LATE NEOPROTEROZOIC ADAKITES OF THE YENISEI RIDGE (Central Siberia): PETROGENESIS, GEODYNAMICS, AND U-Pb AGE
A.E. Vernikovskaya1,2, V.A. Vernikovsky1,2, N.Yu. Matushkin1,2, P.I. Kadil’nikov1,2, I.V. Romanova1,2, A.N. Larionov3
1A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
3A.P. Karpinsky Russian Geological Research Institute, Srednii pr. 74, St. Petersburg, 199106, Russia
Keywords: Adakites, gabbro-anorthosites, Nb-enriched metabasites, U-Th-Pb, Sm-Nd, and Rb-Sr isotope data, late Neoproterozoic, active and transform continental margin, Siberian craton, Yenisei Ridge
Abstract
Based on new geostructural, mineralogical, geochemical, and isotope (Sm-Nd, Rb-Sr, and U-Th-Pb) data for igneous intrusions and metamorphic rocks of the Zimoveinyi massif, an adakite-gabbroid association has been identified for the first time in the Yenisei Ridge (southwestern framing of the Siberian craton). This study demonstrates that the adakites (quartz diorites, tonalites, and plagiogranites) and associated gabbro-anorthosites of this massif formed in the interval 576-546 Ma (U-Th-Pb zircon SHRIMP-II analysis) at the final Neoproterozoic evolution stage of the active continental margin of the Siberian craton. Our results point to a genetic relationship between the adakites and the host Nb-enriched metabasites of the Zimoveinyi massif. The studied late Neoproterozoic adakites might have formed from both crustal and mantle-crustal sources in the setting of transform strike-slip of lithospheric plates during a halt in subduction, similarly to Cenozoic igneous complexes of the transform margin in the eastern framing of Eurasia.
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