|Quadrangle map, 1:250,000-scale||SD|
|Quadrangle map, 1:63,360-scale||D-5|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This altered zone is at an elevation of about 800 feet, about 0.4 mile southwest of the terminus of the Sumdum Glacier. It is about 0.5 mile north-northeast of the center of section 30, T. 47 S., R. 74 E.|
Geologic descriptionThis occurrence is an zone of rusty, siliceous, chlorite schist that is southwest of the toe of the Sumdum Glacier; Brew and Grybeck (1984) assign the schist a Cretaceous metamorphic age. Kimble and others (1984) systematically sampled the zone with a series of 11 samples that extended for 1,150 feet perpendicular to the layering of the metamorphic rocks. All 11 samples contained 0.5 to 1.0 part per million (ppm) silver; 3 contained 15-30 ppm molybdenum, and 2 contained 150-380 ppm zinc. Many of the rocks in the iron-stained zone have sparse disseminated sulfides. The sulfides are mainly pyrrhotite although trace chalcopyrite also occurs. The iron staining is probably due to the weathering of the pyrrhotite.
|Geologic map unit||(-133.488500794609, 57.770685770635)|
|Mineral deposit model||Sparse pyrrhotite and rare chalcopyrite in gneiss.|
|Age of mineralization||Occurs in schist of Cretaceous (metamorphic) age.|
|Alteration of deposit||Iron-staining probably due to weathering of pyrrhotite.|
|Workings or exploration||None beyond sampling by government geologists.|
|Indication of production||None|
Additional commentsThe occurrence is in the Tracy Arm-Fords Terror Wilderness Area which is closed to mineral exploration and mining.
Brew, D.A., and Grybeck, Donald, 1984, Geology of the Tracy Arm-Fords Terror wilderness study area and vicinity, Alaska, in U.S. Geological Survey and U.S. Bureau of Mines, Mineral resources of the Tracy Arm-Fords Terror wilderness study area and vicinity, Alaska: U.S. Geological Survey Bulletin, 1525, p. 19-52.
Kimble, A.L., Still, J.C., and Rataj, J.L., 1984, Mineral deposits and occurrences in the Tracy Arm-Fords Terror wilderness study area and vicinity, Alaska, in U.S. Geological Survey and U.S. Bureau of Mines, Mineral resources of the Tracy Arm-Fords Terror wilderness study area and vicinity, Alaska: U.S. Geological Survey Bulletin 1525, p. 105-210.
|Reporters||Donald Grybeck (U.S. Geological Survey)|
|Last report date||10/8/2004|