云南普朗斑岩铜矿床热液蚀变及脉体系统研究

Study on the Hydrothermal Alteration and Vein Systems of the Pulang Porphyry Copper Deposit in Yunnan Province

云南普朗超大型斑岩铜矿床位于西南三江成矿带中段,形成于岛弧构造环境,是印支期甘孜-理塘洋壳向西俯冲于格咱-中甸微陆块之下,并引发大规模岩浆-成矿作用的结果。本文通过对矿区围岩蚀变及脉体系统的调查和大量的镜下薄片鉴定研究,总结首采区与外围的蚀变分带及脉体特征。结果表明,首采区的围岩蚀变从岩体由内向外,依次为钾硅酸盐化带-绢英岩化带-青磐岩化带-角岩化带,泥化和碳酸盐化多叠加于其它蚀变带之上,不形成独立蚀变带,铜矿化主要发育于钾硅酸盐化带中,以浸染状矿化为主,含矿岩体为石英二长斑岩。北部及东部外围的钾硅酸盐化带缺失或微弱,主要发育绢英岩化带-青磐岩化带-角岩化带-碳酸盐化带,铜矿化多发育于绢英岩化带中,以脉状矿化为主,含矿岩体为石英二长斑岩及闪长玢岩。首采区与外围的脉体系统具多期次-多类型特征,在A、B、D三大类型脉中,前二者对成矿的贡献大。矿区蚀变特征总体与"二长岩"模式相符合,并与国内西藏玉龙、驱龙、多龙及多不杂等斑岩型铜矿床相似。

The Pulang porphyry copper mine is a super-large porphyry copper deposit located in the middle of the Sanjiang area,which was formed in an island arc tectonic environment,and resulted from the subduction of the Ganzi-Litang oceanic crust to the west beneath the Geza-Zhongdian micro land- mass in the Indo-Chinese epoch that caused massive lava magmatic-mineralization. This work built on an analysis of existing data,detailed investigations of alteration of surrounding rock and vein systems as well as a great amount of thin-sheet identification under microscope observations. Then it summarized the alteration zoning and the eharaeteristics of veins system of the mining area. The results show that the alteration zoning of the Pulang porphyry copper depos- it in the primary mining area are successively the K-silicate zone,the quartz-serieite zone,the propylitie zone and hornfels zone from the inner to outside. Mudding and carbonation have no independent alteration belts,often superimposed on other alteration belts. The Cu mineralization is mainly disseminated and the disseminated ore-body mainly formed in the K-silicate zone. The ore-bearing rock mass is quartz-monzonite porphyry. In the peripheral of the pri- mary mining area east and north of the K-silicate zone,the concentric alteration zones from the inner to outside are the quartz-serieite zone-the propylitic zone-Hornfels zone,with the Cu mineralization mainly in big veins, quartz-sericite zones. The ore-bearing rock mass is quartz-monzonite porphyry and quartz diorite porphyrite. The vein system of the primary mining area and its periphery are of the multi-stages-multi-type. The A-and B-type veins have the greatest contribution to the mineralization. The alteration features of the Pulang mining area are consistent with the＂ monzanite＂ model, and similar to the porphyry, copper deposits in Yulong, Qulong,Duolong and Duobuza of Tibet.