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Mantle deformation beneath southern Africa
Author(s) -
Silver Paul G.,
Gao Stephen S.,
Liu Kelly H.
Publication year - 2001
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2000gl012696
Subject(s) - archean , craton , geology , mantle (geology) , lithosphere , seismic anisotropy , shear wave splitting , greenstone belt , anisotropy , seismology , geochemistry , tectonics , physics , quantum mechanics
Seismic anisotropy from the southern African mantle has been inferred from shear‐wave splitting measured at 79 sites of the Southern African Seismic Experiment. These data provide the most dramatic support to date that Archean mantle deformation is preserved as fossil mantle anisotropy. Fast polarization directions systematically follow the trend of Archean structures and splitting delay times exhibit geologic control. The most anisotropic regions are Late‐Archean in age (Zimbabwe craton, Limpopo belt, western Kaapvaal craton), with delay times reduced dramatically in off‐craton regions to the southwest and Early‐Archean regions to the southeast. While thin lithosphere can account for weak off‐craton splitting, small or vertically incoherent anisotropy is a more likely explanation for the Early‐Archean region. We speculate that this difference in on‐craton anisotropic structure is the result of two different continent‐forming processes operating.