Water pumping in mantle shear zones

Précigout, Jacques; Prigent, Christophe; Palasse, Laurie; Pochon, Anthony

doi:10.1038/ncomms15736

Cited by 66 publications

(57 citation statements)

References 67 publications

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“…This is also confirmed by chemical data that show strong enrichments of fine-grained minerals in (proto)mylonites in fluid mobile elements (especially boron; Prigent et al, 2018). This observation is also in agreement with the predominant activation of olivine (001)[100] dislocation slip systems in (proto)mylonites to ultramylonite/UMB (Figure 7), which is generally activated in hydrous conditions (Cao et al, 2015;Harigane et al, 2013;Hidas et al, 2016;Jung et al, 2014;Katayama et al, 2004;Mehl et al, 2003;Michibayashi & Oohara, 2013;Précigout et al, 2017). The geochemistry of newly crystallized fine grains and whole rock isotopic compositions indicate that these aqueous fluids bear a subduction signature (Khedr et al, 2014;Prigent et al, 2018;Yoshikawa et al, 2015).…”

Section: Fluid-assisted Deformation and Fluid Focusing In Shear Zonessupporting

confidence: 84%

“…Different mechanisms have been invoked to account for these combined processes of grain size reduction and phase mixing in ductile mantle shear zones: dislocation-mediated dynamic recrystallization and GBS-related grain switching events (e.g., Linckens et al, 2014), dynamic recrystallization and stress-induced differential cation diffusion (Tasaka et al, 2017), or dispersed nucleation of fine grains through dissolutionprecipitation processes (Hidas et al, 2016;Précigout et al, 2017;Précigout & Stünitz, 2016), associated with metamorphic reactions (De Ronde & Stünitz, 2007;De Ronde et al, 2005;Newman et al, 1999;Toy et al, 2010;Vissers et al, 1995) or melt-rock interaction (Dijkstra et al, 2002;Kaczmarek & Tommasi, 2011). The evidence for dislocation mobility in olivine and pyroxene (undulose extinctions and subgrain walls; Figures 3 and 4) and the occurrence of olivine triple junctions suggest that dynamic recrystallization by subgrain rotation partly contributed to reducing grain size.…”

Section: Mechanism (S) Of Grain Size Reduction and Phase Mixingmentioning

confidence: 99%

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Fluid‐Assisted Deformation and Strain Localization in the Cooling Mantle Wedge of a Young Subduction Zone (Semail Ophiolite)

et al. 2018

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This study reports on feedback mechanisms between fluid migration, ductile deformation, and strain localization processes in an incipiently forming mantle wedge: the basal banded unit of the Semail ophiolite. These peridotites were located right above the plate interface during intraoceanic subduction infancy that ultimately led to ophiolite obduction. During this stage, they were affected by coeval ductile deformation, forming (proto)mylonites at ~900–800 °C to ultramylonites at ~700 °C, and interaction with subduction fluids. From the petrological and microstructural study of these hydrated peridotites and their protolith (preserved lenses of porphyroclastic tectonites), we show that peridotite interaction with hydrous fluids triggered dissolution/precipitation processes. Dissolution of coarser grains and precipitation of new and smaller ones (mainly pyroxenes, spinel, and amphibole) resulted in a drastic grain size reduction, phase mixing and a switch from olivine dislocation to grain size sensitive creep in (proto)mylonites. Data also evidence a feedback process of fluid focusing in actively deforming shear zones. This rapid switch in olivine deformation mechanism, driven by subduction fluid‐peridotite interaction, triggered an intense weakening of the peridotites at ~900–800 °C and a transition from a mechanically decoupled to coupled plate interface (as witnessed by the detachment and underplating of a high‐temperature metamorphic sole to the base of the ophiolite). It also explains the intense strain localization (<1‐km‐thick shear zone) along this ductile portion of the plate interface. Considering that similar mechanisms take place in mature subduction zones, they may explain plate interface coupling at subarc depths in worldwide subduction zones.

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Section: Fluid-assisted Deformation and Fluid Focusing In Shear Zonessupporting

confidence: 84%

Section: Mechanism (S) Of Grain Size Reduction and Phase Mixingmentioning

confidence: 99%

Fluid‐Assisted Deformation and Strain Localization in the Cooling Mantle Wedge of a Young Subduction Zone (Semail Ophiolite)

et al. 2018

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“…Both of these thermometers are based on the closure temperatures of major element diffusion in their host mineral(s). As observed in other studies that have applied multiple thermometers (e.g., Birner et al, 2017;Dygert & Liang, 2015;Hidas et al, 2013;Précigout et al, 2017), the temperatures recorded by each thermometer vary systematically, reflecting differences in closure temperature of the different mineral systems as the peridotite cooled.…”

Section: Geothermometrysupporting

confidence: 57%

Evolution of the Josephine Peridotite Shear Zones: 1. Compositional Variation and Shear Initiation

Kumamoto

Warren

Hauri

2019

Geochem Geophys Geosyst

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Shear localization in the upper mantle, a necessity for plate tectonics, can have a number of causes, including shear heating, the presence of melt, the development of a strong crystal preferred orientation, and the presence of water. The Josephine Peridotite of southwestern Oregon contains shear zones that provide an excellent opportunity to examine the initiation of shear localization. These shear zones are relatively small scale and low strain compared to many shear zones in peridotite massifs, which typically have extreme grain size reduction indicating extensive deformation. We use major, trace, and volatile element analyses of a large suite of harzburgites from the Fresno Bench shear zones to evaluate the mechanisms leading to shear localization. Lithological evidence and geochemical transects across three shear zones show a complex history of melting, melt addition, and melt‐rock interaction. The distribution of aluminum and heavy rare earth elements across the shear zones suggest that melt flow was focused in the centers of the studied shear zones. Water concentrations in orthopyroxene grains of 180–334 ppm H2O indicate a comparatively high degree of hydration for nominally anhydrous minerals. The correlation of water with aluminum and ytterbium in orthopyroxene is consistent with a melt source for this hydration, suggesting that water equilibrated between the melt and peridotite. The presence of melt and hydration of the host rock provide mechanisms for initial weakening that lead to localized deformation.

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“…To date, geological research has identified evidence for creep cavitation in natural ultramylonites from the middle crust (Behrmann and Mainprice, 1987;Mancktelow et al, 1998;Herwegh and Jenni, 2001;Fusseis et al, 2009;Kilian et al, 2011;Rogowitz et al, 2016), the lower crust (Zá-vada et al, 2007;Menegon et al, 2015) and in mantle rocks (Rovetta et al, 1986;Précigout et al, 2017). Experimental work has shown that octachloropropane, quartzite, diabase, feldspar aggregates, anorthite-diopside aggregates, olivineclinopyroxene aggregates and calcite-muscovite aggregates can develop creep cavities (Caristan, 1982;Hirth and Tullis, 1989;Ree, 1994;Dimanov et al, 2007;Rybacki et al, 2008;Delle Piane et al, 2009;Précigout and Stünitz, 2016).…”

Section: Introductionmentioning

confidence: 99%

Hierarchical creep cavity formation in an ultramylonite and implications for phase mixing

et al. 2017

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Abstract. Establishing models for the formation of wellmixed polyphase domains in ultramylonites is difficult because the effects of large strains and thermo-hydro-chemomechanical feedbacks can obscure the transient phenomena that may be responsible for domain production. We use scanning electron microscopy and nanotomography to offer critical insights into how the microstructure of a highly deformed quartzo-feldspathic ultramylonite evolved. The dispersal of monomineralic quartz domains in the ultramylonite is interpreted to be the result of the emergence of synkinematic pores, called creep cavities. The cavities can be considered the product of two distinct mechanisms that formed hierarchically: Zener-Stroh cracking and viscous grain-boundary sliding. In initially thick and coherent quartz ribbons deforming by grain-size-insensitive creep, cavities were generated by the Zener-Stroh mechanism on grain boundaries aligned with the Y Z plane of finite strain. The opening of creep cavities promoted the ingress of fluids to sites of low stress. The local addition of a fluid lowered the adhesion and cohesion of grain boundaries and promoted viscous grain-boundary sliding. With the increased contribution of viscous grainboundary sliding, a second population of cavities formed to accommodate strain incompatibilities. Ultimately, the emergence of creep cavities is interpreted to be responsible for the transition of quartz domains from a grain-size-insensitive to a grain-size-sensitive rheology.

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Water pumping in mantle shear zones

Cited by 66 publications

References 67 publications

Fluid‐Assisted Deformation and Strain Localization in the Cooling Mantle Wedge of a Young Subduction Zone (Semail Ophiolite)

Fluid‐Assisted Deformation and Strain Localization in the Cooling Mantle Wedge of a Young Subduction Zone (Semail Ophiolite)

Evolution of the Josephine Peridotite Shear Zones: 1. Compositional Variation and Shear Initiation

Hierarchical creep cavity formation in an ultramylonite and implications for phase mixing

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