Double layering of a thermochemical plume in the upper mantle beneath Hawaii

Ballmer, Maxim D.; Ito, Garrett; Wolfe, Cecily J.; Solomon, Sean C.

doi:10.1016/j.epsl.2013.06.022

Cited by 85 publications

(108 citation statements)

References 65 publications

(104 reference statements)

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“…The model does not incorporate the effects of small-scale partial melts, volatiles, and/or mantle fabrics, though efforts are underway to add such parameters (e.g., Hier-Majumder and Abbott 2010). For example, dynamical simulations of entrainment of a fertile, presumably subducted basalt component from the deepest mantle, show that compositional zonation can be produced in an upwelling plume, similar to what is observed near Hawaii (Ballmer et al 2013). Likewise, dynamical simulations of small fractions of melt concentrated by flow in the mantle are still needed to understand the seismic signature of melt and volatile transport in the mantle wedge beneath the subduction zones and mid-ocean ridges (Hirschmann 2010;Dasgupta et al 2013).…”

Section: Patterns Of Heterogeneitymentioning

confidence: 79%

“…(2) We assume a reference bulk composition of 20 % basalt and 80 % harzburgite, similar to the basalt/harzburgite fraction calculated for the bulk chemistry of mantle peridotite (18 % basalt, 82 % harzburgite) (Ringwood 1975;Hirschmann and Stolper 1996;Xu et al 2008), and allow basalt fraction to vary from 5 to 35 %. This spread of values is broadly consistent with bulk mantle compositions ranging from depleted mantle harzburgite to that of mantle eclogites (Ritsema et al 2009;Ballmer et al 2013;Khan et al 2015). The final solution(s) for each data stack are obtained by finding the weighted average temperature and basalt fraction(s) for the models that satisfy both of these a priori limits; two example solutions are shown in Fig.…”

Section: Modeling Of Heterogeneitymentioning

confidence: 85%

“…Likewise, deeper heterogeneities from the lower mantle can be entrained into the upper mantle (Farnetani and Samuel 2005). Geodynamical modeling of a hot, compositionally heterogeneous mantle plume containing an enriched, denser component finds that this material would tend to pool at 300-410 km depth, before rising to feed a shallower plume conduit (Ballmer et al 2013). Such models could be influenced by the mechanisms underlying the X, with the implication that detections of the X may be sensitive to upper mantle heterogeneity and the nature of mantle convection processes.…”

Section: Relationship Of Discontinuities To Mantle Heterogeneitymentioning

confidence: 97%

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Imaging Mantle Heterogeneity with Upper Mantle Seismic Discontinuities

Schmerr

2015

The Earth's Heterogeneous Mantle

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We use underside reflections of S wave seismic energy arriving as precursors to the seismic phase SS to image the depth and impedance contrast present across mantle discontinuities in the depth range of 230-380 km beneath the Pacific basin. A number of past studies have identified seismic discontinuities at these depths, known as the X-discontinuities, ascribing the interfaces to a variety of mineral physical mechanisms, including the coesite to stishovite phase transition, the formation of hydrous Phase A, and/or the reorganization of orthopyroxene into a C2/c monoclinic structure. Thus, the presence of the X-discontinuity (abbreviated here as the X) may be indicative of the nature of mantle heterogeneity. This study finds discontinuities associated with the X Pacific-wide, with SS precursory reflections present beneath the subduction, hot spots, and ridges. Where detected, the X is at an average depth of 293 ± 65 km and the precursor amplitudes indicate a mean shear impedance contrast of 2.3 ± 1.6 %. We model mantle heterogeneity by comparing the depth and the impedance contrasts at the X with predictions for seismic structure from a mineral physics model in which the mantle is considered to be a mechanically mixed bulk assemblage of subducted basalt and harzburgite. In this model, the average mantle composition of the Pacific is fit by a mixture of ~20 % basalt and 80 % harzburgite, roughly consistent with the bulk chemistry of mantle peridotite (18 % basalt, 82 % harzburgite). In some regions beneath the hot spots and subduction, there is evidence for a bulk chemistry enriched in basalt (basalt fraction ~30-35 %), lending evidence to the hypothesis that the mantle is laterally heterogeneous and that dynamics are stirring an enriched component, perhaps from the deep or shallow Earth, into the upper mantle.

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Section: Patterns Of Heterogeneitymentioning

confidence: 79%

Section: Modeling Of Heterogeneitymentioning

confidence: 85%

Section: Relationship Of Discontinuities To Mantle Heterogeneitymentioning

confidence: 97%

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Imaging Mantle Heterogeneity with Upper Mantle Seismic Discontinuities

Schmerr

2015

The Earth's Heterogeneous Mantle

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“…Their results suggest that vigorous plumes are able to sample, and to bring side by side, very distant portions of their source region. Using numerical models, Ballmer et al (2013) predicted that a hot, compositional heterogeneous mantle plume containing a denser eclogite component tends to pool at ~ 300-410 km depth before rising to feed a shallower sublithospheric layer. They found that this double-layered structure of a thermochemical plume is more consistent with the tomographic images at Hawaii (Wolfe et al 2009(Wolfe et al , 2011 than the classic plume model.…”

Section: Pacific Hotspotsmentioning

confidence: 99%

Hotspots and Mantle Plumes

Zhao

2015

Multiscale Seismic Tomography

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Seismic images under 62 possible hotspots are reviewed for understanding the origin of hotspots and mantle plumes. Plume-like, continuous low-velocity anomalies are visible beneath Hawaii, Tahiti, Louisville, Iceland, Cape Verde, Reunion, Kerguelen, Amsterdam, Afar, Eifel, Hainan, Yellowstone and Cobb hotspots, suggesting that they may be 13 whole-mantle plumes originating from the core-mantle boundary. These plumes exhibit tilted images, suggesting that plumes are not fixed in the mantle but can be deflected by the mantle flow. Upper-mantle plumes seem to exist beneath Cameroon, Easter, Azores, Vema, East Australia and Erebus hotspots. A mid-mantle plume may exist under the San Felix hotspot. Active intraplate volcanoes in Northeast Asia and Southwest China are caused by hot and wet upwelling flows in the big mantle wedge above the stagnant slab in the mantle transition zone. Although low-velocity zones appear at some depth under other hotspots, their plume features are not clear. The complex images under hotspots reflect strong lateral variations in temperature, viscosity and possibly composition of the mantle, which control the generation and ascent of mantle plumes and the flow pattern of mantle convection.

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“…As the plate accelerated to the northwest, asthenosphere counterflow could have increased in the opposite direction, deflecting the Hawaiian plume to the southeast during its final ascent through the transition zone 28 , reflected in the change in the trend of the Emperor Chain at Kimmei Seamount.…”

mentioning

confidence: 99%

Deformation-related volcanism in the Pacific Ocean linked to the Hawaiian–Emperor bend

et al. 2015

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Ocean islands, seamounts and volcanic ridges are thought to form above mantle plumes. Yet, this mechanism cannot explain many volcanic features on the Pacific Ocean floor 1 and some might instead be caused by cracks in the oceanic crust linked to the reorganization of plate motions 1-3 . A distinctive bend in the Hawaiian-Emperor volcanic chain has been linked to changes in the direction of motion of the Pacific Plate 4,5 , movement of the Hawaiian plume 6-8 , or a combination of both 9 . However, these links are uncertain because there is no independent record that precisely dates tectonic events that a ected the Pacific Plate. Here we analyse the geochemical characteristics of lava samples collected from the Musicians Ridges, lines of volcanic seamounts formed close to the Hawaiian-Emperor bend. We find that the geochemical signature of these lavas is unlike typical ocean island basalts and instead resembles mid-ocean ridge basalts. We infer that the seamounts are unrelated to mantle plume activity and instead formed in an extensional setting, due to deformation of the Pacific Plate. 40

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Double layering of a thermochemical plume in the upper mantle beneath Hawaii

Cited by 85 publications

References 65 publications

Imaging Mantle Heterogeneity with Upper Mantle Seismic Discontinuities

Imaging Mantle Heterogeneity with Upper Mantle Seismic Discontinuities

Hotspots and Mantle Plumes

Deformation-related volcanism in the Pacific Ocean linked to the Hawaiian–Emperor bend

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