Analysis Of Ore-controlling Structures Of The Haoyaoerhudong Gold Deposit Of Inner Mongolia

The Haoyaoerhudong super large gold deposit is located in the northern margin of the North China platform. Occurring in the Black shale ore-hosting formations, this deposit is of low grade, large reserves and be easy to be exploited. The deposit generates in carbonaceous slate and carbonaceous phyllite of the first and second Bilute formation in Bayan Obo Group. The ore body is strictly controlled by stratum and structures. This article focuses on the ore-controlling structure of the deposit. Based on detailed works on the fold, fault and the joint structures, the relationship between structural evolution and the formation of the fold deposit are summarized.The tectonic activity of mining area is strong, the rocks have a strong deformation, the broken and joints phenomenon are obvious. Through the analysis of the large number of joints in the mine area, we realize that the orientation of joints in mining areas are mainly concentrated in the range of 50~70°, 240~260°, secondly, the direction of some of the joints are NNE-SSW. The main stress σ1of the mine is concentrated in NE-SW, and can be divided into three stages.The microscopic tectonic features show that, the mining area has experienced the transition from ductile deformation to brittle deformation. The quartz SR dynamic recrystallization and calcite twin grain type, show that the temperature of the deposit has experienced from high temperature to a low level. By estimating the size of quartz subgrain, we can know that the different stress value of quartz dynamic is between 25.64~55.38 MPa. This data is low in general. Due to the change of the temperature, pressure condition in the mining area, the ore-body deformation change from ductile to brittle and ductile-brittle transition domain occurs. Then the Haoyaoerhudong syncline appears a large number of joints and fracture zone which provide migration path for ore-forming hydrothermal fluid. And then, Hercynian magmatic intrusion activities has brought a lot of magmatic hydrothermal which led to the enrichment of gold in the open space of the Bilute formation.