The Geological Prospecting Significance Of The Dahalajunshan Formation Volcanic Rocks In Yishenjilike Area,Western Tien Shan,Xinjiang

The volcanic rocks of Dahalajunshan formation are widely exposed in Xinjiang Western Tien shan,which have been proved closely related to the mineralization of Cu?Au?Fe element.Yishenjileke mountain located in the southwest of Yili block,Western Tien shan,whose main stara is the Dahalajunshan formation.People have made considerable achievements on the research of the formation,although,the age,tectonic setting and its relationship with mineralization has not reach a consensus.Paper found the volcanic rocks of Dahalajunshan formation in yishijilike area consist of basalt,basaltic andesite,dacite,rhyolite,and large number of Pyroclastic rock,on the basis of 5 km measured section in the east,central and west respectly.The major element of the volcano rocks showed high Si(average value:60.43%),peraluminous(Al₂O₃11.27?17.74%),Rittmann Index(1.2?9.7),Show calc alkaline to alkaline Rocks?characteristics.The K₂O-Si O₂diagram show calcium alkaline magma series.The volcanic rocks rich in LREE,and lack of HREE,with negative Eu anomalies.The trace elements enriched in large ion lithophile elements(Rb,Ba,Th,U),loss high field strength elements(Ta,Ti,Nb,P).The principal amount of trace and rare earth elements tend to feature arc volcano rock.Five groups of volcano rock LA-ICP-MS zircon U-Pb age has been given respectively:328.8+8.4Ma in west,346.5+4.1 Ma?346.3+4.1 Ma in central part,and in the east of the mountain are 341.2±4.6 Ma?344.4±2.6,thought Yishijilike Dahalajunshan volcanic rocks in the age range of 329Ma?356 Ma,combined with previous researchs.The main volcanic rocks formed in the Early Carboniferous.The magma source of the basaltic in the region show the characteristics of transition to depleted mantle.The partial melting of mantle wedge,deposition of continental crust material,formed the andesite magma.The upwilling of the partial melting of mantle magma to the botton of lower crust,made the lower crust partial melting,froming the acid rock magma.The comprehensive combination of petrology petrography,geochemistry and age data,indicated that the Dahalajun formation of the Yishijilike mountain is mainly consisted of Neutral to acidic volcano rocks?volcano clastic rocks,formed in a continental arc environment,in a age of the Early Carboniferous Visean period.Comparing the volcanic rocks'rock assemblages,rock series,geochemical characteristics,age and the tectonic environment of the Dahalajunshan formation in Yishenjilike,with it in the Tulasu-yeliemodun epithermal gold deposit belt and the Awulale volcanic-type iron-copper polymetallic metallogenic belt,concluded that there is a great potential to find large epithermal gold deposit,porphyry copper and gold deposit in Yishenjilike mountain.