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内蒙古额济纳旗老硐沟金矿床多因复成成矿作用分析

Analysis of polygenetic composite metallogenesis of Laodonggou Gold Deposit in Ejina Banner, Inner Mongolia

  • 摘要: 老硐沟金矿床位于北山成矿带内蒙古段,主矿体赋存于中元古界蓟县系圆藻山群大理岩和白云质大理岩中,呈似层状、透镜状产出。按产状、矿物成分和氧化程度,矿体类型可分为原生铜金多金属矿体、原生金银铅矿体和溶洞类氧化矿体。在似层状和透镜状矿体围岩中发现了顺层纹层状构造、同生角砾构造、包卷层理构造、软沉积滑动变形构造等典型海底热水沉积构造,提出了老硐沟金矿床中元古代热水沉积成矿作用。老硐沟金矿床叠生改造成矿作用与志留纪岩浆−热液活动有关,具有同位成矿与后生成矿特征。老硐沟金矿床溶洞类氧化矿石的形成是第四纪地下水活动及岩溶作用的结果。老硐沟金矿床为具层控性的多因复成矿床,导电矿物聚集、金矿床形成与大地电场条件存在因果关系。该研究对推动北山成矿带内蒙古段乃至整个北山成矿带元古宙层控型金矿床的找矿工作具有指导意义。

     

    Abstract: The Laodonggou Gold Deposit is located in the Inner Mongolia section of the Beishan mineralization belt. The main ore bodies are hosted in marble and dolomitic marble of the Yuanzaoshan Group of the Jixian System of the Mesoproterozoic Era. They occur in a layered and lens-shaped manner. According to the ore body’s structure, mineral composition, and oxidation degree, the ore types can be classified into primary copper−gold polymetallic ore, primary gold−silver−lead ore, and cave-type oxidized ore. This study discovered typical submarine hot water sedimentary structures such as bedding-parallel laminated structure, syngenetic breccia structure, convolute bedding structure, and soft-sediment sliding deformation structure in the surrounding rocks of the layered and lens-shaped ore bodies. The study proposed the Middle Proterozoic hot water sedimentary mineralization in the Laodonggou Gold Deposit. The superimposed and modified mineralization in the Laodonggou Gold Deposit is related to the Silurian magmatic−hydrothermal activities and has characteristics of isospatial mineralization and epigenetic mineralization. The formation of cave-type oxidized ore in the Laodonggou Gold Deposit is the result of Quaternary groundwater activity and karstification. The Laodonggou Gold Deposit is a stratabound polygenetic compound deposit. The aggregation of conductive minerals and the formation of the gold deposit are causally related to the geoelectric field conditions. This study has significant implications for promoting the exploration work of Proterozoic stratabound gold deposits in the Inner Mongolia section of the Beishan mineralization belt and the entire Beishan metallogenic belt.

     

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