LATE TRIASSIC SILICEOUS-VOLCANO-TERRIGENOUS DEPOSITS OF THE CHUKCHI PENINSULA: COMPOSITION OF IGNEOUS ROCKS, U-Pb AGE OF ZIRCONS, AND GEODYNAMIC INTERPRETATIONS
G.V. Ledneva1, V.L. Pease2, B.A. Bazylev3
1Geological Institute, Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017, Russia
2Department of Geological Sciences, Stockholm University, Svante Arrhenius vag 8, SE-106 91 Stockholm, Sweden
3Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, ul. Kosygina 19, Moscow, 119991, Russia 2
Keywords: Geodynamic settings of magmatism, basaltic volcanism, U-Pb dating, Late Triassic, Vel’may terrane, Chukchi Peninsula
Abstract
Study of Late Triassic volcanic, subvolcanic, and volcanosedimentary rocks of the Chukchi Peninsula (Vel’may terrane) has shown their different geochemical types. Basalts, dolerites, and tuffs of the lower-middle strata of the Upper Triassic section bear evidence for their formation in suprasubductional geodynamic setting. Basalts and dolerites of the upper strata of this section correspond in composition to within-plate rocks and are similar to Middle-Late Triassic oceanic-plateau basalts and dolerites. U-Pb dating of magmatic zircons from tuffs of the lower-middle strata and from dolerites of the upper strata shows the almost synchronous magmatic activity in the suprasubductional (206 ± 5 Ma) and within-plate (212 ± 4 Ma) geodynamic settings.
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