METASEDIMENTARY ROCKS OF THE YENISEY COMPLEX (southwest of the Siberian craton): U-Pb AGE OF ZIRCON AND MONAZITE, METAMORPHIC CONDITIONS, AND ORIGIN OF PROTOLITHS
V.P. Sukhorukov1, O.M. Turkina1,2
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
2Novosibirsk State University, Novosibirsk, Russia
Keywords: U-Pb dating, zircon, monazite, Yenisey Complex, Yenisey Ridge, Siberian craton
Abstract
The Angara-Kan terrane is located in the southwest of the Siberian Platform and is composed mostly of rocks of the Kan granulite complex and the Yenisey metavolcanosedimentary complex. In this work, we present new data on the metamorphic conditions as well as the composition and age of zircon and monazite of garnet-biotite schists of the Yenisey Complex. The textures, geochemical composition, and wide range of zircon ages indicate that the garnet-biotite schists formed during single-stage metamorphism of terrigenous rocks at P = 7.2-8.2 kbar and T = 700-730 °C. These P - T parameters are similar to those of metavolanic rocks of the Yenisey Complex. The age of the metamorphic generation of zircons and monazites from garnet-biotite schists, 720-730 Ma, is correlated with the time of Neoproterozoic metamorphism of volcanic rocks of the Yenisey Complex. The age spectra of Paleoproterozoic detrital zircons from the garnet-biotite schists show two maxima corresponding to ca. 1.86 and ca. 1.78 Ga. Granulites of the Kan Complex, which underwent two stages of high-grade metamorphism, at 1.89-1.85 and 1.80-1.77 Ga, were probably the source of these zircons. Terrigenous sediments presumably accumulated close in time to the formation of volcanic rocks of the Yenisey Complex, at ca. 1.74 Ga. We assume that most of sedimentary rocks of the Yenisey Group formed after the main orogenic events in the Angara-Kan terrane.
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