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USGS2023

Geology and undiscovered resource assessment of the potash-bearing, Middle Devonian (Givetian), Prairie Evaporite, Elk Point Basin, Canada and United States

The U.S. Geological Survey (USGS) assessed undiscovered potash resources in the Elk Point Basin in Canada and the United States as part of a global mineral resource assessment. The Elk Point Basin is a large, Middle Devonian (Givetian) intracratonic evaporite basin covering approximately 1,200,000 square kilometers (km 2 ) and filled mainly with marine evaporite and minor clastic sedimentary rocks that contain stratabound potash-bearing salt. The potash-bearing salt is concentrated in four stratigraphic members (Patience Lake, Belle Plaine, White Bear, and Esterhazy) in the upper 100 meters (m) of the Prairie Evaporite and are separated by beds of halite (NaCl) that contain lesser—presently non-economic—amounts of sylvite (KCl) and carnallite (KMgCl 3 ·6H 2 O). The principal ore-bearing salt contains mainly sylvite. Four permissive tracts were defined that permit the presence of undiscovered stratabound potash (both sylvite- and carnallite-bearing salt) using geological criteria. Permissive tracts are defined by the spatial extent of each stratigraphic member that is at least 1 m thick, are less than 3 kilometers (km) from the surface, contain at least 4 percent equivalent potassium oxide (K 2 O), and contain the currently known resources. The permissive tracts include known potash deposits and potash occurrences as wells or mines not in production and show where undiscovered potash resources may be present. Well data are used to define the extent, thickness, average K 2 O equivalent grades, and volumes of each member. Data were supplied by the Saskatchewan Geological Survey or were obtained from published National Instrument (NI) 43-101 technical reports and other published reports, such as annual 10-K reports or news releases. The Elk Point Basin is the world’s largest source of potash, producing 23.0 million metric tons (Mt) of potassium chloride (KCl) (the equivalent of about 14.4 Mt of K 2 O) in 2018. In terms of global importance, the Elk Point Basin may contain 40 to greater than 50 percent of the world’s potash resources. Since 1962, potash companies have mined more than 1.5 trillion metric tons of ore containing 605 Mt of KCl (the equivalent of about 380 Mt of K 2 O). The total value of the ore produced through 2018 is on the order of $70 trillion (CAD). Potash is currently produced from eight conventional and three underground solution mines at depths ranging from 900 m to nearly 1,800 m. Estimates of the amount of potash in the Elk Point Basin vary considerably and the data and methods used in those estimations are not well documented. Known potash resources are approximately 99 billion metric tons (Bt) of ore containing 22 Bt of K 2 O equivalent. As a result of new mine openings and increased production capacity at existing mines, the total production capacity of mines in the Elk Point Basin has increased significantly (to about 32.8 Mt of KCl or 22.8 Mt of K 2 O equivalent per year). Additional production capacity of about 31 Mt of KCl (or 17 Mt of K 2 O equivalent) per year could be realized over the next decade if several current (as of 2019) exploration and development projects reach production status. Stratabound potash-bearing salt of the Prairie Evaporite presently underlies a total area of about 188,000 km 2 and has a total volume of about 2,690 cubic kilometers (km 3 ). Post-depositional solution processes considerably modified the mineralogy and presence of the potash-bearing salt. These changes had a profound effect on the volume and grade of potash resources that remained in the Prairie Evaporite and are a major consideration of exploration and mining operations as well as in this assessment of undiscovered potash resources. This USGS assessment includes the locations and possible amounts of undiscovered potash resources in the Prairie Evaporite. Volumes for each stratigraphic member were computed using member thicknesses and areal extent modified by actual, estimated geologic loss owing to salt dissolution and extraction ratios, as well as estimated distribution of carnallite and sylvite. Both sylvite- and carnallite-bearing salts were assessed for potash in this study. The assessment uses modern published grade and tonnage data. The amount of undiscovered potash is estimated by using Monte Carlo simulations to combine volume estimates of the potash-bearing members with probability distributions for average grade and bulk density. Mean potash grades (expressed as percentage of K 2 O equivalent) calculated using drill core analyses are 17.76 for the Patience Lake Member, 15.98 for the Belle Plaine Member, 10.66 for the White Bear Member, and 15.30 for the Esterhazy Member. Geologic losses reported as extraction ratios during mining may range from 27.5 to 41.6 percent and are dependent on mining method and local geologic conditions. The assessment determined that mean estimated undiscovered K 2 O equivalent resources for the Patience Lake, Belle Plaine, White Bear, and Esterhazy Members are 340, 220, 34, and 190 Bt, respectively, and estimated a total mean of 790 Bt for the entire Prairie Evaporite above a depth of 3 km. The total mineralized rock tonnage is estimated to be about 5,000 Bt. Most of the assessed potash is located within Saskatchewan with lesser amounts in Alberta and Manitoba as well as Montana and North Dakota within the United States. Although carnallite is mined for potash in Europe, it has historically been avoided in mining plans for potash-producing companies in Saskatchewan because of mining, processing, and grade considerations. Carnallite-rich salt is locally present in concentrations and volumes that could be a significant resource of magnesium chloride (MgCl 2 ) obtained as a byproduct of processing the carnallite for potash. Previously estimated reserves (not NI 43-101 compliant) of mineralized material from 1955 to 2019 are 695 Mt at 22.1 percent MgCl 2 . The total amount of K 2 O equivalent as carnallite was estimated during this USGS assessment to be about 120 Bt (or 180 Bt KCl). With uncertainties in defining the areal extent of carnallite in each of the potash-bearing members, the amount of MgCl 2 as carnallite in the Elk Point Basin could be approximately 180 Bt.

Elk Point basin↗
USGS1953

Carnotite resources of the Spud Patch area, San Miguel County, Colorado

The Spud Patch area comprises about 8 square in T. 43 M., R. 18 and 19 W., San Miguel County, Colo., and is about 4 miles northeast of Egnar, Colo. Claims of the United States Vanadium Co. and the Vanadium Corp. of America cover about half the area. Claims of other owners, public land, and patented agricultural land, comprise the remainder of the area. The area is about 38 miles from the Government mill at Montecello, Utah, and 55 miles from the Vanadium Corp. of America mill at Naturita, Colo. Between 1940 and 1951, the Spud Patch area yielded about 24,000 short tons of carnotite ore that probably averaged 0.21 percent U 3 O 8 and 2.2 percent V 2 O 5 . The deposits are in a broad sandstone lens near the top of the Salt Wash member of the Jurassic Morrison formation. Although the deposits mined have been mainly impregnations of sandstone by carnotite and gray vanadium-bearing clay minerals, some of the richer deposits found by Geological Survey drilling have a finely disseminated black uranium mineral but no carnotite. The deposits commonly are thin irregular tabular layers, which locally thicken to form elongate masses called "rolls". These rolls have a dominant northeasterly trend. Geologic features found to be most useful as guides to ore are listed. From November 1949 to May 1952, the U.S. Geological Survey drilled 415 diamond-drill holes totaling 67,215 feet in the Spud Patch area. The purpose of this drilling was to find deposits that would make new mines and to appraise the reserves in the unexplored area. As a result of Geological Survey drilling, indicated and inferred reserves computed at the cutoff of 1 foot or more thick and 0.10 percent U 3 O 8 or 1.0 percent V 2 O 5 total 20,500 short tons, averaging 0.28 percent U 3 O 8 and 2.1 percent V 2 O 5 . These reserves and those computed at a lower grade cutoff of 0.05 percent U 3 O 8 or 0.50 percent V 2 O 5 and the pounds of contained metal are summarized in table 1. Potential reserves, whose existence is based on geologic evidence alone, are predicted to total about 42,000 short tons, averaging 0.25 percent U 3 O 8 and 2.0 percent V 2 O 5 . No additional exploratory-type drilling by the Geological Survey is planned in the Spud Patch area. Recommendations are offered for additional development-type drilling, preferably by claim owners or lessees in specific areas in the vicinity of deposits discovered by Geological Survey drilling.

Colorado↗
USGS2008

Questa baseline and pre-mining ground-water quality investigation. 17. Geomorphology of the Red River Valley, Taos County, New Mexico, and influence on ground-water flow in the shallow alluvial aquifer

In April 2001, the U.S. Geological Survey (USGS) and the New Mexico Environment Department (NMED) began a cooperative study to infer the pre-mining ground-water chemistry at the Molycorp molybdenum mine site in the Red River Valley of north-central New Mexico. This report is one in a series of reports that can be used to determine pre-mining ground-water conditions at the mine site. Molycorp’s Questa molybdenum mine in the Red River Valley, northern New Mexico, is located near the margin of the Questa caldera in a highly mineralized region. The bedrock of the Taos Range surrounding the Red River is composed of Proterozoic rocks of various types, which are intruded and overlain by Oligocene volcanic rocks associated with the Questa caldera. Locally, these rocks were altered by hydrothermal activity. The alteration zones that contain sulfide minerals are particularly important because they constitute the commercial ore bodies of the region and, where exposed to weathering, form sites of rapid erosion referred to as alteration scars. Over the past thousand years, if not over the entire Holocene, erosion rates were spatially variable. Forested hillslopes eroded at about 0.04 millimeter per year, whereas alteration scars eroded at about 2.7 millimeters per year. The erosion rate of the alteration scars is unusually rapid for naturally occurring sites that have not been disturbed by humans. Watersheds containing large alteration scars delivered more sediment to the Red River Valley than the Red River could remove. Consequently, large debris fans, as much as 80 meters thick, developed within the valley. The geomorphology of the Red River Valley has had several large influences on the hydrology of the shallow alluvial aquifer, and those influences were in effect before the onset of mining within the watershed. Several reaches where alluvial ground water emerges to become Red River streamflow were observed by a tracer dilution study conducted in 2001. The aquifer narrows where erosion-resistant bedrock, which tends to form vertical cliffs, restricts the width of the valley bottom. Although the presence of a shallow bedrock sill, overlain by shallow alluvium, is a plausible cause of ground-water emergence, this cause was not demonstrated in the study area. The water-table gradient can locally decrease in the downstream direction because of changes in the hydraulic properties of the alluvium, and this may be a contributing cause of ground-water emergence. However, at one site (near Cabin Springs), ground-water emergence could not be explained by spatial changes in geometric or hydraulic properties of the aquifer. Furthermore, the available evidence demonstrates that ground water flowing through bedrock fractures or colluvium entered the north side of the alluvial aquifer, and is the cause of ground-water emergence. At that location the alluvial aquifer was already flowing full, causing the excess water to emerge into the stream. An indirect consequence of altered rock in the tributary watersheds is the rapid erosion rate of alteration scars combined with the hydraulic properties of sediments shed from those scars. Where alteration scars are large the debris fans at the mouths of the tributary watersheds substantially encroach into the Red River Valley. At such locations debris-fan materials dominate the width and thickness of the alluvium in the valley and reduce the rate of flow of ground water within the Red River alluvial aquifer. Most sites of groundwater emergence are located immediately upstream from or along the margins of debris fans. A substantial fraction of the ground water approaching a debris fan can emerge to become streamflow. This last observation has three implications. First, very little water can flow the entire length of the study area entirely within the alluvial aquifer because the ground water repeatedly contacts debris-fan sediments over that length. Second, it follows that emerging water containing unique elemental constituents must have entered the alluvial aquifer at a relatively short distance upstream. Third, a gravel aquifer downstream from a large debris fan can transmit more ground water than flows into it through the debris fan. This observation explains how the water table can be naturally, and permanently, located well beneath the level of the bed of a perennial stream.

New Mexico↗
USGS1982

Selected hydrologic data, Price River basin, Utah, water years 1979 and 1980

The Price River basin in east-central Utah includes a significant part of the Wasatch Plateau and Book Cliffs coal-fields area (pi. 1) and currently (1980) is part of the most active coal-mining areas in the State. This report presents data gathered by the U.S. Geological Survey as part of a hydrologic study carried out during the water years 1979 and 1980 in cooperation with the U.S. Bureau of Land Management. The data were obtained in the field or from private, State, and other Federal agencies. The purpose of this report is to make the data available to those engaged in coal mining, to those assessing water resources that may possibly be affected by coal mining, and to supplement two interpretive reports that will be published at a later date. Other sources of hydrologic data in the Price River basin include Waddell and others, 1978 and Sumsion, 1979.

Open-File Report↗
USGS1977

Preliminary data on some Precambrian deposits of zinc-copper-lead sulfides and zinc spinel (granite) in Colorado

Precambrian sulfide deposits in the Southern Rocky Mountains in Colorado are being studied and re-evaluated according to geologic concepts which were developed in recent years in other parts of the world during successful research regarding economic massive sulfide deposits. These studies, initiated in 1974 in Colorado by the U.S. Geological Survey, have indicated that a new look at areas containing long dormant mines and prospects may well lead to the discovery of minable Precambrian sulfide deposits. The zinc, copper, and lead contents of ores investigated to date, supplemented by silver and gold contents, indicate that many long-forgotten deposits are minable in terms of grade. The deposits occur in Precambrian rocks metamorphosed to the lower amphibolite facies in one major region and to the upper amphibolite facies in other regions. Field studies have provided ample evidence indicating that the search for commercial tonnages can he facilitated by using newer concepts of economic geology regarding ore-host rock associations as prospecting guides and by using structural considerations aimed toward learning how metamorphism and folding have modified the shapes and distribution of the ore bodies. A newly recognized concept, originating from the current studies by the U.S. Geological Survey in Colorado, concerns the potential economic significance of gahnite, a zinc spinel. The field and laboratory data indicate that gahnite can be used by geologists as a prospector's guide to ore and can be considerd by mining engineers as a potential major ore mineral, contributing significant amounts of zinc to the sulfide ores in many of the deposits. Studies to date indicate that the Gunnison area, the Salida area, and the Guffey area are particularly favorable to the search for minable deposits, and the potential is equally present in many other areas.

Colorado↗
USGS2012

The occurrence of trace elements in bed sediment collected from areas of varying land use and potential effects on stream macroinvertebrates in the conterminous western United States, Alaska, and Hawaii, 1992-2000

As part of the National Water-Quality Assessment Program of the U.S. Geological Survey, this study examines the occurrence of nine trace elements in bed sediment of varying mineralogy and land use and assesses the possible effects of these trace elements on aquatic-macroinvertebrate community structure. Samples of bed sediment and macroinvertebrates were collected from 154 streams at sites representative of undeveloped, agricultural, urban, mined, or mixed land-use areas and 12 intermediate-scale ecoregions within the conterminous western United States, Alaska, and Hawaii from 1992 to 2000. The nine trace elements evaluated during this study—arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), mercury (Hg), nickel (Ni), selenium (Se), and zinc (Zn)—were selected on the basis of potential ecologic significance and availability of sediment-quality guidelines. At most sites, the occurrence of these trace elements in bed sediment was at concentrations consistent with natural geochemical abundance, and the lowest concentrations were in bed-sediment samples collected from streams in undeveloped and agricultural areas. With the exception of Zn at sampling sites influenced by historic mining-related activities, median concentrations of all nine trace elements in bed sediment collected from sites representative of the five general land-use areas were below concentrations predicted to be harmful to aquatic macroinvertebrates. The highest concentrations of As, Cd, Pb, and Zn were in bed sediment collected from mined areas. Median concentrations of Cu and Ni in bed sediment were similarly enriched in areas of mining, urban, and mixed land use. Concentrations of Cr and Ni appear to originate largely from geologic sources, especially in the western coastal states (California, Oregon, and Washington), Alaska, and Hawaii. In these areas, naturally high concentrations of Cr and Ni can exceed concentrations that may adversely affect aquatic macroinvertebrates. Generally, Hg concentrations were below the sediment-quality guideline for this trace element but appeared elevated in urbanized areas and at sites contaminated by historic mining practices. Lastly, although there was no distinctive pattern in Se concentrations with land use, median bed-sediment concentrations were slightly elevated in urbanized areas. Macroinvertebrate community structure was influenced by topographic, geologic, climatic, and in-stream characteristics. To account for inherent distribution patterns resulting from these influences, samples of macroinvertebrates were stratified by ecoregion to assess the influence of trace elements on community structure. Cumulative toxic units (CTUs) were used to evaluate gradients in trace-element concentrations in mixture. Correlation analyses among the trace elements under different land-use conditions indicate that trace-element mixtures vary among bed sediment and can have a marked influence on CTU composition. Macroinvertebrate response to bed-sediment trace-element exposure was evident only at the most highly contaminated sites, notably at sites classified as contaminated by the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) as a result of historic mining activities. Results of this study agree with the findings of other studies evaluating trace-element exposure to in-stream macroinvertebrate community structure in that generally lower richness metrics and taxa dominance occur in streams where high trace-element enrichment occurs; however, not all streams in all areas have the same characterizing taxa. In the mountain and xeric ecosystems, the mayfly, Baetis sp.; the Diptera, Simulium sp.; caddisflies in the family Hydropsychiidae; midges in the family Orthocladiinae; and the worms belonging to Turbellaria and Naididae all demonstrated resilience to trace-element exposure and, in some cases, possible changes in physical habitat within stream ecosystems. The taxa characteristics within the Ozark Highland ecoregion were different than other ecoregions as evidenced by generally more diverse mayfly populations. In addition, Baetis sp. was common and dominated many of the mayfly populations found in the Rocky Mountain streams within the Mountain Southern Rockies and Mountain Northern Rockies ecoregions; however, within the Ozark Highland ecoregion, Tricorythodes sp. appeared to be more common than Baetis sp.

Alaska, Arizona, California, Colorado, Hawai'i, Id↗
USGS2005

Assessment, water-quality trends, and options for remediation of acidic drainage from abandoned coal mines near Huntsville, Missouri, 2003-2004

Water from abandoned underground coal mines acidifies receiving streams in the Sugar Creek Basin and Mitchell Mine Basin near Huntsville, Missouri. A 4.35-kilometer (2.7-mile) reach of Sugar Creek has been classified as impaired based on Missouri's Water Quality Standards because of small pH values [< (less than) 6.5]. Samples collected from Sugar Creek from July 2003 to June 2004 did not have pH values outside of the specified range of 6.5 to 9.0. However, large concentrations of iron [416 to 2,320 mg/L (milligrams per liter)], manganese (8.36 to 33.5 mg/L), aluminum (0.870 to 428 mg/L), and sulfate (2,990 to 13,700 mg/L) in acidic mine drainage (AMD) from two mine springs as well as small and diffuse seeps were observed to have an effect on water quality in Sugar Creek. Metal and sulfate loads increased and pH decreased immediately downstream from Sugar Creek's confluence with the Calfee Slope and Huntsville Gob drainages that discharge AMD into Sugar Creek. Similar effects were observed in the Mitchell Mine drainage that receives AMD from a large mine spring. Comparisons of water-quality samples from this study and two previous studies by the U.S. Geological Survey in 1987-1988 and the Missouri Department of Natural Resources in 2000-2002 indicate that AMD generation in the Sugar Creek Basin and Mitchell Mine Basin is declining, but the data are insufficient to quantify any trends or time frame. AMD samples from the largest mine spring in the Calfee Slope subbasin indicated a modest but significant increase in median pH from 4.8 to 5.2 using the Wilcoxan rank-sum test (p <0.05) and a decrease in median specific conductance from 5,000 to 3,540 ?S/cm (microsiemens per centimeter at 25 degrees Celsius) during a 17-year period. AMD samples from the largest mine spring in the Mitchell Mine Basin indicated an increase in median pH values from 5.6 to 6.0 and a decrease in median specific conductance from 3,050 to 2,450 ?S/cm during the same period. Remediation of AMD at or near the sites of the three largest mine springs is geochemically feasible based on alkalinity addition rates and increased pH determined by cubitainer experiments and geochemical mixing experiments using the computer model PHREEQCI. Alkalinity values for seven cubitainer experiments conducted to simulate anoxic treatment options exceeded the targeted value for alkalinity [90 mg/L as calcium carbonate (CaCO3)] specified in Missouri's Total Maximum Daily Load program by 18 percent or more, but maximum pH values were between 6.2 and 6.3, which is less than the targeted pH value of 6.5. Treatment of AMD by mixing with stream water or sewage effluent can further increase pH as indicated by geochemical modeling, but will not totally achieve water-quality goals because of limited discharges. A combination of treatments including settling ponds, oxic or anoxic limestone drains, and possibly successive alkalinity producing systems to remediate AMD will likely be required in the Sugar Creek Basin and Mitchell Mine Basin to consistently meet Missouri's Water Quality Standards.

Scientific Investigations Report↗
USGS1956

Geology and ore deposits of the Chicago Creek area, Clear Creek County, Colorado

The Chicago Creek area, Clear Creek County, Colo., forms part of the Front Range mineral belt, which is a northeast-trending belt of coextensive porphyry intrusive rocks and hydrothermal veins of Tertiary age. More than $4.5 million worth of gold, silver, copper, lead, zinc, and uranium was produced from the mines in the area between 1859 and 1954. This investigation was made by the Geological survey on behalf of the Division of Raw Materials of the U.S. Atomic Energy Commission. The bedrock in the area is Precambrian and consists of igneous rocks, some of which have been metamorphosed , and metasedimentary rocks. The metasedimentary rocks include biotite-quartz-plagioclase gneiss that is locally garnetiferous, sillimanitic biotite-quartz gneiss, amphibolite, and lime-silicate gneiss. Rocks that may be metasedimentary or meta-igneous are quartz monzonite gneiss and granite gneiss and pegmatite. The granite gneiss and pegmatite locally form a migmatite with the biotitic metasedimentary rocks. These older rocks have been intruded by granodiorite, quartz, and granite pegmatite. During Tertiary time the Precambrian rocks were invaded by dikes and plugs of quartz monzonite porphyry, alaskite porphyry, granite porphyry, monzonite porphyry, bostonite and garnetiferous bostonite porphyry, quartz bostonite porphyry, trachytic granite porphyry, and biotite-quartz latite-porphyry. Solifluction debris of Wisconsin age forms sheets filling some of the high basins, covering some of the steep slopes, and filling parts of some of the valleys; talus and talus slides of Wisconsin age rest of or are mixed with solifluction debris in some of the high basins. Recent and/or Pleistocene alluvium is present along valley flats of the larger streams and gulches. Two periods of Precambrian folding can be recognized in the area. The older folding crumpled the metasedimentary rocks into a series of upright and overturned north-northeast plunging anticlines and synclines. Quartz monzonite gneiss, granite gneiss and pegmatite, granodiorite, and quartz diorite and associated hornblendite are metamorphosed during this period. The second period of folding appears to have been the reflection at depth of faulting nearer the surface; it resulted in crushing as well as some folding of the already folded rocks into terrace and monoclinal folds that plunge gently east-northeast. The biotite-muscovite granite, which is the youngest major Precambrian rock unit, is both concordant (phacolithic) and crosscutting along the older fold system and has been fractured by the younger fold system.

Colorado↗
USGS1990

Geology of the fushun coalfield, Liaoning Province, People's Republic of China

The Fushun coalfield is located in Liaoning Province 45 km east of Shenyang in a relatively small east-west-trending exposure of Mesozoic and Cenozoic rocks surrounded by Precambrian terrane. The coal is included in a sequence of early Tertiary rocks consisting of Paleocene basalt and tuff, and Eocene coal, oil shale and mudstone. These units have been folded into a syncline that plunges gently to the east. The overturned north limb of this fold has been partly removed by a thrust fault. The principal coal beds are low-sulfur subbituminous and bituminous in rank, are of limnic origin, and are contained in the 55-m-thick Eocene Guchengzi Formation. The field, which has been active since the turn of the century, has both open pit and underground mines. The largest operation is the West Open Pit mine, which measures 2.0 km wide, 6.6 km long, and 300 m deep. Coal is mined by means of power shovels, trucks, and an electric rail system. Oil shale from the Eocene Jijuntun Formation is also mined.

International Journal of Coal Geology↗
USGS2009

Environmental Impact of the Contact and Sonoma Mercury Mines on Water, Sediment, and Biota in Anna Belcher and Little Sulphur Creek Watersheds, Sonoma County, California

The Contact and Sonoma mercury (Hg) deposits are among the youngest Hg deposits in the Coast Range Hg mineral belt and are located in the western part of the Clear Lake volcanic field in Sonoma County, California. The mine workings and tailings are located in the headwaters of Anna Belcher Creek, which is a tributary to Little Sulphur Creek. The Contact Hg mine produced about 1,000 flasks of Hg, and the Sonoma mine produced considerably less. Waste rock and tailings eroded from the Contact and Sonoma mines have contributed Hg-enriched mine waste material to the headwaters of Anna Belcher Creek. The mines are located on federal land managed by the U.S. Bureau of Land Management (USBLM). The USBLM requested that the U.S. Geological Survey (USGS) measure and characterize Hg and other geochemical constituents in tailings, sediment, water, and biota at the Contact and Sonoma mines and in Anna Belcher and Little Sulphur Creeks. This report is made in response to the USBLM request, the lead agency mandated to conduct a Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) - Removal Site Investigation (RSI). The RSI applies to removal of Hg-contaminated mine waste from the Contact and Sonoma mines as a means of reducing Hg transport to Anna Belcher and Little Sulphur Creeks. This report summarizes data obtained from field sampling of mine tailings, waste rock, sediment, and water at the Contact and Sonoma mines that was initiated on April 20 during a storm event, and on June 19, 2001. Further sampling of water, sediment, and biota in a pond and tributaries that drain from the mine area was completed on April 1, 2003. Our results permit a preliminary assessment of the mining sources of Hg and associated chemical constituents that could elevate levels of monomethyl Hg (MMeHg) in tributaries and biota that are impacted by historic mining.

Open-File Report↗
USGS2009

Environmental Impact of the Helen, Research, and Chicago Mercury Mines on Water, Sediment, and Biota in the Upper Dry Creek Watershed, Lake County, California

The Helen, Research, and Chicago mercury (Hg) deposits are among the youngest Hg deposits in the Coast Range Hg mineral belt and are located in the southwestern part of the Clear Lake volcanic field in Lake County, California. The mine workings and tailings are located in the headwaters of Dry Creek. The Helen Hg mine is the largest mine in the watershed having produced about 7,600 flasks of Hg. The Chicago and Research Hg mines produced only a small amount of Hg, less than 30 flasks. Waste rock and tailings have eroded from the mines, and mine drainage from the Helen and Research mines contributes Hg-enriched mine wastes to the headwaters of Dry Creek and contaminate the creek further downstream. The mines are located on federal land managed by the U.S. Bureau of Land Management (USBLM). The USBLM requested that the U.S. Geological Survey (USGS) measure and characterize Hg and geochemical constituents in tailings, sediment, water, and biota at the Helen, Research, and Chicago mines and in Dry Creek. This report is made in response to the USBLM request to conduct a Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA - Removal Site Investigation (RSI). The RSI applies to removal of Hg-contaminated mine waste from the Helen, Research, and Chicago mines as a means of reducing Hg transport to Dry Creek. This report summarizes data obtained from field sampling of mine tailings, waste rock, sediment, and water at the Helen, Research, and Chicago mines on April 19, 2001, during a storm event. Further sampling of water, sediment, and biota at the Helen mine area and the upper part of Dry Creek was completed on July 15, 2003, during low-flow conditions. Our results permit a preliminary assessment of the mining sources of Hg and associated chemical constituents that could elevate levels of monomethyl Hg (MMeHg) in the water, sediment, and biota that are impacted by historic mining.

Open-File Report↗
USGS2015

Water-quality trends for selected sites in the Boulder River and Tenmile Creek watersheds, Montana, based on data collected during water years 1997-2013

In the Boulder River and Tenmile Creek watersheds in southwestern Montana, there was intensive mining during a 40-year period after the discovery of gold in the early 1860s. Potential effects from the historic mining activities include acid-mine drainage and elevated concentrations of potentially toxic trace elements from mining remnants such as waste rock and tailing piles. In support of remediation efforts, water-quality monitoring by the U.S. Geological Survey began in 1997 in the Boulder River and Tenmile Creek watersheds and has continued to present (2014). The U.S. Geological Survey, in cooperation with the U.S. Forest Service, investigated temporal trends in water quality at 13 sites, including 2 adit (or mine entrance) sites and 11 stream sites. The primary purpose of this report is to present results of trend analysis of specific conductance, selected trace-elements (cadmium, copper, lead, zinc, and arsenic), and suspended sediment for the 13 sites. Trend results for most stream sites in the Boulder River watershed for water years 2000&ndash;13 (water year is the 12-month period from October 1 through September 30 and is designated by the year in which it ends) indicate decreasing trends in flow-adjusted specific conductance, in flow-adjusted concentrations (FACs) for most filtered and unfiltered-recoverable trace elements, and in suspended sediment. Overall, magnitudes of the decreasing trends in FACs of metallic contaminants are largest for Bullion Mine tributary at mouth (site 3), Jack Creek at mouth (site 4), and Cataract Creek at Basin (site 8). For sites 3, 4, and 8, magnitudes of decreasing trends generally ranged from about -5 to -10 percent per year. Notably, the watersheds upstream from sites 3, 4, and 8 have been targeted by substantial remediation activities. Consideration of trend patterns among all stream sites in the Boulder River watershed provides strong evidence that remediation activities are the primary cause of decreasing trends in metallic contaminants. Trend results for sites in the Tenmile Creek watershed generally are more variable and difficult to interpret than for sites in the Boulder River watershed. Trend results for Tenmile Creek above City Diversion (site 11) and Minnehaha Creek near Rimini (site 12) for water years 2000&ndash;13 indicate decreasing trends in FACs of cadmium, copper, and zinc. The magnitudes of the decreasing trends in FACs of copper generally are moderate and statistically significant for sites 11 and 12. The magnitudes of the decreasing trends in FACs of cadmium and zinc for site 11 are minor to small and not statistically significant; however, the magnitudes for site 12 are moderate and statistically significant. In general, patterns in FACs for Tenmile Creek near Rimini (site 13) are not well represented by fitted trends within the short data collection period, which might indicate that the trend-analysis structure of the study is not appropriate for describing trends in FACs for site 13. The large decreasing trend in FACs of suspended sediment is the strongest indication of change in water quality during the short period of record for site 13; however, this trend is not statistically significant.

Montana↗
USGS2025

The geology of Canadian potash: A critical mineral for feeding the world

Potash, potassium-bearing water-soluble salt, is the primary global economic source of potassium. Potash is recognized as a critical mineral in Canada as it is the largest source of potassium used in fertilizers. It is essential for global agricultural productivity and food security. Canada is the world’s largest potash exporter with vast deposits in the widely mined Prairie Evaporite of Saskatchewan, which formed in the epicontinental Elk Point Basin during the Middle Devonian. Potash is also found in the Windsor Group of Atlantic Canada where it formed in a series of tectonically active basins during the Mississippian that have undergone substantial post-depositional subsurface alteration and deformation. Potash deposits were mined in New Brunswick up until 2016. Both deposits are salt giants, recording times in the geologic record of extensive and long-lasting evaporite genesis under arid conditions in restricted seas. This paper reviews the geological and economic significance of Canadian potash, including (1) the genesis of each deposit, (2) diagenetic, erosional, and tectonic modification, and (3) exploration and mining in each basin. Underdeveloped regions, possible undiscovered resources, environmental considerations, and the importance of sustainable practices in light of climate change and socioeconomic risks are also addressed.

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USGS2019

Geological and geophysical data for a three-dimensional view—Inside the San Juan and Silverton Calderas, Southern Rocky Mountains Volcanic Field, Silverton, Colorado

Introduction The San Juan-Silverton caldera complex located near Silverton, Colorado, in the Southern Rocky Mountains volcanic field is an ideal natural laboratory for furthering the understanding of shallow-to-deep volcanic-related mineral systems. Recent advances in geophysical data processing and three-dimensional (3D) model construction will help to characterize shallow properties important for understanding surface water and groundwater quality issues and will also improve knowledge of deep geological structures that may have been conduits for hydrothermal fluids that formed mineral deposits. The study has general applications to mineral resource assessments in other areas of the world and to identifying possible groundwater flow paths and associated geochemistry important in abandoned mine lands cleanup. Silverton, Colorado, is the site of a spectacular succession of igneous rocks that formed beginning about 35 million years ago (Ma). Base metals (copper, lead, and zinc) and precious metals (silver and gold) mined from the late 1870s to 1991 owe their existence to a 25-million-year cycle of igneous activity. The presence of economic, base, and precious metal deposits within a complex geological setting were largely responsible for stimulating studies by the U.S. Geological Survey (USGS) conducted during the early 20th century. The focus of investigations in the late 20th and 21st centuries have broadened in scope to include abandoned mine lands (AML) investigations. The legacy of hard rock mining in headwater catchment areas caused environmental challenges for local communities and downstream water resource users. The Gold King Mine, located a few kilometers north of Silverton, illustrates the potential environmental effects of abandoned mines. On August 5, 2015, during reclamation efforts at the Gold King Mine, a breach of collapsed workings sent approximately 3 million gallons of acidic and metal-rich mine water into the upper Animas River, a tributary to the Colorado River Basin. Mining-related sources of metals and acidity add to geological sources of metals in surface water and groundwater. Weathering processes of altered and mineralized rock have been a source of acid rock drainage that have been ongoing for millennia.

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