Rare Earth Elements And Yttrium Research Articles

The tremendous potential of deep-sea mud as a source of rare-earth elements

Potential risks of supply shortages for critical metals including rare-earth elements and yttrium (REY) have spurred great interest in commercial mining of deep-sea mineral resources. Deep-sea mud containing over 5,000 ppm total REY content was discovered in the western North Pacific Ocean near Minamitorishima Island, Japan, in 2013. This REY-rich mud has great potential as a rare-earth metal resource because of the enormous amount available and its advantageous mineralogical features. Here, we estimated the resource amount in REY-rich mud with Geographical Information System software and established a mineral processing procedure to greatly enhance its economic value. The resource amount was estimated to be 1.2 Mt of rare-earth oxide for the most promising area (105 km2 × 0–10 mbsf), which accounts for 62, 47, 32, and 56 years of annual global demand for Y, Eu, Tb, and Dy, respectively. Moreover, using a hydrocyclone separator enabled us to recover selectively biogenic calcium phosphate grains, which have high REY content (up to 22,000 ppm) and constitute the coarser domain in the grain-size distribution. The enormous resource amount and the effectiveness of the mineral processing are strong indicators that this new REY resource could be exploited in the near future.

Evaluation of trace elements in U.S. coals using the USGS COALQUAL database version 3.0. Part I: Rare earth elements and yttrium (REY)

Coal is a potential source of valuable elements such as rare earth elements and yttrium (REY). In this work, REY concentrations in U.S. domestic coals were evaluated using data from the USGS COALQUAL Database Version 3.0. The database contains a total of 7657 non-weathered, full-bed coal samples. The number of samples containing REY data points varies among elements. Assessment of data quality indicates that some of the REY data are semi-quantitative and should be used with caution. Different analytical instruments and methods with varying accuracies and precisions are thought to be the main sources of errors. Inclusion of qualified data also accounts for the sawtooth pattern of the UCC-normalized REY distribution. A new set of Q factor values was thus proposed to adjust qualified data. Consequently, mean concentrations of REY in U.S. coals were obtained with a total REY concentration of 65.5 ppm on a moisture-free whole coal basis. Further evaluation of REY in 5378 selected coal samples indicates that about 9–13% of the samples fall into the combined category of promising and highly promising coals for REY, according to the classification of Dai et al. (2017). Taking sampling bias into consideration, we further found that bituminous coal, particularly from the central Appalachian region, has the highest probability of being a source for beneficial recovery of REY. More specifically, bituminous coal from eastern Kentucky is likely to be the best option. Finally, we conclude that U.S. domestic coal is a promising, alternative source for beneficial recovery of REY to meet the U.S. REY demand for economic growth.

Distribution of major and trace elements in the bolete mushroom Suillus luteus and the bioavailability of rare earth elements

Fungi are eukaryotic organisms within the kingdom Fungi. They are classified as macrofungi when they produce, usually above-ground, fruit bodies which are often simply referred to as “mushrooms”. Since many species are edible, numerous studies discuss major elements and the accumulation of toxic and radioactive elements. Rare earth elements are economically important metals which are increasingly used for high-technology applications like renewable energies and state-of-the-art electronic devices. Although the significantly increasing anthropogenic input into the environment may affect living organisms, available data on the concentration, distribution and uptake of rare earth elements and yttrium (REY) by fungi are limited and often ambiguous.Here, we present trace element and REY concentrations for the fungus species Suillus luteus and the distribution of major and trace elements between the different compartments of individual fruit bodies separated into cuticle, flesh of cap, tubes & pores, and stipe. Our results show that P, K, Zn, Rb and Cs are the only elements enriched in fruit bodies relative to soil. All elements are unevenly distributed within the fruit bodies and the parts comprising the cap generally contain higher concentrations of trace elements than the stipes. The total REY concentrations in the individual mushroom parts range from 13.1 μg kg−1 in dry matter (DM) to 72.6 μg kg−1 DM, whereas concentrations in the whole mushrooms are 13.4 to 74.2 μg kg−1 DM. The highest of the generally rather low REY concentrations are shown by the cuticles. All mushroom parts have the same rather flat shale-normalized REY patterns very similar to those of ambient soil, but show positive Y anomalies in all and positive La anomalies in most samples. The cuticles and the whole fruit bodies show a slight depletion of light relative to heavy REY (LREY and HREY, resp.), while flesh, tubes & pores and the stipe exhibit no or a small enrichment of LREY relative to HREY. The fractionation between LREY and MREY is only small, whereas the fractionation between MREY and HREY is more pronounced. Soil leaching experiments with the siderophore desferrioxamine B suggest that although Suillus luteus produces siderophores which are important ligands for REY complexation, such hydroxamate siderophores do not significantly affect REY mobilization and transport to the mushrooms. The close similarity of the REY distribution in the fruit bodies of Suillus luteus and ambient soil and the lack of significant fractionation suggest that fungi may have the potential to be developed into bioarchives for tracers used in geochemical exploration.

Mineralogical and Geochemical Compositions of the Lopingian Coals in the Zhongliangshan Coalfield, Southwestern China

The mineralogical and geochemical compositions of the Lopingian coals from an exploratory drill core (ZK4-1) in the Zhongliangshan Coalfield, southwestern China are reported in this paper. The Zhongliangshan coals are medium volatile bituminous in rank (random vitrinite reflectance, average 1.38%), characterized by a medium-ash yield (26.84%) and high sulfur content (3.38%). Minerals in the Zhongliangshan coals are mainly composed of clay assemblages (kaolinite, the illite/smectite mixed layer (I/S) and chamosite), pyrite, quartz, carbonate minerals (calcite, marcasite, ankerite, and dolomite), and anatase, followed by rutile, jarosite, natrojarosite, bassanite, gypsum and K-feldspar, with traces of apatite, rhabdophane and barite. Compared with the average concentrations of the world hard coals, some trace elements including Li, V, Co, Cu, Se, Y, Zr, Nb, rare earth elements (REE), Cd, Ta, Hf and Hg, are enriched in the Zhongliangshan coals. The modes of occurrence of chamosite, barite, rhabdophane, quartz and calcite in the Zhongliangshan coals indicate that the coals have probably been affected by the injection of low-temperature hydrothermal fluids. Based on the concentrations of Sc, V, Cr, Co, Ni, Cu and Zn, the ratios of Al2O3/TiO2 and the upper continental crust-normalized rare earth element and yttrium (REY) distribution patterns of the Zhongliangshan coals, the dominant sediment source regions are the Leshan–Longnvsi Uplift, Hannan Upland, and Dabashan Uplift, with a small proportion of terrigenous materials from the Kangdian Upland. The K7 and the upper portion of K1 coals have the potential as raw materials for the recovery of REY.

Petrology, mineralogy and geochemistry of the Lower Cretaceous oil-prone coal and host rocks from the Laoheishan Basin, northeast China

The coal and host rocks (mainly oil shale partings) in the Laoheishan basin (NE China) are oil-prone. This study uses petrological, mineralogical and geochemical analyses to determine the reasons of high oil yield in the coal, and the origin and modes of occurrence of the minerals and elements in the coal and oil shale partings. The obtained data show that this sub-bituminous B coal has higher oil yield (av. 10%) than oil shale partings (av. 5.7%), consistent with a higher hydrogen content in the coal. This oil-prone coal has potential for comprehensive utilization due to the relatively high gross calorific value (av. 17.23 MJ/kg) in the semi-coke. The maceral composition suggests that the relatively high hydrogen content in the coal is mainly caused by higher resinite content. Palynological analysis of coal and oil shale partings mainly proved the presence of gymnosperms and ferns, revealing that the paleovegetation is dominated by lygodiacean-/osmundacean ground ferns and cupressaceaen/taxodiaceaen canopy trees, these canopy trees would have provided abundant hydrogen rich components (e.g. resin) to the paleomire. All the identified sporopollen suggests a warm-humid subtropical paleoclimate.Minerals in the coal include kaolinite, quartz, illite (and/or illite/smectite), chlorite, feldspar, calcite, and traces of pyrite, rutile and zircon, similar to the oil shale partings. Most of the minerals (quartz, feldspar, clay minerals, rutile and zircon) occur in layers within detrovitrinite and probably are of detrital origin. Pyrite and calcite are of epigenetic origin and probably derived from hydrothermal fluids. Compared with average Chinese coal, the Laoheishan coal is enriched in Zr, Nb, In and Sb. Zirconium and Nb mainly occur in zircon. Indium is both organically and inorganically associated, whereas antimony largely occurs in pyrite. REY (rare earth elements and yttrium) distribution patterns of coals and oil shale partings are dominated by Heavy-REY enrichment, whereas roof and floor samples are Medium-REY enriched. The M-HREY enrichment is probably caused by low-temperature hydrothermal fluids. The sedimentary input is the major controlling factor of geochemical patterns in coal and host rocks. The source rocks are probably felsic-intermediate igneous rocks from the surrounding basement, as indicated by relatively high Al2O3/TiO2 ratios (7–38), cross-plot between Zr/Ti and Nb/Y, negative Eu anomalies (0.28–0.96), the presence of K-feldspar and plagioclase, and lithic fragment types (such as granite and andesite) in the samples. In addition, source rocks of sediments have caused high Zr and Nb concentrations in the coal.

Fast Determination of Yttrium and Rare Earth Elements in Seawater by Inductively Coupled Plasma-Mass Spectrometry after Online Flow Injection Pretreatment.

A method for daily monitoring of yttrium and rare earth elements (YREEs) in seawater using a cheap flow injection system online coupled to inductively coupled plasma-mass spectrometry is reported. Toyopearl AF Chelate 650M® resin permits separation and concentration of YREEs using a simple external calibration. A running cycle consumed 6 mL sample and took 5.3 min, providing a throughput of 11 samples per hour. Linear ranges were up to 200 ng kg−1 except Tm (100 ng kg−1). The precision of the method was <6% (RSDs, n = 5), and recoveries ranged from 93% to 106%. Limits of detection (LODs) were in the range 0.002 ng kg−1 (Tm) to 0.078 ng kg−1 (Ce). Good agreement between YREEs concentrations in CASS-4 and SLEW-3 obtained in this work and results from other studies was observed. The proposed method was applied to the determination of YREEs in seawater from the Jiulong River Estuary and the Taiwan Strait.

Extraction and separation of rare earth elements from hydrothermal metalliferous sediments

Rare earth elements (REE) can be efficiently extracted from umbers, ferromanganese metalliferous sediments of the Troodos ophiolite (Cyprus) by simple leaching and selective precipitation, without accumulation of radioactive by-products. Umbers are dominantly composed of amorphous Fe and Mn oxides with minor goethite, quartz and zeolites, and contain 350–500 mg kg−1 of rare earth elements and yttrium (REY), 200 times lower than many of the major REY source ores. To compensate for relatively low grades, a cost-effective extraction process was developed that utilises a weak lixiviant concentration (0.1–1.5 N) and short reaction times (5 min to 11 h). Acid solutions recover 70–85% of the initial sample REY content even at 20 °C. By contrast, extraction using ionic solutions of NaCl and ammonium sulphate proved ineffective. Acid recoveries of REY increase by nearly 10% at 70 °C and the use of different acids (HCl, HNO3, H2SO4) yields comparable results. The main impurities in the leachate include Ca and Na at even the weakest acid concentration (0.1 N). However, two-step leaching method greatly reduces concentrations of impurities in the REY-rich liquor, although with REY losses approaching 20%. Purification of the leach liquor via selective precipitation of REY as an oxalate is highly efficient although pH dependent. With maximum REY precipitation (96–99%) occurring between pH 1 and 2, the precise adjustment of pH allows separation of REY from other precipitating impurities (Ca). The maximum purity of the precipitate is achieved at pH 1.1 (>65%). Strong and consistent fractionation along the lanthanide series observed during the precipitation experiments has been successfully explained using a speciation modelling software (PHREEQC). The uptake of REY by oxalate in the experiments closely follows the bell-shape distribution of REY-oxalate solid complexes stability constant (−log β (RE2Ox3·nH2O)) replicating the fractionation trends observed at pH < 1.1. In addition, the modelling demonstrates that at equivalent REE concentration in solution, oxalate precipitates fractionate REY in the following order: middle REE > light REE ≫ heavy REE. This ordering and the variable degrees of uptake reflects the interplay of aqueous REY-oxalate complexes (log HOxβ1, Oxβ1 and Oxβ2) with the natural fractionation induced by solid REY-oxalate stability constant distribution. Overall, the combined leaching process and selective oxalate precipitation produces a total enrichment factor ranging between 1400 and 2400 for REY from the sample to the oxalate precipitate in a simple two-step process forming a high-purity end-product of mixed REY.

The European Shale: An improved data set for normalisation of rare earth element and yttrium concentrations in environmental and biological samples from Europe

The distribution of the Rare Earths and Yttrium (REY) in shale is considered representative of that of average Post-Archean upper continental crust regardless of the shale's origin. Hence, shale is commonly used to normalise the REY concentrations of vastly different sample types ranging from chemical sediments and seawater to atmospheric dust and river water, and, in particular, environmental and biological samples. However, discussions with non-specialists such as journalists, decision makers in industry and politics, and the general public are often hampered by their serious doubts that normalisation to Australian or North-American shales produces meaningful results for samples from Europe. Hence, we present REY data for aliquots of the same European Shale composite that had originally been prepared and studied in the mid-1930s by E. Minami under supervision of V.M. Goldschmidt and that is well-established in the geoscience literature. We determined REY concentrations by different methods of sample preparation (acid-pressure digestion and laser-induced flux-free fusion) and analysis (solution ICP-MS and LA-ICP-MS on glass beads) with excellent precision and accuracy. This improved and complete REY data set (Y: 31.9, La: 44.3, Ce: 88.5, Pr: 10.6, Nd: 39.5, Sm: 7.30, Eu: 1.48, Gd: 6.34, Tb: 0.944, Dy: 5.86, Ho: 1.17, Er: 3.43, Tm: 0.492, Yb: 3.26, Lu: 0.485; all concentrations in mg kg−1) is recommended for shale-normalisation of natural materials that originate from Europe. This will simplify discussions with media and broader public, for example when reporting on REY as emerging microcontaminants. Examples given include coastal seawater (North Sea), river water (Rhine River), tap water, waste water treatment plant effluent, marine and freshwater mussel shells, and mushrooms.

Use of trace and rare earth elements to quantify autogenic and allogenic inputs within a lowland karst network

Trace element geochemistry of natural waters has emerged as an important strategy for tracing anthropogenic sources, water mixing, and physicochemical parameters such as redox conditions. In this study, ultra-trace element water geochemistry, with emphasis on the rare earth elements and yttrium (REY), was tested as a tool to fingerprint groundwater origin and pathways within a lowland karst aquifer network. The study area is well-defined from a hydrological perspective and provides an excellent natural system to investigate geochemical characteristics of allogenic and autogenic water mixing within a karst network. The new geochemical data have yielded refined insight into the temporal fluxes of water at different hydrological times of the year and, in particular, proved important for quantifying contributions of autogenic and allogenic runoff to the ephemeral karst lakes (known as turloughs) which emerge after surcharge of the karst conduit network following periods of high flows. Endmember definitions of the allogenic waters derived from rivers draining a catchment of predominantly Devonian Old Red sandstone vs. autogenic waters derived from limestone in contact within the karst network were established from REY pattern slope (Pr/Yb), Y/Ho ratio, and a number of other ratios generated from contrasting enrichments of high-solubility/low-particle reactivity elements that exhibited conservative or near-conservative behaviour (e.g,. Sr, Ba, Li, U, Mo). Under high-flow conditions, waters within the surcharged conduit network fall on mixing lines between the endmembers, and these relationships can be used to quantify the relative contribution of each water source in the conduit network. In contrast, under low-flow conditions the endmembers could still be defined but the geochemical mixing relationships in the aquifer network appear to have been complicated by enhanced particle reactivity in soil reservoirs prior to both autogenic and allogenic recharge. In addition, we show that seawater influx into the karst network influenced the mixed conduit geochemistry under lower flow conditions.

Induced rare earth element fractionation in brines by hydraulic fracturing of their aquifer rocks

Stimulation of rocks deteriorates the equilibrium distribution of rare earth elements and yttrium (REY) between solids and brines. By stimulation of the Permian, Lower Rotliegend formations in the well Groß Schönebeck 3/90 the volcanites are less affected by stimulation than the overlying conglomerate and sandstones. Brines from different lithological sections differ in REY patterns and gain anomalies of Eu, Gd, and Y during processes of recrystallization. The initially small anomalies increase during stimulation but decrease with both ongoing pumping and recrystallization. The REY patterns and their Eu, Gd, Y anomalies of brines from the conglomerate and volcanites distinctively differ from those of the sandstones. The Gd and Y anomalies are strongly correlated and both increase in sandstones with distance from the underlying conglomerate and volcanite. The correlation plot of Gd and Y anomalies does not describe a mixing line between brines from the volcanite and conglomerate but it reveals the extent of recrystallization of rapid precipitations and growth of minerals immediately after the stimulation and the slow re-equilibration of REY between solids and brines in each section of rocks. Extreme recrystallization occurred within the conglomerates, the least ones in the volcanite. REY patterns with their characteristic Eu, Gd, and Y anomalies are reliable indicators of the source of brines after stimulation. The time-dependence of changes of Eu, Gd and Y anomalies reflect the process of recrystallization.

Distribution of rare-earth elements and yttrium in hydrothermal sedimentary ferromanganese crusts of the Sea of Japan (from phase analysis results)

We have first determined the contents of rare-earth elements and yttrium (REY) in four major mineral fractions of hydrothermal sedimentary ferromanganese crusts of the Sea of Japan. It is shown that REY are sorbed mostly by Fe oxyhydroxides (FeOOH). The REY content in the residual aluminosilicate fraction is the second most important factor determining the crust composition. The manganese fractions, composing more than 80 vol.% of the crusts, plays a subordinate role in REY accumulation. The REY pattern of hydrothermal sedimentary crusts in back-arc basins depicts the sum of the REY contents of the FeOOH fraction (hydrogenous) and residual fractions containing the total REY of the products of bedrock disintegration and endogenous (pyroclastic material) and exogenous (desert dust) components.

Sources and distribution of yttrium and rare earth elements in surface sediments from Tagus estuary, Portugal

The distribution and sources of yttrium and rare-earth elements (YREE) in surface sediments were studied on 78 samples collected in the Tagus estuary (SW Portugal, SW Europe). Yttrium and total REE contents ranged from 2.4 to 32mg·kg−1 and 18 to 210mg·kg−1, respectively, and exhibited significant correlations with sediment grain-size, Al, Fe, Mg and Mn, suggesting a preferential association to fine-grained material (e.g. aluminosilicates but also Al hydroxides and Fe oxyhydroxides). The PAAS (Post-Archean Australian Shale) normalized patterns display three distinct YREE fractionation pattern groups along the Tagus estuary: a first group, characterized by medium to coarse-grained material, a depleted and almost flat PAAS-normalized pattern, with a positive anomaly of Eu, representing one of the lithogenic components; a second group, characterized mainly by fine-grained sediment, with higher shale-normalized ratios and an enrichment of LREE relative to HREE, associated with waste water treatment plant (WWTP) outfalls, located in the northern margin; and, a third group, of fine-grained material, marked by a significant enrichment of Y, a depletion of Ce and an enrichment of HREE over LREE, located near an inactive chemical-industrial complex (e.g. pyrite roast plant, chemical and phosphorous fertilizer industries), in the southern margin. The data allow the quantification of the YREE contents and its spatial distribution in the surface sediments of the Tagus estuary, identifying the main potential sources and confirming the use of rare earth elements as tracers of anthropogenic activities in highly hydrodynamic estuaries.

The Chemical Composition of the Nitrogen Thermal Waters of the Khoja-Obi-Garm (Tajikistan) Balneoclimatic Resort

This paper presents new data on the contents of macro- and microcomponents from low-mineral nitrogen thermal water located within the Khoja-Obi-Garm resort (Tajikistan). It was found that these thermal groundwaters contain high contents of F, Si, Li, Al, Rb, Sr, and Cs. Detailed study of the geological and hydrogeological settings of the resort, along with thermodynamic simulations allows us reveal the sources of chemical elements in these waters. A comparison of thermal groundwater from Khoja-Obi-Garm spa with the thermal waters of other regions of Eurasia was carried out; new data on the rare-earth elements and yttrium (REY) concentrations in the studied thermal water are presented as well.

Geochemistry, U-Pb zircon geochronology and Sm-Nd isotopes of the Xincai banded iron formation in the southern margin of the North China Craton: Implications on Neoarchean seawater compositions and solute sources

Banded iron formations (BIFs) that are distal from submarine volcanic activity and generally lack direct relationships with volcanic rocks have been extensively used as proxies to infer the chemical composition of ancient seawater and trace the effects of continental weathering at the time of their deposition. Here, we discuss the major and trace elements and Sm-Nd isotopic geochemistry of the poorly-studied Xincai BIF, located west of the Superior-type Huoqiu BIF along a NW-SE trending supracrustal belt in the southern margin of the North China Craton, to understand the compositions and solute sources of seawater during the Xincai BIF precipitation. U-Pb zircon dating of granitic intrusive rock and biotite schist interlayer of the BIF constrains the depositional age of the Xincai BIF to 2.5–2.7 Ga for the first time, indicating that the Xincai BIF could be part of the Huoqiu BIF or consist of contemporaneous sediments formed in a similar tectonic-depositional environment. Shale-normalized rare earth element and yttrium (REY) patterns of the bulk and individual band samples display features that are characteristic of other Archean BIFs with light REE depletion relative to heavy REE, positive LaSN, GdSN and YSN anomalies, indicative of pure chemical sedimentation. The marine origin of these samples is further supported by their super-chondritic Y/Ho ratios (average Y/Ho = 47). The very low Al, Ti and high field strength element contents of the Xincai BIF indicate an essentially detritus-free component. The bulk BIF samples show a narrow range of εNd(t) values from −1.5 to +1.0, and most of the samples have negative εNd(t) values, −0.3 on average, which is different from Archean BIFs with mantle-derived depleted Nd isotopes. Deviations toward negative εNd(t) values of the iron bands (−0.5 to −0.1) and the silica bands (−4.7 to −0.5) further indicate a continental Nd contribution. In addition, positive EuSN anomalies that were found in all of the bulk and individual band samples indicate that a high-T hydrothermal input also contributed to their REY signatures. It is considered that both high-T hydrothermal fluids and ambient seawater with solutes from erosion and weathering of a nearby landmass can provide their REY signatures.

The chemical composition of the nitrogen thermal waters of the balneoclimatic of Khoja-Obi-Garm Spa (Tajikistan)

The paper presents new data on contents of major and micro components from low TDS nitrogen thermal water located within Khoja-Obi-Garm spa (Tajikistan). It was found that these thermal groundwaters contain high contents of the following components: F, Si, Li, Al, Rb, Sr, Cs. Detailed study of the geological and hydrogeological settings of the spa together with thermodynamic simulations allows us reveal sources of chemical elements into these waters. It was carried out the comparison of thermal groundwater from Khoja-Obi-Garm spa with the thermal waters of other regions of Eurasia, also new data on the rare earth elements and yttrium (REY) concentrations in studied thermal water are presented.

Distribution of Trace Elements in Fractions after Micronization and Density-Gradient Centrifugation of High-Ge Coals from the Wulantuga and Lincang Ge Ore Deposits in China

The Wulantuga (Inner Mongolia) and Lincang (Yunnan Province) germanium ore deposits in China are both considered world-class, coal-hosted Ge deposits. For this paper, two bench coals (WLTG C6-2 from Wulantuga and LC S3-6 from Lincang) were selected to characterize the associations between density fractions (maceral concentrates) and trace elements using micronization, density-gradient centrifugation (DGC), and inductively coupled plasma mass spectrometry (ICP-MS), especially for the abnormally enriched trace elements (including Ge, W, As, Sb, Be, U, and Nb) and rare earth elements and yttrium (REY) in the Wulantuga and/or Lincang high-Ge coals that are widely considered to have varying degrees of organic affinity. Huminite and inertinite contents of WLTG C6-2 account for 58.4% and 40.7%, respectively, whereas LC S3-6 is dominated by huminite (98.7%). Lower peak densities for huminite/inertinite and Gaussian distributions of DGC profiles after HCl-HF demineralization suggest that some minerals still exist ...

Assessing the chemical behavior and spatial distribution of yttrium and rare earth elements (YREEs) in a coastal aquifer adjacent to the Urmia Hypersaline Lake, NW Iran.

This study aims to shed light on the seasonal behavior of yttrium and rare earth elements (YREEs) in the Urmia Aquifer (UA), in the immediate vicinity of Urmia Lake (UL) in Iran. Samples of groundwater, collected under dry and wet conditions in coastal wells of UA, suggest a large degree of variability in both YREE abundance and normalized patterns. Although weathering or water-rock interactions (between the surface/groundwater and rock samples) were predicted to be the most probable source in explaining YREEs in groundwater samples, results to the contrary indicate that the groundwater do not inherit aquifer rock-like YREE signatures in the study area; this might be due to the relative stability of YREEs during the process of water-rock interactions, which suggest that methods based on YREEs can be beneficial in discrimination of water sources. Furthermore, findings demonstrated no significant relationship between Ce/Ce* and salinity (0.08 and 0.05 in wet and dry seasons, respectively), and between Eu/Eu* and salinity (0.1 and -0.04 in wet and dry seasons, respectively). Dissimilarity of patterns of YREEs in rock and water samples reveals YREEs as no conservative tracers in determining the UL saltwater intrusion into coastal groundwater. Therefore, the groundwater YREE concentrations and fractionation patterns in UA warrant controlling by coastal aquifer need to be controlled by other chemical weathering, adsorption, desorption, and solution complexation reactions. Finally, comparison of REE concentration values in groundwater samples with corresponding indicative admissible drinking water concentrations (IAC) demonstrated their suitability for drinking purposes.

Deciphering the diagenetic alteration degree in thrombolites across the Permian-Triassic boundary and the evaluation of REY as a proxy of palaeoseawater

The thrombolites across the Permian-Triassic boundary (PTB) are widely distributed in South China. In order to examine the utility of rare earth element and yttrium (REY) in the thrombolites as a proxy of palaeoseawater, the petrographic and geochemical (Sr, Mn, Fe, REY, δ13C, δ18O) features of thrombolites from Cili and Taiping sections are comparatively studied to determine the diagenetic alteration degrees of the thrombolites and the impact of diagenesis on REY concentrations and distribution patterns. The thrombolites from Cili section, digitate in mesoscopic morphology, are latest Permian in age. In contrast, most of the thrombolites in Taiping section are mottled and formed in the earliest Triassic. The variation in thrombolite morphology across the PTB is probably related to increasing amount of metazoan and increasing intensity of bioturbation after the end-Permian mass extinction. Compared to the thrombolites from Taiping section, those from Cili section underwent more extensive diagenetic alteration, which are characterized by more dolomitic content, lower Sr concentrations, more negative δ18O values, and higher Mn/Sr ratios.The REY concentrations are higher in the thrombolites from Taiping section (5–303ppm, average 48ppm) than in the thrombolites from Cili section (17–34ppm, average 25ppm). Shale-normalized REY distribution patterns of the thrombolites from both sites are similar to those of oxygenated seawater, which are characterized by positive La anomalies (Pr/Pr∗=1.1–1.5), negative Ce anomalies (Ce/Ce∗=0.2–0.9), and light rare earth element (LREE) depletion. The preserved seawater like REY distribution pattern indicates that diagenesis did not alter the REY distribution patterns. The thrombolite samples from Cili section, compared to the counterparts from Taiping, have less positive La anomaly and less negative Ce anomaly. For the thrombolites from Cili section, a positive correlation exists between Ce anomaly and siliciclastic content, suggesting contamination of Ce anomaly by terrigenous input. The results suggest that ancient thrombolites that are isolated from terrigenous inputs are better proxy candidates of palaeoseawater redox condition than thrombolites located closer to land sources.

Hafnium and neodymium isotopes and REY distribution in the truly dissolved, nanoparticulate/colloidal and suspended loads of rivers in the Amazon Basin, Brazil

Radiogenic isotopes in river sediments and river waters have been widely used in provenance studies, as these samples naturally integrate the geology/chemistry of the entire catchment. While the Hf and Nd isotope systems are coupled during igneous processes, they are decoupled during supergene processes at the Earth’s surface, which is reflected by the isotope composition of riverine sediments. We present the first data for both Hf and Nd isotope compositions of the dissolved (0.2μm-filtrates rich in nanoparticles and colloids, NPCs) and the truly dissolved (1kDa-ultrafiltrates) load of rivers. Hafnium and Nd isotope compositions and concentrations of the Rare Earths and Yttrium (REY) and Hf were determined for suspended particles (>0.2μm) as well as for the dissolved and the truly dissolved load of the Rio Solimões, the Amazon’s largest tributary draining the Andes, and of the Rio Negro, an organic NPC- and particle-rich river draining the rainforest of northern Amazonia. We also analyzed the Nd isotope compositions of suspended sediments and 0.2μm-filtered water samples from the Amazon River and its tributaries Rio Tapajos, Rio Xingu and Rio Jari.Our novel results clearly show that the decoupling of the Hf and Nd isotope systems is related to incongruent weathering processes on the continent, as this decoupling can already be observed in the different Hf and Nd pools, i.e. in the particulate, the NPC-dominated dissolved and the truly dissolved load of rivers. In the Rio Negro and Rio Solimões, a strong particle size-dependent difference in Hf isotope composition is observed. Values of εHf become more radiogenic as filter poresize decreases, which can be related to the density- and size-dependent distribution of Hf-rich minerals, e.g. zircons, and their absence from the truly dissolved pool. In contrast, the Nd isotope composition of Amazonian river waters reflects that of their catchment geology. Tributaries draining the Precambrian Brazilian and Guyana shields show very unradiogenic εNd values of −19 to −25 in their dissolved load, whereas the Rio Solimões draining the Andes yields a more radiogenic εNd signal of only −7. The dissolved Nd isotope composition of the Amazon is dominated by its Andean tributaries and averages at −8. Although Nd isotope compositions are thought to not being fractionated by Earth surface processes, significant differences of 1.3–1.9 ε-units can be observed between the dissolved and suspended loads in the Amazon River and its main tributary, the Rio Solimões. In these rivers, the dissolved load is more radiogenic than the suspended sediment, which is likely due to incongruent weathering and related mineral sorting in the Andean headwaters. In contrast, the organic-rich and mineral-poor shield rivers do not show a difference between the truly dissolved, dissolved and suspended load, as the Nd in all these pools is controlled by surface- and solution-complexation and hence isotopically homogenized by continuous exchange and re-equilibration.

The evolution of the Cappadocia Geothermal Province, Anatolia (Turkey): geochemical and geochronological evidence

Cappadocia Geothermal Province (CGP), central Turkey, consists of nine individual geothermal regions controlled by active regional fault systems. This paper examines the age dating of alteration minerals and the geochemistry (trace elements and isotopes) of the alteration minerals and geothermal waters, to assess the evolution of CGP in relation to regional tectonics. Ar–Ar age data of jarosite and alunite show that the host rocks were exposed to oxidizing conditions near the Earth’s surface at about 5.30 Ma. Based on the δ18O–δD relationhip, water samples had a high altitude meteoric origin. The δ34S values of jarosite and alunite indicate that water samples from the southern part of the study area reached the surface after circulation through volcanic rocks, while northern samples had traveled to the surface after interacting with evaporates at greater depths. REY (rare earth elements and yttrium) diagrams of alteration minerals (especially illite, jarosite and alunite) from rock samples, taken from the same locations as the water samples, display a similar REY pattern to water samples. This suggests that thermal fluids, which reached the surface along a fault zone and caused the mineral alteration in the past, had similar chemical composition to the current geothermal water. The geothermal conceptual model, which defines a volcanically heated reservoir and cap rocks, suggests there are no structural drawbacks to the use of the CGP geothermal system as a resource. However, fluid is insufficient to drive the geothermal system as a result of scanty supply of meteoric water due to evaporation significantly exceeding rainfall.