GEOCHEMICAL FEATURES OF METABASITE INCLUSIONS IN GRAY GNEISSES OF THE BAIDARIK BLOCK ( Central Mongolia )
V.A. Belyaev, M.A. Gornova, A.Ya. Medvedev, and N.N. Pakhomova
A.P. Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, ul. Favorskogo 1a, Irkutsk, 664033, Russia
Keywords: Archean, metabasites, tonalite-trondhjemite-granodiorite, Baidarik block, Mongolia
Pages: 321-333
Abstract
The Baidarik block of the Dzavhan microcontinent (Central Asian Fold Belt) includes the Upper Archean Baidaragin gray-gneiss complex. Among gray plagiogneisses, there are metabasic bodies, which are probably relics of early volcanics. By composition, the metabasites are divided into three petrochemical groups, whose protoliths were tholeiitic basalts, Al-undepleted and Al-depleted basaltic komatiites. Only a few samples are similar in REE composition to these protoliths. We have found metabasites with crustal-contamination features. The unusual geochemical properties of the metabasites (LREE enrichment and Nb, Zr, and Ti depletion) are related to their metasomatism.
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