连续电磁剖面法在山前带勘探中的应用

Application of continuous electromagnetic profiling in exploration in foothill belt.

柴达木盆勘探地西缘阿尔金山前带地表及地下地质条件复杂,地震勘探困难,为此在该地区开展了连续电磁剖面法(CEMP)勘探研究。采用波数域低通滤波技术、阻抗张量重构技术、远磁参考处理技术等,利用CEMP技术不受高陡构造及推覆构造屏蔽的优点,采取地震资料与CEMP资料联合建模解决地质问题,取得了较好的地质效果。柴达木盆地西缘电性特征表明,该地区存在4个明显的电性层:第四系,狮子沟组,上、下油砂山组及上干柴沟组为低阻;下干柴沟组-侏罗系为第1次高阻层;古生界基底为第2次高阻层;结晶基底电阻率最高,在1000Ω·m以上,是电性基底的反映。利用CEMP勘探方法,在山前复杂构造区取得了良好的勘探效果。

Seismic survey is hard to carry out in Aerjin foothill belt, western Caidam Basin due to its complex topography and subsurface geology. In stead, continuous electromagnetic profiling (CEMP) was implemented. Through low-pass filtering, reconstruction of impedance tensor, and far reference of magnetic field, CEMP data were jointly used with seismic data to build geology model. There are four conducting layers in western Caidam Basin. The Quaternary, Shizigou Formation, upper and lower Youshashan Formation, and upper Gancaigou Formation were in low resistivity. The lower Gancaigou Formation to Jurassic was the first high resistivity formation. The Paleozoic basement was the second resistivity formation. The crystalline basement was of highest resistivity, and its resistivity was up to more than 1 000 Ω·m.