摘要
主要研究了德兴斑岩铜矿床不同期次脉石英及花岗闪长斑岩石英斑晶中流体包裹体的特征,测定了流体包裹体的均一温度和冰点,估算了成矿流体的盐度、密度等参数.结合花岗闪长斑岩与石英脉中石英氢氧同位素数据的讨论分析,对流体的演化过程和来源进行了探讨.研究表明花岗闪长斑岩石英斑晶中的包裹体代表了岩浆流体的特征,石英脉中的包裹体记录了岩浆流体演化成成矿流体的特征.研究证实成矿流体主要由岩浆流体而来,成矿流体演化晚期有大气降水的加入.
Dexing porphyry copper deposit is a famous ore deposit in China for its great reserves of copper ores. Quartz veins are abundant in the ore bodies and their wall rocks. According to their crosscutting connections and mineral assemblages of quartz veins, three generations of quartz veins can be recognized: early, main and postoreforming stage. On the basis of the characters of phases and salinity of the fluid inclusions at room temperature, they can be classified into three types: Liquidrich biphase inclusions (Type A),Vaporrich inclusions (Type B) and Multiphase inclusions (Type C). Systematic studies on the homogenization temperature, salinity, and types of inclusions in quartz phenocrysts of granodioriteporphyry have revealed that the oreforming fluids undergoes three following stages:The first stage: the fluid inclusions are primary and include Type C and rare Type A inclusions. The salinity is very high, ranging from 45 wt%NaCl equiv. to 51wt%NaCl equiv. The homogenization temperature ranges from 450 ℃ to 525 ℃, which is closest to the rockforming temperature of granodioriteporphyry. The fluid inclusions of this stage represent the characteristics of the early stage magma fluids. The second stage: The fluid inclusions of this stage are secondary inclusions , and are formed in the crannies of quartz phenocrysts during the fluid evolution . The inclusion types include typeA, typeB and rare typeC.The homogenization temperature is 250～425 ℃ and the salinity is 1.5 wt%NaCl equiv.～34.64 wt%NaCl equiv. Compared with the fluid inclusions of the first stage, the salinity of inclusions at this stage is lower and the range of the homogenization temperature is much greater. The third stage: The fluid inclusions are secondary inclusions, mainly includingtype A, and are formed by insert of the oreforming fluids into the quartz phenocrysts. The homogenization temperature is 150～200 ℃, the salinity 9.5 wt%NaCl equiv. ～20.3 wt%NaCl equiv. The average of the homogenization temperature and salinity are lower than those of the above two stages. It is inferred that the fluid inclusions of the second and the third stage may have reflected the evolution from magma fluids to oreforming fluids. Fluid inclusions in quartz veins belong to Types A and B. The characteristics of the homogenization temperature and the salinity of fluid inclusions in the quartz veins are comparable with those of fluids at the end of the second stage and at the beginning of the third stage in the quartz phenocrysts. It is thought that the oreforming fluids were derived from magma fluids and that the deposit was formed during the period from the end of the second evolution stage to the beginning of the third stage. The inclusion studies also show that nonmagmatic fluids with low salinity may have participated in mineralization during the late stage of mineralization. The isotopic studies on granodioriteporphyries and ores reveal that probably the nonmagmatic fluids are meteoric water with low δ18O value.
出处
《南京大学学报（自然科学版）》
CAS
CSCD
北大核心
2003年第3期319-326,共8页
Journal of Nanjing University（Natural Science）
基金
国家重点基础研究发展规划项目(G1999053209)
