HR: 1340h
AN: V33B-1387    [Abstracts]
TI: Mantle support of the East African Rift System
AU: Lin, S
EM: skylin0@ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, 1, section 4, Roosevelt Road, Taipei, 106, Taiwan
AU: * van Keken, P E
EM: keken@umich.edu
AF: Department of Geological Sciences, University of Michigan, 2534 CC Little Building, 1100 North University Avenue, Ann Arbor, MI 48109-1005, United States
AU: Brandenburg, J P
EM: jpbrande@umich.edu
AF: Department of Geological Sciences, University of Michigan, 2534 CC Little Building, 1100 North University Avenue, Ann Arbor, MI 48109-1005, United States
AU: Furman, T
EM: furman@geosc.psu.edu
AF: Department of Geosciences, Pennsylvania State University, 503 Deike Building, University Park, PA 16802, United States
AU: Bryce, J
EM: julie.bryce@unh.edu
AF: Department of Earth Sciences, The University of New Hampshire, 121 James Hall, 56 College Road, Durham, NH 03824, United States
AB: The African Superplume is a region of slow seismic wave velocities in the lower mantle under southern Africa. The uplift, volcanism and rifting that defines the much of eastern and southern Africa suggest a dynamic link between lower mantle dynamics and near-surface processes affecting the African plate. The dynamic link between the lower mantle and the surface, and the structure and dynamics of the upper mantle below the East African Rift System (EARS) remain unclear. As part of a comprehensive geochemical and numerical investigation of basaltic magmatism in the EARS we have modeled the interaction between putative upper mantle plumes and the rifting continental lithosphere. The modeling provides dynamically tested scenarios that explain the observed episodes of Cenozoic volcanism. Results from recent models that provided an explanation for the present day distribution of volcanism (Lin et al., EPSL, 237, 2005) suggest two plumes below Afar and Tanzania whose uplift is influenced by lithospheric topography. In new 3D modeling we provide improved quantification of the mantle involvement in generating EARS volcanism as constrained by the timing of uplift and regional volcanism. The time scales of episodicity of the volcanism observed at Turkana (related to the Tanzania-Kenya plume) since 45 Ma can be explained by deep- seated time-dependent plume activity. We suggest that this time-dependence is due to thermochemical interactions of dense recycled oceanic crust in the thermally hot regions in the African superplume region (Lin and Van Keken, Nature, 436, 2005).
DE: 1037 Magma genesis and partial melting (3619)
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8121 Dynamics: convection currents, and mantle plumes
DE: 8415 Intra-plate processes (1033, 3615)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting