贵州铅锌矿的地球化学特征

Geochemistry of Pb-Zn Mineralization in Guizhou

贵州铅锌矿的分布受断控盆地的控制,主要铅锌矿带沿断控盆地边缘分布,盆地的充填序列—层序对铅锌矿的分布和矿床的地球化学特征有明显的制约作用。由此可在贵州划出索克上部含矿层等多个铅锌矿的含矿层序。同一含矿层序的铅锌矿即使相距很远,其地球化学特征也颇为相似:不同含矿层序的铅锌矿即使近在咫尺,其地球化学特征也迥然不同,表明不同含矿层序有不同矿质来源。根据对矿石铅和岩石中微量铅(岩铅)铅同位素组成特征,以及地层中Pb、Zn等元素背景含量的研究,各含矿层序的矿质主要来源于层序下部的细碎屑岩,个别亦可能来自上下层序紧邻层位的细碎屑岩。铅同位素研究还表明黔东铅锌成矿带形成在加里东晚期,黔西北铅锌成矿区形成在印支期之后。 对铅同位素和稳定同位素地球化学特征的研究表明,贵州铅锌矿多属盆源热液矿床,硫主要来源于含矿层序中的硫酸盐,在成矿过程中存在两种热液:盆源热液和下渗热液,成矿和它们的掺混有一定关系。硫同位素研究还揭示了成矿过程中的pH值变化和成矿体系对硫酸盐的开放程度。

Distribution of the Pb-Zn mineralization in Guizhou were controlled by faultbounded basins. The main metallogenic belts distribut along the margin of the fault-bounded basin-s. The distribution and the geochemistry of Pb-Zn mineralization are distinctly constrained by the sequence filling basins. Some ore-bearing sequences, such as the upper Sauk Sequence has been dividec. Geochemistry of the Pb-Zn mineralization are similar in the same ore-bearing sequence, even if they are far from each other; they are prominently unlike in different ore-bearing sequqence, even thouth they are neighbouring, suggesting diiterent source of ore-forming material in different ore-bearing sequence. According to the study of Pb-isotope composition of the Pb ores and the Pb in rocks and the background value of Pb and Zn in Strata, a conclusion can be come to that the ore-forming material of each ore-bearing sequence derived mainly from the fine clastic rocks of the lower part of this sequence ,and only a few from the one of adjacent part of the upper of lower sequence. Also, the study of Pb-isotope suggests that the Pb-Zn metallogenic belt in East Guizhou formed in late Caledonian and the Pb-Zn metallogenic province in Northwest Guizhou formed after Indo-Sinian. The study of geochemistry of Pb-isotope and stable isotope indicates that the most of Pb-Zn deposits in Guizhou formde by brine, with a doination of S coming mainly from sul-fate in ore-bearing sequences, derived from basin . In the minerogenetic process, there were two types of hydrothermal solution: the brine derived from basin and the seeping-down-ward hydrothermal solution. And the Pb-Zn mineralization is related to their mixing in a degree. The study for S- isotope reveals the change of the pH and the opening level of the metallogenetic system to salfate in the ore-forming process.