Preferential distribution along transcontinental corridors of kimberlites and related rocks of Southern Africa

Jelsma, Hielke A.; Wit, Maarten J. de; Thiart, Christien; Dirks, Paul H.G.M.; Viola, Giulio; Basson, I.J.; Anckar, Eva

doi:10.2113/107.1-2.301

Cited by 122 publications

(87 citation statements)

References 67 publications

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“…The last two best fit the spatial arrangement and age data of the kimberlites (Jelsma et al, 2004). A study of more than 1300 kimberlite occurrences in Southern Africa in relation to regional geological and geophysical data shows that there is a statistical probabability of a pronounced structural control on the location of these rocks (Jelsma et al, 2004, Basson and.…”

Section: Punctuated Kimberlitic Magmatism Across Southern Africamentioning

confidence: 90%

“…This eruption frequency is clearly reflected in a dense regional distribution of kimberlites, carbonatites and other and related rocks across southern African (Figure 7, Skinner et al, 1992;Jelsma et al, 2004). The spatial and temporal distribution of these rocks has frequently been related to: 1. mantle plumes, and hot spots; 2. rifting of continents; 3. major faults or basement trends related to oceanic fracture zones; 4. temporal variations in deviatoric stresses related to changes in the motion vector of the African plate during the Cretaceous.…”

Section: Punctuated Kimberlitic Magmatism Across Southern Africamentioning

confidence: 94%

“…Regional variations in alkaline igneous activity suggest that the horizontal deflection of heat in the mid-mantle is relatively recent (<40 Ma). Earlier, between ~60 and 200 Ma the superplume may have reached higher levels below southern Africa during periods of extensive and widespread alkaline volcanism across southern Africa, (Doucouré and de Wit, 2003a;Jelsma et al, 2004). This is consistent with fission track dating and with accelerated sediment accumulation in the Cretaceous, followed by a distinct unconformity above which relatively low volumes of Cenozoic sediment are preserved around the margins of southern Africa (Dingle et al, 1983;Brown et al, 1995;Tinker, 2005;Tinker et al, 2007 under review;Paton et al, 2007).…”

Section: High Topography Of Africamentioning

confidence: 99%

“…A study of more than 1300 kimberlite occurrences in Southern Africa in relation to regional geological and geophysical data shows that there is a statistical probabability of a pronounced structural control on the location of these rocks (Jelsma et al, 2004, Basson and. Some have attributed the trends to hot spot tracks (e.g.…”

Section: Punctuated Kimberlitic Magmatism Across Southern Africamentioning

confidence: 99%

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The Kalahari Epeirogeny and climate change: differentiating cause and effect from core to space

Wit

2007

South African Journal of Geology

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Southern Africa's high Kalahari plateau and its flanking mountain ranges formed over an extended period of ~200 million years through vertical tectonic processes different from those at convergent plate boundaries. We refer to this as the Kalahari epeirogeny. Episodic uplift and erosion during the Kalahari epeirogeny is inferred from thermo-chronology and from stratigraphy of sediment accumulated around its continental margin. A total thickness of 2 to 7 km of rock (of which basalt was a major component) was eroded from the subcontinent's surface during two punctuated episodes of exhumation, in the early-Cretaceous and in the mid-Cretaceous. Major exhumation was over by the end of the Cretaceous, and the rate of erosion decreased by more than an order of magnitude to remove less than 1 km thickness of rock during the Cenozoic. Cosmogenic dating shows that erosion rates today are almost an order of magnitude less still.The cause for the Kalahari epeirogeny remains elusive, but three striking observations stand out: (i) major exhumation occurred during the late Mesozoic break-up of Gondwana; (ii) large scale basaltic magmatism closely match two accelerated episodes of exhumation: first along the west coast (~132 Ma, Etendeka large igneous province [LIP], associated with vast amounts of underplating along this entire passive margin), and the second flanking the sheared south coast margin (~90 Ma, Agulhas oceanic LIP). Yet exhumation that might have accompanied the vast Karoo LIP (~180 Ma) is not readily detected; (iii) the two main regional episodes of accelerated exhumation and coastal sediment accumulation are near synchronous with two regional 'spikes' of kimberlite intrusions: >450 kimberlites at ~90 Ma, and >200 kimberlites at ~120 Ma. Southern Africa is underlain by an anomalous warm region in the lowermost ~1500 km of the mantle that is linked to core to mantle heat loss. This warm region was inherited from a large Cretaceous thermo-chemical anomaly in the mantle created during long-lived subduction beneath Gondwana. Associated Mesozoic kimberlite genesis and basaltic magmatism may have been sufficient to cause volatile/heat-induced density changes in the lithospheric mantle of southern Africa to sustain the Kalahari plateau. In addition, such changes may have been induced by tectonic uplift and decompressional melting resulting from far-field collision processes between Africa and Europe, and/or final continental lithosphere decoupling between the Falkland plateau and southern Africa. CO 2 released into the ocean-atmosphere system during the Kalahari epeirogeny contributed to the global mid-Cretaceous hot-house conditions. However, because the CO 2 -consumption rate associated with basalt weathering is about eight times that of granite, atmospheric CO 2 was also efficiently sequestrated during the rapid erosion of Karoo basalt. Thus, the Kalahari epeirogeny also may have catalysed the onset of long-term global Cenozoic cooling.

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Section: Punctuated Kimberlitic Magmatism Across Southern Africamentioning

confidence: 90%

Section: Punctuated Kimberlitic Magmatism Across Southern Africamentioning

confidence: 94%

Section: High Topography Of Africamentioning

confidence: 99%

Section: Punctuated Kimberlitic Magmatism Across Southern Africamentioning

confidence: 99%

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The Kalahari Epeirogeny and climate change: differentiating cause and effect from core to space

Wit

2007

South African Journal of Geology

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“…For example, Cullen (1958) concluded that northwesterly trending faulting accompanied folding of Transvaal Supergroup strata prior to emplacement of the MFC. The sub-continental trend of kimberlites in the Kaapvaal Craton is northeast to southwest (Jelsma et al, 2004) although the kimberlite fields in southern Botswana (Jwaneng and Kokong, shown on Figure 3) are also aligned as an east to west trending belt. However, northwest to southeast trending faults locally control the emplacement of individual kimberlites in southern Botswana.…”

Section: Geological Setting Of the Mfc In Botswanamentioning

confidence: 98%

Geophysical Modelling of the Molopo Farms Complex in Southern Botswana; Implications for Its Emplacement Within the 2 Ga Large Igneous Provinces of Southern and Central Africa

Walker

Pouliquen

Gunn

et al. 2010

South African Journal of Geology

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Rapid erosion of the Southern African Plateau as it climbs over a mantle superswell

et al. 2014

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We present new sedimentary flux data confirming that a large pulse of erosion affected the Southern African Plateau in the Late Cretaceous and is likely to be related to a major uplift episode of the plateau. This short phase of erosion (i.e., less than 30 Myr in duration) has commonly been difficult to reconcile with a mantle origin for the plateau anomalous uplift: given its size, the rise of the African superplume is likely to have lasted much longer. Here we demonstrate by using a simple model for fluvial erosion that tilting of the continent as it rides over a wide dynamic topography high cannot only cause rapid uplift of the plateau but also trigger continent-wide drainage reorganization, leading to substantial denudation in a relatively short amount of time. The amplitude and short duration of the sedimentary pulse are best reproduced by assuming a strong erodibility contrast between the Karoo sedimentary and volcanic rocks and the underlying basement. We also present a new compilation of paleoclimate indicators that shows a transition from arid to very humid conditions approximately at the onset of the documented erosional pulse, suggesting that climate may have also played a role in triggering the denudation. The diachronism of the sedimentary flux between the eastern and western margins of the plateau and the temporal and geographic coincidence between the uplift and kimberlite eruptions are, however, better explained by our tilt hypothesis driven by the migration of the continent over a fixed source of mantle upwelling.

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Preferential distribution along transcontinental corridors of kimberlites and related rocks of Southern Africa

Cited by 122 publications

References 67 publications

The Kalahari Epeirogeny and climate change: differentiating cause and effect from core to space

The Kalahari Epeirogeny and climate change: differentiating cause and effect from core to space

Geophysical Modelling of the Molopo Farms Complex in Southern Botswana; Implications for Its Emplacement Within the 2 Ga Large Igneous Provinces of Southern and Central Africa

Rapid erosion of the Southern African Plateau as it climbs over a mantle superswell

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