Pb isotope of the Yangla copper deposit , western Yunnan , China : 1 Implication for ore genesis 2 3

The Yangla copper deposit, situated in the middle section of Jinshajiang tectonic belt between 9 Zhongza-Zhongdian block and Changdu-Simao block, is a representative and giant copper deposit that has been discovered 10 in Jinshajiang-Lancangjiang-Nujiang region in recent years. There are coupled relationship between Yangla granodiorite and 11 copper mineralization in the Yangla copper deposit. Five molybdenite samples yielded a well-constrained Re-Os 12 isochron age of 233.3±3 Ma, the metallogenesis is therefore slightly younger than the crystallization age of the granodiorite. 13 S, Pb isotopic compositions of the Yangla copper deposit indicate that the ore-forming materials were derived from the 14 mixture of upper crust and mantle, also with the magmatic contributions. In the late Early Permian, the Jinshajiang Oceanic 15 plate was subducted to the west, resulting in the formation of a series of gently dipping thrust faults in the Jinshajiang 16 tectonic belt,meanwhile, accompanied magmatic activities. In the early Late Triassic, which was a time of transition from 17 collision-related compression to extension in the Jinshajiang tectonic belt, the thrust faults were tensional; it would have been 18 a favorable environment for forming ore fluids. The ascending magma provided a channel for the ore-forming fluid from the 19 mantle wedge. After the magma arrived at the base of the early-stage Yangla granodiorite, the platy granodiorite at the base 20 of the body would have shielded the late-stage magma from the fluid. The magma would have cooled slowly, and some of 21 the ore-forming fluid in the magma would have entered the gently dipping thrust faults near the Yangla granodiorite, 22 resulting in mineralization. 23 2