Réunion Plume Beat and the Rheology of the mantle – Plum-BeatR

Many hotspots worldwide display evidence of fluctuating magmatic production rates in their history with periodicities varying between 1-20 Myr, indicative of changing melt production within underlying mantle plumes. The recent identification of coeval pulses of magmatic activity in two islands of the Réunion hotspot (La Réunion and Mauritius, Mascarene archipelago) separated by ~230 km with periodicities of ~400 kyr over the past 4 Myr, shorter than any fluctuation found elsewhere, calls our understanding of plume dynamics into question. These short hotspot fluctuations provide promising information about the nature and dynamics of plumes and the elusive mantle rheology.
In the Plum-BeatR project, we first propose to further our observations of Réunion hotspot short-period pulsations, by fully characterising their periodicity, amplitude, and compositional variations. We then aim at unravelling the geodynamic processes behind this beat, to ultimately improve our understanding of mantle rheology and dynamics. To do so, we will combine observational constraints from geology, geochronology, geomorphology, and isotope geochemistry with cutting-edge numerical modelling. We will test whether: 1/ magmatic activity in Rodrigues (the third island of the Mascarenes) shows pulses synchronous with the other islands, 2/ Réunion hotspot pulses are correlated with geochemical variations, 3/ the beat of the plume is due to melt transport in the asthenosphere and/or 4/ it is caused by plume source heterogeneities or by interactions with mantle flow.
The Plum-BeatR team gathers 10 internationally recognized experts strongly motivated to carry out this highly transdisciplinary, surface-to-source exploration of the Réunion plume. We expect that the extremely fast time-scales investigated, the use of two state-of-the art modelling strategies, and the number of trans-disciplinary observations used to discriminate numerical models will help us to better constrain mantle rheology and dynamics.