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Tectonic and Structural Controls to Porphyry and Epithermal Mineralization in the Cenozoic Magmatic Arcs of Southeast Asia and the West Pacific

CET Seminar Series 2013

Steve Garwin

  • Porphyry and epithermal deposits in Southeast Asia and the west Pacific occur largely in middle to late Cenozoic (25 to 1 Ma) magmatic arcs. The combined past production and current resources of these deposits exceeds 15,000 tonnes of gold and 115 million tonnes of copper. Most of these deposits developed during episodes of plate reorganization and local variations in arc stress-regimes during the Early Miocene, Middle Miocene and the Plio-Pleistocene.
  • The majority of the porphyry and epithermal deposits in the region lie above subduction slabs. However, the giant deposits in medial New Guinea (e.g., Grasberg, Ok Tedi and Porgera) lack an active subduction zone and are the product of collisional tectonics in a fold- and thrust-belt. In New Guinea, delamination and sinking of continental crust beneath the orogen is inferred to have contributed to the high heat-flow and mantle-upwelling associated with mineralization from the late Miocene to Pleistocene. 
  • This talk will provide examples of how the subduction of buoyant, aseismic seamounts on the down-going slab effects deformation, magmatism and gold-copper mineralization in the overlying arc. Evidence of regional-scale stress-partitioning within active arcs and the implications for arc-transverse mineral belts will be shown using earthquake hypocenter data. In addition, a mechanism will be proposed for the localization of magmatism and mineralization in medial New Guinea.