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This study presents a significant enhancement to the analytical capabilities of an existing X-ray fluorescence (XRF) spectrometer by integrating an Am-241 excitation-based system. The modification enables precise and cost-effective analysis of rare-earth elements (REEs), expanding the spectrometer's utility. Successful identification and quantification of Scandium (8.1 ± 1.3 mg\kg), Ytterium (7.9 ± 2.0 mg\kg), Lanthanum (27.5 ± 2.1 mg\kg), Cerium (60.4 ± 2.5 mg\kg), Neodymium (29.7 ± 1.2 mg\kg), Samarium (4.6 ± 2.0 mg\kg), Europium (0.8 ± 0.4 mg\kg), Gadolinium (2.6 ± 0.6 mg\kg), and Erbium (3.5 ± 1.2 mg\kg) were achieved using their K-X-rays. The quantitative analysis employed the "Elemental Sensitivities Method" and was validated against established methods like Instrumental Neutron Activation Analysis (INAA) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The modified system demonstrated an accuracy of approximately 80% in analyzing REEs in the IAEA-Soil 7 reference material. [ABSTRACT FROM AUTHOR]

Outer-sphere interactions play an important role in the liquid-liquid extraction and separation of metal ions and they could be used to tune the efficiency and selectivity of recovery. Here, we report the extraction behaviour and separation of trivalent rare-earth elements from aqueous nitric acid solutions with N,N,N',N'-tetra-n-octyl diglycolamide (TODGA), which was preliminarily contacted with an aqueous solution of N-H acid bis[(trifluoromethyl)sulfonyl]imide (triflimide, HTf2N; Tf = CF3SO2) resulting in an adduct TODGA⋅HTf2N. We examined in detail the extraction system composed of TODGA acidified with HTf2N and 1,2-dichloroethane as diluent. The effect of various experimental conditions such as the nature of diluent, aqueous nitric acid concentration, and TODGA⋅HTf2N concentration in the organic phase was studied. It has been found that the distribution coefficient values for metal ions are much greater, especially at low aqueous acidity in the extraction systems with the acidified organic solvent phase. Furthermore, the heavier lanthanides were effectively extracted and the intergroup lanthanide selectivity was greatly improved (separation factors for the Lu/La pair increased by 40 and 2 times for the two systems under study, respectively). [ABSTRACT FROM AUTHOR]

Critical metals (CMs), including rare-earth elements (REEs), lithium (Li), and beryllium (Be), provide the foundation for the development of advanced technologies and are essential to national security and economic development in many countries. While China has most of the world's REE processing capacity, the Democratic People's Republic of Korea (DPRK) reportedly possesses significant untapped CM resources. With the size and total value estimated to be worth trillions of dollars, its large resources are reputedly the DPRK's most significant internal asset. Despite the oft-cited abundance of CMs, evidence-based analyses of the mineral resources are limited. We provide a comprehensive analysis of CM resources in the DPRK based on geological analysis of potential deposits. Three main REE deposits at Ryongpo, Cheolsan, Abdong, and various Li and Be deposits are investigated. Extensive analyses indicate that previous estimates of a large CM resource base for the DPRK are exaggerated. There is no clear evidence for significant resources that are economical. While there remains a possibility of identifying new ore deposits, for the DPRK to access its CM resources, it will need to develop a nationwide exploration and exploitation strategy to attract foreign investments. A strategy of investment and investigation might provide a springboard for cooperation between the DPRK and other nations as these resources are discovered and developed. [ABSTRACT FROM AUTHOR]

In this present study, we developed a new series of sorbents based on phenolic foam resin for the extraction of rare earth elements. Chelating phenolic foams were prepared using appropriate formulation of blowing agent, surfactant and curing acid agent and a prepolymer resulting from an alkaline polymerisation reaction of phenolic diglycolamide derivative with admixture of phenol, catechol or resorcinol in the presence of formaldehyde as crosslinker agent. The foaming copolymer resins were completely described and engaged in sorption studies with three types of lanthanide (La, Eu, Yb), which represent light, medium and heavy REEs, respectively. [ABSTRACT FROM AUTHOR]

In this study, we emphasize the critical role of sample pretreatment. We report on the behavior of NdFeB magnet samples exposed to four different acid media for digestion. NdFeB magnets are becoming a significant source of neodymium, a rare-earth element critical to many technologies and a potential substitute for traditional mining of the element. To address this, we meticulously tested nitric acid, hydrochloric acid, acetic acid, and citric acid, all at a concentration of 1.6 M, as economical and environmentally friendly alternatives to the concentrated mineral acids commonly used in the leaching of these materials. The pivotal stage involves the initial characterization of samples in the solid state using SEM-EDX and XPS analysis to obtain their initial composition. Subsequently, the samples are dissolved in the four aforementioned acids. Finally, neodymium is quantified using ICP-OES. Throughout our investigation, we evaluated some analytical parameters to determine the best candidate for performing the digestion, including time, limits of detection and quantification, accuracy, recovery of spike samples, and robustness. After careful consideration, we unequivocally conclude that 1.6 M nitric acid stands out as the optimal choice for dissolving NdFeB magnet samples, with the pretreatment of the samples being the critical aspect of this report. [ABSTRACT FROM AUTHOR]

Thermal barrier coating (TBC) has been applied to gas turbine components to increase exposure temperature beyond the turbine material limits. The modification in TBC by adding rare-earth elements, gadolinium (Gd) and lanthanum (La), may improve its properties. However, there are few studies on the performance limit of La–Gd–TBCs for crack propagation. Hence, a crack growth model for the modified TBC has been established in this study to evaluate its performance. Thermal oxidation test was conducted to determine the propagation of cracks with time at three different temperatures: 1200°C, 1300°C and 1400°C. The exhibited cracks were measured using a 3D measuring laser microscope and evaluated using scanning electron microscopy (SEM). The exhibitions of cracks are almost similar at 1200°C and 1300°. Some of the cracks were initiated from the topcoat and propagated towards the topcoat–thermally grown oxide (TGO) interface. The rest of the cracks were observed to initiate from the TGO itself. The crack growth model was established, and it was found that over time the crack growth rate reaches almost zero for temperatures 1200°C, 1300°C and 1400°C. Images of cracks captured under SEM were used to verify the measured cracks. Improvement in the reliability of the established model is suggested. [ABSTRACT FROM AUTHOR]

The use of trace rare metals and rare-earth elements (REEs) in diverse areas of the world economy (e.g. agronomy, medicine, industry) has significantly increased during the last decades. At present, the information on the ecotoxicological effects of these elements is scarce and contradictory. This study aims to evaluate the ecotoxicity of 15 REEs (Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu) and 3 trace rare metals (Ga, Ge, and In) to ciliates Paramecium bursaria, which are a symbiosis of Paramecium and green algae Chlorella. Median lethal concentrations (12-h LC50) were assessed in P. bursaria cells at 12 h of exposure. A bioassay method based on galvanotaxis was used to explore the toxicity of non-lethal concentrations of cerium chloride to P. bursaria cells. The results showed a significant inhibition of galvanotactic migration of P. bursaria by CeCl3 in the presence of an electric field. This preliminary work aimed to evaluate the sensitivity of P. Bursaria to trace metals and REEs. [ABSTRACT FROM AUTHOR]

The article presents the results of chemical analysis, microstructural studies, hardness measurements of the deposited layers obtained by manual arc welding through the use of the welding-depositing materials containing rare-earth and rare elements from the Tomtor field and electrodes covered with UONI 13/55. The positive effect of the modifying additive with REM on the formation of a crushed structure in the zone of the metal deposit and at the fusion boundary is indicated. A slight increase in hardness in the metal deposit alloyed with rare earth metals is detected. [ABSTRACT FROM AUTHOR]

The demand for rare earths is expected to keep increasing throughout the following years. Separation of lanthanides in particular is especially challenging because of their chemical similarities. Therefore, improving the separation process is essential. In this work, we present the effect of the counterion nature on the lanthanide extraction by a 1,10-phenanthroline derivative, the N-octyl-N-tolyl-1,10-phenanthroline-2-carboxamide in chloroform. Modification of the counterion yields a drastic change in selectivity, with a shift in the maximum of extraction from the light lanthanides (Pr, Nd, Sm) in the nitrate system to the heavy lanthanides (Dy, Ho) in the perchlorate system. Other salts (NaCl, NaNO2) showed a gradual increase in extraction along the whole lanthanide series or no effect (Na2SO4). This selectivity shift was explained by possible different coordination in the organic phase. The reversed behavior depending on the anion is especially interesting because a cycling extraction/back-extraction of light lanthanides in nitrate/chloride media or a cycling extraction/back-extraction of heavy lanthanides in perchlorate/nitrate media can enhance the separation factors of Nd and Dy/Ho, respectively. [ABSTRACT FROM AUTHOR]

Rare-earth elements (REEs) as Tm+3, Er+3, Yb+3 and Nd+3 have a significant optical photon emission. Therefore, Films of PMMA doped with 5 wt.% of NdCl3, TmCl3, ErCl3 or YbCl3 were prepared using the casting technique. FTIR of the prepared films has been studied. The optical and dispersion behavior of all doped samples have been investigated. The reflectance (R) and the transmittance (T) were measured in the wavelength range of 200–2500 nm. FTIR of all PMMA reveals that, REEs addition to PMMA samples creates new transmission peaks C=O groups and a decrease in the intensity of the absorption band of C–O groups has been obtained. The results showed the dependency of the refractive index and energy gap on the REE electronic transitions nature. The obtained results suggest strongly the applicability of these PMMA derivatives in improving the performance of the polymer optical fiber (POF). [ABSTRACT FROM AUTHOR]

Many face-centred cubic elements and compounds with the number of atoms per unit cell N equal to 8, 12 and 16 are known to be stabilised by forming either a band gap or a pseudogap at the Fermi level. They are conveniently expressed as cF8, cF12 and cF16, respectively, in the Pearson symbol. From the cF8 family, we worked on three tetravalent elements C (diamond), Si and Ge, SZn-type AsGa compound and NaCl-type compounds like BiLu, AsSc, etc. From the cF12 family, more than 80 compounds were selected, with a particular emphasis on ABC- and half-Heusler-type ternary equiatomic compounds. Among cF16 compounds, both the Heusler compounds ABC2 and Zintl compounds were studied. We revealed that, regardless of whether or not the transition metal (TM) and/or rare-earth (RE) elements are involved as constituent elements, the energy gap formation mechanism for cF8, cF12 and cF16 compounds can be universally discussed in terms of interference phenomenon of itinerant electrons with set of reciprocal lattice planes with  = 8, 11 and 12, where refers to square of the critical reciprocal of lattice vector of an fcc lattice. The number of itinerant electrons per unit cell, e/uc, for all these band gap/pseudogap-bearing compounds is found to fall on a universal line called “3/2-power law” when plotted against on a logarithmic scale. This proves the validity of the fulfilment of the interference condition in conformity with other pseudogap compounds with different crystal symmetries and different sizes of the unit cell reported in literature. [ABSTRACT FROM AUTHOR]

Rare-earth (RE) elements are helpful in improving the mechanical properties of cemented carbides. In this work, the formation of Y2O3 in functionally graded cemented carbides is investigated using transmission electron microscopy. The results indicate that Y2O3 can stabilize the Co phase with the face-centred cubic structure (α-Co), since it has a cubic structure similar to the high-temperature Co phase. The α-Co phase has a higher plasticity than ε-Co, and this suggests a possible mechanism for the role of RE elements in toughening cemented carbides. [ABSTRACT FROM AUTHOR]

Three kinds of multicomponent diffusion effects, arising from three distinct physical mechanisms, are evident in stranded diffusion profiles at the rims of partially resorbed garnets from the contact aureole of the Makhavinekh Lake Pluton, northern Labrador. Profiles that display a subtle maximum in Ca concentration are explained by the prevailing ideal mean-field theory of multicomponent diffusion, but models implementing that theory cannot replicate inverted profiles for Li and internal maxima for Nd, Sm, and Eu. The anomalous profiles are quantitatively reproduced, however, by numerical simulations employing a model based on coupled movement of charge-compensating groups during diffusional transport of yttrium and the rare-earth elements (Y+REEs). An alkali-type charge-compensation mechanism for the heterovalent substitution of Y+REEs on dodecahedral sites in garnet produces direct charge coupling between Li+and (Y+REE)3+and leads to co-diffusion of Li+-(Y+REE)3+pairs, with the result that Li profiles closely mimic those for Y+REEs. A menzerite-type charge-compensation mechanism produces indirect charge coupling among all Y+REE components, with the result that the fluxes of low-abundance REEs become partly dependent on the fluxes of Y+REEs present in higher abundance. These findings have implications for the robustness of Li profiles in garnet as monitors of fluid–rock interaction, for geochronology based on the Sm–Nd and Lu–Hf systems, and for future experimental attempts to quantify rates of diffusion in garnet. [ABSTRACT FROM PUBLISHER]

Due to limited data-describing abilities of mushrooms to accumulate platinum group elements (PGEs) and rare-earth elements (REEs), the aim of this study was to determine, by inductively coupled plasma optical emission spectrometry followed by microwave-assisted sample digestion by nitric acid, the content of these elements in 20 mushroom species (10 above ground and 10 growing on wood), mostly edible, collected near a busy trunk road. The highest content of PGEs in above-ground mushroom species was observed inLepista gilvaandSuillus bovinusfruit bodies (0.38 ± 0.05 and 0.37 ± 0.03 mg kg−1DW, respectively), while in mushrooms growing on wood, the highest content was observed inPleurotus ostreatus(0.35 ± 0.04 mg kg−1DW). The mean content of PGEs for both these groups was 0.23 ± 0.08 and 0.26 ± 0.07 mg kg−1DW, respectively. The highest content of REEs inSuillus luteusandTricholoma equestrawas 5.03 ± 0.50 and 2.18 ± 0.56 mg kg−1DW, respectively, but within mushrooms growing on wood inGanoderma applanatumfruiting bodies it was 4.19 ± 0.78 mg kg−1DW. Mean contents of REEs were 1.39 ± 1.21 and 1.61 ± 0.97 mg kg−1DW in above-ground species and species growing on wood, respectively. Generally, the group of mushroom species growing on wood was capable of slightly higher accumulation of both REEs and PGEs. No limits have been established for both the groups until now. [ABSTRACT FROM AUTHOR]

Infectious diseases caused by pathogens have become a life-threatening problem for millions of people around the world in recent years. Therefore, the need of efficient, fast, low-cost and user-friendly biosensing systems to monitor pathogen has increased enormously in the last few years. This paper presents an overview of different fluorescent labels and the utilization of fluorescence-based biosensor techniques for rapid, direct, sensitive and real-time identification of bacteria. In these biosensors, organic dyes, nanomaterials and rare-earth elements are playing an increasing role in the design of biosensing systems with an interest for applications in bacterial analysis. [ABSTRACT FROM AUTHOR]

A series of rare-earth metal complexes with Schiff bases have been prepared by the interactions of hydrated lanthanide(III) chloride with the sodium salts of 1-(2-thienyl)ethanone hydrazinecarbothioamide (L1H) and 1-(2-thienyl)ethanonehydrazinecarboxamide (L2H) in 1:3 molar ratios and characterized by their elemental analyses, molar conductance and IR, NMR (1H and 13C) electronic and EPR spectral studies. The spectral data suggested that the complexes have a hexa-coordinated environment around the central metal atoms. Elemental analyses and NMR spectral data of the ligands and their metal(III) complexes agree with their proposed structures. The synthesized Schiff bases and their new metal complexes have been screened for in vitro antibacterial activity against Gram-negative (Escherichia coli) and Gram-positive (Pseudomonas cepacicola) bacterial strains and for in vitro antifungal activity against Fusarium oxysporum and Macrophomina phaseolina. All compounds showed significant antibacterial and antifungal activities against microbial species. [ABSTRACT FROM AUTHOR]

The performance of inductively coupled plasma–atomic emission spectrometry (ICP‐AES) for the determination of 14 lanthanides and Yttrium was evaluated by comparison with inductively coupled plasma–mass spectral (ICP‐MS) analysis. The geochemical reference samples (GRS), DNC‐1(diabase), AGV‐1(andesite), Sy‐2(syenite), MRG‐1(gabbro), AN‐G(anorthosite), AC‐E(granite), and MAG‐1(marine mud) were chosen as test materials and analyzed for checking the precision and reproducibility of the methods. The mineral garnet is separated from the black sands of the southwest coast of India, and the combined cation exchange–ICP method of AES analysis and MS analysis were carried out for the determination of rare earth elements. Both techniques are within the requirements needed for garnet minerals. The determination of rare‐earth elements in these minerals, which contain other elements as major contribution and trace distribution of rare‐earth elements, shows that ICP applied under the proper working condition lives up to the expectations. Major element analysis gives the formula of garnet of Manavalakurichi (MK) as (FeCaMg) 2.79 Al 2.07 Si 3.05 O 12 approximated to Fe 3 Al 2 Si 3 O 12 , hence of almandine-type garnet. The enrichment of heavy lanthanides compared to the light lanthanides indicates that these lanthanides occupy the coordinaton site of Fe 2+ by replacement. Both techniques are excellent in determining the very low concentration of lanthanides in geological materials, specifically garnet. [ABSTRACT FROM AUTHOR]

Two new sandwich‐type tungstoarsenate complexes [{Ln 3 O 3 (OH 2 ) 2 }(AsW 9 O 34 ) 2 ] 15- (Ln=La, Ce) were synthesized and studied using spectroscopy and cyclic voltammetry. Ion‐exchange experiments provided evidence for covalent, inner‐sphere bonding of the rare‐earth cations to the trilacunary [AsW 9 O 34 ] 9- polyoxometalate. Cyclic voltammograms of [{Ln 3 O 3 (OH 2 ) 2 }(AsW 9 O 34 ) 2 ] 15- exhibited two pairs of waves with negative potential values, which were attributed to the W VI /W V redox processes in the polyoxotungstate framework. Redox studies of the cerium derivative revealed the presence of two types of cerium ions. [ABSTRACT FROM AUTHOR]

Clay minerals, trace elements and isotopic signatures ( 87 Sr/ 86 Sr; 143 Nd/ 144 Nd) were investigated to fingerprint fine-grained sediments ( [ABSTRACT FROM AUTHOR]

The concentration of rare-earth elements and yttrium (REY) was investigated in dissolved phase, suspended particulate matter, and seafloor sediments of the western coastal area of the Gulf of Thailand. The samples show Eu and Gd positive anomalies in the shale-normalized REY patterns, especially in the suspended particulate matter. On the other hand, a very high REE content was detected in the coastal waters, probably due to the weathering produced by the Mae Klong river waters on rare-earth element (REE)-rich accessory minerals coming from terrains and mineral deposits cropping out in the studied area. The shale-normalized patterns of yttrium and REE estimated for the dissolved phase show an enrichment of medium rare-earth elements (MREE), characteristic of extensive water–rock interactions and weathering occurring in the continental environment. The REE concentrations of suspended particulate, normalized to the REE concentrations in each sediment sampled from the tidal flat, show the same behaviour of the experimentally determined apparent REE bulk distribution coefficients 1 for pH values ranging from about 5.5 to 6.2. Since the REY concentration of the water masses is controlled by the oceanographic features of the studied area, riverine inputs, and ionic straight, we suppose that the dissolved phase represents a mix of truly dissolved and colloidal pool ( [ABSTRACT FROM AUTHOR]

We critically discuss a recently proposed technique ((Xian et al. 2004)) used to distinguish igneous (i.e., magmatic) from metamorphic growth of the mineral zircon according to the intensity of the 1461 cm-1 band observed in those author's Raman spectra. The band evaluated by Xian et al. (2004) is actually due to laser-induced photoluminescence of trace amounts of the trivalent rare earth element Er, which, as an analytical artefact, overlays the Raman spectrum when green Ar+ laser excitation is used. We demonstrate that this band is not a Raman band, and discuss why the intensity of Er3+ luminescence is not uniquely indicative of the geologic origin of a zircon crystal. The technique proposed by Xian et al. (2004) may consequently lead to wrong, and thus misleading results. Therefore, we suggest that this technique should not be used for any petrogenetic assignment of the environment of crystallization for zircon. [ABSTRACT FROM AUTHOR]

The extraction of microquantities of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y from HNO3 solutions by bifunctional acidic organophosphorus compounds R2P(O)CH2P(O)Ph(OH), R=Ph (I), R=Oct (II), R=p-Tol (III), R=p-CH3OC6H4 (IV), and Ph2P(O)CH2P(O)(OBu)(OH) (V) in organic diluents has been studied. The effect of HNO3 concentration in the aqueous phase and that of the extractant concentration in the organic phase on the extraction of metal ions is considered. The stoichiometry of the extracted complexes has been determined. The replacement of phenyl radicals in the Ph2P(O)CH2 fragment of (diphenylphosphinylmethyl)phenylphosphinic acid (I) by p-tolyl ones has been found to increase rare-earth ion extraction. The introduction of p-methoxy-phenyl or octyl substituents instead of phenyl ones at the same part of molecule I, facilitates the extraction of Eu–Lu and Y or Tb–Lu and Y, respectively. However, the extraction of other lanthanides from 3 M HNO3 solutions decreases when p-methoxy-phenyl or octyl-substituted compounds in toluene are used as extractants. The replacement of phenyl radical in the P(O)OH fragment of compound I by a butoxy-group brings about a decrease in rare-earth elements (REE) extraction. The effect of octyl radicals substitution by phenyl ones in compound II on the extraction of lanthanide ions decreases as the atomic number of REE increases. The extraction efficiency of octyl-substituted compound II has been observed to be higher than that of phenyl-substituted compound I when HNO3 concentration in the aqueous phase decreased or when diluents with a small Schmidt's diluent parameter (DP) were used. [ABSTRACT FROM AUTHOR]

The extraction of microquantities of U, Th, Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y from HNO3 solutions by bifunctional neutral organophosphorus compounds R2P(O)CH2P(O)Ph(OBu), R = Ph (II), R = Oct (IV), R = p-Tol (V), R = p-CH3OC6H4 (VI) in organic diluents has been studied. The effect of HNO3 concentration in the aqueous phase and that of the extractant concentration in the organic phase on the extraction of metal ions is considered. The stoichiometry of the extracted complexes has been determined and the extraction constants calculated. The replacement of phenyl radicals in the Ph2P(O)CH2-fragment of compound II by p-tolyl or p-methoxy-phenyl ones leads to an increase of metal ions extraction. The introduction of octyl substituents at the same part of molecule II instead of phenyl ones favors the extraction of Th(IV), Sc(III), and heavier Ln(III) ions. However, the extraction of La–Eu from HNO3 solutions decreases when octyl-substituted compound IV is used as an extractant. All effects of substituent replacements were studied with 1,2-dichloroethane as diluent. The extractive efficiency of compounds II, IV, V, and VI is compared with that of tetraphenylmethylene-diphosphine dioxide (I) and dibutyl(diphenylphosphinylmethyl)phosphonate (III). [ABSTRACT FROM AUTHOR]

The Proterozoic Soldiers Cap Group, a product of two major magmatic rift phases separated by clastic sediment deposition, hosts mineralised (e.g. Pegmont Broken Hill-type deposit) and barren iron oxide-rich units at three main stratigraphic levels. Evaluation of detailed geological and geochemical features was carried out for one lens of an apatite–garnet-rich, laterally extensive (1.9 km) example, the Weatherly Creek iron-formation, and it was placed in the context of reconnaissance studies of other similar units in the area. Chemical similarities with iron-formations associated with Broken Hill-type Pb–Zn deposit iron-formations are demonstrated here. Concordant contact relationships, mineralogy, geochemical patterns and pre-deformational alteration all indicate that the Soldiers Cap Group iron-formations are mainly hydrothermal chemical sediments. Chondrite normalised REE patterns display positive Eu and negative Ce anomalisms, consistent with components of both high-temperature, reduced, hydrothermal fluid (≥250°C) and cool oxidised seawater. Major element data suggest a largely mafic provenance for montmorillonitic clays and other detritus during chemical sedimentation, consistent with westward erosion of Cover Sequence 2 volcanic rocks, rather than local mafic sources. Ni enrichment is most consistent with hydrogenous uptake by Mn-oxides or carbonates. Temperatures inferred from REE data indicate that although they are not strongly enriched, base metals such as Pb and Zn are likely to have been transported and deposited prior to or following iron-formation deposition. Most chemical sedimentation pre-dated emplacement of the major mafic igneous sill complexes present in the upper part of the basin. Heating of deep basinal brines in a regional-scale aquifer by deep-seated mafic magma chambers is inferred to have driven development of hydrothermal fluids. Three major episodes of extension exhausted this aquifer, but were succeeded by a final climactic extensional phase, which produced widespread voluminous mafic volcanism. The lateral extent of the iron-formations requires a depositional setting such as a sea-floor metalliferous sediment blanket or series of brine pools, with iron-formation deposition likely confined to much smaller fault-fed areas surrounded by Fe–Mn–P-anomalous sediments. These relationships indicate that in such settings, major sulfide deposits and their associated chemical sediment marker horizons need not overlie major igneous sequences. Rather, the timing of expulsion of hydrothermal fluid reflects the interplay between deep-seated heating, extension and magmatism. [ABSTRACT FROM AUTHOR]

A highly sensitive, selective and accurate spectrophotometric method for the microcolumn on-line preconcentration and determination of the sum of rare earth elements (REEs) was developed. REEs were preconcentrated and separated from matrices by being adsorbed at pH 5.0 on a microcolumn packed with a novel aminophosphonic-carboxylic acid resin (APCR). The adsorbed analytes were desorbed with 1.0 mol L[sup -1] HCl and reacted with Arsenazo III in chloroacetate buffer in a reactor coil for the spectrophotometric detection at 649 nm. The calibration graph was linear up to 1.0 µgmL[sup -1] La[sup 3+]. The detection limit of 4.0 ng mL[sup -1] was achieved with a sample loading flow rate of 2.0 mL min[sup -1] and a sample loading time of 1.0 min. The RSD was less than 4% for 0.20 ·gmL[sup -1]La[sup 3+]. The proposed method was successfully applied to the determination of the sum of REEs in a geological sample and an aluminum alloy sample. [ABSTRACT FROM AUTHOR]