Transcript uranium deposits in the española basin, santa fe county, new mexico

URANIUM DEPOSITS IN THE ESPAÑOLA BASIN, SANTA FE COUNTY,
NEW MEXICO
VIRGINIA T.McLEMORE, 1, DENNIS McQUILLAN2, PATRICK LONGMIRE3, AND DAVID VANIMAN3
1New Mexico Bureau of Geology and Mineral Resources, New Mexico Institute of Mining and Technology, Socorro, New Mexico 87801, [email protected];
2 New Mexico Environment Department, 525 Camino de los Marquez, Suite 1, Santa Fe, New Mexico 87505, [email protected];
3EES-14, MS D469, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, [email protected], [email protected]
TYPES OF URANIUM DEPOSITS
ABSTRACT
Uranium mineralization in the Española Basin is not of sufficient quantity and quality to justify mining. However,
many private water wells in the region produce water with concentrations of uranium (up to 1,820 g/L) that exceed
the safe drinking water standard of 30 g/L. Therefore, it is important to understand the source of the uranium in the
groundwater and the processes involved. Potential sources for uranium in the groundwater include 1) uranium
occurrences in the Tesuque Formation (San Jose mining district); 2) veins, replacements, and pegmatites in
Proterozoic rocks (San Jose and Nambe mining districts); 3) Proterozoic granitic rocks in the Sangre de Cristo
Formation; and 4) rhyolitic ash beds found interbedded within the Tesuque Formation.
URANIUM IN PROTEROZOIC VEINS,
REPLACEMENTS, AND PEGMATITES
Three types of sandstone uranium deposits are found in the San Jose district: 1) medium-grained sandstone with
uranium associated with clay galls and carbonaceous material, 2) poorly consolidated fine- to medium-grained
sandstone with disseminated uranium and little carbonaceous material, and 3) coarse-grained sandstone to
conglomerate with abundant uranium associated with carbonaceous material. Carnotite, schroeckingerite, and metaautunite coat fractures and bedding surfaces in sandstone, siltstone and shale within the Tesuque Formation,
especially near clay galls and carbonaceous material. Uranium also occurs as coatings around opal and chert grains,
with organic debris, and in clay zones. One property, the San Jose No. 13 (NMSF0033), produced 12 lbs (5 kg) of
U3O8 at a grade of 0.05% U3O8 in 1957.
Shaw No. 2 prospect.
INTRODUCTION
Many residents in the Española Basin in Santa Fe
County have high concentrations of uranium and
radon in their drinking water and high
concentrations of uranium are found in both NURE
water and stream-sediment samples (McLemore,
2010a, b). Uranium has been detected in
approximately 50% of the water supply wells in this
area at concentrations exceeding the drinking water
standard of 30 ug/L. At least 27 wells serving 19
public water systems, and 209 private domestic
wells, produce water with excessive uranium.
Concentrations range from less than 1 μg/L to a
maximum of 1820 μg/L. High uranium in drinking
water can cause kidney toxicity. In addition, high
levels of indoor radon are widespread in this region.
EPA’s recommended action level for indoor radon is
4 pCi/L to protect against lung cancer. Radon
concentrations in excess of 20 pCi/L have been
measured in buildings in the area, and abatement
measures have been taken at many locations. Since
some of the uranium concentrations in groundwater
exceed safe drinking water standards and some
homes in the area have excessive indoor radon, it is
important to understand the source of the uranium
in the groundwater and the processes involved.
Uranium with clay galls and
organic material, San Jose mine.
Shaw No. 2 adit.
Uranium is found in veins, shear zones, and pegmatites in Proterozoic rocks in the San Jose
and Nambe mining district. At the Shaw No. 2 prospect (NMSF0034) in section 7, T20N,
R10E (35.9827424°N, 105.9221679°W), pits and 2 short adits expose Precambrian vein
and replacement deposits consisting of secondary uranium minerals disseminated along a
shear zone (N20°E), approximately 1 m thick, in Proterozoic amphibolite schist intruded by
simple quartz-feldspar-biotite pegmatites and granite. The uranium minerals are reported
associated with secondary copper minerals. Hematite, quartz, biotite, feldspar, and uranium
minerals are found along fractures within the shear zone. Radioactivity was approximately
50 times background reading (background 30 cps, high 1500 cps). Reid et al. (1982)
reported a sample contained 47 ppm U and a sample collected for this report contained 48
ppm U.
The uranium occurrences in the Tesuque Formation probably represent natural precipitation and concentration from
uraniferous groundwaters, likely derived from 1) the Sangre de Cristo Mountains to the east, 2) ash beds within the
Tesuque Formation, and/or 3) the alteration of granitic and/or volcanic detritus in the sedimentary host rocks. The
occurrence of uranium in the waters in this area is most likely a result of weathering of uranium from rocks in the
adjoining mountains and subsequent migration of uranium (VI)-carbonate complexes and radon in the groundwater.
Uranium then precipitated from the waters to form the geochemical anomalies found in the stream sediments and
prospects.
SANDSTONE URANIUM DEPOSITS
Oxidized uranium-bearing layer with clay galls.
Note clay lense below oxidized layer (Oxide
Butte, NMSF-158).
Three types of sandstone uranium deposits are found in the San Jose mining district: 1)
medium-grained sandstone with uranium associated with clay galls and carbonaceous
material, 2) poorly consolidated fine- to medium-grained sandstone with disseminated
uranium and little carbonaceous material, and 3) coarse-grained sandstone to conglomerate
with abundant uranium associated with carbonaceous material. Carnotite, schroekingerite, and
meta-autunite coat fractures and bedding surfaces in sandstone, siltstone and shale within the
Tesuque Formation, especially near clay galls and carbonaceous material (Chenoweth, 1979).
Uranium also occurs as coatings around opal and chert grains, with organic debris, and in clay
zones. One property, the San Jose No. 13 (NMSF0033), yielded 12 lbs (5 kg) of U3O8 at a
grade of 0.05% U3O8 in 1957 (U.S. Atomic Energy Commission file data; McLemore, 1983).
Samples assay as much as 800 ppm U.
SOURCES OF URANIUM
Typical rhyolite ash can
contain 10-20 ppm U
and this uranium is
easily leached.
Volcanic ash beds in the Tesuque Formation.
The sandstone uranium occurrences in the Tesuque Formation probably represent natural precipitation
and concentration from uraniferous groundwaters, likely derived from 1) Proterozoic rocks in the
Sangre de Cristo Mountains to the east, 2) volcanic ash beds within the Tesuque Formation, 3) the
alteration of granitic and/or volcanic detritus within the sedimentary host rocks, and 4) uranium-bearing
waters rising along the faults along the eastern boundary of the basin. Uranium in modern groundwaters
likely was derived from the same sources, as well as from leaching and oxidation of older uranium
occurrences in the Tesuque Formation. Green clay lenses in the Tesuque Formation could have formed
from the alteration of leaching of volcanic ash beds. Volcanic ash beds are a well known source of
uranium in sandstones (Zielinski, 1978; Walton et al., 1981; Kizis and Runnels, 1984).
DISTRIBUTION OF URANIUM IN THE SAN JOSE AND NAMBE
MINING DISTRICTS
Green clay beds.
Reworked ash beds.
Typical granites contain 5-10 ppm U
and pegmatites can contain as much
as several percent U. Uraniumbearing minerals are found in many
pegmatites deposits in the Sangre de
Cristo Mountains
(McLemore,
1983).
DEPOSITION MODEL FOR URANIUM DEPOSITS
Typical Proterozoic pegmatite intruding granite.
REFERENCES
Anderson, O.J., 1980, Abandoned or inactive uranium mines in New Mexico: New Mexico Bureau Mines Mineral Resources,
Open-file Report 148, 778 p.
Chenoweth, W.L., 1979, Uranium in the Santa Fe area, New Mexico: New Mexico Geological Society, Guidebook 30, p. 261264.
Collins, G.E., and Freeland, R.E., 1956, A report in the airborne radiometric survey and ground geologic reconnaissance in the
Espanola area New Mexico: U.S. Atomic Energy Commission, Report RME-1075, 16 p.
Devoto, R.H., 1978, Uranium in Phanerozoic sandstone and volcanic rock, in Short course in uranium deposits; their
mineralogy and origin: American Geological Institute, Short Course Handbook 3, p. 293-305.
Green, M.W., and others, 1980, Uranium resource evaluation, Aztec NTMS 1- by 2-degree quadrangle, New Mexico and
Colorado: U.S. Department of Energy, Report PGJ/F-012(82), 79 p.
Hilpert, L.S., 1969, Uranium resources of northwestern New Mexico: U.S. Geological Survey, Professional Paper 603, 166 p.
Kizis, J.A., Jr., and Runnels, D.D., 1984, The mobility of uranium and associated trace elements in the Bates Mountain Tuff,
central Nevada: Economic Geology, v. 79, p. 558-564.
Koning, D.J., 2002, Preliminary geologic map of the Espanola 7.5-minute quadrangle, Rio Arriba and Santa Fe Counties, New
Mexico: New Mexico Bureau of Geology and Mineral Resources, Geologic Open-file Report OF-GM 54, scale 1:24,000
Linhoff, B., Longmire, L., Rearick, M., Perkins, G., Larson, T., Newell, D., McQuillan, D. and Gallegos, R., 2009,
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Longmire, P., Linhoff, B., Rearick, M., Wiman, S., and Siegel, M., 2010, Aqueous geochemistry and environmental fate of
uranium in the Española Basin, New Mexico: New Mexico Water Research Symposium, August 3, Socorro, NM, p. 6.
Sketch of the formation of roll-front uranium
deposit. S=sulfur, Se=selenium, U=uranium.
McLemore, V.T., 1983, Uranium and thorium occurrences in New Mexico: distribution, geology, production, and resources;
with selected bibliography: New Mexico Bureau of Mines and Mineral Resources, Open-file Report OF-182, 950 p., also U.S.
Department of Energy Report GJBX-11(83).
McLemore, V.T., 2010a, Use of the New Mexico Mines Database and ArcMap in Uranium Reclamation Studies: Society of
Mining, Metallurgy and Exploration Annual Convention, Phoenix, Feb 2010, Preprint 10-125
McLemore, V.T., 2010b, Use of the New Mexico Mines Database and ArcMap in Uranium Reclamation Studies: Society of
Mining, Metallurgy and Exploration Transactions, in press.
Location of uranium mining districts, mines, prospects, NURE stream-sediment samples, and NURE water samples in the San
Jose and Nambe mining districts, Santa Fe County, New Mexico (T19-21N, R8, 9E; McLemore, 2010a, b). Note that high
uranium concentrations also are found in the Proterozoic terrain (Nambe district), which are related to radioactive shear zones
and pegmatites that intruded Proterozoic granitic and metamorphic rocks. Stream-sediment samples containing greater than 12
ppm U are considered anomalously high and water samples containing greater than 30 ppb are considered anomalously high
(McLemore, 2010a, b).
Uranium migrated in the groundwater down dip and precipitated from the groundwaters to form the roll-front sandstone uranium
deposits. Uranium precipitated at reduced zones formed by clay, organic material, and possibly at the interface of reduced basin
waters.
Continued oxidation and leaching of uranium from the uranium sources and from older uranium deposits in the Tesuque Formation
and Proterozoic rocks then formed the modern geochemical anomalies found today in the stream sediments and groundwater. Radon
results from the decay of uranium-bearing minerals in the rocks.
This area warrants continued examination to understand the significance of these geochemical anomalies and to determine if public
health is at risk.
McQuillan, D., Longmire, P. Johnson, P.S., Kulis, J., Martinez, F., Counce, D. and Keating, E., 2005, Natural uranium in
ground water in the Espanola Basin in Geologic and hydrogeologic framework of the Espanola Basin; proceedings,
McKinney: U.S. Geological Survey, Open-File Report, p. 11.
Nash, J.T., H.C. Granger, and S.S. Adams, 1981, Geology and concepts of genesis of important types of uranium deposits, in
B.J. Skinner, ed., 75th Anniversary Volume: Economic Geology, 1905-1980, p. 63-116.
Reid, B.E., Griswold, G.B., Jacobsen, L.C., and Lessard, R.H., 1982, Santa Fe Quadrangle, New Mexico: U.S. Department of
Energy, Report PGJ/F-021(82), 41 p.
U.S. Atomic Energy Commission, 1970, Preliminary reconnaissance for uranium in New Mexico, 1950-1958: U.S. Atomic
Energy Commission, Report REM-160, p. 156.
Walton, A.W., Galloway, W.E. and Henry, C.D., 1981, Release of uranium from the volcanic glass in sedimentary sequences:
An analysis of two systems: Economic Geologist, v. 76, p. 69-88.
Zielinski, R.A., 1978, Uranium abundances and distribution in associated glassy and crystalline rhyolites of the western
United States: Geological Society of America, Bulletin, v. 89, p. 409-414.