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The Sheahan Diamond Literature Reference Compilation - Technical, Media and Corporate Articles based on Major Region - Iceland
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
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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]
Pilidou, SA., Priestley, K., Gudmundsson, O., Debayle, E.
Upper mantle S-wave speed heterogeneity and anisotropy beneath the North Atlantic from regional surface wave tomography: the Iceland and Azores plumes.
Geophysical Journal International, Vol. 159, 3, pp. 1057-1076.
Mantle potential temperature at Hawaii, Iceland, and the mid-Ocean Ridge system, as inferred from olivine phenocrysts: evidence thermally driven mantle plumes
Earth and Planetary Science Letters, Vol. 432, pp. 159-168.
Europe, Iceland
Mantle plume
Abstract: The presence of a mantle plume beneath Iceland has long been hypothesised to explain its high volumes of crustal volcanism. Practical constraints in seismic tomography mean that thin, slow velocity anomalies representative of a mantle plume signature are difficult to image. However it is possible to infer the presence of temperature anomalies at depth from the effect they have on phase transitions in surrounding mantle material. Phase changes in the olivine component of mantle rocks are thought to be responsible for global mantle seismic discontinuities at 410 and 660 km depth, though exact depths are dependent on surrounding temperature conditions. This study uses P to S seismic wave conversions at mantle discontinuities to investigate variation in topography allowing inference of temperature anomalies within the transition zone. We employ a large data set from a wide range of seismic stations across the North Atlantic region and a dense network in Iceland, including over 100 stations run by the University of Cambridge. Data are used to create over 6000 receiver functions. These are converted from time to depth including 3D corrections for variations in crustal thickness and upper mantle velocity heterogeneities, and then stacked based on common conversion points. We find that both the 410 and 660 km discontinuities are depressed under Iceland compared to normal depths in the surrounding region. The depression of 30 km observed on the 410 km discontinuity could be artificially deepened by un-modelled slow anomalies in the correcting velocity model. Adding a slow velocity conduit of ?1.44% reduces the depression to 18 km; in this scenario both the velocity reduction and discontinuity topography reflect a temperature anomaly of 210 K. We find that much larger velocity reductions would be required to remove all depression on the 660 km discontinuity, and therefore correlated discontinuity depressions appear to be a robust feature of the data. While it is not possible to definitively rule out the possibility of uncorrected velocity anomalies causing the observed correlated topography we show that this is unlikely. Instead our preferred interpretation is that the 660 km discontinuity is controlled by a garnet phase transition described by a positive Clapeyron slope, such that depression of the 660 is representative of a hot anomaly at depth.
Earth and Planetary Science Letters, Vol. 433, pp. 159-168.
Europe, Iceland
Mantle - 660 km
Abstract: The presence of a mantle plume beneath Iceland has long been hypothesised to explain its high volumes of crustal volcanism. Practical constraints in seismic tomography mean that thin, slow velocity anomalies representative of a mantle plume signature are difficult to image. However it is possible to infer the presence of temperature anomalies at depth from the effect they have on phase transitions in surrounding mantle material. Phase changes in the olivine component of mantle rocks are thought to be responsible for global mantle seismic discontinuities at 410 and 660 km depth, though exact depths are dependent on surrounding temperature conditions. This study uses P to S seismic wave conversions at mantle discontinuities to investigate variation in topography allowing inference of temperature anomalies within the transition zone. We employ a large data set from a wide range of seismic stations across the North Atlantic region and a dense network in Iceland, including over 100 stations run by the University of Cambridge. Data are used to create over 6000 receiver functions. These are converted from time to depth including 3D corrections for variations in crustal thickness and upper mantle velocity heterogeneities, and then stacked based on common conversion points. We find that both the 410 and 660 km discontinuities are depressed under Iceland compared to normal depths in the surrounding region. The depression of 30 km observed on the 410 km discontinuity could be artificially deepened by un-modelled slow anomalies in the correcting velocity model. Adding a slow velocity conduit of ?1.44% reduces the depression to 18 km; in this scenario both the velocity reduction and discontinuity topography reflect a temperature anomaly of 210 K. We find that much larger velocity reductions would be required to remove all depression on the 660 km discontinuity, and therefore correlated discontinuity depressions appear to be a robust feature of the data. While it is not possible to definitively rule out the possibility of uncorrected velocity anomalies causing the observed correlated topography we show that this is unlikely. Instead our preferred interpretation is that the 660 km discontinuity is controlled by a garnet phase transition described by a positive Clapeyron slope, such that depression of the 660 is representative of a hot anomaly at depth.
Abstract: Variations in the temperature of the mantle drive its convective circulation, a process that links the deep mantle with the atmosphere and oceans through volcanic and tectonic activity. Because of this connection, effective models of Earth’s evolution must incorporate the planet’s thermal history, for which a crucial constraint is the mantle’s current temperature. Researchers look at chemistry of Iceland’s newly erupted lava to analyze the temperature of the mantle below. A false-color backscatter electron image of an olivine crystal from Borgarhraun, a lava field in northern Iceland. The crystal contains a spinel inclusion, set in a fine-grained crystalline groundmass. The chemistry of these crystals records the temperatures at which they crystallized. The image is approximately 1.5 millimeters wide. Credit: S. Matthews. Because the mantle’s temperature cannot be measured directly, scientists have devised a number of creative methods to derive this information, but these have produced widely varying results. Now Matthews et al. offer new constraints on this parameter beneath Iceland, one of the few places on Earth where a divergent plate boundary is subaerially exposed because of an anomalously large amount of melting occurring beneath the island. Using a recently developed mineral thermometry technique, the researchers found that lava flows from four different eruptions along Iceland’s Northern Volcanic Zone crystallized at substantially higher temperatures (maximum 1399°C) than average mid-ocean ridge samples that have experienced little melting (maximum 1270°C). Next, the team developed a thermal model of mantle melting and used it, along with other observations such as the local thickness of the crust, to quantify the uncertainties in deriving mantle temperatures from their data. Researchers look at chemistry of Iceland’s newly erupted lava to analyze the temperature of the mantle below. An analysis of fresh lavas from Iceland indicates the mantle below the island is much hotter than beneath other locations on divergent plate boundaries. Credit: Terri Cook and Lon Abbott. Their results indicate that the mantle below Iceland is at least 140°C hotter than that beneath average mid-ocean ridges. This outcome should shed light on the factors that control the extent of melting beneath Iceland, including the ongoing debate about whether the voluminous melting is due to a deep mantle plume and, if so, whether changes in its magma production reflect variations in the plume’s temperature.
Abstract: Helium isotopes provide an important tool for tracing early-Earth, primordial reservoirs that have survived in the planet’s interior1, 2, 3. Volcanic hotspot lavas, like those erupted at Hawaii and Iceland, can host rare, high 3He/4He isotopic ratios (up to 50 times4 the present atmospheric ratio, Ra) compared to the lower 3He/4He ratios identified in mid-ocean-ridge basalts that form by melting the upper mantle (about 8Ra; ref. 5). A long-standing hypothesis maintains that the high-3He/4He domain resides in the deep mantle6, 7, 8, beneath the upper mantle sampled by mid-ocean-ridge basalts, and that buoyantly upwelling plumes from the deep mantle transport high-3He/4He material to the shallow mantle beneath plume-fed hotspots. One problem with this hypothesis is that, while some hotspots have 3He/4He values ranging from low to high, other hotspots exhibit only low 3He/4He ratios. Here we show that, among hotspots suggested to overlie mantle plumes9, 10, those with the highest maximum 3He/4He ratios have high hotspot buoyancy fluxes and overlie regions with seismic low-velocity anomalies in the upper mantle11, unlike plume-fed hotspots with only low maximum 3He/4He ratios. We interpret the relationships between 3He/4He values, hotspot buoyancy flux, and upper-mantle shear wave velocity to mean that hot plumes—which exhibit seismic low-velocity anomalies at depths of 200 kilometres—are more buoyant and entrain both high-3He/4He and low-3He/4He material. In contrast, cooler, less buoyant plumes do not entrain this high-3He/4He material. This can be explained if the high-3He/4He domain is denser than low-3He/4He mantle components hosted in plumes, and if high-3He/4He material is entrained from the deep mantle only by the hottest, most buoyant plumes12. Such a dense, deep-mantle high-3He/4He domain could remain isolated from the convecting mantle13, 14, which may help to explain the preservation of early Hadean (>4.5 billion years ago) geochemical anomalies in lavas sampling this reservoir1, 2, 3.
Earth and Planetary Science Letters, Vol. 483, 1, pp. 90-104.
Europe, Iceland
olivines
Abstract: Trace element variability in oceanic basalts is commonly used to constrain the physics of mantle melting and the chemistry of Earth's deep interior. However, the geochemical properties of mantle melts are often overprinted by mixing and crystallisation processes during ascent and storage. Studying primitive melt inclusions offers one solution to this problem, but the fidelity of the melt-inclusion archive to bulk magma chemistry has been repeatedly questioned. To provide a novel check of the melt inclusion record, we present new major and trace element analyses from olivine macrocrysts in the products of two geographically proximal, yet compositionally distinct, primitive eruptions from the Reykjanes Peninsula of Iceland. By combining these macrocryst analyses with new and published melt inclusion analyses we demonstrate that olivines have similar patterns of incompatible trace element (ITE) variability to the inclusions they host, capturing chemical systematics on intra- and inter-eruption scales. ITE variability (element concentrations, ratios, variances and variance ratios) in olivines from the ITE-enriched Stapafell eruption is best accounted for by olivine-dominated fractional crystallisation. In contrast, ITE variability in olivines and inclusions from the ITE-depleted Háleyjabunga eruption cannot be explained by crystallisation alone, and must have originated in the mantle. Compatible trace element (CTE) variability is best described by crystallisation processes in both eruptions. Modest correlations between host and inclusion ITE contents in samples from Háleyjabunga suggest that melt inclusions can be faithful archives of melting and magmatic processes. It also indicates that degrees of ITE enrichment can be estimated from olivines directly when melt inclusion and matrix glass records of geochemical variability are poor or absent. Inter-eruption differences in olivine ITE systematics between Stapafell and Háleyjabunga mirror differences in melt inclusion suites, and confirm that the Stapafell eruption was fed by lower degree melts from greater depths within the melting region than the Háleyjabunga eruption. Although olivine macrocrysts from Stapafell are slightly richer in Ni than those from Háleyjabunga, their overall CTE systematics (e.g., Ni/(Mg/Fe), Fe/Mn and Zn/Fe) are inconsistent with being derived from olivine-free pyroxenites. However, the major element systematics of Icelandic basalts require lithological heterogeneity in their mantle source in the form of Fe-rich and hence fusible domains. We thus conclude that enriched heterogeneities in the Icelandic mantle are composed of modally enriched, yet nonetheless olivine-bearing, lithologies and that olivine CTE contents provide an incomplete record of lithological heterogeneity in the mantle. Modally enriched peridotites may therefore play a more important role in oceanic magma genesis than previously inferred.
Geophysical Research , Vol. 20, EGU2018-13349 1p. Abstract
Iceland
magmatism
Abstract: Porous rocks represent the products of all explosive volcanic eruptions. As magma ascends to the Earth’s surface, bubbles form as a consequence of the evolving saturation state of volatiles dissolved in the melt. The presence of pores (either filled with pressurized volatiles or not) strongly controls the rheological behaviour of magma and thus influences all volcanic processes (pre- syn- and post-eruptive). Nevertheless, the effects of porosity on the rheology of magma are not well characterised, and a general parameterization is not available yet. Here we present a new set of experiments designed to investigate the rheology of porous melts at high temperature (750-800
C), low strain rates (10^6-10^7 s^-1) and variable porosity. Experiments were performed at 1 atm using a Setaram Setsys vertical dilatometer. The starting materials are 5 x 5 mm cores of natural rhyolitic obsidian from Hrafntinnuhryggur, Krafla, Iceland (vesicle and crystal-free) initially containing 0.11(4) wt% dissolved H2O. The experimental procedure is composed by two steps: 1) synthesis of bubble-bearing materials by heating and expansion due to foaming; 2) deformation of the foamed samples. During the first step, the obsidian cores are heated above the glass transition temperature to 900- 1050
C and held for set amounts of time (2-24 h); the volume of the foamed samples increases because H2O vapour-filled bubbles nucleate and expand. The change in volume (measured by He-pycnometry) is linked to the change in porosity (10-50 vol%). For the second step, two different experimental strategies are employed, hereafter “single-stage” and “doublestage” measurements. Single-stage measurements involve deformation of the samples directly after foaming (without quenching). The sample is cooled down from the foaming T to different target T (750-800
C), a constant load (150 g) is applied by silica or alumina probes to the core, and the cores deform isothermally for 5-20 hours. Conversely, double-stage measurements involve deformation of previously synthesised and quenched pore-bearing cores. In this case the sample is heated up to the target T and deformed under an applied load for similar amount of time (5-20 hours). In both cases, the variation in length (displacement) and volume (porosity) is continuously recorded and used to calculate the viscosity of the foamed cores using Gent’s equations. Preliminary results suggest for single-stage measurements a lower effect of bubbles on the bulk viscosity, compared to double-stage measurements. We suggest that the different behaviour may be related to the different microstructure of the experimental materials. For single-stage measurements, closed and H2O vapour-filled bubbles contribute to the observed higher viscosity, whereas in double-stage measurements, possible gas leaking and melt micro-cracking during quenching are able to weaken the porous material and markedly lower suspension viscosity.
Abstract: Plate tectonics is thought to be a major driver of volatile redistribution on Earth. The budget of nitrogen in Earth's mantle has been suggested to be almost entirely surface-derived. Recycling would contribute nitrogen with relatively heavy 15N/14N isotope ratios to Earth's mantle. This could explain why the Earth's mantle 15N/14N isotope ratio is substantially higher than both solar gases and chondritic parent bodies akin to enstatite chondrites. Here, published nitrogen isotope data of mid-ocean ridge and ocean island basalts are compiled and used to evaluate the nitrogen subduction hypothesis. Nitrogen isotope ratios are used in conjunction with published N2/3He and K2O/TiO2 ratios on the same basalts. Assuming that 3He is not recycled, N2/3He ratios are argued to trace nitrogen addition to mantle sources via subduction. Various mantle source enrichments for basalts are tracked with K2O/TiO2 ratios: elevated K2O/TiO2 ratios are assumed to primarily reflect the contributions of recycled components in the basalts mantle sources. The main result of our data compilation is that for most basalts, ?15N and N2/3He remain constant across a vast range of K2O/TiO2 ratios. Mid-ocean ridge basalts have ?15N signatures that are lower than air by ~4‰ and an average N2/3He ratio of 3.7 (±1.2) x106 (95% confidence, n = 30). Published ?15N and N2/3He are invariant across K2O/TiO2 ratios that vary over a factor of ~20. Using estimates of slab K2O/TiO2 and [TiO2], the observed invariant ?15N and N2/3He may be fit with slabs containing ~0.1 ppm N. A mass balance shows that adding ~10% recycled slabs to the convective mantle only raises the N2/3He by <5%. Lavas from Iceland, Galapagos and Hawaii have high 3He/4He and 15N/14N ratios relative to the convective mantle. Only seven samples show nitrogen isotopic signatures that are unaffected by air contamination, although those samples are poorly characterized for N2/3He. The seven basalts show ?15N between ?2 and 0‰ that do not vary systematically with K2O/TiO2 ratios that vary over a factor of ~5. The N2/3He ratios of these seven basalts is unknown, but the high 3He/4He mantle may be estimated by combining published N2/36Ar to 3He/36Ar ratios. This yields a N2/3He of 2.3 (±1.2) x 106 (1? uncertainty). This is indistinguishable from the MORB estimate of 3.7 (±1.2) x 106. Invariant ?15N across variable degrees of mantle enrichments and MORB-like N2/3He for the high 3He/4He mantle are not consistent with nitrogen addition to plume sources with elevated 3He/4He ratios. A ?15N between ?2 and 0‰ for plume sources, only marginally higher than MORB, could be a primordial feature of undegassed mantle reservoirs. Nonetheless, nitrogen subduction may have contributed to a specific array of mantle sources, as revealed by the few published data on basalts with low 3He/4He ratios. Lavas from the Society plume with low 3He/4He ratios show an enriched mantle source, and they have elevated ?15N ? +0.5‰ and N2/3He > 107. For those, the addition of slabs with concentrations of ~0.1 ppm N to a mantle source can account for the integrated dataset. To summarize, the published data suggest that nitrogen subduction may explain a sub-set of published N isotope data on basalts, but that N recycling has an overall more limited impact on mantle nitrogen than previously thought.