Rare Earth Element Compositions Research Articles

Genesis of a Ag-Pb-Zn-F system: Insights from in situ sulfur isotope and trace elements of pyrite, and rare earth elements of fluorite in the Baiyine'lebu deposit, Inner Mongolia, China

The recently discovered Baiyine’lebu Ag-Pb-Zn-F deposit in the southern Great Xing’an Range is hosted by NNE-trending transgressional fractures within Late Permian granodiorite. The fluorite ore veins in the periphery of the mining area show close spatial association with the Ag-Pb-Zn ore bodies. A total of four mineralization stages are recognized based on the cross-cutting relationships and mineral assemblages, among which three types of pyrite are identified, including: i) coarse-grained pyrite (Py1) from stage I quartz-pyrite vein, ii) fine-grained cubic pyrite (Py2) from stage II quartz sulfide-rich vein, showing association with metallic sulfide minerals, and iii) anhedral, irregular pyrite (Py3) disseminated in Ag-bearing sulfide ore vein from stage III. The stage IV is quartz-fluorite-calcite vein with very rare distribution of pyrite. Here we investigate the texture, trace element and sulfur isotopic composition of pyrite and rare earth elements (REEs) of fluorite to gain insights into the genesis and mineralization process of the Baiyine’lebu Ag-Pb-Zn-F deposit. Systematic trace element analyses indicate that the compatible and some other elements (Co, Ni, Cr and As) were incorporated in the pyrite structure via isomorphism in all pyrite types, whereas ore metals such as Cu, Pb, Zn, and Sn entered pyrite as structurally bound elements or micro/nanosized mineral inclusions. The Ag concentrations significantly increase from Py1 to Py3 in the form of invisible nanoparticles of sulfides or micro- to nano-sized mineral inclusions during the decrease of temperature. The narrow range of sulfur isotopic compositions from −0.80 to 3.88 ‰ (average in 1.17‰) indicates a relatively homogeneous sulfur source. In combination with REE patterns of fluorite, we propose that the ore-forming fluids originated mainly from post-magmatic hydrothermal fluid mixed with meteoric water in stage IV. The hydrothermal fluorite veins in the periphery of the Baiyine’lebu deposit could be genetically linked to the Ag-Pb-Zn veins. The purple fluorites with enriched REEs and positive Eu anomaly can be used as a proxy for prospecting Ag-Pb-Zn deposits. In addition, the high Sn content of pyrite in hydrothermal Ag-Pb-Zn deposit indicates the potential of Sn mineralization in the surrounding area or deeper level of the ore field in the South Great Xing’an Range.

New geochemical evidence constraining the water-rock-gas interaction on geothermal fluids of the Querétaro Graben, northern Trans-Mexican Volcanic Belt

This study examines the water-rock-gas interaction of the Los Geysers geothermal system in the northern Trans-Mexican Volcanic Belt (TMVB). Physico-chemical parameters, δ13C of total dissolved inorganic carbon (TDIC), and Rare Earth Elements (REE) composition on 14 thermal water discharges are reported and discussed. Waters had temperatures ranging from 40 °C to 98 °C, pH from 7.4 to 9.2, and total dissolved solids from 598 mg L−1 to 992 mg L−1. Signals of thermophilic biota, mainly diatom frustules, were found in the suspended particulate matter of spring waters. The range of δ13CTDIC was between −7.55‰ and −4.13‰ (avg. −7.10‰). Although potentially affected by secondary processes, the dissolved C species of the studied waters likely have a predominant deep, mantle-related component. The lanthanoids concentrations (∑REE) were variable over practically one order of magnitude, with average values between 1463 pmol L−1 for Ce and 9 pmol L−1 for Lu. Post-Archean Australian Shale (PAAS)-normalized patterns showed a slight enrichment in middle lanthanides, numerically expressed as [Sm/La]N and [Sm/Yb]N, ranging from 1.43 to 2.06 and 0.84 to 2.03, respectively. We propose that the overall signature of the REE is inherited during the regional migration of the liquid and from the primary aquifer. Moreover, PHREEQC computer code was run to calculate the dominant REE complexing ligands in the geothermal system at different temperatures. Our calculations indicate that F− complexes dominate over CO3 species at outlet temperatures, but oxyhydroxide complexes (REE-O2H, REE-O2–, and REE-O⁺) act as sinks after leaching from the source rock. The 143Nd/144Nd ratio of one of the studied samples was measured (0.512320 ± 0.000019; εNd = −6.20 ± 0.37, 2s.e.). The conceptual model in this paper highlights a mixing waters process between geothermal waters and cold shallow waters in the Queretaro Graben.

Geochemistry, zircon U-Pb geochronology and Sr-Nd-Hf isotopic composition of the Cha Val plutonic rocks in central Vietnam: Implications for Permian-Triassic Paleo-Tethys subduction-related magmatism

together with abundant Permian-Triassic magmatic rocks. This magmatic complex provides important information to reconstruct the tectonic evolution of the Indochina block and surrounding areas. The Cha Val plutonic rocks mainly comprise diorite, quartz diorite, and granodiorite. Geochemically, they are metaluminous with low A/CNK (0.49 to 1.16 with an average of 0.85), medium to high K, low to medium SiO2, and Na2O/K2O>1. Trace and rare earth element compositions display enrichment in Cs, U, Pb, and Nd, but depletion in Ba, Nb, Ta, P, Eu, and Ti, similar to those of continental arc-related magmas. Rock-forming minerals of the Cha Val plutonic rocks are characterized by abundant hornblende. All observed petrographical and geochemical characteristics suggest that the Cha Val plutonic rocks are typical for I-type affinity generated from a subduction regime. LA-ICP-MS U-Pb zircon analyses of three representative samples yielded their crystallization ages between 258.0 Ma and 248.9 Ma, temporally coeval with Late Permian-Early Triassic magmatism previously reported in the Truong Son belt. The (87Sr/86Sr)i ratios (0.7081 to 0.7244), negative whole-rock εNd(t) values (-4.5 to -2.9), zircon εHf(t) values (-1.04 to 2.71), and whole-rock Nd and zircon Hf model ages (TDM2) (1394 Ma to 1111 Ma) indicate that the Cha Val plutonic rocks are derived from melting of Mesoproterozoic crustal materials with a minor contribution of mantle-derived melt. Together with other Permian-Triassic magmatic complexes along the Song Ma suture zone and the Truong Son Belt, the Cha Val plutonic rocks are a representative of magmatism associated with the subduction-collision that amalgamated the South China and Indochina blocks after the closure of a branch of Paleo-Tethys along the Song Ma suture zone during the Late Permian-Early Triassic Indosinian orogeny.

Distribution and Origin of Major, Trace and Rare Earth Elements in Wild Edible Mushrooms: Urban vs. Forest Areas.

This paper investigates the composition of major, trace, and rare earth elements in 15 different species of wild edible mushrooms and the possible effect of urban pollution on elemental uptake. The collected mushrooms include different species from the green areas of the city, exposed to urban pollution, and from the forests, with limited anthropogenic influence. Through a comprehensive approach that included the analysis of 46 elements, an attempt was made to expand knowledge about element uptake by mushroom fruiting bodies. The results showed a wide variability in the composition of mushrooms, suggesting a number of factors influencing their element uptake capacity. The data obtained do not indicate significant exposure to anthropogenic influences, regardless of sampling location. While major elements’ levels appear to be influenced more by species-specific affinities, this is not true for trace elements, whose levels presumably reflect the geochemical characteristics of the sampling site. However, the risk assessment showed that consumption of excessive amounts of the mushrooms studied, both from urban areas and from forests, may have adverse health effects.

Juvenile continental crust evolution in a modern oceanic arc setting: Petrogenesis of Cenozoic felsic plutons in Fiji, SW Pacific

Viti Levu, Fiji, provides one of the best exposed Phanerozoic analogues for the formation of juvenile continental crust in an intra-oceanic setting. Tonalites and trondhjemites are present in several large (75–150 km2) adjacent, mid-Cenozoic plutons. We report major and trace element data including rare earth element (REE) and high-precision high field strength element (HFSE) compositions, new Hf-Nd-Sr-Pb isotope data, and zircon U/Pb-ages, O-Hf isotopes, and trace elements, from five different plutons. The Eocene Yavuna pluton and the Miocene Colo plutons are mainly composed of tonalites and trondhjemites and represent the exposed middle crust of the former Vitiaz island arc. The plutons can be divided into three suites. One suite is light REE (LREE) depleted with some trace element ratios lower than average normal mid-ocean ridge basalts (N-MORB). A second suite has flat REE patterns similar to local island arc basalts. Both suites occur near the coast of Viti Levu, include a wide compositional spectrum from gabbro to tonalite, and can be produced mostly by fractional crystallization of mafic precursor melts. The third suite is characterized by LREE enrichments with higher LaN/YbN (2.3–4.9), higher Zr/Y (4.3–7.1), and lower Nb/Ta (9.6–12.4). They occur closer to the center of the island and are bimodal trondhjemite-gabbro intrusions. These characteristics are consistent with formation mostly by partial melting of mafic crust. Trace element modeling shows that the trace element ratios of the third suite can be produced by 10–20 % melting of the mafic crust in the presence of residual amphibole, resulting in the retention of the medium REE (MREE) and diagnostic trace element ratios including low Nb/Ta and high Zr/Y. Geochemical similarities of the LREE enriched suite to typical “low”-pressure Archean tonalites-trondhjemites-granodiorites (TTGs) imply a common petrogenetic origin and similar mechanisms for the generation of juvenile Archean and modern differentiated crust by partial melting of mafic crust with residual amphibole. In modern oceanic arcs, genetically unrelated felsic plutonic as well as volcanic rocks co-exist, and in this regard, the Fijian plutons accompany major tectonic disruptions to arc processes.

Importance of the Spatial Distribution of Rare Earth Elements in the Bottom Sediments of Reservoirs as a Potential Proxy for Tracing Sediments Sources. A Case Study in the Dominican Republic

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.

REE-Bearing Minerals in Tin Waste Dumps of Singkep Island: Geochemical Identification and Recovery

DOI:10.17014/ijog.9.1.15-26Instead of environmental hazard, tailing might contain resources which could be reworked with the development of mining and separation technologies. Tailing dumps and waste ponds which associated with the long period of tin mining are easily found in Singkep Island. The waste should be processed to recover and purify precious metals within, and to reduce environmental degradation. REE-bearing minerals identification in tin tailing based on trace and rare earth element abundances is the aim of this study. Concise mineral beneficiation is illustrated for any further re-work strategy. The tailings collected from four locations in Singkep were analyzed for their trace and rare earth element compositions using ICP-MS at The Centre for Geological Survey. REE content in concentrates was upgraded at the range of 9 to 94 folds of the corresponding wastes. Monazite-(Ce), xenotime, and zircon are the REE-bearing minerals of the studied samples according to the elemental composition. Gravity, flotation, magnetic, and electrostatic methods would be applicable to separate the REE-bearing minerals from the tailing.

Tracing mantellic vs. crustal sources of clastic sediments in continental rifts using geochemical and Sm[sbnd]Nd and Sr isotope compositions: Insights from paleogene alluvial deposits of the Resende Basin, SE-Brazil

This work presents combined whole-rock element and SmNd and Sr isotopes of the Eocene syn-rift I alluvial sediments of the Resende Basin (SE-Brazil), aiming the assessment of sedimentary provenance. Geochemical compositions are used to evaluate the potential effects of hydrodynamic sorting and weathering in the SmNd and Sr isotopic compositions. Mudstone, sandstone, and conglomerate samples were collected for analysis. Chemical data indicate that the major element composition of the Resende Basin sediments is compromised by present-day weathering conditions and cannot be used for source areas weathering interpretations. Similar trace and rare earth elements composition in sandstones and mudstones imply poorly mixed sediments and provenance is associated with felsic and intermediated igneous sources with a subordinate mafic component. Mudstones are enriched in elements typically associated with heavy minerals (Ti, Zr, Hf, and Y). Weathering and mineral sorting affect mainly the major and trace element compositions of the Resende Basin sediments, while most of the isotopic composition's variations are due to differences in provenance caused by different source areas and/or degrees of source mix. Based on its conspicuous contrasting isotopic signature, the Cretaceous alkaline igneous source component can be tracked in the Resende Basin sedimentary record. Samples with εNd(t) < −10 have more than 60% of alkaline-derived provenance. The Resende Basin was compartmentalized by at least two depocenters separated by a structural high. The depocenters had very proximal sources but were connected by an axial fluvial system. The structural high acted as a barrier, retaining the sediment supply coming from the Itatiaia alkaline massif. These results are compatible with what is seen in other rift-related sedimentary environments, such as the Rio Grande and the North Sea deposits, where Nd and Sr composition of first-cycle clastic sediments reflect their parental source isotopic signature.

Fluorite Mineralization Related to Carbonatitic Magmatism in the Western Transbaikalia: Insights from Fluid Inclusions and Trace Element Composition

Fluorite mineralization associated with different types of magmatism is common in the Western Transbaikalia. This study deals with Arshan, Yuzhnoe, and Ulan-Ude fluorite occurrences, which are the most significant examples of carbonatite-related fluorite mineralization in the region. The present paper focused on new fluorite geochemistry and fluid inclusion data, is aimed at revealing conditions of the fluorite mineralization formation, highlighting its genetic relationship with magmatism, compared to other deposits of this type. All the three locations belong to the Late Mesozoic Central Asian carbonatite province. Fluorites here are characterized by high rare earth elements (REE), Sr, and elevated La/Yb values. Fluid inclusions data imply that the formation of fluorite mineralization is a long process extending from late magmatic to the hydrothermal stage. Early fluorite crystallized from sulfate-carbonate orthomagmatic fluids at temperatures up to 500 °C. True hydrothermal fluorite was formed from the same fluids that were probably mixed with meteoric waters, which caused the temperature to drop to below 420 °C and led to an increase in the chloride component. The REE compositions of fluorite from the studied locations are similar to compositions of REE-rich fluorites from carbonatite-related deposits around the world.

Granitic rocks from Rwanda: Vital clues to the tectonic evolution of the Karagwe–Ankole Belt

Petrological, geochemical and geochronological studies of granitic rocks from the Karagwe–Ankole Belt (KAB) have helped to establish the tectonic setting of the orogenic belt. Four categories of granitic rocks have been recognized, providing constraints on the geodynamics and evolution of the KAB. Anorogenic (A-type) garnet-biotite granite was emplaced at 1372 ± 5 Ma along deep, weak crustal structures. Its major, trace and rare earth element composition, TDM model age of 2.33–1.96 Ga, high initial 87Sr/86Sr (0.71193–0.72159) and negative ƐNd (−1.9 to −4.0), indicates derivation from a much older mafic source, probably originated from lower-crustal granulitic residue or lower continental lithospheric mantle contaminated by crustal material. Ascent of the small-batch A-type magma was aided by a localized crustal-scale zone of weakness within Archaean crust underlying both the Eastern and Western Domains of the KAB. The rest of the granites have S-type orogenic characteristics. Large batholiths of two-mica granite emplaced at 1369 ± 5 Ma have major, trace and rare earth element compositions, high initial 87Sr/86Sr (0.70808–0.71795), strongly negative ƐNd (−9.4 to −10.1) and a TDM model age of 2.82–2.40 Ga, indicative of derivation by partial melting of a pelitic source containing Palaeoproterozoic and Archaean components, possibly with a minor contribution from magma of lower crustal derivation. This magmatism occurred during the amalgamation of the Congo and Tanzania cratons at an early stage of Rodinia formation. Muscovite granite and leucogranite, derived from fluid-fluxed partial melting of metapelites, were emplaced at 1011 ± 18 to 976 ± 11 Ma in a late to post-collisional setting during final Rodinia formation. Their high initial 87Sr/86Sr (0.72893–0.74456) and strongly negative ƐNd (−6.8 to −12.4) indicate a supracrustal source. One younger S-type leucogranite (614 ± 9 Ma) was emplaced in a volcanic-arc setting during the assembly of West Gondwana. The combined available evidence points to tectonic evolution of the Mesoproterozoic KAB during accretion-collisional tectonism.

Three Types of Mantle Eclogite from Two Layers of Oceanic Crust: A Key Case of Metasomatically-Aided Transformation of Low-to-High-Magnesian Eclogite

AbstractReconstructed whole-rock (RWR) and mineral major- and trace-element compositions, as well as new oxygen isotope data, for 22 mantle eclogite xenoliths from the Catoca pipe (Kasai Craton) were used to constrain their genesis and evolution. On the basis of mineralogical and major-element compositions, the Catoca eclogites can be divided into three groups: high-alumina (high-Al) (kyanite-bearing), low-magnesian (low-Mg#), and high-magnesian (high-Mg#) eclogites. The high-Al Catoca eclogites contain kyanite and corundum; high Al2O3 contents in rock-forming minerals; rare earth element (REE) patterns in garnets showing depleted LREEs, positive Eu anomalies (1.03–1.66), and near-flat HREEs; and high Sr contents in garnets and whole-rock REE compositions. All of these features point to a plagioclase-rich protolith (probably gabbro). RWR compositions (major elements, MREEs, HREEs, Li, V, Hf, Y, Zr, and Pb) and δ18O of 5.5–7.4‰ of the low-Mg# Catoca eclogites are in good agreement with the compositions of picrite basalts and average mid-ocean ridge basalt (MORB). The depleted LREEs and NMORB-normalised Nd/Yb values of 0.07–0.41 indicate that the degree of partial melting for the majority of the low-Mg# eclogites protolith was ≥30%. The narrow δ18O range of 5.5–7.4‰ near the ‘gabbro–basalt’ boundary (6‰) obtained for the high-Al and low-Mg# Catoca eclogites reflects the influence of subduction-related processes. This case shows that mantle eclogites represented by two different lithologies and originating from different protoliths—plagioclase-rich precursor, presumably gabbro (for high-Al eclogites), and basalt (low-Mg# eclogites)—can provide similar and overlapping δ18O signatures on account of the influence of subduction-related processes. Chemical compositions of the high-Mg# eclogites indicate a complicated petrogenesis, and textural signatures reveal recrystallisation. The presence of Nb-rich rutile (8–12 wt% of Nb2O5) enriched with high field strength elements (HFSE) (Zr/Hf of 72.6–75.6) and multiple trace-element signatures (including RWR, NMORB-normalised Ce/Yb of 3.9–10.6 and Sr/Y of 5.8–9.6, MgO contents of 15.7–17.9 wt%, and high Ba and Sr) provide strong evidence for deep metasomatic alteration. High Cr contents in clinopyroxene (800–3740 ppm), garnet (430–1400 ppm), and accessory rutile (700–2530 ppm), together with extremely low Li contents of 1.0–2.4 ppm in clinopyroxene, may indicate hybridisation of the eclogites with peridotite. Comparison of the chemical compositions (major and trace elements) of (1) unaltered fresh cores of coarse-grained garnets from the low-Mg# eclogites, (2) secondary garnet rims (ubiquitous in the low-Mg# eclogites), (3) proto-cores in the coarse-grained garnet (high-Mg# eclogites), and (4) homogeneous recrystallised fine-grained garnets (high-Mg# eclogites) suggests that the high-Mg# eclogites formed through recrystallisation of low-Mg# eclogite in the presence of an external fluid in the mantle. Four of the five high-Mg# samples show that mantle metasomatism inside the Kasai craton mantle beneath the Catoca pipe occurred at a depth range of 145–160 km (4.5–4.8 GPa).

Geochemical behavior and fractionation characteristics of rare earth elements (REEs) in riverine water profiles and sentinel Clam (Corbicula fluminea) across watershed scales: Insights for REEs monitoring

The increasing global demand for rare earth elements (REEs) has led to their recognition as emerging contaminants; however, the effect that biota have on the cycling of these elements at the watershed scale is not currently well understood. In this study, water samples and field freshwater clams Corbicula fluminea were concurrently collected along watershed gradients, and concentration profiles of 14 naturally occurring REEs were measured in operationally defined water fractions and soft tissues of the freshwater clams. Moreover, Post Archean Australian Shale (PAAS) normalized REE patterns, fractionation indices, and anomalous values were determined to further extract characteristic features. As a result, both the water and biological samples had variable REE compositions, with higher concentrations of light REEs (LREEs) than middle REEs (MREEs) and heavy REEs (HREEs), while decreasing concentrations were generally observed as filter pore size decreased, implying that large colloidal and particulate fractions were important carriers of REEs. The spatial distribution patterns of REEs revealed a clear site effect among profiles, with variability more pronounced among watersheds and with peaks in sites from a small watershed near the hotspots of the mining area, and then exhibited a decreasing trend with distance from there. Meanwhile, significant bioaccumulation of REEs was observed potentially reflecting different degrees of contamination gradients among the watersheds. The PAAS-normalized distribution patterns tended to be slightly enriched in MREEs, producing a peculiar “roof-shaped” feature and characteristic fractionation. Remarkably, bio-concentration factors (BCFs) highlighted the importance of large colloidal and particulate phases in assessing biologically available REEs for filter-feeding species. Collectively, our study strongly favored that accumulation patterns and fractionation characteristics of REEs in C. fluminea can serve as a reliable indicator of geochemical behavior, providing a promising biomonitoring tool to quantitatively denote different degrees of REE contamination and assess possible impacts in mining watersheds.

The Timing, Duration and Conditions of UHT Metamorphism in Remnants of the Former Eastern Gondwana

AbstractEarly Palaeozoic ultrahigh-temperature (UHT) metamorphism in eastern Gondwana was an event that started with Gondwana amalgamation at c. 580 Ma and lasted at least 50 Myr. Sapphirine + quartz, Mg–Al granulites preserve a record of the timing and duration of the event along the metamorphic belt. U–Th–Pb dating of zircon and monazite shows that metamorphism peaked almost simultaneously in Antarctica (554.0 ± 4.7 Ma), Sri Lanka (555.5 ± 4.6 Ma), southern India (548.1 ± 8.1 Ma) and Madagascar (550.6 ± 6.0 Ma), and ended in all locations at the same time, 530–520 Ma. Rare earth element (REE) compositions of the metamorphic zircon zones can be matched to the REE zoning in the associated garnet. Phase-diagram modelling indicates that the peak UHT P–T conditions in Antarctica, Sri Lanka, and India were very similar, 1020–1040 °C at 0.8 GPa. Peak conditions in Madagascar were at higher T and similar P: 1090 °C and 0.8 GPa. The East African Orogeny before 600 Ma preconditioned the crust of the eastern Gondwanan terranes by thickening it and harbouring heat-producing elements, heating the crust over c. 60 Myr; such that UHT conditions were reached when East and West Gondwana collided.

Applicability of rare earth elements in eolian sands from desert as proxies for provenance: A case study in the Badain Jaran Desert, Northwestern China

Rare earth elements (REEs) have been widely used to infer the provenance of sediments. However, sedimentary sorting and chemical weathering may produce REE compositions within sediments that vary with grain size, leading to complications and uncertainty when tracing possible source areas. In desert areas, the extent to which REE compositions within eolian sands are affected by sedimentary sorting along with which REE proxies can be used to indicate provenance requires further study. During our work, 73 samples were collected from the Badain Jaran Desert (BJD) and some nearby regions. These were analyzed for trace elements and REEs. Our results showed that the REE composition of these eolian sands varied considerably among the various grain-size fractions. We conclude that the REE composition of these eolian sands in the BJD is a function of sedimentary sorting and provenance rather than of chemical weathering. Among the REE proxies considered, variations in (La/Yb)N and Y/REE values seem mainly to have been affected by sedimentary sorting, whilst δCe, (La/Sm)N, (La/Gd)N, Y/Tb, Y/Er, and Ce/Nd ratios appeared primarily to have been governed by provenance. Therefore, we can infer that care is needed when using (La/Yb)N and Y/REE as proxies for determining eolian sand provenance; however, δCe, (La/Sm)N, (La/Gd)N, Y/Tb, Y/Er, and Ce/Nd ratios offer a more reliable perspective. Moreover, by using (La/Sm)N and (La/Gd)N as provenance proxies, we determined that hinterland lacustrine sediments are an important source of < 125 μm fractions in the eolian sands of the BJD.

Büyük Kuluncak (Malatya) Nb-U-NYE-Zr-Li Yatağının Cevherleşme Özellikleri ile Alterasyon ilişkisi

Rare Earth Elements (REE) + Niobium (Nb) + Uranium (U) + Zircon (Zr) + Lithium (Li) formations are investigated which are related with alkaline Upper Cretaceous - Lower Paleocene Kuluncak Syenitoid that settled by cutting the Kuluncak ophiolite in the north of Kuluncak (Malatya) town. The alkaline magma-related Büyük Kuluncak REE - Nb - U deposit, which is enriched with regard to rare metals (Nb, Zr, and Rb), is the first economic deposit of our country. The deposit formed related to alkaline characterized foid syenite, sodalite syenite, syenite, alkaline feldspar syenite rocks which intruded into Triassic - Lower Cretaceous limestones of the Domuzdağı Nappe. The REE and fluorites with related elements formed in magmatic rocks, the contact zone of these rocks with limestones, in pegmatitic intrusions and in fluorites formed with the effect of the contact metasomatism. The purpose of this study is to interpret ore properties and the alteration grade of the rocks which formed the deposit. The REE are enriched in argillized and highly argillized samples. However, the REE composition of fresh samples are relatively low. Therefore, the REE are enriched twice or three times due to the effects of alteration and argillization of the hydrothermal fluids in the parent rock and contact metasomatism and alterations that occur both syn- and post-emplacement of syenite.

Major, Trace, and Rare-Earth Element Geochemistry of Nb-V Rich Andradite-Schorlomite-Morimotoite Garnet from Ambadungar-Saidivasan Alkaline Carbonatite Complex, India: Implication for the Role of Hydrothermal Fluid-Induced Metasomatism

In situ major, trace and rare-earth element composition of Ti-rich garnets from Ambadungar-Saidivasan alkaline carbonatite complex (ASACC) are presented to constrain its likely genesis. The garnets are characterized by high andradite (42.7–57.3), schorolomite (22.0–31.0), and morimotoite (15.6–26.5) end members. No distinct chemical zonation is noticed except for minor variations in Ti content. The garnets are enriched in LREE (average 731 ppm) and relatively depleted in HREE (average 186 ppm) and show an M-type first tetrad that leads to a convex upward pattern between Ce and Gd. Mildly positive to no Eu anomalies are observed (Eu/Eu* = 1.06–1.17). The REE patterns (LaN/YbN = 1.11–2.11) are similar to those of garnets from skarn deposits. The presence of tetrad effect in the LREE pattern suggests an active role of metasomatic processes involving hydrothermal fluids during the growth of the garnets. These garnets also contain high Nb (282–2283 ppm) and V (1083–2155 ppm) concentrations, which stand out against the composition of the host rock. Therefore, late-stage metasomatic reactions of earlier formed minerals with hydrothermal fluid enriched in Fe, Si, LREE, Nb, V, and Ti led to the formation of garnet. The primary source for these elements could be magnetite, ilmenite, and pyrochlore present in different varieties of carbonatites in the ASACC, with the required elements being released during their interaction with the hydrothermal fluid. The hydrothermal fluid was likely to be moderately acidic, and having fluoride and sulfate as the primary ligands.

Fiber optic probe with functional polymer composites for hyperthermia.

We demonstrate a fiber optic probe incorporating functional polymer composites for controlled generation of photothermal effects. The probe combines carbon-based and rare-earth composites on the tip of standard multimode fibers, thus yielding a compact fiber optic photothermal probe (FOPP) whose temperature can be measured simultaneously through fluorescent thermometry. We evaluate the thermal features of the probe through experiments and numerical calculations showing that large thermal gradients are obtained within the vicinity of the heating zone. The temperatures achieved with the FOPP are within the ranges of interest for hyperthermia and can be attained using low optical powers (< 280 mW).

Geochemical characteristics and geologic significance of rare earth elements in oil shale of the Yan’an Formation in the Tanshan area, in the Liupanshan Basin, China

In the Tanshan area, in the Liupanshui Basin, abundant oil shale resources are associated with coals. We analyzed the cores, geochemistry of rare earth elements (REE), and trace element of oil shale with inductively coupled plasma mass spectrometry technology to define the paleo-sedimentary environment, material source, and geologic significance of oil shale in this area. The results of the summed compositions of REE, and the total REE contents (ΣREE), in the Yan’an Formation oil shale are slightly higher than the global average of the composition of the upper continental crustal and are lower than those of North American shales. The REE distribution pattern is characterized by right-inclined enrichment of light REEs (LREE) and relative loss of heavy REEs (HREE), which reflects the characteristics of crustal source deposition. There is a moderate degree of differentiation among LREE, whereas the differences among HREE are not obvious. The [Formula: see text] values indicate a weak negative anomaly, and the [Formula: see text] values indicate no anomaly, which are generally consistent with the distribution of REE in the upper crust. The characteristics of REE and trace elements indicate that the oil shale formed in an oxygen-poor reducing environment and that the paleoclimatic conditions were relatively warm and humid. The degree of differentiation of REE indicates that the sedimentation rate in the study area was low, which reflected the characteristics of relatively deep sedimentary water bodies and distant source areas. The results also proved that the source rock mainly consisted of calcareous mudstone, and a small amount of granite was also mixed in.

Heavy Metal, Rare Earth Element and Pb Isotope Dynamics in Mussels During a Depuration Experiment in the Gulf of Aqaba, Northern Red Sea

Mussels are considered highly efficient marine biomonitors, tracing anthropogenic and natural variations in heavy metals and various organic compounds. While heavy metals depuration processes in biomonitors are of growing interest, less knowledge is available regarding their Pb isotopes and rare earth elements (REEs) accumulation-release dynamics, and their response to short-term anthropogenic and terrigenous perturbations. Here, we report the results of a relocation experiment where a group of mussels (Brachidontes pharaonis) were extracted from a contaminated lagoon in the Gulf of Aqaba, northern Red Sea, and placed in water tanks that were flushed continuously with fresh, uncontaminated seawater. Specimens were removed periodically from the water table over a period of 13 weeks and trace and REEs and Pb isotopic compositions were determined separately for mussel’s shells and soft tissues. The results display a clear decrease over time in the concentrations of various heavy metals and REEs in the soft tissue, in concert with a similar shift in the Pb isotopic compositions toward seawater values. By contrast, the elemental and Pb isotopic composition of the shell presents little change over time. Coupling between the Pb isotopic composition of corresponding soft tissue and shell samples allows back-calculation of the timing and magnitude of abrupt pollution events and presents a novel approach for monitoring short-term pollution events. Nevertheless, given the coastal setting of the studied samples, it is important to consider the effects of terrigenous material on the results. Accordingly, Al-normalized element concentrations, Pb isotopes and calculated Ce anomalies, are used to identify two distinct terrigenous end members controlling the contaminated lagoon and the pristine site. The study demonstrates the potential of using mussels as robust biomonitors of natural and anthropogenic environmental perturbations through the combination between elemental concentrations and the isotopic composition of Pb.

Rare earth element geochemistry of lake sediments from the eastern Nanling Mountain area (South China) and its implication for East Asian monsoon related chemical weathering over the past ~47 000 years

Chondrite‐normalized rare earth element (REE) data of a ~47.0‐ka lake sedimentary sequence from the Dahu Swamp in the eastern Nanling Mountain area were used to determine climatic variations within the region. These sediments proved to be valuable proxies of climatic changes and their origin is discussed. The influences of grain size, organic matter absorption and Fe‐Mn oxides on REE composition were determined to not be significant. The dominant source of sediments was ascertained to be the weathered granite residues from the catchment, enriched in light rare earth elements (LREE). Intensified East Asian summer monsoon (EASM) resulted in intensive chemical weathering, leading to enhanced REE and LREE fractionations in the weathered residues; this caused the increase in REE and LREE, and decrease in heavy rare earth element (HREE) fractionation degrees in the sediment. Therefore, our results indicate that changes in LREE/HREE, (La/Yb)N, (La/Sm)N) and (Gd/Yb)N, the proxies of REE, LREE, and HREE fractionations, can serve as proxies of regional climate‐induced chemical weathering and thus serve to constrain EASM changes.