|Quadrangle map, 1:250,000-scale||AN|
|Quadrangle map, 1:63,360-scale||D-2|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||Near upper reaches of Glacial Fan Creek, southern flank of Sheep Mountain, 3,300 ft south of VABM Gun. Accurate within 1.5 miles. Locality 48 of Cobb (1972) and locality 37 of MacKevett and Holloway (1977).|
Early Jurassic greenstone and minor interbedded sandstone and shale is intruded by numerous mafic dikes and at least one body of unmineralized Jurassic granite. Greenstone has been hydrothermally altered and contains at least 6 separate gypsiferous deposits in altered zones along joints and shear zones. Deposits composed of pods and stringers of gypsum, quartz, alunite, kaolin minerals, pyrite and serpentine minerals (Eckhart, 1953). The gypsum-bearing material averages 25 to 30 percent gypsum, with a maximum of 50 percent.In addition also reported from same general area are: (1) small irregular quartz-calcite-epidote veins in greenstone containing chalcopyrite, malachite, azurite and possibly bornite and chalcocite (Berg and Cobb, 1967); (2) disseminated chalcopyrite in greenstone over 5 ft thick zone subparallel to bedding (Martin and Mertie, 1914); (3) trace gold in samples of pyritic greenstone (Berg and Cobb, 1967); and (4) minor anomalous concentrations of copper and gold associated with some of the alteration zones and nearby veins (MacKevett and Holloway, 1977).
|Geologic map unit||(-147.472196878459, 61.8394867733951)|
|Age of mineralization||Jurassic or younger; mineralization hosted by an Early Jurassic greenstone.|
|Alteration of deposit||Large area of south flank of Sheep Mountain is strained dark red from oxidation of pyrite in greenstone (Berg and Cobb, 1967). Oxidation of Cu minerals.|
|Workings or exploration||The gypsiferous material averages 25 to 30 percent gypsum, with a maximum of 50 percent. The six deposits indicated and inferred reserves contain about 659,000 short tons of gypsum material, of which about 50 tons of this material had been mined (Eckhart, 1953). In addition, about 55 tons of clay was mined for the manufacture of fire brick and boiler lining. Samples of pyritic greenstone assayed trace gold (Berg and Cobb, 1967), and nearby veins in alteration zones show concentrations of copper and gold (MacKevett and Holloway, 1977).|
|Indication of production||Yes; small|
|Reserve estimates||The six deposits indicated and inferred reserves contain about 659,000 short tons of gypsum material (Eckhart, 1953).|
|Production notes||About 50 tons of gypsum had been mined (Eckhart, 1953). In addition, about 55 tons of clay was mined for the manufacture of fire brick and boiler lining.|
Berg, H.C., and Cobb, E.H., 1967, Metalliferous lode deposits of Alaska: U.S. Geological Survey Bulletin 1246, 254 p.
Brooks, A.H., 1913, Mineral resources of Alaska, report on progress of investigations in 1912: U.S. Geological Survey Bulletin 542, 308 p.
|Reporters||D.P. Bickerstaff (USGS contractor); S.W. Huss (USGS)|
|Last report date||7/30/1998|