冈底斯斑岩铜矿带冲江铜矿含矿流体的形成和演化:来自流体包裹体的证据

Characteristics of ore-forming fluids and their evolution for Chongjiang copper deposit in Gangdise porphyry copper belt,Tibet:Evidence from fluid inclusions.

对冲江斑岩铜矿含矿斑岩中石英斑晶和含矿石英脉中包裹体进行岩相学、显微测温分析、包裹体中气液相成分的激光拉曼显微探针(LRM)分析和子矿物的扫描电镜/能谱(SEM/EDS)分析。研究表明含矿流体来自富含挥发分的岩浆的出溶作用,最初从岩浆中出溶的流体为近饱和的超临界流体,其最低捕获温度在362～389℃左右,盐度在17．7%～18．9% NaCl_(eq)左右。随着出溶流体温度压力的下降,超临界流体发生相分离,并分离出低盐度的气相和高盐度的液相。在石英绢云母化阶段进一步发生高盐度液相包裹体的沸腾作用,形成子矿物溶化温度高于气液相均一温度的高盐度包裹体和富气相包裹体。与粘土化有关的流体为流体演化的晚期产物,属低温、低盐度流体。

Inclusion petrography, microthermometry, LRM and SEM/EDS to the daughter mineral were performed for the inclusions in the ore-beating quartz vein and the quartz phenocryst in ore-bearing porphyry of Chongjiang porphyry copper deposit. According to the analysis data it is thought that the ore-forming fluid came from the magmatic exsolution with rich volatile constituent. The fluids freshly deriving from magma is near-saturated supereritical one,with the undermost captured temperature of 362℃ - 389℃ and the salinity of 17.7% - 18.9% NaCleq. Because of degression of temperature and pressure, the supercritical fluid is seperated into vapor phase with low salinity and liquid phase with high salinity. Further more, at the stage of quartz sericitizing the high salinity fluids boiled and then the inclusions which is rich in vapor phase and the higher salinity inclusions in which the melting temperature of the daughter mineral is higher than the homogenization temperature of the vapor and liquid phases formed. The fluids related to argillation formed in late evolution stage and is of lower temperature and lower salinity.