Utilize este identificador para referenciar este registo: http://hdl.handle.net/10400.21/1323
Título: Multi-stage evolution of a sub-aerial volcanic ridge over the last 1.3 Myr: S. Jorge Island, Azores Triple Junction
Autor: Hildenbrand, Anthony
Madureira, Pedro
Marques, Fernando Ornelas
Cruz, Inês
Henry, Bernard
Silva, Pedro
Palavras-chave: Sao Jorge
Azores Triple Junction
MAR; K/Ar
Geochemistry
Volcanic Ridge Evolution
Mid-Atlantic Ridge
Nui French-Polynesia
South-Pacific
Ocean Island
Mantle Plume
K-AR
Isotope Geochemistry
Spreading Center
Terceira Island
Plate Boundary
Data: 15-Set-2008
Editora: Elsevier Science BV
Citação: Hildebrand A, Madureira P, Marques F O, Cruz I, Henry B, Silva P.Multi-stage evolution of a sub-aerial volcanic ridge over the last 1.3 Myr: S. Jorge Island, Azores Triple Junction. Earth and Planetary Science Letters. 2008; Volume: 273, Issue: 3-4, Pages: 289-298.
Relatório da Série N.º: 273;
Resumo: New K/Ar dating and geochemical analyses have been carried out on the WNW-ESE elongated oceanic island of S. Jorge to reconstruct the volcanic evolution of a linear ridge developed close to the Azores triple junction. We show that S. Jorge sub-aerial construction encompasses the last 1.3 Myr, a time interval far much longer than previously reported. The early development of the ridge involved a sub-aerial building phase exposed in the southeast end of the island and now constrained between 1.32 +/- 0.02 and 1.21 +/- 0.02 Ma. Basic lavas from this older stage are alkaline and enriched in incompatible elements, reflecting partial melting of an enriched mantle source. At least three differentiation cycles from alkaline basalts to mugearites are documented within this stage. The successive episodes of magma rising, storage and evolution suggest an intermittent reopening of the magma feeding system, possibly due to recurrent tensional or trans-tensional tectonic events. Present data show a gap in sub-aerial volcanism before a second main ongoing building phase starting at about 750 ka. Sub-aerial construction of the S. Jorge ridge migrated progressively towards the west, but involved several overlapping volcanic episodes constrained along the main WNW-ESE structural axis of the island. Malic magmas erupted during the second phase have been also generated by partial melting of an enriched mantle source. Trace element data suggest, however, variable and lower degrees of partial melting of a shallower mantle domain, which is interpreted as an increasing control of lithospheric deformation on the genesis and extraction of primitive melts during the last 750 kyr. The multi-stage development of the S. Jorge volcanic ridge over the last 1.3 Myr has most likely been greatly influenced by regional tectonics, controlled by deformation along the diffuse boundary between the Nubian and the Eurasian plates, and the increasing effect of sea-floor spreading at the Mid-Atlantic Ridge.
Peer review: yes
URI: http://hdl.handle.net/10400.21/1323
ISSN: 0012-821X
Aparece nas colecções:ISEL - Eng. Civil - Artigos



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