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| Titel |
Dynamics of magma recharge, ascent and convection in magmatic reservoirs |
| VerfasserIn |
C. P. Montagna, A. Longo, P. Papale |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250062865
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| Zusammenfassung |
| Shallow magmatic reservoirs are periodically rejuvenated by new magma inputs bringing
volatiles and contributing to volcano degassing. Quite often, such new magmatic
inputs shortly precede a volcanic eruption, likely as a consequence of increased
pressure in the hosting reservoir. In spite of their relevance for both understanding the
evolution of magmatic bodies and forecasting the hazard related to the occurrence of a
new eruption, the dynamics of magma injection in shallow chambers are poorly
known to-date. Here we present the results of numerical simulations through which
such dynamics are investigated in details. We consider a 2D magmatic system that
extends vertically for several km, representing a deep volatile-rich reservoir hosting
less chemically evolved magma connected through a dyke to a shallow, smaller,
volatile-depleted chamber hosting a more differentiated magma. The relevant properties
density and viscosity, and the non-ideal equilibrium between dissolved and exsolved
H2O+CO2 volatiles, are computed locally as a function of P - T - X conditions. The
numerical code that we have developed solves the Navier-Stokes equations for the 2D
homogeneous multi-component system through finite elements and by making use of robust
numerical schemes adequate for incompressible-to-compressible conditions. An
initial interface between the two magma types, that further differ for their chemical
composition, is destabilized by buoyancy forces, giving rise to complex patterns
of magma convection and mixing. We analyze the convective patterns associated
to plume ascent dynamics and the corresponding pressure variations at various
levels in the simulated system, in a parametric study where simulations are repeated
by varying only the geometry of the shallow magma chamber or the contrast in
volatile contents of the two magma types. Among several other aspects, the results
show that oblate (sill-like) chambers are much less effective than prolate (vertically
extended) chambers in developing overpressure, suggesting a physical reason for the
widespread occurrence of sill-like intrusions not associated with volcanic eruptions. |
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