We used magnetotelluric data from 352 sites in Botswana to derive a
nationwide electrical conductivity model of the crust and upper mantle
structure. A robust methodological scheme and 3D inversion were used to
derive a 3D electrical conductivity model with unprecedented spatial
coverage. The model results show interesting features, including the
major cratonic blocks and the mobile belts in Botswana. A distinctive
resistive structure was imaged in southwest Botswana, which suggests the
existence of the Maltahohe microcraton as a separate cratonic unit as
proposed by other studies. Furthermore, the model gives new insight into
the extension of the East African Rift System to Botswana and the
incipient rifting in the Okavango Rift Zone. In northern Botswana, the
electrical conductivity model shows a high conductivity structure
beneath the Okavango Rift Zone, which connects with a deeper high
conductivity structure that we attribute to the East African Rift System
due to its vicinity to Lake Kariba, the last surface expression of the
rift system. We suggest that ascending fluids or melt from the East
African Rift System causes the weakening of the lithosphere and plays a
significant role in the incipient continental rifting in the Okavango
Rift Zone.