Rare Earth Elements in Egyptian Phosphorites

Egyptian phosphorites from Abu Tartur(Western Desert),El Mahamide mine(Nile Valley) and Rabah mne(Eastern Desert)show variable degrees of relative REE enrichment.Black plateau phosphorites of Abu Tartur are substantially enriched in REE as compared to the Red Sea and Nile Valley phosphorites.P-rich organic matter from the Abu Tartur and Rabah mines recorded negative Ce and positive Eu anomalies.Positive Eu anomaly reveals an anoxic event prior to the phase of Late Cretaceous phosphate formation.Ce is a redox indicator.Mixing of sea water and upwelling during the Late Cretaceous was responsible for the recording of positive Eu and negative Ce anomalies in the Egyptian phosphorites.     

Rare earth elements,iron formations and sea water

Iron formations probably formed as chemical sediments when an Fe-rich solution entered the sedimentary environment. The REE patterns of such sediments are affected by the amount and type of precipitating and detrital phases, the REE pattern of the iron source solution, the REE pattern of the sea water into which the solution flows, and the mixing which takes place between input solution and sea water. What is known about the different types of iron formation suggests that all of these factors may vary from one type to another. Therefore, variations in REE patterns cannot be attributed solely to changes in sea water REE patterns. Comparison of the REE patterns of Archean and Ordovician iron formations of the Algoma type shows that similar iron formations have similar REE patterns regardless of age. This implies similar genetic histories.     

Rare earth elements in ‘Younger’ granites,Northern Portugal

Rare earth elements (REE) were determined in two suites of Hercynian ‘Younger’ granodiorites and granites, one massive and the other porphyritic. Within each suite, the REE abundances decrease towards the more felsic granite while the REE patterns are almost identical. The patterns of the porphyritic types are only slightly more fractionated than those of the massive rocks. Negative Eu-anomalies are observed in all rocks although those of the granodiorites are smaller than those of the granites. Modeling of the data indicates that the granitic magmas may be derived, by partial melting, from the greywackes and pelites of the orogenic belt, the melts being in equilibrium with a residuum composed of quartz, plagioclase, garnet, orthopyroxene or cordierite, and, possibly, biotite.     

Solid inclusions of magmatic halite and sylvite in felsic granitoids, Sierra Norte, Córdoba, Argentina

This study provides evidence for the existence of halite and sylvite solid inclusions in igneous quartz and feldspars, the first to be reported in intrusive rocks, and to partially constrain the physicochemical environment that lets halides crystallize under magmatic conditions.Halite and sylvite solid inclusions were found included in quartz and feldspars from a micrographic–granophyric assemblage in a miarolitic aplite and, rarer, in alkali-feldspar from a miarolitic monzogranite. Monzogranite and aplite represent I-type, K-enriched postcollisional rocks of the Late Cambrian–Early Ordovician Sierra Norte–Ambargasta batholith in the Eastern Sierras Pampeanas. Both granitoids fall among the most evolved felsic rocks of the batholith, with aplite approaching haplogranitic compositions. Halite is far more common than sylvite and the presence and distribution of one or both halides are erratic within the felsic intrusive bodies. Halides occur as small skeletal grains, commonly in cross-shaped aggregates of less than 50 μm. No K or Na was found at the detection limits of EDS in either halite or sylvite respectively. Textural relationships suggest that the alkali-chlorides separated from the melt near the minima along the quartz–feldspar cotectics of P_H2O > 160 < 200 MPa in a silica-, and potassium-rich magmatic system at approximately 750–700 °C, prior to the H₂O-vapor saturated miarole-forming stage.Computed ratios for the magmatic volatile phase (MVP) coexisting with melt at the early stage of aplite crystallization are: NaCl/HCl = 0.11–0.97 and KCl/HCl = 0.24–1.62, being the highest range of values (0.79–0.97 and 1.45–1.62, respectively) found in those alkali-chloride-bearing samples. Maximum HCl/ΣCl_(MVP) (0.28 to 0.31) indicates higher total Cl concentration in the MVP of alkali-chloride-bearing aplites, which is much higher in the halite-free aplite samples (HCl/ΣCl_(MVP) = 0.59 to 0.74). One miarolitic monzogranite sample, where halite solid inclusions are present, also yielded the highest ratios for NaCl/HCl_(MVP) (0.91) and KCl/HCl_(MVP) (1.46), and the HCl/ΣCl_(MVP) is 0.30. A high HCl concentration in the fluid phase is suggested by the log f(HF)/f(H₂O) = − 4.75 to − 4.95, log f(HCl)/f(H₂O) = − 3.73 to − 3.86, and log f(HF)/f(HCl) = − 0.88 to − 1.22, computed at 750 °C after biotite composition. The Cl concentrations at 800 °C, computed with a D^v/l_Cl = 0.84 + 26.6P (P at 200 MPa), yielded values within the range of  70 to 700 ppm Cl in the melt and  4000 to 40 000 ppm Cl in the coexisting MVP. The preferential partitioning of Cl in the vapor phase is controlled by the D^v/l_Cl; however, the low concentration of Cl in the melt suggests that high concentrations of Cl are not necessary to saturate the melt in NaCl or KCl.Cl-saturation of the melt and coexisting MVP might have been produced by a drop in Cl solubility due to the near-haplogranitic composition of the granitoids after extreme fractionation, probably enhanced by fluctuating reductions of the emplacement pressure in the brittle monzogranite host. Liquid immiscibility, based in the differential viscosity and density among alkali-chloride saturated hydrosaline melt, aluminosilicate felsic melt, and H₂O-rich volatiles is likely to have crystallized halite and sylvite from exsolved hydrosaline melt. High degrees of undercooling might have been important at the time of alkali-chloride exsolution. The effectiveness of alkali-chloride separation from the melt at magmatic temperatures is in line with the interpretation of “halite subtraction” as a necessary process to understand the origin of the “halite trend” in highly saline fluid inclusions from porphyry copper and other hydrothermal mineralizations, despite the absence of the latter in the Cerro Baritina aplites, where this process preceded the exsolution of halite-undersaturated fluids.Pervasive alteration of the monzogranite country rock as alkali-metasomatic mineral assemblages, the mineral chemistry of some species, and the association of weak molybdenite mineralization are compatible with the activity of alkaline hypersaline fluids, most likely exsolved during the earliest stages of aplite consolidation.     

Rare earth elements in seawater: particle association,shale-normalization,and Ce oxidation

Dissolved (<0.04 μm, not <0.4 μm) and total acid-soluble concentrations of rare earth elements (REEs) and yttrium were measured by using ICP mass spectrometry in the seawaters obtained from various depths in the western North Pacific near Japan. The difference, i.e., acid-soluble particulate fraction, was found to be small, 2–5% for all tri-valent light and middle REEs and less than 1% for heavy REEs and yttrium. The high particulate fraction of 31% for Ce is consistent with its predicted oxidation state of tetra-valence. Elevated particulate fraction of all REEs was found within ∼80 m above the bottom due to contribution of flocculated resuspended particles. The vertical profiles of REE(III)s show smoothly increasing convex curves with depth similar to those reported previously. Dissolved Ce concentration decreases from ∼6 pmol/kg near the surface to a minimum at 2.5 pmol/kg around 400 m where the North Pacific Intermediate Water penetrates, and then approaches to nearly constant value of ∼4 pmol/kg below 800 m. Particulate Ce concentration significantly increases from the surface to 200 m depth suggesting oxidation of Ce(III) to Ce(IV) and subsequent scavenging in the upper water column. However, there is no evidence in our data showing that Ce oxidation is continuously taking place even in the deep sea.Shale-normalized patterns of dissolved REEs were examined in detail, based on three datasets of composite shales available in the literature. Distinctively positive La and only slightly positive Gd anomalies were identified together with well-documented negative Ce-anomaly as common features of seawater. These anomalies systematically change with depth. Rapid changes occur in the upper several hundred meters suggesting that their distributions are largely governed by ocean circulation and biogeochemical cycling.     

Rare earth elements and yttrium in lithotypes of Bulgarian coals

Rare earth element and yttrium abundances in vitrain, xylain, liptain, fusain and whole coal samples from Bulgarian coal deposits have been studied. Vitrain, xylain, and liptain are depleted, while fusain is enriched in REE and Y as compared to the whole coal samples from which they were selected. Chondrite-normalized patterns show relative enrichment of light (LREE) against heavy (HREE) rare earth elements, negative Eu anomaly, and positive Lu anomaly. The shale-normalized patterns of the lithotypes reveal an increase from LREE to HREE, while those of the whole coal samples and mineral interlayers are less fractionated. The petrographic composition of the coals is of secondary importance for the concentration of the REE and Y. The main factors are the source area and the input of dissolved REE and Y into the coal depositional sites.     

Rare earth elements in ferromanganese nodules and other marine phases

The concentrations of rare-earth elements (REE) have been measured in 31 ferromanganese nodules from the Pacific and Indian Oceans and vary by almost a factor of 5. Too few nodules have been analyzed to define possible regional trends. The shale-normalized patterns, however, permit division of nodules into two groups: those from depth greater than 3000–3500 m and those from less depth. The factors that determine this change in the relative concentration of REE may be related to the mineralogy of manganese phases and/or the transport of REE to the deep ocean by particulate matter.Comparison of the REE patterns of nodules with those of phillipsite, phosphorite, clays, CaCO₃ and seawater suggests that the patterns of these phases reflect fractionation from an initial pattern closely resembling that of shale. By assuming that the accumulation rate of REE in clays, CaCO₃ and nodules is represented by that for surface sediments, it has been possible to estimate an accumulation rate of phillipsite in pelagic sediments of the Pacific of 0.02 mg/cm²/yr.     

Rare earth elements in groundwater from different Alpine aquifers

Rare earth elements (REE) were determined in 39 groundwater samples collected at 14 sites under low- and high-flow conditions. Water samples derived from aquifers hosted in crystalline, molasse, flysch, carbonate and evaporite rocks located in Western Switzerland. The concentration of REE in groundwater circulating in different rocks showed large variations: lowest concentrations (ΣREE≤10 ng/L) occurred in groundwater from evaporite aquifers; highest concentrations (ΣREE up to 516 ng/L) were observed in carbonate aquifers, although REE in these waters do vary under different hydrological conditions; groundwater from other aquifers had ΣREE from 10 to 100 ng/L. Distinct REE signatures were observed in waters draining specific rocks. The REE patterns in groundwater from crystalline, molasse and flysch aquifers showed heavy-REE enrichment at different degrees. Groundwaters circulating in crystalline rocks were distinguished by negative anomalies in Ce and Eu, whereas those from carbonate aquifers were nearly flat with ΣREE and the magnitude of negative anomaly in Ce is likely to be controlled by iron concentrations. The REE-Post-Archean Australian Shales (PAAS) normalized patterns appear useful to recognize the aquifer type and suggest the possibility to use the REE as geochemical tracers.     

福建丁家山铅锌矿稀土元素特征

通过对福建丁家山矿区铅锌矿床不同类型岩石和矿石的稀土元素地球化学特征的研究,探讨了岩石和矿石中稀土元素地球化学行为。结果显示,丁家山铅锌矿区的稀土元素呈现轻稀土富集、重稀土亏损的地球化学特征,说明成矿流体和围岩具有继承性,丁家山铅锌矿虽呈层状,但该矿床具有热液矿床的特征。热液在运移过程中,随着温度不断降低,在成矿有利部位形成低温蚀变矿物,如绿泥石、绿帘石、阳起石等,同时伴随着Cu、Pb、Zn、Ag等成矿元素和稀土元素的沉淀富集。     

Rare earth elements in the early Archaean Isua iron-formation, West Greenland

The rare earth element (REE) patterns in the 3.8 Ga-old Isua iron-formation are generally flat, resembling those of some primitive basalts. Samples with positive, negative or no europium anomaly were found. It is shown that diagenesis and metamorphism did not significantly change the REE patterns. The presence or absence of europium anomalies in iron-formations cannot be used as an indicator of the presence or absence of oxygen in the atmosphere during the Archaean and Precambrian. The REE contents cannot be used to distinguish Algoma-type from Superior-type iron-formations. There appears to be a striking similarity between the Archaean submarine exhalations and modern submarine hydrothermal systems. It is considered likely that Archaean and early Precambrian seawater had a chondritic REE pattern with a slight enrichment of light REE.     

Rare earth elements in some igneous rocks in the Oslo rift, Norway

Rare earth element (REE) concentrations have been determined for 27 plutonic rocks in the Permian Oslo rift, including kjelsåsite/larvikites, lardalites, nordmarkites, ekerites and Drammen granites.

The kjelsåsite/larvikites from different parts of the rift have very similar REE concentrations and must be derived from a source or sources homogeneous with respect to REE.

The genetic relations between the kjelsåsite/larvikites and the other rocks were tested by comparing observed REE enrichment factors with calculated ones based on hypothetical fractionation relations derived from petrographic mixing calculations. Several of the analyzed nordmarkites may be derived from kjelsåsitic/larvikitic parent magmas: the ekerites are closely related to the nordmarkites.     

Rare earth elements in the peats of Moscow and Tver oblasts

Noticeable amounts of rare-earth elements were first detected in the peats of the earlier drained bogs of Moscow and Tver oblasts. The analysis was carried out by inductively coupled plasma mass spectrometry on an ELAN DRC II instrument (PerkinElmer, United States). The contents of REEs in peat ash of certain deposits are higher than their average contents in the basic rocks and vary in the range of 0.5–60 and 0.1–41.3 mg/kg for the cerium and yttrium groups, respectively.     

Rare earth elements in Quaternary clays of the Numedal area, southern Norway

Rare earth elements (REE) in the clay fraction (< 2μ) of the Quaternary deposits in the Numedal area, southern Norway, have been determined by a spark source mass spectrometric method. The REE content was studied in relation to weathering and sedimentological factors.

The total REE content varies from 100 to 1300 ppm. An average of the similar fraction of 16 non-marine clays, mostly tillitic, gave 527 ppm REE. An average of 38 glacial and postglacial marine clays from the lower part of the Numedal valley gave 335 ppm REE (max. 781 ppm). After removal of adsorbed ions the average total REE content of morainian and marine clays decreased to 186 ppm.

The content and distribution of the REE in the Numedal clays are strongly influenced by environmental factors. Under neutral and alkaline conditions the REE are accumulated by adsorption on clay minerals, and by increasing the hydrogen ion concentration the adsorbed ions are readily removed.     

Rare earth elements in a sampled coal from the Pirin deposit,Bulgaria

Rare earth elements (La, Ce, Sm, Eu, Tb, Yb, and Lu) in a columnar section of the coal of the Pirin deposit, Bulgaria, have been determined by neutron activation analyses.The REE content in the coals is lower than the average REE content of shales from North America, Europe, and the Soviet Union. The REE abundances increase with the increasing ash content of the coals. The bottom of the seam is slightly enriched in REE, the trend being more pronounced in HREE (Tb, Yb, Lu). The REE content depends on the thickness of the coal layers: the thin coal layers are enriched in REE as compared to the thick ones.The chondrite-normalized distribution patterns are very uniform. They are characterized by a negative Eu anomaly whose mean value is 0.30 (varying in the individual samples from 0.21 to 0.49) and a positive Lu anomaly. It is supposed that the Eu anomaly is inherited from the source rocks.The shale-normalized distribution patterns show a distinct relative enrichment in HREE and a negative Eu anomaly. The relative enrichment in HREE is a specific feature of the REE geochemistry in the Pirin deposit. The LREE/HREE ratio is lower than that of composite shale; it increases with the increasing ash content of the coals and from the bottom to the top of the coal bed.REE are bound predominantly to the aluminosilicates of the mineral matter in the coals. All REE are positively correlated to the ash, Si, Al, Fe, and Na.The source of REE in coals is mainly the suspended terrigenous material. The specific enrichment of REE in the ash of low-ash coals is a result of the interaction between the dissolved REE and the products of disintegration and decay of organic substances, mainly the humic acids.     

Rare earth elements in corals from the Isla de Sacrificios Reef,Veracruz, Mexico

Rare earth elements (REE) analysis was carried out in two coral species Diploria strigosa and Copophyllia natans from Isla de Sacrificios Reef (ISR) (19° 10′ 51.6″N; 96° 5′ 45.6″W) Veracruz, Mexico. Both corals were cut at the top, middle and bottom parts to detect possible differences in REE concentrations related to water masses and sediment inputs. An enrichment in heavy rare elements (HREE) compared to light rare elements (LREE) at the top of Diploria strigosa and Copophyllia natans, evidenced by (La/Lu)_SN <0.5, (La/Yb)_SN <0.5 and (Pr/Yb)_SN <0.5 is observed. This HREE enrichment in both corals is probably due to the high pH and CO₃^2? content in the seawater. A negative Ce anomaly is observed throughout Diploria strigosa and Copophyllia natans, probably linked with well oxygenated, highly oxidative modern shallow waters, and high nutrients related to suspended matter. Positive Eu anomalies in both corals are due to development of the ISR in shallow waters. Ce/Ce* vs. (Pr/Yb)_SN diagram suggests the input of terrigenous material, as all samples have Ce/Ce* and Pr/Yb values outside the seawater range signature. However, the Nd/Yb and (Nd/Yb)_SN suggest that the top of Diploria strigosa and Copophyllia natans are associated with coastal waters at about 50 m depth.     

Rare earth elements in waters from the albitite-bearing granodiorites of Central Sardinia, Italy

With the aim of contributing to the knowledge of the geochemical behaviour and mobility of the rare earth element (REE) in the natural water systems, the ground and surface waters of the Ottana-Orani area (Central Sardinia, Italy) were sampled. The study area consists of albititic bodies included in Hercynian granodiorites. The waters have pH in the range of 6.0-8.6, total dissolved solid (TDS) of between 0.1 and 0.6 g/l, and major cation composition dominated by Ca and Na, whereas predominant anions are Cl and/or HCO₃.The pH and the major-element composition of the waters are the factors affecting the concentration of REE in solution. The concentrations of ∑REE+Y in the samples filtered at 0.4 μm vary between 140 and 1600 ng/l, with La of between 14 and 314 ng/l, and Yb of between <6 and 12 ng/l. A negative Ce anomaly, especially marked at high pH, is observed in the groundwaters. The surface waters show lower REE concentrations, which are independent of pH, and negligible Ce anomaly.Speciation calculations, carried out with the EQ3NR computer program, showed that the complexes with the CO₃²⁻ ligand are the dominant REE species at pH in the range of 6.7-8.6. The REE³⁺ ions dominate the speciation at pH <6.7 and only in the light REE (LREE).The relative concentrations of REE in water roughly reflect those in the aquifer host rocks. However, when concentrations of REE in water are normalised relative to the parent rocks, a preferential fractionation of heavy REE (HREE) into the water phase can be observed, suggesting the greater mobility and stability of HREE in aqueous solution.     

Rare earth elements of the Altar Desert dune and coastal sands, Northwestern Mexico

Twenty-one surficial sand samples from the Altar Desert coastal and desert dune systems were analysed for rare earth elements (REE) content. This was done to observe the provenance signatures for four strategic dune localities near the Colorado River Delta, the El Pinacate dune fields, and the beaches of the north of the Gulf of California in the state of Sonora, Mexico. Our goals are to show which mechanisms (i.e., aeolian, marine) exert more influence on the composition of the Altar Desert dune sands. This study also shows the usefulness of REE spatial distribution to determine the relative mobility of the sand. Some sand samples from the dune systems in San Luis Río Colorado (SLRC), Golfo de Santa Clara (GSC), and Puerto Peñasco (PP) displayed dissimilar REE concentrations with respect to the rest of the sand samples from the same sites. These differences can be related to short aeolian transport distance in the sands with high REE concentrations and long aeolian transport distance in the sands with low REE concentrations. Besides, high REE concentration in the sands might be due to their closeness to the Colorado River Delta sediments and to recycled sands derived from granitic rocks. In contrast, all the sand samples from the El Pinacate (EP) site have similar REE concentration values, suggesting that the El Pinacate dune sands are influenced by more selective aeolian processes and less diverse heavy mineral content. The Altar Desert dune sands are derived from granitic sources eroded by the Colorado River. Our results also indicate that the Altar Desert dune sands are low in heavy mineral content (with the exception of Fe and Ti bearing minerals) and enriched in carbonates with phosphates (especially at the PP site) yielding poor correlations between REE and major element concentrations. The REE geographical distribution values in the Altar Desert dune sands indicate that light and heavy REE concentration values are related to aeolian transport, maturity of the sands, their low weathering rates, proximity of the source rocks, and the biogenic debris input from beach sands into the dune.     

Rare earth elements in modern coral sands: an environmental proxy

The concentration rare earth elements and Yttrium (REE + Y) were determined in coral sands from Kavaratti Island, Arabian Sea, India. Chondrite-normalized REE + Y patterns show: (1) high REE concentration particularly light REE (LREE) enrichment; (2) consistent negative Ce anomaly; (3) nearly chondritic Y/Ho ratios. All these features are consistent with the geochemistry of well oxygenated seawater with significant terrestrial contribution. The seawater composition of Nd/Yb ratio inferred from the coral record point to the dominance of LREE more than the heavy REE (HREE). The high terrestrial input rich in LREE and property of adsorption/scavenging processes of LREE than that of HREE may be the cause. Terrigenous contributions were detected on the basis of co-occurring trace element concentrations (Sc, Hf and Th) and Y/Ho ratio. Except for La, the REE distribution coefficients, KD(REE)s, are between 100 and 300. KDs are high comparing to the other elements in biogenic calcite which is attributed to detrital contamination during elemental incorporation. This study may not reflect original seawater chemistry but it can be a good proxy to indicate proximity of corals to terrigenous input sources.     

Rare earth elements in the water column of Lake Vanda, McMurdo Dry Valleys, Antarctica

We present data on the composition of water from Lake Vanda, Antarctica. Vanda and other lakes in the McMurdo Dry Valleys of Antarctica are characterized by closed basins, permanent ice covers, and deep saline waters. The meromictic lakes provide model systems for the study of trace metal cycling owing to their pristine nature and the relative simplicity of their biogeochemical systems. Lake Vanda, in the Wright Valley, is supplied by a single input, the Onyx River, and has no output. Water input to the lake is balanced by sublimation of the nearly permanent ice cap that is broken only near the shoreline during the austral summer. The water column is characterized by an inverse thermal stratification of anoxic warm hypersaline water underlying cold oxic freshwater.Water collected under trace-element clean conditions was analyzed for its dissolved and total rare earth element (REE) concentrations by inductively coupled plasma mass spectrometry. Depth profiles are characterized by low dissolved REE concentrations (La, Ce, <15 pM) in surface waters that increase slightly (La, 70 pM; Ce, 20 pM) with increasing depth to ∼55 m, the limit of the fresh oxic waters. Below this depth, a sharp increase in the concentrations of strictly trivalent REE (e.g., La, 5 nM) is observed, and a submaximum in redox sensitive Ce (2.6 nM) is found at 60- to 62-m depth. At a slightly deeper depth, a sharper Ce maximum is observed with concentrations exceeding 11 nM at a 67-m depth, immediately above the anoxic zone. The aquatic concentrations of REE reported here are ∼50-fold higher than previously reported for marine oxic/anoxic boundaries and are, to our knowledge, the highest ever observed at natural oxic/anoxic interfaces. REE maxima occur within stable and warm saline waters. All REE concentrations decrease sharply in the sulfidic bottom waters. The redox-cline in Lake Vanda is dominated by diffusional processes and vertical transport of dissolved species driven by concentration gradients. Furthermore, because the ultraoligotrophic nature of the lake limits the potential for organic phases to act as metal carriers, metal oxide coatings and sulfide phases appear to largely govern the distribution of trace elements. We discuss REE cycling in relation to the roles of redox reactions and competitive scavenging onto Mn- and Fe-oxides coatings on clay sized particles in the upper oxic water column and their release by reductive dissolution near the anoxic/oxic interface.