Rheology of oceanic lower crust during asymmetric back-arc spreading

Abstract

We show that a simple plagioclase flow law can be employed to explain the microstructural evolution of gabbroic mylonites and ultramylonites that occur extensively along the surface of fault-induced asymmetric spreading over the ∼125 km length of the Godzilla megamullion, at a temperature of 650 to 900 degree C and a remarkably higher strain rate of ∼10E-9 s-1 to 10E-10 s-1. Our results indicate that superplastic flow within the lower crust played a significant role in movement along the detachment fault that formed the megamullion during asymmetric back-arc rifting.