Structure and metamorphism of the McPartlan Pass - Sentinels area

Abstract

Low metamorphic grade Precambrian quartzites and phyllites of the Mc. Partlan Pass Sentinels area have been subjected to polyphase deformation and polyphase metamorphism. The earliest recognizable folds are tight to isoclinal and they have a penetrative foliation, with syntectonic mineral growth parallel to their axial surface. F2 folds, which are also tight to isoclinal and nearly coplanar with F1, have an associated S2 crenulation cleavage, with syntectonic mineral growth. The dominant folds in this area are of the third generation and they control the orientation of earlier structures. F3 are tight to close, upright folds in phyllites, and are of more open style in quartzites. They have a moderate to steep north-westerly plunge. The S3 cleavage may be a crenulation cleavage, a fracture cleavage, or a more isotropic foliation. D4 structures occur sporadically throughout the area. EventsD1 to D4 are of probable Precambrian age. The latest structures include two distinct sets of kink bands, which may have been produced during a Palaeozoic orogeny.