This prospect is a copper-stained quartz vein about 1 foot thick that cuts fine-grained gabbro and minor pyroxenite. Nearby sparse float of gabbro contains disseminated chalcopyrite and pyrrhotite (Rose, 1966 [ADMM GR 19]). The vein strikes N10W and dips vertically.The rocks are part of the Tangle ultramafic-mafic intrusive complex of Late Triassic age, which may be a lopolithic feeder of the Nikolai greenstone basalt flows of the Wrangellia Terrane (W.T. Ellis, oral communication, 2001). The Tangle complex is a north-dipping layered intrusion of dunite, peridotite, and gabbro that varies from less than 2,000 feet thick to more than 4,000 feet thick and extends for more than 12 miles in length (W.T. Ellis, oral communication, 2001). The complex intrudes the Tangle Formation of Permian age (Nokleberg and others, 1991). It may connect with the Fish Lake complex at depth below the Amphitheater synform. Magmatic mineralization is synchronous with emplacement of Tangle complex, which is part of a 120-mile-long belt of mafic-ultramafic and associated rocks in the east-central Alaska Range.