2
included in the U.S. Department of Energy (DOE) critical
materials list published in 2023, which uses different crite-
ria to determine criticality.
With its historic production of what are now con-
sidered critical minerals, as well as the potential for addi-
tional critical minerals such as REE and PGE, the Zuni
Mountains serves as a practical choice for reinvestigation.
As part of a multi-state USGS Earth Mapping Resources
Initiative (Earth MRI) project focused on critical miner-
als in the Colorado Plateau, the New Mexico Bureau of
Geology and Minerals Resources (NMBGMR) conducted
a regional stream sediment survey to assess the critical min-
eral potential of the district. This stream sediment survey
was performed in conjunction with a graduate level course
in exploration geochemistry taught at New Mexico Tech
by the co-author. The course provided an opportunity for
graduate students to help design and implement a stream
sediment survey to explore for critical minerals.
METHODS
Sample Collection
Streams and drainages in the Zuni Mountains were identi-
fied using topographic maps and potential sample locations
were chosen based on land status, distance from potential
sources of contamination, and bedrock geology. In the
field, sample locations may have been adjusted to avoid
heavily vegetated areas, or areas with minimal sediment. As
nearly all streams and drainages in the district are ephem-
eral, most of the sediments that were collected were dry.
Dry sediments were collected using a shovel or trowel and
sieved with a 2 mm sieve into a bucket where the sample
was homogenized and split into labeled plastic bags for
geochemical analysis and archive. Some sediments were too
damp to be sieved while in the field and were brought back
to the NMBGMR where they were air dried, sieved, and
split as above. At each sample site, field notes recorded the
GPS coordinates, the bedrock geology where possible, as
well as a description of the sediment.
Whole-rock and Trace Element Geochemistry
Samples were submitted to the USGS where a contract
laboratory performed whole-rock and trace element
geochemical analyses. Borate fusion followed by X-ray
fluorescence (XRF) analysis provided concentrations of
major elements and oxides. Four acid digestion followed by
inductively coupled plasma mass spectrometry (ICP-MS)
provided concentrations for trace elements. Additional
information on geochemical analyses along with QA/QC
will be described in future reports. IMDEX ioGAS and
Microsoft Excel were used to analyze and present geochem-
ical data.
RESULTS
76 stream sediment samples were collected for this project,
with most of the samples collected in the central to south-
eastern portion of the district (Figure 1).
Whole-Rock and Trace Element Geochemical Data
Initial whole-rock and trace element geochemical results
show a wide range of concentrations for many critical
minerals of potential interest in the district. Summary
statistics of selected critical minerals with average upper
continental crust (UCC) values are shown in Table 1. Of
Figure 1. Map showing the location of stream sediment
samples in the Zuni Mountains
Table 1. Summary statistics of selected critical minerals in stream sediment samples with
average upper continental crust (UCC) values. All units in ppm
n =76 As Ba Bi Co Cr Cu Ni Sb V Zr TREE
Minimum 5 269 0.2 2.7 10 10 5 0.2 14 69.3 69
Maximum 700 2122 25.8 24.5 88 638 145 111 172 497 249
Mean 29 776 1 7 25 28 21 5 51 214 134
UCC avg. 5.7 624 0.2 15 73 27 34 0.08 106 193 149
included in the U.S. Department of Energy (DOE) critical
materials list published in 2023, which uses different crite-
ria to determine criticality.
With its historic production of what are now con-
sidered critical minerals, as well as the potential for addi-
tional critical minerals such as REE and PGE, the Zuni
Mountains serves as a practical choice for reinvestigation.
As part of a multi-state USGS Earth Mapping Resources
Initiative (Earth MRI) project focused on critical miner-
als in the Colorado Plateau, the New Mexico Bureau of
Geology and Minerals Resources (NMBGMR) conducted
a regional stream sediment survey to assess the critical min-
eral potential of the district. This stream sediment survey
was performed in conjunction with a graduate level course
in exploration geochemistry taught at New Mexico Tech
by the co-author. The course provided an opportunity for
graduate students to help design and implement a stream
sediment survey to explore for critical minerals.
METHODS
Sample Collection
Streams and drainages in the Zuni Mountains were identi-
fied using topographic maps and potential sample locations
were chosen based on land status, distance from potential
sources of contamination, and bedrock geology. In the
field, sample locations may have been adjusted to avoid
heavily vegetated areas, or areas with minimal sediment. As
nearly all streams and drainages in the district are ephem-
eral, most of the sediments that were collected were dry.
Dry sediments were collected using a shovel or trowel and
sieved with a 2 mm sieve into a bucket where the sample
was homogenized and split into labeled plastic bags for
geochemical analysis and archive. Some sediments were too
damp to be sieved while in the field and were brought back
to the NMBGMR where they were air dried, sieved, and
split as above. At each sample site, field notes recorded the
GPS coordinates, the bedrock geology where possible, as
well as a description of the sediment.
Whole-rock and Trace Element Geochemistry
Samples were submitted to the USGS where a contract
laboratory performed whole-rock and trace element
geochemical analyses. Borate fusion followed by X-ray
fluorescence (XRF) analysis provided concentrations of
major elements and oxides. Four acid digestion followed by
inductively coupled plasma mass spectrometry (ICP-MS)
provided concentrations for trace elements. Additional
information on geochemical analyses along with QA/QC
will be described in future reports. IMDEX ioGAS and
Microsoft Excel were used to analyze and present geochem-
ical data.
RESULTS
76 stream sediment samples were collected for this project,
with most of the samples collected in the central to south-
eastern portion of the district (Figure 1).
Whole-Rock and Trace Element Geochemical Data
Initial whole-rock and trace element geochemical results
show a wide range of concentrations for many critical
minerals of potential interest in the district. Summary
statistics of selected critical minerals with average upper
continental crust (UCC) values are shown in Table 1. Of
Figure 1. Map showing the location of stream sediment
samples in the Zuni Mountains
Table 1. Summary statistics of selected critical minerals in stream sediment samples with
average upper continental crust (UCC) values. All units in ppm
n =76 As Ba Bi Co Cr Cu Ni Sb V Zr TREE
Minimum 5 269 0.2 2.7 10 10 5 0.2 14 69.3 69
Maximum 700 2122 25.8 24.5 88 638 145 111 172 497 249
Mean 29 776 1 7 25 28 21 5 51 214 134
UCC avg. 5.7 624 0.2 15 73 27 34 0.08 106 193 149