Tectonic Evolution And Its Metallogenic Control In Jinwozi Gold Mining Area,Xinjiang Province

The geotectonic position of the Jinwozi gold field of Hami Gold Company is located in the north of Beishan tectonic zone in this paper.The tectonic dynamics Environment of the whole Beishan area has been complicated since Early Palaeozoic Era.Previous studies on the gold field were concentrated in 1990 s.The understanding of the gold field is that first the deposition of the Jinwozi Formation of the Upper Devonian,then the Jinwozi intrusion,finally formed the Jinwozi gold deposit.However,through field research,we discovery that the north and the south boundary of the Jinwozi granite and the Jinwozi formation of Upper Devonian is a fault contact.The eastern boundary of Jinwozi granite and the Jinwozi formation of Upper Devonian is a sedimentary contact.The previous understanding of the whole evolution of the gold field is not consistent with the geological facts of the gold field,and there is no reasonable explanation.Under the guidance of plate tectonics theory and continental dynamics theory,this paper uses Mapgis,Rocscience Dips,structural analysis software and U-Pb dating to identify the process of tectonic activity in the whole gold field and the control effect of tectonic movement on the mineralization of the gold field based on the existing results of geological research and field sampling survey.The following points are obtained:1.The Jinwozi granite and the Jinwozi formation of Upper Devonian were affected by tectonic movement after formation through field investigation,observation of distribution of mineral in the Jinwozi granite and the Jinwozi formation of Upper Devonian under the microscope,and metamorphism occurred.While the whole gold field showing that the north zone is a North East to high angle imbricate reverse faults,the south zone is a low angle reverse faults,oblique arrayhigh angle translational normal faults with near North and South directions in the middle.These fracture structures control different types of mineralization,tensile fracture mainly controls quartz vein mineralization,while compressive fracture mainly controls altered rock mineralization.According to regional stress analysis,the mining area is subjected to NW compressive stress,and the high-angle normal faults near the North-South syncline are controlled by NE-trending FII-1 and FII-2 reverse faults,which are secondary high-angle tensional faults formed under the condition of both FII-1 and FII-2 reverse faults with left strike-slip.2.We carry out the zircon dating of controversial Jinwozi granite,the sample is taken from the interior of the granite,we got it the data is 413±Ma.The granite was formed in Early Devonian.Therefore,the evolution process of development of gold field is formed first Jinwozi granite,then formed the Jinwozi formation of Upper Devonian,final mineralization.This is the opposite of the previous understanding.3.Through the research on the joints of the Jinwozi area,it is clear that the azimuth of the joint advantage of the whole gold field is in accordance with the main tectonic line of the gold field.Study on conjugate joints determines the main Jinwozi area were influenced by three major tectonic movement.The first tectonic stress is NNE,It represents the tectonic stress environment after the formation of the early Devonian Jinwozi granite and before the formation of Jinwozi formation of Upper Devonian or a period of time.NWW trending tectonic stress represents the tectonic stress environment before the formation of the gold deposit and ore control structure in the upper Devonian or a period of time.The third tectonic stress is northwestward.It is believed that the Middle Triassic mining area is in the NW trending tectonic stress environment.4.Tectonic evolution controls the sources of ore-forming material,that is the Jinwozi formation of Upper Devonian and the Jinwozi granite with high gold concentration clark.In the tectonic movement,the high angle imbricate thrust fault in the northern area of the gold field,the high angle translational normal faults in the middle zone,and the 210 low angle ductile brittle shear zone in the southern zone are the guiding channels for the gold field as well as the ore hosting sites in the gold field.The tectonic movement provides the activation,migration and sedimentation of minerogenetic materials with the driving energy,and the intraplate tectonic activity in the Mesozoic and Cenozoic controls the erosion and preservation of the deposits.