Net Acid Production, Acid Neutralizing Capacity, and Associated Mineralogical and Geochemical Characteristics of Animas River Watershed Igneous Rocks Near Silverton, Colorado

Yager, Douglas B.; Choate, LaDonna M.; Stanton, Mark R.

doi:10.3133/sir20085063

Cited by 7 publications

(10 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The volcanic site is underlain by Tertiary rocks of the San Juan Formation and is dominated by porphyritic dacites deposited as lava flows approximately 26 Ma. These monotonous dacites are composed of approximately 50% feldspar+quartz phenocrysts in a aphantic groundmass and exhibit evidence of substantial chemical weathering likely resulting from a regional propylitic alteration [ Yager et al , 2008] and weathering prior to the formation of modern soils. They exhibit thick weathering rinds and a greenish surface hue, owing to the presence of chlorite.…”

Section: Methodsmentioning

confidence: 99%

The accretion of aeolian dust in soils of the San Juan Mountains, Colorado, USA

2011

View full text Add to dashboard Cite

[1] Recent observations suggest a contemporary aeolian dust flux of at least 5-10 g m −2 yr −1 to high-elevation ecosystems of the San Juan Mountains of southwestern Colorado. To better quantify the influence of dust on San Juan soil geochemistry, we used Sr and Nd isotopic mixing models to estimate the total mass of accreted dust in soils of two alpine basins underlain by bedrocks of different geochemical composition. In order to minimize the potentially confounding effects caused by transient soil pools of Sr and Nd, we implemented a sequential leaching procedure that isolates the residual mineral fraction of soils and their putative parent materials, including local saprolite and exogenous dust inputs. Using this approach, we calculated masses of accreted dust in soils, which were similar across the two isotopic tracers and differing local geologies. Long-term rates of dust accretion were estimated to be slightly higher than contemporary rates of dust deposition. We conclude that dust inputs comprise from 10% to 40% of the total soil mass in these ecosystems. Our observations suggest that dust inputs have exerted a primary control on soil development in the San Juan Mountains and have likely influenced the physical and chemical characteristics of soils in this region.

show abstract

Section: Methodsmentioning

confidence: 99%

The accretion of aeolian dust in soils of the San Juan Mountains, Colorado, USA

2011

View full text Add to dashboard Cite

show abstract

“…Propylitic-alteration of igneous rocks can introduce a secondary, acid neutralizing mineral assemblage (calcite, chlorite, and epitdote) (Yager et al, , 2008a. While historically overlooked, this environmental rock property (if known) could be a useful physical characteristic to include in the database, especially to mine planners who will use this information to help mitigate acid mine drainage issues prior to a mine's startup.…”

Section: Acid Generating or Neutralizing Propertiesmentioning

confidence: 98%

Development of an igneous rock database with geologic functions: Application to Neogene bimodal igneous rocks and mineral resources in the Great Basin

et al. 2010

Self Cite

View full text Add to dashboard Cite

Geologists routinely use sample data (descriptive, qualitative, quantitative) to characterize a hierarchy of larger geologic features that each have their own independent attributes, use physical relationships between geologic features to establish their relative ages, combine this information with dated features to understand evolutionary histories of study areas at various scales, and produce maps to display such information in space and time relative to other features of interest. This paper demonstrates how we integrated such routine geologic functions into an existing igneous rock relational database designed to store, organize, update, query, and retrieve sample data that have well-defined locations. The resulting igneous rock database is utilized to capture information on Neogene bimodal igneous rocks in northern Nevada and the eastern Great Basin Province. The database is a useful tool that facilitates queries to generate geographical information system displays and petrologic plots that elucidate the time-space-composition relationships of volcanic centers to one another and to geophysical anomalies, structural features, and mineral deposits. Database information is parsed into the following data tables: physical hierarchy of scale, absolute and relative age, chemistry, paleomagnetic, rock mode, image, cross section, X-ray diffraction, and igneous-related structure. Information is organized in a telescoping geologic hierarchy schema: igneous province, volcanic field, volcanic system or caldera, extrusive flow or intrusion, sample, and various subsamples. Absolute radiometric age determinations on samples from geologic features and expert interpretations of relative age relationships between different features may be captured and used together to constrain the ages of undated features. Such age information is linked to features of various scales in the hierarchy. Common attributes that are shared between the relational database and geographic information system (GIS) features include feature-identification or sample-identification, and they permit linking of geographic entities and tabular data for query, analysis, and display in GIS or derivative tables. Relational database keys merge analytical, map, and image data across this geologic hierarchy-age-location schema to facilitate queries that address geologic problems. Data acquired at the sample scale of observation is linked to increasingly larger features that have their own independent attributes using GIS. This schema enables users to retrieve information on one or more hierarchical features for input into external software for various GIS, statistical, petrologic, and other display, analysis, or comparison purposes. Fundamental interpretations resulting from such analyses or displays, e.g., rock classification, may be used to populate additional fields in the database. The database is designed for flexibility and can accommodate information resulting from both detailed and reconnaissance studies. The geologic functions that were developed and that we added to an existing igneous rock database (Lehnert et al., 2000) for this study have wide applicability and could readily be integrated into other geoscience databases.

show abstract

“…Figure 1. Location map and geographic features referred to in this and previous ANC studies (Yager et al, 2005;2008B).…”

Section: Study Areamentioning

confidence: 99%

“…Results of these analyses are available in Yager et al, (2005;2008b) and downloadable from: http://pubs.usgs.gov/of/2005/1433/ and http://pubs.usgs.gov/sir/2008/5063/.…”

Section: Sample Preparation and Analysesmentioning

confidence: 99%

See 1 more Smart Citation

Acid Neutralizing Capacity and Leachate Results for Igneous Rocks, With Associated Carbon Contents of Derived Soils, Animas River Aml Site, Silverton, Colorado

Yager¹,

Stanton²,

Choate³

et al. 2009

JASMR

Self Cite

View full text Add to dashboard Cite

Mine planning efforts have historically overlooked the possible acid neutralizing capacity (ANC) that local igneous rocks can provide to help neutralize acidmine drainage. As a result, limestone has been traditionally hauled to mine sites for use in neutralizing acid drainage. Local igneous rocks, when used as part of mine life-cycle planning and acid mitigation strategy, may reduce the need to transport limestone to mine sites because these rocks can contain acid neutralizing minerals. Igneous hydrothermal events often introduce moderately altered mineral assemblages peripheral to more intensely altered rocks that host metal-bearing veins and ore bodies. These less altered rocks can contain ANC minerals (calcite-chlorite-epidote) and are referred to as a propylitic assemblage. In addition, the carbon contents of soils in areas of new mining or those areas undergoing restoration have been historically unknown. Soil organic carbon is an important constituent to characterize as a soil recovery benchmark that can be referred to during mine cycle planning and restoration. This study addresses the mineralogy, ANC, and leachate chemistry of propylitic volcanic rocks that host polymetallic mineralization in the Animas River watershed near the historical Silverton, Colorado, mining area. Acid titration tests on volcanic rocks containing calcite (2-20 wt %) and chlorite (6-25 wt %), have ANC ranging from 4-146 kg/ton CaCO 3 equivalence. Results from a 6-month duration, kinetic reaction vessel test containing layered pyritic mine waste and underlying ANC volcanic rock (saturated with deionized water) indicate that acid generating mine waste (pH 2.4) has not overwhelmed the ANC of propylitic volcanic rocks (pH 5.8). Sequential leachate laboratory experiments evaluated the concentration of metals liberated during leaching. Leachate concentrations of Cu-Zn-As-Pb for ANC volcanic rock are one-to-three orders of magnitude lower when compared to leached solution from mine waste used in the kinetic reaction vessel test. This finding suggests that mine waste and not ANC rock may generate the majority of leachable metals in a field scenario. The organic carbon content of naturally reclaimed soils derived from weathering of propylitically-altered andesite was determined in catchments where ANC studies were initiated. Soils were found to have total carbon concentrations (TOC) that exceed global average soil TOC abundances by as much as 1.5-5 times. These data support an environmental management system involving use of ANC rocks as part of life-cycle mine planning to reduce post-mine closure acid mitigation measures. Carbon contents of undisturbed soils in mined catchments can possibly be used to validate post-reclamation success and help quantify carbon sequestration for CO 2 emission offset trading as carbon markets mature.

show abstract

Net Acid Production, Acid Neutralizing Capacity, and Associated Mineralogical and Geochemical Characteristics of Animas River Watershed Igneous Rocks Near Silverton, Colorado

Cited by 7 publications

References 9 publications

The accretion of aeolian dust in soils of the San Juan Mountains, Colorado, USA

The accretion of aeolian dust in soils of the San Juan Mountains, Colorado, USA

Development of an igneous rock database with geologic functions: Application to Neogene bimodal igneous rocks and mineral resources in the Great Basin

Acid Neutralizing Capacity and Leachate Results for Igneous Rocks, With Associated Carbon Contents of Derived Soils, Animas River Aml Site, Silverton, Colorado

Contact Info

Product

Resources

About