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Genesis of the metalliferous porphyry Cu systems of Southern Tibet

Where do they come from, and what do they reveal about regional tectonics and exploration potential?

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Yongjun Lu

Current models for the genesis of post-subduction porphyry copper systems in Tibet cannot be reconciled with the hydrous character and geochemical signatures of the associated intrusive bodies - presenting a dilemma to conventional efforts to understand these deposits in a mineral systems context. Resolving this conflict requires the addition of water to the dry sub-Tibetan crust. We propose here that this hydration was achieved by the deep emplacement of hydrous potassic magmas produced from partial melting of enriched lithospheric mantle below Tibet. Although probably not themselves physically involved in the development of the post-subduction mineral systems, underplating and crystallization of these melts released water into the juvenile Tibetan lower crust, catalyzing melting and producing the hydrous intrusions and associated porphyry deposits observed.