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| Title: | Southern African crustal evolution and composition: Constraints from receiver function studies |
| Author (s): | Nair, S. K. Gao, Stephen S. Liu, Kelly H. Silver, P.G. |
| Department/Lab Affiliations: | Geological Sciences & Engineering |
| Keywords: | Poisson's ratio continental crust receiver functions |
| Issue Date: | 2006-02-17 |
| Publisher: | American Geophysical Union |
| Citation: | Nair, S.K., S.S. Gao, K.H. Liu, and P.G. Silver, Southern African crustal evolution and composition: Constraints from receiver function studies, Journal of Geophysical Research, 111, B02304, doi:10.1029/2005JB003802, 2006. |
| Abstract: | Stacking of approximately 1500 radial receiver functions recorded at about 80 broadband seismic stations deployed in southern Africa reveals systematic spatial variations in the ratio of crustal P and S wave velocities (φ), crustal thickness (H), and the amplitude of the converted Moho phases (R). The eastern Zimbabwe and the southern Kaapvaal cratons are characterized by small H (∼38 km), small φ (∼1.73), and large R (∼0.15) values, suggesting that the relatively undisturbed Archean crust beneath southern Africa is separated from the mantle by a sharp Moho and is felsic in composition. The Limpopo belt, which was created by a collisional event at 2.7 Ga, displays large H (∼43 km) but similar φ and R values relative to the cratonic areas. The Bushveld Mafic Intrusion Complex and its surrounding areas show large φ (∼1.78), large H (∼43 km), and small R (∼0.11) values, reflecting the intrusion of mafic material into the original crust as a result of the Bushveld event at 2.05 Ga. Excluding the Bushveld, the spatially consistent and age-independent low φ accentuate the difference between felsic crustal composition and more mafic island arcs that are thought to be the likely source of continental material. Within such an island arc model, our data, combined with xenolith data excluding mantle delamination in cratonic environments, suggest that the modification to a felsic composition (e.g., by the partial melting of basalt and removal of residue by delamination) is restricted to have occurred during the collision between the arcs and the continent. |
| Type: | Article - Journal text |
| In Title: | Journal of Geophysical Union |
| Copyright Notice: | This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder. An edited version of this paper was published by AGU. Copyright 2006 American Geophysical Union. FULL COPYRIGHT INFORMATION: |
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| title | Southern African crustal evolution and composition: Constraints from receiver function studies |
| contributor.author | Nair, S. K. |
| contributor.author | Gao, Stephen S. |
| contributor.author | Liu, Kelly H. |
| contributor.author | Silver, P.G. |
| contributor.deptlab | Geological Sciences & Engineering |
| subject | Poisson's ratio |
| subject | continental crust |
| subject | receiver functions |
| date.issued | 2006-02-17 |
| publisher | American Geophysical Union |
| identifier.citation | Nair, S.K., S.S. Gao, K.H. Liu, and P.G. Silver, Southern African crustal evolution and composition: Constraints from receiver function studies, Journal of Geophysical Research, 111, B02304, doi:10.1029/2005JB003802, 2006. |
| identifier.pub.URI | |
| description.abstract | Stacking of approximately 1500 radial receiver functions recorded at about 80 broadband seismic stations deployed in southern Africa reveals systematic spatial variations in the ratio of crustal P and S wave velocities (φ), crustal thickness (H), and the amplitude of the converted Moho phases (R). The eastern Zimbabwe and the southern Kaapvaal cratons are characterized by small H (∼38 km), small φ (∼1.73), and large R (∼0.15) values, suggesting that the relatively undisturbed Archean crust beneath southern Africa is separated from the mantle by a sharp Moho and is felsic in composition. The Limpopo belt, which was created by a collisional event at 2.7 Ga, displays large H (∼43 km) but similar φ and R values relative to the cratonic areas. The Bushveld Mafic Intrusion Complex and its surrounding areas show large φ (∼1.78), large H (∼43 km), and small R (∼0.11) values, reflecting the intrusion of mafic material into the original crust as a result of the Bushveld event at 2.05 Ga. Excluding the Bushveld, the spatially consistent and age-independent low φ accentuate the difference between felsic crustal composition and more mafic island arcs that are thought to be the likely source of continental material. Within such an island arc model, our data, combined with xenolith data excluding mantle delamination in cratonic environments, suggest that the modification to a felsic composition (e.g., by the partial melting of basalt and removal of residue by delamination) is restricted to have occurred during the collision between the arcs and the continent. |
| type | Article - Journal |
| type.DCMIType | text |
| type.status | Postprint |
| rights | This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder. An edited version of this paper was published by AGU. Copyright 2006 American Geophysical Union. |
| rights.URI | |
| relation.isPartOf | Journal of Geophysical Union |
| date.accessioned | 2007-04-11T17:00:48Z |
| date.available | 2008-05-13T14:04:22Z |
| identifier.persist.URI |