Melting conditions of granitoid xenoliths in contact with alkaline mafic magma (Gusinoozerskaya Dyke, Western Transbaikalia): To the problem of the origin of ultrapotassic acid melts

V. B. Khubanov, T. T. Vrublevskaya, A. A. Tsygankov, A. G. Vladimirov, M. D. Buyantuev, E. N. Sokolova, V. F. Posokhov, E. A. Khromova

    Research output: Contribution to journalArticlepeer-review

    2 Citations (Scopus)

    Abstract

    The alkaline mafic (lamprophyric) Gusinoozerskaya dyke in West Transbaikalia is composed of partially melted granite xenoliths. Among the xenoliths, two melted substrates are observed: (1) plagioclase and quartz, and (2) alkaline feldspar and quartz. Few millimeters thick microfelsite and microgranophiric rims are the products of melting around the granite xenoliths. Ultra-acid glass is observed in the inner parts of the xenoliths at the boundary of quartz and feldspars. A distinctive feature of the fresh melts (regardless of the composition of the protolithic substrate) is an increased content of potassium with K2O/Na2O≥2. Having compared the compositions of the products of contact melting with the experimental data, we conclude that melting took place in the presence of alkaline-chloride and/or alkaline-carbonic fluid released from the crystallizing host alkaline-basic magma. The probable geotectonic conditions for the occurrence of ultrapotassic acid magmas are estimated.

    Original languageEnglish
    Pages (from-to)347-368
    Number of pages22
    JournalGeodynamics and Tectonophysics
    Volume8
    Issue number2
    DOIs
    Publication statusPublished - 1 Jan 2017

    Keywords

    • Alkaline mafic magma
    • Calc-alkaline lamprophyre
    • Contact melting
    • Granitoid xenoliths
    • Gusinoozerskaya dyke
    • Petrogenetic and tectonic conditions
    • Transbaikalia
    • Ultrapotassic acidic melt

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