摘要
本文矿区位于西非克拉通南部马恩(Man)地盾太古宙成矿区,是典型的沉积变质型铁矿床。采用高精度磁法测量、EH4大地电磁测深和钻探验证等方法对矿区内需选铁矿体开展了地质勘查及研究工作。通过高精度磁测结果推测磁异常与出露地表或浅层矿体有关,利用EH4大地电磁测深测量结果对磁异常进行解析,推测出成矿有利区,并经过钻探成功验证;结合地质背景、物探成果和钻探,建立了矿区的地质-地球物理模型。研究结果表明:该区域磁异常基本呈现正磁-负磁-正磁异常分带的明显特征;经钻探验证,正磁异常为地表露头(或一定覆盖)的反应,负磁异常为矿体向下延伸以及向斜的核部区域。综合高精度磁测和EH4大地电磁测成果表明,区内岩层形态为向斜构造,矿体赋存于该向斜内。结合综合物探方法和地质工程,建立了矿区地质-地球物理模型。该模型对探讨沉积变质型铁矿床成因以及寻找矿区外围和区域上同类型矿床具有一定的借鉴意义。同时,矿区内潜水位埋藏不深,对物探结果进行解析时应综合考虑地下水富集和热液活动带来的多金属化学晕及硫化物富集等原因。本次研究发现该区矿体分布形态复杂,局部地段造成磁异常很弱,甚至磁异常不明显,因此,在后续工作中或者寻找同类型矿体时,可利用密度差异、投入重力测量确定位置。
The Liberian iron ore deposit,is a typical sedimentary magnetite deposit,located in the Archean metallogenic area of the Man Earth Shield in the southern part of the West African Craton.High precision magnetic survey,EH4 magnetotelluric sounding and drilling verification are used to carry out geological exploration and research on the selected iron ore body in the study area.It is inferred that the magnetic anomaly is related to the exposed surface or shallow ore body based on the high-precision magnetic survey results.And then the EH4 magnetotelluric sounding results are used to analyze the magnetic anomaly to infer the favorable metallogenic area,which is verified successfully by drilling.The geological geophysical model of the study area is established in combination with the geological background,geophysical results and drilling.The results show that the magnetic anomalies in this area basically show the obvious characteristics of positive negative positive magnetic anomaly zoning.Through drilling verification,the positive magnetic anomaly is the response of the surface outcrop(or certain coverage),and the negative magnetic anomaly is the downward extension of the ore body and the core area of the syncline.The magnetic anomaly in this area basically presents the obvious characteristics of positive magnetic-negative magnetic-positive magnetic anomaly zoning.Through drilling verification,the positive magnetic anomaly is the response of the surface outcrop(or certain coverage),and the negative magnetic anomaly is the downward extension of the ore body and the core area of the syncline.The comprehensive high-precision magnetic survey and EH4 magnetotelluric survey results show that the rock formation in the area is a syncline structure,and the ore body occurs in the syncline.The geological geophysical model of the study area is established combined with comprehensive geophysical methods and geological engineering.This model has certain reference significance for discussing the genesis of sedimentary metamorphic iron deposits and searching for the same type of deposits in the periphery and region of the mining area.At the same time,the groundwater level in the study area is not deeply buried,and the reasons such as groundwater enrichment,polymetallic chemical halo and sulfide enrichment caused by hydrothermal activities should be comprehensively considered when analyzing the geophysical prospecting results.According to this study,it is found that the distribution of ore bodies in this area is complex,and the magnetic anomaly is weak or even not obvious in some sections.Therefore,in the subsequent work or in the search for the same type of ore bodies,the density difference and gravity measurement can be used to determine the location.
作者
张俊
刘振超
吴迪
邢贤阳
张苗苗
ZHANG Jun;LIU Zhenchao;WU Di;XING Xianyang;ZHANG Miaomiao(No.2 Institute of Geological&Mineral Resources Survey of Henan,Zhengzhou 450001,China)
出处
《中国矿业》
2023年第4期154-161,共8页
China Mining Magazine
基金
中央企业“一带一路”投资项目资助(编号:2013-79)。