Abstract
The southeastern Kaapvaal craton exposes several Paleoarchean granitoid-greenstone terranes
that have received relatively little attention by the geosciences community. These terranes
represent an exceptional opportunity to probe into the chemical composition of the Early Earth
mantle including processes leading to crustal evolution during the Archean. In this study,
samples were collected from the Buffalo River and Nondweni greenstone belts, and an
investigation of the geological, geochemical and isotopic characteristics of these two Archean
greenstone belts located in KwaZulu-Natal was carried out. While the Buffalo River
Greenstone Belt records olivine spinifex textured komatiitic lava flows and associated basaltic
rocks, the Nondweni Greenstone Belt is devoid of komatiites, which are known to be restricted
mainly to the Archean and Paleoproterozoic. The Buffalo River greenstones show a local crosscutting
relationship with various granitoids, and the new U-Pb zircon age determinations from
these felsic plutonic rocks constrain a minimum age of 3.26 Ga for komatiite magma
emplacement. An older minimum age of 3.47 Ga is suggested by a granodiorite, but no
intrusive contact with the greenstone succession is observed. Bulk rock geochemical analysis
identified three types of komatiites from the Buffalo River inliers, each exhibiting distinct
geochemical signatures that are comparable to the different types of archetypal Barberton
komatiites. The identified komatiite types include an Al-depleted type with subchondritic
Al2O3/TiO2 and high (Gd/Yb)N, an Al-undepleted type with near chondritic Al2O3/TiO2 and
high (Gd/Yb)N ratios, and an Al-enriched komatiite type with suprachondritic Al2O3/TiO2 and
low (Gd/Yb)N ratios. The co-existence of the three geochemically distinct komatiite types
within a single volcanic succession demonstrates the role of multiple magmatic pulses from a
single ascending mantle plume source linked by varying degrees of partial melting.
Abundances of highly siderophile elements in the mantle source to the Buffalo River komatiites
were calculated and reveal an HSE proportion between 60 and 80% of the total modern bulk
silicate earth (BSE), which suggests that this mantle reservoir was located at great depth and
had not yet received its full HSE complement of the meteoritic late-veneer by ca. 3.5 Ga.
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In addition, this research thesis presents geochemical data for komatiitic basalts and basalts
from the Nondweni Greenstone Belt, which are used to determine the nature of their mantle
source and to compare with the source characteristics of the Buffalo River komatiites and
basalts. The ultramafic-mafic volcanic rocks are classified geochemically into high-Ti and low-
Ti suites indicative of varying mantle sources or degrees of mantle melting. The basaltic rocks
are associated with a komatiitic basaltic suite that is characterized by strongly depleted LREE
but HREE enrichment formed by moderately large degrees of partial melting of a peridotitic
mantle source that had previously been depleted in trace elements. The Nondweni Greenstone
Belt volcanic succession contains a VMS-type mineralization, and in the absence of simpler
direct geochronological methods that can be used to determine its age, we determined a CAID-
TIMS U-Pb zircon age of ca. 3.53 Ga for the rhyolite unit that hosts the Zn-Cu-Pb-Ag
sulfide mineralization at the abandoned St James mine. Geochemical modelling suggests a
petrogenetic link between the rhyolites and basalts, where moderate degrees of partial melting
(ca. 15%) of hydrothermally altered basalt led to rhyolitic magma formation. Multiple sulfur
isotope data (δ34S and Δ33S) support a model involving intense alteration of basaltic ocean floor
near a back-arc spreading ridge accompanied by hydrothermal metal sulfide deposition. This
integrated PhD study provides insights into the magmatic and hydrothermal processes
operating in Paleoarchean greenstone belts and their significance in understanding early Earth
dynamics including ore-forming processes.