|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||The location of the Marble Heart prospect is uncertain. The primary and almost only description of it is by Brooks (1902). Herreid and Rose (1966) place it just outside the area they mapped. The Herreid and Rose location used for this record is about 1.8 miles south of the head of Twelvemile Arm and about 0.2 mile west of the center of section 36, T. 75 S., R. 83 E.|
Geologic descriptionAs described by Brooks (1902), the Marble Heart prospect consists of a small vein of galena in intensely folded and metamorphosed limestone. The limestone is part of the Wales Group of Cambrian and older age (Eberlein and others, 1983; Brew, 1996). The workings consist of a shaft about 20 feet deep and a short adit.
|Geologic map unit||(-132.734138319402, 55.322097772646)|
|Mineral deposit model||Galena vein in limestone.|
|Age of mineralization||Galena vein in limestone of Cambrian or older age.|
|Workings or exploration||The workings consist of a shaft about 20 feet deep and a short adit.|
|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.
Brooks, A.H., 1902, Preliminary report on the Ketchikan mining district, Alaska, with an introductory sketch of the geology of southeastern Alaska: U.S. Geological Survey Professional Paper 1, 120 p.
Cobb, E. H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Craig quadrangle, Alaska: U.S. Geological Survey Open-File Report 78-869, 262 p.
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|