridotites with low to moderate Al2O3 (0.4-1.8?wt.%) usually have CaO?>?Al2O3, and some have pockets of calcite texturally equilibrated with olivine and garnet. Such carbonates, exceptional in mantle xenoliths and reported here for the first time for the Siberian mantle, provide direct evidence for modal makeover and Ca and LREE enrichments by ephemeral carbonate-rich melts. Peridotites rich in CaO and Al2O3 (2.7-8.0?wt.%) formed by reaction with silicate melts. We infer that the mantle lithosphere beneath Obnazhennaya, initially formed in the Mesoarchean, has been profoundly modified. Pervasive inter-granular percolation of highly mobile and reactive carbonate-rich liquids may have reduced the strength of the mantle lithosphere leading the way for reworking by silicate melts. The latest events before the kimberlite eruption were the formation of the carbonate-phlogopite pockets, fine-grained pyroxenite veins and spinel-pyroxene symplectites. The reworked lithospheric sections are preserved at Obnazhennaya, but similar processes could erode lithospheric roots in the SE Siberian craton (Tok) and the North China craton, where ancient melting residues and reworked garnet-bearing peridotites are absent. The modal, chemical and Os-isotope compositions of the Obnazhennaya xenoliths produced by reaction of refractory peridotites with melts are very particular (high Ca/Al, no Mg#-Al correlations, highly variable Cr, low 187Os/188Os, continuous modal range from olivine-rich to low-olivine peridotites, wehrlites and websterites) and distinct from those of fertile lherzolites in off-craton xenoliths and peridotite massifs. These features argue against the concept of ‘refertilization’ of cratonic and other refractory peridotites by mantle-derived melts as a major mechanism to form fertile to moderately depleted lherzolites in continental lithosphere. The Obnazhennaya xenoliths represent a natural rock series produced by ‘refertilization’, but include no rocks equivalent in modal, major and trace element to the fertile lherzolites. This study shows that ‘refertilization’ yields broad, continuous ranges of modal and chemical compositions with common wehrlites and websterites that are rare among off-craton xenoliths.
DS201911-2578
2019
Xu, Y.Xu, Y., Tang, W., Hui, H., Rudnick, R.L., Shang, S., Zhang, Z.Reconciling the discrepancy between the dehydration rates in mantle olivine and pyroxene during xenolith emplacement. Lashaine, Eledoi, KisiteGeochimica et Cosmochimica Acta, Vol. 267, pp. 179-195.Africa, Tanzaniaperidotite

Abstract: Hydrogen concentration profiles through olivine and pyroxene in peridotite xenoliths carried in rift basalts from northern Tanzania (Lashaine, Eledoi, and Kisite localities) show bell-shaped distributions, indicating that diffusive hydrogen loss has occurred in all minerals. Homogeneous major element concentrations and equilibration of hydrogen between the cores of olivine and coexisting pyroxene suggest that hydrogen loss resulted from diffusive degassing during host magma emplacement. For these samples, hydrogen diffusivities in olivine and coexisting pyroxene must be within the same order of magnitude, similar to experimentally determined diffusivities, but in contrast to previous observations made on xenolithic peridotites. We demonstrate here, for the first time using natural samples, that significant differences in activation energy is likely the primary parameter that causes the discrepancy between hydrogen diffusion in olivine and pyroxene observed in different suites of mantle xenoliths. Because hydrogen diffuses faster in olivine than in pyroxene as temperature increases, hydrogen loss in the Tanzanian mantle xenoliths must have occurred at relatively low temperatures (~750 - ~900 °C), whereas hydrogen loss observed in previous xenolith studies likely occurred at higher temperatures (~950 to > 1200 °C). Thus, the diffusive loss of hydrogen in the Tanzanian mantle xenoliths may have occurred at shallow depths or at the Earth’s surface.
DS202004-0502
2020
Xu, Y.Cawood, P.A., Wang, W., Zhao, T., Xu, Y., Mulder, J.A., Pisarevsky, S.A., Zhang, L., Gan, C., He, H., Liu, H., Qi, L., Wang, Y., Yao, J., Zhao, G., Zhou, M-F., Zi, J-W.Deconstructing south China and consequences for reconstructing Nuna and Rodinia.Earth-Science Reviews, in press available, 70p. PdfChinatectonics

Abstract: Contrasting models for internal and external locations of South China within the Nuna and Rodinia supercontinents can be resolved when the current lithotectonic associations of Mesoproterozoic and older rocks units that constitute the craton are redefined into four lithotectonic domains: Kongling, Kunming-Hainan, Wuyi, and Coastal. The Kongling and Kunming-Hainan domains are characterized by isolated Archean to early Paleoproterozoic rock units and events and crop out in northern and southern South China, respectively. The Kunming-Hainan Domain is preserved in three spatially separated regions at Kunming (southwestern South China), along the Ailaoshan shear zone, and within Hainan Island. Both domains were affected by late Paleoproterozoic tectonothermal events, indicating their likely juxtaposition by this time to form the proto-Yangtze Block. Late Paleoproterozoic and Mesoproterozoic sedimentary and igneous rock units developed on the proto-Yangtze Block, especially in its southern portions, and help link the rock units that formed along the shear zone at Ailaoshan and on Hainan Island into a single, spatially unified unit prior to Paleozoic to Cenozoic structural disaggregation and translation. The Wuyi Domain consists of late Paleoproterozoic rock units within a NE-SW trending, fault-bounded block in eastern South China. The Coastal Domain lies east of the Wuyi domain and is inferred to constitute a structurally separate block. Basement to the domain is not exposed, but zircon Hf model ages from Mesozoic granites suggest Mesoproterozoic basement at depth. The Archean to Paleoproterozoic tectonothermal record of the Kongling and Kunming-Hainan domains corresponds closely with that of NW Laurentia, suggesting all were linked, probably in association with assembly and subsequent partial fragmentation of the Nuna supercontinent. Furthermore, the age and character of Mesoproterozoic magmatism and detrital zircon signature of sedimentary rocks in the proto-Yangtze Block matches well with western Laurentia and eastern Australia-Antarctica. In particular, the detrital zircon signature of late Paleoproterozoic to early Mesoproterozoic sedimentary units in the block (e.g. Dongchuan Group) share a similar age spectrum with the Wernecke Supergroup of northwest Laurentia. This, together with similarities in the type and age of Fe-Cu mineralization in the domain with that in eastern Australia-Antarctica, especially northeast Australia, suggests a location adjacent to northwest Laurentia, southern Siberia, and northeast Australia within the Nuna supercontinent. The timing and character of late Paleoproterozoic magmatic activity in the Wuyi domain along with age of detrital zircons in associated sedimentary rocks matches the record of northern India. During rifting between Australia-Antarctica and Laurentia in the late Mesoproterozoic, the proto-Yangtze Block remained linked to northeast Australia. During accretionary orogenesis in the early Neoproterozoic, the proto-Yangtze Block assembled with the Wuyi Domain along the northern margin of India. The Coastal domain likely accreted at this time forming the South China Craton. Displacement of the Hainan and Ailaoshan assemblages from southwest of the Kunming assemblage likely occurred in the Cenozoic with the activation of the Ailaoshan-Red River fault system but could have begun in the early to mid-Paleozoic based on evidence for tectonothermal events in the Hainan assemblage.
DS202007-1136
2020
Xu, Y.Doucet, L.S., Xu, Y., Klaessens, D., Hui, H., Ionov, D.A., Mattielli, N.Decoupled water and iron enrichments in the cratonic mantle: a study on peridotite xenoliths from Tok, SE Siberian craton.American Mineralogist, Vol. 105, pp. 803-819.Russia, Siberia peridotites

Abstract: Water and iron are believed to be key constituents controlling the strength and density of the lithosphere and, therefore, play a crucial role in the long-term stability of cratons. On the other hand, metasomatism can modify the water and iron abundances in the mantle and possibly triggers thermo-mechanical erosion of cratonic keels. Whether local or large scale processes control water distribution in cratonic mantle remains unclear, calling for further investigation. Spinel peridotite xenoliths in alkali basalts of the Cenozoic Tok volcanic field sampled the lithospheric mantle beneath the southeastern margin of the Siberian Craton. The absence of garnet-bearing peridotite among the xenoliths, together with voluminous eruptions of basaltic magma, suggests that the craton margin, in contrast to the central part, lost its deep keel. The Tok peridotites experienced extensive and complex metasomatic reworking by evolved, Ca-Fe-rich liquids that transformed refractory harzburgite to lherzolite and wehrlite. We used polarized Fourier transform infrared spectroscopy (FTIR) to obtain water content in olivine, orthopyroxene (Opx), and clinopyroxene (Cpx) of 14 Tok xenoliths. Olivine, with a water content of 0-3 ppm H2O, was severely degassed, probably during emplacement and cooling of the host lava flow. Orthopyroxene (49-106 ppm H2O) and clinopyroxene (97-300 ppm H2O) are in equilibrium. The cores of the pyroxene grains, unlike olivine, experienced no water loss due to dehydration or addition attributable to interaction with the host magma. The water contents of Opx and Cpx are similar to those from the Kaapvaal, Tanzania, and North China cratons, but the Tok Opx has less water than previously studied Opx from the central Siberian craton (Udachnaya, 28-301 ppm; average 138 ppm). Melting models suggest that the water contents of Tok peridotites are higher than in melting residues, and argue for a post-melting (metasomatic) origin. Moreover, the water contents in Opx and Cpx of Tok peridotites are decoupled from iron enrichments or other indicators of melt metasomatism (e.g., CaO and P2O5). Such decoupling is not seen in the Udachnaya and Kaapvaal peridotites but is similar to observations on Tanzanian peridotites. Our data suggest that iron enrichments in the southeastern Siberian craton mantle preceded water enrichment. Pervasive and large-scale, iron enrichment in the lithospheric mantle may strongly increase its density and initiate a thermo-magmatic erosion. By contrast, the distribution of water in xenoliths is relatively “recent” and was controlled by local metasomatic processes that operate shortly before the volcanic eruption. Hence, water abundances in minerals of Tok mantle xenoliths appear to represent a snapshot of water in the vicinity of the xenolith source regions.
DS202007-1150
2020
Xu, Y.Ionov, D.A., Liu, Z., Li, J., Golovin, A.V., Korsakov, A.V., Xu, Y.The age and origin of cratonic lithospheric mantle: Archean dunites vs paleoproterozoic harzburgites from the Udachnaya kimberlite, Siberian craton.Geochimica et Cosmochimica Acta, Vol. 281, pp. 67-90. pdfRussia, Siberiadeposit - Udachnaya

Abstract: Cratonic lithospheric mantle is believed to have been formed in the Archean, but kimberlite-hosted coarse peridotites from Udachnaya in the central Siberian craton typically yield Paleoproterozoic Re-depletion Os isotope ages (TRD). By comparison, olivine megacrysts from Udachnaya, sometimes called “megacrystalline peridotites”, often yield Archean TRD ages, but the nature of these rare materials remains enigmatic. We provide whole-rock (WR) Re-Os isotope and PGE analyses for 24 olivine-rich xenoliths from Udachnaya as well as modal and petrographic data, WR and mineral major and trace element compositions. The samples were selected based on (a) high olivine abundances in hand specimens and (b) sufficient freshness and size to yield representative WR powders. They comprise medium- to coarse-grained (olivine??1?cm) dunite, olivine megacrysts and low-orthopyroxene (11-21% opx) harzburgites equilibrated at 783-1154?°C and 3.9-6.5 GPa; coarse dunites have not been previously reported from Udachnaya; two xenoliths contain ilmenite. The harzburgites and dunites have similar WR variation ranges of Ca, Al, Fe, Cr and Mg# (0.917-0.934) typical of refractory cratonic peridotites, but the dunites tend to have higher MgO, NiO and Mg/Si. Mineral abundances and those of Ca and Al are not correlated with Mg#WR; they are not due to differences in melting degrees but are linked to metasomatism. Several samples with high 187Re/188Os show a positive linear correlation with 187Os/188Os with an apparent age of 0.37?Ga, same as eruption age of host kimberlite. Robust TRD ages were obtained for 16 xenoliths with low 187Re/188Os (0.02-0.13). TRD ages for low-opx harzburgites (1.9-2.1?Ga; average 2.0?±?0.1?Ga, 1 s) are manifestly lower than for dunites and megacrysts (2.4-3.1?Ga); the latter define two subsets with average TRD of 2.6?±?0.1?Ga and 3.0?±?0.1?Ga, and TMA of 3.0?±?0.2?Ga and 3.3?±?0.1?Ga, respectively. Differences in olivine grain size (coarse vs. megacrystalline) are not related to age. The age relations suggest that the dunites and megacrysts could not be produced by re-melting of harzburgites, e.g. in arc settings, nor be melt channel materials in harzburgites. Instead, they are relict fragments of lithospheric mantle formed in the Archean (likely in two events at or after 2.6?Ga and 3.0?Ga) that were incorporated into cratonic lithosphere during the final assembly of the Siberian craton in the Paleoproterozoic. A multi-stage formation of the Siberian lithospheric mantle is consistent with crustal basement ages from U-Pb dating of zircons from crustal xenoliths at Udachnaya and detrital zircons from the northern Siberian craton (1.8-2.0, 2.4-2.8 and 3.0-3.4?Ga). The new data from the Siberian and other cratons suggest that the formation of strongly melt-depleted cratonic lithosphere (e.g. Mg# =0.92) did not stop at the Archean-Proterozoic boundary as is commonly thought, but continued in the Paleoproterozoic. The same may be valid for the transition from the ‘Archean’ (4-2.5?Ga) to modern tectonic regimes.
DS202104-0598
2021
Xu, Y.Pearson, D.G., Li, D., Xu, Y., Liu, S-A., Chu, Z., Chen, L-H., Li, S.Oxidation of the deep mantle wedge by recycled carbonates: constraints from highly siderophile elements and osmium isotopes.Geochimica et Cosmochimica Acta, Vol. 295, pp. 207-223.Chinanephelinites, basanites

Abstract: Widespread Cenozoic intraplate basalts from eastern China offer the opportunity to investigate the consequences of interaction between the stagnant Pacific slab and overlying asthenosphere and chemical heterogeneity within this “big mantle wedge”. We present and compile a comprehensive study of highly siderophile elements and Mg-Zn isotopes of this magmatic suite (60 samples including nephelinites, basanites, alkali basalts and tholeiites). The large-scale Mg-Zn isotopic anomalies documented in these basalts have been ascribed to mantle hybridization by recycled Mg-carbonates from the stagnant western Pacific plate. Our results reveal that the nephelinites and basanites are characterized by unfractionated platinum-group element (PGE) patterns normalized to primitive upper mantle (PUM) (e.g., PdN/IrN normalized to PUM?=?1.1?±?0.8, 1s), relatively high total PGE contents (e.g., Ir?=?0.25?±?0.14?ppb) and modern mantle-like 187Os/188Os (0.142?±?0.020). These characteristics are coupled with lighter Mg isotope (d26Mg?=?-0.48?±?0.07‰) and heavier Zn isotope (d66Zn = +0.46?±?0.06‰) compositions compared to the mantle values (d26Mg: -0.25?±?0.07‰; d66Zn: +0.18?±?0.05‰). Together, these data are interpreted to reflect the oxidative breakdown of low proportions of mantle sulfides in the sources of these small-degree melts, likely caused by recycled carbonates, which then release chalcophile-siderophile elements into carbonatitic melts. By contrast, the contemporaneous alkali basalts and tholeiites are characterized by highly fractionated PGE patterns (e.g., PdN/IrN?=?4.4?±?3.3; Ir?=?0.037?±?0.027?ppb) and radiogenic 187Os/188Os (0.279?±?0.115) coupled with less fractionated Mg-Zn isotope compositions (d26Mg: -0.39?±?0.05‰; d66Zn: +0.35?±?0.03‰). In combination with other isotopic (e.g., Sr-Nd) and chemical (SiO2, Ce/Pb, Ba/Th, Fe/Mn) constraints, the alkali basalts and tholeiites were derived from higher degree melting of ancient pyroxenite-bearing mantle in addition to mixing with the aforementioned nephelinitic and basanitic melts. Collectively, we suggest that deep recycled carbonates promoted melting within the "big mantle wedge" leading to the generation of Cenozoic intraplate basalts across eastern China and the "redox freezing of carbonates" may cause the oxidation of Fe0 and S2-. This process may provide an important mechanism to oxidize mantle sulfides and transfer precious metals from deep mantle to crust.
DS1992-1708
1992
Xu, Y.G.Xu, Y.G., Mercier, J.C.C., Ross, J.V., Lin, C.Y., Shi, L.B.A first insight into the upper mantle beneath a lithospheric fault zone:the spinel-lherzolite xenoliths from Yitong bsalts, north-eastern ChinaInternational Symposium Cenozoic Volcanic Rocks Deep seated xenoliths China and its, Abstracts pp. 102ChinaMantle, Xenoliths
DS1998-1607
1998
Xu, Y.G.Xu, Y.G., Bodinier, J.L., Bedini, R.M., Menzies, M.A.Xenolith evidence for melt rock reaction at the lithosphere plumeboundary.Mineralogical Magazine, Goldschmidt abstract, Vol. 62A, p. 1671-2.FrancePetrography, geochemistry, Harzburgites, Boree P type
DS2001-1271
2001
Xu, Y.G.Xu, Y.G.Thermo-tectonic destruction of the archean lithospheric keel beneath the Sino-Korean craton: evidence, timingPhysics and Chemistry of the Earth, Vol. 26, pt. A. No. 9-10, pp. 747-57.ChinaGeodynamics, Tectonics
DS2001-1272
2001
Xu, Y.G.Xu, Y.G.Thermo tectonic destruction of the Archean lithospheric keel beneath the sino-Korean Craton in China: evidencePhysics and Chemistry of the Earth Pt. A. Solid Earth, Vol. 26, No. 9-10, pp. 747-57.ChinaLithospheric mantle, Tectonics
DS2001-1273
2001
Xu, Y.G.Xu, Y.G., Menzies, M.A., Thirwall, M.F., Xie, G.H.Exotic lithosphere mantle beneath the western Yangtze craton: petrogenetic links to Tibet using ultrapotassicGeology, Vol. 29, No. 9, Sept. pp. 863-866.China, Tibet, Asiaultra high pressure (UHP), ultrapotassic highly magnesian, Metasomatism
DS2002-1753
2002
Xu, Y.G.Xu, Y.G., Sun, M., Yan, W., Liu, Y., Huang, X.L., Chen, X.M.Xenolith evidence for polybaric melting and stratification of the upper mantle beneath South China.Journal of Asian Earth Sciences, Vol. 20,8, pp. 937-54.ChinaMelt - xenoliths
DS2003-0566
2003
Xu, Y.G.He, B., Xu, Y.G., Chung, S.L., Xiao, L., Wang, Y.Sedimentary evidence for a rapid kilometer scale crustal doming prior to eruption of theEarth and Planetary Science Letters, Vol. 213, 3-4, pp. 391-405.GlobalBasalts - not specific to diamonds, tectonics
DS2003-1514
2003
Xu, Y.G.Xu, Y.G., Menzies, M.A., Thirwall, M.F., Huang, X.L., Liu, Y., Chen, X.M.Reactive harzburgites from Huinan, NE China: products of the lithosphereGeochimica et Cosmochimica Acta, Vol. 67, 3, pp. 487-505.China, northeastHarzburgites
DS200412-0808
2003
Xu, Y.G.He, B., Xu, Y.G., Chung, S.L., Xiao, L., Wang, Y.Sedimentary evidence for a rapid kilometer scale crustal doming prior to eruption of the Emeishan flood basalts.Earth and Planetary Science Letters, Vol. 213, 3-4, pp. 391-405.TechnologyBasalts - not specific to diamonds Tectonics
DS200412-2163
2004
Xu, Y.G.Xu, Y.G., Huang, X.L., Wang, Y.B., Iizuka, Y., Xu, J.F., Wang, Q., Wu, X.Y.Crust mantle interaction during the tectono-thermal reactivation of the North Chin a Craton: constraints from SHRIMP zircon U PbContributions to Mineralogy and Petrology, Vol. 147, 6, pp. 750-767.China, ShandongGeothermometry, geochronology
DS200512-1204
2004
Xu, Y.G.Xiao, L., Xu, Y.G., Mei, H.J., Zheng, Y.F., He, B., Pirajno, F.Distinct mantle sources of low Ti and high Ti basalts from the western Emeishan large igneous province, SW China: implications for plume?? lithosphere interactionEarth and Planetary Science Letters, Vol. 228, 3-4, pp. 525-546.ChinaMantle mineralogy, titanium
DS200612-1557
2006
Xu, Y.G.Xu, Y.G., Blusztajn, J., Ma, J.L., Hart, S.R.In searching for old lithospheric relict beneath North Chin a Craton: Sr Nd Os isotopic composition of peridotite xenoliths from Yangyuan.Geochimica et Cosmochimica Acta, Vol. 70, 18, p. 3. abstract only.ChinaGeochronology
DS200612-1558
2005
Xu, Y.G.Xu, Y.G., Ma, J.L, Frey, F.A., Feigenson, M.D., Liu, J.F.Role of lithosphere asthenosphere interaction in the genesis of Quaternary alkali and tholeitic basalts from Datong, western North Chin a Craton.Chemical Geology, Vol. 224, 4, pp. 247-271.ChinaAlkalic
DS201709-1973
2017
Xu, Y.G.Choudhary, B.R., Xu, Y.G., Ernst, R.E., Pandit, D.Ti- rich garnet core in spinel in a kimberlite: evidence for metasomatic origin.Goldschmidt Conference, abstract 1p.Indiadeposit, P-5 Wajrakarur

Abstract: EPMA data are obtained from the P-5 kimberlite from the Wajrakarur field in the Eastern Dharwar craton of southern India (EDC). The studied sample consists of xenocrysts and xenoliths set in a variable grain size groundmass of olivine (with two textures: rounded-anhedral and subhedraleuhedral), phlogopite, perovskite, spinel, pyroxene, spinel and spinel containing Ti-garnet core. Ti-rich garnet associated with spinel is a rare occurrence in kimberlites. Two types of spinel have been identified (a) fine grained (<80 µm) and compositionally non titaniferous, and (b) large macrocrysts (>100 µm) having replacement cores having distinctly Ti-rich (TiO2 up to 28.51 wt %) compositions. Spinel is an abundant phase varying from <20 to >300 µm in size, mostly subhedral to euhedral in shape. Pipe-5 has atolland necklace-textured spinels in addition to the euhedral groundmass spinels. Apart from individual grains in ground mass spinel there are also spinel intergrowths with perovskite (no apparent reaction texture observed), and sieve-like intergrowths. The composition of groundmass spinel is extensively used as petrogenetic indicator mineral (Roeder and Schulze 2008). Ti-garnets contain significant Ti (21.25-28.51wt.% TiO2), Ca (15.45-27.69 wt.% CaO), Fe (2.62-24.46 wt.% FeO) and low Cr (0.08-1.52 wt.% Cr2O3) and low Al (1.40-3.87 wt.% Al2O3). Ti- garnets and their paragenetic relationships to spinel are considered here as vital petrogenetic indicators of metasomatic fluids (Dongre et al., 2016; Cheng et al., 2014), and textural association with spinel shows that Ti-garnet formed when early crystallizing spinel interacted with residual melt during magma crystallization.
DS1993-1784
1993
Xu, YG.Xu, YG., Ross, J.V., Mercier, J.C.C.The upper mantle beneath the continental rift of Tanlu, eastern China-evidence for the intra-lithospheric shear zones.Tectonophysics, Vol. 225, No. 4, October 30, pp. 337-360.ChinaMantle, Tectonics -rifting
DS200812-1284
2008
Xu, Y-G.Xu, Y-G., Blusztajn, J., Ma, J-L., Suzuki, K., Liu, J.F., Hart, S.R.Late Archean to Early Proterozoic lithospheric mantle beneath the western North Chin a craton: Sr Nd Os isotopes of peridotite xenoliths from Yangyuan and FansiLithos, Vol. 102, 3-4, pp.25-42.ChinaGeochronology
DS201012-0295
2010
Xu, Y-G.Huang, X., Niu, Y., Xu, Y-G., Chen, L-L., Yang, Q.Mineralogical and geochemical constraints on the preogenesis of post collisional potassic and ultrpotassic rocks from Western Yunnan, SW China.Journal of Petrology, Vol. 51, 8, pp. 1617-1654.ChinaAlkalic
DS201012-0440
2010
Xu, Y-G.Li, J.,Xu, J-F., Suzuki, K., He, B., Xu, Y-G., Ren, Z-Y.Os, Nd and Sr isotope and trace element geochemistry of the Muli picrites: insights into the mantle source of the Emeishan large igneous province.Lithos, in press available, 15p.ChinaGeochronology
DS201312-0536
2014
Xu, Y-G.Li, J., Wang,-C., Ren, Z-Y., Xu, J-F., He, B., Xu, Y-G.Chemical heterogeneity of the Emeishan mantle plume: evidence from highly siderophile element abundances in picrites.Journal of Asian Earth Studies, Vol. 79, A, pp. 191-205.ChinaPicrite
DS201312-0955
2013
Xu, Y-G.Wang, X-C., Li, Z-X., Li, X-H., Xu, Y-G., Li, X-H.Diamond mining in Russia…. Chart of reserves.Earth and Planetary Science Letters, Vol. 377-378, pp. 248-259.MantlePlume
DS201812-2844
2018
Xu, Y-G.Ma, Q., Xu, Y-G., Deng, Y,m Zhengm J-P., Sur, M., Griffin, W.L., Xia, B., Yan Wang, C.Similar crust beneath disrupted and intact cratons: arguments against lower crust delamination as a decratonization trigger. North China cratonTectonophysics, in press available 31p.Chinacraton

Abstract: The continental lithosphere is not forever; some cratons have lost their original roots during the course of their evolution. Yet, it is not clear whether gravitational instability of dense lower crust is the primary driver of decratonization. This is addressed here with emphasis being placed on the North China Craton (NCC), because it represents one of the best examples of craton-root disruption in the world, and a place where models can be tested. If lower-crustal delamination was the trigger for decratonization, we would expect a clear contrast in crustal structure and composition between disturbed (rootless) and intact cratons. However, the eastern (disturbed) and western (intact) parts of the NCC show virtually identical physical structure and composition (a thin mafic lower crust and a predominantly intermediate composition overall) although the crust in the disturbed part is thinner than in the intact craton. This suggests that delamination of the lower crust was not a viable mechanism of craton-root disruption in the NCC case. Indeed, the crust beneath the NCC largely resembles those of stable Archean cratons worldwide. Therefore the delamination, if it occurred, may have taken place much earlier (Archean) than previously thought, rather than in the Mesozoic. Delamination may have been a common phenomenon in the early evolution of cratons, probably due to relatively higher mantle temperatures in the Archean Eon.
DS201907-1585
2019
Xu, Y-G.Wu, F-Y., Yang, J-H., Xu, Y-G., Wilde, S.A., Walker, R.J.Destruction of the North China craton in the Mesozoic.Annual Reviews of Earth and Planetary Sciences, Vol. 47, pp. 173-195.Chinacraton

Abstract: The North China Craton (NCC) was originally formed by the amalgamation of the eastern and western blocks along an orogenic belt at ~1.9 Ga. After cratonization, the NCC was essentially stable until the Mesozoic, when intense felsic magmatism and related mineralization, deformation, pull-apart basins, and exhumation of the deep crust widely occurred, indicative of destruction or decratonization. Accompanying this destruction was significant removal of the cratonic keel and lithospheric transformation, whereby the thick (~200 km) and refractory Archean lithosphere mantle was replaced by a thin (<80 km) juvenile one. The decratonization of the NCC was driven by flat slab subduction, followed by a rollback of the paleo-Pacific plate during the late Mesozoic. A global synthesis indicates that cratons are mainly destroyed by oceanic subduction, although mantle plumes might also trigger lithospheric thinning through thermal erosion. Widespread crust-derived felsic magmatism and large-scale ductile deformation can be regarded as petrological and structural indicators of craton destruction.
DS202010-1841
2020
Xu, Y-G.Dymshits, A., Sharygin, I., Liu, Z., Korolev, N., Malkovets, V., Alifirova, T., Yakovlev, I., Xu, Y-G.Oxidation state of the lithospheric mantle beneath Komosomolskaya-Magnitnaya kimberlite pipe, Upper Muna field, Siberian craton.Minerals, Vol. 10, 9, 740 10.3390/ min10090740 24p. PdfRussiadeposit - Muna

Abstract: The oxidation state of the mantle plays an important role in many chemical and physical processes, including magma genesis, the speciation of volatiles, metasomatism and the evolution of the Earth’s atmosphere. We report the first data on the redox state of the subcontinental lithospheric mantle (SCLM) beneath the Komsomolskaya-Magnitnaya kimberlite pipe (KM), Upper Muna field, central Siberian craton. The oxygen fugacity of the KM peridotites ranges from -2.6 to 0.3 logarithmic units relative to the fayalite-magnetite-quartz buffer (?logfO2 (FMQ)) at depths of 120-220 km. The enriched KM peridotites are more oxidized (-1.0-0.3 ?logfO2 (FMQ)) than the depleted ones (from -1.4 to -2.6 ?logfO2 (FMQ)). The oxygen fugacity of some enriched samples may reflect equilibrium with carbonate or carbonate-bearing melts at depths >170 km. A comparison of well-studied coeval Udachnaya and KM peridotites revealed similar redox conditions in the SCLM of the Siberian craton beneath these pipes. Nevertheless, Udachnaya peridotites show wider variations in oxygen fugacity (-4.95-0.23 ?logfO2 (FMQ)). This indicates the presence of more reduced mantle domains in the Udachnaya SCLM. In turn, the established difference in the redox conditions is a good explanation for the lower amounts of resorbed diamonds in the Udachnaya pipe (12%) in comparison with the KM kimberlites (33%). The obtained results advocate a lateral heterogeneity in the oxidation state of the Siberian SCLM.
DS201112-0611
2011
Xu, Yi-G.Liu, J., Rudnick, R.L., Walker, R.J., Gao, S., Wu, F-y., Piccoli, P.M., Yuan, H., Xu, W-l., Xu, Yi-G.Mapping lithospheric boundaries using Os isotopes of mantle xenoliths: an example from the North Chin a Craton.Geochimica et Cosmochimica Acta, Vol. 75, 13, pp. 3881-3902.ChinaGeochronology
DS2001-1278
2001
Xu, Z.Yang, J., Xu, Z., Zhang, J., Chu, C.Y., Zhang, R., LiouTectonic significance of early Paleozoic high pressure rocks in Altun Qaidam Qilian Mountains, northwest.Geological Society of America Memoir, No. 194, pp. 151-70.China, northwestTectonics, ultra high pressure metamorphism
DS2001-1303
2001
Xu, Z.Zhang, J., Zhang, Z., Xu, Z., Yang, J., Cui. J.Petrology and geochronology of eclogites from the western segment of the Altyn Tagh, northwestern China.Lithos, Vol. 56, No. 2-3, Mar.pp. 187-206.ChinaGeochronology, Eclogites
DS2002-0957
2002
Xu, Z.Liu, F., Xu, Z., Liu, J.G., Katayama, Masago, Maruyama, YangUltra high pressure mineral inclusions in zircons from gneissic core samples of the Chinese continental drilling site in eastern China.European Journal of Mineralogy, No. 3, pp. 499-512.China, easternUHP, Mineral inclusions
DS2003-0656
2003
Xu, Z.Ji, S., Saruwateri, K., Mainproce, D., Wirth, R., Xu, Z., Xia, B.Microstructures, petrofabrics and seismic properties of ultra high pressure eclogitesTectonophysics, Vol. 370, 1-4, pp. 49-76.ChinaGeophysics - seismics, UHP, subduction
DS2003-1313
2003
Xu, Z.Song, S., Yang, J., Liou, J.G., Wu, C., Shi, R., Xu, Z.Petrology, geochemistry and isotopic ages of eclogites from the Dulan UHPM terraneLithos, Vol. 70, 3-4, pp. 195-211.ChinaUHP, geochronology
DS200412-0915
2003
Xu, Z.Ji, S., Saruwateri, K., Mainproce, D., Wirth, R., Xu, Z., Xia, B.Microstructures, petrofabrics and seismic properties of ultra high pressure eclogites from Sulu region, China: implications forTectonophysics, Vol. 370, 1-4, pp. 49-76.ChinaGeophysics - seismics UHP, subduction
DS200412-1156
2004
Xu, Z.Liu, F., Xu, Z., Liou, J.G., Song, B.SHRIMP U Pb ages of ultrahigh pressure and retrograde metamorphism of gneisses, south western Sulu terrane, eastern China.Journal of Metamorphic Geology, Vol. 22, 4, pp. 315-326.ChinaGeochronology, UHP
DS200412-1878
2003
Xu, Z.Song, S., Yang, J., Liou, J.G., Wu, C., Shi, R., Xu, Z.Petrology, geochemistry and isotopic ages of eclogites from the Dulan UHPM terrane, the North Qaidam NW China.Lithos, Vol. 70, 3-4, pp. 195-211.ChinaUHP, geochronology
DS200412-2169
2003
Xu, Z.Yang, J., Xu, Z., Dobrzhinetskaya, L.F., Green, H.W., Pei, X., Shi, R., Wu, C., Wooden, J.L., Zhang, J., WanDiscovery of metamorphic diamonds in central China: an indication of a > 4000 km long zone of deep subduction resulting from mulTerra Nova, Vol. 15, pp. 370-379.ChinaSubduction, Central Orogenic Belt, UHP
DS200512-0413
2004
Xu, Z.Hearn, T.M., Wang, S., Ni, J.F., Xu, Z., Yu,Y., Zhang, X.Uppermost mantle velocities beneath Chin a and surrounding regions.Journal of Geophysical Research, Vol. 109, 11, DOI 10:1029/2003 JB002874ChinaGeophysics - seismics
DS200512-0648
2005
Xu, Z.Liu, F., Liou, J.G., Xu, Z.U Pb SHRIMP ages recorded in the coesite bearing zircon domains of paragneisses in the southwestern Sulu terrane, eastern China: new interpretations.American Mineralogist, Vol. 90, pp. 790-800.ChinaUHP, geochronology
DS200512-1164
2005
Xu, Z.Wang, Q., Ji, S., Salisbury, M.H., Xia, B., Pan, M., Xu, Z.Pressure dependence and anisotropy of P wave velocities in ultrahigh pressure metamorphic rocks from the Dabie Sulu orogenic belt: implications for seismic propertiesTectonophysics, Vol. 398, 1-2, pp. 67-99.ChinaMantle reflections, subduction slabs
DS200512-1165
2005
Xu, Z.Wang, Q., Shaocheng, J., Salisbury, M.H., Xia, B., Pan, M., Xu, Z.Shear wave properties and Poisson's ratios of ultrahigh pressure metamorphic rocks from the Dabie Sulu orogenic belt, China: implications for crustal composition.Journal of Geophysical Research, Vol. 110, B8, pp. B08411 10.1029/2004 JB003435Asia, ChinaUHP
DS200512-1210
2004
Xu, Z.Xu, Z., Jiang, M., Yang, J.Mantle structure of Qinghai Tibet Plateau: mantle plume, mantle shear zone and delamination of lithospheric slab.Earth Science Frontiers, Vol. 11, 4, pp. 329-344. Ingenta 1045384775China, TibetSubduction
DS200612-1242
2006
Xu, Z.Schneider, J., Jahn, B-M., Okamoto, K., Tong, L., Lizuka, Y., Xu, Z.Rb Sr and Sm Nd isotope analyses of CCSD eclogites ( Sulu, China): a test for the closure temperature concept.Geochimica et Cosmochimica Acta, Vol. 70, 18, p. 12, abstract only.ChinaUHP, geochronology
DS200612-1506
2005
Xu, Z.Wang, Q., Ji, S., Salisbury, M.H., Xia, B., Pan, M., Xu, Z.Shear wave properties and Poisson's ratios of ultrahigh pressure metamorphic rocks from Dabie Sulu orogenic belt.Journal of Geophysical Research, Vol. 110, B8, BO8208.ChinaUHP
DS200612-1559
2006
Xu, Z.Xu, Z., Griffin, W.L., Zhao, D., O'Reilly, S.Y.Modification of subcontinental lithospheric mantle in SE China.Geochimica et Cosmochimica Acta, Vol. 70, 18, p. 2. abstract only.ChinaGeochemistry
DS200612-1560
2006
Xu, Z.Xu, Z., Wang, Q., Ji, S., Chen, J., Zeng, Yang, Chen, Liang, WenkPetrofabrics and seismic properties of garnet peridotite from the UHP Sulu terrane: implications for olivine deformation mechanism in subducting slab.Tectonophysics, Vol. 421, 1-2, pp. 111-127.MantleSubduction - cold, dry continental slab
DS200612-1561
2006
Xu, Z.Xu, Z., Zeng, L., Liu, F., Yang, J., Zhang, Z., McWilliams, M., Liou, J.G.Polyphase subduction and exhumation of the Sulu high pressure ultrahigh pressure metamorphic terrane.Geological Society of America, Special Paper, No. 403, pp. 93-114.ChinaSubduction UHP
DS200612-1596
2005
Xu, Z.Zhang, Z., Xiao, Y., Hoefs, J., Xu, Z., Liou, J.G.Petrogenesis of UHP metamorphic crustal and mantle rocks from the Chinese continent in the main hole pre-pilot hole 1 Sulu Basin.International Geology Review, Vol. 47, 11, pp. 1160-1177.Asia, ChinaUHP
DS201412-0512
2014
Xu, Z.Liang, F., Xu, Z., Zhao, J.In-situ moissanite in dunite: deep mantle Luobusa ophiolite, Tibet.Acta Geologica Sinica, Vol. 88, 2, pp. 517-529.Asia, TibetMoissanite
DS201809-2010
2018
Xu, Z.Chen, Y., Yang, J., Xu, Z., Tian, Y., Shengmin, L.Diamonds and other unusual minerals from peridotites of the Myitkyin a ophiolite, Myanmar.Journal of Asian Earth Sciences, Vol. 164, pp. 179-193.Asia, Myanmarperidotites

Abstract: Peridotites from the Myitkyina ophiolite are mainly composed of lherzolite and harzburgite. The lherzolites have relatively fertile compositions, with 39.40-43.40?wt% MgO, 1.90-3.17?wt% Al2O3 and 1.75-2.84?wt% CaO. They contain spinel and olivine with lower Cr# (12.6-18.2) and Fo values (88.7-91.6) than those of the harzburgites (24.5-59.7 and 89.6-91.6 respectively). The harzburgites have more refractory compositions, containing 42.40-46.23?wt% MgO, 0.50-1.64?wt% Al2O3 and 0.40-1.92?wt% CaO. PGE contents of the peridotites show an affinity to the residual mantle. Evaluation of petrological and geochemical characteristics of these peridotites suggests that the lherzolites and harzburgites represent residual mantle after low to moderate degrees of partial melting, respectively, in the spinel stability field. The U-shaped, primitive mantle-normalized REE patterns and strong positive Ta and Pb anomalies of the harzburgites suggest melt/fluid refertilization in either a MOR or SSZ setting after their formation at a MOR. Mineral separation of the peridotites has yield a range of exotic minerals, including diamond, moissanite, native Si, rutile and zircon, a collection similar to that reported for ophiolites of Tibet and the Polar Urals. The discovery of these exotic minerals in the Myitkyina ophiolite supports the view that they occur widely in the upper oceanic mantle.
DS202105-0762
2021
Xu, Z.Dong, B., Shi, C., Xu, Z., Wang, K., Luo, H., Sun, F., Wang, P., Wu, E., Zhang, K., Liu, J., Song, Y., Fan, Y.Temperature dependence of optical centers in 1b diamond characteristics by photoluminescence spectra. CVDDiamond & Related Materials, Vol. 116, 108389, 10p. PdfGlobalsynthetics
DS200512-1243
2005
Xu, Z.Q.Zhang, J.X., Yang, J.S., Mattison, C.G., Xu, Z.Q., Meng, F.C., Shi, R.D.Two contrasting eclogite cooling histories, north Qaidam HP/UHP terrane, western China: petrological and isotopic constraints.Lithos, Vol. 84, 1-2, Sept. pp. 51-76.ChinaEclogite, UHP, geochronology
DS201112-0600
2011
Xu, Z.Q.Li, Z.H., Xu, Z.Q., Gerya, T.V.Flat versus steep subduction: constrasting modes for the formation and exhumation of high to ultrahigh pressure rocks in continental collision zones.Earth and Planetary Science Letters, Vol. 301, 1-2, pp. 65-77.MantleSubduction
DS1985-0746
1985
Xu ChangyuXu ChangyuMine Block Stability Problems During Change from Open Pit To Underground Mining in the Meng Yin Diamond Mine China.Institute of Mining and Metallurgy. Conference ASIAN MINING '85, PP. 315-319.ChinaMining Methods
DS1991-1925
1991
Xu DehuanZhang Andi, Xu Dehuan, Xie Xiing, Guo Lihe, Zhou Jianzong, Wang WuyiThe status and future of diamond exploration in ChinaProceedings of Fifth International Kimberlite Conference held Araxa June 1991, Servico Geologico do Brasil (CPRM) Special, pp. 10-12China, Russia, Australia, South AfricaSinokorean, Yangtze, Tarim, Fuxiam, Tieling, Huanren, Mengyi, Lamproites
DS1986-0522
1986
Xu J.Mao, H-K., Xu J., Bell, P.M.Geophysical experiments: Ruby and diamond fluorescence measurements at 0.2-0. 5 terapascals ( 2-5 megabars)Eos, Vol. 67, No. 16, April 22, p. 368. (abstract.)GlobalDiamond morphology
DS1997-1267
1997
Xu LiangWood, E.F., Lettenmaier, Xu Liang, Njssen, B., Wetzel, S.Hydrological modeling of continental scale basinsAnnual Review of Earth and Planetary Sciences, Vol. 25, pp. 279-300GlobalReview - basin stratigraphy
DS1992-1704
1992
Xu ShutongXu Shutong, Jiang Laili, Liu Yican, Zhang YongTectonic framework and evolution of the Dabie Mountains in Anhui, EasternChina.Acta Geologica Sinica, Vol. 5, No. 3, September pp. 221-238.ChinaTectonics, Coesite, diamonds
DS1982-0645
1982
Xu TaoXu TaoZircons of Maping Kimberlites, Guizhou and Pengjiabang, Hubei.*chiBulletin. Yichnag Institute Geol. Min. Res. Chi. Acad. Geol. Sci., *CHI, 1982, No. 5, pp. 28-39ChinaGeochronology
DS1982-0646
1982
Xu TaoXu TaoThe Zircons in the Kimberlites from Maping, Guizhou Province and from Penjiabang, Hubei Province.Bulletin. YICHENG Institute GEOL. MIN. RES. (CHINESE ACAD. GEOL. SCI, No. 5, PP. 28-39.ChinaZircon, Mineral Chemistry
DS1983-0420
1983
Xu tao, LU DENGGRONG.Ma daquan, ZHAO ZIJIE, Xu tao, LU DENGGRONG.On the Petrological Characteristics of Micaceous Kimberlite and Accompanied Meta-alkaline Ultrabasic Rocks at Maping, Quizhou Province.Bulletin. Institute GEOL. GEOL. (CHINESE ACAD. GEOL. SCI.), No. 7, PP. 65-75.China, QuizhouMineralogy, Petrology, Micaceous
DS1983-0421
1983
Xu tao, LU DENGRONG.Ma daquan, ZHAO ZIJIE, Xu tao, LU DENGRONG.The petrological characteristics of micaceous kimberlite and accompanied meta alkaline ultrabasic rocks at Maping, Guizhou.*CHIBulletin. Yichang Institute Geol. and Min. Res.*CHI, Vol. 7, pp. 65-75ChinaPetrology, Kimberlite
DS1992-1705
1992
Xu WeniangXu Weniang, Chi Xiaoguo, Yuan Chao, Yiang RuiyangThe upper mantle and lower crust in the central North Chin a PlatformInternational Symposium Cenozoic Volcanic Rocks Deep seated xenoliths China and its, Abstracts pp. 98-101ChinaMantle, Xenoliths
DS1991-0262
1991
Xu XiangChen Jiangfeng, Foland, K.A., Xing Fengming, Xu Xiang, Zhou TaixiMagmatism along the southeast margin of the Yangtse block: Precambrian collision of the Yangtse and Cathysia blocks of ChinaGeology, Vol. 19, No. 8, August, pp. 815-818ChinaTectonics, Ophiolites
DS1991-0999
1991
Xu ZhiqiangLiu Guangliang, Xu ZhiqiangNew type lamproite of the Dahongshan area, Hubei Province, ChinaProceedings of Fifth International Kimberlite Conference held Araxa June 1991, Servico Geologico do Brasil (CPRM) Special, pp. 234-236ChinaLamproites, Classification, geochronology
DS2003-1524
2003
Xu. ZQYang, Y.S., Wooden, J.L., Wu. C.L., Liu, F.L., Xu. ZQ, Shi, R.D., Katayama, I.SHRIMP U Pb dating of coesite bearing zircon from the ultrahigh pressureJournal of Metamorphic Geology, Vol. 21, 6, pp. 551-60.ChinaUHP
DS201809-2016
2018
Xuan, Ni.Duan, Yunfei, Sun, Ningyu, Wang, Siheng, Li, Xinyang, Guo, Xuan, Ni.Phase stability and thermal equation of state of delta -AIOOH: implication for water transportation in the deep lower mantle.Earth and Planetary Science Letters, Vol. 494, 1, pp. 92-98.Mantlewater

Abstract: In this study, we present new experimental constraints on the phase stability and thermal equation of state of an important hydrous phase, d-AlOOH, using synchrotron X-ray diffraction up to 142 GPa and 2500 K. Our experimental results have shown that d-AlOOH remains stable at the whole mantle pressure-temperature conditions above the D? layer yet will decompose at the core-mantle boundary because of a dramatic increase in temperature from the silicate mantle to the metallic outer core. At the bottom transition zone and top lower mantle, the formation of d-AlOOH by the decomposition of phase Egg is associated with a ~2.1-2.5% increase in density (?) and a ~19.7-20.4% increase in bulk sound velocity (VF). The increase in ? across the phase Egg to d-AlOOH phase transition can facilitate the subduction of d-AlOOH to the lower mantle. Compared to major lower-mantle phases, d-AlOOH has the lowest ? but greatest VF, leading to an anomalous low ? /VF ratio which can help to identify the potential presence of d-AlOOH in the region. More importantly, water released from the breakdown of d-AlOOH at the core-mantle boundary could lower the solidus of the pyrolitic mantle to cause partial melting and/or react with Fe in the region to form the low-velocity FeO2Hx phase. The presence of partial melting and/or the accumulation of FeO2Hx phase at the CMB could be the cause for the ultra-low velocity zone. d-AlOOH is thus an important phase to transport water to the lowermost mantle and helps to understand the origin of the ultra-low velocity zone.
DS1996-1574
1996
Xue, F.Xue, F., Rowley, D.B., Baker, J.Refolded syn-ultrahigh pressure thrust sheets in south Dabie Mountaincomplex: field evidence and tectonics.Geology, Vol. 24, No. 5, May pp. 455-458.ChinaMetasomatism, Tectonics
DS1997-0064
1997
Xue, F.Baker, J., Matthews, A., Mattey, D., Rowley, D., Xue, F.Fluid-rock interactions during high pressure metamorphism, Dabie Shan, China.Geochimica et Cosmochimica Acta, Vol. 61, No. 8, April pp. 1685-1696.ChinaEclogites, metamorphism
DS1997-0979
1997
Xue, F.Rowley, D.B., Xue, F., Davis, A.Ages of ultrahigh pressure metamorphism and protolith orthogneisses From the eastern Dabie Shan: uranium-lead (U-Pb) zirconEarth and Planetary Science Letters, Vol. 151, No. 3-4, Oct. 1, pp. 191-204.ChinaGeochronology, Dabie Shan metamorphic
DS1999-0419
1999
Xue, H.Liu, X., Dong, S., Xue, H., Zhou, J.Significance of allanite ( Ce) in granitic gneisses from the ultrahigh pressure metamorphic terrane...Mineralogical Magazine, Vol. 63, No. 4, Aug. pp. 579-86.Chinametamorphism, Dabie Shan area
DS200712-0637
2006
Xue, H.Liu, F., Liou, J.G., Xue, H.Identification of UHP and non-UHP orthogneisses in the Sulu UHP terrane, eastern China: evidence from SHRIMP U-Pb dating of mineral inclusion bearing zircons.International Geology Review, Vol. 48, 12, pp. 1067-1086.ChinaUHP, geochronology
DS200612-0827
2006
Xue, H.M.Liu, F.L., Gerdes, A., Liou, J.G., Xue, H.M., Liang, F.H.SHRIMP U Pb zircon dating from Sulu Dabie dolomitic marble, eastern China: constraints on prograde, ultrahigh pressure and retrograde metamorphic ages.Journal of Metamorphic Geology, Vol. 24, 7, Sept. pp. 569-589.ChinaGeochronology UHP
DS200812-0290
2008
Xue, H.M.Dong, S.W., Li, Q.S., Gao, R., Liu, F.T., Liu, X.C., Xue, H.M., Guan, Y.Moho mapping in the Dabie ultrahigh pressure collisional orogen, central China.American Journal of Science, Vol. 308, 4, pp. 517-528.ChinaUHP
DS200912-0445
2009
Xue, H.M.Liu, F.L., Gerdes, A., Xue, H.M.Differential subduction and exhumation of crustal slices in the Sulu HP-UHP metamorphic terrane: insights from mineral inclusions, trace elements, U-Pb and Lu Hf isotope analyses of zircon in orthogneissJournal of Metamorphic Geology, Vol. 27, 9, pp. 805-825.ChinaUHP
DS2000-1033
2000
Xue, L.F.Xu, M., Midleton, M.F., Xue, L.F., Wang, D.P.Structure of the lithosphere and Mesozoic sedimentary basins in western Liaoning Northern Liaoning.International Geology Review, Vol. 42, No. 3, March pp. 269-78.China, northeastTectonics
DS200512-0012
2005
Xue, M.Allen, R.M., Xue, M.Constraining the geometry and flow of the Iceland mantle upwelling.www Chapman Conference held in Scotland August 28-Sept. 1 2005, 1p. abstractEurope, IcelandMantle plume
DS201012-0869
2010
Xue, M.Xue, M., Allen, R.M.Mantle structure beneath the western United States and its implications for convection processes.Journal of Geophysical Research, Vol. 115, B07303.United StatesTectonics
DS201802-0282
2018
Xue, S.Xue, S., Ling, M-X., Liu, Y-L., Su, W.Recycling of subducted carbonates: formation of the Taohuala Mountain carbonatite, North Chin a craton.Chemical Geology, Vol. 478, pp. 89-101.Chinasubduction

Abstract: Carbonatitic magmatism plays a significant role in Earth's carbon cycle, which is also a lithoprobe of crust-mantle interaction, mantle metasomatism and partial melting. Due to different mineral assemblages and geochemical compositions, and diverse tectonic settings, the origin of carbonatite has long been debated. At subduction zones, sediments (including carbonates) are subducted into the mantle with the downgoing oceanic slab. However, the detailed mechanism of how subducted carbonates contribute to carbonatitic magmatism remains unclear. Here we present geochronological, geochemical and isotopic study on the Taohuala Mountain carbonatite at the southern margin of the Alxa Block, North China Craton. The classification of carbonatite from the Taohuala Mountain relies strongly on the observations of obvious intrusion contact relationships and flow structures in field outcrop. The Taohuala Mountain carbonatite has SiO2 ranging from 2.37 wt.% to 11.45 wt%, high CaO (45.93-53.86 wt%) and low MgO (0.51-4.39 wt%), and is characterized by enrichment of LILE (Ba, Sr), depletion of HFSE (Nb, Ta, Zr, Hf), and slightly negative Ce and Eu anomalies. Carbonates in the samples have high 87Sr/86Sr (0.70686-0.70694) and low 143Nd/144Nd (0.511635-0.511924). Remarkably, the highly fractionated d18OVSMOW (11.83-25.92‰) indicates components of both sedimentary and mantle origin. Detailed zircon in situ U-Pb dating and oxygen isotope analysis exhibit contrast ages and d18OVSMOW from core to rim, i.e., old ages (mainly > 800 Ma), high Th/U (mainly > 0.5) and low d18OVSMOW (6.37-11.44‰) in cores (inherited), whereas young ages (~ 400 Ma), low Th/U (mainly < 0.01) and high d18OVSMOW (20.04-24.54‰) in rims, suggesting that the Taohuala Mountain carbonatite may have been generated from melting of subducted sedimentary carbonates. Considering all these evidences, and that the collision along Qilian Mountains was older than the carbonatite, we propose that a large volume of sedimentary carbonates subducted and remained in the lithospheric mantle under the Alxa block during the closure of the Paleo-Qilian Ocean. Subsequently, the carbonatite was formed by melting of carbonates with minor contributions from the mantle during the breakoff or rollback of the Paleo-Asian oceanic slab.
DS202008-1458
2020
Xue, S.Xue, S., Ling, M-X., Liu, Y-L., Kang, Q-Q., Huang, R-F., Zhang, Z-K., Sun, W.The formation of the giant Huayangchuan U-Nb deposit associated with carbonatite in the Qinqling orogenic belt.Ore Geology Reviews, Vol. 122, 103498, 16p. PdfChinacarbonatite

Abstract: Carbonatitic magmatism plays a significant role in outgassing carbon from mantle and the formation of rare earth element (REE), rare metal (e.g., Nb and Th) and other types of deposits. The mechanism of REE mineralization associated with carbonatite have been widely studied. However, it is hard to understand U-Nb mineralization without Th enrichment associated with carbonatite. Here we report a carbonatite-hosted U-Nb deposit in Huayangchuan, located in the north Qinling Orogenic Belt. Field observation, mineralogy and geochemical analysis on a suite of drillhole samples were conducted to decipher the mineralization mechanism and its relationship with carbonatite. Huayangchuan carbonatite samples mainly consist of calcite and augite with small volume of accessory minerals (e.g., allanite, fluorapatite, barite and celestite). Betafite [(Ca,U)2(Ti,Nb,Ta)2O6(OH)] is the major ore-bearing mineral in Huayangchuan deposit. The carbonatite shows high CaO, low MgO and alkali contents, which should be products to be differentiated from primary carbonatite (high MgO and alkali contents). The immiscibility and crystallization processes could explain the high CaO/(CaO + MgO + FeO) ratios and the enrichment of LILE. Numerical modeling also indicates positive d18OSMOW (7.29 to 15.53‰) and negative d13CPDB (-5.26 to -10.08‰) shifts are induced by reduced sediments assimilation from source consistent with there being enriched Sr-Nd and low Mg isotopic compositions. LA-ICP-MS zircon U-Pb dating of Huayangchuan carbonatite yielded Triassic ages of 229 ± 3 Ma, which corresponds to the post-collision stage of Qinling Orogen during the middle-late Triassic. We then proposed that the recycling of subducted sediments and later re-melting of those materials in shallow mantle generated the Huayangchuan carbonatite and subsequently formed the Huayangchuan deposit. Fluorine concentration decrease, caused by fluorapatite crystallization, ultimately resulted in betafite mineralization.
DS2003-1515
2003
Xue-Cheng, Y.Xue-Cheng, Y., Klemperer, S.L., Wen-Bang, T., Lai-Xiang, L., Chetwin, E.Crustal structure and exhumation of the Dabie Shan ultrahigh pressure orogen, easternGeology, Vol. 31, 5, pp. 435-8.ChinaGeophysics - seismics, UHP - ultra high pressure
DS200412-2164
2003
Xue-Cheng, Y.Xue-Cheng, Y., Klemperer, S.L., Wen-Bang, T., Lai-Xiang, L., Chetwin, E.Crustal structure and exhumation of the Dabie Shan ultrahigh pressure orogen, eastern China, from seismic reflection profiling.Geology, Vol. 31, 5, pp. 435-8.ChinaGeophysics - seismics UHP - ultra high pressure
DS1997-0655
1997
Xueming, Y.Le Bas, M.J., Spiro, B., Xueming, Y.Oxygen, carbon and strontium isotope study of the carbonatitic dolomitehost of the Bayan Obo rare earth elements (REE) depositMineralogical Magazine, No. 407, August pp. 531-542.ChinaCarbonatite, Deposit - Bayan Obo
DS200712-0607
2007
Xueming, Y.LeBas, M.J., Xueming, Y., Taylor, R.N., Spior, B., Milton, J.A., Peishan, Z.New evidence from a calcite dolomite carbonatite dyke for the magmatic origin of the massive Bayan Obo ore bearing dolomite marble, Inner Mongolia China.Mineralogy and Petrology, Vol. 91, 3-4, pp. 287-China, MongoliaCarbonatite
DS200812-0635
2008
Xueming, Y.Le Bas, M.J., Xueming, Y., Taylor, R.N., Spiro, B., Milton, J.A., Peishan, Z.New evidence from a calcite dolomite carbonatite dyke for the magmatic origin of the massive Bayan Obo ore bearing dolomite marble, Inner Mongolia, China.Mineralogy and Petrology, Vol. 90, 3-4, pp. 223-248.China, MongoliaCarbonatite
DS1997-1276
1997
Xueyi, X.Xueyi, X., et al.Phlogopite amphibole pyroxenite xenoliths in Langao, Shaanxi Province:evidence for mantle MetasomatismChin. Journal of Geochem., Vol. 16, No. 4, pp. 318-29.ChinaXenoliths - petrology
DS1998-0645
1998
Xu-FengHu, Xu-Feng, Robinson, P.T.Mineralogy, of diamond bearing chromitites, Luobusa ophiolite, southernTibet.Geological Association of Canada (GAC)/Mineralogical Association of Canada (MAC) Abstract Volume, p. A81. abstract.China, TibetOphiolite - Luobusa, Mineralogy
DS2000-1035
2000
Xu-Feng, H.Xu-Feng, H., Robinson, P.T., Wenji Bai, ZhouDiamonds in ophiolites - fact or fictionGeological Association of Canada (GAC)/Mineralogical Association of Canada (MAC) Calgary May 2000, 3p.China, TibetOphiolite - Luobusa, podiforM.
DS1992-1709
1992
Xureen WangXureen Wang, Jin ZhangTwo methods of orthogonally stepwise discrimination and theirapplicationsMathematical Geology, Vol. 24, No. 2, February pp. 203-218GlobalGeostatistics, Discrimination
DS201911-2509
2019
Xydous, S.Baziotis, I., Xydous, S., Asimow, P.D., Mavrogonatos, C., Flemetakis, S., Klemme, S., Berndt, J.The potential of phosphorous in clinopyroxene as a geospeedometer: examples from mantle xenoliths.Geochimica et Cosmochimica Acta, Vol. 266, pp. 307-311.United States, California, Africa, Moroccometasomatism

Abstract: We investigate the potential to use concentrations and zoning patterns of phosphorus (P) in clinopyroxene as indicators of the rates of igneous and metasomatic processes, comparable to recent applications of P in olivine but applicable to more evolved rocks and lower temperatures of crystallization. Few high-P pyroxenes have been previously reported, and none have been analyzed in detail for the mechanism of P enrichment or the implications for mineral growth kinetics. Here, we report the discovery and characteristics of exotic phosphorus-rich secondary clinopyroxene in glassy pockets and veins in composite mantle xenoliths from the Cima Volcanic Field (California, USA) and the Middle Atlas Mountains (Morocco, West Africa). These glass-bearing xenoliths preserve evidence of melt infiltration events and the contrasting behavior of P in their pyroxene crystals constrains the different rates of reaction and extents of equilibration that characterized infiltration in each setting. We report optical petrography and chemical analysis of glasses and minerals for major elements by electron microprobe microanalyzer and trace elements by laser-ablation Inductively Coupled Plasma Mass Spectrometry. The Cima Volcanic Field specimen shows one end-member behavior, with unzoned P-rich clinopyroxene in a melt pocket. We attribute this occurrence to a slow crystallization process that occurred after the melt temperature reached near-equilibrium with the host rock and during which the P concentration in the melt was buffered by apatite saturation. In the Morocco xenolith, by contrast, clinopyroxene exhibits zonation with P increasing all the way to the rim, in contact with the glass. We ascribe this feature to a rapid growth process in which excess P was incorporated into the growing clinopyroxene from a diffusive boundary layer. We demonstrate quantitative agreement between the enrichment of P and other trace elements and their expected diffusion and partitioning behavior during rapid growth. We suggest that P has not been widely reported in clinopyroxene in large part because it has rarely been looked for and that its analysis offers considerable promise as a kinetic indicator both in xenoliths and volcanic rocks.
DS2003-0231
2003
XZaitsev, A.N.Chakhmouradian, A.R., Mitchell, R.H., XZaitsev, A.N.Evolution of carbonatitic magmas: insights from accessory minerals (on the example ofGeological Association of Canada Annual Meeting, Abstract onlyRussiaCarbonatite, Magmatism
DS200412-0302
2003
XZaitsev, A.N.Chakhmouradian, A.R., Mitchell, R.H., XZaitsev, A.N.Evolution of carbonatitic magmas: insights from accessory minerals (on the example of Turiy Mys complex, Russia).Geological Association of Canada Annual Meeting, Abstract onlyRussiaCarbonatite, magmatism
Author Index
A-An Ao+ B-Bd Be-Bk Bl-Bq Br+ C-Cg Ch-Ck Cl+ D-Dd De-Dn Do+ E F-Fn Fo+ G-Gh Gi-Gq Gr+ H-Hd He-Hn Ho+ I J K-Kg Kh-Kn Ko-Kq Kr+ L-Lh
Li+ M-Maq Mar-Mc Md-Mn Mo+ N O P-Pd Pe-Pn Po+ Q R-Rh Ri-Rn Ro+ S-Sd Se-Sh Si-Sm Sn-Ss St+ T-Th Ti+ U V W-Wg Wh+ X Y Z
 
 

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