THE CHERNAYA SOPKA TESCHENITE-SYENITE COMPLEX OF THE NORTHWESTERN EAST SAYANS: AN EXPRESSION OF EARLY DEVONIAN PLUME MAGMATISM
A.V. Lavrenchuk, A.E. Izokh, G.V. Polyakov, D.V. Metelkin, N.E. Mikhal'tsov, and A.V. Travin
United Institute of Geology, Geophysics and Mineralogy, Siberian Branch of RAS, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
Keywords: Teschenite, alkaline magmatism, petrology, paleomagnetism, plume, East Sayans
Pages: 618-634
Abstract
The teschenite-syenite mass of Mt. Chernaya Sopka was studied by a complex of petrological and paleomagnetic methods. It was shown by 40Ar/39Ar age method that the mass dates from the Lower Devonian (406-402 Ma). There are several mineral parageneses in the rocks: high-temperature assemblage of phenocrysts, low-temperature assemblage of groundmass, and interstitial assemblage of anorthoclase with analcite. Lateral changes in composition of rocks and minerals have been established, which can be related to flow differentiation. It has been substantiated that the gabbroids of the first phase of intrusion and syenites of the second phase are two discrete groups of rocks and have different sources. The data obtained suggest that the mass is a feeding conduit for the Lower Devonian volcanic rocks of the Upper Karym Subformation and that the subalkalic gabbroids of the massif are of plume nature.
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