Platinum Group Elements(PGE) Geochemistry of Pobei Ni-Cu Sulfide Deposit in Xinjiang Province and Its Implication for Ore Genesis

Pobei Cu-Ni sulfide deposit is located in the Beishan rift belt northeast of Tarim Craton. The ore bodies are maily hosted in the peridote. They are scattered or disseminated in the peridote. The total Platinum Group Elemets (PGE) content is low in the ore and wall rock. Platinum PGE (PPGE) content is a little higher than Iridium PGE (IPGE). The content of PGE is controlled by the sulfur content. According to the Ni/Cu-Pd/Ir discrimination diagram, the primary magma of Pobei pluton is Mg-rich basalt without PGE negative anomaly. Assuming the primary magam is picritic basalt with out PGE negative anomaly, simulation calculated parental magma of Pobei pluton is PGE negative. Deep sulfide exsolution may be the major factor for the PGE depletion of the parental magma and ore, that the sulfide exsolution degree is 0.023% and the ratio (R) of magma and sulfide is ca. 4775.