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Master Thesis

Pétrologie et géochimie des laves du Mont Etinde, ligne volcanique du Cameroun

Abstract : The Cameroun Volcanic Line (CVL) is a magmatic alignment, extending on both oceanic and continental sectors, from Pagalù Island (or Annobón - Golf of Guinea) to Lake Chad. Active since Cretaceous, this structure is usually linked to the St-Helena plume emplacement. However, the lack of correspondence between age and magmatic activity does not support the classic hotspot model for the CVL. The origin and persistence of the magmatic alkaline activity, with the last Mt Cameroun eruption in 2000, remain misunderstood. Mount Etinde, the last continental volcano before the oceanic sector, is the only one of the CVL displaying strongly undersatured mafic rocks. This study, based on new majors and trace elements and isotopic geochemical data, allows us to define three main lithological groups. Nephelinites are enriched in incompatible elements and have the most radiogenic Pb isotopic compositions ever measured for the CVL (206Pb/204Pb = 20,14-20,58). Two others groups, basalts and tephrites, are close to Mt Cameroon basalts, which constitute the basement of Mt Etinde. LREE and HFSE enriched compositions may be explained by melting of a heterogeneous metasomatized lithospheric mantle beneath the continent/ocean boundary. The geochemical zoning of the lithospheric mantle seems to control this magmas genesis with extreme compositions.
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Submitted on : Monday, July 7, 2014 - 3:10:56 PM
Last modification on : Tuesday, February 2, 2021 - 9:52:02 AM
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  • HAL Id : dumas-01019935, version 1



Mathieu Rospabé. Pétrologie et géochimie des laves du Mont Etinde, ligne volcanique du Cameroun. Volcanologie. 2014. ⟨dumas-01019935⟩



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