82 documents found, page 1 of 9
Age dependent variation of the magnetic fabric of dike swarms and implications ...
Moreira, Mário; Mata, João; Madeira, José; Represas, Patricia; Martins, SofiaABSTRACT: Magnetic fabric analysis of dikes is a powerful technique when assessing magma transfer processes. This study presents an integrated analysis combining magnetic susceptibility and anisotropy of magnetic susceptibility, magnetic mineralogy, geochemistry and new 40Ar/39 Ar dating of dikes intruding formations ranging from the Lower Cretaceous to the Miocene on the island of Maio, in the Cabo Verde archi...
The old central igneous complexes of Sal, Boa Vista and Maio islands: Implicati...
Villaseca, Carlos; Orejana, David; Huertas, Maria J.; Ancochea, Eumenio; Ignacio, Cristina; Mata, João; Caldeira, Rita; Garcia-Rodriguez, MariaABSTRACT: The central igneous complexes of the easternmost islands (Sal, Boa Vista and Maio) preserve some of the most ancient outcropping rocks of the Cape Verde (CV) archipelago. These Early to Middle Miocene (about 25 to 12 Ma) complexes show marked isotopic differences between mafic rocks from the northern (Sal and Boa Vista) and the southern Maio Island, the latter showing lower 143Nd/144Nd, 206Pb/204Pb, 2...
Geochemical comparison of circular plutonic complexes with extrusive rocks from...
Garcia-Rodriguez, Maria; Villaseca, Carlos; Ignacio, Cristina; Orejana, David; Mata, João; Caldeira, RitaABSTRACT: Sal island is located in the northeast and is the oldest of the Cape Verde archipelago, with magmatic activity starting ~25 Ma ago. It presents a series of circular plutons that could represent the subvolcanic roots of the exposed extrusive rocks. In this work we compare the geochemical characteristics of melagabbro-gabbro of circular (~16.3 Ma) intrusions in the Old Eruptive Complex, with basaltic an...
Crustal and uppermost mantle structure near the Gloria Fault, North Atlantic, f...
Pinzón, Juan I.; Custódio, Susana; Silveira, Graça; Krüger, Frank; Mata, João; Matias, LuisIn this work, we present both 1-D and 3-D shear wave velocity (Vs) models of the oceanic crust and uppermost mantle below the Deep OCean Test ARray area, located similar to 70 km north of the central section of the Gloria Fault, in the eastern North-Atlantic Ocean. The velocity models are inferred from the dispersion of surface waves recorded on ocean bottom seismometers. Dispersion measurements are obtained fr...
Late Cretaceous magmatism offshore the central West Iberian Margin
Pereira, Ricardo; Escada, Cláudia; Represas, Patricia; Mata, João; Rosas, Filipe M.; Ramalho, R.S.SUMÁRIO: A análise de dados de reflexão sísmica, combinados com modelos de inversão de dados potenciais (gravimetria-magnética), revela a presença, natureza e detalhes de um sistema magmático localizado no offshore da Margem Oeste Ibérica. As evidências incluem o vulcão de Fontanelas com escoadas de lavas associadas, a Intrusão do Esporão da Estremadura, e diversos complexos de soleiras, enquanto manifestações ...
Late Cretaceous post-rift magma emplacement offshore the West Iberian Margin [A...
Pereira, Ricardo; Escada, Cláudia; Represas, Patricia; Ramalho, R.S.; Mata, João; Rosas, Filipe M.ABSTRACT: The West Iberian Margin is a prime example of a magma-poor hyperextended continental margin. However, the margin is punctuated by three discrete Mesozoic magmatic events, from which the last, occurring 20-40 M.a. after complete lithospheric breakup of the Iberia-Newfoundland conjugate margin, is related to the late Cretaceous Atlantic Alkaline Province. It is characterised onshore by multiple outcropp...
The alkaline intraplate Pliocene-Quaternary lavas from the Middle Atlas Volcani...
Benamrane, Mohammed; Francisco Santos, José; Mata, João; Talbi, El Hassan; Helena Mendes, Maria; Portela, Luís; Ribeiro, Sara; Jadid, MohamedThe Middle Atlas Volcanic Field (MAVF) covers an area of 1500 km2, with a total erupted volume of solid products (DRE) estimated at more than 80 km3. In this study we present and discuss new petrological, mineralogical, and geochemical data of mafic rocks from the Timahdite and Lechmine N'kettane maars and of the Hebri, Habri (H1) and Boutagarouine scoria cones. For these volcanic areas we report the exclusive ...
Heterogeneous seismic anisotropy beneath Madeira and Canary archipelagos reveal...
Schlaphorst, David; Silveira, Graça; Mata, João; Krüger, Frank; Dahm, Torsten; Ferreira, Ana M GMid-plate upward mantle flow is a key component of global mantle convection, but its patterns are poorly constrained. Seismic anisotropy is the most direct way to infer mantle flow as well as melt distribution, yet the convection patterns associated with plume-like mantle upwelling are understudied due to limited seismic data coverage. Here, we investigate seismic anisotropy beneath the Madeira and Canary hotsp...
New evidence of Late Cretaceous magmatism on the offshore central West Iberian ...
Escada, Cláudia; Represas, Patricia; Santos, Fernando Monteiro; Pereira, Ricardo; Mata, João; Rosas, Filipe M.ABSTRACT: The West Iberian Margin (WIM) is a key example of a magma-poor passive margin, punctuated by several postrift magmatic manifestations that are part of the Late Cretaceous Atlantic Alkaline Province. In this work, potential field (gravity and magnetics) data, constrained by 3D multichannel seismic reflection data, are used to describe and characterise the geometry and nature of magmatic features locate...
The Carboniferous shoshonitic (s.l.) gabbro-monzonitic stocks of Veiros and Val...
Amaral, João Lains; Mata, João; Santos, José FranciscoPost-collisional potassium-rich rocks are a critical petrogenetic and geodynamic marker across the European Variscan Belt. We present a detailed characterization of the only potassium-rich mafic intrusions identified so far in the Ossa-Morena Zone (Iberian Massif). Using new major, trace and Smsingle bondNd isotopic whole-rock analyses, as well as mineral chemistry analyses, we discussed the petrogenesis of the...