Study On The Structure Deformation Of Chagangnuoer Iron Ore Deposits In The Western Tianshan,Xinjiang,NW China

Chagangnuoer iron ore deposits is located at the Boluokenu mountains in the northeastern corner of the Yili basin, tectonic belt of northern margin of the western Tianshan, belongs to Carboniferous island arc zone. It is an important part of the Awulale Iron Metallogenic Belt (AMB). This deposits has experienced multipahse tectonism, frequently volcanic activities, and associated poly-period metallogenesis, become an ideal area for the study of tectonic deformation and metallogenesis. Many works inlcuding geochronology, geochemistry and mineral deposits had been conducted in the Chagangnuoer iron ore deposits to improve the understanding of the types and genesis of this deposit, but till now the deformation characteristics and sequence of this deposits are still equivalent, the relationship between deformation and metallogenesis have not been well studied. In this thesis, based on existing research data, focused on the tectonism and tectonic features, with the detailed field geological survey, has deeply profiled tectonic features, determined the deformation sequence and analysed the relationship between tectonic deformation and metallogenesis in the region of Chagangnuoer iron ore deposits, including Chagangnuoer, Zhibo, Songhu and Taertage deposits. The results show that the deposits is mainly developed of the NW-NWW high angle ductile-brittle to ductile strike-slip faults and overthrust faults, near east-west and north-south oriented high angle conjugate brittle (ductile) strike-slip faults, and near north-south oriented brittle right-lateral strike-slip faults. Above the faults superimposed on the axis of nearly north-south wide and gentle folds, together constitute the basic structural framework of mining area. Combining the mutual relationship of faults in different directions, kinematics characteristics and ESR chronology of fault rock data(2.3Ma-89.9Ma), we have preliminarily determined the tectonic deformation sequence and its relation with the ore body of the deposits.(1) the late Yanshanian-early Himalayan period:the deposits is mainly developed the larger scale NW-NWW high angle ductile-brittle to ductile strike-slip faults, consists of a series of secondary faults and the attitudes are basically consistent, sometimes branching, sometimes compounding, twisting, along the strike the attitudes of rock are varied, but the overall trend remains the same. The faults formed early in the area, and they are also the important regional ore controlling structures. NW-NWW overthrust faults are the dominant controlling structures in mining area, after development in the previous strike-slip faults, and clipping the strike slip fault and its controlled the magnetite ore body. In mining area, positive, recoil faults are common, the two direction of the thrust composed the complex deformation system.(2) the mid-Himalayan period: the deposits is mainly formed the near east-west and north-south oriented high angle multi-directions conjugate brittle (ductile) strike-slip faults, the same or slightly later than the overthrust fault, and accompany with the thrust faults. They have the more intense effect on the destruction and reconstruction of the ore bodies, especially the high angle strike-slip fault is in the partial control of the ore body, or make the ore body strongly crushing and altering in powder form;(3) the late Himalayan period:this is the last period of tectonic activity in the region, reveal that the near north-south oriented brittle right-lateral strike-slip faults, the overall displacement is smaller. Mainly exposeded in Chagangnuoer and Zhibo deposits, the rest were not observed.(4) the faults of Chagangnuoer and Zhibo deposits are mainly manifested the role of destruction and transformation for ore bodies. Whereas, at the Songhu and Taertage deposits, ductile-ductile to brittle shear zone is the main ore controlling structure, main veins closely associated with structure, and is closely related to metallogenesis of magnetite, chlorite and epidotization, carbonatization etc, the alteration mainly occurred along with structure, there are different thickness of magnetite ore body filling with the strong deformation zone, forming a grid-like magnetite veinlets, composite parts of the ore body become thicker.