The Economic Geology of Scandium, the Runt of the Rare Earth Element Litter

Williams‐Jones, Anthony E.; Vasyukova, O. V.

doi:10.5382/econgeo.2018.4579

Cited by 74 publications

(42 citation statements)

References 64 publications

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“…In particular, the high enrichment factor of V in the aerosol samples from P1 are consistent with a derivation from magnetite bearing ores, such those outcropping in the Yukon‐Koyukuk region (https://thediggings.com/commodities/vanadium/usa/alaska) which is, in fact, the source of the BB event. On the other hand, the relatively higher Sc, Ti, Mn, and Fe amounts in P2 are compatible with a provenance from the limonitic weathering crust deposits of the Tomtor carbonatite, NE Russia (Williams‐Jones & Vasyukova, ). The elevated concentrations of the rare earth elements, including Sc, are a typical feature of these exploitable Sc deposts.…”

Section: Resultssupporting

confidence: 61%

Individual Particle Characteristics, Optical Properties and Evolution of an Extreme Long‐Range Transported Biomass Burning Event in the European Arctic (Ny‐Ålesund, Svalbard Islands)

et al. 2020

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This paper reports an exceptional biomass burning (BB) advection event from Alaska registered at Ny‐Ålesund from 10 to 17 July 2015 with particular interest on the influence of the airborne particle characteristics on the optical properties of the aerosol during the event. To this purpose we considered two DEKATI 12‐stage aerosol samples spanning the entire advection and analyzed them by scanning electron microscopy techniques. Aerosol chemical data and microphysical properties were also evaluated in order to correlate any change of individual particle characteristics with the bulk properties of the aerosol. The results of individual particle analysis depict a complex event characterized by a first phase (P1) of massive input of BB carbonaceous particles (i.e., tar balls, popcorn refractory particles, and organic particles), and by a second phase (P2) dominated by inorganic salts. The peculiar feature of this BB event is the exceptionally large grain size of the subspherical organic particles at the beginning of the event with respect to the background. At these conditions a significant increase of the scattering efficiency may occur even for a small increase of the size parameter. Results of the simulation of the complex refractive indices (n‐ik) confirm this evaluation. Aerosol evolution during the event resulted from the combination of three distinct occurrences: (a) progressive rotation of air mass circulation toward non‐BB source areas, (b) development of a thick fog layer in the planetary boundary layer, and (c) sea salt spray direct advection of local/regional provenance.

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Section: Resultssupporting

confidence: 61%

Individual Particle Characteristics, Optical Properties and Evolution of an Extreme Long‐Range Transported Biomass Burning Event in the European Arctic (Ny‐Ålesund, Svalbard Islands)

et al. 2020

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“…Elements from this group share similar chemical properties, such as a trivalent oxidation state, rare processes that result in concentration and occurrence together in the same mineral deposits. In particular, major REE deposits are related to tropical weathering of carbonatite or granite (Verplanck, 2017) and Sc enrichment is common in laterites (Williams-Jones and Vasyukova, 2018). However, critical-zone (CZ, the interface between geological, hydrological and atmospheric compartments where rocks interact with air, water and biota) studies indicate differences between REE and Sc behaviour.…”

Section: Introductionmentioning

confidence: 99%

Australian laterites reveal mechanisms governing scandium dynamics in the critical zone

Chassé

Griffin

O’Reilly

et al. 2019

Geochimica et Cosmochimica Acta

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Scandium is often considered as immobile during chemical weathering, based on its low solubility. In contrast to other conservative (i.e. relatively immobile) elements incorporated into accessory minerals resistant to weathering (e.g. zirconium, thorium or niobium), the scarcity of scandium minerals indicates that the processes accounting for scandium's immobilisation are distinctive. However, the evolution of scandium speciation during weathering is unknown, limiting the understanding of the processes controlling its dynamics in the critical zone. Exceptional scandium concentrations in east Australian laterites provide the possibility of unravelling these mechanisms. We follow scandium speciation through thick lateritic profiles (> 30 m) using a multiscale mineralogical and spectroscopic approach involving electron microprobe, laser-ablation-inductively coupled plasma mass spectrometry, selective leaching and X-ray absorption near-edge structure spectroscopy, complemented by mass-transfer calculations. We show that the initial reservoir of scandium contained in the parent rock is preserved under reducing conditions occurring in the lowest horizons of the profiles. The dissolution of scandium-bearing clinopyroxene generates smectitic clays that immobilise and concentrate scandium. It is subsequently trapped in the lateritic duricrust by goethite. Scandium mobilisation appears in this horizon and increases upward as a result of the dissolution of goethite, possibly assisted by dissolved organic matter, and the precipitation of hematite. Molecular-scale analyses demonstrate that changes in speciation govern scandium dynamics, with substitution in smectitic clays and adsorption on iron oxyhydroxides playing a crucial role in scandium immobility in the saprolite and lower lateritic duricrust. The higher affinity of scandium for goethite relative to hematite drives scandium mobilisation in the upper lateritic duricrust, leading to its concentration downward in the lower lateritic duricrust. These successive mechanisms illustrate how the unique complexity of the critical zone leads to scandium concentrations that may form new types of world-class scandium deposits. Comparison with conservative elements and with rare-earth elements, expected to have similar geochemical properties, emphasizes the unique behaviour of scandium in the critical zone. While scandium remains immobile during the early stages of weathering, intense and long-term alteration processes, observed in lateritic contexts, lead to scandium mobilisation. This study highlights the dependence of scandium mobility on weathering conditions.

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“…Carbonate ions are also known to form strong complexes with REEs [58,71], and the positive correlation between REE enrichment and CO 2 activity has been well established in hydrothermal carbonatite-related deposits such as at Bayan Obo and Maoniuping in China, the Wicheeda deposit in Canada, and the Sin Quyen deposit in NW Vietnam [2,13,67,72]. Moreover, REE sulfate and carbonate complexes are particularly important in high-temperature and mildly acidic to near-neutral pH conditions [60,69,76]. Large and giant REE deposits generally contain large amounts of fluorine-and sulfate-bearing minerals such as fluorite, fluorapatite, barite, and celestite as the main gangue minerals.…”

Section: Magmatic-hydrothermal Ree Enrichmentmentioning

confidence: 99%

REE Enrichment during Magmatic–Hydrothermal Processes in Carbonatite-Related REE Deposits: A Case Study of the Weishan REE Deposit, China

Jia

Yan

2019

Minerals

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The Weishan carbonatite-related rare earth element (REE) deposit in China contains both high- and low-grade REE mineralization and is an informative case study for the investigation of magmatic–hydrothermal REE enrichment processes in such deposits. The main REE-bearing mineral is bastnäsite, with lesser parisite and monazite. REE mineralization occurred at a late stage of hydrothermal evolution and was followed by a sulfide stage. Barite, calcite, and strontianite appear homogeneous in back-scattered electron images and have high REE contents of 103–217, 146–13,120, and 194–16,412 ppm in their mineral lattices, respectively. Two enrichment processes were necessary for the formation of the Weishan deposit: Production of mineralized carbonatite and subsequent enrichment by magmatic–hydrothermal processes. The geological setting and petrographic characteristics of the Weishan deposit indicate that two main factors facilitated REE enrichment: (1) fractures that facilitated circulation of ore-forming fluids and provided space for REE precipitation and (2) high ore fluorite and barite contents resulting in high F− and SO42− concentrations in the ore-forming fluids that promoted REE transport and deposition.

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The Economic Geology of Scandium, the Runt of the Rare Earth Element Litter

Cited by 74 publications

References 64 publications

Individual Particle Characteristics, Optical Properties and Evolution of an Extreme Long‐Range Transported Biomass Burning Event in the European Arctic (Ny‐Ålesund, Svalbard Islands)

Individual Particle Characteristics, Optical Properties and Evolution of an Extreme Long‐Range Transported Biomass Burning Event in the European Arctic (Ny‐Ålesund, Svalbard Islands)

Australian laterites reveal mechanisms governing scandium dynamics in the critical zone

REE Enrichment during Magmatic–Hydrothermal Processes in Carbonatite-Related REE Deposits: A Case Study of the Weishan REE Deposit, China

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