Advancing exploration hydrogeochemistry using single particle inductively coupled plasma–time-of-flight mass spectrometry at the Bear Lodge alkaline complex, Wyoming, USA

Rare earth elements (REE) in deep groundwater from granite and fracture-filling calcite in the Tono area, central Japan: Prediction of REE fractionation in paleo- to present-day groundwater

REE geochemistry of fine-grained sediments from major rivers around the Yellow Sea

High-resolution coral records of rare earth elements in coastal seawater: biogeochemical cycling and a new environmental proxy

Origin, distribution, and behaviour of rare earth elements in river bed sediments from a carbonate semi-arid basin (Tafna River, Algeria)

The geochemical composition of rare earth elements (REE) in the bottom sediments of two Dominican reservoirs and in soils from their catchments was studied to identify possible sources of the deposited materials. Knowledge of the origin of the sediments will serve to control the excessive rates of erosion and sedimentation that occur annually due to periodic extreme climatic events that promote excessive silting of the lakes, followed by loss of storage capacity and degradation of water quality. The REE contents of sediments and soils were normalized to the North American Shale Composite (NASC) and the ratio of light/heavy rare earths (LREE/HREE ratio), Ce and Eu anomalies, and some fractionation parameters were determined. The REE patterns are more homogeneous in the sediments, indicating uniform sedimentation in both deposits. The sediment data reflect depletion of REE from the sources, enrichment of light REE (LREE) and some middle REE (MREE), and positive Eu and Ce anomalies. All data were plotted in correlation diagrams between some fractionation parameters of light–middle–heavy REE and anomalies of Ce and Eu. The similarity of the ratios between these parameters in all samples and the overlap of data from soils and rocks on the sediment projection in the diagrams allowed a good discrimination of the main sources of the materials.

The Rare Earth Elements (REE) archived in carbonate rocks retain a wealth of information on paleo-seawater chemistry and local-regional redox conditions. However, interpretations are often ambiguous due to the potential for REE remobilization in marine environments. In this regard, many carbonate rocks that retain primary seawater isotopic signatures exhibit non-seawater-like REE patterns, implying either unusual REE behaviour in seawater or diagenetic overprinting of otherwise well-preserved rock samples. Here, we apply sequential leaching to constrain the possible effects of different REE-bearing phases on measured carbonate REE patterns in order to address this quandary. Our results show that the exchangeable phase contains negligible REE, but could be an important host phase for other elements such as Sr, Ba and K. The acidified hydroxylamine hydrochloride leach is shown here not only to dissolve Fe–Mn oxides but also phosphate minerals, which induces middle REE enrichment in corresponding leachates of dolostone samples in our study. The demonstrable Fe–Mn oxide phase in limestone samples is characterized by middle and/or light REE enrichment and positive Eu anomalies, which are attributed to hydrothermal processes and continuing exchange with marine fluids after initial precipitation. The non-seawater-like REE patterns observed in the carbonate phase of otherwise well-preserved limestones resemble those of the co-existing Fe–Mn oxide fraction, and are interpreted to reflect the dissolution of REE carrier phases during early diagenesis. This view is supported by fluid-rock interaction modelling, which shows how REE can be mobilized at relatively low fluid/rock ratios in shallow porewaters. Non-seawater-like REE patterns may therefore be caused by the incorporation of REE from shallow porewaters before final lithification due to an elevated flux of particulate REE carrier phases, e.g. Fe–Mn oxides and organic matter, to the seafloor. In spite of the sensitivity of carbonate REE patterns to early diagenetic exchange, the co-occurrence of non-seawater-like patterns with primary strontium and carbon isotope values suggests that REE should not be viewed as a general indicator for the preservation of other geochemical proxies. Importantly, Ce anomalies of the carbonate phase will also be affected by porewaters, masking primary seawater values. Our results favour a reevaluation of redox interpretations by taking into account REE patterns as a whole.

Rare earth elements (REEs) of 39 anhydrite samples from different textural settings and from three different areas on the active TAG hydrothermal mound have been analyzed to examine the geochemical evolution of the circulating fluid. All of the chondrite-normalized REE patterns of anhydrite are characterized by positive Eu anomalies that range from 2 to 18 and varying levels of light rare earth (LREE) enrichment with Nd N/YbN values from 5 to 25. No systematic variations in the REE patterns are observed with depth or with textural setting. In the TAG-1 area, the samples fall into two groups when normalized to the composition of the end-member black smoker hydrothermal fluid. The first group shows relatively flat REE patterns (Nd FL/YbFL of 0.8-2.8) with only a small or no Eu anomaly ranging from 0.8 to 1.5. If it is assumed that the Group I anhydrites were derived from mixing of seawater with an endmember black smoker hydrothermal fluid, then this implies that, during the precipitation of this type of anhydrite from the cir culating fluid, all of the REEs, including Eu, are taken up in proportions that reflect their relative distribution in the flui d. Consideration of the redox conditions of the hydrothermal fluid during mixing with either cold or conductively heated seawater indicates that both divalent and trivalent Eu may be present. Hence, a possible explanation for the flat REE patterns relative to hydrothermal fluid is that the trivalent Eu was not discriminated against during precipitation, and hence there was no fraction ation of Eu relative to the other REEs. Mixing of a hydrothermal fluid with seawater would result in a decrease in temperature and an increase in fO 2 in the mix relative to the hydrothermal fluid, both of which would result in more Eu being present as the trivalent ion. An alternative possibility that cannot be ruled out is that the Group I anhydrites precipitated from mixing of s eawater with a hydrothermal fluid of different composition. The second group is characterized by a distinct negative Eu anomaly ranging from 0.2 to 0.7 relative to the end-member hydrothermal fluid. This implies that during the precipitation of this anhydrite group, Eu is excluded relative to the other RE Es, resulting in an increase in the concentration of Eu in the fluid while the concentrations of other REEs in the fluid decrease. There is an inverse correlation between Eu anomaly and the absolute REE concentrations in anhydrite suggesting that the Eu anomaly can be used as an indicator of the degree of evolution of the hydrothermal fluid. In addition, an increase in the LREE enrichment as the fluid evolves is also observed, which may be related to the greater stability of LREE chloride complexes in high temperature, low pH fluids. In the TAG-2 area, the Eu anomalies in the anhydrite are more strongly developed than in the TAG-1 area, suggesting that they have formed from hydrothermal fluids that had previously mixed with seawater and precipitated anhydrite to a greater degree than those in the TAG-1 area. The chondrite-normalized pattern of the one anhydrite sample from the TAG-5 area shows some distinct differences from the other samples analyzed. The absolute REE concentrations in this sample, with the exception of Eu, are the highest found in this study and the Eu anomaly, although still positive, is extremely small. Possible mechanisms to explain this REE pattern in these samples include mixing between a hydrothermal fluid that has undergone conductive cooling prior to mixing, or addition of REEs to the hydrothermal fluid prior to mixing with seawater by dissolution of anhydrite. The REE data provide evidence for the entrainment of seawater and mixing with hydrothermal fluids down to at least 58.68 mbsf. The mixing process is complex and chaotic at all scales, and shows no systematic variations either laterally or verticall y on the mound scale, or even within an individual vein.

Abstract— This paper explores the possible origin of the light rare earth element (LREE) enrichments observed in some ureilites, a question that has both petrogenetic and chronologic implications for this group of achondritic meteorites. Rare earth element and other selected elemental abundances were measured in situ in 14 thin sections representing 11 different ureilites. The spatial microdistributions of REEs in C‐rich matrix areas of the three ureilites with the most striking V‐shaped whole‐rock REE patterns (Kenna, Goalpara, and Novo Urei) were investigated using the ion imaging capability of the ion microprobe.All olivines and clinopyroxenes measured have LREE‐depleted patterns with little variation in REE abundances, despite large differences in their major element compositions from ureilite to ureilite. Furthermore, we searched for but did not find any minor mineral phases that carry LREEs. The only exception is one Ti‐rich area (∼20μm) in Lewis Cliff (LEW) 85400 with a major element composition similar to that of titanite; REE abundances in this area are high, ranging from La ≅ 400 × CI to Lu ≅ 40 × CI. In contrast, all ion microprobe analyses of C‐rich matrix in Kenna, Goalpara, and Novo Urei revealed large LREE enrichments. In addition, C‐rich matrix areas in the three polymict ureilites, Elephant Moraine (EET) 83309, EET 87720, and North Haig, which have less pronounced V‐shaped whole‐rock REE patterns, show smaller but distinct LREE‐enrichments. The C‐rich matrix in Antarctic ureilites tends to have much lower LREE concentrations than the matrix in non‐Antarctic ureilites. There is no obvious association of the LREEs with other major or minor elements in the C‐rich areas. Ion images further show that the LREE enrichments are homogeneously distributed on a microscale in most C‐rich matrix areas of Kenna, Goalpara, and Novo Urei. These observations suggest that the LREEs in ureilites most probably are absorbed on the surface of fine‐grained amorphous graphite in the C‐rich matrix. It is unlikely that the LREE enrichments are due to shock melts or are the products of metasomatism on the ureilite parent body. We favor LREE introduction by terrestrial contamination.

The geochemistry of rare earth elements (REEs) was studied in rock samples from host formations, ore samples from two mineral deposits (the Hetaoping Cu-Pb-Zn mine: HTP and the Heiyanao Fe-Cu-Pb-Zn mine: HYA) and the overlying or nearby soils to better understand REE concentrations, distributions and behaviour during weathering from different parent materials at the regional scale, Baoshan area, Yunnan Province, SW China. The mudstone and sandstone formations have the highest total REE (ΣREE) contents. Chondrite-normalized diagrams for rocks and ores show significant light REEs (LREEs) enrichments and Eu depletion (except for ores in HYA). Cerium displays an obvious negative anomaly in carbonate rocks (Є-3-R, C-R, D-R, T-1-R and T-2-R). Soils overlying carbonate rock formations (T-1-S, C-S and Є-3-S) have the highest ΣREE contents, while soils overlying basalts have the lowest ΣREE contents. Soils show enrichments in LREEs with negative Eu anomalies and slight Ce anomalies in the studied soils. Soils with high ∑LREE/∑heavy REE (HREE) values may result from the preferential absorption of LREEs by organic matter. Negative Eu anomalies in soils occur for parent materials in the study area lacking feldspar, especially soils developed from carbonates. Compared to the parent materials, most soils show REE enrichment because alkali metals are removed and REEs are concentrated by low mobility in surficial processes and positive Ce anomalies because of weathering dissolution of other trivalent REEs with ionic radii similar to that of Ca 2+ . Supplementary material: Additional data (Tables S1 and S2) and sample locations (Fig. S1) are available at https://doi.org/10.6084/m9.figshare.c.5303140

Advanced characterization of hydrothermal flows within recharge and discharge areas using rare earth elements, proved through a case study of two-phase reservoir geothermal field, in Southern Bandung, West Java, Indonesia

Modem marine authigenic carbonates, barytes and phosphates incorporate seawater rare earth element (REE) patterns, which display an enrichment in heavy REE and a pronounced relative depletion in cerium (a negative cerium anomaly). The Ce anomaly relates to the decrease in solubility which accompanies the oxidation of Ce(III) to Ce(IV), while the size of the Ce anomaly may correlate with the oxidation potential, age (German and Elderfield, 1990), pH (Tricca et al., 1997) and/or depth of a water body (Piepgras and Jacobsen, 1992). Several authors have attempted to use Ce anomaly to proxy ocean anoxia through time by measuring REE concentrations in authigenic minerals. However, all such studies have run against apparently irreconcilable problems of early diagenetic alteration. Although, late diagenetic alteration of REE distributions is considered uncommon in carbonates (Banner et al., 1988) due to the high fluid/rock ratios required, recycling of REE and reduced forms of Fe, Mn and Ce related to organic decay may reset Ce anomalies in authigenic minerals during early diagenesis. Elderfield and Pagett (1986) reported that although apatitic icthyoliths in marine sediments retained superficially similar REE patterns to seawater, those deposited in 'shallow, nearshore, anoxic sediments underlying high productivity environments' recorded positive Ce anomalies, while those from 'cores of deep ocean sediment undergoing oxic diagenesis' exhibited negative Ce anomalies. Presumably, all these icthyoliths possessed original ly a seawater derived Ce anomaly. The authors conclude that authigenic minerals will only preserve a negative Ce anomaly if no suboxic or anoxic diagenesis has taken place, and this appears to have become the prevailing view among marine geochemists. However, if this is true, how can we explain the preservation of marked Ce anomalies in ancient, often sulphidic sediments and robust stratigraphic trends (data herein). It appears that these 'exceptions' have managed to retain a seawater Ce anomaly despite the ubiquitously anoxic or suboxic nature of shallow marine diagenesis. We report Ce anomaly and REE data for two s e p a r a t e s e d i m e n t a r y s e c t i o n s f rom the Neoproterozoic (Tsagaan Gol, W Mongolia) and the early Cambrian (Meishucun, Yunnan, S China). For Tsagaan Gol, calcite was measured from >95% pure limestones and for Meishucun, we measured carbonate fluorapatite from dolomitic phosphorites. Both studies reveal robust stratigraphic trends in Ce anomaly. Unlike the Elderfield and Pagett study, pronounced Ce anomalies were found in samples deposited in shallow waters, whereas those from laminated, more organic rich (also Fe, Mn, REE rich), deeper water samples showed little fractionation among the light REE. Instead of concluding that diagenesis was oxic in shallow waters and anoxic in deeper waters, we interpret this relation as suggesting the existence of redox stratification in late Precambrian/Cambrian seawater. In the case of Tsagaan Gol, that the REE, Fe and Mn are really contained within the calcite phase has been confirmed by sequential leaching procedures using K6nigswasser, HNO3, HC1, acetic acid and alpha-hiba reagent buffered to a pH of 4.5, which reveal no change in Ce anomaly of the leachate. Initial results of this work are published in Shields et al. (1997). In this presentation, we describe a second more detailed data set from Tsagaan Gol, which although based on unrelated samples from a second sampling excursion shows the same features as the first. We argue that correlation of Ce anomaly with other primary parameters implies that trends in Ce anomaly in this study reflect changes in seawater chemistry: 1. Preservation of primary Sr isotope ratios, and Sr contents up to 3000 ppm in these samples confirm that the diagenetic system was closed to isotopic

Rare earth element geochemistry of laminated diatom mats from tropical West Pacific: Evidence for more reducing bottomwaters and higher primary productivity during the Last Glacial Maximum

Recent increases in the demand for rare earth elements (REE) have contributed to various countries' interest in exploration of their REE deposits, including within Canada. Current limited knowledge of REE distribution in undisturbed subarctic environments and their bioaccumulation within northern species is addressed through a collaborative community-based environmental monitoring program in Nunavik (Quebec, Canada). This study provides background REE values (lanthanides + yttrium) and investigates REE anomalies (i.e., deviations from standard pattern) across terrestrial, freshwater, and marine ecosystems in an area where a REE mining project is in development. Results are characteristic of a biodilution of REE, with the highest mean total REE concentrations (ΣREE) reported in sediments (102 nmol/g) and low trophic level organisms (i.e., biofilm, macroalgae, macroinvertebrates, common mussels, and reindeer lichens; 101–102 nmol/g), and the lowest mean concentrations in higher-level consumers (i.e., goose, ptarmigan, char, whitefish, cod, sculpin and seal; 10−2 - 101 nmol/g). The animal tissues are of importance to northern villages and analyses demonstrate a species-specific bioaccumulation of REE, with mean concentrations up to 40 times greater in liver compared to muscle, with bones and kidneys presenting intermediate concentrations and the lowest in blubber. Further, a tissue-specific fractionation was presented, with significant light REE (LREE) enrichment compared to heavy REE (HREE) in consumer livers (LREE/HREE ≅ 101) and the most pronounced negative cerium (Ce) anomalies (<0.80) in liver and bones of fish species. These fractionation patterns, along with novel negative relationships presented between fish size (length, mass) and Ce anomalies suggest metabolic, ecological, and/or environmental influences on REE bioaccumulation and distribution within biota. Background concentration data will be useful in the establishment of REE guidelines; and the trends discussed support the use of Ce anomalies as biomarkers for REE processing in animal species, which requires further investigation to better understand their controlling factors.

Rare Earth Element (REE) patterns of plutonic rocks across the Peninsular Ranges batholith vary systematically west to east, transverse to the long axis and structural trends of the batholith. Three major parallel elongate geographic regions are each defined by distinct REE pattern types. Rocks from the western region display slight light REE enrichment, flat heavy REE, and negative Eu anomalies. An abrupt transition to rocks with middle and heavy REE fractionated and depleted REE patterns with no or positive Eu anomalies occurs in the central region of the batholith. Further to the east a second transition to strongly light REE enriched rocks some of which have positive or negative Eu anomalies occurs. Some gabbros may show divergent patterns. These large variations are observed even in similar lithologies across the three regions and notably in tonalites, the major rock type of the batholith. The slopes of the REE patterns within rocks of each region are largely independent of rock type, and no consistent variations in REE abundances and Eu anomalies with lithology are noted with the exception of some gabbros. Most of the leucogranodiorites of the western region have larger negative Eu anomalies than nearby tonalites. Granodioritic rocks of the central and eastern regions may have positive, negative, or no Eu anomalies. These results are the first report of systematic variations in REE characteristics across a granitic batholith whose geologic setting at a convergent plate boundary has been established. Some similarities and contrasts to REE variations across modern volcanic arcs are noted. Along the westernmost margin of the batholith in northern Baja California, Mexico, leucotonalitic rocks of the San Telmo pluton display essentially flat REE patterns strongly resembling those observed for near-trench volcanic rocks. The REE patterns of quartz gabbros and tonalites of the western region correspond closely to those of circum-Pacific high-alumina basalts. The heavy REE depleted and fractionated patterns observed in the rocks of the central and eastern regions of the batholith do not have counterparts in oceanic island volcanic arcs, and few counterparts in continental margin volcanic arcs. The REE variations generally correlate with other transverse asymmetries in major petrologic and geochemical characteristics. The abrupt depletion and fractionation in the middle to heavy REE and elimination of negative Eu anomalies appear coupled to an increase in Sr concentration and a marked restriction in lithologic diversity. This transition occurs over a range of initial 87Sr/86Sr ratios. The light REE enriched rocks of the eastern region are distinguished from the central and western regions by higher initial ratios. Geographic discontinuities in δ18O and age distributions in the batholith correlate approximately with the REE discontinuities, but locally diverge by the dimensions of one or two plutons. Determinations of REE abundances in major and trace phases of a representative eastern region granodiorite indicate accessory sphene and allanite are the major reservoirs of REE in this rock. Hornblende is the only significant REE site in the major minerals, and in some batholithic lithologies it may be the dominant site. High-level crystal fractionations involving hornblende and accessory phases do not appear capable of producing the observed geographic characteristics. Contamination processes including upper crustal material also seem ruled out. The REE and other geochemical variations across the batholith appear to originate in deep-seated sources. Partial melting in source rocks in which assemblages rich in plagioclase give way laterally to garnet-bearing assemblages in source regions of broadly basaltic composition which are already zoned in light REE abundances, 87Sr/86Sr, δ18O, and possibly Sr content appears to account for most of the observed features. The geologic context of the source material remains largely undefined and may include mantle and crustal components. However, the source regions for all parts of the batholith must have bulk compositions and phase assemblages capable of producing the dominant tonalite and low-K2O granodiorite lithologies. This major constraint appears to strongly limit the amount of sialic crustal material permitted to be present in the source regions. The geometry of the convergent boundary appears to have determined the elongate form of the batholith, and, probably, the general alignment of all the geochemical variations along its length. The results of this study may be useful in comparing possibly related crust-forming processes and products in other orogenic-plutonic terrains.

With the increasing release of rare earth elements (REE) into the environment due to their use in decarbonizing energy technologies, medicine, agriculture, and other sectors, understanding their distribution and behaviour in soil-plant systems is becoming increasingly important. This need is especially pronounced in coastal vegetated ecosystems, where studies on REE are still limited. In this study, we employed sequential extractions to better understand the soil-to-plant transfer and fractionation of REE in seagrass meadows under varying environmental conditions. Soil samples were collected from 9 seagrass meadows located near reefs, sandy beaches, and mangroves in Todos os Santos Bay, Northeastern Brazil. As expected, the highest concentrations of REE were found in the residual fraction (51-82% of the total), followed by the carbonate (15-47%) and organic matter (1-16%) fractions. The oxyhydroxide Fe-Mn (1-7%) and easily soluble and ion-exchangeable fractions (0.02-0.2%) had the lowest percentages. PAAS normalization for the residual fraction from soils of seagrass near mangroves and sandy beaches showed little fractionation, with enrichment in light REE (LREE) and medium REE (MREE). In contrast, soils near reefs showed enrichment towards the heavy REE (HREE). In the carbonate fraction, soils of seagrass near reefs showed a flat pattern, while mangroves and sandy beaches soils showed an enrichment in LREE and MREE. PAAS normalization in organic matter and oxy-hydroxide Fe-Mn fractions, showed enrichment in LREE, MREE, and Tm, except for soils from seagrasses near reefs, which showed enrichment in MREE and HREE in oxy-hydroxide Fe-Mn fraction. Soils showed enrichment in HREE in the easily soluble and ion-exchangeable fractions. The strong association between REE and carbonates in soils near sandy beaches facilitates REE transfer from soil to plants, explaining the higher bioaccumulation of REEs in seagrasses in these environments. The relative importance the geochemical phases varied according to environmental conditions. Our study demonstrates that REE speciation in soils, rather than total concentration, governs REE bioaccumulation in seagrasses.