摘要
西藏甲玛矿床是冈底斯成矿带中东段目前勘查程度最高、第一个规模化开发的超大型斑岩成矿系统,主要由矽卡岩铜多金属矿体、斑岩钼(铜)矿体以及角岩铜钼矿体构成。文章以甲玛矿床角岩矿体和斑岩矿体中典型的"上铜下钼"现象为切入点,借助流体包裹体显微测温、激光拉曼测试、同步辐射X射线荧光分析(SR-XRF)等研究方法,分析了甲玛矿床铜钼矿化阶段成矿流体的物化条件差异及微量元素迁移行为。流体包裹体研究结果表明:铜矿化阶段流体温度(大致在235~451℃,主要集中在340~380℃之间)总体上大于钼矿化阶段流体温度(大致在213~500℃,主要集中在310~360℃之间),但两种成矿流体的盐度大致相似,主要位于<18%NaCleqv与>30%NaCleqv这两个区间,缺乏盐度中间过渡区,说明成矿流体经历了沸腾作用。激光拉曼显微探针测试结果表明,Cu矿化阶段的流体氧化性较Mo矿化阶段更强,而Mo矿化阶段流体略呈还原性。单个流体包裹体同步辐射X射线荧光分析显示,Cu、Au、Fe、Mn、S、As等元素主要在气相中广泛分布,而Mo则主要残留在液相中迁移富集。因此,本文认为甲玛矿床中角岩型和斑岩型矿体呈现"上铜下钼、早铜晚钼"现象,主要由铜、钼元素本身的物化性质,含矿岩浆性质和侵位顺序与深度,以及含矿岩浆后期所分异出的成矿流体的氧化还原性以及其中S含量的差异所致。
With the highest exploration and the first large-scale exploitation,Jiama copper polymetallic deposits is a supper-large skarn-porphyry deposit,located at the middle-eastern section of gangdise in Tibet. In this paper,taking the typical phenomenon＂copper upside and molybdenum underside＂ of hornfels-and porphyry-orebodies from Jiama deposit as the starting point,the differences of ore forming fluids among physical and chemical conditions and the migrating behavior of trace elements in the copper and molybdenum mineralization stages have been discussed in virtue of microthermometry,laser Raman testing,synchrotron radiation X-ray fluorescence analysis（ SR-XRF） and other researching methods. The results of fluid inclusions microthermometry show that the temperature of ore-forming fluid in the copper mineralization stage（ roughly 235 ~ 451℃,mainly between 340 and 380℃） is overall greater than that in the molybdenum stage（ roughly 213 ~ 500℃,mainly between 310 and 360℃）,sharing the similar salinity that is less than 18% Na Cleqv and more than 30% Na Cleqv,and lack of the transition zone,which explained ore-forming fluids had experienced boiling. And the results of Raman microprobe show that the oxidizability of ore-forming fluids in the copper mineralization stage is a little stronger than that in the molybdenum mineralization stage,while the reducibility is reverse. Synchrotron radiation X-ray fluorescence analysis of single fluid inclusion indicates that Cu,Au,Fe,Mn,S,As and other elements are mainly and widely distributed in the gas phase,while the residual Mo is mainly concentrated in the liquid phase. Thus it can be concluded the main controlling factors leading to ＂copper earlier and molybdenum later and copper upside and molybdenum underside＂of hornfels-and porphyry-orebodies in the Jiama deposit are the physical and chemical properties of copper and molybdenum,the natures of ore-bearing magma,and their emplacing sequence and depth,along with the different redox and the ulfur content
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2017年第2期495-514,共20页
Acta Petrologica Sinica
基金
国家自然科学基金项目(41302060)
基本科研业务项目(K1302)
地质大调查项目(12120113093700)
国家"973"项目(2011CB403103)联合资助
关键词
铜钼分离
成矿流体
同步辐射X射线荧光分析
甲玛斑岩成矿系统
西藏
Separation of copper and molybdenum
Metallogenic fluid
Synchrotron radiation X-ray fluorescence analysis
Jiama porphyry metallogenic system
Tibet
