Thermal evolution of a portion of the Sevier Hinterland: The Northern Ruby Mountains‐East Humboldt Range and Wood Hills, northeastern Nevada

Conventional thermobarometry and Gibbs' Method modeling have been used to obtain new information pertaining to the Mesozoic‐Tertiary thermal evolution of the Ruby Mountains‐East Humboldt Range and Wood Hills metamorphic complexes, northeastern Nevada. Kyanite‐grade assemblages from Clover Hill, in the extreme northeastern part of the East Humboldt Range, were produced at temperatures of 780–810 K and depths in excess of 35 km; previously published geochronologic data suggest an Early Cretaceous or Late Jurassic age for this event. The Clover Hill area subsequently experienced a major unroofing interval prior to Late Cretaceous time, during which it was brought roughly 20 km closer to the surface. The lack of stratigraphic evidence for substantial Cretaceous erosion in the region and the topology of the pressure‐temperature paths for the Clover Hill samples suggest that the unroofing mechanism may have been tectonic denudation related to the relaxation of large topographic gradients produced by crustal thickening in the hinterland of the Sevier orogen. Metamorphic rocks at Clover Hill and within the Wood Hills core complex equilibrated at 820–900 K and 500–640 MPa (18–24 km) in Cretaceous time, prior to 115 Ma. Other parts of the Ruby Mountains‐East Humboldt Range metamorphic complex, presently structurally separated from the Clover Hill sequence, were intruded extensively by Late Cretaceous granitic magmas and attained substantially higher temperatures than the Clover Hill‐Wood Hills block. Sillimanite‐grade assemblages from these areas apparently underwent roughly 10 km of unroofing and 130 K of cooling prior to final equilibration at 820–920 K and 360–430 MPa (13–16 km) during Oligocene extension.