Petrography and Geochemistry of the Crawfish Inlet and Krestof Island Plutons, Baranof Island, Alaska

The Sanak-Baranof plutonic belt (SBPB) includes a series of biotite tonalite, granodiorite, and granite neartrench plutons that intrude the Campanian to Eocene flysch of the Chugach-Prince William terrane (CPW) for 2100 km along the southern Alaskan margin (Hudson et al., 1979; Hill et al., 1981; Bradley et al., 2003; Haeussler et al., 2003). SBPB intrusions have been interpreted to be the result of subduction of the Kula-Farallon or Kula-Resurrection spreading ridge at a trench-ridge-trench triple junction (Bradley et al., 2003; Haeussler et al., 2003; Cowan, 2003). The Crawfish Inlet and Krestof Island plutons, located on Baranof Island, have long been considered part of the SBPB (Hudson et al., 1979, Bradley et al., 2003 and references therein). In this study I use petrologic and geochemical data to evaluate the relationship between the Crawfish Inlet and Krestof Island plutons to other igneous rocks of the SBPB and coeval plutons of the northern Coast Plutonic Complex (located ~200 km southeast of Baranof Island). I also use the data to evaluate the petrogenesis of magmas emplaced as enclaves into these host plutons.