The Contentnea Creek Granite : Constraints On Late Paleozoic Magmatism And Deformation, Eastern Piedmont Fault System, North Carolina

Abstract

The Alleghanian orogeny is manifested in eastern North Carolina by dextral transpressional faulting on the Eastern Piedmont Fault system and spatially associated granitic magmatism. The Contentnea Creek granite in Wilson County, North Carolina, is exposed over ~20 km² and is spatially associated with the Hollister mylonite zone, a component of the Eastern Piedmont Fault system. For this study, field observations and laboratory analyses are used to characterize fabric variation, geochemical signature, and the timing of the Contentnea Creek pluton, with the goal of understanding its place in the regional Alleghanian thermo-tectonic history. Multiple fabrics exist in the Contentnea Creek pluton. On the eastern margin of the pluton magmatic fabric exists. On the western margin of the pluton high-temperature solid-state fabric exists and preserves evidence of syn-magmatic shearing within the Hollister mylonite zone. The high-temperature solid-state fabric is locally overprinted by low-temperature solid-state fabric that formed in zones of high strain rates. Isolated clusters of mineralized shear fractures overprint both solid-state fabrics and likely formed much later, after these rocks were exhumed into the upper crust. Whole-rock major and trace element geochemical data demonstrate that the pluton is homogenous within the exposed area and is similar to other Alleghanian granitoids in the southern Appalachians. ID-TIMS U/Pb geochronology on zircon yields a 305.70 ± 0.22 Ma crystallization age. These new data from the Contentnea Creek pluton refine our understanding of the spatial and temporal relationship between regional Alleghanian magmatism and faulting. Mineralized shear fractures overprint late Paleozoic Alleghanian structures after their exhumation into the upper crust. Paleostress analysis suggests late brittle fractures may have formed due to Cenozoic reactivation of the Eastern Piedmont Fault system, as has been observed elsewhere to the north and south, along the strike of this major late Paleozoic structure.