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Overview

bastnäsite sample
Photograph of a hand sample (approximately six inches across) from the Mianning area, China, with coarse-grained bastnäsite (mottled brown to pinkish-orange), calcite (white), and fluorite (purple). Bastnäsite is a light rare earth element rich mineral and the primary source of the world's neodymium. Photograph by Anthony Mariano and published in Verplanck et al., 2016.

Science Issue and Relevance

Critical elements are essential to the economy and have potential supply chain disruptions, but compared to most base (common and inexpensive) and precious metals, little work has been undertaken to 1) determine favorable environments for exploration, and 2) identify where these elements reside when enriched. Critical element enrichment in carbonatites is extremely complex and poorly understood. Carbonatites are a relatively rare type of igneous rock and currently supply the worlds light rare earth elements and niobium. Carbonatites can be enriched in other critical elements including heavy rare earth elements. Multiple processes may influence elemental enrichments including the nature of the source material, the evolution of the magma, and late stage interactions between magma, crystals, and fluids. Understanding why some carbonatites are enriched in various elements and others are not is an essential component in identifying favorable exploration tracts. Additionally, understanding the nature of where these elements reside in a deposit is essential for designing cost-effective extraction methodologies. Identification of new critical-mineral resources decreases the "criticality" of a mineral or element.

Research Activities

Our project's objectives are to determine the processes responsible for critical-element enrichments in carbonatites. Elements of interest include Nd, Dy, Tb, Y, Nb, Sc, and Ta, with other elements included as needed. Two specific objectives are 1) to evaluate at a global scale why some carbonatites are enriched in an element of interest and others are not, and 2) to determine where (and why) an element of interest resides in enriched zones to gain insight into enrichment processes and extraction requirements. To constrain critical element enrichent processes, integrated chemical petrographic, scanning electron microscopy, cathodoluminescence spectroscopy, mineal chemistry, and isotopic characterization is needed.

Project Contact

Philip Verplanck
Phone: 303-236-1902
Email: plv@usgs.gov
Central Mineral and Environmental Resources Science Center

Mineral Resources Program Science Priority

The use of firm, trade, and brand names is for identification purposes only and does not constitute endorsement by the U.S. government.

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