Subduction zone rheology
نویسندگان
چکیده
Rheological flow laws can be obtained from studies using multi-anvil high-pressure systems with synchrotron-based piezometers and strain metrics. The high flux X-ray source provides minute-scale time resolution with accurate measurement of diffraction patterns and direct sample images. Measurements of length changes with an accuracy of one part in 104 are being developed and will provide a new generation of rheological tools. Flow laws derived from peak broadening agree well with literature data for corundum, spinel, and olivine. Properties of several mantle phases are compared for the temperature and pressure regime appropriate to a subducting slab. Temperature dependence of these properties exhibits a strong, temperature insensitive low temperature region, a thermally softened region and a weak high temperature region. The middle of these could be related to the seismogenic zone of a subduction zone. The progression of the temperature for softening with mineral phase suggests that earthquakes deeper than 400 km correspond to higher temperatures than for olivine in the upper 400 km. Plastic instabilities are suggested by these data as the origin of deep earthquakes. © 2001 Elsevier Science B.V. All rights reserved.
منابع مشابه
Controls on trench topography from dynamic models of subducted slabs
A finite element method with constrained elements and Lagrange multipliers is used to study tectonic faults in a viscous medium. A fault, representing the interface between overriding and subducting plates, has been incorporated into a viscous flow model of a subduction zone in which both thermal buoyancy and the buoyancy associated with the phase change from olivine to spinel are included. The...
متن کاملA Numerical Study on the Effects of Surface Boundary Condition and Rheology on Slab Dynamics
A thin-shell program for modeling neotectonics of regional or global lithosphere with faults. Influence of fore-arc structure on the extent of great subduction zone earthquakes. 1994: Effects of multiple phase transitions in a three-dimensional spherical model of convection in Earth's mantle. 2000: Role of temperaturedependent viscosity and surface plates in spherical shell models of mantle con...
متن کاملHigh-resolution models of subduction zones: Implications for mineral dehydration reactions and the transport of water into the deep mantle
[1] Arc volcanism is intimately linked to mineral dehydration reactions in the subducting oceanic mantle, crust, and sediments. The location of slab dehydration reactions depends strongly on the temperature and pressure conditions at the top of the subducting plate and hence on the detailed thermal structure of subduction zones. A particularly important physical property of subduction zone ther...
متن کاملInteraction of subducted slabs with the mantle transition-zone: A regime diagram from 2-D thermo-mechanical models with a mobile trench and an overriding plate
Transition zone slab deformation influences Earth’s thermal, chemical, and tectonic evolution. However, the mechanisms responsible for the wide range of imaged slab morphologies remain debated. Here we use 2-D thermo-mechanical models with a mobile trench, an overriding plate, a temperature and stress-dependent rheology, and a 10, 30, or 100-fold increase in lower mantle viscosity, to investiga...
متن کاملSubduction zones: observations and geodynamic models
This review of subduction and geodynamic models is organized around three central questions: (1) Why is subduction asymmetric? (2) Are subducted slabs strong or weak? (3) How do subducted slabs interact with phase transformations, changes in mantle rheology, and possibly chemical boundaries in the mantle? Based on laboratory measurements of the temperature dependence of olivine, one would concl...
متن کاملThe effect of a power-law mantle viscosity on trench retreat rate
S U M M A R Y The subduction of lithospheric plates is partitioned between subducting platemotion and lateral slab migration (i.e. trench retreat and advance). We use 3-D, dynamic models of subduction to address the role of a power-law mantle viscosity on subduction dynamics and, in particular, rates of trench retreat. For all numerical models tested, we find that a power-law rheology results i...
متن کامل