吉林省珲春市敬信盆地大地电磁探测

Magnetotelluric sounding in the Jingxin Basin,Jilin,China

2012年4月,国务院批准在中俄朝三国交界的珲春市设立"中国图们江区域(珲春)国际合作示范区".珲春地区蕴藏丰富矿产资源和煤炭资源.该地区二叠系油气地质调查已经开始.然而,关于珲春地区深部地质信息非常匮乏.为服务珲春地区经济,了解深部地质信息,2014年,我们在敬信盆地采集一条贯穿盆地大地电磁(MT)剖面.MT数据编辑后,通过阻抗极化图和基于阻抗张量分解的多测点-多频点统计分析技术确定地电走向.通过对视电阻率和阻抗相位曲线、拟断面图进行分析,定性解释地层电性纵向变化.由于采集的垂直磁场分量质量高,对倾子振幅和倾子相位拟断面进行探讨性的分析,定性解释地层电性横向变化.对正则化参数,底板误差,敏感度实验等进行了分析,采用非线性共轭梯度法对TE和TM模式数据进行联合反演,经过多次试验,得到了一个合理的电阻率模型.结合水文钻井、地质资料,对古近系敬信盆地的基底进行了刻画,识别了深部断裂带,提供了敬信盆地属于裂谷型盆地的依据.

In April,2012,the ＂Tumenjiang Area International Cooperation Demonstration Zone＂was established in Hunchun city,situated among China,Russia,North Korea. There are abundant coal and mineral resources in Hunchun area. Permian hydrocarbon exploration has started. There are few publicly available geological and geophysical literatures on deep structures in Hunchun area.Consequently,we collected one NS-trending magnetotelluric profile in the Jingxin Basin, China in 2014. Through impedance polarization diagram analysis and multi-station, multi-frequency statistic techniques of impedance decomposition, the geoelectric strike was determined. After data edit,the curves and pseudosections of apparent resistivity and impedance phase were analysed.The vertical resitivity variations of geological subsurface were disclosed. Moreover, Due to high quality of vetical magnetic components,the pseudo-sections of tipper amplitude and tipper phase were analysed. Afer optimal selection of regularization parameter, Non-linear conjugate gradient inversion method was adopted on TE and TM modes. By trial and error,One reasonable resitivity model was obtained. Integrated with hydrogeological boreholes,geolocial information,the basement of Paleogene Jingxin Basin was delineated. And the deep faut zone in the middle was discovered,which demonstrated it is a rift basin.