The relation between ore-deposit formation and subduction: Mass balance considerations

Abstract Mass balance calculations indicate that the potential supply of metals resulting from subduction of oceanic crust and sediment far exceeds that required for mineralization in island ares. Subduction of oceanic crust is more important than that of sediment in supplying these metals and the subduction of manganese nodules makes only a negligible contribution. The nature and extent of mineralization in island ares therefore depend on the nature, geometry and rate of subduction. In the Pacific, two types of subduction system occur: the high-stress (Chilean) type, characterized by shallow subduction and the formation of porphyry copper deposits in andesitic ares, and the low-stress (Mariana) type, characterized by deep subduction and the formation of Kuroko deposits in the back-arc basin, and porphyry copper and epithermal gold deposits in the island are. Kuroko deposits are analogous to the epithermal deposits but are formed from saline hydrothermal fluids under much higher hydrostatic pressure.