New insight into water-obsidian interaction

Abstract

Hydration of obsidian samples in isotopic water H$_2 ^{18}$O was performed at temperatures from 75$^{\circ}$C to 200$^{\circ}$C. The depth distributions of $^1$H and $^{18}$O in the obsidians measured by SIMS were found to be drastically different. This led us to the conclusion that water molecules split into hydrogen and oxygen at the obsidian surface and then the atomic hydrogen and $^{18}$O isotope diffused into the obsidian via two different mechanisms. The hydrogenated obsidians were heated in vacuum without hydrogen emission. A hypothesis is put forward that the obsidian hydrogenation results from a chemical reaction between atomic hydrogen and a glass network. A new linear-parabolic equation is suggested for obsidian hydrogenation dating. Aluminosilicate glass is considered as a promising material for hydrogen fusion cells.