TRIASSIC VOLCANICLASTIC AND IGNEOUS ROCKS OF THE PRONCHISHCHEV RIDGE (East Siberia, Arctic): COMPOSITION, STRUCTURE, GENESIS, AND AGE
A.Yu. Popov1,2, A.Ya. Shevko3, E.S. Sobolev1, A.V. Yadrenkin1, B.L. Nikitenko1,2, A.V. Travin3,4
1Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
2Novosibirsk State University, Novosibirsk, Russia
3V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
4Novosibirsk State Technical University, Novosibirsk, Russia
Keywords: Diatreme, Permian, Lower Triassic, East Siberia, Arctic
Abstract
Petrographic and geochemical studies of igneous and volcaniclastic rocks of the middle part of the Pronchishchev Ridge and the Terpei lowland provided new data on their composition and structure. The subdivision of the Permian-Lower Triassic strata enclosing igneous and volcanicalstic bodies has been clarified by lithological/stratigraphic methods. The Lower Triassic Ulakhan-Yuryakh, Chekanovsky, Ystanakh, and Pastakh formations have been traced for the first time in the ridge area. It is shown that the studied dolerite body and adjacent breccias in the field of middle-upper Permian rocks are part of the volcanic pipe. The tuffite sand gritstones in the field of Lower Triassic rocks are parts of an eroded tephra ring around this diatreme. The confinedness of the tuffite bodies to the Ystanakh Formation makes it possible to determine the age of the pipe as the beginning of the late Olenekian. The obtained 40Ar/39Ar dates for the dolerites of the volcanic pipe and one of the dikes of the Pronchishchev dike belt indicate the repeated tectonomagmatic activity of the studied area in the Triassic.
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