Study On The Geological-geochemical Characteristics And Origin Of The Katebasu Gold-copper Deposit,West Tianshan,Xinjiang

"Asian gold belt" is a well-known giant metallogenic belt, it is found that many large-super large deposits of porphyry type, skarn type, orogenic type, epithermal, showing great prospecting foreground and potentiality. The "Asian gold belt" extends into West Tianshan Mountains in Xinjiang,Katebasu gold-copper deposit is located in the south of Nalati fracture on the northern margin of the West Tianshan Mountains. The deposit’s the geological structure and metallogenic condition is complex, and the study of the deposit used to be inadequate, the research of scholars view is inconsistent on geological characteristics, ore rock’s chronology and tectonic background, metallogenic epoch, sources of metallogenic matter and metallogenic model etc. and is lack of in-depth study. Based on previous research work, this article comprehensively collected basic geological data about regional and study area, discussed geological characteristics, sources of metallogenic matter, ore-controlling factors and ore genesis, determined the type of deposit. Main achi evements as following:(1) The basic-acidic tuff, limestone, marble, etc. of Upper-Silurian Bayinbuluke Formation is the main strata of the mining area; The tectonic activity of the mining area is strong and has multiple stages, based on fault fracture zone and joint structure, joint divided into metallogenic tectonic and structure after mineralization; Intrusive rocks are mainly monzogranite, diorite, syengranite, the main host rock is monzogranite and diorite(2) Monzogranite is the main ore rock in mining area and formed in the early Early Carboniferous(348.9 ± 6 Ma), which has the characteristics of I-type granite, belong to metaluminous – peraluminous, calc-alkaline series, and formed in volcanic arc under the stretching environment after the collision of South Tianshan Ocean and Central Tianshan.(3) In the eastern and western part of the shallow mining area, ore body produce in fault fracture zone of adamellite, deep in the western part, ore body produce in skarn and fracture zone nearby skarn contact zone of adamellite,diorite vein with marble capture. At different spatial positions, mining alteration and mineralization are different. In the eastern and western part of the shallow, wall rock alteration from the center of shattered fault zone to the sides are potassium, silicification, sericitization, chloritization, etc, mineralization is mainly gold mineralization; deep in the western part, alteration are garnetization, diopsidization, tremolite, epidotization, actinolitization and marmarization, mineralization is mainly gold-copper mineralization.(4) According to the ore texture and structure intercalated relationship, the mining area is divided into two magmatic hydrothermal mineralization: I.Mineralization is mainly based on gold mineralization, which is related to adamellite magmatic hydrothermal; Ⅱ.mineralization is mainly based on gold mineralization, which is related to diorite-dyke magmatic hydrothermal. Two hydrothermal formed two mineralization and alteration, later gold copper orebody superimpose on earlier gold orebody in local place, later skarn locally superimpose on earlier skarn in deep of the western part.(5) The hydrogen and oxygen isotopic compositions show that in the early period ore-forming fluids were mainly made up of magmatic water, and mixed precipitate water in later. The characteristics of sulfur isotope show that sulfur source is complicated, it presumably caused by the deeper part of the ore-bearing magmatic fluids in the upwelling process mixing the sulfur of stratum. The characteristics of lead isotope indicate that they are mixture of crust and mantle.(6) Laser Raman component analysis of fluid inclusion shows that ore-forming fluids are complicated, the presence of a large number of N2 and H2 in gas indicates fluid may come from the deep crust or mantle.(7) Deposit is controlled by many factors for stratum, tectonic, magmatic rocks.etc and has complex causes, mineralization is closely linked to magmatic hydrothermal, a large number of strike-slip shear fault and overthrust structure become a prerequisite for mineral’s migration and precipitation.It is considered that the deposit which is related to the multi-stage magmatic hydrothermal belongs to skarn-fracture zone altered rock type deposit by comprehensively analyzing various metallogenic factors.