Identification of rare-earth minerals associated to K-feldspar: Capacsaya project in Peru

A recently discovered the rare-earth-rich site in Capacsaya, located at 123 km northwest of Cusco, at the south of Peru, contains significant quantities of light and heavy rare-earth elements such as neodymium, lanthanum, cerium, europium, and yttrium. This work reports the identification of rare-earth elements and their associated minerals using scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction analyses. Five (5) samples extracted from different locations at the Capacsaya site were characterized and identified K-feldspar as the mineral associated with the rare-earth elements in a representative sample with a high concentration of lanthanum and cerium. The results showed rare-earth elements contained within the mineral phase monazite, being cerium the dominant element in the phase (La, Ce, Nd)PO$$_4$$ 4 . Finally, through the electrostatic separation process we demonstrate that it was possible to achieve an efficient separation of the K-feldspar phase in the particle size range 75–150 $$\upmu$$ μ m.

Archipelagic Archives

This article examines the intertwined cultural politics of geology, mining, and archival media in the context of Japan’s development as an archipelagic empire. The first Japanese geological map (1876) was completed by American geologist Benjamin Smith Lyman, who surveyed mineral deposits in Hokkaidō, Japan’s northern island, long inhabited by the Indigenous Ainu people. Following decolonial and archipelagic thoughts, the author reads across earthly archives of geological strata and colonial archives of historical documents to elucidate the conceptual duality of archipelago as a geological formation and a geopolitical territory. In tracing this formative era of Japan’s resource extraction and settler colonialism, which precedes and informs the current rush to extract rare earth minerals necessary to maintain global digital infrastructures, this article aims to both de-Westernize the methodological orientation known as media geology and offer a prehistory of contemporary rare earth mining in the Pacific Ocean.

Spatio-Temporal Variability of Gamma Radiation Profile Along the Southern-Indian Coastline (Poompuhar to Nagapattinam Stretch)

The present study is aimed at evaluating the radiation profile along the coast of the Poompuhar- Nagore range, which is known to be hydrodynamically active and is enriched with anthropogenic activities. The study of radiation on the coastal belt and evaluating their dynamics (magnitude and spatio-temporal variability) is crucial both for the coastal inhabitants as well as possible exploration of rare-earth minerals. The effective gamma radiation during the new moon along the coastal range varies between 0.9 to 3.55 ?sv.h-1, respectively. The annual equivalent dose is estimated up to gamma radiation of 0.26 to 2.80 ?sv.h-1. Generally, the concentrations of the gamma radiation measured are elevated in certain areas namely Chinnagudi, Kuttiyandiyur, and Chandrapadi. In particular, the gamma radioactivity is high at Chandrapadi and Chinnagudi during the new moon as it shows considerable amounts of radiation. There is a definite variation due to the moon phase on the gamma radiation profile of the area studied. Out of the eight coastal villages under study, about 60% of the coastal line shows high levels of gamma radiation during both new moon and full moon phases.

Effects of Rare Earth Elements on Bacteria in Rhizosphere, Root, Phyllosphere and Leaf of Soil-Rice Ecosystem

The effects of rare earth mining on rice biomass, rare earth element(REE) content and bacterial community structure was studied by pot experiment. The research showed that the REE content in rice roots, shoots and grains was significantly positive correlated with that in soil, and the dry weight of rice roots, shoots and grains was highly correlated with soil physical and chemical properties, nutrient elements and REE contents; The exploitation of rare earth minerals inhibited a-diversity of endophytic fungi in rhizosphere, root, phyllosphere and leaf of rice, significantly reduced the abundance index, OTU number, Chao, Ace index and also significantly reduced the diversity index-Shannon index and Inv-Simpson index, also reduced uniformity index: Pielou’s evenness index, Simpson’s evenness index, etc, which caused β-diversity of bacteria to be quite different. The exploitation of rare earth minerals reduces the diversity of bacteria, but forms dominant bacteria, such as Burkholderia, Bacillus, Buttiauxella, Acinetobacter, Bradyrhizobium, Candida koribacter, which can degrade the pollutants formed by exploitation of rare earth minerals, alleviate the compound pollution of rare earth and ammonia nitrogen, and also has the function of fixing nitrogen and resisting rare earth stress; The content of soil available phosphorus in non mining area is low, forming the dominant bacteria of Pantoea, which has the function of improving soil phosphorus availability. Rare earth elements and physical and chemical properties of soil affect the community structure of bacteria in rhizosphere and phyllosphere of rice, promote the parallel movement of some bacteria in rhizosphere, root, phyllosphere and leaf of rice, promote the construction of community structure of bacteria in rhizosphere and phyllosphere of rice, give full play to the growth promoting function of Endophytes, and promote the growth of rice. The results showed that the rice biomass in mining area was guaranteed due to the growth promoting effect of endophytic bacteria, However, the mining of mineral resources causes the compound pollution of rare earth and ammonia nitrogen, which makes REE content of rice in mining area significantly higher than that in non mining area.

Bulk composition of a zoned rare-earth minerals-bearing pegmatite in the Pikes Peak granite batholith near Wellington Lake, central Colorado, U.S.A.

ABSTRACT A previously undescribed small lenticular (~5 × 5 × 5 m) pegmatite, located near Wellington Lake in the NW part of the 1.08 Ga ‘A-type’ (anorogenic) ferroan Pikes Peak granite batholith, ~15 km SW of the South Platte pegmatite district in central Colorado, is concentrically zoned around a mostly monomineralic quartz core with interconnected miarolitic cavities. Major constituents of the Wellington Lake pegmatite are quartz, perthitic microcline, albite (variety cleavelandite), hematite, and biotite. Accessory minerals include fluocerite, bastnäsite, columbite, zircon (var. ‘cyrtolite’), thorite, and secondary U phases. Fluorite is conspicuously absent, although it is a common phase in the South Platte district NYF-type pegmatites, which are rich in niobium (Nb), yttrium (Y), fluorine (F), and heavy rare-earth elements (HREE). Notable for the Wellington Lake pegmatite are a small quantity of well-developed tabular crystals of fluocerite that reach up to 4 cm in diameter, with sub-mm epitaxial bastnäsite overgrowths, suggesting formation from F- and CO2-bearing solutions rich in light rare-earth elements (LREE), with decreasing a(F-)/a(CO32-) during the last crystallization phase. An Nd-isotope value of εNd1.08Ga = -1.6 for the fluocerite is within the range of εNd1.08Ga = -0.2 to -2.7 of the host coarse-grained, pink K-series Pikes Peak Granite (PPG), indicating that REE and other pegmatite constituents derived from the parental PPG magma. A calculation of total pegmatite composition based on whole-rock chemistry and volume estimates of the different pegmatite zones reveals an overall composition similar to the PPG with respect to Si, Al, Na, and K. Yet the pegmatite is depleted in Fe, Mg, Ca, Ti, Mn, and P, the high-field-strength elements (HFSE; Zr, Hf, Nb, Y, Th), and, most significantly, total REE compared to the PPG. Despite containing the LREE minerals fluocerite and bastnäsite, the lack of a net overall REE enrichment of the pegmatite compared to the PPG reflects the large amount of REE-poor silicate minerals forming the wall, intermediate, and core zones of the pegmatite. The calculated total pegmatite composition suggests that the pegmatite formed by the separation from the PPG magma of an F-poor H2O-saturated silicate melt depleted in REE and HFSE compared to the F-rich melts, which formed the NYF-type HREE-rich (LaN/YbN < 1) pegmatites in the South Platte district. Homogenization temperatures of < 500°C for possibly primary fluid inclusions in large quartz crystals from the core of the Wellington Lake pegmatite are consistent with recent models of pegmatite petrogenesis leading to nucleation controlled mega-crystal growth resulting from supercooling.

Application of Eh-pH Diagrams on Acid Leaching Systems for the Recovery of REEs from Bastnaesite, Monazite and Xenotime

Bastnaesite, monazite and xenotime are rare earth minerals (REMs) that are typical sources for rare earth elements (REEs). To advance the understanding of their leaching and precipitation behavior in different hydrometallurgical processes, Eh-pH diagrams were constructed and modified using the HSC 9.9 software. The aqueous stability of rare earth elements in H2O and acid leaching systems, i.e., the REE-Ligands-H2O systems, were depicted and studied based on the Eh-pH diagrams. This study considers the most relevant lixiviants, their resulting equilibrium states and the importance in the hydrometallurgical recovery of rare earth elements (REMs). A literature review was performed summarizing relevant Eh-pH diagrams and associated thermodynamic data. Shifting stability regions for REEs were discovered with additions of acid ligands and a narrow stability region for soluble REE-(SO4/Cl/NO3) complexes under highly acidic conditions. As such, the recovery of REEs can be enhanced by adjusting pH and Eh values. In addition, the Eh-pH diagrams of the major contaminants (i.e., Fe, Ca and Al) in leaching systems were studied. The resulting Eh-pH diagrams provide possible insights into potential passivation on the particle surfaces due to the formation of an insoluble product layer.

Thermal Decomposition Kinetics of Rare Earth Minerals in Tailings with Addition of MgO

Due to the advantage in deactivating fluorine and enhancing the decomposition of rare earth (RE) minerals, MgO was applied to the magnetizing roasting of Bayan Obo tailings in this work. The effects of MgO dosages, roasting temperature, and holding time on the decomposition rate of RE minerals were experimentally studied. With a MgO dosage of 10 wt.%, the decomposition rate of RE minerals reached 98.09% at 750 °C. The phase composition of roasted samples was characterized by XRD and SEM-EDS. The incomplete decomposition rate was investigated with the observation of leaching residual by SEM-EDS. The decomposition kinetics of the RE minerals with the addition of MgO was analyzed with the Ginstling-Brundshtein model, where the reaction rate was controlled by chemical reaction.

Mineralogical and geochemical specificity of carbonaceous rocks from the area of Ust'-Kara astrobleme (Pay-Khoy)

We studied Upper Paleozoic (P1pt-ng) carbonaceous shales and siltstones from the area of the Ust'-Kara astrobleme (PayKhoy). We analyzed mineralogical and geochemical features of carbonaceous rocks of the target in the vicinity of the Ust'-Kara astrobleme event using a complex of modern methods to identify possible mobilization, redeposition and concentration of ore substance under intensive post-impact hydrothermal activity. Geochemical features of carbon deposits, altered by post-impact hydrothermal processes in the vicinity of the Ust'-Kara impact structure, have been determined. We found anomalous contents of Ti, Mn, Cr, Zr, Ni, Li, Co, Sc and REE. Inherent rare metal and rare earth minerals (monazite, florensite), sulfides (pyrite, chalcopyrite, marcasite, sphalerite), apatite, barite, anatase, chrome spinels were diagnosed.

Research on the Increase of Mineral Dissociation Degree by High Pressure Water Jet

The traditional grinding technology of ball mill has many problems, such as high energy consumption, unable to maintain the original crystal shape, and it is difficult to obtain high quality and high purity ultrafine powder. The high-pressure water jet mineral dissociation technology is a new technology which is developed in response to these requirements. The experiment shows that the water jet technology has a strong ability of ultrafine grinding. With the increase of jet velocity, the crushing effect is more obvious. The high-pressure water jet pulverization is superior to ball milling for the separation of rare earth minerals, which has the characteristics of high dissociation degree and relatively uniform particle size. The water jet pulverization is more beneficial to the separation and recovery of rare earth minerals.