Geochemistry of clinopyroxenes and petrogenesis of mantle xenoliths from Pliocene basanites of the Dzhilinda River

(Vitim volcanic field)

K. D. Litasov, Yu D. Litasov, A. S. Mekhonoshin, V. G. Mal'kovets

Research output: Contribution to journalArticle

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Abstract

Three series of peridotite xenoliths from basanites of the Dzhilinda River were analyzed. The trace-element patterns of clinopyroxenes of lherzolites of series 1 and 2a correspond to low-degree partial melting of the primitive mantle. Poikiloblastic harzburgites composed of minerals with low Mg# and characterized by a dome-like REE patterns in their relict clinopyroxene occur at the depth of garnet facies. Their origin is attributed to reworking of peridotites by percolated melt under high melt/matrix ratio (4-5%). Some peridotites of series 2a are characterized by a depleted composition and contain clinopyroxenes enriched in LREE and depleted in HFSE, which might be due to percolation of small portions of melt. We have established a rare type of interaction of melt with mantle substance producing high-Ti peridotites rich in pyroxenes and spinel (series 3). The high Ti content is indicative of the ilmenite-containing source. The high contents of Cr, Ni, Zn, and V suggest that dunite or harzburgite were initial rocks. The REE patterns in clinopyroxenes indicate a MORB-like composition of the coexisting melt. The Al-augite pyroxenites contain clinopyroxene with trace-element features pointing to their joint origin with low-temperature Cr-diopside pyroxenites. The trace-element patterns of the clinopyroxene megacrysts evidence their origin from fractional crystallization of alkaline basaltic or picrobasaltic melt. Shallow-depth skarn-like clinopyroxenites contain clinopyroxene whose REE pattern has a bend near Sm and show drastic enrichment in LREE. This suggests secondary transformation of rocks under the effect of fluid-rich melt, and these rocks were, probably, clinopyroxenite or gabbro with the primary characteristics of MORB.

Original languageEnglish
Pages (from-to)1557-1574
Number of pages18
JournalGeologiya i Geofizika
Volume41
Issue number11
Publication statusPublished - 2000

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Keywords

  • Melt fractionation
  • Peridotites
  • Pyroxenites
  • Reactional percolation
  • Trace elements

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