A numerical study of the interaction between the mantle wedge, subducting slab, and overriding plate

Research areas:

• Intérieurs planétaires (2011 - 2016)

Year:

2002

Authors:

• MA Eberle
• Olivier Grasset
• Christophe Sotin

Journal:

PHYSICS OF THE EARTH AND PLANETARY INTERIORS

Volume:

134

Number:

3-4

Pages:

191-202

Month:

DEC 22

ISSN:

0031-9201

BibTex:

@article{WOS:000179620500005, author = "MA Eberle and Olivier Grasset and Christophe Sotin", abstract = "We have formulated a numerical model with strongly temperature-dependent viscosity to calculate thermal structure and flow-field in subduction zones. One important particularity of the model is that the overriding plate is not fixed over its whole thickness in order to allow material exchange between the wedge and the upper lithosphere. Numerical problems due to very high-viscosity contrasts are avoided by coupling a finite difference method and a finite element method for solving the energy conservation equation and the Stockes equation, respectively. In this model, a temperature decrease from 1400 to 1300 degreesC increases the viscosity by an order of magnitude. We study the temperature structure and the velocity field of the subducting slab and mantle wedge. Surface heat flow, velocity anomalies, and geometry of the partial melting zone are also calculated. To study the effect that boundary conditions play on the interaction between the mantle wedge, overriding plate and subducting plate, we examine models with both fixed and free-slip conditions applied to the overriding plate. When the overriding plate is allowed to move laterally (free-slip), the subducting slab is thick, and both the temperature field and the convective motions in the mantle wedge are similar to those observed when using constant viscosity numerical models or analytical corner flow models. If the surface of the overriding plate is fixed, the subducting slab is thin and the mantle wedge impinges upon the overriding plate forming a high-temperature nose between the overriding plate and subducting lithosphere. Furthermore, viscous decoupling occurs implicitly at shallow depth between the slab and the wedge because hot material from the wedge is entrained close to the trench. In that case, the subducting slab tectonically erodes the lower lithosphere of the overriding plate leading to high-temperatures, low seismic velocities, high attenuation and high heat flow beneath volcanic arc, in agreement with geophysical observations. (C) 2002 Elsevier Science B.V. All rights reserved.", doi = "10.1016/S0031-9201(02)00157-7", extra = "PICL", issn = "0031-9201", journal = "PHYSICS OF THE EARTH AND PLANETARY INTERIORS", month = "DEC 22", number = "3-4", pages = "191-202", title = "{A} numerical study of the interaction between the mantle wedge, subducting slab, and overriding plate", volume = "134", year = "2002", }

Abstract:

We have formulated a numerical model with strongly temperature-dependent
viscosity to calculate thermal structure and flow-field in subduction
zones. One important particularity of the model is that the overriding
plate is not fixed over its whole thickness in order to allow material
exchange between the wedge and the upper lithosphere. Numerical problems
due to very high-viscosity contrasts are avoided by coupling a finite
difference method and a finite element method for solving the energy
conservation equation and the Stockes equation, respectively. In this
model, a temperature decrease from 1400 to 1300 degreesC increases the
viscosity by an order of magnitude. We study the temperature structure
and the velocity field of the subducting slab and mantle wedge. Surface
heat flow, velocity anomalies, and geometry of the partial melting zone
are also calculated. To study the effect that boundary conditions play
on the interaction between the mantle wedge, overriding plate and
subducting plate, we examine models with both fixed and free-slip
conditions applied to the overriding plate. When the overriding plate is
allowed to move laterally (free-slip), the subducting slab is thick, and
both the temperature field and the convective motions in the mantle
wedge are similar to those observed when using constant viscosity
numerical models or analytical corner flow models. If the surface of the
overriding plate is fixed, the subducting slab is thin and the mantle
wedge impinges upon the overriding plate forming a high-temperature nose
between the overriding plate and subducting lithosphere. Furthermore,
viscous decoupling occurs implicitly at shallow depth between the slab
and the wedge because hot material from the wedge is entrained close to
the trench. In that case, the subducting slab tectonically erodes the
lower lithosphere of the overriding plate leading to high-temperatures,
low seismic velocities, high attenuation and high heat flow beneath
volcanic arc, in agreement with geophysical observations. (C) 2002
Elsevier Science B.V. All rights reserved.