Creep Rheology of Antigorite: Experiments at Subduction Zone Conditions

Abstract

Novel fluid medium pressure cells were used to deform antigorite under constant stress creep conditions at low temperature, low strain rate (10−9 − 10−4 1/s), and high pressure (1 GPa) in a Griggs-type apparatus. Antigorite cores were deformed at constant temperatures between 75°C and 550°C, by applying 8–12 stress-strain steps per temperature. The microstructures of deformed samples share features documented in previous work (e.g., shear microcracks), and highlight the importance of basal shear and kinks to antigorite plasticity. Rheological data were fit with a low temperature plasticity law, consistent with a deformation mechanism involving large lattice resistance. When applied at geologic stresses and strain rates, the extrapolated viscosity agrees well with predictions based on subduction zone thermal models.