 |
| Titel |
Controls on the Flow Regime and Thermal Structure of the Subduction Zone Mantle Wedge: A Systematic 2-D and 3-D Investigation |
| VerfasserIn |
Giuseppe Le Voci, Rhodri Davies, Saskia Goes, Stephan Kramer, Cian Wilson |
| Konferenz |
EGU General Assembly 2014
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250088077
|
| Publikation (Nr.) |
 EGU/EGU2014-2152.pdf |
|
|
|
|
|
| Zusammenfassung |
| Arc volcanism at subduction zones is likely regulated by the mantle wedge’s flow regime and
thermal structure and, hence, numerous studies have attempted to quantify the principal
controls on mantle wedge conditions. Here, we build on these previous studies by
undertaking the first systematic 2-D and 3-D numerical investigation, across a wide
parameter-space, into how hydration and thermal buoyancy influence the wedge’s flow
regime and associated thermal structure, above a kinematically driven subducting plate. We
find that small-scale convection (SSC), resulting from Rayleigh-Taylor instabilities, or drips,
off the base of the overriding lithosphere, is a typical occurrence, if: (i) viscosities are
< 5x1018 Pa s; and (ii) hydrous weakening of wedge rheology extends at least
100-150 km from the trench. In 2-D models, instabilities generally take the form
of ‘drips’. Although along-strike averages of wedge velocities and temperature
in 3-D structure are consistent with those in 2-D, fluctuations are larger in 3-D.
Furthermore, in 3-D, two separate, but interacting, longitudinal Richter roll systems form
(with their axes aligned perpendicular to the trench), the first below the arc region
and the second below the back-arc region. These instabilities result in transient
and spatial temperature fluctuations of 100-150K, which are sufficient to influence
melting, the stability of hydrous minerals and the dehydration of crustal material.
Furthermore, they are efficient at eroding the overriding lithosphere, particularly in
3-D and, thus, provide a means to explain observations of high heat flow and thin
back-arc lithosphere at many subduction zones, if back-arc mantle is hydrated. |
|
|
|
|
|
|