A systematic 2‐D investigation into the mantle wedge's transient flow regime and thermal structure: Complexities arising from a hydrated rheology and thermal buoyancy

Voci, G. Le; Davies, D. Rhodri; Goes, Saskia; Kramer, Stephan C.; Wilson, C. R.

doi:10.1002/2013gc005022

Cited by 34 publications

(55 citation statements)

References 94 publications

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“…Models incorporating such effects as well as thermal buoyancy predict the appearance of transient instabilities that perturb mantle corner flow redistributing heat and thus modifying temporarily the viscosity structure in the mantle wedge [e.g., Arcay et al , ; Honda and Saito , ]. However, the time scale of these instabilities are likely to be greater than time scale relevant to fluid migration [ Le Voci et al , ].…”

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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“…We thus conclude that the presence of water is responsible for the detected seismic signature. The effectiveness of subduction‐related processes in modifying the physical properties of plate surrounded by active convergent margins, such as the Philippine and Sunda plates, has important geodynamical implications [e.g., Faccenna et al , ; van Keken , ; Le Voci et al , ]. For example, dehydration in the slab, mostly active in the top 200 km [ Schmidt and Poli , ], can alter the rheological properties of the back‐arc region and small‐scale convection can be facilitated [ Le Voci et al , ].…”

Section: Discussion and Interpretationmentioning

confidence: 99%

Hydration of marginal basins and compositional variations within the continental lithospheric mantle inferred from a new global model of shear and compressional velocity

et al. 2015

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We present a new global model of shear and compressional wave speeds for the entire mantle, partly based on the data set employed for the shear velocity model savani. We invert Rayleigh and Love surface waves up to the sixth overtone in combination with major P and S body wave phases. Mineral physics data on the isotropic δlnVS/δlnVP ratio are taken into account in the form of a regularization constraint. The relationship between VP and VS that we observe in the top 300 km of the mantle has important thermochemical implications. Back‐arc basins in the Western Pacific are characterized by large VP/VS and not extremely low VS at ∼150 km depth, consistently with presence of water. Most pronounced anomalies are located in the Sea of Japan, in the back‐arc region of the Philippine Sea, and in the South China Sea. Our results indicate the effectiveness of slab‐related processes to hydrate the mantle and suggest an important role of Pacific plate subduction also for the evolution of the South China Sea. We detect lateral variations in composition within the continental lithospheric mantle. Regions that have been subjected to rifting, collisions, and flood basalt events are underlain by relatively large VP/VS ratio compared to undeformed Precambrian regions, consistently with a lower degree of chemical depletion. Compositional variations are also observed in deep lithosphere. At ∼200 km depth, mantle beneath Australia and African cratons has comparable positive VS anomalies with other continental regions, but VP is ∼1% higher.

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“…We find that viscosity exerts the main control on whether or not SSC occurs, which is consistent with previous wedge flow studies [e.g., Honda and Yoshida , ; Wirth and Korenaga , ; Le Voci et al ., ]. Figure illustrates the thermal structure and flow regime for a damp case with a 120 Myr old upper plate and a subduction velocity of 5 cm/yr, at t = 32 and t = 38 Myr.…”

Section: ‐D Ssc Styles and Controlsmentioning

confidence: 99%

“…In this paper, we extend our systematic 2‐D study of SSC in the subduction zone mantle wedge [ Le Voci et al ., ] to 3‐D. We explore a range of (dry to hydrous) mantle viscosities, subduction velocities, and upper plate ages.…”

Section: Introductionmentioning

confidence: 99%

The mantle wedge's transient 3‐D flow regime and thermal structure

Davies

Voci

Goes

et al. 2016

Geochem Geophys Geosyst

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Arc volcanism, volatile cycling, mineralization, and continental crust formation are likely regulated by the mantle wedge's flow regime and thermal structure. Wedge flow is often assumed to follow a regular corner-flow pattern. However, studies that incorporate a hydrated rheology and thermal buoyancy predict internal small-scale-convection (SSC). Here, we systematically explore mantle-wedge dynamics in 3-D simulations. We find that longitudinal ''Richter-rolls'' of SSC (with trench-perpendicular axes) commonly occur if wedge hydration reduces viscosities to Շ1 Á 10 The modulating influence of subback-arc ridges on the subarc system increases with stronger wedge hydration, higher subduction velocity, and thicker upper plates. We find that trenchparallel averages of wedge velocities and temperature are consistent with those predicted in 2-D models. However, lithospheric thinning through SSC is somewhat enhanced in 3-D, thus expanding hydrous melting regions and shifting dehydration boundaries. Subarc Richter-rolls generate time-dependent trench-parallel temperature variations of up to $150 K, which exceed the transient 50-100 K variations predicted in 2-D and may contribute to arc-volcano spacing and the variable seismic velocity structures imaged beneath some arcs.

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A systematic 2‐D investigation into the mantle wedge's transient flow regime and thermal structure: Complexities arising from a hydrated rheology and thermal buoyancy

Cited by 34 publications

References 94 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

Hydration of marginal basins and compositional variations within the continental lithospheric mantle inferred from a new global model of shear and compressional velocity

The mantle wedge's transient 3‐D flow regime and thermal structure

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