闽中裂谷块状硫化物型铅锌矿床的地质特征及找矿意义

The Geological Characteristics of the Massive Sulfide Pb-Zn Mineral Deposits in the Central Fujian Rift and Its Implications for Deposit Exploration

中—新元古代闽中地区铅锌多金属矿床形成的古构造环境、主要矿床地质特征及矿床成因研究是了解华夏古陆前寒武纪构造成矿演化及进一步找矿的关键。地层层序及岩相学研究表明闽中地区马面山群东岩组并不是一次火山旋回的产物,而是经历了至少3期双峰式火山作用。地球化学研究表明赋矿地层东岩组的原岩属海相细碧—石英角斑质火山岩系,形成于中—新元古代的大陆裂谷环境。典型矿床地质研究表明闽中地区在新元古代形成海底火山喷流沉积块状硫化物铅锌矿床(或矿胚层),燕山晚期受到了强烈的构造及岩浆热液的叠加改造,并形成一定规模的矿床。在此基础上初步探讨了中—新元古代古裂谷环境与块状硫化物矿床形成的成因联系。根据闽中地区铅锌矿床的主要特征、找矿方法的分析,总结了该类矿床的找矿标志,并对该区的找矿前景进行了初步分析。

Investigations on the paleo-tectonic setting, major characteristics and origin of deposits in central Fujian Province are key parts to a better understanding of the Precambrian tectono-magmatic evolution and further ore explorations in the Cathaysia Block. The stratigraphic sequence and petrography indicate that the Dongyan Formation of the Mamianshan Group underwent at least three generations of bimodal volcanism instead of the result of one period of volcanism. Geochemical analysis suggests that the protoliths of the Dongyan Formation, host strata of the major deposits, were marine spilite-quartz keratophyre series, which resulted from the continental rifting during the Meso-Neoproterozoic. Detailed analyses on the typical deposits reveal that the massive sulfide deposits or mineralization embryos were formed by seafloor volcanic exhalation in Neoproterozoic. These deposits underwent tectonic deformation and magmatic-hydrothermal superposition in later Mesozoic and led the formation of some deposits. Based on the research mentioned above, the relationships between the origin of the massive sulfide deposits and the Meso-Neoproterozoic rifting tectonic settings are discussed. The geologic features and markers which could be used as clues for deposit exploration have been summarized and the favorable prospecting regions are discussed.