| Abstrakt: |
The Ashe Metamorphic Suite (AMS) in the Blue Ridge Mountains of North Carolina, Virginia, and Georgia represents a metamorphosed and deformed ophiolite, which was accreted onto Laurentia during the Taconic orogeny. Small tabular or lensoid bodies of ultramafic rocks within the AMS contain a range of mineral assemblages due to varying protoliths and metamorphic assemblages. Here, we present detailed geologic mapping, petrography, and whole-rock geochemistry of the two largest ultramafic bodies near the North Carolina-Virginia border, the Todd and Edmonds ultramafic bodies. These enigmatic rocks help to understand at finer granularity the orogenic events that assembled the Appalachian Mountains. Our mapping in this study revises the boundaries of the Todd body: rather than a large, single body of ultramafic rock, the Todd body is broken into at least two more tabular slices with quartzofeldspathic gneisses between them. Both ultramafic bodies contain coarse-grained (1-1.5 cm) olivine, which is interpreted as part of the original assemblage. The Todd body contains anthophyllite-bearing assemblages, indicating temperatures of 650-750 °C. Microstructural relationships indicate that the fabric-forming anthophyllite event was overprinted by a post-deformational tremolite-talc-bearing assemblage. The Edmonds body, farther to the northeast, contains evidence of dynamic recrystallization of olivine, overprinted by syn- and post-deformational tremolite- and talc-bearing assemblages indicating temperatures between 500-650 °C. These conditions indicate differential heating during the M3 amphibolite-facies metamorphic event that likely accompanied Acadian deformation. This work builds upon and confirms the findings of Raymond and others (2016). [ABSTRACT FROM AUTHOR] |
