SP12RTS: a degree-12 model of shear- and compressional-wave velocity for Earth's mantle

Koelemeijer, Paula; Ritsema, Jeroen; Deuss, Arwen; Heijst, H. J. van

doi:10.1093/gji/ggv481

Cited by 170 publications

(196 citation statements)

References 73 publications

(151 reference statements)

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“…For a thermochemical layer to be swept away from downwelling slab regions to form piles, they must generally be less negatively buoyant than the slab material that displaces them. This is supported by geodynamical studies that examine the radial stresses imposed on the CMB interface from thermochemical convection 60 , as well as supported by the recent normal mode work 4 . The geodynamic studies predict that the CMB is most depressed beneath subduction regions and relatively flat and less depressed (or even slightly uplifted) beneath pile regions.…”

Section: Relationship To Deep Mantle Convectionmentioning

confidence: 59%

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Continent-sized anomalous zones with low seismic velocity at the base of Earth's mantle

2016

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Section: Relationship To Deep Mantle Convectionmentioning

confidence: 59%

“…two structure, in addition to a lesser but significant degree three contribution 1,3,4 . The strongest lateral gradients in V S perturbations occur at LLSVP boundaries (Fig.…”

mentioning

confidence: 99%

Continent-sized anomalous zones with low seismic velocity at the base of Earth's mantle

2016

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“…We have carried out the same analysis on HSML-S , GyPSuM (Simmons et al 2010), TX2011 (Grand 2002) and SP12RTS (Koelemeijer et al 2016), and obtained fairly similar results. However, in order to keep the vote map more easily understandable, we present the results on the five most recent models which are parametrized at least up to degree 18.…”

Section: Cluster Analysismentioning

confidence: 66%

Morphology of seismically slow lower-mantle structures

Cottaar¹,

Lekić²

2016

Geophysical Journal International

141

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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“…A possible Si-enrichment of these lithological assemblages (see above) may further reconcile the anti-correlation of bulk-sound and shear-wave speed that has been localized within LLSVPs by joint body-wave seismic tomography (Koelemeijer et al, 2016;Moulik and Ekström, 2016;Tesoniero et al, 2015). Deschamps et al (2012) …”

Section: Hybridization During Incremental Overturnsmentioning

confidence: 77%

Reconciling magma‐ocean crystallization models with the present‐day structure of the Earth's mantle

Ballmer

Lourenço

Hirose

et al. 2017

Geochem Geophys Geosyst

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Terrestrial planets are thought to experience episode(s) of large‐scale melting early in their history. Fractionation during magma‐ocean freezing leads to unstable stratification within the related cumulate layers due to progressive iron enrichment upward, but the effects of incremental cumulate overturns during MO crystallization remain to be explored. Here, we use geodynamic models with a moving‐boundary approach to study convection and mixing within the growing cumulate layer, and thereafter within the fully crystallized mantle. For fractional crystallization, cumulates are efficiently stirred due to subsequent incremental overturns, except for strongly iron‐enriched late‐stage cumulates, which persist as a stably stratified layer at the base of the mantle for billions of years. Less extreme crystallization scenarios can lead to somewhat more subtle stratification. In any case, the long‐term preservation of at least a thin layer of extremely enriched cumulates with Fe# > 0.4, as predicted by all our models, is inconsistent with seismic constraints. Based on scaling relationships, however, we infer that final‐stage Fe‐rich magma‐ocean cumulates originally formed near the surface should have overturned as small diapirs, and hence undergone melting and reaction with the host rock during sinking. The resulting moderately iron‐enriched metasomatized/hybrid rock assemblages should have accumulated at the base of the mantle, potentially fed an intermittent basal magma ocean, and be preserved through the present‐day. Such moderately iron‐enriched rock assemblages can reconcile the physical properties of the large low shear‐wave velocity provinces in the present‐day lower mantle. Thus, we reveal Hadean melting and rock‐reaction processes by integrating magma‐ocean crystallization models with the seismic‐tomography snapshot.

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SP12RTS: a degree-12 model of shear- and compressional-wave velocity for Earth's mantle

Cited by 170 publications

References 73 publications

Continent-sized anomalous zones with low seismic velocity at the base of Earth's mantle

Continent-sized anomalous zones with low seismic velocity at the base of Earth's mantle

Morphology of seismically slow lower-mantle structures

Reconciling magma‐ocean crystallization models with the present‐day structure of the Earth's mantle

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