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Russian Geology and Geophysics

2010 year, number 5

MIDDLE PALEOZOIC AND EARLY MESOZOIC ANOROGENIC MAGMATISM OF THE SOUTH YENISEI RIDGE: FIRST GEOCHEMICAL AND GEOCHRONOLOGICAL DATA

A.E. Vernikovskayaa, V.A. Vernikovskya, N.Yu. Matushkina, I.V. Romanovaa, N.G. Berejnayab, A.N. Larionovb and A.V. Travinc
aA.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, prosp. Akad. Koptyuga 3, Novosibirsk, 630090, Russia
bA.P. Karpinsky Russian Geological Research Institute, Srednii prosp. 74, St. Petersburg, 199106, Russia
cV.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, prosp. Akad. Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: South Yenisei Ridge, Yenisei suture zone, alkali syenites and trachytes, A-type leucogranites, U-Pb and Ar-Ar geochronology, continental rifting
Pages: 548-562

Abstract

In this paper we present complex geological, petrographic, and geochronological data of the study of intermediate-composition and acid intrusive and volcanogenic rocks from the Porozhnaya massif of the South Yenisei Ridge. For the first time in the Yenisei Ridge, Devonian and Triassic U-Pb age values (SHRIMP method) have been obtained for leucogranites - 387±5 Ma and alkaline trachytes - 240±3 Ma, which allows us to attribute them to two different complexes, despite the fact that these rocks were formed within the same Severnaya riftogenic structure. Geochronological Ar-Ar data (392-387 Ma) for micas from paragneisses and leucogranitic dikes of the Yenisei suture zone, on whose extension the Severnaya riftogenic structure is located, are also given in this study. These data on Devonian tectonic-magmatic events in the South Yenisei Ridge agree well with coeval events of continental rifting - the formation of intrusive and volcanogenic rocks of the Agul graben in the Prisayan region and the Minusa basin in the Altai-Sayan folded area. The formation of alkali trachytes and alkali syenites of the Severnaya riftogenic structure, for which an age of 240±3 Ma has been established, is related to the trap magmatism of the Siberian Platform.