Total Amount Of Rare Earth Elements Research Articles

Rare Earth Element Characteristics of Shales from Wufeng-Longmaxi Formations in Deep-Buried Areas of the Northern Sichuan Basin, Southern China: Implications for Provenance, Depositional Conditions, and Paleoclimate.

To explore the sedimentary environment and the background of the source area of organic-rich shales in the Wufeng-Longmaxi Formations in the northern Sichuan Basin, samples from Well XX1 in the area were subjected to geochemical testing and analysis of organic carbon content, trace elements, and rare earth elements (REEs). The results show that the total content of REE (ΣREE) of the shale in the Wufeng-Longmaxi Formations varied from 183.08 to 234.66 μg/g with an average of 212.59 μg/g, which is significantly higher than the content of the North American shale composite. The fluctuations in the total amount of REEs in the shale of the Wufeng-Longmaxi Formations reflect certain differences in the geochemical conditions of the Upper Ordovician-Lower Silurian shale. The ratios of LREE/HREE, LaN/YbN, LaN/SmN, and GdN/YbN and the distribution of normalized REE patterns indicate that the source supply or sedimentary structural background may have changed during the shale deposition period of the Wufeng Formation, while the shale deposition period of the Longmaxi Formation may be in a relatively stable source supply and sedimentary structural background. There is no significant correlation between δCe and ΣREE, and the obviously negative Eu abnormity and the weak Ce abnormity indicated that the diagenesis had a limited impact on REEs. Geochemical parameters such as values of ∑REE, δEu, δCe, Ceanom, and LaN/YbN indicate that the climate during the Wufeng-Longmaxi Formation shale deposition period was warm and humid, and the shale was deposited mainly in the suboxic-anoxic water environment. The deposition rate was stable and slow, providing good conditions for the production and preservation of organic matter. At the same time, this shows that the water environment of Wufeng Formation is more anoxic and reductive than that of Longmaxi Formation, which is more conducive to the preservation of organic matter. The correlation between ΣREE and the content of Sc, Ti, Cr, Co, Zr, Nb, Th, Hf, Ta, and other elements indicates that the sources of REEs in the shale of Wufeng and Longmaxi Formations in the study area are similar, mainly terrestrial clasts, and some may come from the sea. The REE distribution pattern shows that the shale provenance of the Wufeng-Longmaxi Formations mainly comes from the upper crust. The La/Yb-∑REE diagram shows that the sediment-parent rocks are mainly early sedimentary rocks and these sediment-parent rocks have granite provenance characteristics. Compared to La/Yb, LREE/HREE, LaN/YbN, and other REE characteristic parameters, it is inferred that the tectonic background of the study area is dominated by passive continental margin.

Geochemical Characteristics and Factors of Transfer and Accumulation of Rare Earth Elements in Rock-Soil-Tea of the Mengku Tea Region in Yunnan Province, China

Rare earth elements (REEs) in tea are usually determined by the soil, but their transfer characteristics and influencing factors have been rarely studied and reported. In order to determine the transfer and accumulation characteristics of REEs, rock, soil, and tea samples were collected in the Mengku tea region. Levels of 15 REEs (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y) in samples were determined by inductively coupled plasma atomic emission spectrometry (ICP-MS). The results showed that light rare earth elements (LREEs) were easily enriched in rock, soil, and tea. The average total concentration of REEs in investigated rocks was 199 mg·kg−1, which was lower than the element abundance of China’s continental crust but higher than the standard value of element abundance in the upper continental crust (UCC). The average total REE concentration in the investigated soil was 225 mg·kg−1, which was lower than the background value of soil in Yunnan Province. The chondrite-normalized levels of Ce and Eu in rocks and Eu in soil showed negative anomalies, while Ce levels in soil showed slightly positive anomalies. The total amount of REEs in tea was relatively low and the chondrite-normalized values of Eu in tea showed significantly positive anomalies. Eu anomalies in tea were closely correlated with soil pH (pH < 5, negative anomalies; pH > 5, positive anomalies). K, Na, Ca, and Mg were the main factors affecting the transfer of REEs. LREEs were mainly enriched in tea through Na+ channels. Mg and K affected the differentiation and enrichment of heavy rare earth elements (HREEs) in tea. Calcium showed a significantly positive correlation with Eu in tea. The human health risk assessment showed that the risk of drinking tea to the human body was far below the reference value. Ce, Y, and La in tea were the main elements that affected non-carcinogenic risk and carcinogenic risk.

Analysis on Black Shale Sedimentary Paleoenvironment and Tectonic Setting of the First Member of Luzhai Formation of Lower Carboniferous, Rongshui Area of Guangxi, China

In order to promote the discovery of new shale gas exploration areas in Guangxi, based on the latest drilling data, through detailed observation and description of logging data and cores, this paper selects high-quality shale samples of the target layer for X-ray diffraction analysis and testing of clay minerals and whole rock, major and trace elements (including rare-earth elements), TOC, and other related analysis and testing. The study shows that the total amount of rare-earth elements in the first member of Lower Carboniferous Luzhai Formation in Rongshui area, Guangxi, is low; δ EU and δ CE show negative abnormality. The average value of w V / V + Ni , Th / U ratio, and Mo-TOC covariant model diagram of the first member of Luzhai Formation show that it was the condition of anoxic reduction at that time. At the same time, Ba-Sr diagram, Sr/Cu ratio, and total rare-earth elements reflect that the area was in an arid, hot, and marine salt water paleoenvironment during the sedimentary period. Most of the sample parent rocks of the first member of Luzhai Formation are in shale area, and some samples are close to felsic igneous rock area, which is of mixed origin. The tectonic background of the source area is mainly continental island arc and active continental margin, indicating that the sedimentary environment was unstable and highly active under the background of extensional rifting at that time.

Optimized photometric technique for rare-earth elements determination in phosphate ore

The Socialist Republic of Vietnam is 21st in the list of the world’s countries for phosphate ore reserves. The largest apatite ore deposit Lao Cai with the stretch of over 100 km and the total area of 45.56 km2 situated along the right bank of the Hong River has been in operation since 1940. According to the prospecting data, the Lao Cai ore reserves exceed 30 mln tons. As the mining operations keep expanding and the environmental regulations grow stricter, it is necessary to monitor the concentration of rare-earth metals in the apatite ore. Inductively coupled plasma mass spectrometry (ICP–MS), a method that enables to directly analyze mineral raw materials and sites for rare-earth elements, cannot be consistently utilized by industrial sector. An alternative spectrophotometric technique, which helps determine the total amount of rare-earth elements in analyzed objects, is time- and labour-consuming. This paper describes the results of a trial that was conducted for an optimized spectrophotometric technique. The advantage of the optimized technique is that it skips the stage when a sample gets decomposed with a mixture of hydrofluoric, nitric and sulphuric acids, which saves time and labour and improves the work safety. The results obtained from both conventional and optimized spectrophotometric techniques have good convergence: the discrepancy between them is 1.68%, which does not exceed the applicable error. The authors performed parallel analysis of two samples of ground Lao Cai apatite ore for rare-earth elements determination. Thus, ICP-MS, as well as conventional and optimized spectrophotometric techniques were applied. The authors determined what caused the errors in the case of the latter and how such errors can be minimized.

Rare Earth Elements (REE) in Al- and Fe-(Oxy)-Hydroxides in Bauxites of Provence and Languedoc (Southern France): Implications for the Potential Recovery of REEs as By-Products of Bauxite Mining

Bauxites in southern France (Provence and Languedoc) have been exploited since the beginning of the last century. Though most of the deposits are now subeconomic or mined-out, these bauxites represent model analogs for other economic bauxites of the world. These Cretaceous karst-type deposits lie directly on Jurassic carbonates, and have been formed through a combination of different processes: in-situ alteration of siliciclastic sediments deposited on carbonate platforms, and reworking of early bauxites in the karst network. In this study, we present preliminary bulk rock geochemical and in-situ laser ablation (LA) -ICP-MS analyses on Al- and Fe-oxy-hydroxides of Provence (Les Baux-de-Provence) and Languedoc (Villeveyrac, Loupian) bauxites, with the aim of evaluating the concentrations of rare earth elements (REEs) and their deportment in these minerals. REEs have total average concentrations of 700 mg/kg in the analyzed samples, which are mostly composed of boehmite, γ-AlO(OH), and Fe-oxy-hydroxides (hematite and goethite). Maximum REEs concentrations are commonly associated with positive Ce anomalies in chondrite-normalized patterns. In contrast with other examples from the literature, it has been observed that high REE concentrations also occur in samples apparently devoid or poor of REE-minerals. In these samples, the total amount of REEs is positively correlated with that of Ga (commonly contained in boehmite). LA-ICP-MS trace element analyses on boehmite and Fe-oxy-hydroxides have shown that while the Al-hydroxide contains the suite of REEs, goethite and hematite are preferentially enriched only in Ce. Considering that Al-hydroxides are digested during the Bayer process, an interesting issue to develop in the future is whether (and how) REEs released during Al-hydroxide digestion could be recovered together with Al from the pregnant leach liquor, as routinely done for Ga.

Chemical effect of pesticide application on soils: evidence from rare earth elements

The main objective of this study is to investigate the distribution of rare earth elements (REEs) in Lolium perenne L. plant species which has been grown on vineyard soils treated with pesticide commonly used in the study area. These plants have been grown on two types of soils: (1) brown calcareous soils developed on loess and (2) brown to calcic brown soils developed on conglomerates. The significant correlation observed between the concentrations of phosphorus and the total amount of REEs, in addition to the enrichment in middle REEs (MREEs), suggests the complexation of REEs with phosphates and organic matter. The soils were enriched in REEs due to pesticide application but the plants were depleted. The ratio of REEs in plant over REEs in soil before application of pesticides is higher than that after application of pesticides. Application of pesticides to crops did not affect the fractionation of REEs neither in leaves nor in roots. No selectivity in uptake of REEs occurred because of pesticides except for Ce and Eu which show a negative anomaly relative to the other REEs.

Extraction of rare-earth elements with solutions of di-(2-ethylhexyl)phosphoric acid in flow-through system under local vibrational treatment

Results obtained in a study of the influence exerted by the vibrational treatment in the dynamic interfacial layer on the extraction of rare-earth elements with solutions of di-(2-ethylhexyl)phosphoric acid in a diluent in a flow-through system are presented. It was shown that the coefficient of extraction acceleration under a local vibrational treatment of the dynamic interfacial layer is smaller than that in the static system and is determined by the nature of an element being extracted and a solvent, frequency and amplitude of oscillations of the vibration element, and fluid flow rate. The degree of extraction of rare-earth elements in a certain time is noticeably higher and can reach a double excess if there is a local vibrational treatment of the dynamic interfacial layer. In this case, the accumulation of a lanthanide in the dynamic interfacial layer is substantially lower, and it does not exceed 10% of the total amount of rare-earth elements in the system.

Study on Ecological and Chemical Properties of Rare Earth Elements in Tropical Marine Organisms

Abstract A total of 30 kinds of fish samples, 5 kinds of shellfish samples and 4 kinds of crustacean samples from the Nansha sea area in China were digested using a microwave digestion system with HNO 3 -H 2 O 2 as the digestion reagent. Then, the contents (ICP-MS determination) and ecological chemical characteristics of rare earth elements (REEs) were studied. The results showed that the method of microwave digestion-ICP-MS for the determination of rare earth elements was perfect, and the linear relationship for each element was good with r ≥ 0.9997. The detection limit reached ng L −1 level with a relative standard deviation (RSD, n = 3) of less than 5.0%. The recovery of REEs was between 91.5% and 106.7%. The total amount of REEs in fishes, shellfishes, and crustaceans were (5.0–34.8) μg kg −1 , (30.4–1481) μg kg −1 , and (103–863) μg kg −1 , individually. The order of the enrichment average contents of the REEs in the three species was crustacean>shellfish>fish. The 14 kinds of REE contents in fish/shellfish/crustacean showed a significantly positive correlation ( r > 0.80). The contents of light REEs (from La to Eu) were higher than those of heavy REEs (from Gd to Lu). The light and heavy REEs demonstrated obvious fractionation, and the REE distribution pattern in fish/shellfish/crustacean was consistent with the negative anomaly of Gd. The σ Eu values had negative anomalies, which were similar to the σ Eu values in the corresponding area sediment, and σ Ce values showed positive anomalies, which showed that Ce followed a different oxidation and reduction process in the organism and sediment deposition. At the same time, the enrichment relationship of REEs in sediment and organism was also studied. In this study, the content and distribution of REEs in the tropical marine fish/shellfish/shellfish were analyzed, which could provide basic data for the study of the level, migration, and accumulation of REEs in the environment of South China Sea.

Analysis of Contents and Distribution Patterns of Rare Earth Elements in the Surface Sediments of the South Mid-Atlantic Ridge

A microwave digestion system was employed to digest sediment samples from 16 stations in the South Mid-Atlantic Ridge with HNO3-H2O2-HF as the digestion reagent. Rare earth elements (REEs) in the sediments were determined through inductively coupled plasma-mass spectrometry (ICP-MS), and the REE distribution characteristics were studied. The microwave digestion-ICP-MS method was used to determine the REEs with significant linear relationships (r = 0.9997–1.0000) for each element. The detection limit was at ng L−1 level, with relative standard deviation (RSD, n = 3) of less than 3% and the relative error within 6%. Moreover, the total amount of REEs (∑REEs) in the sediment samples from the 16 stations ranged from 37.25 to 134.8 μg g−1, the ratio range of the light/heavy REEs (LREEs/HREEs) was 0.61–1.70, the average value was 1.27, and the enrichment light rare earth elements in sediments was obvious. The REE distribution patterns in each station were similar, with obvious fractionation between the LREEs and HREEs. The REE distribution patterns in the sediments from different sources were also similar, but those between the terrestrial and marine sediments exhibited slight differences. The δEu and δCe in the sediments had negative anomalies, which showed that the REEs in the sediments originated from seawater. The content and distribution of the REEs in the South Atlantic were initially investigated in this study to provide data and technical support for the further study of REE distributions in the Atlantic region.

The geochemical characteristics of aqueous rare-earth elements in shallow karst groundwater in Guiyang City, China

Fifty-seven shallow groundwater samples were collected from Guiyang karst basin, China, to analyze the aqueous rare-earth elements in low-water seasons and it is shown that the total amount of rare-earth elements (ΣREE) in karst groundwater is exceedingly low compared with that in carbonate rocks or weathering crusts of carbonate rocks, and ranges from 0.01 to 0.43, from 0.03 to 0.27, from 0.03 to 0.19 and from 0.05 to 1.38 μg·L−1 for dolomite, dolomitic & limestone, limestone and clastic rock aquifer, respectively. Both distributions and contents of rare-earth elements (REE) in karst groundwater reflect the lithology of host rocks or weathering crusts of carbonate rocks through which groundwater flows. The chondrite-normalized patterns show a non-flat profile with higher enrichment of slightly light rare-earth elements (LREE) than heavy rare-earth elements (HREE), prominent fractionation between LREE and HREE, negative Ce anomalies and negative or positive Eu anomalies. There is more obvious fractionation between LREE and HREE in groundwater than that in carbonate rocks and their weathering crusts due to high contents of HCO3− and PH in groundwater. In shallow karst groundwater, REE(CO3)n2n−3 (n=1 and 2) is the main inorganic species of REE. But for a clastic rock aquifer, both REESO4+ and REECO3+ are the main inorganic species of REE. Species of REE in groundwater is closely associated with the hydrochemical type of groundwater which is predominated by the lithology of host rocks, groundwater-rock interaction and weathering-pedogenesis of carbonate rocks.

Environmental biogeochemical characteristics of rare earth elements in soil and soil-grown plants of the Hetai goldfield, Guangdong Province, China

Very few studies deal with the biogeochemical behaviors of rare earth elements (REEs) in goldfields. This paper presents the geochemical and biogeochemical characteristics of REEs within the soil–plant system in the Hetai goldfield, Guangdong, China. The samples from the goldfield region show anomalies in distribution patterns and behavioral characteristics of REES as compared with those from the background areas. The REEs in rocks, soils, and plants prove to be much higher than those in the surrounding regions. The distribution patterns of REEs are characterized by LREE-enrichment and HREE-depletion, with the REE concentrations in Layer A being the highest. Differentiations between LREEs and HREEs may lead to some extent of negative Eu anomaly in the soils. Research results demonstrate that the REEs in a soil profile can be transferred and accumulated during the mineral formation and supergenic geochemical processes, and the anomalies are obviously related to the geological settings for the REE-bearing ore-forming processes and to the geochemical characteristics of the habitats for the REE-bearing plants. For Dicranopteris dichotoma, the total amount of REEs in the tissues shows an order of leaf > root > stem, while for Pinus massoniana the order becomes root > leaf > stem. The distribution patterns of REEs in Pinus massoniana leaves are similar to those in soils where the plants grow up in the mineralization area. However, in the background areas the REE distribution patterns for Pinus massoniana stems are similar to those for soils where the plants grow up. Parameters such as biological absorption coefficients and biological transfer coefficients show the differences in REE absorption features among plants and indicate that REEs can be transferred among plant organs. The two coefficients can reveal the different survival mechanisms for the two plant species, which are subject to long-term REE-affected stress conditions in the gold mineralization zone.

Rare earth elements in sediments of the Vigo Ria, NW Iberian Peninsula

The abundance and distribution of rare earth elements (REE) and their signatures in the Vigo Ria were studied from 50 samples of surface sediments and related to the geological formation in its watershed. The total amount of REE in the Ria is heterogeneous. It ranges from 220 mg kg −1 in the southern middle Ria margin in the vicinity of the Galiñeiro geological shore complex, which contains REE-enriched minerals, to 2 mg kg −1 near the Ria mouth due to dilution with high levels of carbonated biogenic particles (31% of Ca). Rare earth elements of the Ria sediments are considerably enriched in light-REE relative to heavy-REE (a LREE/HREE ratio of 9.7±1.6) and also show a slightly negative Eu-anomaly. Low European shale normalised REE patterns were distinguished in the innermost sediments of Vigo Ria, but were not correlated with Al. This suggests a minor contribution of REE from upstream freshwater inputs to the sediments in the middle Vigo Ria zone. Normalised REE ratios in the middle Ria imply that fine particles enriched in REE may be exported from the Ria to shelf mud patches and REE can be useful as sediment tracers of Ria input on the shelf.

Characteristics of rare-earth elements (REE), strontium and neodymium isotopes in hydrothermal fluorites from the Bailashui tin deposit in the Furong ore field, southern Hunan Province, China

In this paper the authors present the REE concentrations and Sr and Nd isotopic compositions of fluorites from the Bailashui tin deposit of the Furong ore field, southern Hunan Province. The results showed that the total amount of REE in fluorites is usually low, ranging from 0.705 to 8.785 μg/g with the chondrite-normalized REE distribution patterns similar to those of the Qitianling granites in the study area, characterized by LREE-enrichment patterns with pronounced negative Eu anomalies. The fluorites vary in Sr isotopic composition within the range of 0.7083–0.7091, the values are lower than those of the granites and higher than those of the host carbonate rocks in this area. The ɛNd(t) values of fluorites vary between −9.4 and +10.3, revealing that both the crust-and mantle-source materials were involved in the ore-forming hydrothermal fluids. Combined with previous studies on this ore deposit, the Bailashui tin deposit is temporally and spatially closely related with granitic magmatism in this area. The hydrothermal fluorites are the product of fluid/rock interactions between granitic magmatic hydrothermal fluid and marine carbonate rocks. The REE and F in the ore-forming fluid were derived from the granites, whereas Sr in the ore-forming fluid came mainly from the granitic magmatic hydrothermal fluid and marine carbonate rocks, although variations in Sr isotopic composition cannot be explained by a simple mixture of these two end-members. Evidence demonstrated that the ore-forming fluids are of crustal-mantle mixing origin, but that the fluids were probably incompletely homogenized and this may be caused by inhomogeneous mixing of the fluids of different sources.

Silicalites of hydrothermal origin in the Lower Cambrian black rock series of South China

A silicalite bed was found in the hanging wall and foot wall of the sulfide-rich bed of the Lower Cambrian black rock series in South China. Its origin was not described before. On the oxide (SiO2-Al2O3, SiO2-MgO, SiO2-K2O + Na2O) diagrams for discriminating silicalites of chemical, biological and volcanic origins (Liu Xiufeng, 1991), most of the data points of silicalites fall within the areas representing silicalites of chemical and volcanic origins. On the Al-Fe-Mn diagram for discriminating silicalites of hydrothermal and biological origins (Yamamoto, 1987), the data points fall within the areas representing silicalites of hydrothermal and hydrothermal-biological origins. On the SiO2-Al2O3 diagram for discriminating silicalites of hydrothermal and hydrogenous origins (Bonatti, 1975), the data points mostly fall within the hydrothermal area. The ratios of SiO2/Al2O3, SiO2/(K2O+ Na2O), SiO2/MgO, and K2O/ Na2O in the silicalites stand between those of volcanic sediments and of seafloor hydrothermal sediments. The total amount of rare-earth elements in the silicalites is low; the North American Shale-normalized REE patterns decline leftward with obvious negative Ce anomaly. The trace elements Mo, Zn, As, Sb, Se, U, and Ba are higher than those in non-hydrothermal sediments and U/Th ≥1. The present authors think that the silicalites are derived from seafloor hot brines which had attracted elements from igneous rocks.

Spectrophotometric determination of the total amount of rare-earth elements in agricultural samples with p-chloro-chlorophosphonazo

A simple, sensitive and accurate spectrophotometric method for determination of the total amount of rare-earth elements in agricultural samples with p-chloro-chlorophosphonazo [ pCCPA, i.e., 2-(4′-chloro-2′-phosphon-benzylazo)-7-(4″-chlorophenyl)-1,8-dihydroxynaphthalene-3,6-disulphonic acid] in sulphuric acid medium has been developed. The apparent molar absorptivity of RE xO y (the general formula of rare-earth oxides)- pCCPA complex is 8.17 × 10 4 1.mole −1 cm −1 at 676 nm, and Beer's law is obeyed for the mixture of RE xO y in the range 0–12 μg/25 ml. The proposed method has been successfully applied to the determination of the total amount of rare-earth elements in soils, herbs, vegetables, dried stems of maize, water samples and rare-earth microelement fertilizer samples with satisfactory results.

Effects of traces of rare earth elements on the protozoanBlepherisma and on mice

The growth of the protozoan Blepherisma is stimulated by Lanthanum (La) at concentrations as low as 0.32 ppm. In mice Yttrium (Y) and Ytterbium (Yb) are absorbed, accumulated, and metabolized. Both rare earth elements (RE) exhibit a high affinity for teeth and bones, accumulation occurs and metabolism is slow. In the livers of RE-exposed mice, concentrations are variable. The liver is apparently capable of absorbing and discharging RE in a manner depending on metabolic activity. The main route of discharge for ingested REs is the alimentary canal. Exposure of pregnant mice to RE leads to rapid placental transfer of RE; 14.1% of the total amount of RE administered was detected in newborn mice. Young, developing organisms appear to be especially susceptible to RE accumulation.

Rare earths in Archean graywackes from Wyoming and from the Fig Tree Group, South Africa

Six graywackes from the Archean greenstone belt in the Wind River of Wyoming and 11 graywackes and three shales from the Archean Fig Tree Group, South Africa, were analyzed for the rare earth elements (REE). There are real deviations beyond analytical uncertainty among sediments from the same formation. The absolute abundance of the REE (∑REE) is somewhat lower than that of the North American shale composite (NASC) which is representative of younger sedimentary rocks. Still, the results confirm previous suggestions that the RE pattern in Precambrian sediments is the same as the NASC but that, relative to the heavy REE, graywackes are slightly enriched in the light REE, shales are depleted, and there is a slight enrichment in Eu relative to the NASC. The average abundance of Eu relative to the other REE for all the Precambrian sediments is the same as that in chondritic meteorites. Attesting to the complexity of graywacke genesis, there is no correlation between the variations in the REE parameters and the variations in major or minor element concentrations. In particular, there is no obvious correlation between the excess Eu and Sr abundance. The total amount of REE, the La Yb ratio, and the Eu enrichment factor, however, all increase in the graywackes with the amount granite-gneiss detritus in the rocks. In general, the REE distributions in Archean graywackes and shales appear to be related to the relative amounts of clastic feldspar, mica, and minor phases which concentrate the REE.