The Mount Hay block is a ̃12-km-thick, deep continental crustal section exposed in the Arunta inlier in central Australia. The ̃4-km-wide, granulite-facies (770-776 ± 38 °C) Capricorn ridge shear zone cross-cuts the dominant granulite-facies fabric of the Mount Hay block. In its present geometry, the Capricorn ridge shear zone contains a steeply south-southeast-dipping foliation, steeply east-southeast-plunging lineation, and south-side-up shear-sense indicators. When post-granulite-facies tilting is removed, the shear zone restores to a shallowly to moderately (30-50°) dipping, normal shear zone in which the lineation is oblique to the inferred Proterozoic plate boundary, suggesting oblique divergence. The fi eld observations and reconstruction indicate that strain can be localized in the high-temperature, deep-crustal roots of extensional fault systems. This geometry of a discrete, moderately dipping, deep-crustal shear zone is consistent with simple-shear conceptual models of crustal extension.