Structure and morphology of submarine volcanism in the hotspot region around Reunion Island, western Indian Ocean

The form of the Deccan-Maldives-Mascarene-Reunion hotspot trace suggests that it has, at least in part, been strongly controlled by crustal structures, especially fracture zones. This makes it difficult to assess the present-day or past location of the hotspot, and thus complicates the interpretation of African plate motion reconstruction. We present here results of a cruise to the Reunion area of which the aims were: (a) to determine the extent of present-day volcanism associated with the Reunion hotspot in the region; and (b) to examine the role of pre-existing oceanic crustal structures in controlling the location of present-day volcanism. Additionally, we examined the morphology and geology of the important extinct spreading centre southwest of Reunion abandoned when spreading jumped to separate Seychelles from India during the Deccan flood basalt episode some 60-65 Ma ago. The extensive bathymetric, seismic and geological investigation shows that significant present-day hotspot volcanism is confined to the Piton de la Fournaise edifice on Reunion Island itself. Apparently, the location of recent Reunion volcanism has not been controlled by a crustal fracture and the major fracture zones on both sides of the island are not acting as magma conduits. For plate motion reconstruction and plume flux calculation purposes, Piton de la Fournaise must be taken as the present location of the Reunion hotspot. Accretion at the extinct spreading centre progressively ceased at the time of anomaly A27 (63 Ma), and was associated with marked propagation of the rift tips. (C) 1998 Elsevier Science B.V. All rights reserved.