基于XRD-Rietveld全谱拟合技术定量分析花岗岩风化壳中矿物组成  

Quantitative Analysis of Mineral Composition in Granite Regolith Based on XRD-Rietveld Full-Spectrum Fitting Method

作　　者：付伟[1,2] 彭召[2] 曾祥伟 覃建勋 李学彪 赖胜[2] 李晓婷 张银梦 FU Wei;PENG Zhao;ZENG Xiang-wei;QIN Jian-xun;LI Xue-biao;LAI Sheng;LI Xiao-ting;ZHANG Yin-meng(Collaborative Innovation Center for Exploration of Hidden Nonferrous Metal Deposits and Development of New Materials in Guangxi,Guilin University ofTechnology,Guilin 541004,China;Department of Earth Sciences,Guilin University of Technology,Guilin 541004,China;Guangzhou Geological Survey Institute,Guangzhou 510440,China;Guangxi Geological Survey Institute,Nanning 530023,China;China Nouferrous Metal（Guilin）Geology and Mining Co.,Ltd.,Guangxi Nonferrous Metal Engineering Research Center,Guilin 541004,China)

机构地区：[1]广西有色金属隐伏矿床勘查及材料开发协同创新中心,桂林理工大学,广西桂林541004 [2]桂林理工大学地球科学学院,广西桂林541004 [3]广州市地质调查院,广东广州510440 [4]广西地质调查院,广西南宁530023 [5]中国有色桂林矿产地质研究院有限公司,广西有色金属工程技术研究中心,广西桂林541004

出　　处：《光谱学与光谱分析》2018年第7期2290-2295,共6页Spectroscopy and Spectral Analysis

基　　金：国家自然科学基金项目(41462005); 广西自然科学基金项目(2014GXNSFAA118304); 广西高校重点实验室基金项目(桂科隐12-A-02-01,桂科能15-140-27-10); 桂林理工大学研究生创新项目(SS201601)资助

摘　　要：XRD-Rietveld全谱拟合方法突破了传统XRD定量分析的众多技术局限,在解决复杂多相混合物的定量问题方面具有显著优势。将XRD-Rietveld全谱拟合方法引入风化壳矿物学研究,有助于解决长期以来地学界对风化壳中矿物组分缺乏准确定量认知的技术瓶颈。在制定专门针对风化样品的全谱拟合精修策略基础上,以广西玉林大容山地区的花岗岩风化壳为研究对象,对发育在两组不同岩性之上的风化剖面(剖面A和剖面B)进行了对比研究。结果表明,风化剖面A(母岩为粗粒黑云母花岗岩)的矿物组合及含量变化范围为:高岭石(6.05%~44.67%)+伊利石(15.85%~49.59%)+石英(29.72%~46.15%)+钾长石(12.04%~22.85%)+斜长石(24.33%~32.70%);风化剖面B(母岩为细粒黑云母花岗岩)的矿物组合及含量变化范围为:高岭石(3.12%~11.47%)+伊利石(13.95%~31.94%)+石英(26.60%~58.05%)+钾长石(13.70%~43.47%)+斜长石(17.95%~23.47%)。两组剖面的全谱拟合修正因子Rwp值<15且gof值<5,计算谱与原始谱拟合效果好,指示矿物定量数据可靠,且能与地质规律较好匹配。在地质意义上,本研究通过母岩原生矿物与次生矿物的含量同步变化,深入揭示了研究区内花岗岩的化学风化过程,厘定了长石类矿物在亚热带气候环境下所经历的长石→伊利石→高岭石演变序列。基于剖面A与剖面B中粘土矿物总量和矿物构成出现显著差异,研究认为在研究区内粗粒黑云母花岗岩比细粒黑云母花岗岩更易遭受强烈的化学风化作用。XRD-Rietveld full-spectrum fitting method broke through many technical limitations of traditional XRD quantitative analyses and is of great significance in solving the quantitative problem of multi-phase mineral system.Our efforts in this study focused on a comparative study on two granite weathering profiles（A and B profile）in Darongshan area in Yulin,Guangxi.These two profiles were developed adjacent with similar climatic and topographic condition but different parent rock lithology.In order to achieve an accurate and reliable quantitative result,a special fitting strategy was set for the granite weathering samples.Analytical results showed that A and B profile contained similar mineral composition as a whole,mainly including Quartz,Kfeldspar,kaolinite,illite and plagioclase.Quantitatively,A profile derived from coarse-grained biotite granite was composed by kaolinite（6.05%～44.67%）＋illite（15.85%～49.59%）＋ quartz（29.72%～46.15%）＋ K-feldspar（12.04%～22.85%）＋ plagioclase（24.33%～32.70%）.In contrast,B profile derived from fine-grained biotite granite was composed by kaolinite（3.12%～11.47%）＋illite（13.95%～31.94%）＋ quartz（26.60%～58.05%）＋ K-feldspar（13.70%～43.47%）＋ plagioclase（17.95%～23.47%）.Both Rwpvalue（less than 15）and gof value（less than 5）indicated that the calculated spectrum fitted well with the original spectrum,and thus the final quantitative data of minerals was reliable.Also,the analytical results were consistent with geological observations.The geological significance of this study lied in providing quantitative evidence to indicate the weathering process of granite-forming minerals,especially for feldspar group minerals which show an evolution path as feldspar→illite→ kaolinite.In addition,based on the significant difference in total clay minerals contents between A and B profile,this study suggested that the granite with coarse-grained texture was more susceptible to suffer intense chemical weathering than those with f

关 键 词：XRD-Rietveld全谱拟合 矿物定量 风化壳 花岗岩 广西 

分 类 号：O657.3[理学—分析化学]