Volcano-Stratigraphic and Structural Evolution of Brava Island (Cape Verde) Based on 40Ar/39Ar, U–Th and Field Constraints
Journal of Volcanology and Geothermal Research 196 (2010) 219–235 Contents lists available at ScienceDirect Journal of Volcanology and Geothermal Research journal homepage: www.elsevier.com/locate/jvolgeores Volcano-stratigraphic and structural evolution of Brava Island (Cape Verde) based on 40Ar/39Ar, U–Th and field constraints José Madeira a,b,c,⁎, João Mata a,d, Cyntia Mourão a,d, António Brum da Silveira a,b,c,Sofia Martins a,d, Ricardo Ramalho b,e, Dirk L. Hoffmann f,1 a Faculdade de Ciências da Universidade de Lisboa, Departamento de Geologia (GeoFCUL), Campo Grande, Edifício C6, 1749-016 Lisboa, Portugal b LATTEX, Laboratório de Tectonofísica e Tectónica Experimental, Lisboa, Portugal c Instituto Dom Luiz, Laboratório Associado (IDL–LA), Lisboa, Portugal d Centro de Geologia da Universidade de Lisboa (CeGUL), Lisboa, Portugal e Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol, BS8 1RJ, UK f School of Geographical Sciences, University of Bristol, University Road, Bristol, BS8 1SS, UK article info abstract Article history: Three volcano-stratigraphic units were identified at Brava Island in the Cape Verde Archipelago on the basis Received 2 February 2010 of field relationships, geologic mapping and 40Ar/39Ar and U–Th ages. The Lower Unit comprises a 2-to-3 Ma- Accepted 18 July 2010 old submarine volcanic sequence that represents the seamount stage. It is composed of nephelinitic/ Available online 24 July 2010 ankaramitic hyaloclastites and pillow lavas, which are cut by abundant co-genetic dikes. Plutonic rocks of an alkaline–carbonatite complex, which intruded the submarine sequence 1.8 to 1.3 Ma ago, constitute the Keywords: Middle Unit.
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