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安庆铜铁矿床系长江中下游铁铜成矿带中一典型矽卡岩型矿床。矿体产于月山岩体与下三叠统南陵湖组碳酸盐岩之间的接触带,外接触带矽卡岩中透辉石富集,以铁铜矿化为主;内接触带矽卡岩中石榴子石富集,以铜矿化为主。岩相学研究表明研究区含铜矽卡岩演化经历了矽卡岩期和热液蚀变期,其中,矽卡岩期包括早期矽卡岩阶段、磁铁矿阶段和晚期矽卡岩阶段;热液蚀变期包括早期热液交代阶段、石英-硫化物阶段和石英-碳酸盐阶段。大规模的黄铜矿化发生于石英-硫化物阶段。矿物学研究表明,石榴子石均为钙铁榴石,早期矽卡岩阶段的粒状石榴子石发育韵律环带,其FeO和Al2O3含量表现为振荡变化。与粒状石榴子石相比,晚期矽卡岩阶段脉状石榴子石的And组分更高。早期矽卡岩阶段的粒状辉石为透辉石,具有环带结构,由核部到边部MgO含量减少,FeO含量增加;晚期矽卡岩阶段的脉状辉石为钙铁辉石。空间上,从外接触带到内接触带,辉石的MgO含量与石榴子石的Al2O3含量分别减少,而FeO含量均分别增加。岩相学、矿物学,结合已有地球化学研究成果综合表明,安庆铜铁矿矽卡岩为岩浆热液接触交代成因,Mg来自碳酸盐岩,由外带向内带迁移;Fe来自岩浆热液,由内带向外带迁移,由于磁铁矿阶段的温压条件改变,Fe在外接触带以磁铁矿的形式沉淀富集。
The Anqing copper-iron deposit is a typical skarn-type deposit in the Fe-Cu metallogenic belt in the middle and lower reaches of the Yangtze River. The ore body is produced in the contact zone between the Yueshan pluton and the carbonate rocks of the Lower Triassic Nanlinghu Formation and enriched in diopside in the outer contact skarns, mainly by iron-copper mineralization. The inner contact zone Skarn garnet in skarn enrichment, dominated by copper mineralization. The study of petrography shows that the evolution of copper-bearing skarn in the study area experienced skarn and hydrothermal alteration stages. The skarn period includes early skarn stage, magnetite stage and late skarn stage. The hydrothermal alteration phase includes the early hydrothermal stage, quartz-sulphide stage and quartz-carbonate stage. Large-scale chalcopyrite occurs during the quartz-sulphide stage. Mineralogical studies show that the garnet are all calcareous garnets. The early stage skarn parenchyma garnet developed rhythmic zone, and the contents of FeO and Al2O3 showed oscillatory changes. Compared with the granular garnet, the And component of vein-like garnet in the late skarn stage is higher. In the early skarn stage, the particulate pyroxene is diopside with an annulus structure. The MgO content decreases from the core to the periphery and the content of FeO increases. The pyroxene in the late skarn stage is the calcium-iron pyroxene. Spatially, the MgO content of pyroxene and the Al2O3 content of garnet decrease from the outer contact zone to the inner contact zone respectively, while the content of FeO increases respectively. Petrography and mineralogy, combined with the existing geochemical research results show that the Anqing copper-iron skarn is formed by magmatic hydrothermal contact metasomatism. Mg comes from carbonate rocks and migrates from the outer zone to the inner zone. Fe is derived from magma Hydrothermal fluid migrates from the inner zone to the outer zone. As the temperature and pressure conditions of the magnetite stage change, Fe is precipitated and enriched as magnetite in the outer contact zone.