SSA could not be possible without the generous support of Drs. Herbert A. and Betty Lou Lubs and the Science, Society, and the Arts Research Conference Endowment. We are deeply grateful!
The Rockfish Valley Deformation Zone in Central Virginia is a 1-10 km wide zone of mylonitic rocks separating two differently hydrated massifs. Significant disagreement exists around the timing, extent, and significance of low-grade deformation in the Rockfish Valley Deformation Zone, and the proposed timing of deformation in this zone ranges from pre-750 Ma to approximately 350 Ma. Based on petrologic evidence, I propose that the variation between the similar but distinct basement units to the east and west of the deformation zone may be explained by fluid-assisted retrogression of the seaward unit during collision. Further, syn-kinematic titanite grains identified in mylonites and protomylonites of the shear zone which have incorporated Uranium into their chemical structures suggest an age of 396±230 Ma, the timing of low grade deformation.
