Early Cretaceous Basalt and Picrite Dykes of the Southern Etendeka Region, NW Namibia: Windows into the Role of the Tristan Mantle Plume in Paraná–Etendeka Magmatism

Thompson, R. N.; Gibson, S. A.; Dickin, A. P.; Smith, P. V.

doi:10.1093/petrology/42.11.2049

Cited by 126 publications

(89 citation statements)

References 83 publications

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“…Our fi ndings show that the base of the lithospheric lid resided at a similar depth (~60 km) immediately before, during, and after the eruption of the Ambenali Formation, and therefore that the Wai Subgroup lava pulse was not associated with a major lithospheric extension or delamination event. This contrasts with fi ndings from other continental fl ood basalt provinces, such as the North Atlantic (Kerr, 1994), Paraná-Etendeka (Thompson et al, 2001), and Siberia (Sobolev et al, 2011;Elkins-Tanton and Hager, 2000). As for the dike orientation and isotopic data, these results on MREE/HREE abundances are consistent with the impact triggering hypothesis for the Wai Subgroup outburst, since this mechanism requires no lithospheric thinning, and they also seem to preclude alternative mechanisms involving a sudden pulse of tectonic extension or lithospheric instability/delamination.…”

Section: Rare Earth Element Constraints On Lithospheric Thinningcontrasting

confidence: 41%

Triggering of the largest Deccan eruptions by the Chicxulub impact

Richards

Álvarez

Self

et al. 2015

Geological Society of America Bulletin

176

151

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Section: Rare Earth Element Constraints On Lithospheric Thinningcontrasting

confidence: 41%

Triggering of the largest Deccan eruptions by the Chicxulub impact

Richards

Álvarez

Self

et al. 2015

Geological Society of America Bulletin

176

151

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“…Several recent studies on the structure, geochronology, and petrology of the Karoo province are not readily compatible with the traditional mantle plume hypothesis (Le Gall et al, 2002Watkeys, 2002;Jourdan et al, 2004Jourdan et al, , 2005Jourdan et al, , 2006Jourdan et al, , 2007aJourdan et al, , 2009Coltice et al, 2009;Hastie et al, 2014;cf. Ferraccioli et al, 2005;Curtis et al, 2008).…”

Section: Implications For the Karoo Cfbs And Indian Ocean Magmatismmentioning

confidence: 90%

Low-3He/4He sublithospheric mantle source for the most magnesian magmas of the Karoo large igneous province

Heinonen

Kurz

2015

Earth and Planetary Science Letters

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Keywords:Karoo large igneous province continental flood basalts helium isotopes mantle sourceThe massive outpourings of Karoo and Ferrar continental flood basalts (CFBs) ∼180 Ma ago mark the initial Jurassic rifting stages of the Gondwana supercontinent. The origin and sources of these eruptions have been debated for decades, largely due to difficulties in defining their parental melt and mantle source characteristics. Recent findings of Fe-and Mg-rich dikes (depleted ferropicrite suite) from Vestfjella, western Dronning Maud Land, Antarctica, have shed light on the composition of the deep sub-Gondwanan mantle: these magmas have been connected to upper mantle sources presently sampled by the Southwest Indian Ocean mid-ocean ridge basalts (SWIR MORBs) or to high 3 He/ 4 He plume-entrained non-chondritic primitive mantle sources formed early in Earth's history. In an attempt to determine their He isotopic composition and relative contributions from magmatic, cosmogenic, and radiogenic He sources, we performed in-vacuo stepwise crushing and melting analyses of olivine mineral separates, some of which were abraded to remove the outer layer of the grains. The best estimate for the mantle isotopic composition is given by a sample with the highest amount of He released (>50%) during the first crushing step of an abraded coarse fraction. It has a 3 He/ 4 He of 7.03 ± 0.23 (2σ ) times the atmospheric ratio (R a ), which is indistinguishable from those measured from SWIR MORBs (6.3-7.3 R a ; source 3 He/ 4 He ∼6.4-7.6 R a at 180 Ma) and notably lower than in the most primitive lavas from the North Atlantic Igneous Province (up to 50 R a ), considered to represent the epitome magmas from non-chondritic primitive mantle sources. Previously published trace element and isotopic (Sr, Nd, and Pb) compositions do not suggest a direct genetic link to any modern hotspot of Indian or southern Atlantic Oceans. Although influence of a mantle plume cannot be ruled out, the high magma temperatures and SWIR MORB-like geochemistry of the suite are best explained by supercontinent insulation of a precursory Indian Ocean upper mantle source. Such a model is also supported by the majority of the recent studies on the structure, geochronology, and petrology of the Karoo CFBs.

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“…The Tafelkop and Brandberg dykes have generally been interpreted as being sourced from the Tristan plume, with variable amounts of crustal contamination (e.g. Thompson et al 2001).…”

Section: Previous Workmentioning

confidence: 99%

“…These correlations confirm, at least for the Etendeka, that the range in olivine δ 18 O values from those of normal mantle towards higher values is a magmatic feature and not the result of alteration, and is qualitatively consistent with contamination by felsic upper crustal material. Etendeka picrite dykes of similar composition and from the same area have been studied in detail by Thompson et al (2001Thompson et al ( , 2007 who concluded that contamination by up to 7 % Damara metasedimentary rocks, or 15 % lower crustal granulites of the Congo Craton, took place.…”

Section: Variation Of Phenocryst δ 18 O With Composition and Nd- Sr-mentioning

confidence: 99%

The oxygen isotope composition of Karoo and Etendeka picrites: High δ18O mantle or crustal contamination?

Harris

Roux

Cochrane

et al. 2015

Contrib Mineral Petrol

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Explanations for the high δ 18 O values in Tuli/Mwenezi picrites are limited to (1) alteration, (2) crustal contamination, and (3) derivation from mantle with an abnormally high δ 18 O. Previously, a variety of models that range from crustal contamination to derivation from the 'enriched' mantle lithosphere have been suggested to explain high concentrations of incompatible elements such as K, and average εNd and εSr values of −8 and +16 in Mwenezi (Nuanetsi) picrites. However, the primitive character of the magmas (Mg# 73), combined with the lack of correlation between δ 18 O values and radiogenic isotopic compositions, MgO content, or Mg# is inconsistent with crustal contamination. Thus, an 18 O-enriched mantle source having high incompatible trace element concentration and enriched radiogenic isotope composition is indicated. High δ 18 O values are accompanied by negative Nb and Ta anomalies, consistent with the involvement of the mantle lithosphere, whereas the high δ 18 O themselves are consistent with an eclogitic source. Magma δ 18 O values about 1 ‰ higher than expected for mantle-derived magma are also a feature of the Bushveld mafic and ultramafic magmas, and the possibility exists that a long-lived 18 O-enriched mantle source has existed beneath southern Africa. A mixed eclogite peridotite source could have developed by emplacement of oceanic lithosphere into the cratonic keel during Archaean subduction.

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Early Cretaceous Basalt and Picrite Dykes of the Southern Etendeka Region, NW Namibia: Windows into the Role of the Tristan Mantle Plume in Paraná–Etendeka Magmatism

Cited by 126 publications

References 83 publications

Triggering of the largest Deccan eruptions by the Chicxulub impact

Triggering of the largest Deccan eruptions by the Chicxulub impact

Low-3He/4He sublithospheric mantle source for the most magnesian magmas of the Karoo large igneous province

The oxygen isotope composition of Karoo and Etendeka picrites: High δ18O mantle or crustal contamination?

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