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- New evidence of Late Cretaceous magmatism on the offshore central West Iberian Margin (Estremadura Spur) from potential field dataPublication . 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 located offshore the central segment of the margin, the Estremadura Spur. The estimated geometry and nature of the magmatic features was achieved through the integration of 3D gravity and magnetic inversion and 2D magnetic forward modelling. The results provide an insightful 3D subsurface model revealing that: 1) the Estremadura Spur Intrusion represents a 28 x 15 km wide laccolith with an overall granitic nature and an estimated density of 2490-2640 kg/m3 and 0.01-0.05 SI magnetic susceptibility, 2) the 26 x 17 km Fontanelas buried volcano is dominantly basaltic, with density values of 2500-2821 kg/m3 and magnetic susceptibility of 0.01 to 0.0875 SI, and 3) multiple sill complexes intruded the region, thus producing a higher magnetic background on otherwise inconspicuous anomalies The models allowed achieving a confident fit suggesting that both the ESI and the Fontanelas volcano are coeval with the outcropping magmatic features from this same magmatic event. Additionally, the results support that Late Cretaceous alkaline magmatism on the West Iberian Margin is more significant than anticipated and provide further evidence to clarify unclear geometrical aspects of similar intrusions observed onshore. Acknowledging the geometry and nature of these magmatic entities allows to better understand the role of postrift intra-plate magmatism on continental hyper-extended rifted margins by clarifying how shallow plumbing systems evolve in these settings.
- Late Cretaceous post-rift magma emplacement offshore the West Iberian Margin [Abstract]Publication . 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 outcropping intrusive (Sintra, Sines and Monchique) and extrusive (e.g., the Lisbon Volcanic Complex) alkaline suites of magmatism, and offshore by conspicuous and enigmatic magnetic anomalies, suggesting additional magmatic features.
- Late Cretaceous magmatism offshore the central West Iberian MarginPublication . 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 da Província Alcalina Atlântica, do Cretácico superior. Este sistema magmático sugere implicações nos modelos de ascensão adiabática no manto, tentativamente associados a uma pluma mantélica duradoura e enraizada na anomalia centro-este atlântica.