A new model for the evolution of the volcanic island of Réunion (Indian Ocean)

Abstract

The island of Réunion has been studied using data from airborne and shipborne magnetic surveys. The subaerial history of Réunion spans the last 2.1 million years. The Brunhes‐Matuyama geomagnetic reversal enables differentiation of volcanic rocks older and younger than 0.78 Ma. The lower submarine flanks are poorly magnetized and are interpreted as landslide deposits. The core of the island is composed of highly magnetized rocks. Piton des Neiges volcano is composed mostly of rocks older than 0.78 Ma. Only its western flank and central area include thick piles of younger rocks. Piton de la Fournaise is a highly and normally magnetized edifice, but its northern and eastern flanks are underlain at shallow depth by reversely magnetized formations. The latter are regarded as remnants of Les Alizés volcano, associated with the Grand‐Brûlé hypovolcanic complex. At the Matuyama‐Brunhes transition the island was composed of at least two main volcanoes (Piton des Neiges and Les Alizés) and perhaps also of a third old volcano (Takamaka) at the center‐north of the island. Piton de la Fournaise grows on the flank of Les Alizés and is a relatively young focus of volcanism. These volcanoes have had successive phases of construction and destruction. The analysis of magnetic anomalies over Réunion was decisive in defining a new coherent model for the evolution of the island.

Investigating the deepest part of a volcano plumbing system: Evidence for an active magma path below the western flank of Piton de la Fournaise (La Réunion Island)

“…It can, therefore, only be speculated that this could correspond to a combination of subvertical faults and magma intrusions within the mantle lithosphere. We finally propose that the orientation of the Songit Lineament, which is almost constant from depth (N130°) to surface (N135°), and roughly parallel to that of regional structures (paleo-ridges) around La Réunion (Lénat et al, 2001;Michon et al, 2007), is controlled by the reactivation of lithospheric structures under a persistent weak extensional stress field with a horizontal NNE-SSW-directed minimum principal stress σ 3 . This would permit intermittent magma ascent directly from the deep plumbing system that is subsequently followed by fluids up to the surface.…”

Recurrence of major flank landslides during the last 2-Ma-history of Reunion Island

“…Recent geophysical studies de Voogd et al 1999;Gallart et al 1999;Malengreau et al 1999;LØnat et al 2001) are in disagreement with this two-volcano model. The evolution model proposed by LØnat et al (2001) is more complex.…”

“…The evolution model proposed by LØnat et al (2001) is more complex. It comprises (1) the activity of two major primitive volcanic systems, Piton des Neiges in the northwest part of the island and Les AlizØs volcano in the southeast; (2) the possible contribution of a third focus, Takamaka volcano, in the northeast of the axis, which connects the major centers; (3) the Fig.…”

“…In particular, recent geophysical studies have provided valuable data on the interior of the island through seismic de Voogd et al 1999;Gallart et al 1999), gravity (Malengreau et al 1999), and magnetic investigations (LØnat et al 2001). However, the geological structure and the evolution of this volcanic system remain insufficiently understood, partly due to a lack of studies on its submarine part.…”

Crustal and uppermost mantle structure variation beneath La Réunion hotspot track

“…First eruptions forming La Réunion Island (Figs 2b and c) are estimated to be around 5 Ma (e.g. Gillot et al 1994) or even older, around 7 Ma (Lénat et al 2001). The present-day volcanic activity on the hotspot track is located on the Piton de la Fournaise volcano (Figs 2c and d), which is active since ca.…”