||At the IGWS, we will contribute to two tasks (Task 1 and 2) of the project
Task 1. Basinal CORE-CM Resources Assessment
In this task, available geological, geophysical, and geochemical data related to areas of potential CORE-CM resources in Indiana will be collected and evaluated, with a special emphasis on the Pennsylvanian strata. Data from published and unpublished sources will be examined and assembled in a project-specific database. Recent studies related to REE or other critical minerals in Pennsylvanian coals and associated lithologies (Mastalerz et al., 2019; Mastalerz et al., 2020; Kolker et al., 2021) will be of a special interest with regard to addressing methodologies and REE analysis and their advantages and drawbacks. For example, Mastalerz et al. (2020) show that for the coals and shales having low concentrations of some REY elements, like Tb, Ho, Tm, and Lu in the Pennsylvanian coals and shales, the selection of analytical technique is very important to avoid analytical artifacts, and techniques with lower detection limits than ICP-OES should be used to obtain accurate concentrations of these elements.
The existing data will be used to identify the most potential CORE-CM resources in Indiana and also to indicate the existing data gaps that will need to be addressed. In their study, Mastalerz et al. (2020) identified that some Brazil and Staunton Formations coals have elevated REE content compared to the coals of other formations, whereas Kolker et al. (2021) show that some waste from coal preparation plant in Indiana is a promising REE source. Such information will be the basis for developing short- and long-term data acquisition plan to obtain the optimal resource characterization and assessment.
Task 2. Basinal Strategies for Reuse of Waste Streams
In this task, an assessment of coal waste streams in Indiana will be conducted and will include: a) waste from coal mines (coal refuse and other coal mining byproducts; b) coal combustion by-products; and c) acid-mine drainage (AMD). Indiana has a good inventory of slurry ponds and gobs (Harper et al., 2009) and data from these locations will be evaluated with respect to REE potential. Similar analysis will be done for coal combustion byproducts (fly and bottom ash). Millions of tons of coal ash have been produced in Indiana over decades, with about 6.8 million tons produced in 2018 (Hoosier Environment Council, 2020).
With regard to AMD-related occurrences in Indiana, preliminary investigations indicate that a more diverse mineralization, usually indicated by the elevated presence of aluminum and magnesium, show potential of containing elevated REYs. The aluminum- and magnesium-enriched mineralized waters are associated with gob piles containing substantial amounts of country rock entrained in the waste pile during preliminary coal cleaning that generates the coarse waste material. The combination of highly acidic water enriched in sulfuric acid generated from oxidation of abundant sulfide mineral content in gob piles, with diverse mineralogy and substantial organic matter being aggressively dissolved by the sulfuric acid, results in the mobilization of significant concentrations of REYs. Preliminary analysis of chemical data collected from a limited number of AMD seeps occurring on Indiana AML sites show the strongest correlation within factor 1 of a Principal Component Analysis (PCA) between aluminum, magnesium, zinc and REYs. This indicates that a larger set of seeps can be evaluated using PCA to calculate the factors on less expensive standard metal analyses for AMD. In those seeps showing a strong correlation between aluminum and magnesium (and zinc) as part of factor 1, this method predicts the greatest likelihood exists for elevated REY concentrations.
For the purpose of evaluating the potential for economic deposits of REYs in Indiana, we will locate and map the extent of abandoned mine land (AML) gob piles, and evaluate the chemical composition of AMD leaching from them. Both surface and underground mine gob piles qualify for this approach to locating REY-enriched waste streams. Such piles can be found from Vigo County in western Indiana down to Warrick County on the Ohio River in southern Indiana.
Harper, D., Dintaman, C., Mastalerz, M., and Letsinger, S., 2009, Reconnaissance of Coal-Slurry Deposits in Indiana: Indiana Geological Survey Occasional Paper 69, 20 p.
Hoosier Environment Council, 2020, Our Water Et Risk – Part 2. The impact of coal ash on Indiana’s water resources. https://www.hecweb.org/wp-content/uploads/2020/11/Our-Waters-at-Risk-Part-2.pdf.
Mastalerz, M., Cortland, E., Drobniak, A. Ames, P.R., McLaughlin, P., 2020. Rare Earth Elements and Yttrium in Pennsylvanian coals and shales in the eastern part of the Illinois Basin, International Journal of Coal Geology 231, 103620. https://doi.org/10.1016/j.coal.2020.103620.
Mastalerz, M., Drobniak, A., Ames, P., McLaughlin, P.I., 2019. Application of pXRF elemental analysis in Pennsylvanian coal-bearing strata: an example from the Indiana part of the Illinois Basin. International Journal of Coal Geology 216, 103342 https://doi.org/10.1016/j.coal.2019.103342.
Kolker, A., Scott, C., Lefticariu, L., Mastalerz, M, Drobniak A., Scott, A., 2021. Trace element partitioning during coal preparation: Insights from U.S. Illinois Basin coals, International Journal of Coal Geology 243, 103781. https://doi.org/10.1016/j.coal.2021.103781