CO₂ Diffusion in Basaltic Melts: The Role of H₂O

Carbon dioxide (CO₂) is the second most abundant volatile component in magmatic systems after H₂O and plays a crucial role in controlling magma ascent, bubble nucleation, and eruption dynamics. Accurate knowledge of CO₂ solubility and diffusivity in silicate melts is therefore fundamental for understanding and modeling volcanic processes. Despite its significance, experimental constraints on CO₂ diffusion in silicate melts—particularly under hydrous conditions—remain limited.

This study presents new experimental data on CO₂ diffusion in basaltic melts, with a specific focus on the effect of dissolved H₂O. Diffusion couple experiments were conducted at 300 MPa and temperatures between 1200 and 1350 °C using a rapid-quench, internally heated pressure vessel. The resulting glass charges were doubly polished and analyzed using Fourier-transform infrared (FT-IR) micro-spectroscopy to obtain concentration–distance profiles. CO₂ diffusion coefficients (DCO₂) were calculated by fitting these profiles with error functions.

Preliminary results from anhydrous basaltic compositions exhibit clear Arrhenian behavior, with DCO₂ values consistent with previous measurements in Fe-free systems. Ongoing experiments are aimed at quantifying the influence of dissolved H₂O on CO₂ diffusivity, providing new insights into volatile mobility and transport mechanisms in hydrous basaltic melts.