ИСТОЧНИКИ И ПАЛЕОГЕОДИНАМИЧЕСКАЯ ОБСТАНОВКА НАКОПЛЕНИЯ ТЕРРИГЕННЫХ ОТЛОЖЕНИЙ НИЖНЕКЕМБРИЙСКОЙ БЫСТРИНСКОЙ СВИТЫ АРГУНСКОГО МАССИВА

Abstract

The article presents the results of mineralogical, geochemical, isotopic, and geochemical (Sm-Nd) studies on siltstones from the upper Bystraya subformation of the Argun continental massif, as well as U-Pb dating of detrital zircon grains from them. The main goal of the research was to identify the main sources of clastic material, reconstruct the paleogeodynamic environment of accumulation, and constrain the lower age limit for the formation of terrigenous rocks of the upper Bystraya subformation. The mineralogical composition of the studied rocks indicates their accumulation in an environment associated with subduction processes. The trace element composition of siltstones from the subformation suggests the presence of rocks of mixed composition in the source area in terms of their silica content. Based on Sm-Nd isotopic and geochemical data, it was established that the main sources of clastic material for siltstones of the stratigraphic unit were Paleoproterozoic rocks and (or) younger rocks whose formation is associated with the reworking of the Paleoproterozoic continental crust. Most of the zircons from the studied sample of siltstones of the upper Bystraya subformation are Neo- and Paleoproterozoic in age. Their sources are probably Neo- and Paleoproterozoic igneous rocks widespread within the Argun massif in China. The age of the youngest zircons (556 ± 9 and 566 ± 10 Ma) isolated from siltstones of the upper Bystraya subformation was used to constrain the lower limit of their accumulation in the middle of the Ediacaran.