Geochemistry characters of platinum-group elements and its significances on the process of mineralization in the Kalatongke Cu-Ni sulfide deposit, Xinjiang, China.

Kalatongke Ni-Cu Sulfide deposit, which occurring in the northern margin of the Junggar terrane, northern Xinjiang, NW China, three of 11 small mafic intrusions (#1, #2 and #3) are the main economic Ni-Cu sulfide ore bodies. The ore is comprised of disseminated sulfides ( including weakly-disseminated and heavily-disseminated) and massive sulfides, in the former they have transition relationship, but the latter has penetration contact relationship with the former. The total concentrations of PGE in rock and ore samples are low, their dominant elements are PPGE, generally decrease with basic degree decrease in rocks and increase with sulfide contents increase in ores, suggest that PGE distribution in the deposit is mainly controlled by ore phases derived from sulfides segregation. On the basic of 100% sulfide recalculated, the average concentrations of total PGE concentrations in ores are 573 x 10(-9). The composition of the total PGE show no notable difference among the disseminated of all intrusions. Rock and ore samples have similar mantle-normalized PGE patterns with relative enrichment of Pt and Pd. The diagram of Pd/Ir against Ni/Cu, and geochemistry of rocks reveal that primary magma of Kalatongke is basaltic magma with high MgO content, which is undepleted in platinum group element. Assuming the primary magma is similar to the continental tholeiite, simulanting result reveals that the parental magma visibly depleted PGE, at the same time, Ir depleted more than Pt and Pd, owing to the sulfide segregation in the deep crust. The Pd/Pt ratios of rocks and ores, binary variations of Cr versus Ni, Ir, Ru and Rh, and S isotope combining with petrology show that the fractionation of olivine and chromite is likely the main factor leading to sulfur saturation and segregation. The diversity between IPGE and PPGE of different type ores, its pertinency linking and the macroscopical geological fact, we conclude that the disseminated ores come from the undepleted initial magma, then the olivine and chromite crystallization and segregation and sulfide segregation in the deep crust, resulting in the parental magma depleted in PGE, in the end, the crystal-bearing magma ascend and intrude the present level in the crust. But the massive ore maybe derived from the sulfide melt which laterly segregated from the parental magma depleted in PGE, and then inject into disseminated ores.