We are pleased to announce a Petrology Lunch with Dmitry Bondar on the topic of: From rhyolitic to peridotitic glasses: compositional dependence of molar absorptivities and precise water quantification by FTIR.
Abstract
Water is the most abundant volatile component in magmas and strongly influences the physical and chemical properties of silicate melts. Accurate determination of dissolved water is therefore essential for understanding magmatic processes. Fourier transform infrared (FTIR) spectroscopy is one of the most widely used methods for measuring water contents in silicate glasses, but existing calibrations are largely restricted to relatively polymerized compositions.
In this talk, I will present new FTIR calibrations that extend from rhyolitic to highly depolymerized peridotitic glasses, covering the widest compositional range investigated to date. Hydrous peridotitic glasses were synthesized using a rapid-quench multi-anvil technique, which will also be briefly introduced, and absolute water concentrations were determined by elastic recoil detection analysis. By combining our new measurements with a critical compilation of more than 350 published molar absorptivity values, we establish systematic compositional trends for the principal infrared absorption bands of water. These relationships enable accurate prediction of molar absorptivities as a function of glass composition, significantly improving FTIR-based water quantification across a broad range of natural and synthetic silicate glasses.