江西省全南县大吉山钨矿成矿流体演化特征
摘要
大吉山钨矿位于南岭W、Sn成矿省,是我国著名的大型W矿床。本文旨在通过对大吉山脉形钨矿2513号脉中的包裹体进行详细的岩相学及显微测温学研究,对成矿流体的演化过程及矿床形成深度进行探讨。包裹体的岩相学研究表明,包裹体类型复杂主要由富液包裹体、含CO2、CH4三相包裹体及含子矿物包裹体组成;包裹体组合复杂,各种类型的包裹体常叠加在一起;原生、次生包裹体产状区别明显,较易识别,原生包裹体主要由含CO2、CH4三相包裹体及充填度较小的富液包裹体组成,次生包裹体主要为充填度较大的富液包裹体。显微测温分析发现不同类型的包裹体的盐度、均一温度差别显著,呈现复杂的流体演化过程。包裹体的爆裂曲线显示,曲线有高低温两个起爆点,分别对应原次生包裹体包裹体群的起爆温度;由深部到浅部,原生包裹体的起爆温度逐渐降低。利用显微共焦激光拉曼探针仪对原生包裹体进行成分分析发现,成矿流体主要由H2O-NaCl和H2O-CO2-CH4-NaCl体系组成。包裹体的显微测温结果显示,成矿流体演化经历了自然冷却、不混溶作用和混合作用等过程,各种过程相互作用造成了钨的沉淀。通过对不混溶包裹体的测温数据进行计算,得出大吉山脉型钨矿成矿流体的压力约为114~132MPa,矿床形成深度约为4.6~5.3km。
Dajishan tungsten deposit,located in the Nanling metallogenic province of tungsten and tin,is a famous large tungsten deposit in China.This paper studied No. 2513 vein in the Dajishan tungsten vein-type deposit using facieology and microthermometry,and then discusses the evolution and depth of ore-forming fluid.The facieology study on the fluid inclusions reveals a variety of fluid inclusions: aqueous inclusions,bearing CO2/CH4 three phases fluid inclusions and bearing daughter mineral fluid inclusions.The assemblage of fluid inclusion are quite complex,with different types of fluid inclusions generally overprinted.It is easy to distinguish between primary fluid inclusion and secondary ones based on their different filling characteristics.Primary fluid inclusions consist of bearing CO2/CH4 three phases fluid inclusion or low filling degree aqueous inclusion,while secondary fluid inclusions are high filling degree aqueous inclusion.Microthermometry analysis data indicates that the salinity and homogeneous temperature differ with fluid inclusions types markedly,manifesting a complicated fluid evolution process.TThe dercepitation temperature curves display that there are two initial dercepitation temperatures which correspond to primary and secondary fluid inclusions respectively.The dercepitation temperature of primary fluid inclusions declines from deep to shallow level.The analysis on the components of primary fluid inclusions using confocal Raman microscopy demonstrates that the ore-forming fluid is H2O-NaCl or H2O-CO2-CH4-NaCl system.According to microthermometry data,it is identified that ore-forming fluid evolutions in Dajishan tungsten deposit are composed of cooling,immiscibility and mixing processes.Employing microthermometry data of immiscibility fluid inclusions,following conclusions can be drawn on: a) the ore-forming pressure is about 114~132Mpa;and b) the ore-forming depth is about 4.6~5.3km.
Dajishan tungsten deposit,located in the Nanling metallogenic province of tungsten and tin,is a famous large tungsten deposit in China.This paper studied No. 2513 vein in the Dajishan tungsten vein-type deposit using facieology and microthermometry,and then discusses the evolution and depth of ore-forming fluid.The facieology study on the fluid inclusions reveals a variety of fluid inclusions: aqueous inclusions,bearing CO2/CH4 three phases fluid inclusions and bearing daughter mineral fluid inclusions.The assemblage of fluid inclusion are quite complex,with different types of fluid inclusions generally overprinted.It is easy to distinguish between primary fluid inclusion and secondary ones based on their different filling characteristics.Primary fluid inclusions consist of bearing CO2/CH4 three phases fluid inclusion or low filling degree aqueous inclusion,while secondary fluid inclusions are high filling degree aqueous inclusion.Microthermometry analysis data indicates that the salinity and homogeneous temperature differ with fluid inclusions types markedly,manifesting a complicated fluid evolution process.TThe dercepitation temperature curves display that there are two initial dercepitation temperatures which correspond to primary and secondary fluid inclusions respectively.The dercepitation temperature of primary fluid inclusions declines from deep to shallow level.The analysis on the components of primary fluid inclusions using confocal Raman microscopy demonstrates that the ore-forming fluid is H2O-NaCl or H2O-CO2-CH4-NaCl system.According to microthermometry data,it is identified that ore-forming fluid evolutions in Dajishan tungsten deposit are composed of cooling,immiscibility and mixing processes.Employing microthermometry data of immiscibility fluid inclusions,following conclusions can be drawn on: a) the ore-forming pressure is about 114~132Mpa;and b) the ore-forming depth is about 4.6~5.3km.
引文
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滕建德.1990.大吉山矿区矿化垂直带状分布.矿山地质.11(2):13~23.
周师立.1988.爆裂法测温中几个问题的探讨.江苏地质.(1):51~54.
张国新,谢越宁,虞福基,张鸿斌.1997.江西大吉山钨矿床不同成矿阶段稳定同位素地球化学.地球学报,18(增刊):197~199.
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张文兰,华仁民,王汝成等.2006.赣南大吉山花岗岩成岩与钨矿成矿年龄的研究.地质学报,80(7):956~962.
朱焱龄,李祟佑,林运淮.1981.赣南钨矿地质.北京:人民出版社,440.
Bakker R J.2003a.Package FLUIDS1.Computer programs foranalysis of fluid inclusion data and for modeling bulk fluidproperties.Chmecal Geology.193:3~23.
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Diamond L W.1994.Introduction to phase relations of CO2-H2Ofluidinclusions2003.In De Vivo B,et al.(eds).Fluid inclusionsin minerals:methods and applications2003.I MA Short CourseVolume,131~158.
Nebelek P,Temes K.1997.Fluid inclusions in the Harney PeakGranite,Black Hills,South Dakota,USA:I mplications forsolubility and evolution of magmatic volatiles and crystallizationof legucogranite magmas.Geochi m.Cosmochi m.Acta,61(7):1447~1465.
Roedder E.1984.Fluid inclusions.Reviews in mineralogy.12:212~220.
蒋国豪.2004a.氟、氯对热液钨、铜成矿的制约---以江西得兴铜矿、大吉山钨矿为例.中国科学院地球化学研究所博士论文,1~100.
蒋国豪,胡瑞忠,谢桂青等.2004b.江西大吉山钨矿成矿年代学研究.矿物学报,24(3):253~256.
卢焕章,施继锡,喻茨玫.1974.华南某矿区成岩成矿温度的研究.地球化学,(3):145~156.
卢焕章,施继锡,喻茨玫.1975.某含铌钽花岗岩成岩成矿温度的研究.地球化学,(3):210~223.
卢焕章,范宏瑞,倪培等.2004.流体包裹体.北京:科学出版社,269~282.
刘斌.1999.流体包裹体热力学.北京:地质出版社,207~249
刘斌.2000.流体包裹体计算软件及算例.北京:地质出版社,14~35.
马秀娟.1988.大吉山钨矿包裹体地球化学研究.见李荫清,马秀娟,魏家秀编.流体包裹体在矿床学和岩石学中的应用.北京:科学技术出版社,61~112.
邱检生,McInnes BI A,徐夕生等.2004.赣南大吉山五里亭岩体的锆石ELA-ICP-MS定年及其与钨成矿关系的新认识.地质论评,50(2):125~133.
阙梅登,夏卫华.1988.江西大吉山脉钨矿床矿化富集特征及其机理初探.地球科学---中国地质大学学报,13(2):177~185.
芮宗瑶,李荫清,王龙生,王义天.2003.从流体包裹体研究探讨金属矿床成矿条件.矿床地质,22(1):13~23.
孙恭安,史明魁,张宏良等.1989.大吉山花岗岩体岩石学、地球化学及成矿作用的研究.见:中国地质科学院宜昌地质矿产研究所编.南岭地质矿产科研报告集(二).武汉:中国地质大学出版社,326~363.
滕建德.1990.大吉山矿区矿化垂直带状分布.矿山地质.11(2):13~23.
周师立.1988.爆裂法测温中几个问题的探讨.江苏地质.(1):51~54.
张国新,谢越宁,虞福基,张鸿斌.1997.江西大吉山钨矿床不同成矿阶段稳定同位素地球化学.地球学报,18(增刊):197~199.
张文兰,华仁民,王汝成,李惠民,陈培荣.2004.江西大吉山五里亭花岗岩单颗粒锆石U-Pb同位素年龄及其地质意义探讨.地质学报,78(3):352~358.
张文兰,华仁民,王汝成等.2006.赣南大吉山花岗岩成岩与钨矿成矿年龄的研究.地质学报,80(7):956~962.
朱焱龄,李祟佑,林运淮.1981.赣南钨矿地质.北京:人民出版社,440.
Bakker R J.2003a.Package FLUIDS1.Computer programs foranalysis of fluid inclusion data and for modeling bulk fluidproperties.Chmecal Geology.193:3~23.
Bakker RJ,Brown P E.2003b.Computer modelinginfluidinclusionresearch2003.In Iain Samson,Alan Anderson,et al.(eds).Fluid inclusions:analysis and interpretation.MineralogicalAssociation of Canada Short Course Volume,175~212.
Diamond L W.1994.Introduction to phase relations of CO2-H2Ofluidinclusions2003.In De Vivo B,et al.(eds).Fluid inclusionsin minerals:methods and applications2003.I MA Short CourseVolume,131~158.
Nebelek P,Temes K.1997.Fluid inclusions in the Harney PeakGranite,Black Hills,South Dakota,USA:I mplications forsolubility and evolution of magmatic volatiles and crystallizationof legucogranite magmas.Geochi m.Cosmochi m.Acta,61(7):1447~1465.
Roedder E.1984.Fluid inclusions.Reviews in mineralogy.12:212~220.
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