mobility and fractionation of rare earth elements in argillaceous sediments implications for dating diagenesis and low grade metamorphism abstract we report sm nd and rb sr data for the fine fractions of lower paleozoic argillaceous rocks from wales uk and new york usa spanning the range of low grade metamorphic conditions from the diagenetic zone zeolite facies to the epizone greenschist facies in all cases leaching of the fine fractions results in a high 147 sm 144 nd 0 09 0 29 acid soluble component and a complementary low 147 sm 144 nd 0 05 0 14 residual component the observed fractionation is an ancient feature related to diagenesis burial and metamorphism the magnitude of sm nd fractionation between leachates and residues as well as the resulting sm nd ages vary as a function of grain size and metamorphic grade uncleaved welsh mudrocks of the diagenetic zone yield sm nd leachate residue ages of 453 484 ma in agreement with their llanviian to caradocian biostratigraphic ages whereas higher grade rocks of the anchizone and epizone yield sm nd ages as young as 413 ma these ages are transitional between the time of deposition and the time of regional deformation related to the acadian orogeny at 390 ma distinct convex upward rare earth element ree patterns of the leachates suggest that the precipitation of early diagenetic apatite controls the trace element budget of the rock forcing a depletion of middle rees on the subsequently formed diagenetic phyllosilicates the amount of organic matter present and the extent of later prograde reactions are probable modifiers of this fractionation process ordovician and devonian clastic rocks associated with the trenton and onondaga limestones of new york yield single sample and multi sample sm nd isochron ages that agree well with their biostratigraphic ages of 454 ma and 390 ma respectively the ree fractionation observed in shale leachates of the ordovician utica formation is related to ca mg of the bulk rock and hence to the composition of the diagenetic carbonate cement in all cases the sm nd system remained closed subsequent to the peak of diagenesis or metamorphism including the north american rocks that show no evidence of being isotopically reset during widespread remagnetization of the subjacent limestone units in the late paleozoic

geochemical features of fe mn micronodules in deep sea sediments of the western north pacific ocean potential for co product metal extraction from rey rich mud abstract rare earth element and yttrium rey rich mud around minamitorishima island japan in the western north pacific ocean has received significant attention as a novel rey resource in rey rich muds industrially critical metals such as co ni and mo occur in relatively high concentrations we show that fe mn micronodules separated from rey rich muds are significantly enriched in these elements we measured co contents of almost 3000 ppm and ni contents that exceed 39 000 ppm through experiments we demonstrated that reductive chemical leaching can be used to extract major portions generally 80 of the metals associated with fe mn oxyhydr oxides from rey rich muds the fe mn micronodules were of an oxic diagenetic origin a simple mass balance calculation indicated that the contribution of the fe mn micronodules to the bulk fe mn oxyhydr oxides in the sediment can amount to 8 50 median 18 the other metals associated with fe mn oxyhydr oxides seem to be hosted in mn microparticles probably of a hydrogenetic origin we estimate that the most promising site for rey rich mud development contains 9 3 0 6 102 t 1 6 0 1 103 t and 2 8 0 2 102 t of leachable co ni and mo respectively in 1 km2 0 10 m below seafloor these amounts account for 0 66 0 04 0 061 0 004 and 0 097 0 007 of present annual global productions of co ni and mo respectively the feasibility of extracting these metals as co products during rey rich mud development depends on the cost efficiency of the recovery process which ultimately depends on their market price in the near future

variations in the nd isotopic composition of foraminifera from atlantic ocean sediments 143nd 144nd ratios have been measured in recent core top foraminifera from 25 sites throughout the atlantic ocean the average nd 0 value from this study agrees well with previous estimates of the average nd isotopic composition of the atlantic based on analyses of ferromanganese deposits and seawater samples however the larger data base and the nature of the samples have allowed us to identify distinct provenances of nd isotopes in the atlantic

latitudinal temperature gradient during the cretaceous upper campanian middle maastrichtian y18o record of continental vertebrates latitudinal variations in model biogenic apatite d18o values were calculated using fractionation equations of vertebrates and weighted rainfall y18o values along with mean annual air temperatures provided by iaea wmo meteorological stations the reference equation obtained was used to compute a continental temperature gradient for the late campanian middle maastrichtian interval by using published and new d18o values of phosphate from vertebrates samples are mainly tooth enamel from crocodilians and dinosaurs that lived at paleolatitudes ranging from 83 4 n alaska to 32 3 s madagascar the temperature gradient was less steep 0 4 0 1 c latitude than the present day one 0 6 c latitude with temperatures that decreased from about 30 c near the equator to about 5 c at the poles above 30 of paleolatitude air temperatures were higher than at present the validity of these results is discussed by comparison with climatic criteria inferred from paleontological paleobotanical and sedimentological data the latitudinal distribution of oxygen isotope compositions of continental vertebrates is potentially a powerful tool for quantifying mesozoic terrestrial climates

neodymium isotopic composition of ordovician conodonts as a seawater proxy testing paleogeography 1 to evaluate recent ordovician paleogeographic reconstructions end values were determined in conodonts as a proxy for the isotopic variations in ancient seawater using samples from the major cratons and microplates isotopic variations reveal the existence of distinct oceanic masses and epeiric seas that constrain the position of plates and terranes relative to these water masses and hence constrain models of regional and global paleogeography the isotopic patterns show a consistent picture of the changes in the ordovician oceans the end values for water masses associated with laurentia are strongly negative 28 to 18 in the early ordovician evolving over time to higher values in the range 13 to 5 the early ordovician signature of laurentia is in marked contrast to other cratons and microplates which have a range of values from 10 to 5 samples from south china show interesting signals that reflect a greater similarity to laurentia than other peri gondwana terranes the isotopic variations are a function of both regional geology and global tectonic processes the most obvious being the taconic orogeny and onset of the closure of the iapetus ocean regional and global models of paleogeography are considered in light of these proxy signals this study also reveals that conodonts are powerful geochemical tools for obtaining information on ancient water masses the use of the nd isotopic signatures from conodonts provides a method independent of paleomagnetism and biogeography to test paleogeographic models by integrating such information a more multidisciplinary approach is possible

the assessment of ree patterns and 143nd 144nd ratios in fish remains abstract the ree content and isotopic composition of sr and nd have been determined in fish teeth ranging in age from the trias to the present and from various localities mostly around the atlantic these measurements have been carried out on selachian and teleost remains from the same locality in togo and show no appreciable difference which suggests with the help of a mass balance calculation of the ce anomaly that diagenetic effects are not responsible for the ree enrichment of biogenic phosphates one group of fossil teeth has about 3 times the ree abundances of shale and a shale normalized pattern with a minimum at sm it is thought to reflect deposition in the open sea environment a second group has ree concentration about 10 times higher than the first group with either a regular light ree enrichment or more frequently a maximum in the middle ree both being probably indicative of deposition in estuarine or near shore conditions the shape of the ree spectra and the size of the ce anomaly can be used semi quantitatively to determine the depth of deposition the results presented here on late cretaceous eocene fish teeth samples from morocco reflect an increasing influx of deep waters with a lowla yb ratio and strong negative ce anomaly which agrees well with the evolution of sediment chemistry and microfauna associations in contrast nd is typical of the water mass in which the fish debris decayed examples of nearly isolated basins identified with nd isotopes include the south atlantic prior to the lutetian nd 13 5 the miocene persian gulf nd 3 1 and bolivia during the late cretaceous nd 12 8 togo and guinea bissau results suggest that in the south atlantic the meridional oceanic circulation had not started before 45 ma ago combination of ree and nd data suggests that the assignment of jurassic cretaceous samples measured so far to open sea water masses is still ambiguous

rare earth element fluxes and geochemical budget in the eastern equatorial pacific rare earth element ree patterns and flux measurements of sediment traps sediments and nodules from the eastern tropical pacific demonstrate the dominance of ree supply to the sea floor by particle settling quantitative partitioning of the particle flux reveals that biogenic debris is the major ree carrier in shallow depths however the labile particles are surpassed in importance by alumino silicate particles at greater depths regeneration of biogenic associated ree appears responsible for la ce variations in the particle flux with depth and provides the primary source of ree accreted by nodules

influence of the mediterranean outflow on the isotopic composition of neodymium in waters of the north atlantic the isotopic composition of neodymium in the water column of the eastern north atlantic near the strait of gibraltar has been determined for several depths the data show that the mediterranean outflow results in a significant shift in e nd 0 toward more radiogenic values of 143 nd 144 nd in the water column at a 1000 m depth this corresponds to a depth in the neighborhood of the salinity maximum associated with the mediterranean outflow the core of the mediterranean outflow gives e nd 0 9 8 as compared to e nd 0 12 in overlying and underlying waters demonstrating that the mediterranean waters are distinct from the atlantic from mixing considerations we estimate that pure mediterranean waters have e nd 0 6 possible sources of this relatively radiogenic nd could be from drainage of young continental terranes or the injection of remobilized nd from deep sea sediments that have a young radiogenic volcanic component new data from a depth profile in the western atlantic is presented comparison of nd data for the eastern north atlantic with that for the western north atlantic shows fundamental differences in the water column structures for e nd 0 while both regions show a pronounced maximum in e nd 0 the western basin maximum occurs at the near surface rather than at 1000 m in addition deep waters of the eastern basin are found to be more radiogenic than the western basin these differences indicate several sources of isotopically distinct nd in the north atlantic the deep waters of the north atlantic 1000 m have the lowest values of e nd 0 measured in the oceans we believe that the source of these low e nd 0 values which we associate with north atlantic deep water is either from freshwater drainage off the precambrian shields of north america and asia into the arctic ocean or from the injection of older continentally derived ree from deep sea sediments sm and nd concentrations are found to increase with depth and e nd 0 changes with depth indicating both vertical and lateral transport processes from different sources this suggests a surface source of nd and injection of ree into the water column from deep sea sediments or large scale bottom currents with high ree concentrations

eocene to oligocene benthic foraminiferal isotopic record in the bay of biscay we present here oxygen and carbon isotopic records of eocene to oligocene benthic f oraminif era from two bay of biscay deep sea drilling project dsdp sites 119 and 401 18o of benthic foraminifera increases 1 9 from a middle eocene minimum zones p10 p11 to an earliest oligocene maximum zone np21 approximately 1 4 of the increase in benthic foraminiferal 18o occurs during the late eocene to earliest oligocene zones p15 16 np21 previous results from other north atlantic dsdp sites 400a and 398 have significantly lower 18o values of benthic foraminifera some by as much as 2 refs 1 3 we believe that these differences result from diagenetic alteration of the sediments in the deeper buried sites 400a and 398

isotope compositions c o sr nd of vertebrate fossils from the middle eocene oil shale of messel germany implications for their taphonomy and palaeoenvironment abstract the middle eocene oil shale deposits of messel are famous for their exceptionally well preserved articulated 47 myr old vertebrate fossils that often still display soft tissue preservation the isotopic compositions o c sr nd were analysed from skeletal remains of messel s terrestrial and aquatic vertebrates to determine the condition of geochemical preservation authigenic phosphate minerals and siderite were also analysed to characterise the isotope compositions of diagenetic phases in messel diagenetic end member values of the volcanically influenced and due to methanogenesis 12 c depleted anoxic bottom water of the meromictic eocene maar lake are isotopically very distinct from in vivo bioapatite values of terrestrial vertebrates this unique taphonomic setting allows the assessment of the geochemical preservation of the vertebrate fossils a combined multi isotope approach demonstrates that enamel of fossil vertebrates from messel is geochemically exceptionally well preserved and still contains near in vivo c o sr and possibly even nd isotope compositions while bone and dentine are diagenetically altered enamel of the hippomorph perissodactyl propalaeotherium has low 13 c values 9 0 7 typical for c 3 plant feeders dentine of the same teeth has 13 c values 15 17 higher amongst the highest 13 c bioapatite values reported for terrestrial vertebrates this reflects diagenetic carbonate exchange with the strongly 12 c depleted anoxic lake bottom water enamel 87 sr 86 sr values 0 711 0 001 are consistent with propalaeotherium feeding on palaeozoic bedrocks surrounding lake messel and suggests that the basaltic tuff ring around the maar was already eroded 640 ka after its formation dentine has however much lower volcanically influenced 87 sr 86 sr 0 706 due to diagenetic sr uptake from the lake water oil shale enamel 18 o p values 18 0 6 of propalaeotherium are 2 3 lower than those of bones and scales of aquatic vertebrates that lived in the 18 o enriched lake water using transfer functions a 18 o h 2 o value of 5 1 for meteoric water and a mat of 18 2 5 c were reconstructed for messel

rare earth element deposition in pelagic sediment at the cenomanian turonian boundary exmouth plateau odp site 762 eastern indian ocean includes a section of sediment that spans the cenomanian turonian boundary ctb and was deposited along a continental margin during a period of widespread oceanic 09 deficiency the rare earth element ree content of pre and post boundary sediment is similar to that of present day continental slope material deposited in well oxygenated seawater whereas the ctb section is characterized by significantly depleted ree abundances a bulk ce anomaly that increases to maximum of 1 0 and a ree pattern that resembles that of present day fluvial material we suggest the change in ree patterns reflects release of scavenged rees upon reductive dissolution of authigenic fe mn oxyhydroxides such that sediment deposited during the ctb is dominated by the lithogenous ree fraction these results are consistent with recent models concerning pervasive fractionation of mn and fe and redirection of mn in pelagic ctb waters

isotopic composition of neodymium in waters from the drake passage the isotopic composition of neodymium has been determined in seawaters from the drake passage the antarctic circumpolar current which controls interocean mixing flows through this passage the parameter e nd 0 which is a function of the ratio of neodymium 143 to neodymium 144 is found to be uniform with depth at two stations with a value which is intermediate between the values for the atlantic and the pacific and indicates that the antarctic circumpolar current consists of about 70 percent atlantic water cold bottom water from a site in the south central pacific has the neodymium isotopic signature of the waters in the drake passage by using a box model to describe the exchange of water between the southern ocean and the ocean basins to the north together with the isotopic results an upper limit of approximately 33 million cubic meters per second is calculated for the rate of exchange between the pacific and the southern ocean concentrations of samarium and neodymium were also determined and found to increase approximately linearly with depth these results suggest that neodymium may be a valuable tracer in oceanography and may be useful in paleo oceanographic studies

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

trace elements and their isotopes in bones and teeth diet environments diagenesis and dating of archeological and paleontological samples fossil biogenic apatites display trace element te compositions that can record environmental and biological signals give insights into past water compositions or be used for dating paleontological and archeological bones and teeth processes of te incorporation into apatites of skeletal phosphatic tissues are described ranging from those active in living organisms to those active during diagenesis abiotic incorporation mechanisms have been modeled theoretically and experimentally and include crystallographic controls on te partitioning coefficients inorganic surface adsorption and adsorption mediated through chelation and diffusion adsorption processes each leading to specific fractionation patterns predictions from models and experiments have been tested against te concentration and isotopic composition data on remains of contemporary wild or raised animals and on fossils of various ages and environments in living organisms tes incorporated in apatite are separated in two categories non essential elements whose concentration is compared to that of an essential element with similar behavior e g sr ca to reconstruct trophic chains and essential elements whose isotopic ratios are used to trace metabolic activity diet etc in fossils elements are incorporated during diagenesis such as rare earth elements rees and trace diagenetic processes ranging from very early quantitative adsorption likely mediated by chelators protracted diagenesis through inorganic adsorption and fractionation through diffusion adsorption to low grade metamorphism associated with intense redistribution under crystal chemical control these different steps are also identified as steps of radionuclide incorporation only samples where the earliest steps can be deciphered are useful for determining stratigraphic and archeological ages other samples will date late diagenetic events that have obliterated the paleoenvironmental signals but may be of geological significance e g tectonic events

p sh conversions in layered media with hexagonally symmetric anisotropy a cookbook reflectivity synthetic seismograms demonstrate that the type layering and orientation of 1 d anisotropy influences strongly the coda of teleseismic p waves at periods t 1 sec particularly p sh converted waves we assume the simplest form of anisotropy described by an elastic tensor with a symmetry axis of arbitrary orientation the resulting phase velocities vary as cos 2 with respect to that axis using three families of simple crustal models we compare the effects of an anisotropic surface layer with reverberations caused by both thick and thin layers of anisotropy at depth if anisotropy in the surface layer is significant the polarization of direct p can be distorted to generate a transverse component followed by ps and a prominent shear reverberation converted from direct p at the free surface if the anisotropic layer is buried the first and often the most prominent arrival on the transverse component is the p to sh conversion at its upper surface if the anisotropic layer is sufficiently thin p to sh conversions from its boundaries interfere to form a derivative pulse shape on the transverse component which could be mistaken as the signature of shear wave splitting if is horizontal compressional p and shear s anisotropy both produce similar waveform perturbations with four lobed azimuthal patterns suggesting that a weighted stack of p coda from different back azimuths would improve signal to noise for tilted between the horizontal and vertical however the effects of p and s anisotropy differ greatly the influence of p anisotropy on p to s conversion is greatest for a symmetry axis tilted at 45 to the vertical where its azimuthal pattern has two lobes rather than four combinations of p and s anisotropy typically lead to a composite azimuthal dependence in the p coda reverberations

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

rare earth element evolution of phanerozoic seawater recorded in biogenic apatites rare earth element ree contents of marine biogenic apatites have been shown to record seawater compositions a data base of available and newly acquired rare earth element ree contents of marine biogenic apatites has been created to assess the past seawater ree compositions to ensure that this data base contains only the pristine ree signals altered samples characterized by very low la sm n ratios where n stands for ree ratios normalized to the nasc composition gromet et al 1984 geochim cosmochim acta 48 1984 2469 acquired during apatite recrystallization are not included in the database these data reveal a change in the tethyan seawater composition between 110 and 80 ma after the end of the cretaceous the ree chemistry of seawater remains constant until present day this seawater composition change is likely due to concurrent changes in ree scavenging processes a strong correlation between decreasing sm yb n ratios and increasing ce anomalies for samples deposited during the 80 110 ma period is observed as ce anomalies are attributed to ocean water redox conditions changes in ree scavenging could reflect an evolution from stratified and poorly oxygenated waters towards well mixed and oxygenated waters this could have resulted from changing current patterns stemming from the contemporaneous opening of the atlantic ocean a major change in middle and late cretaceous oceanic circulation linked to plate tectonics would have favored the colonization of pelagic environments

high resolution stratigraphy with strontium isotopes the isotopic ratio of strontium 87 to strontium 86 shows no detectable variation in present day ocean water but changes slowly over millions of years the strontium contained in carbonate shells of marine organisms records the ratio of strontium 87 to strontium 86 of the oceans at the time that the shells form sedimentary rocks composed of accumulated fossil carbonate shells can be dated and correlated with the use of high precision measurements of the ratio of strontium 87 to strontium 86 with a resolution that is similar to that of other techniques used in age correlation this method may prove valuable for many geological paleontological paleooceanographic and geochemical problems

water mass exchange and variations in seawater temperature in the nw tethys during the early jurassic evidence from neodymium and oxygen isotopes of fish teeth and belemnites article i nfo oxygen and neodymium isotope analyses performed on biostratigraphically well dated fish remains recovered from the hettangian to toarcian of the paris basin were used to reconstruct variations of early jurassic seawater temperature and to track oceanographic changes in the nw tethys our results indicate a strong correlation between 18 o trends recorded by fish remains and belemnites confirming the paleoenvironmental origin of oxygen isotope variations interestingly temperatures recorded by pelagic fishes and nektobenthic belemnites and bottom dwelling fishes are comparable during the late pliensbachian sea level lowstand but gradually differ during the early toarcian transgressive episode recording a difference in water temperatures of 6 c during the bifrons zone this could suggest that the surface bottom water temperature difference was not large enough during regressive phases to be recorded by organisms living near the lower and upper part of the water column the globally unradiogenic nd budget of euro boreal waters through the early jurassic suggests that these waters were strongly affected by continental neodymium input from surrounding emerged areas and that exchange with more radiogenic waters from the tethys and panthalassa oceans remained limited this supports the existence of a southward directed current in the euro boreal area for most of the early jurassic the only exception is observed at the early late pliensbachian transition where a positive end excursion is recorded suggesting northward influx of low latitude tethyan or panthalassan waters which may have contributed to the warming of nw tethyan seawater recorded at this time the absence of a marked negative excursion in end concomitant with a negative 18 o shift recorded during the falciferum zone exaratum subzone argues against the influence of less radiogenic arctic water influxes with low 18 o values during this interval instead we suggest that

protracted diagenetic alteration of ree contents in fossil bioapatites direct evidence from lu hf isotope systematics abstract fossil bones and teeth are potentially important repository for geochemical proxy data and a target for radiometric dating the concentration of many trace elements in bones and teeth increases by orders of magnitude after death and it is this diagenetic incorporation that forms the basis for several areas of geochemical study the use of bones and teeth in this context relies on two assumptions first that target metal ions are incorporated rapidly after death reflecting a known environmental signal and second that after early incorporation the bone or tooth remains as an essentially closed system resistant to later diagenetic change a wide literature has developed exploring these assumptions but relatively little direct evidence has been used to assess the long term diagenetic stability of trace elements within bones and teeth in this study we use the lu hf isotope system to show that bones and teeth of cretaceous and triassic age from both terrestrial and marine settings experience continued long term diagenetic change most likely through gradual addition of trace elements modelling suggests that diagenetic addition after initial recrystallisation may account for 50 of the total ree content in the sampled bones the extent depending on initial uptake conditions tooth enamel and enameloid may be more resistant to late diagenetic changes but dentine is probably altered to the same extent as bone these results have significant implications for the use of bones and teeth as hosts of chronological palaeoceanographic palaeoenvironmental and taphonomic information particularly in mesozoic and palaeozoic contexts

la icp ms analysis of rare earth elements in marine reptile bones from the middle triassic bonebed upper silesia s poland impact of long lasting diagenesis and factors controlling the uptake abstract the rare earth elements ree contained in fossil bones are widely used for provenance and palaeoenvironmental studies earlier works suggested that the ree uptake is limited to early diagenesis but more recent research provided evidence of long term open system diffusion in fossil bones we analysed thin walled reptile bones all collected from the same middle triassic 245 ma marine bonebed comprising vertebrate remains of likely different ages to check the influence of the long term diagenesis on the concentrations of ree in terms of impact of pore water the upper parts of the bones are contained in a low permeability crinoidal limestone whereas their lower parts have been affected by diagenetic fluids for a long time we measured ree and other trace element contents in 29 bones using la icp ms totally 660 spots in 45 depth profiles neither the absolute concentrations of the ree and the ree intra bone paas normalised patterns nor the inter element ratios and the la ce and eu anomalies appear useful to distinguish between the likely older and younger bones in the bonebed the mree n enrichment combined with the flat intra bone distributions of the ree lead to conclusion that ree fractionation and substitution for ca were the most important processes responsible for the selective uptake the low permeability host rock and diagenetic fluids had a significant impact on the trace element uptake and their intra bone distribution patterns the lower parts of the bones that likely had a long lasting contact with the diagenetic fluids reveal a relative enrichment in the ree and their easier diffusion into the bone centres the ability of fossil bones to incorporate trace elements over a long time span strongly limits the usage of particularly the older samples for provenance and palaeoenvironmental reconstructions additionally the presented new analyses fill the gap between the available databases of trace element concentrations in fossil bones with regard to middle triassic samples

more reducing bottom water redox conditions during the last glacial maximum in the southern challenger deep mariana trench western pacific driven by enhanced productivity abstract the modern southern mariana trench is characterized by oligotrophic surface waters resulting in low primary productivity and well oxygenated bottom waters this study investigates changes in the redox conditions of bottom waters in the southern mariana trench during the last glacial maximum lgm and their potential causes we measured major trace and rare earth elements ree in three gravity cores gc03 gc04 and gc05 and one box core bc11 retrieved from the southern challenger deep at water depths from 5289 to 7118 m the upper sediment layers of both gc05 and bc11 are dominated by valve fragments of the giant diatom ethmodiscus rex forming laminated diatom mats ldms 14c ams dates of bulk organic matter show that the ldms accumulated between 18 4 and 21 8 kyr b p corresponding to the lgm modest enrichments of u and mo along with weak or absent ce anomalies in the ldm point to suboxic conditions during the lgm in contrast non ldm samples exhibit little to no enrichment of redox sensitive elements as well as negative ce anomalies indicating deposition under oxic bottom water conditions the ce anomalies are considered valid proxies for bottom water redox conditions because ree signatures were acquired in the early diagenetic environment as indicated by strong p ree correlations and middle ree enrichment associated with early diagenetic cycling of fe mn oxyhydroxides in the sediment column followed by capture of the ree signal by biogenic and or authigenic apatite we postulate that the more reducing bottom water conditions during the lgm were linked to increased primary productivity induced by enhanced asian dust input as shown in earlier studies the increased primary productivity associated with ethmodiscus rex blooms in the eastern philippine sea played a significant role in capturing atmospheric co2 during the lgm consequently the magnitude of atmospheric co2 sequestration by giant diatom blooms during the lgm may have been greater than previously envisaged

geochemical decoupling of water masses in the variscan oceanic system during late devonian times abstract neodymium isotope data obtained from conodonts collected in morocco and poland attest a geochemical decoupling of seawater in the variscan realm during the late devonian the water masses on the shelves were characterized by unradiogenic e nd values from about 7 to 12 the surface water in the bordering oceans the rheic ocean and the variscan sea yielded more radiogenic e nd values ranging from about 1 to 6 a compilation of nd and c isotope signatures from the moroccan meseta suggests that the shelf and the surface oceanic water differed also in their carbon isotope evolution the geochemical decoupling constrains a restricted water exchange between shelves and the ocean oceanic waters entered far into the shelf areas only during the semichatovae transgression in the frasnian zone 11 sea level fluctuations constituted the major force that modified circulation and thus controlled the mixing of shelf and surface oceanic seawater the nd conodont data reveal that the surface water of the variscan oceanic water resembled the seawater of the modern pacific ocean rather than those of the atlantic and indian oceans the geochemical character of the variscan oceanic water is consistent with the geotectonic regime of the variscan realm in late devonian and carboniferous times

rare earth distributions with a positive ce anomaly in the western north atlantic ocean from the vertical distributions of the rare earth elements ree in the sargasso sea we now report the first profiles of pr tb ho tm and lu in seawater together with profiles for la ce sm eu and yb the first observations of positive ce anomalies in seawater are ascribed to reducing inshore sediments as a source for ce ref 1 all vertical profiles are consistent with adsorption of trivalent rare earths by settling particles possibly siliceous or calcareous followed by their release at or near the sea floor on dissolution of the carriers the very different ce profile demonstrates the additional effects of oxidation reduction reactions

diagenetic uptake of rare earth elements by bioapatite with an example from lower triassic conodonts of south china abstract the distribution patterns of rare earth elements rees are frequently used as proxies for ancient seawater chemistry or paleomarine environmental conditions however recent work has shown that diagenesis can lead to remobilization and inter elemental fractionation of rees and that these effects often occur in conjunction with redox reactions in sediment porewaters here we review existing literature on the diagenetic fluxes of rees in marine sediments and porewaters in order to systematize existing knowledge on this subject rees undergo significant redistribution among sediment phases during both early and late diagenesis as a consequence of adsorption and desorption processes remobilization of rees commonly leads to inter elemental fractionation variously leading to enrichment or depletion of the light middle or heavy ree fractions further ree remobilization can be facilitated by redox changes e g through reductive dissolution of host phases in suboxic and anoxic porewaters characteristic ree distribution patterns develop through these processes 1 a flat distribution signifying predominantly terrigenous siliciclastic influence 2 a middle ree bulge probably due to adsorption of light and heavy rees to mn and fe oxyhydroxides respectively and 3 heavy ree enrichment indicative of hydrogenous seawater influence note all patterns in this paper are normalized to the ree composition of average upper continental crust or ucc in the second part of this study we undertake an analysis of the ree distributions in conodonts and whole rock samples from west pingdingshan a permian triassic boundary section in south china using ree th and y ho ratios we show that almost all of the conodont samples have a strong diagenetic overprint and that the hydrogenous ree fraction is small and not isolatable furthermore the conodonts contain two diagenetic ree components one characterized by low ree 100 300 ppm high ree th ratios 1000 strong middle ree enrichment and eu eu ratios of 1 5 2 0 and the second by high ree 300 2000 ppm low ree th ratios 20 30 little or no middle ree enrichment and eu eu ratios of 1 0 the first component exhibits a pronounced middle ree bulge that represents an early diagenetic signature associated with suboxic conditions possibly related to adsorption of rees onto fe mn oxyhydroxides in the shallow subsurface environment the second component shows a flat ree distribution that is similar to both our whole rock samples and average ucc indicating derivation from rees released from detrital siliciclastics e g clay minerals probably at a range of burial depths from shallow to deep failure of the conodont samples to yield an isolatable hydrogenous component demonstrates that bioapatite does not always preserve a primary marine ree signature given that bioapatite rees have been widely used for this purpose often on the assumption of minimal or no diagenetic influence our findings are likely to necessitate a re evaluation of the results of many earlier studies in general we counsel caution in inferring a hydrogenous origin for rees in bioapatite owing to frequent diagenetic alteration of ree distributions

rare earth elements in old biogenic apatites abstract the ree distributions in individual upper devonian conodonts have been measured by ion probe the patterns of all analyzed conodonts are enriched in middle ree eu gd and have a weak or no ce anomaly concentrations and la yb or la sm ratios vary very little within or among individuals from the same zone which suggests that uptake of labile ree from sediments was essentially quantitative therefore the ree signature of the primary carriers probably organic and oxyhydroxides particulates from marine suspensions was efficiently transferred to biogenic apatites and survived late diagenetic processes ree patterns of conodonts do not resemble those of present day seawater and post cretaceous biogenic phosphates which are typically depleted in nd and sm with a negative ce anomaly since ree distributions in the modern water column mimic those of nutrients we assume that in pre cretaceous seawater they were not controlled by surface biological activity we assume instead that ree in pre cretaceous seawater can be explained by mechanism of desorption adsorption on particle surfaces progressive extraction of lree from river water by oxyhydroxides leads to precipitates enriched in middle ree a simple quantitative model was calculated in order to illustrate the proposed mechanism

rare earth elements and neodymium isotopes in ferromanganese oxide coatings of cenozoic foraminifera from the atlantic ocean abstract an evaluation has been made of the method of establishing the ree contents and patterns and nd isotopic compositions of sea water over cenozoic time from their record in the femn oxide coatings of foraminiferal calcite using 0 60 ma samples from the rio grande rise dsdp site 357 it has been established that the ree contents of the coatings are generally similar to those of recent samples however in the cenozoic samples the surface coatings have been diagenetically modified under suboxic conditions resulting in a distinctly different ree pattern although the original 143 nd 144 nd ratios appear to have been preserved the nd isotopic curve for cenozoic sea water in the s atlantic shows clear temporal trends although these are not so extreme as to show 143 nd 144 nd ratios outside the range observed in modem sea water with the principal exception of the oldest samples there is an approximate inverse relationship between the nd and sr isotopic compositions of the foraminifera it is suggested that the changes reflect both global changes in the relative proportions of nd and sr derived from continental input and from the weathering of volcanic debris together with short term and local variations to which the sr curve is insensitive reflecting the different response times of the two elements to changes in oceanic input functions the nd isotope curve appears to be a potentially useful tracer of ocean palaeochemistry

nd isotopic composition of jurassic tethys seawater and the genesis of alpine mn deposits evidence from sr nd isotope data jurassic metabasalts metasediments and mn ores from the pennine realm of the alps were examined in order to establish the nd isotopic composition of the jurassic tethys seawater and to elucidate the genesis of the mn deposits the highly positive initial epsilon sub nd values 7 to 9 8 of the metabasalts and their low sup 87 sr sup 86 sr ratios 0 7028 to 0 7049 indicate that they originated from a depleted mantle the initial epsilon sub nd values of the cherts range between minus 5 and minus 9 the sm nd isotope data indicate that they are primary mixtures of basalt and continental detritus the smaller than 2 mu m fractions of the cherts and of a marble which probably represent the formerly authigenic material show initial epsilon sub nd values ranging between minus 5 9 and minus 6 6 the average initial sr isotopic composition of five mn ores is 0 70730 plus minus 22 identical to that of contemporaneous jurassic seawater the initial nd isotopic composition values of the mn ores are very homogeneous the average value of five ores a leachate and residue of one of them calculated for an age of 170 ma is 0 512082 plus minus 19 it is suggested that the ores together with the smaller than 2 mu mmore fractions of the sediments define the jurassic tethys seawater isotopic composition the resulting average sup 143 nd sup 144 nd initial value is 0 512089 plus minus 17 epsilon sub nd minus 6 5 plus minus 0 6 less

rare earth major and trace elements in chert from the franciscan complex and monterey group california assessing ree sources to fine grained marine sediments abstract rare earth element ree major and trace element analyses of 77 samples from the mesozoic franciscan complex and miocene monterey group of california usa indicate that magnitudes of the ce anomaly ce ce and total ree abundances sree in these rocks are controlled dominantly by a the amount of included metalliferous material b the amount of direct terrigenous input and c the overall burial rate the relative importance of these individual processes varies across an ocean basin in such a way that ree relative fractionations and sree correspond with its depositional environment our conclusions are supported by an extensive review of published ree data from various river coastal open ocean and ridge influenced waters as well as terrigenous pelagic and metalliferous sediment the chert sequences record deposition in spreading ridge open ocean basin and continental margin environments the relative importance of metalliferous and terrigenous influences and the role of scavenging from seawater may be estimated from a sample s inferred depositional distance km from the spreading ridge the major element chemistry and the stratigraphie context the ce ce values are low 0 29 in the vicinity of spreading ridges and trend to successively higher 1 values with decreasing metalliferous and increasing terrigenous influences other ree indicators ree lu n la n eu eu also respond to metalliferous and terrigenous influences near the spreading ridge chert ree appears determined by burial rate while shale ree responds to metalliferous abundance in open ocean and continental margin environments ree is controlled by sediment exposure time and therefore is related inversely to burial rate ree data are consistent with the major elements fe2o3 mno and al2o3 in reflecting the respective metalliferous and terrigenous sources p2o5 and cao do not vary with ce ce in any environment but cao shows a weak negative correlation with ree trace element trends e g v cr cu ge si rb sr y th u in general can similarly be accounted for in the context of depositional position relative to metalliferous and terrigenous inputs rees in chert appear less affected by post depositional processes than either major or trace elements indicating that rees are better tools for paleoceanographic or tectonic reconstructions that are based on chert chemistry this work complements recent efforts to elucidate the factors determining large scale ree distributions in marine sediments and has direct bearing on previous attempts to use the ce anomaly in older rocks and sediments as a recorder of secular variations and anoxic events in the overlying water column

strontium isotope systematics of conodonts middle devonian eifel mountains germany abstract the eifel mountains lithological profile the stratotype for the middle devonian was densely sampled for conodonts to delineate the sr isotopic evolution of coeval sea water the 87sr 86sr curve obtained shows oscillations around a mean of about 0 7078 that have a frequency in the 105 106 yr range and an amplitude in the 10 5 10 4 range these oscillations mimic those obtained on coeval brachiopods diener et al 1996 but are shifted into more radiogenic domains by up to 10 4 model calculations suggest that the shift is due to partial 30 40 early diagenetic equilibration of conodonts with their enclosing bulk rock matrix the reality of partial recrystallisation is supported by visible neoformed blocky apatite crystals on the surface of the conodonts despite their otherwise apparently excellent preservation with cai values of 1 5 2 5 we therefore suggest that studies anticipating use of conodonts as a recorder of paleoceanographic events should be confined to specimens embedded in a relatively clean matrix such as pure limestone even these results should be cross checked by comparison with data on coeval low mg shells such as brachiopods or belemnites

neodymium isotopic study of baffin bay water sources of ree from very old terranes water samples were collected from baffin bay and surrounding areas in order to evaluate this region as a potential source of nd from old continental material to atlantic water the isotopic data ranged from e nd 0 9 0 to 26 with most of the data around e nd 0 20 compared with values of north atlantic deep water nadw with e nd 0 13 5 the concentration of nd in baffin bay waters was as high as 6 10 12 g g compared with 2 5 10 12 g g for nadw the combination of low e nd and high nd concentration indicates that baffin bay may be a significant source of nd from very old crustal material a simple box model was used to evaluate the contribution to the nd budget of nadw and it was concluded that a substantial fraction of the nd from ancient crustal sources that is required to maintain the isotopic composition of nadw could be supplied by baffin bay outflow

oxygen strontium and neodymium isotope composition of fossil shark teeth as a proxy for the palaeoceanography and palaeoclimatology of the miocene northern alpine paratethys the upper marine molasse sediments of southern germany were deposited during the early to middle miocene a period of significant change for the global miocene palaeoceanography palaeoclimate and the regional palaeogeography because of the ongoing alpine himalayan orogeny to address the influence of the alpine uplift on climate and oceanography of the northern alpine molasse basin a combined o sr and nd isotope study was undertaken on fossil teeth from sharks synodontaspis sp galeocerdo cf aduncus chaenogaleus sp and button like teeth from the bony fish of the upper marine molasse chrysophrys molassica average 18o values for hydroxyapatite of teeth from two sites are 20 3 1 0 6 and 21 2 1 0 5 while their average 87sr 86sr and 143nd 144nd ratios are 0 70850 0 00001 2 and 0 70882 0 00003 2 and 0 51220 and 0 51223 both at 0 00001 2 respectively by comparison to the sr evolution curve for the global ocean the sr isotope compositions suggest ages of about 22 and 17 ma for the teeth these ages are in good agreement with the depositional ages which suggests open marine conditions open marine conditions are also compatible with 1 lower average 18o values and 87sr 86sr ratios for the one site compared to higher 18o values and higher 87sr 86sr ratios for the other site 2 estimates for seawater temperatures which are similar to other estimates from deposits of similar latitude and age 3 a comparison of seawater temperatures with average ambient air temperature estimates deduced from continental palaeoclimate indicators nd isotope compositions are compatible with an influence of the north atlantic on the paratethys assuming constant salinity and seawater oxygen isotope composition a 4 c cooling can be inferred from average 18o values of the teeth between 22 and 17 ma this is similar to trends observed for foraminiferal records from the mediterranean tethys but different from foraminiferal and molluscan records of the north atlantic and the north sea during this period and allows for the possibility that the alpine orogeny had an influence on the regional circum alpine climate

sm nd in marine carbonates and phosphates implications for nd isotopes in seawater and crustal ages this study explores the possibility of establishing nd isotopic variations in seawater over geologic time calcite aragonite and apatite are examined as possible phases recording seawater values of nd modern biogenic and inorganically precipitated calcite and aragonite from marine environments were found to have nd concentrations of from 0 2 to 70 ppb showing that primary marine caco 3 contains little ree and that nd ca is not greatly enhanced relative to seawater during carbonate precipitation very young marine limestone and dolomite containing no continental detritus have 200 ppb nd all the carbonates are lree enriched 0 16 sm nd 0 45 modern and very young atlantic and pacific carbonates have nd in the range of shallow atlantic and pacific seawater respectively implying that they derive their ree from local seawater the nd in well preserved carbonate fossils is 4 10 4 ppb much greater than in their modern counterparts but like the high values found for carbonates in other studies we believe the high ree contents at the 500 ppb level in some detritusfree carbonates are due to ree rich fe hydroxide in on the carbonate in favorable cases such material may record seawater nd values however introduction of extraneous ree may obscure the original isotopic composition of pure caco 3 because of its very low intrinsic primary ree abundance modern biogenic apatite is also shown to have very low ree content 150 ppb nd but appears to quickly scavenge ree from seawater inorganically precipitated apatite from phosphorites has high concentrations of seawater derived ree young phosphorite apatite from the atlantic and pacific oceans has nd in the range of the seawater from these oceans older apatite samples of similar age from different localities bordering common oceans record similar values of nd t sedimentary apatite has sr t values in good agreement with the curves for 87 sr 86 sr of seawater as a function of time individual conodonts from a single formation yield the same sr t and nd t other workers have shown that sedimentary apatite preserves seawater ree patterns these characteristics suggest that sedimentary apatite can be used to determine nd t in ancient seawater the seawater values so inferred range between 1 7 and 8 9 over the last 700 my and lie in the range of modern seawater showing no evidence for drastic changes high values of seawater nd t in the triassic and latest precambrian may correlate with the breakup of large continental landmasses the initial nd t 15 0 of a 2 ae old phosphorite implies the presence of 1 5 ae old continental crust at 2 ae ago the approach outlined here can be used to constrain the age of the exposed crust as a function of time

mass balance for nd in the mediterranean sea abstract the mass balance for nd in the mediterranean sea has been assessed through the measurement of nd isotope ratios in particulates from rivers entering the mediterranean sea floor clays and ferromanganese crusts and samples of atmospheric dusts nd values for the po and rhone rivers respectively are 10 8 and 9 7 whereas the nile seyhan and tarsus have 3 3 6 2 and 6 3 sea floor clays and ferromanganese crusts range from 2 0 to 10 1 and dust samples vary from 8 2 to 11 0 the relatively radiogenic nd isotope composition of the mediterranean seawater ed 6 to 7 compared to the atlantic nd 12 reflects partial equilibration of the particulate input into the basin rather than merely the dissolved input

nd isotope evidence for the evolution of the paleocurrents in the atlantic and tethys oceans during the past 180 ma the nd isotopic composition of atlantic and tethys seawater as deduced from marine phosphorites varied considerably during the past 180 ma the early tethys and central atlantic seawater from 180 to 160 ma ago early middle jurassic had a nd isotopic signature identical to that of the pacific end 6 suggesting that pacific seawater entered the newly forming tethys basin however with time continental runoff draining into the young basin became more important and led to a decrease in the nd isotopic composition and finally a decoupling from the pacific ocean during the late early cretaceous 120 90 ma ago atlantic and tethys seawater reached continental crust like nd isotopic composition values end 10 which could reflect high weathering rates induced by the warm and humid climate at that time in the time span between 80 and 50 ma late cretaceous early tertiary the nd isotopic composition of both tethys and atlantic seawater strongly increased towards pacific seawater values in the case of the atlantic ocean this change has been correlated with the opening of the south atlantic which enabled the more radiogenic pacific seawater to travel westwards around the southern edge of africa into the south and finally the north atlantic in the case of tethys seawater we have to assume that during this period large masses of pacific seawater entered the tethys again directly through the indian tethys seaway the renewed importance of this seaway might be related to the late cretaceous early tertiary first order global sea level highstand the most abrupt change towards lower more crust like values occurred in the early miocene 25 17 ma ago in the south and north atlantic as well as in the tethys during this period the143nd 144nd isotope ratios dropped from 0 5124 end 4 2 down to 0 5122 end 8 this change indicates a diminishing influx of pacif seawater into the atlantic and tethys oceans and can be correlated with the breakdown of the circum equatorial circulation patterns of the world oceans due to plate tectonics from 20 to 17 ma ago miocene the nd isotopic composition of the atlantic ocean increased again and reached values as high as 0 5123 end 6 6 whereas tethys seawater remained at low values this decoupling can be correlated with the incipient complete isolation of the tethys the nd isotopic composition was henceforth controlled by the continental runoff from surrounding land masses the major increase in the nd isotopic composition observed in the atlantic can be related to the opening of the drake passage and establishment of the circum antarctic current system this allowed pacific seawater to enter directly the south atlantic around antarctica a renewed drop in the nd isotopic composition of atlantic seawater during the late miocene can be related to the onset of north atlantic bottom water formation and its subsequent upwelling

luminescence of uranium and rare earth elements in apatite of fossil fish teeth abstract time delayed laser induced luminescence of uranium and rare earth elements ree in apatite of fossil fish teeth from the phosphorites of the senonian mishash formation israel were investigated before and after thermal treatment the unheated samples show luminescence of uo 2 2 luminescence of ree 3 sm eu pr is observed only after heating the samples at 1100 k in air the spectral properties indicate that uo 2 2 in the unheated samples is located in two different positions as aqua complexes of uranyl ions and associated with organic matter the ree in the unheated samples are accommodated in non luminescent form after heating the ree 3 sm eu pr are located in the ca 2 ii site presumably due to thermal diffusion

3d mapping hydrodynamics and modelling of the freshwater brine mixing zone in salt flats similar to the salar de atacama chile abstract salt flat brines are a major source of minerals and especially lithium moreover valuable wetlands with delicate ecologies are also commonly present at the margins of salt flats therefore the efficient and sustainable exploitation of the brines they contain requires detailed knowledge about the hydrogeology of the system a critical issue is the freshwater brine mixing zone which develops as a result of the mass balance between the recharged freshwater and the evaporating brine the complex processes occurring in salt flats require a three dimensional 3d approach to assess the mixing zone geometry in this study a 3d map of the mixing zone in a salt flat is presented using the salar de atacama as an example this mapping procedure is proposed as the basis of computationally efficient three dimensional numerical models provided that the hydraulic heads of freshwater and mixed waters are corrected based on their density variations to convert them into brine heads after this correction the locations of lagoons and wetlands that are characteristic of the marginal zones of the salt flats coincide with the regional minimum water brine heads the different morphologies of the mixing zone resulting from this 3d mapping have been interpreted using a two dimensional 2d flow and transport numerical model of an idealized cross section of the mixing zone the result of the model shows a slope of the mixing zone that is similar to that obtained by 3d mapping and lower than in previous models to explain this geometry the 2d model was used to evaluate the effects of heterogeneity in the mixing zone geometry the higher the permeability of the upper aquifer is the lower the slope and the shallower the mixing zone become this occurs because most of the freshwater lateral recharge flows through the upper aquifer due to its much higher transmissivity thus reducing the freshwater head the presence of a few meters of highly permeable materials in the upper part of these hydrogeological systems such as alluvial fans or karstified evaporites that are frequently associated with the salt flats is enough to greatly modify the geometry of the saline interface