综合地球物理在内蒙古多伦县核桃坝地区铀矿勘查中的应用

Application of comprehensive geophysics in uranium exploration in the Hetaoba area of Duolun County,Inner Mongolia

核桃坝地区铀成矿条件优越,在该区东部已取得较好的找矿成果,西部尚未取得找矿突破。研究区铀矿化受断裂构造、破碎带控制明显,查明该区断裂构造格架和构造破碎、蚀变带的分布,推断成矿有利区,为进一步挖掘该地区的铀成矿潜力提供地球物理资料。通过音频大地电磁测量、土壤氡测量和地面高精度磁测3种物探方法的联合应用,圈定了土壤氡异常;查明断裂F_(13)北西部断裂呈现NE向和NW向“田”字格排列,断裂F_(12)南东部断裂呈现NE向。断裂F_(13)、F_(12)夹持部位断裂呈现近SN向和NW向;推断构造蚀变、破碎带6处。结合该区铀矿化特征,构造蚀变、破碎带S1、S2、S3、S4,处于断裂交汇、夹持部位,规模较大,且周围分布多个土壤氡异常,异常幅值可达35000 Bq/m^(3),为成矿有利地段。经钻探验证,钻孔ZKH24深部发现了构造蚀变、破碎带和富厚铀矿体,后续在S2构造蚀变带内发现了多个工业铀矿孔,并发现了矿体较好的钻孔ZKH7-1,落实了铀矿产地,说明此3种物探方法联合应用在该地区铀矿找矿工作中具有较好的效果,可在该类型铀矿勘查工作中推广应用。

[Objective]The Hetaoba area in Inner Mongolia has superior uranium metallogenic conditions.Grea tore-prospecting results have been achieved in the eastern part of the study area.However,breakthrough has not been made in the western area.Uranium mineralization is significantly controlled by faults and fractured zones.To identify the distributions of fault framework,structural fracture and alteration zones,and further to infer the favorable metallogenesis areas,geophysical data are provided to explore the uranium metallogenic potential.[Methods]Through the comprehensive applications of three geophysical methods,including audiomagnetotelluric surveys,soil radon measurements,and ground high-precision magnetic measurements,soil radon anomalies are delineated in the study area.The northwest fault F_(13) shows a northeast-and northwest-trending with a Chinese word"Tian"grid shape,while the southeast fault F_(12) presents a northeast-trending grid shape.The faults of F_(13) and F_(12) present nearly north-south and northwest trendings in the pinched zones.There are six structural alterated and fractured zones to be inferred.[Results]Based on the characteristics of uranium mineralization,it is inferred that the structural alteration and fracture zones of S1,S2,S3 and S4 are located at the intersection and pinched zone of faults,with a large scale.Multiple soil radon anomalies are distributed with an anomaly amplitude up to 35000 Bq/m^(3),which are the favorable areas for metallogenesis.[Conclusion]After verification of the drilling results,the structural alteration,fracture zones and thick uranium ore bodies are discovered in the deep of borehole ZKH24.Many industrial uranium ore holes are discovered in the S2 structural alteration zone.Borehole ZKH7-1 has good ore findings,confirming the origin place of the uranium ore.The study indicates that the comprehensive application of the three geophysical methods has effective results in uranium ore exploration and can be promoted to uranium ore prospecting.