Creep Rheology of Antigorite: Experiments at Subduction Zone Conditions

Abstract

Subduction zones are among the most seismically active tectonic environments on Earth. The wide spectrum of brittle and ductile behavior in the down-going slab and nearby mantle control seismic coupling, deep fluid transport, and local mantle convection. The interplay between rheology and metamorphic reactions is key to understanding tectonic dynamics and evolution of subduction structure at depth. To explain a range of observations from subduction zones (e.g., heat flow, location of volcanic front, slab seismicity, seismic structure of the mantle wedge), thermal models require slab decoupling from the mantle wedge down to a depth of approximately 80 km (e.g., Syracuse et al., 2010;Wada et al., 2008). Owing to its relative weakness compared to other lithospheric minerals, the presence of serpentine along the interface has been called on to promote this decoupling (e.g., Wada & Wang, 2009). In altered oceanic lithosphere and mantle wedge, antigorite is the stable serpentine polytype at these high pressure/high temperature conditions (Schwartz et al., 2013;Wunder & Schreyer, 1997).The rheology of antigorite at high pressure has been investigated in a wide range of experimental studies. Flow laws constrained by strain rate stepping experiments from these studies have reported both dislocation creep behavior (

High‐Pressure Mechanical Properties of Talc: Implications for Fault Strength and Slip Processes

“…This analysis provides an upper bound to the strength of faults, as the roles of pore‐fluid pressure and lower strain rate are not included. However, the experimental strain rate used here (10 −5 1/s) is consistent with the range of strain rates expected for slow slip events (e.g., Oncken et al., 2022) and the rate dependence of deformation under high confining pressures of phyllosilicates is typically low (e.g., Burdette & Hirth, 2022). Nonetheless, the compelling comparisons shown in Figure 8 motivate further studies on the rheology of talc and especially its strength sensitivity to strain rate.…”

Computing Rates and Distributions of Rock Recovery in Subduction Zones

“…In the numerical experiments, our rheological model and implementation of serpentine formation in the upper mantle creates a weak interface. A stronger rheology (e.g., quartz or a mixed melange zone, Beall et al., 2019; Ioannidi et al., 2021), or a stronger serpentine flow law (Burdette & Hirth, 2022), would yield greater heating and higher T's from enhanced viscous dissipation (calculated as the product of deviatoric stress and strain rate in our experiments, Gerya, 2019) along the subduction interface (similar to increasing shear heating, e.g., Kohn et al., 2018). In principle, a stronger rheology might shift the overall PT distribution of markers to higher T's and help fill in the marker recovery gap around 2 GPa and 550°C, and/or possibly change flow to extract rocks more broadly along the subduction interface.…”

The effect of muscovite on the microstructural evolution and rheology of quartzite in general shear

“…The creation of voids in kink bands and ripplocations in naturally deformed micas suggests a large activation volume in mica deformation mechanisms, implying pressure could play an important role on the strength of mica. Additionally, if micas are deforming by a glide-controlled mechanism, the stress exponent will be temperature-dependent (Frost and Ashby, 1982;Burdette and Hirth, 2022). Extrapolating mica flow laws to lower stress eclogite facies conditions is also problematic, because the combination of high pressure and temperature may promote dissolution-precipitation creep, owing to the increased solubility of SiO 2 (e.g., Manning, 2018).…”