P-T ESTIMATES OF “RETROGRESSED ECLOGITES” IN THE EASTERN BLUE RIDGE
Using the CAMECA SXFive EMPA at the American Museum of Natural History (New York), X-ray maps and quantified profiles were obtained on thin sections from both sites and processed using XMapTools 3.4.1 (Lanari et al., 2014). Application of the Zr-in-rutile thermometry model established by Ferry & Watson (2007) generated the following temperature estimates: In three samples from Bakersville, rutile inclusions in garnet yield prograde temperatures of 625-630°C, while rutile grains in the matrix recorded peak temperatures of 700-720°C. Two samples from Boone contain some rutile grains mostly at the edge of garnet and in the matrix that both yield temperatures of 600-620°C.
These preliminary results allow for refinement of the previous estimates obtained using mineral equilibrium on Bakersville samples, as rutile in garnet crystallized during prograde path at ~630°C (previously estimated at 400-680°C) and matrix rutile during peak metamorphism at 700-720°C (previously estimated at 600-800°C). Previous estimates for Boone peak metamorphism are approximately 720°C based on re-integrated omphacite. Our results for rutile included in garnet are significantly lower at 600-620°C, which may indicate that rutile crystallized during prograde path.