鄂尔多斯盆地西南部多元地学特征及其找铀意义

The Characteristics of Multi-source Geo-information and Its Significance to Uranium Exploration in the Southwest of Ordos Basin

研究区位于鄂尔多斯盆地铀成矿区(带)西南部,区内中、小比例尺航磁、重力等物探方法已覆盖,但大比例尺、高精度物探资料较少,尤其是航放仍是空白,加上由于中央古隆起的存在导致了主要找矿目的层埋深大,严重制约了该区找矿突破。通过对最新实测的1∶5万高精度航放、航磁及收集的重力资料的分析,认为航磁梯度带、航放高场区、航放活性铀迁入区、局部重力高异常边缘复合区是与已知铀矿化有关的多元地学信息,航放异常是寻找铀矿化的直接标志。提出了在对航放数据进行地质单元编码统计、去除背景干扰后,利用活性铀迁入区(<0)缩小找矿范围,用古铀>2.00×10^-6、活性铀<-0.05×10^-6、铀归一>0.30×10^-6、铀增量>0.20×10^-6、sm9>0.30×10^-6套合区识别隐伏铀矿化的航放弱信息提取技术。综合上述研究成果,结合铀成矿地质条件,建立了找矿标志,圈定铀成矿远景区5片。对其中1片开展了地面查证,结果显示地面伽马能谱测量铀含量最高达556×10^-6,岩石取样化学分析铀含量最高为0.018%(边界品位0.01%),具有重要的找矿前景。

The research area is located in the ur anium mineralization belt of southwestern Ordos basin which is covered by middle to small scale aeromagnetic and gravity data.However,The exploration has been seriously restricted due to the lack of large scale and high accuracy geophysical data,especially the airborne radioactive data.By analyzing the new measured 1∶50000 aeromagnetic,airborne radioactive data and the collected gravity data,we believed that the multi-source geo-information related to uranium mineralization are aeromagnetic gradient belt,airborne radioactive high-field zone,immigration zone of active uranium extracted from airborne radioactive survey,compound edge zone of local gravity anomalies,and the airborne radioactive anomalies are the direct sign for uranium mineralization.A weak information extraction and predict method was built up based on geological unit encoding statistics of airborne radioactive data and removing the background interference,which is composed of narrowing the scope of prospecting by active uranium migration area(<0),identifying the deep uranium mineralization by the compound zone of paleo-uranium over 2.00×10^-6,active uranium below-0.05×10^-6,normalized uranium over 0.30×10^-6,uranium increments over 0.20×10^-6 and sm9 over 0.30×10^-6.Based on the above research results and the analyses on uranium mineralization geological conditions,the exploration marks have been set up and 5 uranium prospects have been delineated.One of the prospects was verified by ground survey the prospect,uranium content calculated from the ground gamma spectrometry is up to556×10^-6,and the assayed uranium content is up to 0.018%(cut grade 0.01%),which showed great prospecting potential.