Canadian Mineralogist

ABSTRAcT The metarnorphism of the small, early Tertiary Finger Bay pluton on Adak Island in the central Aleutians occur-red under low pressure (<3 kbar) and subgreenschist-to-greenschist facies conditions (325-400"C); it is similar to that of other Aleutian early-stage arc rocks. The primary cause of metamorphism was a hydrothermal circulation of meteoric water associated with later magmatic activity, rather than a separate discrete event such as oceanic-ridge subduction. On all scales, the intensity of metamorphic recrystallization correlates with the proximity of fracture zones. Variable assemblages and compositions of metamor-phic minerals, both within and between samples, and the maintenance of igneous whole-rock compositions, suggest only a very local redistribution of elements, consistent wit