INITIAL STEPS IN EXPLORING UNCONVENTIONAL RARE EARTH ELEMENT RESOURCES IN THE UNITED STATES: FORAYS INTO GLACIOGENIC, SILICICLASTIC AND VOLCANIC SEDIMENTS

Rare earth elements (REEs) are intrinsically linked to renewable energy, consumer electronics, pollution reduction, and defense technology, among other market sectors. The U.S., as is much of the world, is highly dependent on China for rare earth resources with 79% of REEs extracted in 2017 coming from China and 100% of REEs demanded by the U.S. being imported since 2016. Classic carbonatite and placer-type REE deposits are limited in the U.S. hence the motivation behind evaluating the potential of unconventional REE resources as market demand increases. Preliminary evaluation case studies of rare earth mineralogy and geochemistry from the Eureka Quartzite, glaciogenic river sediment from the Great Miami River, a typical Wisconsin age glacial till, and Quaternary basaltic volcanic deposits from New Mexico, are presented to assess feasibility of unconventional REE extraction. These will then be further considered within the context of potential extraterrestrial REE resources. From current results, and as expected, the absolute concentrations of REEs in all of the studied deposits are low compared to carbonatite and placer ores. However, the mineralogy and texture of the other geologic materials leaves possibilities for REE refinement open in some cases. Investigations of quaternary basalt sediment indicated a low probability for success as discrete REE minerals were not commonly observed. The texture and mineralogy of the glacial till unit also indicated a low probability for success for REE extraction based on the high proportions of clay present. However, samples of the Eureka Quartzite and Great Miami River sediment hold some promise. The Eureka Quartzite could hypothetically be processed for silicon using plasma furnace technology, the by-product of which would be an attractive REE and gold resource. In addition, the extracted silicon could support solar panel and electronics industries. Some potential exists for the Great Miami River sediment as rare earth phosphate could be concentrated into a fine-grained cast off in mining. Plasma furnace technology currently requires extensive investment whereas mineral separation from sand and gravel castoff should be less costly by comparison although extensive further study and the development of large-scale mineral separation technology is likely needed.