Studies On The Metallogenic Model Of Tulargen Ni-Cu Sulphide Deposits, Hami, Xinjiang

In the past twenty years more than 20 magmatic Ni-Cu-(PGE) sulfide deposits have been discovered in northern Xinjiang, where is one of the most important Cu-Ni ore belts in China. As the most important latest discoveries in East Tianshan, the Tulargen Cu-Ni-Co deposit is obviously controlled by secondary fractures in the Kangguertage-Huangshan regional ductile-sheer zone. The ore body delivers inversely-high-grade ore above and lean ore under, disobeying the general rule of the Ni-Cu sulfide deposit. To understand the origin of these mafic-ultramafic intrusions which the Tulargen Ni-Cu deposit bears in is potentially important to the guidance exploration on Ni-Cu-(PGE) sulfide deposits in orogenic belt.Thus, Tulargen intrusion is chosen for objects in this dissertation. The characteristics of petrology, mineralogy and geochemistry on these intrusions are investigated for the metallogenic processes. The following results have been obtained.(1)Tulargen intrusion is ferrous-ultramafic rocks, being featured by low total alkalis, low Ti, low Al2O3 and low CaO. It is similar to the petrochemical characteristics of the Huangshan and Xiangshan mafic-ultramafic complex bearing in Huangshan-Jing'erquan belt.(2)The No.1 and No.2 mafic-ultramafic intrusions in the Tulargen ore district share only one magma conduit at depth and originated from the same magma source. This can be indicated by the REE distribution patterns, trace element, transition element spider grams and the MT section across both the No.1 and No.2 intrusions. The two are comagmatic and supplementary.(3)The magma source area of the Tulargen mafic-ultramafic intrusions is the postcollisional setting related to lithospheric delamination and magmatic underplating. The primitive magmas are derived from the low partial (about10-20%) melting asthenospheric mantle contaminated by previously subduction material. The parental magmas are talc-alkaline magma and little contamination with crustal material during the emplacement of the intrusion.(4)Pd-Ni ratios show that no pre-segregation happened ever and neither did sulfide fractionation happen. This is the prerequisite for the formation of the Tulargen large-scale Ni-Cu sulfide ore deposit.(5)The metallogenic model of Tulargen Cu-Ni sulphide deposits is the deep-seated magmatic liquation-injection mineralization with inverse rule. Structure played important role during the emplacement of the intrusion.