青海大场金矿床地质地球化学找矿模型

Geological and Geochemical Prospecting Model of the Dachang Gold Deposit,Qinghai Province

大场金矿床位于巴颜喀拉造山带北缘西段。矿区内主要赋矿地层为三叠系巴颜喀拉山群砂岩、粉砂岩及炭质板岩。矿体严格受NW向逆冲断裂构造控制,呈带状、透镜状沿NWW向构造破碎带产出,具有波状弯曲、分支复合特征。矿(化)体具有平面上左行右阶、垂向上右行左阶,并向SE方向侧伏的展布规律。硅化、黄铁矿化、毒砂化等蚀变与成矿关系密切。成矿过程可划分为贫矿化石英、金-硫化物-石英、金-辉锑矿-石英、石英-碳酸盐4个阶段。土壤地球化学测量Au、As、Sb 3种元素异常明显,浓集中心突出,带状异常与矿体分布基本吻合。剖面上元素含量变化曲线峰值与矿体位置对应良好。据此建立了大场金矿床地质-地球化学找矿模型,经工程验证,证实其对大场国家级整装勘查区构造蚀变岩型金矿的进一步找矿勘查工作具有重要指导意义。

The Dachang gold deposit is located in the west of the north Bayan Har Orogen.The main orebearing strata is the Triassic Bayan Har Mountain Group,consisting of sandstone,siltite and carbonaceous slate.Orebodies are controlled strictly by the NW thrust faults,and commonly outcropped along NWW structural fracture in strips and lenses.They are characterized by wave-shaped bending and branchingcomplexing.In the plane,they are left-lateral right-step,however dextral left-step in the vertical,with a lateral trending of SE.Ore-related hydrothermal alteration is well developed and dominated by silicification,pyrite and arsenopyrite mineralization with a banded alteration zonation.The ore-forming process can be divided into four stages：barren mineralized quartz stage,gold-sulfide-quartz stage,gold-stibnite-quartz stage and quartz-carbonate stage.In addition,the results of soil geochemical survey for Au,As and Sb show the anomalies are obvious and have a prominent concentration center.The zonal anomalies are mainly coincident with the distribution of the orebodies.On the section,the peaks of content variation trend can also have a good correspondence to the orebodies.Combined with geological and soil geochemical characteristics of the Dachang gold deposit,the authors propose a prospecting model.According to the test,the model can provide the important reference in search of new orebodies for the prospecting work of the tectonic altered rock type gold deposit in Dachang,a national level equipped exploration district.