电磁法物探在北方中新生代盆地产铀性评价中试验研究

The experimental study on assessment of uranium ore prospecting in Mesozoic and Cenozoic basins in the north China with electromagnetic geophysical survey

北方中新生代盆地砂岩型铀矿床是我国一种重要的铀矿类型,使用现代地球物理探测技术对典型产铀盆地进行探测,在划分盆地结构、查明铀成矿地质环境方面可以发挥巨大作用,且可有效缩短找矿周期。文章选取新疆伊犁盆地南缘加格斯泰地区为试验区,在两条地质情况已知剖面上开展音频大地电磁法(AMT)与可控源音频大地电磁法(CSAMT)对比试验,其结果表明:(1)AMT与CSAMT对断裂构造和砂体均有明显的反映,所展示的盆地电性结构基本一致,清晰刻画了地质体面貌及相互关系,均可投入生产应用。(2)AMT与CSAMT在细节表现上又有所不同,AMT由于频点数量多、偶极距短,因此分辨率较高,能识别较小的地质体,但是具有低阻屏蔽效应;CSAMT抗电磁干扰能力强,能获得较高质量的数据,对盆地内砂体、断裂构造等地质要素探测效果较好。

Sandstone type uranium deposit in Mesozoic and Cenozoic basins is an important uranium deposit type in north China.Modern geophysical prospecting methods used in uranium ore prospecting in the uranium ore-producing basins have played an important role in structure division of the basins and check of the geological and metallogenic environment and the prospecting cycle can be shortened.The experiment was carried out in Jiagesitai area at the south margin of Yili Basin in Xinjiang.Along two sections whose geology are known AMT and CSAMT were comparatively conducted.The result is:1)the generally coincident electrical property of the basin and faults and sand bodies are clearly reflected by data of the both surveys,Morphology and relationship of geological bodies clearly thus the data can be applied to production;2)details of the two methods are varied.ATM is high in resolution due to numerous frequency points and shorter dipole distance and smaller bodies can be recognized but the low resistance shielding effect appears,CSAMT possesses stronger electromagnetic interference resistance,can obtain higher quality data,and has the positive effect on sand body in basin,fault structure and other geological factors.