Sunday Lake

Prospect, Active

Commodities and mineralogy

Main commodities Cb; Ce; Dy; Er; Eu; Gd; Ho; La; Lu; Nd; Pm; Pr; Sm; Tb; Th; Tm; U; Y; Yb; Zr
Ore minerals allanite; ree minerals

Geographic location

Quadrangle map, 1:250,000-scale DE
Quadrangle map, 1:63,360-scale D-1
Latitude 54.9295
Longitude -132.1724
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Sunday Lake prospect is at an elevation of about 750 feet, about 1.2 miles northwest of Bokan Mountain and about 0.7 mile east-southeast of the center of section 17, T. 80 S., R. 88 E. Its location relative to the other uranium and REE prospects in the vicinity of Bokan Mountain is best shown on Plate 1 of MacKevett (1963).

Geologic setting

Geologic description

This and several other nearby uranium-thorium-REE deposits (DE015, DE016, and DE18 to DE031) are spatially and genetically related to a stock of Jurassic, peralkaline granite about 2 miles in outcrop diameter centered on Bokan Mountain. It commonly is referred to as the Bokan Mountain peralkaline granite or Bokan Mountain complex. The intrusion and its deposits have been mapped in detail several times using slightly different subdivisions of the granite (MacKevett, 1963; Thompson and others, 1980, 1982; Saint-Andre and others, 1983; Gehrels, 1992; Thompson, 1997). This description largely follows Gehrels' (1992) map units. The intrusion is a ring-dike complex with an outer border zone up to 14 meters thick of pegmatite and aplite; a nearly complete intermediate zone of aegirine granite porphyry, 15 to 180 meters thick; and a core of several varieties of riebeckite granite porphyry. It has been dated by several methods at 151 Ma to 191 Ma (Lanphere and others, 1964; Saint-Andre and others, 1983; Armstrong, 1985; Gehrels, 1992; Thompson, 1997). The peralkaline granite mainly intrudes a regionally extensive body of Silurian or Ordovician quartz monzonite, granite, and quartz diorite that makes up much of the southeast tip of Prince of Wales Island. The south and west sides of the peralkaline granite are in contact with a band up to about 3,000 feet wide of shale and argillite of the Silurian or Ordovician Descon Formation. The Bokan Mountain complex and surrounding Paleozoic rocks are cut by numerous pegmatite, andesite, dacite, and aplite dikes. The dikes are genetically related to the complex and commonly are associated with the uranium, thorium, and REE deposits. The deposits are marked by intense albitization, pervasive or fracture-controlled chloritization, calcite-fluorite replacement of aegirine, and hematitization. Three types of U-Th-REE deposits occur in the Bokan Mountain complex: 1) irregular cylindrical pipes; 2) steep, shear-zone-related pods or lenses ('veins'); and 3) quartz veins.
The Sunday Lake prospect has been explored by two short trenches and a small pit (Warner and Barker, 1989), and three holes were drilled in the fall of 2009 (Ucore Uranium, 2009b). The deposit is controlled by steeply dipping, north-northwest-trending shear zones and fractures which can be traced for about 300 feet in riebeckite granite. Allanite is locally abundant. Where exposed, the deposit is 3 to 7 feet thick and consists of highly radioactive, mottled, iron- and manganese-stained gouge and crushed rock.
In 2009, Ucore Uranium announced that samples taken at or near this prospect contained a significant content of heavy and light rare-earth elements (Ucore Uranium, 2009a). The analyses of the samples were reported as the light rare-earth-element oxides or LREO (lanthanum, cerium, praseodymium, neodymium, and samarium) and the heavy rare-earth-element oxides or HREO (europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and yttrium); together they are termed the TREO, the total rare-earth-element oxides. The two samples contained 7.19 and 0.37 percent HREO and 2.39 and 15.17 percent HREO. The analyses indicate that nearly all of the rare-earth-element oxides are the heavy rare-earth-element oxides. By early fall of 2009, two of the three Ucore holes cut high grade intercepts of rare-element minerals (Ucore Uranium, 2009b). The notable intercepts were 4.80 meters with 0.10 percent LREO and 1.93 percent HREO, 0.80 meters with 0.13 percent LREO and 3.82 percent HREO, and 1.72 meters with 0.07 percent LREO and 0.81 percent HREO. In other words, 92 to 97 percent of the rare-earth-element oxides were the heavy rare-earth-element oxides.
According to Warner and Barker (1989), the deposit has an inferred resource of 27,000 short tons of material that contains 26,000 pounds of columbium, 1,728,000 pounds of thorium, 270,000 pounds of uranium, 437,000 pounds of yttrium, 151,000 pounds of zirconium.
Geologic map unit (-132.174043405956, 54.9291582806978)
Mineral deposit model U-Th-REE deposit associated with peralkaline granite.
Age of mineralization Genetically related to the Jurassic, Bokan Mountain peralkaline granite stock.
Alteration of deposit This prospect and the other uranium, thorium, and REE deposits associated with the Bokan Mountain peralkaline granite are marked by albitization, chloritization, and argillization. Minor calcite, fluorite, quartz, sulfide minerals, and tourmaline are common in the altered rocks and hematite often occurs in the periphery of high-grade ore zones.

Production and reserves

Workings or exploration Two short trenches and a small prospect pit to 2008. In 2009, Ucore Uranium sampled the prospect and drilled three holes.
Indication of production None
Reserve estimates According to Warner and Barker (1989), the deposit has an inferred resource of 27,000 short tons of material that contains 26,000 pounds of columbium, 1,728,000 pounds of thorium, 270,000 pounds of uranium, 437,000 pounds of yttrium, 151,000 pounds of zirconium.
Production notes None.



Armstrong, R. L., 1985, Rb-Sr dating of the Bokan Mountain granite complex and its country rocks: Canadian Journal of Earth Sciences, v. 22, p. 1233-1236.
Collett, B., 1981, Le granite albitique hyperalcalin de Bokan Mountain, S.E. Alaska et ses mineralisations U-Th. Sa place dans la cordillere canadienne: Doct. 3 degree cycle theseis, Montpellier II University, Montpellier, France, 238 p.
Lanphere, M. A., MacKevett, E. M., and Stern, T. W., 1964, Potassium-argon and lead-alpha ages of plutonic rocks, Bokan Mountain area, Alaska: Science, v. 145, p. 705-707.
Saint-Andre, Bruno de, Lancelot, J. R., and Collot, Bernard, 1983, U-Pb geochronology of the Bokan Mountain peralkaline granite, southeastern Alaska: Canadian Journal of Earth Sciences, v. 20, p. 236-245.
Staatz, M. H., 1978, I and L uranium and thorium vein system, Bokan Mountain, southeastern Alaska: Economic Geology, v.73, p. 512-523.
Thompson, T. B., 1988, Geology and uranium-thorium mineral deposits of the Bokan Mountain granite complex, southeastern Alaska: Fluid Inclusion Research, v. 21, p. 193-210.
Thompson, T.B., 1988, Geology and uranium-thorium mineral deposits of the Bokan Mountain granite complex, southeastern Alaska, in Gabelman, J. W., ed., Unconventional uranium deposits: Ore Geology Reviews, v. 3, p 193-210.
Thompson, T.B., 1997, Uranium, thorium, and rare metal deposits of Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral deposits of Alaska: Economic Geology Monograph 9, p. 466-482.
Thompson, T. B., Lyttle, Thomas, and Pierson, J. R., 1980, Genesis of the Bokan Mountain, Alaska, uranium-thorium deposit: U.S. Department of Energy, Bendix Field Engineering Report GJBX-38(80), 232 p.
Thompson, T. B., Pierson, J. R., and Lyttle, T., 1982, Petrology and petrogenesis of the Bokan granite complex, southeastern Alaska: Geological Society of America Bulletin, v. 93, p. 898-908.
Ucore Uranium, 2009a, Ucore reports 15.6% TREO at new zone, 7% of which are heavy REE's: (News release dated August 20, 2009)
Ucore Uranium, 2009b, Ucore confirms new rare earth discovery at Sunday Lake, intersecting 4.8 meters of 1.8% TREO and 95% heady rare earth content: (News release dated November 30, 2009).
Reporters D.J. Grybeck (Contractor, U.S. Geological Survey)
Last report date 4/2/2010