Carol Ann; Carol Ann No. 1; Carol Ann No. 2; Carol Ann No 3; Dotson Prospects, Bokan Mountain, Prince of Wales Island, Ketchikan Mining District, Prince of Wales-Hyder Census Area, Alaska, USAi

Regional Level Types
Carol Ann; Carol Ann No. 1; Carol Ann No. 2; Carol Ann No 3; Dotson Prospects	Group of Prospects
Bokan Mountain	Mountain
Prince of Wales Island	Island
Ketchikan Mining District	Mining District
Prince of Wales-Hyder Census Area	Census Area
Alaska	State
USA	Country

Location: The three Carol Ann prospects are associated with a series of parallel mineralized dikes that extend about N45W for at least 3,000 feet. The coordinates are at near the center of the prospect area, about 1.9 miles southeast of Bokan Mountain, near the middle of the N1/2 section 26, T. 80 S., R. 88 E. The locations of the Carol Ann prospects relative to the other uranium and REE prospects in the vicinity of Bokan Mountain are best shown on Plate 1 of MacKevett (1963).
Geology: This and several other nearby uranium-thorium-REE deposits (DE015 to DE026 and DE028 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 peralkakline 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. MacKevett (1963) describes three prospects under the name Carol Ann as surface pits on three claims located in 1955. The prospects are on a series of steep, subparallel, allanite-bearing andesite dikes that strike about N60-75W for at least 3,500 feet. The dikes radiate out from the Bokan Mountain peralkaline granite into Silurian or Ordovician quartz monzonite. Warner and Barker (1989) describes these prospects under the name Dotson and extend the dikes northwest to the I & L Nos. 3-5 prospects (DE023) at the periphery of the Bokan Mountain alkaline granite. Several parallel dikes occur over a width of less than 100 feet to 200 feet; the individual dikes vary in width from 0.6 feet to 3.1 feet. To northwest, near the Bokan Mountain granite, the dikes are pegmatitic; to the southeast, they generally are medium- to fine-grained and equigranular. The mineralization occurs in microfractures or in the interstices between silicate grains. The dominant radioactive mineral is allanite. Scanning electron microscope study shows that the REE minerals are mainly thalenite, bastnaesite, and allanite, with subordinate tengerite, parisite, synchysite, an unnamed REE flurocarbonate mineral, monazite, and xenotime. The columbium-bearing mineral is mainly euxenite-polycrase, accompanied by subordinate columbite-tantalite, samarskite, fergusonite, and aeschynite. The main radioactive mineral is thorite but uranothorite is also present. Warner and Barker (1989) estimate a total indicated resource of 2,039,000 short tons of rock in the Dotson dike system that contains 2,353,000 pounds of columbium, 326,000 pounds of uranium, 3,666,000 pounds of yttrium, 2,541,000 pounds of thorium, and 4,567,000 pounds of REE. The total inferred resource is 8,490,000 short tons of rock that contains 12,260,000 pounds of columbium, 7,726,000 pounds of thorium, 1,647,000 pounds of uranium, 18,457,000 pounds of yttrium, 33,280,000 pounds of zirconium, and 30,428,000 pounds of REE.
Workings: Only prospect pits.
Age: Genetically related to the Jurassic, Bokan Mountain peralkaline granite.
Alteration: These prospects 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.
Reserves: Warner and Barker (1989) estimate a total indicated resource of 2,039,000 short tons of rock in the Dotson dike system that contains 2,353,000 pounds of columbium, 326,000 pounds of uranium, 3,666,000 pounds of yttrium, 2,541,000 pounds of thorium, and 4,567, 000 pounds of REE. The total inferred resource is 8,490,000 short tons of rock that contains 12,260,000 pounds of columbium, 7,726,000 pounds of thorium, 1,647,000 pounds of uranium, 18,457,000 pounds of yttrium, 33,280,000 pounds of zirconium, and 30,428,000 pounds of REE.

Commodities (Major) - Cb, REE, Th, U, Y
Deposit Model: U-Th-REE deposit associated with peralkaline granite.

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Link to USGS - Alaska:	DE027

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References