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Magmatic flow and structural control in dikes of the West Iberia Late Cretaceous Alkaline Province between Cabo Raso and Oeiras based on field work and marine magnetic data
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Resumo(s)
This study investigates the magmatic flow and structural control of dikes belonging to the West Iberia Late Cretaceous Alkaline Province, within the area between Cabo Raso and Oeiras. Field work is integrated, supported by cartographic data from LNEG and the interpretation of offshore magnetic anomalies acquired through the TAGUSMAG survey. The combined onshore and offshore approach provides new insights into the geometry, orientation, and emplacement mechanisms of the dike swarm in this sector of the Portuguese margin. Field observations and structural analysis suggest that the dikes are organised in two main orientation groups. One orientation group, NNW-SSE is interpreted as being associated with a preexisting shear corridor of Mid-Jurassic age, indicating that inherited tectonic structures exerted a strong control on the emplacement of the dikes, while the other one, NNE-SSW, is associated with the radial pattern that comes directly from the Cabo Raso magnetic anomaly. Some dikes propagate from south to north, directly linking the dike swarm to the Cabo Raso anomaly rather than to the Lisbon Volcanic Complex or Sintra Igneous Complex. In addition, the identification of previously undocumented conduits associated with Cabo Raso, some of which extend offshore, establishes a clear connection between this anomaly and the regional dike network. Taken together, these results suggest that Cabo Raso anomaly functioned as a key magma feeder zone, with the dike swarm likely contributing to the activity of the Lisbon Volcanic Complex. While time constraints limited the application of Anisotropy of Magnetic Susceptibility (AMS) methods, which could have refined the determination of magma flow directions, the present study highlights the structural and magmatic complexity of the region. Future work integrating AMS analyses with offshore geophysical data will be crucial for further constraining the dynamics of magma transport in this sector of the West Iberia Margin.
Descrição
Relatório de estágio de mestrado, Geologia (Geodinâmica e Recursos Geológicos), 2025, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
magmatic dikes magma flow WILCAP structural cartography Cabo Raso magnetic anomaly