The Minerogenesis And Metallogenic Potential Of Kalatongke Nickel-Copper Sulfide Deposit, Xinjiang, China

The Central Asian Orogen belt is an important metallogenic zone hosting many Ni-Cu magmatic sulfide deposits in the world. Kalatongke deposit is the biggest and representative one in Xinjiang, it is associate with small rock masses and lack of ultramafic rocks, which is charactered by concentrative industrial ore bodies with high tenor. All these provide some investigative advantages for the ore genesis of magmatic sulfide deposit. Kalatongke deposit was selected for detailed study on the base of petrology, mineralogy, PGE geochemistry, Nd, Sr, Pb and Os isotope geochemistry, focusing on the key issues of magmatic sulfide deposits:â‘ the metallogenes and its deep process;â‘¡the factors controlling on the sulfide segregation, the relationship between crustal contamination and sulphide segregation;â‘¢what is the cause for the decoupling of the Sm-Nd-O and Re-Os isotopic systems. Systematically comparison for the characters of PGE between Kalatongke and the other ones such as Jinchuan, Baimazhai, Huangshandong and Voisey's Bay deposit.were carried out, the characters and distribution regularity of PGE, Ni and Cu from Kalatongke deposit were studied, in order to analyse its metallogenic potential. The following are the main results:(1)The PGE content of rocks, ores and platinum-group mineral (PGM) from the Kalatongke Ni-Cu sulfide deposit, have been analyzed by the ICP-MS and electron microprob respectively, analytic results enriches the researchful data of Kalatongke Ni-Cu deposit.(2)The microcosmic characters such as grain scale and its hosting minerals have been researched. Studies on the oregenesis of PGM are performed using mass balance calculation and phase plots. All these provide not only first-hand data for PGE beneficiation, but also mineralogical evidence for research on the metallogenes and enrichment regularity of PGE.(3)The Kalatongke deposit has similar mantle-normalized pattern, and smaller Co/Ni ratio than the unity of most sulfides, showing that the rock bodies from Y1 to Y9 and G21 derived from the same magma system, it is consisted with the genesic information from the main oxides of rocks.(4)Petrogeochemistry, district rock assemblage, structure and chronology have proved that, Kalatongke sulfide deposit formed in the postcollisional extension setting at the early Permian. Its mantle source is composed of mantle wedge components matasomasised by the fluid from the subducting slab and aesethenosphere, aesethenosphere melt because of the decompression and underwell. Then, the mantle wedge melted by 14 percent degree and gave rise to a tholeitiitic basalt, which should be undepleted in platinum group element.(5)The characteristics of PGE suggest that Kalatong parental magma is likely of a high magnesium tholeitiitic basalt, and similar to that of the Jinchuan deposit, consisting of "crystal mushes" formed by accumulation of suspended olivine crystals and sulfide melt. Primary magma underwent minor crustal contamination to some extent locally in the stage chamber. Olivine, pyroxene and chromite crystallization is the main control factor resulting in the magma sulfur saturation and segregation, minor sulfide presegregation induced the parental magma depleted in platinum group element.(6)The select contamination would heighten the Os content and the initial Os composition, on the contrary, it has little influence on the Sr, Nd,O isotopic system resulting in decoupling of the Os and Sr, Nd,O isotopic due to the lower Sr,Nd,REE contents in sulfide.(7)PGM are predominated by the (Pt, Pd, Ni)-Te-Bi solide solution mainly closed in sulfide. Mineral assemblage, mass balance calculation and phase charts show that PGE are at large in PGM, most of which are from the magma segregation, individual one maybe come from the hydrothermal fluid.(8)The disseminated ores from the different ore body of Kalatongke deposit, which is the earliest mineralization than the massive ores in macro scale, have similar Pd/Ir,Pt/Pd and Cu/Pd ratio, imply that they have slight fractionation between the IPGE and PPGE due to the faster cooling and in situ crystallization and fractionation of the parental magma. On the contrary, for the dense massive ores with visible fractionation between the IPGE and PPGE, they have the mineralization characters injected in the magma conduit and more depleted in IPGE than PPGE. As suggest that the sulfide melt suffered more separation and crystallization of olivine and chromite in deep, then, the sulfid melt laterly injected the structure crash belt and came into being the massive ores, which consists of monosulfide solide solution underwent separation crystallization.(9)Mineralization mode focusing on the minerogenesis and deep mineralization process is established, on the base of continental kinetic setting of Kalatongke deposit. (10)Comparison for the characters of PGE among the five deposits mentioned above show that, they are all depleted in PGE due to minor sulfide presegregation event in deep, but it maybe play an import role for the mineralization of Cu and Ni.. So Kalatongke deposit has limited metallogenic potentiality for PGE, but has better capacity of Cu and Ni in the operational exploration depth.