粤北302铀矿床成矿机制探讨——来自流体包裹体的证据

Mineralization Mechanism of 302 Uranium Deposit,North Guangdong Province: Evidence from Fluid Inclusions

在对粤北302铀矿床岩相学研究的基础上,划分矿物生成世代,并对成矿期流体包裹体进行岩相学观察,得出成矿期流体包裹体主要有三种类型,按其成分划分为盐水包裹体、含CO2三相包裹体、纯CO2包裹体。盐水包裹体冰点温度为-0.8^-3.4℃,均一温度为106~254℃,盐度为2.39%~5.55%wtNa Cl equiv;含CO2三相包裹体充填度为20%~90%,均一温度为198~354℃,盐度为3.76%~9.24%wtNa Cl equiv;纯CO2包裹体均一温度为17.8~22.1℃。流体包裹体岩相学观察结合显微测温数据说明成矿流体经历过沸腾作用,其成矿温度大约在250℃,压力约为(1.0~1.1)×108Pa,流体沸腾作用可能是导致302铀矿床成矿的重要机制。

The studies of petrography, mineral paragenesis, and fluid inclusion of 302 uranium deposit show there are three types of fluid inclusion that include H2O-type, H2O-CO2-type, and CO2-type, occur in pitchblendequartz veins and alteration quartz grains. The melting of ice of H2O inclusions is from - 0.8 ℃ to - 3.4 ℃, corresponding to the salinities between 2.39 % wtNaCl equiv and 5.55% WtNaCl equiv, the homogenization temperatures range from 106 ℃ to 254 ℃. About the H2O - CO2 inclusions, their filling degree are commonly from 20% to 90% , with total homogenization temperatures are from 198 ℃ to 354 ℃, and salinities span from 3.76% wtNaCl equiv to 9.24% wtNaCl equiv. The homogenization temperatures of COs inclusions are from 17.8 to 22.1 ℃. The petrography observation and microthermometry of fluid inclusion suggest the ore - forming fluid has experienced CO2 effervescence which is probably the important mineralization mechanism. The mineralization temperature is about 250 ℃, with pressure is about （ 1.0 - 1.1 ） × 10^8 Pa.