JURASSIC U-Pb AND Re-Os AGES FOR THE NEWLY DISCOVERED XIETONGMEN Cu-Au PORPHYRY DISTRICT, TIBET, PRC: IMPLICATIONS FOR METALLOGENIC EPOCHS IN THE SOUTHERN GANGDESE BELT

The Gangdese belt in southern Tibet includes the Cretaceous to early Eocene Gangdese continental magmatic arc, a newly recognized Middle Jurassic magmatic arc, and post-Gangdese arc magmatism of Miocene age that is well known for its association with important copper-molybdenum deposits. Although the tectonic history of the Gangdese continental arc is relatively well constrained, the tectonomagmatic setting of the Jurassic and Miocene magmatic events was poorly constrained previously. Geochronological analysis of samples from the Xietongmen copper-gold porphyry district has identified a previously unknown metallogenic event related to Middle Jurassic arc magmatism. The occurrence of several metallogenic epochs within the southern Gangdese belt highlights the importance of systematic metallogenic studies of this belt.