Ghosts of lithospheres past: Imaging an evolving lithospheric mantle in southern Africa

Kobussen, A. F.; Griffin, William L.; O’Reilly, Suzanne Y.; Shee, S. R.

doi:10.1130/g24868a.1

Cited by 68 publications

(56 citation statements)

References 34 publications

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“…It may also have resulted in the deep intersection of the volatile-rich peridotite solidus and production of partial melts that have pervasively metasomatised and refertilised the deep mantle root, leading to "loss" of 40 km of the Kaapvaal root by asthenospherisation. However, unradiogenic Os retained in some of the deepest and hottest samples suggests that the root has not been completely replaced (Kobussen et al, 2008;Begg et al, 2009;O'Reilly and Griffin, 2010). The deep metasomatised root has warmed substantially (Bell et al, 2003) and become in parts almost indistinguishable from asthenospheric mantle.…”

Section: Accepted M Manuscriptmentioning

confidence: 99%

“…GPa), while age dating demonstrates a close temporal link to the older Group II and subsequent Group I kimberlite magmatism (80-90 Ma) or to the preceding Karroo magmatic event (Konzett et al, 1998(Konzett et al, , 2000(Konzett et al, , 2013Grégoire et al, 2002;Bell et al, 2005;Kobussen et al, 2008;Giuliani et al, 2013Giuliani et al, , 2014Giuliani et al, , 2015b. Phlogopite-bearing polymict breccias from 110-115 km depth have also been linked to group I kimberlite magmatism and were interpreted as failed kimberlite intrusions that paved the way for subsequent kimberlite eruption (Giuliani et al, 2014).…”

Section: Accepted M Manuscriptmentioning

confidence: 99%

See 1 more Smart Citation

Origins of cratonic mantle discontinuities: A view from petrology, geochemistry and thermodynamic models

Aulbach

Massuyeau

Gaillard

2017

Lithos

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Section: Accepted M Manuscriptmentioning

confidence: 99%

Section: Accepted M Manuscriptmentioning

confidence: 99%

Origins of cratonic mantle discontinuities: A view from petrology, geochemistry and thermodynamic models

Aulbach

Massuyeau

Gaillard

2017

Lithos

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“…The xenolith-based approach, however does not inform about on the current geotherm present in the region of origin of the xenoliths (e.g., Kobussen et al, 2008 2005). Clearly, parts of the lithospheric mantle can be cooler than the pressure-corrected Curie temperature of magnetite (<600ºC), for example, in cratonic interiors (e.g.…”

Section: Reason 3 Temperature Of the Uppermost Mantle In Cold Geothementioning

confidence: 99%

Eight good reasons why the uppermost mantle could be magnetic

et al. 2014

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Wasilewski et al. (1979) concluded that no magnetic remanence existed in the uppermost mantle and that even if present, such sources would be at temperatures too high to contribute to long wavelength magnetic anomalies (LWMA). However, new collections of unaltered mantle xenoliths indicate that the uppermost mantle could contain ferromagnetic minerals. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 2/39This is most easily explained as a thermoremanent magnetization acquired by pre-existing ferromagnetic minerals as xenoliths cool rapidly at the Earth's surface from magmatic temperatures, acquired during ascent. 7. Modern experimental data suggest that the wüstite-magnetite oxygen buffer and the fayalite-magnetite-quartz oxygen buffer extend several tens of km within the uppermost mantle. 8. The magnetic properties of mantle xenoliths vary consistently across tectonic settings. In conclusion, the model of a uniformly non-magnetic mantle should be revisited.

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“…Interestingly, the geologically inferred craton boundary is located farther northeast when compared with the onset of high resistivity material. While direct surface observations of the boundary are impossible due to the thick sedimentary cover of the Karoo basin, geochemical analysis of xenoliths from this area (Kobussen et al, 2008) support a modified boundary location.…”

Section: Making a Continent -Case Studiesmentioning

confidence: 99%

Making and Breaking of a Continent: Following the Scent of Geodynamic Imprints on the African Continent Using Electromagnetics

Weckmann

2011

Surv Geophys

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The African continent inherits a long history of continental accretion and breakup. The stage of "making" a continent goes back to the Archean, when the first continental masses formed cratons which mostly remained stable ever since. Subsequent collision of weaker continental masses was followed by several extension and compression episodes that resulted in the formation of supercontinents. After the assemblage of Gondwana, a period of predominantly "breaking" , i.e. the breakup of supercontinents, took over. The modern day African continent exhibits different types of margins; continental rifting occurs side by side with recent collision. Since the late 1960's Magnetotelluric (MT) experiments have played an important role in studies of the electrical conductivity structure of Africa. The early results significantly shaped the MT community's understanding of continental scale conductivity belts and basic characteristics of cratons and mobile belts on both crustal and lithospheric mantle scale for some decades. Modern MT studies in Africa have generally supported earlier results with high resistivities observed on cratons and low resistivities observed across mobile belts. Advances in instrumentation, data processing and interpretation resulted in higher resolution images of the lithosphere which in consequence induce an improved understanding of tectonic processes and geological prerequisites for the occurrence of natural resources. The high electrical conductivity of mobile belts and their relation to reactivated fault and detachment zones were often interpreted to characterize mobile belts as tectonic weak zones, which can accommodate stress and constitute zones along which continents can break. Recent breaking of the African continent can be studied on land across the East African rift; however, the lack of amphibian MT experiments across today's margins does not allow for good resolution of remnants of continental break-up processes. Naturally, the regions and the focus of the MT studies in Africa are diverse, but they all contribute to the story of making and breaking a continent.

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Ghosts of lithospheres past: Imaging an evolving lithospheric mantle in southern Africa

Cited by 68 publications

References 34 publications

Origins of cratonic mantle discontinuities: A view from petrology, geochemistry and thermodynamic models

Origins of cratonic mantle discontinuities: A view from petrology, geochemistry and thermodynamic models

Eight good reasons why the uppermost mantle could be magnetic

Making and Breaking of a Continent: Following the Scent of Geodynamic Imprints on the African Continent Using Electromagnetics

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