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Russian Geology and Geophysics

2015 year, number 1-2

STRUCTURAL LOCATION, COMPOSITION, AND GEODYNAMIC NATURE OF DIAMOND–BEARING METAMORPHIC ROCKS OF THE KOKCHETAV SUBDUCTION–COLLISION ZONE OF THE CENTRAL ASIAN FOLD BELT (northern Kazakhstan)

M.M. Buslov1,2, N.L. Dobretsov3,2, G.M. Vovna4, V.I. Kiselev4
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
3A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
4Far Eastern Geological Institute, Far Eastern Branch of the Russian Academy of Sciences, pr. 100 Let Vladivostoku 159, Vladivostok, 690022, Russia
Keywords: Subduction, collision, diamond-bearing calc-silicate rocks, eclogites, protoliths, olistostrome, exhumation, thrusts, tectonic rocks, geochronology, geochemistry, Kokchetav microcontinent

Abstract

We present data on different aspects of geology, mineralogy, petrology, geochemistry, and geochronology of diamond-bearing metamorphic rocks of the Kumdy-Kol terrane, which show the similarity of their protolith to the sedimentary rocks of the Kokchetav microcontinent. The structural location of the studied objects in the accretion-collision zone evidences that the subduction of the Kokchetav microcontinent beneath the Vendian-Cambrian Ishim-Selety island arc is the main mechanism of transport of graphite-bearing terrigenous carbonate rocks to zones of their transformation into diamond-bearing metamorphic rocks. The sedimentary rocks of the Kokchetav microcontinent, which are enriched in graphite and iron sulfides and carbonates, contain all components necessary for diamond crystallization in deep-seated subduction zone. This is in agreement with the experimental data and the compositions of fluid-melt inclusions in the minerals of diamond-bearing rocks.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.004