摘要
内蒙古乌努格吐山(简称乌山)斑岩铜钼矿床位于得尔布干深断裂北侧的额尔古纳地体。作为兴蒙造山带的一部分,额尔古纳地体经历了古生代俯冲增生、早中生代碰撞造山和晚中生代—新生代期间的与太平洋板块俯冲有关的碰撞后构造演化。乌山矿床形成于侏罗纪,是陆-陆碰撞体制斑岩矿床的典型实例,其地质地球化学特征有助于理解碰撞环境的斑岩矿床的成因,因此本文报道该矿床流体包裹体显微测温学、激光拉曼光谱和扫描电镜/能谱研究结果。乌山矿床流体成矿过程包括早、中、晚3个阶段,分别以石英-钾长石化、石英-绢云母-多金属硫化物化和伊利石-石英-碳酸盐化为特征。石英中可见水溶液包裹体、含子晶和含 CO_2三相流体包裹体,但晚阶段石英中缺乏后两类包裹体。早阶段流体包裹体均一温度>510℃,盐度最高达75.8 wt%Nacl eqv,包裹体的子晶矿物有石盐、黄铜矿以及指示氧化条件的赤铁矿,气相成分富含 CO_2,液相成分以水为主,且多含 CO_3^(2-)。矿化主要发生在中阶段,可分为早期的钼矿化阶段和晚期的铜矿化阶段,其成矿温度分别为340℃～510℃和240℃～340℃。该阶段流体盐度介于6.3～52.0 wt%NaCl eqv。中阶段包裹体含石盐和黄铜矿子矿物,富气相、富液相与含子晶包裹体共存,且具有相近的均一温度,而盐度相差悬殊,指示流体发生沸腾,成矿物质快速沉淀。晚阶段流体温度降低至100℃～240℃,盐度则低于12.4 wt%NaCl eqv。总之,早阶段成矿流体来自岩浆,以高温、高盐度、高氧逸度、富 CO_2为特征;中阶段流体发生沸腾,导致 CO_2逸失、氧逸度降低、成矿物质快速沉淀;晚阶段流体以低温、低盐度、无子晶、贫 CO_2为特征,可能属大气降水热液。
The Wunugetushan porphyry Cu-Mo deposit, Inner Mongolia, occurs in the Erguna terrane which is bounded by the NE-trending Derbugan fault to the southeast. Within the Mongolia-Hinggan Orogen, the Erguna terrane evolved in the Paleozoic subduction related accretion and Early Mesozoic collision and Late Mesozoic-Cenozoic post-collision tectonics related to Pacific plate subduction. The Wunugetushan deposit, formed in Jurassic, is a typical example of porphyry ore systems developed in continental collision regime. Its geological and geochemical characteristics may be an ideal reference to understand the origin of porphyry oresystems formed in collisional settings. This paper reports the research results on fluid inclusions obtained by microthermometric study and compositional identification using Laser Raman Spectroscope and Scanning Electron Microscope combined with Energy Spectrum. The hydrothermal ore-forming process of the Wunugetushan deposit includes three stages, i.e. the early, middle and late stages, characterized by mineral assemblages of quartz-potassic feldspar, quartz-serlcite-polymetallic sulfides and illite-carbonate-quartz, respectively. In hydrothermal quartz three types of fluid inclusions can be observed. They are NaCl-H2O solution, daughter mineral- bearing, and CO2-rich. However, the latter two types cannot be observed in the late-stage quartz. Homogenization temperatures of fluid inclusions in early stage are above 510℃ , with the highest salinities up to 75.8 wt% NaCl eqv. Fluid inclusions contain daughter minerals including halite, chalcopyrite and hematite which possibly represent an oxidizing environment. Vapor bubbles are mainly composed of CO2, and the liquids are dominated by H2O and generally contain CO3^2-. Mo and Cu are mainly mineralized in the middle stage, and in the temperature spans of 510℃ - 340℃ and 340℃ - 240℃ , respectively, with fluid salinities ranging from 6.3 to 52.0 wt% NaCl eqv. In middle stage, daughter minerals in fluid inclusions, such as halite and chalcopy
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2007年第9期2177-2188,共12页
Acta Petrologica Sinica
基金
国家973项目2006CB4035008
2006CB403501课题
自然科学基金项目(编号40352003和40425006)
关键词
斑岩铜钼矿床
流体包裹体
碰撞造山作用
乌努格吐山
兴蒙造山带
Porphyry Cu-Mo deposit, Fluid inclusion, Collisional orogeny, Wunugetushan, Mongolia-Hinggan Orogen
