Post-collisional porphyry Cu deposits: A new class unrelated to subduction

Category Tectonic & Seismotectonic
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Hou, Zengqian۱; White, Noel۲; Qu, Xiaoming۳; Yang, Zhiming۱; Mo, Xuanxue۴; Pan, Xiaofei۱; Rui, Zongyao۳
Holding Date 11 October 2008

Porphyry Cu deposits are the world’s primary source of Cu. Their potentially giant sizes make them important and attractive exploration targets. It is well known that most porphyry deposits form in association with subduction-related calc-alkaline magmas and occur in magmatic arcs worldwide, though some data indicates these deposits also occur in intra-continental settings. It remains unknown as to which of a range key processes, including generation of fertile magmas, enrichment of metallic Cu, and volatile exsolution, contributed to the formation of the deposits in non-arc settings. Here, we report a newly-discovered Miocene porphyry Cu belt unrelated to subduction in southern Tibet. Detailed studies of the porphyry-type mineralization and their host rocks, combined with previously-reported data, have led us to regard these porphyry Cu deposits as a new class, which formed in a collisional zone or intra-continental setting in association with post-collisional potassic magmas derived from a newly-formed mafic lower-crust source. We infer that juvenile mantle components contributed metallic Cu and the breakdown of amphibole in the source region during melting most likely provided volatiles to the Cu-rich magmas.