Deep seismic structure of the Kaapvaal craton

Vinnik, Lev; Green, R.W.E.; Nicolaysen, L. O.; Kosarev, G. L.; Petersen, N.

doi:10.1016/0040-1951(96)00012-1

Cited by 43 publications

(28 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The troughs seem sufficiently prominent to suggest that the reduced wavespeed gradient zone does in fact exist beneath the Kaapvaal craton. Our observations suggest, however, that the upper boundary of the zone occurs at depth different to those suggested by Vinnik et al (1996), Qui et al (1996) and Priestley (1999). Our result is consistent with results from Freybourger et al (2001), who showed there is no evidence for such a zone at depth less than 250 km.…”

Section: Existence Of a Sub-continental Low Velocity Zonesupporting

confidence: 83%

“…The Kimberley array results give a travel time of the converted S-wave through the transition zone as 23.8 s. Vinnik et al (1996) observed the two phase arrivals at 41.8 and 65.6 s, respectively, also implying a travel time of 23.8 s. The inferred time difference is also very close to the 23.9 s predicted by the iasp91 Fig. 9.…”

Section: Transition Zone Thickness and Wavespeedsupporting

confidence: 65%

“…The existence of the low velocity zone has been suggested but the depth has remained enigmatic. From surface wave studies Qui et al (1996) and Priestley (1999) suggested its upper bound to be shallower than 200 km, while Vinnik et al (1996) use converted phases to claim that the zone does not extend further than 50 km above the 410 km discontinuity.…”

Section: Existence Of a Sub-continental Low Velocity Zonementioning

confidence: 99%

“…LeFevre and Helmberger, 1989;Vinnik et al, 1996). If the upper boundary of such a zone has a sufficiently steep gradient, or is discontinuity, it will produce a P-to-S converted wave which would register a trough in the receiver function.…”

Section: Existence Of a Sub-continental Low Velocity Zonementioning

confidence: 99%

“…James et al, 2001), and further information about possible internal lithosphere structure must be deciphered using different seismological techniques 1 More information on the Kaapvaal project can be found on http://kaapbase.uct.ac.za or http://www.ciw.edu/kaapvaal. (Vinnik et al, 1996). Here we attempt to analyse in greater detail the structure of the crust and the upper mantle beneath this old craton using receiver function analysis.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Crustal thickness, discontinuity depth, and upper mantle structure beneath southern Africa: constraints from body wave conversions

Stankiewicz

Chevrot

Hilst

et al. 2002

Physics of the Earth and Planetary Interiors

View full text Add to dashboard Cite

The technique of receiver function analysis is applied to the study of crustal and upper mantle structures beneath the Kaapvaal craton in southern Africa and its surroundings. Seismic data were recorded by the seismic array of 82 sites deployed from April 1997 to April 1999 across southern Africa, as well as a dense array of 32 sites near Kimberley, in operation from December 1998 to June 1999. Arrival times for phases converted at the Moho are used to determine crustal thickness. The Moho depth in the south-western section of the craton was found to vary between 37 and 40 km, except for one station that recorded a depth of 43 km (SA23). Farther north along the western block of the craton (into Botswana) the depth increases up to 43 km. The depth increases even further in the north-eastern section of the craton, where results vary from 40 to 52 km. Just north of the Kaapvaal craton, in the neighbouring Zimbabwe craton, the crustal thickness drops significantly. The results obtained there varied from 36 to 40 km. For the Kimberley area, using the dense array, the Moho depth was found to be 37.3 km. Arrivals of the Ps and Ppps phases were used to determine the Poisson's ratio in the region. This was found to be 0.26 ± 0.01. Arrivals of phases from the 410 and 660 km mantle discontinuities are used to interpret the relative positions of these discontinuities, as well as for comparison of mantle temperatures and seismic velocities in the region with global averages. In the Kimberley area the 410 and 660 km discontinuities were found at their expected depth, implying that mantle temperatures in the region are close to the global average. The seismic velocities above the '410' were found up to 5% faster than the averages from the global iasp91 model, which is fast even by Precambrian standards. In other sections of the Kaapvaal craton, the velocities are also faster than global averages, but not as fast as beneath Kimberley. In these sections, the '410' is also slightly elevated, while the '660' is depressed, which implies a slightly lower mantle temperature relative to the global average. Beneath the Kaapvaal craton we find evidence suggesting the presence of a zone with a reduced wavespeed gradient at an upper bound of approximately 300 km, which may mark the lower chemical boundary of the craton.

show abstract

Section: Existence Of a Sub-continental Low Velocity Zonesupporting

confidence: 83%

Section: Transition Zone Thickness and Wavespeedsupporting

confidence: 65%

Section: Existence Of a Sub-continental Low Velocity Zonementioning

confidence: 99%

Section: Existence Of a Sub-continental Low Velocity Zonementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Crustal thickness, discontinuity depth, and upper mantle structure beneath southern Africa: constraints from body wave conversions

Stankiewicz

Chevrot

Hilst

et al. 2002

Physics of the Earth and Planetary Interiors

View full text Add to dashboard Cite

show abstract

Seismic evidence for stratification in composition and anisotropic fabric within the thick lithosphere of Kalahari Craton

Sodoudi

Yuan

Kind

et al. 2013

Geochem Geophys Geosyst

View full text Add to dashboard Cite

[1] Based on joint consideration of S receiver functions and surface-wave anisotropy we present evidence for the existence of a thick and layered lithosphere beneath the Kalahari Craton. Our results show that frozen-in anisotropy and compositional changes can generate sharp Mid-Lithospheric Discontinuities (MLD) at depths of 85 and 150-200 km, respectively. We found that a 50 km thick anisotropic layer, containing 3% S wave anisotropy and with a fast-velocity axis different from that in the layer beneath, can account for the first MLD at about 85 km depth. Significant correlation between the depths of an apparent boundary separating the depleted and metasomatised lithosphere, as inferred from chemical tomography, and those of our second MLD led us to characterize it as a compositional boundary, most likely due to the modification of the cratonic mantle lithosphere by magma infiltration. The deepening of this boundary from 150 to 200 km is spatially correlated with the surficial expression of the Thabazimbi-Murchison Lineament (TML), implying that the TML isolates the lithosphere of the Limpopo terrane from that of the ancient Kaapvaal terrane. The

show abstract

Geochemical and geophysical constrains on the dynamic topography of the Southern African Plateau

Jones

Afonso

Fullea

2017

Geochem Geophys Geosyst

View full text Add to dashboard Cite

The deep mantle African Superswell is considered to contribute to the topographic uplift of the Southern African Plateau, but dynamic support estimates vary wildly depending on the approach and data used. One reason for these large disparities is that the role of lithospheric structure, key in modulating deep dynamic contributions to elevation, is commonly ignored or oversimplified in convection studies. We use multiple high‐quality geophysical data coupled with xenolith‐based geochemical constraints to compute the isostatic lithospheric contribution to the elevation of the Plateau, facilitating isolation of the current dynamic component from the total observed elevation. We employ a multiobservable stochastic algorithm to invert geoid anomaly, surface‐wave dispersion data, magnetotelluric data, and surface heat flow to predict elevation in a fully thermodynamically and internally‐consistent manner. We find that a compositionally layered 230 ± 7 km thick lithosphere is required to simultaneously fit all four data types, in agreement with abundant independent xenolith evidence. Our stochastic modeling indicates a lithospheric contribution to elevation of the order of 670 m, which implies dynamic support arising from the convecting sublithospheric mantle of ∼650 m. Our results have important implications for the understanding of lithospheric‐deep mantle feedback mechanisms and for calibrating dynamic topography estimates from global convection studies.

show abstract

Deep seismic structure of the Kaapvaal craton

Cited by 43 publications

References 24 publications

Crustal thickness, discontinuity depth, and upper mantle structure beneath southern Africa: constraints from body wave conversions

Crustal thickness, discontinuity depth, and upper mantle structure beneath southern Africa: constraints from body wave conversions

Seismic evidence for stratification in composition and anisotropic fabric within the thick lithosphere of Kalahari Craton

Geochemical and geophysical constrains on the dynamic topography of the Southern African Plateau

Contact Info

Product

Resources

About