Olivines in main-group pallasites: magma-ocean cumulates or partial melting residues?
|Author(s)||Barrat Jean-Alix1, 2, Ferrière L.3|
|Affiliation(s)||1 : Univ. Brest, CNRS, UMR 6538 (Laboratoire Géosciences Océan), Institut Universitaire Européen de la Mer (IUEM), Place Nicolas Copernic, 29280 Plouzané, France
2 : Univ. Brest, CNRS, UMR 6539 (Laboratoire des Sciences de l’Environnement Marin), LIA BeBEST, Institut Universitaire Européen de la Mer (IUEM), Place Nicolas Copernic, 29280 Plouzané, France
3 : Natural History Museum, Burgring 7, A-1010 Vienna, Austria
|Source||Geochemical Perspectives Letters (24103403) (European Association of Geochemistry), 2021-01 , Vol. 16 , P. 47-52|
|Keyword(s)||Pallasite, early solar system, trace elements, rare earth elements, differentiation|
Main-group pallasites (MGPs) are meteorites mainly composed of Fe-Ni metal and olivines, the latter being considered as one of the largest sampling of extraterrestrial mantle material available for study on Earth. We analysed the rare earth element (REE) concentrations of olivines from six MGPs to understand better the processes of formation of their parent mantle. All the investigated samples display very low REE abundances, and enrichments in both light REEs and heavy REEs. We interpret the light REE enrichments as a fingerprint of terrestrial contamination. The least contaminated olivines have higher heavy REE enrichments than those inferred for olivines directly crystallised in a magma ocean. Such enrichments in heavy REEs are possible if the mantle of the MGPs parent body is a residue of partial melting from a chondritic source. Alternatively, re-melting of magma ocean cumulates would explain both the homogeneity of the Ä17O values of MGPs, and the heavy REE enrichments of the olivines.