胶东大邓格金—多金属矿床热液蚀变过程中的元素迁移

Element Migration during the Period of Hydrothermal Alteration of Dadengge Gold—Polymetallic Deposit in Jiaodong Area

摘要:

为探讨胶东大邓格金—多金属矿床热液蚀变过程中元素的迁移规律及其与矿化的关系，本文对不同蚀变程度的赋矿围岩和矿体进行了岩石地球化学分析，采用元素迁移质量平衡计算方法（Isocon），以Al2O3作为不活动组分进行了质量平衡计算。研究表明：从远矿围岩到近矿围岩主要发育绢英岩化蚀变，Mg、Na、Ti、P、Ca、Zn、Ni、Pb、Be、Sr、Th、U、Zr、Li、V、Nb、Ga、Ta、Sc、Hf、REE（除La、Ce、Pr）等元素迁入，Si、K、Cu、Cr、Co等元素迁出，Fe、Mn、Rb平均含量基本不变；从近矿围岩到矿体主要发育黄铁绢英岩化蚀变，Fe、Na、Mn、Ti、Mg、Cu、Zn、Sr、V、Sc、Zr、Co、REE等元素迁入，K、Ni、Pb、Be、Li、Rb、Cs、Th、U、Cr、Nb、Ta等元素迁出，Si、Al、P、Ca、Ga、Hf平均含量基本不变。Cu、Zn等成矿元素在绢英岩化过程中被活化进入成矿流体中，在黄铁绢英岩化过程中沉淀，形成黄铁矿、黄铜矿、闪锌矿等硫化物。受古太平洋板片俯冲后撤的影响，胶东地区在中生代发生了大规模的岩浆活动和强烈的地壳隆升，所产生的热隆伸展构造为该区大规模成矿提供了有利条件在围岩蚀变过程中，Au可能以［Au(HS)2］络合物的形式进行迁移。伴随着热液蚀变过程中成矿流体的不断演化，氧逸度降低，体系处于还原环境，大量与金矿化相关的硫化物（黄铁矿、黄铜矿、闪锌矿等）伴随金沉淀富集成矿。

Abstract:

In order to study the law of element migration and its relationship with mineralization in the hydrothermal alteration process of Dadengge gold polymetallic deposit in Jiaodong area, the rock geochemical analysis of orebearing surrounding rocks and orebodies with different degrees of alteration have been analyzed in this paper. The element migration mass balance calculation method (Isocon) is used to calculate the mass balance with Al2O3 as an inactive component. It is showed that sericite alteration mainly developed from the distant surrounding rock to the near ore surrounding rock. Mg, Na, Ti, P, Ca, Zn, Ni, Pb, Be, Sr, Th, U, Zr, Li, V, Nb, Ga, Ta, Sc, Hf, REE (except La, Ce, Pr) and other elements migrated in, while Si, K, Cu, Cr, Co and other elements moved out.The average content of Fe, Mn, Rb is basically unchanged. Pyrite sericite alteration is mainly developed from near ore surrounding rock to the ore body. Fe, Na, Mn, Ti, Mg, Cu, Zn, Sr, V, Sc, Zr, Co, REE and other elements moved in, while K, Ni, Pb, Be, Li, Rb, Cs, Th, U, Cr, Nb, Ta and other elements migrated out. The average content of Si, Al, P, Ca, Ga, Hf and other elements is basically unchanged. Oreforming elements, such as Cu and Zn are activated into the oreforming fluidf during sericitization and precipitated in the process of pyrite sericitization to form pyrite, chalcopyrite and sphalerite. Affected by the subduction and retreat of the ancient Pacific plate, largescale magmatic activity and strong crustal uplift occurred in Jiaodong area in Mesozoic. The thermal uplift extensional structure provided favorable conditions for largescale mineralization in this area. During the alteration of surrounding rock, Au may migrate in the form of ［Au(HS)2 ］complexes. Accomapnying with continuous evolution of the mineralizing fluid during hydrothermal alteration, the oxygen escape degree decreases, the system is in a reduced environment, and a large number of sulfides related to gold mineralization (pyrite, chalcopyrite, sphalerite, etc.) are accompanied by gold precipitation of rich integrated ore.