significance of europium anomalies in silicate melts and crystal melt equilibria a re evaluation although europium speciation in silicate melts partly reflects prevailing oxygen fugacities melt composition and structure play the major role in determining eu2 eu3 ratios and europium partitioning into mineral phases experimental evidence by different investigators on the magnitude of the compositional effect on eu2 eu3 provides consistent results only if account is taken of the oxygen buffer system employed in the experiments the medium dependent reduction of europium can be understood in terms of the preferential stabilization of eu2 by a strong aluminosilicate complex in the melt phase and to a much lesser degree by metasilicate complexes the stability of these complexes increases as the field strength of the associated cation species decreases hence eu2 aluminosilicate complexes are preferentially stabilized relative to trivalent lanthanides in melts of appropriate composition and their presence minimizes the enthalpy of the melt the influence of these complexes is particularly pronounced in melts with a high feldspathic component and a strongly polymerized structure their petrogenetic influence is best documented through the behaviour of europium relative to the other lanthanides during anhydrous anatexis in high grade metamorphic terrains and in the anomalous europium partition coefficients of phenocryst phases which formed during the crystallization of highly silicic magmas

rare earth element geochemistry of colour lake an acidic freshwater lake on axel heiberg island northwest territories canada a lake column profile was collected in 24 m of water from colour lake axel heiberg island northwest territories canada in early june of 1991 beneath 1 8 m of lake ice the rare earth element ree concentrations of the acidic fresh waters of colour lake were analyzed along with the major solute chemistry in order to investigate ree distribution and speciation in the low ph waters previous studies indicate the lake is dominated by ca2 mg2 and so42 and has no measurable carbonate alkalinity shale normalized ree patterns for the lake waters are all enriched in the middle ree s mree s as compared to the light ree s lree s and heavy ree s hree s dissolved ree concentrations in colour lake e g 2 3 22 nmol kg 1 for nd mean value of 20 nmol kg 1 are typically less than values obtained for the acid saline waters of the lake tyrrell playa system in australia as well as the slightly acidic groundwaters of the carnmenellis region of england but greater than ree concentrations measured in the alkaline saline waters of mono lake california u s a the speciation of the ree s in colour lake was modelled based on the major solute chemistry using a combined specific ion interaction and ion pairing model these calculations suggest that in the relatively high sulfate low ph waters of colour lake the ree s exist as either free metal so42 or f complexes our calculations indicate that so42 complexes dominate over the free metal and fluoride species for the majority of the ree s in the lake water and that in general for acidic high sulfate waters sulfate complexes with the ree s may increase the dissolved concentrations of the ree s over natural waters where relatively low sulfate concentrations prevail

uranium and rare earth elements in co2 rich waters from vals les bains france abstract waters from springs at vals les bains result from the mixing of a co2 rich highly mineralized water with dilute shallow subsurface water total content of dissolved species vary from 5 mmol 1 to 100 mmol 1 for many elements mixing of these waters is non linear non conservative and further water rock reactions take place the ph is controlled by co2 outgassing redox conditions are controlled by both the iron hydroxide siderite buffer and the introduction of oxygen with shallow subsurface waters among the major elements concentrations of ca mg mn fe are related to mixing co2 outgassing and carbonate precipitation uranium shows a complex behaviour controlled by carbonate complexing redox conditions mixing of waters and leaching from the rocks the 234 u 238 u activity ratio is near secular equilibrium in the more dilute waters dissolved rare earth element ree patterns are almost flat with a slight negative eu anomaly in the concentrated waters heavy rare earth elements gd yb hree are strongly enriched relative to light rare earth elements ce eu lree we relate the enrichment in hree to water chemistry and to complexing with carbonate species

differentiation of strongly peraluminous perphosphorus granites the pedrobernardo pluton central spain the pedrobernardo pluton 295 2 ma initial 87sr 86sr 0 7122 is a layered sheet like granite body with distinct vertical zoning biotite muscovite bearing granites in the lower zone muscovite biotite leucogranites in the middle zone and muscovite bearing aplites and pegmatites in the upper zone the magma was anatectically generated intruded almost free of restite and evolved as a closed system by crystallization in situ geochemical modelling indicates that the lower and middle zones followed an equilibrium crystallization path with no separation between solids and melt and the upper zone followed a fractional crystallization path magmatic fractionation produced leucocratic differentiates with high p concentrations and a p ca ratio higher than in apatite the excess p is located in plagioclase and k feldspar monazite apatite fractionation in the lower and middle zones produced extreme depletions in th u y and the rees and chondrite normalized ree patterns with low lrees hrees and a slight discontinuity between nd and sm about 90 of the th u y and rees reside in accessory minerals especially in monazite biotite and muscovite have very low ree contents with small positive or no eu anomalies k feldspar and plagioclase in both the lower and upper zones have moderate ree contents with positive eu anomalies feldspars from the upper zone in contrast have negative eu anomalies and have very low ree contents compared to available data from literature dsr ba th u y reesbio mineral are lower by one to three orders of magnitude and dreesplag kfsp are also lower by one order of magnitude these huge discrepancies are attributed not only to contamination with ree rich inclusions in mineral concentrates used in previous studies but to real differences in geochemical behavior of trace elements in peraluminous systems with respect to subaluminous systems biotite melt and probably k feldspar melt distribution coefficients for th u y and the rees in peraluminous magmas must be much lower than previously considered

rare earth elements as geochemical tracers of regional groundwater mixing abstract the rare earth elements ree were analyzed in a groundwater system from south central nevada i e ash meadows national wildlife refuge the spring mountains pahranagat national wildlife refuge and the nevada test site in order to investigate their potential use as tracers of regional groundwater flow previous investigations using conservative tracers e g deuterium and uranium isotopes identified recharge in local mountains as the primary source 60 70 of total discharge for the springs in the regional discharge zone i e ash meadows with the remaining contribution being interbasin flow from the northeast initial mixing calculations for these groundwaters using shale normalized ree patterns agreed well with the previous studies however because the rees are not expected to behave conservatively in natural waters the effect of both solution complexation which acts to enhance the stability of the rees in solution as well as surface complexation responsible for the particle reactive behavior of the rees were examined in subsequent mixing calculations in order to assess the roles of solution and surface complexation relative partitioning coefficients were estimated for each ree in each groundwater by evaluating the ratio of the ionic strength corrected co 3 1 ree co 3 2 ree and co 3 2 f to the first hydrolysis binding constants for the rees the relative partitioning coefficients were then used to calculate ree patterns expected to develop and persist in solution as a consequence of solution and surface complexation the calculated ree values closely resembled the actual measured ree concentrations suggesting that the rees are in fact controlled by solution and surface complexation in these groundwaters the calculated ree concentrations were subsequently used to determine mixing ratios the results of which coincided with the initial calculations as well as the previous studies the results of this study suggest that solution complexation of the rees is sufficient to overcome to a certain degree the affinity of the rees to be adsorbed onto surface sites in the aquifers such that distinctive ree signatures develop and persist in solution in groundwaters from different aquifers the ability of solution complexation to overcome surface complexation is likely related to the formation of the negatively charged dicarbonato complex i e ln co 3 2 where ln is any ree which accounts for significant fractions of each ree in these groundwaters

rare earth elements yttrium and h o c sr nd and pb isotope studies in mineral waters and corresponding rocks from nw bohemia czech republic the sparkling waters from the area of kyselka near karlovy vary at the western slope of the doupovske hory bohemia czech republic and co2 poor waters from two underground boreholes at jachymov krusne hory bohemia have been studied with the aim of characterizing the distribution of rare earth elements yttrium and h o c sr nd pb isotopes during the low temperature alteration processes of the host rocks additionally leaching experiments were performed at ph 3 on the granitic and basaltic host rocks from kyselka and the granite of jachymov all ree patterns of the granite and the basalt derived waters from the kyselka area are different from those of their source rocks and the leachates of the latter this elucidates the inhomogeneous distribution of ree and y among the solid phases in the altered magmatic rocks the eu and ce anomalies in granite derived waters are inherited the y anomaly is achieved by fluid migration yttrium is always preferentially leached by mineral waters whereas y ho ratios of rocks and their leachates are very similar the ree abundances in waters from the wells in jachymov are derived from rocks intensely leached and depleted in easily soluble ree bearing minerals whereas the granites and basalts from kyselka still contain soluble ree bearing minerals a comparison of ree ca patterns of the experimental leachates with those of the mineral waters elucidate the high retention of ree in rocks during water rock interaction in strongly altered rocks sr isotope ratios of mineral waters and rocks differ widely whereas the corresponding nd isotope ratios are very similar 207pb 208pb 206pb 208pb and 206pb 207pb ratios in mineral waters are independent from u th ratios in the rocks 206pb 208pb and 206pb 207pb are lower in mineral waters than in their source rocks and their leachates which indicates that pb is primarily derived from solid phases that do not contain significant contents of leachable u and th thus mineral waters although co2 rich only interact with surface films on minerals and not with the bulk of the minerals as in the leaching experiments calculation of mixing ratios of waters from the granitic and basaltic sources of the waters from the kyselka area yield about 40 of water from the underlying granite in water recovered from the basalt whereas the granite derived water is mixed with only about 5 of the water from the basalt

rare earth elements geochemistry in springs from taftan geothermal area se iran abstract concentrations of rare earth elements rees were determined in springs and andesitic dacitic rocks of taftan geothermal field hydrochemical results of major ions indicate that thermal springs are na so 4 cl and ca so 4 cl types concentrations of rees are in ranges of 10 4 to 1 2 and 49 to 62 times of chondrite for springwater and rock samples respectively the thermal sts and tts and the cold aps springs with low ph values exhibit a very high ree contents 0 64 to 3 15 mg l saturation index indicates that fe and al phases can control dissolved ree concentration in fts and pf cold springs the speciation of ree complexes indicates dominant presence of lnso 4 and free ion in the taftan thermal springs in aps cold spring with ph 4 fluoride complexes are dominate over the free ion and sulfate species while in pf and fts cold springs with ph 6 4 and 7 respectively carbonate complexes lnco 3 are predominant species chondrite normalized pattern for the low ph waters show very distinctive gull wing patterns characteristic feature of acid sulfate geothermal systems and are similar to those of the host rocks chemical characteristics of rare earth elements in spring and volcanic rock samples indicate that rees are originated from the andesitic dacitic host rocks whole rock normalized ree patterns and petrographic evidences show that rare earth elements leached mainly from marginal alteration of minerals and matrix decomposition in volcanic rocks in chondrite normalized ree patterns significant negative eu anomaly in the cold springs compare to the thermal and acidic springs indicates that alteration of plagioclase is more intense in the later corresponding to increasing in temperature and acidic state of reactant water

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

rare earth element and oxygen isotope studies of altered variscan granites the western harz germany and southern sardinia italy abstract studies on whole rock samples and mineral separates from granitoids of the harz mountains germany and southern sardinia italy have revealed postmagmatic changes of rare earth element ree concentrations and isotopic composition of oxygen the ree distribution patterns of the altered rocks do not deviate significantly from the unaltered samples but the ree patterns of the feldspars and biotites show characteristic changes some of the feldspars lost their typical positive eu anomalies whereas some of the biotites gained negative ce anomalies in the altered samples the quartz feldspar oxygen isotopic fractionation is either too low or even reversed relative to primary magmatic pairs the observed effects are discussed as the interactions of the cooling granitoids with either surface or magmatic waters it is concluded that a high temperature water rock interaction with essentially magmatic waters best explains the observed phenomena

reconstructing random topography from preserved stratification one of the fundamental problems of interpreting the sedimentary record is reconstructing the original heights of palaeotopographical features such as bedforms or river channels this requires an understanding of the relationship between topography and set thickness but at present an exact theory exists only for periodic topography of uniform height the applicability of this simple theory is severely limited by the random variability characteristic of many sedimentary systems in this paper we develop an exact theory for the probability density function pdf of sets generated from topography of random height we focus on the limiting case of zero net deposition in order to provide a lower bound for the set thickness and derive an analytical set thickness pdf that is determined by one parameter of the pdf for topographical height this parameter measures the breadth of the tail of the topographical pdf the mean set thickness is 0 8225 for bedforms and 1 645 for river channels if the topographical height is gamma distributed the preservation ratio defined as mean thickness of preserved sets mean topographical height is 0 8225 r2 for bedforms and 1 645 r2 for river channels where r is the coefficient of variation standard deviation mean of the generating topography in a comparison with data from laboratory current ripples our analytical predictions compare well with observations of both mean set thickness and thickness distribution the preservation ratio for the ripples is about 0 5 whilst measured dune heights give a preservation ratio of about 0 12 depth data from two modern braided streams yield preservation ratios ranging from 0 4 to 0 75 as more data on the distributions of topographical height in modern environments become available calculations such as these should help provide reliable error bounds for quantitative topographical reconstruction

major and trace elements of river borne material the congo basin the congo river basin is the second largest drainage basin in the world after the amazon the materials carried by its main rivers provide the opportunity to study the products of denudation of a large fraction of the upper continental crust of the african continent this paper presents the chemical composition of the different phases carried in the congo rivers and is followed by a companion paper devoted to the modelling of major and trace elements the congo river between bangui and brazzaville as well as its main tributaries including a few organic rich rivers also called black rivers were sampled during the 1989 high water stage the three main phases suspended load dissolved load and bedload were analysed for twenty five major and trace elements concentrations normalized to the upper continental crust show that in each river suspended sediments and dissolved load are chemical complements for the most soluble elements ca na sr k ba rb and u while these elements are enriched in the dissolved loads they are considerably depleted in the corresponding suspended sediments this is consistent with their high mobility during weathering another type of complementarity is observed for zr and hf between suspended sediments and bedload related to the differential velocity of suspended sediments and zircons which are concentrated in bedloads compared to other rivers absolute dissolved concentrations of ca na sr k ba rb and u are remarkably low surprisingly high dissolved concentrations are found in the congo waters for other trace elements e g rees especially in the black rivers on a world scale these concentrations are among the highest measured in rivers and are shown to be ph dependent for a number of dissolved trace elements the dissolved loads are systematically normalized to the suspended loads for each river in order to remove the variations of the element abundances owing to source rock variations normalized diagrams for rees are presented and extended to the other elements they strongly support the argument that the apparent higher solubility of trace elements in the congo waters is due to the presence in the dissolved load of a colloidal phase as a result of 0 2 m filtration an important result is that these colloids are strongly depleted in fe and al with respect to the other elements finally the comparison of the dissolved suspended and sandy transport fluxes of each element in the congo basin rivers shows that although the proportions of for example the rees in the dissolved loads of the majority of the congo basin rivers is close to 10 of the total transport flux up to 80 of the rees are transported by the so called dissolved load in the black rivers

determination of easily accessible metal fractions in rocks by batch leaching with acid cation exchange resin the easily accessible fraction of metals in rocks is derived from leaching experiments aliquots of rock powders are mixed with ion exchange resin and distilled water the ph self adjusts to a value of 3 after batch leaching times of 2 48 hr at 70 c the resin is quantitatively separated from the rock powder and eluted with 4 n hno3 the metal contents of the leachates are determined and related to the respective contents of the whole rock the leaching kinetics of each element is related to that of a reference element aluminium is most commonly chosen as a reference element because it is considered to represent the dissolution behaviour of the main rock forming minerals the easily accessible trace element fraction eat is given as the percentage of leached element at 1 al dissolution these eat values are reproducible and independent from grain size and sample resin ratio the procedure is tested on basaltic glass and variably altered gneisses the glass shows congruent release of all metals a slightly crystalline glass of the same chemical composition displays heterogeneous leaching behaviour the leaching kinetics of variably altered gneisses provide insight into the mineralogical siting of elements and their accessibility to fluids consequences for rb sr dating of rocks are discussed

petrology and geochemistry of silurian triassic sedimentary rocks in the tongling region of eastern china their roles in the genesis of large stratabound skarn ore deposits abstract this paper describes the petrology and geochemistry of the silurian triassic sedimentary rocks in the tongling area in eastern china aiming to establish a genetic link between different stratabound skarn deposits and sedimentary lithologies the results from this study show that some devonian triassic transitional lithological units with compositions varying between siliceous rock and carbonate especially thinly layered impure carbonate control the distribution of some large stratabound skarn ore deposits in the tongling region interlayer detachment faults in the transitional lithology rocks are particularly important controlling the final locations of the deposits the transitional lithological zones may have also served as source rocks likely providing some ore forming metals to the deposits gypsum evaporites in rocks from carboniferous sources may have supplied some sulphur to the hydrothermal systems five of such transitional lithological units enriched in organic matter are spatially and closely associated with some large stratabound skarn ore deposits in the tongling region suggesting that organic matter may have served as an absorbent or reducing agent during ore formation

late alteration in titanite catisio5 redistribution and remobilization of rare earth elements and implications for u pb and th pb geochronology and nuclear waste disposal abstract translucent dark coloured titanites from a wide variety of geological environments are commonly partly replaced by very fine grained aggregates of ree rich minerals including allanite monazite and bastnasite rutile quartz calcite apatite and chlorite along grain fractures and boundaries the aggregates of ree rich minerals are bordered by an irregular zone of altered titanite which by secondary ion mass spectrometry sims is considerably lower in rees u and th than the adjacent unaltered matrix light rees and th are differentially depleted in the altered zone and correspondingly enriched in secondary minerals additionally hrees and u have been lost to the external system the loss of hrees being in proportion to the increase in atomic number natural radiation damage was not an important factor in promoting the late alteration of titanite titanite which has been subjected to late hydrothermal activity would not remain a closed system in respect to either u or th decay series and therefore cannot be used for u pb and th pb geochronology the observed leaching and partial dissolution of titanite under hydrothermal conditions are generally consistent with laboratory experimentation indicating that proper isolation from any communication with hydrothermal fluids is essential in the application of titanite based ceramics for the immobilization of radioactive waste

the geochemical balance of the rare earth elements and neodymium isotopes in the oceans profiles of ree concentrations and neodymium isotope measurements in the western indian ocean are consistent with published data from the other major oceans ree concentrations show a strong hydrographic control the influence of intermediate water masses is particularly significant surface water concentrations vary with salinity paniculate rees are less than 5 of dissolved concentration except for ce where up to 20 of total rees are present as 0 4 m particles in contrast to dissolved profiles concentration profiles of paniculate rees including ce all increase with depth ree concentrations correlate with silica over all but the deepest waters although in detail correlations are complex the neodymium isotopic composition of indian ocean seawater avg nd 0 8 3 is intermediate between that for the atlantic and pacific oceans comparison of ree data from the major oceans shows that the hrees behave more like si than do the lrees sm nd ratios are near constant for all oceans whereas ernd ratios vary between the atlantic indian and pacific oceans the fractionation of the rees in surface seawaters can be explained by fractionation factors relative to silica from 0 12 for la to 0 05 for er use of a seven box model shows that the interoceanic variations in neodymium isotopic compositions and nd concentrations cannot be reconciled unless particle water exchange is invoked the degree of exchange required is consistent with particle residence times of 1 10 yr

thermodynamic study of the association and separation of copper and gold in the shizishan ore field tongling anhui province china abstract the shizishan ore field is the largest gold copper ore field in the tongling ore district of anhui province china copper and gold deposits in the district are present as one commodity deposits or as deposits with both commodities copper and gold mineralization are either cogenetic or are temporally and spatially distinct we present the results of systematic geochemical analysis of fluid inclusions from typical au cu deposits in the shizishan ore field these data are used to determine the solubility of cu and au in the ore forming fluids and to ascertain the mechanisms and factors that controlled variations in the association and separation of copper and gold mineralization our results indicate that copper in the ore forming fluids was transported as cucl2 and cucl0 complexes and that the solubility of copper was controlled by variations in cl concentration in addition the precipitation of copper was controlled by changes in temperature ph fo2 and fo2 in comparison gold in the ore forming fluids was transported as au hs 2 and au2s hs 22 complexes and the solubility of gold was controlled by variations in total sulfur concentration the precipitation of gold was controlled by temperature ph fo2 and fo2 these differences between the two elements meant that copper and gold in the ore forming fluids responded in different ways to changes in physicochemical conditions copper precipitated under relatively acidic conditions at high temperatures while gold precipitated under weakly alkaline conditions at relatively low temperatures this dissociation resulted in the temporal and spatial separation and zonation of copper and gold mineralization in the shizishan ore field

characteristics and evolution of ore forming fluids associated with yanshanian magmatic activity in dongguashan copper deposit anhui province china based on petrography microthermometry and lrm analysis of fluid inclusions in garnet diopside quartz and calcite this paper has discussed characteristics and evolution of ore forming fluids in the dongguashan copper deposit the ore forming fluids of yanshanian magmatism evolved from high temperature high salinity and k rich fluids via moderate high temperature and co2 ch4 rich fluids to moderate low temperature and low salinity fluids the analytical results suggest that the dominant volatiles in the ore forming fluids are h2o co2 and ch4 with minor c2h6 h2s n2 etc na k as well as ca2 mg2 are dominant cations whereas cl and so42 are major anions high k and co2 ch4 constitute the main feature of the ore forming fluids related to yanshanian magmatism

development and application of a sensitive and rapid analytical method to determine the rare earth elements in surface waters abstract a new cost effective method to determine the 14 rare earth elements ree s in waters to levels as low as 0 2 1 0 ng l 1 ppt has been established inductively coupled plasma mass spectrometry icp ms is used for measurement following automated preconcentration using the dionex metpac cc 1 resin of iminodiacetate functionality the free ree ion is chelated onto the resin while alkali and alkaline earth elements are washed through and separated enabling the method to be applied to seawater as well as fresh water the eluant 0 8 m hno 3 provides an ideal medium for analysis by icp ms and the suite of elements determined can be expanded to include first row transition elements cd pb and u based on replicate analyses of control samples and data for field and laboratory duplicate samples lakes and streams relative standard deviations are better than 10 except where concentrations are below 5 ng l 1 application of this method to 135 lake waters in the baie d espoir region of newfoundland indicates a contamination is not introduced from sampling bottles nalgene lpe or during the filtering and acidification process even at low ng l 1 levels b there is a high degree of correlation in element distribution patterns between lake waters and their corresponding centre lake sediments for yb and tb c the chondrite normalized plots for water and sediment are similar in shape and show consistent patterns within geological units but are distinct between such units and d the powerful potential of ree concentrations in surface water for geochemical mapping

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