A NEW 1:24,000-SCALE GEOLOGIC MAP OF THE MOUNT MITCHELL 7.5-MINUTE QUADRANGLE, YANCEY AND BUNCOMBE COUNTIES, NORTH CAROLINA

The North Carolina Geological Survey has produced a new 1:24,000-scale bedrock geologic map of the Mount Mitchell 7.5-minute quadrangle in Buncombe and Yancey Counties, cooperatively funded through the STATEMAP component of the National Cooperative Geologic Mapping Program. The quadrangle has never been mapped at this detailed scale even though it contains Mount Mitchell, highest peak east of the Mississippi River. Bedrock geology of the map area is comprised of the Neoproterozoic Ashe Metamorphic Suite (AMS).

The AMS lithologies on the Mount Mitchell quadrangle include metagraywacke, schistose metagraywacke, porphyroblastic kyanite gneiss and schist, garnet-mica schist, amphibolite, and altered ultramafic bodies. These interlayered lithologies are complexly deformed and locally migmatitic. Amphibolite and associated ultramafic bodies occur as relatively thin discontinuous lenses that are commonly on-strike with one another, many of which are too small to show at 1:24,000-scale. A larger body of amphibolite is present in the northwest corner of the Mt. Mitchell quadrangle near the contact with Mesoproterozoic basement gneisses on the Barnardsville quadrangle. The porphyroblastic kyanite gneiss and schist unit is characterized by kyanite, up to 15 cm in length, and porphyroblastic muscovite. Kyanite and sillimanite, locally coexisting, are abundant in the gneiss and schist units. The AMS lithologies on the quadrangle have been metamorphosed to upper amphibolite facies.

Compositional layering and schistosity are generally parallel to one another and complexly folded in the study area. Foliations typically strike NE-SW and dip moderately to steeply to the NW and SE. Joint data indicate a prominent, steeply-dipping, WNW-ESE trending fracture set. The majority of measured fold axes have a shallow NNE or SSW plunge. Whole rock geochemical analyses (57 elements) were performed for ten representative samples. Five stream sediment samples from relatively unmodified watersheds were analyzed to determine heavy mineral concentrations.