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Investigating Potential Melt Sources for the Magma-Poor Albertine-Rhino Graben of the East African Rift System Using 3D Geodynamic Modeling with ASPECT
  • Asenath Kwagalakwe
Asenath Kwagalakwe
Virginia Tech

Corresponding Author:[email protected]

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The leading paradigm for rift initiation suggests “magma-assisted (wet)” rifting is required to weaken strong lithosphere such that only small tectonic stresses are needed for rupture to occur. However, there is no surface expression of magma along the 300 km long Albertine-Rhino Graben (except at its southernmost tip within the Tore Ankole Volcanic Field), which is the northernmost rift in the Western Branch of the East African Rift System. The two prevailing models explaining magma-poor rifting are: 1) Melt is present at depth weakening the lithosphere, but it has not reached the surface or 2) far-field forces driving extension are accommodated along weak pre-existing structures without melt at depth. The goal of this study is to test the hypothesis that melt is generated below the Albertine-Rhino Graben from Lithospheric Modulated Convection (LMC) using the 3D finite element code ASPECT. We develop a regional model of a rigid lithosphere and an underlying convecting sublithospheric mantle that has dimensions 1000 by 1000 by 660 km along latitude, longitude, and depth, respectively. We solve the Stokes equations using the extended Boussinesq approximation for an incompressible fluid which considers the effects of adiabatic heating and frictional heating. We include latent heating such that we can test for melt generation in the sublithospheric mantle from LMC. Using LITHO1.0 as the base of our lithosphere, our preliminary results suggest melt could be generated beneath the Albertine-Rhino graben given a mantle potential temperature of 1800 K. These early results indicate LMC can generate melt beneath the northernmost Western branch of the East African Rift System.