Petrochemische, isotopengeochemische und einschlussanalytische Untersuchungen (Silikat- und Fluideinschluesse) in Einsprenglingen und Xenolithen der Magmatite des Reunion-Hotspots. Teilprojekt: SONNE-Fahrt SO-87 Abschlussbericht

A contribution to geochronology and evolution of the young volcanic island of Runion, magmatite samples from the southern, southwestern and northeastern flank of Reunion gathered during cruise SO-87 have been charcterized by optical microscopy, electron beam microprobe, microthermal, high-temperature and "1"8O isotopic investigations. Chromium spinels and ilmenitic crystals have been identified as oxidic daughter phases of phenocrysts/xenoliths forming pyroxenes, olivines and plagioclases. From the density (0.27-0.77 g/cm"3) of carbon dioxide inclusions and based on the relation between pressure and carbon dioxide solubility in tholeitic melts, conclusions have been drawn on the initial magma carbon dioxide content. "1"8O content varies strongly from mineral to mineral (5.1-13.2 permille) and points to a more recent magma contamination at least in some cases. (WEN)Available from TIB Hannover: F96B373+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Einschluss- und isotopengeochemische Untersuchungen von Magmatiten und Xenolithen eines rezenten HIMU-Hotspots (St. Helena). Teilprojekt: SONNE-Fahrt SO-84 Abschlussbericht

As part of the SO-84 cruise program, vulcanites of the research area St. Helena/Mid-Atlantic Ridge have been characterized by "1"8O isotopic and inclusion geochemical investigations. Maximum values of the endogenically determined oxygen isotopic ratios in the plagioclases have been deduced and discussed. More detailed information on the alteration processes are expected from a future combined discussion with corresponding strontium and neodymium isotopic data. Besides silicatic phases, in plagioclase phenocrystals almost pure carbon dioxide is included accompanied by silicate and sulfide inclusions. Based on the different densities of the included carbon dioxide (0.34-0.86 g/cm"3) the age of the vulcanites and the distance to the spreading centre have been estimated. It is concluded that the seamounts Kutusov, Bonaparte and Bagration have been formed about 11 millions of years ago during the activity climax of the St. Helena vulcanoes. (WEN)SIGLEAvailable from TIB Hannover: F96B370+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman