中国还原性斑岩矿床研究进展及判别标志  

Advances and its diagnostic criteria in the study of the reduced porphyry ore deposits in China

作　　者：申萍[1,2,3] 潘鸿迪 SHEN Ping;PAN HongDi(Key Laboratory of Mineral Resources,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Innovation Academy of Earth Science,Chinese Academy of Sciences,Beijing 100029,China;University of Chinese Academy of Sciences,xi'an 710054,China;College of Earth Sciences,Chang’an University,xi'an 710054,China)

机构地区：[1]中国科学院矿产资源研究重点实验室,中国科学院地质与地球物理研究所,北京100029 [2]中国科学院地球科学研究院,北京100029 [3]中国科学院大学,北京100049 [4]长安大学地球科学与资源学院,西安710054

出　　处：《岩石学报》2020年第4期967-994,共28页Acta Petrologica Sinica

基　　金：中国科学院国际合作局国际伙伴计划(132A11KYSB20190070);国家重点研发计划重点专项课题(2017YFC0601206、2018YFC0604004);国家自然科学基金项目(91962213、41772089、U1303293、41272109);国家科技支撑计划课题(2011BAB06B01)联合资助.

摘　　要：世界上大多数斑岩矿床的成矿流体为氧化流体(CO2>>CH4)。然而,Rowins(2000)提出一些斑岩Cu-Au矿床的成矿流体为富含CH4的还原流体,矿床缺乏磁铁矿、赤铁矿和硬石膏等表征高氧逸度的矿物,而发育大量的磁黄铁矿,矿床规模小,矿床形成与含钛铁矿的还原性的Ⅰ型花岗岩类有关,并将其称之为还原性斑岩Cu-Au矿床。我国学者研究发现,中国不但发育还原性斑岩铜矿床,还发育还原性斑岩-矽卡岩铜矿床和还原性斑岩钼矿床,我们建议将这三种矿床统称为还原性斑岩矿床。本文基于课题组近十年来的研究工作,并结合前人的研究成果,综合分析了中国发育的大中型还原性斑岩矿床的典型实例,在此基础上,重点阐明中国大型还原性斑岩矿床的特点、流体中CH4来源及其有关的成矿作用、容矿围岩特点、成矿岩浆氧化还原状态及其成因、矿床形成的构造背景等。与Rowins(2000)提出的还原性斑岩铜矿床规模小的特点不同,中国发育的一些还原性斑岩矿床规模大;我们研究还识别出该类矿床发育独特的热液矿物和矿石矿物,比如,还原性斑岩铜矿发育热液钛铁矿,矿石矿物以黄铜矿为主,罕见斑铜矿、辉铜矿等矿物;还原性斑岩钼矿床出现热液钛铁矿,矿石矿物以辉钼矿为主,罕见黑钨矿和锡石等矿物;还原性斑岩-矽卡岩铜矿床的矽卡岩期发育钙铝榴石、钙铁辉石等还原性矽卡岩矿物和大量的磁黄铁矿,热液期以发育黄铜矿而非斑铜矿和辉铜矿等矿石矿物为特征。因此,还原性斑岩矿床除了Rowins(2000)提出的发育富CH4还原流体和磁黄铁矿等识别标志之外,还可辅以独特的脉石矿物(如钛铁矿、钙铝榴石、钙铁辉石等)和简单的矿石矿物(如黄铜矿、辉钼矿等)这两个标志进行识别。中国还原性斑岩矿床含矿岩体的围岩中普遍发育还原性岩石(如含碳质沉积岩或火山沉积岩、含亚铁的火山岩Most porphyry ore deposits wor-ldwide have fluid inclusions with CO2>>CH4 that are indicative of high oxygen fugacity(fO2).However,Rowins(2000) proposed that some porphyry Cu-Au deposits lack primaiy hematite,magnetite and anhydrite,but contain abundant hypogene pyrrhotite,which commonly have carbonic-rich ore fluids with substantial CH4.These porphyry Cu-Au deposits,associated with ilmenite-bearing,reduced Ⅰ-type granitoids,are small in size,and are called the reduced porphyry Cu-Au deposits.Recently,Chinese scholars recognized the reduced porphyry-skarn Cu deposits and the reduced porphyry Mo deposits besides the reduced porphyry Cu deposits in China.We named all of them as the reduced porphyry ore deposits.Based on lots of investigations and studies in recent ten years done by the authors,combined with the previous researches,this paper tentatively makes a comprehensive elucidation of typical reduced porphyry deposits in China and focuses on the characteristics of large reduced porphyry deposits and their wall rocks,the source of CH4 in the ore-forming fluid and related mineralization,the redox state of the ore-forming magmas and its genesis,and the metallogenic tectonic setting.Unlike the small-size reduced porphyry Cu deposits proposed by Rowins(2000),many reduced porphyry deposits in China are large-size.Our-study also identified some unusual hydrothermal alteration and metallogenic characteristics.For example,the hydrothermal alteration of the reduced porphyry Cu deposit is characterized by predominant ilmenization rather than magnetization and its ore minerals are chalcopyrite with rare bomite,chalcocite;the hydrothermal alteration of the reduced porphyry Mo deposit occurs ilmenization and its ore minerals is molybdenite,without wolframite and cassiterite.The reduced porphyry-skarn Cu deposits are marked by a reduced skarn mineralogy(e.g.hessonite and hedenbergite) and abundant pyrrhotite in the skarn stage and by major-chalcopyrite rather than bomite and chalcocite in the hydrothermal stage.The diagnos

关 键 词：还原性斑岩矿床 还原流体 CH_(4)来源 钛铁矿 判别标志 

分 类 号：P611[天文地球—矿床学]