地史早期岩石中的铅锌演化——狼山—渣尔泰山中元古代铅锌成矿的物质基础

THE EVOLUTIONS OF LEAD AND ZINC IN THE ROCKS OF THE EARLY EARTH'S HISTORY——ORE-FORMING MATERIAL SOURCE OF THE PROTEROZOIC SEDEX TYPE Pb-Zn DEPOSITS FROM THE LANGSHAN-ZHAERTAISHAN DISTRICT IN INNER MONGOLIA,CHINA.

以中国内蒙古狼山-渣尔泰山中元古代SEDEX型铅-锌成矿带为例,研究了该区从太古代到中元古代地壳岩石的铅锌含量和变化关系以及与成矿的关系.研究发现,从早到晚,岩石SiO2和K2O含量升高,铅含量也与二者同步增加;FeO、MgO、CaO及Na2O含量呈下降趋势,锌含量也同步降低.在太古代时,岩石的Zn/Pb比值一般>8,中元古代时这一比值降低为2～4.矿石的Zn/Pb比值与基底岩石Zn/Pb比值具有很好的一致性.铅锌这种随时间的变化与中元古代铅的暴发性成矿及大规模铅锌共生矿床的形成是同步的,说明基底岩石中的铅和锌是该成矿带SEDEX矿床成矿的物质基础.

As exemplified by the Proterozoic SEDEX-type Pb-Zn mineralizing zone of the Langshan-Zhaertaishan district in Inner Mongolia, this paper presents the Pb and Zn contents of the crustal rocks from Archaean to Middle Proterozoic in age and studies their variation and relationships with mineralization. The results show that the SiO2, K20 and Pb contents of the rocks increased, and the FeO, MgO, CaO, and zinc contents decreased gradually from early to late. Zn/Pb ratios in the Archaean rocks are larger than eight and those in the Middle Proterozoic rocks are 2 - 4. Zn/Pb ratios in ores from some SEDEX type Pb-Zn deposits in North China are consistent with those of the basement rocks of every deposit. The temporal variations of Pb and Zn are synchronous with the extensive mineralization of Pb and the formation of large-scale associated Pb-Zn deposits in the Middle Proterozoic. This indicates that the evolution of Pb and Zn in the basement rocks from early to late provided the ore-forming material for mineralization of the SEDEX-type Pb-Zn deposits in the Langshan-Zhacrtaishan district.