Geologic Studies in Alaska by the U.S. Geological Survey, 1992

GEOCHEMICAL EVALUATION OF STREAM-SEDIMENT DATA 183
Table 2. Factor loadings for first five factors after R-mode
analysis with Varimax rotation of stream-sediment data
[Variance explained by five factors equals 80 percent. -, loadings less
than 0.50 that have been omitted]
Element 1 2 3 4 5
A1 ................
As ...............
Ba ...............
Ca ...............
Ce ...............
Co ...............
Cr ................
Cu ...............
Dy ...............
Eu ...............
Fe ................
H f ................
K .................
La ................
Lu ...............
Mg ..............
Mn ..............
Na ...............
Ni ................
Pb ................
Sc ................
Sm ..............
Th ...............
Ti ................
U .................
Percent total
variance ....
stream-sediment samples from the two quadrangles.
Samples with high scores for factor 1, collected from the
toe of Yakataga Glacier and 12 km inland from the mouth
of the Duktoth River, indicate that localized heavy-mineral
concentrations continue inland from the coast. Eight of
the 18 samples from the study area with anomalous gold
were collected between Crooked Creek and the mouth of
the Duktoth River.
Samples with high scores for factor 2 are enriched in
Co-Mg-Cu-Fe-Ni-Sc and show a strong spatial correlation
with both Late Jurassic intrusive bodies and outcrops of
basaltic to andesitic volcanic rocks of the Wrangellia ter-
rane. Stream-sediment samples containing as much as
12.8 percent Fe, 3.2 percent Mg, 50 pprn Co, 123 pprn Cu,
70 pprn Ni, and 45 pprn Sc cluster along the East and
North Forks of the Kiagna River and throughout the Goat
Creek watershed. Samples with high factor 2 scores scat-
tered along the west side of Logan Glacier suggest that the
source for the element enrichments extends perhaps 25 km
east of Goat Creek. Many of the 30 sediment samples in
this belt also contain anomalous amounts of Ag, As, Au,
Cr, Mn, Ti, and V. A sediment sample, likely collected
from medial morainal material, where Baldwin Glacier
joins Logan Glacier contained 149 pprn Cu and 186 pprn
As, the latter being the highest arsenic concentration from
the NURE survey.
Some of these high element concentrations in the
north-central part of the Bering Glacier quadrangle reflect
high geochemical background values for many elements in
mafic country rocks. But many of the anomalous samples
are from drainages within the Chitina Valley bathoIith.
They hint at upstream mineral occurrences similar to the
porphyry-related vein systems described by MacKevett
(1976) a few kilometers to the north. A number of the
stream-sediment samples with high scores for factor 2 are
notably enriched in pathfinder elements for the Cu-rich
veins and are the most suggestive samples of upstream
metallic mineral occurrences in the Bering Glacier quad-
rangle. One sample on Goat Creek, 8 km below the toe of
the unnamed glacier at its source, contained 50 pprn Co,
123 pprn Cu, and 10.5 percent Fe; another from 12 km
below the glacier contained 49 pprn Co, 107 pprn Cu, 12.8
percent Fe, and 58 pprn As; a third from 4 km below the
glacier contained 82 pprn As. It is uncertain whether these
samples collected during the NURE survey were taken
from Goat Creek or from tributary streams, but they most
likely represent pyrite, chalcopyrite, or arsenopyrite within
the area. The stream-sediment sample from the head of
the North Fork of the Kiagna River contained 0.12 pprn
Au. Very few samples were collected in the Chitina Val-
ley batholith east of Goat Creek. However, the sample
described above collected from near the toe of Baldwin
Glacier indicates that Cu-dominant mineral occurrences
likely continue far to the east. Four of the seven samples
with detected silver are in the group of anomalous samples
derived from the batholith, further suggesting the presence
of hydrothermal mineral occurrences.
The East Fork of the Kiagna River defines the western
boundary of this belt of samples with high scores for fac-
tor 2. A sample collected 2 km below the toe of the un-
named glacier at the head of the East Fork of the Kiagna
River contained 108 pprn Cu, 8.8 percent Fe, 2,505 pprn
Mn, 5 pprn Ag, 70 pprn As, and 0.19 pprn Au. Two other
samples collected along the river were also anomalous in
gold, as well as many of the siderophile and chalcophile
elements. It is uncertain whether the source area for the
gold-bearing sediment is also rocks of the Chitina Valley
batholith, or instead may be the mafic volcanic rocks of
the Wrangellia terrane and (or) rocks of the Chugach ter-
rane near the crest of the Granite Range.
A single site with a high score for factor 2, either
draining Ross Green Lake or a small, unnamed glacier im-
mediately to the southwest, is defined by concentrations of
79 pprn Co, 178 pprn Cu, 11.7 percent Fe, 3.6 percent Mg,
137 pprn Ni, 37 pprn Sc, 2253 pprn Ba, 194 pprn Cr, 9.6
pprn Cs, 5.0 percent K, 197 pprn Rb, and 0.96 percent Ti.
These are the highest concentrations of Co, Cu, Mg, Ni,
Cs, K, and Rb determined for any of the 436 sediment