广西大化和贵州罗甸软玉的谱学特征及产地示踪研究

doi:10.3964/j.issn.1000-0593(2021)04-1294-06

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摘要：广西大化和贵州罗甸软玉是近年来我国南方具有一定开采规模的软玉品种，两个产地的软玉矿地理位置较接近，软玉品种既有相似性也有差异。为了对比研究两个产地的软玉品种的光谱学特征及颜色成因，针对产自广西大化和贵州罗甸的玉石样品进行了宝石学常规测试、傅里叶变换红外光谱、激光拉曼光谱和激光剥蚀等离子体质谱等现代谱学仪器测试。研究发现：红外光谱仪测试结果显示大化软玉样品出现1 033，932，771，699，524，490和427 cm^-1的吸收峰，罗甸软玉出现1 032，932，773，700，525，490和426 cm^-1的吸收峰，其中1 033，1 032和932 cm^-1附近较尖锐的吸收谱带归因于O—Si—O的反对称伸缩振动、O—Si—O对称伸缩振动和Si—O—Si反对称伸缩振动；773，771，700和699 cm^-1附近的吸收谱带是由Si—O—Si的对称伸缩振动导致的。525，524，490，427和426 cm^-1附近的吸收谱带由Si—O的弯曲振动和M—O晶格振动导致。不同于前人的研究结果，该研究在大化软玉样品的红外光谱中发现了850 cm^-1附近的肩状吸收带，推测是样品中少量的透辉石所致。通过激光剥蚀等离子质谱仪分析大化软玉的主要化学成分为SiO₂（58.91%），MgO（25.77%）和CaO（13.67%）；罗甸样品的主要化学成分为SiO₂（57.07%），MgO（24.85%）和CaO（17%），钙含量较大化软玉稍高，两个产地的软玉样品中还含有少量的FeO，MnO，Al₂O₃，Na₂O，K₂O，P₂O₅和TiO₂，Mg/Mg+Fe值大化样品的平均值为97.3%，罗甸样品的平均值为98.8%，证实两地软玉主要矿物均为透闪石，罗甸软玉样品中V的含量随着青色调的加深而上升，故认为V对罗甸软玉的青色调有贡献。研究了大化青玉的致色离子，大化软玉样品中Cr和Fe的含量随着青色调的加深而上升，认为Cr和Fe是大化青玉致色的原因。利用稀土元素特征值的差异，可以很好地区分两个产地的软玉，并且通过产地示踪树状图，可以有效地判定目前国内已知不同产地来源的软玉。

关键词：大化；罗甸；软玉；谱学特征；产地示踪（溯源）

Abstract：Nephrites from Dahua Yao Autonomous County, Guangxi Zhuang Autonomous Region and nephrites from Luodian County, Guizhou province have formed mining scales, both of which have many similar and different characteristics in gemology, spectroscopy and mineralogy. In recent years, a large number of nephrites from these two localities began to appear at domestic and foreign markets. In order to analyze spectroscopic characteristics and color-causing mechanisms of nephrites from these two different sources, the standard gemological methods including refractive index testing, hydrostatic specific gravity testing, an observation by the naked eye and gem microscope were used to their research gemological properties of them. Also, Fourier transforms infrared spectroscopy (FTIR), laser Raman spectroscopy and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was also used to research spectral characteristics and chemical composition of these nephrites. The research result shows that the infrared spectrum of samples from Dahua County showed main absorption bands at 1 033，932，771，699，524，490 and 427 cm^-1, and Fourier transform infrared spectrum of Luodian nephrites samples mainly showed absorption bands at 1 032，932，773，700，525, 490 and 426 cm^-1. Infrared absorption bands at 1 033，1 032 and 932 cm^-1 are induced by O—Si—O anti-symmetric stretching vibration, O—Si—O symmetric stretching vibration and Si—O—Si anti-symmetric stretching vibration. Infrared absorption bands at 773，771，700 and 699 cm^-1 are induced by Si—O—Si symmetric stretching vibration. Infrared absorption bands at 525，524，490，427 and 426 cm^-1 are induced by Si—O bending vibration and M—O lattice vibration. Unlike previous studies, the absorption band at 850 cm^-1 is first discovered in Dahua nephrites, which may be attributed to minor amounts of diopside pyroxene in the sample. This absorption band has not been reported in the previous studies on Dahua nephrites. According to results of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), the main chemical compositions of nephrites samples from Dahua are SiO₂ (58.91%), MgO (25.77%) and CaO (13.67%). The main chemical compositions of Luodian nephrites samples are SiO₂ (57.07%)，MgO (24.85%) and CaO (17%). The average content of calcium in Luodian nephrites samples is a little higher than that of Dahua nephrites samples. A spot of FeO，MnO，Al₂O₃，Na₂O，K₂O，P₂O₅ and TiO₂ were also found in our samples. The value of Mg/Mg+Fe is 97.3% in Dahua and 98.8% in Luodian nephrites respectively. This means the main mineral composition of both location nephrites is tremolite. According to our research, Dahua nephrites and Luodian nephrites have different green color-causing mechanisms. Testing results of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) showed that the content of vanadium in Luodian nephrites samples increased with the green deepening, which showed that the color-causing ion of Luodian green nephrites is probably vanadium (V). This article discussed the green color-causing mechanism of Dahua nephrites for the first time. We think that chrome (Cr) and ion (Fe) are color-causing ions of Dahua nephrites because the content of chrome (Cr) and ion (Fe) increased with green deepening. The trace element values can be used to identify the location of the two site nephrites from Dahua and Luodian. Identifying a location tree can be used to distinguish all the known sites of nephrite in China now.

Key words：Dahua; Luodian; Nephrite; Spectral characteristics; Trac to the source

收稿日期: 2020-10-22 修订日期: 2021-01-18

中图分类号:

O657.3

基金资助: 国家自然科学基金项目（41973032），湖北省珠宝工程技术研究中心科研项目（CIGTXM-03-202001），云南省高校宝石及材料工艺工程研究中心（ZX20200201）资助

通讯作者: 王文薇，尹作为

作者简介: 江翠，女，1980年生，中国地质大学（武汉）珠宝学院讲师 e-mail：jiangcuijane@163.com
彭帆，1993年生，中国科学院上海硅酸盐研究所博士研究生 e-mail：gicpengfan@126.com
江翠，彭帆：并列第一作者

引用本文:

江翠，彭帆，王文薇，尹作为. 广西大化和贵州罗甸软玉的谱学特征及产地示踪研究[J]. 光谱学与光谱分析, 2021, 41(04): 1294-1299.
JIANG Cui, PENG Fan, WANG Wen-wei, YIN Zuo-wei. Comparative Study on Spectroscopic Characteristics and Coloration Mechanism of Nephrite From Dahua and Luodian. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2021, 41(04): 1294-1299.

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