GEOCHEMICAL, ISOTOPIC, AND GEOCHRONOLOGICAL EVIDENCE FOR SUBSYNCHRONOUS ISLAND-ARC MAGMATISM AND TERRIGENOUS SEDIMENTATION (Predivinsk terrane of the Yenisei Ridge)
A.D. Nozhkin1, N.V. Dmitrieva1,2, I I. Likhanov1, P.A. Serov3, P.S. Kozlov4
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
3Geological Institute, Kola Scientific Center of the Russian Academy of Sciences, ul. Fersmana 14, Apatity, 184209, Russia
4A.N. Zavaritsky Institute of Geology and Geochemistry, Ural Branch of the Russian Academy of Sciences, Pochtovyi per. 7, Yekaterinburg, 620075, Russia
Keywords: Late Precambrian, volcanosedimentary rocks, LA-ICP-MS dating, SHRIMP II, Sm-Nd isotopy, Predivinsk terrane, Yenisei Ridge
Abstract
In this study we present data on the geologic setting, geochemical and isotopic compositions, timing and P - T conditions of metamorphism of Neoproterozoic terrigenous metasediments, and associated island-arc metavolcanics of the Predivinsk terrane of the Yenisei Ridge. Relatively immature terrigenous rocks were eroded from a local source which is associated with island-arc magmatic complexes. The geochronological constraints indicate that the terrigenous rocks were eroded from juvenile crustal sources represented primarily by magmatic rocks, which are similar to those of the Predivinsk terrane. This is supported by a similar range of model ages, positive εNd values of terrigenous and magmatic rocks, and correspondence between the concordant ages of detrital zircons from metasedimentary rocks (610-640 Ma) and the U-Pb ages of zircons from rhyolites (ca. 620-640 Ma) from two suites within different sequences. The P-T conditions for volcanosedimentary rocks of the Predivinsk terrane correspond to the epidote-amphibolite facies and the transition from epidote-amphibolite to amphibolite facies. The most likely age of metamorphism due to Vendian accretion/collision events is given by Ar-Ar dates of 600-610 Ma.
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