KINEMATIC HISTORY OF GRANITIC GNEISSES AT THE FALLS OF THE NOTTOWAY IN THE CAROLINA TERRANE, EASTERN PIEDMONT, VIRGINIA
Gneissic rocks are L>S tectonites with a N- to NE-trending subhorizontal penetrative lineation, and a weak N- to NE-striking subvertical foliation. The lineation is defined by rod-like quartz and feldspar aggregates with aligned biotite and muscovite. Fabric analysis of quartz aggregates yields K-values of 1.2 - 2.5 (apparent constriction) and D-values between 0.3 - 1.2. Microstructures preserved in the granitic gneisses are consistent with deformation at the amphibolite facies (500 - 600˚ C). These rocks experienced general shear with a dextral asymmetry, and record NW-SE contraction and strike-parallel (orogen-parallel) elongation.
Pegmatite dikes are cut by a plethora of quartz veins and fractures. Quartz precipitated within dilational shear fractures indicating that these features are contemporaneous. The majority of the fractures, including all right-lateral fractures, are predominantly E-striking, while those with left-lateral kinematics are N-striking. There are two sets of quartz veins with N- and E-strikes. Shear fractures and quartz vein orientations are consistent with a NW-SE oriented σ1 during brittle deformation.