Timing Vapor–Melt Equilibration in Silicic Magmas
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Magmas experiencing pressure changes can follow equilibrium or nonequilibrium degassing paths that determine the rate of gas exsolution and the composition of gases exsolved. Many variables influence timescales of equilibration between vapor and melt after a perturbation in pressure, temperature, or other factors, and the magnitude of this equilibration time determines whether the system experiences equilibrium degassing or not. In order to create a simplified framework for assessing degassing regime, we constructed a numerical diffusion model to test the sensitivity of equilibration time to variables such as bubble size, spacing, melt temperature, initial and final system pressures, and water content. We then determined the degassing regime for a range of bubble-spacing and decompression rates as an initial simplified framework to build on. We also attempted the first mixed-volatile continuous decompression experiments in order validate our model and further improve analyses and interpretations of volatile gradients in natural samples.