Global receiver function observations of the X-discontinuity reveal recycled basalt beneath hotspots

Pugh, Stephen; Jenkins, Jennifer; Boyce, A.; Cottaar, Sanne

doi:10.1016/j.epsl.2021.116813

Cited by 26 publications

(72 citation statements)

References 56 publications

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“…Multiple X‐discontinuities have also been observed by Pugh et al. (2021) beneath Marquesas, Samoa, and St. Helena hotspots. They attributed this observation to multiple mechanisms for the genesis of X‐phase.…”

Section: Discussionsupporting

confidence: 54%

“…Similar observations of double X-discontinuities are also reported by Schmerr (2015) in Big Island of Hawaii, East Pacific Rise, Cascadia, Aleutian, and Tonga subduction zones. Multiple X-discontinuities have also been observed by Pugh et al (2021) beneath Marquesas, Samoa, and St. Helena hotspots. They attributed this observation to multiple mechanisms for the genesis of X-phase.…”

Section: Remnant Tethyan Slab Causing a Deeper X-discontinuitymentioning

confidence: 94%

“…Below the northern Pacific region of the Kuril trench, the observed X-discontinuity is 292 km deep (Revenaugh & Sipkin, 1994), and beneath the subduction zone of Ryukyu this discontinuity is at 295 km (Cui et al, 2018). A recent global study by Pugh et al (2021) identified the X-discontinuity between 244 and 344 km beneath hotspots. Interestingly, most of the above studies are concentrated in the oceanic regions and a comprehensive study of the X-discontinuity has not been performed in any continental scenario.…”

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confidence: 94%

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confidence: 99%

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X‐Discontinuity Beneath the Indian Shield—Evidence for Remnant Tethyan Oceanic Lithosphere in the Mantle

et al. 2021

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Mantle layering greatly influences the dynamics of the Earth's interior, which is responsible for its evolution. Over the last few decades, the search for upper mantle discontinuities using various seismological techniques has gained a lot of momentum. There is a general agreement that in addition to the ubiquitous 410-and 660-km discontinuities (Shearer & Masters, 1992), there exists a weak seismic discontinuity called the X-discontinuity (Revenaugh & Jordan, 1991), in the depth range of 250-350 km, sometimes referred to as the 300 km discontinuity. The X-discontinuity shows a weak, sharp, positive (velocity increasing downward) impedance contrast and is only intermittently observed, unlike the global transition zone discontinuities. Because of its sporadic nature, the origin of X-discontinuity is controversial. However, all the proposed mechanisms are related to the chemical and thermal properties of the mantle, hence the presence of X-discontinuity has implications on mantle dynamics and geochemical signature of the mantle.Seismologically, it has been mostly detected in active subduction and hotspot regions. Figure 1 and Table S1 (Supporting Information) summarize the global disposition of X-discontinuities identified by numerous researchers along with their probing tools and plausible interpretations. Figure 1 shows that the depth of the X-phase below North America is between 290 and 320 km (

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Section: Discussionsupporting

confidence: 54%

Section: Remnant Tethyan Slab Causing a Deeper X-discontinuitymentioning

confidence: 94%

mentioning

confidence: 94%

mentioning

confidence: 99%

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X‐Discontinuity Beneath the Indian Shield—Evidence for Remnant Tethyan Oceanic Lithosphere in the Mantle

et al. 2021

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“…We need to evaluate whether our null compositional hypothesis is valid by allowing for the presence of a substantial fraction of recycled crust in the plume source ( 32 ). We expect the addition of recycled crust (eclogite) to increase the inferred T ex because eclogite is seismically faster than DMM ( 33 ).…”

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confidence: 99%

On the relative temperatures of Earth’s volcanic hotspots and mid-ocean ridges

Bao

Lithgow‐Bertelloni

Jackson

et al. 2022

Science

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Hotspot cool down Deep-seated mantle plumes are responsible for volcanic island chains such as Hawai’i. Upwelling from the deep interior requires that the plumes are hotter than the surrounding mantle to make it all the way up to the surface. However, Bao et al . found that some of these “hotspots” are surprisingly cool. The temperature is actually low enough to challenge a deep mantle origin for some hotspots. In these specific cases, deep plumes may be entrained and cooled or possibly originate in the upper mantle instead. —BG

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Mantle Phase Changes Detected from Stochastic Tomography

Cormier¹,

Lithgow-Bertollini

Stixrude

et al. 2022

Preprint

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Stochastic tomography, made possible by dense deployments of seismic sensors, is used to identify previously undetected and poorly detected changes in the composition and mineral structure of Earth's mantle. This technique inverts the spatial coherence of amplitudes and travel times of body waves to determine the depth and lateral dependence of the spatial spectrum of seismic velocity. The inverted spectrum is interpreted using predictions from the thermodynamic stability of different compositions and mineral phases as a function of temperature and pressure, in which the metamorphic temperature derivative of seismic velocities can be used as a proxy for the effects of heterogeneity induced in a region undergoing a phase change. Peaks in the metamorphic derivative of seismic velocity are found to closely match those found from applying stochastic tomography to elements of Earthscope and FLEX arrays. Within ± 12 km, peaks in the fluctuation of P velocity at 425, 500, and 600 km depth beneath the western US agree those predicted by a mechanical mixture of harzburgite and basalt in a cooler mantle transition zone. A smaller peak at 250 km depth may be associated with chemical heterogeneity induced by dehydration of subducted oceanic sediments, and a peak at 775 km depth with a phase change in subducted basalt. Non-detection of a predicted endothermic phase change near 660 km is consistent with its width being much less than 10 km. These interpretations of the heterogeneity spectrum are consistent with the known history of plate subduction beneath North America.

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Global receiver function observations of the X-discontinuity reveal recycled basalt beneath hotspots

Cited by 26 publications

References 56 publications

X‐Discontinuity Beneath the Indian Shield—Evidence for Remnant Tethyan Oceanic Lithosphere in the Mantle

X‐Discontinuity Beneath the Indian Shield—Evidence for Remnant Tethyan Oceanic Lithosphere in the Mantle

On the relative temperatures of Earth’s volcanic hotspots and mid-ocean ridges

Mantle Phase Changes Detected from Stochastic Tomography

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