ZHU Ying, DING Hong-rui, LI Yan, LI Yan-zhang, XU Xiao-ming, LU An-huai*
(Key Laboratory of Orogenic Belts and Crustal Evolution, Beijing Key Laboratory of Mineral Environmental Function, Peking University, Beijing 100871, China)
Abstract: We have utilized infrared emission spectroscopy to investigate the infrared emission spectrum characteristics of forsterite, tremolite, serpentine, and albite in this paper. By integral calculation of spectra within the infrared band of 400－1650 cm-1 at 120 oC, it is found that forsterite has the highest emissivity of 0.988 among selected 4 kinds of silicate minerals, while albite has the lowest emissivity of 0.947. Furthermore, all 4 silicate minerals have a wide low emission band ranging from 850 to 1300 cm-1 and a relatively sharp low emission band around 470 cm-1, which are related to the stretching vibration and bending vibration of the (Si, Al)-O bond in tetrahedral layers of silicates, respectively. With the gradual increase of SiO2 polymerization degrees from island, chain, sheet, to framework silicates, the location of the strongest emission valley in emissivity patterns is gradually shifted towards the high emission band, indicating that the position of stretching vibration band in the Si-O tetrahedron is restricted by the atomic ratio of Si and O (n(Si)/n(O)). Moreover, in radiant energy patterns, ranges of the strongest emission valley for forsterite, tremolite, serpentine, and albite are 115, 162, 225 and 247 cm-1, respectively, indicating that the increase of radiant energies with the enhancement of SiO2 polymerization degrees of those silicates. In conclusion, it can be speculated that the strong emissivity of silicate minerals could be associated with the vibration mode of Si-O bond in the silica tetrahedron, SiO2 polymerization degree, and range of the strongest emission valley in the spectrum.
Keywords: Silicate mineral; Infrared absorption spectroscopy; Thermal infrared emission spectroscopy; Emissivity
ACTA MINERALOGICA SINICA Vol. 39, No.2, 2019, page 173-182
