HR: 13:40h
AN: V32F-01    [PDF]
TI: Spatial and Temporal Variability in the Circulation and Thermal Evolution of the Mantle in Subduction Zones: Insights From 3-D Laboratory Experiments.
AU: * Kincaid, C
EM: kincaid@gso.uri.edu
AF: Graduate School of Oceanography University of Rhode Island, S. Ferry Rd., Narragansett, RI 02882
AU: Griffiths, R W
EM: ross.griffiths@anu.edu.au
AF: Research School of Earth Sciences, Australian National University, Canberra, ACT 0200 Australia
AB: The subduction of oceanic lithosphere plays a key role in plate tectonics, the thermal evolution of the mantle and recycling processes between Earth's interior and surface. The majority of subduction models are two-dimensional (2-D), assuming limited variability in the direction parallel to the trench. Observationally based models increasingly appeal to three-dimensional (3-D) flow associated with trench migration and the sinking of oceanic plates with a translational component of motion (rollback). We report results from laboratory experiments that reveal fundamental differences in 3-D mantle circulation and temperature structure in response to subduction with and without a rollback component. In our experiments the upper mantle is simulated with glucose syrup and the subducting plate is represented with a Phenolic sheet that is forced to sink into the glucose along prescribed trajectories. An array of 40 thermisters embedded within the plate is used to monitor slab surface temperatures (SSTs). We vary the relative magnitude of downdip and translational components of slab motion and also consider cases where the plate steepens with time. Another parameter is the initial thickness of the thermal boundary layer (TBL) beneath the overriding plate. Without rollback motion, flow in the mantle wedge is sluggish, there is no mass flux around the plate, and plate edges heat up faster than plate centers. Rollback subduction drives flow around and beneath the sinking plate, velocities increase within the mantle wedge and are focussed towards the center of the plate and the surface of the plate heats more along the centerline. In addition to lateral variability in flow and mantle temperatures, results highlight temporal variability in SSTs and 3-D mantle flow trajectories associated with the initiation of subduction and variations between periods of predominantly downdip versus rollback sinking.
DE: 8120 Dynamics of lithosphere and mantle--general
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting