The application of near-infared spectral data in studying the chloritized rocks

Near-Infrared Spectroscopic Study of Chlorite Minerals

“…The weak band near 4525 cm −1 was assigned to the combination of OH stretching and deformation vibrations of Al-OH groups in 2 : 1 layers, and this band was also observed at a similar frequency in kaolinites [34]. Another weak band near 4361 cm −1 was tentatively attributed to an Mg-OH combination band [10]. The absorptions near 4440 and 4270 cm −1 are intense and The energy required for the combination band is the sum of the stretching and bending bands in the case of evenly spaced energy levels.…”

“…Post and Crawford [9] observed a shift in the overtone band from 7102 cm −1 to 7205 cm −1 and suggested that this shift might make the identification of chlorite by remote sensing more difficult. Yang et al [10] and Laakso et al [11] observed a hydroxyl absorption shift (4424 cm −1 to 4456 cm −1 ) toward higher frequency with increasing Mg and toward lower frequency with increasing Fe, but they did not discuss the hydroxyl absorption band near 4273 cm −1 . Petit et al [12] assigned the NIR features of octahedral smectites (2 : 1 layer) near 4550 cm −1 and 4370 cm −1 to the combination of hydroxyl stretching and bending modes.…”