## Trace Metal and Acid-Volatile
Sulfide Concentrations in Sediments from the Forest Queen Wetland
Near Silverton, Colorado: Implications for the Removal of Metals
From Acid Drainage Waters

On-line edition

by

Mark R. Stanton*



Open-File
Report 00-115

2000





This report is preliminary and has not been
reviewed for conformity with U.S. Geological Survey editorial
standards and stratigraphic nomenclature. Any use of trade, product,
or firm names is for descriptive purposes only and does not imply
endorsement by the U.S. Government.



U.S. DEPARTMENT OF THE INTERIOR
U.S. GEOLOGICAL SURVEY

*Denver, Colorado

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

ABSTRACT

INTRODUCTION

Site Description

Sampling Methods

Analytical Methods

Core Locations, Descriptions, and Results

Core FQ3

Core FQ4

Core FQ5

Core FQ7

Core FQ9

Core FQ10

DISCUSSION

AVS Content

Metals Concentrations

CONCLUSIONS

ACKNOWLEDGMENTS

REFERENCES
CITED

APPENDIX

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



ABSTRACT

The Forest Queen wetland near Silverton, Colorado, receives
acidic (pH 4.7) metal-bearing drainage issuing from a collapsed
mine adit. The wetland was studied for the ability of organic/clastic
sediments to neutralize the acidity and remove trace metals from
the influent waters.

Core samples taken from the wetland in October 1997 were leached
with 6N HCl and analyzed to determine concentrations of trace
metals and reduced sulfur (as acid-volatile sulfides, AVS). Results
indicate that sulfate (SO42-) reduction
was active but variable with depth and location during the fall
sampling period and that metals have been incorporated into AVS
phases. However, the highest concentrations of trace metals are
not consistently associated with black, organic-rich, AVS-bearing
samples. High metal concentrations are also present in organic-rich
(but generally AVS/H2S-poor) intervals and in red Fe-oxide
solids.

Metal removal is not directly related to inflow metal concentrations.
Compared to the adit and upstream (surface) waters, Pb, Zn, and
Al are lower in the wetland outflow, but Fe is leaving the wetland
in concentrations greater than in the influent waters. Thus, other
hydrological, geochemical, or biological factors are influencing
the mobility of metals that enter (via the adit and streams) or
exit (via outflows) the wetland, so that some of the wetland metal
load reaches the E. Fork of the Animas River. This results, in
part, from sulfate reduction that is discontinuous with depth
and distance throughout the wetland in the fall. The inconstancy
of sulfate reduction in the wetland results in variability of
sediment metal and AVS concentrations.



INTRODUCTION

Site Description

The Forest Queen wetland is 10.4 km (6.5 mi) northeast of Silverton,
Colorado, (San Juan County) along the East Fork of the Animas
River at an altitude of approximately 2990 meters (9800 ft; Figure 1). The wetland area is approximately
1 hectare (2.5 acres), and the organic+sediment layer(s) ranges
from less than 0.6m (2 ft) to at least 3 m (10 ft) in thickness
in sections that were cored.

As a result of geologic and anthropogenic processes, surficial
material in and around the wetland is composed of differing amounts
of country rock, road and railroad aggregate, mine waste rock
and tailings, and river-transported tailings and rock debris from
upstream locations (Figure 2).
Landslides of unknown age from higher slopes above the wetland
have deposited country rock rubble into the wetland area. Most
country rock in the area contains pyrite (G. Desborough, personal
commun., 1997), but whether the landslide-deposited rock is mineralized
with trace metals is unknown. Areas east (upslope) and north (valley
of E. Fork of Animas River) of the wetland were mined from the
late 1890's until the early 1950's (Bird, 1999).

















Abandoned grades of railroads which hauled ore from further
up the valley are adjacent to the western and southern edges of
the wetland (Figure 2). A 4-m-high (12 ft) waste tailings mound
is present in the northeast section of the wetland. The East Fork
of the Animas River and the road along the river pass next to
the western edge of the wetland.

Elevated aqueous concentrations of metals (primarily Fe, Al,
Pb, Zn, and Cu) and acidity (imparted as sulfuric acid; H2SO4
==> 2H+ + SO42-)
derived from weathering of metal-bearing sulfides are implicated
as major acid rock/acid mine drainage components in the Animas
River basin (Church and others, 1997). One purpose for studying
the wetland was to determine if it is capable of attenuating influent
metal and SO42- concentrations, thus improving
the quality of effluent waters. Dissolved trace metals form insoluble
sulfide minerals upon reaction with aqueous H2S (total
aqueous sulfide = H2S(aq) + HS-(aq)).
Sulfide in organic-rich sediments is produced via reduction of
sulfate ion.

Sulfate reduction at the temperatures and pressures present
in the Forest Queen wetland is accomplished through the action
of sulfate- reducing bacteria, primarily of the genus Desulfovibrio
(Berner, 1970). These microbes couple sulfate reduction with organic
carbon oxidation to produce sulfide (S2-) and ultimately
H2S; the reaction yields energy for growth of the microbes.
Sulfate reduction is an anaerobic process, occurring in the absence
or at very low (sub-ppm) levels of molecular oxygen [O2].
Sulfate reduction with organic matter oxidation is summarized
by the reaction SO42- + 2CH2O
==> H2S + 2HCO3-,
where CH2O symbolizes organic matter. Active sulfate-reduction
in the wetland sediments was evidenced by the odor of H2S
in many core samples and waters. Sulfate-reduction leads to an
increase in the mine water pH via HCO3-
production. Additional neutralization of acidic water occurs via
ammonia and ammonium ion formation as a result of protein decomposition
(NH3 + H2O Æ
NH4+ (ammonium) + OH-). Most
aqueous metals become less soluble as pH increases towards neutral
and alkaline values; pH values as high as 7 (neutral) were observed
in the wetland. Thus, a rise in pH may also help mitigate elevated
concentrations of soluble metals.

Water enters the wetland wetland from the Forest Queen Mine
adit, which resembles a flowing spring as a result of adit collapse.
At the time of the October 1997 sampling, the adit inflow contained
0.66 ppm zinc (Zn), 0.014 ppm lead (Pb), 400 ppm sulfate (SO42-),
24 ppm iron (Fe), 1.8 ppm aluminum (Al) (T. Wildeman, Colorado
School of Mines, unpub. data), and had a pH of 4.7. Water flows
down from the adit on a gentle slope for about 16 m (50 ft), passes
through a narrow aluminum culvert, then reaches a 5m (15 ft) diameter
by 1m (3 ft) deep pool that is heavily encrusted with Fe-oxide
(Figure 2). From this pool, the primary surface water flow is
directly west out of the Fe-oxide pond. Water exits the wetland
at several points and ultimately discharges into the E. Fork of
the Animas River. These effluent waters contain dissolved Zn that
ranges from 0.12-0.17 ppm and dissolved Pb from 0.001-0.008 ppm
(T. Wildeman, Colorado School of Mines, unpub. data). Thus, Pb
and Zn concentrations in outflow waters are only about 25% of
those in the inflow waters during the sampling period. Aluminum
was also lower (0.33-0.81 ppm) while Fe was higher in some outflow
waters (1.9-32 ppm), a strong indication that Fe is mobile in
the wetland environment.

This report describes the organic+clastic sediment stratigraphy
of 6 cores from the Forest Queen wetland and focuses on trace
metals potentially associated with acid-volatile sulfides. Additional
core and water samples from a springtime sampling are currently
being analyzed and the geochemical data is being compiled for
comparison to the results presented here.

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Sampling Methods

Cores were obtained by driving a 1.5 to 3 m (5-10 ft) length
of 5 cm (2 in.) diameter PVC pipe into the organic + clastic sediment
layers. No progress could be made beyond about 3 m (10 ft) by
this method. Often, two or three insertions in the same location
were made to ensure that the maximum thickness of sediment had
been sampled. Smaller cores (1.25 cm [1/2-in.] diameter) were
taken at the edges of the wetland and in other locations where
coring with PVC proved unworkable. The smaller-diameter cores
were no deeper than approximately 1 meter. Shallow (<1
m) samples were taken with an auger when PVC or 1.25-cm coring
could not penetrate the root mat. Capping the top of the PVC pipe
before pulling the core aided retention of cored sediments. After
being pulled, cores were measured for recovery and excess PVC
pipe was sawn off. The sediment was then closed off from the air
by sealing the ends with PVC caps (or plastic caps for 1.25 cm
cores) and cloth tape.

Recovery in each core or in an interval was variable but ranged
from 50% in organic-rich layers to >90% in clay-rich layers.
The midpoint (average) depth of each extracted core interval is
used to identify samples in the tables or on downhole plots. For
example, in Core 7, the midpoint of the 107-125 cm interval is
116 cm; this value is used to place the data points on downhole
plots. Because of sediment compression, the actual recovery in
a sampled interval was less than the full thickness reported for
that interval. Composite samples of macroscopically-similar (color;
organic and clastic content) materials were best-suited as representative
of each sediment interval.

Cores were taken within approximately 2 m (6 ft) of piezometers
that had been installed and sampled 2 weeks earlier as part of
a water-quality study directed by the Colorado School of Mines
(T. Wildeman, Colorado School of Mines, personal commun., 1997).
While direct comparisons of sediment data to the water-quality
data cannot be made, the two data sets are considered representative
of geochemical conditions in the wetland and adit during comparable
times of the year (in this case, fall). Each core was kept at
<15°C until transported to the lab.

On-site analyses for pH, dissolved oxygen (DO), specific conductivity
(SpC), alkalinity (H2SO4 titration), ferrous
iron (Fe2+), and total iron (Fe(tot)) were
made. Ferric iron (Fe3+) was determined by difference
(Fe3+ = Fe(tot) - Fe2+). The
two iron species were measured using a portable spectrophotometer
(Hach Chemical Co., 1997).



Analytical Methods

The term "acid-volatile sulfide" is usually restricted
to Fe-S phases that are soluble in 6N HCl (Berner, 1970): greigite
(Fe3S4), amorphous FeS (FeS(am)),
and mackinawite (crystalline FeS(c)). Pyrite (FeS2)
is insoluble in 6N HCl. The AVS definition is expanded here to
include other HCl-soluble metal sulfides such as PbS (galena),
ZnS (sphalerite), and Cu2S (chalcocite) that may have
been present in the sediment.

Cores were stored upright at 4°C in the lab. When a core
was opened, the stratigraphy was immediately described and then
a composite sample over each interval was taken for use in the
acid-volatile sulfide (AVS) analysis. Samples were taken under
an N2(g) stream to prevent oxidation of AVS solids
but were not dried. The type of sample taken depended on color,
amount of material available, organic matter and/or clastic sediment
content, presence of visible "fresh" or existing sulfides,
and grain size. The amounts used ranged from 10 to 50 grams (wet
weight).

The sample was placed in a round-bottom flask. After addition
of 6N HCl (20 mL 6N HCl per every 10 g sample) and a 10% w/v SnCl2
suspension (to prevent Fe3+ from oxidizing sulfide
to higher oxidation states such as S°), the flask was connected
to the speciation apparatus. The flask containing the sample +
HCl was heated from 25°C to 90°C over 1/2-hour under an
N2 atmosphere to release the AVS (Rice and others,
1993). H2S(g) released during this acid/heating
step is swept by the N2 gas into a series of 3 glass
traps. Phosphate buffer (pH 4.0) in the first trap maintains sulfide
as H2S(g); the last two traps contain 0.1
M AgNO3 that precipitates the sulfide as Ag2S.

After AVS was recovered as Ag2S, the organic-clastic
residue + HCl solution was rinsed with deionized water (DI) through
a 0.45 mm filter, air dried (25°C), and weighed. The filtered
HCl solution was analyzed for major and trace element concentrations
using inductively coupled plasma-atomic emission spectroscopy
(ICP-AES; Briggs, 1990). The total amount of sulfide recovered
was determined using a gravimetric conversion for Ag2S
and is reported as ppm total sulfide (S2-(tot)).
The presence of recoverable AVS and trace metal(s) in a sample
is not proof that the metal resides in a sulfide phase. However,
in organic-rich, sulfidic sediments, trace metals are likely to
be associated with organics or AVS but not an oxidized phase like
Fe-oxide.

Organic content was estimated by the proportion of peat plus
wood fragments (or "chips") to clastic sediment. Fragments
are tan-to-dark brown macroscopic pieces of wood that generally
do not exceed 2.5 cm (1 in.) along any dimension. Visible high
organic content was one of the major criteria used to separate
samples into the different intervals.

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Core Locations,
Descriptions, and Results

Thirty-eight samples from six cores in the wetland were treated
to recover AVS; the leachates were then analyzed for 40 major
and trace elements. This data is tabulated and presented in Appendix
1. Core locations are shown on the map on Figure 1, and core stratigraphy,
element abundances, and FeS recovery (yield) are described below.
The variation and abundance of metals in the AVS fraction are
illustrated using downhole plots of (1) major elements (Ca, Al,
Fe, K, Mg, P, Si, Ba, and Mn) and (2) trace metals (Cd, Co, Cr,
Cu, Ni, Pb, V, and Zn). For each core, the first plot shows major
elements while the second plot shows trace metals. On both plots,
total sulfide (in ppm S2-(tot)) is also
shown.

The discussion that follows focuses on the major elements Fe
and Al, and the trace metals Pb, Zn, and Cu, although other elements
on the plots are discussed as needed. These 5 elements, as noted
previously, are among the most abundant in sediment and water
samples from Animas Basin watersheds (Church and others, 1997).



Core FQ3

This core was taken 9 m (30 ft) southwest of the Fe-oxide pond
and contains the lowest concentrations of Al, Fe, Pb, Zn, and
Cu of the 6 cores (Figure 3A).
The analyzed samples cover a depth interval from 41 to 163 cm
(16-64 in.).









The maximum Fe value (240 ppm) is found in the 41-71 cm interval;
Fe then decreases towards the bottom of the core to 28 ppm in
the 132-163 cm interval. Although the uppermost interval (0-41
cm) was not analyzed, its macroscopic appearance was similar to
other core intervals except that it lacked wood fragments. Aluminum
values cluster in a narrow range from 27 to 34 ppm, including
30 ppm in the 41-71 cm interval. From the surface to bottom of
the core, Ba decreases slightly, Ca and Mn increase slightly,
and other major element concentrations vary only slightly, as
illustrated by the nearly vertical lines on Figure 3A.

Pb in the 41-71 cm and 132-163 cm intervals was 0.17 and 0.13
ppm, respectively; Pb was not detected in the 2 middle layers
(71-102 cm and 102-132 cm). Zn was the only metal present in detectable
concentrations in the 6N HCl solution from all 4 intervals, and
ranged from 1.6 to 5.9 ppm (Figure 3B).
Cd, Cr, and Cu were not detected in any interval.









Thus, both Pb and Zn have their maximum abundance in the 41-71
cm interval. Similarly, other trace metals either had detectable
concentrations in only the 41-71 cm interval (Ni, V) or were undetectable
(Cd, Cr). Co in the 41-71 cm interval was 0.32 ppm, but in the
71-102 cm interval, Co was only 0.03 ppm, a value very close to
the detection limit (0.02 ppm). Co was not detected in the 2 deepest
intervals. If metal sorption by the solids is actively occurring
in Core #3, it appears to happen in the uppermost 71 cm (28 in.)
which consists almost wholly of organic matter.

The 41-71 cm sample was black but had lower organic content
(50-75%, primarily peat) than deeper levels and no H2S
odor, whereas the other 3 deeper intervals were also black, had
a strong H2S odor, and equal or higher organic matter
content (~75%, primarily wood fragments). The black color in all
4 intervals suggests FeS, yet trace metal abundances in the AVS-leached
solution are low compared to other cores.

The results from Core #3 are somewhat surprising because the
high S2-(tot) yields below 71 cm (28 in.)
indicate abundant FeS and thus potential immobilization of metals
in AVS solids. However, as Figure 3A illustrates, trace metal
abundances are low (compared to cores "downstream" (south)
of the pond), and only Zn shows some variability in the core.
The relative lack of metals in Core #3 suggests the area is not
well-connected hydrologically with inflow (surface and possibly
subsurface) waters at depths greater than about 71 cm. Core #3
is located SE and away from the Fe-oxide pond whose major outflow
is directly to the west. Although FeS formation is active, dissolved
metals from surface flow are either not reaching this area or
not transported to deeper parts of the wetland; thus metals are
not being sequestered within AVS. Alternatively, metals may be
most strongly associated with Fe-oxide in the uppermost 41 cm.
When the core was extracted, the wetland surface was damp but
not flooded, and coated by large amounts of Fe-oxide, suggesting
little recent flow of water into the area and oxidation of aqueous
Fe.

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Core FQ4

This core is 9 m (30 ft) directly west of the Fe-oxide coated
pond and directly in the path of the major surface outflow from
the pond. The length of analyzed core covers the interval from
20 to 152 cm (8-60 in.). As before, composite samples were used
for AVS work, and in addition, a "discrete" 1-cm sample
at 41 cm was taken to qualify the effect that "dilution"
by compositing had on the metal values.

Most major element concentrations do not vary greatly within
the organic-rich layers up to the 81 cm depth (Figure
4A), although the sample at 41 cm showed higher Ba,
Si, P, and Fe values. Below 81 cm, most major metal values tend
to increase, especially in the 99-117 cm interval, but Fe and
Si show slight decreases. The highest Fe (750 ppm) is present
in the upper organic-rich interval at 41 cm and decreases with
depth as in core #3. The high Fe in the upper levels is probably
a result of the sediments being in the direct path of the Fe-oxide
pond outflow. Periodic flushing of the pond (spring runoff?) probably
results in delivery of large amounts of solid Fe-oxide to this
area of the wetland.









In contrast to Fe, Al generally increases with depth and reaches
its maximum abundance (210 ppm) at the bottom (142-152 cm) of
the core. Most other major elements tend to follow Al in this
respect. The increases may be due to a larger proportion of silicate
sediment in the deeper levels of the core that provides a source
of "leachable" elements (Ca and Mg, for example).

There are 2 intervals in Core #4 where trace metals (Zn, Pb,
Cu) are found in relatively-higher concentration in the 6N HCl
leach solution - the 41-61 cm (including the 41 cm sample) and
142-152 cm intervals (Figure 4B).
Zn and Cu in the 41-61 cm interval are 6.8 and 0.30 ppm, respectively,
while Pb and Zn in the 142-152 cm interval are 4.0 and 6.6 ppm,
respectively. The highest Zn concentration was 13 ppm in the 41
cm sample, while Pb was highest in the 142-152 cm interval.









This result issimilar to Core #3 where the greatest
Zn concentration was in the organic-rich uppermost 60 cm of core,
and suggests Zn is being adsorbed in the upper layers as metal-bearing
water flows over and/or percolates into the upper organic-rich
layers. The dominantly dark-gray color of sediment in this interval
(despite some red color on outer surfaces) is indicative of FeS.
As Figure 4B shows, Zn steadily decreases to less than 2 ppm at
the 99-117 cm interval, then increases to 6.6 ppm in the 142-152
cm interval. Cu was present in the four upper organic-rich samples,
but not in the silicate-sediment intervals below 81 cm. Pb generally
mimics Zn in the upper 81 cm, but then increases in the organic-rich
99-117 cm and 142-152 cm intervals that contain black lenses.

AVS data from Core 4 indicate that sulfate reduction ceases
below approximately 102 cm (40 in.) in this area. No sulfide was
recovered from the 6N HCl leach of 2 of the deepest intervals
(99-117 cm and 142-152 cm) in this core.

The high metal content in the 41-61 cm interval is probably
associated with organic matter or Fe-oxides because S2-(tot)
recovered from the 6N HCl leach was relatively low (16.8 ppm).
In the 142-152 cm interval, there were black lenses that indicated
"fresh" FeS, but the zero yield of Ag2S (i.e., no sulfide)
argues against these black lenses containing any AVS.

The only black, organic-rich layer in this core (99-117 cm)
showed lower Zn but higher Pb compared to lighter-colored, organic-rich
layers. Zinc decreases from its highest concentration (6.8 ppm)
at 41-61 cm to 1.1 ppm at 99-117 cm. The lack of sulfide in the
41-61 cm sample interval correlates with the lowest Zn concentration,
suggesting FeS is not responsible for trapping Pb and Zn in this
particular core at or below 99 cm (39 in.). Zn is therefore associated
with either organic matter or Fe-oxide but not FeS.

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Core FQ5

Core #5 is located about 10 meters (30 ft) northwest of the
Fe-oxide pond and represents an interval from 0-183 cm (0-72 in.).

As in Core #4, samples from Core #5 contain relatively-high
major and trace metal abundances at 2 different levels (Figures 5A and 5B). Pb and Zn are
highest in the 81-102 cm interval at 5.4 and 12.0 ppm, respectively.
Cu and Al are highest in the 122-145 cm interval at 1.1 and 210
ppm, respectively. Fe differs from other metals in that it remains
high (290-350 ppm) over the 4 intervals (76-81 cm to 122-145 cm)
where these higher metal values are present.















The two organic-rich intervals containing higher metals (81-102
cm and 122-145 cm) are separated by a gray layer of silt-clay
sediment at 102-122 cm that shows evidence of Fe-oxidation, primarily
rootlets whose outer surfaces are colored red (assumed to be Fe-oxide).
Pb and Zn concentrations in the 102-122 cm interval (Pb=4.0 ppm;
Zn=8.8 ppm) do not vary greatly from those in the organic-rich
layers that encompass it, illustrating that both clastic and organic
layers can contain similar trace metal concentrations.

The black interval with a strong H2S odor from 145-165
cm did not show the highest metal abundances. In fact, Pb and
Zn are about one-half their values in the intervals covering 81-145
cm. Furthermore, the 165-173 cm interval shows an even sharper
decrease in Pb and Zn concentrations compared to the 145-165 cm
interval. The 165-173 cm interval contains 20% clay, much woody
material, and had only a slight H2S odor. The 173-183
cm interval exhibits an increase in Pb and Zn concentrations,
however, relative to the 165-173 cm interval.

Despite the varied types of host materials, the differences
in metal concentrations in 6N HCl leachates from Core 5 samples
are small over the entire interval from 81-183 cm, where Pb ranges
from about 3 to 5 ppm and Zn ranges from about 5 to 12 ppm. The
exception is the 165-173 cm interval where Pb and Zn both decrease.
The similarity of metal contents in Core #5 suggests that clastic
and organic sediment are equally capable of sorbing metals in
the wetland. However, the residence of metals within specific
mineral phases in the clastic sediements or specific compounds
in the organic fraction is not known.



Core FQ7

Core #7, about 45 m (150 ft) west of the Fe-oxide pond on the
western edge of the wetland, encompasses the 0-246 cm (0-97 in.)
interval and is enclosed (at the surface) on 3 sides by ponded
water (seeFigure 2). Core #7 is the deepest of the cores
and illustrates the complexity of the wetland stratigraphy. As
shown on Figure 6A (major
elements) and Figure 6B (trace
metals), organic-rich upper layers are succeeded by increasingly
clastic (clay, silt, and sand) sediments with depth.















Al and Fe are at fairly high values (>100-400 ppm) downhole
until 183-206 cm where Fe drops dramatically from 300 ppm to 45
ppm. Al, however, changes less dramatically, from 400 to 300 ppm.
In the next interval, 206-221 cm, Fe and Al increase to nearly
equal values of 600 ppm, then both drop below 100 ppm at 221-226
cm before increasing once more to ~250 ppm from 226-246 cm. The
large variations in Al and Fe abundances, especially from approximately
183-246 cm (72-97 in.), suggest significant changes in local chemistry
or sediment composition. Because the sulfide content is fairly
uniform over the 183-246 cm interval, the increasing clastic and
decreasing organic content is likely responsible for the variable
element concentrations.

Regression plots of Fe, Cu, Zn, and Pb vs S2-(tot)(Figures 7A-D) indicate
two sample populations in Core 7. This is interpreted as 2 different
associations of each metal - an amount associated with monosulfide
and an amount not associated with monosulfide. The non-monosulfide
component is probably detrital sulfide-bearing material derived
from sources such as mineralized country rock, or ore spilled
from railroad cars or used for road ballast. This material, particularly
if it consisted of larger grains or FeS2, ZnS, or PbS,
would not dissolve in 6N HCl. (The outlying sample, the 40-59
cm interval, is excluded. When included, it "forces"
a strong correlation with Pb but the other 3 metals show little
change in correlation with sulfide).











The gently-sloping lines on the right sides of Figures 7A-D
indicate slightly-increasing metal content with large increases
in monosulfide.Steeply-sloping lines on the left sides of Figures
7A-D, where metal content increases sharply with only slight increases
in monosulfide, indicate the ore sulfide (detrital) component.
The steep metal increase is probably due to metal associations
with ore sulfide rather than with monosulfide.

Generally, the steeper line is made up of the samples having
higher clastic (sand, silt, and clay) content, while the lower-sloping
lines are primarily organic-rich intervals. However, much of the
clastic material is at too great a depth to have been deposited
by anthropogenic means (mining, railroad and road building). Thus,
it appears that the original detritus deposited at the base the
Forest Queen wetland was enriched in Pb and Zn.

In traversing the wetland from east to west (from Core 3 towards
Core 7), the sediments change from having a high organic content
to those that have an increasingly clastic content, particularly
below about 61 cm (24 in.). Although no ages for these deeper
clastic sediments have been determined, they were probably present
(i.e., deposited by the E. Fork of the Animas River) prior to
building of the railroad and automobile road.

Vincent (USGS, personal commun., 1999) obtained 14C
dates for several layers in the wetland. An accumulation rate
of approximately 1 m peat (organic matter) per 1,000 years was
postulated for the "growth" of the wetland. Thus, metals
found in sediments below about 0.1 m (which would be have been
deposited >100 years ago, before the advent of mining in the
area) may have been fixed in the sediments prior to mining. However,
more exact methods (e.g., Pb-210 geochronology or isotopic work)
would be needed to determine the timing of metal fixation during
wetland accumulation. Fe-oxide staining was present in 2 intervals
in Core 7, the upper 0-16 cm and in the 59-68 cm interval. Except
for the deeper clastics, the sediments were dark gray-brown to
black, with several intervals exhibiting an H2S odor.

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Core FQ9

This core was taken approximately 25 m (80 ft) southeast of
the Fe-oxide pond. Core #9 is a short interval 0-76 cm (0-30 in.)
and consists almost wholly of organic material. Because of the
limited interval and consistent composition, only 3 samples were
analyzed from this core. The middle interval, 20-61 cm, produced
the largest sulfide yield of all samples (430 ppm).

As Figure 8A illustrates,
most major element abundances down this core vary little and show
similar trends. With the exceptions of Si and P, major elements
increase from the 0-20 cm interval to the 61-76 cm interval. Fe
and Al show systematic increases in concentrations with increasing
depth.

Despite the moderate-to-high sulfide yields from all intervals
(and a very high yield of 430 ppm from the middle (20-61 cm) interval),
trace metals are relatively low in these core samples (Figure 8B). Zn ranges from 2.3 to
7.1 ppm, and similar to most cores, is in greatest abundance in
the uppermost sample (0-20) cm rather than in deeper samples.
Pb is present in low concentration in the 6N HCl leachate, ranging
from 0.49 to 0.61 ppm. Other trace metals were present in varying
but small abundances, and except for Co, were not detected in
every sample. For example, Cu and Cd were detected in only the
upper 0-20 cm while Cr was found only in the 61-76 cm interval.
Vanadium was present in the 2 lower intervals, whereas Ni was
found in the upper and lower, but not middle, intervals.

















Organic content was at least 60% and up to 100% in the upper
61 cm, and major Fe-oxide staining was noted primarily in the
upper 0-20 cm. In the lowest 61-76 cm, organic matter still comprised
about 40% of the sample and Fe-oxide staining was not observed.
Unidentified mineral(s) in the 61-76 cm interval resembled pyrite,
but the presence of FeS2 in the sample has not been
confirmed. The moderate to high yields of sulfide in these core
samples indicate that sulfate reduction activity was high. However,
abundant Fe-oxide in the upper 20 cm (8 in.) indicates that a
strongly-reducing environment had not been established in this
level and area of the wetland at the time of sampling. At the
bottom of the 20-61 cm interval (which produced the highest sulfide
yield), only minor Fe-oxide was noted; this may have been an artifact
of storage.

Thus, high sulfide yields in core #9 showed only relatively
small concentrations of trace metals, indicating that metal trapping
by monosulfide is inefficient or not occurring in this portion
of the wetland.



Core FQ10

This core was taken at the greatest distance from the source
of influent adit waters at approximately 55 m (180 ft) west of
the Fe-oxide pond on a small point of dry land 2m (6 ft) higher
than the wetland and 5m (15 ft) east of the automobile road. The
core covers an interval from 0-58 cm (0-23 in.). In contrast to
all other cores examined, the uppermost 53 cm (21 in.) of Core
10 is dominantly brown to light-yellow sand and clay, rather than
organic matter; organic material is present only in the bottom
53-58 cm. Because of the generally similar (brown, sandy, no visible
organics) character of the upper 53 cm of sediment, only samples
from the lower sandy interval (33-53 cm) and the black organic
interval (53-58 cm) were analyzed. The results described below
concern only these two samples.

Fe concentrations in the 6N HCl leachates are 540 ppm (33-53
cm) and 95 ppm (53-58 cm) as shown on Figure
9A. The zero AVS yield and lower Fe from the black
53-58 cm layer clearly demonstrate a lack of any AVS, and especially
FeS. Al exhibits a decrease similar to Fe, from 190 ppm in the
upper layer to 60 ppm in the lower layer.

Pb, Zn, and Cu concentrations are at much lower concentrations
(Figure 9B) than Fe or Al
but show similar downhole decreases. Pb and Zn are also relatively
higher in the samples from Core #10. In the 33-53 cm interval,
Pb is 6.6 ppm and Zn is 20 ppm (equal to the highest Zn concentration
in any 6N HCl leachate). In the 53-58 cm interval, Pb is 3.7 ppm
and Zn is 12 ppm.















Core 10 contains the two samples with the highest measured
Cu abundances of all cores, 6.3 ppm in the 33-53 cm interval and
5.4 ppm in the 53-58 cm interval. Interestingly, Cu in the 33-53
cm interval is associated with the oxidized yellow sands and clays
(clastic layers in the wetland were almost always gray or dark-gray),
whereas high Cu in the 53-58 cm interval is associated with the
black, organic-rich layer.

All other wetland cores contain approximately 50-100% organic
matter in the upper 53 cm (24 in.). The presence of the black
layer of organic material at the base of Core 10 suggests this
area was once part of the wetland but was isolated at some time
in the past, perhaps as a result of automobile road or railroad
grade construction. Based on the sediment type (sand, clay), grain
size, and color, and the lack of organic matter, water, and any
"fresh" (AVS) sulfides in the upper section of the core,
the area where Core 10 was taken appears to be no longer sedimentologically
or hydrologically connected to the wetland. And because this core
is closest to the road and railroad grade, it is likely that clastic
sediment higher in the core is windblown or anthro-pogenically-transported
material used for road and railroad maintenance.

Fe-oxide may have been present in the 33-53 cm interval as
evidenced by a dark brown color but was not visible in the black
53-58 cm layer. AVS was not recovered from the 6N HCl leach of
either of these high-Cu samples. Therefore, Fe-oxide or "ore"
sulfide must be responsible for the high Cu in the 33-53 cm interval,
and organic matter may be the reason for high Cu in the 53-58
cm interval, but AVS could not be the residence for Cu in either
sample.

The black color in the 53-58 cm interval of Core 10 is probably
Mn-oxide; isolated thin layers (2-7 cm [1-3 in.] thick) of Mn-oxide
were observed in other areas away from the center of the wetland.
Mn in the black layer is 17 ppm; among all cores, this is the
4th-highest Mn concentration. Mn in the 33-53 cm interval is the
highest of all samples (64 ppm), however, no black color is imparted
to the sediment. The dark brown color of the 33-53 cm interval
may represent a mixed Mn/Fe-oxide, but the mineralogy of the layer
has not been determined.

Back to Top



DISCUSSION

AVS Content

Yields of sulfide (as ppm S2-(tot)) varied
widely from sample to sample in each core. The largest yields
(>200 ppm) came from dark (black, brown), organic-rich layers.
The smallest yields (0-10 ppm) came from lighter-colored or red
(Fe-oxide-stained) organic or silicate sediment layers. Intermediate
FeS yields (>10-200 ppm) were from dark-gray to brown organic
layers and from silicate sediment with small black lenses which
appeared to be "fresh" FeS forming in place.

The highest yields of AVS do not consistently coincide with
the highest major or trace metal abundances (Al, Fe, Pb, Zn, Cu),
and high metal abundances are present in samples that produced
little or no AVS. While high metal concentrations in the 6N HCl
leachate were often observed when FeS yields were large, this
was not always the case. For example, the highest Pb (27 ppm)
and Zn (20 ppm) in Core 7 come from a layer that contains about
50% gray clay and 50% organic matter, and produced an intermediate
yield of 36 ppm S2-(tot). Yet, the second-highest
Pb and Zn values (10 and 17 ppm, respectively) in Core 7 are from
a yellow-sand, gray-clay layer immediately below the high Pb/Zn
layer which has minor organic matter content and produced only
6 ppm S2-(tot). In contrast, Pb and Zn are
quite low (0.49 ppm and 2.3 ppm, respectively) in the sample from
Core 9 that produced the highest AVS yield (430 ppm S2-(tot))
of all samples.



Metals Concentrations

Major and trace metals present in high concentrations in the
6N HCl leachates were Fe, Al, Pb, Zn, and Cu. However, concentrations
of these metals associated with the AVS fraction are not always
elevated, even though they are all present in water that drains
into the wetland from the adit. Pb and Zn were detected in nearly
all samples from each core; in contrast, Cu was detected in far
fewer samples from each core. Among all core samples, the maximum
value of Pb is 27 ppm (Core 7); Zn is 20 ppm (Cores 7 and 10);
and Cu is 6.3 ppm (Core 10); see Figure
10. The variable trace metal concentrations associated
with the AVS indicate that metal removal by sulfide is sporadic,
perhaps slow, and subject to oxidation that may release AVS-metals.
These results also indicate that metals are associated with non-AVS
phases, such asorganic matter, clastic (silicate or sulfide) sediment,
and Fe-oxide. Because the samples were not dried prior to AVS
treatment, an unknown concentration of metal in each sample is
also associated with the aqueous phase (residual water). Based
on aqueous analyses (T. Wildeman, written commun., 1998) which
show Pb and Zn present in water at an order of magnitude less
than in the solids, the total amount of metal associated with
residual water in the core samples is likely to be small relative
to that in the solid phases.









Fe and Al exceed several hundred ppm in many samples; this
is not unexpected because of the large input of Al and Fe into
the wetland. The large pond located a few feet above and east
of the wetland (Figure 2) is coated with several mm of Fe-oxide,
and Al substitutes for Fe to a great extent in Fe-oxides such
as goethite (Fortin et al., 1993).

Al and Fe concentrations in AVS leachates are relatively consistent
downhole (100-500 ppm) in most cores. Increases in Fe are usually
seen when a red or brown zone (indicative of oxidized Fe) is encountered;
Al concentrations generally increase when a clastic sediment layer
is present.

Figures 11 and 12 show
Pb and Zn concentrations from several cores aligned N-S (cores
5, 4, and 3) and E-W (cores 4, 9, 7, and 10). Pb and Zn concentrations
are generally higher in the upper portions of cores, and decrease
from N to S and from E to W. This suggests that Pb and Zn fixation
happens closest to the adit (source) waters, that Pb and Zn fixed
in the (upper) core solids originated from the adit source waters,
and that fixation is strongest in the upper, usually organic-rich,
layers. However, some high Pb and Zn is found in the deeper parts
of cores 4 and 7 (see Figure 10). Those values suggest that another
deeper source of metal-bearing water or solid may be present.





















Back to Top

CONCLUSIONS

Trace metal contents associated with AVS are not greatly elevated
in solid samples, and high or maximum metal concentrations are
not always associated with black intervals or those with H2S
(for example, core 3). Often, intervals that exhibited some red
staining also had high metal values. The highest abundances of
Pb, Zn, Cu, Al, and Fe are often but not consistentlyfound
in black, organic-rich layers, with equal or lesser concentrations
in red or brown organic layers, and the smallest concentrations
generally in clastic sediments. Core 10 is an exception in having
high metals in clastic sediments; those sediments probably originated
in part from ore that fell from railroad cars or was used in road
building.

The variable red-to-brown staining indicative of iron oxide
may have resulted from oxidation during short-term core storage.
However, even during sampling, Fe oxide was observed in samples
up to 1 m (3 ft) deep. Sulfate reduction was not occurring in
all core locations or at similar depths in the wetland, and at
this time of year the wetland appeared to be drying out, as evidenced
by low water level. In contrast, during the spring sampling, 3-4
cm of water covered about 70% of the wetland surface, and H2S
was measured in every core and water sample taken. Drying and
lowered water levels allow air diffusion and Fe-oxidation to take
place at greater depths in the wetland sediments. Thus, sulfate
reduction, metal immobilization by AVS formation, or metal release
by AVS oxidation, are all subject to variability as a result of
seasonal changes.

While no single explanation for the variability in metal concentrations
in the solid phases is evident, it appears that the hydrologic
flowpath in the wetland is changeable and leads to fluctuations
in the delivery of aqueous phase metals to isolated pockets of
sulfate reduction or Fe-oxidation within the sediment column.
The presence of 2 zones of relatively-enriched trace metal (Pb
and Zn) concentrations implies that aqueous metals may be moving
along 2 different paths in the wetland sediments. The most obvious
path is metal-bearing surface (adit) water percolating downward
into the sediments. Another potential path is (metal-rich? acidic?)
regional groundwater moving downgradient from higher slopes which
then upwells beneath the wetland (Pavlik and others, 1999). Upon
encountering the sulfate-reducing zones, metals could become entrapped
by reaction or co-precipitation with sulfide phases.

The Forest Queen wetland will likely continue to provide scattered
removal of metals by sequestration within AVS, Fe-oxide, and organic
solid phases. However, storage of metals in these solid phases
is probably short-lived as a result of seasonal fluctuations of
sulfate-reduction. In the absence of sulfate-reduction to buffer
pH, metals could be resolubilized by newly-introduced acidic water
that would aid Fe-oxide dissolution. Acidic pH would also tend
to desorb metals from organics. And, lowered water levels in the
fall season would allow AVS oxidation and release of sorbed or
co-precipitated metals to occur. Thus, the combination of seasonal
variations and variable flowpaths leads to intermittent, scattered
removal and storage of metals in the wetland.

The efficiency of the FQ wetland in trapping metals from influent
waters is also variable and intermittent. Improvement in the wetland's
"cleansing" ability might be improved if aqueous flowpaths
could be directed to areas where sulfate reduction appears to
be maximum. The wetland area around cores 3, 4, 5, and 9 shows
the highest sulfide yields and sulfate reduction activities. Artificial
methods that enhance sulfate reduction, such as addition of specific
nutrients or maintenance of anaerobic conditions by keeping the
wetland flooded, might also improve the metal-removal capability
(by AVS) in the sediments. These methods could be instituted as
part of an engineering program aimed at controlling direction
and flowrate of influent waters into the wetland, similar to constructed
wetlands that have produced some success in applications to mine
drainage remediation.



ACKNOWLEDGMENTS

Ken Leib and John Evans of the USGS-WRD District Office in
Durango provided invaluable assistance with collection of sediment
cores and on-site analysis of water samples during the fall and
spring sampling. Tom Wildeman of the Colorado School of Mines
provided access to the wells and additional water data. Funding
for this work was provided through Rob Robinson of the Bureau
of Land Management (BLM).



REFERENCESCITED

Berner, R.A., 1970, Sedimentary pyrite formation: American
Journal of Science, v. 268, p. 1-23.

Bird, A.G., 1999, Silverton Gold: The Story of Colorado's Largest
Gold Mine.

Church, S.E., Kimball, B.A., Fey, D.L., Ferderer, D.A., Yager,
T.J., and Vaughn, R.B., 1997, Source, transport, and partitioning
of metals between water, colloids, and bed sediments of the Animas
River, Colorado. U.S. Geological Survey Open-File Report 97-151,
135 p.

Fortin, D., Leppard, G.G., and Tessier, A., 1993, Characteristics
of lacustrine diagenetic iron oxyhydroxides: Geochimica et Cosmochimica
Acta, v. 57, p. 4391-4404.

Hach Chemical Co., 1997, User's Manual.

Rice, C.A., Tuttle, M.L., Reynolds, R.L., 1993, The analysis
of forms of sulfur in ancient sediments and sedimentary rocks:
comments and cautions. Chemical Geology, v. 107, p.83-95.

Pavlik, M.C., Kolm, K.E., Winkler, S., Emerick, J., Wildeman,
T.R., and Robinson, R., 1999, Hydrogeologic controls on the geochemical
function of the Forest Queen wetland, Colorado. Proceedings of
6th International Conference on Tailings and Mine Waste, Ft. Collins,
Colo., January 1999, p. 647-655.

Back to Top

APPENDIX

Geochemical data for Forest Queen wetland cores, numbers 3,
4, 5, 7, 9, and 10. All units are ppm (parts per million). "<"
signifies values below the detection limit. Ctr Dpth, cm = center
depth of sampled interval, in centimeters.

Geochemical data, Forest
Queen Cores 3 and 4.



|                              |             |        |        |        |        |        |        |        |        |        
|----------------------------- | ----------- | ------ | ------ | ------ | ------ | ------ | ------ | ------ | ------ | -------
|Field
      No/Depth Interval | Ctr Dpth,cm | Al ppm | Ca ppm | Fe ppm | K ppm  | Mg ppm | Na ppm | P ppm  | Si ppm | Ti ppm 
|FQ3
      C-5 41-71           | 56          | 30     | 30     | 240    | 2      | 2.3    | < 1    | 2      | 5.8    | < 1    
|FQ3
      C-5 71-102          | 86          | 27     | 53     | 89     | 1.6    | 3.2    | < 1    | 1.8    | 6.5    | < 1    
|FQ3
      C-5 102-132         | 117         | 34     | 49     | 34     | 1.9    | 3.6    | < 1    | 2      | 5.9    | < 1    
|FQ3
      C-5 132-163         | 147         | 31     | 58     | 28     | 1.6    | 3.8    | < 1    | 2.6    | 6      | < 1    
|                              |             |        |        |        |        |        |        |        |        |        
|FQ4
      C-1 20-41           | 30          | 32     | 25     | 380    | 3.1    | 4.5    | < 1    | 7.9    | 6.8    | < 1    
|FQ4
      C-1 @ 41            | 41          | 27     | 19     | 750    | 2      | 2.5    | < 1    | 17     | 12     | < 1    
|FQ4
      C-1 41-61           | 51          | 37     | 19     | 540    | 1.8    | 1.7    | < 1    | 13     | 14     | < 1    
|FQ4
      C-1 61-81           | 71          | 17     | 14     | 580    | 1.2    | 1.6    | < 1    | 10     | 9.8    | < 1    
|FQ4
      C-2 99-117          | 108         | 88     | 39     | 370    | 4.8    | 41     | < 1    | 7.8    | 5.2    | < 1    
|FQ4
      C-2 142-152         | 147         | 210    | 84     | 240    | 11     | 86     | 1      | 13     | 7.4    | < 1    
|                              |             |        |        |        |        |        |        |        |        |        
|Field
      No/Depth Interval | Ctr Dpth,cm | Ag ppm | As ppm | B ppm  | Ba ppm | Be ppm | Bi ppm | Cd ppm | Ce ppm | Co ppm 
|FQ3
      C-5 41-71           | 56          | < 0.04 | < 0.2  | < 0.1  | 0.47   | < 0.02 | < 0.2  | < 0.4  | 0.13   | 0.32   
|FQ3
      C-5 71-102          | 86          | < 0.04 | < 0.2  | < 0.1  | 0.18   | 0.04   | < 0.2  | < 0.4  | < 0.8  | 0.03   
|FQ3
      C-5 102-132         | 117         | < 0.04 | < 0.2  | < 0.1  | 0.09   | 0.05   | < 0.2  | < 0.4  | < 0.8  | < 0.2  
|FQ3
      C-5 132-163         | 147         | < 0.04 | < 0.2  | < 0.1  | 0.07   | 0.1    | < 0.2  | < 0.4  | < 0.8  | < 0.2  
|                              |             |        |        |        |        |        |        |        |        |        
|FQ4
      C-1 20-41           | 30          | < 0.04 | < 0.2  | < 0.1  | 0.78   | < 0.02 | < 0.2  | 0.04   | 0.09   | 0.17   
|FQ4
      C-1 @ 41            | 41          | < 0.04 | < 0.2  | < 0.1  | 1.6    | < 0.02 | < 0.2  | < 0.4  | < 0.8  | 0.15   
|FQ4
      C-1 41-61           | 51          | < 0.04 | < 0.2  | < 0.1  | 1.1    | < 0.02 | < 0.2  | 0.24   | < 0.8  | 0.25   
|FQ4
      C-1 61-81           | 71          | < 0.04 | < 0.2  | < 0.1  | 1.2    | < 0.02 | < 0.2  | < 0.4  | < 0.8  | 0.09   
|FQ4
      C-2 99-117          | 108         | < 0.04 | < 0.2  | < 0.1  | 1.3    | < 0.02 | < 0.2  | < 0.4  | 0.38   | 0.09   
|FQ4
      C-2 142-152         | 147         | < 0.04 | < 0.2  | < 0.1  | 1.2    | 0.03   | < 0.2  | < 0.4  | 0.71   | 0.1    
|                              |             |        |        |        |        |        |        |        |        |        
|Field
      No/Depth Interval | Ctr Dpth,cm | Cr ppm | Cu ppm | La ppm | Li ppm | Mn ppm | Mo ppm | Ni ppm | Pb ppm | Sb ppm 
|FQ3
      C-5 41-71           | 56          | < 0.2  | < 0.2  | 0.04   | < 0.4  | 0.3    | < 0.04 | 0.13   | 0.17   | < 0.1  
|FQ3
      C-5 71-102          | 86          | < 0.2  | < 0.2  | < 0.4  | < 0.4  | 0.66   | < 0.04 | < 0.4  | < 0.8  | < 0.1  
|FQ3
      C-5 102-132         | 117         | < 0.2  | < 0.2  | < 0.4  | < 0.4  | 0.81   | < 0.04 | < 0.4  | < 0.8  | < 0.1  
|FQ3
      C-5 132-163         | 147         | < 0.2  | < 0.2  | < 0.4  | < 0.4  | 0.63   | < 0.04 | < 0.4  | 0.13   | < 0.1  
|                              |             |        |        |        |        |        |        |        |        |        
|FQ4
      C-1 20-41           | 30          | < 0.2  | 0.11   | < 0.4  | 0.04   | 0.76   | < 0.04 | 0.08   | 0.19   | < 0.1  
|FQ4
      C-1 @ 41            | 41          | < 0.2  | 0.3    | < 0.4  | < 0.4  | 0.67   | < 0.04 | 0.1    | 0.22   | < 0.1  
|FQ4
      C-1 41-61           | 51          | < 0.2  | 0.29   | < 0.4  | < 0.4  | 0.54   | < 0.04 | 0.09   | 0.15   | < 0.1  
|FQ4
      C-1 61-81           | 71          | < 0.2  | 0.15   | < 0.4  | < 0.4  | 0.44   | < 0.04 | 0.07   | 0.13   | < 0.1  
|FQ4
      C-2 99-117          | 108         | < 0.2  | < 0.2  | 0.2    | 0.15   | 1.9    | < 0.04 | 0.08   | 0.33   | < 0.1  
|FQ4
      C-2 142-152         | 147         | 0.08   | < 0.2  | 0.44   | 0.48   | 7.8    | < 0.04 | 0.1    | 4      | < 0.1  
|                              |             |        |        |        |        |        |        |        |        |        
|Field
      No/Depth Interval | Ctr Dpth,cm | Sn ppm | Sr ppm | Th ppm | V ppm  | W ppm  | Y ppm  | Zn ppm | Zr ppm | S2- ppm
|FQ3
      C-5 41-71           | 56          | 80     | 0.41   | < 0.08 | 0.04   | < 0.1  | 0.52   | 5.9    | < 0.04 | 12     
|FQ3
      C-5 71-102          | 86          | 88     | 0.68   | < 0.08 | < 0.4  | < 0.1  | 0.17   | 1.6    | < 0.04 | 64     
|FQ3
      C-5 102-132         | 117         | 81     | 0.71   | < 0.08 | < 0.4  | < 0.1  | 0.06   | 3.3    | < 0.04 | 219    
|FQ3
      C-5 132-163         | 147         | 76     | 0.8    | < 0.08 | < 0.4  | < 0.1  | 0.04   | 2      | < 0.04 | 84     
|                              |             |        |        |        |        |        |        |        |        |        
|FQ4
      C-1 20-41           | 30          | 61     | 0.39   | < 0.08 | < 0.4  | < 0.1  | 0.11   | 5.5    | < 0.04 | 18     
|FQ4
      C-1 @ 41            | 41          | 97     | 0.35   | < 0.08 | < 0.4  | < 0.1  | 0.09   | 13     | < 0.04 | 52     
|FQ4
      C-1 41-61           | 51          | 74     | 0.32   | < 0.08 | < 0.4  | < 0.1  | 0.14   | 6.8    | < 0.04 | 17     
|FQ4
      C-1 61-81           | 71          | 65     | 0.23   | < 0.08 | < 0.4  | < 0.1  | 0.06   | 3.2    | < 0.04 | 28     
|FQ4
      C-2 99-117          | 108         | 74     | 0.58   | < 0.08 | 0.26   | < 0.1  | 0.15   | 1.1    | < 0.04 | 0      
|FQ4
      C-2 142-152         | 147         | 89     | 1.4    | < 0.08 | 0.36   | < 0.1  | 0.34   | 6.6    | < 0.04 | 0      



Geochemical data, Forest
Queen Core 5.



|                              |             |        |        |        |        |        |        |        |        |        
|----------------------------- | ----------- | ------ | ------ | ------ | ------ | ------ | ------ | ------ | ------ | -------
|Field
      No/Depth Interval | Ctr Dpth,cm | Al ppm | Ca ppm | Fe ppm | K ppm  | Mg ppm | Na ppm | P ppm  | Si ppm | Ti ppm 
|FQ5
      C-2A 61-69          | 65          | 100    | 44     | 86     | 7.8    | 21     | < 1    | 9.6    | 6      | < 1    
|FQ5
      C-2B 69-76          | 72          | 6.5    | 22     | 240    | < 1    | 1.2    | < 1    | 1.8    | 5.5    | < 1    
|FQ5
      C-2C 76-81          | 79          | 8.5    | 22     | 350    | < 1    | 1.4    | < 1    | 3.1    | 7.8    | < 1    
|FQ5
      C-2 81-102          | 91          | 200    | 74     | 260    | 8.2    | 110    | < 1    | 19     | 9.5    | < 1    
|FQ5
      C-2E 102-122        | 112         | 170    | 62     | 300    | 8.2    | 87     | < 1    | 16     | 6.7    | < 1    
|FQ5
      C-2D 122-145        | 133         | 210    | 72     | 290    | 12     | 120    | < 1    | 20     | 7      | < 1    
|FQ5
      C-2C 145-165        | 155         | 120    | 50     | 120    | 11     | 54     | < 1    | 9.7    | 3.6    | < 1    
|FQ5
      C-2B 165-173        | 169         | 64     | 37     | 31     | 2.2    | 6.4    | < 1    | 6      | 8.1    | < 1    
|FQ5
      C-2A 173-183        | 178         | 170    | 80     | 100    | 12     | 54     | < 1    | 12     | 7.1    | < 1    
|                              |             |        |        |        |        |        |        |        |        |        
|Field
      No/Depth Interval | Ctr Dpth,cm | Ag ppm | As ppm | B ppm  | Ba ppm | Be ppm | Bi ppm | Cd ppm | Ce ppm | Co ppm 
|FQ5
      C-2A 61-69          | 65          | < 0.04 | < 0.2  | < 0.1  | 0.51   | < 0.02 | < 0.2  | < 0.4  | 0.29   | 0.03   
|FQ5
      C-2B 69-76          | 72          | < 0.04 | < 0.2  | < 0.1  | 0.45   | < 0.02 | < 0.2  | 0.08   | < 0.8  | 0.11   
|FQ5
      C-2C 76-81          | 79          | < 0.04 | < 0.2  | < 0.1  | 0.68   | < 0.02 | < 0.2  | 0.1    | < 0.8  | 0.07   
|FQ5
      C-2 81-102          | 91          | < 0.04 | < 0.2  | < 0.1  | 1.6    | 0.03   | < 0.2  | 0.06   | 0.89   | 0.18   
|FQ5
      C-2E 102-122        | 112         | < 0.04 | < 0.2  | < 0.1  | 1.5    | 0.02   | < 0.2  | 0.05   | 0.73   | 0.19   
|FQ5
      C-2D 122-145        | 133         | < 0.04 | < 0.2  | < 0.1  | 1.9    | 0.02   | < 0.2  | 0.04   | 0.96   | 0.37   
|FQ5
      C-2C 145-165        | 155         | < 0.04 | < 0.2  | < 0.1  | 0.95   | < 0.02 | < 0.2  | < 0.4  | 0.6    | 0.11   
|FQ5
      C-2B 165-173        | 169         | < 0.04 | < 0.2  | < 0.1  | 0.23   | < 0.02 | < 0.2  | < 0.4  | 0.14   | < 0.2  
|FQ5
      C-2A 173-183        | 178         | < 0.04 | < 0.2  | < 0.1  | 1      | < 0.02 | < 0.2  | < 0.4  | 0.63   | 0.05   
|                              |             |        |        |        |        |        |        |        |        |        
|Field
      No/Depth Interval | Ctr Dpth,cm | Cr ppm | Cu ppm | La ppm | Li ppm | Mn ppm | Mo ppm | Ni ppm | Pb ppm | Sb ppm 
|FQ5
      C-2A 61-69          | 65          | 0.03   | < 0.2  | 0.16   | 0.26   | 2.5    | < 0.04 | 0.05   | 1.5    | < 0.1  
|FQ5
      C-2B 69-76          | 72          | < 0.2  | 0.13   | < 0.4  | < 0.4  | 0.32   | < 0.04 | 0.05   | 0.35   | < 0.1  
|FQ5
      C-2C 76-81          | 79          | < 0.2  | 0.12   | < 0.4  | < 0.4  | 0.36   | < 0.04 | 0.05   | 0.2    | < 0.1  
|FQ5
      C-2 81-102          | 91          | 0.1    | 0.89   | 0.52   | 0.42   | 9.5    | < 0.04 | 0.14   | 5.4    | < 0.1  
|FQ5
      C-2E 102-122        | 112         | 0.07   | 0.84   | 0.42   | 0.32   | 7.3    | < 0.04 | 0.14   | 4      | < 0.1  
|FQ5
      C-2D 122-145        | 133         | 0.11   | 1.1    | 0.54   | 0.36   | 20     | 0.06   | 0.17   | 5.3    | < 0.1  
|FQ5
      C-2C 145-165        | 155         | 0.06   | 0.5    | 0.38   | 0.19   | 14     | < 0.04 | 0.08   | 2.7    | < 0.1  
|FQ5
      C-2B 165-173        | 169         | < 0.2  | < 0.2  | 0.08   | 0.04   | 0.76   | < 0.04 | < 0.4  | 0.21   | < 0.1  
|FQ5
      C-2A 173-183        | 178         | 0.06   | 0.37   | 0.35   | 0.38   | 3.7    | < 0.04 | 0.06   | 3.3    | < 0.1  
|                              |             |        |        |        |        |        |        |        |        |        
|Field
      No/Depth Interval | Ctr Dpth,cm | Sn ppm | Sr ppm | Th ppm | V ppm  | W ppm  | Y ppm  | Zn ppm | Zr ppm | S2- ppm
|FQ5
      C-2A 61-69          | 65          | 63     | 0.78   | < 0.08 | 0.12   | < 0.1  | 0.15   | 2.7    | < 0.04 | 138    
|FQ5
      C-2B 69-76          | 72          | 67     | 0.24   | < 0.08 | < 0.4  | < 0.1  | 0.06   | 3.4    | < 0.04 | 5      
|FQ5
      C-2C 76-81          | 79          | 50     | 0.27   | < 0.08 | < 0.4  | < 0.1  | 0.07   | 4.9    | < 0.04 | 71     
|FQ5
      C-2 81-102          | 91          | < 0.1  | 1.1    | < 0.08 | 0.49   | < 0.1  | 0.23   | 12     | < 0.04 | 4      
|FQ5
      C-2E 102-122        | 112         | < 0.1  | 0.94   | < 0.08 | 0.4    | < 0.1  | 0.19   | 8.8    | < 0.04 | 23     
|FQ5
      C-2D 122-145        | 133         | < 0.1  | 1.2    | < 0.08 | 0.54   | < 0.1  | 0.2    | 9.4    | < 0.04 | 144    
|FQ5
      C-2C 145-165        | 155         | < 0.1  | 0.78   | < 0.08 | 0.26   | < 0.1  | 0.16   | 5.4    | < 0.04 | 97     
|FQ5
      C-2B 165-173        | 169         | 0.1    | 0.54   | < 0.08 | < 0.4  | < 0.1  | 0.12   | 1.8    | < 0.04 | 77     
|FQ5
      C-2A 173-183        | 178         | 0.4    | 1.5    | < 0.08 | 0.2    | < 0.1  | 0.26   | 3.2    | < 0.04 | 15     



Geochemical data, Forest
Queen Core 7.



|                              |             |        |        |        |        |        |        |        |        |        
|----------------------------- | ----------- | ------ | ------ | ------ | ------ | ------ | ------ | ------ | ------ | -------
|Field
      No/Depth Interval | Ctr Dpth,cm | Al ppm | Ca ppm | Fe ppm | K ppm  | Mg ppm | Na ppm | P ppm  | Si ppm | Ti ppm 
|FQ7
      C-3 20-41           | 30          | 130    | 48     | 130    | 7.1    | 44     | < 1    | 9.5    | 5      | < 1    
|FQ7
      C-3 41-71           | 56          | 300    | 77     | 300    | 20     | 150    | 1      | 18     | 3      | < 1    
|FQ7
      C-3 71-99           | 85          | 180    | 56     | 200    | 9.8    | 74     | < 1    | 14     | 3.5    | 1      
|FQ7
      C-3 102-150         | 126         | 210    | 57     | 220    | 9.8    | 84     | 1      | 18     | 5.1    | < 1    
|FQ7
      C-3 150-173         | 161         | 380    | 98     | 440    | 16     | 210    | 1      | 27     | 4.1    | < 1    
|FQ7
      C-3 173-183         | 178         | 460    | 95     | 300    | 18     | 130    | 1      | 47     | 28     | < 1    
|FQ7
      C-3 183-206         | 194         | 370    | 35     | 46     | 1.6    | 12     | < 1    | 34     | 10     | < 1    
|FQ7
      C-3 206-221         | 213         | 600    | 100    | 630    | 16     | 210    | 1      | 49     | 20     | < 1    
|FQ7
      C-3 221-226         | 224         | 88     | 17     | 44     | 1.9    | 19     | < 1    | 6.7    | 19     | < 1    
|FQ7
      C-3 226-246         | 236         | 280    | 74     | 240    | 16     | 97     | 1      | 21     | 8.6    | < 1    
|                              |             |        |        |        |        |        |        |        |        |        
|Field
      No/Depth Interval | Ctr Dpth,cm | Ag ppm | As ppm | B ppm  | Ba ppm | Be ppm | Bi ppm | Cd ppm | Ce ppm | Co ppm 
|FQ7
      C-3 20-41           | 30          | < 0.04 | < 0.2  | < 0.1  | 0.73   | < 0.02 | < 0.2  | 0.05   | 0.54   | 0.14   
|FQ7
      C-3 41-71           | 56          | < 0.04 | 0.3    | < 0.1  | 1.9    | 0.03   | < 0.2  | 0.12   | 1.3    | 0.16   
|FQ7
      C-3 71-99           | 85          | < 0.04 | < 0.2  | < 0.1  | 1.1    | < 0.02 | < 0.2  | 0.04   | 0.69   | 0.15   
|FQ7
      C-3 102-150         | 126         | 0.1    | < 0.2  | < 0.1  | 1.2    | < 0.02 | < 0.2  | 0.14   | 0.84   | 0.25   
|FQ7
      C-3 150-173         | 161         | 0.05   | 0.2    | < 0.1  | 2.5    | 0.03   | < 0.2  | 0.14   | 1.6    | 0.26   
|FQ7
      C-3 173-183         | 178         | 0.04   | 0.3    | < 0.1  | 2      | 0.09   | < 0.2  | < 0.4  | 1.7    | 0.26   
|FQ7
      C-3 183-206         | 194         | < 0.04 | 0.2    | < 0.1  | 0.32   | 0.06   | < 0.2  | 0.04   | 0.56   | 0.16   
|FQ7
      C-3 206-221         | 213         | 0.05   | 0.4    | < 0.1  | 4.3    | 0.09   | < 0.2  | 0.1    | 2      | 0.71   
|FQ7
      C-3 221-226         | 224         | 0.08   | < 0.2  | < 0.1  | 0.21   | < 0.02 | < 0.2  | < 0.4  | 0.18   | 0.04   
|FQ7
      C-3 226-246         | 236         | < 0.04 | < 0.2  | < 0.1  | 1.6    | 0.03   | < 0.2  | 0.04   | 1.2    | 0.2    
|                              |             |        |        |        |        |        |        |        |        |        
|Field
      No/Depth Interval | Ctr Dpth,cm | Cr ppm | Cu ppm | La ppm | Li ppm | Mn ppm | Mo ppm | Ni ppm | Pb ppm | Sb ppm 
|FQ7
      C-3 20-41           | 30          | 0.05   | 0.6    | 0.29   | 0.27   | 2.7    | < 0.04 | 0.09   | 7.1    | < 0.1  
|FQ7
      C-3 41-71           | 56          | 0.13   | 2.1    | 0.78   | 0.77   | 11     | 0.04   | 0.15   | 7.7    | < 0.1  
|FQ7
      C-3 71-99           | 85          | 0.08   | 0.53   | 0.38   | 0.42   | 4      | < 0.04 | 0.1    | 5.4    | < 0.1  
|FQ7
      C-3 102-150         | 126         | 0.09   | 2      | 0.44   | 0.47   | 6.5    | < 0.04 | 0.16   | 27     | < 0.1  
|FQ7
      C-3 150-173         | 161         | 0.18   | 2.7    | 0.87   | 1      | 16     | 0.05   | 0.22   | 10     | < 0.1  
|FQ7
      C-3 173-183         | 178         | 0.15   | 2      | 0.95   | 0.86   | 10     | 0.08   | 0.2    | 6.3    | < 0.1  
|FQ7
      C-3 183-206         | 194         | 0.03   | 0.48   | 0.17   | 0.11   | 1.4    | < 0.04 | 0.06   | 0.74   | < 0.1  
|FQ7
      C-3 206-221         | 213         | 0.16   | 3.4    | 0.74   | 1.7    | 19     | 0.2    | 0.34   | 8.7    | < 0.1  
|FQ7
      C-3 221-226         | 224         | <0.02  | 0.2    | 0.09   | 0.12   | 2      | < 0.04 | 0.05   | 0.6    | < 0.1  
|FQ7
      C-3 226-246         | 236         | 0.1    | 0.8    | 0.61   | 0.58   | 6.3    | < 0.04 | 0.15   | 3.4    | < 0.1  
|                              |             |        |        |        |        |        |        |        |        |        
|Field
      No/Depth Interval | Ctr Dpth,cm | Sn ppm | Sr ppm | Th ppm | V ppm  | W ppm  | Y ppm  | Zn ppm | Zr ppm | S2- ppm
|FQ7
      C-3 20-41           | 30          | < 0.1  | 0.82   | < 0.08 | 0.32   | < 0.1  | 0.32   | 10     | < 0.04 | 9      
|FQ7
      C-3 41-71           | 56          | < 0.1  | 1.3    | < 0.08 | 0.65   | < 0.1  | 0.37   | 14     | < 0.04 | 22     
|FQ7
      C-3 71-99           | 85          | < 0.1  | 0.99   | < 0.08 | 0.47   | < 0.1  | 0.25   | 8.8    | < 0.04 | 4      
|FQ7
      C-3 102-150         | 126         | < 0.1  | 0.92   | < 0.08 | 0.5    | < 0.1  | 0.46   | 20     | < 0.04 | 36     
|FQ7
      C-3 150-173         | 161         | < 0.1  | 1.5    | < 0.08 | 0.86   | < 0.1  | 0.44   | 17     | < 0.04 | 6      
|FQ7
      C-3 173-183         | 178         | < 0.1  | 1.5    | < 0.08 | 0.65   | < 0.1  | 0.57   | 14     | < 0.04 | 5      
|FQ7
      C-3 183-206         | 194         | < 0.1  | 0.54   | < 0.08 | 0.09   | < 0.1  | 0.35   | 7.8    | < 0.04 | 6      
|FQ7
      C-3 206-221         | 213         | < 0.1  | 1.9    | < 0.08 | 0.84   | < 0.1  | 0.72   | 20     | < 0.04 | 6      
|FQ7
      C-3 221-226         | 224         | 0.29   | 0.25   | < 0.08 | 0.08   | < 0.1  | 0.14   | 1.5    | < 0.04 | 2      
|FQ7
      C-3 226-246         | 236         | < 0.1  | 1.3    | < 0.08 | 0.6    | < 0.1  | 0.47   | 10     | < 0.04 | 13     



Geochemical data, Forest
Queen Cores 9 and 10.



|                              |             |        |        |        |        |        |        |        |        |        
|----------------------------- | ----------- | ------ | ------ | ------ | ------ | ------ | ------ | ------ | ------ | -------
|Field
      No/Depth Interval | Ctr Dpth,cm | Al ppm | Ca ppm | Fe ppm | K ppm  | Mg ppm | Na ppm | P ppm  | Si ppm | Ti ppm 
|FQ9
      0-20                | 10          | 23     | 13     | 78     | 1.6    | 2.9    | < 1    | 4.9    | 7.6    | < 1    
|FQ9
      20-61               | 41          | 62     | 34     | 120    | 3.8    | 14     | < 1    | 4.2    | 6.6    | < 1    
|FQ9
      61-76               | 69          | 92     | 55     | 200    | 5      | 34     | < 1    | 7.6    | 4.4    | < 1    
|                              |             |        |        |        |        |        |        |        |        |        
|FQ10B
      32-52             | 42          | 190    | 38     | 540    | 9.9    | 99     | < 1    | 23     | 13     | < 1    
|FQ10A
      52-56             | 54          | 60     | 20     | 95     | 4.4    | 19     | < 1    | 6.4    | 4.5    | < 1    
|                              |             |        |        |        |        |        |        |        |        |        
|Field
      No/Depth Interval | Ctr Dpth,cm | Ag ppm | As ppm | B ppm  | Ba ppm | Be ppm | Bi ppm | Cd ppm | Ce ppm | Co ppm 
|FQ9
      0-20                | 10          | < 0.04 | < 0.2  | < 0.1  | 0.18   | < 0.02 | < 0.2  | 0.1    | < 0.8  | 0.08   
|FQ9
      20-61               | 41          | < 0.04 | < 0.2  | < 0.1  | 0.45   | < 0.02 | < 0.2  | < 0.4  | 0.2    | 0.04   
|FQ9
      61-76               | 69          | < 0.04 | < 0.2  | < 0.1  | 0.74   | < 0.02 | < 0.2  | < 0.4  | 0.38   | 0.08   
|                              |             |        |        |        |        |        |        |        |        |        
|FQ10B
      32-52             | 42          | 0.05   | 1      | < 0.1  | 2.7    | 0.02   | < 0.2  | 0.2    | 0.92   | 0.29   
|FQ10A
      52-56             | 54          | < 0.04 | < 0.2  | < 0.1  | 0.51   | < 0.02 | < 0.2  | 0.12   | 0.33   | 0.04   
|                              |             |        |        |        |        |        |        |        |        |        
|Field
      No/Depth Interval | Ctr Dpth,cm | Cr ppm | Cu ppm | La ppm | Li ppm | Mn ppm | Mo ppm | Ni ppm | Pb ppm | Sb ppm 
|FQ9
      0-20                | 10          | < 0.2  | 0.17   | < 0.4  | < 0.4  | 1.1    | < 0.04 | 0.05   | 0.61   | < 0.1  
|FQ9
      20-61               | 41          | < 0.2  | < 0.2  | 0.11   | 0.08   | 1.8    | < 0.04 | < 0.4  | 0.49   | < 0.1  
|FQ9
      61-76               | 69          | 0.02   | < 0.2  | 0.2    | 0.15   | 2.9    | < 0.04 | 0.06   | 0.45   | < 0.1  
|                              |             |        |        |        |        |        |        |        |        |        
|FQ10B
      32-52             | 42          | 0.25   | 6.3    | 0.55   | 0.34   | 64     | 0.1    | 0.24   | 6.6    | < 0.1  
|FQ10A
      52-56             | 54          | 0.02   | 5.4    | 0.35   | 0.06   | 17     | < 0.04 | < 0.4  | 3.7    | < 0.1  
|                              |             |        |        |        |        |        |        |        |        |        
|Field
      No/Depth Interval | Ctr Dpth,cm | Sn ppm | Sr ppm | Th ppm | V ppm  | W ppm  | Y ppm  | Zn ppm | Zr ppm | S2- ppm
|FQ9
      0-20                | 10          | 65     | 0.19   | < 0.08 | < 0.4  | < 0.1  | 0.09   | 7.1    | < 0.04 | 65     
|FQ9
      20-61               | 41          | 200    | 0.46   | < 0.08 | 0.1    | < 0.1  | 0.2    | 2.3    | < 0.04 | 430    
|FQ9
      61-76               | 69          | 62     | 0.77   | < 0.08 | 0.21   | < 0.1  | 0.2    | 2.9    | < 0.04 | 15     
|                              |             |        |        |        |        |        |        |        |        |        
|FQ10B
      32-52             | 42          | < 0.1  | 0.44   | < 0.08 | 0.42   | < 0.1  | 0.22   | 20     | < 0.04 | 0      
|FQ10A
      52-56             | 54          | 0.38   | 0.23   | < 0.08 | 0.1    | < 0.1  | 0.16   | 12     | < 0.04 | 0      

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