Source of copper in the giant Shimensi W-Cu-Mo polymetallic deposit, South China: Constraints from chalcopyrite geochemistry and oxygen fugacity of ore-related granites

摘要

Porphyry-type copper mineralization is generally considered to be related to ore-forming fluid exsolution from oxidized, magnetite-bearing intermediate- to felsic magmas. However, copper deposits associated with ilmenite-bearing per-aluminous evolved granites also exist and their origin remains obscure. The Shimensi W-Cu-Mo polymetallic deposit, located in the northern segment of the Jiangnan Orogen (South China) composed mainly of the Neoproterozoic Shuangqiaoshan Group meta-sediments/volcanic rocks and biotite granite, is one of the largest tungsten deposits in the world. The W-Cu-Mo polymetallic orebodies occur at the contact zone between the Mesozoic ilmenite-bearing, fluorite-bearing F-rich highly fractionated granite and the Neoproterozoic granite. The reason for the accompanying Cu mineralization within ilmenite-bearing granites is unclear. In this paper, we present a detailed study of chalcopyrite geochemistry including S-Pb isotopes, trace elements and Nd isotopes, and oxygen fugacity (fO(2)) of ore-related granites in the Shimensi deposit to constrain the origin of copper.