Origin, Mobility and Concentration of the Rare Earth Elements in the Crust

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Geochemistry and Geochronology".

Deadline for manuscript submissions: closed (31 October 2023) | Viewed by 2994

Special Issue Editors


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Guest Editor
Departament de Geologia, Universitat Autònoma de Barcelona, Edifici Cs, 08193 Bellaterra, Spain
Interests: ore deposits; geochemistry; reactive transport models; dolomitization; REE minerals

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Guest Editor
Departament de Mineralogia, Museu de Ciències Naturals de Barcelona, Passeig Picasso s/n, 08003 Barcelona, Spain
Interests: ore deposits; mineralogy; critical elements

Special Issue Information

Dear Colleagues,

Rare earth elements (REEs), which are not that rare as the name of the group implies, have gained significant interest in the last several decades because they play a crucial role in the upcoming energy and mobility transition towards a greener world. REEs are critical in the development of wind turbines, solar cells, batteries, electric vehicles, and green H2 generation, among other applications. This is why they are generally known as the vitamins of industry. Therefore, exploration for REE mineral resources has become essential. Although REE mineralization is often associated with igneous rocks, they can also occur in metamorphic rocks as well as sedimentary formations due to the occurrence of superficial processes that may concentrate REEs in placers or bauxites. Despite the evidence for REE mobilization in different environments, REEs have been considered non-responsive to alteration. In fact, some REE minerals have been classically used for absolute dating. In addition, the differential concentration of REEs in certain minerals or in the whole rock delineated patterns have also been used as tracers of hydrothermal or igneous processes and origins. There are many studies about REE mobilization in different types of fluids, with diverse pH or ligands, but further research is needed to be able to predict their concentration potential. On the other hand, many devices already contain small amounts of REEs that are being released into the environment in urban dump sites and roads. How they affect our health or if they could be economically recovered should be evaluated as well. Therefore, this Special Issue aims to enhance the knowledge with respect to all aspects of REE origin, mobility and concentration in the inner Earth’s crust and its surface.

Dr. Mercè Corbella
Dr. Marc Campeny
Guest Editors

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Keywords

  • sources of REE
  • low-T transport of REE
  • high-T transport of REE
  • REE mineralogy in igneous environments
  • REE mineralogy in metamorphic rocks
  • REE concentration in evaporites
  • REE non-conventional mineral deposits
  • REE as proxies for geological processes
  • kinetics of REE minerals
  • stability of REE minerals
  • REE minerals of anthropogenic origin
  • REE retention in soils
  • REE bio-concentration
  • REE urban mining

Published Papers (1 paper)

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Research

34 pages, 31258 KiB  
Article
Mineralogy and Distribution of REE in Oxidised Ores of the Mount Weld Laterite Deposit, Western Australia
by Nigel J. Cook, Cristiana L. Ciobanu, Benjamin P. Wade, Sarah E. Gilbert and Robert Alford
Minerals 2023, 13(5), 656; https://doi.org/10.3390/min13050656 - 10 May 2023
Cited by 2 | Viewed by 2582
Abstract
The Mount Weld rare earth element (REE) deposit, Western Australia, is one of the largest of its type on Earth. Current mining exploits the high-grade weathered goethite-bearing resource that lies above, and which represents the weathering product of a subjacent carbonatite. The mineralogy, [...] Read more.
The Mount Weld rare earth element (REE) deposit, Western Australia, is one of the largest of its type on Earth. Current mining exploits the high-grade weathered goethite-bearing resource that lies above, and which represents the weathering product of a subjacent carbonatite. The mineralogy, petrography, deportment of lanthanides among the different components, and variation in mineral speciation, textures, and chemistry are examined. Microanalysis, involving scanning electron microscope (SEM) imaging, electron probe microanalysis (EPMA) and laser ablation inductively coupled-plasma mass spectrometry (LA-ICP-MS), was conducted on sized fractions of three crushed and ground laterite ore samples from current and planned production, and a representative sample from the underlying carbonatite. High-magnification imaging of particles in laterite samples show that individual REE-bearing phases are fine-grained and extend in size well below the micron-scale. Nanoscale inclusions of REE-phosphates are observed in apatite, Fe-(Mn)-(hydr)oxides, and quartz, among others. These have the appearance, particularly in fluorapatite, of pervasive, ultrafine dusty domains. Apart from the discrete REE minerals and abundant nano- to micron-scale inclusions in gangue, all ore components analysed by LA-ICP-MS contain trace to minor levels of REEs within their structures. This includes apatite, where low levels of REE are confirmed in preserved igneous apatite, but also Fe- and Mn-(hydr)oxides in which concentrations of hundreds, even thousands of ppm are measured. This is significant given that Fe-(Mn)-(hydr)oxides are the most abundant component of the laterite and points to extensive mobility and redistribution of REEs, and especially HREE, during progressive lateritisation. Late-formed minerals, notably tiny grains of cerianite, reflect a shift to oxidising conditions. REE-fluorocarbonates are the main host for REEs in carbonatite and are systematically replaced by hydrated, Ca-bearing REE-phosphates (largely rhabdophane). The latter displays varied compositions but is characteristically enriched in HREE relative to monazite in the same sample. Fine-grained, compositionally heterogeneous rhabdophane is accompanied by minor amounts of other paragenetically late, hydrated phosphates with enhanced MREE/HREE relative to LREE (although still LREE-dominant). Minor, relict xenotime and zircon are significant HREE carriers. Ilmenite and pyrochlore group members contain REE but contribute only negligibly to the overall REE budget. Although the proportions of individual mineral species differ, the chemistry of key ore components are similar in different laterite samples from the current resource. Mineral signatures are, however, subtly different in the lower grade southeastern part of the deposit, including higher concentrations of HREE relative to LREE in monazite, rhabdophane, florencite and Fe-(Mn)-(hydr)oxides. Full article
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