沉积盆地中的流体活动及其成矿作用

Basin Fluids and Their Related Ore Deposits

盆地流体是指在沉积盆地演化过程中活动并参与了沉积物的各种成岩－后生变化的复杂流体相，包括来自盆地内部沉积物压实和相变所释放出的流体，以及主要由盆地边缘大陆隆起区补给的下渗大气降水。流体的流动机制主要有重力驱动流和压实驱动流两种。各种沉积有机质的广泛参与，乃是盆地流体区别于其它地壳流体的最基本特征。这对流－岩反应、对盆地流体及其周围环境的物理化学参数、对成矿金属迁移的形式和能力以及对成矿金属的沉淀就位等过程都有着十分重要的影响。盆地流体具典型的低温热液地球化学特性，流体的同位素组成和流体中的溶解组份与沉积物的特征以及沉积体系的空间分布密切相关。盆地流体广泛参与了沉积物的成岩、后生、成油、成气和成矿过程。沉积体系的空间分布（不均匀介质）、同沉积断裂体系、欠压实异常高压地层以及古地形联合控制着盆地流体的流动迁移和汇聚成矿。有关的矿床类型主要包括：沉积喷流型（ｓｅｄｅｘ型）矿床、密西西比式（ＭＶＴ）铅锌矿床、大陆砂页岩型矿床以及沉积岩容矿的微细浸染型金矿床等。

In the present paper, basin fluids refer to extremely complex aqueous solutions which are very active in all the diageneticepigenetic processes of sediments during the evolution of sedimentary basins. They mainly include fluids produced by compaction and phase change of sediments inside the basin as well as meteoric water driven downwards into the sedimentary basin by the gravitational potential along uplifting continental margins adjoining the basin. Basin fluids show typical features of lowtemperature hydrothermal geochemistry, with temperatures mainly ranging 80-150℃. Isotope composition and dissolved compositions of basin fluids are controlled by sediment types (decided by fluidmineral interactions) and their spatial distribution. The contribution of organic matters plays a very impotant role in such aspects as the fluidmineral interaction, the change in physicalchemical parameters of basin fluids themselves and their environments, the dissolution, transport, deposition and oreforming process of metals and the formation of secondary porosity of sedimentary rocks.Basin fluids make a very important contribution to diageneticepigenetic processes of sediments, oilgas production and oreformation in sedimentary basins. Spatial distribution of sediment systems, together with syndepositional faulting systems, uncompacted overpressure systems and paleotopography of sedimentary basins controlled the migration and accumulation of basin fluids and the metals carried in the fluids. Ore deposits genetically related to basin fluids can be classified into four groups, viz. sedex type deposits, MVT leadzinc deposits, continental sandstone type deposits, and sedimenthosted microdisseminated gold deposits.Two examples of deposits in China formed by basin fluids, one belonging to sedex type and the other to sedimenthosted microdisseminated gold deposit, are beiefly discussed in this paper.