Melting in the deep upper mantle oceanward of the Honshu slab

Bagley, Brian; Courtier, A. M.; Revenaugh, J.

doi:10.1016/j.pepi.2009.03.007

Cited by 35 publications

(35 citation statements)

References 60 publications

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“…Although an accurate characterization of the melt layer is beyond the scope of this work, our results nonetheless suggest that the water filter hypothesis is only likely to be operative on a local/regional scale. The locations include western, central, and eastern United States (Courtier & Revenaugh, 2006;Jasbinsek & Dueker, 2007;Song et al, 2004;Song & Helmberger, 2006), Siberian platform (Vinnik & Farra, 2007), Arabian Plate (Vinnik et al, 2003), off the coast of Japan (Bagley et al, 2009;Revenaugh & Sipkinf, 1994), Southwest Pacific (Courtier & Revenaugh, 2007), and Afar Triple Junction in East Africa (Thompson et al, 2015). The locations include western, central, and eastern United States (Courtier & Revenaugh, 2006;Jasbinsek & Dueker, 2007;Song et al, 2004;Song & Helmberger, 2006), Siberian platform (Vinnik & Farra, 2007), Arabian Plate (Vinnik et al, 2003), off the coast of Japan (Bagley et al, 2009;Revenaugh & Sipkinf, 1994), Southwest Pacific (Courtier & Revenaugh, 2007), and Afar Triple Junction in East Africa (Thompson et al, 2015).…”

Section: Transition Zone Temperature and Water Contentmentioning

confidence: 99%

Stochastic Inversion of Geomagnetic Observatory Data Including Rigorous Treatment of the Ocean Induction Effect With Implications for Transition Zone Water Content and Thermal Structure

et al. 2018

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In this paper we estimate and invert local electromagnetic (EM) sounding data for 1‐D conductivity profiles in the presence of nonuniform oceans and continents to most rigorously account for the ocean induction effect that is known to strongly influence coastal observatories. We consider a new set of high‐quality time series of geomagnetic observatory data, including hitherto unused data from island observatories installed over the last decade. The EM sounding data are inverted in the period range 3–85 days using stochastic optimization and model exploration techniques to provide estimates of model range and uncertainty. The inverted conductivity profiles are best constrained in the depth range 400–1,400 km and reveal significant lateral variations between 400 km and 1,000 km depth. To interpret the inverted conductivity anomalies in terms of water content and temperature, we combine laboratory‐measured electrical conductivity of mantle minerals with phase equilibrium computations. Based on this procedure, relatively low temperatures (1200–1350°C) are observed in the transition zone (TZ) underneath stations located in Southern Australia, Southern Europe, Northern Africa, and North America. In contrast, higher temperatures (1400–1500°C) are inferred beneath observatories on islands, Northeast Asia, and central Australia. TZ water content beneath European and African stations is ∼0.05–0.1 wt %, whereas higher water contents (∼0.5–1 wt %) are inferred underneath North America, Asia, and Southern Australia. Comparison of the inverted water contents with laboratory‐constrained water storage capacities suggests the presence of melt in or around the TZ underneath four geomagnetic observatories in North America and Northeast Asia.

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Section: Transition Zone Temperature and Water Contentmentioning

confidence: 99%

Stochastic Inversion of Geomagnetic Observatory Data Including Rigorous Treatment of the Ocean Induction Effect With Implications for Transition Zone Water Content and Thermal Structure

et al. 2018

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“…Vinnik and Farra (2007) detected also such a zone below several globally distributed seismic stations. Bagley and Revenaugh (2008) and Bagley et al (2009) studied the transition zone in the Pacific region using ScS reverberations and saw no low-velocity zone atop the 410, except at the Japan slab (50-75 km thick). Vinnik et al (2009Vinnik et al ( , 2010 identified in P and S receiver functions a lowvelocity zone above the 410 in South Africa and in California.…”

Section: Sharpness Of 410 and 660mentioning

confidence: 99%

Deep Earth Structure - Transition Zone and Mantle Discontinuities

Kind

2015

Treatise on Geophysics

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“…These seismic studies determined that the X possesses a relatively low positive shear impedance contrast (3-5 %) but is seismically sharp, with the gradient constrained to be <5 km across the discontinuities (Revenaugh and Jordan 1991;Zheng et al 2007;Bagley and Revenaugh 2008). The X is primarily observed beneath the regions of subduction (Zhang and Lay 1993), continents (Wajeman 1988), and a few hot spots (Courtier et al 2007;Bagley et al 2009). …”

Section: Introductionmentioning

confidence: 99%

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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Melting in the deep upper mantle oceanward of the Honshu slab

Cited by 35 publications

References 60 publications

Stochastic Inversion of Geomagnetic Observatory Data Including Rigorous Treatment of the Ocean Induction Effect With Implications for Transition Zone Water Content and Thermal Structure

Stochastic Inversion of Geomagnetic Observatory Data Including Rigorous Treatment of the Ocean Induction Effect With Implications for Transition Zone Water Content and Thermal Structure

Deep Earth Structure - Transition Zone and Mantle Discontinuities

Imaging Mantle Heterogeneity with Upper Mantle Seismic Discontinuities

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