Magnetic fabric in a Cretaceous sill (Foz da Fonte, Portugal): flow model and implications for regional magmatism

Interplay of tectonics and magmatism during post‐rift inversion on the central West Iberian Margin (Estremadura Spur)

“…Based on previous evidence from potential field data (Escada et al, 2019;Neres et al, 2014;Silva et al, 2000), a geophysical anomaly stands out on regional maps (Figure 1), that could either be assigned to an uplifted crustal block or the effect of an intrusive body, buried underneath Meso-Cenozoic sediments. However, the integration of gravimetric and magnetic data, presented by Escada (2019), unravelled the first detailed study of the extension, geometry and nature of the geophysical anomalies, that is broadly characterised by a free-air gravimetric anomaly in excess of 50 mGal and a total magnetic field (IGRF removed) over 90 nT, which, combined with the seismic dataset presented ahead, suggests that it is, in fact, an intrusive feature emplaced into the sedimentary strata.…”

“…Grange et al, 2010;Miranda et al, 2009;Rock, 1982). Less well known are the proposed offshore magmatic occurrences (Escada, 2019;Escada et al, 2019;Neres et al, 2014Neres et al, , 2018Silva et al, 2000;Simões et al, 2020), for which a detailed imaging was still lacking. However, the absence of any absolute age determinations for any of these magmatic features hinders further conclusions on the exact timing of the corresponding volcanic event.…”

“…The first two are associated with rifting extension (Martins et al., 2008; Mata et al., 2015), whereas the latter, corresponds to a post‐rift and syn‐tectonic event dissimilarly affecting the continental and oceanic domains of the margin (Grange et al., 2010; Merle et al., 2009; Miranda et al., 2009). Geophysical models have been recently applied for the first time on the proximal margin to help characterising in detail some of the outcropping alkaline massifs (Neres et al., 2014; Ribeiro et al., 2013; Terrinha et al., 2017; Figure 1b), and to carry out gravimetry‐magnetic modelling of conspicuous subsurface features off SW Iberia (Neres et al., 2018).…”

“…Analysis of the offshore segments of the WIM, and specifically of the Estremadura Spur (ES; Figure 1), revealed that in this region the magmatism associated with the third cycle is abundant, comprising numerous sills, buried volcanic edifices and several voluminous plutonic intrusions (Escada et al., 2019; Miranda et al., 2010; Neres et al., 2014; Pereira et al., 2017; Pereira & Barreto, 2018; Simões et al., 2020). Nevertheless, all these features are still poorly investigated, requiring both new data and subsequent integrated analysis in order to gain a new overall insight on their tectono‐magmatic evolution and possible geodynamic causes.…”

40Ar/39Ar ages and petrogenesis of the West Iberian Margin onshore magmatism at the Jurassic–Cretaceous transition: Geodynamic implications and assessment of open-system processes involving saline materials

“…The second cycle (late-to syn-rift) dykes intruded mainly along syn-rift faults, while the third cycle (post-rift) dykes do not show any extensional control. As examples, we refer to the radial dyke complex around the Late Cretaceous Mafra intrusion and a W-E 350 km long dyke corridor (N 39º 50') striking across the WIM just south of the study area (Neres et al, 2014). As proposed by these authors, these dykes used W-E striking faults parallel to the oceanic transform faults that separated previously extended blocks during rifting and oceanic break up.…”