Studies On The Geological-Geochemical Characteristics And Genesis Of The Haxi Gold Deposit,in Western Junggar,Xinjiang

The West Junggar region,located in the intersection of Siberia,Kazakhstan and Tarim plate,is the major gold-producing area in the north of Xinjiang.It belongs to the oriental prolongation of the Central Asia Metallogenic Zone-Balkhash metallogenic belt.This area has experienced the stage of continental basement formation,Paleo-Asian Ocean Continental accretion and intracontinental block lift in geological history,so lots of favorable metallogenic environment is created in this region.The Haxi gold deposit is a high metallogenic potential deposit,which is located in the south of the Hatu mountain in the northwestern margin of the Junggar basin and discovered in recent years.Based on collection and collation of the previous research results,the author carried out a series of work such as field geological survey,petrography,fluid inclusion geochemistry and isotope geochemistry in order to analyze the geological characteristics,the ore-forming fluid evolution,the source of ore-forming material and the metallogenic mechanism.The ore body of Haxi gold deposit is divided into two types:altered rock type and quartz vein type,they often yielded by gradient and transitional.The ore minerals are mainly Pyrite,Arsenopyrite,Chalcopyrite,Gersdorffite,Pyrrhotite and some native Gold.The native Gold from the Haxi gold deposit is various in morphological characteristic,mainly in form of fissure gold,intergranular gold and inclusion gold.The electron microprobe analysis showed that the fineness of the native Gold is highly,the average value is 953.55.According to the mineral assemblage,the mineralization process can be divided into two epochs and four stages.The fluid inclusions in quartz show that,the number is large,the size is tiny and divergent-phase homogenizations of fluid inclusions with contrasting salinities at similar temperatures.The studies indicated that original homogeneous fluid experienced immiscibility.The ore-forming fluid is characterized by medium temperature,low salinity,low density and medium-deep.It's possibly a reductive magmatic hydrothermal system,which experienced multiple stages and mixture of different hydrothermal fluids.The studies of hydrogen and oxygen isotopes indicate that the ore-forming fluid is not a single source,but a process of circulation flow.The ore-forming fluid is mainly related to deep sources,with mixture of the meteoric water.The sulfur isotopic compositions show the characteristics of a deep source and highly homogenization.The lead isotopic compositions suggest that the ore-forming lead originated from mantle,possibly suffered a slight contamination of crust lead.In general,the Haxi gold deposit is a gold deposit that related with the collision orogeny plate,extension and deep fluid activities,evolution.Experienced many times and multiple forms evolution,in the process of formation.Ore deposit form and types has transition superposition of mineralization characteristics.