Gross Brukkaros, A Probable Carbonatite Volcano in the Nama Plateau of Southwest Africa

Janse, A.J.A.

doi:10.1130/0016-7606(1969)80[573:gbapcv]2.0.co;2

Cited by 31 publications

(14 citation statements)

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“…Marsh (1975) has described late Karoo central complexes in the Luderitz Province, which were emplaced 133 + 2 Ma ago, based on a K-Ar age (recalculated using revised decay constants in Steiger & Jager, 1977) on biotite from the Granitberg Complex. Alkaline rocks associated with the Gross Brukkaros volcano include both carbonatites and kimberlites (Janse, 1969). K-Ar ages of 29-31 Ma (A. J.…”

Section: Geologic Settingmentioning

confidence: 99%

Timing of post–Karoo alkaline volcanism in southern Namibia

et al. 1990

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New radiometric age data are reported for alkaline centres in southern Namibia, and are discussed together with published age data in terms of models put forward to account for post-Karoo (Mesozoic-Recent) alkaline magmatism within the African plate. Agreement between K-Ar and Rb-Sr ages indicate emplacement of the Dicker Willem carbonatite in southern Namibia at 49 + 1 Ma. Alkaline rocks associated with the Gross Brukkaros volcano show a discordant radiometric age pattern, but the best estimate for the age of this complex is 77 + 2 Ma, similar to that obtained for the neighbouring Gibeon carbonatite-kimberlite province. The Dicker Willem carbonatite is therefore younger than the Luderitz alkaline province (133 ± 2 Ma), and the Gross Brukkaros volcano, but is older than the Klinghardt phonolite field (29-37 Ma). The new age data argue against a distinct periodicity in alkaline igneous activity in southern Africa, thereby ruling out possible controls by episodic marginal upwarping of the subcontinent. Although the available age data do not appear to be consistent with the passage of one or even two hotspots under southern Namibia, it is argued that the surface expression of hotspots under continents may be so large and overlapping that within-plate magmatism attributed to these thermal anomalies need not necessarily be confined to narrow linear belts or show an age progression. The role of hotspots in continental alkaline magmatism is most likely one of melt generation, while local crustal structure probably controls the distribution and timing of eruption. Major tectonic boundaries in the Precambrian basement underlying southern Namibia seem to have controlled the development of Tertiary alkaline centres in that region.

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Section: Geologic Settingmentioning

confidence: 99%

Timing of post–Karoo alkaline volcanism in southern Namibia

et al. 1990

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“…1). The most distant dykes occur up to 13 km away from the centre of Gross Brukka- Janse (1969). Note that the intersection point of the dykes is north of Gross Brukkaros at its intersection with the Balcony area (rectangle).…”

Section: Introductionmentioning

confidence: 97%

“…Gross Brukkaros (Janse 1969;Stachel et al 1994aStachel et al ,b, 1995 is a volcano-shaped inselberg in southern Namibia rising approximately 600 m above the surrounding Namaland plain. It is an updomed structure with a central crater-like depression, a former sagging caldera.…”

Section: Introductionmentioning

confidence: 98%

“…Note that the intersection point of the dykes is north of Gross Brukkaros at its intersection with the Balcony area (rectangle). Original data and data from Janse (1969) and Stachel et al (1994a) ros and thus mark the extent of the Volcanic Field. In addition to the dykes, 74 carbonatite diatremes are exposed at the present land surface.…”

Section: Introductionmentioning

confidence: 98%

“…Carbonatite sills are present on the north side of Gross Brukkaros near diatreme J1. The designation of the diatremes by letters and numbers is taken from Janse (1969).…”

Section: Introductionmentioning

confidence: 99%

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Volcanological features of a low-viscosity melt: the carbonatitic Gross Brukkaros Volcanic Field, Namibia

Kurszlaukis¹,

Lorenz²

1997

Bulletin of Volcanology

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In the Upper Cretaceous Gross Brukkaros Volcanic Field, southern Namibia, a radial dyke system surrounds a dome structure and its 74 closely related carbonatite diatremes. This paper focuses on volcanological features which seem to be typical for a low-viscosity melt in various settings such as dykes, sills and diatremes. The total or near absence of vesicles in carbonatite ash grains and lapilli inside the diatremes is evidence against explosive exsolution of volatile phases and in favour of a phreatomagmatic fragmentation mechanism and thus for a phreatomagmatic eruption mechanism of the carbonatite diatremes.

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A Selective Lamprophyre Bibliography

Rock

1991

Lamprophyres

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Gross Brukkaros, A Probable Carbonatite Volcano in the Nama Plateau of Southwest Africa

Cited by 31 publications

References 0 publications

Timing of post–Karoo alkaline volcanism in southern Namibia

Timing of post–Karoo alkaline volcanism in southern Namibia

Volcanological features of a low-viscosity melt: the carbonatitic Gross Brukkaros Volcanic Field, Namibia

A Selective Lamprophyre Bibliography

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