Isotopen- und Spurenelementuntersuchungen an Basalten von Mittelozeanischen Rücken, der Cook-Austral Inselkette, sowie von Tristan da Cunha und Gough

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A detailed geochemical study of basalts from the Cook-Austral chain, St. Helena, Tristan da Cunha and Gough as well as mid ocean ridge basalts (MORB) is proposed (Sr, Nd, Pb, and Hf isotope and major and trace element measurements). Basalts from the Cook-Austral chain cover two thirds of the ocean island basalt (OIB) isotopic array and range from HIMU-like (acronym for basalts with high Pb isotope ratios) to EM-like basalts (acronym for basalts with high Sr, low Nd and Pb isotope ratios). HIMU-like basalts group into two different types. One is isotopically similar to St. Helena basalts, the other is similar to enriched MORB. A detailed investigation of CookAustral basalts and MORB will show whether these two signatures have a common genetic origin. In addition, the potential role of recycled sediment in the mantle source of the Cook-Austral, Gough and Tristan da Cunha basalts will be investigated. Only combining major and trace element with isotopic data allows complete characterization of mantle sources, but can also provide information about the cause of melting, melt extraction mechanisms and the scale of the heterogeneous mantle materials. This information is essential for interpreting geochemical data in terms of global mantle structure and evolution models.