Earth Science Frontiers ›› 2022, Vol. 29 ›› Issue (1): 459-469.DOI: 10.13745/j.esf.sf.2021.1.58

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Middle and far infrared spectroscopic analysis of calcite, dolomite and magnesite

ZHU Ying(), LI Yanzhang, LU Anhuai*(), DING Hongrui*(), LI Yan, WANG Changqiu   

  1. Beijing Key Laboratory of Mineral Environmental Function and Ministry of Education Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, China
  • Received:2020-05-10 Revised:2021-01-22 Online:2022-01-25 Published:2022-02-22
  • Contact: LU Anhuai,DING Hongrui

Abstract:

We used Raman and infrared (IR) spectroscopy in this study to investigate the spectral characteristics and infrared emission performance of calcite, dolomite and magnesite. We found substituting Mg for Ca would influence symmetric stretch (ν1), out-of-plane bend (ν2), asymmetric stretch (ν3) and in-plane bend (ν4) of CO32-and cause blue shift in all characteristic vibration bands in Raman, mid-IR absorption, far-IR absorption and IR emission spectra. According to blackbody radiation theory and radiation energy spectra of samples in the range of 400 to 2000 cm-1at 80 ℃, we found the emissivities of calcite, dolomite and magnesite were 0.951, 0.938, 0.895, respectively. The positions of vibration bands in the infrared absorption/emission spectra of the three minerals are significantly affected by the fundamental frequency of CO32-. All minerals produce a broad low absorption band in the 1300-1650 cm-1 range, which is related to asymmetric stretching of CO32-. Moreover, there is a negative correlation between the C-O absorption range (202, 236, 272 cm-1) and emissivity. Therefore, when the strongest chemical bond vibration gives rise to narrow absorption band in the emission spectrum, relatively high radiation energy and emissivity are indicated. Besides, the mineral crystal structure can also affect emissivity. Larger ionic radius or unit cell volume and longer bond length can reduce absorption energy thus enhance radiation emission in the radiation process. In conclusion, the atomic mass of cations in carbonate minerals can affect Raman and infrared vibrational frequency, and emissivity may be associated with C-O low-absorption band range, crystal structure and strongest absorption band controlling lowest emissivity. This study presents the necessary spectral information and thermal emissivity data for the characterization of carbonate minerals, which provides a reference for the spectroscopic characterization of similar minerals as well as establishes a basis for the characterization of carbonate minerals from the crust of the Earth and for exoplanet exploration by remote sensing.

Key words: carbonate minerals, mid-infrared absorption spectroscopy, far-infrared absorption spectroscopy, infrared emission spectroscopy, crystal structure, emissivity

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