Sum Of Rare Earth Elements Research Articles

Geochemical behavior of rare earth elements (REE) in urban reservoirs: the case of Funil Reservoir, Rio de Janeiro State, Brazil.

Rare earth elements (REE) have unique chemical properties, which allow their use as geochemical tracers. In this context, the present study aims to assess the role of Funil Reservoir on REE biogeochemical behavior. We collected water samples upstream of the reservoir (P-01) in the city of Queluz, inside the reservoir (P-02), and downstream of Funil Reservoir (P-03) in the city of Itatiaia, RJ. In the field, physicochemical parameters were measured using a probe (pH, temperature, electrical conductivity, and dissolved oxygen). In the laboratory, water samples were filtered (0.45µm) and properly packed until chemical analysis. Chlorophyll a concentrations were determined by a spectrophotometric method and suspended particulate matter (SPM) by a gravimetric method. Ionic concentrations were determined by ion chromatography technique and REE concentrations were determined by ICP-MS. Chlorophyll a concentrations were higher in Funil Reservoir. Ionic concentrations in Queluz (P-01) suggest anthropic contamination. The sum of REE in the dissolved fraction ranged from 2.12 to 12.22µg L-1. A positive anomaly of La in Queluz indicates anthropic contamination. The observed patterns indicate that Funil Reservoir acts as a biogeochemical barrier, modifying the fluvial transport of REE. Nonetheless, another factor that probably influences REE behavior is the algal bloom that occurs in reservoirs during the rainy season. The seasonal behavior of algae can influence REE biogeochemistry through the incorporation and release of trace metals.

Geology, mineralogy and geochemistry of the Morro Preto Alkaline-carbonatite complex, Goiás, Brazil

The Morro Preto Complex, located in the northern portion of the Cretaceous Goiás Alkaline Province, is unique in the region due to the large predominance of carbonatites and phosphate mineralization. It comprises two circular intrusions (Morro Preto North and Morro Preto South) of apatite-rich magnesiocarbonatites gradually transitioning to ferrocarbonatites. The complex also hosts fenites produced by carbonatite metasomatism at the contacts with the Neoproterozoic country rocks. Kamafugite dykes with carbonate globules suggest an immiscibility link between silicate and carbonatite magma.The magnetite-apatite-dolomite carbonatites vary in texture and modal composition from cumulates to magnesiocarbonatites with variable apatite and magnetite, with minor barite and traces of pyrochlore, phlogopite, baddeleyite and zircon. In the ferrocarbonatites, magnetite and apatite are rare or absent, and the dominant carbonate varies from Fe-dolomite to ankerite and siderite, with traces of bastnaesite, monazite, thorium-rich monazite and sulfides. SiO2, Fe2O3, MnO, BaO:SrO and the sum of rare earth elements (REEs) increase from magnesiocarbonatites to ferrocarbonatites, whereas the CaO, MgO and P2O5 contents decrease.Four main apatite types are recognized in the complex: (i) high P-REE primary magmatic sub-euhedral apatites (type 1), (ii) fluorapatite associated with ferrodolomite-rich zones (type 2), (iii) fine-grained, Na-rich metasomatic apatite (type 3) and (iv) secondary fluorapatite filling veinlets and cavities (tuupe 4). In general, the apatite morphological and compositional variations correlate with carbonate evolution and with stable isotope data. Dolomite and type 1 apatite represent the primary group (+9.49 to +11.88‰ δ18O and −5.1 o −4.66‰ δ13C). Ferrodolomite, iron-rich carbonates, along with types 2 and 4 fluorapatite have heavier isotope compositions (up to +21.59‰ δ18O and −3.33‰ δ13C), indicating metasomatic reworking related to late-stage carbonatite-derived fluids.Geological, geochemical and mineral chemistry data are consistent with the evolution of the complex by crystal fractionation, liquid immiscibility, metasomatic overprinting and late hydrothermal events. The K fenitization and late-stage carbohydrothermal events suggest that the Morro Preto Alkaline-Carbonatite Complex represents the uppermost parts of a carbonatite magmatic system.

Research of rare-earth elements in salt deposits of drinking water of the Pavlodar region (Republic of Kazakhstan)

Ecologic and geochemical assessment of the territory of Pavlodar region, influenced by natural and anthropogenic factors of environment, is conducted in the article. Salt deposits of drinking water are proposed to be used as indicative environment. The research method is the instrumental neutron activation analysis of limescale samples, conducted in Tomsk Polytechnic University. Content of rare earth elements (La, Ce, Sm, Eu, Tb, Yb, Lu) is assessed, and elemental ratio (La/Ce, La/Yb, La+Ce/Sm+Eu, La+Ce/Yb+Lu) in salt deposits of drinking water of Pavlodar region is defined. Schematic maps of distribution of rare earth elements in salt deposits of drinking water of Pavlodar region, which demonstrate preferential accumulation in the northern part of the region, were constructed. The source of the given elements is of a natural and athropogenic genesis, caused by location of titanium-zirconium deposits in this part of region. Ratio of light lanthanides to heavy lanthanides demonstrates that salt deposits of drinking water of the research territory tends to light lanthanides, except for the limescale of Baynaul, Sharbakty, Aktogay districts. Ratio of the sum of rare earth elements to radioactive elements demonstrates that limescale is preferentially characterized as with high content of uranium, except for the salt deposits of drinking water from Irtyshsk district. Key words: rare earth elements, geochemistry, limescale, Pavlodar region.

Mafic dikes of the Mariinsky Taiga Alkaline Province, Kuznetsk Alatau terrane, southwestern Siberia: Intraplate alkaline magmatism in the Central Asian Orogenic Belt

The Mariinsky Taiga Alkaline Province (MTAP) is located in the Kuznetsk Alatau terrane of southwestern Siberia, which is part of Altai-Sayan orogenic system, of the Central Asian Orogenic Belt. The MTAP consists of a wide distribution of Paleozoic alkaline-basite magmatism (volcanic, subvolcanic and intrusive), which has been recently characterized with the recognition of at least two main timings, ca. 500 and ca. 400 Ma (herein labeled MTAP-1 and MTAP-2, respectively). We newly characterize the petrology, geochemistry, and age constraints of NNW and NNE trending alkaline dikes which cross-cut the alkaline intrusions and host volcanogenic and carbonate units and which are inferred to belong to MTAP-2. The dikes consist of ultrabasic foidolites (urtites, urtite-porphyry, ijolite-porphyry, microijolites), basic foidolites (plagioclase ijolites), alkaline basites (gabbro-diabase, labradorite porphyrites, camptonites and tamaraites), and nepheline, analcime and alkaline syenites. Their chemical composition is characterized by a wide range in silica (SiO 2 = 38.7–60.7 wt%), and alkalinity (Na 2 O + K 2 O = 4–18.7 wt%; Na 2 O/K 2 O = 0.5–8.3 wt%), low titanium (TiO 2 = 0.07–2.15 wt%) and high alumina content (Al 2 O 3 = 11.1–28.5 wt%), which corresponds to the K-Na differentiates of the basic alkaline magmatic series. The sum of rare-earth elements (ΣREE) increases from alkaline basite (ΣREE = 103.58–218.94 ppm), to the main foidolites (ΣREE = 137.74–217.61 ppm), and then to the ultrabasic foidolites (ΣREE = 55.56–268.88 ppm). Maximum REE content occurs in nepheline syenites and microsyenites (ΣREE = 73.24–1566.96 ppm) and they are the final product of the differentiation of foidite and basite melts. All dike varieties are characterized by low concentrations of the most highly charged elements (Th, Nb, Ta, Hf, and Y), which, according to their concentrations, plot between oceanic island basalt (OIB) and island arc basalt (IAB). The presence of a negative Nb-Ta anomaly and the relative enrichment of Rb, Ba, Sr and U indicate probable interaction of a mantle plume melts with lithospheric mantle metasomatized in an earlier subduction event. The primary isotope ratio 87 Sr/ 86 Sr(t) = 0.705388–0.706025 and the range of ɛNd(t) from +3.5 to +6.53 in the rocks indicate interaction of mantle derived melts with crustal components. Sm-Nd and U-Pb dating of the alkaline-basite dikes matches the boundary of the Early-Middle Devonian (406–389 Ma) and indicates membership in MTAP-2, which can be linked to the regional ca. 400 Ma Altai-Sayan Large Igneous Province/Rift System. Both the NNW and NNE trending dikes are associated with, and probably fed from, nearby alkaline intrusions such as i.e. Kiya-Shaltyr pluton which are also ca. 400 Ma (part of MTAP-2), but are independent of older ca. 500 Ma intrusions (which belong to MTAP-1) such as the University pluton and which are suggested to belong to a older plume-generated regional event. • Characterization of NNW and NNE trending dike belts in the MTAP, western Siberia. • They formed in the Middle Paleozoic (406–389 Ma) in a plume-rifting event. • Isotopic parameters ɛSr(t) indicate a strong contamination by crustal components. • The dike represent intraplate magmas emplaced in a shear setting.

Rare Earth Elements and Bioavailability in Northern and Southern Central Red Sea Mangroves, Saudi Arabia.

Different hypotheses have been tested about the fractionation and bioavailability of rare earth elements (REE) in mangrove ecosystems. Rare earth elements and bioavailability in the mangrove ecosystem have been of significant concern and are recognized globally as emerging pollutants. Bioavailability and fractionation of rare earth elements were assessed in Jazan and AlWajah mangrove ecosystems. Comparisons between rare earth elements, multi-elemental ratios, geo-accumulation index (Igeo), and bio-concentration factor (BCF) for the two mangroves and the influence of sediment grain size types on concentrations of rare earth elements were carried out. A substantial difference in mean concentrations (mg/kg) of REE (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) was established, except for mean concentrations of Eu, Gd, Tb, Tm, and Lu. In addition, concentrations of REEs were higher in the Jazan mangrove ecosystem. However, REE composition in the two mangroves was dominated by the lighter REE (LREE and MREE), and formed the major contribution to the total sum of REE at 10.2–78.4%, which was greater than the HREE contribution of 11.3–12.9%. The Post Archean Australian Shale (PAAS) normalized values revealed that lighter REE (LREE and MREE) were steadily enriched above heavy REE. More so, low and negative values of R(H/M) were recorded in the Al Wajah mangrove, indicating higher HREE depletion there. The values of BCF for REEs were less than 1 for all the REEs determined; the recorded BCF for Lu (0.33) and Tm (0.32) were the highest, while the lowest BCF recorded was for Nd (0.09). There is a need for periodic monitoring of REE concentrations in the mangroves to keep track of the sources of this metal contamination and develop conservation and control strategies for these important ecosystems.

Geochemical studies of snow over mineral accumulations under conditions of their overlap by sedimentary rocks of the platform cover

In geochemical exploration, the seasonal snow cover is a convenient natural material for identifying under deep covered mineral accumulations. Snow has shielding and accumulating properties sufficient for the occurrence of dispersion of geochemical halos. The snow horizon of geochemical sampling is protected from atmospheric and landscape factors of replenishment of its chemical composition for most of the winter. The filtrate of snow melted water is cleaned of large-sized solid material, and chemical compounds are in the dissolved and finely dispersed solid phase of submicron dimension. Therefore, in terms of the physical and chemical properties of the analyzed substance, snow geochemical survey is close to selective methods. Test surveys were carried out on single profiles of snow sampling at two ore occurrences (Au, Pb-Zn) and an oil field within the West Siberian plate. Concentrations of a wide range of chemical elements in snowmelt water filtrate were determined by the ICP-MS method. As a result of statistical processing of geochemical data, a low variability of concentrations of chemical elements has been established. Correlation and regression analyzes demonstrate the presence of linear dependences in the distribution of trace elements, which reflect the ability of elements to form easily soluble and hardly soluble occurrence forms. The variability of the local geochemical background is mainly due to the content of hardly soluble phases that entered the snow layer during its deposition on the ground. Presumably, they are represented by particles of aeolian dust, needles and scales of tree bark captured by snow from tree and shrub crowns. In the area of study with high heterogeneity of elementary landscapes, the influence of this factor is comparable in amplitude to the contrast of superimposed geochemical halos. Normalization of the concentrations of trace elements by the sum of rare earth elements (REE) allows to strengthen the useful geochemical signal. Geochemical anomalies detected in snow in space quite accurately coincide with the position of mineral deposits buried the platform cover terrains, and also find confirmation in the chemical composition of soils and soil air. The good potential of snow metallometric surveying for prospecting of deep-seated mineral resources needs to be confirmed by studying the vertical and lateral migration of chemical elements in the snow cover.

Selective incorporation of rare earth elements by seaweeds from Cape Mondego, western Portuguese coast

This study examined the mechanism of incorporation of the rare earth elements (REEs), La, Ce, Nd, Eu, Gd, Tb, Yb, into green (Codium tomentosum, Ulva rigida), red (Gracilaria gracilis, Osmundea pinnatifida, Porphyra sp), and brown seaweeds (Saccorhiza polyschides, Undaria pinnatifida) collected from a single site near the coastline of the Cape Mondego, western Portugal. The concentrations of REEs, Mg, Ca, Al, Fe, Zn, and Cu in the biomasses were determined by inductively-coupled plasma mass spectrometry (ICP-MS). The species showed differences in their incorporation and fractionation of REEs from the same environment: the sum of REEs was higher in U. rigida, C. tomentosum, G. gracilis, and O. pinnatifida (0.7–1.7 μg g−1) than in Porphyra sp., S. polyschides, and U. pinnatifida (0.1–0.2 μg g−1). Ratios of Ce/Yb ranged from 13 (in S. polyschides) to 103 (in U. rigida), indicating different proportions of light and heavy REEs among species. Good correlations were found between Al and Fe (R2 = 0.98), and between these elements and La, Ce, Nd, Gd (R2 = 0.88–0.97) and Yb (R2 = 0.66–0.71) for all species except C. tomentosum and G. gracilis. Profiles of REE values normalised to average upper-continental crust composition indicated positive anomalies of Eu and Tb that reinforced the singularity of these elements in the REE group. Correlations between the REEs and Al or Fe suggest that detrital terrigenous particles, adhered to seaweed walls, may be an important mechanism for the incorporation of REEs by seaweeds. Different patterns for C. tomentosum and G. gracilis may also be indicative of the higher influence of cell wall composition on REE incorporation.

Application of PCA and HCA in geochemical parameters to distinguish depositional paleoenvironments from source rocks

Oil-producing rocks can be characterized by organic, inorganic and palynological geochemical parameters to assess the quantity and quality of organic matter. In the present study, samples of source rocks collected from different formations (Fm) from the sedimentary basins of the Parnaíba (Pimentairas Formation) and Paraná (Irati and Ponta Grossa Formations) were evaluated through the geochemical correlation between the types of organic matter and their different depositional paleoenvironments using chemometric tools. Among the inorganic geochemical parameters used in this evaluation are the concentrations and the diagnostic ratios between the transition elements (Co, Ni, V, and Mo) and internal transition (lanthanides and U). The analysis of the transition and internal transition elements were performed by ICP OES (Ni and V) and ICP MS (Co, Mo, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb, Lu, and U). The organic geochemical parameters selected for the characterization of the quantity and quality of the organic matter present in the samples of source rocks involved the determination of their total carbon content (%TOC) and sulfur (%TS), of the potential generator (S2) the amount of hydrocarbons produced by Rock-Eval pyrolysis and the calculation of the hydrogen (HI) and oxygen (OI) indexes. To compose the matrix of the multivariate analysis (PCA), were used ratios Ni/Co, V/Ni, U/Mo, V/V + Ni, TOC/TS the values of S2, HI, OI and the sum of rare earth elements (REE). The kerogen type, obtained through the HI and OI data, were also included in the matrix, information on the origin of the organic matter, and on the type of depositional paleoenvironment of each sample, obtained from previous works. It was observed the formation of three groups of data characterizing the formations Irati, Ponta Grossa and Pimenteiras according to the type of kerogen and organic matter, and also of its depositional paleoenvironment, showing that the exploratory data analysis allows the obtaining of rapid and efficient information on the chemical similarity between the complex samples from each formation.

Rare earth elements in surface specific urban runoff in Northern Beijing

Rare earth elements (REEs) have been increasingly diffused to the environment through mining activities and the extensive use in modern commodities, vehicular activities, coal burning and various environmental and agricultural applications. Studies of REEs in urban environments are limited with no data on REEs in urban runoff. To investigate the concentration and distribution of REEs, a total of 150 runoff samples were collected from trafficked areas, rooftops and residential parking lots in a moderate to densely populated area in Beijing, China. The runoff samples were separated into dissolved and particulate phases and analyzed by ICP-MS. The REEs were mainly (>80%) found in the runoff particulate material. The sum of REEs (ΣREE) total concentrations in urban stormwater runoff samples ranged from 0.16 to 185 μg/l. The observed mean total concentration of ΣREE in the runoff samples were 3–14 folds higher and dissolved fractions 1.5 to 6 times higher than published concentrations for recipients such as sewage channels and rivers. The distribution of REEs in runoff was dominated by light REE. Cluster analysis and Pearson's correlations revealed a strong association between the individual REEs pointing to a similar source. Higher Ce concentrations compared to other REEs indicated strong influence from traffic emission particulates. The La/Sm (5.90–8.05), La/Ce (0.53–0.58) and Ce/Yb (31.0–42.7) ratios pointed to REE sources from traffic emissions and coal burning thus defining an urban fingerprint.

Patterns of the Distribution of Rare-Earth Elements in Waters of Mud Volcanoes

The original data on the distribution of rare-earth elements in waters of mud volcanoes of Sakhalin Island, Taman Peninsula, and Azerbaijan are presented. It has been shown that the mud volcano waters with a sum of rare-earth elements less than 0.5 μg/l are enriched with heavy lanthanides and characterized by a deficiency of Ce. As illustrated by the Yuzhno-Sakhalinsk mud volcano, the content of rare-earth elements is higher in active gryphons.

Morphology and Chemistry of Zircons from the Paleoproterozoic Cu (±Mo±Au) Hosting Granitoids of Malanjkhand Mine Area, Central India

Abstract Morphology and chemistry of zircons from Paleoproterozoic granitoids (~2470 Ma) of Malanjkhand mine area, central India have been used to understand nature of parental magma and its evolutionary history. External morphology of non-metamict zircons belongs to S3, S1-2, G1, P2, S24 and S25 subtypes of Pupin’s typological scheme, which crystallized in a calc-alkaline, metaluminous hybridizing magma. The Zr/Hf ratios of zircons point to a low degree of differentiation of parental magma. Most zircons bear low sum of rare earth elements (ΣREE<700 ppm) indicating late stage of crystallization, whereas a zircon with anomalously high LREE and ΣREE probably indicates at an early stage of its crystallisation in the absence of other REE bearing accessory phases or might have been influenced later by hydrothermal fluids. The Nb content of zircons is similar to those commonly formed in high-K, calc-alkaline granitoid magma series. The zircon (Th/U>1) with high ΣREE (5019 ppm) and Ti (56 ppm) contents provides zircon crystallization temperature (TZr) of 938°C suggesting its crystallisation in a relatively high-T intermediate magma composition. However, zircons with Th/U<1 bear Ti content below the detection limit (33 ppm) due to their crystallization in a relatively more evolved aluminous melt fraction of parental calc-alkaline magma. All zircons exhibit positive Ce- and negative Eu-anomalies, which probably indicate mildly oxidising magma condition of zircon crystallization synchronous with plagioclase.

Aluminium leaching from red muds for their complexing reprocessing

Complexing processing of «red muds» (R.M.) - waste of bauxite reprocessing by the Bayer's method, is one of the important tasks of toxic industrial waste utilization. Studied the possibility of aluminum leaching from the R.M. which content reach 14 %, received from Bogoslovsky aluminum plant of JSC «Siberian-Urals Aluminium Company» by aqueous solutions of NaOH. The process was carried out at atmospheric pressure and temperatures near to the boiling point of leaching solutions with the utilization of the residual alkali. The time’s dependence of the aluminum leaching degree from the R.M. by aqueous solutions of NaOH passes through the maximum due to the formation of secondary precipitation of aluminum. The cause of secondary sedimentation is the interaction of silicon with aluminum with formation of insoluble aluminosilicates, for example, Nа2Аl2Si2O8·2Н2O. The conditions of leaching, under which the formation of stable aluminate solutions during the time do not form of secondary precipitations were established. The maximum achieved values of the aluminum leaching degree in autoclave-free conditions was reach 20-25 %. The removal of alkali and part of aluminum under the first stage of complexing processing of R.M. leads to their enrichment in iron. The cakes from aluminum leaching and next carbonate scandium leaching can be used for pyrometallurgical recovery of iron and slag, in which untreated elements are passed, including residual aluminum, scandium, sum of rare earth elements, titanium and zirconium. A significant decrease in the volume of slag opens more opportunities for further isolation their components by acidic methods.

Distribution of Rare Earth Elements in Sediments of the Marine Lake Mir (Dugi Otok, Croatia)

The Lake Mir represents a small, isolated, and shallow marine lake situated in the south-eastern part of the Dugi otok Island, in a karstic landscape of the eastern Adriatic coast. The surrounding karstic background, with occasional occurrences of red soil, characterizes the sediments in the lake as coarse grained and carbonate rich. Previous studies suggested the prevailing influence of the lake bathymetry, that is, the proportion of carbonates and grain size characteristics of the sediments, on the variability of the element composition of the lake sediments. To confirm previous assumptions and obtain a better understanding of the factors influencing sediment composition of this marine lake, the distribution of rare earth elements in sediments of the Lake Mir and the nearby Telašćica Bay, as well as surrounding soils, was investigated. In the lake sediments, the sum of rare earth elements, including Y (hereinafter referred as ΣREY), ranged from 10.6 mg kg−1 to 25.3 mg kg−1; in the Telašćica Bay sediments, ΣREY were higher compared to the lake and ranged from 56.4 mg kg−1 to 85.2 mg kg−1, while the highest ΣREY, from 83.3 mg kg−1 to 227 mg kg−1, were observed in soils surrounding the lake. Despite the difference in the levels of the rare earth elements, the REY normalized patterns and associated fractionation parameters (ΣLREE/ΣHREE, (La/Yb)N, and (Nd/Yb)N) showed similarities between the lake sediments and the surrounding soils, confirming a significant influence of local lithology on the lake composition. The results of the statistical analysis, on the other hand, suggest the contribution of both the carbonate (e.g., calcite) and non-carbonate minerals (i.e., alumosilicates and Al–Fe-hydroxides) on the total REY content in the lake sediments.

Structural control and hydrothermal evolution model of unusual, high-grade metasandstone-hosted iron deposits, mesoproterozoic eastern chapada diamantina, Brazil

The Ibicoara high-grade, hypogene hematite deposits are located in the São Francisco Craton, in the Chapada Diamantina Fold Thrust belt. Iron mineralization host rocks are quartz and arkose sandstones from the Tombador Formation, which present planar stratification. Regionally, three deformational phases are identified. The first D1 phase developed kink with subordinate chevron folds, shear zones related to flexural slip with S/C structures, stretch lines (LX1), slickenlines and slickensides. The second phase D2 is represented by dextral and sinistral, reverse high-angle shear zones with NNW-SSE and NW-SE orientation trends, respectively, high-angle tension fractures with an ENE-WSW orientation. During the third deformation phase D3, dextral and sinistral shear zones with ENE-WSW and NE-SW orientations are developed. The richest hematite domains are massive, having Fe2O3total contents to 98%. These irregular-massive domains are distributed along the primary sedimentary foliation (plane-parallel stratification and tangential cross-bedding), of D2 shear zones, or tension fractures generated during D2. The irregular-massive hematite domains grade laterally into platy and stringer domains. In addition, there are vein, stockwork and breccia mineralization styles that crosscut irregular-massive domains or host rock. Chemical analyses of hematite in irregular-massive domains show that Fe2O3 correlates negatively with SiO2, Zr, Th, Sr, Nb, Hf and Ba. On the other hand, it correlates positively with Zn, V, U, Cu, Co, and with the sum of rare earth elements (REE). When normalized to the post-Archean Australian Shale (PAAS), the distribution of REE generally show negative Eu anomalies, and a weak enrichment of light rare earth elements (LREE) compared to the heavy rare earth elements (HREE). The paragenetic succession shows the existence of three groups of hematite. Groups 1 and 2 are mainly related to the irregular-massive domains controlled by rock stratification and the S0//S2 foliation in shear zones. The distinction between them is given by the finer grain size of the first generation of hematite and the presence of breccia domain in the second group. The third group is related to massive-vein domains. For each group, the hematite grain size increases successively, and there is a relative increase in the HREE in relation to the LREE. Furthermore, similarities between the chemical signatures of the first groups 1 and 2 hematite generation with the signatures of the host rock reveal an important influence of the chemical composition of the original rock. This is not the case for the late hematite of massive domains, as well as vein-style hematite, suggesting high fluid-rock conditions. The hematite hydrothermal alteration at Ibicoara has structural control, with dilational structures associated with D2 shear zones. The host lithotype was also a contributing factor due to its porosity and permeability, and the presence of sedimentary structures that favored flow of the hydrothermal fluid from shear zones. Replacement and direct precipitation took place and are responsible for the transfer of solutions and formation of hematite-rich areas. The hydrothermal fluid probably leached components from the Espinhaço Supergroup metasedimentary units and dikes that are regionally present, and carried these during the deformational phases that inverted the Paramirim Aulacogen. The Espinhaço Supergroup is characterized by a sequence of siliciclastic rocks, predominantly metasandstones, and felsic metavolcanic rocks, sterile in iron, which were deposited between the Statherian and Stenian periods. In the Chapada Diamantina area, the Espinhaço Supergroup is comprised from base to top by the Serra da Gameleira Formation and the Rio dos Remédios, Paraguaçu, and Chapada Diamantina groups. The Chapada Diamantina Group contains the Tombador Formation that hosts the high-grade iron deposits investigated in the present study. In light of the tectonic context, and existence of shear-related gold and baryte hydrothermal deposits nucleated during the Paramirim Aulacogen inversion, the Chapada Diamantina Thrust and Fold Belt is considered a potential regional exploration target.

Pattern of blood concentrations of 47 elements in two populations from the same geographical area but with different geological origin and lifestyles: Canary Islands (Spain) vs. Morocco

The Canary Islands are one of the outermost regions of the European Union (EU), which are located barely 100 km from the coasts of Morocco. Although these islands are located in Africa, the degree of socioeconomic development and lifestyle in this archipelago is comparable to that of any other region of Europe. It is well established that the main determinants of human exposure to elements have to do both, with their place of residence and with habits related to their lifestyle. For this reason, we wanted to study the pattern of contamination by elements of these two populations so geographically close, but so different both in their lifestyle, and the geological origin of the territory where they live. Thus, we have determined the blood concentrations of 47 elements (including 25 rare earth elements (REE) and other minority elements (ME) widely employed in the hi-tech industry) in a paired sample of Moroccans (n = 124) and Canary Islands inhabitants (n = 120). We found that the levels of iron, selenium, zinc, arsenic, cadmium, strontium, and specially lead, were significantly higher in Moroccans than in Canarians, probably due to the intensive mining activity in this country. We also found significantly higher levels of the sum of REE and ME in Moroccans than in Canarians, possibly related to the inappropriate management of e-waste in this country. On the other hand, in the inhabitants of the Canary Islands we found higher levels of manganese, probably related to a higher degree of exposure to heavy traffic and exposure to Saharan dust of the people living in this region, and niobium and bismuth, probably related to the higher economic development in these islands. Our results indicate that the vicinity of both territories is not a major determinant of each other's contamination.

Human health and environmental assessments of small-scale and artisanal mining activities in the Gold City of Ijeshaland, Southwestern Nigeria

BackgroundThis study assessed the health and environmental impacts of artisanal gold mining in Ijesha-land, Osun State, Southwestern Nigeria. Fifty-four environmental samples were collected between 2011 and 2012 and analyzed for major, trace and rare earth elements using standard procedures. Samples were collected from surface water (rivers and streams), groundwater, bottom sediments, fish (Tilapia) and aquatic plants (ferns). Data collected were analysed for simple descriptive and inferential statistics using Statistical Package for Social Sciences (SPSS) for Windows (16.0). Human health risk assessment of noncarcinogenic adverse effects of elements in water and fish samples was determined.ResultsHigher concentrations of most major and trace elements were found in groundwater than surface water, while rare earth elements (REEs) were more concentrated in groundwater than surface water. Bottom sediment samples showed highest concentrations of Ti, Cs and Eu for major, trace and rare earth elements, respectively. The major and trace elements were most concentrated in the fish guts. The sum of REEs was observed highest in the fish guts (31.83 ± 35.90 µg kg−1), followed by muscle (18.70 ± 19.37 µg kg−1), while the lowest ΣREEs was measured in the gills (15.78 ± 22.45 µg kg−1). The human health risk assessment revealed low hazard quotient and hazard index values less than 1.0 for trace and rare earth elements in environmental samples.ConclusionsThe data obtained in this study showed that, the artisanal gold mining activities in the study area may contribute to long term environmental and human health risk.

Late-Holocene atmospheric dust deposition in eastern Canada (St. Lawrence North Shore)

Dust deposition in two ombrotrophic peatlands (Baie and Ile du Havre peatland (IDH) bogs) of the Estuary and Gulf of the St. Lawrence in eastern Canada was reconstructed using elemental geochemistry. The rare earth elements (REEs) and other lithogenic element concentrations were measured by ICP-oES and Q-ICP-MS along two peat cores spanning the last 4000 years. Principal component analyses on the geochemical profiles show that REEs display the same behavior as Al, Ti, Sc, and Zr, all conservative elements, which suggests that REEs are immobile in the studied peat bogs and can be used as tracers of dust deposition. Plant macrofossils were also used to infer past environmental and humidity changes. The dust fluxes were reconstructed using the sum of REEs (ΣREE). The range of dust deposition varies from 0.2 to 3.8 g m−2 yr−1 in the Baie bog, while the IDH bog shows lower fluxes ranging between 0.1 and 1.2 g m−2 yr−1. The highest dust fluxes in the Baie bog were recorded from 1750–1000 cal. BP to 600–100 cal. BP and occur at the same time as periods of high variability in the macrofossil record (i.e. successive layers dominated by Sphagnum or Ericaceae). The timing of these events in the dust and macrofossil records also corresponds to documented cold periods. These two periods have been identified as episodes of climatic instability, which could have been caused by changes in the wind regime.

Composition, origin and industrial suitability of the Aswan ball clays, Egypt

Although Aswan ball clays occur in relatively large reserves, information on their geochemistry and source is still lacking. This paper presents detailed petrographic, mineralogical, and geochemical investigations on these clays to examine their source as well as their possible use as raw materials for ceramic and refractory industries.Aswan ball clays occur as gray, yellowish gray, reddish to brownish gray, massive to faint laminated, and moderately hard clays. Grain-size distributions indicate the dominance of clay fractions (45–57wt.%). Low-ordered kaolinite is the main constituent (39–60wt.%) along with quartz (24–46wt.%) and low crystalline illite (10–19wt.%). Fine-grained anatase is reported as a minor constituent (~2wt.%). Aswan clays are typically ball clays (SiO2/Al2O3=2.3–4.1) with relatively high Fe2O3 and TiO2 contents. The trace elements occur in two assemblages. Elements associated with the Fe-bearing phases include Cu, Ni, Co, Zn, V, and Pb as indicated from the positive correlations with the Fe2O3 contents. Elements occur as silicate minerals but not in clay minerals such as Nb, Zr, Y, Hf, Ta, and U as revealed from the positive correlations of these elements with the SiO2 and the negative correlations with the Al2O3 contents. The sum of rare earth elements (REEs) ranges from 291 to 335ppm with negative correlations with the Al2O3 and positive correlations with the SiO2 suggesting the occurrence of REE as silicates but not in clay minerals. Chondrite-normalized REE patterns exhibit light rare earth element enrichment relative to heavy rare earth elements ((La/Yb)N=9.2–11.7) and slightly negative Eu anomalies (Eu/Eu*=0.74–0.83) without Ce anomalies (Ce/Ce*=0.96–1.03).Major, trace, and rare earth elements geochemistry of the clay fractions indicates a mixture of more than rock types as a source of the Aswan ball clays. The high Zr and Y contents and La/Yb ratios suggest a contribution of granitic rock, while the relatively high contents of TiO2 and Ti are suggestive for a contribution of mafic source rock. Plot of the study clays in the Rb-K2O and Hf–La/Th binary plots supports mixed felsic and mafic source rocks of the study clays. In addition, high Nb contents indicate a contribution of alkaline source rock. Plot of the study clays in the phyllite and schist field in the Co–Th binary diagram also indicates contribution of metamorphic source rock to the source of the clays.The abundance of clay size fractions (<2μm), low-order kaolinite and illite, absence of I/S minerals, low fluxing agents such as alkali oxides (Na2O and K2O) and alkaline earth oxides (CaO and MgO), low S and Cl contents, and low contents of toxic elements (As, Cd, Hg, and Pb) reveal the suitability of the Aswan ball clays as a good quality and environment-friendly raw material for ceramic and refractory industries.

Sorption-spectrophotometric determination of lanthanum, gadolinium, and ytterbium using chlorophosphonazo III on a PANF-Chel adsorbent

The possibilities of the sorption-spectroscopic determination of the sum of rare-earth elements have been studied on an example of La, Gd, and Yb as representatives of the light, middle, and heavy rare earth elements. The determination is carried out after the sorption from solutions with pH 3 onto the surface polyacrylonitrile fiber loaded with a Chel-100 ion exchanger followed by complexation with Chlorophosphonazo III. A dynamic version of the sorption-spectroscopic determination of the sum of La, Gd, and Yb has been developed for the concentration range 5–30 ng/mL with a detection limit of 3 ng/mL. The method was tested in the analysis of model solutions of CaCl2, FeCl3, and TiCl4; RSD < 20%.

Rare-earth elemental systematics of mixed-layered illite–smectite from sedimentary and hydrothermal environments of the Western Carpathians (Slovakia)

Mixed-layered illite–smectite separates of various sizes from bentonites and shales collected in sedimentary and hydrothermal units of the Western Carpathians were analyzed for their major-, trace- and rare-earth elements (REEs). The major elements fairly reflect the changes in the clay mineralogy related to illitization, but a lack of correlation between this chemical composition and the REE contents suggests that their incorporation and fractionation by nucleating and growing illite-type particles is complex during both burial-induced diagenesis and hydrothermal activity. During crystal growth of illite-type fundamental particles, illitization driven by burial-related temperature increase does not fractionate the REEs incorporated in the mineral structures, but it increases their contents, suggesting that the bentonite and shale units of the sedimentary sequence act as closed systems. The amount of smectite layers in the I–S does not relate to the sum of REE or to the La/Lu ratio in the bentonites and shales of the East Slovak Basin sedimentary sequence, outlining that REE incorporation and fractionation concern s the illite layers, not the smectite layers. Alternatively, the hydrothermal system of Dolná Ves acts as an open system with supply of the REEs by external hot fluids, so that the REE contents are not determined by the precipitation of illite. The mixed-layers illite–smectite of the shales yield a narrow span of total REE abundances from 17.3 to 36.5 μg/g, compared to those of the associated bentonites, from 1.20 to 93.7 μg/g, of the same basin. These differences result from varied origins of the original REE-carriers. The Eu anomaly relates to alteration of the authigenic minerals in the sedimentary bentonites acting as a closed system, or to the chemistry of the percolating hot fluids in the Dolná Ves hydrothermal deposit. The data also indicate that no-detectable zircon, apatite, monazite, or any other REE-carrier occurred in the size fractions, at least in the finest, and if any, these minerals had no significant impact on the REE contents and distribution patterns of the varied analyzed size fractions consisting mainly if not exclusively of mixed-layered illite–smectite.