REE AND CRITICAL MATERIALS – THE ROLE OF EXPLORATION AND ECONOMIC GEOLOGY

Throughout history humans have relied on natural resources to meet basic needs of food, shelter, and comfort. However, with population growth and higher living standards human needs sometimes have outpaced available resources resulting in shortages, price spikes, and even war. The most recent concern has been about rare earth elements (REE) and several bills dealing with REE availability are currently under consideration in Congress. But REEs are somewhat the “flavor of the day” and it is predictable that several years down the road other commodities such as lithium, helium, or phosphorus may be in short supply.

Recent reports by the National Academy of Sciences, Department of Energy, and American Physical Society have addressed issues of critical materials by focusing on the cycle from mining through manufacturing to recycling, but without considering the all-important pre-mining step of exploration. Without exploration and discovery there is nothing to mine or produce.

Exploration consists of several important steps ranging from target selection based upon conceptual models to physical testing by geophysical, geochemical, and geologic surveys. The ultimate physical test is drilling and all of these steps precede the delineation of an ore body in terms of a defined reserve that can then feed into classifications and models of commodity abundance such as summarized annually by the USGS.

Economic geology is the science of ore discovery. Ore deposit models based upon known occurrences provide the predictive basis for future discoveries. For many of the present and future critical elements, ore deposit models are lacking or out of date because the basic research to develop such models has not been adequately funded at the federal or state level, and university research has lagged behind.

For REE a useful exploration model starts with first principles of ionic charge and radius to track the enrichment of these elements through magmatic, hydrothermal, and supergene processes. Specific magmatic suites such as alkalic rocks and carbonatites, and alteration assemblages such as K feldspar and fenitization can be indicative of prospective geologic terranes. Economic geology and predictive exploration models should be at the forefront of the country’s critical materials strategy.