Geologic description
This occurrence consists of sulfide-bearing copper-stained fine-grained andesite of the Slana Spur Formation of Pennsylvanian age. The sulfide pods and sulfide-bearing quartz veins cutting the andesite contain pyrite and chalcopyrite (W.T. Ellis, oral communication, 2001). Airborne magnetic data suggest that the area may also be underlain by a southeast extension of the the Rainy ultramafic-mafic intrusion of Late Triassic age (see MH164). Samples of quartz veins and semimassive sulfide pods contain as much as 0.73 percent copper and 4.3 ppm silver. The Rainy ultramafic-mafic complex is a steeply north dipping tabular intrusion of dunite, peridotite, and gabbro that varies from less than 100 feet thick to more than 6,000 feet thick and extends for more than 12 miles in length (W.T. Ellis, oral communication, 2001). Discontinuous marginal gabbro extends along most of the southern (lower) contact and is less continuous along the northern (upper) contact. The complex intrudes the Slana Spur Formation of Pennsylvanian age (Nokleberg and others, 1991). Magmatic mineralization is synchronous with emplacement of the Rainy complex, which is part of a 120-mile-long belt of mafic-ultramafic and associated rocks in the east-central Alaska Range. |
