There are extensive intermediate-acid intrusive rocks along the border between Batang and Mangkang County, in the eastern Tibet. These rocks distributed band-like along the west bank of Jinsha River, which occur as complex batholiths and apophyses that intruded in Early Permian Bingfeng Group limestone formation and the upper position of Jinshajiang Early Permian metamorphic rocks. The intrusive rocks are mainly granite and granodiorite. So far, the genesis of these granitites, including their formation age and tectonic significance, has been poorly studied. In this paper, we chose the Batang granitoids in this region for geochemical studies and LA-ICP-MS U-Pb dating. Three granite samples were used for LA-ICP-MS U-Pb dating, the ages of the samples are 235.2±1.4 Ma, 229.6±1.4 Ma and 229.1±1.6 Ma, respectively, suggesting formation ages in Late Triassic period. Geochemical studies indicate that these granites belong to shoshonite series and high K calc-alkali series, enriched in Rb, Th, K, and LILEs, but depleted in Nb, Ta, P, Zr, Ti and HFSES. Whole-rock Sr-Nd isotopic compositions show that samples were derived from the Kangding complex but mixed with a small amount of sedimentary rocks. In addition, the geochemical studies show that these granites were formed in a post-collisional tectonic extensional setting of the late age of orogeny. In combination with regional studies, we confer that the closure of Jinshajiang ocean was completed before Late Triassic.
Wang Xinyu Wang Shifeng Wang Chao Chen Longyao. LA-ICP-MS zircon U-Pb age, geochemistry and tectonic significance of Late Triassic granites in Jinshajiang belt of Batang area, eastern Tibet[J]. Chinese Journal of Geology, 2017, 52(4): 1160-1180.