New insights from modeling and geophysical observations of cratonic mantle keels

David W S Eaton, University of Calgary, Department of Earth, Energy, and Environment, Calgary, AB, Canada and Tannistha Maiti, University of Calgary, Calgary, AB, Canada

Contact First Author: David W S Eaton; eatond@ucalgary.ca

Previously Published Material: Some of this work has been published in Nature Geoscience (2013).

Abstract ID#: 34514

 

English Abstract:
Cratons are ancient continental nuclei, characterized by relatively cold and unusually thick (> 200 km) lithospheric mantle keels. At present, an approximately isopycnic state of near-neutral buoyancy exists due the competing effects of positive and negative buoyancy from the strongly melt-depleted composition and low temperature, respectively. Advances in our understanding of the present state, composition, anisotropy and architecture of cratons are being driven by new seismological and magnetotelluric observational platforms including Earthscope. Mounting seismological evidence points toward the widespread presence of a mid-lithospheric discontinuity beneath cratons. Modelling studies are currently underway to evaluate inferences based on geophysical proxies. This model includes a hypothetical craton that is smoothly embedded within a standard global Earth model. Physical properties of the regional model (i.e. anisotropic elastic moduli, density, electrical conductivity, thermal and rheological parameters) match prescribed surface heat-flow and geoid boundary conditions and are computed using an approach based on thermodynamics, mineral physics, geochemistry, petrology, and solid-Earth geophysics. Seismic anisotropy is incorporated into the model through both mantle-flow calculations and prescribed fossil anisotropy within cratonic lithosphere.
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