云南哈播斑岩铜(-钼-金)矿床流体包裹体研究

哈播斑岩Cu-(Mo-Au)矿床产于哀牢山富碱斑岩带的南段,形成于青藏高原后碰撞阶段构造转换环境,属于陆-陆碰撞型斑岩矿床.根据脉体的交切关系,确定哈播矿床各种脉的演化序列为早期石英脉→石英-黄铜矿脉→石英辉钼矿脉.脉中流体包裹体的岩相学、显微测温和激光拉曼光谱分析等研究结果显示,各期脉中均有富气相包裹体、富液相包裹体和含子矿物多相包裹体,各种包裹体的气相均含有CO2、SO2、H2O等气体.各期脉中多种包裹体并存并具有相似的均一温度范围,富液相包裹体均一温度149～427℃,盐度ω(NaCleq)6.0％～15.0％;富气相包裹体均一温度205～405℃,盐度ω(NaCleq) 3.4％～19.0％;含子矿物多相包裹体均一温度305～516℃,盐度w(NaCleq) 33.5％～61.0％.哈播矿床的初始成矿流体由稳定共存、不混溶的低盐度流体和高盐度流体组成,高盐度流体是哈播矿床成矿元素迁移的主要载体.成矿流体在400℃左右发生“二次沸腾”、分相,温度下降和挥发分持续逃逸可能是Cu-Au成矿的诱因.Mo元素在成矿流体多次沸腾、分相过程中,持续优先分配进入高盐度流体中而逐步富集;温度下降,使含钼硫化物在流体中溶解度降低、沉淀,形成石英-辉钼矿±黄铜矿脉.

Fluid inclusions of Habo porphyry Cu-(Mo-Au) deposit, Yunnan Province

The Habo porphyry Cu-(Mo-Au) deposit is located in the south of Jinshajiang-Ailaoshan orogenic belt.It is a typical post-subduction porphyry deposit formed in a Tibetan post-collision transformation setting.Intense K-feldspar and biotite alteration associated with quartz stockwork occurs in the Habo deposit alteration center,which is surrounded and overprinted by later feldspar-destructive alteration.Several stages of veinlets can be observed,and the evolution sequence of vein types is magnetite-quartz veinlets→early quartz veinlets→quartz-chalcopyrite veinlets→quartz-molybdenite veinlets→quartz-sericite-pyrite veinlets →pyrite-chalcopyrite veinlets.Early quartz,quartz-chalcopyrite and quartz-molybdenite veinlets were selected to perform fluid inclusion study.The cathodoluminescence images of early quartz,quartz-chalcopyrite and quartz-molybdenite veinlets indicate that they all were overprinted by later hydrothermal fluids.Vapor-aqueous inclusions,aqueous inclusions,and high brine halite-bearing inclusions were found in all the three types of veinlets,and CO2-bearing inclusions were found locally.Using Laser Raman analysis,the authors found that CO2 and SO2 are very abundant in all these inclusions.In early quartz,quartz-chalcopyrite and quartz-molybdenite veinlets,vapor-aqueous inclusions were homogenized within 149～427℃ with salinity w(NaCleq) of 6.0%～15.0%,aqueous inclusions were homogenized within 205～405℃ with salinity w(NaCleq) of 3.4%～19.0%,and high brine halite-bearing inclusions gained homogenization within 305～516℃ with salinity w(NaCleq) of 33.5%～60.8%.Vapor-aqueous and high brine halite-bearing inclusions are abundant in early quartz veins,and their homogenization temperatures are similar,which shows that in the Habo deposit the silicate melt directly exsolved two coexisting fluid phases,a vapor and a hypersaline liquid,and the hypersaline fluid is the main carrier of metals.When the fluids migrated upward,at the temperature of ～400℃,the hypersaline liquid entered the two-phase separation field,causing intense boiling and phase separation.With the vapor fluids escaping,the solubility of Cu-Au in the hypersaline fluid decreased,accompanied by intense Cu-Au mineralization.Mo was partitioned into hypersaline fluid during the whole fluid evolution and enriched gradually.On progressive cooling and boiling,the solubility of both Mo and silicates decreases,which accounts for Mo saturation and deposition.