天柱大河边重晶石矿床铅同位素特征及来源探讨

Lead isotope geochemistry and lead source of the Dahebian barite deposits, Guizhou Province

对取自天柱大河边重晶石矿床的重晶石样品和含方铅矿黑色页岩样品进行了铅同位素测定与研究。结果表明,在Zartman铅构造模式图中,重晶石矿石、含方铅矿黑色页岩和黑色页岩有大致相同的铅同位素分布区,均沿上地壳铅演化线分布,表明它们之间具有同源关系;重晶石矿石及其赋矿黑色页岩的铅同位素组成与基底地层的铅同位素组成在Zartman铅构造模式图中具有完全不同的分布范围,表明重晶石矿石中的铅不大可能来源于基底地层;结合重晶石矿石及其赋矿黑色页岩的铅同位素组成在Zartman铅构造模式图和Δγ-Δβ铅来源分类图的分布,天柱大河边重晶石矿床的铅主要具上地壳铅、壳幔混合的俯冲带铅和热水沉积作用铅的混合来源特点,这为天柱大河边重晶石矿床的热水沉积成因提供了铅同位素证据。

The most recent lead isotope data from samples of the Dahebian barite deposits are presented. Most lead isotope data from barite ores, galena-bearing black shales and black shales （host rock） are plotted on or around the extended line of upper crust, indicating an isogenetic origin. On the other hand, obvious isotopic differences between barite ores and Precambrian are observed, suggesting their different sources of lead isotopes. Based on the isotopic characteristics of barites, it can be concluded that the lead source of the Dahebian barite deposits covers the upper crust, the upper crust-mantle mixed subduction zone, and the submarine hydrothermal sediments as well.Therefore, the Pb isotopic characteristics can be taken as an evidence for the submarine hydrothermal exhalative genesis of the Dahebian and Xinhuang barite deposits.