(1. 中南大学 有色金属成矿预测与地质环境监测教育部重点实验室，长沙 410083； 2. 湖南省国土资源规划院 国土资源评价与利用湖南省重点实验室，长沙 410007； 3. 贵州省有色金属和核工业地质勘查局，贵阳 550005； 4. 中国科学院 广州地球化学研究所，广州 510640)
摘 要: 通过详细的野外调研和室内鉴定，将土地坪铅锌矿床成矿作用分为3个阶段，即闪锌矿-白云石阶段(Ⅰ)、闪锌矿-方铅矿-重晶石-萤石阶段(Ⅱ)与方铅矿-方解石阶段(Ⅲ)。利用(红外)显微测温和激光拉曼分析，对闪锌矿和伴生脉石矿物(方解石、萤石、重晶石)中的流体包裹体的对比研究显示：成矿流体在Ⅰ、Ⅱ阶段为中-低温、中高盐度、含有一定量CaCl2的NaCl-MgCl2-H2O体系，Ⅲ阶段变为低温、中盐度的NaCl-H2O体系；Ⅰ~Ⅲ阶段，气相成分主要为H2O及还原性组分CH4和H2S，后者含量先增后减。闪锌矿及伴生脉石矿物流体包裹体均表现出流体混合和氧逸度先降后升的特征，暗示两者可能来源于同一流体体系，但前者呈现“演化滞后”现象。Ⅰ、Ⅱ阶段金属矿物沉淀主要与流体混合背景下的硫酸盐热化学还原(TSR)反应有关，Ⅲ阶段金属矿物沉淀还受到大气降水的降温和稀释作用的影响。TSR反应与碳酸盐岩溶蚀的耦合作用是影响该矿床金属矿物沉淀的重要因素。
关键字: 成矿流体；铅锌矿床；土地坪；金属矿物沉淀；硫酸盐热化学还原反应
（1. Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring, Ministry of Education, Central South University, Changsha 410083, China; 2. Hunan Key Laboratory of Land and Resources Evaluation and Utilization, Hunan Planning Institute of Land and Resources, Changsha 410007, China; 3. Non-Ferrous Metals and Nuclear Industry Geological Exploration Bureau of Guizhou, Guiyang 550005, China; 4. Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China）
Abstract:Detailed field investigation and petrological observation on the Tudiping Pb-Zn deposit indicated that the mineralization could be subdivided into three stages: (Ⅰ) sphalerite-dolomite, (Ⅱ) sphalerite-galena-barite-fluorite and (Ⅲ) galena-calcite stages. A comparative investigation was performed on fluid inclusions trapped in sphalerite and coexisting gangue minerals, by (infrared) microthermometry and laser Raman analysis. The results reveal that the ore-forming fluid is a moderate-low temperature, moderate-high salinity NaCl-MgCl2-H2O system with considerable amounts of CaCl2 at stage Ⅰ and Ⅱ, and a low temperature and moderate salinity NaCl-H2O system at stage Ⅲ. The vapor phase composition comprises H2O, CH4 and H2S, and the concentrations of the reductive gas increase from stage Ⅰ to Ⅱ and decrease from stage Ⅱ to Ⅲ. Both fluid inclusions trapped in sphalerite and coexisting gangue minerals are featured by fluid mixing and oxygen fugacity change, indicative of being derived from the same fluid system. However, an evolution delay was found in fluid inclusions trapped in sphalerite. The ore deposition is related to thermochemical sulfate reduction (TSR) under the background of fluid mixing at stages Ⅰ and Ⅱ, and influenced by dilution and cooling resulting from meteoric water at stage Ⅲ. The coupling effect between TSR and carbonate dissolution plays a significant role in the ore deposition mechanism of the Tudiping Pb-Zn deposit.
Key words: ore-forming fluid; lead-zinc deposit; Tudiping; ore deposition; thermochemical sulfate reduction
