Modeling alteration potential in cooling lava domes
Abstract
Modeling the state of hydrothermal circulation in cooling lava domes can contribute significantly to assessments of dome stability and collapse hazards. Alteration processes may transform primary minerals in dome rock to weaker secondary products such as clay minerals, while secondary mineral precipitation may also affect the porosity and permeability of dome rock with respect to fluids and gas. However, directly imaging the hydrothermal system of a lava dome is impossible without concentrated geophysical investigations, which are often not feasible on rugged volcanic terrains. To circumvent this problem, we turned to porous flow modeling (FEHM), combining finite volume simulations of idealized lava dome geometries with Rock Alteration Index (RAI) calculations. This allowed us to determine likely locations in cooling lava domes where alteration and secondary mineral precipitation, with associated cementing/sealing effects, are most likely to occur. Our results show that mineral dissolution is likely to occur at the base of a cooling lava dome, and precipitation/formation of alteration minerals is likely to occur at the interface between the hot core of a dome and its overlying talus. This suggests that alteration-induced collapses are most likely to initiate at shallow levels in the dome such as in the talus. Such collapses may continue as a series of retrogressive failures and result in major dome collapses. Additionally, precipitating silica minerals at the core/talus interface could create a sub-talus cap of reduced permeability that could restrict fluid and gas circulation, which might contribute to gas pressurization and associated destabilization.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.V33C2755B
- Keywords:
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- 8424 VOLCANOLOGY Hydrothermal systems;
- 4300 NATURAL HAZARDS;
- 1034 GEOCHEMISTRY Hydrothermal systems