Comparison On Magma Evolution And Mineralization Process Of Xiangshanzhong And Baixintan Ni-Cu Sulfide Deposit In Eastern Tianshan

Eastern Tianshan in Xinjiang is a major resource of magma-type Cu-Ni deposits,these founded deposits recently are distributed along Kangguer-Huangshan mafic-ultramafic intrusions belt.Recent years,Baixintan and Lubei Cu-Ni deposits were founded in the western part of Eastern Tianshan,which makes the discussion of Cu-Ni mineralization and ore potential on the west of Tudun possible.Former studies in the eastern part of East Tianshan,especially these along the Kangguer-HuangShan ductile shear zone and the mafic and ultra-mafic rock mass with high degree research,have made a lot of research results.However,as to the magma evolution process of the deposits and the reasons for sulfur saturation and the enrichment of sulfides,it still has some research to make improvement.Scholars did little research on the mafic and ultramafic rock masses in the western part of East Tianshan.Moreover,the difference between the eastern and western rock mass in the process of formation and evolution still remains to be further studied.So,the Xiangshanzhong intrusions in the eastern part of East Tianshan and the Baixintan intrusions in the western part of East Tianshan are chosen for the objects in this dissertation.Based on the previous studies,further systematic research on the lithology,mineral crystal chemistry and lithogeochemistry of the intrusions are done for the purpose as follows:to discuss the property and composition of the parental magma,as well as the property of magma source;to discover the mineralization process of the two intrusions and the key reathe son for the sulfur saturation;to summerize the similarity and difference of the eastern and western ore-bearing rock masses and their relationship;to provide reference for metallogenic regularity and prospecting direction of the Cu-Ni deposits in the East Tianshan.The following are the main results:Two intrusions have the similar mineral crystallization temperature and depth.The sequences of the crystallization are the same,which is spinel?olivine?orthopyroxene?clinopyxene?plagioclase?amphibole.Both of the intrusions experience a sufficient magma evolution process,and Xiangshanzhong intrusion experience more sufficient magma evolution process.The two intrusions are enriched in LREEs,depleted in HREEs and HFSEs,the enrichment of the large ion lithophile elements,and obvious Nb and Ti negative anomaly.They also have the lower value of(⁸⁷Sr/⁸⁶Sr)_I and the higher positive value of?Nd?t?.The magma source of the two intrusions are both the ashospheric mantle affected by the material from the subduction zone.Both of the parental magma are the tholeiite magma,which makes the transition to the calc-alkaline magma.Both of the two intrusions are affected by a lower degree of crustal material contamination.The degree of contamination in the Xiangshanzhong intrusions range from 3%to 7%,while it is from 7%to 12%in the Baixintan intrusions.The simulation calculation indicates that both of the olivine crystallization separation processes are along with sulfides melting away.In the formation processes of the two intrusions,there is the replenishment of fresh magma.In the Xiangshanzhong intrusions,the grades of Cu and Ni are obviously higher in the interval where there is the replenishment of fresh Ni none-loss magma,which means that the replenishment of fresh Ni none-loss magma is the key reason for the enrichment of sulfides.The Baixintan intrusions and Xiangshanzhong intrusions have the similar diagenetic and metallogenic epoch,the nature of the parental magma,magma source and the formation and evolution process.They can be regarded as the west extension part of the Kangguer-Huangshan Ni metallogenic belt.