Study On The Geological-Geochemical Characteristics And Genesis Of The Kalagailei Copper-Gold Deposit,Zhaosu, Xinjiang

Kalagailei copper-gold deposit, located in the western section of Nalati tectonic belt of Western Tianshan, Xinjiang, is the first Cu-dominated volcanic-magmatic hydrothermal deposit accompanied by Au-Co etc. found in this metallogenic belt in recent years. The study of the deposit used to be inadequate and the deposit is lack of meticulous and in-depth study in tectonic background, geologic feature, ore-controlling factors, enrichment regularity and genesis. Based on collecting geological and geochemical materials of the study areas, the paper has analyzed metallogenic background, ore-controlling conditions, features of ore-forming fluids, sources of metallogenic matter, metallogenic epoch etc. and has probed into deposit genesis by conducting field geological survey cooperating with indoor microscopic identification and experimental testing. Main achievements as following:(1)The Dahalajunshan Formation, ore-bearing strata in the study area, is a set of strata predominent in intermediate-acid volcanic rocks and clastic rocks and mainly consists of calc-alkaline volcanic rock series, including partial tholeiite series. Through the geochemical analysis and comparative study with regional tectonic evolution, it is confirmed that it occured in submature continental arc environment.(2)The copper orebody mainly occured in the cryptoexplosive breccia chimney and in the fissures of structural fracture zone or in the micro-fractures of schistosity and cleavage, the ore-bearing wall rocks are basaltic tuffs, greenschist facies metamorphic rocks. And the volcanic edifice is a significant ore-controlling structure. Siliconization, chloritization, tourmalinization are the alteration indications of high-grade ores.(3)Based on the ore texture and stucture, mineral assemblages and intercalated relationship, the deposit is divided into three metallogenic periods:volcanic sedimentary period, hydrothermal period, hypergene period. And the hydrothermal period is the main mineralization stage.(4)The characteristics of sulfur isotope show that the sulfur sources originate from the deep part, accompaning with the interfusion of strata sulfur. The sources of lead are mixture of crust and mantle, revealing that the deep mantle materials are likely to be involved in the mineralization. The hydrogen and oxygen isotopic compositions show that ore-forming fluids were mainly made up of magmatic water in the early period and added by various degree of rainwater as the metallogenic environment getting open in the later period.(5)The microthermometry study of fluid inclusions indicates that ore-forming fluids are the ones with intermediate-low temperature and salinity during the main mineralizing stages of the deposit and that the mineralization goes shallowly.(6)The Re-Os istopic model age of molybdenite is259.6±9.7Ma, indicating early stage mineralization age of the deposit falls into the mid-late Permian.It is considered that the deposit genesis belongs to volcanic-magmatic hydrothermal type by integrating various metallogenic factors and discussing metallogenic evolution process.