黑龙江三道湾子金矿床流体包裹体特征及矿床成因分析

三道湾子金矿床是一个与偏碱性岩有关的含碲化物低硫化浅成低温热液矿床。矿体赋存于侏罗系上统塔木兰沟组中基性、偏碱性粗安岩、粗安质火山角砾岩中。矿石类型主要为贫硫石英脉型,矿石矿物主要由碲金矿、碲金银矿、碲银矿、针碲金银矿和斜方碲金矿等组成。矿区内发育硅化、黄铁矿化、绢云母化、高岭石化、绿泥石化、碳酸盐化和萤石化等矿化蚀变,典型的低硫化型浅成低温热液蚀变组合。流体包裹体的研究表明:石英中主要发育气液二相及少量单液相包裹体,成矿流体属H2O-NaCl体系;包裹体均一温度集中在230～270℃;盐度大多小于3%,密度集中在0.68～0.88 g/cm3,成矿流体属中低温、低盐度、低密度的体系;成矿深度平均为1.73 km,属浅成低温环境;氢、氧同位素分析表明成矿流体δD为-110‰～-85‰,平均-95.8‰,δ18 O水为-14.3‰～-8.7‰,均值为-11.1‰,表明成矿流体主要来自大气降水。根据矿床低硫富碲特点、矿物组合、矿化蚀变组合及流体特征,进一步确定三道湾子金矿床为与偏碱性岩有关的含碲化物低硫化浅成低温热液型金矿床。

Analysis on fluid inclusion characteristics and genesis of Sandaowanzi gold deposit in Heilongjiang

Sandaowanzi gold deposit is an alkaline rock-related low sulfidation telluride-containing epithermal gold deposit. The ore bodies oecured in intermediate-basic, alkaline trachyandesite, trachyandeso-volcanic breccia of Tamulangou formation in upper Jurassic. The main ore type is sulfur-poor quartz vein, and the ore minerals mainly consist of ealaverite, antamokite, hessite, petzite, sylvanite and krennerite. Alterations in mining area are silicification, pyritization, sericitization, kaolinitization, chloritization, carbonatization and fluoritization, which are the typical alteration assemblage of low sulphidation epithermal deposit. Fluid inclusion studies show that： gas-liquid two-phase fluid inclusions are well developed in quartz and including small amount of single-phase inclusions, that further suggesting the ore-forming fluid is H2O-NaCl fluid system;the homogenization temperatures concentrate in 230 -270 ℃ ; the salinity is usually less than 3 % NaCl eqv, and the density concentrates in 0.68 -0.88g/cm3, indicating the ore-forming fluid is of a low temperature, low salinity, low-density fluid system;an average metallogenic depth of 1.73 km, implys epithermal environment ;hydrogen and oxygen isotope analysis show that 8D is between- 110 ‰ - -85‰, the average is -95.8 ‰, 6180 water is between - 14.3 ‰- -8.7 ‰, the average is - 11.1‰, indicating the oreforming fluid came from meteoric water. According to the characteristics of low sulfidation and rich tellurium of the gold deposit, ore and alteration assemblage as well as fluid characteristics, it can be further determined that Sandaowanzi gold deposit is a low sulfidation epithermal telluride-containing gold deposit that associates with alkaline rocks.