The chronological study of the late carboniferous pillow lava assemblage at Xiaopinggou, Dabancheng, Xinjiang

Abstract

Xiaopinggou, the northeast area of the Dabancheng, outcrop a set of pillow lava assemblage which has exposed this area completely. In this paper, we have taken this place as an example and explained the geological meaning of the U-Pb age of the single zircon grain which was based on magmatic crystallization and statistical theory. It provided an important clue for the geotectonic setting and geological age of the evolution of the Bogda structural belt. Rocks like Pillow basalt, dacite, and pyroclastic are found in the Xiaopinggou region of the Dabancheng pillow lava assemblage. The weighted average age of 21 single zircon grains in dacite using LA-ICP-MS U-Pb dating data was 326.0±2.8Ma. Only the primary zircon crystallization ages in the magma chamber were represented by these ages. The Pillow lava assemblage in Xiaopingou was not diagenetically older than the early stage of the Late Carboniferous (the end-stage of the Bashkirian), according to the four single-grain zircon ages of the most recent crystallization, which yields a concordant age of 315.4±1.3Ma. This age is consistent with the geological age determined by the fossils in the Liushugou formation.