Geological And Genesis Of Volcanic Hydrothermal Type Copper (Gold) Deposites (Points) In Taerbahatai- Sawuer Area, West Junggar

The Western Junggar metallogenic belt is the eastward extension of the Kazakhstan-Balkhash porphyry copper metallogenic belt in the Central Asian metallogenic domain. It includes the east part of four metallogenic belts, which locate in Balkhash-Junggar Metallogenic province in our country. Compared with the proficiency of overseas research, it's unsatisfactory at home. In particular, the research on mineral exploration in Taerbahatai-sawuer area lag far behind.The analysis and synthesis of this paper is based on national science and technology support project:" Large deposit prospecting target area selection and evaluation of Taerbahatai-sawuer area ". Sufficient data of research area is delicately collected. Through the detailed analysis of geological work and indoor experimental research, systematica summary has been made on the ore-forming geological background, mining area geological features, geochemical characteristics and chronology characteristics of the volcanic hydrothermal type copper (gold) deposits (points) in Taerbahatai-sawuer area. In addition, the research probes into the genesis of copper (gold) deposits (points) in the research area. The research findings can be stated as follows.(1) Taerbahatai-sawuer area developed is closely related to the copper (gold) deposit (point) of the Kayinde, Wulanhaote, Bahan, Ayide, Xiemisitai and Aermuqiang,which are closely related to the volcanic rock strata in West Junggar. In terms of the above-mentioned copper (gold) deposits (points), the ore texture is shape-half automorphic granular structure; the ore structure can be mainly divided into thin vein, disseminated and star point. What's more, the type of the mineralization includes chalcopyrition, malachition and developepidotion, chlorition, silicification and carbonatization, they're the characteristics of volcanic hydrothermal type copper (gold) deposit.(2) Through the LA-ICP-MS zircon U-Pb dating, the age of copper (gold) deposit (point) volcanic of Kayinde, Wulanhaote, Ayide, Xiemisitai, Aermuqiang and Bahan is obtained as follows:455.1±5.4Ma,428.6±4.6Ma,428.8±7.2Ma, 424.3±4.3Ma,426.5±5.0Ma, and 411.7±4.7Ma. Based on the data, the age of the above-mentioned copperd (gold) deposits (points) can be divided into three phases: the late Ordovician, the middle Silurian and the early Devonian. Among them, the middle Silurian plays the dominant. In view of the close relation between mineralization and volcanic rock, the mineralogenetic epoch can also be divided into three phases, which is the same as shown in the division of ore-forming age.(3) The data of Ayide copper-gold point and Bahan copper point fluid inclusions show that the ore-forming fluid is characterized by low temperature, low salinity and low CO2 brine system. In addition, daughter minerals hasn't been found in fluid inclusions, which distinctively show the blending of hydrotherm, which is influenced by the late volcanic-subvolcanic magmatism, and groundwater of low temperature and low salinity.(4) The genesis of the Aermuqiang copper deposit is directly relevant to the volcanic activity and controlled by the basement faults. The ore structure is obviously influenced by the superimposed transformation of late ore bearing hydrothermal (low temperature). Combined with alteration features, it is the shallow low temperature hydrothermal type deposit. According to the mineral assemblages and their mutual interpenetration relationships, the metallogenic period of Aermuqiang copper deposit will be divided into early hypabyssal low temperature hydrothermal stage and supergene stage. The ore-forming process is divided into pyrite stage, quartz sulfide stage and carbonate stage.(5) The volcanic rocks of the late Ordovician, the middle Silurian and the early Devonian mainly formed in island arc environment. The ore bearing volcanic rocks all experienced the typical process of differentiation. There is no obvious contamination of crustal materials during the ascent and emplancement of magma.(6) The main ore controlling factors of the copper (gold) deposits (points), whose genesis is closely related to volcanic hydrotherm. Those controlling ore factors can be classified into strata, tectonic setting, rock type, alteration, ore controlling structure and so on in the Taerbahatai-sawuer area, and they are beneficial clues for copper (gold) mineralization. Meanwhile, the neutral-basic volcanic rock, in middle Silurian volcanic rocks from in the depth of the associated with volcanic mechanism or shallow intrusive rocks which may exist in the volcanic rock are the targets that should be more attention.