KINEMATIC AND TIMING CONSTRAINTS OF THE GREENBRIER FAULT, SURROUNDING THE ELA AND BRYSON CITY DOMES, NORTH CAROLINA

Detailed field mapping, structural analysis and geothermobarometry of the Greenbrier fault, which bounds the Ela dome and Bryson City dome has helped clarify some of the timing and kinematic uncertainties surrounding the fault. Here the Greenbrier fault juxtaposes the Grenvillian basement within the domes against the overlying Thunderhead formation. The shear zone is characterized by annealed mylonite orthogenesis ~50-200 meters thick that is well developed around the northern edge of the Bryson City dome and the southern edge of the Ela dome. Shear-sense indicators record dominantly top-down-NE shear sense, but opposite shear sense indicators are present. Poor exposure makes it difficult to consistently trace the mylonite zone around the entirety of the domes; however evidence for continuity of the sheared contact is provided by float near the contact. Mylonite adjacent to the fault is better developed in the footwall where it is strongly foliated and locally lineated. The foliation becomes progressively weaker towards the center of the dome suggesting the mylonite developed during movement along the Greenbrier fault. Mylonite foliation is transposed to the main foliation (S₂) in the Grenville basement and Thunderhead formation. The main foliation, which is axial planar to local (F₂) tight to isoclinals folds, becomes steep to overturned near the contact. Crenulations have developed in the Thunderhead formation parallel to open (F₃) folds. Lineations are parallel to (F₄) folds that are attributed to dome formation. Peak metamorphic temperature and pressures at those temperatures (641°C ±64 and 9.7 kbars ±1.1) were calculated for a staurolite-kyanite schist sampled from the Thunderhead formation. Staurolite and kyanite porphyroblasts grew parallel to main foliation indicating syn-kinematic grew during (S₂) foliation development.