广西大厂矿田深部成矿预测及成矿机制研究

A study of deep metallogenic prediction and metallogenic mechanism of the Dachang deposit in Guangxi

大厂矿田作为大型锡多金属矿之一,成矿演化过程复杂,隐伏矿产资源繁多。为了研究大厂矿田笼箱盖岩体外围隐伏矿床的分布位置和成矿机制,对覆盖大厂矿田的音频大地电磁数据进行精细的处理,得到了地下3 km以内的二维电性结构模型。根据电性资料结果,推断了隐伏花岗岩和矿体的位置。花岗岩呈高阻特征,埋深约1.5 km,沿断裂构造成脊状隆起;低阻矿体位于花岗岩顶部中泥盆统地层中,推测矿体发育自底部花岗岩体,表明花岗岩具有明显的控矿作用。根据大厂矿田近铜远锡的分带特点和地表元素异常,以找到矽卡岩型锌铜矿体和锑钨矿床的可能性最大。研究表明,晚白垩世时期,中、下地壳(及少量上地幔)岩浆热液沿NW向基底断裂上涌到地壳浅层泥盆系地层,后经结晶分异与围岩产生成矿作用。

As one of the large tin-polymetallic deposits in the world,the Dachang deposit has complicated metallogenic mechanism and rich hidden mineral resources.In order to detect the distribution and study mineralization mechanism of the concealed deposits around the cage and cover rock in the Dachang ore district,the authors finely processed the audio magnetoelectromagnetic data covering the Dachang ore district,and obtained a two-dimensional electrical structure model within the depth of 3 km.According to the results of resistivity model,the location of concealed granite and orebody was determined.Granite is characterized by high resistance and is buried at a depth of about 1.5 km,with the formation of ridge uplift along the fault structure.The low-resistivity orebody is located in the middle Devonian strata at the top of granite,so it is inferred that the orebody was developed from the granite at the bottom,which indicates that granite has an obvious ore-controlling effect.According to the zonal characteristics of copper in the near place and tin in the distant place as well as anomalies of metallic elements in the Dachang ore district,it is most possible to find skarn type Zn-Cu deposits and Sb-W deposits.The research shows that,in the late Cretaceous period,the magmatic hydrothermal fluids of the middle and lower crust together with a small amount of upper mantle rose to the shallow Devonian strata of the crust along the basement fault in the NW direction,and then formed mineralization with surrounding rocks through crystallization differentiation.