银川盆地东缘上地壳电性结构特征及地热勘探方向

Electrical structure characteristics and geothermal exploration directions ofthe upper crust on the eastern margin of the Yinchuan Basin

随着银川盆地东缘地热井的成功实施,指明了围绕黄河断裂及其次级断裂寻找地热的新方向。为了进一步研究黄河断裂对银川盆地东缘地热资源的控制作用及缩小勘探靶区,共布设了4条MT测线,获得了71个测深点。通过对大地电磁测深资料进行预处理及二维反演,获得了研究区10 km以浅的二维电性结构。综合研究区以往地质、重力、微动、可控源音频大地电磁测深资料,对银川盆地东缘地层、断裂构造进一步解释,认为大地电磁测深测线所反映的奥陶系基底高阻内出现的相对低阻可能是黄河断裂后缘次级断裂发育部位,由奥陶系破碎充水所致,具有地热资源勘探的潜力。

The successful operation of geothermal wells on the eastern margin of the Yinchuan Basin suggests a new geothermal exploration orientation around the Huanghe fault and its secondary faults.To further investigate the controlling effect of the Huanghe fault on geothermal resources in the study area and pinpoint the exploration target,this study arranged four magnetotelluric(MT)lines,obtaining 71 survey points.The preprocessing and two-dimensional inversion of MT data yielded a two-dimensional electrical structure of the study area within a depth of 10 km.Based on the previous geological,gravity,microtremor,and controllable source audio magnetotellurics(CSAMT)data in the study area,this study further interpreted the strata and fault structures of the study area.It posited that the relatively-low-resistivity zone within the high-resistivity zone of the Ordovician basement reflected by the MT lines may be the secondary-fault development site at the rear edge of the Huanghe fault,which is caused by the fragmentation and water filling of Ordovician strata,showing certain exploration potential for geothermal resources.