Results of petrographic research of Early Cretaceous granitoids of the Sea of Japan

Abstract

Petrographic research of granitoids of the Early Cretaceous complex have been carried out, mineralogical-structural and tectonic features have been established. The main stages of underwater geological studies of magmatism of the Sea of Japan were dredging, deep-water drilling, box corers and bottom-grabs sampling during obligatory investigation of bottom relief and geophysical fields. As a result of the analysis of actual material, the authors determined morphological types of zircons, which help investigating the stages of granitoid magmatism. Two stages of the possible formation of granitoids of the Ulleung Plateau are identified: the first stage - the formation of granitoids in the conditions of the continental crust and the second stage - the rise of the territory in the Upper Cretaceous and further destruction of the outskirts of Asia during the formation of the Sea of Japan in the Cenozoic. At the first stage, during the development of foci of crustal magmogeneration, as a result of plastic deformations, various directive textures were formed, expressed in the orientation of quartz, dark-colored minerals and feldspars, which are difficult to combine with massive textures typical for completely melted phases. In the second stage, various forms of cataclase appear in both directive and massive textures. At the stage of the consolidated crust, the processes of metasomatic transformations and the subsequent, possible, protrusive flow occur, manifested in the form of dislocation and cataclase.