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

早期的克拉通成核和稳定过程可以从物理上连贯的壳幔剖面的地球化学和岩石学信息中破译出来。来自南非Star钻石矿的包体(60个泥质麻粒岩，15个方辉橄榄岩，27个大型橄榄岩石榴石包裹体)为探索稳定的太古宙大陆区域的壳幔剖面提供了一个独特的机会。我们将研究a)从下地壳到上地幔的深度分布和成分剖面，b)地壳和地幔过程的年代学比较，c)岩石圈的热演化。深度剖面将通过温压测量和岩石成因格网的评价获得，这也将提供化学地层学结合微量元素分析的结果。后者还将使我们能够估计橄榄岩组合中的亏损和再富集程度，并限制泥质前体及其组分的性质。年龄信息将从a)方辉橄榄岩的Re-Os同位素系统，b)亚钙石榴石的Lu-Hf和Sm-ND同位素系统，以及c)麻粒岩中的锆石和石榴石的U-Pb测年获得。这些信息将被合并到东卡帕瓦尔克拉通岩石圈的热演化史中。

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.