BOUNDARY RELATIONSHIPS OF THE LOOKING GLASS PLUTON, SHINING ROCK QUADRANGLE, TRANSYLVANIA COUNTY, NORTH CAROLINA

Looking Glass pluton intruded biotite-white mica gneiss of the Ash Metamorphic Suite. There is no apparent macroscopic evidence for a contact aureole within the gneiss, however structurally overlying garnet mica schist has a kyanite zonation that seems spatially related to the pluton. The exposed upper surface of the pluton is of low relief and undulatory but several masses, e.g. Looking Glass Rock and Cedar Rock, rise 300 meters above the general level of the pluton. The configuration of structurally overlying gneiss and schist reflects this uneven surface. On the northeast flank of the pluton, intrusive rocks interfinger with the gneiss forming a series of closely spaced sills that extend 3.5 kilometers from the main body of the pluton, are generally coarsely crystalline to pegmatitic in nature, and are usually no more than two meters thick. In the valley of Davidson River southwest of Looking Glass Rock, there occurs within the pluton a thin slab of gneiss, which is less than 10 meters thick but at least 2.5 kilometers long and 1.0 kilometer wide. On a mesoscopic scale the contact between this slab and the pluton is jagged and sharp. Quartz diorite of the pluton is very weakly foliated, yet along the southwest flank of the pluton, a modest NE-SW oriented horizontal mineral elongation lineation developed. This parallels a foliation in the country rock, which is associated with the Brevard Zone. A similar but more strongly developed mineral elongation lineation occurs within the plutonic rocks near the northwest boundary of the pluton. This boundary is interpreted here to be a fault, is very abrupt, runs straight on a bearing of N30E for at least 7 kilometers and truncates multiple lithologies of country rock. A yet to be explored northeast extension of this trend would bring it to the southeast side of the Pink Beds pluton, thus suggesting a genetic connection between the two plutons and a dextral sense of displacement along the fault.