Temperature and pressure of mylonitization in a Tertiary extensional shear zone, Ruby Mountains-East Humboldt Range, Nevada: Tectonic implications

In the northern Ruby Mountains-East Humboldt Range metamorphic core complex, a kinematically coupled mylonitic shear zone and brittle-plastic detachment fault compose a low-angle extensional fault system that is mid-Tertiary in age. Geothermobarometry of pelitic schists from the mylonitic shear zone yields a temperature and pressure estimate of 820-900 K (580-620 °C) and 310-370 MPa (3.1-3.7 kbar) for mylonite petrogenesis. The shear-zone-detachment-fault system excised 11-12 km of crustal section and accommodated at least 15-17 km of normal-sense dip slip.