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The relationship between the olivine modal abundance calculated by Ol (wt%) = 144.27ln((Fe + Mg + Ca + 2Na) / Si) and the bulk MgO content suggests that both peridotite and pyroxenite show large variations in the MgO content with a constant olivine content (Fig. 1 b). Our model suggests that if < 30 wt% MORB is mixed with DMM …
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Pyroxenite is an ultramafic igneous rock consisting essentially of minerals of the pyroxene group, such as augite, diopside, hypersthene, bronzite or enstatite. Pyroxenites are classified into clinopyroxenites, orthopyroxenites, and the websterites which contain both types of pyroxenes (see diagram below). Closely allied to this group are the ...
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Pyroxenite is a type of ultramafic igneous rock composed mainly of dark pyroxene minerals. Learn about its formation, composition, occurrence, and examples from various scientific …
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Formation of magnesioferrite and high melting point slag with low FeO content in the fired pellets could be attributed to the improved performance of pyroxenite pellets. View Show abstract
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A composition of a ceramic pigment has been developed using pyroxenite, including pyroxene minerals — augite and enstatite—with forsterite, serpentine and coloring oxides of iron and chromium being present. The compositions of the crystalline phases in pigments were investigated by means of XPAand microanalysis as a function of the …
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The modeled seismic impedance contrasts at the boundaries between peridotite and pyroxenite (red) and pyroxenite and eclogite (orange) are given in the figure. Modeling has been done for typical mantle assemblages expected at 350 km (median depth of origin of our majorite inclusions), but using elastic properties and …
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Stable phase assemblages calculated with pMELTS [Ghiorso et al., 2002] for the Cr-free pyroxenite composition MIX1G as a function of temperature and pressure.The solidus and liquidus are labeled and shown as heavy red curves. The mass fraction of liquid is contoured in weight percent (dotted or dashed red lines; the 5% melt contour is shown …
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The North China Craton (NCC) has experienced widespread post-Mesozoic thermo-tectonic reactivation, which resulted in a dramatic transformation of the lithospheric mantle from an old, thick, cold, refractory Archean cratonic mantle into a young, thin, hot, fertile Phanerozoic lithospheric mantle (e.g., Griffin et al., 1998; Menzies et al., 1993; Xu, …
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Peridotites are dense, coarse-grained, dark-colored ultramafic plutonic rocks with at least 40% olivine by volume. Members are dunite, kimberlite, harzburgite, wehrlite and lherzolite.Others are hornblende and pyroxene-hornblende peridotites. These silica-poor (< 45 wt.% SiO2) ultrabasic rocks have at least 90 vol. % mafic minerals.Their …
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The mantle constitutes the most significant volatile reservoir on Earth, and the release of volatiles (e.g. H, C, O, and S) through volcanic degassing governs the composition of the atmosphere 1,2
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Abstract The Aniyapuram Mafic and Ultramafic Complex (AMUC) is a dismembered ophiolite of Neoarchean to Paleoproterozoic age, exposed in south-central part of the Cauvery Suture Zone (CSZ), Southern Granulite Terrane (SGT), India. The complex comprises ultramafic rocks like serpentinized peridotites of harzburgite variety …
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Pyroxene, any of a group of important rock-forming silicate minerals of variable composition, among which calcium-, magnesium-, and iron-rich varieties predominate. Pyroxenes are the most significant and abundant …
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In fact, the low silica content of OIB from recycled sources could be explained by partial melting of a range of peridotite compositions. However, experimentally ... Thus, a pyroxenite with less SiO 2 than MIX1G can produce partial melts with less SiO 2 and less Al 2 O 3 contents, that is, liquids more similar to OIB parental liquids at similar ...
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Pyroxenite samples are comprised primarily of pyroxene, olivine, magnesium-rich amphibole (anthophyllite) and chromite. Peridotite samples observed to have olivine, pyroxene, ... The ferrous iron content in the ultramafic rocks is dominant and complies with the deeper absorption band around 1.03 µm. For dunite, ...
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Partial melts of hybrid peridotite-pyroxenite sources have higher NiO and SiO 2 and lower CaO and MgO than melts of pure peridotite, on this basis it was suggested that pyroxenite contributes ~30% ...
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Ferrous iron and Mg occupy the same sites in cpx and garnet, so we tie the partitioning of Fe 2+ to Mg in both phases using an Fe-Mg exchange coefficient, K D …
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Based on the abundance of pyroxenites in the melting region of subduction zones as well as the lower solidi temperatures and higher melt productivities of these lithologies compared to peridotite (Lambart et al., 2013), preferential melting of pyroxenite may supply disproportionate volumes of magma to the arc budget, especially at thick …
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The assimilation of continental crustal material is a critical differentiation mechanism which drives sulfide segregation and sulfide-controlled metal storage, according to petrological and ...
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Rudolph et al. [] analyzed the long-wavelength nonhydrostatic geoid, allowing the depths of possible viscosity jumps to vary, and found that the best fitting models require significant viscosity increase in the 800–1200 km depth range.They speculate that this results from either variation in the relative abundance of ferric versus …
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Pyroxenite is denser than eclogite but also has higher bulk and shear moduli, which make it seismically faster. The impedance contrast across a possible pyroxenite …
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Garnet pyroxenite xenoliths from Hawaii have 256–467 ppm bulk H 2 O.. These H 2 O concentrations are 2 to 4 times higher than the MORB source.. The pyroxenite H 2 O/Ce ratios (35–115) are lower than the MORB source.. The high H 2 O, low H 2 O/Ce suggests a link between pyroxenites and EM-type OIB.. We suggest a link …
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Keywords: majoritic garnet, inclusions in diamonds, pyroxenite, mantle transition zone, sandwich experiments, eclogite-peridotite reaction. PDF: PDF+ SI: Share this article ... We calculated the Ca content of the M2 clinopyroxene site by assuming that Na+Ca on this site is 0.95 cations per formula unit, thus allowing 0.05 of (Mg+Fe) on the ...
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Pyroxenes are labeled as ferromagnesian minerals in allusion to their excessive content of magnesium and iron. Their …
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Comparison of the G2 bulk composition (open square) used in experiments with composition of MORB and of pyroxenites from peridotite massifs, xenoliths, and eclogites from the compilation of Hirschmann and Stolper.G2 pyroxenite is near the average of eclogite, having high total alkalis and low Mg# as well as average CaO and …
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The oxidation state of iron in Earth's mantle is well known to depths of approximately 200 km, but has not been characterized in samples from the lowermost upper mantle (200–410 km depth) or ...
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Pyroxenite, dark-coloured, intrusive igneous rock that consists chiefly of pyroxene. Pyroxenites are not abundant; they occur in discrete inclusions, in layered sills (tabular …
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Analyses of these minerals from peridotite xenoliths and less abundant mantle pyroxenites using Möss spectroscopy indicate that the Fe 3+ content of …
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The mineralogy of pyroxenite rock revealed lizardite, olivine, enstatite, grunerite, clinoferrosilite, and chromite. The study of melting behavior showed that the melting of pyroxenite samples starts at 1491.5 °C, and complete melting occurs at 1514.7 °C.
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A pyroxenite is an ultramafic plutonic rock consisting of ≫60% pyroxene (either clino- or orthopyroxene, or both). Other phases include olivine, hornblende, micas, garnet, feldspar, spinel, ilmenite, and sulfides. They have a gradational relationship with peridotites.
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Previous work suggested that the fractionation of a pyroxenite assemblage with 30 modal % garnet from a hydrous primitive magma can remove up to 60% of the Fe from the melt while increasing its fO 2 by as much as six logarithmic units. In the absence of measured ferrous-ferric garnet–melt partition coefficients, the model of Tang et al.
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