Understanding the formation and stabilization of Archean crust is important for our knowledge about geological processes that operated on the early Earth. The eastern Kaapvaal Craton in southern Africa represents a unique and well-preserved fragment of Paleo- to Mesoarchean continental crust that is ideal to shed some light on this conundrum. Hence, this dissertation aims to answer the following questions: I) Was the early Earth´s crust solely formed in the Archean or did Hadean crustal or

more »

... e-derived material contribute to Archean crust formation?; if so, what was the nature of these Hadean reservoirs? II) How did the mantle sources that contributed material to crustal thickening evolve throughout the Paleo- to Mesoarchean, and in what kind of geological setting did this crust formation occur, early plate subduction or mantle plume-controlled magmatism? The methods applied to answer these two questions are major and trace element analysis in combination with analysis of the whole-rock 176Lu-177Hf, 147Sm-143Nd, and 146Sm-142Nd isotope systems. The long-lived 176Lu-177Hf and 147Sm-143Nd isotope systems were applied to trace mantle differentiation in the Archean, whereas the short-lived 146Sm-142Nd isotope system was applied to trace crust-mantle differentiation in the Hadean. To answer the first research question whether or not Hadean crust or mantle-derived material contributed to Archean crust formation, granitoids and amphibolites of the eastern Kaapvaal Craton, namely the Ancient Gneiss Complex (AGC) of Swaziland and the Barberton Greenstone Belt (BGB) in the Mpumalanga Province of South Africa were investigated for abundance variations of 142Nd. The well-preserved crustal and mantle-derived samples cover an age range from 3.66 to 3.22 Ga and are representative of major geological units of the AGC and the lower Onverwacht Group of the BGB. The investigated samples yielded μ142Nd values ranging from -8 ppm to +3 ppm with typical uncertainties smaller than ± 4.4 ppm, relative to the JNdi-1 terrestrial standar [...]