The Study Of Audio-frequency Magnetotelluric2D Inversion Using Nonlinear Conjugate Gradients Algorithm In Jiurui Ore Concentration Area

Audio-magnetotelluric (AMT) has been widely used in all aspects of geophysics,such as deep prospecting, environmental engineering, etc, recently one-dimensional andtwo-dimensional inversion methods are often used for data inversion interpretation;nonlinear conjugate gradient has the dual advantage, that are fast convergence ofQuasi-Newton’s method and program simple of the steepest descent method, whichmakes it become one of the important two-dimensional inversion methods in practice,but, above the parameters setting and impact of acquisition parameters, there is less study.Therefore, this thesis does the subject on the basis of " Twelfth Five-Year Plan" nationalscience and technology support project" three-dimensional detection of Ore-controllingstrata, rock mass and the research of Prospecting prediction in Jiurui ore concentrationarea of Jiangxi province (No.2011BAB04B03)", On the basis of doing the study oneffect of Audio-frequency Magnetotelluric2D inversion result using nonlinear conjugategradients algorithm by setting up theoretical models, doing the inversion interpretation ofAMT data in Jiurui ore concentration area, which reveals the electrical structure of thearea, and provides the basis for deep prospecting.The paper aims at the problem of Inversion parameters and acquisition parametershad great influence on the2D inversion results using nonlinear conjugate gradientsalgorithm, carrying out a study of the two-dimensional inversion parameters andacquisition parameters. The result shows that: In terms of selecting inversion parameters,the TE and TM combination mode has better response than a single mode about layeredinterface of surrounding rock, the size and position of abnormal body; making resistivityvalues of the surrounding rock where abnormal body as the initial model has a bettereffect; it is better when regularization parameter is10. In terms of selecting acquisitionparameters, ine length should be twice longer than detection depth and the width of the target body, when it is three times, the effect is the best; in the case of transverseresolution, at the top of abnormal body, the measuring points should not be less thanthree, five is the best; frequency points in the range of exploration depth must be not lessthan three, more than5is the best.For testing flexibility of the research results about inversion parameters andacquisition parameters, the results are used to do2D inversion for AMT data in Jiurui oreconcentration area by using nonlinear conjugate gradient, and carrying outcomprehensive geological interpretation for the inversion results of AMT data in Jiuruiarea, the result shows that: break structure develops in the area, break transition happensbetween each other, diamond mesh structure forms. Those situation restricts pathways ofthe ore fluid migration and the place of ore; from south to north, survey line shows asyncline and anticline alternating characteristics, poor continuity of strata folds; from eastto west, the northern high resistance region of survey line continues to surface elevation,speculating that thrusting is increasing from south to north, the northern one has the trendof uplift. Finally, setting up the distribution characteristics of electrical structure in Jiuruiore concentration area built by3D visualization technology, which provides a referencefor the deep prospecting.