摘要
本文通过对安徽金寨县沙坪沟斑岩钼矿床不同蚀变-矿化带石英脉中的流体包裹体岩相学、显微测温学和显微激光拉曼探针等系统研究,来探讨成矿流体的特征和演化过程.研究结果显示该矿床主要发育三类流体包裹体:气-液两相包裹体(Ⅰ型),富气相包裹体(Ⅱ型),多相包裹体(Ⅲ型).成矿早期硅化带中的石英主要发育Ⅰ型包裹体,均一温度平均为422℃,盐度平均为13.77wt%NaCl.主成矿期钾化带中的石英则主要发育Ⅱ型和Ⅲ型包裹体,其平均均一温度和盐度分别为333℃、4.04wt%NaCl;350℃、41.85wt%NaCl.主成矿期黄铁绢英岩化带石英中也发育Ⅱ型和Ⅲ型包裹体,Ⅱ型包裹体的均一温度平均为296℃,盐度平均为2.91wt%NaCl;Ⅲ型包裹体爆裂温度范围为220℃～315℃,盐度大于32.92wt%～39.34wt%NaCl.而成矿晚期绿泥石化带则发育Ⅰ型包裹体,其均一温度平均为255℃,盐度平均为2.82wt%NaCl.从成矿早期到成矿晚期,成矿流体的均一温度呈下降的趋势.主成矿期钾化带和黄铁绢英岩化带石英脉中富气相包裹体与多相包裹体密切共存,两者的平均均一温度非常相近,但盐度相差很大,表明该阶段成矿流体曾发生过沸腾作用.显微激光拉曼探针分析显示,在沸腾包裹体群中Ⅱ型包裹体含有CO2,而Ⅲ型包裹体仅含极少量或者不含CO2,这表明在流体减压沸腾过程中,可能存在CO2与水的不混溶过程,从而产生含CO2的低盐度Ⅱ型包裹体和贫CO2的高盐度Ⅲ型包裹体两个端员.沸腾作用和CO2的不混溶作用是矿质沉淀的主要机制.成矿早期硅化带石英脉中的流体包裹体含有CO2,主成矿期钾化带以及黄铁绢英岩化带石英脉中的流体包裹体亦含CO2,成矿晚期绿泥石化带石英脉中的流体包裹体中仅含有水蒸汽,这表明了成矿流体经历了从早期富含CO2到晚期仅含有水蒸气的演化过程.
Based on the detailed petrographic, microthermometric and Raman analysis on the fluid inclusions in the quartz veins from the Shapinggou porphyry molybdenum deposit, Jinzhai, Anhui province, we try to constrain the characteristics and evolution of ore-forming fluids. Our results show that three types of fluid inclusions exist： liquid （H2O）-rich fluid inclusions （type I ）, gas-rich fluid inclusions （type II ）, and multiphase fluid inclusions （type III ）. In the silica alteration zone, the average homogenization temperature and salinity of type I fluid inclusion are 422 ℃ and 13.77 wt% NaCl; in the K-feldspar alteration zone, the homogenization temperatures and salinities of types II , III fluid inclusions are 333 ℃ ,350 ℃ and 4.04 wt% NaCl, 41.85 wt% NaCl, respectively; in the pyrite sericite alteration zone, the homogenization temperatures and salinities of type II fluid inclusion are 296 ℃ and 2.91 wt% NaCl, the decrepitation temperature of type III fluid inclusion is among 220 ℃ -315 ℃ and the salinity of type III fluid inclusion is 〉 32.92 - 39.34 wt% NaC1; in the chlorite alteration zone, the homogenization temperature and salinity of type I fluid inclusion is 255 ℃ and 2.82 wt% NaCl, and the homogenization temperature decreased with the time. Types II and III fluid inclusions in the same areas have generally similar homogenization temperatures and distinct salinities, implying boiling ore-forming fluids at this stage. Raman spectra of these assemblage of boiling fluid inclusions indicate CO2 is rich in some types I and II fluid inclusions but rare in type III fluid inclusions, which can be explained that at the time of boiling of ore-forming fluids, CO2 and water are immiscible. Boiling and immiscibility of fluid are very important for mineralization. The fluid inclusions at the early stage contain CO2, and at the ore-forming stage also contain CO2, but at the late stage only contain H2O. Therefore, the ore-forming fluids have experienced a variance from rich in COz at the e
出处
《南京大学学报（自然科学版）》
CSCD
北大核心
2012年第3期240-255,共16页
Journal of Nanjing University（Natural Science）
基金
安徽省公益性地质(科技)项目(2009-19)
关键词
流体包裹体
石英
斑岩钼矿
沙坪沟
安徽
fluid inclusions, quartz
porphyry molybdenum deposit, Shapinggou, Anhui
