DEFORMATION OF THE ERRATICS AT HENDERSON SUMMIT, VININI CREEK, MINERAL HILL, AND LONE MOUNTAIN IN EUREKA COUNTY, NEVADA

During the Late Devonian-Early Mississippian Antler Orogeny, siliciclastic Ordovician-Devonian strata deposited on the slope and continental rise of western Laurentia, or Roberts Mountains Allochthon (RMA), were thrusted more than 200 km eastward along the Roberts Mountains thrust (RMT) and over the coeval, shallow-marine, Cambrian-Devonian carbonate rocks (Finney et al., 2015). Presently, several large, autochthonous carbonate masses in the Roberts Mountains, Nevada precariously overlie the siliceous rocks of the RMA. They were first interpreted to be windows through the Roberts Mountains thrust (Merriam and Anderson, 1942) and then later reinterpreted to be emplaced due to gravity sliding off structural highs (Winterer, 1968). However, recent geologic studies provide an entirely new interpretation for the occurrence of these carbonate masses, or tectonic erratics (Finney et al., 2015). It was observed that the masses in the Roberts Mountains occur above the previously unidentified Henderson thrust, which duplicated the stratigraphy and structure of the RMA. The carbonate masses were plucked from the underlying autochthonous succession and carried in the base of the upper plate of the Henderson thrust as it ramped upwards and eastwards (Finney et al., 2015). Data collected on the carbonate masses at Henderson Summit, Vinini Creek, Mineral Hill, and Lone Mountain (located on the eastern and southern flanks of the Roberts Mountains) suggest that the tectonic erratic hypothesis is applicable to these locations. Kinematic indicators in the form of folds and fractures within the carbonate outcrops show a general eastward stress direction and intense brecciation was observed along the lower contact between the carbonates and underlying siliceous rocks. From this data, it can be interpreted that the carbonate masses at Henderson Summit, Vinini Creek, Mineral Hill, and Lone Mountain are tectonic erratics. Extending the boundary that these tectonic erratics occur can have significant implications for petroleum and mineral exploration in the region.