Influence of shear heating on microstructurally defined plate boundary shear zones
John P. PlattSubmitted 2014, SCEC Contribution #1903
In plate-boundary scale lithospheric shear zones that have been defined by micro-structural weakening mechanisms, shear heating may lead to significant temperature increases, of the order of 100K in the initially strongest parts of the lithosphere. Where lithospheric strength is highest, shear zones are likely to be narrow (~1 km), and on plate-tectonic time-scales, conductive heat loss creates a thermal boundary zone much wider than the initial shear zone. Thermal gradients within the original shear zone are very low, and there is no tendency for increased localization. The temperature increase results in significant thermal weakening, but this is partly offset by the effect of grain growth related to the drop in stress. In shear zones of the order of 10 km width, shear stress, strain rate, and hence heat generation are lower, but sufficient gradients are created by conductive heat loss from the shear zone margins to cause some additional strain localization within the shear zone, although the effect is not large. Wider shear zones have too low a rate of heat generation to cause any significant change in rheology.
Citation
Platt, J. P. (2014). Influence of shear heating on microstructurally defined plate boundary shear zones. Geophysical Research Letters, (submitted).
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