Near Infrared Spectroscopic Study of Trioctahedral Chlorites and Its Remote Sensing Application

Abstract

The mineral chemistry of thirteen trioctahedral chlorite samples from four regions in northwestern China, having a wide range of Fe and Mg contents and relatively constant Al and Si contents, were studied via raman spectroscopy, near infrared (NIR) spectroscopy, X-ray diffraction (XRD) analysis and electron - probe microanalysis. Five absorption features of the twenty samples near 4525, 4440, 4350, 4270 and 4180 cm−1 were observed, and two diagnostic features at 4440 and 4270 cm−1 were recognized. Assignments of the two diagnostic features were made for two combination bands ((ν+δ)(AlAl)O−OH and (ν+δ)(SiAl)O−OH) by regression with Raman fundamental absorptions. Furthermore, the determinant factors of the NIR band position were found by comparing the band positions with relative components. The results showed that Fe2+/(Fe2++Mg) values are negatively correlated with the two NIR combination bands. The findings provide an interpretation of the NIR band formation and demonstrate a simple way to use NIR spectroscopy to discriminate between chlorites with different components. More importantly, a simple example of mapping Fe-rich and Mg-rich chlorites were executed using remote sensing data based on this theory. The spectroscopic detection of mineral chemical variations in chlorites provides geologists with a tool with which to collect information on hydrothermal alteration zones from hyperspectral-resolution remote sensing data.

Distinguishing Features and Identification Criteria for K-Dioctahedral 1M Micas (Illite-Aluminoceladonite and Illite-Glauconite-Celadonite Series) from Middle-Infrared Spectroscopy Data

“…Slonimskaya et al [13] and Besson and Drits [17,18], who analyzed the 1M K-dioctahedral micas within a wide compositional range (illites, glauconites, aluminoceladonites and celadonites), only focused on the OH-stretching vibrations. The most recent IR studies deal with geological applications of spectroscopy data on white mica (e.g., [29,31] or with other groups of silicate minerals [32,33]). Recently, a number of diagnostic features that include the band positions and profile in the regions of Si-O bending, Si-O stretching, and OH-stretching vibrations were suggested for the illite-aluminoceladonite series [7] and the Fe-bearing K-dioctahedral micas [8].…”

Impact melt rock from Jänisjärvi astrobleme: Study of the iron‐bearing phases using Raman spectroscopy, X‐ray diffraction, and Mössbauer spectroscopy

“…(1991) and Yang et al. (2019) and references therein. For example, the band around 200 cm –1 can be assigned to symmetric stretching of the octahedral sites while a weak peak near 280 cm –1 can be related to the tetrahedral movements in chamosite.…”

From Operando Raman Mechanochemistry to “NMR Crystallography”: Understanding the Structures and Interconversion of Zn-Terephthalate Networks Using Selective 17O-Labeling

“…Because structural rearrangements occur around the water molecules/hydroxyls during the Zn-BDC transformations described above, being able to follow this by Raman spectroscopy appeared to us as an important goal to increase our insight into the transformations taking place. Unfortunately, it was not possible to follow the evolution of the O–H stretching modes upon synthesis by BM with our Raman setup because it only allowed spectra to be recorded from 220 to 3120 cm –1 , while ν­(OH) bands most often appears at higher wavenumbers. − …”