Mineralogical and Geochemical Features, Source Areas, and Formation Settings of Middle Permian Terrigenous Rocks of the Barabash Formation in Southwestern Primorye (Russia)

In the southwestern part of Primorye, the widespread Permian volcanosedimentary frocks are a part of the Paleozoic–Early Mesozoic Laoeling–Grodekovo terrane, a fragment of the eastern end of the Central Asian Foldbelt. The Middle Permian Barabash Formation is exposed fragmentarily in the southern part of the terrane, and the material composition of its terrigenous rocks is almost unstudied. The aim of the study was to investigate specific features of the material composition of sandy rocks of the Barabash Formation and, based on its interpretation, to identify paleogeodynamic environments of the formation of rocks, as well as to determine the composition and age of the sources of clastic material. The obtained results show that the sandstones (graywackes and, in part, lithic arenites) are petrogenic or “first cycle” rocks that underwent one cycle of redeposition, and they were deposited due to the destruction of moderately weathered rocks in source areas. A comprehensive analysis and paleogeodynamic interpretation of the mineralogical and geochemical composition of sandy rocks indicate that the rocks were deposited in a basin associated with an active continental margin environment and, in all likelihood, complicated by strike-slip dislocations along transform faults. The main source of clastic material was continental land – cratons and uplifted basement blocks composed of granite-metamorphic complexes and, in part, sedimentary rocks enriched with ancient clastic components. Additional source was fragments of an ancient, deeply eroded island arc composed of basic and ultramafic rocks. U–Pb dating of detrital zircon grains from sandstones of the Barabash Formation made it possible to determine the age of igneous rocks, which that served as the main sources of clastic material, and to reconstruct their probable location.