Compositional Heterogeneity in the Bottom 1000 Kilometers of Earth's Mantle: Toward a Hybrid Convection Model

Hilst, R. D. van der; Kárason, H.

doi:10.1126/science.283.5409.1885

Cited by 365 publications

(174 citation statements)

References 81 publications

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“…A surprising conclusion of our synthesis is the degree to which continental material is recycled deep into the upper mantle and perhaps deeper via subduction zones and to a lesser extent in delaminating lower crustal material. Significant deep recycling is consistent with geophysical models for whole mantle convection (Kellogg et al, 1999;van der Hilst and Karason, 1999), as well as with geochemical evidence that subducted crust is important in the formation of mantle plume sources (White and Hoffman, 1982;Phipps Morgan and Morgan, 1999;Workman et al, 2008).…”

Section: Discussionsupporting

confidence: 82%

Crustal redistribution, crust–mantle recycling and Phanerozoic evolution of the continental crust

Clift

Vannucchi

Morgan

2009

Earth-Science Reviews

199

151

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Section: Discussionsupporting

confidence: 82%

Crustal redistribution, crust–mantle recycling and Phanerozoic evolution of the continental crust

Clift

Vannucchi

Morgan

2009

Earth-Science Reviews

199

151

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“…This suppression of lateral variations in V P at ∼1,700 km correlates with a similar and well-known global feature (36) believed to correspond to a compositional transition (37) to a denser (∼4%) layer in the deep lower mantle (38). For comparison, the spin crossover in Fp increases the density of a chemically homogeneous pyrolitic mantle by ∼0.7%.…”

Section: Significancesupporting

confidence: 77%

Spin crossover in ferropericlase and velocity heterogeneities in the lower mantle

Wentzcovitch

2014

Proc. Natl. Acad. Sci. U.S.A.

109

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Deciphering the origin of seismic velocity heterogeneities in the mantle is crucial to understanding internal structures and processes at work in the Earth. The spin crossover in iron in ferropericlase (Fp), the second most abundant phase in the lower mantle, introduces unfamiliar effects on seismic velocities. Firstprinciples calculations indicate that anticorrelation between shear velocity (V S ) and bulk sound velocity (V φ ) in the mantle, usually interpreted as compositional heterogeneity, can also be produced in homogeneous aggregates containing Fp. The spin crossover also suppresses thermally induced heterogeneity in longitudinal velocity (V P ) at certain depths but not in V S . This effect is observed in tomography models at conditions where the spin crossover in Fp is expected in the lower mantle. In addition, the one-of-a-kind signature of this spin crossover in the R S/P (∂ ln V S =∂ ln V P ) heterogeneity ratio might be a useful fingerprint to detect the presence of Fp in the lower mantle.seismic tomography | lateral heterogeneity | elastic modulus | density functional theory | mantle plume F erropericlase (Fp) is believed to be the second most abundant phase in the lower mantle (1, 2). Since the discovery of the high-spin (HS) to low-spin (LS) crossover in iron in Fp (3), this phenomenon has been investigated extensively experimentally and theoretically (4-14). Most of its properties are affected by the spin crossover. In particular, thermodynamics (14) and thermal elastic properties (15)(16)(17)(18)(19)(20) are modified in unusual ways that can change profoundly our understanding of the Earth's mantle. However, this is a broad and smooth crossover that takes place throughout most of the lower mantle and might not produce obvious signatures in radial velocity or density profiles (20, 21) (see Figs. S1 and S2). Therefore, its effects on aggregates are more elusive and indirect. For instance, the associated density anomaly can invigorate convection, as demonstrated by geodynamics simulations in a homogeneous mantle (22)(23)(24). The bulk modulus anomaly may decrease creep activation parameters and lower mantle viscosity (10, 24, 25) promoting mantle homogenization in the spin crossover region (24), and anomalies in elastic coefficients can enhance anisotropy in the lower mantle (16). Less understood are its effects on seismic velocities produced by lateral temperature variations.The present analysis is based on our understanding of thermal elastic anomalies caused by the spin crossover. It has been challenging for both experiments (15-19) and theory (20) to reach a consensus on this topic. Measurements often seemed to include extrinsic effects, making it difficult to confirm the spin crossover signature by different techniques and across laboratories. A theoretical framework had to be developed to address these effects. However, an agreeable interpretation of data and results has emerged recently (20). With increasing pressure, nontrivial behavior is observed in all elastic coefficients, aggregate mo...

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“…This hypothesis has been challenged, based on widespread geochemical evidence for recycling (e.g. Hofmann et al, 1997), coupled with evidence for penetration of subducted slabs into the lower mantle (van der Hilst and Karson, 1999). Alternative models for unradiogenic noble gases require that helium be more compatible than Th and U during silicate melting, which could leave behind an ancient residue of depleted mantle (rather than undegassed).…”

Section: Heliummentioning

confidence: 99%

Geology, geochemistry and earthquake history of Lṑihi Seamount, Hawaìi's youngest volcano

et al. 2006

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A half century of investigations are summarized here on the youngest Hawaiian volcano, Lō`ihi Seamount. It was discovered in 1952 following an earthquake swarm. Surveying in 1954 determined it has an elongate shape, which is the meaning of its Hawaiian name. Lō`ihi was mostly forgotten until two earthquake swarms in the 1970's led to a dredging expedition in 1978, which recovered young lavas. This led to numerous expeditions to investigate the geology, geophysics, and geochemistry of this active volcano. Geophysical monitoring, including a realtime submarine observatory that continuously monitored Lō`ihi's seismic activity for three months, captured some of the volcano's earthquake swarms. The 1996 swarm, the largest recorded in Hawai`i, was preceded by at least one eruption and accompanied by the formation of a ~300-m deep pit crater, renewing interest in this submarine volcano. Seismic and petrologic data indicate that magma was stored in a ~8-9 km deep reservoir prior to the 1996 eruption.Studies on Lō`ihi have altered conceptual models for the growth of Hawaiian and other oceanic island volcanoes and led to a refined understanding of mantle plumes. Petrologic and geochemical studies of Lō`ihi lavas showed that the volcano taps a relatively primitive part of the Hawaiian plume, producing a wide range of magma compositions. These compositions have become progressively more silica-saturated with time reflecting higher degrees of partial melting as the volcano drifts towards the center of the hotspot. Seismic and bathymetric data have highlighted the importance of landsliding in the early formation of an ocean island volcano.Lō`ihi's internal structure and eruptive behavior, however, cannot be fully understood without installing monitoring equipment directly on the volcano.

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Compositional Heterogeneity in the Bottom 1000 Kilometers of Earth's Mantle: Toward a Hybrid Convection Model

Cited by 365 publications

References 81 publications

Crustal redistribution, crust–mantle recycling and Phanerozoic evolution of the continental crust

Crustal redistribution, crust–mantle recycling and Phanerozoic evolution of the continental crust

Spin crossover in ferropericlase and velocity heterogeneities in the lower mantle

Geology, geochemistry and earthquake history of Lṑihi Seamount, Hawaìi's youngest volcano

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