controls on the geochemistry of rare earth elements along a groundwater flow path in the carrizo sand aquifer texas usa groundwater samples were collected along a groundwater flow path in the carrizo sand aquifer in south texas usa field measurements that included ph specific conductivity temperature dissolved oxygen do oxidation reduction potentials eh in mv alkalinity iron speciation and h2s concentrations were also conducted on site the geochemistry i e concentrations shale normalized patterns and speciation of dissolved rare element elements rees in the carrizo groundwaters are described as a function of distance along a flow path eh and other redox indicators i e do fe speciation h2s u and re indicate that redox conditions change along the flow path in the carrizo sand aquifer within the region of the aquifer proximal to the recharge zone groundwaters exhibit both highly oxidizing and localized mildly reducing conditions however from roughly 10 km to the discharge zone groundwaters are reducing and exhibit a progressive decrease in redox conditions dissolved ree geochemical behavior exhibits regular variations along the groundwater flow path in the carrizo sand aquifer the changes in ree concentrations shale normalized patterns and speciation indicate that rees are not conservative tracers with flow down gradient redox conditions ph and solution composite and adsorption modify groundwater ree concentrations fractionation patterns and speciation

rare earth element concentrations and speciation in alkaline lakes from the western u s a the rare earth element ree concentrations of lake water from five alkaline lakes i e mono walker abert summer and goose lakes within the great basin of the western u s a are reported all of the lakes exhibit hree enriched shale normalized patterns the speciation of the rees was determined and in all cases species greater than 99 of each of the rees exist as ln co3 2 complexes the only exception to this is summer lake where minor amounts of phosphate species were also predicted the large enrichments in the hrees observed in these lakes are the result of the formation of stable carbonate complexes in solution where the hrees preferentially form stronger carbonate complexes than the lrees activity product calculations for ree phosphate coprecipitates in these lakes indicate the lakes are close to saturation with respect to these phases and suggest that these precipitates may limit the maximum dissolved ree concentrations in the lakes

distribution and mobilization of cerium lanthanum and neodymium in the morro do ferro basin brazil abstract the distribution of the light rare earth elements lree s ce la and nd in the morro do ferro ore body and drainage basin is presented the ore body which contains an estimated 3 10 7 kg th and more than 1 10 8 kg ree is located near the summit of the hill the ree s are chemically similar to the trivalent actinides and therefore can be studied as analogues for certain of these elements ce is concentrated in the surface i e 0 50 cm layer of both the ore body and the drainage basin there appears to be an association between ce and th and also between nd and la in samples collected from the surface and at depths extending to 60 m enrichment of ce is especially evident in soils over the ore body while la and nd appear to be depleted in this zone the mobilization rate of la by groundwater solubilization is tentatively estimated to be 1 8 10 9 yr 1 which is very close to the rate previously estimated for th the mobilization rate of la due to stormflow erosion is on the order of 10 6 yr 1 and is similar to that reported earlier for th

rare earth element complexation behavior in circumneutral ph groundwaters assessing the role of carbonate and phosphate ions rare earth element ree concentrations were determined in circumneutral ph 7 ph 9 groundwaters from south central nevada and the mojave desert in eastern california u s a the inorganic speciation of the rees in these water were evaluated primarily to assess the relative importance of carbonate lnhco32 lnco3 and ln co3 2 and phosphate lnh2po42 lnhpo4 ln hpo4 2 and lnpo40 complexes other ree complexes with sulfate hydroxyl chloride and fluoride ions were also assessed as was the significance of the free metal ion species i e ln3 our speciation calculations indicate that ree carbonate complexes dominate and typically account for more than 99 of each ree in solution moreover carbonato complexes lnco3 were predicted to be the dominant species for the light rees and dicarbonato complexes ln co3 2 were predicted to increase in importance with increasing atomic number all other complexes were predicted to be negligible furthermore the combined percentage of all ree phosphate complexes never accounted for more than 0 1 of the dissolved rees and generally much less than 0 1 phosphate complexes can not compete with carbonate complexes in these groundwaters because of the low po43 concentrations 0 3 1 58 mol kg the much lower concentrations of the free phosphate ion i e po43 f 10 9 10 6 mol kg due to ion pair formation with ca2 and mg2 and the much higher free carbonate ion concentrations co32 f 0 32 87 mol kg

mobilization and redistribution of rees and thorium in a syenitic lateritic profile a mass balance study abstract ree th geochemistry and mineralogy have been studied in a lateritic profile derived from a syenite at akongo in sw cameroon ree and th mass balance calculations for the host rock minerals show that at least 70 of the lree s and 50 of the hrees are contained in allanite apatite titanite and epidote and at least 50 of the th is controlled by the same accessory minerals which represent about 2 wt of the unaltered syenite these accessory phases are destroyed during the first stages of weathering causing most of the rees and th to be rapidly released into the soil comparison of the variation in the zr ti and th content as a function of the apparent density of the different zones of the saprolite shows that th is the least mobile element the presence of secondary thorianite tho2 the etched surface on zircon grains and the presence of ti in secondary cerianite support this geochemical interpretation the concentration of thorium was therefore chosen as invariant relative to the concentration of the other elements especially the rees in mass balance calculations most of the rees are leached in the iron rich upper horizons loose nodular horizon iron crust and top of mottled clay horizon where the groundwater table moves saprolite and bottom of the mottled clay horizon the rees are fractionated and redistributed there is a juxtaposition of leached and accumulation zones with precipitation of lree aluminous hydrated phosphates this study supports the existence of two different cycles for the redistribution of elements in the soil 1 1 as dissolved ions in the saprolite horizon and 2 2 as individual particles in the upper part of the profile

geochemistry of the rare earth elements in hypersaline and dilute acidic natural terrestrial waters complexation behavior and middle rare earth element enrichments rare earth element ree speciation was modelled in acid 2 9 ph 3 5 hypersaline groundwaters from australia and from the palo duro basin in texas usa using a combined specific ion interaction pitzer model and ion pairing model the free metal ion species i e ln3 is the dominant form of dissolved rees in these systems accounting for 40 70 of the dissolved metal in groundwater from lake tyrrell victoria australia 50 90 of the rees in groundwater from lake gilmore western australia and always 90 of each ree in the texas groundwaters lakes tyrrell and gilmore are actually dry lakes that act as groundwater discharge zones the abundance of the free metal ion species increases in these waters with increasing ionic strength and with decreasing ph the free metal ion species is followed in abundance by ree sulfate and ree chloride complexes that account for 20 50 and 10 15 respectively of the dissolved rees in the groundwaters from lake tyrrell 15 30 and 5 20 respectively in the groundwaters from lake gilmore and 3 and 7 respectively in the palo duro basin groundwaters the groundwaters of the lake tyrrell system and the palo duro basin are enriched in the middle rees mrees compared to both the light rees lrees and the heavy rees hrees only nd sm and dy were determined in the lake gilmore groundwaters and consequently it is unclear whether these acid groundwaters are also enriched in the mrees previous investigators suggested that fe rich organic flocs ree phosphate complexation and solid liquid exchange reactions between terrestrial waters and mree enriched surface fe mn coatings suspended particulates or secondary mineral phases within aquifer materials may promote the development of mree enrichments in natural waters we propose that organic colloids and ree phosphate complexes are insignificant in acidic natural waters in regards to mree enrichments instead solid liquid exchange reactions or dissolution of surface coatings suspended particulates and or secondary phases as well as sulfate complexation more likely controls the development of mree enrichments in acidic natural terrestrial waters

rare earth elements in river waters we measured rare earth element ree concentrations in river waters to characterize the suspended and dissolved river flux of the ree to the oceans the ree pattern of river suspended materials is sensitive to drainage basin geology a positive correlation is observed between la yb ratios and nd model ages for the rivers studied major rivers have light ree enriched patterns relative to the north american shale composite nasc with la yb n 1 6 2 7 river water dissolved material 0 2 m is heavy ree enriched relative to suspended material and the most pronounced negative ce anomalies occur in rivers of high ph light ree concentrations vary by approximately 3 orders of magnitude and are inversely related to ph and major cation concentrations from these data we estimate that typical major river runoff has heavy ree depleted suspended material with la yb n 1 9 we conclude that the terrigenous input to the oceans from major rivers is heavy ree depleted relative to shales from the available data average river water dissolved material appears to be heavy ree enriched with la yb n 0 4 estuarine removal processes lower the dissolved ree river flux by approximately 60 and result in a flux that is more heavy ree enriched with la yb n 0 2 calculated oceanic residence times with respect to river input range from 2300 to 21 000 years are shortest for ce and greatest for the heavy ree and la such long residence times may suggest the presence of additional sources of ree in seawater

light rare earth elements enrichment in an acidic mine lake lusatia germany abstract the distribution of rare earth elements ree was investigated in the acidic waters lake and groundwater of a lignite mining district germany the fe and so4 rich lake water ph 2 7 displays high ree contents e g la 70 g l ce 160 g l and an enrichment of light ree lree in the nasc normalised pattern considering the hydrodynamic model and geochemical data the lake water composition may be calculated as a mixture of inflowing quaternary and mining dump groundwaters the groundwater of the dump aquifer is lree enriched nevertheless the leachates of dump sediments generally have low ree contents and display flat nasc normalised patterns however geochemical differences and ree pattern in undisturbed lignite lree enriched pattern and low water soluble ree contents and the weathered lignite of the dumps flat ree pattern and high water soluble ree contents suggest that lignite is probably the main ree source rock for the lake water

the geochemistry of rare earth elements in groundwater from the carnmenellis area southwest england shallow groundwater samples from the carnmenellis area of southwest england collected from wells boreholes springs adits and stream baseflow represent recently recharged waters of low salinity their major ion concentrations closely reflect the lithology of their host rocks which comprise the carnmenellis granite and devonian metasediments and metabasite of greenschist grade groundwaters from the granite are predominantly na cl or na ca cl type whilst those from the metasediment are na ca mg cl hco3 waters with a larger range of compositions the major ion compositions are predominantly a function of water rock interaction processes and the larger range of metasediment water compositions probably reflects the greater lithological variation the ph of groundwater samples circulating through granite is typically lower than that of groundwater in the metasediments the range being 4 3 to 7 2 median 5 7 and 4 7 to 8 0 median 6 6 respectively rare earth element ree concentrations of 0 45 m filtered groundwater samples have been determined by inductively coupled plasma mass spectrometry icp ms a large range of concentrations exists and many are below detection limits but levels reach up to 229 g 1 1 6 m total rees the rees are strongly controlled by ph with higher levels in groundwaters of ph 6 chondrite normalised profiles are light rare earth element lree enriched compared to heavy rare earths hrees with a common slight negative eu anomaly both features reflecting the compositions of their host rocks ree profiles therefore appear to be controlled by water rock interactions involving predominantly ree enriched minerals in the granite the rees are probably derived mainly from the accessory minerals monazite and apatite as well as the high ree framework minerals biotite and muscovite the source of rees in groundwater from the metasediments is more uncertain but probably includes clay minerals chlorite and carbonate ree compositions normalised to shale have flatter profiles although many are slightly convex with higher normalised sm eu and gd values a few metasediment derived waters with high total ree concentrations have lree enriched shale normalised patterns it is suggested that the bulk of the rees in these few samples is colloidal rather than totally dissolved groundwaters from the metasediments have a notable depletion in ce which is distinct from waters in the granite this depletion is problematic in that it is difficult to see how redox processes could be the dominant control since groundwaters from the metasediments are unlikely to be more oxidising than those from the granite likewise variations in ph fail to totally explain the distinctions in ce concentration and la ce ratios between the two water types it is therefore suggested that the ce contents are largely source related rather than process related the observed ree compositions of granite and metasedimentderived groundwaters from the carnmenellis area are so distinctive that the rees in general and ce in particular might be useful as future tracers in studies of water rock interaction and groundwater provenance

rare earths and yttrium hydrostratigraphy along the lake kinneret dead sea arava transform fault israel and adjoining territories rare earth elements and y rey have been analysed in 49 groundwaters from localities in the areas of lake kinneret and the jordan and arava valleys these waters originate from various aquifers and the rey abundances are expected to be controlled by the aquifer rocks the rey pattern allow one to distinguish interaction of waters with basalts basalt limestone interaction zones silicified limestones limestones from the judea and avdat groups upper cretaceous and eocene respectively and sandstones of the lower cretaceous kurnub group groundwater from the quaternary alluvial fill dead sea group are either controlled by judea group limestone or kurnub group sandstone the rey patterns show characteristic features for each group in hydrogeological systems the rocks of natural replenishment areas are usually not the same as rock units from which the waters are collected this becomes evident by comparing the lithostratigraphic groups from which the waters were collected and the hydrochemical grouping according to rey patterns with their characteristic trends and anomalies in many cases there is a correspondence between the lithostratigraphic and the hydrochemical grouping in other cases the 2 groupings disagree this disagreement proves inter aquifer flow of groundwater in some cases the geologically derived aquifers rocks of origin differ from those indicated by rey patterns thus applying the rey grouping new fundamental information for hydrological models can be given and sources of salinisation can be elucidated

cerium sequestration and accumulation in fractured crystalline bedrock the role of mn fe hydr oxides and clay minerals abstract this study focuses on the mechanisms of ce sequestration and accumulation in the fracture network of the upper kilometer of the granitoid bedrock of the baltic shield in southeast sweden laxemar area sweden the material includes 81 specimens of bulk secondary mineral precipitates fracture coatings collected on fracture walls identified in 17 drill cores and 66 groundwater samples collected from 21 deep boreholes with equipment designed for retrieval of representative groundwater at controlled depths the concentrations of ce in the fracture coatings although varying considerably 10 90th percentiles 67 438 mg kg 1 were frequently higher than those of the wall rock 10 90th percentiles 70 118 mg kg 1 linear combination fitting analysis of ce l iii edge x ray absorption near edge structure xanes spectra obtained for 19 fracture coatings with relatively high ce concentrations 145 mg kg 1 and a wide range of ce anomaly values revealed that ce iv occurs frequently in the upper 10 m of the fracture network ce iv ce total 0 06 1 00 in 8 out of 11 specimens and is mainly associated with mn oxides modeled as ce oxidatively scavenged by birnessite these features are in line with the strong oxidative and sorptive capacities of mn oxide as demonstrated by previous studies and abundant todorokite and birnessite like mn oxides identified in 3 out of 4 specimens analyzed by mn k edge x ray absorption spectroscopy xas in the upper parts of the fracture network down to 5 m for a specimen with very high ce concentration 1430 mg kg 1 and nasc normalized ce anomaly 3 63 the analysis of ce xanes and mn xas data revealed i a predominance of ce oxide in addition to ce scavenged by mn oxide and ii a large fraction of poorly crystalline hexagonal birnessite and aqueous mn 2 suggesting a recent or on going oxidation of mn 2 in this fracture in addition the ce oxide precipitates on this fracture observed by in situ sem eds contained considerable amounts of mn these spectroscopic and microscopic features led us to suggest that the remarkable accumulation of ce iv in this fracture is a result of repeated formation and dissolution of mn oxides that is formation of mn oxide followed by oxidative scavenging of ce as ce oxide nanoparticles which largely remained during the subsequent reductive dissolution of the mn oxides in addition the xanes data indicate that goethite has the capability to oxidize ce at near neutral ph under our experimental conditions goethite reacted with 0 001 m ce for 48 h in a glove box with o 2

the behaviour of the rare earth elements during mixing of river and sea waters rare earth element concentrations have been measured in organic rich luce river water and coastal sea water concentrations e g 350 1850 pmol kg nd in the water of luce and 45 350 pmol kg nd in luce bay are related to the presence of particles with 30 60 of the ree associated with 0 4 0 7 m particles and to riverine fe concentrations ree fractionation occurs in the river water the submicrometre river water is heavy ree enriched whereas the coarser fraction has a more shale like ree pattern laboratory experiments show that the ree in organic rich river waters are chiefly associated with feorganic matter colloids which flocculate during estuarine mixing preferential removal of heavy ree 95 relative to light ree 60 occurs but no ce anomaly is developed in contrast no ree removal occurs during estuarine mixing with organic poor river water

sequential leachates of multiple grain size fractions from a clay rich till saskatchewan canada implications for controls on the rare earth element geochemistry of porewaters in an aquitard porewater ree concentrations vary by an order of magnitude over 45 vertical m in a thick clay rich till aquitard in southern saskatchewan to address controls on aqueous ree the till was disaggregated into seven size fractions 850 425 850 295 425 180 295 150 180 75 150 and 75 m each fraction was sequentially leached with water l1 1 m naoac ph 5 l2 0 25 m nh2oh hcl l3 1 m nh2oh hcl l4 12 m hcl kclo3 4 m hno3 l5 and the residue digested in na2o2 l6 aqueous leachate of the 75 m size fraction has a near flat ree pattern at 0 1 paas and carries 99 of ree relative to the total from all l1 leached size fractions aqueous leachates of the coarser size fractions have flat patterns 1 to 2 orders of magnitude lower leachate l2 extracts metals held electrostatically on inorganic or organic material the ree also plot at 0 1 paas with a convex up pattern and a maximum at gd leachate l3 of amorphous fe and mn oxyhydroxides carries more ree than l1 l2 or l4 and like l2 has a mildly convex up pattern there are lower ree abundances associated with crystalline fe and mn oxides l4 than with amorphous counterparts and hree are fractionated and depleted leaching of organic matter l5 produces ree patterns comparable to those of l4 the residue l6 has convex down ree patterns at 0 1 to 0 4 paas with prominent positive eu anomalies from plagioclase feldspar excepting the 75 m size fraction natural porewaters have mildly fractionated patterns with lree and mree depletion versus convex up patterns for leachates l1 l2 and l3 lree and mree may readily sorb onto clays or clay coatings in the till and be desorbed during leaching

upper soil horizons control the rare earth element patterns in shallow groundwater several studies dedicated to the aquatic geochemistry of rare earth elements rees have displayed a wide topography related spatial variability in the ree signatures of shallow groundwater the aim of this study was to understand the processes leading to this specific ree signature notably with regard to the size of the ce anomaly soils were sampled in order to encompass the expected topographic variability in the organic carbon oc fe mn ratio leaching experiments were performed with the uppermost horizons of the soil the ree patterns that developed in the soil leaching solution were similar to the ree patterns for the shallow groundwater collected in this catchment the negative ce anomaly evolves in a similar manner according to the topography this spatial variation is strongly correlated with the soil oc fe ratio for a low oc fe ratio the negative ce anomaly amplitude in the soil solution is large whereas a high oc fe ratio generates a small or insignificant ce anomaly reductive dissolution experiments using soil with low oc fe ratios demonstrated that the ree pattern for soil fe oxyhydroxides exhibited a positive ce anomaly and hree enrichment indicating a preferential association of these elements with fe oxyhydroxides the rare earth element signature observed in the shallow groundwater is affected by fe oxyhydroxides present in the upper soil horizons in contrast in soil with a high oc fe ratio the ree pattern obtained under reducing conditions did not exhibit any ce anomaly suggesting that in the bottomland the ree signature is affected by the oc content in the uppermost soil this study highlights the impact of organic matter on the fe pedofeatures which control the development of a negative ce anomaly in shallow groundwater

rare earth element resources in coal mine drainage and treatment precipitates in the appalachian basin usa abstract drainages from abandoned coal mines in the appalachian basin represent a potential source of rare earth elements and yttrium rey many of which are considered to be critical resources due to their use in electronics and batteries we report rey data from coal mine drainage cmd sites and precipitates from cmd treatment systems throughout pennsylvania most cmd discharges are enriched in total rare earth elements relative to concentrations expected in unaffected surface or ground waters generally by 1 4 orders of magnitude relative to the north american shale composite nasc which approximates the rock with which mine waters interact cmd waters generally show a pattern of enrichment in the middle ree including several identified as critical resources nd eu dy tb low ph discharges tend to have higher rey concentrations than circumneutral discharges and a precipitous drop in concentration around ph 6 6 suggests adsorption of rey in the mine water flow path at near neutral ph values treatment precipitates including fe oxy hydroxides ca mg lime slurries and si and al rich precipitates are enriched in rey relative to the average cmd discharge value by factors of 103 104 while the discharges and precipitates analyzed in this study did not overlap in space and time the overall rey pattern of the precipitates approximate those of the cmd but with a slight depletion in light rare earth elements the higher rey concentrations in precipitates from systems treating low ph discharges most likely reflects the generally higher rey concentrations in these discharges but this needs to be established through direct comparisons over multiple seasonal cycles we estimate that coal mine drainage outflows in the appalachian basin generate a total of about 538 metric tons of rey per year in a dissolved state with 83 of that from low ph

rare earth elements in tributaries of lake baikal siberia russia abstract ree dissolved in waters from sixty five sampled tributaries of lake baikal show diversity in abundances ree 0 02 2 16 g l and distribution patterns la yb n 0 20 5 58 la tb n 0 30 2 59 total ree contents vary seasonally and yearly while ree patterns remain generally similar the ree patterns in stream waters correlate with those in the drained rocks and hence seem to be predominantly controlled by watershed lithology rivers having small watersheds around lake baikal belong to six lithological provinces with different stream water ree patterns the olkha plateau and the ranges of primorsky baikalsky barguzin ulan burgassy and khamar daban the khamar daban province in turn is lithologically heterogeneous and comprises four subprovinces with different respective patterns of dissolved ree rock water interaction in subsurface aquifers that feed the baikal inlets provides much stronger lithological control of ree than the weak interaction of short and rapid streams with rocks on the surface ree fractionation in stream waters show negative ce anomalies in almost all samples ce anom 0 12 0 97 except for those of large rivers selenga turka barguzin upper angara and kichera the reason is that the great length relatively slow current and the presence of streambed fine alluvium make the water chemistry more uniform and the ree patterns less dependent on local variations in watershed lithology the sampled tributaries represent a range of physico chemical and geomorphological conditions which can be used as reference for calibrations in future studies of sediment sources and possibly as a valuable tool for mineral exploration

lateral migration of linear dunes in the strzelecki desert australia linear dunes in the strzelecki desert trend roughly south north sand transport which is toward the nne has caused the dunes to migrate eastward while they extend or migrate northward eastward lateral migration is evidenced by 1 asymmetrical shape of the dunes east facing slopes are several times as steep as west facing slopes 2 asymmetrical accumulation of loose recently transported sand relatively abundant on east facing slopes 3 asymmetrical outcropping of older semiconsolidated aeolian sand on the dune surface more abundant on west facing slopes and 4 east dipping foreset beds that underly the west facing flanks of some dunes dunes in the strzelecki desert are still active in the sense that sand is transported along and across many dune crests however the dunes are composed primarily of pleistocene strata indicating that the trend of the dunes was established before the holocene the obliquity of the dunes to the transport direction is not merely an aberration of the wind regime of the last few decades preferential accumulation of sand on east facing flanks indicates that the dunes migrated eastward several metres during the holocene moreover the west facing flanks of some dunes have experienced a minimum of tens of metres of erosion this asymmetric erosion and deposition were caused by dune obliquity and lateral migration that may have begun as early as the pleistocene dunes in the strzelecki desert and in the adjacent simpson desert display a variety of grossly different internal structures computer graphics experiments demonstrate that many of these differences in structure can be explained by different angles of climb of the dunes

rare earth element systematics in hydrothermal fluids abstract rare earth element concentrations have been measured in hydrothermal solutions from geothermal fields in italy dominica valles caldera salton sea and the mid atlantic ridge the measured abundances show that hydrothermal activity is not expected to affect the ree balance of either continental or oceanic rocks the ree enrichment of the solutions increases when the ph decreases high temperature solutions 230 c percolating through different rock types may show similar ree patterns

the effect of diagenesis and fluid migration on rare earth element distribution in pore fluids of the northern cascadia accretionary margin analytical challenges in obtaining high quality measurements of rare earth elements rees from small pore fluid volumes have limited the application of rees as deep fluid geochemical tracers using a recently developed analytical technique we analyzed rees from pore fluids collected from sites u1325 and u1329 drilled on the northern cascadia margin during the integrated ocean drilling program iodp expedition 311 to investigate the ree behavior during diagenesis and their utility as tracers of deep fluid migration these sites were selected because they represent contrasting settings on an accretionary margin a ponded basin at the toe of the margin and the landward tofino basin near the shelf s edge ree concentrations of pore fluid in the methanogenic zone at sites u1325 and u1329 correlate positively with concentrations of dissolved organic carbon doc and alkalinity fractionations across the ree series are driven by preferential complexation of the heavy rees simultaneous enrichment of diagenetic indicators doc and alkalinity and of rees in particular the heavy elements ho to lu suggests that the heavy rees are released during particulate organic carbon poc degradation and are subsequently chelated by doc ree concentrations are greater at site u1325 a site where shorter residence times of poc in sulfate bearing redox zones may enhance ree burial efficiency within sulfidic and methanogenic sediment zones where ree release ensues cross plots of la concentrations versus cl li and sr delineate a distinct field for the deep fluids z 75 mbsf at site u1329 and indicate the presence of a fluid not observed at the other sites drilled on the cascadia margin changes in ree patterns the presence of a positive eu anomaly and other available geochemical data for this site suggest a complex hydrology and possible interaction with the igneous crescent terrane located east of the drilled transect

the development of acidic groundwaters in coal bearing strata part i rare earth element fingerprinting abstract this study examines the rare earth element ree pattern of acidic mine discharges in the durham basin ne england as a means of fingerprinting their sources and understanding the water rock interactions although whole rock compositions proved to be unhelpful mimicking acid mine water generation in a series of selective leachates of the coal and coal bearing strata gave ree patterns similar to those measured in the emergent waters ree ratios and anomalies were used as indicators of specific interactions in the development of acidic groundwater the implications of the findings for the classification and evolution of acid mine discharges are discussed

behavior of rare earth elements in groundwater during flow and mixing in fractured rock aquifers an example from the dandenong ranges southeast australia a previously defined flow system is used to investigate ree behavior at different stages along groundwater flow paths in fractured basalt and sedimentary aquifers results from this study indicate that ree concentrations and patterns predominantly reflect different types and rates of reactions taking place to those controlling major ion chemistry in areas where recharge is through sediments ree concentrations are high nd 8 62 31 61 ng l and localised processes such as source heterogeneity control ree patterns and concentrations increased concentrations of rees in these groundwaters where ph 6 1 is a result of early stage ree mobilisation in the flow system in contrast where groundwater recharges through basalt ree concentrations are low nd 2 40 4 75 ng l and ree concentrations are relatively constant along groundwater flow paths indicating steady state conditions groundwater from both the sediment and basalt aquifer systems flows into the local discharge area in contrast to tds contents and major ion ratios groundwater from the discharge area has ree concentrations nd 1 84 4 18 ng l and patterns that reflect a larger component of flow from the basalt aquifer lower ree concentrations of groundwater from the regional sedimentary aquifer may result from progressive ree sorption or co precipitation as indicated by an increase in y ho cl cn ratios and hree enrichment for groundwater with ph not vert similar 7 1 due to greater abundances of hree vs lree dicarbonato complexes

rare earth elements neodymium and strontium isotopic systematics in mineral waters evidence from the massif central france abstract rare earth elements rees and sr and nd isotope distributions have been studied in mineralized waters from the massif central france the co 2 rich springs are characterized by a neutral ph 6 7 associated with total dissolved solids tds from 1 to 7 g l 1 the waters result from the mixing of very mineralized water pools thought to have equilibrated at a temperature of around 200 c with superficial waters these two mineral water pools evidenced by sr isotopes and dissolved rees could reflect 2 different stages of water rock interaction and an equilibrium with different mineral assemblages the concentrations of individual dissolved rees and total dissolved rees ree in the mineral waters examined vary over several orders of magnitude but are not dependent on the main parameters of the waters tds t c ph total organic c the dissolved ree concentrations presented as upper continental crust normalized patterns show hree enrichment in most of the samples the time evolution of ree patterns does not show significant fluctuations except in 1 borehole located in the limagne d allier area which was sampled on 16 occasions over an 18 month period ten samples are hree enriched whereas 6 samples show flat patterns the aqueous speciation of rees shows that co 2 3 complexes dominate 80 over the free metal f so 2 4 and hco 3 complexes the detailed speciation demonstrates that the fractionation of rees i e the hree enrichment in co 2 rich and ph neutral fluids is due essentially to the predominance of the co 2 3 complexes the sr isotopic composition of the mineral waters in the massif central shows different mixing processes in the cezallier area at least 3 end member water types exist the most dilute end member is likely to originate as poorly mineralized waters with minimal groundwater circulation two other mineralized end members are identified although the link between the geographical location of spring outflow and the mixing proportion between the 2 end members is not systematic the range in nd 0 for mineralized waters in the massif central correlates well with that of the known parent rocks except for 4 springs one way to explain the nd 0 in these instances is a contribution from drainage of volcanic rocks the isotopic systematics help to constrain the hydrogeological models for this area

diverse fractionation patterns of rare earth elements in deep fracture groundwater in the baltic shield progress from utilisation of diffusive gradients in thin films dgt at the aspo hard rock laboratory abstract rare earth elements rees were studied in groundwater in fractures at depths between 144 m and 450 m in proterozoic granitoids on the baltic shield at a coastal site in south eastern sweden aspo hard rock laboratory a specially designed device was used to sample the groundwater under in situ high pressure and low redox conditions the rees were measured via both diffusive gradients in thin films dgt samplers after approximately three week deployment times and after conventional filtration 0 45 m membrane filters the concentrations of reedgt were lower than the ree0 45 m concentrations in all 14 studied groundwaters this is explained by development of a diffuse boundary layer dbl in the solution at the dgts caused by the low flow and in some of the groundwaters additionally by the presence of organically complexed ree that diffuse slowly in the diffusive gel of the dgt among the 14 studied groundwaters there was a huge range in reedgt fractionation patterns ranging from enrichment to a nearly three order of magnitude depletion of the heavy rees hrees despite a relatively homogenous bedrock granitoids the hree enrichment is explained by preservation of the fractionation signature as hree enriched sea water intruded and flowed through the fractures supported by the high proportion of modelled ree fulvic acid complexes in these waters the strong hree depletion which occurred in saline groundwater was ascribed to an advanced ree equilibrium between the groundwater and primary and or secondary minerals and the pore water in the bedrock yet other groundwaters had flat or moderately hree depleted patterns which in some cases may have been caused by mixing of small portions of surficial waters with saline groundwater

behavior of sm and nd in a lateritic soil profile a study of lateritic soils and samples of ground and river waters was carried out in the nsimi zoetele a tropical watershed in the southern cameroon the nd isotopic compositions and concentrations of nd and sm were determined it was found that the nd isotopic composition of the river waters was much more radiogenic than the parent rocks and that the nd in the waters is not homogeneous but is carried by different dissolved and complexed components that are not isotopically homogenized the soil profile shows a regular increase in e nd going from the parent rock e nd 36 to e nd 18 near the top of the profile the nd transported in the river is thus not representative of the parent rock but reflects the results of differential weathering of constituent minerals and the redeposition of ree in phosphates and a significant contribution of radiogenic nd from dust the concentration of nd in the river water is far above that found in temperate climate rivers and thus this type of tropical river may play a dominant role in the marine nd and ree budget it is suggested that the correlation of ree with doc is related to doc fixing some dissolved ree but that the ree in solution is governed by other mechanisms no major shifts were found in sm nd however a regular progression from the parent rock through the lateritic profile was found the upper laterite profile shows large almost uniform depletions in all ree below tb and enrichment above complementary behavior was found in the lower part of the section the concentration of nd relative to the immobile elements zr and ti in the laterite is depleted by a factor of 10 th nd and sm are enriched in the lowest zone sampled and must reflect redeposition of ree from the upper part of the weathering section and is associated with phosphate formation it is concluded that the soil evolution involves both differential dissolution of primary phases from the parent rock significant to major input of ree from atmospheric dust from other regions and the formation of diagenetic phases particularly phosphates

adsorption of rare earth elements onto carrizo sand experimental investigations and modeling with surface complexation rare earth element ree adsorption onto sand from a well characterized aquifer the carrizo sand aquifer of texas has been investigated in the laboratory using a batch method the aim was to improve our understanding of ree adsorption behavior across the ree series and to develop a surface complexation model for the rees which can be applied to real aquifer groundwater systems our batch experiments show that ree adsorption onto carrizo sand increases with increasing atomic number across the ree series for each ree adsorption increases with increasing ph such that when ph 6 0 98 of each ree is adsorbed onto carrizo sand for all experimental solutions including when actual groundwaters from the carrizo sand aquifer are used in the experiments rare earth element adsorption was not sensitive to ionic strength and total initial ree concentrations in our batch experiments it is possible that the differences in experimental ionic strength conditions i e 0 002 0 01 m nacl chosen were insufficient to affect ree adsorption behavior however cation competition e g ca mg and zn did affect ree adsorption onto carrizo sand especially for light rare earth elements lrees at low ph rare earth element adsorption onto carrizo sand can be successfully modeled using a generalized two layer surface complexation model our model calculations suggest that ree complexation with strong surface sites of carrizo sand exceeds the stability of the aqueous complexes lnoh 2 lnso4 and lnco3 but not that of ln co3 2 or lnpo4 in carrizo groundwaters thus at low ph 7 3 where major inorganic ligands did not effectively compete with surface sites for dissolved rees free metal ion ln 3 adsorption was sufficient to describe ree adsorption behavior however at higher ph 7 3 where solution complexation of the dissolved rees was strong rees were adsorbed not only as free metal ion ln 3 but also as aqueous complexes e g as ln co3 2 in carrizo groundwaters because heavy rare earth elements hrees were preferentially adsorbed onto carrizo sand compared to lrees original hree enriched fractionation patterns in carrizo groundwaters from the recharge area flattened along the groundwater flow path in the carrizo sand aquifer due to adsorption of free and solution complexed rees copyright 2005 elsevier ltd

produced fluids and shallow groundwater in coalbed methane cbm producing regions of alberta canada trace element and rare earth element geochemistry abstract the production of coalbed methane cbm represents a vital new source of natural gas supply in western canada there are however concerns over potential negative environmental impacts on groundwater resources caused by potential contamination with fluids and gases from coal bearing strata this paper provides a brief description of the geochemistry and a detailed discussion of trace element and rare earth element ree concentrations of the produced fluids from two major coal deposits in western canada the mannville formation and the horseshoe canyon belly river group hscn brg and shallow groundwater sgw in this region it evaluates how the depositional environment redox conditions and water rock interactions influence the trace element and rare earth element distributions in the produced fluids and sgw of the study area produced waters from the mannville formation are a saline na cl type and a high boron content is indicative of a brackish marine depositional environment in contrast the hscn brg produced fluids are a na hco3 water type and have lower total dissolved solids tds and lower boron concentrations shallow groundwater has a na hco3 to na hco3 so4 water type with often high concentrations of sulphate and low tds some groundwater samples many hscn brg and all mannville fluids had low sulphate concentrations often with elevated 34s values indicating that bacterial sulphate reduction had occurred making the redox environment suitable for methanogenesis dissolved gas from the mannville formation had a notable thermogenic component whereas dissolved gas from the hscn brg and free gas in shallow groundwater contained methane predominantly or exclusively of biogenic origin mannville produced waters are up to 70 times more concentrated in trace elements compared to the hscn brg waters and up to 300 times more concentrated than shallow groundwater in the mannville fluids trace elements such as as se and pb occurred in concentrations often exceeding drinking water guidelines 5 g l 10 g l and 10 g l respectively whereas most samples in the hscn brg contained only se above drinking water guidelines and a few samples contained as and pb slightly above the maximum allowable concentrations for drinking water therefore the potential risk of trace metal contamination of shallow groundwater with hscn brg swabbing fluids is low because of their comparatively low trace metal content rare earth elements in the mannville produced fluids indicate interaction with silicate dominated host rocks in contrast the rees of the hscn brg produced fluids show interaction with carbonate rich material the shallow groundwater shows a similar pattern to the hscn brg suggesting that rees are not a suitable parameter to monitor potential contamination of shallow groundwater with cbm fluids from the hscn brg however several other geochemical and isotopic parameters are sufficiently distinct between shallow groundwater hscn brg and mannville fluids so that cross contamination with produced fluids or gases should be identifiable with a suitable geochemical monitoring program

ree chemistry and sm nd systematics of late archean weathering profiles in the fortescue group western australia two weathering profiles each consisting of an upper sericite rich zone and a lower chlorite rich zone are preserved between flows of the mt roe basalt in the fortescue group hamersley basin western australia ree concentrations in samples from these two profiles which originally developed ca 2 760 ma show large variations depending on stratigraphic position lree abundances and la yb n are greatest at depths of 3 6 m below the paleosurface of the mt roe 1 profile and are somewhat lower in samples above this level the lrees reach concentrations 6 9 times greater than in the underlying basalt and thus appear to have been mobilized downward in the paleosol and concentrated in its middle part lree concentrations in the 2 profile show a similar distribution but with a sharp increase in all ree concentrations within 50 cm of the paleosurface the distinction between the ree profiles in the two paleosols may be related to the difference in the overlying material the 1 paleosol is overlain by a few meters of sediments and then by basalt whereas the 2 paleosol is directly overlain by basalt the lrees appear to have been mobilized both during chemical weathering of the parental basalt and during later lower greenschist facies metamorphism and metasomatism of the paleosols remobilization of the rees during the regional metamorphism of the fortescue group is confirmed by a whole rock sm nd reference isochron of mt roe 1 samples with an age of 2 151 360 ma variable initial 143nd 144nd values of unweathered basalt samples which may represent the paleosol protolith prevents a confident determination of the magnitude of lree mobility both the initial mobilization of the rees during weathering and the metasomatic remobilization appear to have taken place under redox conditions where ce was present dominantly as ce3 because ce anomalies are not developed within the sericite zone samples regardless of concentration europium anomalies in the paleoweathering profile are somewhat variable and were probably modified by mobilization of eu2 at metamorphic conditions in all samples the hrees appear to have been relatively immobile and correlate with al ti cr v zr and nb sm nd systematics and ree patterns of four unweathered basalt samples indicate derivation of the mt roe basalts from a heterogeneous and enriched source having epsilon nd between 4 0 and 7 4 initial 143nd 144nd values of these basalts are even lower than those reported by nelson et al 1992 for fortescue group basalts and indicate a substantial crustal component in the generation of mt roe basalts

major and trace elements in river borne materials from the cuyuni basin southern venezuela evidence for organo colloidal control on the dissolved load and element redistribution between the suspended and dissolved load abstract the cuyuni basin is a metallogenic rich area located in southern venezuela in the precambrian guyana shield it comprises two geologically distinct zones one with granite domes and intercalated greenstone belts in the northern and western part of the basin and the other with stratified arenaceous deposits in the south the suspended dissolved and total load of the rivers draining these contrasting zones show similar characteristics to those observed in other major tropical rivers such as the congo and amazon and vary in composition between the different source areas although the river borne material in this basin varies in composition from one river to another and contains highly variable proportions of dissolved constituents the ratio between the suspended and the dissolved load msusp mdiss appears related to the ratio of suspended to dissolved organic carbon contents ss doc according to the relationship m susp m diss k i ss doc the coefficient of proportionality ki in this equation varies from one element to another this relationship leads us to recognize a the important role of organo colloidal phases in controlling the elements in solution b the occurrence of a re distribution of elements between the suspended and dissolved load in the river environment according to this analysis coefficients ki appear to represent partition coefficients between two phases the suspended load and the organic rich colloidal fraction of the dissolved load these coefficients estimated from analysis of the total dissolved load versus ss doc diagrams yield values which classify in an order similar to that classically proposed for the relative capacity of the elements to form organic ligands or their adsorption capacity the coefficients actually vary as a function of the hydrolysis constants of the respective elements theoretical considerations show that equilibrium processes between the surfaces of suspended material and those of colloidal type species in solution are able to explain the observed relationship we show that such surface equilibria can be extended to the whole products in conditions which may prevail in tropical river waters that is suspended matter primarily consisting of phases for which surface complexation is important as is the case of clays or iron manganese oxides produced by the present day weathering of tropical soils finally we analyse the specific behaviour of the ree in rivers of the cuyuni basin

distribution of the rare earth elements in porewaters from a clay rich aquitard sequence saskatchewan canada a 91 4 m thick porewater profile of the rare earth elements rees is presented from a thick clay rich pleistocene till 0 80 m and cretaceous clay 80 156 m aquitard sequence saskatchewan canada the upper 3 4 m of till is weathered absolute aqueous concentrations of the rees vary by more than one order of magnitude aqueous ree concentrations decrease with depth through the weathered till to a depth of about 15 m below ground below which the concentrations in the unweathered till remain relatively consistent the only porewater sample from the clay 91 4 m has the highest total ree concentration elevated ree concentrations in the oxidized zone attributed to geochemical weathering there is no significant seasonal variation in aqueous ree concentrations within the water columns in the piezometers redox conditions and solution complexation reactions exert predominant controls on the aqueous ree concentrations the majority of ree patterns are coherent characterized by overall negatively fractionated ree with convex down profiles from la to pr or nd and convex up from nd to tb in the porewater sample from the clay the lrees are an exception with a flat normalized profile hree lree fractionations in the porewaters are depth dependent and are mainly controlled by solution complexation with dissolved sulfate phosphate free carbonate ions and doc porewaters in the unweathered till 5 76 2 m are characterized by negative ce anomalies which may reflect in part negative ce anomalies in the host till geochemistry the negative ce anomalies are magnified relative to the host tills during water rock interaction and ree transportation porewaters from the weathered till exhibit strong positive ce anomalies relative to paas the host rocks and their leachates the ce anomalies are predominantly controlled by the redox conditions and solution complexation the large positive ce anomalies in these porewaters are probably caused by the oxidation of ce iii to ce iv that was stabilized in solution through complexation with high contents of inorganic and organic ligands positive eu anomalies relative to paas the host rocks and leachates of the host rocks result from hydrolysis of plagioclase feldspar the limited depth profile for total dissolved rees across the weathered unweathered till boundary is retarded with respect to that previously established for na k mg2 so42 and tds suggesting that chemical reactions control the migration of dissolved rees

using multivariate statistical analysis of groundwater major cation and trace element concentrations to evaluate groundwater flow in a regional aquifer groundwater samples were collected from 11 springs in ash meadows national wildlife refuge in southern nevada and seven springs from death valley national park in eastern california concentrations of the major cations ca mg na and k and 45 trace elements were determined in these groundwater samples the resultant data were subjected to evaluation via the multivariate statistical technique principal components analysis pca to investigate the chemical relationships between the ash meadows and death valley spring waters to evaluate whether the results of the pca support those of previous hydrogeological and isotopic studies and to determine if pca can be used to help delineate potential groundwater flow patterns based on the chemical compositions of groundwaters the results of the pca indicated that groundwaters from the regional paleozoic carbonate aquifers all of the ash meadows springs and four springs from the furnace creek region of death valley exhibited strong statistical associations whereas other death valley groundwaters were chemically different the results of the pca support earlier studies where potentiometric head levels 18o and d geological relationships and rare earth element data were used to evaluate groundwater flow which suggest groundwater flows from ash meadows to the furnace creek springs in death valley the pca suggests that furnace creek groundwaters are moderately concentrated ash meadows groundwater reflecting longer aquifer residence times for the furnace creek groundwaters moreover pca indicates that groundwater may flow from springs in the region surrounding scotty s castle in death valley national park to a spring discharging on the valley floor the study indicates that pca may provide rapid and relatively cost effective methods to assess possible groundwater flow regimes in systems that have not been previously investigated copyright 1999 john wiley sons ltd

chemical weathering in the drainage basin of a tropical watershed nsimi zoetele site cameroon comparison between organic poor and organic rich waters abstract this study deals with the weathering processes operating at the scale of a small catchment nsimi zoetele cameroon and is focused on the role of organic colloids on mineral weathering and transport of elements in natural waters samples of river spring and groundwaters from nsimi zoetele were filtered through membranes of decreasing pore size 0 22 m 0 025 m or 300 000 da 5000 da to separate colloidal fractions from the truly dissolved one major and trace elements and dissolved organic carbon doc were analysed in each fraction two kinds of waters can be distinguished in the catchment clear and coloured waters clear waters exhibit low concentrations of major and trace elements and doc elements are carried in these solutions in a true dissolved form except al and rare earth elements rees by contrast the higher abundances of al fe and trace elements in coloured waters are controlled by the colloidal fraction thermodynamic equilibrium calculations show that clear waters are in equilibrium with kaolinite and iron oxi hydroxide which are major minerals in the weathered soil for coloured waters the aqueous speciation of ca mg cu fe al la and th was calculated taking into account the complexes with humic acids speciation calculations for cu fe al la th show a strong complexation with humic acids in good agreement with the results of the filtration experiments by contrast although filtration experiments show a strong control of major cations by organic matter for example 75 for ca speciation calculations reveal that their complexes with humic ligands do not exceed a few percent of total dissolved elements this discrepancy is explained as an artefact induced by the organic colloids and occurring during the filtration procedure finally both filtration experiments and speciation calculations show that organic matter plays an important role in natural doc rich waters organic acids increase significantly the dissolution rates of silicates and oxi hydroxides and thus the amounts of solutes and of complexed elements leaving the catchment

removal of oceanic ree by authigenic precipitation of phosphatic minerals abstract early diagenetic phosphatic minerals containing rare earth elements ree are widespread in australian shallow marine sandstones of all ages most common is the aluminophosphate florencite ree al 3 po 4 2 oh 6 but the isomorphous and chemically intergrading phases crandallite gorceixite and goyazite all with up to several percent ree substituted for their major cation ca ba and sr respectively may also be present together they comprise up to 0 144 wt average 0 0134 wt of their host rocks the authigenic phosphates xenotime and apatite are also widespread but less common they all apparently precipitated within the diagenetic zones of sulphate reduction and methanogenesis as a result of reverse weathering reactions after the release of ree and po 4 by reduction of fe mn oxyhydroxides and the decomposition of organic material coating detrital particles as the aluminophosphates and apatite are enriched in light ree whereas xenotime concentrates heavy ree they collectively deposit light ree at a much greater rate la 129 10 9 g cm 2 yr 1 than heavy yb 0 40 10 9 g cm 2 yr 1 the total burial flux of light ree by shallow marine phosphatic precipitation is about 50 times greater than previously determined for deep sea sediments whereas heavy ree are buried at comparable rates this new sink produces a major imbalance in the marine ree budget requiring the existence of a substantial but currently unknown source to restore balance its size has important implications for the use of ree abundances distributions and isotopes as monitors of marine geochemical processes

europium redox equilibria in aqueous solution thermochemical data and recent advances in theoretical aqueous solution chemistry enable prediction of the relative stabilities of aqueous eu2 and eu3 over a wide range of temperatures and pressures at low temperatures near earth surface conditions the aqueous geochemistry of europium should be dominated by the trivalent state except possibly in the most reducing alkaline pore waters of anoxic marine sediments however at temperatures greater than about 250 c and elevated pressures divalent europium should predominate even with significant amounts of complexing trivalent europium is not stable at elevated temperatures and pressures consequently under most hydrothermal and metamorphic conditions europium in aqueous solution should be divalent at intermediate temperatures around 100 c significant activities of both eu2 and eu3 and related complexes can occur in aqueous solutions depending on the oxidation state and the ph of the solutions and the activities of potential ligands such as sulfate carbonate and chloride the predicted stability of divalent europium in aqueous solution at elevated temperatures is consistent with the large positive europium anomalies in rare earth element patterns of high temperature barites of hydrothermal and metamorphic origin reported by guichard et al 5 and with the observed depletion of europium as a result of high temperature sericitization of feldspar bearing assemblages discovered by alderton et al 1 it is suggested that significant fractionation of europium relative to the other rare earth elements may take place during high temperature hydrothermal alteration processes such as in the mid oceanic ridge systems because of the expected stability of divalent europium during these processes

rare earth elements ree in deep groundwater from granite and fracture filling calcite in the tono area central japan prediction of ree fractionation in paleo to present day groundwater rare earth elements rees combined with yttrium yree in deep groundwater from granite and fracture filling calcite are being studied at the mizunami underground research laboratory miu tono area central japan the groundwater was sampled from cored boreholes drilled from the miu galleries at 200 300 400 and 500 m depths the fracture filling calcite was collected from the same boreholes and dissolved in 1 m nh4 acetate buffer solution ph 4 8 major chemical composition of groundwater changed with depth and the concentrations of some major elements na k ca2 mg2 cl br and b increased with depth while alkalinity so42 and f decreased isotopic compositions of 18o and d indicated that the groundwater originated from meteoric water yree patterns of groundwater also changed with depth with heavy ree hree enrichment in shallow groundwater 200 to 400 m and light ree lree enrichment in deep groundwater 500 m the predominant yree species are yreeco3 and yree co3 2 laco3 65 70 la co3 2 8 27 luco3 20 38 and lu co3 2 53 77 the lree enrichment in the shallow groundwater resulted in preferential scavenging of positively charged yreeco3 by negatively charged bedrock surfaces in slightly alkaline groundwater ph 7 4 8 6 because of the construction and operation of the underground facility the shallow groundwater has been influenced by infiltration of surface water undersaturated in calcite in contrast the deep groundwater was barely affected by the mixing of surface water indicating that the yree originated from yree fractionation by bedrock granite irrespective of depth a negative ce anomaly preserved in the groundwater is probably indicative of paleo oxic conditions during paleo recharge the negative ce anomaly in the groundwater was possibly fractionated from sedimentary calcite with positive ce anomalies during the paleo recharge the yree patterns of the fracture filling calcite were enriched in lree the isotopic variations of 18o and 13c in the fracture filling calcite indicated that it originated from a mixture of sea water and fresh water at a temperature 100 c the yree patterns of paleo groundwater from which the fracture calcite precipitated were calculated using yree abundances in the fracture calcite and distribution coefficient reported in previous laboratory experiments the paleo groundwater was found to be enriched in lree and hree depending on the aqueous yree species our results suggest that changes in the paleo to present day yree fractionation range roughly from that of present day shallow to deep groundwater

environmental geochemistry of rare earth elements in cu porphyry mine tailings in the semiarid climate conditions of sarcheshmeh mine in southeastern iran abstract sarcheshmeh mine is one of the largest oligo miocene porphyry cu deposits in the world it is located in the kerman cenozoic magmatic arc in southeastern iran this paper discusses the geo environmental behavior of rare earth elements rees in the sarcheshmeh dammed tailing pond situated in semiarid climate for this purpose solid and water samples were collected to consider 1 weathering oxidation reactions and upward migration of soluble elements 2 super saturation and formation dissolution of the secondary evaporative phases 3 hydro geochemical changes of the surface and groundwater resources 4 flotation of the cu sulfide ore and tailing management strategies the mean values of the rees for fresh and weathered tailings and the evaporative phases were 113 0 103 7 and 74 6 mg kg respectively when compared with the fresh and weathered tailings the evaporative phases showed significant enrichment of hrees and a well depleted pattern of lrees except for that of eu this geochemical pattern suggests a higher solubility and mobility potential of hrees and eu compared with lrees resulting in good fractionation and enrichment of these elements in the surface evaporative layer formed on top of the weathered tailings the water samples showed a range of hydro geochemical features under acidic ph of 2 5 to 4 7 near neutral ph of 6 4 to 7 9 alkaline ph of 8 to 10 and highly alkaline ph 10 conditions the maximum concentration of rees was observed in the acidic waters produced by the weathered tailings after rainfall rees of 489 to 1903 g l although rees decreased as the ph value increased the general trend was compatible with the highest concentration of hrees rather than lrees the speciation calculations indicate that lnso4 ln so4 2 and ln3 are the primary forms of dissolved rees at acidic and near neutral ph and the dominant species was lnso4 lnco3 40 78 ln co3 2 31 68 and lnso4 31 07 were the dominant species under alkaline conditions at high alkaline ph the speciation pattern changed to lnoh2 53 15 ln co3 2 44 88 and lnco3 2 61 where ln denotes lanthanide based on the results and considering previous works it appears that ionic potential plays an important role in the geo environmental behavior of rees of adsorption tendency mobility potential and ionic substitution

tectonic environment of the devonian gramscatho basin south cornwall framework mode and geochemical evidence from turbiditic sandstones the portscatho formation within the allochthonous unit of the middle and upper devonian gramscatho group is a thick sequence of deep water sandstones and interbedded slates deposited by southerly derived turbidity currents into the gramscatho basin of south cornwall throughout an approximately 3 5 km thick sequence the portscatho formation is petrographically and chemically coherent except that the upper section shows a higher proportion of metamorphic clasts high but variable cr and low uniform zr abundances complementary framework mode and bulk geochemistry indicate that the sandstones were derived from a dissected continental magmatic arc of predominantly acidic composition similar to average upper continental crust but with an admixture of minor intermediate basic material flysch deposition took place in a fore arc setting the presence of an arc to the south of cornwall during the devonian implies that there was subduction at the margin of the gramscatho basin whose ultimate closure was accommodated by the northward stacking of flysch ophiolite nappes

fluid geochemistry of the cuopu high temperature geothermal system in the eastern himalayan syntaxis with implication on its genesis abstract high temperature geothermal fluids dissolve constituents pertinent to water rock interaction and magmatic volatile absorption resulting in high total dissolved solid tds values however this study focuses on the hydrochemical evolution of the low salinity hco3 na type high temperature geothermal fluid in cuopu eastern himalayas the geothermal water is recharged by local precipitation and glacier water from surrounding mountains the tds values are below 834 mg l and the constituents are mainly products of the water carbon dioxide rock interactions lacking magmatic volatile dissolved in the fluid the geothermal water reaches an almost complete chemical equilibrium with the feldspar or plagioclase enriched reservoir rock in a reducing condition the reservoir temperature is between 175 c 200 c while the temperature could reach up to 400 c in the deep crustas indicated by the carbon isotopic exchange equilibrium between co2 and ch4 the infiltrated glacier water was heated during its circulation within the hot thickened crust and continued dissolving the crustal metamorphic gas such as radiogenic helium and limestone metamorphic co2 until the junction of the two sets of faults provided an ascending channel for it upon rising along the conduit the geothermal water mixed with cold groundwater to different degrees approximately 0 015 mol l co2 escaped from the geothermal fluid when it scattered as bubbling hot springs on the surface of the anisotropic porous quaternary sediments such kind ofhydrochemical evolution of lowsalinity alkaline hco3 na type water represents a typical formation mechanism of the high temperature geothermal systems along the himalayas

geochemical behavior of rare earth elements during the evolution of co2 rich groundwater a study from the kangwon district south korea abstract a hydrochemical study of co 2 rich groundwaters in the kangwon district south korea was conducted to elucidate the behavior of rare earth elements ree as a result of mixing of co 2 rich waters the ree fractionation during the formation of carbonate precipitates was also investigated the co 2 rich waters can be classified into three chemical types na hco 3 ca na hco 3 and ca hco 3 with characteristic isotope compositions chemical and isotope data indicate that the na hco 3 waters were influenced by a deep co 2 supply at depth while other waters were formed by mixing between na hco 3 water and less saline shallow groundwater concentrations of total dissolved ree ree in co 2 rich waters varied according to the water types and were highest in the na hco 3 waters up to 3456 ng l their ree concentrations showed excellent correlations with parameters such as tds ph alkalinity 18 o and tritium indicating progressive mixing with shallow groundwater the distribution of dissolved ree concentration showed different patterns dependent upon water type the na hco 3 waters displayed an s shape pattern with strong heavy ree hree enrichment in contrast the ca na hco 3 water was characterized by a slight hree enrichment while the ca hco 3 water exhibited a relatively flat scattered low ree lree enrichment pattern the ree patterns of the precipitates formed from the original waters and of the residual waters after removal of the precipitates were similar to those of the original co 2 rich waters indicating that no ree fractionation occurred between precipitates and residual waters

tidally induced groundwater circulation in an unconfined coastal aquifer modeled with a hele shaw cell we use a scaled hele shaw cell to mimic tidally induced nearshore groundwater motion in an unconfined aquifer the low slope angle of sandy beaches contributes to a strongly asymmetric pattern of fluid exchange across the water sediment interface during tidal cycles this asymmetry leads to a time averaged groundwater circulation centered beneath the low tide level horizontal and vertical components of motion are of the same order horizontal seaward flow extends a significant depth beneath the interface consonant with a time averaged water table that is elevated above mean sea level providing the hydraulic gradient necessary to drive this deeper export of mass equal to the time averaged inflow by infiltration this tidally forced flow behavior likely contributes to observed fluctuations in submarine seepage rates moreover the circulation largely involves a subsurface cycling of seawater that infiltrates during the rising tide measurements of submarine seepage near the tidal zone therefore likely involve this cycled seawater as well as freshwater flows

seasonal variations of rare earths and yttrium distribution in the lowland havel river germany by agricultural fertilization and effluents of sewage treatment plants abstract ree and y rey distribution in the lowland havel river passing the federal state of berlin germany depends on contributions of point sources such pharmaceutical and high tech industries acid water from the open pit lignite mining and medical application of very stable organic gd chelates another omnipresent dispersed source of rey are water soluble ca phosphates containing micro amounts of eu ii bearing barite as components of common agricultural fertilizers after distribution in the field during the cold season october through march these ca phosphates dissolve and secondary phosphates and calcite precipitate both being enriched in light ree heavy ree are preferably exported by runoff together with part of the micro contaminant barite leading to high yb nd ratios in the havel water and rey distribution patterns with only small eu deficits during the warm season april through september light ree together with phosphate are leached from secondary soil minerals by runoff the micro component barite is retained in vegetation covered soil thus rey patterns of havel water show significant eu deficits the high gd anomalies result from medical applications of gd chelates which after urination pass the sewage treatment plants the seasonal variations of total gd in the havel river are artifacts based on seasonal locally varied discharge of effluents from sewage treatment plants the natural gd concentration of 8 pmol l in the northern havel is enhanced to 3300 pmol l when the havel river leaves berlin territory the elimination of phosphate from lake tegel water affects the fractionation of ree but not the concentration of total gd although enhanced in total phosphorus tp the ree concentrations in the water from the spree river and the teltow canal are less than in the havel water before their confluence only yb and lu do not decrease the contributors of the havel river are high in total organic carbon toc and dissolved organic carbon doc compared to the havel water before their indicating that rey are preferentially sorbed by settling organic matter applying phreeqc and assuming that only 10 of tp is present as ortho phosphate yields that only carbonate complexes are essential