【作者】 张勇；

【导师】 叶高峰； 安志国；

【作者基本信息】 中国地质大学(北京) ， 工程硕士（专业学位）， 2023， 硕士

【摘要】 巴丹吉林沙漠地处阿拉善地块,该地块西接塔里木板块、北临中亚造山带和东邻华北板块。与一般沙漠不同的是,巴丹吉林沙漠湖泊众多,地下水丰富。为了研究地下水位分布以及地下水来源,本文主要采用了大地电磁测深法,结合地下水知识以及钻井资料,对巴丹吉林沙漠深部电性结构进行了研究。本文的重点研究区域为集中了绝大部分沙漠湖泊(海子)的沙漠东南部。首先应用Win GLink挑选高质量的大地电磁数据,然后通过MATLAB程序编辑生成适当的初始模型、输入数据文件以及相应的反演参数文件,利用基于非线性共轭梯度法编写的Mod EM反演软件进行全区151个测点的一、三维反演。最终获得研究区电阻率分区,得到了研究区低阻顶界面图,以此作出地下近似等潜水位图。获得各测点一维反演电阻率模型,并与从三维模型提取到的各点电阻率分层模型相对比,选定最终分层模型。然后结合了区域地质、地球物理资料对三维电性结构模型做出合理解释。最终根据电阻率模型估算地下水位,获得研究区地下水位分布图,并与该区地下水已有研究成果对比。根据电阻率模型获到的地下水位分布表明研究区地下水总体自西向东,自南向北流动,与区域地势一致。但位于沙漠东南部的湖泊群为一局部地下潜水位较低的区域,受水力梯度的影响,湖泊周边的地下水汇聚于此。湖泊主要以沙漠东南缘的雅布赖山和南边的北大山山前地下水通过潜水径流和承压水层进行补给,少部分补给来自当地大气降水,沙漠下1-2km深度基岩与沉积层可作为承压水层的隔水层,在湖泊群下方承压水层排泄区可能是深层地下水向上越流补给给湖泊和浅层地下水的主要通道。最后,利用改进的Archie公式进行了含盐流体体积百分含量的估算。得到满足含水层电阻率/电导率范围的条件为:当含盐流体连通时,含盐流体百分含量需达到3%;而当含盐流体不连通时,含盐流体百分含量需达到13%。更多还原

【Abstract】 The Badain Jaran Desert is located in the Alxa Block,which borders the Tarim Plate to the west,the Central Asian Orogenic Belt to the north,and the North China Plate to the east.Unlike ordinary deserts,the Badain Jaran Desert has numerous lakes and abundant groundwater.In order to study the distribution of groundwater level and the source of groundwater,this article mainly adopts the magnetotelluric sounding method,combined with groundwater knowledge and drilling data,to study the deep electrical structure of the Badain Jaran Desert.The focus of this article is on the southeastern part of the desert,where the vast majority of desert lakes(Haizi)are concentrated.First,Win GLink is used to select high-quality magnetotelluric data,and then the appropriate initial model,input data file and corresponding inversion parameter file are generated through MATLAB program editing.The Mod EM inversion software based on nonlinear conjugate gradient method is used to carry out 1-D and 3-D inversion of 151 survey points in the whole area.Finally,the resistivity zoning of the study area was obtained,and the low resistivity top interface map of the study area was obtained,which was used to create an approximate groundwater level map.Obtain one-dimensional inversion resistivity models for each measurement point,and compare them with the resistivity layered models extracted from the three-dimensional model,and select the final layered model.Then,a reasonable explanation of the three-dimensional electrical structure model was made by combining regional geological and geophysical data.Finally,the groundwater level was estimated based on the resistivity model,and a distribution map of groundwater level in the study area was obtained,which was compared with existing research results on groundwater in the area.The distribution of groundwater level obtained from the resistivity model indicates that the groundwater in the study area generally flows from west to east and from south to north,consistent with the regional terrain.However,the lake group located in the southeast of the desert is an area with low groundwater levels,and due to the influence of hydraulic gradients,groundwater around the lake converges here.The lakes are mainly recharged by groundwater from the Yabulai Mountains on the southeastern edge of the desert and the Beidashan Mountains in the south through phreatic runoff and confined water layers.A small portion of the recharge comes from local atmospheric precipitation.Bedrock and sedimentary layers at a depth of 1-2km below the desert can serve as aquifers for confined water layers.The discharge area of confined water layers below the lake group may be the main channel for deep groundwater to flow upwards and supply lakes and shallow groundwater.Finally,the improved Archie formula was used to estimate the volume percentage content of saline fluids.The conditions for meeting the range of aquifer resistivity/conductivity are: when the saline fluid is connected,the percentage content of the saline fluid needs to reach3%;When the saline fluid is not connected,the percentage content of the saline fluid needs to reach 13%.更多还原