|Quadrangle map, 1:250,000-scale||CR|
|Quadrangle map, 1:63,360-scale||B-3|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This occurrence is in an outcrop on the east side of the Hydaburg road at the bridge over locally-named Cable Creek. It is near the center of the NW1/4 section 20, T. 75 S., R. 83 E.|
Geologic descriptionThis mineralization, at a roadside outcrop, has been known since at least the 1980s, when industry was searching for volcanogenic massive-sulfide deposits and staked claims throughout the area. The outcrop consists of about 200 feet of chlorite-quartz schist and sericite-quartz schist, possibly derived from a felsic volcanic protolith. The rocks are part of the Wales Group of Late Proterozoic and Cambrian age (Eberlein and others, 1983; Brew, 1996). Locally, the rocks contain chalcopyrite, sphalerite, and up to 20 percent pyrite; there is minor copper staining. Grab samples of the sulfide-rich layers contained up to 1 part per million (ppm) silver, 2,000 ppm copper, and 500 ppm zinc (D.J. Grybeck, unpublished analyses, 1991). A selected sample collected by Maas and others (1995) contained 2.5 percent copper, 1.0 percent zinc, 790 parts per billion gold, and 11.6 ppm silver. They conclude that while the mineralization at this outcrop is limited in extent, it suggests the potential for volcanogenic massive sulfide deposits nearby in Wales Group rocks.
|Geologic map unit||(-132.839673566314, 55.3535679390007)|
|Mineral deposit model||Probably a Kuroko massive sulfide deposit (Cox and Singer, 1986; model 28a).|
|Mineral deposit model number||28a|
|Age of mineralization||A volcanogenic massive-sulfide deposit in Cambrian or older rocks.|
|Workings or exploration||This roadside outcrop has been sampled several times by government and industry geologists since at least the 1980s.|
|Indication of production||None|
Brew, D.A., 1996, Geologic map of the Craig, Dixon Entrance, and parts of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2319, 53 p., 1 sheet, scale 1:250,000.
Eberlein, G.D., Churkin, Michael, Jr., Carter, Claire, Berg, H.C., and Ovenshine, A. T., 1983, Geology of the Craig quadrangle, Alaska: U.S. Geological Survey Open-File Report 83-91, 52 p.
|Reporters||D.J. Grybeck (Applied Geology)|
|Last report date||5/1/2004|