HR: 1330h
AN: V32A-0998    [PDF]
TI: Sampling the Cape Verde Mantle Plume: Evolution of Santo Ant\~{a}o, Cape Verde Islands
AU: * Holm, P M
EM: paulmh@geo.geol.ku.dk
AF: Geological Institute, University of Copenhagen, Geocenter Copenhagen Oster Voldgade 10, Copenhagen, DK-1350 Denmark
AU: Wilson, J R
EM: jrw@geo.au.dk
AF: Department of Earth Sciences, University of Aarhus, Universitetsparken, Aarhus, DK-8000 Denmark
AU: Christensen, B P
AF: Geological Institute, University of Copenhagen, Geocenter Copenhagen Oster Voldgade 10, Copenhagen, DK-1350 Denmark
AU: Hansen, L
AF: Department of Earth Sciences, University of Aarhus, Universitetsparken, Aarhus, DK-8000 Denmark
AU: Hansen, S L
AF: Geological Institute, University of Copenhagen, Geocenter Copenhagen Oster Voldgade 10, Copenhagen, DK-1350 Denmark
AU: Hein, K M
AF: Geological Institute, University of Copenhagen, Geocenter Copenhagen Oster Voldgade 10, Copenhagen, DK-1350 Denmark
AU: Mortensen, A K
AF: Department of Earth Sciences, University of Aarhus, Universitetsparken, Aarhus, DK-8000 Denmark
AU: Pedersen, R
AF: Department of Earth Sciences, University of Aarhus, Universitetsparken, Aarhus, DK-8000 Denmark
AU: Plesner, S
AF: Department of Earth Sciences, University of Aarhus, Universitetsparken, Aarhus, DK-8000 Denmark
AU: Runge, M K
AF: Geological Institute, University of Copenhagen, Geocenter Copenhagen Oster Voldgade 10, Copenhagen, DK-1350 Denmark
AB: The 7.5 - 0.1 Ma old volcanics of the northwesternmost Cape Verde Island of Santo Ant\~{a}o show a change from early incompatible element enriched basanite-phonolite series to more enriched nephelinite/melilite nephelinite-phonolite series volcanics all of HIMU OIB type. Mantle melts were derived by 1-4 % melting and had around 12 wt.% MgO. Olivine Fo88-91 is found in many primitive volcanics. Incompatible element modelling shows that the geochemical change of the composition of the primary magmas requires source enrichment by silicate melts of mainly two compositional types. One of these is MORB. Isotopically the $>$ 2 Ma Old Volcanics group can largely be explained by mixing of two components both with relatively radiogenic Sr and unradiogenic Nd of which one is a young HIMU type source ($\Delta$ 8/4 $\sim$ 0 and $\Delta$ 7/4 $\sim$ -5). The period 2 - 0.7 Ma saw two component mixing of two other end members of which one is a young HIMU source with less radiogenic Sr, more radiogenic Nd, $\Delta$ 8/4 $\sim$ -38 and $\Delta$ 7/4 $\sim$ -5, which isotopically is identical to an end member of carbonatites from the neighbouring island of S\~{a}o Vicente and the southern island Santiago. The youngest volcanics show stronger source enrichment, the most silica undersaturated magmas and an old HIMU-type component ($\Delta$ 7/4 $>$ 2). The characteristic EM1-type enrichment of the southern Cape Verde Island is not detected on Santo Ant\~{a}o. We argue that the main components of Santo Ant\~{a}o volcanism are plume derived and reflect vertical variation in composition of rising plume material. The inter island variation of the Cape Verdes may reflect a lateral variation of the plume or lithosphere derived components in the southern island volcanics
DE: 1010 Chemical evolution
DE: 1040 Isotopic composition/chemistry
DE: 1065 Trace elements (3670)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting