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云南大坪金矿含金石英脉中高结晶度石墨包裹体:下地壳麻粒岩相变质流体参与成矿的证据 预览 被引量:24

Graphite Inclusions with High Crystal linity in the Auriferous Quartz Veins from Daping Gold Deposit in Yunnan Province, China: Evidence for Involvement of Metamorphic Fluid from Granulite-Facies Lower Crust in the Mineralization
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摘要 石墨作为各种岩浆岩和变质岩的副矿物可作为主岩形成条件的指示剂。本文利用激光拉曼光谱分析在大坪金矿含金脉石英中发现了大量孤立的石墨固体包裹体,进一步利用激光拉曼光谱和显微测温分析了其寄主矿物的流体包裹体特征,据此探讨了这些石墨包裹体的形成条件和本区成矿流体的来源。结果表明:所有大坪石墨的拉曼光谱都在1576~1580cm^-1处出现尖锐的有序O峰,而绝大多数在1355cm^-1附近不出现无序的D锋,表明这些石墨具有完全有序结构和完好的结晶度;其寄主矿物流体包裹体主要是纯CO2包裹体和富CO2包裹体。根据大坪石墨的拉曼光谱D2O峰强度比,估计这些石墨形成于麻粒岩相变质温度条件下,与石英中富CO2流体包裹体的均一温度(300.0~420.0℃)极不相称;含金石英脉中包裹体的类型和成分也表明本区不存在从流体中直接沉淀石墨的物理化学条件,因此推测这些石墨形成于下地壳麻粒岩相变质环境下。本区喜马拉雅期切割较深的韧性剪切带从下地壳麻粒岩相变质基底中汲取大量富CO2的流体的同时,还从下地壳携带微粒石墨,富含CO2和高结晶度石墨的成矿流体沿剪切带上升,并在闪长岩体内脆性断裂中沉淀成矿。本文的研究成果再次证实了下地壳流体对大坪金矿成矿的贡献。 Laser Raman spectroscopy analyses found plentiful graphites solid inclusions with size of 1 - 5μm in the auriferous quartz veins in Daping gold mine in Yunnan Province, China. For the sake of carrying out Daping graphite's function as an indicator of its host rock's forming condition and the source of the mineralizing fluid. the fluid inclusions in the graphite-bearing quartzes were investigated by laser raman spectroscopy and a cooling/ heating stage in dominated by pu and CO revealed. this work. The result showed that The fluid inclusions in the graphite-bearing quartzes were re CO2 inclusions and CO2-enriched aqueous inclusions with a little of N2 and without H2, CH4 The laser raman spectra of all the graphite inclusions showed a sharp high intensity ordered "O,, peak indicatin ratios, at 1576~1580cm-1 shift, but most of them didn't show a disordered "D" peak near 1355cm^-1 shift , g that the graphites possess full-ordered structure and high crystallinity. Based on D'O peak intensity ese graphite inclusions formed at granulite-facies metamorphic temperature, which is much higher than the homogeneous temperature (300.0- 420.0℃) of the CO2-enriched fluid inclusions in the graphitebearing quartzes. Types and composition of the fluid inclusions in the auriferous quartz veins confirmed that the graphite could not be precipitated directly from the ore-forming fluid. Therefore, it is suggested that the Daping graphites formed in the lower crust under granulite-facies metamorphic condition. The Ailaoshan ductile shear zone generated during Himalayan movement probably cut the crust quite deeply, and pumped a great deal of CO2 enriched fluid, and simultaneously small grains of graphites, from the granulite-faceis metamorphic basement in the lower crust. The CO2 enriched fluid carrying high-crystallized graphites ascended along the shear zone, and finally the graphites precipitated in the brittle faults in the diorite with plentiful ore minerals. The results in this study reconfirmed that the lowe
作者 熊德信 孙晓明 翟伟 石贵勇 王生伟 XIONG Dexin, SUN Xiaoming, ZHAI Wei, SHI Guiyong, WANG Shengwei( 1 ) Department of Earth Sciences, Sun Yatsen University, Guangzhou, 510275 ; 2 ) Zhaoqing University, Zhaoqing , 526061 ; 3 ) National Key Laboratory of MetaUogenesis, Nanjing , 21 0093)
出处 《地质学报》 CAS CSCD 北大核心 2006年第9期 1448-1456,T0006,共10页 Acta Geologica Sinica
基金 本文为国家重点基础研究发展规划“973”项目(编号2002CB412610)、国家自然科学基金(编号40173025)、国家教育部跨世纪优秀人才培养计划基金和南京大学成矿作用国家重点实验室开放基金的资助成果.本次研究野外工作得到云南元阳大坪金矿地质科的大力支持,矿区资料的收集工作得到云南省地质调查院、云南省地质矿产勘查开发局、武警黄金部队第十三支队的大力帮助激光拉曼光谱分析工作得到中国科学院地球化学研究所拉曼光谱实验室王英老师和中山大学现代测试中心陈健老师的支持和指导,在此谨表谢忱!
关键词 含金石英脉 石墨包裹体 激光拉曼光谱 富CO2 流体 下地壳麻粒岩相变质基底 韧性剪切带 Auriferous quartz veins, Graphite inclusions, Laserinclusions, Granulites-facies metamorphic basement in the lower crust,raman spectroscopy,Ductile shear zoneCO2-enriched fluid
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