Evolution structurale du volcan actif du Piton de la Fournaise,Ile de la Réunion — Océan indien occidental |
| |
| Authors: | L Chevallier P Bachelery |
| |
| Institution: | 1. Institut Dolomieu, Géologie, rue Maurice Gignoux, 38000, Grenoble
2. Laboratoire de Géologie, Université de Clermont Ferrand, 5 rue Kessler, 63000, Clermont Ferrand
|
| |
| Abstract: | This structural study shows that the Piton de la Fournaise volcano was built over four periods separated by 3 calderas. Each stage, dated by K/Ar and CI4 data, and characterized by its own stratigraphy, intrusive system and collapses, is analysed in detail. The stratigraphical study shows lithological and petrological units within some of these stages. The lavas of Piton de la Fournaise are alkaline basalts ranging in composition from picrite to hawaiite. The feeder dikes systems are radial and converging to the volcanic paleocenters of each period. However, the majority of intrusions and surface cones are concentrated along rifts named « Reunion type » because of there wideness. The uplift of magma in these rift zones causes displacement and sumpling of the unsupported seaward flank of the volcano. Collapse structures with variable diameter, formed at different phases of the volcano history. Some are compared to calderas in relation to an intermediate magma chamber, others seem to be due to the bulge and strecht of the massif. The 3 calderas of great size (8–15 km) separating each stage are related to a lower and larger magmatic chamber. This geological study of Fournaise leads us to purpose an evolutive pattern of the volcano based on paleogeographical and paleostructural reconstitutions. The first Fournaise was built over a rift trending N 120 of the old neighbouring volcano of Piton des Neiges. The activity of this rift progressively decreased all through time with the development of a curved intrusive system where most eruptions took place. As in the Hawaiian rifts, the influence of gravitational stresses is invoked to explain the migration of the intrusive zones. |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
