Jurassic–Cenozoic tectonics of the Pequop Mountains, NE Nevada, in the North American Cordillera hinterland

Abstract The Ruby Mountains–East Humboldt Range–Wood Hills–Pequop Mountains (REWP) metamorphic core complex, northeast Nevada, exposes a record of Mesozoic contraction and Cenozoic extension in the hinterland North American Cordillera. timing, magnitude, style crustal thickening succeeding thinning have long been debated. Pequop Mountains, comprising Neoproterozoic through Triassic strata, are least deformed part this composite compared to migmatitic mylonitized ranges west, provide clearest field relationships for Mesozoic–Cenozoic tectonic evolution. New field, structural, geochronologic, thermochronological observations based on 1:24,000-scale geologic mapping northern insights into multi-stage history REWP. Polyphase cooling reheating middle-upper crust was tracked over range <100 °C 450 via novel 40Ar/39Ar multi-diffusion domain modeling muscovite K-feldspar apatite fission-track dating. Important new interpretations include: (1) crosscutting show that most contractional deformation region occurred just prior to, or during, Middle-Late Jurassic Elko orogeny (ca. 170–157 Ma), with negligible Cretaceous shortening; (2) temperature-depth data rule out deep burial Paleozoic stratigraphy, thus refuting models incorporate large cryptic overthrust sheets; (3) Jurassic, Cretaceous, Eocene intrusions associated thermal pulses metamorphosed lower Paleozoic–Proterozoic rocks, various thermochronometers conductive near original stratigraphic depths; (4) east-draining paleovalleys ∼1–1.5 km relief incised before ca. 41 Ma were filled by 41–39.5 volcanic rocks; (5) low-angle normal faulting initiated after Eocene, possibly as early late Oligocene, although basin-generating from high-angle began middle Miocene. Observed shortening is coeval structures Luning-Fencemaker thrust belt other strain documented across central-east Nevada Utah, suggesting ∼100 Sierra retroarc. This phase correlates terrane accretion Sierran forearc, increased American–Farallon convergence rates, enhanced arc magmatism. Although spatially variable, Cordilleran high plateau developed it (i.e., hypothesized Nevadaplano) involved dynamic pulsed evolution significant phases both Late deformation. Collapse postdated all contraction. complex set stage Carlin-type gold deposit at Long Canyon, located along eastern flank may important clues future exploration.