Publication 193
Structure of the Lithosphere beneath the Barotse Basin, Western Zambia from Magnetotelluric Data
Evans, R.L., J. Elsenbeck, J. Zhu, M.G. Abdelsalam, E. Sarafian, D. Mutamina, F. Chilongola, E. Atekwana, and A.G. Jones
Abstract
A magnetotelluric (MT) survey in the Barotse Basin of western Zambia shows clear evidence for
thinned lithosphere beneath an orogenic belt. The uppermost asthenosphere, at a depth of 60-70
km, is highly conductive, suggestive of the presence of a small amount of partial melt, despite
the fact that there is no surface expression of volcanism in the region. Although the data support
the presence of thicker cratonic lithosphere to the southeast of the basin, the lithospheric
thickness is not well resolved and models show variations ranging from ~80km to 150km in this
region. Similarly variable is the conductivity of the mantle beneath the basin and immediately
beneath the cratonic lithosphere to the southeast, although the conductivity is required to be
elevated compared to normal lithospheric mantle. In a general sense, two classes of model are
compatible with the MT data; one with a moderately conductive mantle and one with more
elevated conductivities. This latter class would be consistent with the impingement of a stringer
of plume-fed melt beneath the cratonic lithosphere, with the melt migrating upslope to thermally
erode lithosphere beneath the orogenic belt that is overlain by the Barotse Basin. Such processes
are potentially important for intraplate 42 volcanism and also for development or propagation of
rifting as lithosphere is thinned and weakened by melt. Both models show clear evidence for
thinning of the lithosphere beneath the orogenic belt, consistent with elevated heat flow data in
the region.
Source
Tectonics, 38, 666-686, doi: 10.1029/2018TC005246.
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