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| Titel |
Rheology of shallow crust of large calderas and relation with eruptions: the Campi Flegrei caldera (Italy). |
| VerfasserIn |
S. Carlino, R. Somma |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250023235
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| Zusammenfassung |
| This work analysed the relationship occurring between the rheology of the shallow crust
(elastic or visco-elastic) and its inference on the magma storage vs eruption, at Campi Flegrei
caldera (CFc) Southern Italy. Assuming a viscoelatic condition, below the CFc, the encasing
rocks are subjected to stress (overpressure) produced by both new magma arrival
within a deep magmatic chamber and/or fluid influx reaching a shallow “hybrid”
source (magmatic-hydrothermal). This two cases are evaluated to understand when
the condition for elastic failure (eruption) or viscous regime (magma storage) are
achieved.
The boundary conditions (i.e. rocks viscosity, magma or fluid influx and volume of the
source involved) are assumed taking into account the recent geophysical and volcanological
investigations of the area and the previous caldera eruptive models.
Both magma and hydrothermal fluids are considered incompressible, while the wall rocks
are assumed viscoelastic with different values of viscosity (μwr =1016 to 1019 Pa sec). The
magma influx of deep chamber (volume range from 400 to 2000 km3) is calculated
considering that a 40 km3 of magma recharge occurred between the last main explosive
eruptions (Campanian Ignimbrite 39 Kyrs B.P. and Neapolitan Yellow Tuff eruption
15,6 Kyrs. B.P.) The obtained influx magma value (0,002 km3y-1) is in agreement
with the average values inferred for others large calderas . In the case of shallow
hybrid source (volume of only few km3) the fluid influx has been considered from
0,009 to 0,02 km3y-1 according to previous studies. The analysis show that, the
viscous regime prevails for the deep magmatic source case, taking into account all the
viscosity range; while for the shallower hybrid source the viscous regime is less
dominant.
Furthermore, the results suggest that, at CFc, magma storage (viscous regime), rather than
its eruption (elastic failure) is enhanced by different factors such as high geothermal gradient,
wall rocks viscosity, heterogeneity of the crust and extensional tectonic strain rate of the area. |
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