rare earth elements in Wyoming

the Tie Siding pegmatites. The altered pegmatite
(Sample 20121107JC-D) is enriched in all of the
HREE (except europium) and yttrium. It is also
enriched more than five times crustal abundance
in ytterbium and lutetium and contains more than
0.02 percent thorium and nearly 0.03 percent
niobium. The unaltered biotite granite pegmatite
(Sample 20121107JC-F) is enriched in the HREE
(except europium) and yttrium, and contains more
than five time crustal abundance of thulium, ytterbium,
and lutetium; it also contains more than
0.03 percent thorium (table 6, Tie Siding Conc).
Holiday Place Pegmatite, SE¼SW¼ sec. 32, T.
13 N. , R. 71 W., Southern Albany County
Griffin and Warner (1982) found a trace of allanite
here, and reported up to 1,000 ppm lanthanum,
greater than 200 ppm yttrium, 50 ppm niobium,
and 198 ppm cU 3 O 8 . This pegmatite is exposed
figure 7. Allanite collected from the Holiday Place pegmatite. A, closeup
of allanite; the largest sample exhibits a cut face. B, plane-polarized
photomicrograph of the allanite.
27
in a prospect pit in a hill on the east side of Dale
Creek. Background radioactivity near the pit was
about 100 cpm. The pegmatite is similar to pegmatites
#3 and #4, but it lacks the radiating biotite
books and hosts 30 x 60 cm (12 x 24 in) nodules of
allanite (Sample 20121107JC-K) (fig. 7).
The allanite nodules exhibit radioactivity up to
5,000 cpm and are centers for radial fractures that
extend into the surrounding alkali feldspar. The
sampled allanite nodule contains more than 15
percent REE and yttrium, and also contains nearly
0.1 percent uranium and more than 0.5 percent
thorium (table 6). As observed in outcrop, the
nodules appear to account for 1 percent or less of
the entire volume of the pegmatite.
Unnamed Pegmatite, NE¼NW¼ sec. 36, T. 13
N., R. 72 W., Southern Albany County
A granitic pegmatite, not previously mentioned in
the literature, is exposed in a prospect
pit at this location. This pegmatite is
similar in composition to pegmatite
#1, but has biotite- and hematiterich
seams similar to those present
in pegmatite #4. These biotite- and
hematite-rich seams are associated
with altered pegmatitic alkali feldspar
with inclusions of hematite, biotite,
and a vitreous black mineral (Sample
20121129BG-1) that is enriched to
greater than five times crustal abundance
in Er, Tm, Yb, and Lu, as well as
Nb and Ta (table 6).
Laramie range Pegmatites
Areas of REE enrichment are present
within granitic rocks along the length
of the Laramie Range (King and Harris,
2002). Allanite and euxenite have
been reported in granitic pegmatites
within the Sherman Granite in secs. 1
and 2, T. 15 N., R. 71 W. within the
Medicine Bow National Forest (Griffin
and Warner, 1982). Additionally,
REE-enrichment and REE-bearing
minerals, including allanite and xenotime,
have been reported within intrusive
rocks of the Laramie Anorthosite