The history of an eclogite sample and a mica schist sample from the western Teslin zone are discussed in view of garnet zoning profiles. The preliminary metamorphic results support the contention (de Keijzer et al., in press), based on earlier regional and structural arguments, of a structural contact (the "basal thrust" of de Keijzer et al., in press) between the Last Peak eclogite (part of the Anvil assemblage) and metasedimentary rocks of North American affinity to the west of it. Consequently, the eclogite is considered "exotic" with respect to the metasedimentary rocks. The proposed position of the Last Peak eclogite, a few hundred metres above the interpreted basal thrust within the zone of ductile thrusting, explains why it has experienced pervasive amphibolitization (hydration) since fault zones commonly act as conduits for fluid. It is unclear how much of the amphibolite-to-greenschist facies Anvil rocks surrounding the eclogite have experienced earlier high-pressure metamorphism.
