Silica controls on hydration kinetics during serpentinization of olivine: Insights from hydrothermal experiments and a reactive transport model

Effect of normal stress on the frictional behavior of brucite: application to slow earthquakes at the subduction plate interface in the mantle wedge

“…These observations indicate that the serpentinite layer at the subduction plate interface may contain brucite because of low silica metamorphism as brucite itself has sometimes been found (Kawahara et al, 2016;Mizukami et al, 2014). Hydrothermal experiments also support the finding that SiO 2 is effectively consumed and brucite can stably exist with antigorite (Oyanagi et al, 2015(Oyanagi et al, , 2020. Although deformation may localize at the metasomatic region (Hirauchi et al, 2013;Tarling et al, 2019), the foliated structure of the serpentinite matrix implies that the serpentinite layer still accompanies some portion of deformation at the subduction plate interface.…”

“…As serpentinite has been observed in various important tectonic settings and is consid-ered to contribute to the weakness of serpentinite-dominant areas, the frictional properties of serpentinite have been investigated for several decades (see Guillot et al, 2015, and, for a review). A large volume of serpentinite is located in mantle wedges in which olivine-rich rock of the upper mantle is hydrated by slab-derived water and composes the subduction plate interface, as suggested by geological and seismological studies (Bostock et al, 2002;Christensen, 2004;Guillot and Hattori, 2013;Hyndman and Peacock, 2003;Kawahara et al, 2016;Kawakatsu and Watada, 2007;Mizukami et al, 2014;Peacock and Hyndman, 1999;Reynard, 2013). Because of the mechanical weakness of serpentinite, the relationship between the presence of serpentinite and the aseismic behavior below the downdip limit of seismogenic zones has been argued (Hyndman and Peacock, 2003;Oleskevich et al, 1999).…”

“…Serpentinite in the mantle wedge is mainly composed of an antigorite-olivine assemblage in warm subduction zones like Cascadia, whereas a brucite-antigorite assemblage dominates in the case of cold subduction zones such as that in NE Japan (Peacock and Hyndman, 1999). Because fluids from subducting slabs have a high SiO 2 content, talc is stable in the vicinity of slab-mantle boundaries (Hirauchi et al, 2013;Peacock and Hyndman, 1999). Serpentinite is made up of serpentinite-related minerals, such as antigorite, brucite, and talc, and as those minerals show different frictional behavior, the frictional properties of each mineral should be understood to interpret the mechanical behavior of bulk serpentinite.…”

“…However, brucite has rarely been considered in previous studies, as it is challenging to detect brucite under natural conditions because of its fine-grained nature (Hostetler et al, 1966). Brucite is not thermodynamically stable when the slab-derived water contains high SiO 2 content, and the mantle wedge may undergo silica metamorphism (Manning, 1997;Peacock and Hyndman, 1999). However, geological works on exhumed mantle wedge regions suggest that silica metamorphism has not occurred widely within the shallow mantle wedge because talc zones and metasomatic reactions are often limited in the narrow part near the meta-sedimentary rocks (Angiboust and Agard, 2010;D'Antonio and Kristensen, 2004;French and Condit, 2019;Guillot et al, 2009;Kawahara et al, 2016;Mizukami et al, 2014;Nagaya et al, 2020;Reynard, 2013;Tarling et al, 2019).…”

Fluid Infiltration Through Oceanic Lower Crust in Response to Reaction‐Induced Fracturing: Insights From Serpentinized Troctolite and Numerical Models

“…In contrast, the Type 2 veins are characterized by Al-rich serpentine + magnetite. Serpentinization of olivine without production of brucite indicates that the silica activity was high, and supplied by pyroxene and/or plagioclase, as observed in harzburgite, wehrlite, and troctolite (e.g., Beard et al, 2009;Katayama et al, 2010;Oyanagi et al, 2018), and in hydrothermal experiments that simulate the hydration of olivine in contact with orthopyroxene, plagioclase, and quartz (Ogasawara et al, 2013;Oyanagi et al, 2018Oyanagi et al, , 2020 Olivine Water Silica Serpentine :…”