Research On The Spatial Variation Of Fault Structure In Gaosong Mining Field Of Gejiu Mining Are

As a kind of important structure in geoscience,the spatial distribution and evolution model of fracture structure are of great significance in the research and production of geoscience related fields.As an objective phenomenon widely distributed in nature,fracture structure,including faults and joints,and has the form of multi-scale existence from macro to micro.Combiend with the basic definition of fractures,the fractures in the ore field are divided into two types: fault structures and joint structures.Based on the existing theoretical basis of rock mass fracture and a large number of detailed field sampling data,and on the basis of accurately grasping the geological background conditions of Gaosong Oredield in Gejiu mining area,this paper makes an in-depth statsitics and studies on the main parameter attributes such as the direction and abundance of the fracture.At the same time,according to the theory of geostatistics,the variability of fracture structure is discussed,and the main understandings are as follows:(1)Under the action of multi-stage tectonic stress,the east-west fracture group,the north-east fracture group,the north-west fracture group,the north-south fracture group have been formed in Gaosong ore field.At the same time,for the joint groups generated in a certain period and under the action of a certain tectonic stress field,they correspond to the dominant joint groups in four directions,among which NE and NW joint groups are the most developed.The occurrence of these joint groups is not exactly the same,but has a normal distribution around a certain center.(2)By using the improved circular scanning method,the fracture attributes on the side of Wuzishan complex anticline and Lianhuashan fault can be better extracted and the data results are more accurate.At the same time,based on the directional semivariogram function tool in geostatistics,two indexes,variability volumes and relative variability ratios,are creatively put forward of fracture strength and fracture density to quantitatively describe the spatial variability of fracture structures.(3)The data processed by Gislib program show that the general attribute values of fracture strength and fracture density(average value and standard variance)decrease with the increase of fault distance,and the coeddicient of variation increases with the increase of fault distance.(4)The calculation results of semivariogram function diagram,variability volumes and relative variability ratios in the study area show that the spatial variability of fracture strength and fracture density in the fracture structure decreased with the increase of the distance from the fault.The fracture structure shows obvious anisotropy in space,which is related to the axial direction of Wuzishan complex anticline and the fault strike on Lianhuashan fault.The direction with the least spatial correlations is perpendicular to the fault near the fault,and the maximum direction is parallel to the fault near the fault.The direction of the least spatial correlation at the proximal end of the fold is perpendicular to the axial plane of the fold,and the maximum direction is parallel to the axial plane of the fold.(5)For Wuzishan complex anticline in the study area,the dip angle of the strata is mostly concentrated in 15-25°,which belongs to the slow dip strata,corresponding to the second stage of the fold evolution model.At the same time,the horizontal strata began to arch upward,the amplitude of the main fold area increased,the wing strata gradually began to tilt,and the local stress in the fold area also changed.The conjugate shear surface of the vertical plane formed in the early stage was not strongly damaged,meanwhile,the local tensile stress gradually accumulated at the turning point,and the longitudinal tensile fracture began to form.In this tectonic period,the longitudinal depth of the tensional fault is relatively small,and with influence of external dynamic geological action,the top of the anticline is eroded,resulting in the wing fault exposed to the surface,forming a fracture structure parallel to the axial plane of the fold.(6)This paper discusses that the spatial variability of fracture structure is affected by fold and fault factors,and provides a method of hierarchial comparison,which enables us to judge the factors that have the greatest influence on the spatial variability of fracture structure.It is helpful to build a more accurate and applicable modes,so as to better serve the reality.