Petrographic and Geochemical characterization of distal K/Pg impact ejecta from the Umbria-Marche sequence (Italy)

Samenvatting

This thesis provides a detailed petrographic and geochemical characterisation of distal Cretaceous/Paleogene boundary spherules originating from the Chicxulub crater (approximately 65 Ga). Spherules are abundantly present within the PGE enriched K-Pg clay layer, and have been collected at three K-Pgsections in the Umbria Marche region (Italy). Distal spherules, also termed 'microkrystites', are interpreted as the condensation products from the expanding vapour plume formed upon impact, consisting of a mixture of vaporized target and meteorite impactor material. As meteorites are highly enriched in siderophile elements (highly siderophile platinum group elements Pt, Ir, also termed PGEs, and moderately siderophile Ni, Cr, Co), in this context, studying the distribution of the siderophile elements is of special interest in obtaining important information regarding condensation and fractionation processes within this impact cloud. Previous studies indicated the presence of three types of spherules composed mainly of sanidine, glauconite and goethite. Goethite spherules have been found to be relatively more enriched in iridium and other siderophile elements. Within the highly altered groundmass of these spherules, Ni rich magnesioferrite spinel crystals were found and interpreted as the only probable relict high temperature phases that survived diagenetic alteration. In addition, they it has been suggested that they are a possible carrier phase for the siderophile elements. As the precise carrier phase remains still unknown today, in situ analysis of the spherules will be attempted in this thesis.

Datum prijs	28 mei 2013
Originele taal	English
Prijsuitreikende instantie	KU Leuven
Begeleider	Philippe Claeys (Promotor) & Joke Belza (Advisor)