Lithospheric structures and Precambrian terrane boundaries in northeastern Botswana revealed
through magnetotelluric profiling as part of the Southern African Magnetotelluric Experiment
M.P. Miensopust, A.G. Jones, M.R. Muller, X. Garcia and R. L. Evans
Within the framework of the Southern African MagnetoTeluric EXperiment (SAMTEX) a focused study
was undertaken to gain improved knowledge of the lithospheric geometries and structures of the
westerly extension of the Zimbabwe Craton into Botswana, with the overarching aim of increasing
our understanding of southern African tectonics.
The area of interest is located in northeastern Botswana, where Kalahari sands
cover most of the geological terranes and very little is known about lithospheric structures
and thicknesses. Some of the regional scale terrane boundary locations, defined based on
potential field data, are not sufficiently accurate for local scale studies.
Investigation of the NNW-SSE orientated, 600 km long ZIM line profile crossing the Zimbabwe
craton, Magondi mobile belt and Ghanzi-Chobe belt showed that the Zimbabwe craton is characterized
by thick(~220 km) resistive lithosphere, consistent with geochemical and geothermal estimates
from kimberlite samples of the nearby Orapa and Letlhakane pipes (~175 km west of the profile).
The lithospheric mantle of the Ghanzi-Chobe belt is resistive but its lithosphere is only about 180 km thick.
At crustal depths a northwards-dipping boundary between the Ghanzi-Chobe and the
Magondi belts is identified, and two mid- to lower-crustal conductors are discovered in the Magondi belt.
The crustal terrane boundary between the Magondi and Ghanzi-Chobe belts is found to be located further to
the north, and the southwestern boundary of the Zimbabwe craton might be further to the west,
than previously inferred from the regional potential field data.
Journal of Geophysical Research - Solid Earth, 116, B02401, doi:10.1029/2010JB007740.
MTNet Home Page
Alan's Home Page
Alan G Jones / 06 May 2011 /