The structure of Guadeloupe, Maderas and Mt Cameroon volcanoes and the impact of strike-slip movements

Abstract

There are three kinds of strike-slip faults: pure strike-slip, transtensional and transpressional. They have been recognized in all geodynamic environments and are the most common fault type associated with volcanic activity. Many volcanic edifices are built in the vicinity of a fault with strike-slip motion. The impact of strike-slip fault movements on a volcanic cone has been addressed by several studies over the last decade. This study considers a broad range of fault and volcano geometries through three natural examples: the Guadeloupe volcanoes in the Lesser Antilles, Mt Cameroon in West Africa and Maderas volcano in Nicaragua. Detailed field and remote sensing studies are used to establish structural maps of these three little studied volcanoes. These maps are then compared with experimental structures that have developed in analogue cones deformed by strike-slip, transtensional and transpressional faults. The study of Guadeloupe volcanoes leads to a new interpretation of its constructional phases. A regional NW-SE striking sinistral transtensional fault on which the Guadeloupe volcanoes have been built is responsible for their alignment, for the dyke strikes and for the major collapse events. On Mt Cameroon, the rift zone and elongated morphology are controlled by the inactive strike-slip fault on which the volcano has been built. This study also reveals that Mt Cameroon volcano has spread over its weak sedimentary substratum. On Maderas volcano, the summit graben, vent alignment, lower flank half-grabens and summit lineaments are related to gravitational spreading and to regional tectonic movements. The orientation of these structures indicates that the Maderas volcano was built above a NW-SE striking dextral transtensional fault. The theoretical model of strike-slip motion and volcanic cone interaction established with the analogue models can be applied to these and to other volcanoes to determine the location, slip, kinematics and strike of structures hidden by recent eruptions and intense erosion.