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Komatiites erupted billions of years ago as pulsating streams of white-hot lava. Their unusual chemical compositions and exceptionally high formation temperatures produced highly fluid lava that crystallized as spectacular layered flows. Investigation of the extreme conditions in which komatiites formed provides important evidence about the thermal and chemical …
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Geochemical data from this study indicate that Paleoproterozoic komatiites in the Pulju Greenstone Belts and Archean komatiites in the Enontekiö area are prospective for nickel-sulphide ...
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In this paper, we report Re-Os concentrations and isotopic compositions of whole rocks and chromite separates from a suite of ca. 2.7-Ga komatiites and komatiitic basalts in …
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The chalcophile element contents, particularly the platinum group element contents, of mantle derived and ore-associated magmas have been extensively reviewed, for komatiites by (Fiorentini et al ...
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Platinum group element geochemistry of komatiites from the Alexo and Pyke Hill areas, Ontario, Canada 1. ... and crushed in an alumina-faced jaw crusher. A 100- to 150-g aliquot of crushed sample was ground in an alumina shatter box and finely reground in an alumina-faced disk mill, and was used for the geochemical studies. The rest of the ...
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In the komatiite, IPGE spectra are homogeneous across the chromite grains and IPGE appear to have partitioned into the chromite. Mass balance calculations show that all of …
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Hafnium isotopic compositions were measured in Al-depleted and Al-enriched komatiites from the 3,450 Ma old Barberton greenstone belt, southern Africa. All samples have initial {var epsilon}{sub Hf} values close to zero. Such values are at variance with the strongly negative or positive values that should be observed if these rocks came from ...
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Ruth Well komatiites were derived from deep mantle melting in the majorite stability field, which resulted in depletions in Al and heavy REE. This source was also depleted in highly incompatible lithophile trace elements. 2.2. Hypothesis 2. The mantle source of the Ruth Well komatiites evolved with long-term chondritic Re/Os. 2.3. Hypothesis 3
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the komatiites, depending upon the FeO content of the liquid. This data indicates that the most magnesian olivines in komatiites could have crystallized from liquids with 22-25% MgO, in contrast to previous estimates of 30-33% MgO. These liquids will have liquidus temperatures of 1500°C at 1 atm pressure. More MgO-rich komatiites have probably ...
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komatiites. In the Ruth Well komatiites, Os abundances are controlled solely by olivine fractionation. This is typical of early Archean komatiites due to higher temperatures of the mantle. The Os abundances are higher than the Schapenburg and are more similar to late Archean komatiites. II. Background The drill core samples were collected by Prof.
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Komatiites are Al-depleted and Al-undepleted (Al2O3/TiO2 12–28 and (Gd/Yb)N, ≥1) endorsing a zoned plume and/or melting over a range of depths. The boninite-series rocks …
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Komatiites and komatiitic basalts in the Abitibi greenstone belt exhibit pronounced spatial and temporal variations in major and trace element geochemistry that provide important constraints …
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MORPHOLOGY AND COMPOSITION OF CHROMITE IN KOMATIITES FROM THE BELINGWE GREENSTONE BELT, ZIMBABWE MEI.FU ZHOU AND ROBERT KERRICH Department of Geological Sciences, IJniversity of Saskatchewan, Saskatoon, Saskatchewan S7N 0W0 ABSTRACT Chromite grains in nearly fresh Archean komatiites from the late Archean …
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Upper Paleozoic, probably Permian, komatiites have been found in the Paleo-Tethys suture zone in NE Iran. These rocks are divided into three groups: (i) differentiated and undifferentiated komatiite lava flows, (ii) komatiitic basalts, and (iii) ultramafic–mafic pillow lavas. The rocks have a wide range of textures including random olivine ...
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Most talcose and carbonate rocks were derived by the hydrothermal alteration of komatiites. Associated magnesiopelites have a unique character, reflecting derivation from a komatiite-dominated source.
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477 All whole-rock powders were prepared using a ceramic jaw crusher and an agate mill. Rhenium and Os concentrations and Os isotopic compositions were obtained on 0.1–0.5 g of rock powder using a low-blank Carius tube acid-digestion method, modified from that described in Shirey & Walker (1995), the details of which are described in Lambert ...
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Komatiites and komatiitic basalts in the Abitibi greenstone belt exhibit pronounced spatial and temporal variations in major and trace element geochemistry that provide important constraints on their petrogenesis and tectonic setting. ... …
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Archean komatiites form an important host rock for Ni-Cu sulfide deposits in the world. In this study, we examined Archean komatiites and komatiitic basalts from four areas in the Vedlozero-Segozero greenstone belt and two areas in the Tikshozero greenstone belt, Russian Karelia, to constrain their Ni-Cu sulfide mineralization potential using chalcophile element geochemistry.
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Komatiites are high-temperature, fluid, magnesium-rich lavas typically of Archaean age. A striking characteristic feature of such lavas is 'spinifex' texture—plate-like crystals of olivine ((Mg,Fe)2SiO4), millimetres to decimetres long, in a fine-grained matrix of spherulitic clinopyroxene (Ca(Mg,Fe,Al)(Si,Al)2O6), dendritic chromite ((Mg,Fe)(Cr,Al,Fe)2O4) and …
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komatiites and hence promoting ore genesis (Lesher et al. 2001). However, this study questions the role of crustal ... a ceramic-faced jaw crusher. A 100–150 g aliquot of crushed sample was ground in an agate mill and was used for geochemical studies. Figure 2 (a) Simplified geological map of the Mt Keith domain, showing the location of the ...
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sbm sbm mining gold quartz rock in komati... Find file Blame History Permalink sbm · 34e52685
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komatiites, called "Al-undepleted" or Munro-type, has near chondritic ratios of Al2O3/TiO2 and Gd/Yb. A third type, Al-enriched komatiite, is common in komatiites from Gorgona Island, …
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the komatiites in the Yilgarn Craton, Western Australia (Fig. 1). The samples were selected to represent the observed diversity of chromite occurrences, morphologies and textural relationships ...
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lithophile trace elements Archean komatiites mantle plumes primordial magma ocean majorite garnet Early Depleted Reservoir hidden enriched reservoir In this study, we present Lu-Hf isotope systematics and Lu and Hf abundances for komatiites from the lowermost part of the 2.8 Ga Kostomuksha greenstone belt in the Baltic Shield and compare these ...
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The komatiites of the Volotsk suite were derived from a mantle source characterized by depletions in highly incompatible lithophile trace elements, with the magnitude of the time-integrated LREE depletion (initial εNd = +2.7 ± 0.2) typical of this period in the Earth's mantle history. Yet this source had an initial γ 187 Os = −0.4 ± 0.4 ...
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In this study, we report Re-Os isotope and HSE abundance data for ~2.9 Ga komatiites and basalts from the Sumozero-Kenozero greenstone belt in the SE …
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Komatiites are often classified into three types based on bulk-rock major and trace element compositions (Fig. 2 and ... Approximately 25 g of each sample were crushed in a steel jaw crusher and then finely ground using an agate mortar for HSE and Re-Os and Sm-Nd isotopic analyses at the Centre de Recherches Pétrographiques et Géochimiques ...
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Komatiites are rare, ultramafic extrusive igneous rocks formed with a very high degree of partial mantle melt (30-60%) (in comparison, basalt forms with ~8-15%) that requires a hotter Archean mantle and greater plume activity (Sproule et al., 2002). High volume komatiitic melts are favored under thickened lithosphere (Begg et al. 2010).
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Two spinifex-textured komatiites yielded significantly high 3 He/ 4 He ratios of about 30Ra (where Ra denotes the atmospheric 3 He/ 4 He ratio) in fractions released by sequential crushing. These results are the first confirmation of the occurrence of high 3 He/ 4 He component in Archaean komatiites after the intriguing finding by [Richard et ...
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