The Yanzigou gold deposit in Danbacounty, Sichuan, is located in the Songpan-Ganzeorogenic belt. The ores can be divided into quartz vein gold ore and layered carbonaceous slate gold ore. Gold mineralization consists of pre-mineralization, main mineralization and post-mineralization periods. The fluid in the Yanzigou gold deposit is acidic and belongs to a CO2-H2O-NaCl system. Fluid inclusions can be divided into two types. Fluid inclusions in pre-mineralization and main metallogenic period have the typical characteristics of orogenic gold metamorphic hydrothermal fluid: medium homogenization temperature, low salinity, low density and high CO2. However, the fluid inclusions of post metallogenic period shows the characteristics of meteoric water, characterized with low homogenization temperature range, low salinity, low density and low CO2. During pre-mineralization and main mineralization periods, gold was mainly transported as [Au(Cl)4]- complex compound and [Au(HS)2]-, respectively. During the transition process from compression to transpression, the P-T conditions of fluids changed greatly, coupled with penetration of meteoric water into tensile fractures, resulting in boiling and mixing of fluids. With increasingof gold-sulfur complex content, and change of physical and chemical conditions such as PH, Eh, fO2, and fS, ore-forming materials started to precipitate and form ore bodies. According to the characteristics of the ore-forming fluids, the Yanzigou gold deposit belongs to orogenic gold deposit.%丹巴燕子沟金矿区在大地位置上处于松潘-甘孜造山带,金矿体分为石英脉型和碳质板岩型,其成矿作用包括成矿前期、主成矿期和成矿期后3个期次.丹巴燕子沟金矿流体属CO2-H2O-NaCl体系,溶液呈酸性,流体包裹体分为两大类,成矿前期和主成矿期流体包裹体具有典型造山型金矿变质热液特点,以均一温度中等、低盐度、低密度、高CO2为特征；成矿期后流体包裹体则具有大气降水的特点,具有均一温度低、低盐度、低密度、低CO2的特征.成矿前期和主成矿期金的主要迁移形式为[Au(Cl)4]-氯络合物,成矿期后以[Au(HS)2]-硫络合物为主,在构造由压扭向张扭转变的过程中,流体温压条件发生较大的变化,加之大气降水沿张性裂隙的渗入,使得流体发生沸腾作用、流体混合作用,硫金络合物含量逐渐升高,pH、Eh、fo2.、fs等物理化学条件发生变化,矿质逐渐沉淀,形成矿体.从流体特征来看,丹巴燕子沟金矿属于造山型金矿床.
展开▼
