Crustal and upper Mantle Imaging of Botswana Using Magnetotelluric
Method: What Can We Learn from Country-wide Magnetotelluric Imaging?
- Stephen Akinremi,
- Islam Fadel,
- Mark van der Meijde
Abstract
Botswana is located at the centre of southern Africa, where major
tectonic features intersect and interact, e.g., the anomalous topography
of the African-superswell, the termination of the East African Rift
System, and the boundaries of the cratons and mobile belts. Moreover,
Botswana is a major player in the production of critical raw earth
materials. Therefore, the study of Botswana's crust and upper mantle
gives more insight into the tectonic development of the region and
improves our understanding of the distribution of Earth resources and
natural hazards. Although novel country-wide geophysical data have been
compiled and processed in the last two decades, some unclear and debated
hypotheses about important tectonic features and the geodynamics of
Botswana from various geophysical studies still exist. This includes the
debate about the existence of a buried Maltahohe microcraton in the
southwest region, the mechanism of the rifting in the Okavango Rift
Zone, and the further extension of the East African Rift System to
central Botswana. This research presents a homogenous 3-D electrical
model with unprecedented spatial coverage, using a robust 3-D
methodological scheme. We used magnetotelluric data from 355 stations
throughout Botswana to derive an electrical conductivity model. The
result of this research provides straightforward, connected, and precise
geologic interpretations about different arguments raised in the
literature on the tectonics and structure of the crust and upper mantle
beneath Botswana. The model shows interesting features, including the
major cratonic blocks, a separate cratonic structure -- Maltahohe
microcraton in southwest Botswana, and the mobile belts. Furthermore,
the model gives new insight into the Okavango Rift Zone and the
extension of the East African Rift System to Botswana. Our results
overcome the fragmented nature of the previous studies and the
incoherent methodologies and approaches that have led to some misleading
or conflicting interpretations.