Magma flow in dyke swarms of the Karoo LIP: Implications for the mantle plume hypothesis

Hastie, Warwick W.; Watkeys, M. K.; Aubourg, Charles

doi:10.1016/j.gr.2013.08.010

Cited by 99 publications

(47 citation statements)

References 110 publications

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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: Discussionsupporting

confidence: 67%

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: Discussionsupporting

confidence: 67%

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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“…Campbell and Griffiths, 1990) invokes the passive release of fertile lithosphere material, trapped within ancient lithosphere sutures, upon extension, to provide a significant contribution to the voluminous Deccan Trap magmatism (Sheth, 2005b). Similar models involving high mantle fertility beneath Iceland and heat accumulation beneath the Karoo Large Igneous Province (Hastie et al, 2014), provide further support for the generation of excessive volcanism during rifting in the absence of a mantle plume. Post IndiaeSeychelles rifting, the Indian peninsula continued to drift northwards, undergoing variable plate-motions (Cande and Stegman, 2011), and directional changes resulting from the initial interactions of the Indian and Eurasian continents (Patriat and Achache, 1984) that collided between 57 Ma and 50 Ma (Green et al, 2008).…”

Section: Plate Tectonic Settingmentioning

confidence: 90%

“…We suggest models that account for the generation of excessive volcanism during rifting in the absence of a mantle plume (e.g. Sheth, 2005b;Hastie et al, 2014) should be given consideration as viable alternatives to explain the geology of these regions, rather than a widespread acceptance of the plume-head model that has, in the case of the Deccan, been shown to poorly explain many aspects of the regional geology (Sheth, 2005a(Sheth, , 2007.…”

Section: Regional Context and Implicationsmentioning

confidence: 99%

Complex rift geometries resulting from inheritance of pre-existing structures: Insights and regional implications from the Barmer Basin rift

Bladon

Clarke

Burley

2015

Journal of Structural Geology

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a b s t r a c t Structural studies of the Barmer Basin in Rajasthan, northwest India, demonstrate the important effect that pre-existing faults can have on the geometries of evolving fault systems at both the outcrop and basin-scale. Outcrop exposures on opposing rift margins reveal two distinct, non-coaxial extensional events. On the eastern rift margin northwest-southeast extension was accommodated on southwest and west-striking faults that form a complex, zig-zag fault network. On the western rift margin northeast-southwest extension was accommodated on northwest-striking faults that form classical extensional geometries.Combining these outcrop studies with subsurface interpretations demonstrates that northwest-southeast extension preceded northeast-southwest extension. Structures active during the early, previously unrecognised extensional event were variably incorporated into the evolving fault systems during the second. In the study area, an inherited rift-oblique fault transferred extension from the rift margin to a mid-rift fault, rather than linking rift margin fault systems directly. The resultant rift margin accommodation structure has important implications for early sediment routing and depocentre evolution, as well as wider reaching implications for the evolution of the rift basin and West Indian Rift System. The discovery of early rifting in the Barmer Basin supports that extension along the West Indian Rift System was long-lived, multi-event, and likely resulted from far-field plate reorganisations.

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“…Field observations indicate that dikes are volumetrically minor components of sill complexes ( Fig. 7; e.g., the Karoo-Ferrar LIP; Leat, 2008;Hastie et al, 2014;Muirhead et al, 2014). Recent analogue experiments conducted by Kavanagh et al (2015) may provide an alternative explanation for the apparent lack of dikes in sill complexes.…”

Section: Role Of Dikesmentioning

confidence: 99%

Lateral Magma Flow in Mafic Sill‐complexes

Magee

Muirhead

Karvelas

et al. 2016

Acta Geologica Sinica (Eng)

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The structure of upper crustal magma plumbing systems controls the distribution of volcanism and influences tectonic processes. However, delineating the structure and volume of plumbing systems is difficult because (1) active intrusion networks cannot be directly accessed; (2) field outcrops are commonly limited; and (3) geophysical data imaging the subsurface are restricted in areal extent and resolution. This has led to models involving the vertical transfer of magma via dikes, extending from a melt source to overlying reservoirs and eruption sites, being favored in the volcanic literature. However, while there is a wealth of evidence to support the occurrence of dike-dominated systems, we synthesize field-and seismic reflection-based observations and highlight that extensive lateral magma transport (as much as 4100 km) may occur within mafic sill complexes. Most of these mafic sill complexes occur in sedimentary basins (e.g., the Karoo Basin, South Africa), although some intrude crystalline continental crust (e.g., the Yilgarn craton, Australia), and consist of interconnected sills and inclined sheets. Sill complex emplacement is largely controlled by host-rock lithology and structure and the state of stress. We argue that plumbing systems need not be dominated by dikes and that magma can be transported within widespread sill complexes, promoting the development of volcanoes that do not overlie the melt source. However, the extent to which active volcanic systems and rifted margins are underlain by sill complexes remains poorly constrained, despite important implications for elucidating magmatic processes, melt volumes, and melt sources.

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Magma flow in dyke swarms of the Karoo LIP: Implications for the mantle plume hypothesis

Cited by 99 publications

References 110 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

Complex rift geometries resulting from inheritance of pre-existing structures: Insights and regional implications from the Barmer Basin rift

Lateral Magma Flow in Mafic Sill‐complexes

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