山东旧店金矿成因矿物学研究及其意义

Mineralogy Study and Its Significance of the Origin of Jiudian Gold Deposit in Shandong Province

摘要:

平度旧店金矿床位于华北板块之胶北隆起区内，其赋矿围岩为晚侏罗世玲珑花岗岩，矿床成因为岩浆期后热液裂隙充填石英脉型金矿。据成矿物质沉淀时序可分为Ⅰ黄铁矿化绢英岩化、Ⅱ石英磁黄铁矿中粗粒黄铁矿、Ⅲ石英黄铁矿微细粒黄铁矿、Ⅳ石英多金属硫化物和Ⅴ石英碳酸盐岩等5个成矿阶段，其中Ⅱ，Ⅲ，Ⅳ阶段为金的主要富集成矿阶段。该文在对山东平度旧店金矿床中黄铁矿和石英矿物标型特征研究的基础上，根据成矿阶段，划分出5个时代的黄铁矿，即形成于黄铁绢英岩中的Ⅰ阶段黄铁矿、黄铁矿石英脉中的Ⅱ阶段黄铁矿、石英黄铁矿矿石中的Ⅲ阶段黄铁矿、多金属硫化物矿石中的Ⅳ阶段黄铁矿和产于石英碳酸岩细脉中的Ⅴ阶段黄铁矿。黄铁矿晶形主要为{100}，{210}，{111}单晶形态，{100}+{210}，{100}+{111}和{100}+{210}+{111}的聚形晶态，随着成矿阶段的变化，立方体出现率逐渐减小，五角十二面体、立方体+五角十二面体的聚形晶出现率则逐渐增加，直至晚期成矿阶段又有出现率高的立方体黄铁矿。旧店金矿在石英黄铁矿成矿阶段（Ⅲ阶段）中黄铁矿晶形以{100}+{210}为主，在多金属硫化物成矿阶段（Ⅳ阶段）中，黄铁矿晶形以{100}+{111}和{100}+{210}+{111}聚形为主，而在早期阶段和晚期阶段，黄铁矿晶形简单，以{100}，{210}，{111}单晶为主。对黄铁矿主成分的研究表明，成矿阶段黄铁矿表现为早期亏S、富Fe的特点，在主成矿阶段Ⅲ，Ⅳ阶段中，黄铁矿则表现富S、亏Fe的特点，反映了在多金属硫化物成矿阶段，不仅是金大量沉淀形成的时期，也是载金矿物黄铁矿快速富集沉淀的时期，说明富S、亏Fe的地球化学环境有利于金的沉淀。黄铁矿物理特征及石英标型亦佐证了在多金属硫化物阶段的黄铁矿、石英晶胞参数稍高，说明同波谱段反射率和晶胞参数的变化与金含量有对应关系。

Abstract:

Jiudian gold deposit is located in the North China plate in Jiaobei uplift. Its ore-bearing country rocks are late Jurassic Linglong granite. The origin of this deposit is post magmatic hydrothermal fissure filling quartz vein type gold deposit. According to metallogenic materials, precipitation sequences can be divided into five mineralization stages, such as pyritization-sericite quartz alteration (Ⅰstage), quartz-magnetic pyrite and medium-coarse grained pyrite (Ⅱstage), quartz-pyrite and fine grained pyrite (Ⅲ stage), quartz and multi-metal sulfide (Ⅳ stage) and quartz-carbonate rocks (Ⅴ stage). Among them, Ⅱstage, Ⅲ stage and Ⅳ stage are major gold enrichment and mineralization stages. On the basis of studying standard type characteristics of pyrite and quartz in Jiudian gold deposit in Shandong province, according to the mineralization stages, five generations of pyrite have been divided, they are pyrite of Ⅰstage formed in beresite, pyrite of Ⅱstage formed in pyrite quartz vein, pyrite of Ⅲ stage formed in quartz pyrite, pyrite of Ⅳ stage formed in polymetallic sulfide ores and pyrite of Ⅴ stage formed inquartz carbonate veins. Major pyrite crystal forms are single crystal as {100}, {210}, {111} and combination forms as {100}+{210}, {100}+{111} and {100}+{210}+{111}. Accompanying with changes in the mineralization stage, cube occurrence rate gradually decreases, while occurrence rate of combination forms in pentagonal dodecahedron, cube + pentagonal dodecahedron gradually increased. In late stage of mineralization, cubic pyrite with high occurrence rate occurred. Crystal forms of pyrite in the pyrite quartz mineralization stage (Ⅲ stage) in Jiudian gold deposit are mainly composed of {100}+{210} , while in pyrite polymetallic sulfide mineralization stage (stage IV), crystal forms are minly composed of combination forms as {100}+{111} {100}+{210}+{111}. In the early and late stage, pyrite crystals are very simple. They are mainly composed of single crystal form as {100}, {210}, {111} . Through study on main components of pyrite, it is showed that pyrite mineralization stage perform the charactetistics of loss in S and rich in Fe. In the main metallogenic stage( Ⅲ, Ⅳ stage), pyrite is rich in S and loss in Fe. It reflects that the mineralization stage of polymetallic sulfide is not only the stage of gold enrichment, but also rapid enrichment of pyrite. It is indicated that geochemical environment with rich sulfur and loss of Fe is favorable for the precipitation of gold ore. The physical characteristics of pyrite and quartz scale also show that the parameters of pyrite and quartz are slightly higher in the polymetallic sulfide stage, which indicate that there is a corresponding relationship between the variation of reflectivity and unit cell parameters.