江西大吉山钨多金属矿床流体包裹体研究

大吉山钨矿床是赣南地区的一个大型钨多金属矿床,由石英脉型钨矿体和花岗岩浸染型钨、钽、铌、铍矿体构成.在详细的岩相学观察的基础上,文章采用“流体包裹体组合”法,对石英脉型矿体和花岗岩浸染型矿体石英中的流体包裹体进行了显微测温和拉曼探针分析.研究表明,与石英脉型矿体成矿相关的流体为中-高温、中-低盐度的NaCl-H2O-CO2-CH4±N2体系,与花岗岩浸染型矿体成矿相关的流体为高温、中-低盐度的NaCl-H2O±CO2±CH4体系,两者流体的性质不同.笔者认为,在流体体系冷却过程中,所发生的以CO2逸失为特征的流体不混溶作用是石英脉型矿体的主要形成机制,而花岗岩浸染型矿体中金属元素的沉淀则主要由流体体系的冷却作用所致,这两类矿体的成矿流体的来源可能不同.

Fluid inclusion studies of Dajishan tungsten deposit in Jiangxi Province

The Dajishan tungsten deposit, a large W-polymetallic deposit in southern Jiangxi Province, consists of quartz-vein type ore bodies and granite-disseminated type ore bodies. Based on detailed petrographic observations and using the means of Fluid Inclusion Assemblage (FIA), the authors carried out microthermometric and Raman microspectroscopic studies of fluid inclusions in quartz vein type and granite disseminated type ore bodies in the Dajishan tungsten deposit. The results show that the quartz vein-type ore mineralization was related to mesothermal-hypothermal fluids of the NaCl-H₂O-CO₂-CH₄±N₂ system with low salinities, while granite-disseminated mineralization was related to hypothermal fluids of the NaCl-H₂O±CO₂±CH₄ system with mid-low salinities, suggesting that the properties of these two ore-forming fluids were different. The characteristics of fluid inclusions in the Dajishan tungsten deposit indicate that the fluid immiscibility caused by CO₂ escaping possibly led to the precipitation of metals in the quartz-vein type ore body during the cooling process of the fluid system, and the cooling of the fluid led to the precipitation of metals in the granite disseminated type ore body. The sources of ore-forming fluids for the two types of ore bodies were probably different.