安庆铜矿床典型矽卡岩矿物形成过程数值模拟

Numerical simulation of formation process of typical skarn minerals in Anqing copper deposit

安庆铜矿床位于长江中下游成矿带内安庆-贵池矿集区,为典型的矽卡岩型矿床。为了更好地理解安庆铜铁矿床矽卡岩成因及矽卡岩成岩过程对后续成矿的影响,文章基于矿区地质条件、矿物学特征和矿床学相关研究成果,利用数值模拟方法开展定量化研究。模拟结果验证了安庆矽卡岩型矿床是以双交代作用为主形成的。其中,Mg来自碳酸盐岩地层,主要从外带向内带方向迁移,因此外接触带相对富集透辉石。而侵入体中的含Fe热液则从岩体向碳酸盐岩一侧扩散,因此内接触带相对富集石榴石。岩体一侧形成的矽卡岩孔隙度较碳酸盐岩地层大,从而使得更多的含矿热液进入孔隙通道中,继续形成矽卡岩矿物;另一方面,岩体一侧的矽卡岩隔离了含矿热液与碳酸盐岩的直接接触,使得含Fe热液保持一定的活性,有利于后期磁铁矿的形成。同时,这种矽卡岩正反馈的结果为后期磁铁矿的形成提供了一个有利的场地。模拟结果可以提高对安庆铜铁矿床矽卡岩成岩过程的理解。

Anqing copper deposit is located in Anqing-Guichi mineralization zone in the middle and lower reaches of the Yangtze River. It is a typical skarn type deposit. In order to better understand the genesis of skarn in Anqing copper-iron deposit and the influence of skarn diagenesis on subsequent mineralization, the geological features, mineralogical features and diagenetic geochemical processes of this area are considered by computer simulation. The simulation results show that the skarn deposits in Anqing are mainly formed by bimetasomatism. Among them, Mg comes from carbonate strata and migrates mainly from outer belt to inner belt, so the outer contact zone is relatively rich in diopside. The Fe-bearing hydrothermal solution in the intruder diffuses from the rock mass to the carbonate rock side, so the inner contact zone is relatively rich in garnet. The porosity of the skarn formed on the side of the rock mass is larger than that of the carbonate formation, so more hydrothermal fluid enters the pore channels and continues to form skarn. On the other hand, the skarn on the side of the rock mass isolates the direct contact between the hydrothermal solution and carbonate rocks, thus the hydrothermal fluid maintains a certain activity and flows to the far reaction front of the carbonate rocks and continues to form skarn. At the same time, the results of positive feedback of skarn provide a favorable site for the formation of magnetite. These results can improve the understanding of skarn diagenesis in Anqing copper-iron deposit.