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

The North Carolina Geological Survey, in conjunction with the United States Geological Survey STATEMAP program, has produced a new 1:24,000-scale bedrock geologic map of the southern half of the Mount Mitchell 7.5-minute quadrangle in Buncombe and Yancey Counties, N.C. The quadrangle has never been mapped at this detailed scale even though it contains Mount Mitchell, the highest peak east of the Mississippi River. Bedrock geology of the map area is comprised of the Neoproterozoic to Cambrian Ashe Metamorphic Suite (AMS).

The AMS lithologies on the quadrangle include metagraywacke, schistose metagraywacke, aluminous porphyroblastic migmatite, garnet-mica schist, amphibolite, and altered ultramafic bodies. These lithologies are complexly deformed, interlayered, and migmatitic. Amphibolite and associated ultramafic bodies occur as relatively thin discontinuous lenses that are commonly on-strike with one another. Many of these are too small to show at 1:24,000-scale. The aluminous migmatite is characterized by medium- to coarse-grained leucosome with kyanite, up to 6 inches in length, and porphyroblastic muscovite. The AMS lithologies on the quadrangle have been metamorphosed to upper amphibolite facies. Kyanite and sillimanite are abundant in the migmatite and schist units.

Compositional layering and schistosity are 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-trending fracture set. 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.