闽东北地区金银矿床的水系沉积物地球化学特征

闽东北地区位于政和—大埔断裂带东侧。在晚侏罗世—早白垩世,该地区经历了十分强烈的火山活动,形成了分布广泛、厚度巨大的陆相火山沉积岩系,其下伏基底地层中的迪口组与福建省金矿或矿化关系极为密切,是福建省重要的含金矿源层,有较好的成矿条件。水系沉积物异常重现性试验及元素的表生迁移研究表明,不同采样批次、不同季节、不同年份在相同采样介质和采样点获得的主要成矿元素异常重现性较好。与全国水系沉积物元素平均含量相比,Au、Ag、Pb、Zn异常较明显。水系沉积物元素异常统计揭示,Au、Ag、As、Sb的成矿能力评价最高。这种元素异常组合表明,与火山岩有关的金矿是本区最有利的成矿矿种,并在闽东北地区经钻探验证,取得了良好的找矿效果。

Geochemical characteristics of stream sediments around Au-Ag deposit in Northeast Fujian

Northeast Fujian is located on the east side of the Zhenghe-Dapu deep fault zone. During late Jurassic to early Cretaceous, the area suffered intense volcanic activities, thick and widely distributed continental volcanic sedimentary sequences were formed. The Dikou Formation, as one of the underlying basement of the volcanic sedimentary sequences, was of fine ore mineralization condition and closely related to the gold deposit mineralization in the province. The pretest for stream sediment survey and research for supergene transportation of ore-forming elements showed that the main ore-forming elements in samples collected from different sampling batches, seasons and years were of good reproducibility of geochemical anomalies. Compared to the nationwide average values of elements in stream sediments in China, the contents of Au, Ag, Pb, Zn had obviously positive anomalies. Statistics of element anomalies in stream sediments revealed that Au, Ag, As and Sb were of best directing property for potential deposit or mineralization. The characteristic association of pathfinder elements implied that gold deposit related with volcanic rock would be the most potential mineralization type in Northeast Fujian, and indeed, the stream sediment survey using these elements as geochemical indicator were applied and obtained good prospecting result verified by drilling in Northeast Fujian.