The Application Of ATM In Geological Mapping In Sandui Region Of North Longmen Mountains

The study area is located in the the sandui town of the northern part Longmen mountain tectonic belt. Because the surface structure in the study area is complex, such as many of the key features of surface geology geological mapping area is not clear, which Geologic stratigraphic unit and fault structure are fuzzy, seriously affecting the regional geological mapping work. Especially the fault shows brittle characteristics, no obvious boundary geological information on the surface, the deep extension of the situation is not clear; klippes in surface boundary location, fuzzy deep tectonic style distribution unclear. Based on the above reasons, only through surveys carried out deep geological mapping has great limitations, deep geophysical data support the deep geological mapping needed. Audio frequency magnetotelluric method(AMT) is a kind of exploration in the shallow exploration technology, has the advantages of high working efficiency, high resistivity layer shielding and the low resistance layer resolution is relatively high, so the local audio magnetotelluric(AMT) exploration of underground structure.In this paper, the geological and geophysical characteristics of the study area was first introduced; then according to the above problems the geological survey, combined with the research data of geological and physical properties in the District, established the fault, fold and klippes model, forward modeling and inversion calculation on the simulation results of the model using the finite element method, the effect of each model inversion analysis method of AMT model, to investigate the feasibility of AMT in the area of detection; then using SSMT2000 and MTSOFT-2D software for processing the collected data, get the resistivity profile line, combined with the geological data in the study area of geological and geophysical comprehensive interpretation of section; finally in geological modeling of AMT profile constraint the use of GOCAD software.Through the above research, the main achievements are as follows:(1) the resistivity of rock test results in the study area showed that, the main target of different rock strata of different internal, obvious electric difference, meet the physical basis of electrical prospecting in the survey area, can reasonable arrange lines, to obtain high quality data, it can achieve a good exploration effect.(2) for processing audio frequency magnetotelluric sounding data, the single point sounding curve and apparent resistivity and phase section of qualitative research, then, choose the nonlinear conjugate gradient(NLCG) inversion method of inversion of magnetotelluric data, combined with surface geological mapping data for the interpretation of AMT results, the clear understanding of pear dam area in the deep fault tectonic style, lotus stone klippes underground distribution.(3) GOCAD geological modeling results show that it can solve the deep fault pear dam extension, klippes deep tectonic style and main stratigraphic survey area of deep geological boundary problem in AMT data constraints, results show that the audio magnetotelluric(AMT) detection results can provide reliable reference for deep geological survey and 3D modeling.