FIELD RELATIONS, METAMORPHISM, AND DEFORMATION IN THE GOLD SAND 7.5-MINUTE QUADRANGLE, FRANKLIN COUNTY, NORTH CAROLINA

The study area is located in the Raleigh terrane of the southern Appalachian eastern Piedmont, within a metamorphic reentrant between the late Paleozoic Rolesville and Castalia plutons in northern Franklin County, North Carolina. The Raleigh terrane is a Neoproterozoic infrastructural terrane that has been subjected to Alleghanian upper-greenschist to amphibolite facies metamorphism and deformation. In this vicinity, the Raleigh terrane is separated from the Carolina terrane to the west by the Nutbush Creek fault zone and from the Spring Hope terrane to the east by the Macon fault zone.

This EDMAP-supported project, the first detailed 1:24,000 scale geologic mapping effort in this area, has revealed a complexly interlayered sequence of pelitic schist and gneiss, biotite schist and gneiss, and granitic gneiss. These rocks were subjected to multiple Alleghanian deformational events and intruded by late Paleozoic granite and pegmatite. Multiple pulses of amphibolite facies metamorphism are suggested by the presence of both sillimanite and kyanite, together with complex microstructures. In the eastern part of the area, a later Alleghanian northeast-trending, moderately northwest-dipping shear zone has overprinted the regional Alleghanian foliation. Preliminary analysis of foliations, crenulations, and stretching lineations suggests sub-horizontal or shallow vertical movement along the shear zone, which may be associated with the Macon fault zone. Very strong but sporadic crenulations adjacent to the Rolesville batholith at the western edge of the study area may indicate deformation of the wall rocks due to local ballooning of the batholith during emplacement. It is anticipated that further field and lab work will verify and elucidate these preliminary observations.