International Geologiical Congress - Oslo 2008

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MRD-20 Porphyry-type deposits

 

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

 

Zengqian Hou, Institute of Geology, Chinese Academy of Geological Sciences (China)
Noel White, Centre for Ore Deposit Research, University of Tasmania (Australia)
Xiaoming Qu, Institute of Mineral Resources, Chinese Academy of Geological Sciences (China)
Zhiming Yang, Institute of Geology, Chinese Academy of Geological Sciences (China)
Xuanxue Mo, China University of Geosicences (China)
Xiaofei Pan, Institute of Geology, Chinese Academy of Geological Sciences (China)
Zongyao Rui, Institute of Mineral Resources, Chinese Academy of Geological Sciences (China)
 

 

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.

 

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