Study On The Identification Of Deep Structure And Lithology Of Comprehensive Geophysical Interpretation

Xiangshan western region is located in the west of Xiangshan volcanic basins. With complex geological structures and intense cutting of terrains, it boasts excellent metallogenic geological conditions. Although here centralizes a large amount of deposits, multiple and high-grade ores, the approved shallow deposit location can by no means make people rest easy. Considering the sustainable supply of resources, it is an indispensable way to exploit deep for mineral resources in the future. It is thus necessary to reinforce experience summation and theory formation throughout the practical process to improve exploration methods and to prospect deep ore bodies in prospective areas and old mining areas. With the region a key area in deep exploitation in Xiangshan, the study of Xiangshan western region is of great significance not only for itself but also to provide new theories, new methods and new directions for the increasing amount of energy resources.On the basis of the geological background and the geological characteristics of the deposits in the Xiangshan uranium mineral field, this thesis firstly renewedly summarized the general geology of the west part of Xiangshan complex. After collecting and analyzing the rock samples, the author respectively made certain of the characteristics in lithology density, magnetic susceptibility and electrical resistivity of the study area and laid the theoretical basis for the latter lithology identification. Based on this, the author designed lattice, extracted the surface geology and drilling information with the help of one software named Mapgis, established three-dimensional gravity and magnetic constraint files, and modeled them. With the constrained geological information of surface and drill, the 3D gravity and magnetic inversion experiment constrained by geological information can effectively reduce inversion errors and increase the the reliability of the inversion results. This thesis gives a brief introduction of the method of 3D gravity and magnetic inversion constrained by geological information, illustrates how to use it and underlines the data preparation, mesh generation, parameter setting and the evaluation standard of results during the experiment and its results. In particular, the complex changes at density and magnetic susceptibility in the central part of the experimental area can be found after separating the potential field of gravity and magnetic data. Combined with relevant geological and physical properties materials, the author puts forward that the physical properties of complex changes areas is featured with multifarious geological structure and can be regarded as the important sign for further exploit concealed ores. In addition, Applying Non-linear conjugate gradient( NLCG) 2D inversion for the audio frequency magnetotelluric data observed in the study area of three survey lines that the inversion results can better delineate the distribution of different lithologies, burial depth and deep faults in survey area, providing technical support for comprehensive interpretation. The author identified a certain fault structures in the north-west, north-east as well as the north-south direction of the study area with the Euler deconvolution method. Meanwhile, with the reference of physical characteristics of rocks and geological data on hand, the author analyzed the results of 3D physical property inversion of Gravity and Magnetic and affirmed that high magnetic susceptibility and low density area indicates the volcanic feeder, confirmed that there exists a center of magmatic activity in the west of Niutouling(one ridge like a cow’s head) due to the high magnetic susceptibility and low density; while high density and low magnetic susceptibility area represents metamorphic rock series, mainly in the northeast and southwest corner of the study area. Integrated interpretation techniques of Gravity, magnetic and electrical will provide additional information for the method.With the guidance of the integrated interpretation techniques of gravity, magnetic and electrical method, the thesis identified the deep structure and lithology distribution, which can provide technical reference for deep exploitation and give solid support for delineating metallgonetic target areas in Xiangshan western region in the future.