HR: 1340h
AN: S33A-1049    [Abstracts]
TI: Crustal Structure And Tectonic Evolution Of The Kaapvaal Craton
AU: Kgaswane, E
EM: eeikgasw@geosc.psu.edu
AF: Council for Geoscience, 280 Pretoria Street Silverton, Private Bag X112, Pretoria, 0001, South Africa
AU: * Nyblade, A
EM: andy@geosc.psu.edu
AF: Penn State University, Department of Geosciences Deike Building, State College, PA 16802, United States
AU: Dirks, P
EM: Paul.Dirks@wits.ac.za
AF: University of the Witwatersrand, School of Geosciences Private Bag 3, Johannesburg, 2050, South Africa
AU: Pasyanos, M
EM: pasyanos@rayleigh.llnl.gov
AF: Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, United States
AU: Julia, J
AF: Penn State University, Department of Geosciences Deike Building, State College, PA 16802, United States
AB: The joint inversion of Rayleigh wave group velocities and body wave receiver functions is used to constrain the shear wave velocity structure across the Kaapvaal craton and surrounding mobile belts. The joint inversion results indicate the presence of mafic lithologies in the lower crust predominantly around the northern and eastern parts of the Kaapvaal craton, Limpopo Belt and southern parts of the Zimbabwe craton. The rest of the south and central portions of the Kaapvaal craton including the adjacent post-Archaean belts show a lower crust that is probably intermediate-felsic in composition. The P-to-SV conversions and crustal reverberations (PpPmS) from the receiver function results show higher amplitudes for localities with a lower crust that is intermediate-to- felsic in composition. The results further show a thinner crust within the cratonic areas (typically 34 to 45 km). The post-Archaean regimes show a thicker crust: Limpopo Belt (42 to 53 km), Namaqua-Natal Belt (42 to 50 km), Bushveld Province (44 to 49 km). However, the Cape Fold and Kheis Belts show Moho depths that are also thinner and comparable to those within the cratonic areas (34 to 40 km). Results for this study suggest that most of the south-western and central parts of the craton could be intermediate-to-felsic in composition. It is plausible that the lack of the mafic lithologies in the lower crust in the central and south-western parts of the craton could have resulted from cycles of extensional deformation in the post-Archaean associated with a number of extensional events (e.g. Ventersdorp and Transvaal). Because of crustal thinning during these events, the lower crust, which was orignally mafic in compostion, could have been thinned a sufficient amount such that it cannot now be resolved seismically.
DE: 1209 Tectonic deformation (6924)
DE: 7203 Body waves
DE: 7205 Continental crust (1219)
DE: 7218 Lithosphere (1236)
DE: 7255 Surface waves and free oscillations
SC: Seismology [S]
MN: 2007 Fall Meeting