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Traction and strain-rate at the base of the lithosphere: an insight into cratonic survival

Paul, Jyotirmoy and Ghosh, Attreyee and Conrad, Clinton P (2019) Traction and strain-rate at the base of the lithosphere: an insight into cratonic survival. In: GEOPHYSICAL JOURNAL INTERNATIONAL, 217 (2). pp. 1024-1033.

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Official URL: https://dx.doi.org/10.1093/gji/ggz079


Cratons are the oldest parts of the lithosphere, some of them surviving since Archean. Their long-term survival has sometimes been attributed to high viscosity and low density. In our study, we use a numerical model to examine how shear tractions exerted by mantle convection work to deform cratons by convective shearing. We find that although tractions at the base of the lithosphere increase with increasing lithosphere thickness, the associated strain-rates decrease. This inverse relationship between stress and strain-rate results from lateral viscosity variations along with the model's free-slip condition imposed at the Earth's surface, which enables strain to accumulate along weak zones at plate boundaries. Additionally, we show that resistance to lithosphere deformation by means of convective shearing, which we express as an apparent viscosity, scales with the square of lithosphere thickness. This suggests that the enhanced thickness of the cratons protects them from convective shear and allows them to survive as the least deformed areas of the lithosphere. Indeed, we show that the combination of a smaller asthenospheric viscosity drop and a larger cratonic viscosity, together with the excess thickness of cratons compared to the surrounding lithosphere, can explain their survival since Archean time.

Item Type: Journal Article
Additional Information: copyright for this article belongs to Oxford University Press
Keywords: Mantle processes; Numerical modelling; Cratons; Dynamics of lithosphere and mantle
Department/Centre: Division of Mechanical Sciences > Centre for Earth Sciences
Date Deposited: 11 Sep 2020 07:16
Last Modified: 11 Sep 2020 07:16
URI: http://eprints.iisc.ac.in/id/eprint/62876

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