Dynamics of Superplumes in the Lower Mantle

Yuen, David A.; Monnereau, M.; Hansen, Ulrich; Kameyama, Masanori; Matyska, Ctirad

doi:10.1007/978-1-4020-5750-2_9

Cited by 13 publications

(9 citation statements)

References 92 publications

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“…If lower mantle material flows across the transition zone, then this material would continue to rise through the upper mantle and provide the excess heat needed to drive the rifting and plateau uplift (Figure 11a). Alternatively, if the superplume simply heats the base of the transition zone, then several smaller plumes above the 660 km discontinuity could form, rise through the upper mantle, and lead to extension and surface uplift [e.g., Yuen et al, 2007;Maruyama et al, 2007].…”

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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“…And is there mantle flow across the 660 km discontinuity? If the 660 km discontinuity creates a barrier to the rising superplume material in the lower mantle [Davies, 1995], then warm superplume material ponding beneath the 660 km discontinuity could heat the bottom of the transition zone, generating secondary thermal plumes that rise from within the transition zone toward the surface [e.g., Yuen et al, 2007;Farnetani and Hofmann, 2009]. Helium isotopic evidence suggests that there could be some flux of lower mantle material across the 660 km discontinuity [Pik et al, 2006;Hilton et al, 2011], as do some radiogenic isotopic data [Rooney et al, 2012].…”

Section: Discussionmentioning

confidence: 99%

Mantle transition zone thinning beneath eastern Africa: Evidence for a whole‐mantle superplume structure

Mulibo

Nyblade

2013

Geophysical Research Letters

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P to S conversions from the 410 and 660 km discontinuities observed in receiver function stacks reveal a mantle transition zone that is ~30–40 km thinner than the global average in a region ~200–400 km wide extending in a SW‐NE direction from central Zambia, across Tanzania and into Kenya. The thinning of the transition zone indicates a ~190–300 K thermal anomaly in the same location where seismic tomography models suggest that the lower mantle African superplume structure connects to thermally perturbed upper mantle beneath eastern Africa. This finding provides compelling evidence for the existence of a continuous thermal structure extending from the core‐mantle boundary to the surface associated with the African superplume.

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“…The small‐scale hotspot plumes originating from the 660‐km phase transition zone are observed in the results of mantle convection models with the ‘second asthenosphere’ below the 660‐km depth (Cserepes & Yuen 2000; Cserepes et al 2000), self‐consistently moving plates (Yoshida 2004), or other complex mantle properties (e.g. Matyska & Yuen 2005; Yuen et al 2007), and detected by well‐resolved seismic tomography models (e.g. Montelli et al 2004).…”

Section: Discussionmentioning

confidence: 99%

Temporal evolution of the stress state in a supercontinent during mantle reorganization

Yoshida¹

2010

Geophysical Journal International

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S U M M A R YPrevious numerical simulation models of isoviscous mantle convection in both 2-D and 3-D geometries have revealed that the presence of a supercontinental lid produces large-scale horizontal mantle flow, thereby reorganizing the thermal structure of the mantle interior. Large-scale upwelling plumes arising from the core-mantle boundary (CMB) beneath the supercontinent are observed in some models. These upwelling plumes have been hypothesized to produce tensional stresses in the supercontinent and to be responsible for the subsequent continental lifting and breakup. In this study, numerical simulations using a 3-D spherical shell model are conducted in order to elucidate temporal changes in stress state in an idealized supercontinent during mantle reorganization. The model supercontinent is assumed to be an undeformable, highly viscous supercontinental lid (HVSL) with respect to the mantle. The mantle is heated from the base and from within. The HVSL is imposed abruptly on well-developed convection systems and remains fixed during the simulations. I first consider the scenario in which the HVSL is imposed on isoviscous or weakly temperature-dependent viscosity convection exhibiting short-wavelength thermal structures. The simulation results reveal that a tensional stress regime rapidly predominates throughout the HVSL (within 50-100 Myr in model time) in response to the horizontal mantle flow beneath the HVSL. The subsequent large-scale plumes upwelling from the CMB also induce tensional stresses in the supercontinent, but the effects of these stresses on the overall stress state appear to be secondary. For most of the models investigated herein, the maximum deviatoric tensional stress generated in the HVSL once convection is re-established is 30-90 MPa, which is probably comparable to the minimum stress magnitude required to break up the supercontinent. To investigate the effects of the HVSL on other convection regimes, I next consider the scenario in which an HVSL having a viscosity contrast of 10 is imposed on much longer-wavelength (i.e. degree-one-or degree-two-dominant) convection systems with moderately temperaturedependent viscosity. The patterns of such low-degree-dominant convection are affected little by the imposition of the HVSL, and notable mantle reorganization does not occur. On the other hand, when a reasonable yielding stress is imposed at the continental margins, newly formed, weak upwelling plumes develop due to enhanced downwelling at the margins, rather than large-scale mantle reorganization. However, the newly upwelling plumes do not seem to produce a visible tensional stress regime in the HVSL interior, and the spatial distributions of the stress regime and stress magnitude in the HVSL depend on the spatial relationship between the HVSL and the convection pattern. Since the Series L models of the present study do not include the yield stress in the oceanic part of the lithosphere, plate-like behaviour and subducting plates are not actualized. The results for Series S models, in ...

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Dynamics of Superplumes in the Lower Mantle

Cited by 13 publications

References 92 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

Mantle transition zone thinning beneath eastern Africa: Evidence for a whole‐mantle superplume structure

Temporal evolution of the stress state in a supercontinent during mantle reorganization

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