TY - JOUR
T1 - Lithospheric Boundaries and Upper Mantle Structure Beneath Southern Africa Imaged by P and S Wave Velocity Models
AU - White-Gaynor, A. L.
AU - Nyblade, A. A.
AU - Durrheim, R.
AU - Raveloson, R.
AU - van der Meijde, M.
AU - Fadel, I.
AU - Paulssen, H.
AU - Kwadiba, M.
AU - Ntibinyane, O.
AU - Titus, N.
AU - Sitali, M.
N1 - Funding Information:
The sources of data used in this study are listed in section 4 . We would like to thank colleagues at the Namibia Geological Survey and the IRIS PASSCAL Instrument Center for help with installing and operating the 2015–2018 Africa Array Namibia seismic network and the Botswana Geological Survey for installing and maintaining the NARS‐Botswana network. We would also like to thank Stewart Fishwick and an anonymous reviewer for constructive and helpful comments, Ian Bastow for helpful discussions about modeling procedures, and Joao Fonseca and George Helffrich for providing data from the MOZART project. This work was supported by Grant ALW‐GO‐AO/11‐30 from the Nederlandse Organisatievoor Wetenschappelijk Onderzoek (NWO) and Grants 0440032, 0530062, 0824781, 1128936, and 1634108 from the National Science Foundation. Data used in this study can be obtained from the IRIS Data Management Center ( https://ds.iris.edu/ds/ ).
Funding Information:
The sources of data used in this study are listed in section 4. We would like to thank colleagues at the Namibia Geological Survey and the IRIS PASSCAL Instrument Center for help with installing and operating the 2015?2018 Africa Array Namibia seismic network and the Botswana Geological Survey for installing and maintaining the NARS-Botswana network. We would also like to thank Stewart Fishwick and an anonymous reviewer for constructive and helpful comments, Ian Bastow for helpful discussions about modeling procedures, and Joao Fonseca and George Helffrich for providing data from the MOZART project. This work was supported by Grant ALW-GO-AO/11-30 from the Nederlandse Organisatievoor Wetenschappelijk Onderzoek (NWO) and Grants 0440032, 0530062, 0824781, 1128936, and 1634108 from the National Science Foundation. Data used in this study can be obtained from the IRIS Data Management Center (https://ds.iris.edu/ds/).
Publisher Copyright:
©2020. American Geophysical Union. All Rights Reserved.
PY - 2020/10/1
Y1 - 2020/10/1
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85094162458&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85094162458&partnerID=8YFLogxK
U2 - 10.1029/2020GC008925
DO - 10.1029/2020GC008925
M3 - Article
AN - SCOPUS:85094162458
VL - 21
JO - Geochemistry, Geophysics, Geosystems
JF - Geochemistry, Geophysics, Geosystems
SN - 1525-2027
IS - 10
M1 - e2020GC008925
ER -