Lower Silurian Terrigenous Rocks of the Laoeling–Grodekovo Terrane, Southern Primorye: Composition and Formation Settings

The original results of a study of the composition of terrigenous rocks of the Early Silurian Kordonka Formation of the Paleozoic–Early Mesozoic Laoeling–Grodekovo Terrane (southern Primorye) are considered. The aim of the study was to interpret the paleogeodynamic setting of the rocks of the formation and to determine the type and the composition of the parental rocks of the source areas on the basis of genetic interpretation of the composition of studied rocks. It was found that, according to mineralogical–geochemical parameters, the rocks of the formation are typical graywackes and petrogeneic (first cycle) rocks, which formed mostly due to mechanical erosion of rocks of the source areas. The rocks exhibit a low degree of maturity and a high rate of burial of clastic material and weak lithodynamic reworking of the parental rocks. The results of a comprehensive study of the rock composition have been interpreted using comparison with that of ancient rocks and present-day sediments accumulated in certain geodynamic settings. Our data indicate that the rocks of the Kordonka Formation accumulated in an oceanic island-arc sedimentary basin. The clastic material was sourced from the arc, which was composed of mafic and intermediate volcanic rocks and igneous and sedimentary rocks of its basement.