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Mapping mantle flow during retreating subduction: Laboratory models analyzed by feature tracking
Author(s)
Language
English
Status
Published
JCR Journal
JCR Journal
Peer review journal
Yes
Title of the book
Issue/vol(year)
/111 (2006)
Publisher
Agu
Pages (printed)
B03402
Issued date
2006
Keywords
Abstract
Three-dimensional dynamically consistent laboratory models are carried out to model
the large-scale mantle circulation induced by subduction of a laterally migrating slab.
A laboratory analogue of a slab–upper mantle system is set up with two linearly viscous
layers of silicone putty and glucose syrup in a tank. The circulation pattern is
continuously monitored and quantitatively estimated using a feature tracking image
analysis technique. The effects of plate width and mantle viscosity/density on mantle
circulation are systematically considered. The experiments show that rollback subduction
generates a complex three-dimensional time-dependent mantle circulation pattern
characterized by the presence of two distinct components: the poloidal and the toroidal
circulation. The poloidal component is the answer to the viscous coupling between
the slab motion and the mantle, while the toroidal one is produced by lateral slab
migration. Spatial and temporal features of mantle circulation are carefully analyzed.
These models show that (1) poloidal and toroidal mantle circulation are both active since
the beginning of the subduction process, (2) mantle circulation is intermittent, (3) plate
width affects the velocity and the dimension of subduction induced mantle circulation
area, and (4) mantle flow in subduction zones cannot be correctly described by models
assuming a two-dimensional steady state process. We show that the intermittent toroidal
component of mantle circulation, missed in those models, plays a crucial role in
modifying the geometry and the efficiency of the poloidal component
the large-scale mantle circulation induced by subduction of a laterally migrating slab.
A laboratory analogue of a slab–upper mantle system is set up with two linearly viscous
layers of silicone putty and glucose syrup in a tank. The circulation pattern is
continuously monitored and quantitatively estimated using a feature tracking image
analysis technique. The effects of plate width and mantle viscosity/density on mantle
circulation are systematically considered. The experiments show that rollback subduction
generates a complex three-dimensional time-dependent mantle circulation pattern
characterized by the presence of two distinct components: the poloidal and the toroidal
circulation. The poloidal component is the answer to the viscous coupling between
the slab motion and the mantle, while the toroidal one is produced by lateral slab
migration. Spatial and temporal features of mantle circulation are carefully analyzed.
These models show that (1) poloidal and toroidal mantle circulation are both active since
the beginning of the subduction process, (2) mantle circulation is intermittent, (3) plate
width affects the velocity and the dimension of subduction induced mantle circulation
area, and (4) mantle flow in subduction zones cannot be correctly described by models
assuming a two-dimensional steady state process. We show that the intermittent toroidal
component of mantle circulation, missed in those models, plays a crucial role in
modifying the geometry and the efficiency of the poloidal component
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article
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