No evidence for Brunhes age excursions, Santo Antão, Cape Verde

Brown, M. C.; Singer, Brad S.; Knudsen, Mads Faurschou; Jicha, Brian R.; Finnes, Evan Michael; Feinberg, Joshua M.

doi:10.1016/j.epsl.2009.07.039

“…Two suitable candidates would include the fully reversed Réunion event recorded on Réunion Island and the complex excursions recorded in lava sequences from northern Iceland (Kristjánsson, 2015). Knudsen et al (2003) reported fully reversed polarity directions in two Brunhes age lava sequences on Santo Antão, Cape Verde; however, new radiometric dating and more detailed palaeomagnetic analysis by Brown et al (2009) demonstrated that neither of these sections record an excursion.…”

Section: Relationship Between Intensity and Directional Variationsmentioning

confidence: 94%

A simple model for geomagnetic field excursions and inferences for palaeomagnetic observations

Brown

¹

,

Korte

²

2016

Physics of the Earth and Planetary Interiors

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“…The Cape Verde Rise is situated 2000 km East of the Mid-Atlantic Ridge in the Central Atlantic, between 15 and 17°N and approximately 500 km West of Dakar, Senegal (Figure 1). The Cape Verde Rise forms a gigantic bathymetric swell reaching circa 2 km above the surrounding ocean crust and covers an area of more than 0.3 million km 2 (Crough, 1982;McNutt, 1988;Jørgensen & Holm, 2002;Lodge and Helffrich, 2006;Holm et al, 2008;Masson et al, 2008;Brown et al, 2009). The Cape Verde islands and seamounts are located in the Southwest of the Cape Verde Rise (Figure 1; Rona, 1971;Egloff, 1972;Dash et al, 1976).…”

Section: The Cape Verde Archipelagomentioning

confidence: 99%

Magma storage at Ocean Islands: insights from Cape Verde

Barker

¹

,

Rydeblad

²

,

Silva

³

2021

Preprint

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The Cape Verde archipelago is a group of Ocean Islands in the Central Atlantic that forms two chains of islands trending Northwest and Southwest. Several of the islands are considered to be volcanically active, with frequent eruptions on Fogo. We examine the mineral chemistry and thermobarometry of the southern islands; Santiago, Fogo and Brava together with the Cadamosto Seamount. Our objective is to explore the magmatic storage system and implications for volcanic eruptions and associated hazards at Cape Verde. The volcanic rocks at Cape Verde are alkaline and dominantly mafic, whereas the island of Brava and the Cadamosto Seamount are unusually felsic. Clinopyroxene compositions range from 60 to 90 Mg# at Santiago and Fogo. In contrast, at Brava and the Cadamosto Seamount the clinopyroxene compositions are 5 to 75 Mg#. Mineral chemistry and zonation records fractional crystallization, recharge, aggregation of crystals, magma mixing and variations in thermal conditions of the magma at temperatures from 925 to 1250ºC. Magma storage depths at Santiago, Fogo, Brava and the Cadamosto Seamount are between 12 and 40 km, forming deep sub-Moho magma storage zones. Transient magma storage in the crust is suggested by fluid inclusion re-equilibration and pre-eruption seismicity. A global compilation of magma storage at Ocean Islands suggests deep magma storage is a common feature and volcanic eruptions are often associated with rapid magma ascent through the crust. Shallow magma storage is more variable and likely reflects local variations in crustal structure, sediment supply and tectonics. Petrological constraints on the magma plumbing system at Cape Verde and elsewhere are vital to integrate with deformation models and seismicity in order to improve understanding and mitigation of the volcanic hazards.

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“…The Cape Verde Rise is situated 2000 km East of the Mid-Atlantic Ridge in the Central Atlantic, between 15 and 17°N and approximately 500 km West of Dakar, Senegal (Figure 1). The Cape Verde Rise forms a gigantic bathymetric swell reaching circa 2 km above the surrounding ocean crust and covers an area of more than 0.3 million km 2 (Crough, 1982;McNutt, 1988;Jørgensen & Holm, 2002;Lodge and Helffrich, 2006;Holm et al, 2008;Masson et al, 2008;Brown et al, 2009). The Cape Verde islands and seamounts are located in the Southwest of the Cape Verde Rise (Figure 1; Rona, 1971;Egloff, 1972;Dash et al, 1976).…”

Section: The Cape Verde Archipelagomentioning

confidence: 99%

Magma Storage at Ocean Islands

Barker

¹

,

Rydeblad

²

,

Silva

³

2021

Geophysical Monograph Series

View full text Add to dashboard Cite

The Cape Verde archipelago is a group of Ocean Islands in the Central Atlantic that forms two chains of islands trending Northwest and Southwest. Several of the islands are considered to be volcanically active, with frequent eruptions on Fogo. We examine the mineral chemistry and thermobarometry of the southern islands; Santiago, Fogo and Brava together with the Cadamosto Seamount. Our objective is to explore the magmatic storage system and implications for volcanic eruptions and associated hazards at Cape Verde. The volcanic rocks at Cape Verde are alkaline and dominantly mafic, whereas the island of Brava and the Cadamosto Seamount are unusually felsic. Clinopyroxene compositions range from 60 to 90 Mg# at Santiago and Fogo. In contrast, at Brava and the Cadamosto Seamount the clinopyroxene compositions are 5 to 75 Mg#. Mineral chemistry and zonation records fractional crystallization, recharge, aggregation of crystals, magma mixing and variations in thermal conditions of the magma at temperatures from 925 to 1250ºC. Magma storage depths at Santiago, Fogo, Brava and the Cadamosto Seamount are between 12 and 40 km, forming deep sub-Moho magma storage zones. Transient magma storage in the crust is suggested by fluid inclusion re-equilibration and pre-eruption seismicity. A global compilation of magma storage at Ocean Islands suggests deep magma storage is a common feature and volcanic eruptions are often associated with rapid magma ascent through the crust. Shallow magma storage is more variable and likely reflects local variations in crustal structure, sediment supply and tectonics. Petrological constraints on the magma plumbing system at Cape Verde and elsewhere are vital to integrate with deformation models and seismicity in order to improve understanding and mitigation of the volcanic hazards.

show abstract

No evidence for Brunhes age excursions, Santo Antão, Cape Verde

Cited by 11 publications

References 72 publications

A simple model for geomagnetic field excursions and inferences for palaeomagnetic observations

A simple model for geomagnetic field excursions and inferences for palaeomagnetic observations

Magma storage at Ocean Islands: insights from Cape Verde

Magma Storage at Ocean Islands

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