Zircon inclusion suite analysis of the Ashe Metamorphic Suite, North Carolina: Implications for exhumation history of eclogite

Previous research suggests the Ashe Metamorphic Suite (AMS) in northwestern North Carolina contains individual eclogite blocks which were entrained within an amphibolite-facies accretionary wedge. However, garnet inclusions within zircon from AMS amphibolite and amphibolite-facies biotite-hornblende gneiss preserve a record of near-peak eclogite-facies metamorphism. The Raman spectra from these garnet inclusions match a Raman spectrum from garnet inclusion within zircons in AMS eclogite. This indicates garnet inclusions from zircon in AMS amphibolite, biotite-hornblende gneiss, and eclogite have a similar composition forming under comparable P/T conditions. Inclusions in zircon from AMS eclogite include pyrope-rich garnet and omphacite, suggesting that zircon formed at near syn-peak eclogite-facies metamorphism. Therefore, growth of zircon in AMS amphibolite and biotite-hornblende gneiss occurred at near-eclogite facies conditions. These findings provide evidence that AMS eclogite, amphibolite, and biotite-hornblende gneiss once constituted a regional eclogite-facies terrane. This regional eclogite-facies terrane was likely exhumed by either extensional unroofing or slab extrusion.