Abstract
M.Sc.
Known outcrops of the supracrustal Mesoarchean Mozaan Group of the Pongola
Supergroup occur in north-eastern Kwazulu-Natal and southern Mpumalanga in South
Africa, and southern Swaziland. Outcrops of the Mozaan succession in Swaziland are
preserved in the Ntungulu-Mahlangatsha and Kubuta-Mooihoek areas. The succession is
composed of polymictic conglomerate, poorly sorted scour based quartzite,
orthoquartzite, shale, iron-formation, polymictic diamictite and lava. In the Kubuta-
Mooihoek area a 3000m thick succession is preserved and correlates almost bed for bed
with that in the Hartland area in South Africa. The succession is preserved from the
Dipka member of the Sinqeni Formation at the base to the Tobolsk lava at the top. The
depositional environment ranges essentially between fluvial and marine with two distinct
glaciogenic diamictite units and one unit of lava near the top of the succession. Seven
unconformity bounded sequences are recognised in the succession and from these a
relative sea-level curve could be constructed.
Trace element geochemistry of the shale reveals that the source area was predominantly
felsic with a mafic component probably derived from the uplifted pre-Pongola granitoids
and Nsuze Group. The petrography of the quartzite in the succession suggests a change
in provenance from a low-lying deeply weathered to uplifted moderately weathered
source area higher up in the stratigraphy. Part of the tectonic uplift may have been
associated with isostatic rebound related to melting of continental glaciers. The Tobolsk
lava is a continental flood basalt also possibly related to a tectonic uplift event. There are
indications of sediment recycling in the upper part of the succession where
conglomerates are predominantly composed of chert clasts
A pretectonic quartz porphyry sill, folded with the strata, provides an upper age limit of
2837±5 Ma for the deposition of the Mozaan Group. The Mooihoek granite (2824±6 Ma)
that intrudes and deforms the synclinal structure along its eastern flank, provides an
upper age limit of the folding event. This suggests that the deformation of the Mozaan succession took place in the intervening 13 Ma period between 2824 and 2837 Ma ago.