浙西北漓渚地区与岩浆岩有关铁多金属矿床类型、成矿时代及找矿前景

摘要

The Lizhu iron polymetallic mineralization district is located in the northeastern end of the Qin-Hang metallogenic belt, northwest of the Jiangshan-Shaoxing deep fault. The mineralization is closely related with North-East striking folds, faults, stratums and intrusive rock in this district. Ore deposit types in the district include skarn type, deposition-modification type, magmatic hydrothermal vein type and disseminated-veinlet type. Re-Os model ages of six molybdenite extracts vary in range of 153.9±4.8 Ma to 148.6±2.2 Ma, with the weight average age of 150.7±1.6 Ma (MSWD=1.5), and isochrom age of 149.6±1.8 Ma (MSWD=1.7). The dating result is consistent with the zircon U-Pb age of the Shanxi diorite and the Guangshan granite (150.1±2.6 Ma-147.2±1.7 Ma) within error, indicating that the mineralization took place in Late Jurassic. The intrusion of the plutons and ore mineralization occurred during the transition of compression to extension in the Late Jurassic and lithosphere thinning in the Early Cretaceous. The Lizhu district experienced mainly the NW-SE folding in the Indochina period, subduction in Middle-Late Jurassic, and regional compression-extension shift during the Late Jurassic-Early Cretaceous, whereas the magmatic intrusions and ore mineralization took place in the third stage of the tectonism. Due to the closely spatial and temporal association of ore deposits and the porphyries, more attention should be paid to the porphyry deposit in concealed rocks and dispersed elements in skarn deposit in the future exploration program.%漓渚铁多金属矿区位于钦杭成矿带浙江段的北东端,江山–绍兴深大断裂北西缘,成矿与区内发育的北东向褶皱、断裂、地层及侵入岩密切相关。矿床类型主要为矽卡岩型、沉积–改造型、岩浆热液脉型以及细脉浸染型,构成与岩浆侵入作用有关的成矿系列。对该成矿系列中沉积改造型和岩浆热液脉型矿床中发育的辉钼矿进行 Re-Os 同位素分析,获得模式年龄为153.9±4.8~148.6±2.2 Ma,加权平均值为150.7±1.6 Ma,等时线年龄为149.6±1.8 Ma (MSWD=1.7),与区内栅溪闪长岩类–广山花岗岩类锆石U-Pb年龄150.1±2.6~147.2±1.7 Ma在误差范围内一致,表明成岩成矿时代均为晚侏罗世末期。成岩成矿处于华南地区由晚侏罗世俯冲挤压向早白垩世区域伸展和岩石圈减薄转换的构造背景下；漓渚地区主要经历了印支期NW-SE向的褶皱造山运动、中晚侏罗世俯冲挤压逆冲断裂构造活动以及晚侏罗世–早白垩世区域挤压伸展转换岩浆侵入成矿过程。通过岩浆岩成矿类型研究分析区域成矿和找矿潜力大,今后勘查中应注意在深部隐伏岩体内部斑岩型矿床的寻找,及矽卡岩型矿床中伴生分散元素(In、Ga、Ge等)的综合评价。