Geological Exploration Meaning Of Silurian System Volcanics In The Bayinbuluke District,Western Tianshan

There is a pack of volcanics of Silurian System located in the Bayinbuluke district in the Western Tianshan,the forming background and geological exploration meaning are paid closely attention to.The volcanics of Bayinbuluke Formation which is typically grown in the Qiaohuote Copper Deposit located in the Central Tianshan that is between the Nicolaev-The Northern Nalati Fault Belt and Atbash-InylchekThe Northern Nalati Fault Belt.The Bayinbuluke Formation are mostly composed of intermediate-basic volcanics,the evolved trend is evidently that is basic-intermediate basic-felsic,but the felsic volcanics are few.Based on a systemic research on volcanics petrology,petrography,geochemistry,zircon U-Pb chronology and Sr-Nd isotope in this paper, and combined with others’ data in this deposit,we can demonstrate volcanic petrogenesis and geotectonic environment in this district,discuss the forming background,petrogenesis and the magma evolution,discussing the relative meaning of geology exploration,we have obtained the following understanding and recognition: 1 、 The Bayinbuluke Formation are composed of basalt- basaltic andesite—rhyolite.The LA-ICP-MS age of volcanics is 424±1.9Ma,is the late Early Silurian,not the Late Silurian.The late Early Silurian is the active period of Southern Tianshan Ocean,the Bayinbuluke Formation are the results of Southern Tianshan Ocean when dived into the Central Tianshan in the late Early Silurian.2、The volcanics of Bayinbuluke Formation are enriched in LILES with(La/Yb)N values 1.20~4.42, and depleted in HFSEs, especially Nb and Ta negative anomaly with Nb/La values 0.17~0.80,mean value is 0.32, similar to the magmatic rock in island arc(about 0.3) settings. Much coral and the fossil of Brachiopoda had been found in the limestone which located on the top of the Bayinbuluke Formation,which indicated that the volcanics were forming in the oceanic island arc environment. 3、The volcanics of Bayinbuluke Formation Zr/Nb ratios(18.82~57.08) and Hf/Ta ratios(6.33~20.35), εNd(t)=(+1.4~+6.5) and(87Sr/86Sr)i=(0.70454~0.70593),the characteristic of trace element suggested that the primitive magma of the Qiaohuote Copper deposit volcanics is mostly metasomated by slab-fluids,indicating their sources are depleted mantle sources similar to N-MORB. 4、The forming depth of Bayinbuluke Formation volcanics is deep,high content of Cu element,these factors provide good material basis to the formation of important deposit;Analyse the nature of magma,geological background,enrichment machinism of Cu element comprehensivly,discuss the potention of relative deposit.