Geologic description
Patton and others (1977) describe the rocks in the area of these occurrences as Permian to Jurassic, spilitic basalt and diabase largely metamorphosed to greenstone, and Lower Cretaceous, massive, poorly-sorted conglomerate with pebble- to cobble-size clasts, chiefly of mafic igneous rocks and chert. Dillon and others (1983) describe the rocks as greenschist-grade, lower Mesozoic and upper Paleozoic basalt, diabase, hornblende gabbro, and basaltic volcaniclastic rocks. The dominant rock type at the occurrences is meta-basalt (greenstone). Small bodies of medium-grained biotite granite, aplite, pegmatite, and leucocratic granite also crop out in the area. The granitic rocks are assumed to be Lower Cretaceous in age based on a K-Ar date of 111+/- 3 Ma on biotite from the Melozitna pluton which is probably related to the granitic rocks at this site (Patton and others, 1977). The Alaska Division of Geological & Geophysical Surveys collected 8 rock samples and a panned-concentrate sample in and near the area of these occurrences (Solie and others, 1993 [Public-data file 93-18]). Two float samples of greenstone or gabbro with sulfides contained up to 64 parts per million (ppm) bismuth, 252 ppm copper, 1,467 ppm manganese, 94 ppm tin, 43 ppm tellurium, 452 ppm vanadium, and 133 ppm zinc. Bedrock samples included layered mafic rock with probable chromite; basalt with sparse chalcopyrite and malachite; magnetite-bearing pyroxene-plagioclase gabbro; gabbro with whitish veins; and ultramafic rock. These samples contained up to 1.3 ppm silver, 10 parts per billion (ppb) gold, 73 ppm bismuth, 1,491 ppm chromium, 930 ppm copper, 20 ppb palladium, 20 ppb platinum, 64 ppm tin, 45 ppm tellurium, 966 ppm vanadium, and 113 ppm zinc. |
