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| Titel |
Incorporation of cooling-induced crystallization into a 2-dimensional axisymmetric conduit heat flow model |
| VerfasserIn |
David Heptinstall, Caroline Bouvet de Maisonneuve, Jurgen Neuberg, Benoit Taisne, Amy Collinson |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250124192
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| Publikation (Nr.) |
 EGU/EGU2016-3580.pdf |
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| Zusammenfassung |
| Heat flow models can bring new insights into the thermal and rheological evolution of
volcanic 3 systems. We shall investigate the thermal processes and timescales in a
crystallizing, static 4 magma column, with a heat flow model of Soufriere Hills Volcano
(SHV), Montserrat. The latent heat of crystallization is initially computed with MELTS, as a
function of pressure and temperature for an andesitic melt (SHV groundmass starting
composition). Three fractional crystallization simulations are performed; two with initial
pressures of 34MPa (runs 1 & 2) and one of 25MPa (run 3). Decompression rate was
varied between 0.1MPa/˚ C (runs 1 & 3) and 0.2MPa/˚ C (run 2). Natural and
experimental matrix glass compositions are accurately reproduced by all MELTS
runs. The cumulative latent heat released for runs 1, 2 and 3 differs by less than
9% (8.69E5 J/kg*K, 9.32E5 J/kg*K, and 9.49E5 J/kg*K respectively). The 2D
axisymmetric conductive cooling simulations consider a 30m-diameter conduit that
extends from the surface to a depth of 1500m (34MPa). The temporal evolution of
temperature is closely tracked at depths of 10m, 750m and 1400m in the centre
of the conduit, at the conduit walls, and 20m from the walls into the host rock.
Following initial cooling by 7-15oC at 10m depth inside the conduit, the magma
temperature rebounds through latent heat release by 32-35oC over 85-123 days to a
maximum temperature of 1002-1005oC. At 10m depth, it takes 4.1–9.2 years for the
magma column to cool by 108-131oC and crystallize to 75wt%, at which point it
cannot be easily remobilized. It takes 11-31.5 years to reach the same crystallinity
at 750-1400m depth. We find a wide range in cooling timescales, particularly at
depths of 750m or greater, attributed to the initial run pressure and the dominant
latent heat producing crystallizing phase, Albite-rich Plagioclase Feldspar. Run 1 is
shown to cool fastest and run 3 cool the slowest, with surface emissivity having the
strongest cooling influence in the upper tens of meters of the conduit in all runs. |
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