Mantle Circulation Models: Applications to Lithospheric Deformation, Subduction and Plumes

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O'Connell 0001046 The proposed research is to study flow and circulation (i.e. the development of flow over time) in the mantle over the past 150 My. The work will involve Earth models that incorporate the geometry and motions of lithospheric plates and is constrained by seismic tomographic models of mantle heterogeneity and observed subducted slabs. The changes of plate geometry and motions over the last 150 My, and the evolution of the internal density field are also included in the model. The flow models have previously been used to predict the motions of plumes and hotspots in the mantle. The investigators will apply models of mantle flow to several geophysical phenomena and observations. One aim is to model the tractions on lithospheric plates and to construct finite element models of stress and deformation in the lithosphere. The results will be compared to global stress observations, as well as areas of intraplate deformation. The effects of the rheological and strength heterogeneity of continents will be investigated. They will also calculate the strain field and evolution of the upper mantle in order to compare it with observations of seismic anisotropy, particularly beneath the Pacific plate. The flow models will also be used to compare predicted flow patterns with the orientations of subducted slabs. These should provide strong constraints on mantle viscosity models and seismic inferences of mantle density heterogeneities, and lead to a better understanding of the dynamics of plate motion and subduction.