The evolution of lithospheric mantle beneath the Kalahari Craton and its margins

Griffin, William L.; O’Reilly, Suzanne Y.; Natapov, Lev M.; Ryan, C.G.

doi:10.1016/j.lithos.2003.07.006

Cited by 254 publications

(217 citation statements)

References 59 publications

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“…[33] Mantle velocities can be strongly influenced by temperature variations and to a lesser extent by compositional variations, partial melt, water, and anisotropy [e.g., Sobolev et al, 1996;Goes et al, 2000;Griffin et al, 2003]. For eastern Africa, water content is not considered to be an important factor because there has not been any subduction in this region for !500 Ma.…”

Section: Discussionmentioning

confidence: 99%

The P and S wave velocity structure of the mantle beneath eastern Africa and the African superplume anomaly

Mulibo

Nyblade

2013

Geochem Geophys Geosyst

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P and S relative arrival time residuals from teleseismic earthquakes recorded on over 60 temporary AfricaArray broadband seismic stations deployed in Uganda, Tanzania, and Zambia between 2007 and 2011 have been inverted, together with relative arrival time residuals from earthquakes recorded by previous deployments, for a tomographic image of mantle wave speed variations extending to a depth of 1200 km beneath eastern Africa. The image shows a low‐wave speed anomaly (LWA) well developed at shallow depths (100–200 km) beneath the Eastern and Western branches of the Cenozoic East African rift system and northwestern Zambia, and a fast wave speed anomaly at depths ≤ 350 km beneath the central and northern parts of the East African Plateau and the eastern and central parts of Zambia. At depths ≥350 km the LWA is most prominent under the central and southern parts of the East African Plateau and dips to the southwest beneath northern Zambia, extending to a depth of at least 900 km. The amplitude of the LWA is consistent with a ∼150–300 K thermal perturbation, and its depth extent indicates that the African superplume, originally identified as a lower mantle anomaly, is likely a whole mantle structure. A superplume extending from the core‐mantle boundary to the surface implies an origin for the Cenozoic extension, volcanism, and plateau uplift in eastern Africa rooted in the dynamics of the lower mantle.

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Section: Discussionmentioning

confidence: 99%

The P and S wave velocity structure of the mantle beneath eastern Africa and the African superplume anomaly

Mulibo

Nyblade

2013

Geochem Geophys Geosyst

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“…In this perspective, it is logical to wonder whether the fertile mantle xenoliths represent refertilized or pristine mantle. Several authors have ascribed the chemical stratification of cratonic lithosphere and/or its temporal evolution to metasomatic refertilization (Lee and Rudnick, 1999;Kopylova and Russell, 2000;Griffin et al, 2003). In this scheme, fertile (predominantly lherzolitic), off-craton lithosphere may be viewed as the ultimate transformation of cratonic lithosphere after one or several cycles of igneous refertilization.…”

Section: Discussionmentioning

confidence: 99%

The Lherz spinel lherzolite: Refertilized rather than pristine mantle

Roux

Bodinier

Tommasi

et al. 2007

Earth and Planetary Science Letters

325

196

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Differentiation of the Earth's mantle and formation of continental and oceanic crust occur principally through partial melting and extraction of basaltic melt. Among the mantle rocks occurring at the Earth's surface, as tectonically-emplaced massifs, abyssal peridotites or xenoliths, the harzburgites (b 5% clinopyroxene) are widely considered as refractory mantle residues left after extraction of a basaltic component. In contrast, the most fertile lherzolites (15% clinopyroxene) are generally regarded as pristine mantle, only weakly affected by partial melting. In this paper we present new convergent structural and geochemical data from the Lherz massif, the type-locality of lherzolite, indicating that the lherzolites from Lherz do not represent pristine mantle. Detailed structural mapping clearly shows that the lherzolites are secondary rocks formed at the expense of the harzburgites. Variations of major, minor and trace elements through the harzburgite-lherzolite contacts indicate that the lherzolites were formed through a refertilization process involving interaction of refractory, lithospheric mantle with upwelling asthenospheric partial melts. Combined with previously published indications of refertilization in orogenic peridotites, our new observations in Lherz suggest that most lherzolite massifs represent secondary (refertilized) rather than pristine mantle. Together with geochemical data on mantle xenoliths, this indicates that melt transport and melt-rock reaction play a key role on the rejuvenation and erosion of the lithospheric mantle.

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“…It may also develop complex compositional stratification due to several accretion events, as in the Archean Slave province, Canada [Aulbach et al, 2004]. Another complication is that continental lithosphere may be refertilized by metasomatic fluids [Griffin et al, 2003]. For these reasons, it is valuable to develop compact scaling laws allowing rapid comparisons of different cases.…”

Section: Model System and Methodsmentioning

confidence: 99%

Penetration of mantle plumes through depleted lithosphere

et al. 2005

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[1] Laboratory experiments and numerical calculations are used to study how a laminar thermal plume deforms and penetrates a buoyant and viscous layer, which serves as an analog for continental lithosphere. The viscosity contrast between the two liquids and the buoyancy ratio B (the ratio between the intrinsic chemical density contrast and the thermal density contrast due to temperature differences) are varied by 3 orders of magnitude and 1 order of magnitude, respectively. The manner of plume-lithosphere interaction is not sensitive to the viscosity contrast, which sets the timescale for displacement of the interface, and depends mostly on the B value, which sets the magnitude and shape of interface deformation. Heating of the upper layer by plume material plays an important role. For B > 0.6, plume material spreads beneath the interface and applies a buoyancy force which deforms the interface. For B < 0.6, true plume penetration into the upper layer occurs with a significant vertical velocity component. With time, the upper layer may become unstable and develop an active upwelling which entrains material from the lower layer. Approximate scaling laws allow prediction of interface displacement as a function of time for the whole parameter range studied. Applied to the continental lithosphere, these results show that true plume penetration through Archean lithosphere requires thermal anomalies larger than 300 K corresponding to buoyancy fluxes in excess of those determined today for the Hawaiian plume. Mantle plumes have different effects on lithospheres of different ages and composition, which precludes diagnosis of a single ''typical'' plume signature.Citation: Jurine, D., C. Jaupart, G. Brandeis, and P. J. Tackley (2005), Penetration of mantle plumes through depleted lithosphere,

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The evolution of lithospheric mantle beneath the Kalahari Craton and its margins

Cited by 254 publications

References 59 publications

The P and S wave velocity structure of the mantle beneath eastern Africa and the African superplume anomaly

The P and S wave velocity structure of the mantle beneath eastern Africa and the African superplume anomaly

The Lherz spinel lherzolite: Refertilized rather than pristine mantle

Penetration of mantle plumes through depleted lithosphere

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