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王璇,杨林,邓军,李华健,于华之,董超一. 2018. 北衙金矿多期热液成矿作用识别:来自地质、岩相学、流体包裹体和H-O-S同位素证据. 岩石学报, 34(5): 1299-1311
北衙金矿多期热液成矿作用识别:来自地质、岩相学、流体包裹体和H-O-S同位素证据
作者单位E-mail
王璇 中国地质大学地质过程与矿产资源国家重点实验室, 北京 100083  
杨林 中国地质大学地质过程与矿产资源国家重点实验室, 北京 100083  
邓军 中国地质大学地质过程与矿产资源国家重点实验室, 北京 100083 djun@cugb.edu.cn 
李华健 中国地质大学地质过程与矿产资源国家重点实验室, 北京 100083  
于华之 中国地质大学地质过程与矿产资源国家重点实验室, 北京 100083  
董超一 中国地质大学地质过程与矿产资源国家重点实验室, 北京 100083  
基金项目:本文受国家重点基础研究发展计划"973"项目(2015CB452606、2009CB421008)和国家重点研发计划(2016YFC0600307)联合资助.
摘要:
      北衙超大型金矿床是三江特提斯成矿域中喜山期斑岩-矽卡岩型矿床的典型代表,长期以来大量研究均围绕斑岩-矽卡岩成矿作用开展并取得了丰硕成果,然而对于北衙金矿是否存在多期热液成矿作用尚不明确。本次研究基于详细野外调查、岩相学与矿相学研究,流体包裹体显微测温及成分分析、H-O-S同位素分析等多种手段,识别了北衙金矿成矿晚期存在新一期热液成矿事件。主要证据如下:(1)野外调查发现北衙金矿发育NW向陡倾断裂控制的石英多金属硫化物脉,其切割矽卡岩矿体与矽卡岩晚期石英硫化物矿脉;(2)本次研究矿脉中原生流体包裹体类型主要为富CO2三相水溶液包裹体、含CO2三相水溶液包裹体及气液两相水溶液包裹体,而矽卡岩晚期硫化物脉中除上述三种类型外还发育含子晶三相水溶液包裹体;(3)成矿流体均一温度分布范围为204~426℃,盐度为1.0%~14.2% NaCleqv,整体表现为中高温、中低盐度的NaCl-CO2-H2O流体体系,而矽卡岩晚期硫化物脉成矿流体体系具有中温、中高盐度的特征;(4)该矿脉中石英的δ18O、δD范围分别为7.5‰~9.4‰与-102.0‰~-75.0‰,指示岩浆水来源,而矽卡岩晚期硫化物脉具有岩浆水和大气水混合来源。本次研究的多金属硫化物矿脉δ34S值范围为-0.97‰~1.40‰,与矽卡岩期和矽卡岩晚期硫化物脉中黄铁矿S同位素一致,表明多期矿化成矿物质均具有幔源贡献。结合北衙矿集区成岩成矿动力学背景,推测始新世大规模地壳拆沉、软流圈上涌导致的强烈的壳幔相互作用可能是北衙金矿多期成矿作用的诱因。
英文摘要:
      The giant Beiya gold deposit is considered to be a typical porphyry-skarn deposit in the Himalayan period, which is located in the Sanjiang Tethys metallogenic domain. In long-term studies, scholars worldwide have conducted exhaustive research on various aspects of the deposit and have achieved remarkable results. However, it is not yet clear whether there are multistage events of the hydrothermal mineralization in this deposit. Field investigation, petrography, microthermometry and composition analysis of the fluid inclusion and H-O-S isotopes were implemented in this study with aims to identify a new event of hydrothermal mineralization in this deposit and explore the source of this mineralization. The main evidence that is different from the other type of mineralization are as follows:(1) the field investigation shows that the NW trending sulfide veins controlled by the steep faults were identified, which cut the skarn ore body and the sulfide veins of the late skarn stage. (2) The primary fluid inclusions in this studied sulfide veins are mainly include three types:CO2-bearing fluid inclusions, CO2-rich fluid inclusions and aqueous two phase fluid inclusions, while, besides the types mentioned above, the sulfide veins of the late skarn stage develop daughter mineral-bearing multiphase fluid inclusions. (3) The homogenization temperature and sanity of the studied veins range from 204℃ to 426℃ and 1.0% NaCleqv to 14.2% NaCleqv respectively. The ore fluids belong to NaCl-CO2-H2O system with the medium-high temperature and medium-low salinity, whereas the ore fluids of the sulfide veins in the late skarn stage are characterized by the medium temperature and medium-high salinity. (4) The δ18O and δD values of the quartz in the studied veins range from 7.5‰ to 9.4‰ and -102.0‰ to -75.0‰, respectively, indicating a source of the magmatic water, while the late skarn sulfide veins have a mixed source of the magmatic water and atmospheric water. In addition, the δ34S value from studied sulfide veins range from -0.97‰ to 1.40‰, which is consistent with the skarn stage pyrite and the sulfide vein pyrite studied before, showing that the metallogenic materials of all multiphase mineralization possibly have a contribution of mantle source. Combined with the diagenetic and metallogenic dynamics background, we inferred that the intensive crust mantle interaction resulting from the crustal delamination and the asthenosphere upwelling during the Eocene might be responsible for the multiperiodic mineralization in the Beiya gold deposit.
关键词:流体包裹体  H-O-S同位素  多期热液成矿  北衙  扬子西缘
投稿时间:2017-10-22  修订日期:2018-03-01
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主办单位:中国矿物岩石地球化学学会
印刷版(Print): ISSN 1000-0569 网络版(Online): ISSN 2095-8927
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