Genetic Significances From Mineralogy Of Xiarihamu Ni-Cu Sulfide Deposit,Eastern Kunlun Orogenic Belt

Xiarihamu Deposit is a newly-discovered super-large magmatic Ni-Cu sulfide deposit in EKOB?Eastern Kunlun Orogenic Belt?.Several great significances are reconsidered by its discovery,such as metallogenic belt,metallogenic age,deposit size and so on.Previous research has made some achievements,but there are also some controversy,and mineralogical study of the deposit is poor.In this paper,on the basis of detailed field geological survey,systematic drill core catalog and a large number of thin sections analysis,research has been carried out on main rock-forming minerals?olivines,pyroxenes?and chromian spinels.New findings are listed below:?1?Fo and Ni contents of the olivines hosted by"giant"orthopyroxene are elevated from the core to the rim,which can only beexplained bymultiple sulfide-bearing magma pulses.And the minimum number of the magma pulses is two.?2?Olivine and chromian spinel analysises suggest that the parental magma of Xiarihamu is with Mg^#value=0.73,W_MgO/W_FeO=1.53,about 13.28%Al₂O₃ content and low TiO₂ content?about 0.60%?.And magma temperature of Xiarihamu was higher than 1360¹411?in the early stages.Combined with clinopyroxene and PGE analysis,the datas above suggest that the parental magma of Xiarihamu is alow Ti,highMg tholeiitic magma and probably originated from the asthenosphere.?3?Model calculationsuggests that the magma was saturated with sulfide after minor olivine crystallization?<3%?.Only a small amount of sulfide segregated by the olivine crystalization,and the mass ratio ofbetween olivine and sulfide melt is 20:1during the early stages.?4?Chromian spinels from Xiarihamu usually have higher ZnO contents?¹.8%?,which can be explained by numerous sulfide segregation and may be further used as a indicator for the Ni mineralization of the regional contemporary mafic-ultramafic intrusions.?5?Fe³⁺-Cr-Al diagram and Cr^#-Mg^#diagram of chromian spinels and TiO₂-Fe³⁺diagram ofclinopyroxenes show that Xiarihamu was probably not formed in island arc settings.Combined with the petrography and regional tectonic evolution,this paper speculate that Xiarihamu Deposit was formed in a post-collision extensional environment of orogenic belt.