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    皖南外桐坑金矿床地质、地球化学特征及找矿模型

    Geological and geochemical characteristics and prospecting model of the Waitongkeng gold deposit in southern Anhui Province

    • 摘要: 外桐坑金矿位于江南造山带东北缘太平断裂褶皱带,是受断裂控制的热液蚀变型金矿床。为进一步分析该矿床的成矿规律,明确找矿方向,提高找矿效果,在开展野外地质调查的基础上,采用土壤地球化学测量、岩石地球化学剖面测量等技术手段开展了地质、地球化学特征及找矿模型研究。土壤地球化学测量结果显示,Au、As异常显著,主要沿NE向次级断裂分布;岩石地球化学剖面测量结果显示,矿区NE向张性次级断裂显著富集Au、As、Ag、Sb,可有效指示金矿化的分布特征。金矿体赋存于志留纪霞乡组中,成矿物质及热源主要来自于燕山期花岗岩岩浆热液,成矿构造为NE向榔桥—里东坑张性断裂,含矿构造为主断裂上盘NE向硅化、毒砂矿化、黄铁矿化、绢云母化蚀变破碎带。依据成矿规律,构建了外桐坑金矿"构造-岩浆岩"成矿体系地质-地球化学找矿预测模型,明确次级断裂破碎带、金砷地球化学异常、绢英岩化蚀变等可作为外桐坑外围金矿找矿标志,指出矿区内破碎蚀变带、矿区深部以及外围沿榔桥—里东坑断裂分布的水系沉积物Au异常区具有较好的找矿前景。

       

      Abstract: The Waitongkeng gold deposit is located in the Taiping fault fold belt on the northeast margin of the Jiangnan Orogenic Belt, belonging to a hydrothermal altered gold deposit controlled by fault. On the basis of field investigation, the authors carried out soil geochemical survey, rock geochemical profile measurement and other technical means to analyze the metallogenic regularity of the mining area, clarified the ore-prospecting direction and improved the prospecting effect. Soil geochemical survey results show significant gold and arsenic anomaly in the soil distributing along the NE-trending secondary faults. The rock profile measurement results reveal that gold, arsenic, silver and antimony are enriched in the NE-trending extensional secondary fault, which effectively indicate the the occurrence and mineralization of gold. The gold ore body is hosted in Silurian Xiaxiang Formation, and the ore-forming material and heat source mainly came from the magmatic hydrothermal fluid of Yanshanian granite. The metallogenic structure of the mining area is the NE-trending Langqiao-Lidongkeng tensional fault, and the main ore-bearing structure is the NE-trending fracture zone with silicification, arsenopyrite, pyrite and sericitization on the hanging wall of the fault. This paper proposed a geological-geochemical prospecting prediction model of "tectonic-magmatic rock" metallogenic system of the Waitongkeng gold deposit according to the metallogenic law. It is considered that the secondary fault fracture zone, gold and arsenic geochemical anomaly as well as silicification-sericitization alteration can be used as prospecting indicators for the surrounding areas of the Waitongkeng gold deposit. The fractured alteration zone, the deep mining area and Au anomalies of stream sediments distributing along the Langqiao-Lidongkeng fault have good prospecting prospects.

       

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