Re. Hanson et al., GEOLOGIC EVOLUTION OF THE NEOPROTEROZOIC ZAMBEZI OROGENIC BELT IN ZAMBIA, Journal of African earth sciences, and the Middle East, 18(2), 1994, pp. 135-150
The Neoproterozoic Zambezi belt links with the Mozambique belt Lufilia
n are, and the inland branch of the Damara belt within the regional Pa
n-African tectonic framework of southern Africa. The belt contains a t
hick supracrustal sequence deposited on older sialic basement and pene
tratively deformed with it during Neoproterozoic (Pan-African) orogene
sis. In Zambia, where the entire width of the orogen is exposed, local
bimodal Volcanic rocks at the base of the sequence are overlain by ps
ammites and pelites, which in turn are succeeded by extensive carbonat
e and calc-silicate rocks. Abundant scapolite in metamorphic assemblag
es within the belt is taken as evidence for the original presence of e
vaporites. The nature of the rock types and the inferred stratigraphic
sequence are consistent with deposition in an intracontinental rift b
asin invaded by marine waters. Available isotopic age brackets for the
timing of supracrustal deposition show that the basin developed betwe
en 880 and 820 Ma. Main-phase deformation in the belt involved both tr
anscurrent shearing and south- to southwest-vergent thrusting and was
associated with predominantly amphibolite-facies regional metamorphism
. Mineral assemblages throughout much of the belt in Zambia, together
with limited thermobarometric data, indicate typical Barrovian-type in
termediate P/T conditions during metamorphism. Eclogites and other hig
h-pressure metamorphic assemblages in parts of the belt, however, prov
ide evidence that significant crustal. thickening occurred, presumably
in relation to thrusting. Reworked basement and syntectonic granite w
ere subjected to extensive mylonitization related to strike-slip and o
blique, reverse-slip shearing. The major orogenic event is dated at c.
820 Ma, based on an igneous age for a sheet-like, syntectonic batholi
th injected into a transcurrent shear zone within the central part of
the belt. Pan-African orogenesis along the Zambezi-Lufilian-Damara tre
nd was diachronous and records closure of intracratonic basins in the
Zambezi belt and Lufilian are, with evidence for the involvement of oc
eanic Lithosphere present only in the Damara belt.