Elsevier

Gondwana Research

Volume 27, Issue 2, February 2015, Pages 776-785
Gondwana Research

GR focus review
Rare earth elements in sedimentary phosphate deposits: Solution to the global REE crisis?

https://doi.org/10.1016/j.gr.2014.10.008Get rights and content
Under a Creative Commons license
open access

Highlights

  • The discovery of high-REE phosphorites might solve the global REE supply crisis.

  • Marine REE chemistry is a powerful proxy for the chemical evolution of Earth's ocean.

  • Secular variation in ocean REEs is a predictive tool for identifying high-REE deposits.

Abstract

The critical role of rare earth elements (REEs), particularly heavy REEs (HREEs), in high-tech industries has created a surge in demand that is quickly outstripping known global supply and has triggered a worldwide scramble to discover new sources. The chemical analysis of 23 sedimentary phosphate deposits (phosphorites) in the United States demonstrates that they are significantly enriched in REEs. Leaching experiments using dilute H2SO4 and HCl, extracted nearly 100% of their total REE content and show that the extraction of REEs from phosphorites is not subject to the many technological and environmental challenges that vex the exploitation of many identified REE deposits. Our data suggest that phosphate rock currently mined in the United States has the potential to produce a significant proportion of the world's REE demand as a byproduct. Importantly, the size and concentration of HREEs in some unmined phosphorites dwarf the world's richest REE deposits. Secular variation in phosphate REE contents identifies geologic time periods favorable for the formation of currently unrecognized high-REE phosphates. The extraordinary endowment, combined with the ease of REE extraction, indicates that such phosphorites might be considered as a primary source of REEs with the potential to resolve the global REE (particularly for HREE) supply shortage.

Keywords

Phosphorites
REE
Economic geology
Ocean chemistry
Anoxia

Cited by (0)

Poul Emsbo is a Research Geologist with the U.S. Geological Survey in Denver, Colorado. He received his B.S. from Union College (1986) and earned his M.Sc. (1993) and Ph.D. (1999) in Economic Geology–Geochemistry from the Colorado School of Mines. Since arriving at the USGS in 1989, Poul has investigated the genesis of Carlin Au, MVT, sedex, sedimentary copper deposits, and high salinity brines. For the past several years he has explored the interplay between ocean chemistry, seafloor hydrothermal deposits, marine sediment-hosted deposits, and metalliferous black shales.

Patrick McLaughlin is an Associate Professor with the Wisconsin Geological and Natural History Survey (University of Wisconsin—Extension). He obtained his B.Sc. degree from Illinois State University (1999) and completed his M.Sc. (2002) and Ph.D. (2006) at the University of Cincinnati (2006) where he studied sequence and event stratigraphy as a doctoral fellow. Pat's interest in high-resolution chronostratigraphic approaches to Earth systems history has led him to develop new stratigraphic approaches to C-isotope and handheld XRF analysis of marine rocks and time-specific facies concepts. His field-based studies span the Proterozoic to Pliocene on three continents, with an emphasis on the lower Paleozoic of eastern North America.

George Breit is an emeritus Research Geochemist with the U.S. Geological Survey, Denver Colorado. He received his B.S. from Penn State University (1977) and M.Sc. (1980) and Ph.D. (1986) degrees in Geochemistry from the Colorado School of Mines. He worked for the U.S. Geological Survey from 1980 through 2013 investigating water–rock interaction in a range of systems. George's varied work assignments have included studies of sandstone-hosted uranium deposits, sediment diagenesis, hydrothermal mineral alteration on active volcanoes, sources of natural groundwater contamination, as well as processes responsible for metal enrichment in black shales and metal mobility during weathering of those shales.

Edward A. du Bray is a research geologist working as part of the U.S. Geological Survey Mineral Resources Program in Denver, Colorado, having obtained a M.S. degree in geology from Stanford University in 1977. He combines geologic mapping with petrologic and geochemical studies of igneous rocks throughout the western United States to understand the processes that govern the evolution of magmatic systems and their associated ore deposits. Recent studies of the 45–3 Ma ancestral Cascades arc along western North America characterize protracted continental arc magmatism and define the time–space-compositional variations that have controlled the evolution of subduction-related magmatism in this area. Presently, he is engaged in a study of voluminous ~ 1.4 Ga magmatism in the United States and evaluating relations between the petrogenesis of these rocks and associated REE deposits.

Alan Koenig is a Research Geologist and laboratory manager of the Laser Ablation ICP-MS Trace Element Microanalysis Facility at the Geological Survey in Denver, Colorado, USA. He obtained a B.Sc (1999) and M.Sc. (2009) from Colorado State University. He has run the Trace Element Microanalysis Facility at the USGS since 2004. He was a product manager for a laser ablation manufacturer from 2002 to 2004 where he worked on the development of new laser ablation systems. His worked has focused on the use of LA–ICP-MS for deciphering the nature and residence of trace elements in minerals. Much of his work has utilized LA–ICP-MS for quantitative trace element mapping starting with the first LA–ICP-MS trace element maps of garnet in 2001. The applications have ranged from fossil bones, teeth, tissues, minerals and trees. For the past several years his work has focused on novel applications of LA–ICP-MS including the analysis of bulk powders and trace element mapping as well as integration of complimentary techniques such as Raman, SEM and micro-XRF with LA–ICP-MS.