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Research about Jefferson County, Montana

Source-linked reports with geographic coverage including Jefferson County, Montana.

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USGS1982

Multielement chemical and statistical analyses from a uranium hydrogeochemical and stream-sediment survey in and near the Elkhorn Mountains, Jefferson County, Montana. Part I: Surface water

Fifty-two surface-water samples, collected from an area south of Helena, Jefferson County, were analyzed for 51 chemical species. Of these variables, 35 showed detectable variation over the area, and 29 were utilized in a correlation analysis. Two populations are distinguished in the collected samples and are especially evident in the plot of Ca versus U. Samples separated on the basis of U versus Ca proved to represent drainage areas of two differing lithologies. One group was from waters that drain the Boulder batholith, the other from those that drain the Elkhorn Mountains volcanic rocks. These two groups of samples, in general, proved to have parallel but different linear trends between U and other elements. Therefore, the two groups of samples were treated separately in the statistical analyses. Over the area that drains the Boulder batholith, U concentrations in water ranged from 0.37 to 13.0 μ g/l , with a mean of 1.9 μ g/l. The samples from streams draining volcanic areas ranged from 0.04 to 1.5 μ g/l, with a mean of 0.42 μ g/l. The highest U values (12 and 13 μ g/l) occur along Badger Creek, Rawhide Creek, Little Buffalo Gulch, and an unnamed tributary to Clancy Creek. Conductivity, hardness, Ba, Ca, CI, K, Mg, Na and Sr are significantly correlated with U at or better than the 95 percent confidence limit in both populations. For water draining the Boulder batholith, uranium correlates significantly with akalinity, pH, bicarbonate, Li, Mo, NO2+NO3, P04, SiO2, SO4, F, and inorganic carbon. These correlations are similar to those found in a previous study of water samples in north-central New Mexico (Wenrich-Verbeek, 1977b). Uranium in water from the volcanic terrane does not show correlations with any of the above constituents, but does correlate well with V. This relationship with V is absent within the Boulder batholith samples.

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USGS1982

Multielement chemical and statistical analyses from a uranium hydrogeochemical and stream-sediment survey in and near the Elkhorn Mountains, Jefferson County, Montana: Part II, Stream sediments

Fifty-two stream-sediment samples, collected from an area south of Helena, Jefferson County, Montana, were sieved into two size fractions (<88 ?m, and between 88 and 149 ?m) and analyzed for 80 different chemical species. Of these species, 43 showed detectable variation over the area, 31 were subjected to correlation analysis for the fine size fraction, and 30 for the coarse-size fraction. Two populations distinguished in the surface water samples of this study (Suits and Wenrich, 1981) are not as clearly evident in the stream sediments. However, stream-sediment samples from streams draining the Boulder batholith and from streams draining volcanics and volcanogenic sediments (referred to only as volcanics) do show differences in their geochemical relationships, especially between SiO2, Al203 and Na2O versus U. Thus, the sediments were also treated statistically as two lithologic populations as well as two populations based on size fraction. In the fine fraction samples, U ranged from 1.3 to 78 ppm, averaging 25 ppm for the Boulder batholith samples and 8 ppm for the volcanics samples. The range for the coarse fraction was 1.9 to 55 ppm with an average of 17 for the Boulder batholith group and 7 for the volcanics group. High U values (>50 ppm for the fine fraction) were encountered in samples from the Warm Springs Creek drainage area, along Prickly Pear Creek near Welmer and Golconda Creeks and along Muskrat Creek. All groups showed a significant correlation at the 99 percent confidence level (r between 0.73 and 0.77) between U and Th. Uranium was found to correlate significantly only with Th (as mentioned above) and with -Ni in the fine fraction of the volcanics group. U correlates significantly with -Al2O3, Ba, organic C, -K2O, -Sr and Y in both size fractions for the Boulder batholith. Correlations between U and each of several elements differ for the fine and coarse fractions of the Boulder batholith group, suggesting that the U distribution in these stream sediments is in large part controlled by grain size. Correlations were found between U and CaO, Cr, Fe203, -Na2O, Sc, -SiO2, TiO2, Yb and Zr in the coarse fraction but not in the fine fraction. U correlates weakly (to the 90% confidence level, crc<.37) with -Co and -Cu in the fine but not the coarse fraction. These results are compared to a previous study in the northern Absaroka mountains. Correlation coefficients between all other elements determined from these samples are also shown in Tables 12 to 15.

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USGS1978

Natural radioactivity in geothermal waters, Alhambra Hot Springs and nearby areas, Jefferson County, Montana

Radioactive hot springs issue from a fault zone in crystalline rock of the Boulder batholith at Alhambra, Jefferson County, in southwestern Montana. The discharge contains high concentrations of radon, and the gross alpha activity and the concentration of adium-226 exceed maximum levels recommended by the Environmental Protection Agency for drinking water. Part of the discharge is diverted for space heating, bathing, and domestic use. The radioactive thermal waters at measured temperatures of about 60&deg;C are of the sodium bicarbonate type and saturated with respect to calcium carbonate. Radium-226 in the rock and on fractured surfaces or coprecipitated with calcium carbonate probably is the principal source of radon that is dissolved in the thermal water and discharged with other gases from some wells and springs. Local surface water and shallow ground water are of the calcium bicarbonate type and exhibit low background activity. The temperature, percent sodium, and radioactivity of mixed waters adjacent to the fault zone increase with depth. Samples from most of the major hot springs in southwestern Montana have been analyzed for gross alpha and beta activity. The high level of radioactivity at Alhambra appears to be related to leaching of radioactive material from siliceous veins by ascending thermal waters and is not a normal characteristic of hot springs issuing from fractured crystalline rock in Montana.

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USGS1977

Natural radioactivity in geothermal waters, Alhambra Hot Springs and nearby areas, Jefferson County, Montana

Radioactive hot springs issue from a fault zone in crystalline rock of the Boulder batholith at Alhambra, Jefferson County, in southwestern Montana. The discharge contains high concentrations of radon, and the gross activity and the concentration of radium-226 exceed maximum levels recommended by the Environmental Protection Agency for drinking water. Part of the discharge is diverted for space heating, bathing, and domestic use. The radioactive thermal waters at measured temperatures of about 60°C are of the sodium bicarbonate type and saturated with respect to calcium carbonate. Radium-226 in the rock and on fractured surfaces or coprecipitated with calcium carbonate probably is the principal source of radon that is dissolved in the thermal water and discharged with other gases from some wells and springs. Local surface water and shallow ground water are of the calcium bicarbonate type and exhibit low background radio-activity. The temperature, percent sodium, and radioactivity of mixed waters adjacent to the fault zone increase with depth. Samples from most of the major hot springs in southwestern Montana have been analyzed for gross alpha and beta. The high level of radio-activity at Alhambra appears to be related to leaching of radioactive material from fractured siliceous veins by ascending thermal waters, and is not a normal characteristic of hot springs issuing from fractured crystalline rock in Montana.

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USGS1953

Preliminary report on the Clancy Creek area, Jefferson City quadrangle, Jefferson County, Montana

Several radioactivity anomalies and secondary uranium minerals have been found in the Clancy Creek area near the northern margin of the Boulder batholith. These are principally associated with chalcedonic zones that consist of one or more discontinuous stringers and veins of cryptocrystalline silica and fine-grained quartz in silicified quartz monzonite and alaskite. Uranium ore has been produced at the W. Wilson mine from one of these vein zones, and exploration work is being done on another--the G. Washington-A. Lincoln. Some very fine-grained pyrite and minute quantities of other sulfides have been recognized in deposits of this type. At the Lone Eagle mine small amount of uranium ore has been developed along a siliceous vein that contains sooty pitchblende (?) in small irregular fractures; significant amounts of galena and sphalerite are distributed sporadically along the vein. In the Clancy Creek area, no anomalous radioactivity has been detected in the pre-batholithic volcanic rocks or in the post-batholithic dacite and andesite.

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USGS1952

Uranium-bearing deposits west of Clancey, Jefferson County, Montana

Nine uranium deposits occur in a small area vest of Clancey,Jefferson County, Mont. These deposits are all in or near silicifiedfracture zones in quarts monsonite and related rocks of the Boulderbatholith. The deposits contain pockets of uranium minerals in cavities in brecciated silicified rock. The primary uranium mineral pitch-blende has been found in one pod. Secondary uranium minerals occur as fracture linings and in pore spaces in and adjacent to the silicified zones. Uranium in the Clancey district was deposited probably during oneof the later of at least four periods of silicification. The quartsmonsonite, rather than the younger alaskitic dike rocks, is the host rock of the deposits. Newmont Mining Corp. has leased the properties containing theuranium deposits and has begun development of one of these deposits.

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USGS1952

Preliminary report on the Comet area, Jefferson County, Montana

Several radioactivity anomalies and a few specimens of sooty pitchblende and other uranium minerals have been found on the mine dumps of formerly productive base-and precious-metal mines along the Comet-Gray Eagle shear zone in the Comet area in southwestern Montana. The shear zone is from 50 to 200 feet wide and has been traced for at least 5 1/2 miles. It trends N. 80&deg; W. across the northern part of the area and cuts the quartz monzonitic rocks of the Boulder batholith and younger silicic intrusive rocks, as well as the pre-batholitic volcanic rocks, and is in turn cut by dacite and andesite dikes. The youngest period of mineralization is represented by chalcedonic vein zones comprising one or more discontinuous stringers and veins of cryptocrystalline silica in silicified quartz monzonite and in alaskite that has not been appreciably silicified. In some places these zones contain no distinct chalcedonic veins, but are represented only by silicified quartz monzonite. These zones locally contain uranium in association with very small amounts of the following minerals: pyrite, galena, ruby silver, argentite, native silver, molybdenite, chalcopyrite, arsenopyrite, and barite. At the Free Enterprise mine, uranium has been produced from a narrow chalcedonic vein that contains disseminated secondary uranium minerals and local small pods of pitchblende and from disseminated secondary uranium minerals in the adjacent quartz monzonite. Undiscovered commercial deposits of uranium ore may occur spatially associated with the base-and precious-metal deposits along the Comet-Gray Eagle shear zone, and chalcedonic vein zones similar to the Free Enterprise.

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USGS1952

Geology of the area adjacent to the Free Enterprise uranium-silver Mine, Boulder District, Jefferson County, Montana

Uranium minerals.occur in pods associated with cryptocrystalline silica, silver minerals, and scattered sulfide mineral grains in a hydrothermal vein that cuts quartz monzonite and alaskite at the Free Enterprise mine, 2 miles west of Boulder, Mont. The Free Enterprise vein is one of many silicified reef-like structures in this area, most of which trend about N. 60° E. The cryptocrystalline silica zones of the area are lenticular and are bordered by an altered zone where quartz monzonite is the wall rock. No alteration was noticed where alaskite is adjacent to silica zones. No uranium minerals were observed at the surface, but radioactivity anomalies were noted at 57 outcrops. Underground mining has shown that leaching by downward percolating waters has removed most of the uranium from the near-surface part of the Free Enterprise vein and probably has enriched slightly, parts of the vein and the adjacent wall rock from the bottom of the leached zone to the ground-water level. It is possible that other veins that show low to moderate radioactivity at the surface may contain significant concentrations of uranium minerals at relatively shallow depth. The quartz monzonite appears to be a more favorable host rock for the cryptocrystalline silica and associated uranium minerals than the alaskite. The alaskite occurs as vertical_dikes plug-like masses, and as irregularly shaped, gently dipping masses that are believed to have been intruded into open fractures formed during the cooling of the quartz monzonite.

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