Study on genesis of the concealed Cu-rich ore body in the Jinchuan Cu-Ni deposit and its prospecting in depth

The Jinchuan deposit is hosted by the olivine-rich ultramafic rock-body, which is the third-largest being exploited magmatic sulfide Ni-Cu deposit in the world. After it has been exploited for about fifty years, the problem that seeking new relaying resources in its deep and border becomes more and more important. The characteristics of ore body, ore and geochemistry of concealed Cu-rich ore body are researched. Through spatially analyzing and comparing with neighboring Ill main ore body, the mineralization-rule of concealed Cu-rich ore body is summed up. Meanwhile, it is implied that there may exist a Cu-rich magma between Ni-rich magma and ore-pulp during liquation-differentiation in deep stage-chambers, which derives from deep mantle high-MgO basalts magma. It is concluded that the ore body has the feature of both magmatic liquation and late reconstruction action; it has experienced three stages: first, deep-liquation and pulsatory-injection of the Cu- and PPGE-rich magma; second, concentration of tectonic activation; third, the later magma hydrothermal alteration. In addition, the data of Pb isotope shows the forming age of 16 Concealed Cu-rich ore body is about 800Ma, which is earlier than that of massive Ni-rich ore bodies; the Pb and S isotope indicate the magma of 16 Concealed Cu-rich ore body originates predominantly from mantle, however it is interfused by minute crust material. Finally, it is inferred that the genesis of Cu-Ni sulfide deposit is complex, and the prospect of seeking new deep ore bodies in deep and border of Jinchuan Deposit is promising, especially seeking Cu-rich ore bodies; the F6 fault may be the emplacing conduit of 16 Concealed magma, and one of the emplacing conduits of III magma.