The brittle-ductile transition in a deformation-mechanism map for halite

Abstract

The brittle-ductile transition in rock deformation has been studied extensively, but is still poorly quantified. Progress in our understanding of this and other transitions in mechanical behavior and deformation mechanisms is facilitated by use of deformation-mechanism maps. A preliminary deformation-mechanism map for halite is presented, based on shear experiments at room temperature (22°C) over the range of normal stress up to 350 MPa and average shear-strain rates between 10° to 10 −6 s −1. The map illustrates that transitions in mode-of-failure, mechanical behavior and dominant deformation mechanism, which often are referred to collectively as the brittle-ductile transition, do not necessarily coincide. The analysis also suggests that the transition from dominantly cataclastic to crystal-plastic deformation-mechanism fields is adequately described by the distinct and independent mechanism field of semi-brittle flow.