The Application And Research Of CSAMT And MT For Geological Survey In Yamansu Area Of Xinjiang Province

With the rapid development of the national economy, a variety of reasons, suchas, the large-scale development trend of construction, the drying up of shallow earthsolid mineral resources, and so on, prompted the focus of geological and geophysicalexploration work shift from the earth’s surface to a few miles deep. However, overlydependent on exposed on the surface of the earth, the high cost of geological drillingmeans, and many other factors determine the traditional geological prospecting meansnot qualified for this deep geological exploration work which is becomingincreasingly urgent. Therefore, the selecting of advanced and appropriate surveytechnical means for the different deep geological prospecting tasks has become animportant research topic.In recent years, the geophysical method is gradually emerging in all kinds ofgeological prospecting field, and especially the frequency domain electromagneticmethod represented by the CSAMT, AMT and MT, etc, have the larger explorationdepth, convenient data acquisition process, high resolution, not easily affected byinterference and many other advantages, so these geophysical methods is presentsbetter application prospect in the large deep geophysical prospecting task. So underthese research background, the thesis is completed based on The site evaluationproject of candidate high-level radioactive waste disposal in Yamansu area ofSinkiang. In order to find out the basic engineering geological conditions of targetarea, CSAMT and MT were been chosen to complete deep geological explorationtasks of those area. At the same time, the thesis will explore the application effect oftwo kinds of methods in this kind of deep geophysical detection field and try tosummarize some valuable experience in the process of data collection and processing.On the basis of collection and analysis for a large number of relevant literature,the thesis briefly describes the development situation of deep geophysical explorationtechnology at first; Then several key problems in the practical application process ofCSAMT method, such as, the estimation of lowest sampling frequency, thedetermination of the distance between receiver and launcher, the selection of the receive and launch polar’s distance, the influence of the power supply current and thechoice of measurement methods, have been carried on the preliminary discussion onthe basis of systematically expounding the basic formula of electromagnetic field andthe method principle of CSAMT; Secondly, the thesis described the basic principle offinite element method and then established four kinds of typical geological bodys’simple geoelectric model, including the undulating bedrock, the filling undergroundcavity and goaf, the low resistivity rock layer of thickness variation and the fillingfault. The finite element method was used to forward modeling calculation in thesefour models and then the calculated data has been inversion become the final resultsin using respectively three different patterns of the TE, TM and TM&TE mode, thenthe characteristics of abnormal reflect and difference of applicability for thesedifferent types of geological body have been summed up through comparison andanalysis of the final results of different patterns; Under the support of the aboveresearch achievements, the thesis did processing and inversion work for the CSAMTand MT data of7lines which have been collected in Yamansu candidate area and thenfinished geological interpretation assisted in the related geological data. Finally, themorphological and characteristics of Granite rock mass, the Quaternary overburdenand the Fault in the target area have been deduced through the interpretation results,and the engineering geological conditions characterized of the target area was finallyfound out.The later geological data showed, the comprehensive electromagnetic methodwhich contains CSAMT and MT is very effective reflects the deep general geologicalsituation of the target area. The above research results have successfully provided apractical effective reference for the site evaluation work of candidate, and, at the sametime, summarized much valuable reference and application experiences for the deepgeological and geophysical prospecting work in the future.