LATE PALEOPROTEROZOIC VOLCANIC ASSOCIATIONS IN THE SOUTHWESTERN SIBERIAN CRATON (Angara-Kan block)
A.D. Nozhkin1, O.M. Turkina1,2, I.I. Likhanov1, N.V. Dmitrieva1,2
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
Keywords: Volcanic associations, geochemistry, U-Pb age, Paleoproterozoic, geodynamics, correlation, metamorphism, southwestern Siberian craton
Abstract
We present data on the geologic setting, mineral composition, and conditions of metamorphism of volcanics of andesite-dacite-trachyrhyodacite, leucobasalt-basalt, basalt-andesite-basalt-trachyandesite, and basalt associations in the Yenisei amphibolite-gneiss complex of the Angara-Kan terrane. We have determined the age of zircon (SHRIMP-II U-Pb dating) from two samples of volcanics of the andesite-dacite-trachyrhyodacite association. The volcanics formed in the Late Paleoproterozoic (~1.74 Ga) and were metamorphosed at 750 Ma. Inherited zircon and the Sm-Nd model age (2.4-2.5 Ga) of intermediate-felsic volcanics testify to their formation predominantly from the ancient crustal source. The Late Paleoproterozoic (1.78-1.74 Ga) sedimentation and volcanism in the Angara-Kan terrane followed the main collision events: high-temperature metamorphism (1.89-1.87 Ga) and formation of the first-phase granitoids of the Taraka massif (1.84 Ga). The volcanics have a predominantly bimodal character and belong to the tholeiitic and subalkalic series; this testifies to their formation in an extension setting. The formation of the volcanics of the Yenisei complex correlates with the intrusion of the intraplate granites of the Taraka massif, whereas the terrigenous sediments correlate with the sediments of the middle Subluk Group in the Urik-Iya graben. The rocks of the Yenisei complex are characterized by inhomogeneous metamorphism, which corresponds to the conditions of transition from epidote-amphibolite to amphibolite facies and to the entire PT -range of the amphibolite facies.
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