FTIR and13C NMR Spectrum Characterization and Significance of Amber from Different Origins
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摘要: 采用傅里叶变换红外光谱仪并配合固体高分辨核磁共振波谱仪，对不同产地的琥珀和柯巴树脂的红外光谱（FTIR）和核磁共振谱（13C NMR）进行了测试与分析。结果表明，由C—H饱和键伸缩振动致红外吸收强谱带致2 930，2 870 cm-1红外吸收强谱带，与之对应的CH2—CH3弯曲振动致1 460～1 443 cm-1和1 384～1 375 cm-1红外吸收中强谱带，为不同产地琥珀的特征红外光谱；与琥珀相比较，柯巴树脂所特有的吸收谱峰为由C═CH2反对称伸缩振动致红外吸收弱谱带3 080 cm-1，C═C伸缩振动致红外吸收谱带1 645 cm-1和C—H面外变形振动致红外吸收谱带890 cm-1；分析不同产地琥珀的FTIR和13C NMR谱学表征，其相对石化成熟度亦有差异，缅甸琥珀、辽宁琥珀、多米尼加琥珀、墨西哥琥珀的相对年龄依次变新，且δ＝14×10-6～18×10-6和δ＝215×10-6～220×10-6处的13C NMR共振谱峰仅出现在柯巴树脂中，表明其石化成熟度相对偏低。文中对不同产地琥珀的谱学表征差异与其石化程度的关系及其意义一并给予了分析。Abstract: Some pieces of amber from different origins and copal resin were tested and analyzed by FTIR and13C NMR.From testing results，amber from difference origins has the basically similar FTIR characteristics，such as absorption bands at 2 930，2 870 cm-1caused by the saturated C—H bond stretching vibration，and the corresponding infrared absorption bands 1 460～1 443 cm-1and 1 384～1 375 cm-1induced by CH2—CH3bending vibration. Compared with the amber，FTIR characteristics of copal resin show infrared absorption weak band at 3 080 cm-1induced by C═CH2antisymmetric stretching vibration，infrared absorption bands at 1 645 cm-1induced by C═C stretching vibration and infrared absorption band at 890 cm-1caused by C—H out of plane deformation vibration.Analyses of FTIR and 13C NMR characterize amber from different origins and natural resin with relative different petrochemical maturity degree. The age of amber from Burma，Dominica，Liaoning and Mexico reduce in turn．Peaks of 13C NMR spectrum at δ=14×10-6～18×10-6 and δ=179×10-6～220×10-6 only appear in copal resin，showing that the petrochemical maturity is relatively low．This paper finally concludes the FTIR and 13C NMR spectrum characterization and significance of amber from different origins．
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Keywords:
- amber /
- copal resin /
- FTIR /
- 13C NMR /
- origin
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表 1 温度估算结果表(温度由Al、Cr、Ca-橄榄石温度计估算)Table 1. Results of the temperature estimates (temperature is estimated by Al, Cr, Ca in olivine thermometer)
Thermometer Type Average Temperature /℃ TAl in ol 926 TCr in ol 946 TCa in ol 995 表 2 基于橄榄石化学成分，使用线性判别及机器学习模型对橄榄石产地判别的准确率统计Table 2. Accuracy statistics of identification of olivine origin using linear discrimination and machine learning model based on olive petrochemical compositionsModel Accuracy/% Sample quantity：296 Sample quantity：313 B-LDA 83.4 84.3 Extra tree 93.3 93.6 Random Forest 86.5 88.3 Xgboost 92.1 88.3 Logistic Regression 79.8 85.0 lightgbm 95.5 83.0 catboost 89.9 92.6 Naive Bayes 80.9 80.9 注：产地判别选取Mn，Zn，Na，Al，Sc，V，Cr，P，Ti及REE十种元素，不同模型的准确率基本都高于80%;第一次使用296颗宝石级橄榄石样品进行判别，第二次加入17颗非宝石级橄榄石进行判别，两次判别不同模型的准确率均有所变化，表明样品数量和橄榄石品质对模型准确率有不同程度的影响 ![]()
图 1 橄榄玄武岩样品照片及试验结果：(a)橄榄石晶体及其玄武岩围岩；(b)橄榄玄武岩的BSE图像中可见橄榄石、辉石、赤铁矿-钛铁矿、角闪石、磷灰石等矿物。橄榄石和辉石呈自形-半自形，赤铁矿-钛铁矿常呈规则的六边形，角闪石大多为短柱状，平行或近垂直排列，磷灰石成近六边形穿排列在橄榄石和辉石附近；(c)橄榄玄武岩中主要矿物的拉曼光谱；(d)玄武岩微量元素(原始地幔标准化)配分模式蛛网，玄武岩中稀土元素呈右倾形分布，轻重稀土分异明显Figure 1. Photographs of the olivine basalt samples and test results: (a) peridot crystals and basalt samples; (b) BSE images of olivine basalt showing the presence of olivine, diopside, enstatite, hematite-ilmenite, hornblende, apatite, etc. Olivine and diopside exhibit idiomorphic to hypautomorphic. Hematite-ilmenite typically forms regular hexagons. Hornblende is predominantly observed as short columnar shapes, arranged parallel or nearly perpendicular. Apatite forms near-hexagonal prisms arranged in clusters adjacent to olivine and pyroxene; (c) Raman spectra of the main minerals in the olive basalts; (d) spider diagrams of trace elements (normalized by primitive mantle) in basaltic matrix. The trace elements show a right-dipping distribution, with obvious differences between light and heavy rare earths.Di: Diopside; En: Enstatite; Hem-Ilm: Hematite-Ilmenite; Pl: Plagioclase; Ol: Olivine; Ap: Apatite; Hb: Hornblende -
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