Mantle Structure Beneath the Damara Belt in South-Central Africa Imaged Using Adaptively Parameterized P-Wave Tomography

Many seismic tomography studies have indicated that the African Large Low Velocity Province (LLVP) extends from the lower mantle beneath southern Africa into the upper mantle beneath eastern Africa; however, it has been questioned whether the LLVP structure may also extend to the north or northwest beneath south-central Africa. Debates regarding the upper mantle structure beneath the Damara Belt contribute to this uncertainty. Some studies suggest the Damara Belt is underlain by thermally perturbed upper mantle; however, other studies indicate the region is not associated with anomalous structure. Here, we use a comprehensive P-wave travel-time data set and an adaptive model parameterization to develop a new tomographic model for the Damara Belt and surrounding regions. Our results show that seismically slow structure beneath the Damara Belt is relegated to depths greater than similar to 1,200 km, indicating that the LLVP is not significantly affecting this region. However, further to the northeast, the LLVP structure obliquely rises and crosses the mantle transition zone near the Irumide Belt, where it then extends into the upper mantle. The seismic structure beneath the Damara Belt and neighboring areas in our model correlates well with tectonic observations at the surface, including variations in heat flow, the distribution of geothermal features, the locations of rifts, and estimates of dynamic topography. The African Large Low Velocity Province (LLVP) is an anomalous feature in the Earth's mantle, thought to be associated with unique temperature and compositional characteristics. Many prior studies have shown that the LLVP originates near the core-mantle boundary beneath southern Africa but then ascends to the northeast, reaching the upper part of the mantle beneath eastern Africa. However, it is unclear whether the LLVP also extends to the north or northwest beneath the Damara Belt in south-central Africa. Using the travel-times of earthquake signals recorded by stations across the continent, we have created a new model of the seismic velocity structure beneath south-central Africa, which can be interpreted in terms of thermal and compositional variations. Slow velocities associated with the LLVP are constrained to depths greater than similar to 1,200 km beneath the Damara Belt, which indicates that the LLVP has little affect on this region. However, the slow LLVP structure rises to the northeast, moving into the upper mantle beneath the Irumide Belt and the East African Rift System. The trend of the LLVP structure in our model well matches various features observed at the surface. New P-wave tomography model highlights the structure of the Large Low Velocity Province beneath south-central Africa Anomalously slow seismic velocities beneath the Damara Belt are constrained to depths below similar to 1,200 km Slow velocities ascend to the northeast, crossing into the upper mantle beneath the Irumide Belt and the East African Rift System