Geology topics

Philip L. Verplanck

Publications and source records attributed to Philip L. Verplanck.

At least 37 records · Page 2Linked to original sources

USGS2014

Quantifying biomineralization of zinc in the Rio Naracauli (Sardinia, Italy), using a tracer injection and synoptic sampling

Streams draining mined areas throughout the world commonly have high concentrations of Zn. Because Zn is not easily removed from stream water and because it can be toxic to aquatic organisms, its presence is a persistent problem. The discovery of biomineralization of Zn-bearing solids in the mine drainage of Rio Naracauli, in Sardinia, Italy, provides insights into strategies for removing Zn and improving water quality in streams affected by mine drainage. Until now, the transport and attenuation of Zn has not been quantified in this stream setting. A continuous tracer injection experiment was conducted to quantify the biomineralization process and to identify the loading of constituents that causes a change from precipitation of hydrozincite [Zn 5 (CO 3 ) 2 (OH) 6 ] in the upstream reach to precipitation of a Zn-silicate phase downstream. Based on the mass-load calculations derived from the tracer experiment, about 1.2 kg/day of Zn is sequestered in hydrozincite. This biomineralization represents nearly 90% removal of Zn. Other elements such as Pb and Cd also are sequestered, either in the hydrozincite, or in a separate phase that forms simultaneously. In the lower 600 m of the stream, where the Zn-silicate forms, as much as 0.7 kg/day Zn are sequestered in this solid, but additions of Zn to the stream from groundwater discharge lead to an overall increase in load in that portion of the Rio Naracauli.

Sardinia↗

USGS2014

The rare-earth elements: Vital to modern technologies and lifestyles

Until recently, the rare-earth elements (REEs) were familiar to a relatively small number of people, such as chemists, geologists, specialized materials scientists, and engineers. In the 21st century, the REEs have gained visibility through many media outlets because of (1) the public has recognized the critical, specialized properties that REEs contribute to modern technology, as well as (2) China's dominance in production and supply of the REEs and (3) international dependence on China for the majority of the world's REE supply. Since the late 1990s, China has provided 85–95 percent of the world’s REEs. In 2010, China announced their intention to reduce REE exports. During this timeframe, REE use increased substantially. REEs are used as components in high technology devices, including smart phones, digital cameras, computer hard disks, fluorescent and light-emitting-diode (LED) lights, flat screen televisions, computer monitors, and electronic displays. Large quantities of some REEs are used in clean energy and defense technologies. Because of the many important uses of REEs, nations dependent on new technologies, such as Japan, the United States, and members of the European Union, reacted with great concern to China’s intent to reduce its REE exports. Consequently, exploration activities intent on discovering economic deposits of REEs and bringing them into production have increased.

Fact Sheet↗

USGS2014

A deposit model for carbonatite and peralkaline intrusion-related rare earth element deposits

Carbonatite and alkaline intrusive complexes, as well as their weathering products, are the primary sources of rare earth elements. A wide variety of other commodities have been exploited from carbonatites and alkaline igneous rocks including niobium, phosphate, titanium, vermiculite, barite, fluorite, copper, calcite, and zirconium. Other elements enriched in these deposits include manganese, strontium, tantalum, thorium, vanadium, and uranium. Carbonatite and peralkaline intrusion-related rare earth element deposits are presented together in this report because of the spatial, and potentially genetic, association between carbonatite and alkaline rocks. Although these rock types occur together at many locations, carbonatite and peralkaline intrusion-related rare earth element deposits are not generally found together. Carbonatite hosted rare earth element deposits are found throughout the world, but currently only five are being mined for rare earth elements: Bayan Obo, Daluxiang, Maoniuping, and Weishan deposits in China and the Mountain Pass deposit in California, United States. These deposits are enriched in light rare earth elements, including lanthanum, cerium, praseodynium, and neodynium. The principal rare earth element-minerals associated with carbonatites are fluocarbonates (bastnäsite, parisite, and synchysite), hydrated carbonates (ancylite), and phosphates (monazite) with bastnäsite being the primary ore mineral. Calcite and dolomite are the primary gangue minerals. At present, the only rare earth element production from a peralkaline intrusion-related deposit is as a byproduct commodity at the Lovozero deposit in Russia. Important rare earth element minerals found in various deposits include apatite, eudialyte, loparite, gittinsite, xenotime, gadolinite, monazite, bastnäsite, kainosite, mosandrite, britholite, allanite, fergusonite, and zircon, and these minerals tend to be enriched in heavy rare earth elements. Carbonatite and alkaline intrusive complexes are derived from partial melts of mantle material, and neodymium isotopic data are consistent with the rare earth elements being derived from the parental magma. Deposits and these associated rock types tend to occur within stable continental tectonic units, in areas defined as shields, cratons, and crystalline blocks; they are generally associated with intracontinental rift and fault systems. Protracted fractional crystallization of the magma leads to enrichment in rare earth elements and other incompatible elements. Rare earth element mineralization associated with carbonatites can occur as either primary mineral phases or as mineralization associated with late stage orthomagmatic fluids. Rare earth element mineralization associated with alkaline intrusive complexes may occur as primary phases in magmatic layered complexes or as late-stage dikes and veins. The greatest environmental challenges associated with carbonatite and peralkaline intrusion-related rare earth element deposits center on the associated uranium and thorium. Considerable uncertainty exists around the toxicity of rare earth elements and warrants further investigation. The acid-generating potential of carbonatites and peralkaline intrusion-related deposits is low due to the dominance of carbonate minerals in carbonatite deposits, the presence of feldspars and minor calcite within the alkaline intrusion deposits, and only minor quantities of potentially acid-generating sulfides. Therefore, acid-drainage issues are not likely to be a major concern associated with these deposits. Uranium has the potential to be recovered as a byproduct, which would mitigate some of its environmental effects. However, thorium will likely remain a waste-stream product that will require management since progress is not being made towards the development of thorium-based nuclear reactors in the United States or other large scale commercial uses. Because some deposits are rich in fluorine and beryllium, these elements may be of environmental concern in certain locations.

Scientific Investigations Report↗

USGS2014

Deposit model for heavy-mineral sands in coastal environments

This report provides a descriptive model of heavy-mineral sands, which are sedimentary deposits of dense minerals that accumulate with sand, silt, and clay in coastal environments, locally forming economic concentrations of the heavy minerals. This deposit type is the main source of titanium feedstock for the titanium dioxide (TiO 2 ) pigments industry, through recovery of the minerals ilmenite (Fe 2+ TiO 3 ), rutile (TiO 2 ), and leucoxene (an alteration product of ilmenite). Heavy-mineral sands are also the principal source of zircon (ZrSiO 4 ) and its zirconium oxide; zircon is often recovered as a coproduct. Other heavy minerals produced as coproducts from some deposits are sillimanite/kyanite, staurolite, monazite, and garnet. Monazite [(Ce,La,Nd,Th)PO 4 ] is a source of rare earth elements as well as thorium, which is used in thorium-based nuclear power under development in India and elsewhere. The processes that form coastal deposits of heavy-mineral sands begin inland. High-grade metamorphic and igneous rocks that contain heavy minerals weather and erode, contributing detritus composed of sand, silt, clay, and heavy minerals to fluvial systems. Streams and rivers carry the detritus to the coast, where they are deposited in a variety of coastal environments, such as deltas, the beach face (foreshore), the nearshore, barrier islands or dunes, and tidal lagoons, as well as the channels and floodplains of streams and rivers in the coastal plain. The sediments are reworked by waves, tides, longshore currents, and wind, which are effective mechanisms for sorting the mineral grains on the basis of differences in their size and density. The finest-grained, most dense heavy minerals are the most effectively sorted. The result is that heavy minerals accumulate together, forming laminated or lens-shaped, heavy-mineral-rich sedimentary packages that can be several meters and even as much as tens of meters thick. Most economic deposits of heavy-mineral sands are Paleogene, Neogene, and Quaternary in age; some are modern coastal deposits. Superimposed on these basic processes of ore formation are a multitude of contributing and modifying factors, such as the following: Strong, sustained wave action moves sand from offshore to the shore, where the sand and heavy minerals are sorted by size and density. Mineral sorting occurs mainly on the upper part of the hightide swash (wave) zone. Fine-grained sands and heavy minerals on the foreshore can be remobilized by winds, forming heavy mineral-rich sand dunes behind the beach. Longshore drift combined with the geomorphology of the coast exert strong influence on the location of the heavy-mineral sands deposits. Sea level changes are a function of climatic changes, such as ice ages. Rises in regional sea level (transgression) and lowering of sea level (regression) strongly influence the deposition and preservation of heavy-mineral sands. The majority of heavy-mineral sands accumulation appears related to seaward progradation of the shore during regression events. Local faulting may affect the geomorphology of the coast, which controls the distribution of heavy mineral deposition in a coastal basin. Heavy mineral grains appear to weather primarily after their deposition in the coastal plain; this weathering is caused by groundwaters, humic acids, and other intrabasinal fluids. This weathering can enhance the TiO 2 content of ilmenite. Iron is leached from ilmenite during weathering, which thereby upgrades the TiO 2 content of the ilmenite, forming leucoxene. The resulting deposits of heavy-mineral sands can be voluminous. Individual bodies of heavy mineral-rich sands are typically about 1 kilometer wide and more than 5 kilometers long. Many heavy-mineral sands districts extend for more than 10 kilometers and contain several individual deposits that are spread along an ancient or modern strandline. Reported thicknesses of economic deposits range from 3 to 45 meters. Individual ore deposits typically comprise at least 10 megatonnes of ore (the total size of the individual sand-silt body), whose overall heavy-mineral content is 2 to greater than 10 percent. Heavy-mineral sands deposits are relatively easy to mine because they are weakly to poorly consolidated, and they are relatively easy to process. From a geoenvironmental standpoint, mining of heavy mineral-sands generates little or no acid or solubilized metals. However, environmental and human health concerns related to such mining include potential effects on indigenous flora and fauna, effects on local hydrology, and issues related to processing and storing thorium-bearing monazite, owing to its radioactivity. Regional exploration for deposits of heavy-mineral sands can utilize the analyses of stream sediment samples for Ti, Hf, the rare earth elements, Th, and U, and geophysical surveys, particularly radiometric (gamma-ray spectrometry for K, U, and Th) and magnetic methods. Geophysical anomalies may be small, and surveys are generally more successful when conducted close to sources of interest.

Scientific Investigations Report↗

USGS2013

Links between climate change, water-table depth, and water chemistry in a mineralized mountain watershed

Recent studies suggest that climate change is causing rising solute concentrations in mountain lakes and streams. These changes may be more pronounced in mineralized watersheds due to the sensitivity of sulfide weathering to changes in subsurface oxygen transport. Specific causal mechanisms linking climate change and accelerated weathering rates have been proposed, but in general remain entirely hypothetical. For mineralized watersheds, a favored hypothesis is that falling water tables caused by declining recharge rates allow an increasing volume of sulfide-bearing rock to become exposed to air, thus oxygen. Here, we test the hypothesis that falling water tables are the primary cause of an increase in metals and SO4 (100-400%) observed since 1980 in the Upper Snake River (USR), Colorado. The USR drains an alpine watershed geologically and climatologically representative of many others in mineralized areas of the western U.S. Hydrologic and chemical data collected from 2005 to 2011 in a deep monitoring well (WP1) at the top of the USR watershed are utilized. During this period, both water table depths and groundwater SO4 concentrations have generally increased in the well. A numerical model was constructed using TOUGHREACT that simulates pyrite oxidation near WP1, including groundwater flow and oxygen transport in both saturated and unsaturated zones. The modeling suggests that a falling water table could produce an increase in metals and SO4 of a magnitude similar to that observed in the USR (up to 300%). Future water table declines may produce limited increases in sulfide weathering high in the watershed because of the water table dropping below the depth of oxygen penetration, but may continue to enhance sulfide weathering lower in the watershed where water tables are shallower. Advective air (oxygen) transport in the unsaturated zone caused by seasonally variable recharge and associated water table fluctuations was found to have little influence on pyrite oxidation rates near WP1. However, this mechanism could be important in the case of a shallow dynamic water table and more abundant/reactive sulfides in the shallow subsurface. Data from WP1 and numerical modeling results are thus consistent with the falling water table hypothesis, and illustrate fundamental processes linking climate and sulfide weathering in mineralized watersheds.

Applied Geochemistry↗

USGS2013

Estimating instream constituent loads using replicate synoptic sampling, Peru Creek, Colorado

The synoptic mass balance approach is often used to evaluate constituent mass loading in streams affected by mine drainage. Spatial profiles of constituent mass load are used to identify sources of contamination and prioritize sites for remedial action. This paper presents a field scale study in which replicate synoptic sampling campaigns are used to quantify the aggregate uncertainty in constituent load that arises from (1) laboratory analyses of constituent and tracer concentrations, (2) field sampling error, and (3) temporal variation in concentration from diel constituent cycles and/or source variation. Consideration of these factors represents an advance in the application of the synoptic mass balance approach by placing error bars on estimates of constituent load and by allowing all sources of uncertainty to be quantified in aggregate; previous applications of the approach have provided only point estimates of constituent load and considered only a subset of the possible errors. Given estimates of aggregate uncertainty, site specific data and expert judgement may be used to qualitatively assess the contributions of individual factors to uncertainty. This assessment can be used to guide the collection of additional data to reduce uncertainty. Further, error bars provided by the replicate approach can aid the investigator in the interpretation of spatial loading profiles and the subsequent identification of constituent source areas within the watershed. The replicate sampling approach is applied to Peru Creek, a stream receiving acidic, metal-rich effluent from the Pennsylvania Mine. Other sources of acidity and metals within the study reach include a wetland area adjacent to the mine and tributary inflow from Cinnamon Gulch. Analysis of data collected under low-flow conditions indicates that concentrations of Al, Cd, Cu, Fe, Mn, Pb, and Zn in Peru Creek exceed aquatic life standards. Constituent loading within the study reach is dominated by effluent from the Pennsylvania Mine, with over 50% of the Cd, Cu, Fe, Mn, and Zn loads attributable to a collapsed adit near the top of the study reach. These estimates of mass load may underestimate the effect of the Pennsylvania Mine as leakage from underground mine workings may contribute to metal loads that are currently attributed to the wetland area. This potential leakage confounds the evaluation of remedial options and additional research is needed to determine the magnitude and location of the leakage.

Colorado↗

USGS2012

Climate-change-driven deterioration of water quality in a mineralized watershed

A unique 30-year streamwater chemistry data set from a mineralized alpine watershed with naturally acidic, metal-rich water displays dissolved concentrations of Zn and other metals of ecological concern increasing by 100–400% (400–2000 μg/L) during low-flow months, when metal concentrations are highest. SO 4 and other major ions show similar increases. A lack of natural or anthropogenic land disturbances in the watershed during the study period suggests that climate change is the underlying cause. Local mean annual and mean summer air temperatures have increased at a rate of 0.2–1.2 °C/decade since the 1980s. Other climatic and hydrologic indices, including stream discharge during low-flow months, do not display statistically significant trends. Consideration of potential specific causal mechanisms driven by rising temperatures suggests that melting of permafrost and falling water tables (from decreased recharge) are probable explanations for the increasing concentrations. The prospect of future widespread increases in dissolved solutes from mineralized watersheds is concerning given likely negative impacts on downstream ecosystems and water resources, and complications created for the establishment of attainable remediation objectives at mine sites.

Environmental Science & Technology↗

USGS2012

Geologic processes influence the effects of mining on aquatic ecosystems

Geologic processes strongly influence water and sediment quality in aquatic ecosystems but rarely are geologic principles incorporated into routine biomonitoring studies. We test if elevated concentrations of metals in water and sediment are restricted to streams downstream of mines or areas that may discharge mine wastes. We surveyed 198 catchments classified as “historically mined” or “unmined,” and based on mineral-deposit criteria, to determine whether water and sediment quality were influenced by naturally occurring mineralized rock, by historical mining, or by a combination of both. By accounting for different geologic sources of metals to the environment, we were able to distinguish aquatic ecosystems limited by metals derived from natural processes from those due to mining. Elevated concentrations of metals in water and sediment were not restricted to mined catchments; depauperate aquatic communities were found in unmined catchments. The type and intensity of hydrothermal alteration and the mineral deposit type were important determinants of water and sediment quality as well as the aquatic community in both mined and unmined catchments. This study distinguished the effects of different rock types and geologic sources of metals on ecosystems by incorporating basic geologic processes into reference and baseline site selection, resulting in a refined assessment. Our results indicate that biomonitoring studies should account for natural sources of metals in some geologic environments as contributors to the effect of mines on aquatic ecosystems, recognizing that in mining-impacted drainages there may have been high pre-mining background metal concentrations.

Ecological Applications↗

USGS2012

Geospatial database for regional environmental assessment of central Colorado.

In conjunction with the future planning needs of the U.S. Department of Agriculture, Forest Service, the U.S. Geological Survey conducted a detailed environmental assessment of the effects of historical mining on Forest Service lands in central Colorado. Stream sediment, macroinvertebrate, and various filtered and unfiltered water quality samples were collected during low-flow over a four-year period from 2004–2007. This report summarizes the sampling strategy, data collection, and analyses performed on these samples. The data are presented in Geographic Information System, Microsoft Excel, and comma-delimited formats. Reports on data interpretation are being prepared separately.

Colorado↗

USGS2011

Evaluating remedial alternatives for an acid mine drainage stream: A model post audit

A post audit for a reactive transport model used to evaluate acid mine drainage treatment systems is presented herein. The post audit is based on a paired synoptic approach in which hydrogeochemical data are collected at low (existing conditions) and elevated (following treatment) pH. Data obtained under existing, low-pH conditions are used for calibration, and the resultant model is used to predict metal concentrations observed following treatment. Predictions for Al, As, Fe, H + , and Pb accurately reproduce the observed reduction in dissolved concentrations afforded by the treatment system, and the information provided in regard to standard attainment is also accurate (predictions correctly indicate attainment or nonattainment of water quality standards for 19 of 25 cases). Errors associated with Cd, Cu, and Zn are attributed to misspecification of sorbent mass (precipitated Fe). In addition to these specific results, the post audit provides insight in regard to calibration and sensitivity analysis that is contrary to conventional wisdom. Steps taken during the calibration process to improve simulations of As sorption were ultimately detrimental to the predictive results, for example, and the sensitivity analysis failed to bracket observed metal concentrations.

Colorado↗

USGS2011

Spring runoff water-chemistry data from the Standard Mine and Elk Creek, Gunnison County, Colorado, 2010

Water samples were collected approximately every two weeks during the spring of 2010 from the Level 1 portal of the Standard Mine and from two locations on Elk Creek. The objective of the sampling was to: (1) better define the expected range and timing of variations in pH and metal concentrations in Level 1 discharge and Elk Creek during spring runoff; and (2) further evaluate possible mechanisms controlling water quality during spring runoff. Samples were analyzed for major ions, selected trace elements, and stable isotopes of oxygen and hydrogen (oxygen-18 and deuterium). The Level 1 portal sample and one of the Elk Creek samples (EC-CELK1) were collected from the same locations as samples taken in the spring of 2007, allowing comparison between the two different years. Available meteorological and hydrologic data suggest that 2010 was an average water year and 2007 was below average. Field pH and dissolved metal concentrations in Level 1 discharge had the following ranges: pH, 2.90 to 6.23; zinc, 11.2 to 26.5 mg/L; cadmium, 0.084 to 0.158 mg/L; manganese, 3.23 to 10.2 mg/L; lead, 0.0794 to 1.71 mg/L; and copper, 0.0674 to 1.14 mg/L. These ranges were generally similar to those observed in 2007. Metal concentrations near the mouth of Elk Creek (EC-CELK1) were substantially lower than in 2007. Possible explanations include remedial efforts at the Standard Mine site implemented after 2007 and greater dilution due to higher Elk Creek flows in 2010. Temporal patterns in pH and metal concentrations in Level 1 discharge were similar to those observed in 2007, with pH, zinc, cadmium, and manganese concentrations generally decreasing, and lead and copper generally increasing during the snowmelt runoff period. Zinc and cadmium concentrations were inversely correlated with flow and thus apparently dilution-controlled. Lead and copper concentrations were inversely correlated with pH and thus apparently pH-controlled. Zinc, cadmium, and manganese concentrations near the mouth of Elk Creek did not display the pronounced increase observed during high flow in 2007, again perhaps due to remedial activities at the mine site or greater dilution in 2010. Zinc and cadmium loads near the mouth of Elk Creek were generally greater than those at the Level 1 portal for the six sample days in 2010. Whereas metal loads in September 2007 suggested that Level 1 portal discharge was the primary source of metals to the creek, metal loads computed for this study suggest that this may not have been the case in the spring of 2010. d18O values are well correlated with flow, becoming lighter (more negative) during snowmelt in both Level 1 discharge and Elk Creek. Seasonal variations in the chemistry of Level 1 discharge, along with portal flow tracking very closely with creek flow, are consistent with geochemical and environmental tracer data from 2007 that indicate short residence times (<1 year) for groundwater discharging from the Standard Mine.

Colorado↗

USGS2011

Carbonatite and alkaline intrusion-related rare earth element deposits–A deposit model

The rare earth elements are not as rare in nature as their name implies, but economic deposits with these elements are not common and few deposits have been large producers. In the past 25 years, demand for rare earth elements has increased dramatically because of their wide and diverse use in high-technology applications. Yet, presently the global production and supply of rare earth elements come from only a few sources. China produces more than 95 percent of the world's supply of rare earth elements. Because of China's decision to restrict exports of these elements, the price of rare earth elements has increased and industrial countries are concerned about supply shortages. As a result, understanding the distribution and origin of rare earth elements deposits, and identifying and quantifying our nation's rare earth elements resources have become priorities. Carbonatite and alkaline intrusive complexes, as well as their weathering products, are the primary sources of rare earth elements. The general mineral deposit model summarized here is part of an effort by the U.S. Geological Survey's Mineral Resources Program to update existing models and develop new descriptive mineral deposit models to supplement previously published models for use in mineral-resource and mineral-environmental assessments. Carbonatite and alkaline intrusion-related REE deposits are discussed together because of their spatial association, common enrichment in incompatible elements, and similarities in genesis. A wide variety of commodities have been exploited from carbonatites and alkaline igneous rocks, such as rare earth elements, niobium, phosphate, titanium, vermiculite, barite, fluorite, copper, calcite, and zirconium. Other enrichments include manganese, strontium, tantalum, thorium, vanadium, and uranium.

Open-File Report↗

USGS2010

Development of a new toxic-unit model for the bioassessment of metals in streams

Two toxic-unit models that estimate the toxicity of trace-metal mixtures to benthic communities were compared. The chronic criterion accumulation ratio (CCAR), a modification of biotic ligand model (BLM) outputs for use as a toxic-unit model, accounts for the modifying and competitive influences of major cations (Ca 2+ , Mg 2+ , Na + , K + , H + ), anions (HCO 3 − , CO 3 2− ,SO 4 2− , Cl − , S 2− ) and dissolved organic carbon (DOC) in determining the free metal ion available for accumulation on the biotic ligand. The cumulative criterion unit (CCU) model, an empirical statistical model of trace-metal toxicity, considers only the ameliorative properties of Ca 2+ and Mg 2+ (hardness) in determining the toxicity of total dissolved trace metals. Differences in the contribution of a metal (e.g., Cu, Cd, Zn) to toxic units as determined by CCAR or CCU were observed and attributed to how each model incorporates the influences of DOC, pH, and alkalinity. Akaike information criteria demonstrate that CCAR is an improved predictor of benthic macroinvertebrate community metrics as compared with CCU. Piecewise models depict great declines (thresholds) in benthic macroinvertebrate communities at CCAR of 1 or more, while negative changes in benthic communities were detected at a CCAR of less than 1. We observed a 7% reduction in total taxa richness and a 43% decrease in Heptageniid abundance between background (CCAR = 0.1) and the threshold of chronic toxicity on the basis of continuous chronic criteria (CCAR = 1). In this first application of the BLM as a toxic-unit model, we found it superior to CCU.

Environmental Toxicology and Chemistry↗

USGS2010

Reactive solute-transport simulation of pre-mining metal concentrations in mine-impacted catchments: Redwell Basin, Colorado, USA

With the increased importance of water resources in the western United States and many areas worldwide, the remediation of impacts from historical mining becomes ever more important. A possible process of making decisions about remediation for a catchment might include identification of principal sources of metals in the catchment, classification of the sources as natural or anthropogenic, and simulations to evaluate different options for removal of anthropogenic sources. The application of this process is based on understanding the pre-mining conditions in the catchment, so that remediation goals appropriately correct for the impacts of mining. A field experiment in Redwell Basin, Colorado, provided a setting to demonstrate this process and to evaluate pre-mining concentrations through reactive solute-transport modeling. The field experiment provided spatially detailed stream and inflow samples that were the basis for model calibration. Only two inflows along the study reach were affected by mining or mine exploration. To simulate pre-mining conditions, these inflows were removed from the model calibration; the result was a simulation of the stream with all the non-mining inputs. At a point downstream from the two mining inflows, the simulated pre-mining pH would have been 5.1, up from the measured 3.8. At the higher pH, the streambed likely would have been coated with Al precipitate. Simulated pre-mining Zn and Cu would have been 1300 µg/L and 18 µg/L, lower than the measured concentrations of 3340 and 93 µg/L. Despite these changes, the pre-mining conditions would not have met aquatic-life standards.

Colorado↗

USGS2010

Evaluating the behavior of gadolinium and other rare earth elements through large metropolitan sewage treatment plants

A primary pathway for emerging contaminants (pharmaceuticals, personal care products, steroids, and hormones) to enter aquatic ecosystems is effluent from sewage treatment plants (STP), and identifying technologies to minimize the amount of these contaminants released is important. Quantifying the flux of these contaminants through STPs is difficult. This study evaluates the behavior of gadolinium, a rare earth element (REE) utilized as a contrasting agent in magnetic resonance imaging (MRI), through four full-scale metropolitan STPs that utilize several biosolids thickening, conditioning, stabilization, and dewatering processing technologies. The organically complexed Gd from MRIs has been shown to be stable in aquatic systems and has the potential to be utilized as a conservative tracer in STP operations to compare to an emerging contaminant of interest. Influent and effluent waters display large enrichments in Gd compared to other REEs. In contrast, most sludge samples from the STPs do not display Gd enrichments, including primary sludges and end-product sludges. The excess Gd appears to remain in the liquid phase throughout the STP operations, but detailed quantification of the input Gd load and residence times of various STP operations is needed to utilize Gd as a conservative tracer.

Environmental Science & Technology↗

USGS2010

Chemistry of selected core samples, concentrate, tailings, and tailings pond waters: Pea Ridge iron (-lanthanide-gold) deposit, Washington County, Missouri

The Minerals at Risk and for Emerging Technologies Project of the U.S. Geological Survey (USGS) Mineral Resources Program is examining potential sources of lanthanide elements (rare earth elements) as part of its objective to provide up-to-date geologic information regarding mineral commodities likely to have increased demand in the near term. As part of the examination effort, a short visit was made to the Pea Ridge iron (-lanthanide-gold) deposit, Washington County, Missouri in October 2008. The deposit, currently owned by Wings Enterprises, Inc. of St. Louis, Missouri (Wings), contains concentrations of lanthanides that may be economic as a primary product or as a byproduct of iron ore production. This report tabulates the results of chemical analyses of the Pea Ridge samples and compares rare earth elements contents for world class lanthanide deposits with those of the Pea Ridge deposit. The data presented for the Pea Ridge deposit are preliminary and include some company data that have not been verified by the USGS or by the Missouri Department of Natural Resources, Division of Geology and Land Survey (DGLS), Geological Survey Program (MGS). The inclusion of company data is for comparative purposes only and does not imply an endorsement by either the USGS or MGS.

Missouri↗

USGS2009

Questa baseline and pre-mining ground-water quality investigation, 7. A pictorial record of chemical weathering, erosional processes, and potential debris-flow hazards in scar areas developed on hydrothermally altered rocks

Erosional scar areas developed along the lower Red River basin, New Mexico, reveal a complex natural history of mineralizing processes, rapid chemical weathering, and intense physical erosion during periodic outbursts of destructive, storm-induced runoff events. The scar areas are prominent erosional features with craggy headwalls and steep, denuded slopes. The largest scar areas, including, from east to west, Hottentot Creek, Straight Creek, Hansen Creek, Lower Hansen Creek, Sulfur Gulch, and Goat Hill Gulch, head along high east-west trending ridges that form the northern and southern boundaries of the lower Red River basin. Smaller, topographically lower scar areas are developed on ridge noses in the inner Red River valley. Several of the natural scar areas have been modified substantially as a result of large-scale open-pit and underground mining at the Questa Mine; for example, much of the Sulfur Gulch scar was removed by open pit mining, and several scars are now partially or completely covered by mine waste dumps.

New Mexico↗

USGS2009

Geochemistry of standard mine waters, Gunnison County, Colorado, July 2009

In many hard-rock-mining districts water flowing from abandoned mine adits is a primary source of metals to receiving streams. Understanding the generation of adit discharge is an important step in developing remediation plans. In 2006, the U.S. Environmental Protection Agency listed the Standard Mine in the Elk Creek drainage basin near Crested Butte, Colorado as a superfund site because drainage from the Standard Mine enters Elk Creek, contributing dissolved and suspended loads of zinc, cadmium, copper, and other metals to the stream. Elk Creek flows into Coal Creek, which is a source of drinking water for the town of Crested Butte. In 2006 and 2007, the U.S. Geological Survey undertook a hydrogeologic investigation of the Standard Mine and vicinity and identified areas of the underground workings for additional work. Mine drainage, underground-water samples, and selected spring water samples were collected in July 2009 for analysis of inorganic solutes as part of a follow-up study. Water analyses are reported for mine-effluent samples from Levels 1 and 5 of the Standard Mine, underground samples from Levels 2 and 3 of the Standard Mine, two spring samples, and an Elk Creek sample. Reported analyses include field measurements (pH, specific conductance, water temperature, dissolved oxygen, and redox potential), major constituents and trace elements, and oxygen and hydrogen isotopic determinations. Overall, water samples collected in 2009 at the same sites as were collected in 2006 have similar chemical compositions. Similar to 2006, water in Level 3 did not flow out the portal but was observed to flow into open workings to lower parts of the mine. Many dissolved constituent concentrations, including calcium, magnesium, sulfate, manganese, zinc, and cadmium, in Level 3 waters substantially are lower than in Level 1 effluent. Concentrations of these dissolved constituents in water samples collected from Level 2 approach or exceed concentrations of Level 1 effluent suggesting that water-rock interaction between Levels 3 and 1 can account for the elevated concentration of metals and other constituents in Level 1 portal effluent. Ore minerals (sphalerite, argentiferous galena, and chalcopyrite) are the likely sources of zinc, cadmium, lead, and copper and are present within the mine in unmined portions of the vein system, within plugged ore chutes, and in muck piles.

Colorado↗