Geological And Geochemical Characteristics Of Kalagailei Cu-Au Deposit In Zhaosu County,Xinjiang

The porphyry copper molybdenum deposit in Tianshan area is mainly distributed in the North Tianshan and East Tianshan Mountains,Southwest Tianshan area has not found a typical porphyry deposit,and in the north and south sides of the Middle Tianshan Mountains,world-class large super large gold deposits concentrate output,constitute the"Asian gold belt",lead to the world's attention.Kalagailei deposit is located in the Western Tianshan Mountains,the western part of the north side of the North Nalati Fault,near the border of Chinese with Kazakhstan,is a Cu-Au deposit,a similar deposit nearby is Shuimogou copper and gold deposit.The study of Kalagailei ore formation process in this paper has an important significance on the prospecting and exploration of porphyry copper deposit and orogenic gold deposit in this area.Based on previous study,this paper studied the geological characteristics of Kalagailei copper gold deposit,stratigraphic characteristics of wall rock,S?Pb isotopic material source and the molybdenite Re-Os isotope Metallogenic Epoch detailed,probed into the deposit formation based on the above information.Obtained a new understanding that the area of Dahalajunshan volcanic rock Formation belongs to the Early Paleozoic,the metallogenic epoch was late Ordovician,and that the South Tianshan Oceanic Belt began to subduct before516Ma.Made the following understanding in detail:(1)Kalagailei copper gold deposit is located in the Western Tianshan Mountains,the western part of the north side of the North Nalati Fault.The orebody is hosted in the volcanic tuff in Dahalajunshan volcanic rock Formation near Xiate at vein like and lens shape.Measurement of fluid inclusions shows that the ore-forming fluids are mainly in low temperature,low salinity fluid,mineralization depth is shallow.(2)The main sulfide in the Kalagailei ore deposits?³⁴S_V-CDT(‰)values ranged from 3.7 to 6.6,that means sulfur with the crust mantle mixed source characteristics of island arc magma mixing caused with the subduction of the oceanic plate closely.Lead isotope ²⁰⁸Pb/²⁰⁴Pb=38.01?39.214,average 38.51;²⁰⁷Pb/²⁰⁴Pb=15.602?15.723,average 15.64;²⁰⁶Pb/²⁰⁴Pb=17.984?20.416,average 18.69.According to the values,the main mineral lead is from the crust mantle mixing origin of orogenic belt,mainly from crustal material.The content of Re in molybdenite show that the mineral is derived mainly from the crust,some mantle materials are mixed.Molybdenite Re-Os isochron age is 449.9±7.6Ma,representing that the deposit forming age is Late Ordivician(O₃).(3)The initial ore forming magmatic fluid was mainly from the dehydration of subducting plate.Late Ordovician(O₃),the South Tianshan oceanic crust subducted to the island arc zone in Nalati,was under the early stage of subduction.Dahalajunshan volcanic rocks and volcaniclastic rocks that ore body occurred in formed earlier than 450Ma.The Dahalajunshan Formation near Xiate should belong to the early Paleozoic.(4)The southern Tianshan oceanic crust subducted under Yili plate in the early stage in Late Ordovician,because of the dehydration of the oceanic crust,and the subducted plate interferes with the convection of the mantle,which leads to upwelling of the mantle materials,Partial melting of upper crust,mixture of ore-forming materials with the mixed magmatic melt intruded into the previously formed volcanic rocks up along the fault intersections,crypto explosive mineralization formed in the shallow part beneath the ground.(5)Metallogenic material of Kalagailei copper gold deposit is mainly from upper crust,mantle material is involved.Kalagailei ore deposit is a volcanic rock type hydrothermal deposit that closely related to volcanic-subvolcanic hydrothermal action.The massive volcanic activities in West Tianshan Mountains occurred in the Carboniferous,but in this area,magmatism and metallogenic time occurred in the Late Ordovician,the region has a certain potential for prospecting in the stratum of Ordovician.