Open AccessMeasurement of H2O Molecule and Hydroxyl Concentrations in Hydrous Rhyolitic Glass by UV–Vis–NIR Dispersive Microspectroscopy
Author(s) -
Takahiro Miwa
Publication year - 2019
Publication title -
journal of disaster research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.332
H-Index - 18
eISSN - 1883-8030
pISSN - 1881-2473
DOI - 10.20965/jdr.2019.p0780
Subject(s) - rhyolite , volcano , analytical chemistry (journal) , volcanic glass , solubility , mineralogy , spectroscopy , infrared spectroscopy , ultraviolet , chemistry , materials science , geology , volcanic rock , environmental chemistry , geochemistry , physics , optoelectronics , organic chemistry , quantum mechanics
The speciation of water in volcanic glass, as indicated by the relative proportions of H 2 O and OH - , provides information on the processes of volcanic eruptions. Earlier studies of water species used ultraviolet–visible–near-infrared (UV–Vis–NIR) dispersive spectroscopy to examine the NIR spectra of volcanic glass but were unable to confirm whether areas as small as 100 μm across could be studied. Here, UV–Vis–NIR dispersive microspectroscopy was applied in a study of hydrous rhyolitic glass synthesized by decompression in a cold-seal pressure vessel at 880°C. The concentrations of water species were determined by transmittance spectroscopy, with results consistent with those of Fourier-transform infrared microspectroscopy. The measured total water contents were consistent with the known solubility of water in rhyolitic magma, and, therefore, it is concluded that UV–Vis–NIR microspectroscopy can be applied in determining the concentrations of H 2 O and OH - in hydrous rhyolitic glass.