综合物探法在砂岩型铀矿中深部找矿中的实践与分析——以新疆昭苏盆地为例

Prospecting Middle and Deeply Buried Sandstone-Type Uranium Deposits Beneath the Zhaosu Basin,Xinjiang by Integrated Geophysical Methods

为了探查新疆昭苏盆地砂岩型铀矿的异常信息,选择可控源音频大地电磁测量、高精度磁测和土壤氡气测量三种物探方法,并简要介绍各方法的工作原理。通过分析昭苏盆地的地质特征、物性特征和本区的找矿难点,对昭苏盆地综合物探数据所蕴含的信息进行地质-物探综合解译。实践证明:可控源音频大地电磁测量对低阻和高阻体均有良好的电性响应,可以划分地层、推断断裂构造;高精度磁测可以推断氧化还原界面,辅助解释断裂构造;土壤氡气测量可辅助解释断裂构造,对地下铀矿体有指示作用,三种方法的技术特性相互补充,提高了物探解释的准确性。突破了伊犁盆地以往600 m的找矿深度,并以电性稳定的中阻厚层、磁测异常、氡异常偏高晕和峰-谷状曲线作为预测标志,解决了深埋藏条件下赋矿地质体的圈定难点,在昭苏盆地砂岩型铀矿中、深部找矿工作中取得了良好的效果。

The objective of this work was to explore the deeply buried sandstone-type uranium deposits beneath the Zhaosu Basin,Xinjiang by integrated geophysical methods.Three geophysical methods were used,including controllable-source audio magnetotellurics(CSAMT),high-precision magnetics(HPM),and gamma-ray-logging-based soil radon measurement(SRM).Combined with the data of geology and physical properties in the basin,the survey anomalies were interpreted for ore-search information.Results show that the CSAMT has good electrical response to low-and high-resistance targets,permitting to divide strata and infer fault structure.The HPM can assist to explain the fault structure and morphology of the basement,and SRM can also assist in the interpretation of fault structure with an indicator of uranium deposits.Due to distinct technical characteristics,the three methods complement each other and improve the accuracy of geophysical interpretation.This work broke through the limit of the previous 600 m prospecting depth in the Yili Basin,found the prediction marks as the medium resistivity thick layer,high radon anomaly and peak-valley curve,and solved the difficulties of delineating ore-bearing geological bodies at depth.In sum,a good effect has been obtained in the prospecting of middle and deeply-buried sandstone-type uranium deposits in the Zhaosu Basin.