Geochemistry and metallogenesis in the lower part of the Yangtze metallogenic valley: A case study of the Shaxi-Changpushan porphyry Cu-Au deposit and a review of the adjacent Cu-Au deposits

The Yangtze valley is one of the most important metallogenic regions of the Jurassic-Cretaceous period in China. The Shaxi-Changpushan porphyry Cu-Au deposit is located in the middle part of the Yangtze valley, east China. In this paper, geological and geochemical aspects of the Shaxi-Changpushan porphyry Cu-Au deposit and several adjacent Cu-Au deposits related to the Jurassic-Cretaceous intrusives with sulfide mineralization are examined. Our research includes chemical analyses of bulk rocks, rare earth and trace elements, fluid inclusions, and S, H and 0 isotopes. Detailed geological backgrounds of the deposits and significant proofs for the Cu-Au mineralization are presented as well as the ore-forming processes and conditions. Based on the results of our analyses, the possibility of a formation of a large porphyry copper deposit in the Shaxi-Changpushan area is proposed. The present study indicates that the interaction of igneous rocks with meteoric water plays a key role in the ore-forming process. There is a great likelihood that a large porphyry copper deposit has formed in the Shaxi-Changpushan area.