The School of Earth and Atmospheric Sciences Presents Dr. Cynthia Ebinger, Tulane University

Strain Localization at Cratonic Edges: Constraints from East Africa

Sutures between Archaean cratons and younger orogenic belts represent some of Earth’s largest lateral heterogeneities:  > 170 km-thick, buoyant and relatively dry lithosphere juxtaposed to ~100 km-thick, more volatile-rich mantle lithosphere.   We use new and existing data from the African continent to examine the role of pre-existing lithospheric thickness and composition variations on the time-space localization of magmatism, faulting, and basin formation.   

Seismic tomography and magneto-telluric models, crust and mantle xenolith chemistry, earthquakes, reveal consistent patterns in the style of basin formation and distribution of magmatism.  We evaluate models of mantle upwelling beneath a variable thickness lithosphere with spatial variations in the direction and magnitude of seismic anisotropy, which is strongly influenced by mantle flow patterns along lithosphere-asthenosphere topography, fluid-filled cracks, and pre-existing strain fabrics.   Enhanced mantle flow and melt extraction at craton edges may localize strain in thick lithosphere, as indicated by energetic lower crust and upper mantle earthquakes.