TESTING THE CHEMICAL FINGERPRINT OF AMPHIBOLITES FROM THE CENTRAL BLUE RIDGE CARTOOGECHAYE AND MARS HILL TERRANES, NC BLUE RIDGE
Major element compositions for these samples are similar to amphibolites previously analyzed from the Webster-Addie-Willets region, and are distinct from amphibolites near the Buck Creek complex (BC has higher Mg, Al and lower Ti). Mineral chemistry results indicate fairly consistent prograde metamorphic assemblages (Hbld+plag+/-Gt+/-ilmenite) . Quartz and apatite are present in the more Si-rich amphibolites, and one sample includes hypersthene, suggesting peak metamorphic conditions that edge into the granulite facies. By contrast, garnet is absent in Buck Creek amphibolites, and titanite is abundant in most samples. Epidote+chlorite retrograde assemblages are similar regionally, and are consistent with regional lower amphibolite to greenschist facies conditions.
REE compositions are similar in pattern and concentration to mafic rocks from the Mars Hill Terrane (Ownby et al, 2004) and from the Webster-Addie region (Soraruf et al, 2002). Most samples are weakly to moderately LREE enriched with chondrite-normalized concentrations between 10-100. REE data from the Buck Creek, Carroll Knob and Lake Chatuge complexes show distinctly lower REE concentrations and are generally LREE depleted.
A mafic sample from the Trimont Ridge complex is distinctly different from all of the other mafic rocks in this study, with a steep REE pattern and Eu anomaly, similar to Western Blue Ridge data of Carrigan et al. (2003).