Abstract

Textural studies and detailed field mapping in the Brevard–Poor Mountain belt in northwestern South Carolina indicate that this zone experienced at least two periods of polyphase deformation and metamorphism. The first deformation, F1, produced sheared-out isoclinal folds. Progressive metamorphism, M1a, in the almandine-amphibolite facies accompanied F1, as did dislocation metamorphism, M1b, and retrogressive metamorphism, M1c, produced by the attenuation and shearing out (tectonic slides) of the isoclines.

A second deformation, F2, nearly coplanar and coaxial with F1, also was accompanied by polyphase metamorphism, M2. The first phase of this metamorphism, M2a, was progressive, attaining the upper greenschist or greenschist-amphibolite facies. Dislocation metamorphism, M2b, and retrogressive metamorphism, M2c, occurred during the waning stage of F2 deformation.

Tentatively, we correlate F1 and M1 with the Taconic orogeny and F2 and M2 with the Acadian orogeny. All aspects of F1, M1 are more intense than F2, M2, indicating that Ordovician tectonism was the most important diastrophism affecting this portion of the Brevard's development.

A third retrogressive metamorphism, M3(?), is proposed but the evidence is not conclusive. The distribution and structural relations of this third phase of retrogressive metamorphism suggest that it is probably mainly related to late Paleozoic faulting.

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