Fluids in Rare Earth Element (REE) Ore Genesis

Science Center Objects

The project objective is to better understand the role fluids play in the formation of ore-grade rare earth element enrichment. In many rare earth element deposits, enrichment of rare earth elements is largely controlled by their transport in fluids (orthomagmatic, hydrothermal, groundwater). The project focuses on carbonatite-related deposits because these deposits are the world's primary source of light rare earth elements.

Science Issue and Relevance

In many rare earth element deposits, enrichment of rare earth elements is largely controlled by their transport in fluids (orthomagmatic, hydrothermal, groundwater). The processes controlling the fate and transport of rare earth elements in fluids is poorly understood because a complex set of variables affect rare earth element solubility including solution chemistry, pH, redox conditions, solid phase mineralogy and composition, temperature, and pressure. Rare earth elements may not behave uniformly as light and heavy (atomic number) rare earth elements can fractionate in aqueous systems. Understanding the fundamental processes that control the fate and transport of rare earth elements can help guide exploration for key lanthanides (chemical elements with atomic numbers 57 - 71).

Methods to Address Issue

The project's objective is to better understand the role fluids play in the formation of ore-grade rare earth element enrichment. The project focuses on carbonatite-related deposits because these deposits are the world's primary source of light rare earth elements: lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Ne), samarium (Sm), and europium (Eu), and also the transition metal niobium (Nb). Carbonatites have been mined for phosphates, fluorine (F), copper (Cu), vanadium (V), titanium (Ti), and tantalum (Ta) and are potential sources of other critical elements: thorium (Th), yttrium (Y), and other rare earth elements. Carbonatite-related deposits include multiple styles of mineralization, allowing for comparison of ore-grade enrichment styles and the evaluation of the role of fluids in rare earth element deposit formation.

carbonatite mineralization SEM photo

Two examples of late-stage, ore-grade rare earth element (REE) mineralization, Elk Creek carbonatite, NE. Secondary electron microscope (SEM) backscatter images displaying (A) fine-grained, intergrown lathes of parisite and synchysite filling a void in dolomitic carbonatite, and (B) fine-grained crystals of monazite filling a void in dolomitic carbonatite. Ln in mineral formula designates lanthanide elements (REEs). Images from the USGS Denver Microbeam Laboratory.

(Credit: Denver MIcrobeam Laboratory, U.S. Geological Survey. Public domain.)

 

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