Hydration adjacent to a deeply subducting slab: The roles of nominally anhydrous minerals and migrating fluids

Hebert, L. B.; Montési, Laurent G. J.

doi:10.1002/2013jb010497

Cited by 19 publications

(19 citation statements)

References 128 publications

(206 reference statements)

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“…The values are consistent with those estimated in the models of Wilson et al [] with relatively low and moderate fluid mobilities. In nature, fluid velocity might be at least 1 order of magnitude higher than the subduction velocity [ Wilson et al , ; Hebert and Montési , ].…”

Section: Discussionmentioning

confidence: 99%

Fluid migration in the mantle wedge: Influence of mineral grain size and mantle compaction

Cerpa

Wada

Wilson³

2017

JGR Solid Earth

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Mineral grain size in the mantle affects fluid migration by controlling mantle permeability; the smaller the grain size, the less permeable the mantle is. Mantle shear viscosity also affects fluid migration by controlling compaction pressure; high mantle shear viscosity can act as a barrier to fluid flow. Here we investigate for the first time their combined effects on fluid migration in the mantle wedge of subduction zones over ranges of subduction parameters and patterns of fluid influx using a 2‐D numerical fluid migration model. Our results show that fluids introduced into the mantle wedge beneath the forearc are first dragged downdip by the mantle flow due to small grain size (<1 mm) and high mantle shear viscosity that develop along the base of the mantle wedge. Increasing grain size with depth allows upward fluid migration out of the high shear viscosity layer at subarc depths. Fluids introduced into the mantle wedge at postarc depths migrate upward due to relatively large grain size in the deep mantle wedge, forming secondary fluid pathways behind the arc. Fluids that reach the shallow part of the mantle wedge spread trench‐ward due to the combined effect of high mantle shear viscosity and advection by the inflowing mantle and eventually pond at 55–65 km depths. These results show that grain size and mantle shear viscosity together play an important role in focusing fluids beneath the arc.

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Section: Discussionmentioning

confidence: 99%

Fluid migration in the mantle wedge: Influence of mineral grain size and mantle compaction

Cerpa

Wada

Wilson³

2017

JGR Solid Earth

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“…Previous workers have stressed the importance of water incorporation into NAMs in the mantle wedge as an effective way to transport water into the deep Earth's interior (Hebert & Montési, ; Horiuchi & Iwamori, ; Iwamori, ). Hydrous defects are dominated by Si vacancies under the relevant conditions for the mantle wedge ( T > 900°C and P > 3 GPa, Figure ).…”

Section: Discussionmentioning

confidence: 99%

A Subsolidus Olivine Water Solubility Equation for the Earth's Upper Mantle

Padrón‐Navarta

Hermann

2017

JGR Solid Earth

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The pressure and temperature sensitivity of the two most important point hydrous defects in mantle olivine involving Si vacancies (associated to trace amounts of titanium [TiChu‐PD] or exclusively to Si vacancies [Si]) was investigated at subsolidus conditions in a fluid‐saturated natural peridotite from 0.5 to 6 GPa (approximately 20–200 km depth) at 750 to 1050°C. Water contents in olivine were monitored in sandwich experiments with a fertile serpentine layer in the middle and olivine and pyroxene sensor layers at the border. Textures and mineral compositions provide evidence that olivine completely recrystallized during the weeklong experiments, whereas pyroxenes displayed only partial equilibration. A site‐specific water solubility law for olivine has been formulated based on the experiments reconciling previous contradictory results from low‐ and high‐pressure experiments. The site‐specific solubility laws permit to constrain water incorporation into olivine in the subducting slab and the mantle wedge, as these are rare locations on Earth where fluid‐present conditions exist. Chlorite dehydration in the hydrated slab is roughly parallel to the isopleth of 50 ± 20 ppm wt H2O in olivine, a value which is independent of the pressure and temperature trajectory followed by the slab. Hydrous defects are dominated by [Si] under the relevant conditions for the mantle wedge affected by fluids coming from the slab dehydration (slab‐adjacent low viscosity/seismic low‐velocity channel, P > 3 GPa). In cold subduction zones at 5.5 km from the slab surface the storage capacity of the mantle wedge at depths of 100–250 km ranges from 400 to 2,000 ppm wt H2O.

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“…Our model approach is essentially instantaneous and has an isoviscous mantle, thus implying that our models do not capture potential increases in the mantle's resistance to slab sinking in and below the transition zone. However, it has been shown that viscosity in the transition zone drops due to high water content (Hebert and Montési, 2013), and high resistance to upper mantle slabs may not be expected at these depths. Resistance to slab sinking will increase at some depth below the transition zone, depending on the viscosity profile of the mantle.…”

Section: Numerical Model Limitations Summarymentioning

confidence: 99%

Pacific plate slab pull and intraplate deformation in the early Cenozoic

et al. 2014

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Abstract. Large tectonic plates are known to be susceptible to internal deformation, leading to a range of phenomena including intraplate volcanism. However, the space and time dependence of intraplate deformation and its relationship with changing plate boundary configurations, subducting slab geometries, and absolute plate motion is poorly understood. We utilise a buoyancy-driven Stokes flow solver, BEM-Earth, to investigate the contribution of subducting slabs through time on Pacific plate motion and plate-scale deformation, and how this is linked to intraplate volcanism. We produce a series of geodynamic models from 62 to 42 Ma in which the plates are driven by the attached subducting slabs and mantle drag/suction forces. We compare our modelled intraplate deformation history with those types of intraplate volcanism that lack a clear age progression. Our models suggest that changes in Cenozoic subduction zone topology caused intraplate deformation to trigger volcanism along several linear seafloor structures, mostly by reactivation of existing seamount chains, but occasionally creating new volcanic chains on crust weakened by fracture zones and extinct ridges. Around 55 Ma, subduction of the PacificIzanagi ridge reconfigured the major tectonic forces acting on the plate by replacing ridge push with slab pull along its northwestern perimeter, causing lithospheric extension along pre-existing weaknesses. Large-scale deformation observed in the models coincides with the seamount chains of Hawaii, Louisville, Tokelau and Gilbert during our modelled time period of 62 to 42 Ma. We suggest that extensional stresses between 72 and 52 Ma are the likely cause of large parts of the formation of the Gilbert chain and that localised extension between 62 and 42 Ma could cause late-stage volcanism along the Musicians volcanic ridges. Our models demonstrate that early Cenozoic changes in Pacific plate driving forces only cause relatively minor changes in Pacific absolute plate motion directions, and cannot be responsible for the Hawaiian-Emperor bend (HEB), confirming previous interpretations that the 47 Ma HEB does not primarily reflect an absolute plate motion event.

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Hydration adjacent to a deeply subducting slab: The roles of nominally anhydrous minerals and migrating fluids

Cited by 19 publications

References 128 publications

Fluid migration in the mantle wedge: Influence of mineral grain size and mantle compaction

Fluid migration in the mantle wedge: Influence of mineral grain size and mantle compaction

A Subsolidus Olivine Water Solubility Equation for the Earth's Upper Mantle

Pacific plate slab pull and intraplate deformation in the early Cenozoic

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