Late Triassic granites from the northwestern margin of the Tibetan Plateau, the Dahongliutan example: petrogenesis and tectonic implications for the evolution of the Kangxiwa Palaeo-Tethys

ABSTRACTThe Dahongliutan granitic pluton consists of two-mica granites and is located in the eastern part of the Western Kunlun Orogen, northwestern Tibetan Plateau. Zircon separates from the pluton yield a SIMS U–Pb age of 217.5 ± 2.8 Ma. Rocks from the pluton contain relatively high and uniform SiO2 (72.32–73.48 wt%) and total alkalis (Na2O + K2O = 8.07–8.67 wt%) and are peraluminous and high-K calc-alkaline to shoshonitic in composition. The Dahongliutan granites are relatively depleted in the high-field-strength elements and the heavy rare earth elements (HREEs) and have relatively high Rb, and low Ba and Sr concentrations. They contain low total rare earth element (REE) concentrations. The light REEs are strongly enriched relative to the HREEs, with (La/Yb)N values of 28.56–37.01. The eNd(t) values range from −10.6 to −8.8, and (87Sr/86Sr)i = 0.7142–0.7210. Zircons from the pluton yield eHf(t) values of −13.8 to −1.6, and δ18O = 10.5–11.6‰. Petrographic and geochemical features of the pluton indicate...