Palaeomagnetism, rock magnetism and AMS of the Cabo Magmatic Province, NE Brazil, and the opening of South Atlantic

Font, Eric; Ernesto, Márcia; Silva, Pedro da; Correia, Paulo B.; Nascimento, Marcos Antônio Leite do

doi:10.1111/j.1365-246x.2009.04333.x

Cited by 20 publications

(9 citation statements)

References 54 publications

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“…This seems to also be corroborated by palaeomagnetic data (e.g. Font et al, 2009). Younger ages of ~90Ma (mostly K-Ar) have been noted in the Potiguar Basin (equatorial region) and as some ages from south of Brazil (Mizusaki et al, 2002;Souza et al, 2003).…”

Section: Accepted Manuscriptsupporting

confidence: 65%

Volcanic constraints on the unzipping of Africa from South America: Insights from new geochronological controls along the Angola margin

et al. 2019

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The breakup of Africa from South America is associated with the emplacement of the Paraná-Etendeka flood basalt province from around 134 Ma and the Tristan da Cunha plume. Yet many additional volcanic events occur that are younger than the main pulse of the Paraná-Etendeka and straddle the rift to drift phases of the main breakup. This contribution reports on new geochronological constraints from the Angolan part of the African Margin. Three coastal and one inland section have been sampled stretching across some 400 Km, with 39 Ar/ 40 Ar, U-Pb and Palaeontology used to provide age constraints. Ages from the new data range from ~100 to 81 Ma, with three main events (cr. 100, 91 and 82-81 Ma). Volcanic events are occurring within the Early to Late Cretaceous, along this part of the margin with a general younging towards Namibia. With the constraints of additional age information both onshore and offshore Angola, a clear younging trend at the early stages of rift to drift is recorded in the volcanic events that unzip from North to South. Similar age volcanic events are reported from the Brazilian side of the conjugate margin, and highlight the need to fully incorporate these relatively low volume volcanic pulses into the plate tectonic breakup models of the South Atlantic Margin.

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Section: Accepted Manuscriptsupporting

confidence: 65%

Volcanic constraints on the unzipping of Africa from South America: Insights from new geochronological controls along the Angola margin

et al. 2019

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“…(d) Mean Cretaceous paleomagnetic poles rotated into African coordinates compared to the global APWP. (e) Comparison with mean Cretaceous poles from Africa (compilation from Font et al [2009]). All representations are in the southern hemisphere.…”

Section: Discussionmentioning

confidence: 99%

“…One explanation for this is that, even if the GAPWP of Torsvik et al [2008] is considered as the most reliable model for paleomagnetic reconstructions, it is not free of error. To test for such scenario, we plotted a recent compilation of African poles gathered by Font et al [2009], which are only poles from igneous rocks, in order to minimize uncertainties in the paleomagnetic record of sedimentary rocks due to problems of inclination shallowing and time of magnetization acquisition. Figure 10e shows that despite their lower quality (i.e., large α 95 angles) in comparison to the Iberian poles, the African mean pole at 140 to110 Ma is in agreement with the GAPWP [ Torsvik et al , 2008].…”

Section: Discussionmentioning

confidence: 99%

Reconciling Cretaceous paleomagnetic and marine magnetic data for Iberia: New Iberian paleomagnetic poles

Neres¹,

Font²,

Miranda³

et al. 2012

J. Geophys. Res.

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[1] The Cretaceous paleogeography and the kinematic evolution of the Iberian plate are poorly constrained. Especially problematic is to reconcile Iberian paleomagnetic data with paleomagnetic data of the neighboring plates and with Euler poles derived from seafloor magnetic anomalies. The first limitation arises from the Cretaceous Normal Polarity Superchron where paleogeographic reconstruction using marine magnetic anomalies is handicapped. The second arises from the paucity of reliable paleomagnetic poles with satisfactory statistical criteria and age. In order to address these shortcomings and provide new high quality paleomagnetic poles for Iberia, we conducted a detailed rock magnetic and paleomagnetic study of two Cretaceous magmatic sills, the Paço de Ilhas (PI) and Foz da Fonte (FF) sills, from the Lusitanian Basin, Portugal, recently dated at about 88 and 94 Ma, respectively. Our results show that the magnetic mineralogy of the sills is primary, i.e., acquired during magma cooling, and essentially represented by titanomagnetite. The corresponding paleomagnetic poles match the synthetic APWP from the African plate at 80 and 100 Ma. On the basis of a rigorous selection of Iberian Cretaceous poles, we then calculated mean paleomagnetic poles for different time intervals and found that Iberian paleomagnetic data fit well the global APWP between 70 and 120 Ma, but move far away from the APWP at pre-rift times. Our approach shows that new and better constrained paleomagnetic poles can aide in solving part of the contradiction between Iberian and African APWPs.

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“…According to some authors (e.g. Font et al, 2009;Font et al, 2014;Kruiver et al, 2001), the differences in B 1/2 and DP values can be interpreted as: varying degrees of oxidation of magnetite for component 1; different Ticontent in the Ti-poor magnetite for component 2; and different magnetic grain sizes for component 3. Sant'Ovaia (1993) in the Vila Pouca de Aguiar Pluton showed that the Vila Pouca de Aguiar and Pedras Salgadas granites have similar magnetic behavior.…”

Section: Magnetic Susceptibility and Isothermal Remanent Magnetizatiomentioning

confidence: 99%

Magnetic mineralogy of Variscan granites from northern Portugal: an approach to their petrogenesis and metallogenic potential

Cruz

Sant'Ovaia

Noronha³

2020

GeA

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Northern Portugal is characterized by the occurrence of numerous W hydrothermal deposits spatially associated with granites. The primary goal of this work is to establish a relationship between the magnetic behavior of the granites and the redox conditions during magma genesis, as this can influence the occurrence of mineralizations, namely of W (Mo). To this end, the magnetic mineralogy of the granites of the Lamas de Olo Pluton, a posttectonic pluton in northern Portugal, with associated W (Mo) occurrences was characterized and compared with the magnetic mineralogy of other post-tectonic Variscan plutons. This pluton is composed of different biotite granites: Lamas de Olo, Alto dos Cabeços and Barragem. To better characterize its magnetic behavior, different analytical techniques that complement previous magnetic susceptibility studies were performed. The magnetic mineralogy of Lamas de Olo Pluton was then compared with other post-tectonic Variscan plutons such as the Vila Pouca de Aguiar, Peneda-Gerês and Lavadores-Madalena plutons. The presence of magnetite in some of these granites is important because it points to melt-oxidized conditions not commonly found in Iberian Variscan granites. Our study shows that granite areas where magnetite and/or magnetite/ilmenite coexist are important targets for W (Mo) mineralizations. The results indicate that a few plutons have granites with a complex redox history which leads to the formation of magnetite and ilmenite. Magnetic mineralogy. Variscan granites. Post-D 3 biotite granites. Central Iberian Zone. W-Mo mineralizations. KEYWORDS

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Palaeomagnetism, rock magnetism and AMS of the Cabo Magmatic Province, NE Brazil, and the opening of South Atlantic

Cited by 20 publications

References 54 publications

Volcanic constraints on the unzipping of Africa from South America: Insights from new geochronological controls along the Angola margin

Volcanic constraints on the unzipping of Africa from South America: Insights from new geochronological controls along the Angola margin

Reconciling Cretaceous paleomagnetic and marine magnetic data for Iberia: New Iberian paleomagnetic poles

Magnetic mineralogy of Variscan granites from northern Portugal: an approach to their petrogenesis and metallogenic potential

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