“黑碧”OH振动光谱产生分裂原因探究

doi:10.3964/j.issn.1000-0593(2021)12-3864-05

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摘要： “黑碧”指颜色为黑色，主要成分为阳起石的碧玉。电子探针、激光剥蚀电感耦合等离子体质谱仪分析显示“黑碧”为阳起石碧玉。拉曼光谱和红外光谱的OH振动处产生3个主峰，归属于MgMgMg-OH，MgMgFe²⁺-OH（Fe²⁺_M1Mg_M1Mg_M3-OH，Mg_M1Mg_M1Fe²⁺_M3-OH），MgFe²⁺Fe²⁺-OH（Mg_M1Fe²⁺_M1Fe²⁺_M3-OH，Fe²⁺_M1Fe²⁺_M1Mg_M3-OH），但与常见和田玉不同，“黑碧”的三个主峰在拉曼光谱OH的振动区（3 600～3 700 cm^-1）和红外光谱OH的倍频振动区（7 200～7 100 cm^-1）产生分裂现象。将“黑碧”分为5个区域：HB-1，HB-2，HB-3，HB-4和HB-5，进行原位的电子探针和拉曼光谱分析，拉曼光谱在3 600～3 700 cm^-1出现3个主峰（A，B，C），将主峰进行分峰拟合处理，显示分裂成6个次级峰（A′和A″，B′和B″，C′和C″），次级峰之间的平均波数差为5 cm^-1。前人对角闪石在OH振动处主峰分裂现象的观点各不相同。结合“黑碧”的原位电子探针数据和相关研究文献，认为角闪石中B(M4)位置上的阳离子分布是分裂谱产生的主要原因。角闪石中的B(M4)位置虽然没有直接与W位置的OH相连接，但B(M4)位置上的阳离子通过影响TO₄上的桥氧，间接影响W位置上的OH，从而引起OH振动光谱产生一定变化。对比存在类似分裂谱的角闪石样品和“黑碧”的晶体化学式，发现所有的样品在B(M4)位置上均存在Ca²⁺和Mn²⁺分布，而其他位置的阳离子占位情况都不相同，表明“黑碧”OH振动光谱产生分裂与B(M4)位置上的Ca²⁺和Mn²⁺分布有关。故认为“黑碧”中OH振动光谱产生分裂原因为Ca²⁺和Mn²⁺在B(M4)位置上的占位，且高波数峰位归属于Ca²⁺，低波数峰位归属于Mn²⁺，即A′，B′，C′归属于Ca²⁺，A″，B″，C″归属于Mn²⁺。

关键词：“黑碧”；角闪石；OH振动光谱；分裂

Abstract：“Heibi” refers to serpentinite-related black nephrites whose main components are actinolite. Electron probe microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis showed that “Heibi” was jasper (actinolite). There are three main peaks in OH vibration of Raman spectrum and infrared spectrum, which to MgMgMg-OH，MgMgFe²⁺-OH（Fe²⁺_M1Mg_M1Mg_M3-OH，Mg_M1Mg_M1Fe²⁺_M3-OH），MgFe²⁺Fe²⁺-OH（Mg_M1Fe²⁺_M1Fe²⁺_M3-OH，Fe²⁺_M1Fe²⁺_M1Mg_M3-OH), but differing from the common Hetian jade is that the three main peaks of “Heibi” split in the vibration region of OH (3 600～3 700 cm^-1) in Raman spectrum and frequency doubling vibration region of OH (7 200～7 100 cm^-1) in infrared spectrum. The “Heibi” was divided into five regions: HB-1, HB-2, HB-3, HB-4, HB-5. The in-situ EPMA and Raman spectroscopy analysis that there are main peaks (A, B, C) in the Raman spectrum from 3 600 to 3 700 cm^-1. The main peaks were divided into six secondary peaks (A′ and A″, B′ and B″, C′ and C″), and the average wavenumber difference between the secondary peaks was 5 cm^-1. Previous views on the splitting of the main peak at OH vibration of amphibole are various. Based on the in-situ EPMA data of “Heibi” and previous studies, it is found that the cation distribution at B(M4) position in amphibole is the main reason for the splitting. The B(M4) position of amphibole is not directly connected with the OH at W position, the cations on B (M4) position indirectly affect OH at W position by affecting oxygen bridging atoms of TO₄, thus causing certain changes in OH vibration spectrum. Comparing the crystal-chemical formula of amphibole samples with “Heibi” which have similar splitting spectrum, it is found there are Ca²⁺ and Mn²⁺ distributing in B (M4) position of all samples.While the cation occupation in other positions is various, which proves that the splitting of OH vibration spectrum of “Heibi” is related to the distribution of Ca²⁺ and Mn²⁺ at B(M4). Therefore, it is considered that splitting of OH vibration spectrums in “Heibi” ascribe to occupations of Ca²⁺ and Mn²⁺ in B(M4), the high-wavenumber peaks ascribe to Ca²⁺, and the low-wavenumber peaks ascribe to Mn²⁺, which is A′, B′, C′ ascribe to Ca²⁺, and A″, B″, C″ ascribe to Mn²⁺.

Key words：“Heibi”; Amphibole; OH vibration spectrum; Splitting

收稿日期: 2020-10-19 修订日期: 2021-01-22

中图分类号:

O657.3

基金资助: 国家重点研发计划项目（2018YFF0215403）资助

通讯作者: 杨明星 E-mail: yangc@cug.edu.cn

作者简介: 代路路，1992年生，中国地质大学（武汉）硕士研究生 e-mail: 1289139813@qq.com

引用本文:

代路路，杨明星. “黑碧”OH振动光谱产生分裂原因探究[J]. 光谱学与光谱分析, 2021, 41(12): 3864-3868.
DAI Lu-lu, YANG Ming-xing. Research on the Cause of Splitting of OH Vibration Spectrum in “Heibi”. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2021, 41(12): 3864-3868.

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