THE LEGEND OF GREER HOLLOW: TACONIC HIGH PRESSURE METASOMATISM IN SOUTHERN APPALACHIA

Greer Hollow is an ultramafic body located within the Ashe Metamorphic Suite (AMS) located in the North Carolina Appalachians. The AMS has been recognized as a unit predominantly made up of pelitic and amphibolite schist that contains pods of both high-pressure metamorphosed mafic rocks and variably altered ultramafic bodies, that has been interpreted to be an accretionary complex related to Taconic subduction (Abbott and Raymond, 1984). These pods have been extensively studied geochemically, and are considered to have an N-MORB to depleted MORB compositional affinities (Misra and Conte, 1991). Previous works in Greer Hollow have highlighted metasomatic reactions between the ultramafic pods and its host pelitic schist, however the protolith and the elemental fluxes necessary to generate these metasomatic lithologies has remained enigmatic (Raymond et al., 2016; Stapor et al, 2010). One of these localities is largely comprised of three rock types, a tremolite schist, a magnetite-chlorite schist, and a garnet-magnetite-chlorite schist. These zones are located between the presumed end-members, an ultramafic dunite, and a pelitic host rock respectively. We performed bulk Lu-Hf garnet geochronology on the garnet-magnetite-chlorite schist within the reaction zone, resulting in a 455+/- 1.6 Ma age, suggesting that this fluid-driven metamorphism may have been (Taconic) subduction-derived. These garnet-bearing rocks provide useful information related to fluid-rock interactions during high-pressure metamorphism, as well as the conditions under which these rheologically-weak chlorite-rich rocks are being created during subduction, which can affect mechanical properties along this interface (Hoover et al., 2022). Oxygen isotopes in garnet will be used to determine temperatures and fluid sourcing, while garnet major and trace element chemistry paired with phase-equilibria modeling will help further constrain the pressure and temperature conditions as well as the fluid evolution.