Circum-Pacific modes of subduction, collision, and metallogenesis
Tectonic processes in trench-arc-back-arc regions, as depicted on the Plate-Tectonic Map of the Circum-Pacific Region, are controlled by different modes of subduction. In one end member, the Chilean or high-stress subduction zone, the stress regime in the overriding lithosphere is compressive; whereas in the other end member, the Mariana or low-stress subduction zone, extensional tectonics prevails. The two modes are characterized by porphyry copper and massive sulfide metallogenesis, respectively. In both modes, sediment that fills grabens on the subducting plate may be subducted. When a large buoyant feature such as drifting continental crust arrives at the trench, collision-accretion tectonics with a strong compressive stress ensues. In such a collision zone, however, buoyant subduction of the light crust continues to a considerable extent, such as in the doubling of crust under Tibet and the subduction of the Izu block under central Japan. When continental crust and oceanic sediments subduct, they can begin melting at low temperature and shallow depth, generating more felsic granitoids than those that originate at greater depth under andesitic volcanic arcs. In the northwest Pacific, felsic granitic arcs are extensive, mostly S type, and ilmenite bearing, and they are accompanied by the world's largest tin and tungsten belt. They contrast with, but are parallel to many andesitic volcanic arcs characterized by rich copper-zinc-gold metallogenesis. The authors speculate that the extensive tin-tungsten granitic arcs have their genesis in the buoyant subduction, remelting, and large-scale anataxis of sediment-dominated crust as a result of collision-accretion tectonism.
- Research Organization:
- Northwest Quadrant Panel of the Circum-Pacific Map Project, Tokyo, Japan
- OSTI ID:
- 6988920
- Report Number(s):
- CONF-8608105-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Vol. 70:7; Conference: 4. circum-Pacific energy and mineral resource conference, Singapore, China, 17 Aug 1986
- Country of Publication:
- United States
- Language:
- English
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