GENESIS OF ULTRAMAFIC ROCKS OF THE ALKHADYR TERRANE (
East Sayan, Siberia): IMPLICATIONS FROM THE DATA ON Cr-SPINEL COMPOSITIONS
Yu.P. Benedyuk1, V.A. Simonov2,3, A.S. Mekhonoshin1,4, T.B. Kolotilina1, S.I. Stupakov2, A.A. Doroshkov1
1A.P. Vinogradov Institute of Geochemistry, Siberian Branch, Russian Academy of Science, ul. Favorskogo 1a, Irkutsk, 664033, Russia
2V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
3Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
4Irkutsk State Technical University, ul. Lermontova 83, Irkutsk, 664074, Russia
Keywords: Spinel-group minerals, melt inclusions, parental melt
Abstract
This paper presents the first geochemical data on Cr-spinels from ultramafic rocks of the Alkhadyr terrane, which were obtained on a representative collection of samples using modern research methods. The compositional data on melt inclusions allowed the identification of three generations of Cr-spinels on the basis of their morphology, composition, and relationships with the rock-forming minerals. Different types of geochemical zoning were recognized in heterogeneous Cr-spinel grains. The composition of parental melt and crystallization temperatures of the minerals in ultramafic rocks were derived from the compositional data on Cr-spinels and trapped melt inclusions.
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