High-Entropy Pyrochlore A2B2O7 with Both Heavy and Light Rare-Earth Elements at the A Site

A novel class of high-entropy pyrochlore ceramics (HEPCs) with multiple heavy and light rare-earth elements at the A site were successfully synthesized via solid-state reaction. Both the XRD patterns and Raman spectroscopy demonstrated the single pyrochlore structure feature of seven kinds of HEPCs. Electron microscopic images revealed the typical morphology and the homogeneous distribution of all rare-earth elements. It can be concluded that the significance of configuration entropy in the HEPC system has promoted the tervalent lanthanide nuclides to form a single pyrochlore structure. This work is expected to provide guidance for the further design of high-entropy pyrochlore/fluorite ceramics.

SEIXOS DE FOSFATOS-SULFATOS DOS MINERAIS DO SUPERGRUPO ALUNITA NOS ALUVIÕES DIAMANTÍFEROS DE PAININN ÀS MARGENS DO TAPAJÓS EM ITAITUBA (PARÁ): GOYAZITA-FLORENCITA-GORCEIXITA-CRANDALLITA-ESVANBERGITA/WOODHOUSEITA

The diamond alluvium gravels from the Painin garimpos, on the right bank of the Tapajós River, in Itaituba, Pará, stand out for the marked presence of pebbles from <1 cm to about 10 cm in diameter consisting of aluminum phosphate-sulfates (APS minerals) from the alunite supergroup: goyazite-florencite-gorceixite-crandallite-esvanbergite/woodhouseite. They are light gray pebbles, still containing small amounts of pyrite, kaolinite, goethite and anatase. The total chemical and trace element analyzes confirm the indicated mineralogical constitution alongside the XRD. The florencite member is mainly dominated by Ce, La, Nd and Sm, the light rare earth elements, and also contains anomalous concentrations of Nb, Y, Pb, U and Th. This chemical nature of these pebbles, in part, makes it possible to compare them with the diamond satellite beans (favas) in secondary deposits in Brazil, but chemically only with the phosphates from Malawi and Sayan.

Structural and Compositional Features of Garnet-Containing Samples Synthesized in a System with Samarium at High Pressure and High Temperature

A distinctive feature of garnets associated with diamonds is specific containing of “light” rare earth elements. In the paper, the garnet-containing samples obtained at high pressure and high temperature in the system introduced with samarium (Sm) are studied. The experiments are carried out using a multianvil high-pressure apparatus of the “split-sphere” type (BARS) at a pressure of 5 GPa and a temperature of 1300 °С. The accuracy of measuring the pressure and temperature is ± 0.2 GPa и ± 25 °С, respectively. As a result, pyrope grains are synthesized with a CaO content no higher than 0.15 wt.% and Cr2O3 concentration within the range of 3.61-7.55 wt.%. The garnets are characterized by the stable presence of an impurity in the form of the Sm constituent. The garnets contain a significant amount of olivine inclusions. Crystals of the synthesized spinel are observed mainly in the interstices. This study demonstrates that the interaction of the components in the serpentine — chromite — corundum — Sm system leads to the crystallization of pyrope garnet, which forms large intergrowths of individual grains. The zoning observed in garnet is due to the transfer of components by fluid during the experiment. It is concluded that the Sm content in garnet can significantly increase depending on its content in the system.

Li-Co–Ni-Mn-(REE) veins of the Western Erzgebirge, Germany—a potential source of battery raw materials

Situated in the western Erzgebirge metallogenetic province (Vogtland, Germany), the Eichigt prospect is associated with several quartz-Mn-Fe-oxyhydroxide veins that are exposed at surface. Bulk-rock geochemical assays of vein material yield high concentrations of Li (0.6–4.1 kg/t), Co (0.6–14.7 kg/t), and Ni (0.2–2.8 kg/t), as well as significant quantities of Mn, Cu, and light rare earth elements, a very unusual metal tenor closely resembling the mixture of raw materials needed for Li-ion battery production. This study reports on the results of a first detailed investigation of this rather unique polymetallic mineralization style, including detailed petrographic and mineralogical studies complemented by bulk rock geochemistry, electron microprobe analyses, and laser ablation inductively coupled mass spectrometry. The mineralized material comprises an oxide assemblage of goethite hematite, hollandite, and lithiophorite that together cement angular fragments of vein quartz. Lithiophorite is the predominant host of Li (3.6–11.1 kg/t), Co (2.5–54.5 kg/t), and Ni (0.2–8.9 kg/t); Cu is contained in similar amounts in hollandite and lithiophorite whereas light rare earth elements (LREE) are mainly hosted in microcrystalline rhabdophane and florencite, which are finely intergrown with the Mn-Fe-oxyhydroxides. 40Ar/39Ar ages (~ 40–34 Ma) of coronadite group minerals coincide with tectonic activity related to the Cenozoic Eger Graben rifting. A low-temperature hydrothermal overprint of pre-existing base metal sulfide-quartz mineralization on fault structures that were reactivated during continental rifting is proposed as the most likely origin of the polymetallic oxyhydroxide mineralization at Eichigt. However, tectonically enhanced deep-reaching fracture-controlled supergene weathering cannot be completely ruled out as the origin of the mineralization.

Potential role of mycorrhizae combined with Pinus tabuliformis in repairing soil contaminated by lanthanum and cerium

In order to repair light rare earth soil effectively, plant and mycorrhizae technology were applied together. It will provide theoretical basis for ecological restoration of light rare earth contaminated soil. The method of greenhouse pot experiment was used in this study. The concentrations of lanthanum (La) in tested soil samples were 107.15, 329.41, and 2,031.71 mg/kg and cerium (Ce) were 362.11, 741.81, 4,162.03 mg/kg. The ectomycorrhiza (Boletus luridus Schaeff.(BLS),Inocybe lilacina(Boud.)Kauffm.(ILK)༌Russula foetens(Pers.)Pers.(RFP)༌Lactarius sanguifluus (Paul.) Fr.(LSF)) was inoculated on Pinus tabuliformis. The inoculation rate and biomass of mycorrhiza, as well as the absorption, transfer and root retention of La and Ce, light rare earth elements (LREE) by plants were determined to provide the theoretical basis for the treatment of La and Ce contaminated soil. The results showed that a symbiotic relationship was established between ectomycorrhiza and Pinus tabuliformis. The mycorrhizal infection rate of Pinus tabulaeformis ranged from 0.51–64.81%, The biomass results showed that the dry weight of aboveground organs and roots increased by 1.46, 1.67 and 1.88 times, 1.73, 1.98 and 2.08 times, respectively. With the increase of the concentration of La and Ce in the soil, the increase of one LREE in the host plants inoculated with mycorrhizae was greater than that in the blank control group. Following mycorrhizal inoculation, La and Ce transfer coefficients in P. and root retention coefficients increased, which may lead to the decrease of absorption and transfer capacity of hyperaccumulators. This study showed that mycorrhizae can improve the absorption of La and Ce by host plants, demonstrating potential value in the environmental remediation of LREE contaminated soil.