The fate of magmatic gases during deep-sea volcanic eruptions: Implications for lava domes, hydrothermal systems and mineral ore deposits
As magma ascends towards the surface during volcanic eruptions, dissolved volatile components (H2O, CO2, S, Cl and F) will exsolve from the melt into the vapor phase. This vapor will either: i) remain trapped in bubbles within the melt (where it may later re-condense at low pressure and temperature), ii) be released into the overlying ambient medium through a vent via vertical "outgassing", or iii) outgas laterally into the crust surrounding the volcanic conduit. In the submarine environment, active volcanic centers are commonly associated with intense hydrothermal activity owing to the percolation, heating and recycling of seawater through sediments and the shallow crust. These hot, sediment- and fluid-rich regions surrounding submarine volcanic conduits are ideal localities for the precipitation and growth of secondary minerals, and, eventually, the development of ore deposits. In this study, we used numerical modelling of magma ascent and vapor outgassing to constrain lateral and vertical fluxes of volatiles through the conduit during a large submarine eruption of Havre Volcano on the Kermadec Arc in 2012. By applying existing geochemical knowledge, we calculated the masses of H2O and halogens lost into the surrounding crust and into the adjacent hydrothermal zones during the eruption. We also consider vapour fluxes through an open vent into the ocean vs. fluxes into an overlying lava dome structure. By applying a dome cooling model, we find that the rapid ingestion of seawater into a submarine dome carapace can trap outgassing vapor in the interior of a dome. These trapped, acidic fluids may react with the dome groundmass resulting in significant precipitation of vapor-phase cristobalite - a metastable silica polymorph. The growth of cristobalite on a large scale can deteriorate the interior dome groundmass, thus potentially decreasing dome strength leading to hazardous flank collapse.
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- 0810 Post-secondary education;
- 0815 Informal education;