The Geochemical Characteristics And Genesis Of Pentlandite And Pyrrhotite In Xiarihamu Deposit,East Kunlun

Xiarihamu deposit in East Kunlun is the second largest magmatic Cu-Ni sulfide deposit discovered after Jinchuan deposit in China.It is also the largest magmatic Cu-Ni sulfide deposit discovered in the background of orogenic belt.Many researches have been made on the metallogenic age,metallogenic geological background and magmatic intrusion stage.According to the metallogenic stage of Xiarihamu deposit,there is no detailed study on the metallogenic stage,which limits the understanding of metallogenic mechanism and affects the understanding of the whole deposit.Starting from the main ore bearing lithofacies,peridotite facies and pyroxenite facies of Xiarihamu deposit,this paper systematically analyzes the main metal sulfides(pentlandite and pyrrhotite)by means of geochemical methods,hoping to provide some help for the study of metallogenic stages of Xiarihamu deposit from the perspective of sulfides.In addition,the occurrence form of cobalt in Xiarihamu deposit is discussed at the end of this paper,hoping to provide some information for the research,development and utilization of cobalt.Recognize as follows:1?According to its occurrence form,pentlandite of peridotite facies star point mineralization in Xiarihamu deposit can be divided into five mineralization stages according to its crystallization sequence: pentlandite wrapped by pyrrhotite,pentlandite distributed on the edge of pyrrhotite and dissolved in pyrrhotite,pentlandite associated with pyrrhotite and isolated pentlandite.2?The pentlandite in peridotite facies of Xiarihamu deposit can be divided into two stages according to its Ni / Fe atomic ratio and Co content,which proves that xiarihamu deposit experienced at least two stages of magmatic mineralization.In the early stage of mineralization,there were few sulphides and high Co content,forming high Co pentlandite and hexagonal pyrrhotite;in the late stage,there were many sulphides and low Co content,forming Co poor pentlandite and monoclinic pyrrhotite.3?The sulfur fugacity increases gradually during the crystallization of pentlandite,from pentlandite surrounded by low cobalt pentlandite and pyrrhotite to pentlandite associated withpyrrhotite.4?In Xiarihamu deposit,the Co content of pentlandite with sponge,disseminated and star point mineralization decreased in turn.Compared with sulfide,Co is more concentrated in arsenide.5?The arsenide found in Xiarihamu deposit are all hydrothermal minerals.In addition,the unbalanced distribution of Ni and Co elements in pentlandite,the change of Co,Ni and Cu contents in pyrrhotite and the vein state indicate that Xiarihamu experienced hydrothermal process.