The petrography and major- and trace-element chemistry of pyroxenite xenoliths from Miocene picrite basalts of the Vitim plateau suggest an origin by polybaric fractional crystallization of mantle melts. High-temperature giant-grained black pyroxenites and clinopyroxene megacrysts make a long trend (Fe# = 0.12 to 0.23%) corresponding to polybaric Cpx-Ga cotectic fractionation, possibly, associated with formation of a pre-eruption vein system. Low-temperature black pyroxenites are products of interaction of residual melts with the lower crust material. High-temperature hybrid websterites may have been produced by mixing of basaltic melts with fused (<5–10% partial melting) metasomatic mantle lherzolites or by AFC processes with Ga-Cpx dissolution. Anatectic Cr pyroxenites were formed mostly by segregation of partial melts from lherzolite material and remelting of former veins. Low-temperature hybrid garnet pyroxenites result from interaction of metasomatic lherzolites (or earlier Cr-diopside veins) with volatile-enriched differentiated basaltic melt. Remelting of earlier mineral generations, which occurs in all rising melt systems, is reflected by mirror-like peaks on spidergrams, spikes on TRE diagrams, and LREE and HFSE (and ore element) enrichment.
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Research Article|
April 01, 2002
PYROXENITE XENOLITHS IN PICRITE BASALTS (Vitim Plateau): ORIGIN AND DIFFERENTIATION OF MANTLE MELTS
I.V. Ashchepkov;
I.V. Ashchepkov
United Institute of Geology, Geophysics and Mineralogy, Siberian Branch of the RAS, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
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L. André
L. André
*
Musée Royal de l’Afrique Centrale, Département de Géologie, Leuvensesteenweg 13, Tervuren, 3080, Belgium
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I.V. Ashchepkov
United Institute of Geology, Geophysics and Mineralogy, Siberian Branch of the RAS, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
L. André
*
Musée Royal de l’Afrique Centrale, Département de Géologie, Leuvensesteenweg 13, Tervuren, 3080, Belgium
Publisher: Novovsibirsk State University
Accepted:
16 Jul 2001
Received:
20 Dec 2002
First Online:
29 Oct 2022
Online ISSN: 1878-030X
Print ISSN: 1068-7971
© 2002 UIGGM, SIBERIAN BRANCH OF THE RAS
UIGGM, SIBERIAN BRANCH OF THE RAS
Russ. Geol. Geophys. (2002) 43 (4): 343–363.
Article history
Accepted:
16 Jul 2001
Received:
20 Dec 2002
First Online:
29 Oct 2022
Citation
I.V. Ashchepkov, L. André; PYROXENITE XENOLITHS IN PICRITE BASALTS (Vitim Plateau): ORIGIN AND DIFFERENTIATION OF MANTLE MELTS. Russ. Geol. Geophys. 2002;; 43 (4): 343–363. doi:
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Index Terms/Descriptors
- Asia
- assimilation
- basalts
- Buryat Russian Federation
- Cenozoic
- chemical composition
- Commonwealth of Independent States
- electron probe data
- fractional crystallization
- garnet group
- geologic barometry
- geologic thermometry
- ICP mass spectra
- igneous rocks
- inclusions
- magmas
- major elements
- mantle
- mass spectra
- megacrysts
- melting
- metals
- metasomatism
- mineral composition
- Miocene
- Neogene
- nesosilicates
- orthosilicates
- P-T conditions
- partial melting
- petrography
- phase equilibria
- picrite
- plutonic rocks
- pyroxenite
- rare earths
- Russian Federation
- silicates
- solution
- spectra
- Tertiary
- trace elements
- ultramafics
- veins
- Vitim Plateau
- Vitim River
- volatile elements
- volcanic rocks
- websterite
- xenoliths
- Vitim volcanic field
Latitude & Longitude
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