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Russian Geology and Geophysics

2016 year, number 3

SOURCE ROCKS OF CARBONIFEROUS-LOWER CRETACEOUS TERRIGENOUS SEDIMENTS OF THE NORTHEASTERN SIBERIAN PLATFORM: RESULTS OF Sm-Nd ISOTOPE-GEOCHEMICAL STUDIES

S.V. Malyshev1, A.K. Khudoley1, A.V. Prokopiev2, V.B. Ershova1, G.G. Kazakova3, L.B. Terent’eva4
1Institute of Earth Sciences, St. Petersburg State University, Universitetskaya nab. 7/9, St. Petersburg, 199034, Russia
2Diamond and Precious Metal Geology Institute, Siberian Branch of the Russian Academy of Sciences, pr. Lenina 39, Yakutsk, 677007, Russia
3A.P. Karpinsky Russian Geological Research Institute (VSEGEI), Sredny pr. 74, St. Petersburg, 199106, Russia
4Institute of Precambrian Geology and Geochronology, nab. Makarova 2, St. Petersburg, 199034, Russia
Keywords: Сибирский континент, Верхоянская пассивная окраина, Приверхоянский прогиб, карбон, пермь, мезозой, Оµ, источники сноса, Carboniferous, Permian, Mesozoic, Оµ, source rocks, Verkhoyansk foreland basin, Verkhoyansk passive margin, Siberian continent

Abstract

The first Sm-Nd isotope studies of the Carboniferous-Early Cretaceous clastic rocks of the northeastern Siberian Platform have been carried out. Variation in the isotope composition of sediments within this time interval has been determined and interpreted. The high εNd( t ) values for Carboniferous-Permian sediments (from -11 to -2) testify to the large contribution of the products of erosion of island-arc and juvenile complexes localized in the Taimyr-Severnaya Zemlya fold-thrust belt in the Carboniferous. The positive εNd( t ) values for Triassic sandstones suggest erosion of the coeval igneous rocks of the trap association. The Upper Jurassic and, particularly, Cretaceous sediments of the Lena-Anabar depression and Verkhoyansk foreland basin are characterized by extremely negative εNd( t ) values (from -15 to -19), which is evidence for erosion of mature continental crust. The Carboniferous-Triassic complexes of the Verkhoyansk fold-thrust belt, which show higher εNd( t ) values, cannot have been a source of detritus for Cretaceous sandstones. The sediments filling the Verkhoyansk foreland basin accumulated as a result of the decomposition of homogenized distal source rocks with the isotope characteristics of the ancient crust rather than the breakup of the mountain range rising to the east. Salients of the crystalline basement of the Siberian Platform, such as the Aldan Shield, might have been these source provinces.