Concentrations Of Light Rare Earth Elements Research Articles

Geochemistry of rare earth elements within waste rocks from the Montviel carbonatite deposit, Québec, Canada.

Several rare earth element (REE) mine projects around the world are currently at the feasibility stage. Unfortunately, few studies have evaluated the contamination potential of REE and their effects on the environment. In this project, the waste rocks from the carbonatites within the Montviel proterozoic alkaline intrusion (near Lebel-sur-Quévillon, Quebec, Canada) are assessed in this research. The mineralization is mainly constituted by light REE (LREE) fluorocarbonates (qaqarssukite-Ce, kukharenkoite-Ce), LREE carbonates (burbankite, Sr-Ba-Ca-REE, barytocalcite, strontianite, Ba-REE-carbonates), and phosphates (apatite, monazite). The gangue minerals are biotites, chlorite, albite, ankerite, siderite, and calcite. The SEM-EDS analyses show that (i) the majority of REE are associated with the fine fraction (< 106μm), (ii) REE are mainly associated with carbonates, (iii) all analyzed minerals preferably contain LREE (La, Ce, Pr, Nd, Sm, Eu), (iv) the sum of LREE in each analyzed mineral varies between ~ 3 and 10wt%, (v) the heavy REE (HREE) identified are Gd and Yb at < 0.4wt%, and (vi) three groups of carbonate minerals were observed containing variable concentrations of Ca, Na, and F. Furthermore, the mineralogical composition of REE-bearing minerals, REE mobility, and REE speciation was investigated. The leachability and geochemical behavior of these REE-bearing mine wastes were tested using normalized kinetic testing (humidity cells). Leachate results displayed higher LREE concentrations, with decreasing shale-normalized patterns. Thermodynamical equilibrium calculations suggest that the precipitation of secondary REE minerals may control the REE mobility.

Variations in stress-sensitive minerals and elements in the tectonic-deformation Early to Middle Permian coals from the Zhuxianzhuang mine, Anhui Province

The variations in stress-sensitive minerals and elements in tectonically deformed coals (TDCs) were revealed in this paper. Results show that the clay minerals, carbonates and sulfides in the Middle to Lower Permian TDCs of the no. 8 and no. 10 coal seams of the Zhuxianzhuang mine are dominated by kaolinite, iron dolomite and calcite, and pyrite, respectively. The contents of Th are significantly higher than U, indicating that the sedimentary paleo-environment was almost independent of seawater and was characterized by hypoxia during peat accumulation periods. The light rare earth elements (LREEs) are enriched, yielding (La/Lu)N values of 1.00–12.30 and slightly positive Ce anomalies in the no. 8 (0.95–1.44, δCe/δEu=1.30–2.62) and no. 10 coal seams (1.02–1.31, δCe/δEu=1.66–2.17). The cluster results show that stress-sensitive elements in TDCs can be classified as aggregation-type (Si, Al, Ti, K, Fe, Sc, Li, Rb, Nb, Ag, Cd, Ta, Tl, Bi, Th, U, W), dissipation-type (N, H, Cl, Mo, Ni, Y, Sr), and mutant-type (O, Na, Ca, Be, Mn, Co, Ga, Ge, Pb, Bi, As). The enrichment effects of ductile deformations for major elements are more significant than those of brittle deformations. The combinations of (Nb, U), (Th, Rb), and (Li, Sc, Ag, Ta) are good brittle-, ductile-, and brittle-ductile enrichment-type elements, respectively, which can be used as good indicators of the coal's tectonic deformation. Sr records higher loss rates in brittle TDCs than in wrinkle coals. The Mo content gradually decreases with increasing tectonic deformation intensity, which is related to the dynamic metamorphism caused by tectonic deformation. Nucleophilic clay mineral elements (Be, Ga, Pb, Ge) in the no. 8 and no. 10 coal seams record similar trends and are highest in scaly coals, indicating that strong shearing effects can promote the enrichment of these elements. The contents of LREE and heavy rare earth elements (HREEs) both increase with the increasing tectonic deformation intensity. For various TDCs, LREE record higher degrees of fractionation than the HREE.

Distribution and source of rare earth elements in PM2.5 in Xiamen, China.

Particulate matter with diameter ≤2.5 µm (PM2.5 ) is a serious atmospheric pollutant. Composition and source analyses are essential for controlling PM2.5 . Rare earth elements (REEs) have received little attention as a component of PM2.5 . In the present study, PM2.5 samples were collected in urban and suburban areas in Xiamen and analyzed for REEs. The concentration range of total REEs (∑REE) is 12.07 to 98.45 mg/kg, with a mean of 38.53 mg/kg, in urban PM2.5 and 16.44 to 160.62 mg/kg, with a mean of 42.94 mg/kg, in suburban PM2.5 . Light REE concentrations are higher in suburban PM2.5 , whereas heavy REE concentrations are higher in urban PM2.5 , implying distinct sources of REEs in urban and suburban PM2.5 . The scatter plots of δEu-∑REE and La-Ce-Sm suggest that REEs in urban PM2.5 originate from gasoline- and diesel-vehicle exhaust, whereas those in suburban PM2.5 are mainly influenced by gasoline-vehicle exhaust. Environ Toxicol Chem 2017;36:3217-3222. © 2017 SETAC.

Modification of REE distribution of ordinary chondrites from Atacama (Chile) and Lut (Iran) hot deserts: Insights into the chemical weathering of meteorites

AbstractThe behavior of rare earth elements (REEs) during hot desert weathering of meteorites is investigated. Ordinary chondrites (OCs) from Atacama (Chile) and Lut (Iran) deserts show different variations in REE composition during this process. Inductively coupled plasma–mass spectrometry (ICP‐MS) data reveal that hot desert OCs tend to show elevated light REE concentrations, relative to OC falls. Chondrites from Atacama are by far the most enriched in REEs and this enrichment is not necessarily related to their degree of weathering. Positive Ce anomaly of fresh chondrites from Atacama and the successive formation of a negative Ce anomaly with the addition of trivalent REEs are similar to the process reported from Antarctic eucrites. In addition to REEs, Sr and Ba also show different concentrations when comparing OCs from different hot deserts. The stability of Atacama surfaces and the associated old terrestrial ages of meteorites from this region give the samples the necessary time to interact with the terrestrial environment and to be chemically modified. Higher REE contents and LREE‐enriched composition are evidence of contamination by terrestrial soil. Despite their low degrees of weathering, special care must be taken into account while working on the REE composition of Atacama meteorites for cosmochemistry applications. In contrast, chondrites from the Lut desert show lower degrees of REE modification, despite significant weathering signed by Sr content. This is explained by the relatively rapid weathering rate of the meteorites occurring in the Lut desert, which hampers the penetration of terrestrial material by forming voluminous Fe oxide/oxyhydroxides shortly after the meteorite fall.

Rare earth elements and select actinoids in the Canadian House Dust Study.

Nationally representative baseline data are presented for rare earth elements (REE), thorium (Th) and uranium (U) in house dust sampled from 1025 urban homes, in units of concentrations (μgg-1 ), loadings (μgm-2 ), and loading rates (ngm-2 d-1 ). Spearman rank correlations indicate that, in addition to outdoor sources, consumer products and building materials can influence indoor dust concentrations of REE, Th, and U. Correlations (P<.01) with numbers of occupants, dogs, and cats suggest soil track-in. Correlations (P<.01) with hardwood floors suggest release of REE additives used in pigments and coatings during daily wear and tear. Concentrations of light REE are elevated in smokers' homes compared to non-smokers' homes (P<.001), suggesting that a key source is "mischmetal," the REE alloy used in cigarette-lighter flints. Indoor sources include geological impurities in raw materials used in consumer products, such as U and Th impurities in bentonite clay used in cat litter, and REE impurities in phosphates used for a variety of applications including dog food and building materials. Median gastric bioaccessibility (pH 1.5) of most REE in dust ranges from about 20% to 29%. Household vacuum samples correlate with fresh dust samples from the same homes (P<.001 for all investigated elements).

Geochemical features of rare-earth elements in surface and subsurface waters in the field of the Albynskoe Gold-Bearing Placer, Amur oblast

The distribution and fractionation of rare-earth elements (REE) are studied in the surface and subsurface waters and rocks of the Albynskoe Gold-Bearing Placer. The obtained data show the rocks of the placer to be enriched with rare-earth elements and to feature the predominance of light lanthanides over heavy ones. Groundwater show an equality between the groups of light and heavy lanthanides, while in the surface waters the concentration of light REE is much higher than that of heavy ones, thus reflecting the composition of the drained ore rocks. The leaching of rare-earth elements from rocks by atmospheric water is intensified by agents produced by microorganisms in their vital activity.

Contrasting geochemical signatures of fluid-absent versus fluid-fluxed melting of muscovite in metasedimentary sources: The Himalayan leucogranites

Abstract Most of the Himalayan Cenozoic leucogranites are products of partial melting of metapelite sources. In the Malashan-Gyirong area (southern Tibet), the geochemical compositions of leucogranites define two groups with distinct whole-rock major elements, large ion lithophile elements, rare earth elements, high field strength elements, and Sr and Hf isotope ratios. Based on published experimental results that define generalized melting reactions of metapelitic sources, we infer that these leucogranites are the products of two different types of crustal anatexis: fluid-fluxed melting and fluid-absent melting of muscovite in metasedimentary sources. As compared to the leucogranites derived from fluid-absent melting, those from fluid-fluxed melting have relatively higher Ca, Sr, Ba, Zr, Hf, Th, and light rare earth element concentrations, and Zr/Hf, Eu/Eu*, and Nd/Nd*, but lower Rb, Nb, Ta, and U concentrations, Rb/Sr and 87Sr/86Sr ratios, and εHf(t). The geochemical differences can be explained by melting behaviors of major (muscovite, feldspar) and accessory minerals (zircon and monazite) during different modes of crustal anatexis. The systematic elemental and isotopic signatures of different types of crustal anatexis and, in particular, the coupling of major and trace elements that results from common influences on rock-forming and accessory mineral behaviors provide tools with which to refine our understanding of the nature of crustal anatexis.

Trace element and Sr isotope records of multi‐episode carbonatite metasomatism on the eastern margin of the North China Craton

AbstractLherzolite xenoliths entrained in the Changle Cenozoic basalts were analyzed to infer mantle process beneath the eastern block of the North China Craton. These xenoliths were classified into two types. Clinopyroxenes (Cpx) in the type‐1 xenoliths are strongly enriched in large ion lithophile elements and light rare earth elements (LREE) but depleted in high field‐strength elements and heavy rare earth elements, and show high Ca/Al, Zr/Hf, and (La/Yb)N ratios but low Ti/Eu ratios. These features indicate that they were crystallized from a carbonatitic melt. Cpx in the type‐2 xenoliths are mostly characterized by a chemical zonation, that is, LREE and Sr contents and (La/Yb)N and Eu/Ti ratios gradually increase from the cores to the rims. Some fresh cores preserve the original signatures of the depleted mantle. These observations indicate partial modification of pre‐existing Cpx by carbonatite metasomatism. Two episodes of metasomatism were identified based on Sr isotopic compositions of Cpx and carbonate inclusions within olivines. Both the carbonate inclusions and Cpx cores in the type‐2 xenoliths have relatively high 87Sr/86Sr ratios (&gt;0.7033), suggesting metasomatism due to CO2‐rich silicate melt derived from the recycled oceanic crust. However, low 87Sr/86Sr ratios of Cpx rims in the type‐2 xenoliths suggest a late stage of metasomatism by a low‐87Sr/86Sr carbonatitic melt (&lt;0.7024), which might have been caused by upwelling of the asthenosphere mantle. Such multiple metasomatism could have played an important role in changing the chemical composition of mantle from refractory and depleted to fertile and enriched.

Anthropogenic rare earth elements and their spatial distributions in the Han River, South Korea

Rare earth elements (REE) consist of lanthanides (from La to Lu), together with yttrium and scandium, in which anthropogenic REE, such as gadolinium (Gd), lanthanum (La), and samarium (Sm), has emerged as micro-contaminants in natural waters in highly developed countries. Here, we collected water samples in the Han River (HR) and its tributaries flowing through Seoul Capital Area, the world's second largest metropolitan area in order to examine how and to what extent anthropogenic REE anomalies may occur. Water samples show higher light REE concentrations than heavy REE concentrations, while wastewater treatment plant (WWTP) samples display much higher heavy REE concentrations due to high Gd concentration. The PAAS-normalized REE patterns indicate that WWTP samples display the pronounced positive Gd anomalies, in which anthropogenic Gd from magnetic resonance imaging (MRI) diagnostic system occurs as a form of Gd complexation with either Cl− or SO42−. Due to the WWTP, both the HR and tributaries show also positive Gd anomalies and the anthropogenic Gd concentrations increase as a function of the distance from the Paldang dam. This result indicates a positive correlation between populaton, number of MRI instruments, and positive Gd anomaly. Similarly, positive La and Sm anomalies exist in the HR, indicating that the HR is also affected by their point sources. Based on the discharge rate and anthropogenic REE concentrations, their fluxes are estimated to be 952 ± 319 kg/yr, suggesting that this amount of fluxes could disturb REE distribution in the Yellow Sea, and pose harmful effects on aquatic ecosystems.

Origin of unusual HREE-Mo-rich carbonatites in the Qinling orogen, China.

Carbonatites, usually occurring within intra-continental rift-related settings, have strong light rare earth element (LREE) enrichment; they rarely contain economic heavy REE (HREE). Here, we report the identification of Late Triassic HREE-Mo-rich carbonatites in the northernmost Qinling orogen. The rocks contain abundant primary HREE minerals and molybdenite. Calcite-hosted fluid inclusions, inferred to represent a magmatic-derived aqueous fluid phase, contain significant concentrations of Mo (~17 ppm), reinforcing the inference that these carbonatitic magmas had high Mo concentrations. By contrast, Late Triassic carbonatites in southernmost Qinling have economic LREE concentrations, but are depleted in HREE and Mo. Both of these carbonatite types have low δ26Mg values (−1.89 to −1.07‰), similar to sedimentary carbonates, suggesting a recycled sediment contribution for REE enrichment in their mantle sources. We propose that the carbonatites in the Qinling orogen were formed, at least in part, by the melting of a subducted carbonate-bearing slab, and that 10 Ma younger carbonatite magmas in the northernmost Qinling metasomatized the thickened eclogitic lower crust to produce high levels of HREE and Mo.

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.

Subduction-related Late Cretaceous high-K volcanism in the Central Pontides orogenic belt: constraints on geodynamic implications

Mineral chemistry, major and trace elements, 40Ar/39Ar age and Sr–Nd–Pb isotopic data are presented for the Late Cretaceous Hamsilos volcanic rocks in the Central Pontides, Turkey. The Hamsilos volcanic rocks mainly consist of basalt, andesite and associated pyroclastics (volcanic breccia, vitric tuff and crystal tuff). They display shoshonitic and high-K calc-alkaline affinities. The shoshonitic rocks contain plagioclase, clinopyroxene, alkali feldspar, phlogopite, analcime, sanidine, olivine, apatite and titanomagnetite, whereas the high-K calc-alkaline rocks contain plagioclase, clinopyroxene, orthopyroxene, magnetite / titanomagnetite in microgranular porphyritic, hyalo-microlitic porphyritic and glomeroporphyritic matrix. Mineral chemistry data reveal that the pressure condition of the clinopyroxene crystallisation for the shoshonitic rocks are between 1.4 and 6.3 kbar corresponds to 6–18-km depth and the high-K calc-alkaline rocks are between 5 and 12 km. 40Ar/39Ar age data changing between 72 ± .5 Ma and 79.0 ± .3 Ma (Campanian) were determined for the Late Cretaceous Hamsilos volcanic rocks, contemporaneous with the subduction of the Neo-Tethyan Ocean beneath the Pontides. The studied volcanic rocks were enriched in the large-ion lithophile and light rare earth element contents, with pronounced depletion in the contents of high-field-strength elements. Chondrite-normalised rare earth element patterns (LaN/LuN = 6–17) show low to medium enrichment, indicating similar sources of the rock suite. Initial 87Sr/86Sr values vary between .70615 and .70796, whereas initial 143Nd/144Nd values change between .51228 and .51249. Initial 206Pb/204Pb values vary between 18.001 and 18.349, 207Pb/204Pb values between 15.611 and 15.629 and 208Pb/204Pb values between 37.839 and 38.427. The main solidification processes involved in the evolution of the volcanic rocks consist of fractional crystallisation, with minor amounts of crustal contamination ± magma mixing. According to geochemical evidence, the shoshonitic melts in the Hamsilos volcanic rocks were possibly derived from the low degree of partial melting of a subcontinental lithospheric mantle (SCLM), while the high-K calc-alkaline melts were derived from relatively high degree of partial melting of SCLM that was enriched by fluids and/or sediments from a subduction of oceanic crust.

Rare earth elements in raw materials and products of the phosphate fertilizer industry in South America: Content, signature, and crystalline phases

Phosphate ores are well-known for containing rare earth elements (REE) in a wide range of contents. The presence of REE in phosphate (P) products may enhance plant and animal development. Yet, our current understanding of the role of different P products as carriers of REE to soils is still incipient, especially regarding the extent to which the original REE content in raw materials remains in their respective products and the changes in crystalline phases associated with the phosphate ore processing. This study evaluated phosphate concentrates used as raw materials in major phosphate industries in South America as well as final products – including P fertilizers, di-calcium phosphate, and phosphogypsum – in order to characterize their REE contents, signatures, and REE-carrying crystalline phases. The results showed that the REE content in raw materials and products from the phosphate industry in South America is highly variable. Phosphorites from Bayóvar Phosphate Mine showed the lowest REE content among the studied raw materials (~70mgkg−1). Considering materials of igneous origin, the phosphate concentrate from the Catalão Minerochemical Complex presented the highest total REE content (∑REE up to 16,650mgkg−1) and the highest concentrations of light REE (∑LREE/∑REE ~98%), whereas those from the Araxá Minerochemical Complex, especially materials from the F4 Mine, presented the highest contents of heavy REE (∑HREE ~1200mgkg−1). A great variety of mineral phases was found not only in phosphate concentrates but also in final products, with the apatite-group appearing as the main REE-carrying crystalline phase. The REE contents and composition in the final products were generally strongly influenced by their respective raw materials, resulting in a strong match of REE signatures, which reinforces the usefulness of REE signatures as accurate tools for tracing the origin and provenance of final products of the P fertilizer industry.

Distribution and Geochemistry of Rare-Earth Elements in Rivers of Southern and Eastern Primorye (Far East of Russia)

The distribution and geochemistry of rare earth elements (REE) in anthropogenic, technogenic and natural surface waters of southern and eastern Primorye, Far East of Russia, are presented in this study. The obtained results indicated that most of REE (up to 70%) were transported as suspended matter, ratio between dissolved and suspended forms varing from the source to the mouth of rivers. It is shown that all REE (except Ce) in the source of the rivers are predominantly presented in dissolved form, however, the content of light and heavy REE is different. Short-term enrichment of light rare earth elements (LREE) caused by REE-rich runoff from waste dumps and mining is neutralized by the increase in river flow rate. Rivers in urban areas are characterized by high content of LREE in dissolved form and very low in suspended one.

Evidence for dissolution-reprecipitation of apatite and preferential LREE mobility in carbonatite-derived late-stage hydrothermal processes

The Tundulu and Kangankunde carbonatite complexes in the Chilwa Alkaline Province, Malawi, contain late-stage, apatite-rich lithologies termed quartz-apatite rocks. Apatite in these rocks can reach up to 90 modal% and displays a distinctive texture of turbid cores and euhedral rims. Previous studies of the paragenesis and rare earth element (REE) content of the apatite suggest that heavy REE (HREE)-enrichment occurred during the late-stages of crystallization. This is a highly unusual occurrence in intrusions that are otherwise light REE (LREE) enriched. In this contribution, the paragenesis and formation of the quartz-apatite rocks from each intrusion is investigated and re-evaluated, supported by new electron microprobe (EPMA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) data to better understand the mechanism of HREE enrichment. In contrast to the previous work at Tundulu, we recognize three separate stages of apatite formation, comprising an “original” euhedral apatite, “turbid” apatite, and “overgrowths” of euhedral late apatite. The crystallization of synchysite-(Ce) is interpreted to have occurred subsequent to all phases of apatite crystallization. The REE concentrations and distributions in the different minerals vary, but generally higher REE contents are found in later-stage apatite generations. These generations are also more LREE-enriched, relative to apatite that formed earlier. A similar pattern of increasing LREE-enrichment and increased REE concentrations toward later stages of the paragenetic sequence is observed at Kangankunde, where two generations of apatite are observed, the second showing higher REE concentrations, and relatively higher LREE contents. The changing REE distribution in the apatite, from early to late in the paragenetic sequence, is interpreted to be caused by a combination of dissolution-reprecipitation of the original apatite and the preferential transport of the LREE complexes by F- and Cl-bearing hydrothermal fluids. Successive pulses of these fluids transport the LREE out of the original apatite, preferentially re-precipitating it on the rim. Some LREE remained in solution, precipitating later in the paragenetic sequence, as synchysite-(Ce). The presence of F is supported by the F content of the apatites, and presence of REE-fluorcarbonates. Cl is not detected in the apatite structure, but the role of Cl is suggested from comparison with apatite dissolution experiments, where CaCl 2 or NaCl cause the reprecipitation of apatite without associated monazite. This study implies that, despite the typically LREE enriched nature of carbonatites, significant degrees of hydrothermal alteration can lead to certain phases becoming residually enriched in the HREE. Although at Tundulu the LREE-bearing products are re-precipitated relatively close to the REE source, it is possible that extensive hydrothermal activity in other carbonatite complexes could lead to significant, late-stage fractionation of the REE and the formation of HREE minerals.

遵义地区地产茶叶中稀土元素含量特征

稀土元素含量对茶叶品质及质量安全有一定的影响。以贵州省遵义地区地产茶叶为研究对象，采用ICP-MS分析遵义地区5个县区共32份茶叶样品中16种稀土元素含量特征。结果表明：32份样品均检出稀土元素，以稀土氧化物总量计，总残留量范围为0.033~1.785 mg/kg，其中以镧、钇、铈、钪、钕含量较高，且轻稀土含量高于重稀土，占检出总量的66.47%，所有样品均未超出《食品中污染物限量》(GB2762-2012)中规定的茶叶中稀土元素限量标准(≤2.0 mg/kg)，合格率为100%，其研究结果为茶叶质量监管提供一定的参考。 Studies indicated that intake of rare earth (RE) elements content in teas could threaten human health. ICP-MS technique was utilized to analyze sixteen rare earth (RE) elements from thirty-two tea samples, which were obtained from five counties in Zunyi. The results indicated that all samples contained RE elements based on total RE elements oxide content. The range of residuals was from 0.033 to 1.785 mg/kg, mainly consisted of La, Yb, Ce, Sc, and Nd, which were accounted for 66.47% of tested RE elements. The content of light RE elements was higher than heavy RE elements. However, RE element content in thirty-two samples did not exceed the concentration benchmark (≤2.0 mg/kg) of national standard (GB2762-2012). The results obtained from this stu- dy could provide some suggestions on management and pollution monitoring of environmental protection department.

Rare earth elements in surface sediments of a marine coast under heavy anthropogenic influence: The Bohai Bay, China

Surface sediments along four river-to-sea transects from the coastal Bohai Bay were assessed using a four-step sequential extraction procedure to determine the concentrations of rare earth elements (REEs) and the geochemical fractions in which those elements were present. The concentrations of light REEs were slightly depleted than those of the middle REEs and the heavy REEs. No significant Ce anomaly was observed whereas slight Eu-positive anomaly was found. The sequential extraction results revealed that the geochemical fractions of REEs followed the order of residual > reducible > oxidizable > acid soluble. The residual fraction accounted for the majority of the total concentrations of REEs. Middle REEs were more easily leached than other REEs. No obvious river-to-sea transportation was observed and the concentrations of REEs in surface sediments of the coastal Bohai Sea were consistent with the data from the Post-Archean Australian Shale. This study further demonstrated on the basis of our previous inference that the geochemical features of REEs in coastal sediments were generally unaffected by heavy anthropogenic effects.

Levels of rare earth elements, heavy metals and uranium in a population living in Baiyun Obo, Inner Mongolia, China: A pilot study

The Baiyun Obo deposit is the world’s largest rare earth elements (REE) deposit. We aimed to investigate levels of REE, heavy metals (HMs) and uranium (U) based on morning urine samples in a population in Baiyun Obo and to assess the possible influence of rare earth mining processes on human exposure. In the mining area, elevated levels were found for the sum of the concentrations of light REE (LREE) and heavy REE (HREE) with mean values at 3.453 and 1.151μgg−1 creatinine, which were significantly higher than those in the control area. Concentrations of HMs and U in the population increased concomitantly with increasing REE levels. The results revealed that besides REE, HMs and U were produced with REE exploitation. Gender, age, educational level, alcohol and smoking habit were major factors contributing to inter-individual variation. Males were more exposed to these metals than females. Concentrations in people in the senior age group and those with only primary education were low. Drinking and smoking were associated with the levels of LREE, Cr, Cu, Cd and Pb in morning urine. Hence this study provides basic and useful information when addressing public and environmental health challenges in the areas where REE are mined and processed.

Element mobility during the formation of the Uzunisa-Ordu bentonite, NE Turkey, and potential applications

AbstractDacitic andesitic calc-alkaline lavas and their pyroclastic rocks of Upper Cretaceous age are widespread in the Ordu area, eastern Black Sea Coast of Turkey. Ca-bentonite and Ca/Nabentonite deposits with significant economic potential formed in the broader region. The mineralogy and geochemistry of these deposits were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and chemical analyses. The parent rocks (PR) and bentonite samples were analysed for the major and trace element contents, including rare-earth elements, to understand the effect of differential alterations on element mobility. The bentonites contain mainly di-octahedral Ca-montmorillonite with minor amounts of illite, quartz, calcite, dolomite and feldspar. Primary K-feldspar and plagioclase phenocrysts were altered in the bentonite horizons, and were completely leached at greater depth. For this reason, the higher quality bentonites are found at deeper zones. Bentonite horizons are characterized by relatively high loss on ignition (LOI: 9.8–20.8%) and MgO content (3–5%) and low K2O (&lt;0.5%) and Na2O (&lt;2%) contents compared with the least altered parent rocks. Silicon, Ca, Mg, Mn and P are markedly enriched whereas Fe, Na, K and Ti are depleted in the bentonite samples. The chondrite-normalized rare earth element (REE) patterns show identical trends characterized by strong light rare earth element (LREE) enrichment in both the PR and bentonite samples. The LREE contents are higher than those of their heavy counterparts (HREE) in the samples. Alteration of the PR to bentonite is associated with intense chemical leaching and subsequent removal of K and Na in open-system conditions.

The Turner Mountain syenite, Maine, USA: geology, geochemistry, geochronology, petrogenesis, and post-orogenic exhumation

The Turner Mountain syenite is one of the few plutons located entirely within the Norumbega fault system in the northern Appalachian orogen. It is composed of texturally and mineralogically homogeneous biotite-amphibole syenite and is in faulted contact with mylonitic leucogranite and an unmetamorphosed redbed unit. It is intermediate in SiO2 content (58.7–65.1 wt%) and ultrapotassic (6.4–7.9 wt% K2O) with high K2O/Na2O ratios (2.75–4.15), yet is relatively primitive in terms of MgO (2.8–4.9 wt%), Ni (average 90.2 ppm), and Cr (average 210.1 ppm) contents. It has enriched large-ion-lithophile elements relative to high field strength elements, high contents of light rare-earth elements, and initial 87Sr/86Sr ratios (0.7038–0.7068) similar to that of OIB basalts. It differs petrologically and geochemically from the neighboring Lucerne-Deblois plutons but is similar to Lincoln syenite located 100 km to the southwest, also within the Norumbega system. Zircon U-Pb dating using LA-ICP-MS yields a weighted mean age of 410.5 ± 2.4 Ma, slightly younger than the Lincoln syenite (418 ± 1 Ma). Based on their distinctive geochemical signatures, both were probably products of Late Silurian-Early Devonian ultrapotassic magmatism related to Acadian subduction, generated by partial melting of a mantle wedge metasomatized by potassium-rich fluids during west-directed subduction. This unique magmatism could be attributed to decompressional melting during Late Silurian-Early Devonian slab break-off or delamination. Based on Sr-Nd isotopic compositions, the Turner Mountain syenite magma probably had more crustal interaction than that which formed the Lincoln syenite. The syenite was later exhumed tectonically during brittle reactivation of the Norumbega fault. The reactivation involved regional-scale, high-angle, southeast-over-northwest reverse faulting in a transpressional environment and occurred during the Late Devonian and through Mississippian to Permian.