Lithospheric Boundaries and Upper Mantle Structure Beneath Southern Africa Imaged by P and S Wave Velocity Models
Abstract We report new P and S wave velocity models of the upper mantle beneath southern Africa using data recorded on seismic stations spanning the entire subcontinent. Beneath most of the Damara Belt, including the Okavango Rift, our models show lower than average velocities (−0.8% Vp; −1.2% Vs) w...
| Main Authors: | , , , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Wiley
2020-10-01
|
| Series: | Geochemistry, Geophysics, Geosystems |
| Subjects: | |
| Online Access: | https://doi.org/10.1029/2020GC008925 |
| _version_ | 1797638195127517184 |
|---|---|
| author | A. L. White‐Gaynor A. A. Nyblade R. Durrheim R. Raveloson M. van derMeijde I. Fadel H. Paulssen M. Kwadiba O. Ntibinyane N. Titus M. Sitali |
| author_facet | A. L. White‐Gaynor A. A. Nyblade R. Durrheim R. Raveloson M. van derMeijde I. Fadel H. Paulssen M. Kwadiba O. Ntibinyane N. Titus M. Sitali |
| author_sort | A. L. White‐Gaynor |
| collection | DOAJ |
| description | Abstract We report new P and S wave velocity models of the upper mantle beneath southern Africa using data recorded on seismic stations spanning the entire subcontinent. Beneath most of the Damara Belt, including the Okavango Rift, our models show lower than average velocities (−0.8% Vp; −1.2% Vs) with an abrupt increase in velocities along the terrane's southern margin. We attribute the lower than average velocities to thinner lithosphere (~130 km thick) compared to thicker lithosphere (~200 km thick) immediately to the south under the Kalahari Craton. Beneath the Etendeka Flood Basalt Province, higher than average velocities (0.25% Vp; 0.75% Vs) indicate thicker and/or compositionally distinct lithosphere compared to other parts of the Damara Belt. In the Rehoboth Province, higher than average velocities (0.3% Vp; 0.5% Vs) suggest the presence of a microcraton, as do higher than average velocities (1.0% Vp; 1.5% Vs) under the Southern Irumide Belt. Lower than average velocities (−0.4% Vp; −0.7% Vs) beneath the Bushveld Complex and parts of the Mgondi and Okwa terranes are consistent with previous studies, which attributed them to compositionally modified lithosphere resulting from Precambrian magmatic events. There is little evidence for thermally modified upper mantle beneath any of these terranes which could provide a source of uplift for the Southern African Plateau. In contrast, beneath parts of the Irumide Belt in southern and central Zambia and the Mozambique Belt in central Mozambique, deep‐seated low velocity anomalies (−0.7% Vp; −0.8% Vs) can be attributed to upper mantle extensions of the African superplume structure. |
| first_indexed | 2024-03-11T13:00:05Z |
| format | Article |
| id | doaj.art-e6ab10f2f0594e02b8c94e96ad26fb7d |
| institution | Directory Open Access Journal |
| issn | 1525-2027 |
| language | English |
| last_indexed | 2024-03-11T13:00:05Z |
| publishDate | 2020-10-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geochemistry, Geophysics, Geosystems |
| spelling | doaj.art-e6ab10f2f0594e02b8c94e96ad26fb7d2023-11-03T16:55:21ZengWileyGeochemistry, Geophysics, Geosystems1525-20272020-10-012110n/an/a10.1029/2020GC008925Lithospheric Boundaries and Upper Mantle Structure Beneath Southern Africa Imaged by P and S Wave Velocity ModelsA. L. White‐Gaynor0A. A. Nyblade1R. Durrheim2R. Raveloson3M. van derMeijde4I. Fadel5H. Paulssen6M. Kwadiba7O. Ntibinyane8N. Titus9M. Sitali10Department of Geosciences The Pennsylvania State University University Park PA USADepartment of Geosciences The Pennsylvania State University University Park PA USASchool of Geosciences The University of Witwatersrand Johannesburg South AfricaSchool of Geosciences The University of Witwatersrand Johannesburg South AfricaFaculty of Geo‐Information Science and Earth Observation (ITC) University of Twente Enschede NetherlandsFaculty of Geo‐Information Science and Earth Observation (ITC) University of Twente Enschede NetherlandsDepartment of Earth Sciences Utrecht University Utrecht NetherlandsBotswana Geosciences Institute Lobatse BotswanaBotswana Geosciences Institute Lobatse BotswanaGeological Survey of Namibia Windhoek NamibiaGeological Survey of Namibia Windhoek NamibiaAbstract We report new P and S wave velocity models of the upper mantle beneath southern Africa using data recorded on seismic stations spanning the entire subcontinent. Beneath most of the Damara Belt, including the Okavango Rift, our models show lower than average velocities (−0.8% Vp; −1.2% Vs) with an abrupt increase in velocities along the terrane's southern margin. We attribute the lower than average velocities to thinner lithosphere (~130 km thick) compared to thicker lithosphere (~200 km thick) immediately to the south under the Kalahari Craton. Beneath the Etendeka Flood Basalt Province, higher than average velocities (0.25% Vp; 0.75% Vs) indicate thicker and/or compositionally distinct lithosphere compared to other parts of the Damara Belt. In the Rehoboth Province, higher than average velocities (0.3% Vp; 0.5% Vs) suggest the presence of a microcraton, as do higher than average velocities (1.0% Vp; 1.5% Vs) under the Southern Irumide Belt. Lower than average velocities (−0.4% Vp; −0.7% Vs) beneath the Bushveld Complex and parts of the Mgondi and Okwa terranes are consistent with previous studies, which attributed them to compositionally modified lithosphere resulting from Precambrian magmatic events. There is little evidence for thermally modified upper mantle beneath any of these terranes which could provide a source of uplift for the Southern African Plateau. In contrast, beneath parts of the Irumide Belt in southern and central Zambia and the Mozambique Belt in central Mozambique, deep‐seated low velocity anomalies (−0.7% Vp; −0.8% Vs) can be attributed to upper mantle extensions of the African superplume structure.https://doi.org/10.1029/2020GC008925seismic tomographysouthern Africa plateauupper mantlelithospheric structure |
| spellingShingle | A. L. White‐Gaynor A. A. Nyblade R. Durrheim R. Raveloson M. van derMeijde I. Fadel H. Paulssen M. Kwadiba O. Ntibinyane N. Titus M. Sitali Lithospheric Boundaries and Upper Mantle Structure Beneath Southern Africa Imaged by P and S Wave Velocity Models Geochemistry, Geophysics, Geosystems seismic tomography southern Africa plateau upper mantle lithospheric structure |
| title | Lithospheric Boundaries and Upper Mantle Structure Beneath Southern Africa Imaged by P and S Wave Velocity Models |
| title_full | Lithospheric Boundaries and Upper Mantle Structure Beneath Southern Africa Imaged by P and S Wave Velocity Models |
| title_fullStr | Lithospheric Boundaries and Upper Mantle Structure Beneath Southern Africa Imaged by P and S Wave Velocity Models |
| title_full_unstemmed | Lithospheric Boundaries and Upper Mantle Structure Beneath Southern Africa Imaged by P and S Wave Velocity Models |
| title_short | Lithospheric Boundaries and Upper Mantle Structure Beneath Southern Africa Imaged by P and S Wave Velocity Models |
| title_sort | lithospheric boundaries and upper mantle structure beneath southern africa imaged by p and s wave velocity models |
| topic | seismic tomography southern Africa plateau upper mantle lithospheric structure |
| url | https://doi.org/10.1029/2020GC008925 |
| work_keys_str_mv | AT alwhitegaynor lithosphericboundariesanduppermantlestructurebeneathsouthernafricaimagedbypandswavevelocitymodels AT aanyblade lithosphericboundariesanduppermantlestructurebeneathsouthernafricaimagedbypandswavevelocitymodels AT rdurrheim lithosphericboundariesanduppermantlestructurebeneathsouthernafricaimagedbypandswavevelocitymodels AT rraveloson lithosphericboundariesanduppermantlestructurebeneathsouthernafricaimagedbypandswavevelocitymodels AT mvandermeijde lithosphericboundariesanduppermantlestructurebeneathsouthernafricaimagedbypandswavevelocitymodels AT ifadel lithosphericboundariesanduppermantlestructurebeneathsouthernafricaimagedbypandswavevelocitymodels AT hpaulssen lithosphericboundariesanduppermantlestructurebeneathsouthernafricaimagedbypandswavevelocitymodels AT mkwadiba lithosphericboundariesanduppermantlestructurebeneathsouthernafricaimagedbypandswavevelocitymodels AT ontibinyane lithosphericboundariesanduppermantlestructurebeneathsouthernafricaimagedbypandswavevelocitymodels AT ntitus lithosphericboundariesanduppermantlestructurebeneathsouthernafricaimagedbypandswavevelocitymodels AT msitali lithosphericboundariesanduppermantlestructurebeneathsouthernafricaimagedbypandswavevelocitymodels |