The Longmala and Mengya’a skarn Pb–Zn deposits, Gangdese region, Tibet: evidence from U–Pb and Re–Os geochronology for formation during early India–Asia collision

The Longmala and Mengya’a deposits are two representative skarn Pb–Zn deposits of the Nyainqentanglha Pb–Zn–(Cu–Mo–Ag) polymetallic belt in the Gangdese region, Tibet, China. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U–Pb dating of the mineralization-related biotite monzogranite from the Longmala deposit yielded a weighted mean age of 55.7 Ma, which can be interpreted as the emplacement age of the pluton. Re–Os dating of three molybdenite samples from the Longmala deposit yielded model ages of 51.8–54.3 Ma, with a weighted mean age of 53.3 Ma, which is interpreted as the mineralization age of the deposit and overlaps the age of the causative intrusion. The Re–Os dating of four molybdenite samples from the Mengya’a deposit yielded model ages of 60.4–65.8 Ma, with a weighted mean age of 63.6 Ma, which represents the mineralization age of this deposit. Our new precise age data for these two deposits are consistent with the existing ages of ca. 65–51 Ma for other skarn pol...