Date of Award

January 2023

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Geological Engineering

First Advisor

I-Hsuan Ho

Abstract

Rare-earth elements (REE) are a set of elements with unique consumer applications that consist of the lanthanide series of elements which have the atomic numbers from 57 to 71 plus yttrium (Y) and scandium (Sc). Because of their unique properties, REEs are used in a wide array of consumer goods, energy system components, and military defense applications, but currently the United States is 100% import-reliant on these critical materials, and the REE supply chain is considered an issue of national security. Coal and coal by-products have been identified as a promising alternative resource and a focus of much recent research by the Department of Energy (DOE). Some studies on the presence of REEs in coal indicate that there is ‘unintended production’ of 44,000 tons (40,000 metric tons) of rare earths potentially occurring annually in the United States from current coal production. Samples collected in North Dakota lignite coal as well the DOE’s minimum threshold of 300ppm for estimated economically recoverable REEs. This research shows that lignite coal in the Williston Basin of North Dakota has the potential to hold economically recoverable amounts of REEs. The focus on locating coal samples with high REE concentrations opens the potential for further characterization and understanding of REE distribution of the coal seams. Lack of research in the 3D geological modeling of concentration poses potential knowledge gaps in the development of coal as a source of REEs and potentially other critical minerals (CM). Estimations based on current samples collection and analysis can only be calculated based on the spatial understandings of the REEs and their presence in lignite coals and it does not account for the variability of the concentrations of the coal vertically. The work proposed in this thesis aims to apply 3D geologic modeling methodology and techniques to create a workflow and appropriately estimate the concentration of REEs in lignite coal in a site-specific scenario. Using publicly available data from the U.S. Geological Survey (USGS) and wireline logs from private entities a structural model of the Hagel coal seam was created. Through the 3D geological modeling methodology used in this thesis has shown to be able create an estimation of potential REEs in coal based on the limited data available for the targeted area of interest.

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