Thermochemical structure and evolution of cratonic lithosphere in central and southern Africa

Afonso, Juan Carlos; Mansour, Walid; Griffin, William L.; Salajeghegh, Farshad; Foley, Stephen F.; Begg, Graham; Selway, Kate; Macdonald, Andrew; Januszczak, Nicole; Fomin, Ilya; Nyblade, A.; Yang, Yingjie

doi:10.1038/s41561-022-00929-y

Cited by 25 publications

(31 citation statements)

References 59 publications

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“…Of the 3.87% of the analyzed clusters that occur on dry, depleted lithosphere (Type I), 55% of those come from a single place, the Gibeon fields in Namibia. Geophysical estimation of the geotherm at this cluster has the highest misfit rate compared to the xenolith thermobarometric data (Figure S16 in Supporting Information S1), suggesting this region might have experienced lithospheric thinning post-emplacement (Afonso et al, 2022). The remaining Type I clusters are all in South Australia, namely the Cleve, Mt Hope and Truro clusters.…”

Section: Kimberlite Emplacement Typesmentioning

confidence: 96%

The Relationship Between Kimberlitic Magmatism and Electrical Conductivity Anomalies in the Mantle

Özaydın

Selway

2022

Geophysical Research Letters

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Kimberlites are igneous rocks whose formation remains enigmatic due to their severely altered nature, highly variable compositions and rapid ascent through the lithosphere. The spatiotemporal distribution of kimberlites suggests that mantle metasomatism may play an essential role in their emplacement. Since the magnetotelluric (MT) method is sensitive to metasomatic mantle modification in the forms of interconnected minerals and water, we compiled MT models from Australia, Brazil, Botswana, Canada, Namibia, South Africa and the USA, calculated water content variations and compared them to the distribution of kimberlites. Results indicate that kimberlites mostly ascend through hydrated/metasomatized lithosphere and avoid both dry and heavily metasomatized lithosphere. Diamondiferous kimberlites preferentially occur on moderately metasomatized lithosphere, with the diamondiferous rate increasing with the degree of metasomatism in Archean terranes and decreasing in Proterozoic terranes. These results link geophysical observations of mantle metasomatism to kimberlite magmatism and will improve mineral systems models for diamond exploration.

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Section: Kimberlite Emplacement Typesmentioning

confidence: 96%

The Relationship Between Kimberlitic Magmatism and Electrical Conductivity Anomalies in the Mantle

Özaydın

Selway

2022

Geophysical Research Letters

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“…They proposed that the EM1 source derives from upwelling of a deep source along a hot-spot track, and that the HIMU material may either derive from upwelling of mantle plume that then flows westward along the base of the sub-continental lithospheric mantle, or may arise from discrete diapirs of HIMU material rising from the deep mantle. As noted, Alfonso et al (2022) recently proposed that Walvis Ridge (South Atlantic) and the southern Namibia carbonatites lie along a hot-spot track that youngs from the NE to SW, thus supporting the plume model for the HIMU source.…”

Section: Discussionmentioning

confidence: 75%

“…The closest alkaline complex to the TCC is the recently described Tsirub nephelinite intrusions, ∼20 km south of Dicker Willem and ∼35 km ENE of the TCC (Nakashole et al 2020). The extent to which the carbonatites and alkaline complexes lie on a structural lineament (the NE-striking Luderitz lineament), possibly created during a period of Gondwanaland rifting and crustal extension, is uncertain (Reid et al 1990; Woolley, 2001; Alfonso et al 2022). Nevertheless, other anorogenic alkaline provinces aligned along ENE-striking zones in Namibia are suggested to be related to pre-existing crustal zones of weakness (Reid, 1991; Smithies & Marsh, 1996; Homrighausen et al 2018).…”

Section: Geological Settingmentioning

confidence: 99%

“…It has been suggested that emplacement of carbonatites and kimberlites in southern Africa is related to melting of the sub-continental lithospheric mantle initiated by passage of the African plate over a mantle plume (Hartnady & le Roex, 1985). In this context, formation of the southern Namibian carbonatites appears to be related to the passage of the Vesma hot-spot track that first emerged in Late Jurassic/Early Cretaceous times beneath the East African rift, tracked SW, before passing beneath the TCC ∼40–50 Ma, and now lies beneath the South Atlantic (Alfonso et al 2022).…”

Section: Geological Settingmentioning

confidence: 99%

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A preliminary study of the rare earth element-enriched Twyfelskupje carbonatite complex, southern Namibia

Marlow¹,

Palmer

2022

Geol. Mag.

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The Twyfelskupje carbonatite complex, Southern Namibia, exhibits the typical igneous emplacement structures of carbonatites, including plugs, cone sheets and dyke stockworks. The excellent exposure allows for detailed studies of the high-level geochemical and structural evolution of the carbonatite, and the nature of the concomitant rare earth element mineralization. Radiogenic isotope analyses (Sr, Nd, Pb) reveal that, in common with many other carbonatites, the Twyfelskupje carbonatite complex appears to be predominantly derived from mixing between HIMU and EM1 mantle end-members. Following partial melting of these mantle sources, the geochemical and structural evolution of the Twyfelskupje carbonatite complex proceeded by a staged process involving separate magma pulses, a series of emplacement structures, sub-solidus crystallization, fractionation and low-temperature hydrothermal alteration. The dominant rare earth element minerals in the Twyfelskupje carbonatite complex are fluorcarbonates and monazite, and are characterized by variable Ca, high F and light rare earth elements in the order Ce>La>Nd. Comparison between the rare earth element concentrations of the whole rocks, dominant rare earth element minerals and carbonates suggests that ∼95 % of the total rare earth element abundance of the Twyfelskupje carbonatite complex is contained within fluorcarbonates and monazite. Overall, the early calcio-carbonatite plugs are rare earth element enriched (mean 4.47 wt % rare earth oxides) relative to the magnesio-carbonatite cone sheets (mean 2.51 wt % rare earth oxides).

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“…Recently, it has become possible to calculate multi‐parameter physical models of the lithosphere and underlying upper mantle directly from surface‐wave and other geophysical data, by means of inversions using integrated geophysical‐petrological methods (e.g., Afonso, Fullea, Griffin, et al., 2013; Afonso, Fullea, Yang, et al., 2013; Afonso et al., 2022; Altoe et al., 2020; Fullea et al., 2012). With temperature and composition of the upper mantle and the lithospheric thickness being the inversion parameters, steady‐state geotherms and synthetic geophysical observables are calculated directly from them.…”

Section: Introductionmentioning

confidence: 99%

Defining Continental Lithosphere as a Layer With Abundant Frozen‐In Structures That Scatter Seismic Waves

et al. 2023

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The lithosphere is the rigid outermost layer of the Earth where mantle flow is absent due to its high viscosity, and the geotherm is controlled by heat conduction (e.g., Barrell, 1914;Daly, 1940;McKenzie et al., 2005). In the sub-lithospheric upper mantle, flow and stirring take place due to the relatively low viscosity values, leading to a geotherm that is typically close to an adiabatic temperature gradient in the range 0.4-0.6 K/km (e.g., Katsura et al., 2010). The Earth's continental lithosphere is a product of processes spanning the bulk of the existence of our planet. Continental lithosphere hosts rocks as old as 4.03 Ga (Bowring & Williams, 1999) and minerals dating to as early as 4.4 Ga (Valley et al., 2014). While the ability of the continents' Archean cores to resist destruction by tectonic and convective forces makes them an invaluable repository of planetary history, their origins and mechanisms of longevity are yet to be fully understood (

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Thermochemical structure and evolution of cratonic lithosphere in central and southern Africa

Cited by 25 publications

References 59 publications

The Relationship Between Kimberlitic Magmatism and Electrical Conductivity Anomalies in the Mantle

The Relationship Between Kimberlitic Magmatism and Electrical Conductivity Anomalies in the Mantle

A preliminary study of the rare earth element-enriched Twyfelskupje carbonatite complex, southern Namibia

Defining Continental Lithosphere as a Layer With Abundant Frozen‐In Structures That Scatter Seismic Waves

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