摘要
云南个旧锡矿以其超大规模的锡多金属储量而闻名于世。本文利用电子探针EPMA和LA-ICPMS对个旧锡矿高松矿段锡石硫化物矿体中热液黑云母和绿泥石的化学成分进行分析,为约束成矿物理化学条件提供新的证据。结果表明,矿石中的热液黑云母为镁黑云母,形成于氧化物阶段和硫化物阶段,计算得到结晶温度分别为285~350℃和155~245℃,对应的氧逸度lgf_(O2)分别为40.4~34.7和57.3~44.7。绿泥石形成于硫化物阶段,主要为铁叶绿泥石,形成温度为171.2~260.6℃,lgf_(O2)在60.9~48.4,与热液黑云母基本一致。结合前人流体包裹体研究结果,推测氧化物阶段成矿温度为280~440℃,而硫化物阶段温度为180~280℃。此外,从岩浆黑云母到氧化物阶段再到硫化物阶段热液黑云母,卤素地球化学出现有规律的演化。其中fH_(2)O/f_(HF)和fH_(2)O/f_(HCl)逐渐增大,且fH_(2)O/f_(HF)增大程度显著大于fH_(2)O/f_(HCl),而lgf_(O2)和f_(HF)/f_(HCl)则明显减小。表明从岩浆熔体到流体的过程中,Cl少量减少,F有明显变少,暗示高F、高O条件有利于Sn从熔体进入流体。而在成矿过程中,随着氧化物和氟化物的不断结晶,流体中F和O的含量则不断降低。此外,热液黑云母微量元素地球化学特征显示,相较于岩浆黑云母,其异常富集Sn、Li、Rb和Cs,暗示花岗岩浆在结晶过程中,随着温度降低,这些元素趋向从熔体中分异并富集在流体中,为锡成矿提供了丰富的物质条件。
The Gejiu Sn deposit is renowned for its supergiant Sn and polymetallic reserves.In this study,the chemical compositions of hydrothermal biotite and chlorite from the tin-sulfide ores of the Gaosong deposit in Gejiu were determined utilizing electron probe microanalysis(EPMA)and LA-ICP-MS to provide new insights into the mineralization process.The hydrothermal biotite is classified as Mg-biotite and formed during both the oxide and sulfide stages.Calculated formation temperatures for the biotite are 285~350℃for the oxide stage and 155~245℃for the sulfide stage,with corresponding oxygen fugacities(lgf_(O2))of 40.4 to 34.7 and 57.3 to 44.7,respectively.The chlorite formed in the sulfide stage is primarily delessite(Fe-chlorite),with a formation temperature of 171.2~260.6℃and lgf_(O2)of 60.9 to 48.4,consistent with the hydrothermal biotite in the sulfide stage.Combined with results from previous fluid inclusion studies,we infer that the mineralization temperatures range from 280℃to 440℃for the oxide stage and from 180℃to 280℃for the sulfide stage.Furthermore,the halogen geochemistry from magmatic biotite to hydrothermal biotite through the oxide and sulfide stages shows an increase in fH_(2)O/f_(HF)and fH_(2)O/f_(HCl)ratios,along with a decrease in lgf_(O2)and f_(HF)/f_(HCl).Notably,the increase in fH_(2)O/f_(HF)is more significant than that of fH_(2)O/f_(HCl),suggesting that the hydrothermal fluid experienced a slight decrease in Cl and a significant reduction in F compared to the silicate melt.Consequently,the high F and O content of the Gejiu magmas facilitated the migration of Sn from the melt into the fluid,whereas the crystallization of oxides and fluorides during mineralization drove a continuous decrease in F and O concentrations in the fluid.Trace element studies further reveal that hydrothermal biotite is enriched in Sn,Li,Rb,and Cs compared to magmatic biotite.Therefore,these elements tend to fractionate from the melt and accumulate in the fluid as the temperature of granite magma decreases,providing the necessary ore-forming metals for mineralization.
作者
焦骞骞
王星
常华诚
江小均
李文昌
朱平平
芦磊
JIAO Qianqian;WANG Xing;CHANG Huacheng;JIANG Xiaojun;LI Wenchang;ZHU Pingping;LU Lei(Faculty of Land Resources Engineering,Kunming University of Science and Technology,Kunming,Yunnan 650093,China;Yunnan Institute of Geology and Mineral Resource Exploration,Kunming,Yunnan 650051,China;Datun Sn Mine,Yunnan Sn Mining Company(Ltd),Gejiu,Yunnan 661021,China)
出处
《地质学报》
北大核心
2026年第3期979-996,共18页
Acta Geologica Sinica
基金
昆明理工大学“双一流”科技专项项目(编号202202AG050006)
国家自然科学基金重点项目(编号42430111)
云南省自然科学基金面上项目(编号202301AT070447)联合资助的成果。
关键词
热液黑云母
绿泥石
卤素地球化学
成矿物理化学条件
个旧锡矿高松矿段
hydrothermal biotite
chlorite
halogen geochemistry
physicochemical conditions for mineralization
Gaosong section of the Gejiu Sn deposit
