PGE Geochemical Characteristics of the Huangshanxi Magmatic Ni-Cu Sulfide Deposit, East Tianshan, Xinjiang, and its Significance for the Mineralization

Abstract

The Huangshanxi sulfide-bearing intrusion, is located in the centre segment of Tudun-Huangshan-Jing`erquan-Tulargen mafic-ultramafic rock belt, the eastern part of the North Tianshan, controlled by the Kangurtag-Huangshan ductile sheer zone, and it is a multiple intrusion which composes of lherzolite, amphibole peridotite, wehrlite, pyroxenite, norite, gabbro, and diorite. The disseminated sulfides and sideronitic sulfides are the mainly ore types, the scale of the ore body is large and the grade is stable relatively. The total concentration of platinum-group elements (PGEs) in rocks and ores is very low, which average value is 0.93ppb and 8.8ppb respectively and it increases with sulfur content increases in ores. The PGE concentration appeared two peaks in the range of 200~300m and 880~980m depth in the drill core, consistent with the content of the sulfides. Rocks and ores samples have similar mantle-normalized PGE patterns which are shown as the PGE flat and slightly fall to the left, and the lower fractionation between IPGE and PPGE. The primitive magma may be the high MgO tholeiitic magma which should be undepleted in PGE and derived from partial melting of a metasomatized mantle source. Compared with continental tholeiite, simulating result reveals that the parental magma is visibly depleted in PGE, possibly duing to the sulfide pre-segregation of initial magma in deep crust. The platinum-group elements geochemical characteristics and petrochemical data show that the crustal contamination and the fractionation of olivine and pyroxene may be the main factors leading to S-saturation and sulfide segregation in deep crust.