Insight into early craton nucleation and stabilization – a case study from crustal and mantle xenoliths from the Star kimberlite mine, East Kaapvaal craton

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Early craton nucleation and stabilization processes can be deciphered from geochemical and petrological information of a physically coherent crust-mantle section. Xenoliths from the Star diamond mine in South Africa (60 pelitic granulites, 15 harzburgites, 27 large-sized peridotitic garnet xenocrysts) provide a unique opportunity to probe a crust-mantle profile of a stable Archean continental region. We will investigate a) the depth distribution and compositional profile from the lower crust to the upper mantle, b) the geochronological comparison on processes in the crust and mantle and c) the thermal evolution of the lithosphere.The depth profile will be obtained by thermobarometry and by the evaluation of petrogenetic grids, which will also provide a chemical stratigraphy when combined with the results of trace-element analyses. The latter will also enable us to estimate the degrees of depletion and re-enrichment in the peridotitic assemblages and to constrain the nature of the pelitic precursors and their components.Age information will be obtained from a) the Re-Os isotope system of the harzburgites, b) the Lu-Hf and Sm-Nd isotope systems of subcalcic garnets and c) the U-Pb dating of zircon and garnet in granulites. This information will be combined into a thermal evolutional history of the East-Kaapvaal craton lithosphere.