Platinum Group Elements Geochemistry Of Jinchuan Copper-nickel Deposit, NW China

In past years, many Geologists that is at home and abroad have done a lot of research about Jinchuan deposit because of its special status in magmatic Ni-Cu-PGE sulfide deposits. Before writing paper, I try to summarize and extract the previous geological basic data systematically, do the field geological observations and collect the typical samples. The paper study on mineralogy, petrology, geochemistry and platinum group elements geochemistry of the Jinchuan nickel-copper sulfide deposit systematically and concluded the following points:(1) SegmentⅠand segmentⅡintrusions of Jinchuan have the Similar distribution patterns of platinum-group elements, and the geochemistry characteristic of major elements and trace element state clearly that they have the same primary magma composition.(2) The PGE distribution patterns of segmentⅠand segmentⅡintrusions belong to the Pt-Pd type, and the differentiation between IPGE and PPGE is clear, the high content in PPGE and low in IPGE.(3) The PGE characteristic support that the primary magma of Jinchuan is high MgO tholeiitic magma. The Cu/Pd, Ni/Ir ratio (rock 42.59×103,7.87×105; ore 152.71×103, 3.62×106) of rock and ore is much higher than the original mantle (Cu/Pd=7.7×103, Ni/Ir =6.12×105). All of these data suggest the basaltic magma had experienced minor suifide segregation, whose amount is about 0.013% attained by means of quantitative simulation, prior to emplacing the staging magma chamber.(4) The characteristic of major elements, trace element and platinum-group elements show that the fractional crystallization of Olivine, pyroxene and chromite provide suited conditions for the sulfide segregation. A small quantity of sulfide segregation is the main controlling factor lead to the lossing of PGE in primary magma of Jinchuan rather than the low degree of partial melting.(5) The amount of 10% to 40% fractional crystallization of MSS cooled to form the massive ore by means of quantitative simulation. It is consistent with the massive ore characteristic rich in IPGE and poor in PPGE. The formation of other type of massive ore and veined ore which rich in Cu, Pt and Pd relate to the consolidation of the residual sulfide melts that experienced MSS fractional crystallization.