Indicators of geodynamic control of the formation of mineral resources along a convergent plate margin: Sakhalin-South Kuril areas, Russia

Areas of noble, rare metal and polymetallic mineralization and hydrocarbon fields on the Southern Kuril Islands and Sakhalin, in the Okhotsk Sea are located above deep fault zones in the oceanic lithosphere. Such fracture zones, including the Nosappu (Tuskarora), Iturup and Urup transform faults, are known at the southwestern end of the Kuril–Kamchatka Trench, on the northwestern margin of the Pacific Plate. Seismic tomography has established the northwestern continuation of these faults in the oceanic slab, which has been subducted into the mantle transition zone; the former has also been confirmed by focal mechanism solutions of the hypocenters of deep (up to 700 km) earthquakes. In the oceanic lithosphere the fracture zones in the areas of synfault extension enabled the formation of permeable channels that convey asthenospheric heat and fluids. In the southern Sea of Okhotsk area, these fluids penetrate the mantle wedge, initiating metasomatic processes in the sub-lithospheric mantle and the creation of primary magmatic reservoirs in the lower continental lithosphere. Further migration of these fluids enabled the formation intermediate magma chambers in the crust and of domes and ore bodies. Hydrocarbons are abiogenic and of mantle origin and occur in complex, faulted and folded Cenozoic basins.