Shear wave velocity structure of the lower crust in southern Africa: evidence for compositional heterogeneity within Archaean and Proterozoic terrains

Kgaswane, Eldridge M., Nyblade, Andrew A., Julia, Jordi, Dirks, Paul H.G.M., Durrheim, Raymond J., and Pasyanos, Michael E. (2009) Shear wave velocity structure of the lower crust in southern Africa: evidence for compositional heterogeneity within Archaean and Proterozoic terrains. Journal of Geophysical Research: solid earth, 114.

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Abstract

The nature of the lower crust across the southern African shield has been investigated by jointly inverting receiver functions and Rayleigh wave group velocities for 89 broadband seismic stations located in Botswana, South Africa and Zimbabwe. For large parts of both Archaean and Proterozoic terrains, the velocity models obtained from the inversions show shear wave velocities ≥4.0 km/s below ∼20–30 km depth, indicating a predominantly mafic lower crust. However, for much of the Kimberley terrain and adjacent parts of the Kheis Province and Witwatersrand terrain in South Africa, as well as for the western part of the Tokwe terrain in Zimbabwe, shear wave velocities of ≤3.9 km/s are found below ∼20–30 km depth, indicating an intermediate-to-felsic lower crust. The areas of intermediate-to-felsic lower crust in South Africa coincide with regions where Ventersdorp rocks have been preserved, suggesting that the more evolved composition of the lower crust may have resulted from crustal reworking and extension during the Ventersdorp tectonomagmatic event at c. 2.7 Ga.

Item ID: 7930
Item Type: Article (Refereed Research - C1)
Keywords: tomography, seismic structure, kaapvaal craton, Zimbabwe Craton, southern Africa, shear wave velocity
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ISSN: 1934-8592
Date Deposited: 17 Jan 2010 22:30
FoR Codes: 04 EARTH SCIENCES > 0404 Geophysics > 040407 Seismology and Seismic Exploration @ 80%
04 EARTH SCIENCES > 0403 Geology > 040313 Tectonics @ 20%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970104 Expanding Knowledge in the Earth Sciences @ 100%
Citation Count from Web of Science Web of Science 19
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