贵州丫他卡林型金矿床流体包裹体特征及其成矿意义

黔西南丫他金矿床是典型的沉积岩容矿的微细浸染型金矿床。从流体包裹体的角度,探讨了丫他金矿床成矿的温度压力条件和流体演化。各阶段石英、雄黄的流体包裹体岩相学和显微测温研究结果表明:主成矿阶段包裹体主要类型有H2O、CO2和CO2-H2O包裹体,流体包裹体组合呈现CO2-H2O不混溶的特征,晚成矿阶段包裹体类型主要为H2O包裹体;从主成矿阶段到晚成矿阶段,流体包裹体均一温度由139～268℃变化至121～194℃,盐度由2.9%～7.4%变化至2.7%～6.6%。根据共存CO2包裹体和H2O包裹体的等容线计算法,还原主成矿期包裹体捕获温度为260～294℃,捕获压力为59～98 MPa。对比不同类型金矿床中的富CO2流体特征,指出黔西南卡林型金矿床中存在的富CO2流体可能在金的搬运过程中起到一定的作用,CO2-H2O相分离可能是导致矿质沉淀的主要原因。

Fluid Inclusion Characteristics of Yata Carlin-type Gold Deposit,Guizhou Province and Its Metallogenic Significance

Yata gold deposit is a typical sediment-hosted disseminated gold deposit in southwestern Guizhou.Based on the data from fluid inclusions,we discuss the temperature and pressure conditions and the fluid evolution in the ore-forming process.Results from petrographic observation and fluid inclusion microthermometry study of gangue minerals in different stages give us the following conclusions: fluid inclusions in the main mine-ralizing stage can be divided into three categories including H2O,CO2 and CO2-H2O inclusions,which indicates the immiscibility of the ore-forming fluid;while fluid inclusions in the late mineralizing stage are mainly H2O inclusions;homogenization temperatures of H2O inclusions in the main mine-ralizing stage vary from 139 to 268 ℃,salinities range from 2.9% to 7.4%,while homogenization temperatures of H2O inclusions in the late mineralizing stage vary from 121 to 194 ℃,and salinities range from 2.7% to 6.6%.According to the simultaneous solution of isochoric formulas derived from H2O inclusions and CO2 inclusions,the capture temperatures of inclusions in the main mineralizing stage vary from 260 to 294 ℃,while capture pressures range from 59 to 98 MPa.Based on the comparison of characteristics of CO2-rich fluids in different types of gold deposits,we conclude that CO2-rich fluid in Carlin-type gold deposits in southwestern Guizhou may play a role in the transportation of gold,and that phase separation between CO2 and H2O could be the cause for gold deposition.