Mantle Deformation beneath Southern Africa


Seismic anisotropy from the southern African mantle has been inferred from shear-wave splitting measured at 79 sites of the SASE experiment. These data, unprecedented in coverage and density, provide the most dramatic support to date that Archean mantle deformation is preserved as fossil mantle anisotropy. Fast polarization directions, Φ, systematically follow the trend of Archean structures, such as the Limpopo Belt and Great Dyke. Splitting delay times,δ, also exhibit geologic control. The most anisotropic regions are Late Archean in age (Zimbabwe Craton, Limpopo Belt, western Kaapvaal).δ is reduced dramatically when moving to off-craton regions to the southwest, and splitting is essentially undetectable in the Early-Archean southeastern craton. While thin lithosphere accounts for the off-craton weak splitting, the thick lithosphere beneath the Early-Archean region requires another explanation for cratonic differences. We speculate that variations in the vertical coherence of mantle deformation, reflecting the distinct continent-forming processes operating during the Early- and Late-Archean, are the cause.

Meeting Name

AGU Fall Meeting (2000: Dec. 15-19, San Francisco, CA)


Geosciences and Geological and Petroleum Engineering

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Article - Conference proceedings

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© 2000 American Geophysical Union (AGU), All rights reserved.

Publication Date

01 Dec 2000

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