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西藏雄村斑岩型铜(金)矿床Ⅰ、Ⅱ号矿体热液黑云母特征及地质意义
Hydrothermal biotite characteristics and geological significance of No.Ⅰ and No.Ⅱ orebodies of the Xiongcun porphyry copper (gold) deposit in Tibet
投稿时间:2019-10-20  
中文关键词:热液黑云母  雄村铜(金)矿床  结晶温度  氧逸度  冈底斯成矿带
英文关键词:hydrothermal biotite  Xiongcun copper (gold) deposit  crystallization temperature  oxygen fugacity  Gangdise metallogenic belt
基金项目:国家重点研发计划课题(2018YFC0604105);国家自然科学基金项目(41772075,41502079)
作者单位E-mail
肖鸿天 成都理工大学, 四川 成都 610059  
谢富伟 成都理工大学, 四川 成都 610059 xiefuwei@hotmail.com 
郎兴海 成都理工大学, 四川 成都 610059  
冉凤琴 成都理工大学, 四川 成都 610059  
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中文摘要:
      雄村铜(金)矿区位于西藏冈底斯成矿带中段南缘,由Ⅰ、Ⅱ、Ⅲ号矿体和多个矿化体组成。本文以Ⅰ、Ⅱ号矿体钾硅酸盐化蚀变带内的热液黑云母为研究对象,采用光薄片镜下鉴定、电子探针等分析方法,系统研究了热液黑云母的产状和成分特征。结果显示,雄村矿区Ⅰ号矿体黑云母类型主要为金云母和镁质黑云母;Ⅱ号矿体黑云母类型为镁质黑云母。两个矿体黑云母都具有低Ti(TiO2<3%)、高Al(Al2O3>15%)的特点,且具有较高的MgO含量,Mg/Fe>0.5,K/Na>10,显示了与矿化良好的相关性。Ⅰ号矿体热液黑云母平均结晶温度470℃,氧逸度位于镍-氧化镍缓冲剂与磁铁矿-钛铁矿缓冲剂之间(NNO-HM);Ⅱ号矿体热液黑云母平均结晶温度234℃,氧逸度位于镍-氧化镍缓冲剂与铁橄榄石-石英-磁铁矿缓冲剂之间(NNO-FQM),说明Ⅰ号矿体形成于较高温、高氧逸度的热液系统,Ⅱ号矿体形成于相对较低温、低氧逸度的热液系统。此外,Ⅰ号矿体热液黑云母Ⅳ(F)值介于0.61~2.72之间,平均值1.26,Ⅳ(Cl)值介于-5.49~-4.53之间,平均值-5.03,Ⅳ(F/Cl)值介于5.63~7.89之间,平均值6.29;Ⅱ号矿体热液黑云母Ⅳ(F)值介于1.83~3.32之间,平均值2.66,Ⅳ(Cl)值介于-5.64~-4.89之间,平均值-5.31,Ⅳ(F/Cl)值介于7.14~8.68之间,平均值7.97,说明Ⅰ、Ⅱ号矿体都形成于富Cl的热液系统,且Ⅱ号矿体热液较Ⅰ号矿体更富Cl,贫F。富Cl流体易萃取流体中的Cu和Au等金属元素并以Cl的络合物形式运移,在沿构造裂隙向上运移的过程中,物理化学条件发生改变,使得流体中金属元素络合物溶解度降低,促使硫化物沉淀成矿。
英文摘要:
      The Xiongcun copper (gold) ore district in Tibet is located on the southern margin of the middle Gangdise metallogenic belt, mainly composed of No.Ⅰ, No.Ⅱ, and No.Ⅲ orebodies and several mineralized bodies. In this paper, the modes of occurrence and composition of hydrothermal biotite in the potassium silicate alteration zone of No.Ⅰ and No.Ⅱ orebodies were systematically studied by means of microscopic identification and electron microprobe analysis. Biotite of No.Ⅰ orebody in the Xiongcun ore district is mainly phlogopite and magnesium biotite while biotite of No.Ⅱ orebody is mainly magnesium biotite. Biotite of both orebodies is characterized by low Ti (TiO2<3%) and high Al (Al2O3>15%), with high MgO content, Mg/Fe value>0.5, and K/Na value greater than 10, which shows a good correlation with mineralization. The average crystallization temperature of hydrothermal biotite in No.Ⅰ orebody is 470℃, and the oxygen futility is between NNO and HM. The average crystallization temperature of hydrothermal biotite of No.Ⅱ orebody is 234℃, and the oxygen futility is between NNO and FQM, indicating that No.Ⅰ orebody was formed in a hydrothermal system with high temperature and oxygen futility, while No.Ⅱ orebody was formed in a hydrothermal system with relatively low temperature and oxygen futility. The Ⅳ(F) value of hydrothermal biotite in No.Ⅰ orebody ranges from 0.61 to 2.72, with an average value of 1.26. The Ⅳ(Cl) value is from -5.49 to -4.53, with an average value of -5.03. The Ⅳ (F/Cl) value is from 5.63 to 7.89, with an average value of 6.29. The Ⅳ(F) value of hydrothermal biotite in No.Ⅱ orebody ranges from 1.83 and 3.32, with an average value of 2.66. The Ⅳ(Cl) value is from -5.64 to -4.89, with an average value of -5.31. The Ⅳ (F/Cl) value is between 7.14 and 8.68, with an average value of 7.97. These data indicate that No.Ⅰ and No.Ⅱ orebodies were formed in the Cl-rich hydrothermal system, and that the hydrothermal solution of No.Ⅱ orebody was richer in Cl and poorer in F than that of No.Ⅰ orebody. Metallic elements such as Cu and Au were easily extracted and moved in the form of metal complex by Cl-rich fluid. In the process of fluid migration, changing physicochemical conditions would reduce the solubility of metal complex and led to sulfide precipitation.
肖鸿天,谢富伟,郎兴海,冉凤琴,2020,西藏雄村斑岩型铜(金)矿床Ⅰ、Ⅱ号矿体热液黑云母特征及地质意义[J].岩石矿物学杂志,(4):469~480.
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