林西—乌兰浩特地区铀成矿多源信息分析与成矿预测

An analysis of multivariate uranium metallogenic information and metallogenic prognosis in Linxi-Ulanhot area

林西—乌兰浩特地区位于大兴安岭铀成矿省中南段,构造岩浆活动强烈,铀成矿地质条件优越。限于植被发育、覆盖厚等因素制约,单一勘查手段难以满足当前深部找矿的需求。在成矿条件及控矿因素分析的基础上,综合航放、航磁、地球化学、遥感等多源信息,构建了火山岩型铀矿综合找矿模型。利用地理信息系统(GIS)空间分析功能,提取了多源找矿信息,采用证据权重法开展铀矿定量预测,优选了与成矿密切相关的16个证据层。其中上侏罗统满克头鄂博组为主要赋矿地层;晚侏罗世—早白垩世潜火山岩与成矿关系密切;NE-NNE向断裂控矿作用显著,铀矿化多发育在断裂密集带及交切带;航放参数异常(U高场、F高值晕、U/K高值晕、Hu低值晕)、化探异常(Mo、Ag、Pb、W、Sn)及遥感蚀变异常(铁染异常、羟基异常)对铀矿化指示作用明显。依据证据权重法确定的后验概率圈定成矿远景区18处,覆盖了区内多数铀矿床(点),表明预测结果较为可靠,其中7处成矿远景区内尚未发现铀矿床(点),其成矿地质条件优越,找矿线索丰富,找矿前景较好,对进一步找矿具有一定的指导意义。

Located in the south-central part of Da Hinggan Mountains uranium metallogenic province,Linxi-Ulanhot area is characterized by strong tectonic magmatic activity and favorable geological conditions for uranium mineralization.Limited by such factors as vegetation development and thick cover,it is difficult for the single exploration method to meet the demand of the current deep prospecting.Based on the analysis of ore- forming conditions and ore-controlling factors,the authors constructed a comprehensive volcanic-type uranium ore comprehensive prospecting model by integrating such pieces of multivariate information as airborne radioactivity,aeromagnetic survey, geochemistry and remote sensing.Using spatial analysis function of the geographic information system (GIS),the authors extracted the multivariate prospecting information,carried out quantitative prognosis for uranium ore by evidence weighting method,and selected16 evidence layers closely related to mineralization. Among them,the Upper Jurassic Manketouebo Formation is the main ore-bearing strata,the Late Jurassic-Early Cretaceous subvolcanic rocks are closely related to ore formation, the ore-controlling effect of NE-NNE trending fracture is significant,and uranium mineralization is mostly developed in the fault-dense zone and the intersection zone. Such anomalies as airborne radioactive anomalies (U high field,F high value halo, U/K high value halo,H u low value halo), geochemical anomalies (Mo,Ag,Pb,W,Sn) and remote sensing alterations (Iron alteration, hydroxy alteration) play important roles in the indication of volcanic uranium mineralization.According to the posterior probability determined by the evidence weight method,18 prospective areas were delineated, covering most uranium deposits (ore spots) in the area,indicating that the prediction results are reliable.In seven of them, uranium deposits (ore spots) were found for the first time.All these places have excellent metallogenic geological conditions, rich prospecting clues and good prospecting prospects,and the results obtained by the authors have certain guiding significance for further prospecting.