A SINGLE ZIRCON U-Pb AGE FOR THE GRANODIORITE OF KAWABULARK COMPLEX, XINJIANG, CHINA

Abstract

Kawabulark Complex (KWC) located in south of Shanshan County, about 220 kilometers southwest Kami City. It consists of marble, crystalline limestone, silicon-bearing carbonate, grey-greenish slate, schist, granite-gneiss, granodiorite and granite, which stretched in about E-W direction in the eastern Tianshan mountains. According to petrotectonic assemblages, stromatolites, and comparison of regional geological characteristics, KWC contributed to Jixian System, but no single zircon U-Pb age has been obtained till today. We selected the granodiorite of KWC as the analytical object, based on regional geological work, and the sampling location is at 41 °29.5'N, 91°51.2 'E, about 20 km to Kawabulark spring. The zircons for single zircon U-Pb dating were collected from the rocks which underwent gravity separation and magnetic separation. The analysis was done in the laboratory of Tianjin Institute of Geology and Mineral Resources. Single zircon U-Pb age determination with 205Pb-235Umixed spike is a fine dating method in China. By this method, a reliable and accurate isotopic age of 1 141 ± 60 Ma was obtained, which is considered as the main age of the stratigraphic rocks for KWC. At the same time, we have also gained another age of 1 832 ± 48 Ma, and this age may imply a stage of igneous activity of KWC in the early Proterozoic. This is important for studying the igneous rocks' origin and crustal revolution of the Precambian in the area.