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OE/IO/12079-24
ESL-50
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GEOCHEMISTRY OF SELECTED ROCK SAMPLES:
COLAUO GEUTHERMAL AREA, NEVADA
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>
by
Odin o. Christensen
Bruce S. Si bbett
Michael J. Bullett
January
1~81
EA~TH SCIENCE LABORATORY DIVISION
UNIVERSITY OF uTAH RESEARCH INSTITUTE
42U Chipeta Way, Suite 12U
Salt Lake City, UT 841U8
Prepared for the
U.S. DEPARTMENT OF ENERGY
DIVISION OF GEOTHERMAL ENERGY
Under Contract No. DE-ACU7-80ID120/~
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DISCLAIMER
Th,s book was prepared as an account 01 work sponsored by an agency of the United States Government.
N ... ither 1he United SIdles Government nor any agency thereof, nor any of their employees, makes any
Wdrranty. express or Implied, or assumes any legal liability or responSibility for the accuracy.
cOl"'lpleleness, or usefulness of any information, apparatus. product, or process dlscloS8<t or
represents that Its use l'I'3uld no! Infnnge pnvately owned rights. Reference herein to any speCific
comrr>efclal product, process, or serVice by trade name, trademark, manufacturer, or otherWise, does
not necessarily constitute or imply Its endorsement, recommendation, or favormg by the United
Slates Government or any agency thereof. The views and opmions of authors expressed herein do not
necessartly state or reflect those of the United States Government or any agency thereof.
DISTRIBUTION OF THIS /IOCUMflT IS 1IN1iMITro
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NOTICE
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This report was prepared to document work sponsored by the united States
Government.
Neither the United States nor its agent, the United States
Uepartment of Energy, nor any Federal employees, nor any of their contractors,
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subcontractors or their employees, makes any warranty, express or implied, or
assumes any legal liability or responsibility for the accuracy, completeness,
or usefulness of any information, apparatus, product or process disclosed, or
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represents that its use would not infringe privately owned rights.
NOTICE
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l{eference to a company or product name does not imply approval or
recommendation of the product by the University of Utah Research Institute or
the U.S. Uepartment of Energy to the exclusion of others that may be suitable.
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TABLE OF CONTENTS
I
A~smACT
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1
INTRUUUCTI ON
2
lJlSCLISSION •
3
ACKNOWLEDGEMENTS •
9
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I{EFEI{ENCES • • •
• • • 10
ILLUSTRA TI ONS
Fi gure 1
·...............
Sample location map.
4
TABLES
Table 1
Table 2
Taole 3
t
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Geochemi stry of samples
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Summary of geochemical data from gradient nole
cuttings . . . . . . . . . .
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Sample descriptions
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13
17
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ABSTRACT
This report presents the results of the chemical analysis of 30 surface
rock samples from the Colado geothermal area.
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The samples represent a variety
uf materials affected by several hydrothermal events which have formed Au, Sb
and clay deposits within the area.
The active geothermal system is currently
Deing evaluated for electrical power production.
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The elements As, Sb, Au, Ag, Li and Hg have been concentrated
durin~
more
than one of the hydrothermal events which have affected the Colado area.
Distinct chemical signatures do not exist for any particular event, instead,
it appears that this suite of elements has been repeatedly remobilized,
probably in response to similar physical and chemical conditions and
processes.
t
Oelineation of geochemical zoning related to the active geothennal
system is possible only because it is spatially separated from the older
hydrotherma I depos its.
fhe chemical similarity between the older hydrothermal events and the
present hydrothermal system suggest that the Sb and Au mineralization formed
at shallm'l depths in a boi ling geothermal environment.
It is suggested that
new ore zones may be discovered in the Willard mining district if the
geothermal model is applied to exploration •
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1
INTKODUCTION
The Colado geothermal area lies in south-central Pershing County, Nevada,
about 10 km northeast of Lovelock on the western flank of the West Humboldt
Kange.
The geothermal potential of the area for electrical power production
is currently being evaluated by Getty Oil Company in cooperation with the
Division of Geothermal Energy of the U.S. Department of Energy through the
Industry Coupled Case Study program.
The geology of the Colado area has recently been mapped and reviewed by
Siobett and Bullett (198U) and the multielement geochemistry of temperature
gradient hole cuttings evaluated by Christensen (198U).
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During geologic
Inapping of the area, numerous rock samples were collected for petrographic and
geochemical studies.
This report presents the results of the chemical
analyses and evaluates these results within the context of the chemical model
developed from the geochemistry of the gradient hole cuttings.
Thirty rock samples were prepared and analyzed for 38 elements by
inductively-coupled plasma emission spectroscopy (ICP) as described by
Christensen (198U) and Christensen and others (1980).
Statistical reduction
or analysis of chelnical data was not performed since (1) the number of values
is insufficient and (2) the analyzed samples represent a variety of materials
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and thus do not constitute a valid statistical population.
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2
UISCUSSION
The collection locations of samples are shown on Figure 1, sample
descriptions are presented in Table 1, and sample geochemistry is tabulated in
Taole 2.
The samples represent a variety of materials collected from
throughout the geothermal area.
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The Colado geothermal area has been the center of several previous
hydrotnermal events (Sibbett and Bullett, 1980).
These events produced the Sb
and Au deposits east of the present geothermal system, and the cl ay deposi ts
and Cu prospects in tributaries of Coal Creek which collectively are included
in the Willard mining district (Johnson, 1977).
Au ore from the Willard group
of mines (Figure 1) apparently consists of free-milling gold and silver in
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Cu-stained quartz veins containing galena, sphalerite, and garnet.
Cu
prospects on the south side of Coal Canyon apparently explore similar veins
(Johnson, 1977).
The Sb mines have been developed on quartz-stibnite veins that strike
nearly para 11 el to beddi ng withi n the metasedi mentary host rocks.
Sti bnite
occurs as pods and individual crystals in quartz and calcite veins and within
fractures in bedrock.
Reported assays show Sb, Ag, and traces of Au
(Johnson, 1977).
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The clay deposits occur in Tertiary volcanic units where hydrothermal
alteration ofvitric and tuffaceous rocks has been intense.
Montmorillonite
is the principal clay mineral; impurities include cristobalite, quartz,
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feldspar, calcite, zeolites, and gypsum •
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3
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...
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• Gradient Hole Locations
_Rock Sample Locations
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1000
o
2000
.5
3000
4000 FE-ET
1 KILOMETE~
Figure 1. SAMPLE LOCA TIONS
GEOLOGIC BASE FROM SIBBETT AND BULLETT (1980)
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The present geothermal system is centered beneath alluvium along the
western edge of the West Humboldt Range.
Thermal waters probably rise along a
major fault intersection in the Mesozoic rocks then spread out in a shallow
aquifer in the alluvium (Sibbett and Bullett,
I~HO).
Christensen
(I~HU)
has
shown that enrichments of As, Li, Hg and Be are associated with the present
geothennal system.
The samples discussed here were collected in part to evaluate the
Samples
chemical signatures associated with each type of mineralization.
collected from prospect pits, mine dumps and quartz veins in the vicinity of
the Willard Mine include numbers 1, 2, 3, 4,13, 19, 20, 22 and 23. Sample 24
was collected at the Johnson-Heizer mine, the largest Sb mine in the district.
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Samples 0,6, 7,
~,
14, 16, 17 and
volcanic units.
Brecciated and altered materials associated with range-front
1~
represent clay materials associated with
faults include numbers 103, 112, 113, 134, and 137.
The remaining samples are
of a variety of rocks types and veins from throughout the area.
For
comparative purposes, a sUlflmary of geochemical data from the gradient hole
samples investigated by Christensen (19HU) is included as Table 3.
Although the effects of the different periods of mineralization are
recognizably distinct, the suite of characteristic trace elements is largely
the same for all hydrothermal events including the present geothermal system.
i'l\ateri a1s associ ated wi th the preci ous metal mi nera 1i zat i on of the Wi 11 ard
mines are characterized by consistently high concentrations of Li, Cr, Cu, Hg
and As, and some high concentrations of Pb and Ag.
12~U
ppm are especially noted.
Concentrations of As up to
Vein material from the Johnson-Heizer Sb mine
5
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is characterized by unusually large concentrations of Sb, Au and As.
Samples
collected from clay pits in altered Tertiary volcanic rocks have notably high
concentrations of Au and Be and occasionally of Hg.
The brecciated material
associated with range-front faults has anomalous concentrations of As, Sb, Hg
and Au.
The elements As. Sb. Au. Ag. Li and Hg were remobilized and concentrated
during more than one of the hydrothermal events which have affected the Colada
thermal area.
Distinct chemical signatures do not exist for any event.
Instead. it appears that this suite of elements has been repeatedly
remobilized, probably in response to similar physical and chemical conditions
extant during the sequential hydrothermal events •
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Christensen (1980) has shown that a distinctive zoning of As. Hg. Li and
Be exists in gradient hole cuttings from the Colado geothermal area.
Enrichments of these elements outline an area coincident with a thermal
anomaly related to fluid flow within the active geothermal system.
Geochemistry has
been shown to be a useful exploration tool in this situation
where the chemical record of the active system is developed upon the
chemically homogeneous alluvial matrix.
Had the present geothermal system and
the gradient holes been coincident with the older mineralization. it is
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doubtful that the chemical distributions related to the multiple events could
be distinguished.
Such a cOincidence of hydrothermal events and geochemical
signatures has been described for the Cove Fort-Sulphurdale area in Utah
(Ross and others. 1981).
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The chemical similarity between the older hydrothermal events and the
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present geothenoal system strongly suggests that the Sb and Au mineralization
formed at snallow depths in a boiling geothermal environment.
Deposition of
,retals probably occurred as a direct result of boiling or flashing of
hydrothermal fluids, as has been described for modern geothermal systems
(Weissberg, 1Y6Y; White and others, 1971; Weissberg and others, 1980).
Recognition of this genetic relationship suggests that additional ore bodies
may exist at depth, vertically stacked along fluid-flow controlling
structures.
The geothermal model proposed for deposits of the Willard mining district
is essentially that described by Buchanan (1980) for the Guanajuato mining
district, Mexico.
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This model requires an anomalously high geothermal gradient
wnich acts as a driving force behind a convecting hydrothermal system.
Hydro-
thermal fluids become heated, leach alkalies and metals from rocks along their
flow path, and rise toward the surface.
The water rises past the depth where
hydrostatic pressure is insufficient to prevent boiling and boiling occurs,
resulting in significant chemical and physical changes in the solutions and
preCipitation of ore and gangue minerals.
Mineral precipitation frequently results in a self-sealing of fluid
channels, effectively stopping the discharge of fluids upward.
,
Fracturing of
the sealing cap due to tectonic or thermal stress may cause a sudden reduction
in pressure and flashing of the fluid column below the base of the sealing cap
to a depth dependent on the temperature profil e and fl ui d compos it ion.
flashing may lead to mineral precipitation deeper in the system.
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types of boiling are recognized:
hydrostatic boiling and flashing
,
7
Thi s
Thus, two
(Buchanan, 1980).
Two or more levels of mineralization, not necessarily
connected, may be developed.
It is suggested that new ore production zones may be discovered beneath
tne Willard district if the geothermal model is applied.
inclusion studies may serve as useful drilling guides •
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Alteration and fluid
ACKNOwLEUGEMENTS
Analytical work was performed by Ruth Kroneman with the assistance of
Beverly Miller and Tina Cerling.
Critical manuscript reviews by Joe !"1oore.
Howard Ross and Dennis Nielson are appreciated.
Funding for this work was provided by the United States Department of
Erergy, Division of Geothermal Energy to the Earth Science Laboratory under
contract nUinber UE-AC07-HOID12079 •
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9
REFERENCES
L. J., 1Y~u, Ore controls of vertically stacked deposits, Guanajuato, ~exico: Society of Mining Engineers of AIME Reprint ~0-82, 26 p.
~uchanan,
Christensen, 0.0., 1980, Geochemistry of the Co1ado geothermal area, Pershing
County, Nevada: Univ. of Utah Research Inst., Earth Science Laboratory
Rept. 39, 31 p.
•
Christensen, 0.0., Kroneman, R.L., and Capuano, R.M., 1980, Multielement
analysis of geologic materials by inductively coupled plasma-atomic
emission spectroscopy: Univ. of Utah Research Inst., Earth Science
Laboratory Rept. 32, 33 p.
Johnson, M.G., 1977, Geology and mineral deposits of Pershing County, Nevada:
Nevada Bureau of I..,ines and Geology Bulletin 8Y, 115 p.
Ross, H. P., I"'oore, J. N., Glenn, W. L, and Christensen, O. D., 1981, Cove
Fort-Su1phurda1e KGRA: A geological and geophysical case study: Univ. of
Utah Research Inst., Earth Science Laboratory Rept., in preparation.
Sibbett, B.S., and Bullett, I"'.J., 1980, Geology of the Co1ado geothermal area,
Pershing County, Nevada: Univ. of Utah Research Inst., Earth Science
Laboratory Rept. 3~, 34 p.
Weissberg, B. G., 1969, Gold-silver ore-grade precipitates from New Zealand
thermal waters: Econ. Geo1., vol. 64, p. Y5-10~.
Weissberg, B. G., Browne, P. R. L., and Seward, T. M., 1980, Ore metals in
active geothermal systems in Barnes, H. L. (Editor) Geochemistry of
Hydrothermal Ore Oeposits:--John Wiley and Sons, New York, p. 738-780.
White, U. E., i"'uffler, L. J. P., and Truesdell, A. H., 1971, Vapor-dominated
hydrothermal systems compared with· hot-water systems: Econ. Geo1.,
vol. 66, p. 7';)-97.
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TABLE 1
Sample Descriptions
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Sample Number
NVCtiO-l
Description
Mudstone-siltstone from mine working
NVC~O-2
Stained and altered mudstone from prospect pit
NVC~O-3
Stained and altered mudstone from prospect pit
NVCBO-4
Mudstone-siltstone with quartz veining from adit entrance
NVC~O-5
Clay from altered rhyolite
NVCBO-6
Clay from altered rhyolite
NVCBU-7
Perl ite
NVCtiO-B
Clay from altered rhyolite
NVC~U-9
Quartz vein in siltstone from adit
NVC80-1U
Quartz vein in siltstone
NVC~O
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.. l1
Rhyolite sill intruding mudstone/shale
NVC80-13
Mine dump sample: mudstone with quartz veining
NVC~O-14
Clay from altered rhyolite
NVC8U-15
Quartz vein in shale; trench cut
NVC~u-16
Clay prospect; hematite stained
NVCBO-17
Altered ash-flow tuff: clay prospect
NVC8U-IB
Altered rhyolite tuff: clay prospect
NVC80-19
Fracture .. fi 11 i ng
south area
NVC80-20
Quartz vei n mater; a1 from dump of north Wi 11 ard i"1i ne
NVC80-21
Altered rhyolite dike
NVCBO-22
Quartz vei n in mudstone from north Will ard Mi ne dump
NVC8U-23
Quartz and calcite vein, north Willard Mine
quart~
vei n in mudstone at Wi 11 ard
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11
i~i
ne,
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NVC~O-24
Quartz vein in siltstone, Johnson Heizer Mine
NVC~O-103
Silicified breccia in fault zone
NVC80-112
Kaolinite near range-bounding fault
NVC80-113
Altered and hematite-stained andesite between quartz
and calcite veins
NVC80-11B
Si ltstone
NVCBO-133
Conglomerate
NVCBO-134
Altered andesitic flow
NVC80-137
Hematite-stained quartz breccia from fault zone
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12
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TABLE 2 GEOCHEMISTRY OF SAI'1PLES
1
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w
2
3
4
5
6
7
8
Na20, %
K20, %
CaO, %
MgO, %
Fe2°J" %
.116
·2.04
1.02
.447
3.03
.052
1.44
6.13
.692
2.35
.088
2.40
.413
.547
2 .11
.055
2.64
.252
.442
1.00
1.73
2.80
4.94
.788
1.30
2.87
2.71
6.21
.314
1.08
2.98
2.76
.850
.114
1.24
3.06
3.57
1.09
.232
1.40
A1203, ,
n02' %
PlUs. %
Sr, ppm
BaO, %
6.97
.262
.439
254
.106
5.16·
.261
.165
117
.065
7.74
.341
.108
66
.i88
7.33
.309
.050
55
.176
14.41
.064
.131
129
.021
12.53
.056
(,002
86
.012
12.54
.062
<.002
45
.017
12.26
.109
.063
289
.025
Cr, ppm
Mn02,. %
Co,ppm
Ni, ppm
Cu, ppm
67
.012
67
29
39
37
.011
25
11
67
.002
17
11
11
13
38
.002
18
<5
26
<2
.054
2
<5
8
<2
.035
5
<5
<5
<2
.029
17
<5
<5
8
.020
7
<5
<5
Pb,
ln,
Ag,
Au,
As,
25
137
23
<4
1250
10
9
<4
550
13
51
2
<4
200
<10
22
46
<4
425
26
57
<2
6
6
27
49
<2
<4
4
24
55
<2
<4
3
26
60
<2
<4
Sb, ppm
Sn, ppm
Li, ppm
Be, ppm
lr, ppm
81
<5
104
1.6
29
39
<5
106
1.0
20
<30
<5
74
1.7
26
48
<5
94
1.3
31
<30
13
9
4.0
<30
<5
<30
<5
109
3.5
108
<30
<5
9
4.0
122
10
119
La, ppm
Ce, ppm
Hg, ppb
17
28
45
15
19
70
20
31
25
16
23
15
21
31
550
21
33
25
21
23
10
10
19
(5
ppm
ppm
ppm
ppm
ppm
60
:3
6
13
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Table 2 continued
9
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10
11
13
14
15
16
17
Na20, %
K20, %
CaO, %
MgO, %
Fe203, %
.520
1.12
12.84
1.47
1.89
.038
2.44
6.68
2.04
3.83
.397
2.02
1.11
.116
.380
.831
1.77
2.51
1.58
5.44
.757
4.98
1.99
.917
1.10
4.50
2.00
1.74
.184
2.01
.449
2.54
.302
.276
.903
1.30
3.05
2.38
.177
.791
A1203, %
n02, %
1>2 05, %
Sr, ppm
BaD, %
5.51
.220
1.75
286
.102
10.07
.364
.279
119
.281
12.32
.066
.008
87
.085
13 .U1
.737
.234
257
.120
12.49
.171
.077
98
.089
11.15
.278
.147
97
.024
16.67
.213
.009
68
.055
10.73
.133
.047
233
.094
Cr, ppm
Mn02' %
Co, ppm
Ni, ppm
Cu, ppm
Pb, ppm
In, ppm
Ag, ppm
Au, ppm
As, ppm
33
.032
19
16
48
<10
239
4
<4
6
27
.U47
35
21
13
<10
140
<2
4
45
<2
.OU8
24
<5
<5
22
49
<2
<4
10
99
.038
24
36
50
84
4
<4
110
11
.038
10
<5
6
26
18
<2
<4
12
10
.027
24
6
67
11
29
<2
<4
7U
5
.068
18
9
8
78
49
<2
<4
28
4
.044
19
<5
<5
26
18
<2
4
50
Sb, ppm
Sn, ppm
Li, ppm
Be, ppm
lr, ppm
30
<5
21
1.0
32
<30
11
46
1.7
39
<30
<5
90
2.1
111
<30
6
59
3.2
96
<30
<5
61
2.4
92
47
<5
19
1.2
73
<30
<5
74
3.0
122
<30
<5
73
2.2
94
La, ppm
ee, ppm
Hg, ppb
26
37
120
19
25
100
21
40
55
27
43
110
33
52
220
<5
<10
45
26
50
240
34
52
140
17
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•
•
•
...
•
Table 2 continued
......
tTl
18
19
20
Na20, %
K20, %
CaD, %
MgO, %
Fe203' %
1.04
3.82
1.73
.621
1.58
.022
1.68
7.55
.500
1.75
A1203' %
TiQ2' %
P205, %
Sr, ppm
BaO, %
15.31
.159
.003
455
.055
Cr, ppm
Mn02' %
Co, ppm
Ni, ppm
Cu, ppm
Pb, ppm
ln, ppm
Ag, ppm
Au, ppm
As, ppm
Sb,
Sn,
Li,
Be,
21
22
23
.020
1.28
2.56
.388
1.16
.018
2.43
.228
.373
.567
.031
1.50
21.80
.642
1.62
.017
.767
13.50
.158
.624
.474
.523
2.43
1.42
3.35
5.U7
.174
.104
189
.071
4.64
.182
.053
22
.101
11.32
.053
.003
29
.016
5.64
.234
.122
81
.121
2.43
.067
.018
105
.035
4.63
.134
.070
95
.0lD
2
.241
6
<5
8
20
.052
28
9
52
27
.015
35
18
21
<2
.002
18
5
<5
27
.068
22
14
32
11
.156
29
<5
16
13
.057
43
11
11
39
54
<2
10
2
<10
53
<2
5
450
<10
<2
<4
65
20
49
<2
<4
81
<10
282
<2
<4
175
30
76
<2
4
75
15
76
<2
5
300
<30
<5
<30
<5
74
1.3
10
<30
<5
224
1.9
102
<30
<5
43
2.2
23
<30
<5
188
1.6
<5
576
<5
32
1.0
16
11
13
18
35
100
9
7
<10
65
14
18
70
ppm
ppm
ppm
ppm
lr, ppm
3.0
117
35
<5
101
1.7
15
La, ppm
Ce, ppm
Hg, ppb
42
74
10
15
13
45
5
71
220U
13
170
24
•
•
•
-
•
-
Table 2 continued
......
0'1
103
112
113
118
133
134
137
Na2G, %
K20, %
CaO, %
MgO, %
Fe203, %
.038
.051
.616
.059
.120
.429
.019
.022
.027
1.14
.424
1.36
.455
.652
4.17
.219
.126
.096
.090
.528
.042
.657
40.30
.457
7.19
2.07
2.18
9.85
1.81
7.25
.069
.066
.415
.053
10.76
A1203, %
n02, %
P2 05, %
Sr, ppm
BaO, %
4.46
.025
.048
202
.111
31.88
.332
.014
34
.003
8.80
.310
.111
526
.684
13.83
.067
.005
13
.008
3.86
.182
.078
176
.062
14.82
.824
.293
332
.169
7.16
.063
.012
305
.600
Cr, ppm
Mn02' %
Co, ppm
Ni, ppm
Cu, ppm
7
.001
29
<5
5
4
<.001
4
<5
<5
12
.010
18
5
104
<2
.003
15
<5
<5
21
.162
27
50
17
347
.256
37
122
50
<2
.006
14
<5
7
Pb,
Zn,
Ag,
Au,
As,
<10
<5
<2
<4
125
65
<5
<2
8
90
12
59
2
<4
45
17
20
<2
<4
6
17
664
<2
5
50
19
65
<2
2
16
<5
<2
<4
50
Sb, ppm
Sn, ppm
Li, ppm
Be, ppm
lr, ppm
40
<5
28
<0.5
<5
00
<5
20
0.6
194
<30
<5
50
2.4
57
<30
<5
126
1.2
122
<30
18
1.7
31
<30
<5
89
1.9
98
58
<5
32
1.8
36
La, ppm
Ce, ppm
Hg, ppb
5
<10
55
22
51
750
6
13
45
13
32
220
<5
20
490
19
33
25
18
32
550
ppm
ppm
ppm
ppm
ppm
10
III
...
•
TABLE 3
Summary of Geochemical Data from Gradient Hole Cuttings
•
•
•
•
Element
Na, ppm
K, ppm
Ca, ppm
Mg, ppm
Fe, ppm
Al, ppm
Ti, ppm
P, ppm
Sr, ppm
Ba, ppm
V, ppm
Cr, ppm
Mn, ppm
Co, ppm
Ni, ppm
Cu, ppm
Mo, ppm
Pb, ppm
Zn, ppm
Cd, ppm
Ag, ppm
Au, ppm
As, ppm
Sb, ppm
Bi, ppm
U, ppm
Te, ppm
Sn, ppm
Li, ppm
Be, ppm
Zr, ppm
La, ppm
Ce, ppm
Th, ppm
Hg, ppb
Minimum
340
9120
2190
1830
9970
32500
1260
413
19
262
< 150
12
45
13
8
9
< 50
< 10
33
<5
<2
<4
9'
< 30
< 100
<2000
< 50
<5
20
1.5
11
14
23
< 150
10
Maximum
29800
34600
132000
59900
40500
84700
3250
3420
428
2890
< 150
72
1180
875
50
279
< 50
37
2000
10
20
7
275
173
< 100
< 2000
< 50
< 25
96
3.0
107
33
57
< 150
3300
r1ean
8410
21000
52400
10300
22600
56400
2180
956
189
969
< 150
38
388
41
24
28
< 50
Standard Deviation
6670
6220
25200
8010
6550
11000
443
563
111
786
12
173
83
8
26
150
219
47
49
< 100
< 2000
< 50
48
2.1
56
22
32
0.3
25
11
40
9
< 150
265
417
As determined calorimetrically, Hg by gold film detector, all other elements
by ICP.
•
Si lost during. sample digestion; Wand B contaminated during sample preparation
and analysis.
•
•
17