 |
| Titel |
Dynamic regims and evolution of planetary mantles: insights from laboratory experiments with complex rheology fluids |
| VerfasserIn |
A. Davaille, E. Di Giuseppe, E. Mittelstaedt |
| Konferenz |
EGU General Assembly 2012
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250064203
|
|
|
|
|
|
| Zusammenfassung |
| Planetary long-term cooling, as well as surface phenomena such as plate tectonics,
volcanoes and earthquakes, are mainly controlled by the existence and patterns of
convective motions inside the planets solid-state mantles. The planets in the solar system
present very different dynamic regims: plate tectonics (Earth), episodic complete
(Venus?) or partial (Moon, Europa ?) resurfacing, intense volcanism (Io), stagnant lid
convection (Mars), etc... A key ingredient to produce this diversity is probably the
complex rheology of mantle’s material, but this relationship is still not very well
understood.
We report here new laboratory experiments on mantle convection using a fluid, whose
rheology varies from brittle to visco-plastic to purely viscous when its water content and its
temperature change. So as an analogy to cooling from above, the fluid is dryed from above,
its surface being kept at a constant humidity. It is also heated from below to produce active
upwellings. Humidity, temperature, fluid thickness and rheological properties were
systematically varied. As the fluid dries at the surface, a thermo-chemical boundary layer
(CBL) develops, constituted of a thin brittle film on top of a more ductile layer. Folds and
cracks are visible on the surface film. Depending on the intensity of convection, the presence
of hot upwellings and the rheology variation across the top CBL, the different regims
encountered on planets are observed. These are classified in a regime diagram.
The existence of a brittle film seems necessary to observe asymmetric subduction.
Moreover, the experiments demonstrate that a planet does not stay in the same
regime throughout the geological times, but evolves through a suite of different
regimes. |
|
|
|
|
|
|