Magma formation, transport and evolution in an oceanic ultraslow extensional setting

• Applicant: Professor Dr. Karsten Matthias Haase, since 7/2019
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 342370333

The formation of large igneous plateaus results from the eruption of large quantities of melt within relatively short periods of time of few million years. The initial formation and evolution of the melts and their impact on the (Palaeo)environment however, is a matter of active debate. In addition, the impact of local, tectonic features on melt ascent and the interaction with the ascending magmas may be of greater importance than previously established. The submarine Azores Plateau in the central northern Atlantic provides the unique possibility to investigate the impact of an upper mantle melting anomaly on the melting process. In addition, the interaction between the ascending melts and the ultraslow spreading of the Terceira Rift axis will be investigated. We have sampled more than 450 submarine samples both, along the rift zones and in the earlier, plateau-forming lavas during recent expeditions M113 (2015) and M128 (2016, both RV Meteor) and during earlier expeditions (POS232, 1997 and POS286, 2002 both RV Poseidon) in the submarine Azores Plateau. Five stratigraphic profiles in the earlier plateau-forming lavas were sampled using an Remotely Operated Vehicle during M128 in July 2016. These samples allow, for the first time, to better constrain the petrological and geochemical evolution of the initial magmas that formed the Azores Plateau. Comparing these melts to the younger lavas, erupted along the rift zones will provide unique constraints on the interaction between the ascending melts and the local plate tectonics. This project largely aims at petrological and geochemical investigations (major and trace elements and O, Sr, Nd, Pb and Hf isotope compositions) of the available whole rocks, glasses and minerals. The geochemical compositions will be complemented by Ar-Ar age dating on selected Azores lavas. The changes in degrees of partial melting and the increasing influence of the rifting movements of the ultraslow spreading Terceira Rift axis on the composition of the magmas will allow to develop a consistent model of the formation of the Azores Plateau. In addition, the rift zones in a single magmatic edifice and the geochemical variability amongst the melts erupted may provide unique information on the interaction between local tectonics and magma ascent that will also be applicable to other oceanic volcanoes.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Professor Dr. Christoph Beier, until 7/2019