海南抱伦金矿床流体包裹体及成因机理研究

Study on fluid inclusion and genesis mechanism of Baolun gold deposit in Hainan

抱伦金矿床位于海南岛西南部的五指山褶皱带内。矿体呈脉状、透镜状存在于志留系陀烈组的含炭绢云母千枚岩中,主要受NNW向断裂带控制。矿物组合特征表明成矿过程主要分为乳白色粗粒石英—烟灰色细粒石英—碳酸盐和绿泥石3个成矿阶段,中成矿阶段是主要的成矿期,发育自然金、铋碲化物和硫化物。石英中的流体包裹体测试结果显示:①包裹体发育类型相对简单,主要为CO2-H2O包裹体(C型)和水溶液(W型)两种,均一温度变化在130℃~380℃范围内,盐度w(NaCleq)集中在0.2%~11.7%;②不同成矿阶段流体特征不同,早期变质流体具有温度中等、盐度较低的特点,中期具有变质流体和岩浆流体的混合流体特征,成矿流体温度、盐度小幅升高,晚期大气降水参与的热液流体以低温、低盐度为主;③液态不混溶作用主要发生在早、中成矿阶段流体中,致使自然金大量沉淀。综合矿产地质特点及流体演化规律分析,海南抱伦金矿具有非典型的造山型金矿的特征,印支期尖峰岭岩体花岗质岩浆流体参与的混合作用对于抱伦金矿床富集和沉淀有着重要贡献。

Baolun gold deposit is located in Wuzhishan fold belt of Southwest Hainan Island.The orebodies are in the form of veins and lenses which are hosted in the carbonaceous sericite phyllite of Silurian Tuoli Formation,and are mainly controlled by the NNW-trending fault zone.The mineral assemblage indicates that the metallogenic process can be divided into early milky coarse quartz stage,middle smokey gray fine grain quartz stage,and late carbonate-chlorite stage.The middle metallogenic stage is the main metallogenic stage,with natural gold and bismuth telluride and sulfide developed.The test result of fluid inclusions in quartz shows as follows.①The development type of inclusions is relatively simple,mainly including CO2-H2O inclusions(C type)and aqueous solution inclusions(W type).The uniform temperature is in the range of 130℃-380℃,and the salinity w(NaCleq)is concentrated from 0.2%to 11.7%.②The fluid characteristics are different in different metallogenic stages.The early metamorphic fluid has the characteristics of moderate temperature and low salinity,the middle stage is dominated by a mixture of metamorphic fluid and magmatic fluid with a slight increase in temperature and salinity.The hydrothermal fluid involved in the late atmospheric precipitation has a low temperature and a low salinity.③Liquid immiscibility mainly occurs in the fluids of the early and middle metallogenic stages,resulting in a large amount of natural gold precipitation.Based on comprehensive analysis of mineral resources,geological characteristics and fluid evolution,Baolun gold deposit in Hainan has the characteristics of atypical orogenic gold deposit.The mixing effect of granite magmatic fluids in the Jianfengling rock mass of the Indosinian period plays an important role in gold enrichment and precipitation in Baolun gold deposit.