An experimental study into the rheology of synthetic polycrystalline coesite aggregates

Abstract

Abstract. Coesite has been found as a relic in ultrahigh pressure metamorphic (UHPM) crust worldwide and is expected to play a major role in the mechanical behavior of continental crust at UHPM conditions. We performed triaxial compression tests on synthetic polycrystalline coesitite in a solid medium apparatus at confining pressures of 3.1 to 3.7 GPa, temperatures of 700 ø to --1160øC, and strain rates betweeen 6x10 -7 and lx10 -3 s -•. The problem of the limited stress resolution of the solid medium apparatus was addressed by applying two extreme friction corrections that yield lower and upper bounds to the differential stress.

Two-dimensional numerical modeling of tectonic and metamorphic histories at active continental margins

“…Moreover, many HP and UHP metamorphic rocks have remained nearly undeformed (Biino and Compagnoni 1992;Liou and Zhang 1997;Renner et al 2001;Oberha¨nsli et al 2002;Sto¨ckhert 2002). This requires that deformation during subduction and exhumation be localized into weak shear zones.…”

Effect of Water on Subduction of Continental Materials to the Deep Earth

“…For subduction channels, we used quartz-controlled rheology for P < 3.5 GPa and polycrystalline coesite rheology for P ≥ 3.5 GPa as in the previous study (Ichikawa et al 2013b). Namely, A = 6.7 × 10 −6 s −1 Mpa −n , n = 2.4, E * = 156 kJ/mol, and V * = 0 (Ranalli 1995, 1997) for P < 3.5 GPa and A = 10 −1.6 s −1 Mpa −n , n = 2.9, E * = 261 kJ/mol, and V * = 0 (Renner et al 2001) for P ≥ 3.5 GPa. For the mantle wedge, flow law parameters proposed by Kawazoe et al (2009) are used for dry and wet mantle rheologies.…”

Numerical Geodynamic Modeling of Continental Convergent Margins

“…Some authors have argued that rocks under geological conditions are too weak to support significant overpressure (e.g. Brace et al, 1970;Ernst, 1971;Burov et al, 2001;Renner et al, 2001;Green, 2005). Yet, Stüwe and Sandiford (1994) suggested that petrologically derived P-T paths may not record depth changes only but stress changes.…”