江西武山铜矿床形成过程:来自岩相学和矿物学的证据

江西武山铜矿床是长江中下游地区具有代表性的叠加复合矿床之一。文章选取武山铜矿床典型剖面为研究对象,在野外地质调研和室内岩相学研究的基础上,识别出层状硫化物型、层状矽卡岩型和接触交代矽卡岩型三类矿体,及相对应的3种类型矿石。3类矿石在矿物组合、结构构造和矿物学特征等方面有明显差异,分别显示出原生沉积、叠加改造和岩浆热液成因特征。选择代表性脉石矿物和矿石矿物进行矿物化学研究,认为石榴子石是岩浆期后热液渗滤交代作用的产物,层状矽卡岩中石榴子石相对富Fe,而接触交代矽卡岩中石榴子石相对富Al;矿区内存在2类黄铁矿,即胶状黄铁矿和粒状黄铁矿,分别对应原生沉积成因和岩浆热液交代成因;磁铁矿是与矽卡岩有关的岩浆期后热液交代作用的产物,层状矽卡岩中磁铁矿相对富Mg O和Mn O,贫Al2O3,受地层影响明显,而接触交代矽卡岩中磁铁矿相对富Al2O3,贫Mg O和Mn O,受岩浆岩影响明显。武山铜矿床的形成经历了原生沉积作用、岩浆热液交代作用及叠加改造作用等复杂成矿过程。

Formation process of Wushan copper deposit in Jiangxi Province: Evidence from petrography and mineralogy

The Wushan deposit is a typical overprinting compound copper deposit along the Middle and Lower Yangtze River metallogenic belt. A detailed geological and mineralogical study of this deposit was carried out, with the emphasis placed on the ore-forming process. Geological investigation and petrographic observation indicate the occurrence of stratabound sulfide, stratabound skarn, and contact metasomatic skarn orebodies and the existence of three corresponding types of ores. The three types of ores are obviously different in mineral assemblage, texture and structure, and mineral typomorphy, and display signatures of syn-sedimentary, syn-sedimentary with magmatic hydrothermal, and magmatic hydrothermal activities, respectively. The mineralogical chemistry characteristics indicate that the skarn is a product of infiltration metasomatism. The colloidal pyrite is characterized by primary sedimentary signatures, and the grained pyrite, chalcopyrite, and magnetite by magmatic hydrothermal metasomatic signatures. The magnetite in stratabound skarn has high content of MgO and MnO, and low content of Al₂O₃, whereas the magnetite in contact metasomatic skarn has high content of Al₂O₃ and low content of MgO and MnO. In summary, the Wushan copper deposit might have experienced two mineralization periods and three types of mineralization, i.e., syn-sedimentary mineralization, magmatic hydrothermal mineralization and syn-sedimentary with magmatic hydrothermal mineralization.