Rapid magma emplacement in the Karoo Large Igneous Province

Svensen, Henrik; Corfú, Fernando; Polteau, S.; Hammer, Øyvind; Planke, Sverre

doi:10.1016/j.epsl.2012.01.015

Cited by 293 publications

(195 citation statements)

References 27 publications

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“…2). The major thermomagmatic event that affected the Kimberley area before the Barkly West-Boshof orangeite magmatism was the emplacement of Karoo dykes and lavas at B180 Myr ago 54,55 . It is therefore likely that MARID assemblages crystallized from melts produced during the Karoo event, coeval with phlogopiterich metasomatism in the lithospheric mantle beneath the Kimberley region 37 ('LIMA U-Pb' in Fig.…”

Section: Discussionmentioning

confidence: 99%

Did diamond-bearing orangeites originate from MARID-veined peridotites in the lithospheric mantle?

et al. 2015

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Kimberlites and orangeites (previously named Group-II kimberlites) are small-volume igneous rocks occurring in diatremes, sills and dykes. They are the main hosts for diamonds and are of scientific importance because they contain fragments of entrained mantle and crustal rocks, thus providing key information about the subcontinental lithosphere. Orangeites are ultrapotassic, H 2 O and CO 2 -rich rocks hosting minerals such as phlogopite, olivine, calcite and apatite. The major, trace element and isotopic compositions of orangeites resemble those of intensely metasomatized mantle of the type represented by MARID (mica-amphibolerutile-ilmenite-diopside) xenoliths. Here we report new data for two MARID xenoliths from the Bultfontein kimberlite (Kimberley, South Africa) and we show that MARID-veined mantle has mineralogical (carbonate-apatite) and geochemical (Sr-Nd-Hf-O isotopes) characteristics compatible with orangeite melt generation from a MARID-rich source. This interpretation is supported by U-Pb zircon ages in MARID xenoliths from the Kimberley kimberlites, which confirm MARID rock formation before orangeite magmatism in the area.

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Section: Discussionmentioning

confidence: 99%

Did diamond-bearing orangeites originate from MARID-veined peridotites in the lithospheric mantle?

et al. 2015

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“…9,10 Sedimentation in the basin was terminated during Gondwanaland breakup with the emplacement of the Karoo large igneous province (KLIP), which includes an extensive network of dolerite sills and dykes. 11,12 Along the basin's southern margin the Karoo succession attains a maximum composite thickness of 12 km. 10 Here the basin is bound by a narrow zone of deformation known as the Cape Fold Belt (CFB).…”

Section: Introductionmentioning

confidence: 99%

Deflating the shale gas potential of South Africa’s Main Karoo basin

Kock¹,

Beukes²,

Adeniyi³

et al. 2017

S. Afr. J. Sci.

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The Main Karoo basin has been identified as a potential source of shale gas (i.e. natural gas that can be extracted via the process of hydraulic stimulation or ‘fracking’). Current resource estimates of 0.4–11x109 m3 (13–390 Tcf) are speculatively based on carbonaceous shale thickness, area, depth, thermal maturity and, most of all, the total organic carbon content of specifically the Ecca Group’s Whitehill Formation with a thickness of more than 30 m. These estimates were made without any measurements on the actual available gas content of the shale. Such measurements were recently conducted on samples from two boreholes and are reported here. These measurements indicate that there is little to no desorbed and residual gas, despite high total organic carbon values. In addition, vitrinite reflectance and illite crystallinity of unweathered shale material reveal the Ecca Group to be metamorphosed and overmature. Organic carbon in the shale is largely unbound to hydrogen, and little hydrocarbon generation potential remains. These findings led to the conclusion that the lowest of the existing resource estimates, namely 0.4x109 m3 (13 Tcf), may be the most realistic. However, such low estimates still represent a large resource with developmental potential for the South African petroleum industry. To be economically viable, the resource would be required to be confined to a small, well-delineated ‘sweet spot’ area in the vast southern area of the basin. It is acknowledged that the drill cores we investigated fall outside of currently identified sweet spots and these areas should be targets for further scientific drilling projects.

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“…Volcanic basins contain significant volumes of igneous rocks Jerram and Bryan, 2017), e.g., the Karoo Basin (Svensen et al, 2012) and midNorwegian margin (Planke et al, 2005). In addition, they are explored for hydrocarbons all over the world (e.g., Senger et al, forthcoming), onshore and offshore, e.g., the Rockall Basin (e.g., Magee et al, 2014), the Faroe-Shetland Basin (e.g., Smallwood and Maresh, 2002), the Møre and Vøring Basins (e.g., Planke et al, 2005;Cartwright and Hansen, 2006), and the Neuquén Basin (e.g., Kay et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of overburden deformation associated with the emplacement of the Tulipan sill, mid-Norwegian margin

et al. 2017

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The emplacement of igneous intrusions into sedimentary basins mechanically deforms the host rocks and causes hydrocarbon maturation. Existing models of host-rock deformation are investigated using high-quality 3D seismic and industry well data in the western Møre Basin offshore mid-Norway. The models include synemplacement (e.g., elastic bending-related active uplift and volume reduction of metamorphic aureoles) and postemplacement (e.g., differential compaction) mechanisms. We use the seismic interpretations of five horizons in the Cretaceous-Paleogene sequence (Springar, Tang, and Tare Formations) to analyze the host rock deformation induced by the emplacement of the underlying saucer-shaped Tulipan sill. The results show that the sill, emplaced between 55.8 and 54.9 Ma, is responsible for the overlying dome structure observed in the seismic data. Isochron maps of the deformed sediments, as well as deformation of the younger postemplacement sediments, document a good match between the spatial distribution of the dome and the periphery of the sill. The thickness t of the Tulipan is less than 100 m, whereas the amplitude f of the overlying dome ranges between 30 and 70 m. Spectral decomposition maps highlight the distribution of fractures in the upper part of the dome. These fractures are observed in between hydrothermal vent complexes in the outer parts of the dome structure. The 3D seismic horizon interpretation and volume rendering visualization of the Tulipan sill reveal fingers and an overall saucer-shaped geometry. We conclude that a combination of different mechanisms of overburden deformation, including (1) elastic bending, (2) shear failure, and (3) differential compaction, is responsible for the synemplacement formation and the postemplacement modification of the observed dome structure in the Tulipan area.

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Rapid magma emplacement in the Karoo Large Igneous Province

Cited by 293 publications

References 27 publications

Did diamond-bearing orangeites originate from MARID-veined peridotites in the lithospheric mantle?

Did diamond-bearing orangeites originate from MARID-veined peridotites in the lithospheric mantle?

Deflating the shale gas potential of South Africa’s Main Karoo basin

Mechanisms of overburden deformation associated with the emplacement of the Tulipan sill, mid-Norwegian margin

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