A near-infrared spectroscopic study of hydroxyl in natural chondrodite

A chondrodite from a marble from Ambasamudram near the Archankovil shear zone, Kerala Khondalite Belt, India, was characterized by powder X-ray diffraction (XRD), electron microprobe and Fourier Transform Infrared (FTIR) spectroscopic techniques. FTIR measurements were carried out in the range 400-10000 cm-1, to record both fundamental and overtone modes. A set of absorption peaks at 3393, 3411, 3561, 3571, 3650, and 3685 cm-1 were observed in the fundamental OHstretching mode region. In the combination-mode region modes observed at 4103, 4328, and 4440 cm-1 indicate that the majority of M sites in this chondrodite are occupied by Mg. The modes at 3650 and 4520 cm-1 could be due to silanol (Si-OH) groups. A definite band was also observed at 5072 cm-1, whose origin presently is not clear. A weak overtone mode of the strongest OH stretching was observed at 6967 cm-1.

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