Magma Paths at Piton de la Fournaise Volcano

Abstract

Several patterns of magma paths have been proposed since the 1980s for Piton de la Fournaise volcano. Given the significant differences, which are presented here, we propose a reappraisal of the magma intrusion paths using a 17-years-long database of volcano-tectonic seismic events and a detailed mapping of the scoria cones. At the edifice scale, the magma propagates along two N120 trending rift zones. They are wide, linear, spotted by small to large scoria cones and related lava flows and involving magma resulting from high-pressure fractionation of ol ± cpx and presents an eruption periodicity of around 200 years over the last 30 kiloyears. The upper plumbing system originates at the base of the edifice below the Enclos Fouque caldera. It feeds frequent (1 eruption every 9 months on average), short-lived summit and distal (flank) eruptions along summit and outer rift zones, respectively. Summit rift zones are short and present an orthogonal pattern restricted to the central active cone of Piton de la Fournaise whereas outer rift zones extend from inside the Enclos Fouque caldera to the NE and SE volcano flanks. To sum up, rift zones of Piton de la Fournaise present strong geometrical and dynamical differences. On the one hand, the lower plumbing system feeds rift zones showing striking similarities to those developed in Hawaii during the alkaline postshield stage. On the other hand, the rift zones connected to upper plumbing system can be compared the rift system of Mount Etna, whose dynamics is know to be linked with the lateral displacement of the east flank.