Sr-Ba-Rb systematization of the megacrysts of alkali feldspar from the basaltoids of Central Asia

K. D. Litasov, V. G. Mal'kovets

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    Abstract

    Variations in the Sr, Ba, and Rb contents in the megacrysts of anorthoclase and sanidine from the alkali basaltic rocks of Central Asia are described. Two series of these megacrysts have been revealed: low-Ba (Vitim volcanic field, Bartoi volcanoes, Taryat depression, Tokinsk Stanovik) and high-Ba (Udokan plateau, Minusinsk depression). The Ba/Rb ratio varies from 4-35 in the low-Ba series to 35-300 in the high-Ba one. The low-Ba series is close in geochemistry to host basalt, which reflects the peculiar composition of magmatic sources in these regions. It is shown that alkali feldspars might have crystallized from residual magmas after the crystallization of megacryst association - clinopyroxene, ilmenite (titanomagnetite), and biotite. It is supposed that the high-Ba feldspar megacrysts resulted from the basaltic-magma-crust interaction, which led to changes in their isotopic and trace-element characteristics, and is the product of deep differentiation.

    Original languageEnglish
    Pages (from-to)1304-1308
    Number of pages5
    JournalGeologiya i Geofizika
    Issue number9
    Publication statusPublished - Dec 1 1998

    Keywords

    • Alkali basalt
    • Anorthoclase
    • Deep-seated melt
    • Megacryst
    • Sanidine

    ASJC Scopus subject areas

    • Earth and Planetary Sciences (miscellaneous)

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