Frequently Asked Questions

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What concentration do REEs occur in in nature?

Each REE typically occurs in shale rocks at the parts-per-million level, with light REEs (Z=57-64) being about ten times more abundant than heavy REEs (Z=65-71) (See: https://earthref.org/GERMRD/842/). This work found that Each REE typically occurs in continental groundwater at the parts-per-trillion level, again with light REEs more abundant than heavy REEs. This concentration is roughly equivalent to a single grain of sugar thrown into an Olympic swimming pool.

Why study something so dilute?

For two reasons: Firstly, REEs are useful as tracers or 'fingerprints' as material moves through nature. Secondly, REEs are very valuable (See https://www.sciencedirect.com/science/article/pii/S030142071730079X#s0045).

On the first reason, almost every natural process affects all REEs equally. This historically has allowed scientists to identify which of two mountain ranges contributed more sediment to a sedimentary basin. Similarly, scientists might be able to identify when water in one aquifer is leaking into another. This was the original drive for study of REEs under WY-CUSP which considered ideas that could cause water to move around in the deep subsurface.

On the second reason REEs are used in difficult-to-substitute applications in cellphones, renewable energy, and cruise missiles. Most REEs are supplied to the United States by countries it has identified as strategic competitors, so accordingly the United States is looking for other sources. Considerable effort is devoted to developing a low-cost and high-throughput process for extracting REEs from the ocean or continental groundwater. Development of such a process is very challenging and no one has been successful yet.

What is the connection to Geothermal Energy?

Traditional Geothermal Power Stations move large quantities of water into and out of the deep subsurface. As this water changes temperature it can deposit scale on important equipment which reduces efficiency and causes costly downtime for cleaning. If some valuable materials could be extracted from this water beforehand, then not only could scaling be reduced but also a Geothermal Plant could turn a profit selling the valuable minerals it recovers. It would make more efficient use of resources.