Sheath fold in charnockite around Nekkanamalai, Vellore District, Tamil Nadu

A sheath fold with inverted hinge is recorded within the charnockite expose d around Nekkanamalai in the Southern Cranulite Terrain. The area lies with in the NNE-trending Gudiyatham-Bhavani Straight Belt (GBSB) bounded on eith er side by two distinctly different tectono-stratigraphic terranes brought into juxtaposition along major tectonic contacts. Such folds are known in r egions of re-folding, with later folding events of high intensity at high a ngles to the earlier folds, as well as in sheer zones, where the direction of shear is subparallel to the sheath axes. The sheath fold in the area is interpreted to be due to superposed folding resulting from the complicated pattern of deformation produced during the welding of different terranes al ong the GBSB, which had brought about not only plunge reversals but also pl unge inversion of the earlier folds.