Raman spectra of natural carbonaceous materials from a black shale formation

Abstract

Carbonaceous materials in black‐shale rock specimens from three gold‐ore deposits located in Russia and Kazakhstan have been investigated by micro‐Raman spectroscopy using near‐ultraviolet, visible, and near‐infrared wavelength excitation. Only the 325‐nm (3.8 eV) wavelength laser line excitation yielded the Raman spectra for all samples. The first‐order Raman spectra of these carbonaceous materials have facilitated the classification of all the samples obtained from the different deposits into two groups: the observed wavenumber of the G‐band around 1581 cm−1 with a band halfwidth from 23 to 40 cm−1 was observed in samples of the first type, and the observed wavenumber of the G‐band near 1600 cm−1 with a band halfwidth from 46 to 73 cm−1 was characteristic in samples of the second type. From these Raman spectra, it has been possible to estimate the graphitization temperature, which was found to range between 380 and 450°С for samples of the first type and from 250 to 400°С for samples of the second type. It has also been shown that the carbonaceous materials are substantially varied in their structural order both in samples obtained from the same deposit and, to a greater extent, in samples obtained from the black‐shale ore deposits of different types. Copyright © 2015 John Wiley & Sons, Ltd.