Geological characteristics and genetic mechanism of the Aitik Cu-Au deposit in Sweden

The Aitik Cu-Au-Ag（Mo） deposit in the G?llivare area of northern Sweden is the largest open pit copper and gold deposit in Europe，and is also the biggest gold deposit in Sweden. The geology of the Aitik deposit comprises Palaeoproterozoic garnet-bearing biotite schist / gneiss, quartz–muscovite–sericite schist, mica-schist, porphyritic quartz monzodiorite and pegmatite. The copper and gold mineralization areas are mainly located in Palaeoproterozoic volcaniclastic rocks (named Sweden-Finland rock series) and volcano-sedimentary intrusive veins (or stocks) and exhibit veined, stockwork and veinlet dissemination forms, constituting stratified, lenticular, and chambered orebodies. A porphyritic quartz monzodiorite intrusion of subvolcanic origin, which is a composite body, is situated in the structural footwall of the orebody, and its age coincides with the age obtained for the subduction-related Haparanda suite of granitoids in Norrbotten. It is proposed that the Aitik deposit is a product of high-salinity fluids，and represents a Palaeoproterozoic strongly metamorphosed porphyry copper deposit affected by a regional IOCG-type hydrothermal event，and the mineralization experienced a period of 160Ma. Consequently, the Aitik deposit might represent a mixed ore system where later regional IOCG mineralization was superimposed upon the early copper mineralization of porphyry type.