Prospectivity Analysis of Rare Earth Element Content of Selected Coal Deposits

J. M. Ekmann¹, Richard Noceti¹, Eric Lopert¹, Bradley Hartwell¹, and Timothy Skone²
¹Leonardo Technologies, Inc., Bannock, OH, [email protected], [email protected], [email protected], [email protected] 
²National Energy Technology Laboratory, Pgh, PA, [email protected] 

We conducted a prospectivity screening of rare earth element concentrations that have been measured in coal deposits across the United States. This work is based on the USGS Coal Quality Database and other selected data obtained from state geologic surveys. A number of papers have been published establishing the link between elevated concentrations of rare earth elements in some coal fields (compared to U.S. average concentrations) and volcanic eruptions that have been dated to the time when these deposits were being lain down. A string of papers since the 1960’s have identified this phenomena both outside the United States and in the Western US. More recently, evidence has been found linking at least two potential eruptions that could account for higher levels of rare earth elements in some coals in the Eastern US.

This study sought to identify the information needed to determine whether there might be a potential for commercial extraction of these rare earth elements from coals still being actively produced, from mining wastes or abandoned mines that remains accessible, and from fly ash produced during combustion of these coals. The study is not primarily intended to answer this question but rather to determine what information is available, to organize known information, and to identify key unknowns so that it is possible to assess the economic potential for such an approach.

Based on the data available at this time, we will present several estimates of probable resources originally in place in several key coal formations and estimate of reserves that could be extracted from coal being mined and from residual materials left over from prior coal extraction and use. Amongst the various coal deposits showing elevated levels of rare earths, a number of locations evidence a ratio of heavy REE+Y to light REE of 1-to-1 or 1-to-2. These sources may be of particular interest in terms of spurring regional development.

A means of assessing the potential to gather rare earth containing materials and to extract the rare earth minerals will be offered to define recoverable reserves. The concentrations found in coal deposits, on average, barely approach levels judged commercially viable when extracting the rare earths alongside another mineral. However, the nature of REE –rich mineral matter in coal may provide unique opportunities to separate out the REE-rich minerals from the coal and other minerals while producing two commercial products. Research and development needs and the opportunities that successful development might present will be discussed.

AAPG Search and Discovery Article #90154©2012 AAPG Eastern Section Meeting, Cleveland, Ohio, 22-26 September 2012