It is intriguing to speculate on how continental crust evolved and exposed above the sea level during the Archean and which tectonic regimes and magmatic mechanisms were responsible for such a process. The continental nucleus of the Kaapvaal Craton, which includes the Barberton granitoid-greenstone terrane (BGGT) in South Africa and the Ancient Gneiss Complex (AGC) in Swaziland, exhibits the best preserved geological record from 3.6 to 3.0 Ga and thus provides the optimal location to address this issue. In this study, combined U-Pb, O and Lu-Hf isotope and trace element analyses were carried out on detrital zircon grains from two Moodies Group sandstones and three modern river sand samples in the Barberton and Swaziland regions, southern Africa. In addition, the zircon U-Pb ages and O isotopic data were obtained from three metamorphic rocks, one charnockite and two trondhjemites in the AGC. The detrital zircons in the Moodies sandstones had two U-Pb age clusters of 3.25–3.30 Ga and 3.40–3.47 Ga and the oldest age up to 3.57 Ga. This suggests that they were derived from older felsic volcanic rocks of the greenstone belt and the granitoid gneisses in the BGGT and AGC. Using the approach created for Earth’s oldest zircons, we inferred that the source magmas of the studied detrital zircons had average arc-like andesitic compositions (SiO2 = 58.0 ± 5.6 wt. %; Th/Nb = 5.0 ± 3.2), similar to those of the Jack Hills detrital zircons. However, these inferred compositions conflict with the source rocks of the detrital zircons, which have high SiO2 contents (average = 70 ± 4.3 wt. %) and moderate Th/Nb ratios (average = 0.76 ± 0.44). These findings suggest that the inferred average andesitic compositions for the Earth’s oldest zircons should be reevaluated. The concordant zircon U-Pb age data reveal four major magmatic episodes for the eastern Kaapvaal Craton at 3.52, 3.46, 3.26 and 3.10 Ga. The first magmatic episode is suggested to dictate crustal growth, whereas the other three magmatic episodes are predominated by crustal reworking. This process is manifested by major positive changes in εHf(t) and εNd(t) values starting at ~3.5 Ga, gradual decreases in εHf(t) and εNd(t) values afterwards, and increases in δ18O values at ~3.25 Ga. We suggest that modern-style plate tectonic processes may not have been a requirement for crustal growth and reworking in the eastern Kaapvaal Craton during the Paleoarchean. Instead, they could be ascribed to episodic partial convective overturns at different crustal depths. Interestingly, the charnockite and the trondhjemites revealed ultrahigh-temperature melting at low pressure conditions at 3.2 Ga. The three studied metamorphic rocks also record a regional high-T, low-P metamorphic event at 3.2 Ga, and their zircon grains have extremely low δ18O values (to 0.55 ‰), indicating crystallization from protoliths affected by meteoric fluid interaction. Therefore, some parts of the crust of the Kaapvaal Craton may have exposed above sea level before 3.2 Ga, which may be induced by the upwelling of mantle hotspot similar to modern Yellowstone.