Sedimentary rocks and geochemical characteristics as well as detrital zircon of Abushan Formation in Woruobale and Bailong area, Tibet, and their indicating significance for provenance information

From the 1:50000 regional geological and mineral survey of Bailong and Woruobale area, and on the basis of the field rock and sendimentary characteristics, the authors divided the Abushan Formation into two sections, i.e., piedmont alluvial and lacustrine facies clastic sediments. Geochemical characteristics of the sandstone samples from the upper Abushan Formation show that the provenance was mainly from the upper crust, and was mainly felsic rocks. The authors obtained for the first time two detrital zircon samples from Upper Abushan Formation, and the analytical results show that the youngest detrital zircon ages are 85.9Ma and 100.39Ma. The results provide a basis for determining the ages of Abushan Formation. In addition, there exist four peak ages for the two samples, i.e., 10Ma, 440Ma, 820Ma and 1280Ma. Combined with the geochemical characteristics and provenance information of this group, the authors made a discussion on the tectonic evolution of Qiangtang terrane.