黔西南水银洞卡林型金矿构造地球化学及对隐伏矿找矿的指示

Tectono-geochemistry and Concealed Ores Prospecting in the Shuiyindong Gold Deposit of Southwestern Guizhou

水银洞金矿是黔西南地区目前发现最大的隐伏超大型卡林型矿床。该矿床的发现显示了黔西南地区巨大的深部隐伏矿找矿潜力,同时也对隐伏矿地球化学找矿方法提出了严峻的挑战。为探索黔西南隐伏卡林型金矿的找矿方法,沿水银洞金矿床代表性剖面采集了岩石和方解石脉,并沿主要断裂带采集地表土壤。岩石分析了Au、As、Sb、Hg、Tl和U含量,土壤分析了As、Sb、Tl和U含量,方解石分析了C-O同位素和稀土元素组成。剖面岩石中Au等成矿元素主要沿着背斜轴、中—上二叠统之间的构造蚀变体和逆断层富集。岩石中U元素同样沿构造蚀变体和逆断层富集,但却没有沿着背斜轴富集,可能代表了另一期富U的热液活动。低δ^13C(<−2.3‰)、高δ^18O(>22.1‰)和中稀土富集(ΔMREE>1.89)的方解石主要沿背斜轴和逆断层分布。地表裂隙土壤成矿元素构造地球化学异常与深部隐伏矿体具有高度一致的对应关系。背斜轴及相关的逆断层可能是深部成矿信息到达地表的通道。地表裂隙充填物和裂隙附近的细粒级土壤,能够有效提取深部成矿作用信息,达到直接探寻深部盲矿体的目的。

The Shuiyindong deposit is the largest concealed Carlin-type gold deposit ever discovered in southwestern Guizhou.The discovery of the Shuiyindong deposit indicates a huge potential of deep concealed Carlin-type orebody,and also presents a severe challenge to exploration methods for concealed orebodies in southwestern Guizhou.To investigate the exploration methods for concealed ores,the authors collected rocks and calcite veins in drill holes from a representative section,and soil along surficial fractures/faults in the Shuiyindong mining area.The values of Au,As,Sb,Hg,Tl and U for the rocks,the values of As,Sb,Tl and U for the soil,and the compositions of C-O isotopes and rare earth elements for the calcites were analyzed.Rocks along anticline axis,unconformity between middle-upper Permian and reverse faults display elevated values of Au and other ore-forming elements.Rocks with high U concentration also occur along the unconformity and reverse faults,but not occur along the anticline axis,which may record another U-bearing hydrothermal event.Calcites with low δ^13C(<−2.3‰),high δ^18O(>22.1‰),and high concentrations of middle rare earth elements(ΔMREE>1.89)mainly appear along the anticline axis and reverse faults.There are high corresponding relations of ore-forming elements geochemical anomalies between deep concealed orebodies and soil.The anticline axis and reverse faults possibly acted as the upwelling channel for deep ore-forming information.Fillings in surficial fractures/faults and soil around surficial fractures/faults may contain significant mineralization information and have the potential to be a vital tool for identifying drilling targets.