Lanthanide Chemistry Research Articles

Major and trace element geochemistry of tourmalines from Archean orogenic gold deposits: Proxies for the origin of gold mineralizing fluids?

Orogenic style gold mineralizations in the Archean Hattu Schist belt (E Finland) are present in all major host rock lithologies including epiclastic sedimentary and volcanogenic rocks, as well as felsic intrusives. The gold mineralizations occur as dissemination in altered wall rocks and within hydrothermal quartz veins. Hydrothermal tourmalines are often associated with the gold mineralizations occurring in the quartz veins, as alteration minerals in contacts of the metasedimentary host rocks and quartz veins, but also within mineral assemblages of the metasedimentary and magmatic rocks. We characterize and compare the major, trace and rare earth element chemistry of these tourmalines in order to evaluate their suitability as a petrogenetic tool for tracing the fluid sources of the hydrothermal system. By comparing the chemistry of tourmalines from gold mineralization with those from metamorphic and magmatic host rocks, we test whether tourmaline composition can be used to identify the source rocks of the gold transporting hydrothermal fluids. All analyzed tourmalines belong to the alkali super group and plot along the schorl-dravite join. The hydrothermal tourmalines have Li, Sr and V concentrations comparable to metamorphic tourmalines and clearly distinct from magmatic tourmalines. Because the concentrations of Ni, Pb, Cr, Mn, Ga, Zn and Sn show a wide overlap between magmatic, metamorphic and hydrothermal tourmalines, these elements do not permit to discriminate between different source rocks. The co-variations of many elements in hydrothermal tourmalines, when plotted against Li, show more similarity to metamorphic tourmalines and the whole-rock compositions of metasedimentary and metavolcanic host rocks than to their magmatic counterparts. This indicates that the major and trace element composition of hydrothermal tourmalines in the Hattu Schist Belt is predominantly controlled by the host rocks and local fluid-rock interactions, and does not reflect the distal fluid sources. The effect of local fluid-rock interaction is also manifested by the REE patterns of tourmalines. The magmatic tourmalines have distinct LREE enriched patterns resembling the whole-rock REE patterns of granitic intrusives, while the metamorphic and hydrothermal tourmalines have flat or weakly fractionated patterns similar to metavolcanic and metasedimentary host rocks. Taken together, the tourmaline data suggest that hydrothermal tourmalines associated to gold mineralizing fluids are most likely genetically related to metamorphic rock sources without important contributions of magmatic fluids, and that local fluid-rock interaction exerted a major control on tourmaline chemistry.

Rare earth element chemistry indicates chemical alteration of zircons during the evolution of weathering profile

Although rare earth elements (REEs) in magmatic zircons have been widely used to identify the type and compositional evolution of host rocks, REE distribution patterns during the chemical alteration of zircons need clarification. We investigated REE characteristics in zircons with different degrees of chemical weathering through systematic observation of a granodiorite-weathering profile in southeast China. Despite the relatively stable provenance of the studied profile (zircon U–Pb ages are 95.2 ± 4.8 Ma), the zircon REEs exhibited systematic differences in abundance and fractionation patterns from the bedrock to upper layers, e.g. ∑REE, (LREE/HREE)CN, and Ce/Ce*. This evidence suggests chemical alteration of zircons during intensive chemical weathering and an expected influence on REE variability in the weathered products due to the presence of REE-bearing minerals.

Sorption in the chemistry of rare earth elements

Sorption methods for the concentration and separation of rare earth elements are reviewed. Sorbents based on organic polymers, specifically strongly and weakly acidic cation exchangers, anion exchangers, and complexing sorbents, are successively considered. Data on the use of inorganic sorbents and solid phase extractants in the rare earth chemistry are also given. Considerable attention is paid to hybrid organomineral materials constituting a promising class of sorbents. Advantages and disadvantages of using biosorbents, molecularly imprinted sorbents, and nanosorbents for the concentration and separation of rare earths are discussed.

Coordination and silica surface chemistry of lanthanides (III), scandium (III) and yttrium (III) sorption on 1-(2-pyridylazo)-2-napththol (PAN) and acetylacetone (acac) immobilized gels

This article focuses on identifying the coordination and silica surface chemistry of PAN immobilized mesoporous silica gel in the adsorption of Rare earth elements (REE) in comparison to acetylacetone (acac) immobilized gel. PAN is used as an analytical reagent since it has both acidic (pKa 1.9) and basic (pKa 12.2) properties. A strategy for the adsorption of REE has been developed through the analysis on the adsorption of light rare earths (LREEs) and heavy rare earths (HREEs). In this study, the separation of REEs is achieved via the –N group of pyridine/ azo and –OH group of PAN modified silica, at different conditions. The REEs were studied based on different parameters such as pH, kinetics, metal loadings, binding sites, temperature etc. and distinct differences have been observed in separation between ‘d’ and ‘f’ block elements. Ionic radii, lanthanide contraction and REE tetrad effect impact the adsorption process for different pH and metal loading conditions. This eventually influences the binding mechanism as well. The affinity of the modified gel was towards LREEs at lower pHs and HREEs in higher regime. As a validation attempt, the developed separation strategy has been employed in investigating under natural water conditions for varying REE concentration and pH in the presence of competing ions. Silica gel with PAN (SEP) modifications performed superior to Acac modifications (SEA) in terms of REE adsorption under all conditions. The behavior was coherent for both single and multi-component systems where HREE adsorption showed temperature dependency. As SEP demonstrated adsorption even in the acidic range (pH 2), it has the potential to serve a wide range of applications involving acidic industrial waste such as mine water.

Bis(amidinate) ligands in early lanthanide chemistry - synthesis, structures, and hydroamination catalysis.

Bis(amidinate) ligands attached to rigid dibenzofuran and phenanthrene backbones have been introduced into lanthanide chemistry for the first time. Depending on the ligand and on the lanthanide source, either bi- and tetra-metallic macrocycles or monometallic complexes were obtained. The mono- and bi-metallic systems were compared in terms of their reactivity in the intramolecular hydroamination reaction. Depending on the catalyst used (mono vs. bimetallic) different rate laws were observed.

Rare earth elements in conodont apatite: Seawater or pore-water signatures?

Rare earth element (REE) compositions of Lower Palaeozoic conodont microfossils from different sites in Laurentia are presented and compared to modern pore-water REE compositions reported in the literature. These data are modelled to account for matrix-induced fractionation of REEs during uptake by apatite. The apatite-water partition co-efficients (Kd) for adsorption of REEs are applied to a range of modern pore-water compositions (i.e. Pore-waterN×Kd), the resultant data being similar to Palaeozoic conodont apatite compositions. Similar resemblances to modern pore-water REE compositions are shown by palaeofluids derived from conodonts using the inverse relationship in REE adsorption kinetics (i.e. Bioapatite/Kd), with rare low concentration samples yielding HREE-enriched patterns. These results clearly show the importance of matrix effects and hence the post-mortem physico-chemical processes by which elemental uptake occurs in fossil biogenic minerals, which are crucial to consider when interpreting geochemical signatures. Furthermore, the similarities between apatite REE compositions of conodonts and those derived from modern pore-waters challenge prior hypotheses of seawater REE evolution inferred directly from conodont apatite, and question the reliability of conodont apatite as archives of seawater REE chemistry. These outcomes likely have broader implications for fossil bioapatites in general given the physico-chemical processes occurring within marine sediments and the inherent behaviour of apatite-REE systematics.

Lanthanide Chemistry: From Coordination in Chemical Complexes Shaping Our Technology to Coordination in Enzymes Shaping Bacterial Metabolism

Lanthanide chemistry has only been extensively studied for the last 2 decades, when it was recognized that these elements have unusual chemical characteristics including fluorescent and potent magnetic properties because of their unique 4f electrons.1,2 Chemists are rapidly and efficiently integrating lanthanides into numerous compounds and materials for sophisticated applications. In fact, lanthanides are often referred to as "the seeds of technology" because they are essential for many technological devices including smartphones, computers, solar cells, batteries, wind turbines, lasers, and optical glasses.3-6 However, the effect of lanthanides on biological systems has been understudied. Although displacement of Ca2+ by lanthanides in tissues and enzymes has long been observed,7 only a few recent studies suggest a biological role for lanthanides based on their stimulatory properties toward some plants and bacteria.8,9 Also, it was not until 2011 that the first biochemical evidence for lanthanides as inherent metals in bacterial enzymes was published.10 This forum provides an overview of the classical and current aspects of lanthanide coordination chemistry employed in the development of technology along with the biological role of lanthanides in alcohol oxidation. The construction of lanthanide-organic frameworks will be described. Examples of how the luminescence field is rapidly evolving as more information about lanthanide-metal emissions is obtained will be highlighted, including biological imaging and telecommunications.11 Recent breakthroughs and observations from different exciting areas linked to the coordination chemistry of lanthanides that will be mentioned in this forum include the synthesis of (i) macrocyclic ligands, (ii) antenna molecules, (iii) coordination polymers, particularly nanoparticles, (iv) hybrid materials, and (v) lanthanide fuel cells. Further, the role of lanthanides in bacterial metabolism will be discussed, highlighting the discovery that lanthanides are cofactors in biology, particularly in the enzymatic oxidation of alcohols. Finally, new and developing chemical and biological lanthanide mining and recycling extraction processes will be introduced.

Fractionation of rare earth and other trace elements in crabs, Ucides cordatus, from a subtropical mangrove affected by fertilizer industry

Fractionation of rare earth elements (REE) and other trace metal concentrations (Th, U, Cd, Cr, Cu, Ni, Pb, and Zn) between mangrove sediments and claw muscles and shells of male crabs (Ucides cordatus) from a subtropical estuary highly impacted by fertilizer industry activities was investigated. This is the first record of REE distribution in these organisms, and the results showed higher accumulations of these metals, U and Th in shells, probably related to the replacement of Ca during molting. Contents of Cd, Cr and Ni were similar in both tissues, but Cu, Zn and Pb were mostly accumulated in the claw muscle with concentrations above those considered safe for human consumption according to the Brazilian legislation. REE fractionation was different in the analyzed tissues being softer in the shells. The results provided evidences that the water absorbed during molting controls the chemistry of REE in shells. In contrast, the chemistry of REE in the claw muscle, in which was observed preferential absorption of light REE, is controlled by diet. REE fractionation obtained for the claw muscles was closely correlated to the observed in the contaminated substrate and in materials related to the production of phosphate fertilizers (contamination source), which supports their transference to this Ucides cordatus tissue without fractionation by the ingestion of sediments. Our results showed the potential use of crab tissues for monitoring REE and trace element sources in mangrove areas, with claw muscle exhibiting the contaminant source fingerprint.

ChemInform Abstract: Aqueous Lanthanide Chemistry in Asymmetric Catalysis and Magnetic Resonance Imaging

AbstractReview: [41 refs.

Trace element thermometry of garnet-clinopyroxene pairs

We present major and trace element data on coexisting garnet and clinopyroxene from experiments carried out between 1.3 and 10 GPa and 970 and 1400 °C. We demonstrate that the lattice strain model, which was developed for applications to mineral-melt partitioning, can be adapted to garnet-clinopyroxene partitioning. Using new and published experimental data we develop a geothermometer for coexisting garnet and clinopyroxene using the concentration of rare earth elements (REE). The thermometer, which is based on an extension of the lattice strain model, exploits the tendency of minerals at elevated temperatures to be less discriminating against cations that are too large or too small for lattice sites. The extent of discrimination against misfit cations is also related to the apparent elasticity of the lattice site on which substitution occurs, in this case the greater stiffness of the dodecahedral X-site in garnet compared with the eightfold M2-site in clinopyroxene. We demonstrate that the ratio of REE in clinopyroxene to that in coexisting garnet is particularly sensitive to temperature. We present a method whereby knowledge of the major and REE chemistry of garnet and clinopyroxene can be used to solve for the equilibrium temperature. The method is applicable to any scenario in which the two minerals are in equilibrium, both above and below the solidus, and where the mole fraction of grossular in garnet is less than 0.4. Our method, which can be widely applied to both peridotitic and eclogitic paragenesis with particular potential for diamond exploration studies, has the advantage over commonly used Fe-Mg exchange thermometers in having a higher closure temperature because of slow interdiffusion of REE. The uncertainty in the calculated temperatures, based on the experimental data set, is less than ±80 °C.

Pentavalent Lanthanide Compounds: Formation and Characterization of Praseodymium(V) Oxides

AbstractThe chemistry of lanthanides (Ln=La–Lu) is dominated by the low‐valent +3 or +2 oxidation state because of the chemical inertness of the valence 4f electrons. The highest known oxidation state of the whole lanthanide series is +4 for Ce, Pr, Nd, Tb, and Dy. We report the formation of the lanthanide oxide species PrO4 and PrO2+ complexes in the gas phase and in a solid noble‐gas matrix. Combined infrared spectroscopic and advanced quantum chemistry studies show that these species have the unprecedented PrV oxidation state, thus demonstrating that the pentavalent state is viable for lanthanide elements in a suitable coordination environment.

Pentavalent Lanthanide Compounds: Formation and Characterization of Praseodymium(V) Oxides.

The chemistry of lanthanides (Ln=La-Lu) is dominated by the low-valent +3 or +2 oxidation state because of the chemical inertness of the valence 4f electrons. The highest known oxidation state of the whole lanthanide series is +4 for Ce, Pr, Nd, Tb, and Dy. We report the formation of the lanthanide oxide species PrO4 and PrO2 (+) complexes in the gas phase and in a solid noble-gas matrix. Combined infrared spectroscopic and advanced quantum chemistry studies show that these species have the unprecedented Pr(V) oxidation state, thus demonstrating that the pentavalent state is viable for lanthanide elements in a suitable coordination environment.

(Invited) Design of High NIR Emissive Lanthanide Porphyrinoids

Lanthanide (Ln) complexes have been widely used in biological imaging and functional materials due to their attractive optoelectronic and magnetic properties. Strongly absorbing ligand scaffolds such as conjugated macrocycles are of great interest for Ln complex construction, for the maintaining solution stability, preventing coordination of quenching moieties and serving as antennas.1 Porpholactones, in which one porphyrin b,b′-double bond replaced by a lactone moiety, could be potent candidate to further increase NIR emission of lanthanides.2,3 In this talk, we will report the synthesis and characterization of a series of Ln porpholactones as well as their photophysical properties. The lactonization of beta-periphery of porphyrins renders the lower triplate excited states compared to those in porphyrins, which enhances the NIR emission of Ln ions.4 More importantly, through beta-fluorination of porphyrin periphery, the life time of NIR emission is significantly increased, which is considered to block the non-irradtive pathway. Taken together, the beta-modification of porphyrin represent an effective approach to enhance the NIR emission of Ln ions, which has the potential to further improve the practical application of Lanthanide chemistry.4

Aqueous Lanthanide Chemistry in Asymmetric Catalysis and Magnetic Resonance Imaging.

This account describes lanthanide coordination chemistry with a focus on the similarities between lanthanide complexes used in catalysis and those used as contrast agents in magnetic resonance imaging.

Lamp-Shaped Octametallic Lanthanide [Ln8SiO4] Clusters Based on a μ 4-Silicate-Bridge Core

The employment of silicate ion, SiO44−, as a ligand in the coordination chemistry of lanthanides is reported. A series of octanuclear clusters of general formula [Ln8L8(C6H4NH2COO)4SiO4] (H2L = 2-{[(2-hydroxy-3-methoxy-phenyl)methylidene]amino}benzoic acid; Ln = Tb(1), Gd(2), Nd(3), Pr(4), Sm(5)) have been prepared via reactions of lanthanide nitrate salts, H2L and Na2SiO3. The metal skeleton shows rarely observed lamp-shaped conformation with eight metals being connected by a μ4-silicate bridge. Variable-temperature, solid-state dc magnetic susceptibility studies were carried out on polycrystalline samples of 1 and 2. The data in the 2.0–300 K range reveal antiferromagnetic LnIII⋯LnIII exchange interactions in these two clusters. This work demonstrates the synthetic potential of combining Schiff-base ligands with silicate in the preparation of polymetallic lanthanide clusters.

Petrogenesis and provenance of distal volcanic tuffs from the Permian–Triassic Karoo Basin, South Africa: A window into a dissected magmatic province

We present zircon rare earth element (REE) compositions integrated with U-Pb ages of zircon and whole-rock geochemistry from 29 volcanic tuffs preserved in the Karoo Supergroup, South Africa, to investigate the history of magmatism in southern Gondwana. Whole-rock compositions suggest a subduction-driven magmatic arc source for early (before 270 Ma) to middle Permian (270–260 Ma) Karoo tuffs. After ca. 265 Ma, the magmatic source of the volcanic deposits transitioned toward intraplate shallow-sourced magmatism. Zircon U-Pb ages and REE chemistry suggest that early to middle Permian magmas were oxidizing, U- and heavy (H) REE–enriched, melts; middle Permian to Triassic zircons record HREE-depleted, more reduced magmatism. Middle Permian to Triassic tuffs contain increasingly large volumes of zircon cargo derived from assimilated crustal material; therefore magmas may have been zircon undersaturated, resulting in less zircon growth and increased inheritance in late Permian to Triassic Gondwanan volcanics. Zircon U-Pb ages and zircon REE chemistry suggest a shift from arc magmatism in the early Permian to extensional magmatism by the late Permian, which may be associated with development of a backarc magmatic system adjacent to western Antarctica that predates known extensional volcanism elsewhere in Gondwana. Opening of the Southern Ocean in the Jurassic–Cretaceous paralleled this extensional feature, which may be related to reactivation of this Permian–Triassic backarc. This study demonstrates the potential of zircon U-Pb age and REE compositions from volcanic tuffs preserved in sedimentary strata to provide a more complete record of magmatism, when the magmatic province has been largely lost to active tectonism.

ChemInform Abstract: Rare‐Earth Metal π Complexes of Reduced Arenes, Alkenes, and Alkynes: Bonding, Electronic Structure, and Comparison with Actinides and Other Electropositive Metals

AbstractReview: 98 refs.

Aromatic Lateral Substituents Influence the Excitation Energies of Hexaaza Lanthanide Macrocyclic Complexes: A Wave Function Theory and Density Functional Study.

The high interest in lanthanide chemistry, and particularly in their luminescence, has been encouraged by the need of understanding the lanthanide chemical coordination and how the design of new luminescent materials can be affected by this. This work is focused on the understanding of the electronic structure, bonding nature, and optical properties of a set of lanthanide hexaaza macrocyclic complexes, which can lead to potential optical applications. Here we found that the DFT ground state of the open-shell complexes are mainly characterized by the manifold of low lying f states, having small HOMO-LUMO energy gaps. The results obtained from the wave function theory calculations (SO-RASSI) put on evidence the multiconfigurational character of their ground state and it is observed that the large spin-orbit coupling and the weak crystal field produce a strong mix of the ground and the excited states. The electron localization function (ELF) and the energy decomposition analysis (EDA) support the idea of a dative interaction between the macrocyclic ligand and the lanthanide center for all the studied systems; noting that, this interaction has a covalent character, where the d-orbital participation is evidenced from NBO analysis, leaving the f shell completely noninteracting in the chemical bonding. From the optical part we observed in all cases the characteristic intraligand (IL) (π-π*) and ligand to metal charge-transfer (LMCT) bands that are present in the ultraviolet and visible regions, and for the open-shell complexes we found the inherent f-f electronic transitions on the visible and near-infrared region.

Quantitative estimates of Asian dust input to the western Philippine Sea in the mid‐late Quaternary and its potential significance for paleoenvironment

AbstractWe present a new high‐resolution multiproxy data set of Sr‐Nd isotopes, rare earth element, soluble iron, and total organic carbon data from International Marine Global Change Study Core MD06‐3047 located in the western Philippine Sea. We integrate our new data with published clay mineralogy, rare earth element chemistry, thermocline depth, and δ13C differences between benthic and planktonic foraminifera, in order to quantitatively constrain Asian dust input to the basin. We explore the relationship between Philippine Sea and high‐latitude Pacific eolian fluxes, as well as its significance for marine productivity and atmospheric CO2 during the mid‐late Quaternary. Three different indices indicate that Asian dust contributes between ∼15% and ∼50% to the detrital fraction of the sediments. Eolian dust flux in Core MD06‐3047 is similar to that in the polar southern Pacific sediment. Coherent changes for most dust flux maximum/minimum indicate that dust generation in interhemispheric source areas might have a common response to climatic variation over the mid‐late Quaternary. Furthermore, we note relatively good coherence between Asian dust input, soluble iron concentration, local marine productivity, and even global atmospheric CO2 concentration over the entire study interval. This suggests that dust‐borne iron fertilization of marine phytoplankton might have been a periodic process operating at glacial/interglacial time scales over the past 700 ka. We suggest that strengthening of the biological pump in the Philippine Sea, and elsewhere in the tropical western Pacific during the mid‐late Quaternary glacial periods may contribute to the lowering of atmospheric CO2 concentrations during ice ages.

Computational bottom-up design of ytterbium(II) complex with pyridyl amido ligand

Having been designed via bottom-up strategy based on density functional theory(DFT) calculations, a complex of ytterbium(II) with pyridyl amido ligand was successfully synthesized by one-pot reaction in laboratory. DFT calculation shows that pyridyl amido ligands can stabilize the complex via steric and electron effect. This success in integrating computation with synthesis will inspire more explorations in the development of a new complex in lanthanide chemistry.