Petrology of the Duke Island Ultramafic Complex Southeastern Alaska

Duke Island, with an area of about 60 sq. mi., is situated on the North American Pacific Coast at latitude 55° N. The ultramafic complex exposed on the island is the southernmost of some thirty distinctive ultramafic bodies of Early Cretaceous age distributed along the 350-mi. length of southeastern Alaska. A similar belt of corresponding bodies occurs in the Ural Mountain; there are at least two complexes of the same type in British Columbia, a possible occurrence in California, and two in Venezuela.