Karoo large igneous province: Brevity, origin, and relation to mass extinction questioned by new 40Ar/39Ar age data

Jourdan, Fred; Féraud, Gilbert; Bertrand, Hervé; Kampunzu, A.B.; Tshoso, G.; Watkeys, M. K.; Gall, Bernard Le

doi:10.1130/g21632.1

Cited by 215 publications

(143 citation statements)

References 27 publications

(41 reference statements)

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“…In addition, the results of this study suggest crystallisation temperatures (and possibly mantle potential temperatures) that are ~100 °C lower than estimated by earlier studies on the basis of olivine-melt equilibria and melting models of dry lherzolite source (≥ 1600 °C; Hole, 2015). It should be emphasised, however, that although the internal heating model is also compatible with the most of the recent structural and geochronological studies on the Karoo LIP (e.g., Le Gall et al, 2002Jourdan et al, 2004Jourdan et al, , 2005Jourdan et al, , 2006Jourdan et al, , 2009Hastie et al, 2014), influence of a mantle plume or plumes for the generation of Karoo CFBs cannot be ruled out (see Ferraccioli et al, 2005;Curtis et al, 2008). Importantly, the temperature data presented in this study do not discriminate between the two scenarios.…”

Section: Discussioncontrasting

confidence: 35%

Crystallisation temperatures of the most Mg-rich magmas of the Karoo LIP on the basis of Al-in-olivine thermometry

2015

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Calculating reliable temperatures of Mg-rich magmas is problematic because melt composition and K D (Fe-Mg) ol-liq , the key parameters of many traditional thermometers, are difficult to constrain precisely. The recently developed Al-in-olivine thermometer [Coogan, L.A., Saunders, A.D., Wilson, R.N., 2014. Aluminum-in-olivine thermometry of primitive basalts: Evidence of an anomalously hot mantle source for large igneous provinces. Chemical Geology 368, 1-10] circumvents these problems by relying on the temperature-dependent exchange of Al between olivine and spinel crystallising in equilibrium with each other. This thermometer is used to reevaluate the crystallisation temperatures of the most Mg-rich magma type identified from the Karoo large igneous province (LIP), known as the Vestfjella depleted ferropicrite suite. Previous temperature estimates for the suite were based on olivine-melt equilibria and indicated anomalously high crystallisation temperatures in excess of 1600 °C. We also present crystallisation temperatures for another Antarctic Karoo magma type, Group 3 dykes from Ahlmannryggen, which are derived from a pyroxene-rich mantle source. Our high-precision analysis of Al in olivine-spinel pairs indicate crystallisation temperatures from 1391±42 °C to 1481±35 °C for the Vestfjella depleted ferropicrite suite ) and from 1253±64 °C to 1303±40 °C for the Group 3 dykes ). Although the maximum temperature estimates for the former are over 100 °C lower than the previously presented estimates, they are still ~200 °C higher than those calculated for mid-ocean ridge basalts using the same method. Although exact mantle potential temperatures are difficult to estimate, the presented results support elevated sub-Gondwanan upper mantle temperatures (generated by a mantle plume or internal mantle heating) during the generation of the Karoo LIP.

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Section: Discussioncontrasting

confidence: 35%

Crystallisation temperatures of the most Mg-rich magmas of the Karoo LIP on the basis of Al-in-olivine thermometry

2015

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“…1 and 2a) (Elliot, 1992;Elliot and Fleming, 2000;Ferraccioli et al, 2005a;Jourdan et al, 2005;Riley et al, 2005). This dominantly mafic event has been linked with the impact of a mantle plume between South Africa and East Antarctica, potentially a key driver for Gondwana breakup (Fig.…”

Section: Jurassic Magmatismmentioning

confidence: 99%

New geophysical compilations link crustal block motion to Jurassic extension and strike-slip faulting in the Weddell Sea Rift System of West Antarctica

2017

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“…Factors affecting the degree of burning include the temperature of the intrusion, the duration of molten flow and the attitude of the intrusion. Ar geochronology (Duncan et al, 1997;Jourdan et al, 2005), which places them as being of Early Jurassic age.…”

Section: Drakensburg Group and Associated Intrusivesmentioning

confidence: 99%

South Africa's coalfields — A 2014 perspective

Hancox

Götz

2014

International Journal of Coal Geology

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Highlights• South Africa's Coalfields are presented.• The role of Gondwanan coals as palaeoclimate archives is stated.• Future research fields include palynology, sequence stratigraphy, basin fill. AbstractFor well over a century and a half coal has played a vital role in South Africa's economy and currently bituminous coal is the primary energy source for domestic electricity generation, as well as being the feedstock for the production of a substantial percentage of the country's liquid fuels. It furthermore provides a considerable source of foreign revenue from exports.Based on geographic considerations, and variations in the sedimentation, origin, formation, distribution and quality of the coals, 19 coalfields are generally recognised in South Africa. This paper provides an updated review of their exploration and exploitation histories, general geology, and coal seam nomenclature and coal qualities. Within the various coalfields autocyclic variability is the norm rather than the exception, whereas allocyclic variability is much less so, and allows for the correlation of genetically related sequences. During the mid-Jurassic break up of Gondwana most of the coals bearing successions were intruded by dolerite. These intrusions are important as they may cause devolatilisation and burning of the coal, create structural disturbances and related seam correlation problems, and difficulties in mining operations.Whilst many of the coalfields have been extensively explored and exploited, those in the north of the country have until recently received much less attention. Four coalfields occur partly or wholly within the Limpopo Province of South Africa and these may contain as much as 70% of South Africa's remaining coal resources. These coalfields in particular have been the focus of recent exploration due to the presence of large coking and thermal coal resources, as well as for their coal bed methane potential, resources that need to be unlocked regards to maximum benefit and minimal environmental degradation. South Africa's coals have been also recently addressed as palaeoclimate archives recording Gondwana's postglacial climate amelioration by major changes in land plant communities, and proving high-resolution palyno-stratigraphy as a crucial tool to decipher climate change during the Permo-Carboniferous. This aspect of the coals of South Africa is also reviewed.

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Karoo large igneous province: Brevity, origin, and relation to mass extinction questioned by new 40Ar/39Ar age data

Cited by 215 publications

References 27 publications

Crystallisation temperatures of the most Mg-rich magmas of the Karoo LIP on the basis of Al-in-olivine thermometry

Crystallisation temperatures of the most Mg-rich magmas of the Karoo LIP on the basis of Al-in-olivine thermometry

New geophysical compilations link crustal block motion to Jurassic extension and strike-slip faulting in the Weddell Sea Rift System of West Antarctica

South Africa's coalfields — A 2014 perspective

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