Unnamed (near Mallard Bay) (ARDF #DE042) Au, Ce, Cu, La, U

Unnamed (near Mallard Bay)

Occurrence, Probably inactive

Commodities and mineralogy

Main commodities	Au; Ce; Cu; La; U
Other commodities	Y; Zn
Ore minerals	chalcopyrite; monazite; ree minerals
Gangue minerals	chlorite; clay minerals; hematite; quartz

Geographic location

Quadrangle map, 1:250,000-scale	DE
Quadrangle map, 1:63,360-scale	D-1
Latitude	54.7713
Longitude	-132.0094
Nearby scientific data	Find additional scientific data near this location
Location and accuracy	This occurrence is about 0.3 mile north of the northwest head of Stone Rock Bay, in the NW1/4 SW1/4 section 8, T. 82 S., R. 90 E.

Geologic setting

Geologic description The only work at this prospect is a few small pits on several claims. A network of quartz-hematite veins occurs in radioactive, altered andesite(?) dikes that cut Silurian or Ordovician syenite (MacKevett, 1963; Gehrels, 1992). The dikes are largely altered to chlorite and clay minerals and are cut by late-stage calcite veinlets that lack any radioactive minerals. Maas and others (1991) speculatively identified monazite in the quartz-hematite veinlets. They collected several samples of the dikes and syenite that contained up to 132 parts per billion gold, 0.27 percent copper, 331 parts per million (ppm) zinc, 1,080 ppm uranium, 1.44 percent cerium, 0.723 percent lanthanum, and 54 ppm yttrium. A sample nearby of silicified syenite with disseminated chalcopyrite contained 229 to 402 ppb gold and 3,162 to 6,206 ppm copper.
Geologic map unit	(-132.011073300095, 54.7709579894708)
Mineral deposit model	U-REE-bearing dikes.
Alteration of deposit	The radioactive dikes are almost completely altered to chlorite and clay minerals. Syenite nearby is silicified.

Production and reserves

Workings or exploration	Only a few small prospecting pits.
Indication of production	None

References

References Cobb, E. H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Dixon Entrance quadrangle, Alaska: U.S. Geological Survey Open-File Report 78-863, 34 p. Eakins, G.R., 1975, Uranium investigations in southeastern Alaska: Alaska Division of Geological and Geophysical Surveys Geologic Report 44, 62 p. Gehrels, G. E., 1992, Geologic map of southern Prince of Wales Island, southeastern Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map I-2169, 23 p., 1 sheet, scale 1:63,360. Maas, K.M., Bittenbender, P E., and Still, J.C., 1995, Mineral investigations in the Ketchikan mining district, southeastern Alaska: U.S. Bureau of Mines Open-File Report 11-95, 606 p. Maas, K.M., Still, J.C., Clough, A.H., and Oliver, L.K., 1991, Mineral investigations in the Ketchikan mining district, Alaska, 1990: southern Prince of Wales Island and vicinity: U.S. Bureau of Mines Open-File Report 33-91, 139 p., 12 sheets, scale 1:63,360. MacKevett, E.M., Jr., 1963, Geology and ore deposits of the Bokan Mountain uranium-thorium area, southeastern Alaska: U.S. Geological Survey Bulletin 1154, 125 p.
Reporters	D.J. Grybeck (Applied Geology)
Last report date	9/1/2003