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| Titel |
The importance of plumes to trigger subduction of a sluggish lid: examples from laboratory experiments and planets |
| VerfasserIn |
Anne Davaille, Suzanne Smrekar |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250096460
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| Publikation (Nr.) |
 EGU/EGU2014-11967.pdf |
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| Zusammenfassung |
| The possible role of plate tectonics in creating habitable zones and the conditions required to
start plate tectonics are currently hotly debated due to the discovery of many Earth-sized
exoplanets. The initiation of subduction is both the gateway to plate tectonics and a key link
between interior convection and lithospheric rheology. Modeling the details of plate failure
and the initiation of subduction is very challenging due to the complexity of mantle
rocks.
We carried out experiments on convection in aqueous colloidal dispersions heated from
below, and dried and cooled from above. The rheology of these fluids depends strongly on
solid particle fraction fp, being Newtonian at low fp, and presenting yield stress, elasticity,
and brittle properties as fp increases. Such a behaviour is analogue to the rheology
of mantle rocks as temperature decreases. So if drying is sufficiently rapid in the
laboratory, a skin forms on the fluid surface and may participate (or not) to the
convective motions, depending on the experimental parameters. Moreover, we observed
that (1) the existence of upwelling plumes help trigger subduction, the asymmetric
subduction zone being localized on the rim of the plume impingement zone under the
lithosphere; (2) depending on the lithospheric rheology, the nascent subduction
can then either stop as the result of subducted plate necking, or continue to sink
smoothly.
Inspection of the geological record on Earth suggests that such a strong association
between plumes and subduction may have been instrumental in the nucleation and
growth of cratons, the onset of continuous plate tectonics, and present-day initiation
of subduction around some large oceanic plateaus. On Venus, interpretation of
geophysical data sets suggests that Quetzelpetlatl corona overlies an active plume. The
narrow trough found along 2/3 of the margin of the corona has a flexural signature
and is likely an example of subduction initiated at the rim of a plume. If this is
correct, Venus is an example of a sluggish rather than stagnant lid planet in that
convection can produce failure and subduction of the lithosphere. Since subduction
appears to be only limited, this process is distinct from terrestrial style plate tectonics. |
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