江西曾家垄锡矿高分异花岗岩黑云母地球化学组成:对岩浆源区和演化过程的记录  

Biotite in highly evolved granite from the Zengjialong Sn ore deposit,China:Insights into magma source and evolution

作　　者：孙克克 陈伟 SUN Keke;CHEN Wei(School of Earth Sciences and Engineering,Hohai University,Nanjing,Jiangsu 211100,China;State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Beijing 100083,China;Department of Ecology and Environment of Anhui Province,Hefei,Anhui 230031,China;Shanghai Institute of Chemical Industry Testing Co.,Ltd,Shanghai 200000,China)

机构地区：[1]河海大学地球科学与工程学院,江苏南京211100 [2]地质过程与矿产资源国家重点实验室,北京100083 [3]安徽省生态环境科学研究院,安徽合肥230031 [4]上海化工院环境工程有限公司,上海200000

出　　处：《地质学报》2025年第3期760-777,共18页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号42003024);地质过程与矿产资源国家重点实验室(中国地质大学)开放基金(编号GPMR202315);中央高校基本科研业务费项目(编号B240201151)联合资助的成果。

摘　　要：锡是重要的战略性关键金属,对其成矿规律的研究具有重要的理论意义和显著的经济价值。原生锡矿化总是与还原的高分异花岗质岩浆密切相关。相比于普通花岗岩,富锡高分异花岗岩经历了复杂的演化过程,全岩地球化学往往具有多解性且只能给出岩浆体系演化最终产物的信息,难以揭示岩浆经历的演化细节。岩浆中结晶的矿物如石英、黑云母、磷灰石等能够记录岩浆组分的动态变化及全岩组分难以反映的精细演化过程,在花岗岩成因研究中显示出独特的优势。本文对江西省曾家垄锡矿成矿高分异花岗岩中的黑云母开展了系统的地球化学研究。曾家垄花岗岩中的黑云母为岩浆来源。这些黑云母显示低的镁指数(Mg^(#)=5.70~9.93,平均值为7.63)和高的铝饱和指数(A/CNK=1.77~1.98,平均值为1.88),与世界范围内S型花岗岩中黑云母特征一致,表明曾家垄花岗岩为变质沉积岩熔融而成的S型花岗岩。黑云母微量元素结果显示随着K/Rb比值降低,Rb、Cs、Sn的含量逐渐增加而Pb含量逐渐降低,暗示岩浆经历了以钾长石为主的分离结晶过程。值得关注的是黑云母中Sn的含量随着K/Rb比值降低增加了4倍,暗示随着岩浆分异锡在残余岩浆中的含量显著增加。曾家垄花岗岩黑云母具有较低的Ⅳ(F)、Ⅳ(F/Cl)、lg(fHF/fHCl)值,较高的Ⅳ(Cl)值,Ⅳ(Cl)与Ⅳ(F/Cl)之间、lg(f_(H_(2)O)/f_(HF))与lg(f_(HF)/f_(HCl))之间显示明显的负相关性,暗示曾家垄岩浆为富氟贫氯岩浆体系,黑云母结晶过程中伴随有持续的流体出溶。曾家垄花岗岩中黑云母几乎不含Fe^(3+),在Fe^(3+)-Fe^(2)+-Mg三角图解中,黑云母均位于FMQ线之下,表明其氧逸度非常低。曾家垄花岗岩中黑云母记录了岩浆具有富集的源区组成、高程度的分异演化、较低的氧逸度、持续的流体出溶,这些过程有利于最终的矿化富集。结合本文的数据及统计的文献数据表�Tin,a strategically significant metal,necessitates a comprehensive understanding of its mineralization processes,which hold substantial theoretical and economic value.Primary Sn mineralization is typically associated with highly evolved and relatively reduced granitic magmas.Compared to common granites,Sn-rich granites exhibit complex magmatic evolution,making it challenging to determine their early-stage magmatic compositions using whole rock geochemistry alone.This method yields data primarilyfrom the final stages of magmatic evolution,limiting our capacity to fully grasp the sources and evolution of these magmas.However,mineral phases such as quartz,biotite,and apatite,crystallized within the magma,serve as valuable archives of dynamic compositional changes and fine-scale evolutionary processes that often remain concealed in whole rock analyses.This study presents a comprehensive dataset of major and trace elements(including halogen)for biotites from highly evolved granites in the Zengjialong Sn ore deposit.These biotites exhibit magmatic origins,characterized by low Mg^(#)(5.70~9.93,mean=7.63)and high A/CNK values(1.77~1.98,mean=1.88),consistent with biotites in S-type granites worldwide.These compositional characteristics suggest a metasedimentary origin for the parental magmas.Trace element analysis of biotites shows a systematic increase in Rb,Cs,and Sn,accompanied by concurrent decrease in Pb and K/Rb ratios.This trend suggests that crystal fractionation is dominated by K-feldspar.Furthermore,Sn concentrations in biotites increase fourfold due to progressive fractional crystallization,indicating Sn enrichment in the residual magmas.Biotites also exhibit lowⅣ(F),Ⅳ(F/Cl),and lg(f_(HF)/f_(HCl))values,coupled with highⅣ(Cl).These values,coupled with the negative correlations betweenⅣ(Cl)andⅣ(F/Cl)as well as lg(f_(H_(2)O)/f_(HF))and lg(f_(HF)/f_(HCl)),suggest a F-rich,Cl-depleted magma system and continuous fluid exsolution during biotite crystallization.Additionally,the biotites in the Zengjialong g

关 键 词：黑云母 高分异花岗岩 岩浆源区 卤素逸度 华南 

分 类 号：P61[天文地球—矿床学]