MAGMATIC AND TECTONIC INTERACTIONS IN THE HINTERLAND OF THE SEVIER OROGEN: NEW INSIGHTS FROM THE DEEP CREEK RANGE AND KERN MOUNTAINS, EASTERN NEVADA

This project examines three areas in the Deep Creek Range and Kern Mountains where the emplacement of syn-tectonic plutons had a profound effect on deformation and metamorphism in the country rock. The Trout Creek culmination is characterized by a distinct increase in strain intensity and metamorphic grade surrounding the Trout Creek pluton. Bedding and foliations are folded into a dome around the pluton and synkinematic biotite, garnet, andalusite and staurolite are present around the pluton margins and coincide with a zone of high strain. LA-ICP-MS geochronology of zircon from the pluton and monazite from the country rock indicate that pluton emplacement and peak metamorphism were approximately synchronous at ~80 Ma. The spatial and temporal association of metamorphism and deformation with the Trout Creek pluton suggests pluton emplacement caused doming of the country rock, the high strain fabric, and metamorphism. Farther south in the Deep Creek Range, rocks are folded into a map-scale recumbent anticline. Stratigraphy in the overturned limb is thinned significantly and has been affected by two metamorphic aureoles that indicate increasing grade toward the south. U-Pb geochronology of metamorphic monazite is inconclusive but suggests metamorphism occurred in the Late Cretaceous. Although no plutons are exposed here at the surface, the high lateral temperature gradients indicate a localized heat source to the south, most likely one or more plutons concealed beneath alluvium. The Kern Mountains are cored by the ~70 Ma Tungstonia pluton, which has a distinct deformational aureole around its margins. Within the aureole, stratigraphy is deflected into parallelism with the pluton contact and there is a well-developed contact-parallel foliation in both the pluton and country rock that decreases in intensity and dies out completely away from the contact. This aureole likely represents a zone of downward channel flow that accommodated ascent of the magma body. The relationships from these areas show that the emplacement of plutons can result in a complex thermal architecture with isotherms that have significant topography. Moreover, thermal rheologic weakening as well as superimposed forces directly related to pluton emplacement can result in complex strain fields that require careful evaluation.