hydrochemical processes in the lower jordan valley and in the dead sea area abstract changes in the concentrations of major some minor and trace elements occurring in both surface and groundwater of the lower jordan river dead sea drainage basin have been investigated in order to identify the characteristics of the regional aquifers and their recharge areas spider patterns of elements and rare earth distribution patterns pinpoint the characteristic chemical features of groundwater as compared to seawater the high br cl ratios in groundwater are caused either by high br cl ratios in precipitation by leaching of br from bituminous matter or by mixing with brines beyond the epsomite stage the locations of groundwater samples with enhanced b contents coincide with the distribution of gypsum in the beds of the lisan formation which produces water with nearly constant b so 4 2 molar ratios aeolian distribution of the unconsolidated lisan sediments influences the b so 4 ratio in the area of lake tiberias and in the jordan highlands the high gd anomaly in the dead sea water is of geologic origin whereas that in the jordan river and in nahal stream qidron is largely anthropogenic the anthropogenic gd input to the dead sea is insignificant compared to the actual amount in the water of the dead sea hot saline water encountered along the western shores of the dead sea with high gd anomalies indicate that they contain large amounts of ancient dead sea water that mix as hot ascending brines with fresh water the recharge area of groundwater in the lower jordan valley extends largely over limestone and dolomite outcrops of the upper cretaceous judea group weathering of locally underlying lower cretaceous volcanics in the area of pezael beqaot and argaman yield groundwater with 34 s so 4 2 values ranging from 2 to 4 the presence of sulphide bearing bodies in this area is attested to magnetic anomalies detected at depths of several kilometres 34 s so 4 2 indicates very deep groundwater circulation high 34 s so 4 2 15 is typical for marine sulphates from the judea and avedat group limestone the springs located along the northwestern shore of the dead sea discharge water replenished on the eastern judea mountains the increase in the salinity of this water is due to brines flushed from sediments and from adjacent sedimentary rocks which host entrapped brines from the precursors of the dead sea formed during the late stages of lake lisan fresher water flushes out these residual brines as a result of falling sea level salinity increase in groundwater is also affected by the ascent of deep seated hot brines from pre sedom periods along the rift faults calculations of mixing between fresh and highly saline end members show that leaching of anhydrite from sediments precipitation of calcite formation of dolomite albitization of plagioclase and ion exchange with abundant clay minerals control the major element composition of the saline groundwater

potassic dyke swarm in the sapucai graben eastern paraguay petrographical mineralogical and geochemical outlines abstract the western side of the parana basin of brazil extends to central paraguay where repeated and widespread magmatic activity developed from lower cretaceous to oligocene associated with late mesozoic crustal extension trending ne sw in central paraguay this trend is characterized by a zone of nw se normal faults which formed the asuncion sapucai graben up to 45 km wide and 200 km long where alkaline rocks occur as volcanic domes complexes lava flows and dykes these rocks 128 ma aged are dominantly potassic and ne normative a swarm of at least 200 mainley nw se trending dykes occurs in the sapucai region and seems to be formed by two main lineages tephrite to phonolite and peralkaline phonolite and alkali basalt to trachyphonolite they are characterized by ubiquitous diopside to ferrosalite consistently yielding al enrichment trends common olivine fo 81 69 in tephrites and alkaline basalts and up to fo 65 in phonolites zoned megacrysts of hastingsitic hornblende core to kaersutite rim associated with accessory groundmass pargasite in tephrites and phonotephrites k rich hastingsite and k rich ferroan pargasite in the phonolites accessory groundmass mica falls in the annite phlogopite range and consistently yields insufficient si al to satisfy the expected t site occupancy of 8 00 a f u fe ti oxides are ti magnetite rarely ilmenite or haematite phenocrystal i e xenocrystal plagioclase is an 70 20 and an 74 42 in the tephrites and phonolites respectively coexisting groundmass microlites are an 22 14 associated with sodasanidine and sanidine feldspathoids include analcimized leucite and nepheline accessories ti andradite and sphene the two main lineages recognized by distinctive mineralogical variations are consistent with the petrochemical variations complex interaction of discrete and independently evolving magma batches are indicated by intra and or interphase chemical variations suggesting multiple equilibrations of the crystallizing phases under shallow level volcanic pressure regime the observed geochemical trends are quite similar to those of roman region type magma with the same negative anomalies of ta nb zr and ti the most likely mantle source is a garnet peridotite characterized by different enrichment in incompatible elements and which suffered low degree of partial melting 3 7 which has geochemical and isotopic features distinct from those of the adjoining tholeiitic basalts 130 ma and nephelinites 61 39 ma the similarities of the sapucai dyke suite with barton s roman region type magma supports the view that this magma type may not be formed as a result of orogenic and or subduction driven activity in this region therefore a causal relationship of the latter activity with roman region type magma is not supported and remains questionable

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

uptake of elements from seawater by ferromanganese crusts solid phase associations and seawater speciation marine fe mn oxyhydroxide crusts form by precipitation of dissolved components from seawater three hydrogenetic crust samples one phosphatized and two hydrothermal mn oxide samples were subjected to a sequential leaching procedure in order to determine the host phases of 40 elements those host phase associations are discussed with respect to element speciation in seawater the partitioning of elements between the two major phases mn oxide and fe oxyhydroxide can in a first order approximation be explained by a simple sorption model related to the inorganic speciation of the elements in seawater as has been proposed in earlier models free and weakly complexed cations such as alkali and alkaline earth metals mn co ni zn tl i and partly y are sorbed preferentially on the negatively charged surface of the mno2 in hydrogenetic crusts the driving force is a strong coulombic interaction all neutral or negatively charged chloro cd hg tl carbonate cu y pb and u and hydroxide be sc ti fe zr nb in sn sb te hf ta bi th and tl iii complexes and oxyanions v cr as se mo and w bind to the slightly positively charged surface of the amorphous feooh phase while coulombic interaction can explain the sorption of the negatively charged species the binding of neutral species is based on specific chemical interaction organic complexation of elements in deep ocean water seems to be at most of minor importance surface oxidation can explain some strong metal associations e g of co and tl with the mno2 and te with the feooh sorption reactions initially driven by coulombic forces are often followed by the formation of specific bonds between the adsorbate and the atoms of the oxide surface differences in the associations of some metals between the non phosphatized and phosphatized hydrogenetic crusts and between the hydrogenetic and the hydrothermal samples reflect the different physico chemical environments of formation and speciations in oxic seawater vs less oxic fluids especially for the redox sensitive metals such as mo and v these environmental related differences indicate that the methodology of chemical speciation used here in combination with spectroscopic methods may allow for the detection of changes in paleoceanographic conditions recorded during the several tens of millions of years of crust growth

hafnium and neodymium isotopes in seawater and in ferromanganese crusts the element perspective abstract hafnium and nd isotopes are increasingly used as paleoceanographic proxies comparing the mantle crust array and the seawater array in plots of e hf vs e nd it has been observed that for a given e nd value the corresponding e hf value is higher for seawater than it is for terrestrial rocks while this difference had initially been explained by significant hydrothermal input of mantle hf into seawater the currently favoured explanation is incongruent weathering of continental rocks producing radiogenic riverine hf input we here address this topic from the perspective of the behaviour of these two elements in seawater and in ferromanganese fe mn crusts we distinguish between a truly dissolved and a dissolved hf and nd pool the latter being comprised of truly dissolved and colloid bound colloidal hf and nd while there exists a hydrothermal pathway for colloid bound dissolved mantle hf into the oceans there is in marked contrast to nd no important riverine pathway for colloidal or truly dissolved continental hf owing to their respective chemical speciation in seawater there exists truly dissolved nd in the ocean while the amount of truly dissolved hf is insignificant neodymium is in exchange equilibrium between local seawater and both the hydrous fe and mn oxides hydrogenetic fe mn crusts are composed of due to continuous ad and desorption there is continuous isotopic re equilibration and the isotopic composition of nd in a fe mn crust reflects that of truly dissolved nd in local ambient seawater in contrast hf is only associated with the hydrous fe oxides on which it forms surface precipitates that do not exchange with seawater due to this lack of isotopic re equilibration the isotopic composition of hf in a fe mn crust is the average of that of all the hf scavenged during the lifetime of the hydrous fe oxide particles since the hf bearing hydrous fe oxides in a fe mn crust do not form from local ambient seawater at the crust s growth site but are advected as colloids or fine particles their hf isotopic composition depends on the origin and migration pathway of these colloids hence while nd isotopes in fe mn crusts provide reliable information on truly dissolved nd in local ambient seawater hf isotopes rather indicate the origin and pathway of hydrous fe oxide colloids and might differ from truly dissolved hf in local ambient seawater this may explain the occasional decoupling of nd and hf isotopes in fe mn crusts and supports the notion of a significant hydrothermal mantle signal of hf in seawater

glaciology ice sheet advance in antarctica reliable forecasts of sea level rise depend on accurately modelling the dynamics of polar ice sheets a numerical framework that better reflects ice sheet basal drag adds greater realism to such models

internal structure of the dead sea leaky transform rift in relation to plate kinematics abstract the structures along the dead sea transform rift are related to the motions of the sinai and arabia plates which border it and to the irregularities of their boundaries the total slip was 105 km left lateral but the present structures were formed mainly during the last 40 km of slip which probably occurred in the plio pleistocene along the southern half of the transform the strike slip motion takes place on en echelon faults this produces rhomb shaped grabens or pull aparts which are sometimes composite and in which there is local crustal separation thus much of the transform is leaky these structures occur in a morpho tectonic rift valley delimited by normal faults which express a small component of transverse extension along a few segments the shape of the transform is such that lateral motion produces local transverse compression the geometric relations of the structures along the transform define an eulerian pole of relative plate motions at 32 8 n 22 6 e 0 5 the older motion was somewhat different and is described by a pole located about 5 west of the above then the component of transverse extension and crustal separation was much smaller than now while local transverse compression was more important the northern half of the dead sea transform has an irregular shape and the bordering plates did not remain rigid as lateral motion continued here transverse compression is often important

rare earth element concentrations and speciation in organic rich blackwaters of the great dismal swamp virginia usa concentrations of rare earth elements ree major inorganic solutes and dissolved organic carbon doc were measured in waters from the great dismal swamp in southeastern virginia including lake drummond ph 4 3 and its principal surface inflows and outflow concentrations of ree are high in the lake average nd 8 nmol kg and the acidic doc rich inflow and out flow waters i e nd 12 5 nmol kg in jericho washington ditch and 8 nmol kg in feeder ditch respectively the slightly acidic ph 6 6 4 inflow waters from west of the suffolk scarp that comprise the chief source of surface water flow into lake drummond exhibit lower ree concentrations nd 3 4 7 nmol kg great dismal swamp waters are all enriched in the middle rees compared to the light and heavy rees lree and hree when normalized to upper continental crustal ucc values rare earths are positively correlated to doc concentrations in great dismal swamp waters and inversely correlated with ph speciation calculations using a modified version of the well established humic ion binding model v predict that organic matter complexes are the predominant form of dissolved rees in great dismal swamp waters despite significant competition from aqueous fe and al for organic matter binding sites adsorptive cathodic stripping voltammetry acsv was employed using a previously developed competitive ligand equilibration approach that involved adding the o cresolphthalexon ocp ligand to directly investigate ree complexation with natural organic ligands in great dismal swamp waters although preliminary the results of the acs voltammetric titrations are consistent with dominance of organic matter complexes of rees in great dismal swamp waters the results of the speciation modeling and the voltammetric titrations all point towards control of dissolved rees in great dismal swamp waters by complexation of these heavy metals with natural organic matter

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

the behavior of rare earth elements zr and hf during biologically mediated deposition of silica stromatolites and carbonate rich microbial mats abstract venere lake in the pantelleria island thermal system central mediterranean sea consists of a mix of seawater and hydrothermal volcanic fluids containing high levels of dissolved sio 2 close to the lake s thermal springs siliceous stromatolites are deposed under high bacterial activity conditions whereas roughly interlaminated ca carbonates and microbial mats are widely scattered in the lake the dissolved ree speciation in lake waters is dominated by ree co 3 2 ree co 3 and ree h 3 sio 4 2 complexes on the contrary the most abundant zr and hf species are hydroxyl and fluoride complexes the behavior of ree zr and hf in the venere lake waters is controlled by precipitation of amorphous silica carbonates and bacterial activity chondrite normalized ree patterns in stromatolites are characterized by positive la anomalies superchondritic y ho ratios and negative eu anomalies the eu depletion is also found in microbial mats where is associated to a chondritic y ho signature zr and hf differently behave in dissolved phase and in newly formed siliceous and carbonatic material hf reacts easily into amorphous silica surfaces whereas zr is preferentially partitioned onto phosphate binding sites on microbial cell surfaces similar to the observed behavior of heavy ree hree we suggest that the zr hf relationship reflect the interface processes between mineral phases and bacterial membranes or compounds produced by bacterial activity

tracing the source of gypsum in new caledonian soils by ree contents and ssr isotopic compositions gypsum minerals forming in pedogenic environments in new caledonia were examined for their s and sr isotope compositions and ree distributions three possible sources were identified volcanic soil derived and marine however differentiation based only on the ree contents and normalized patterns was not possible but the best preserved volcanic sample yields a negative eueu anomaly and the lowest gdnybn ratio due to the high content of organic matter mixing calculations of the 34s values and 87sr86sr ratios confirmed that the marine gypsum has a 34s value close to 21 and an 87sr86sr ratio close to 0 70912 and that the volcanic gypsum has a 34s value of 0 and an 87sr86sr ratio of about 0 70331 the soil derived gypsum samples yield intermediate values as a result of a mixing between the marine and volcanic end members negative 34s values for the volcanic gypsum are explained by low fo2 of the source rocks while high 87sr86sr ratios for the same gypsum are explained by probable atmospheric input the data confirm also that biological fractionation of 34s if any is limited

the behaviour of rees in thailand s mae klong estuary suggestions from the y ho ratios and lanthanide tetrad effects abstract the concentrations of rare earth elements and yttrium rey were measured in dissolved phase in suspended particulate matter spm and in sediments in seven sampling stations in the mae klong estuarine system inner thailand gulf in order to study their behaviour and distribution pattern the analysed samples generally show high rare earth element ree content in the dissolved phase with high medium rare earth elements mrees and y enrichments in the shale normalized pattern versus paas these chemical features are interpreted in terms of direct influences of weathering processes of ree rich minerals e g phosphates which abundantly out crop in the mae klong watershed these large mree enrichments also suggest that dissolved sulphate complexes play an important role in the dissolved ree fate close to the marine coastal system the shale normalized rees and y ho ratios additionally indicate a direct rey co precipitation with fe oxyhydroxides along the river path and consequent adsorption as coating onto feooh surfaces the rey behaviour in spm appears strongly influenced by al fe and mn content suggesting that the formation of an authigenic fe mn oxyhydroxides and aluminosilicate particulate leads to rey adsorption and or co precipitation the observed variations in the y ho ratios suggest that different y ho fractionation processes take place in the studied estuarine system strong similarities among chondrite normalized ree patterns in both sediments and granitic rocks out cropping in the surrounding regions suggest a generic relationship between the two groups of materials

alteration effects of volcanic ash in seawater anomalous y ho ratios in coastal waters of the central mediterranean sea this paper presents the results of a study based on data collected during the oceanographic cruise ansic 2001 carried out in the ionian sea during the explosive activity of mount etna in the summer of 2001 anomalous low values of y ho ratios in seawater suggest extensive scavenging processes on the surfaces of smectitic alteration products with y and ho fractionation controlled by the differences in their electronic configurations and behaviour during solution surface complexation equilibria these processes can also be traced through the presence of significant tetrad effects recorded in the chondrite normalised rare earth elements and yttrium yrees patterns of suspended particulate matter this suggests that the preferential y scavenging from seawater is due to the formation of inner sphere complexes with oh groups on montmorillonite crystal surfaces the preliminary results of kinetic experiments of yree released from volcanic ash to coexisting seawater and the related effects on y ho ratios and ce anomalies are consistent with the fractionation of light rare earth elements lrees with respect to heavy rare earth elements hrees observed in dissolved phase they suggest a behaviour of y similar to that reported for lrees particularly for ce and pr

rare earth element systematics of the chemically precipitated component in early precambrian iron formations and the evolution of the terrestrial atmosphere hydrosphere lithosphere system irrespective of provenance age and metamorphic grade the chemically precipitated component in early precambrian 2 3 ga iron formations ifs displays smyb cn 1 which reflects the corresponding ratios of contemporaneous seawater in conjunction with end if end shale jacobsen and pimentel klose 1988a b this rare earth element ree signature reveals that the ree distribution in early precambrian ifs must be explained by mixing between a marine bottom and a surface water component and that the rees and by analogy the fe cannot be derived from weathering of a continental source eusm n ratios of detritus free ifs are controlled by the marine bottom water component where eusm cn 1 results from ree input from high temperature high t hydrothermal fluids which received their ree signature during high t alteration of oceanic crust at spreading centres decreasing eusm cn of ifs with decreasing depositional age reflect the vaning importance of high t compared to low t 200 c hydrothermal fluids hence oceanic crust alteration for the ree budget of marine bottom waters and are related to decreasing upper mantle temperatures smyb n ratios of detritus free ifs are controlled by the marine surface water component whose ree distribution is affected by the same processes which operate today in the entire ocean mixing calculations reveal that smyb cn in early precambrian marine surface waters was significantly lower than it is today to explain this difference two mechanisms are discussed on the basis of higher pco2 and lower po2 levels of the precambrian atmosphere 1 1 higher co32 in precambrian river and coastal waters and 2 2 redox cycling of the rees at an oceanwide chemocline which separated anoxic and oxic water masses however these processes are synergetic and could have operated in unison the ree distribution in precambrian ifs is described as a result of mixing in a multicomponent system where high t and low t hydrothermal fluids contributed to the marine bottom water and ree input from the dissolved ree pool in river waters after some modification in estuaries dominated the ree distribution in marine surface waters after mixing of bottom and surface waters their combined ree load was quantitatively scavenged onto precipitating iron oxihydroxides or iron carbonates and deposited with the chemically precipitated component after addition of variable amounts of clastic detritus this eventually resulted in the ree distribution observed in precambrian ifs

oceanography chemical twins separated how the chemical composition of sea water changes on its journey through the world s oceans is poorly understood systematic measurements of dissolved trace metals across the pacific ocean suggest that these metals may help track sources and mixing of water masses

controls of fluid chemistry and complexation on rare earth element contents of anhydrite from the pacmanus subseafloor hydrothermal system manus basin papua new guinea ocean drilling program odp leg 193 successfully drilled four deep holes 126 to 386 m into basement underlying the active dacite hosted pacmanus hydrothermal field in the eastern manus basin anhydrite is abundant in the drill core material filling veins and vesicles cementing breccias and occasionally replacing igneous material we report rare earth element ree contents of anhydrite from a site of diffuse venting site 1188 which show extreme variability in terms of both absolute concentrations e g 0 08 28 3 ppm nd and pattern shape lan smn 0 08 3 78 smn ybn 0 48 23 1 eu eu 0 59 6 1 the range of ree patterns in anhydrite includes enrichments in the middle and heavy rees and variable eu anomalies the patterns differ markedly from those of anhydrite recovered during odp leg 158 from the tag hydrothermal system at the mid atlantic ridge which display uniform lree enriched patterns with positive eu anomalies very similar to tag vent fluid patterns as the system is active the host rock composition is uniform and the anhydrite veins appear to relate to the same hydrothermal stage we can rule out predominant host rock and transport control instead we propose that the variation in ree content reflects waxing and waning input of magmatic volatiles hf so2 and variable complexation of rees in the fluids ree speciation calculations suggest that increased fluoride and possibly sulfate concentrations at pacmanus may affect ree complexation in fluids whereas at tag only chloride and hydroxide complexes play a significant role the majority of the anhydrites do not show positive eu anomalies suggesting that the fluids were more oxidizing than in typical mid ocean ridge hydrothermal systems we use other hydrothermal fluids from the manus basin vienna woods and desmos which bracket the pacmanus fluids in terms of acidity and ligand concentrations to examine the dependence of ree complexation on fluid composition geochemical modeling reveals that under the prevailing conditions at pacmanus ph 3 5 t 250 300 c eu oxidation state and the relative importance of fluoride versus chloride complexing are very sensitive to small variations in oxygen fugacity temperature and ph patterns with extreme mid ree enrichment may reflect speciation effects free ion abundance coupled with crystal chemical control we conclude that the great variability in ree concentrations and pattern shape is likely due to variable fluid composition and ree complexation in the fluids

geochemistry of ree zr and hf in a wide range of ph and water composition the nevado del ruiz volcano hydrothermal system colombia the geochemical behaviour of rare earth elements zr and hf was investigated in the thermal waters of nevado del ruiz volcano system a wide range of ph between 1 0 and 8 8 characterizes these fluids the acidic waters are sulphate dominated with different cl so4 ratios the important role of the ph and the ionic complexes for the distribution of ree zr and hf in the aqueous phase was evidenced the ph rules the precipitation of authigenic fe and al oxyhydroxides producing changes in ree zr hf amounts and strong anomalies of cerium the precipitation of alunite and jarosite removes lree from the solution changing the ree distribution in acidic waters y ho and zr hf twin pairs have a different behaviour in strong acidic waters with respect to the water with ph near neutral yttrium and ho behave as zr and hf in waters with ph near neutral to neutral showing super chondritic ratios the twin pairs showed to be sensitive to the co precipitation and or adsorption onto the surface of authigenic particulate fe al oxyhydroxides suggesting an enhanced scavenging of ho and hf with respect to y and zr leading to superchondritic values in acidic waters a different behaviour of twin pairs occurs with chondritic y ho ratios and sub chondritic zr hf ratios for the first time zr and hf were investigated in natural acidic fluids to understand the behaviour of these elements in extreme acidic conditions and different major anion chemistry zr hf molar ratio changes from 4 75 to 49 29 in water with ph 3 6 in strong acidic waters the fractionation of zr and hf was recognized as function of major anion contents cl and so4 suggesting the formation of complexes leading to sub chondritic zr hf molar ratios

palaomagnetische untersuchungen im schilfsandstein trias km2 westeuropas von insgesamt 46 beprobten profilen aus dem schilfsandstein trias km2 westeuropas wurden bislang 41 profile mit 343 einheiten und 870 handstucken mit 1897 einzelkernen auf ihren palaomagnetischen inhalt untersucht

the hydrochemical identification of groundwater flowing to the bet she an harod multiaquifer system lower jordan valley by rare earth elements yttrium stable isotopes h o and tritium abstract the bet she an and harod valleys in israel are regional recipients and mixing zones for groundwater draining from a multiple aquifer system which includes carbonate and basalt aquifers and deep seated pressurized brines the aquifers drain through two types of outlets distinct and mixed the latter type is mainly conditioned by the occurrence of fault blocks related to the jordan rift system which act as connecting media between the aquifers and facilitate interaquifer flow conjoint application of rare earth element distribution and water isotopes enables detection of the local areas replenishment by rainfall infiltration and in connection with the position of wells or springs the identification of groundwater flow paths once stationary equilibria are established changes of rey composition between rey in groundwater and their surface adsorption are negligible in areas with little soil coverage and vegetation even recharge over young tertiary and diagenetic cretaceous limestones is distinguishable by their rey distribution patterns groundwater recharged over tertiary limestones show higher rey abundance and more significant ce anomalies than those derived from the cretaceous limestones weathering of alkali olivine basalts leads to rey patterns in groundwater depleted in the middle ree the improved knowledge of the hydrological systems is thought to be useful for regional hydrogeological modeling and for designing rational water management schemes

dissolved zirconium and hafnium distributions across a shelf break in the northeastern atlantic ocean abstract dissolved zr and hf distributions have been determined for five stations located across the shelf break in the northeastern atlantic ocean on the celtic approaches for stations in deep water the range in zr concentrations has been found to be 70 180 pmol kg and the range in hafnium concentrations 0 4 1 1 pmol kg the distributions with depth are indicative of a nutrient like scavenging regeneration behavior in seawater although the dissimilarity with silicate and nitrate for samples below the nutricline suggest that other mechanisms are also important in defining the oceanic distribution of these elements in contrast the concentrations of zr and hf at the station located closest to land are highest in surface waters and decrease with depth although salinity does not indicate dilution of seawater with freshwater with high zr and hf concentrations the ratio of dissolved zr to hf in seawater is higher and more variable than is found for the majority of terrestrial rocks or predicted from thermodynamic considerations fractionation due to small differences in their interactions with particulate material is implicated

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

w and m type tetrad effects in ree patterns for water rock systems in the tono uranium deposit central japan abstract abundances of rare earth elements plus y ree were determined for granitic rocks tertiary sedimentary rocks and related groundwater in the tono area central japan tetrad effects concave curves in ree patterns were found for these rocks and groundwater samples conjugate m and w types of tetrad effects were simultaneously observed in these specimens which constitute the water rock system the granitic rocks show the m type tetrad effects while the groundwater and the sedimentary rocks exhibit the w type tetrad effects non chondritic y ho ratios were found especially in the groundwater y ho ratios showed larger values than the chondritic value for the samples showing w type tetrad effects and vice versa these results suggest that 1 preference of the groundwater for a w type tetrad effect and larger y ho ratio than chondrite produces an m type tetrad effects and lower y ho ratios in the granitic rocks during weathering processes 2 the w type tetrad effect and larger y ho ratio for the sedimentary rocks is brought about by the fixation of groundwater ree onto the sedimentary rocks the variation of the tetrad effect and y ho ratio was confirmed by laboratory experiments on the leaching of ree from the granitic rocks the w type tetrad effect and large y ho ratio in the u mineralization zone in the sedimentary rocks were also found by sims analysis which is consistent with the w type tetrad effect and larger y ho ratio in the whole rock abundances of the sedimentary rocks disequilibrium of the u series 234 u 238 u analyzed by sims in the u mineralization zone suggests that the u bearing minerals were formed through precipitation from groundwater as it became reducing these results suggest that the ree in the sedimentary rocks were transported by the groundwater from the granitic rocks in the tono area based on this study it is implied that the degree of the tetrad effects and the variation of y ho ratio can be valuable tools to investigate the migration of ree during water rock interactions in natural systems

hafnium and neodymium isotope variations in ne atlantic seawater the 176hf 177hf ratio of seawater is measured directly with 143nd 144nd in a composite vertical profile in the ne atlantic the value of hf of intermediate and deep water exhibits little variation and averages 1 0 0 8 surface water shows a wider range 5 7 to 3 3 while intermediate and deep water samples plot on or close to the seawater hf nd isotope array defined by ferromanganese deposits near surface seawater samples plot between the seawater and terrestrial rock hf nd arrays it is likely that the shallow water variability in hf arises from a short residence time of hf in surface water and isotopically heterogeneous inputs the difference between surface and intermediate deep water hf may be maintained by the release of surface scavenged hf at depth from a subset of sinking particles the composition of end at middepths reflects overlying surface water and water advected along isopycnals from areas where they outcrop in winter uniform hf values below 1000 m suggest the residence time of hf may be longer than that of nd the radiogenic isotopic composition of seawater hf relative to nd and terrestrial rocks suggests that minerals with high lu hf ratios may be preferentially weathered providing a source of radiogenic hf to the oceans

the development of middle rare earth element enrichments in freshwaters weathering of phosphate minerals abstract many phosphatic minerals of biogenic authigenic and diagenetic origin are distinguished by rare earth element ree compositions which have a well developed middle rare earth element mree enrichment defined by a gradual increase in the shale normalized ratios of ree toward the middle of the ree series la to lu also the ree composition of dissolved matter in the waters of the amazon fly and sepik rivers as well as other river lake and ground waters have well developed mree enrichments the development of mree enrichments was studied through a series of leaching experiments using river bank sediments from the amazon fly sepik and mississippi rivers a well characterized phosphate mineral rich shale with a pronounced mree enrichment in its bulk composition was also leached in order to better assess the relationship between the weathering of phosphate minerals and the formation of mree enriched solutions the two leaching solutions per sediment consisted of filtered lake water at ph 5 and the same water adjusted to ph 2 leaching experiments with the four river sediments result in extensive fractionation whereby the ree compositions of the solutions develop mree enrichments from starting sediments that show no mree enrichments the ph 2 leachates have much higher concentrations of the ree and more fully developed mree enrichments than do the ph 5 leachates the mree enrichments at ph 2 usually form within an hour of starting the experiments the phosphatic shale results show that there is preferential release of large amounts of mree at ph 5 as well as at ph 2 demonstrating the weather ability of the phosphatic minerals at phs of natural freshwaters the sepik river ph 5 experiment also shows significant mree enrichment under near neutral conditions the development and retention of the mree enrichments in the leaching solutions is accompanied by an increase in dissolved phosphate concentrations although the magnitudes of the mree enrichment do not directly correlate with the percent of phosphate released the experimental data suggest that the preferential dissolution of phosphatic minerals during weathering can result in extensive ree fractionation between bulk river sediment and water leading to freshwaters with mree enrichments

the distribution of moho depths beneath the arabian plate and margins abstract in this study three new maps of moho depths beneath the arabian plate and margins are presented the first map is based on the combined gravity model eigen 06c which includes data from satellite missions and ground based studies and thus covers the whole region between 31 e and 60 e and between 12 n and 36 n the second map is based on seismological and ground based gravity data while the third map is based only on seismological data both these maps show gaps due to lack of data coverage especially in the interior of the arabian plate beneath the interior of the arabian plate the moho lies between 32 and 45 km depth below sea level there is a tendency for higher pn and sn velocities beneath the northeastern parts of the plate interior with respect to the southwestern parts of the plate interior across the northern destructive margin with the eurasian plate the moho depths increase to over 50 km beneath the zagros mountains across the conservative western margin the dead sea transform dst moho depths decrease from almost 40 km beneath the highlands east of the dst to about 21 23 km under the southeastern mediterranean sea this decrease seems to be modulated by a slight depression in the moho beneath the southern dst the constructive southwestern and southeastern margins of the arabian plate also show the moho shallowing from the plate interior towards the plate boundaries a comparison of the abruptness of the moho shallowing between the margins of the arabian plate the conjugate african margin at 26 n and several atlantic margins shows a complex picture and suggests that the abruptness of the moho shallowing may reflect fundamental differences in the original structure of the margins

mobility and fractionation of rare earth elements during supergene weathering and gossan formation and chemical modification of massive sulfide gossan primary massive sulfide gossans msg in the bathurst mining camp bmc new brunswick canada are characterized by relative enrichment of au sb and as formation of jarosite group minerals jarosite plumbojarosite and argentojarosite and little or no fractionation in the rare earth elements ree including preservation of large positive eu anomalies average eu eu nasc 4 14 in msg 6 61 in massive sulfide mineralization 0 60 in host rocks the chemical and mineralogical characteristics of msg e g halfmile lake deposit imply low ph 3 and relatively oxidizing conditions during gossan formation oxidation of a volcanogenic massive sulfide body comprising pyrite pyrrhotite sphalerite galena and chalcopyrite with a falling water table the lack of light ree or heavy ree fractionation and preservation of positive eu anomalies characteristic of the original 465 ma hydrothermal fluid is consistent with relatively large water rock ratios during massive sulfide mineralization oxidation and removal of the ree predominantly as sulfate complexes lnso4 ln so4 2 low ph groundwaters recovered from past producing mines in the bmc display ree patterns reflecting those inferred to have occurred during gossan formation gossan at the restigouche deposit in contrast to the halfmile lake deposit displays mineralogical and chemical evidence for having been chemically reworked since primary gossan formation evidence for chemical reworking includes loss of primary massive sulfide mineralization textures replacement of plumbojarosite with anglesite almost complete removal of jarosite minerals loss of au sb and as and apparent preferential removal of eu resulting in loss of positive eu anomalies for most samples average eu eu nasc 1 21 in the gossan with many displaying strong negative anomalies 3 65 in massive sulfide mineralization 0 54 in host rocks based on geochemical modeling conditions inferred for the chemical reworking of the restigouche deposit include near neutral conditions and either relatively oxidizing conditions with eu2 hosted in a preferentially weathered mineral host possibly through substitution for pb in plumbojarosite and beudantite or cycling between reduced and oxidized conditions during gossan reworking