The Method For Gravity And Magnetic Imaging Of Igneous Rock

The method for gravity and magnetic imaging of igneous rock, according to the gravity and magnetic anomaly of igneous rock, virtual density and magnetization depression were inversed. From the inversion results, the spacial distribution of igneous rock was deduced. And the imaging quality depends on the accuracy of the inversion, to the existing location-field 3d inversion technique, the basic idea is to divide the underground field source area into small cuboid units, through modeling element fitting inversively to determine these units. The main inversion problems are of the great amount of calculation and multi-solution seriously. In order to solve these two problems, we use the local gravity and magnetic field feature, and comprehensive geological and local information of drilling to form constraint mechanism, and we realize the quantitative physical property inversion based on the gravity and magnetic anomaly.How to effectively use the morphological characteristics of gravity and magneitic field and the known spatial information to constraint the solution are the key to improve the reliability of the inversion. this paper improve probability tomography scan function, through the introduction of the kernel variance function instead of probability tomography scan function, improve the local convergence of the geological body, using probability imaging technology to constraint the target geological-mass qualitativly. Then, on the basis of qualitative constraints, using geology, drilling and seismic data as quantitative constraints, using the relevant relation of the local characteristics of gravity and magneitc field and geological unit, determine the geological distribution in space by multiple search technology, this will make point constraint or line constraint into volume constraint, through constraint the property value interval of unknown grid, and the more of directly determined grid, the lower of the dimension of solution space, then reduct the dimension of solution space. Then we establish the initial qualitative - semi-quantitative model, and form the feasible 3d gravity and magnetic physical property quantitative inversion algorithm.Geological model is designed based on above research results, test the input parameters and selection principle, and study the imaging results of single source and combined source. Model test shows that this method improves the image resolution of gravity and magnetic field, the boundary of the source of superposition is more elaborate, and can correct of position of stack abnormal body, so as to improve the overall effect of gravity and magnetic imaging.This method was applied to inverse virtual density and magnetization of igneous rock in YangXin area, depending on the intensity of the virtual density and magnetization, and deduced the spatial distribution of igneous, delineating 21igneous in YangXin area, and inosculation higher with drilling information, achieve the basic requirements of gravity and magnetic imaging.