rare earth elements in Wyoming

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Precambrian rocks in the Bald Mountain area are not known to host significant precious metal deposits. However gold paleoplacers within the Flathead conglomerates attracted attention around 1900. The town of Bald Mountain sprang to life for less than a year and then was abandoned when gold values proved insufficient to support commercial mining (McKinney and Horst, 1953; Hausel, 1989). The last gold operation in the area of any size was a mill and jig operation working in disintegrated sandstone and granite, about 3.2 km (2 mi) west of the Bald Mountain townsite in 1903 (McKinney and Horst, 1953). Paleoplacers in the Bald Mountain area occur in the basal part of the Middle Cambrian Flathead Sandstone, near its contact with Precambrian rocks. Gold in the basal Flathead Sandstone in the Bald Mountain area occurs as fine-grained, flat flakes with jagged edges that suggest a nearby source. The paleoplacer gold is accompanied by other heavy minerals, including ilmenite, magnetite, zircon, and monazite. The monazite attracted interest as a source for thorium in 1951 (Wilson, 1951; McKinney and Horst, 1953; Hausel, 1989; King and Harris, 2002). Heavy mineral concentrates from some of the higher grade samples contained 38.3 percent ilmenite, 8.7 percent monazite, 4.0 percent magnetite, 0.2 percent zircon, and 48.8 percent other impurities (McKinney and Horst, 1953). Monazite occurs as reddish-brown grains, up to a few millimeters across, within a limonitic matrix of the basal quartz pebble conglomerate. The dense sandstones overlying the basal conglomerate also host notable monazite, but at much lower concentrations than the basal conglomerate (Wilson, 1951). The entire Flathead Sandstone contains some monazite, but significant concentrations are limited to the lower part. Monazite concentrations within the basal Flathead are highly variable laterally, ranging from trace amounts of scattered grains to more than 9.5 kg/tonne (19 lbs/ton). Greater amounts of monazite are generally associated with poorly cemented areas, an abundance of large quartz pebbles, and with a deep yellowish-red color resulting from the strong presence of hematite or limonite (McKinney and Horst, 1953). The USBM drilled 92 exploration holes in 1952 to test the monazite-bearing conglomerates (fig. 15). Drilling totaled 615.7 m (2,020 ft) from which 24,140 kg (53,214 lbs) of samples were collected for analyses. Depth of drilling was limited by the underlying Precambrian basement. The deepest hole was 14.8 m (48.5 ft), but the average depth was only 6.7 m (22 ft). Some holes were essentially barren, but numerous holes in the area east of Rooster Hill encountered higher-grade, monaziteenriched zones at more than one horizon, with apparent gradations between them. This reinforced the concept of a three-dimensional braided stream depositional environment. From drilling, the USBM estimated a resource of 18 million tonnes (20 million tons) that averaged 1.25 kg/tonne (2.5 lbs/ton) of monazite (McKinney and Horst, 1953; Borrowman and Rosenbaum, 1962). A high-grade zone was estimated to contain 612,000 tonnes (675,000 tons) of conglomerate that averaged 6.6 kg/tonne (13.2 lbs/ton) of monazite (Borrowman and Rosenbaum, 1962). The average chemical assay value for pure monazite showed 8.8 percent ThO 2 and 0.12 percent U 3 O 8 . Gold assays taken from six drill holes in the high-grade monazite area varied from 0.034 to 0.172 ppm (0.001 to 0.005 oz/ton), and averaged 0.103 ppm (0.003 oz/ton) (McKinney and Horst, 1953; Hausel, 1989). Ilmenite, which accounted for as much as 38.3 percent of concentrates from higher-grade portions of the deposit, was suggested by Wilson (1951) and by McKinney and Horst (1953) as providing additional economic potential for the paleoplacers. Although no analyses were noted for REE in any of the early reports, McKinney and Horst (1953, p. 30) stated that economic conditions at the time “based solely on the rare-earth content of monazite would not allow a commercial stripping operation, such an operation could rapidly produce a significant amount of monazite and, therefore, thorium. It is believed that this deposit could be of definite strategic value.” They later mentioned on page 41 that the market price for monazite, at the time their report was written, “…was approximately $375.00 per ton and based solely on the rare-earth 42
43 figure 15. Locations of 1952 USBM drill holes and WSGS Bald Mountain and Rooster Hill samples. Drill data shows maximum grades in pounds of monazite per ton, after McKinney and Horst, 1953. WSGS samples show total REE in ppm. Blue numbers indicate greater than five times average crustal ppm values. Geology modified from Cardinal (1958) and Love and Christiansen (1985).
Page 1 and 2: are earth elements in Wyoming Wayne
Page 3: Rare Earth Elements in Wyoming Wyom
Page 6 and 7: Deacon’s Prayer Group Claims . .
Page 9 and 10: AbstrAct Rare earth elements (REE)
Page 11 and 12: Wyo-DOG is a multi-tiered applicati
Page 13 and 14: neodymium-145 through electron capt
Page 15 and 16: ability and economic factors, inclu
Page 17 and 18: Gosen, Foley, and Cordier, 2010). T
Page 19 and 20: Extraction of rEE Aside from genera
Page 21 and 22: diorites, and their associated pegm
Page 23 and 24: REE deposit in Wyoming and is curre
Page 25 and 26: 17 figure 1. Locations of samples c
Page 27 and 28: accessory aegirine, apatite, stront
Page 29 and 30: Precambrian occurrences Precambrian
Page 31 and 32: 23 figure 5. Sample locations and g
Page 33 and 34: table 6. Concentration of the REE,
Page 35 and 36: the Tie Siding pegmatites. The alte
Page 37 and 38: coarse-grained granite (QAP: 30% Q,
Page 39 and 40: lbs) for 1957 and 450 kg (1,000 lbs
Page 41 and 42: granite to granodiorite with rapaki
Page 43 and 44: 35 figure 10. Sample locations and
Page 45 and 46: table 10. Concentration of the REE,
Page 47 and 48: tertiary-aged Igneous occurrences L
Page 49: downstream from older REE mineral c
Page 53 and 54: samples 20110824WS-C and 20110824WS
Page 55 and 56: Samples of the Flathead were collec
Page 57 and 58: tourmaline, amphibole, spinel, sphe
Page 59 and 60: Mud creek, nW¼nE¼ sec. 19, t. 44
Page 61 and 62: figure 20. Sample locations and geo
Page 63 and 64: interaction between oxidized ground
Page 65 and 66: distinct horizons (plus one unit wi
Page 67 and 68: figure 22. Sample locations and lit
Page 69 and 70: 1977; Love, 1984). REE concentratio
Page 71 and 72: figure 26. Dahllite concretions fro
Page 73 and 74: Moonstone Formation Reefs, SW¼SE¼
Page 75 and 76: EfErEncEs Adams, J.W., Arengi, J.T.
Page 77 and 78: logical Survey of Wyoming [Wyoming
Page 79 and 80: Love, J.D., 1964, Uraniferous phosp
Page 81 and 82: Saywell, T., 2011, Molycorp’s Mou
Page 83 and 84: IndEx A Abandoned Mine Lands 2 acmi
Page 85 and 86: f fergusonite 12, 13, 33 Ferris Mou
Page 87 and 88: monazite 1, 11, 12, 13, 14, 15, 18,
Page 89 and 90: strontianite 18, 19 Stump Formation
Page 91: notes

rare earth elements in Wyoming

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