Hello Guest User, You are visiting this website from a computer with an IP address of 108.162.216.4 with the name of '?' since Fri May 10, 2024 at 9:00:31 AM PT for approx. 0 minutes now.
The Sheahan Diamond Literature Reference Compilation - Technical Articles based on Major Region - Yakutia
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 announcements called 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 Region Index
Sheahan Diamond Literature Reference Compilation - Scientific Articles by Author for all years
Each article reference in the SDLRC is tagged with one or more key words assigned by Pat Sheahan to highlight the main topics of the article. In addition most references have been tagged with one or more region words. In an effort to make it easier for users to track down articles related to a specific region, KRO has extracted these region words and developed a list of major region words presented in the Major Region Index to which individual region words used in the article reference have been assigned. Each individual Region Report contains in chronological order all the references with a region word associated with the Major Region word. Depending on the total for each reference type - technical, media and corporate - the references will be either in their own technical, media or corporate Region Report, or combined in a single report. Where there is a significant number of technical references there will be a technical report dedicated to the technical articles while the media and corporate references are combined in a separate region report. References that were added in the most recent monthly update are highlighted in yellow within the Region Report. The Major Region words have been defined by a scale system of "general", "continent", "country", "state or province" and "regional". Major Region words at the smaller scales have been created only when there are enough references to make isolating them worthwhile. References not tagged with a Region are excluded, and articles with a region word not matched with a Major Region show up in the "Unknown" report.
Kimberlite - diamondiferous
Lamproite - diamondiferous
Lamprophyre - diamondiferous
Other - diamondiferous
Kimberlite - non diamondiferous
Lamproite - non diamondiferous
Lamprophyre - non diamondiferous
Other - non diamondiferous
Kimberlite - unknown
Lamproite - unknown
Lamprophyre - unknown
Other - unknown
Future Mine
Current Mine
Former Mine
Click on icon for details about each occurrence. Works best with Google Chrome.
CITATION: Faure, S, 2010, World Kimberlites CONSOREM Database (Version 3), Consortium de Recherche en Exploration Minérale CONSOREM, Université du Québec à Montréal, Numerical Database on consorem.ca. NOTE: This publicly available database results of a compilation of other public databases, scientific and governmental publications and maps, and various data from exploration companies reports or Web sites, If you notice errors, have additional kimberlite localizations that should be included in this database, or have any comments and suggestions, please contact the author specifying the ID of the kimberlite: [email protected]
Some Information on the Resolution Capacity of Aeromagnetic surveys As Applied to the Search for Anomalies Created by Bodies of Tubular Shape Under Complex Geologic Conditions.
Soviet Geology GEOPHYSICS, Vol. 15, No. 7, PP. 103-107.
Use of Dipole Electric-magnetic Sounding in Determining The thickness of Alluvium During Exploration for Beach Diamond Placers in the Region of Anabar Bay.
Microtopography of Micro Diamonds from Sedimentary Covers In the South Western Part of the Eastern European Platform And a Possible Genetic Interpretation.
Morphological features of microdiamonds, sodium in garnet and potassium inpyroxenes content of two eclogite xenoliths from Udachnaya pipe(Yakutia).(Russian)
Doklady Academy of Sciences Akademy Nauk SSSR, (Russian), Vol. 321, No. 3, pp. 585-592
Russia, Commonwealth of Independent States (CIS), Yakutia
Kimberlite pyropes and chromites morphology and chemistry as indicators of diamond grade in Yakutian and Arkangelsk Provinces.
Mid-continent diamonds Geological Association of Canada (GAC)-Mineralogical Association of Canada (MAC) Symposium ABSTRACT volume, held Edmonton May, pp. 63-70.
Russia, Commonwealth of Independent States (CIS), Yakutia
Theory, methods and some results of quantitative reliability evaluation of prospecting systems (with reference to the practice of diamond prospecting inW.
Classification of failures of prospecting for kimberlite bodies using indicator minerals and heavy mineral concentrates (Malo-Botuobia andDadyn-Alakit).
Diamonds of Yakutia, pp. 143-156.
Russia, Yakutia
Sampling -indicator minerals, Deposit -Mal-Botuobia, Dadyn-Alkit areas
Laboratory techniques for investigating the composition of kimberlites with reference to prospecting and development of primary alluvial diamond deposits.
The structure of the geological prospecting enterprises of Almazy Rossii Sahka company: general technological schemes of prospecting and exploration fordiamonds.
New dat a on the internal structure and formation mechanism of kimberlite hosting fault zones in the Malaya Botuoba region, Yakutian Diamondiferous province
Mathematical modeling of the stress strain state in rock and artificial masses during slice chamber mining of underpit reserves in Internationnapa kimberlite.
Journal of Mining Science, Vol. 41, 3, pp. 215-224.
Some specific features of genesis of microdiamonds of octahedral and cubic habit from kimberlites of the Udachanaya pipe inferred from carbon isotopes - defect
Russian Geology and Geophysics, Vol. 48, pp. 299-304.
Petrochemical characteristics of the kimberlites in the Middle Markha region with application to the problem of the geochemical heterogeneity of kimberlites.
Geochemistry International, Vol. 45, 12, Dec. pp. 1197-1209.
Assignment of igneous rocks to lamproite: major and trace element criteria and implications for the history of the Tomtor pluton ( northwestern Yakutia).
Russian Geology and Geophysics, Vol. 50, pp. 911-916.
Kurszlaukis, S., Mahotkin, I., Rotman, A.Y., Kolesnikov, G.W., Makovchuk, I.V.
Syn and post eruptive volcanic processes in the Yubileinaya kimberlite pipe, Yakutia, Russia and implications for the emplacement of South African style kimberlite
Studying specific features of Daldyn-Alakit Diamondiferous region consolidated crust structure according to regional seismic dat a by CMP method and electrical prospecting by MT sounding.
10th. International Kimberlite Conference Held Bangalore India Feb. 6-11, Poster abstract
Diamonds from the Poiskovaya, Zapolyarnaya and Leningrad kimberlite pipes, northern Yakutia: correlation of carbon isotopic composition and nitrogen content as an indicator of fluid diamond formation.
The age and localization of kimberlite magmatism in the Yakutian kimberlite Province: constraints from isotope geochronology - an overview.
Proceedings of the 10th. International Kimberlite Conference, Vol. 1, Special Issue of the Journal of the Geological Society of India,, Vol. 1, pp. 225-234.
Re-Os dating of sulphide inclusions zonally distributed in single Yakutian diamonds: evidence for multiple episodes of Proterozoic formation and protracted timescales of diamond growth.
Geochimica et Cosmochimica Acta, Vol. 120, pp. 363-394.
Kolesnichenko, M., Zedgenizov, D., Ragozin, A., Litasov, K.
Water content in olivines of mantle xenoliths from Udachnaya kimberlite pipe, Yakutia.
V.S. Sobolev Institute of Geology and Mineralogy Siberian Branch Russian Academy of Sciences International Symposium Advances in high pressure research: breaking scales and horizons ( Courtesy of N. Poikilenko), Held Sept. 22-26, 2p. Abstract
Logvinova, A., Wirth, R., Taylor, L.A., Sobolev, N.V.
Aragonite, magnesite and dolomite inclusions in Yakutian diamonds: TEM observations.
V.S. Sobolev Institute of Geology and Mineralogy Siberian Branch Russian Academy of Sciences International Symposium Advances in high pressure research: breaking scales and horizons ( Courtesy of N. Poikilenko), Held Sept. 22-26, 1p. Abstract
Xenolith of diamond bearing coesite eclogite from the Udachnaya kimberlite pipe, Yakutia.
V.S. Sobolev Institute of Geology and Mineralogy Siberian Branch Russian Academy of Sciences International Symposium Advances in high pressure research: breaking scales and horizons ( Courtesy of N. Poikilenko), Held Sept. 22-26, 2p. Abstract
New dat a on the mineralogy of megacrystalline pyrope peridotite from the Udachnaya kimberlite pipe, Siberian Craton, Yakutian Diamondiferous province.
Doklady Earth Sciences, Vol. 454. no. 2, pp. 179-184.
Sharygin, I., Litasov, K., Shatskiy, A., Golovin, A., Ohtani, E., Pokhilenko, N.
Melting phase relations of the Udachnaya East Group 1 kimberlite at 3.0-6.5 GPA: experimental evidence for alkali-carbonatite composition of primary kimberlite melt.
V.S. Sobolev Institute of Geology and Mineralogy Siberian Branch Russian Academy of Sciences International Symposium Advances in high pressure research: breaking scales and horizons ( Courtesy of N. Poikilenko), Held Sept. 22-26, 2p. Abstract
Paragenesis and origin of olivine macrocrysts from Udachnaya-East hypabyssal kimberlite, Yakutia, Russia.
V.S. Sobolev Institute of Geology and Mineralogy Siberian Branch Russian Academy of Sciences International Symposium Advances in high pressure research: breaking scales and horizons ( Courtesy of N. Poikilenko), Held Sept. 22-26, 2p. Abstract
Repeated kimberlite magmatism beneath Yakutia and its relationship to Siberian flood volcanism: insights from in situ U-Pb and Sr-Nd perovskite isotope analysis.
Earth and Planetary Science Letters, Vol. 404, Oct. pp. 283-295.
Paragenesis and complex zoning of olivine macrocrysts from unaltered kimberlite of the Udachnaya-East pipe, Yakutia: relationship with the kimberlite formation conditions and evolution.
Russian Geology and Geophysics, Vol. 56, 1, pp. 260-279.
Abstract: Eclogite mantle xenoliths from the central part of Siberian craton (Udachnaya and Zarnitsa kimberlite pipes) as well as from the northeastern edge of the craton (Obnazhennaya kimberlite) were studied in detail. Garnet and clinopyroxene show evident exsolution textures. Garnet comprises rutile, ilmenite, apatite, and quartz/coesite oriented inclusions. Clinopyroxene contains rutile (± ilmenite) and apatite precipitates. Granular inclusions of quartz in kyanite and garnet usually retain features of their high-pressure origin. According to thermobarometric calculations, studied eclogitic suite was equilibrated within lithospheric mantle at 3.2–4.9 GPa and 813–1080 °C. The precursor composition of garnets from Udachnaya and Zarnitsa eclogites suggests their stability at depths 210–260 km. Apatite precipitation in clinopyroxenes of Udachnaya and Zarnitsa allows us to declare that original pyroxenes could have been indicative of their high P–T stability. Raman spectroscopic study of quartz and coesite precipitates in garnet porphyroblasts confirms our hypothesis on the origin of the exsolution textures during pressure-temperature decrease. With respect to mineralogical data, we suppose the rocks to be subjected to stepwise decompression and cooling within mantle reservoir.
Abstract: Mantle xenoliths (>150) and concentrates from late autolithic breccia and porphyritic kimberlite from the Sytykanskaya pipe of the Alakit field (Yakutia) were analyzed by EPMA and LAM ICP methods. In P-T-X-f(O2) diagrams minerals from xenoliths show widest variations, the trends P-Fe#-CaO, f(O2) for minerals from porphyric kimberlites are more stepped than for xenocrysts from breccia. Ilmenite PTX points mark moving for protokimberlites from the lithosphere base (7.5 GPa) to pyroxenite lens (5-3.5 GPa) accompanied by Cr increase by AFC and creation of two trends P-Fe#Ol ?10-12% and 13-15%. The Opx-Gar-based mantle geotherm in Alakit field is close to 35 mW/m2 at 65 GPa and 600 °C near Moho was determined. The oxidation state for the megacrystalline ilmenites is lower for the metasomatic associations due to reduction of protokimberlites on peridotites than for uncontaminated varieties at the lithosphere base. Highly inclined linear REE patterns with deep HFSE troughs for the parental melts of clinopyroxene and garnet xenocrysts from breccia were influenced by differentiated protokimberlite. Melts for metasomatic xenoliths reveal less inclined slopes without deep troughs in spider diagrams. Garnets reveal S-shaped REE patterns. The clinopyroxenes from graphite bearing Cr-websterites show inclined and inflected in Gd spectrums with LREE variations due to AFC differentiation. Melts for garnets display less inclined patterns and Ba-Sr troughs but enrichment in Nb-Ta-U. The 40Ar/39Ar ages for micas from the Alakit mantle xenoliths for disseminated phlogopites reveal Proterozoic (1154 Ma) age of metasomatism in early Rodinia mantle. Veined glimmerites with richterite - like amphiboles mark ?1015 Ma plume event in Rodinia mantle. The ?600-550 Ma stage manifests final Rodinia break-up. The last 385 Ma metasomatism is protokimberlite-related.
Deep-seated magmatism, its sources and plumes, Proceedings of XIII International Workshop held 2014., Vol. 2014, pp. 203-232.
Russia, Yakutia
Deposit - Sytykanskaya
Abstract: The concentrate from two phases of the kimberlite (breccia and porphyritic kimberlite) and about 130 xenoliths from the Sytykanskaya pipe of the Alakit field (Yakutia) were studied by EPMA and LAM ICP methods. Reconstructions of the PTXfO2 mantle sections were made separately for the two phases. The porphyritic kimberlites and breccia show differences in the minerals although the layering and pressure interval remains the same. For the porphyritic kimberlite the trends P- Fe# - CaO in garnet, fO2 are sub-vertical while the xenocrysts from the breccia show stepped and curved trends possibly due to interaction with fluids. Minerals within xenoliths show the widest variation in all pressure intervals. PT points for the ilmenites which trace the magmatic system show splitting of the magmatic source into two levels at the pyroxenite lens (4GPa) accompanied by peridotite contamination and an increase in Cr in ilmenites. Two groups of metasomatites with Fe#Ol ~ 10-12% and 13-15% were created by the melts derived from protokimberlites and trace the mantle columns from the lithosphere base (Ilm - Gar - Cr diopside) to Moho becoming essentially pyroxenitic (Cr-diopside with Phl). The first Opx-Gar-based mantle geotherm from the Alakit field has been constructed from15 associations and is close to 35 mw/m2 in the lower part of mantle section but deviates to high temperatures in the upper part of the mantle section. The oxidation state for the protokimberlite melts determined from ilmenites is higher than for the other pipes in the Yakutian kimberlite province which probably accounts for the decrease in the diamond grade of this pipe. The geochemistry of the minerals (garnets and clinopyroxenes) from breccias, metasomatic peridotite xenoliths and pyroxenites systematically differ. Xenocrysts from the breccia were produced by the most differentiated melts and enriched protokimberlite or carbonatite; they show highly inclined nearly linear REE patterns and deep troughs of HFSE. Minerals of the metasomatic xenoliths are less inclined with lower La/Cen ratios and without troughs in spider diagrams. The garnets often show S-shaped patterns. Garnets from the Cr websterites show round REE patterns and deep troughs in Ba-Sr but enrichment in Nb-Ta-U. The clinopyroxenes reveal the inclined and inflected on Gd spectrums with variations in LREE due to AFC differentiation. The 40Ar-39Ar ages for micas from the Alakit field reveal three intervals for the metasomatism. The first (1154 Ma) relates to dispersed phlogopites found throughout the mantle column, and probably corresponds to the continental arc stage in the early stage of Rodinia. Veined highly alkaline and Ti-rich veins with richterite ~1015 Ma corresponds to the plume event within the Rodinia mantle. The ~600-550 Ma stage marks the final Rodinia break-up. The last one near 385 Ma is protokimberlite related.
Deep-seated magmatism, its sources and plumes, Proceedings of XIII International Workshop held 2014., Vol. 2014, pp. 178-202.
Africa, South Africa, Russia, Yakutia
Deposit - Dike Newlands, Nyurbinskaya
Abstract: Green garnets occur in concentrates of diamondiferous kimberlite bodies in Yakutia (Udachnaya, Mir, etc.), South Africa (Newlands, Bellsbank), Venezuela (Guaniamo sills), and Canada (Mud Lake field). Mantle xenoliths of rocks containing such garnets are very rare. We found peridotite xenoliths with green garnet in situ in kimberlites of the Newlands dike. Xenoliths are irregular in form, 4.5*1.9 cm, 1.5*0.8 cm, and 1.0*0.5 cm in size, and have similar modal compositions: gar(70)+ol(28)+sp(2), gar(9)+ol(90)+sp(1) and gar(50)+ol(30)+sp(20). Rock texture is medium-crystalline, while structure is massive. We also identified a garnet macrocryst of 0.5*0.4 cm in size with a pale green kelyphytic rim. Garnet composition in the studied samples is quite constant and is characterized by the high Cr2O3 content (10.94-11.99%) and CaO content (19.52-24.94%) at the reduced contents of TiO2 (0.24-0.52%). The chrome spinel is high Cr2O3 (55%) content and the low TiO2 (0.5-0.6%) content. Olivine is high-Mg (Fo95), but elevated CaO content (0.09%). Isotopic composition of oxygen in garnet (?18O = 4.05-4.25 pm) and olivine (?18O = 4.91 pm) differs drastically from the mantle values. Rb-Sr and Sm-Nd isotopic composition show the relatively "young" model age of the sample relative to the depleted mantle (1.78 billion years), the age of formation of this rocks is also relatively "young" - probable mezoproterozoic. In kimberlites and placers of the Nyurbinskaya pipe (Nakyn field, Yakutia) there are 4 green garnet grains of 0.5-2.0 mm in size, including one intergrowth gar+sp. Most garnets are characterized by the higher CaO (18.06-22.87%) and TiO2 (1.46, 1.65, 1.75%) contents not noted before for similar garnets. Studied green garnets have the similar "sine wave" type of REE distribution for low-Ti garnets and a "raised" type of REE distribution with enrichment in medium and light REE for high-Ti garnet.
All green garnets are characterized by an increased content of light REE and Sc. High-Ti garnets are characterized by an increased content of light and middle REE, as well as titanium, and a particularly sharply increased content of Zr (!). Paragenesis ol+sp is formed at 805oand 23.4 kbar, and paragenesis ol+gar is formed at 1080oand 23.8 kbar. The rocks are characterized by nonequilibrium paragenesis ol+sp+gar and formation at moderate depths (80-90 km) under conditions of high heat flow (52-55 mW/m2). Judging from modal composition of studied xenoliths (absence of clinopyroxene), variations in chemical compositions and trace element compositions, relatively "young" model age and non-mantle isotopy of oxygen in garnets, these rocks are not "wehrlites" and likely represent metasomatic rocks such as uvarovite-chromite veins or schlierens at the moderate depths of upper mantle - it is similar to uvarovite-chromite veins of the metasomatic or a hydrothermal origin in the crustal serpentinites.
Abstract: Coalingite, Mg10Fe2(CO3)(OH)24 • 2H2O, rare Mg -Fe hydrous carbonate, has been found in the course of the mineralogical study of a disintegrated kimberlite breccia from the Manchary pipe of the Khompu -May field located in the Tamma Basin, Central Yakutia, 100 km south of Yakutsk. Coalingite occurs as small reddish brown platelets, up to 0.2 mm in size. It is associated with lizardite, chrysotile and brucite, which are typical kimberlitic assemblage. Coalingite is a supergene mineral, but in this case, it is produced by the interaction of brucite-bearing kimberlite and underground water circulating through a vertical or oblique fault zone.
Doklady Earth Sciences, Vol. 466, 2, Feb. pp. 173-176.
Russia, Yakutia
Deposit - International
Abstract: The results of study of rutile inclusions in pyrope from the Internatsionalnaya kimberlite pipe are presented. Rutile is characterized by unusually high contents of impurities (up to 25 wt %). The presence of Cr2O3 (up to 9.75 wt %) and Nb2O5 (up to 15.57 wt %) are most typical. Rutile inclusions often occur in assemblage with Ti-rich oxides: picroilmenite and crichtonite group minerals. The Cr-pyropes with inclusions of rutile, picroilmenite, and crichtonite group minerals were formed in the lithospheric mantle beneath the Mirnyi field during their joint crystallization from melts enriched in Fe, Ti, and other incompatible elements as a result of metasomatic enrichment of the depleted lithospheric mantle.
Abstract: The results of the first study of the PGE distribution in deformed lherzolites of the Udachnaya kimberlite pipe (Yakutia) are presented here. The complex character of evolution of the PGE composition in the Deformed lherzolites is assumed to be the result of silicate metasomatism. At the first stage, growth in the amount of clinopyroxene and garnet in the rock is accompanied by a decrease in the concentration of the compatible PGE (Os, Ir). During the final stage, the rock is enriched with incompatible PGE (Pt, Pd) and Re possible due to precipitation of submicron-sized particles of sulfides in the interstitial space of these mantle rocks.
Abstract: Paragenetic analysis of pyropes from alluvial deposits of the Muna—Markha interfluve (Sakha-Yakutia Republic) made it possible to distinguish relatively uniform areas that are promising for the discovery of kimberlite bodies.
Abstract: Tychite Na6Mg2(CO3)4(SO3) is a rare natural Na and Mg sulfatocarbonate. It is found only as minor mineral in deposits of saline lakes in the United States, Canada, Uganda, and China. In these continental evaporites tychite has sedimentary genesis. In this study, we report the first occurrence of tychite as a crystal phase in the melt inclusions in olivine from mantle xenoliths of the Udachnaya-East kimberlite pipe. This find provides an evidence for the probability of tychite crystallization from melts; i.e., this rare sulfatocarbonate may have a magmatic origin as well.
Cold Regions Science and Technology, Vol. 123, pp. 140-148.
Russia, Yakutia
Geomorphology
Abstract: The paper presents unique results of studying the composition of the ground ice (major components, trace elements, and rare earth elements - REEs) encountered at a depth of 200-250 m in sedimentary and magmatic rocks in the Western Yakutia diamond-bearing regions. In addition to those established earlier, three new geochemical types of ground ice have been defined: (i) sulfate-hydrocarbonate, (ii) chloride-hydrocarbonate, and (iii) sulfate-chloride types with mixed cation composition. The ground ice geochemical features are caused by evolutionary processes of interaction in the water-rock system during permafrost formation. The enclosed rocks were the source for the addition of sulfate and chlorine ions, as well as trace elements, to the ground waters of the active water exchange zone that had existed before freezing. The distribution pattern of REEs in ground ice has a special form distinct from that of sedimentary rocks, kimberlites, and ocean waters, but similar to the REE pattern in local river waters. This REE pattern features the positive europium (Eu) anomaly and approximate equality of light and heavy REEs. The obtained results essentially expand the insight into ice-formation processes in sedimentary and magmatic rocks.
Abstract: The Dalnyaya kimberlite pipe (Yakutia, Russia) contains mantle peridotite xenoliths (mostly lherzolites and harzburgites) that show both sheared porphyroclastic (deformed) and coarse granular textures, together with ilmenite and clinopyroxene megacrysts. Deformed peridotites contain high-temperature Fe-rich clinopyroxenes, sometimes associated with picroilmenites, which are products of interaction of the lithospheric mantle with protokimberlite related melts. The orthopyroxene-derived geotherm for the lithospheric mantle beneath Dalnyaya is stepped similar to that beneath the Udachnaya pipe. Coarse granular xenoliths fall on a geotherm of 35 mWm?2 whereas deformed varieties yield a 45 mWm?2 geotherm in the 2-7.5 GPa pressure interval. The chemistry of the constituent minerals including garnet, olivine and clinopyroxene shows trends of increasing Fe# (=Fe/(Fe + Mg)) with decreasing pressure. This may suggest that the interaction with fractionating protokimberlite melts occurred at different levels. Two major mantle lithologies are distinguished by the trace element patterns of their constituent minerals, determined by LA-ICP-MS. Orthopyroxenes, some clinopyroxenes and rare garnets are depleted in Ba, Sr, HFSE and MREE and represent relic lithospheric mantle. Re-fertilized garnet and clinopyroxene are more enriched. The distribution of trace elements between garnet and clinopyroxene shows that the garnets dissolved primary orthopyroxene and clinopyroxene. Later high temperature clinopyroxenes related to the protokimberlite melts partially dissolved these garnets. Olivines show decreases in Ni and increases in Al, Ca and Ti from Mg-rich varieties to the more Fe-rich, deformed and refertilized ones. Minerals showing higher Fe# (0.11-0.15) are found within intergrowths of low-Cr ilmenite-clinopyroxene-garnet related to the crystallization of protokimberlite melts in feeder channels. In P-f(O2) diagrams, garnets and Cr-rich clinopyroxenes indicate reduced conditions at the base of the lithosphere at ?5 log units below a FMQ buffer. However, Cr-poor clinopyroxenes, together with ilmenite and some Fe-Ca-rich garnets, demonstrate a more oxidized trend in the lower part of lithosphere at ?2 to 0 log units relative to FMQ. Clinopyroxenes from xenoliths in most cases show conditions transitional between those determined for garnets and megacrystalline Cr-poor suite. The relatively low diamond grade of Dalnyaya kimberlites is explained by a high degree of interaction with the oxidized protokimberlite melts, which is greater at the base of the lithosphere.
Abstract: The results of the study of diamonds with inclusions of high-pressure modification of SiO2 (coesite) by Raman spectroscopy are reported. It is established that the octahedral crystal from the Zapolyarnaya pipe is characterized by the highest residual pressure (2.7 ± 0.07 GPa). An intermediate value of this parameter (2.1 ± 0.07 GPa) was obtained for a crystal of transitional habit from the Maiskaya pipe. The minimal Raman shift was registered for coesite in diamond from the Komsomol’skaya-Magnitnaya pipe and provided a calculated residual pressure of 1.8 ± 0.03 GPa. The residual pressures for crystals from the placer deposits of the Kuoika and Bol’shaya Kuonamka rivers are 2.7 ± 0.07 and 3.1 ± 0.1 GPa, respectively. Octahedral crystals were formed in the mantle at a higher pressure than rhombododecahedral diamonds.
Journal of Mining Science, Vol. 52, no. 2, pp. 332-340.
Russia, Yakutia
Deposit - Mir
Abstract: The article gives new experimental data on spectral characteristics of photoluminescence of natural diamonds extracted from deep horizons of Mir and Internatsionalnaya Pipes, Republic of Sakha (Yakutia) depending on composition of basic and additional optically active structural defects in crystals and on temperature during spectrum recording, considering kinetics of luminescence. It is hypothesized on applicability of low-temperature effects to enhance efficiency of photoluminescence separation of diamond crystals.
Ashchepkov, I., Ntaflos, T., Logvinova, A., Vladykin, N., Ivanov, A., Spetsius, Z., Stegnitsky, Y., Kostrovitsky, S., Salikhov, R., Makovchuk, I., Shmarov, G., Karpenko, M., Downes, H., Madvedev, N.
Abstract: The PTX diagrams for the separate phases in Sytykanskaya (Ashchepkov et al., 2016) Dalnyaya (Ashchepkov et al., 2017), pipes shows that the PK show the relatively simple P-X trends and geotherms and shows more contrast and simple layering. The PK contain most abundant material from the root of the magma generation they are dunitic veins as the magma feeders represented by the megacrysts. New results for the Aykhal, Zarya and Komsomolskaya pipes in Alake field and Zarnitsa and Udachnaya pipes in Daldyn field show that evolution is accompanied by the developing of metasomatites and branching and veining of the wall rock peridotites . In Aykhal pipe in PK the Gar- dunites prevail, the xenoliths from the dark ABK "Rebus" contain Cr-Ti - rich garnets and ilmenites, more abundant compared with the grey carbonited breccia Nearly the same features were found for Yubileinaya pipe. The example of Komsomolskya pipes show that the ABK contain more eclogitic xenolith than PK. The developing of the magma channel shown in satellite Chukukskaya and Structurnaya pipe was followed by the separation of some parts of the magmatic feeders and crystallization of abundant Gar megacrysts near o the walls blocking the peridotites from the magma feeder. This drastically decrease diamond grade of pipes. Such blocking seems to be the common features for the latest breccias. In Zarnitsa pipe, the dark PK and ABK also contain fresh xenoliths but not only dunites but also sheared and metasomatic varieties and eclogites. Most of dark ABK in Yakutia contain the intergrowth of ilmenites with brown Ti- Cpx showing joint evolution trends. The late breccia contains completely altered peridotite xenoliths mainly of dunite- harzburgite type. The comparison of the trace elements of the coexisting minerals in megacryst show that they were derived from the protokimberlites but are not in complete equilibrium as well as other megacrystalline phases. Ilmenites show inflections of the trace element patterns of most Ilmenites but more regular for the Cpx and Garnets revealing the sub parallel patterns elevating LREE with the rising TRE. But commonly these are not continuous sequances because they developed in the pulsing moving systems like beneath Zarnitsa. The minerals from the feeders like dunites also show the inflected or S-type REE patterns. From the earlier to later phases the TRE compositions became more evolved reflecting the evolution of protokimberlites. The wall rocks also often show the interaction with the more evolved melts and sometimes "cut" spectrums due to the dissolution some phases and repeated melting events So we could suggest the joint evolution of the mantle column protokimberlites and megacrysts composition and type of kimberlites with the diamond grade. The mantle lithospheric base captured by the PK. The developing and rising protokimbelrites was followed by the crystallization of the diamonds in the gradient in FO2 zone in wall rocks due to reductions of C -bearing fluids and carbonatites (> 1 QMF) on peridotites ((< -2 -5 QMF). The most intensive reactions are near the graphite - diamond boundary where protokimberlites are breaking and where most framesites are forming.
Abstract: Carbon isotope compositions and the distribution of nitrogen and hydrogen in diamonds from 18 eclogites from Nurbinskaya kimberlites were studied in situ in polished plates. Cathodoluminescence images show that most of the diamonds have complex growth structures with distinctive core, intermediate and rim zones. In some diamonds the cores display dissolution features, and intermediate growth zones are separated from the cores by narrow rounded oscillatory zones. At least three crystals show interrupted multistage diamond growth; variations in ?13C of 2–3‰ occur across the contacts between distinct zones. Generally, ?13C within the diamond cores varies only by 1–2‰, in rare cases up to 3.3‰. ?13C values are usually lower in the intermediate zones and drop further towards the rims by up to 3‰. High-resolution SIMS profiles show that variations in ?13C across the diamond growth zones are sharp with no evidence of diffusive relaxation. Diamonds with predominantly tangential octahedral growth have a wide range in ?13C from ? 15.2‰ up to 9.0‰ (± 0.4‰), and their nitrogen (N) contents vary between 30 and 1500 at. ppm. Six diamonds show little internal variation along the isotopic profiles with changes in ?13C of only 0.3–0.9‰ around mean values ranging from ? 6‰ to ? 3‰. Five crystals are isotopically heavy, with relatively homogeneous ?13C up to 9‰. FTIR data show markedly different N concentrations and nitrogen aggregation states between major growth zones. This implies that the diamonds in eclogitic xenoliths from Nyurbinskaya pipe grew in multiple and interrupted growth events, probably from fluids enriched in K and H. The wide variations of ?13C in the studied eclogitic diamonds and identification of their anomalously positive ?13C values, combined with the wide range of high ?18O in garnets from the diamondiferous xenoliths of the Nyurbinskaya pipe, which are mostly outside of the mantle range, suggest a crustal contribution to the parental mantle-related fluids forming diamonds in these xenoliths and indicate the complex metasomatic evolution of the lithospheric mantle beneath the Nakynsky kimberlite field.
Abstract: We report PGE data in xenoliths of the deformed and granular peridotites. The deformed peridotites are the most deep-seated rocks and represent a narrow range of depth (180-220 km) while granular peridotites are located throughout the section of the lithospheric mantle. PGE distribution in the deformed peridotites [1] generally corresponds to that in our granular peridotites and xenoliths from Lesotho [2]. But in contrast with broad range of PGE concentrations in granular peridotites, the deformed peridotites show nearly flat pattern from Os to Pt, except of Pd (Fig.1). Granular peridotites show good positive correlation between PGE and Fe2O3. We suppose that they enriched in PGE by iron phase during its evolution. As for deformed peridotites we propose that they were depleted in Ir and Os followed by the increase of Ga and Cpx on the first stage of mantle metasomatism. On the last stage the enrichment of Pt, Pd and Re was probably a result of submicron sulphide phase’s presipitation in the interstices of mantle rocks.
Abstract: It has been demonstrated for the first time that the isotopic compositions of carbon (?13C) in magmatic calcites from the Udachnaya–East pipe kimberlite groundmass varies from–2.5 to–1.0‰ (V-PDB), while those of oxygen (?18O) range from 15.0 to 18.2‰ (V-SMOW). The obtained results imply that during the terminal late magmatic and postmagmatic stages of the kimberlite pipe formation, the carbonates in the kimberlite groundmass became successively heavier isotopically, which indicates the hybrid nature of the carbonate component of the kimberlite: it was formed with contributions from mantle and sedimentary marine sources.
Physics and Chemistry of Minerals, Vol. 44, 9, pp. 655-667.
Russia, Yakutia
deposit - Mir
Abstract: In this study, the specific features of structural defects of type IaB diamonds from the Mir kimberlite pipe (Yakutian diamondiferous province) have been characterized using FTIR and photoluminescence spectroscopy. Mineral inclusions in these diamonds [olivine (Ol), orthopyroxene (OPx), chromite (Chr), sulphide (Sf)] correspond to associations of peridotite rocks at the base of the lithosphere. Nitrogen content in type IaB diamonds shows significant variations, suggesting different growth media and/or several growth stages. A specific feature of these diamonds is the absence or very small amount of platelets, which may be related to annealing during their long-term residence at the temperatures of the base of the lithosphere. All studied diamonds show the presence of hydrogen defects that are active in IR spectra with an intense line at 3107 cm?1, and additional weaker lines at 3085 and 3237 cm?1, which correlated with high nitrogen content. Type IaB diamonds are also characterized by the presence of nitrogen-nickel luminescence centres S2, S3 and 523.2 nm. This feature distinguishes them from superdeep diamonds with extreme nitrogen aggregation states, which clearly attest to different growth conditions and crystallization media of type IaB diamonds from the Mir kimberlite pipe.
Doklady Earth Sciences, Vol. 476, 2, pp. 1155-1158.
Russia, Yakutia
deposit - Udachnaya
Abstract: The crystallographic orientation of three diamonds and 19 olivine inclusions from Udachnaya kimberlite pipe was studied using monocrystal X-ray diffractometry. No epitaxial olivine inclusions were found.
Reutsky, V.N., Shiryaev, A.A., Titkov, S.V., Wiedenbeck, M., Zudina, N.N.
Evidence for large scale fractionation of carbon isotopes and of nitrogen impurity during crystallization of gem quality cubic diamonds from placers of North Yakutia.
Geochemistry International, Vol. 55, 11, pp. 988-999.
Russia, Yakutia
alluvials
Abstract: The spatial distribution of carbon and nitrogen isotopes and of nitrogen concentrations is studied in detail in three gem quality cubic diamonds of variety II according to Orlov’s classification. Combined with the data on composition of fluid inclusions our results point to the crystallization of the diamonds from a presumably oxidized carbonate fluid. It is shown that in the growth direction ?13C of the diamond becomes systematically lighter by 2-3‰ (from -13.7 to -15.6‰ for one profile and from -11.7 to -14.1‰ for a second profile). Simultaneously, we observe substantial decrease in the nitrogen concentration (from 400-1000 to 10-30 at ppm) and a previously unrecognized enrichment of nitrogen in light isotope, exceeding 30‰. The systematic and substantial changes of the chemical and isotopic composition can be explained using the Burton-Prim-Slichter model, which relates partition coefficients of an impurity with the crystal growth rate. It is shown that changes in effective partition coefficients due to a gradual decrease in crystal growth rate describes fairly well the observed scale of the chemical and isotopic variations if the diamond-fluid partition coefficient for nitrogen is significantly smaller than unity. This model shows that nitrogen isotopic composition in diamond may result from isotopic fractionation during growth and not reflect isotopic composition of the mantle fluid. Furthermore, it is shown that the infra-red absorption at 1332 ?m-1 is an integral part of the Y-defect spectrum. In the studied natural diamonds the 1290 ?m-1 IR absorption band does not correlate with boron concentration.
Abstract: A classification suggested for alkaline ultramafic rocks of the Ary-Mastakh and Staraya Rechka fields, Northern Anabar Shield, is based on the modal mineralogical composition of the rocks and the chemical compositions of their rock-forming and accessory minerals. Within the framework of this classification, the rocks are indentified as orangeite and alkaline ultramafic lamprophyres: aillikite and damtjernite. To estimate how much contamination with the host rocks has modified their composition when the diatremes were formed, the pyroclastic rocks were studied that abound in xenogenic material (which is rich in SiO2, Al2O3, K2O, Rb, Pb, and occasionally also Ba) at relatively low (La/Yb)PM, (La/Sm)PM, and not as much also (Sm/Zr)PM and (La/Nb)PM ratios. The isotopic composition of the rocks suggests that the very first melt portions were of asthenospheric nature. The distribution of trace elements and REE indicates that one of the leading factors that controlled the diversity of the mineralogical composition of the rocks and the broad variations in their isotopic-geochemical and geochemical characteristics was asthenosphere-lithosphere interaction when the melts of the alkaline ultramafic rocks were derived. The melting processes involved metasomatic vein-hosted assemblages of carbonate and potassic hydrous composition (of the MARID type). The alkaline ultramafic rocks whose geochemistry reflects the contributions of enriched vein assemblages to the lithospheric source material, occur in the northern Anabar Shield closer to the boundary between the Khapchan and Daldyn terranes. The evolution of the aillikite melts during their ascent through the lithospheric mantle could give rise to damtjernite generation and was associated with the separation of a C-H-O fluid phase. Our data allowed us to distinguish the evolutionary episodes of the magma-generating zone during the origin of the Triassic alkaline ultramafic rocks in the northern Anabar Shield.
Journal of Asian Earth Sciences, Vol. 154, pp. 354-368.
Russia, Yakutia
carbonatite -Seligdar
Abstract: The Paleoproterozoic Seligdar magnesiocarbonatite intrusion of the Aldan-Stanovoy shield in Russia underwent extensive postmagmatic hydrothermal alteration and metamorphic events. This study comprises new isotopic (Sr, Nd, C and O) data, whole-rock major and trace element compositions and trace element characteristics of the major minerals to gain a better understanding of the source and the formation process of the carbonatites. The Seligdar carbonatites have high concentrations of P2O5 (up to 18?wt%) and low concentrations of Na, K, Sr and Ba. The chondrite-normalized REE patterns of these carbonatites display significant enrichments of LREE relative to HREE with an average La/Ybcn ratio of 95. Hydrothermal and metamorphic overprints changed the trace element characteristics of the carbonatites and their minerals. These alteration processes were responsible for Sr loss and the shifting of the Sr isotopic compositions towards more radiogenic values. The altered carbonatites are further characterized by distinct 18O- and 13C-enrichments compared to the primary igneous carbonatites. The alteration most likely resulted from both the percolation of crustal-derived hydrothermal fluids and subsequent metamorphic processes accompanied by interaction with limestone-derived CO2. The narrow range of negative ?Nd(T) values indicates that the Seligdar carbonatites are dominated by a homogenous enriched mantle source component that was separated from the depleted mantle during the Archean.
Abstract: Pyrope-almandine garnets (Mg# = 28.3-44.9, Ca# = 15.5-21.3) from a heavy mineral concentrate of diamondiferous kimberlites of the largest diamond deposit, the Yubileinaya pipe, along with kimberlite- like rocks and diamondiferous volcano-sediments of the Laptev Sea coast, have been found to contain polymineral, predominantly acicular inclusions, composed of aggregates of shrilankite (Ti2ZrO6), rutile, ilmenite, clinopyroxene, and apatite. The presence of shrilankite as an inclusion in garnets from assumed garnet-pyroxene rocks of the lower crust, lifted up by diamond-bearing kimberlite, allows it to be considered as an indicator mineral of kimberlite, which expands the possibilities when searching for kimberlite in the Arctic.
Abstract: The first results of study of minerals and diamonds of diamond-bearing eclogites from kimberlites of the Yubileinaya pipe with a variable percent amount of clinopyroxene and garnet are presented. Samples with a garnet content from 30 to 90% of the xenolith volume are dominant among the round to oval xenoliths with diamonds. Five eclogite samples contain grains of accessory rutile, as well as corundum and kyanite. Some samples host two or more diamond crystals.
European Journal of Mineralogy, Vol. 30, 6, pp. 1083-1094.
Russia, Yakutia
deposit - Dalydyn
Abstract: The spatial distribution patterns of Mg-bearing ilmenite (Ilm) composition were studied on 54 kimberlite bodies of the Daldyn field in the Yakutian kimberlite province. The representativity of the ilmenites sampled in this study is ensured by analysing ca. 100 grains from each kimberlite body. The major conclusions are as follows: (1) ilmenites from neighbouring pipes within the same linear cluster have similar average compositions and compositional fields on the MgO-Cr2O3 plots; (2) ilmenites from different clusters of pipes show different average compositions and compositional fields on the MgO-Cr2O3 plots. (3) regardless of belonging to different clusters, low-Mg Ilm across the whole Daldyn field is characterized by a direct correlation between Al2O3 and MgO; (4) significant changes of MgO content are observed in high-Mg Ilm, while Al2O3 content remains at the same level. The similarity of Ilm compositions across the kimberlite field, as shown by the MgO-Al2O3 plots, is due to a common asthenospheric source. The similar Ilm compositions in different bodies within cluster of pipes is accounted for by a single supply of magma via a lithospheric mantle channel for all pipes of the cluster. The composition of the kimberlite melts can be altered owing to the incorporation and assimilation of lithospheric mantle rocks rich in Mg and Cr. These changes of the melt cause corresponding changes in the Ilm macrocryst composition, both during and after crystallization of Ilm. Thus, the Ilm macrocryst composition follows a trend from low-Mg/low-Cr for Ilm crystallizing in the asthenosphere, to high-Mg/high-Cr at higher levels in the lithosphere. The key conclusion of this study is that Ilm can be used to decipher the structure of kimberlite fields. This can provide a reliable geological criterion for grouping an association of pipes together in clusters, which were previously identified only through subjective considerations of the spatial proximity of kimberlite bodies.
Geochemistry International, Vol. 55, 11, pp. 988-999.
Russia, Yakutia
diamond morphology
Abstract: The spatial distribution of carbon and nitrogen isotopes and of nitrogen concentrations is studied in detail in three gem quality cubic diamonds of variety II according to Orlov’s classification. Combined with the data on composition of fluid inclusions our results point to the crystallization of the diamonds from a presumably oxidized carbonate fluid. It is shown that in the growth direction ?13C of the diamond becomes systematically lighter by 2-3‰ (from -13.7 to -15.6‰ for one profile and from -11.7 to -14.1‰ for a second profile). Simultaneously, we observe substantial decrease in the nitrogen concentration (from 400-1000 to 10-30 at ppm) and a previously unrecognized enrichment of nitrogen in light isotope, exceeding 30‰. The systematic and substantial changes of the chemical and isotopic composition can be explained using the Burton-Prim-Slichter model, which relates partition coefficients of an impurity with the crystal growth rate. It is shown that changes in effective partition coefficients due to a gradual decrease in crystal growth rate describes fairly well the observed scale of the chemical and isotopic variations if the diamond-fluid partition coefficient for nitrogen is significantly smaller than unity. This model shows that nitrogen isotopic composition in diamond may result from isotopic fractionation during growth and not reflect isotopic composition of the mantle fluid. Furthermore, it is shown that the infra-red absorption at 1332 ?m-1 is an integral part of the Y-defect spectrum. In the studied natural diamonds the 1290 ?m-1 IR absorption band does not correlate with boron concentration.
Abstract: Identification of the primary compositions of mantle-derived melts is crucial for understanding mantle compositions and physical conditions of mantle melting. However, these melts rarely reach the Earth's surface unmodified because of contamination, crystal fractionation and degassing, processes that occur almost ubiquitously after melt generation. Here we report snapshots of the melts preserved in sheared peridotite xenoliths from the Udachnaya-East kimberlite pipe, in the central part of the Siberian craton. These xenoliths are among the deepest mantle samples and were delivered by kimberlite magma from 180-230?km depth interval, i.e. from the base of the cratonic lithosphere. The olivine grains of the sheared peridotites contain secondary inclusions of the crystallized melt with bulk molar (Na?+?K)/Ca?~?3.4. Various Na-K-Ca-, Na-Ca-, Na-Mg-, Ca-Mg- and Ca-carbonates, Na-Mg-carbonates with additional anions, alkali sulphates and halides are predominant among the daughter minerals in secondary melt inclusions, whereas silicates, oxides, sulphides and phosphates are subordinate. These inclusions can be considered as Cl-S-bearing alkali-carbonate melts. The presence of aragonite, a high-pressure polymorph of CaCO3, among the daughter minerals suggests a mantle origin for these melt inclusions. The secondary melt inclusions in olivine from the sheared peridotite xenoliths and the melt inclusions in phenocrystic olivines from the host kimberlites demonstrate similarities, in daughter minerals assemblages and trace-element compositions. Moreover, alkali-rich minerals (carbonates, halides, sulphates and sulphides) identified in the studied melt inclusions are also present in the groundmass of the host kimberlites. These data suggests a genetic link between melt enclosed in olivine from the sheared peridotites and melt parental to the Udachnaya-East kimberlites. We suggest that the melt inclusions in olivine from mantle xenoliths may represent near primary, kimberlite melts. These results are new evidence in support of the alkali?carbonate composition of kimberlite melts in their source regions, prior to the kimberlite emplacement into the crust, and are in stark contrast to the generally accepted ultramafic silicate nature of parental kimberlite liquids.
Petrography, mineralogy and SIMS U-Pb geochronology of 1.9-1.8 Ha carbonatites and associated alkaline rocks of the Central-Aldan magnesiocarbonatite province ( South Yakutia, Russia).
Abstract: Zircon from Tomtor syenites and kamaphorites was dated following the U-Pb method (SHRIMP-II), and the distribution of trace and rare-earth elements (REE) was studied at the same zircon point using an ion microprobe. The main zircon population from syenites was dated at 402?±?7 Ma, while the age range of single zircon grains was 700-660 M?. Different-aged zircon groups from syenites exhibited the characteristics of magmatic zircon, but their concentrations of REE and other trace elements differed markedly. The REE distribution in 700-660-M? zircon is consistent with that of the typical zircon from syenites (Belousova et al., 2002), while the heavy rare-earth elements (HREE), P, Ti, and Y concentrations of ca. 400-Ma zircon differ from those of older zircon. This is the first isotope-geochemical study of zircon from kamaphorites, and the U-Pb age of ca. 400 M? is within the error limits with of the main zircon population from syenites. The considerable enrichment of REE, C?, Ti, Sr, Y, Nb, and Ba in zircon from kamaphorites may be partly due to the presence of burbankite microinclusions. The trace-element distribution pattern of zircon from kamaphorites is very similar to the geochemical characteristics of zircon from Tiksheozero carbonatites (Tichomirowa et al., 2013). The new age dates for Tomtor syenites and kamaphorites, consistent with 700-660 M? and ca. 400 M? events, support the zircon (Vladykin et al., 2014) and pyrochlore (Antonov et al., 2017) age dates determined following the U-Pb method and those of biotite obtained following the 40Ar-39Ar method (Vladykin et al., 2014).
Journal of Mining Science, Vol. 54, 4, pp. 628-637.
Russia, Yakutia
mining
Abstract: Potential ranges of use of draglines at steeply dipping diamond ore deposits in Yakutia are discussed. Technology of stripping with direct dumping and rehandling by draglines is substantiated for upper overburden layers. A variant of increasing height of stripping benches on haulage horizons through the use of draglines and crane lines is discussed. A resource saving technology is proposed for mining roundish and extended ore bodies with alternating advance of mining front and with internal dumping. The method of estimating efficient thickness of overburden in case of direct dumping is developed using the layer coefficient of overburden rehandling. Expediency of using blasting for displacement of broken overburden to internal dump is specified.
Abstract: Mantle xenoliths brought up by kimberlitic magmas are the main source of data on the composition and physical conditions of cratonic mantle. Temperature varioations in a complete lithospheric mantle section (80-200 km) of the Siberian craton beneath the Upper Muna kimberlite filed are estimated based 49 peridotite xenolith and 330 Cpx grains from the Komsomolskaya-Magnitnaya pipe. Pressure and temperature estimates closely follow the 34.5 mW/m2 conductive geotherm. Thermal lithospere thickness is of ~ 220 km, and “diamond window” in the Paleozoic is ~75 km thick (Fig.1). Olivine compositions range in Mg# from 82 to 94 and the majority of olivenes has very high Mg# > 93. Garnets compositions mainlly follow to harzburgite-dunite and lherzolite trends plotted as Cr2O3 vs CaO. The composition of the minerals indicated the extremly depleted lithospheric mantle beneath the Upper-Muna kimberlite field. Figure 1: Model palaeogeotherms calculated using the program FITPLOT. Komsomolskaya-Magnitnaya - our data, Novinka and Udachaya are from Z16 [1]
Alvaro, M., Mazzucchelli, M.L., Angel, R.J., Murri, M., Campmenosi, N., Scambelluri, M., Nestola, F., Korsakov, A., Tomilenko, A.A., Marone, F., Morana, M.
Abstract: Metamorphic rocks are the records of plate tectonic processes whose reconstruction relies on correct estimates of the pressures and temperatures (P-T) experienced by these rocks through time. Unlike chemical geothermobarometry, elastic geobarometry does not rely on chemical equilibrium between minerals, so it has the potential to provide information on overstepping of reaction boundaries and to identify other examples of non-equilibrium behavior in rocks. Here we introduce a method that exploits the anisotropy in elastic properties of minerals to determine the unique P and T of entrapment from a single inclusion in a mineral host. We apply it to preserved quartz inclusions in garnet from eclogite xenoliths hosted in Yakutian kimberlites (Russia). Our results demonstrate that quartz trapped in garnet can be preserved when the rock reaches the stability field of coesite (the high-pressure and high-temperature polymorph of quartz) at 3 GPa and 850 °C. This supports a metamorphic origin for these xenoliths and sheds light on the mechanisms of craton accretion from a subducted crustal protolith. Furthermore, we show that interpreting P and T conditions reached by a rock from the simple phase identification of key inclusion minerals can be misleading.
2019 Twelth International Conference Oct 1-3. Moscow, IEEE DOI 11.09/MLSD .2019.8911014
Africa, Angola, Russia, Yakutia
geophysics
Abstract: We show how to increase the effectiveness of the prognoses of kimberlite bodies by using airborne geophysical technologies. We show the advantages of electromagnetic and magnetic methods for predicting kimberlite pipes. You will see examples of a regional diamond survey in Angola and Siberia.
Parageneses of garnet inclusions in diamonds from Yakutia kimberlites based on Raman and IR spectroscopy data. Udachnaya, Zapolyarnaya, Komolskaya, Yuibeyana, Aikhal, Mir, Mayskaya.
Geology of Ore Deposits, Vol. 61, 7, pp. 606-612. pdf
Abstract: We present new major element geochemical data, and review the existing data for ilmenite macrocrysts, megacrysts, as well as ilmenite in mantle xenoliths from four diamondiferous kimberlite fields in the Yakutian province. This combined data set includes 10,874 analyses of ilmenite from 94 kimberlite pipes. In the studied samples we identify various different ilmenite compositional distributions (e.g., “Haggerty's parabola”, or “Step-like” trends in MgO-Cr2O3 bivariate space), which are common to all kimberlites from a given cluster, but the compositional distributions differ between clusters. We propose three stages of ilmenite crystallization: 1) Mg-Cr poor ilmenite crystallising from a primitive asthenospheric melt (the base of Haggerty's parabola on MgO-Cr2O3 plots). 2) This primitive asthenospheric melt was then modified by the partial assimilation of lithospheric material, which enriched the melt in MgO and Cr2O3 (left branch of Haggerty’s parabola). 3) Ilmenite subsequently underwent sub-solidus recrystallization in the presence of an evolved kimberlite melt under increasing oxygen fugacity (ƒO2) conditions (right branch of Haggerty’s parabola in MgO-Cr2O3 plots). Significant differences in the ilmenite compositional distribution between different kimberlite fields are the result of diverse conditions during subsequent ilmenite crystallization in a kimberlite melt ascending through the lithospheric mantle, which have different textures and compositions beneath the studied kimberlite fields. We propose that a TiO2 fluid formed due to immiscibility of an asthenospheric melt with low Cr and high Ti contents. This fluid infiltrated lithospheric mantle rocks forming Mg-ilmenite. These features indicate a genetic link between ilmenite and the host kimberlite melt.
Abstract: To provide new constraints on the evolution of ultramafic lamprophyre melts and relation to kimberlites, we examined monomineralic and primary multiphase melt inclusions in rock-forming minerals within damtjernite from Viktoria pipe, Anabar region, Siberia craton, Russia. The studied samples are relatively unaltered nepheline-bearing, carbonate-poor damtjernite with a significant amount of monticellite in the groundmass and as a replacement of olivine. Studied inclusions hosted by groundmass monticellite, magnesian ulvöspinel-magnetite and perovskite. Monomineralic inclusions sized up to 10 ?m are round-toeuhedral in shape and are comprised of monticellite, spinel, perovskite and nepheline. Multiphase melt inclusions sized up to 10-15 ?m have rounded to elongate and amoeboid shapes. These inclusions are heterogeneous in composition and consist of perovskite, spinel group minerals, apatite (including F- and Sr-apatite), feldspathoids, multiphase alkali (Na, K) carbonate and chloride (sylvite/halite), rare K-Naand Ba-sulfates, phlogopite and baddeleyite. Despite the lack of carbonate phases in studied rocks, the composition of multiphase inclusions indicates that lamprophyre melts contained carbonate or carbonate/chlorite components. The CO2 degassing is consistent with the reaction between olivine and carbonate-bearing melt led to decarbonation reaction and generation of montichellite, as described in [1]. The composition of multiphase inclusions within minerals from lamprophyres is close to the composition of multiphase inclusions within olivine, spinel, monticellite, perovskite from kimberlites, thus indicating possible genetic links between parental melts of ultramafic lamprophyre and kimberlite.
Minerals, Vol. 10, 9, 740 10.3390/ min10090755 29p. Pdf
Russia, Yakutia
deposit - Zapplyarnaya
Abstract: Minerals from mantle xenoliths in the Zapolyarnaya pipe in the Upper Muna field, Russia and from mineral separates from other large diamondiferous kimberlite pipes in this field (Deimos, Novinka and Komsomolskaya-Magnitnaya) were studied with EPMA and LA-ICP-MS. All pipes contain very high proportions of sub-calcic garnets. Zapolyarnaya contains mainly dunitic xenoliths with veinlets of garnets, phlogopites and Fe-rich pyroxenes similar in composition to those from sheared peridotites. PT estimates for the clinopyroxenes trace the convective inflection of the geotherm (40-45 mW•m?2) to 8 GPa, inflected at 6 GPa and overlapping with PT estimates for ilmenites derived from protokimberlites. The Upper Muna mantle lithosphere includes dunite channels from 8 to 2 GPa, which were favorable for melt movement. The primary layering deduced from the fluctuations of CaO in garnets was smoothed by the refertilization events, which formed additional pyroxenes. Clinopyroxenes from the Novinka and Komsomolskaya-Magnitnaya pipes show a more linear geotherm and three branches in the P-Fe# plot from the lithosphere base to the Moho, suggesting several episodes of pervasive melt percolation. Clinopyroxenes from Zapolyarnaya are divided into four groups according to thermobarometry and trace element patterns, which show a stepwise increase of REE and incompatible elements. Lower pressure groups including dunitic garnets have elevated REE with peaks in Rb, Th, Nb, Sr, Zr, and U, suggesting mixing of the parental protokimberlitic melts with partially melted metasomatic veins of ancient subduction origin. At least two stages of melt percolation formed the inclined PT paths: (1) an ancient garnet semi-advective geotherm (35-45 mW•m?2) formed by volatile-rich melts during the major late Archean event of lithosphere growth; and (2) a hotter megacrystic PT path (Cpx-Ilm) formed by feeding systems for kimberlite eruptions (40-45 mW•m?2). Ilmenite PT estimates trace three separate PT trajectories, suggesting a multistage process associated with metasomatism and formation of the Cpx-Phl veinlets in dunites. Heating associated with intrusions of protokimberlite caused reactivation of the mantle metasomatites rich in H2O and alkali metals and possibly favored the growth of large megacrystalline diamonds.
Solid Earth Discussions, Vol. 5, pp. 1-75. pdf * note date
Russia, Yakutia
picroilmenites
Abstract: Major and trace element variations in picroilmenites from Late Devonian kimberlite pipes in Siberia reveal similarities within the region in general, but show individual features for ilmenites from different fields and pipes. Empirical ilmenite thermobarometry (Ashchepkov et al., 2010), as well as common methods of mantle thermobarometry and trace element geochemical modeling, shows long compositional trends for the ilmenites. These are a result of complex processes of polybaric fractionation of protokimberlite melts, accompanied by the interaction with mantle wall rocks and dissolution of previous wall rock and metasomatic associations. Evolution of the parental magmas for the picroilmenites was determined for the three distinct phases of kimberlite activity from Yubileynaya and nearby Aprelskaya pipes, showing heating and an increase of Fe# (Fe# = Fe / (Fe + Mg) a.u.) of mantle peridotite minerals from stage to stage and splitting of the magmatic system in the final stages.
High-pressure (5.5-7.0 GPa) Cr-bearing Mg-rich ilmenites (group 1) reflect the conditions of high-temperature metasomatic rocks at the base of the mantle lithosphere. Trace element patterns are enriched to 0.1-10/relative to primitive mantle (PM) and have flattened, spoon-like or S- or W-shaped rare earth element (REE) patterns with Pb > 1. These result from melting and crystallization in melt-feeding channels in the base of the lithosphere, where high-temperature dunites, harzburgites and pyroxenites were formed. Cr-poor ilmenite megacrysts (group 2) trace the high-temperature path of protokimberlites developed as result of fractional crystallization and wall rock assimilation during the creation of the feeder systems prior to the main kimberlite eruption. Inflections in ilmenite compositional trends probably reflect the mantle layering and pulsing melt intrusion during melt migration within the channels. Group 2 ilmenites have inclined REE enriched patterns (10-100)/PM with La / Ybn ~ 10-25, similar to those derived from kimberlites, with high-field-strength elements (HFSE) peaks (typical megacrysts). A series of similar patterns results from polybaric Assimilation + fractional crystallization (AFC) crystallization of protokimberlite melts which also precipitated sulfides (Pb < 1) and mixed with partial melts from garnet peridotites. Relatively low-Ti ilmenites with high-Cr content (group 3) probably crystallized in the metasomatic front under the rising protokimberlite source and represent the product of crystallization of segregated partial melts from metasomatic rocks. Cr-rich ilmenites are typical of veins and veinlets in peridotites crystallized from highly contaminated magma intruded into wall rocks in different levels within the mantle columns. Ilmenites which have the highest trace element contents (1000/PM) have REE patterns similar to those of perovskites. Low Cr contents suggest relatively closed system fractionation which occurred from the base of the lithosphere up to the garnet-spinel transition, according to monomineral thermobarometry for Mir and Dachnaya pipes. Restricted trends were detected for ilmenites from Udachnaya and most other pipes from the Daldyn-Alakit fields and other regions (Nakyn, Upper Muna and Prianabarie), where ilmenite trends extend from the base of the lithosphere mainly up to 4.0 GPa. Interaction of the megacryst forming melts with the mantle lithosphere caused heating and HFSE metasomatism prior to kimberlite eruption.
Minerals, Vol. 10, 702 10.3390/min10080702 24p. Pdf
Russia, Yakutia
deposit - Murun
Abstract: Fedorite is a rare phyllosilicate, having a crystal structure characterized by SiO4-tetrahedral double layers located between continuous layers formed by edge-sharing (Ca,Na)-octahedra, and containing interlayer K, Na atoms and H2O molecules. A mineralogical-petrographic and detailed crystal-chemical study of fedorite specimens from three districts of the Murun alkaline complex was performed. The sequence of the crystallization of minerals in association with fedorite was established. The studied fedorite samples differ in the content of interlayer potassium and water molecules. A comparative analysis based on polyhedral characteristics and deformation parameters was carried out. For the first time, EPR, optical absorption and emission spectra were obtained for fedorite. The raspberry-red coloration of the mineral specimens could be attributed to the presence of Mn4+ ions.
Doklady Earth Sciences, Vol. 493, 1, pp. 513-516. pdf
Russia, Yakutia
subduction
Abstract: The data available indicate the complex evolution of deformed peridotites of mantle xenoliths, the P-T parameters of which indicate that they are fragments of the metasomatized lower part of the cratonic lithosphere. The zoning established in garnets from xenoliths in kimberlite pipes is interpreted as a result of metasomatism that occurred shortly before xenoliths reached the surface. Metasomatic alterations in xenoliths of deformed harzburgites were manifested not only in the development of zoning of minerals. The study results show that there is a discrepancy between the data calculated based on the contents of incompatible elements in minerals of xenoliths and those obtained due to direct measurements of the bulk composition of xenoliths. To determine the balance of incompatible elements, we have carried out experiments on leaching xenoliths of deformed lherzolites from the Udachnaya kimberlite pipe. It was established that a significant part of LREEs in the studied xenoliths occurs in the intergranular space. The distribution pattern of incompatible elements and, in particular, the presence of a positive Eu anomaly indicate that the appearance of the intergranular component is not associated with contamination of xenoliths by the kimberlite melt. Quite a few xenoliths demonstrate a positive Eu anomaly, which indicates the influence of the subducted crustal component at one of the modification stages of xenoliths.
Contributions to Mineralogy and Petrology, Vol. 175, 98 10.1007/s00410-020-01741-w 11p. Pdf
Russia, Yakutia
diamond crystallography
Abstract: The 35 paired diamond intergrowths of rounded colorless transparent and gray opaque crystals from the placers of northeastern Siberian Platform were investigated. Mineral inclusions (KFsp, Coe, E-Grt, Po) detected in studied samples belong to eclogitic paragenesis. The majority of studied samples have uniform ranges of nitrogen content (1126-1982 at. ppm) and carbon isotope composition (??16.8 to ??23.2 ‰). These characteristics pointing towards subducted material are possible sources for their genesis. Two samples consist of a gray opaque crystal with the subduction-related characteristics (?13C ca. ??21‰ and N ca. 1300 at. ppm) and a transparent crystal with low nitrogen content (412 and 29 at. ppm) and a heavy carbon isotopic composition (?13C ??4.2 and ??4.6‰) common for primary mantle range. The higher degree of nitrogen aggregation in the crystals with mantle-like characteristics testifies their longer storage in the mantle conditions. These samples reflect multistage diamond growth history and directly indicate the mixing of mantle and subduction carbon sources at the basement of subcontinental lithospheric mantle of northeastern Siberian Platform.
Abstract: Zircon from Tomtor syenites and kamaphorites was dated following the U-Pb method (SHRIMP-II), and the distribution of trace and rare-earth elements (REE) was studied at the same zircon point using an ion microprobe. The main zircon population from syenites was dated at 402?±?7 Ma, while the age range of single zircon grains was 700-660 M?. Different-aged zircon groups from syenites exhibited the characteristics of magmatic zircon, but their concentrations of REE and other trace elements differed markedly. The REE distribution in 700-660-M? zircon is consistent with that of the typical zircon from syenites (Belousova et al., 2002), while the heavy rare-earth elements (HREE), P, Ti, and Y concentrations of ca. 400-Ma zircon differ from those of older zircon. This is the first isotope-geochemical study of zircon from kamaphorites, and the U-Pb age of ca. 400 M? is within the error limits with of the main zircon population from syenites. The considerable enrichment of REE, C?, Ti, Sr, Y, Nb, and Ba in zircon from kamaphorites may be partly due to the presence of burbankite microinclusions. The trace-element distribution pattern of zircon from kamaphorites is very similar to the geochemical characteristics of zircon from Tiksheozero carbonatites (Tichomirowa et al., 2013). The new age dates for Tomtor syenites and kamaphorites, consistent with 700-660 M? and ca. 400 M? events, support the zircon (Vladykin et al., 2014) and pyrochlore (Antonov et al., 2017) age dates determined following the U-Pb method and those of biotite obtained following the 40Ar-39Ar method (Vladykin et al., 2014).
MDPI Crystals, Vol. 11, 17 dx.doi.org/ 103390/ Qcrystal11010017 24p. Pdf
Russia, Yakutia, Urals, South America, Brazil
deposits - Mir, Udachnaya, Aikal, Yubilenya
Abstract: Ballas diamond is a rare form of the polycrystalline radial aggregate of diamonds with diverse internal structures. The morphological features of ballas diamonds have experienced repeated revision. The need that this paper presents for development of a crystal-genetic classification was determined by a rich variety of combined and transitional forms of ballas-like diamonds, which include aggregates, crystals, and intergrowths. The new crystal-genetic classification combines already-known and new morphological types of ballas as well as ballas-like diamonds discovered in the placers of Yakutia, the Urals, and Brazil. The ballas-like diamond forms include spherocrystals, aggregates with a single crystal core, split crystals, radial multiple twin intergrowths, and globular crystals. The crystal genetic scheme of the evolution of ballas and ballas-like diamonds is a sequence of the morphological types arranged in accordance with the conventional model of the dependence of the mechanism and diamond growth from carbon supersaturation developed by I. Sunagawa. The evolution of the growth forms of ballas and ballas-like diamonds was tracked based on the macrozonal structure of diamonds varying from a flat-faced octahedron to a fibrous cuboid with its transition forms to the radiating crystal aggregates. The morphological diversity of the ballas-like diamonds depends on the level of supersaturation, and abrupt changes of the level of supersaturation engender abrupt changes in a mechanism of crystal growth. The change in the rate of growth under the influence of adsorption and absorption of the mechanic impurities accompanied the sudden appearance of the autodeformation defects in the form of splitting and multiple radial twinning of crystals. The spherical shape of Yakutia ballas-like diamonds is due to the volumetric dissolution that results in the curved-face crystals of the "Urals" or "Brazilian" type associated with ballas diamonds in placers.
Geology of Ore Deposits, Vol. 62, 6, pp. 497-507. pdf
Russia, Yakutia
deposit Yubileinaya
Abstract: An experimental study was carried out on the dissolution of natural octahedral diamonds from the Internatsionalnaya and Yubileinaya kimberlite pipes (Yakutia) in an Fe-S melt at 4 GPa and 1450-1500°C with different sulfur contents (10-25 wt %). It was found that with an increase in sulfur content in the iron melt, the degree of diamond dissolution sharply decreases. The stationary (final) shape of diamond crystal dissolution under the achieved conditions corresponds to an octahedroid with trigonal etching layers, which is confirmed by photogoniometry. Diamonds with similar morphology are common in kimberlite pipes, especially in mantle xenoliths from kimberlites. It was concluded that diamonds with this shape did not undergo natural dissolution in a kimberlite magma, but, similar to flat-faced octahedra, were probably isolated from it in xenoliths. Therefore, the higher the content of octahedroid-shaped diamonds with trigonal layers in a deposit, the smaller the direct influence of an aggressive kimberlite magma on the diamond content.
IOP Conference series: Earth and Environmental Science, 609, 01028 8p. Pdf
Russia, Yakutia
deposit - Manchary, Aprelskaya
Abstract: Picroilmenite is one of the most important indicator minerals of kimberlite rocks, which can be used in solving petrological problems and in the search for diamond deposits. The present study shows the results of studying picroilmenite grains from the Manchary and Aprelskaya pipes within the Khompu-May kimberlite field (Central Yakutia). The rocks composing the pipes are represented by porphyritic kimberlite and kimberlite breccia, between which there are gradual transitions. Rocks forming the upper pipe horizons are highly carbonatized and supergenetically altered. Porphyritic segregations are represented by carbonatized serpentine pseudomorphs from macro-, megacrysts and olivine phenocrysts. Pyrope, picroilmenite mega-, macrocrysts and chromospinellide macrocrysts are found in both pipes. Most weakly altered parts of mesostasis are microgranular and formed mostly by phlogopite, with xenomorphic segregations of calcite and serpentine. Picroilmenite in both kimberlite bodies occurs as irregular and rounded macrorysts ranging from 0.7 to 10 mm and megacrysts ranging from 10 to 25 mm. Micrograins of this mineral were not diagnosed in the mesostasis. Individual grains of picroilmenite from the Manchary pipe are surrounded by a polymineral rim composed of either ferrospinel and magnetite, or perovskite and magnetite. High-and low-chromium varieties which correspond to two parageneses are identified among the picroilmenite grains from the Manchary pipe. Crystallization trend of high-chromium ilmenites from the Manchary pipe is clearly seen in the diagram in the coordinates Fe2O3-FeTiO3-MgTiO3 and associated with the presence of Cr-rich phlogopite from lherzolites xenoliths. Picroilmenite grains from the Aprelskaya kimberlite pipe are more magnesian in comparison with similar grains from the Manchary pipe. Picroilmenite from both pipes in the coordinates Fe2O3-FeTiO3-MgTiO3 is characterized by a magmatic kimberlite trend of the mineral composition evolution. The distribution of mineral composition points from the studied pipes in the diagram in the coordinates MgO - Cr2O3 has form of the "Haggerty parabola" (Haggerty, 1975) - typical for picroilmenites from kimberlites of industrial diamond-bearing middle Paleozoic pipes of Yakutia (Aikhal, Mir, Udachnaya). In general, picroilmenite of Central Yakutia pipes differs from picroilmenite of the Aikhal, Mir and Udachnaya pipes by the presence of the parabola right branch in the Haggerty diagram and an indistinct left branch. The Aikhal, Mir, and Udachnaya pipes are characterized by a clear demonstration of the left branch and a weak right. At the same time, the composition points of the high-chromium picroilmenite variety from the Manchary pipe in the Haggerty diagram coincide with the high-chromium picroilmenite from the Grib kimberlite pipe (Arkhangelsk diamondiferous province). Thus, the study showed the genetic polygeny of picroilmenite from the Manchary and Aprelskaya kimberlite pipes, and also the correlation with mineralogical diamond potential of both pipes traced by comparison with the known industrial ilmenite diamondiferous pipes of Yakutia and Arkhangelsk region.
Abstract: It is widely accepted that granulite xenoliths from kimberlites provide a record of granulite facies metamorphism at the basement of cratons worldwide. However, application of the phase equilibria modeling for seven representative samples of mafic granulites from xenoliths of the Udachnaya kimberlite pipe, Yakutia, revealed that a granulitic garnet + clinopyroxene + plagioclase ± orthopyroxene ± amphibole ± scapolite mineral assemblage was likely formed in the middle crust under amphibolite facies conditions (600-650 °C and 0.8-1.0 GPa) in a deficiency of fluid. Clinopyroxene in the rocks is characterized by elevated aegirine content (up to 10 mol.%) both in the earlier magmatic cores and in the later metamorphic rim zones of the grains. Nevertheless, the phase equilibrium modeling for all samples indicates surprisingly reduced conditions, i.e. oxygen fugacity 1.6-3.3 log units below the FMQ (Fayalite-Magnetite-Quartz) buffer. In contrast, the coexistence of Fe-Ti oxides indicates temperatures of 850-990 °C and oxygen fugacity about lg(FMQ) ± 0.5, conditions which correspond to earlier stages of rock evolution. Reduction of oxygen fugacity during cooling is discussed in the context of the evolution of a complex fluid. The reconstructed P-T conditions for the final equilibration in the mafic granulites indicate that temperatures were ~250 °C higher than those extrapolated from the continental conductive geotherm of 35-40 µW/m2 deduced from peridotite xenoliths of the Udachnaya pipe. Although the granulites resided in the crust for a period for at least 1.4 Ga, they did not re-equilibrate to the temperatures of the geotherm, likely due to the blocking of mineral reactions under relatively low temperatures and fluid-deficient conditions
Abstract: The Arbarastakh ultramafic carbonatite complex is located in the southwestern part of the Siberian Craton and contains ore-bearing carbonatites and phoscorites with Zr-Nb-REE mineralization. Based on the modal composition, textural features, and chemical compositions of minerals, the phoscorites from Arbarastakh can be subdivided into two groups: FOS 1 and FOS 2. FOS 1 contains the primary minerals olivine, magnetite with isomorphic Ti impurities, phlogopite replaced by tetraferriphlogopite along the rims, and apatite poorly enriched in REE. Baddeleyite predominates among the accessory minerals in FOS 1. Zirconolite enriched with REE and Nb and pyrochlore are found in smaller quantities. FOS 2 has a similar mineral composition but contains much less olivine, magnetite is enriched in Mg, and the phlogopite is enriched in Ba and Al. Of the accessory minerals, pyrochlore predominates and is enriched in Ta, Th, and U; baddeleyite is subordinate and enriched in Nb. Chemical and textural differences suggest that the phoscorites were formed by the sequential introduction of different portions of the melt. The melt that formed the FOS 1 was enriched in Zr and REE relative to the FOS 2 melt; the melt that formed the FOS 2 was enriched in Al, Ba, Nb, Ta, Th, U, and, to a lesser extent, Sr.
Abstract: A new classification of kelyphitic rims on garnets from xenoliths of peridotitic and eclogitic parageneses of the mantle section under the Udachnaya-East kimberlite pipe (Yakutia) is presented. Five types of rims are identified: Rim1 develops between garnet and olivine/pyroxene (or rim2) and is composed of high-alumina pyroxenes, spinel, phlogopite; rim2, the coarse grain part of rim1, is located between rim1 and olivine/pyroxene, and mainly consists of phlogopite and less aluminous larger pyroxenes and spinel; rim3 develops between garnet and kimberlite, and presents with phlogopite and Fe-Ti spinel; rim4 sometimes presents instead of rim1/rim2 and consists of zoned high-Cr phlogopite with rare fine grains of chromium spinel; rim5, a “pocket” between garnet and rim1, is represented by microcrystalline aggregates of clinopyroxene, mica, spinel, calcite, and feldspar in different variations. Rims 1, 2, and 3 are typical for garnets of all studied parageneses. Rims 4 and 5 develop on high-Cr subcalcic garnets of the most depleted peridotites. Reactions of the formation of all types of rims are given in the article. Each type of kelyphite demonstrates a clear enrichment with a certain component: Rim1—MgO and alkalis; rim2—TiO2; rim3—FeO and TiO2; rim4—Cr2O3; and rim5—CaO, suggesting the multistage injection of different components by mantle fluid.
Abstract: The results of study secondary crystallized melt inclusions in olivine of a sheared peridotite xenolith from the Komsomolskaya-Magnitnaya kimberlite pipe (Upper Muna field, Yakutia) are reported. Monticellite, phlogopite, tetraferriphlogopite KMg3(Fe3+)Si3O10(F,Cl,OH), apatite, aphthitalite K3Na(SO4)2, burkeite Na6CO3(SO4)2, and carbonates, namely calcite, nyerereite (Na,K)2Ca(CO3)2, shortite Na2Ca2(CO3)3, and eitelite Na2Mg(CO3)2, were detected among the daughter minerals of the melt inclusions by the method of confocal Raman spectroscopy. The abundance of alkali carbonates in the inclusions indicates the alkali-carbonate composition of the melt. Previously, identical inclusions of alkali-carbonate melt were reported in olivine of sheared peridotites from the Udachnaya pipe (Daldyn field). Melt inclusions in sheared peridotites are the relics of a crystallized kimberlite melt that penetrated into peridotites either during the transport of xenoliths to the surface or directly in the mantle shortly prior to the entrapment of xenoliths by the kimberlite magma. If the second scenario took place, the finds of alkali-carbonate melt inclusions in sheared peridotites carried from different mantle depths in the Udachnaya and Komsomolskaya-Magnitnaya kimberlite pipes indicate a large-scale metasomatic alteration of the lithospheric mantle of the Siberian Craton by alkaline-carbonate melts, which preceded the kimberlite magmatism. However, regardless of which of the two models proposed above is correct, the results reported here support the alkali-carbonate composition of primary kimberlite melts.
Abstract: Significant variations in the composition of garnets, both within individual grains and in the rock, are found in the xenolith of deformed garnet lherzolite from the Udachnaya kimberlite pipe. The central parts of the grains, corresponding in composition to the garnets of the lherzolite paragenesis, demonstrate a sinusoidal distribution of rare earth elements (REEs). At the same time, the edge portions have a distribution characteristic of garnet mega-crystals from kimberlites. Despite being depleted in Y and HREE, the cores are enriched in light rare earth elements, Nb, Ta, Th, and U relative to garnet from primitive garnet peridotite. In terms of the REE distribution, the model melts, which are in equilibrium with the edge parts of garnet, are close to kimberlite but are significantly enriched in comparison with kimberlite in Nb, Ta, and Hf and depleted in Sr. Melts in equilibrium with the central parts of garnet are characterized by a steeper negative slope in the region of heavy and medium REEs and approach kimberlite in the region of light REEs. Based on the data obtained, several stages in the evolution of deformed garnet lherzolite are distinguished. The first stage involves the interaction of depleted peridotite with a melt similar in composition to carbonatite melts. This stage is associated with the formation of garnet with a sinusoidal REE distribution. At the next stage, which was preceded by the dissolution of garnet grains, garnet rims with increased Ti, Zr, and Y contents were formed and clinopyroxene appeared. At the final stage, garnet melted, caused by the inflow of a water-carbon dioxide fluid with a high potassium content, leading to polymineral inclusions and kelyphite rims.
Doklady Earth Sciences, Vol. 501, pt. 1, pp. 919-924. pdf
Russia, Yakutia
cathodluminescence
Abstract: The zoning of diamonds was studied using cathodoluminescence (CL) and the chemical composition of mineral inclusions in six typical diamonds from kimberlites of Yakutia. The diamonds were ground on special equipment until inclusions with dimensions of 10-200 ?m were brought to the surface. The inclusions are characterized by a morphology reflecting the influence of the host diamonds. Multiple inclusions and intergrowths of magnesiochromite, olivine, pyrope, and phlogopite are located in both the central and peripheral zones of diamonds. In three diamonds, significant differences in the composition of magnesiochromites in different growth zones were observed, while in the other three such differences were not found. The overwhelming majority (five out of the six diamonds studied), according to the compositional features of magnesiochromite, olivine, and phlogopite, belong to the dunite-harzburgite paragenesis prevailing in diamonds from various diamond-bearing provinces of the Earth. In one of the diamonds, a lherzolite paragenesis, identified by the composition of the pyrope inclusion in magnesiochromite, was observed for the first time. The complex history of diamond growth and the variations in the chemical composition of the included minerals indicate the possibility of coexistence of syngenetic and protogenetic inclusions in the same diamond crystal.
