内蒙古大井铜锡多金属矿床金属硫化物共生体成因分析

Genetic Analysis of Sulfides Intergrowths in the Dajing Tin and Copper Polymetallic Deposit

内蒙古大井矿床为北方较为著名的多金属矿床,发育锡石和多种硫化物矿石。其中,黄铜矿、闪锌矿及磁黄铁矿相互规则交生,形成共生体,如闪锌矿中磁黄铁矿和黄铜矿共生体,黄铜矿中闪锌矿共生体。根据成矿阶段的划分,黄铜矿形成晚于闪锌矿和方铅矿。显微镜观察及能谱分析表明,共生体成因复杂,为出溶作用和交代作用叠加。受晚期富铜流体的温度等因素影响,较早闪锌矿中Fe富集出溶形成磁黄铁矿。在闪锌矿边界新流体交代闪锌矿,形成黄铜矿共生体,同时在叠加部位局部发生Zn的活化和过饱和并在在黄铜矿晶体边界的有利部位形成雪花状和星状的闪锌矿共生体。本次研究对详细解释硫化物共生体形成机制提供很好的理论和实例证据,对查明矿物生成顺序和揭示成矿作用过程具有重要指示意义。

The Dajing polymetallic deposit, which comprises cassiterite and a variety of sulfide ores, is a well-known multi-metal deposit. Chalcopyrite, sphalerite and pyrrhotite intergrow with each other regularly, e.g. the pyrrho- tite and the chalcopyrite intergrow in the sphalerite, and the sphalerite intergrows in the chalcopyrite. The petro- logical ohservations indicated that the chalcopyrite formed later than the sphalerite and the galena did. On the basis of microscopy studies and energy spectra analyses, the authors believed that the sulfides intergrowth is genetically resulted from both exsolution and metasomatism. Pyrrhotite was separated from the earlier Fe-rich sphalerite under the influence of the late copper-rich fluid. On the sphalerite boundary, the new fluid metasomatized sphalerite and the chalcopyrite intergrowed in the sphalerite. Meanwhile, zinc was activated and supersaturated in some super- posed parts to form the snow-like and star-like sphalerite interqrouths in the favorable positions of the ehalcopyrite boundary. This study provided both good theoretical and good empirical evidences in uncovering the sulfides inter- growth formation mechanism, which is significant in identifying the mineral sequence and in revealing the process of mineralization.