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Modelling emplacement of magmatism on the Iberia microplate during the Late Cretaceous
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Resumo(s)
For over a century, the investigation of Late Cretaceous alkaline magmatism in the Western Iberian
Margin (WIM) has focused on individual massifs, notably the Monchique massif, revealing unique rock
types like Foyaite and Monchiquites (Blum, 1861; Hunter & Rosenbusch, 1890; Rock, 1982). Despite
these studies, integrating these occurrences into a comprehensive geodynamic and mantle source
framework has remained challenging. Existing analyses often treated them as isolated entities, relying
on age dating and geochemical profiles (Grange et al., 2008, 2010; Martins et al., 2010; Mata et al.,
2015; Miranda et al., 2009; Neres et al., 2012, 2018).
To establish correlations among these discrete magmatic events, a paleogeographic reconstruction
model was executed via GPlates software. This tool enabled the exploration of tectonic plate positions
over time, coupled with underlying mantle dynamics, seeking explanations for the non-linear
distribution and varied timing of magmatism in the WIM. Three primary hypotheses were evaluated: a
static or mobile Hot Spot model (Courtillot et al., 2003; Elder, 1976; Koppers, 2011; Morgan, 1971,
1972), the Superplume magmatism hypothesis (Civiero et al., 2021; Courtillot et al., 2003; Long et al.,
2020), and Edge-Driven Convection (King, 2007; King & Anderson, 1998; King & Ritsema, 2000;
Matton & Jébrak, 2009; Missenard & Cadoux, 2012).
Results indicate that a persistent and robust Super Plume better explains the distinct magmatic
instances in the Western Iberian Margin than the Hot Spot theory. Edge-Driven Convection is deemed
improbable due to a lack of conditions for initiation. Motion paths were analysed to validate or refute
these hypotheses, including alignments like Tore-Sintra-Sines-Monchique, Tore-Madeira, and
Monchique-Gorringe-Madeira. However, these paths were adjusted to better reflect regional
geodynamics.
Notably, specific motion paths, such as the Lisbon Volcanic Complex, hint at the potential
interconnection of all WIM intrusions, with overlapping patterns suggesting the magmatic plumbing in
locations and time frames matching the intrusion of these formations. Moreover, the study suggests a
potential link between the Madeira Archipelago and other seamounts like Ampère, Seine, and Unicorn,
such as seen in the Ampère motion path.
This research demonstrates the complex interplay of geological and geodynamic processes shaping
the magmatic history of the Western Iberian Margin, shedding light on the intricate relationships
between magmatic occurrences and tectonic processes.
Descrição
Tese de mestrado, Geologia Estrutural, 2023, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Magmatismo Tardi-Cretácico Margem Oeste Ibérica Reconstruções Paleogeográficas Tectónica de Placas GPlates Teses de mestrado - 2023