岩矿测试

文章摘要

乔鑫,周征宇,农佩臻,赖萌,李英搏,郭恺鹏,钟倩,王含,周彦.贫碱结构水类型祖母绿红外光谱特征及其控制因素探究[J].岩矿测试,2019,38(2):169-178

QIAO Xin,ZHOU Zheng-yu,NONG Pei-zhen,LAI Meng,LI Ying-bo,GUO Kai-peng,ZHONG Qian,WANG Han,ZHOU Yan.Study on the Infrared Spectral Characteristics of H₂OⅠ-type Emerald and the Controlling Factors[J].Rock and Mineral Analysis,2019,38(2):169-178.DOI:10.15898/j.cnki.11-2131/td.201804070039

贫碱结构水类型祖母绿红外光谱特征及其控制因素探究

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Study on the Infrared Spectral Characteristics of H₂OⅠ-type Emerald and the Controlling Factors

投稿时间：2018-04-07 修订日期：2018-11-23

DOI：10.15898/j.cnki.11-2131/td.201804070039

中文关键词: 祖母绿红外光谱 Ⅰ型水类质同象替换 (Mg²⁺+Fe²⁺)离子浓度

英文关键词: emerald Infrared Spectrometry H₂OⅠ-type isomorphic substitution (Mg²⁺+Fe²⁺) cations concentration

基金项目:国家自然科学基金项目（41272049）；上海市科委科研计划项目（15DZ2283200，12DZ2251100）

作者	单位	E-mail
乔鑫	同济大学海洋与地球科学学院, 上海 200092
周征宇	同济大学海洋与地球科学学院, 上海 200092 上海宝石及材料工艺工程技术研究中心, 上海 200070 同济大学宝石及工艺材料实验室, 上海 200092	06058@tongji.edu.cn
农佩臻	同济大学海洋与地球科学学院, 上海 200092
赖萌	同济大学海洋与地球科学学院, 上海 200092
李英搏	同济大学海洋与地球科学学院, 上海 200092
郭恺鹏	同济大学海洋与地球科学学院, 上海 200092
钟倩	同济大学海洋与地球科学学院, 上海 200092
王含	同济大学海洋与地球科学学院, 上海 200092
周彦	同济大学宝石及工艺材料实验室, 上海 200092

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中文摘要:

祖母绿红外吸收主要与其硅氧骨干、通道内结构水、相关碱性金属离子和大分子振动有关。国内外相关研究主要集中在峰位归属及谱峰特征对比方面，认为与分子振动和不同类型结构水相关，对更深层的成矿或化学控制因素的研究还较少。本文选取典型4个矿区样品，针对贫碱结构水（Ⅰ型）特征为主的祖母绿进行了近、中红外光谱测定，在此基础上初步探讨其主要控制因素。结果表明：同为Ⅰ型水主控的不同矿区祖母绿呈现一致特征，若干与结构水、碱性离子及大分子相关吸收具有稳定峰位、近似的相对峰强和峰形的特征。分析发现：祖母绿红外谱带特征直接受控于通道中结构水的占位方向和比例，进一步与祖母绿成矿元素Al³⁺的类质同象替换相关，主要受（Mg²⁺+Fe²⁺）离子浓度影响，当其浓度较低时，类质同象替换程度较低，祖母绿结构水占位主要表现为Ⅰ型水特征，其相关元素特征表现为高Si、Al，低Mg、Fe，总体贫碱，对应相应的典型红外特征，指示化学离子浓度与红外谱学特征之间的关系。研究过程表明红外光谱可以辅助对Ⅰ型水祖母绿产地的鉴定和成矿环境的认知。

英文摘要:

BACKGROUND: The infrared absorption mechanism is mainly related to the Si-O lattice, channel structure water, other alkaline metal cations, and vibration of molecules. Relevant research at home and abroad focuses mainly on peak position attribution and spectral peak feature comparison. It is considered that molecular vibration is related to different types of structural water. However, there are few studies on deeper mineralization or chemical controlling factors.
OBJECTIVES: To unravel the controlling factors of H₂OⅠ-type infrared spectral characteristics.
METHODS: The typical H₂OⅠ-type natural emeralds were collected from 4 mining areas, including the Eastern Cordillera mountains in Colombia (EC), the Panjshir valley in Afghanistan(P), the Ural mountains in Russia(U), and the Kaduna/Plateau state in Nigeria (KP). The samples were analyzed by Fourier Transformed Infrared Spectrometer (FTIR). The typical H₂OⅠ-type infrared (IR) spectral characteristics and their controlling factors were studied. The chemical composition data were obtained from the EMPA analyses.
RESULTS: The results show that the spectral characteristics of H₂O Ⅰ-type emeralds from different mining areas share a consistent pattern. Several absorptions related to structural water, basic ions and macromolecules had stable peak positions, approximately similar relative peak intensities and peak shapes. As the analysis proved, the H₂OⅠIR spectra were first directly controlled by the mixed ratio of the two types of the structure water in the channel, and further related to the substitution of Al³⁺, chemically controlled by the (Mg²⁺+Fe²⁺) concentration in the ore fluids. When the concentration of (Mg²⁺+Fe²⁺) was low, the degree of isomorphic substitution was lower, and the emerald structure water was mainly characterized by Ⅰ-type water. The related elements were characterized by high Si and Al but low Mg and Fe, corresponding to the typical infrared characteristics, indicating the relationship between chemical ion concentration and infrared spectral characteristics.
CONCLUSIONS: The research process showed that Infrared Spectroscopy could assist in the identification of Ⅰ-type water emerald production discrimination and the understanding of the metallogenic environment.

主管单位：	中国科学技术协会
主办单位：	中国地质学会岩矿测试技术专业委员会国家地质实验测试中心