关于密西西比河谷型(MVT)铅锌矿床的一些探讨

密西西比河谷型(MVT)铅锌矿床是全球最重要的铅锌矿床类型之一,由于其储量大、开发早,在成矿规律研究等方面均取得了重要进展,如成矿物质来源、成矿流体的驱动机制、成矿金属的迁移机制和沉淀富集机制、成矿时代、成矿模式等。文章在总结前人研究成果的基础上,主要从含矿建造和区域盆地卤水活动两个方面对MVT矿床的成矿规律进行了系统的总结和综合研究,厘定了MVT矿床的含矿建造,主要包括特定的含矿岩性组合、盆地中的红层、生烃层等,分析了区域盆地卤水活动对MVT矿床的制约,主要包括区域白云石化与MVT铅锌矿床的空间分布关系、与MVT铅锌矿床常伴生的其他类型矿床,并对MVT铅锌矿床的成因进行了初步的探讨。最后,认为特定的岩性组合(特别是砂岩、碳酸盐岩、泥页岩组合)、含矿岩系下部碎屑岩的褪色蚀变、区域红层盆地的广泛发育、生烃盆地的边缘、区域白云石化的前锋地带等,是MVT矿床及其伴生矿床找矿勘探的重要参考依据。

A tentative discussion on Mississippi Valley-type deposits

Mississippi Valley-type (MVT) Zn-Pb deposits constitute one of the most important types of Zn-Pb deposits in the world, characterized by large reserves and early exploitation. Significant progress has been made in the study of mineralization regularities of MVT deposits, such as source of ore-forming materials, expulsion of ore-forming fluids, migration and precipitation mechanism of ore-forming metals, ore-forming ages and metallogenic model. On the basis of comprehensive summarization and review of achievements already made, this paper systematically summarizes the mineralization regularity of MVT deposits in two aspects: ore-bearing formations and regional basin brines. The ore-bearing formations of MVT deposits were determined, which mainly consist of mineral-bearing lithologic association, red-bed basin and hydrocarbon formation. The constraints from regional basin brines were analyzed, which include the relationship between regional dolomitization and the mineralization regularity of MVT deposits and the other types of deposits associated with MVT Zn-Pb deposits. The origin of MVT Zn-Pb deposits was also preliminarily discussed. It is held that the specific ore-bearing formations (especially the combination of sandstone, carbonatite and mudstone or shale), the decoloration of clastic rocks below ore-bearing formations, the extensive development of red-bed basins, the margin of the hydrocarbon basin and the front of regional dolomitization are important references for the prospecting and exploration of MVT and associated deposits.