粤西罗定盆地南缘金矿流体包裹体特征及成因意义

Characteristics of the fluid inclusions and its geneticsignificance for gold mineralization in southern marginof Luoding basin,western Guangdong

罗定盆地南缘的金矿脉石英和方解石中发育液相、气相和气液两相3种类型包裹体,以液相包裹体和气液包裹体为主。气液包裹体的气液比为5%～25%。包裹体盐度w(NaCl)为0.9%～10.6%,多数>5%,属于咸水-卤水。包裹体的均一温度显示,金矿有两个成矿阶段:第一阶段形成温度为172℃,第二阶段形成温度为122℃。氢氧同位素组成、流体包裹体成分显示成矿热液来源于大气降水。金矿形成于低温、浅成-超浅成环境,成矿热液可能经历了减压沸腾过程。金矿的成因类型属于浅成-超浅成低温热液型。

Three types of fluid inclusions have been found in quartz and calcite of gold-bearing veins from the southern margin of the Luoding basin,western Guangdong,i.e.liquid inclusion,gas inclusion,gas-liquid inclusion.The liquid inclusions and gas-liquid inclusions are the dominant ones and the gas-liquid inclusions have a gas/liquid volume ratios ranging from 5%～25%.The salinities[w(NaCl)] of inclusions range from 0.9% to 10.6% (usually over 5%),indicating that the ore-forming fluids should be saline water or salt brine.The homogenization temperatures of inclusions show that gold deposits of the studying area can be divided into two mineralizing stages,respectively formed at about 172℃ and 122℃.According to composition and characteristics of fluid inclusions and their O-H isotopic constitution,the ore-forming fluid came from meteoric water,the gold deposits were formed under an environment of low temperature and supergene depth and the mineralizing fluids might endured boiling at a pressure-reduced process.So,the genetic type of gold deposits in this area is a kind of epithermal type.