Thermochemical structure and dynamics of the African superplume

Simmons, N. A.; Forte, A. M.; Grand, S. P.

doi:10.1029/2006gl028009

Cited by 190 publications

(226 citation statements)

References 33 publications

(50 reference statements)

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“…These values are quite close to the value inferred from mineral physics (R /vs =0.2, Karato, (2008)). The R /vs is slightly bigger than the former estimation found through similar geodynamic models (R /vs =0.1 to 0.15 for Forte and Mitrovica (2001), R /vs = -0.01 to 0.07 according to Simmons (2007)), certainly because these previous studies never focused on such shallow depths. The results presented hereafter use a density to velocity heterogeneity ratio R /vs of 0.17.…”

Section: Ratio Of Density Anomaly To Seismic Velocity Anomaly R /Vscontrasting

confidence: 40%

Hotspot Concept: The French Polynesia Complexity

Adam¹

2012

Updates in Volcanology - A Comprehensive Approach to Volcanological Problems

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Section: Ratio Of Density Anomaly To Seismic Velocity Anomaly R /Vscontrasting

confidence: 40%

Hotspot Concept: The French Polynesia Complexity

Adam¹

2012

Updates in Volcanology - A Comprehensive Approach to Volcanological Problems

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“…Seismic tomographic studies on the global-to-regional scale, however, have revealed a broad (~500 km-wide)~3% slow shear wave-speed anomaly that originates at the core-mantle boundary beneath southern Africa and extends toward the base of the lithosphere somewhere beneath Ethiopia (e.g., Grand, 2002;Li et al, 2008;Ritsema and Allen, 2003;Ritsema et al, 2010;Simmons et al, 2007): the African superplume (Figs. 4 and 5).…”

Section: Evidence From Broadband Seismologymentioning

confidence: 99%

The development of extension and magmatism in the Red Sea rift of Afar

et al. 2013

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Despite the importance of continental breakup in plate tectonics, precisely how extensional processes such as brittle faulting, ductile plate stretching, and magma intrusion evolve in space and time during the development of new ocean basins remains poorly understood. The rifting of Arabia from Africa in the Afar depression is an ideal natural laboratory to address this problem since the region exposes subaerially the tectonically active transition from continental rifting to incipient seafloor spreading. We review recent constraints on along-axis variations in rift morphology, crustal and mantle structure, the distribution and style of ongoing faulting, subsurface magmatism and surface volcanism in the Red Sea rift of Afar to understand processes ultimately responsible for the formation of magmatic rifted continental margins. Our synthesis shows that there is a fundamental change in rift morphology from central Afar northward into the Danakil depression, spatially coincident with marked thinning of the crust, an increase in the volume of young basalt flows, and subsidence of the land towards and below sea-level. The variations can be attributed to a northward increase in proportion of extension by ductile plate stretching at the expense of magma intrusion. This is likely in response to a longer history of localised heating and weakening in a narrower rift. Thus, although magma intrusion accommodates strain for a protracted period during rift development, the final stages of breakup are dominated by a phase of plate stretching with a shift from intrusive to extrusive magmatism. This late-stage pulse of decompression melting due to plate thinning may be responsible for the formation of seaward dipping reflector sequences of basalts and sediments, which are ubiquitous at magmatic rifted margins worldwide.

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“…Bull et al 2009) to steep metastable plumes (e.g. Davaille 1999;Simmons et al 2007;Tan et al 2011;Bower et al 2013). Many physical parameters can be varied in such studies, but the most important parameters for the behaviour of a thermochemical pile are its buoyancy and viscosity contrast with the surrounding material (Deschamps & Tackley 2008).…”

Section: Geodynamic Implicationsmentioning

confidence: 99%

Morphology of seismically slow lower-mantle structures

Cottaar¹,

Lekić²

2016

Geophysical Journal International

135

147

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S U M M A R YLarge low shear velocity provinces (LLSVPs), whose origin and dynamic implication remain enigmatic, dominate the lowermost mantle. For decades, seismologists have created increasingly detailed pictures of the LLSVPs through tomographic models constructed with different modeling methodologies, data sets, parametrizations and regularizations. Here, we extend the cluster analysis methodology of Lekic et al., to classify seismic mantle structure in five recent global shear wave speed (V S ) tomographic models into three groups. By restricting the analysis to moving depth windows of the radial profiles of V S , we assess the vertical extent of features. We also show that three clusters are better than two (or four) when representing the entire lower mantle, as the boundaries of the three clusters more closely follow regions of high lateral V S gradients. Qualitatively, we relate the anomalously slow cluster to the LLSVPs, the anomalously fast cluster to slab material entering the lower mantle and the neutral cluster to 'background' lower mantle material. We obtain compatible results by repeating the analysis on recent global P-wave speed (V P ) models, although we find less agreement across V P models. We systematically show that the clustering results, even in detail, agree remarkably well with a wide range of local waveform studies. This suggests that the two LLSVPs consist of multiple internal anomalies with a wide variety of morphologies, including shallowly to steeply sloping, and even overhanging, boundaries. Additionally, there are indications of previously unrecognized meso-scale features, which, like the Perm anomaly, are separated from the two main LLSVPs beneath the Pacific and Africa. The observed wide variety of structure size and morphology offers a challenge to recreate in geodynamic models; potentially, the variety can result from various degrees of mixing of several compositionally distinct components. Finally, we obtain new, much larger estimates of the volume/mass occupied by LLSVPs-8.0 per cent ±0.9 (μ ± 1σ ) of whole mantle volume and 9.1 per cent ±1.0 (μ ± 1σ ) of whole mantle mass-and discuss implications for associating the LLSVPs with the hidden reservoir enriched in heat producing elements.

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Thermochemical structure and dynamics of the African superplume

Cited by 190 publications

References 33 publications

Hotspot Concept: The French Polynesia Complexity

Hotspot Concept: The French Polynesia Complexity

The development of extension and magmatism in the Red Sea rift of Afar

Morphology of seismically slow lower-mantle structures

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