江西银山矿伊利石化过程中围岩化学成分变化及其成矿意义

CHANGES IN CHEMICAL COMPOSITION OF WALL ROCKS IN THE PROCESS OF ILLITIZATION AND THEIR SIGNIFICANCE TO MINERALIZATIONS IN YINSHAN DEPOSIT,JIANGXI PROVINCE

江西银山热液多金属矿床矿体围岩发生了强烈的伊利石化,研究这些伊利石化是认识本矿床成矿作用的关键之一。通过伊利石的化学成分和矿体围岩蚀变前后的化学成分比较等方面的研究,本文得出以下认识:银山矿矿体围岩千枚岩、英安质流纹岩和中酸性次火山岩都发生了强烈的伊利石化,矿石与蚀变千枚岩中伊利石的化学成分最为相近。银山矿矿体蚀变围岩的化学成分以K2O的含量较高、Na2O和CaO的含量都很低(平均值都在0.11%左右)为特征,矿体围岩在伊利石化过程中Ca和Na被大量带出。综合各方面的证据推测,引起强烈伊利石化的热液是以H2O+CO2为主要组份的氧化性火山-次火山热液。

The wall-rocks adjacent to ore-bodies underwent illitization in the Yinshan hydrothermal poly-metallic deposit in Jiangxi Province, hence study on illitization becomes a key to understanding the mineralization in the deposit. Based on analysis of the chemical composition of illites and altered wall-rocks adjacent to ore-bodies as well as unaltered （or weakly-altered） wall-rocks in the Yinshan deposit, it was pointed out in the study that the phyllite, dacite rhyolite and intermediate-acidic volcanic rocks were intensely altered due to massive illitization. The chemical composition of illites in the ores is very similar to that in altered phyllites. The chemical composition of altered wall-rocks adjacent to ore-bodies are enriched in K2O but depleted in Na2O and CaO, with the mean values for CaO and Na2O being both close to 0.11%. These features imply that Ca and Na in the wall-rocks adjacent to ore-bodies have been massively carried away in the process of illitization. Based on other evidences, it is also concluded in the paper that hydrothermal solution resulting in illitization is mainly comprised of H2O ＋ CO, and is a kind of oxidizing volcanic-subvolcanic hydrothermal solution.