Research On Mineralization Characters And Prospective Of Cyprus Type Copper Deposits In North Qilian Mountains

North Qilian mountains is one of the most important copper mineralized belts in China, Volcano-associated massive sulfide (VMS) deposition is the main type in the area. Based on the mineralized tectonics Petrography and ore geochemistry divide the deposits into two types: one is Cu (Pb Zn)type mineralization which formed in the felsic lava of continent rift and IA setting; the other is Cu(Zn) type which formed in the ocean crust. The former have been studing for a long time since the exploration of BaiYinChang deposits, in contrary, the later is discussed only for the founding of ShiJuLi(XueQuan) deposits in these years, then shows immense exploitation potential. Through analyze the tectonic setting geological character geochemistry fluid inclusion regional mineralization potential ,we know this kind of deposits formed in the Late Ordovician back-arc basin setting in North Qilian Mountains, with the eruption of basic lavas .Magma hydrothermal blended with ocean water, and produced hydrothermal circulation system .Therefore the mineralization elements were send into ocean valley along the cranny which developed in the volcanic system in the zone we studied, and then mineral elements were enriched. At last it formed the Cyprus type deposits. The basic lava developing Late Ordovician back-arc basin ophiolites is the very important place to exploration Cyprus type deposits.Shijuli, Jiugequan, Zhuzuiyaba ,Yindonggou and all typical Cyprus-type copper deposits all lie in the intermediate and basic lava of the ophiolite suite of back-arc basin in Ordovician. Most of the ore bodies are lenticle, stratiform and ubiquitous altera. Generally, the ore are massive and retiform, and mainly are copper , zinc mineralization and trace elements with less of lead. The trace elements rations in pyrites show that Co/Ni>1, S/Se<15000,which indicate that it's influenced by thermal fluid. The components analysis of fluid inclusion in Shijuli shows the gas phase composition are much water , and they are mainly SO₄^2- and Cl^- , and SO^4- > Cl ^- It indicates the trace of seawater. The CO₂ volume of gas phase inclusion in Zhuzuiyaba is more than that of Shijuli, it indicate the character of admixture of...