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Minerals
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Rare-Earth Carbonates
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Rare-Earth Carbonates

A special issue of Minerals (ISSN 2075-163X).

Deadline for manuscript submissions: closed (31 August 2017) | Viewed by 36847

Special Issue Editor

Dr. Juan Diego Rodriguez-Blanco

E-Mail Website
Guest Editor
Department of Geology, Trinity College Dublin, Dublin, Ireland
Interests: geochemistry; crystallisation; mineralogy; carbonates; rare-earths; synchrotron; biomineralisation; geology
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Rapid technological development is demanding the use of ever-greater numbers of rare-earth elements. These elements are present at trace concentrations in the Earth’s crust and are being identified by many countries as being of high strategic importance, not only in terms of exploration and extraction, but also in determining their natural cycling and primary industrial sources to the environment. Most naturally-occurring rare earths are associated with the exotic carbonate minerals found in carbonatite deposits (e.g., Mountain Pass in California and Bayan Obo in China). These are broadly defined as igneous rocks with greater than 50% carbonate minerals. Carbonatites encompass a range of compositions and mineral assemblages, including those dominated by calcite, dolomite, ankerite and alkali carbonate minerals.

This Special Issue aims to publish papers on recent progress in the study of rare-earth carbonates. Papers providing data on synthesis, crystallography, structure, spectroscopies, thermodynamics and kinetics of crystallisation, as well as their behaviours in surface, subsurface, and ore-forming processes are welcome. Contributions combining novel experimental and computational approaches are also encouraged, as well as field-based studies.

Dr. Juan Diego Rodriguez-Blanco
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • rare-earths
  • carbonates
  • carbonatite
  • ancylite
  • bastnasite
  • kozoite
  • tengerite
  • lanthanite

Published Papers (5 papers)

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Research

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48115 KiB  
Article
Short-Range Stacking Disorder in Mixed-Layer Compounds: A HAADF STEM Study of Bastnäsite-Parisite Intergrowths
by Cristiana L. Ciobanu, Alkis Kontonikas-Charos, Ashley Slattery, Nigel J. Cook, Benjamin P. Wade and Kathy Ehrig
Minerals 2017, 7(11), 227; https://doi.org/10.3390/min7110227 - 20 Nov 2017
Cited by 25 | Viewed by 5243
Abstract
Atomic-scale high angle annular dark field scanning transmission electron microscopy (HAADF STEM) imaging and electron diffractions are used to address the complexity of lattice-scale intergrowths of REE-fluorocarbonates from an occurrence adjacent to the Olympic Dam deposit, South Australia. The aims are to define [...] Read more.
Atomic-scale high angle annular dark field scanning transmission electron microscopy (HAADF STEM) imaging and electron diffractions are used to address the complexity of lattice-scale intergrowths of REE-fluorocarbonates from an occurrence adjacent to the Olympic Dam deposit, South Australia. The aims are to define the species present within the intergrowths and also assess the value of the HAADF STEM technique in resolving stacking sequences within mixed-layer compounds. Results provide insights into the definition of species and crystal-structural modularity. Lattice-scale intergrowths account for the compositional range between bastnäsite and parasite, as measured by electron probe microanalysis (at the µm-scale throughout the entire area of the intergrowths). These comprise rhythmic intervals of parisite and bastnäsite, or stacking sequences with gradational changes in the slab stacking between B, BBS and BS types (B—bastnäsite, S—synchysite). An additional occurrence of an unnamed B2S phase [CaCe3(CO3)4F3], up to 11 unit cells in width, is identified among sequences of parisite and bastnäsite within the studied lamellar intergrowths. Both B2S and associated parisite show hexagonal lattices, interpreted as 2H polytypes with c = 28 and 38 Å, respectively. 2H parisite is a new, short hexagonal polytype that can be added to the 14 previously reported polytypes (both hexagonal and rhombohedral) for this mineral. The correlation between satellite reflections and the number of layers along the stacking direction (c*) can be written empirically as: Nsat = [(m × 2) + (n × 4)] − 1 for all BmSn compounds with S ≠ 0. The present study shows intergrowths characterised by short-range stacking disorder and coherent changes in stacking along perpendicular directions. Knowing that the same compositional range can be expressed as long-period stacking compounds in the group, the present intergrowths are interpreted as being related to disequilibrium crystallisation followed by replacement. HAADF STEM imaging is found to be efficient for depiction of stacking sequences and their changes in mixed-layer compounds, particularly those in which heavy atoms, such as rare-earth elements, are essential components. Full article
(This article belongs to the Special Issue Rare-Earth Carbonates)
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1858 KiB  
Article
REE Incorporation into Calcite Individual Crystals as One Time Spike Addition
by Rinat I. Gabitov, Aleksey Sadekov and Artas Migdisov
Minerals 2017, 7(11), 204; https://doi.org/10.3390/min7110204 - 26 Oct 2017
Cited by 11 | Viewed by 4180
Abstract
Experiments on the incorporation of trace elements into calcite were performed, and rare earth elements (REE) were used to mark the growth zones of individual crystals. Experiments were conducted at different pH (7.7 to 8.8) and temperatures (2 °C to 24.6 °C) in [...] Read more.
Experiments on the incorporation of trace elements into calcite were performed, and rare earth elements (REE) were used to mark the growth zones of individual crystals. Experiments were conducted at different pH (7.7 to 8.8) and temperatures (2 °C to 24.6 °C) in NH4Cl + CaCl2 solutions, where REE were rapidly consumed by growing calcite. LA-ICP-MS line-scans yielded the distribution of (REE/Ca)calcite within individual crystals in a manner consistent with the addition of REE into fluid. A sharp decrease of (REE/Ca)calcite toward the crystal edge suggests the fast depletion of (REE/Ca)fluid due to strong REE consumption by growing calcite. An attempt was made to estimate the lower limit of the partition coefficients between calcite and fluid using selected REE/Ca data within individual calcite crystals and the amount of REE added into fluid. Full article
(This article belongs to the Special Issue Rare-Earth Carbonates)
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19755 KiB  
Article
Rare Earth Element Fluorocarbonate Minerals from the Olympic Dam Cu-U-Au-Ag Deposit, South Australia
by Danielle S. Schmandt, Nigel J. Cook, Cristiana L. Ciobanu, Kathy Ehrig, Benjamin P. Wade, Sarah Gilbert and Vadim S. Kamenetsky
Minerals 2017, 7(10), 202; https://doi.org/10.3390/min7100202 - 23 Oct 2017
Cited by 29 | Viewed by 9526
Abstract
Olympic Dam is a world-class breccia-hosted iron-oxide copper-gold-uranium ore deposit located in the Gawler Craton, South Australia. It contains elevated concentrations of rare earth elements (REE) which occur as the REE minerals bastnäsite, synchysite, florencite, monazite, and xenotime. This is the first study [...] Read more.
Olympic Dam is a world-class breccia-hosted iron-oxide copper-gold-uranium ore deposit located in the Gawler Craton, South Australia. It contains elevated concentrations of rare earth elements (REE) which occur as the REE minerals bastnäsite, synchysite, florencite, monazite, and xenotime. This is the first study to focus on the mineralogy and composition of the most abundant REE mineral at Olympic Dam, bastnäsite, and subordinate synchysite. The sample suite extends across the deposit and represents different sulfide mineralization styles (chalcopyrite-bornite and bornite-chalcocite) and breccias of various types, ranging from those dominated by clasts of granite, dykes, and hematite. The REE-fluorocarbonates (bastnäsite and synchysite) typically occur as fine-grained (<50 μm) disseminations in Cu-Fe-sulfides and gangue minerals, and also within breccia matrix. They are also locally concentrated within macroscopic REE-mineral-rich pockets at various locations across the deposit. Such coarse-grained samples formed the primary target of this study. Three general textural groups of bastnäsite are recognized: matrix (further divided into disseminated, fine-grained, and stubby types), irregular (sulfide-associated), and clast replacement. Textures are largely driven by the specific location and prevailing mineral assemblage, with morphology and grain size often controlled by the associated minerals (hematite, sulfides). Major element concentration data reveal limited compositional variation among the REE-fluorocarbonates; all are Ce-dominant. Subtle compositional differences among REE-fluorocarbonates define a spectrum from relatively La-enriched to (Ce + Nd)-enriched phases. Granite-derived hydrothermal fluids were the likely source of F in the REE-fluorocarbonates, as well as some of the CO2, which may also have been contributed by associated mafic-ultramafic magmatism. However, transport of REE by Cl-ligands is the most likely scenario. Stubby bastnäsite and synchysite may have formed earlier, coincident with hydrothermal alteration of granite releasing Ca from feldspars. Other categories of bastnäsite, notably those co-existing with sulfides, and reaching the top of the IOCG mineralization at Olympic Dam (chalcocite + bornite zone) are relatively younger. Such an interpretation is concordant with subtle changes in the REE patterns for the different categories. The common association of bastnäsite and fluorite throughout the deposit is typical of the hematite breccias and can be deposited from neutral, slightly acidic fluids (sericite stability) at T ≈ 300 °C. Full article
(This article belongs to the Special Issue Rare-Earth Carbonates)
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8838 KiB  
Article
On the Origin of Bastnaesite-(La,Nd,Y) in the Nissi (Patitira) Bauxite Laterite Deposit, Lokris, Greece
by Sofia Kalatha, Maria Perraki, Maria Economou-Eliopoulos and Ioannis Mitsis
Minerals 2017, 7(3), 45; https://doi.org/10.3390/min7030045 - 21 Mar 2017
Cited by 12 | Viewed by 7073
Abstract
A detailed geochemical study and a thorough mineralogical description of the rare-earth elements (REE)-minerals and associated minerals were carried out in two vertical profiles of approximately 4 m length, from the Nissi (Patitira) bauxite laterite deposit, Lokris, Greece, characterized by the presence of [...] Read more.
A detailed geochemical study and a thorough mineralogical description of the rare-earth elements (REE)-minerals and associated minerals were carried out in two vertical profiles of approximately 4 m length, from the Nissi (Patitira) bauxite laterite deposit, Lokris, Greece, characterized by the presence of goethite in small sizes resembling bacterial cell coated by goethite and a significant REE enrichment. The enrichment of the REE concentrated in bastnaesite-group minerals, the intergrowths between REE-minerals and Al–Ni–silicates with significant sulfur contents and their association with goethite microtextures interpreted as bacteriomorphic, indicate REE remobilization along with iron bio-leaching and re-precipitation on karstified limestone. In addition to the previous-reported hydroxylbastnaesites, a (La,Nd,Y)(CO3)F member of the bastnaesite-group associated with Al–Ni–silicates were identified, the stability of which may reflect the dependence on the source rocks and the local variations of pH-Eh. Interaction between downward percolating water and carbonate rocks seems to be a very effective mechanism for REE fluorocarbonates deposition under alkaline and reducing conditions. Full article
(This article belongs to the Special Issue Rare-Earth Carbonates)
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Review

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24 pages, 5277 KiB  
Review
Trends in Structure and Thermodynamic Properties of Normal Rare Earth Carbonates and Rare Earth Hydroxycarbonates
by Paul Kim, Andre Anderko, Alexandra Navrotsky and Richard E. Riman
Minerals 2018, 8(3), 106; https://doi.org/10.3390/min8030106 - 07 Mar 2018
Cited by 58 | Viewed by 8016
Abstract
A general overview of the trends in structural and thermodynamic properties that have been identified within the hydrated normal rare earth carbonates and the rare earth hydroxycarbonates is presented. Based upon available literature, we demonstrate the trends in crystallographic unit cell parameters, thermal [...] Read more.
A general overview of the trends in structural and thermodynamic properties that have been identified within the hydrated normal rare earth carbonates and the rare earth hydroxycarbonates is presented. Based upon available literature, we demonstrate the trends in crystallographic unit cell parameters, thermal stability, aqueous solubility, and thermochemical properties. These trends can be attributed to both the unique chemistry and strong similarity of the rare earth elements. There are also inconsistent trends that signal research needs to better understand the structure–energy relationships of the rare earth carbonates. Full article
(This article belongs to the Special Issue Rare-Earth Carbonates)
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