Distinct Rare Earth Element Research Articles

Synthetic Roadmap to a Large Library of Colloidal High-Entropy Rare Earth Oxyhalide Nanoparticles Containing up to Thirteen Metals.

Nanoparticles of high-entropy materials that incorporate five or more elements randomized on a crystalline lattice often exhibit synergistic properties that can be influenced by both the identity and number of elements combined. These considerations are especially important for structurally and compositionally complex materials such as multimetal multianion compounds, where cation and anion mixing can influence properties in competitive and contradictory ways. Here, we demonstrate the synthesis of a large library of colloidal high-entropy rare earth oxyhalide (REOX) nanoparticles. We begin with the synthesis of (LaCePrNdSmEuGdDyHoErYbScY)OCl, which homogeneously incorporates 13 distinct rare earth elements. Through time point studies, we find that (LaNdSmGdDy)OCl, a 5-metal analogue, forms through in situ generation of compositionally segregated core@shell@shell intermediates that convert to homogeneously mixed products through apparent core-shell interdiffusion. Assuming that all possible combinations of 5 through 13 rare earth metals are synthetically accessible, we propose the existence of a 7099-member REOCl nanoparticle library, of which we synthesize and characterize 40 distinct members. We experimentally validate the incorporation of a large number of rare earth elements using energy dispersive X-ray spectra, despite closely spaced and overlapping X-ray energy lines, using several fingerprint matching strategies to uniquely correlate experimental and simulated spectra. We confirm homogeneous mixing by analyzing elemental distributions in high-entropy nanoparticles versus physical mixtures of their constituent compounds. Finally, we characterize the band gaps of the 5- and 13-metal REOCl nanoparticles and find a significantly narrowed band gap, relative to the constituent REOCl phases, in (LaCePrNdSmEuGdDyHoErYbScY)OCl but not in (LaNdSmGdDy)OCl.

Rare earth elements in biology: From biochemical curiosity to solutions for extractive industries.

Rare earth elements (REEs) are critical for our modern lifestyles and the transition to a low-carbon economy. Recent advances in our understanding of the role of REEs in biology, particularly methylotrophy, have provided opportunities to explore biotechnological innovations to improve REE mining and recycling. In addition to bacterial accumulation and concentration of REEs, biological REE binders, including proteins (lanmodulin, lanpepsy) and small molecules (metallophores and cofactors) have been identified that enable REE concentration and separation. REE-binding proteins have also been used in several mechanistically distinct REE biosensors, which have potential application in mining and medicine. Notably, the role of REEs in biology has only been known for a decade, suggesting their considerable scope for developing new understanding and novel applications.

A distinctive rare earth element signature for pyrite oxidation and glacial weathering

The application of rare earth elements (REE) and neodymium (Nd) isotopes to authigenic Fe-(oxyhydr)oxide phases leached from marine sediments can be used for reconstructing past ocean circulation and chemical weathering patterns on nearby continental landmasses. To explore the behaviour of REE during chemical weathering in glacial environments, we analyzed the authigenic fraction of glacimarine sediments from the continental shelf off northern Svalbard (Arctic Ocean), where the evolution of ice sheet dynamics since the last deglaciation is well constrained. Our results show that leached authigenic fractions in Svalbard sediments exhibit shale-normalized REE patterns characterized by anomalously high mid-REE enrichment relative to both light- and heavy-REE, as expressed by concavity index values (CI > 2.5) that significantly depart from typical REE signatures for leached fractions in marine and river sediments worldwide. Using a compilation of literature data, we provide compelling evidence that the occurrence of pronounced mid-REE enrichment in authigenic fractions of Svalbard marine sediments links to terrestrial oxidation of pyrite following glacial weathering. While future investigation will be required to further understand the detailed mechanism accounting for the observed REE decoupling and its link to pyrite oxidation, we propose that preferential dissolution of mid-REE-enriched rock-bearing minerals such as apatite following glacial erosion, sulfide weathering and subsequent release of sulfuric acid could release a distinctive REE signature in glacial surface environments. Our findings suggest that the use of authigenic REE in the sedimentary record could provide a means for tracing glacial weathering and associated biogeochemical sulfur and iron cycling across geological times.

Unveiling the connection between lode gold mineralization and the metamorphic core complex evolution from the large Yangzhaiyu gold deposit, North China Craton

Abstract The Xiaoqinling gold province, located in the Neoarchean–Paleoproterozoic uplifted footwalls of the Xiaoqinling metamorphic core complex (XMCC), is one of China’s largest gold producers; however, achieving a consensus regarding their metallogenic model remains elusive. Scheelite is an indicator mineral that commonly occurs in lode gold deposits worldwide used to recognize deposit types and understand hydrothermal evolution and the origin of features. Xenotime, monazite, and rutile are common hydrothermal minerals in association with lode gold deposits worldwide. Here, we provide textual, in situ U-Pb geochronology of xenotime, monazite, and rutile, and in situ elemental and Sr-Nd isotopic compositions of scheelite within different stages from the large Yangzhaiyu lode gold deposit, aiming to elucidate its genesis and, for the first time, establish a holistic correlation between the lode gold mineralization and the evolution of the XMCC. Notably low εNd(t) values (−30.7 to −23.7), high 87Sr/86Sr ratios (0.72659–0.75914), and distinct rare earth elements, Sr, Mo, and As contents of scheelite confirm a metamorphic crustal source. Xenotime U-Pb dating and pre-ore (Stage I) scheelite reveal that ore-barren metamorphic fluids at ca. 140 Ma were oxidized with low Bi contents and buffered by greenschist facies metamorphism when the XMCC initiated. Monazite and rutile U-Pb dating combined with ore-stage scheelite geochemistry indicate a compositional shift in the more reduced auriferous metamorphic fluids, which dominated during major gold deposition periods (stages II and III) from 130 Ma to 120 Ma, characterized by significantly depleted Na and increased Bi contents. This resulted from the prograde greenschist-to-amphibolite metamorphism at mid-lower crustal depths as the result of the XMCC isostatic doming and the lithospheric mantle thinning after 130 Ma. This study highlights the crucial role of metamorphic core complexes in governing the timing, locations, and resources of the lode gold metallogenic system.

Microbially induced fabrics in the Upper Ediacaran coated grain dolostone, Northeast Sichuan Basin, SW China: Implications for reconstruction of the paleoceanic environment

In the Upper Ediacaran Dengying Formation of the Sichuan Basin, the presence of abundant, well-preserved microbial carbonates provides a unique opportunity to study Precambrian paleoceanography and microbial carbonate origins. Particularly, the underexplored coated grain dolostones of this formation, characterized by distinct microbially induced fabrics and intragranular dissolution, offer crucial insights for understanding late Ediacaran microbial mineralization and diagenetic sequences. Utilizing selected typical samples, we conducted detailed petrographic and geochemical analyses, revealing a dynamic interplay between microbial processes and sedimentary dynamics. We observe the coexistence of constructive micrite envelopes with microbially induced fabrics such as clots and laminations, highlighting microbial biomineralization's key role in fabric formation. The sedimentary dynamics critically determines the formation processes of the coated grains: low-energy settings foster grain agglomeration and consolidation through clot precipitation between grains, while high-energy settings favor smaller grains binding to microbial mats. Geochemically, micrite envelopes play an essential role in preserving distinct rare earth element (REE) signatures. The weak negative Ce anomalies and positive Eu anomalies within these envelopes point to a suboxic to anoxic depositional environment, directly indicative of the microenvironmental conditions conducive to microbial mineralization processes. Furthermore, our study sheds light on the structural evolution of coated grains with hollow nuclei, proposing that their internal pore formations are influenced by both mineral instability and selective dissolution by meteoric freshwater. These findings not only provide fresh insights into complex diagenetic processes in the Dengying Formation but also substantially advance our understanding of early microbial life and environmental adaptations during the Precambrian.

Ocean–Continent Conversion in Beishan Orogenic Belt: Evidence from Geochemical and Zircon U-Pb-Hf Isotopic Data of Luotuoquan A-Type Granite

Devonian magmatism is one of the most important tectonothermal events in the Central Asian Orogenic Belt (CAOB). However, little is known regarding the petrogenesis and geodynamic setting of the widely distributed Devonian granitoids in the eastern Southern Beishan Orogenic Belt (SBOB). Early-Devonian granitic magmatism has been recognized from the Luotuoquan area, and the granites were emplaced between 404.9 Ma and 399.4 Ma according to LA-ICPMS zircon U–Pb dating. Geochemically, the granites exhibit high SiO2 and Al2O3 contents and are enriched in light rare earth elements as well as Rb, Th, Nd, Zr, and Hf, while being depleted in heavy rare earth elements and Ba, U, Sr, and Ti, with distinct rare earth element fractionation and pronounced negative Eu anomalies. According to the comprehensive analysis, they closely resemble the features typically associated with A-type granites. The zircons εHf(t) values are within the range of +0.90–+5.19 (averaged 3.23) for the monzogranite and syenogranite, whereas their TDM2 values fall between 1.05 and 1.34 Ga, suggesting that the magma source of the monzogranite–syenogranite originated from the partial melting of the Mesoproterozoic crust dominated by metagreywackes. Furthermore, the monzogranite and syenogranite exhibit high temperatures (average 782 °C), thin crustal thickness (average 30 km), and A-type characteristics, suggesting their formation in post-collision extensional settings. We propose the closure of the Beishan Ocean occurred before the early Devonian, followed by a transition in the Southern Beishan Orogenic Belt from a compressional to an extensional setting.

Magma process of the ore-forming gabbrodiorite porphyry of the Meishan iron deposit, eastern China: Insights from the phenocrysts chemistry

Mesozoic iron deposits in the Ningwu volcanic basin in eastern China are genetically linked to the gabbrodiorite porphyries, which have long been regarded as the subvolcanic intrusive of the andesitic volcanics. Compared with abundant research conducted on the mineralization process, the magmatic process of the ore-forming intrusion has been poorly understood. This study performed petrographic and in situ analyses of representative phenocrysts from the ore-forming gabbrodiorite porphyry of the Meishan iron deposit to gain new insights into the magmatic process. The phenocrysts are composed of clinopyroxene and plagioclase, which commonly exhibit disequilibrium features, such as reverse zoning and sieved textures, suggesting that the gabbrodiorite porphyry evolved in an open-system andesitic-magma reservoir into which mafic magma was repeatedly recharged. The zoned clinopyroxene phenocrysts show consistent trace-element distribution patterns and a narrow range of 87Sr/86Sr of 0.7037–0.7049, which suggest that the recharged mafic magma was the primitive basaltic magma and crystal fractionation dominated the evolution from basaltic magma to andesitic magma. Pressure estimations based on clinopyroxene phenocryst compositions indicate that the magma reservoirs were emplaced at the uppermost mantle. Comparison of clinopyroxene phenocryst compositions between the Meishan gabbrodiorite porphyry and published andesitic volcanics shows distinct rare earth element distribution patterns, which don't support a volcanic–subvolcanic relationship between the gabbrodiorite porphyry and andesitic volcanics. Estimated pressures indicate that the primitive magma of andesitic volcanics evolved in lower crust reservoir, which was much shallower than the reservoirs of the ore-forming gabbrodiorite porphyry. Therefore, the Meishan gabbrodiorite porphyry was not the subvolcanic intrusive of the andesitic volcanics and probably represented an independent magmatic pulse. This understanding suggests that the exploration target of iron deposits in the Ningwu basin is not necessarily limited to the contact zone between gabbrodiorite porphyry and andesitic volcanics.

Multistage fluorite mineralization in the southern Black Forest, Germany: evidence from rare earth element (REE) geochemistry

Abstract. The Black Forest hosts a wide range of hydrothermal mineralization, including fluorite–barite vein deposits. In a detailed investigation of the Finstergrund and Tannenboden deposits in the Wieden mining district (southern Black Forest), the diversity, geochemical evolution and relative chronology of multistage fluorite precipitation is tracked on the basis of rare earth element (REE) geochemistry, geologic field relationships and crystal zoning. Geochemical discrimination and mathematical λ coefficients suggest a total of seven fluorite REE groups, at least three distinguishable post-Variscan fluid mobilization events and independent formation histories for the deposits despite their spatial proximity. Fluorite vein mineralization at the Finstergrund deposit evolved over three fluid generations, was derived from gneissic source aquifers and comprises five distinct fluorite REE groups: the first fluid generation is characterized by fluorite precipitation above 200 ∘C (“group III”), below 200 ∘C (“group I”) and after fractional crystallization (“group IV”); the second generation comprises remobilized fluorite (“group II”); and the third generation revealed fluorite precipitation by meteoric water mixing (“group V”). Fluorite vein formation at the Tannenboden deposit is associated with two distinct fluorite REE patterns derived from the same fluid generation: fluorite precipitation above 200 ∘C (“group VII”) and after cooling below 200 ∘C (“group VI”). Its fluid source aquifer lithology best matches migmatites contrary to previous models that suggest either gneissic or granitic aquifer rocks for fluorite vein precipitation in the Black Forest. The decoupled formation history between the deposits is tectonically controlled as suggested by a new genetic model for the Wieden mining district. The model argues for a change in the local fluid percolation network and the termination of hydrothermal activity at the Tannenboden deposit after the first fluid mobilization event. The geochemical evolution of multistage fluorite mineralization, as exemplified by the Tannenboden and Finstergrund deposits in combination with other fluorite mineralizations in the Black Forest, provides unique insights into the lithospheric origin and precipitation behaviour of fluorite by various fluid–rock interaction processes occurring in large hydrothermal systems. The local diversity of REE patterns emphasizes the need for detailed investigations of individual hydrothermal vein deposits.

Petrogenesis of the Late Carboniferous Trondhjemite in Central Inner Mongolia in North China and Constraints of Intra-Oceanic Subduction in the Southern Paleo-Asian Ocean

Intra-oceanic subduction is a fundamental process on Earth, the study of which can improve the understanding of plate tectonic processes and the history of continental growth. Here, we report on newly recognized trondhjemite in the north of Diyanmiao ophiolite belt in North China. The trondhjemite was found along the Erenhot-Hegenshan suture zone. U-Pb zircon dating revealed that the trondhjemite crystallized at 309 ± 2.1 Ma. The trondhjemite had a high amount of SiO2 (68.94–76.45 wt %), Al2O3 (13.37–15.90 wt %), and Sr (232–601 ppm); and a low amount of K2O (1.57–2.70 wt %), Y (6.91–9.39 ppm), Ni (1.10–4.19 ppm), and Cr (1.55–13.50 ppm). The Na2O/K2O ratios were 1.90–4.37. There was a lack of negative Eu anomalies. It was relatively enriched in large-ion lithophile elements (LILEs) such as Rb, Ba, K, and Sr; was depleted in high-field-strength elements (HFSEs) such as Nb, Ta, Ti, and P; and had low total rare-earth element (REE) contents (27.73–49.63 ppm) with distinct REE fractionation (chondrite-normalized (La/Yb)N of 5.76–10.52), which was similar to adakitic rocks formed by partial melting of subducted oceanic crust. The trondhjemite, together with Diyanmiao ophiolite (335.6 Ma), may have formed during the stages of intra-oceanic subduction, suggesting that in the Early Carboniferous–Late Carboniferous, the southern Paleo-Asian Ocean was in its subduction stage.

Distinct Depositional Environments Of Two Internal Reference Materials With Marine Sediment Matrix From Nearby Bangka Island

Internal reference materials are generated by laboratories to overcome the high cost and limited matrix of certified reference materials (CRM). Rare earth elements (REE) are strategic metals which is used in modern technology and explored within different matrices. Rare earth elements exploration surely needs appropriate reference materials for accurate interpretation. The current study aims to explain internal standard reference materials generation of marine sediment matrices from nearby the tin Bangka Island, especially the rare earth elements character, to overcome the CRM dependency. The first sample was taken with a dredger while the second one using a suction vessel. Repeated samples measurements were done by applying inductively coupled plasma - mass spectrometry (ICP-MS) from the Center for Geological Survey Indonesia for repeatability tests. The samples were analyzed in another certified laboratory in Indonesia using the same device for reproducibility assessment. The two candidates should be deposited in different environments with different influx material due to their distinct rare earth elements characters. Most of the analytes’ contents are suitable to be set as internal reference material values according to acceptable repeatability and reproducibility evaluations. The internal reference materials are ready for studying suitable matrices in the future.

Zircon reveals multistage, magmatic and hydrothermal Rare Earth Element mineralization at Debert Lake, Nova Scotia, Canada

Rare Earth Element (REE) mineralization at Debert Lake (Nova Scotia, Canada) is hosted by the anorogenic Hart Lake-Byers Lake granites which are associated with the Late Devonian to Early Carboniferous Wentworth plutonic complex in the Cobequid Highlands. Mineralized zones contain up to 1.2 wt% REE2O3, 3.4 wt% ZrO2, and 0.4 wt% Nb2O5 produced by multiple, separate mineralizing events. We use a multi-faceted approach combining whole-rock and mineral geochemistry, together with U-Pb radiometric dates to uncover complex formative processes and resolve the timing for REE mineralization.Episodic mineralization yielded distinct REE assemblages including Nb-oxide (pyrochlore and fergusonite) phases, chevkinite, zircon, thorite, monazite, and titanite, formed during multiple magmatic-to-hydrothermal stages in the rare-metal bearing granites. Zircon, as a persistent phase of the REE assemblages, occurs with variable texture, morphology, and composition in all granites. Zircon grains, displaying intergranular to interstitial textures in REE rich granite, have spongy cores in which Y, Th, and Zr were redistributed by magmatic fluids. U-Pb dating of these zircons yields an age of 355 to 360 Ma, approximately coeval with igneous monazite crystallization, dated at 366 ± 5 Ma. These findings document a late-magmatic REE mineralization event. A subsequent pulse of post-magmatic hydrothermal mineralization associated with Zr-F-rich fluid complexes produced two other zircon populations, dated at ca. 309 and 318 Ma, with unusual habits and REE patterns that are interpreted to be of hydrothermal origin. Principal Component Analysis (PCA) separates zircon populations based on element concentrations and element associations. The LREE-rich hydrothermal zircon types with their distinct geochemical patterns revealed by PCA are characterized by the relative enrichment of either Na or Ca, reflecting differences in the composition of hydrothermal fluids driving sodic and calcic alteration processes, respectively

Isothermal and enzyme-free MicroRNA assay based on catalytic hairpin assembly and rare earth element labeled probes

MicroRNAs (miRNAs) are a category of short non-coding RNA molecules which play essential roles in regulating gene expression. Correspondingly, the aberrant expression of miRNAs is commonly related to the development of various diseases including cancers and cardiovascular diseases. Hence, miRNA is considered as an ideal biomarker for disease diagnosis and its quantification is highly demanded. Herein, an isothermal and enzyme-free miRNA assay based on catalytic hairpin assembly (CHA) amplification coupled with inductively coupled plasma mass spectrometry (ICP-MS) detection is proposed. Two hairpin probes are employed in CHA reaction with rare earth element tag on H1 for ICP-MS detection and biotin on H2 for immobilization on magnetic beads. In the presence of target miRNA, the two independent probes open up their stem-loop structure and hybridize. The target miRNA will be released after the hybridization to trigger another CHA reaction. Ultimately, one target miRNA molecule promotes a number of CHA cycles and produces several copies of hybridized complex leading to the enhanced ICP-MS signal. Based on this approach, miRNA-141 was successfully analyzed with high sensitivity and specificity. The limit of detection (LOD) was 88 fmol with a linear range 0.1–2 pmol. Compared with fluorescence mediated CHA method and ICP-MS mediated basic sandwich method, the current strategy displayed the lowest LOD. The developed method was also applied to analyze miRNA-141 and miRNA-21 simultaneously to demonstrate its multiple detecting capability and practical applicability. Furthermore, this miRNA assay has the potential to become a high-throughput method by employing more distinct rare earth elements.

Biotite as a geoindicator of rare earth element contamination in Gomati River Basin, Ganga Alluvial Plain, northern India.

Rare earth elements (REE) are emerging as modern high-technology-related novel micro-contaminants in freshwater aquatic systems and are therefore attracting global attention due to their potential human health risks. The Gomati River (a tributary of the Ganga River) sediments were analyzed for REE concentrations to establish REE contamination and to identify biotite mica mineral as a geoindicator. Chondrite-normalized REE pattern of the river sediments and biotite mica mineral were similar and depict a strong light REE (LREE) enrichment and relatively flatter heavy REE (HREE). The maximum total REE (∑REE) concentration increased from 323µg/g in 2012 to 673µg/g in 2019. In the ∑REE, LREE contribution was > 80%, because of anthropogenic inputs, mainly petroleum-cracking catalysts and other high-technology-based products. The XRD analysis and the geochemical signature of the Gomati River sediments reveal the meaningful existence of biotite mica mineral. A distinct downstream REE enrichment pattern was identified in biotite from the mica-rich bedload sediments. The scanning electron microscopy-energy dispersive X-ray (SEM-EDX) mapping images of biotite also revealed the precipitation of Lanthanum, at the weathered edges, during the early stage of mineral weathering. Biotite mica was identified as a geoindicator for the assessment of REE contamination in the Gomati River and the Hindon River Basin of the Ganga Alluvial Plain. Future research is needed for the application of biotite mica mineral as a geoindicator that can help the environmental scientists to contribute more effectively to the interdisciplinary efforts in River Science.

In situ LA ICP-MS analysis of trace elements in scheelite from the Xuefeng Uplift Belt, South China and its metallogenic implications

Abstract The Xuefeng Uplift Belt (XUB), in the western part of the Jiannan Orogenic Belt (JOB) South China, hosts numerous low-temperature W-Sb-Au deposits, including the Woxi W-Sb-Au deposit, the Zhazixi Sb-W deposit and the Darongxi W deposit. In order to understand the origin of these low-temperature W deposits and the difference from other moderate-high temperature tungsten deposits in the South China Block, Cathodoluminescene (CL) and LA-ICP-MS are employed to investigate the detailed texture of scheelite , and to identify trace element composition and distribution in scheelite, especially rare earth elements (REEs). LA-ICP-MS results show that the most abundant trace elements in scheelite in this study were Sr, Y, Nb, Mo, Zr, Hf, Ta and REEs. Six types of scheelite can be classified according to variations of REEs pattern. Type I and II scheelites from the Zhazixi Sb-W deposit and the Woxi W-Sb-Au deposit have elevated concentration of Sr, low concentrations of Nb, Mo and variable Nb/Ta ratio, reflecting low temperature ( skarn deposit, Type IV scheelite from the Dabaoshan polymetallic deposit, Type V scheelite from the Niutangjie skarn W deposit and Type VI scheelite from the Daping W deposit have relatively higher Nb, Mo and relatively constant Nb/Ta ratios, and lower Sr concentration, consistent with the feature of moderate to high temperature oxidizing environments. Type I scheelite from the Zhazixi Sb-W deposit can be subdivided into Ia, Ib and Ic, which cover a wide range from MREE-rich to MREE-depleted, indicating a complete dynamic evolution process. Type II scheelite from the Woxi W-Sb-Au deposit has uniform patterns with significant depletion of LREE and enrichment of MREE, revealing that the substitutions of MREE into scheelite lattices are dominated by crystallographic factors, especially the Ca-site size in scheelite crystals rather than the REE concentrations and REE complex stability in hydrothermal fluids . Type III scheelite from the Darongxi W deposit shows two distinctive REE patterns, types IIIa and IIIb, which are likely to be two end members, suggesting that successive precipitation results in changes in REE concentrations and Eu anomalies. Type IV scheelite from the Dabaoshan polymetallic deposit inherited the signature of the granitic porphyry . Type IV b and IVc are similar to those Type V scheelites from Niutangjie, both showing the characteristics of skarn type scheelite mineralization. Trace element variations suggest the predominant control factors differ according to temperature. Trace element concentrations and distribution of scheelite formed at low temperature were mainly controlled by crystallographic factors, which contrasted with fluid-controlled feature of the medium–high temperature scheelite mineralization.

The Role of Blueschist Stored in Shallow Lithosphere in the Generation of Postcollisional Orogenic Magmas

AbstractIn regions with small ocean plates and continental blocks, such as the Mediterranean in the Cenozoic and modern Indonesia, many blueschists may be stored at shallow depth in the mantle lithosphere that is newly formed during the amalgamation of small continental blocks and oceans. Melting of these blueschists at low pressures in the mixed lithosphere of this type during postcollisional relaxation may be involved in the generation of postcollisional orogenic magmas. Here, we have conducted a series of melting experiments on three blueschist samples with differing protoliths at 800–850°C, 2 GPa to investigate phase relations, mineral compositions, and trace element partitioning (using laser ablation‐inductively coupled plasma‐mass spectrometry [LA‐ICP‐MS]/nanoscale secondary ion mass spectrometry [NanoSIMS]), including the first results for clinozoisite. Dacitic/rhyolitic melts (SiO2 60 to 66 wt%) containing ~13 wt% volatiles are produced in all runs. Mn‐rich and Mn‐poor almandine garnets exhibit distinct rare earth element (REE) distribution patterns, while Mn‐rich garnets are effective preconcentrators of heavy REEs (HREEs) for later metamorphic processes. Melts produced from fluid‐affected blueschists of terrigenous origin show the most large‐ion lithophile element (LILE) enrichment, whereas those from terrigenous blueschists with no fluid history exhibit the lowest K/Th and Ba/Th and strongest Ce/Pb and Nb/U fractionations. Melts of blueschists derived from mid‐ocean ridge basalt (MORB) have relatively consistent, MORB‐like Ba/Th and Nb/U (~3) but the lowest Ce/Pb ratios (3.3). V/Sc and Zr/Hf ratios remain constant at ≥850°C regardless of the origin of the blueschist. Dehydration melting in new mantle lithosphere where blueschist is stored at shallow depth will significantly affect trace element behavior and should be considered carefully when examining chemical cycling and magmatism in postcollisional orogenic settings.

Aspects of rare earth element enrichment in Central Appalachian coals

The concentration of lanthanides, Y, and Sc, collectively rare earth elements (REE), and their modes of emplacement in Appalachian coals, with emphasis on Manchester and Fire Clay coals in eastern Kentucky are the focus of this investigation. Those coals have distinct REE concentrations and relationships related to the position of the lithotype within the coal seam, such as the ratio of light to heavy lanthanides (LREE/HREE). In the Manchester coal, the high-S upper lithotypes have lower REE concentrations and different LREE/HREE than the low-S lithotypes. In the Fire Clay coal, the position of the lithotype relative to the REE-enriched tonstein is important, with the coal immediately below the tonstein having significantly higher REE than other lithotypes. Lithotypes in the middle of the coal bench above the tonstein have high LREE/HREE, possibly indicating a hydrothermal influence on the REE emplacement.

Geochemical insights into the relationship of rock varnish and adjacent mineral dust fractions

Rock varnishes are μm-thin, dark, manganese(Mn)-rich crusts that accrete in the order of few μm/ka on weathering-resistant lithologies. Although these crusts can form in all climates, they are best known in arid to semi-arid settings. Aeolian dust is understood as a major contributor to the distinct trace metal and REE enrichments in rock varnish. However, the exact proportions of abiotic and biotic formation mechanisms that may explain the oxidation-reactions of Mn2+ to Mn4+, present as Mn oxyhydroxides in the varnish, are still a matter of ongoing debate.We present here the first systematic study of trace element enrichment processes between the uppermost layer of the varnish sequence and their adjacent <50 μm and >50 μm dust fractions across a selection of 41 major and trace elements. This approach is used to investigate samples from three fully arid deserts: the An Nafud in Saudi Arabia, the Negev in Israel, and the Mojave in the USA, which are compared to the significantly different environment of the semi-arid Knersvlakte in South Africa. A new in situ trace element analysis protocol was developed to perform femto- and nanosecond sector-field LA-ICP-MS microanalyses at high-spatial resolution, which allows us to measure the most recent varnish layers for their comparison with recent dust. In agreement with previous studies, all varnishes are enriched in Mn, Pb, Ce, Co, Ba, Zn, Ni, and the Rare-Earth Elements (REE). Here we demonstrate that fine (<50 μm) dust is characterized by similar trace element trends as the varnishes, at overall lower mass fractions. Dust >50 μm has low trace element mass fractions, and enrichment patterns plotting distinctly away from varnish and fine dust. Based on these geochemical patterns, our results indicate a general enrichment mechanism from fine dust to varnish. Previous studies suggested dust to play an integral role in providing the trace elements that are incorporated into the varnish by pH-Eh fluctuations in short-term rain and fog events. We amalgamate and refine previous growth models by providing direct evidence that leaching of about 10% of the Mn and other trace elements from clay minerals in rain or fog droplets at pH ~5 and subsequent scavenging on varnish surfaces at pH ~8 leads integrated over time to the distinct enrichment patterns of the varnish, while initial Mn oxyhydroxide formation is suggested to follow pathways of metal oxide mediated photo-catalysis.For the semi-arid occurrence in the Knersvlakte we present a distinct growth model as both environment, varnish, and dust composition differ significantly from the arid settings. Here, thick, metallic-looking varnish occurs mainly on the rim of quartz pebbles, lacks microlamination, and likely has upscaled growth processes. Among other aspects, we suggest a more complex interplay between photo-catalysis, nocturnal condensation events on quartz pebbles with subsequent water trapping at the rock-soil-atmosphere interface, due to a salic top-soil layer, to mainly account for these differences.

Rare Earth Elements in Dinosaur Bones Across the Embryo-Adult Spectrum

There is broad consensus that many bones of extinct vertebrates contain Rare Earth Elements (REE) and other trace minerals that have been incorporated and enriched into the fossil during diagenesis. During fossilization, apatite minerals in vertebrate bones recrystallize from metastable biogenic forms to thermodynamically more stable inorganic apatite minerals while incorporating REEs from their environment. More than ~95% of the REE in fossil bones are diagenetically incorporated postmortem and bones in different environments have different and distinct REE signatures, generally viewed to be controlled by sedimentological and taphonomic processes. The REE pattern in fossils is generally stable and the normalized concentration patterns provide unique “fingerprints” or signatures that have been used for various geological and paleontological investigations. The discovery of embryos and their adults at the same site, a previously unrecorded occurrence in the fossil record, allowed us to compare for the first time the relationship between REE concentrations in the same taxon at widely differing ontogenetic stages. Here we compare REE patterns in bones from two distinct sites in Yunnan, China, both preserving embryonic and adult bones of Early Jurassic sauropodomorph dinosaurs. These dinosaurs are closely related to each other and close in geological age, and their bones show very similar REE patterns. However, the embryonic bones have significantly lower levels of total REEs when compared to their adult counterparts. We attribute the tenfold difference to the level of ossification of the bones and the dramatically lower concentration of apatites in the embryonic than in the adult bones. We conclude that the ontogenetic stage of fossil materials can have a significant impact on REE concentrations, and discuss the impact of these results on future work.

Authentication of meat and dairy products using rare earth element labeling and detection by solution based and laser ablation ICP-MS

In order to meet the increasing customer demand for local food products, various methods for verification of food origin by means of region specific trace element fingerprinting have been developed. However, for products from conventional agriculture, without a close relationship to the local soil, other methods for food authentication are required. In an alternative approach, foodstuffs produced in a certain region, by a specific producer or under certain conditions can be safeguarded against imitation by chemical labeling.The objective of the present study was to develop a method for labeling lamb meat and goat milk by selective enrichment of terbium and thulium in the feed for the animals. Therefore, a distinctive rare earth element (REE) pattern is artificially introduced which can be determined in labeled food products. Detection of REE labels was carried out using inductively coupled plasma mass spectrometry (ICP-MS) after acid digestion. Alternatively, laser ablation ICP-MS (LA-ICP-MS) was applied, allowing direct analysis of bone samples and analysis of meat and milk samples after dry ashing and pressing pellets.After three weeks of administering 1000-fold terbium and thulium enriched feed to lambs, terbium and thulium enrichment was detected in all sample types except blood, following the trend bones > kidney > liver > heart > meat > kidney fat. Similarly, goat milk was successfully labeled after three weeks of feeding 500-fold terbium and thulium enriched feed.Hence, the present method allows discrimination of labeled from unlabeled animal products, while REE contents in all labeled products remained low enough to avoid any health risk for the consumer.

Subduction initiation in the southeastern Palaeo‐Asian Ocean: Constraints from early Permian adakites in suprasubduction zone ophiolites, central Inner Mongolia, North China

Here, we investigate early Permian adakites from Inner Mongolia, North China. The adakites are found along the Hegenshan suture zone, were emplaced into the late Carboniferous Meilaotewula suprasubduction zone (SSZ) ophiolite and consist mainly of fine‐ to medium‐grained granodiorites. U–Pb zircon dating reveals that the Meilaotewula adakites crystallized at 292 Ma. The adakites belong to the low‐K tholeiitic and medium‐K calc‐alkaline series. They are characterized by high SiO2(65.20–70.05 wt.%), Al2O3(16.46–19.27 wt.%), and Sr (343–666 ppm); low MgO (1.26–1.95 wt.%), Yb (0.65–1.16 ppm), and Y (8.08–10.6 ppm) contents; and Na2O/K2O ratios (3.26–10.73). They are relatively enriched in large‐ion lithophile elements, such as K, Rb, and Sr, and depleted in high‐field‐strength elements, such as Nb, Ta, Zr, Ti, and P, and have low total rare‐earth element (REE) contents (27.73–49.63 ppm), with distinct REE fractionation (chondrite‐normalized La/Yb of 3.05–8.88) and no pronounced negative Eu anomalies. The rocks have relatively low initial87Sr/86Sr values (0.70285–0.70326), high εNd(t) values (+8.8 to +10.8), and relatively high zircon εHf(t) values (11.9 to 15.9), indicating that the magma was derived from young juvenile oceanic crust derived from depleted mantle, similar to adakitic rocks formed by partial melting of subducted oceanic crust. The relatively high Mg#of the adakites indicates that the melts interacted with mantle peridotite during ascent. The adakites, together with Meilaotewula ophiolite (308 Ma), may have formed during the early stages of intra‐oceanic subduction, demonstrating that subduction initiation in the southeastern Palaeo‐Asian Ocean occurred during the late Carboniferous to early Permian.