Age of host igneous rocks and tectonic setting of the Ikan, Vostochnyi Dvoinoi, and Elnichnoe porphyry Au–Cu–(Mo) ore deposits in the northeastern Erguna Massif, Russia

Eastern Asia experienced large-scale Mesozoic magmatism and contains numerous ore deposits related to late Mesozoic magmatism. In this paper, we report whole-rock geochemical and 40Ar/39Ar geochronological data for the host igneous rocks of the Ikan, Elnichnoe, and Vostochnyi Dvoinoi porphyry Au – Cu–(Mo) deposits in the northeastern Erguna Massif, Russia, to establish the age of late Mesozoic magmatism and mineralization, and its tectonic setting. The deposits record three Early Cretaceous magmatic events with ages of 142–125, 123–113, and 110–100 Ma, which correspond to regional magmatic events in the Great Xing’an Range in northeastern China. The studied igneous rocks are dominantly calc-alkaline and are similar to adakites in association with Early Cretaceous intrusions and volcanic rocks. Enrichments in large-ion lithophile elements and depletions in high-field-strength elements indicate an active continental margin tectonic setting. The magmatic events at 142–125 and 123–113 Ma were associated with Au – Cu–(Mo) mineralization. There is a significant time gap between Early – Middle Jurassic closure of the Mongol – Okhotsk Ocean and the Early Cretaceous magmatic/mineralization events. We suggest that the studied Early Cretaceous porphyry ore deposits were related to large-scale delamination of thickened lower crust and lithospheric mantle or intracontinental extension related to lithospheric thinning that resulted from subduction of the Palaeo-Pacific oceanic slab. Slab break off environment might also have contributed to the formation of the Early Cretaceous ore deposits.