Particular H₂O dissolution mechanism in iron‐rich melt: Application to martian basaltic melt genesis

Abstract

Martian basalts are different from Earth by their iron‐rich abundance with 18 wt% FeOtot in average for Mars upper crust. The H2O dissolution mechanism in this atypical melt composition is not well understood. We have synthesized H2O‐bearing martian basaltic glass analogs (10 < FeOtot < 16 wt%) under high pressures (0.5–1.5 GPa) and temperatures (>1500°C) conditions. We used Raman and Fourier transform infrared spectroscopies to investigate the effect of H2O as well as the high FeOtot content on the molecular structure of Fe‐rich glasses. Increasing Fe content appears to inhibit the dissolution of H2O in the melt. In fact, it appears that Free OH groups are formed at relatively low H2O content in Fe‐rich melts (1 wt%), whereas they only appeared at high H2O content (~6.5 wt%) for Fe‐poor glasses. We suggest that the Free OH are bonded to Fe2+ cations in the melt forming isolating clusters of Fe (OH)2. Such configurations are suspected to induce an increase in the melt polymerization. The presence of free hydroxyls dissolved in the melt is likely to have a major impact on the genesis of aqueous fluid phase at the surface of Mars.

A chemical threshold controls nanocrystallization and degassing behaviour in basalt magmas

“…It would thus appear that the formation of nanolites depletes the melt from structurally bonded water to form quasi-crystalline domains and thus further increases magma viscosity. This agrees with recent findings 41 suggesting that the formation of isolated Fe(OH) 2 cluster could occur in iron-rich Martian basalts. We therefore hypothesize here that a different tendency toward nanolite formation and gas-melt coupling could play a key role in modulating different eruptive styles during paroxysmal events at Mt.…”

“…However, our results have implications that are potentially further-reaching than the laboratory, since nanocrystals have been identified in various rocks formed during explosive eruptions 21,32,33,[37][38][39][40][41][42][43][44][45][46][47][48][49][50][51] .…”

Immobilization of 129I in nuclear waste glass matrixes synthesized under high-pressure conditions: an experimental study

“…During the high-pressure experiments, using talc-Pyrex assemblies, the fO2 has been estimated to be close to QFM+1 in relative to the solid oxygen buffer Quartz-Fayalite-Magnetite. 71,72 These conditions are relatively oxidizing. For instance, in C-and S-bearing high-pressure systems, the oxidized CO2 and SO2 (or SO3) are the dominant species in both the fluid phase and the melt phase.…”

Synthesis of Large Amounts of Volatile Element-Bearing Silicate Glasses Using a Two-Stage Melting Process

“…Volatile-rich starting material glasses can be synthesized at high pressures, e.g., using internally heated pressure vessels or the piston-cylinder apparatus. , However, the high-pressure synthesis of glasses yields only small amounts (at best in the order of a few 100 mg) of undegassed and homogeneous glasses, which is probably not enough material for a systematic series of evaporation experiments or as a reference material for microanalysis.…”