Petrogenesis of the Late Triassic Habake granitic pluton, the West Kunlun Orogen, Western China: Tectonic implications for the evolution of the Paleo-Tethys

Abstract

Recent discoveries of rare metal pegmatite deposits in the West Kunlun region are believed to be related to Triassic granites. However, the tectonic background of the mineralization in this region is currently unclear. Additionally, the mineralization potential of the granite must be determined to assess whether further exploration is warranted. This paper reports whole-rock elemental and Sr-Nd isotopic compositions, and zircon U-Pb ages and Lu-Hf isotopic compositions for the Habake granitic pluton. The zircon U–Pb dating revealed that these rocks formed in the Late Triassic (210–205 Ma). The two-mica granites are strongly peraluminous high-K calc-alkaline series rocks, with initial 87Sr/86Sr ratios of 0.71294 ∼ 0.71428, εNd(t) values of −7.79 ∼ -8.15, and εHf(t) values of −1.77 ∼ −32.22; these values are similar to those of Triassic BaryanHar Group graywacke rocks. The other granites are weakly peraluminous high-K calc-alkaline series rocks, with initial 87Sr/86Sr ratios of 0.70820 ∼ 0.70823 and 0.70942 ∼ 0.71041, εNd(t) of −3.81 ∼ -4.11 and −5.33 ∼ -5.40, and εHf(t) of −0.90 to +7.02 and −1.39 to −7.68, indicating that the granodiorite and biotite granite were respectively derived from partial melting of the juvenile crust and older lower crust in continental collision stage. Our new data show that the end of the continental collision between the South Kunlun Terrane (SKT) and Tianshuihai terrane (TST) likely occurred after 209 Ma. After analysis of the ore-forming parent rocks of the rare metal pegmatites, the graywacke-derived Habake two-mica granites, has lower Li contents that too low(<150 ppm), indicating that they did not form the rare metal pegmatites.