GEOCHEMICAL FEATURES AND GEODYNAMIC SETTING OF FORMATION OF THE LUKINDA DUNITE-TROCTOLITE-GABBRO MASSIF ( southeastern framing of the Siberian Platform )
I.V. Buchkoa, A.A. Sorokina, V.A. Ponomarchukb, and A.E. Izokhb
aInstitute of Geology and Nature Management, Far Eastern Branch of the Russian Academy of Sciences, ul. B. Khmel'nitskogo 2, Blagoveshchensk, 675000, Russia
bV.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Layered intrusions, ultrabasite-basites, petrology, geochemistry, isotope dating
Pages: 636-648
Abstract
The Lukinda dunite-troctolite-gabbro massif in the Selenga-Stanovoy superterrane on the southeastern framing of the Siberian Platform was earlier considered Precambrian. The performed 40Ar/39Ar dating of the massif plagioclase yielded an Early Permian age (285±7.5 Ma). The main specific petrochemical features of the intrusion rocks during their crystallization differentiation are an increase in SiO2 and CaO contents and a decrease in FeOtot content, with TiO2 content remaining low and showing minor variations. A specific geochemical feature of the Lukinda massif ultrabasite-basites is a slight domination of LREE over HREE, with (La/Yb)N = 1.0-8.2. The depletion of the massif rocks in LILE (except for Sr and Ba), REE, and HFSE suggests that the massif formed on an active continental margin.
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