rare earth elements in Wyoming

figure 26. Dahllite concretions from the Cretaceous Thermopolis
Shale near the Wyoben bentonite mine, northwest of Greybull.,
A, sample 20121018JC-E. B, interior of a dahllite concretion.
stained vein quartz, mineralized with chalcopyrite,
pyrite, bornite, malachite, and hematite, analyzed
for this report yielded 17.25 ppm (0.50 oz/ton)
gold, 41.3 ppm (1.20 oz/ton) silver, and 2.62
percent copper.
Gold Coin Mine, SW¼ sec. 11, T. 15 N., R. 87
W., Southern Carbon County
63
The Gold Coin mine targeted copper, lead,
gold, and silver mineralization within a 0.3
m (1.0 ft) wide quartz vein (Beeler, 1902;
Hausel, 1997). The vein is concentrated
within a fissure that trends 75˚ and dips to
the south at a high angle (Spencer, 1904).
The vein cuts the regional foliation of the
hosting Late Archean black diorite (Beeler,
1902; Spencer, 1904). A sample of vein
quartz with abundant limonite (possibly replacing
sulfides), galena, chalcopyrite with
chalcocite rims, and minor malachite (Sample
20121203WSGS-B) from the Gold
Coin mine yielded 318 ppm (9.27 oz/ton)
silver, 0.11 ppm (0.003 oz/ton) gold, 0.11
percent copper, and 14.6 percent zinc.
Section 8 Mine, S½SE¼ sec. 8, T. 14 N.,
R. 85 W., Southern Carbon County
The Section 8 mine targeted copper
mineralization hosted in pyritized banded
chert within amphibolite of the Silver
Lake Metavolcanics, though the exact
field relationship between the amphibolite
and chert is unknown. In addition to the
amphibolite, chlorite garnet schist is also
present in the Silver Lake Metavolcanics
in the vicinity of the Section 8 mine. The
banded chert has a trend of 81˚ and dips
52˚ SE. Mineralization is concordant with the local
banding in the chert. A sample from the mine
yielded 2.61 percent copper but no detectable gold
(Hausel, 1986; 1997); no silver was reported. A
sample of pyrite- and chalcopyrite-bearing banded
chert (Sample 20121203WSGS-D) yielded 27.4
ppm (0.80 oz/ton) silver and 6.75 percent copper.
table 22. Concentration of the REE, P 2 O 5 , uranium, and thorium in dahllite concretions from the Thermopolis Shale
near Greybull. Bold values indicate concentrations greater than five times crustal abundance.
Element La (ppm) Ce (ppm) Pr (ppm)
Wyo-Ben mine dahllite
Nd (ppm) Sm (ppm) Eu (ppm) Gd (ppm) Tb (ppm) Dy (ppm) Ho (ppm)
20121018JC-E 65.4 135 20.1 93.2 24.4 6.32 31.9 4.83 26.7 4.96
Element Er (ppm) Tm (ppm) Yb (ppm) Lu (ppm) Sc (ppm) Y (ppm) Cumulative
REE (ppm)
P O (%) 2 5 U (ppm) Th (ppm)
20121018JC-E 10.8 1.15 5.56 0.72 9 187.5 627.5 33.6 3.75 1.03