excess 40ar in biotite and hornblende from the noril sk 1 intrusion siberia implications for the age of the siberian traps the siberian traps represent the largest known phanerozoic manifestation of continental flood volcanism the general agreement is now that the volcanism was of short duration 1 m y and was synchronous with the permian triassic boundary discrepancies between different geochronologic results prevent rigorous evaluation of the age and duration of magmatism several alkalic mafic intrusions associated with the siberian traps represent subvolcanic feeders for the trap lavas the noril sk 1 intrusion is intruded into the earliest flows and is chemically and isotopically related to stratigraphically overlying flows biotites from the noril sk 1 intrusion have previously yielded 40ar39ar plateau dates 254 251 ma that are significantly older than seemingly reliable 40ar39ar plateau dates 250 247 ma on plagioclase and whole rock samples from trap basalts that are geologically constrained to be older than the intrusion possible explanations of this discrepancy include 1 plagioclase and whole rock samples are anomalously young due to 40ar loss via alteration or episodic outgassing and or 2 the biotites contain excess 40ar detailed laser heating 40ar39ar analysis of six individual grains of biotite in a total of 214 steps yield data that permit characterization of multiple components of ar through isotope correlation patterns an isochron age of 250 1 1 5 ma 2 and an excess ar component with 40ar36ar 565 39 are obtained by regression of the 115 highest temperature steps step heating of a bulk hornblende sample also reveals excess ar with 40ar36ar 327 10 and an isochron age of 249 3 1 6 ma neglecting uncertainties in the ages of neutron fluence monitors the two dates just overlap at 2 but are distinctly younger than the previous mean plateau date 253 9 1 6 ma for biotite the different initial 40ar36ar for the two phases is interpreted as reflecting the evolution of an initial lower mantle composition towards increasing crustal contamination

comment on columbia river volcanism the question of mantle heterogeneity or crustal contamination by r w carlson g w lugmair and j d macdougall abstract strontium and neodymium isotopic data on basalts from the columbia river province are consistent with an unfractionated source for the magmas and do not necessarily indicate large amounts of crustal contamination this conclusion is based on the observation that 1 1 the nd values of 99 of the basalts are positive and sharply bounded at nd 0 2 2 the trace element patterns can be modelled without crustal assimilation 3 3 there is no associated rhyolitic volcanism and 4 4 the isotopic ratios correlate with geographic position as well as chemical composition

limited impact of eolian and riverine sources on the biogeochemical cycling of cd in the tropical atlantic we present coupled cadmium cd concentrations and cd isotopic compositions expressed as 114cd in seawater profiles along the northeast southwest geotraces ga11 section in the tropical atlantic ocean the ga11 section encompasses three contrasting regions including the amazon river plume the north african dust plume and the guinea dome oxygen deficient zone odz given the long oceanic residence time of cd 104 to 105 yr local inputs such as atmospheric and riverine sources are generally considered to be of little importance for the open ocean cd budget and the limited cd isotope dataset available thus far has prevented any unambiguous conclusions on the importance of these processes the ga11 section is ideally located for assessing the influence of external natural and anthropogenic riverine and eolian inputs as well as internal processes on the cd mass balance in the tropical atlantic ocean as in previous cd isotope studies this dataset documents that both surface consumption regeneration of micronutrients within the water column and deep water mass mixing exert the prime control on the cycling of cd however we do observe some near surface samples with lower than expected 114cd signatures along the western section of the transect surface waters sampled at the margin of the amazon freshwater plume show no resolvable difference in cd and 114cd compared to waters outside of the plume suggesting that the amazon river is not an important source of cd to the open ocean although the eastern ga11 transect is directly downwind of the saharan dust plume atmospheric cd deposition accounts for 1 of the inferred upwelling flux indicating that atmospheric inputs to the surface north atlantic ocean even within the main saharan dust plume only have a relatively minor influence on the cd budget in the subsurface tropical atlantic 100 200 m water depth there is a clear deviation from a tight linear cd po4 correlation toward lower cd concentrations for a given po4 concentration our new cd data show that this cd po4 decoupling is likely a feature of the entire tropical atlantic and may possibly reflect po4 enrichment via preferential re mineralization of organically bound phosphorus alternatively the decoupling may arise from subsurface cd depletion caused by precipitation of cd sulphide within sinking organic particulate microenvironments as has been suggested in recent studies

siderophile and chalcophile metals as tracers of the evolution of the siberian trap in the noril sk region russia abstract in this study cu ni and platinum group elements pge were determined in a sequence of basaltic and picritic lavas from the siberian trap in the noril sk area of russia to constrain genetic relationships between the basalts and the petrogenesis of ni cu pge sulfide deposits associated with the talnakh and noril sk intrusions in the most primitive basalts 8 19 wt mgo of the tuklonsky tk suite pt and pd concentrations range from 4 13 ppb increasing with decreasing mgo content whereas ir contents decrease with mgo from 0 8 0 05 ppb the contrasting behavior of these elements which all have very high sulfide silicate partition coefficients as well as the primitive mantle like ratios of cu y and pd y suggests that these magmas were not sulfide saturated the high pge abundances imply that their parental magmas were also not sulfide saturated during partial melting in the mantle due to sulfide segregation the overlying basalts of the nadezhdinsky nd series are low in cu and ni 52 and 38 ppm respectively highly depleted in all pge and have very low cu y pd y and pd cu ratios however in stratigraphically higher levels cu ni and pge concentrations increase systematically through the morongovsky mr suite to reach a concentration plateau in the uppermost mokulaevsky mk suite pt 8 ppb pd 9 ppb ir 0 12 ppb rh 0 4 ppb at the same time ratios such as cu y increase and approach primitive mantle values however ratios involving pge such as pd y remain low suggesting the removal of small amounts of sulfide 0 01 0 03 the compositional variations in the basalts and the sulfide liquids can be quantitatively described by fractional segregation of a sulfide liquid in an open or closed system magma chamber the latter model suggests that the basalts represent the eruption products of a zoned magma chamber in which light magma with crustal components contaminated overlies less contaminated denser magma crustal contamination caused sulfide saturation and the resulting sulfide liquids settled through a magma column and accumulated at the bottom of the chamber in this model the sulfide liquid is not in equilibrium with the whole magma mass and sulfide segregation is compared with the zone refining process of metallurgy the sulfides become more enriched as they move through the magma and although the magma left behind is depleted in pge cu and ni their concentrations also increase with depth eventually the magma chamber is emptied from the top to the bottom producing the flood basalt sequence and the associated intrusions and ore deposits in the open system model sulfide saturation was initially caused by assimilation of crustal material by the tuklonsky magma continuous and simultaneous replenishment assimilation and crystallization processes formed the lower nd lavas the concurrent removal of 0 5 1 sulfide strongly depleted these magmas in chalcophile and siderophile metals due to the continuous replenishment of the magma chamber with uncontaminated pge rich magma succeeding lavas mr mk show diminishing signs of crustal contamination and become less sulfide saturated as indicated by the increasing ni cu and pge abundances during the evolution of the chamber the magma remained sulfur saturated and sulfides accumulated at the base the composition of the sulfide ores could be regarded as a mixture consisting of low ni cu and pge sulfides derived with a low silicate sulfide ratio 100 from the tk nd magma and high ni cu and pge sulfides formed with a high ratio 10 000 from the mr mk magma

geochemistry of the siberian trap of the noril sk area ussr with implications for the relative contributions of crust and mantle to flood basalt magmatism the sequence investigated of the siberian trap at noril sk ussr consists of at least 45 flows that have been divided into six lava suites the lower three suites consist of alkalic to subalkalic basalts the ivakinsky suite overlain by nonporphyritic basalts the syverminsky suite and porphyritic and picritic basalts the gudchikhinsky suite the upper three suites are tholeiitic the uppermost 750 m of dominantly non porphyritic basalt belong to the mokulaevsky suite and are characterized by a nearly constant mg number 0 54 0 56 sio2 48 2 49 1 wt ce 12 18 ppm and ce yb 5 8 the underlying 1100 m of dominantly porphyritic basalt belong to the morongovsky and nadezhdinsky suites there is a continuous increase in sio2 48 1 55 2 wt ce 12 41 ppm and ce yb 5 18 from the top of the mokulaevsky to the base of the nadezhdinsky with little change in the mg number 0 53 0 59 mokulaevsky magmas have trace element signatures similar to slightly contaminated transitional type mid ocean ridge basalts the change in major and trace element geochemistry in the upper three suites is consistent with a decline in the degree of anatexis and assimilation of tonalitic upper crust by mokulaevsky magma the nadezhdinsky and underlaying lavas thicken within and thus appear to be related to an elongate basin centred on the noril sk talnakh mining camp the mokulaevsky and morongovsky lavas thicken to the east and appear to be related to a basin centred more than 100 km to the east of the noril sk region these magmas may have risen up out of a different conduit system

ndsr isotopes petrochemistry and origin of the siberian flood basalts ussr the siberian flood basalt province sfbp of permo triassic age is one of the largest flood basalt provinces with an estimated area of exposure of 337 000 km2 average thickness of 1 km and a magma volume of 337 000 km3 forty seven basaltic rocks from two main subprovinces norilsk 5 10 of area thickness up to 3 km and putorana 90 95 of area thickness of more than 2 km were selected on the basis of petrography and volcano stratigraphic relation for major element analysis twentysix of these basalts twelve from norilsk and fourteen from putorana were analyzed for nd and srisotopic compositions the norilsk and putorana basalts show some contrasting behavior in terms of the ratios of the highly incompatible elements of ti p and k as a function of their mg the norilsk basalts are more variable suggesting the role of fractional crystallization assimilation in their evolution in contrast the putorana basalts show remarkable uniformity in their bulk chemical compositions there is no overall apparent correlation between the mg and the initial nd for the basalts most of the putorana and some norilsk lavas show a narrow range of initial nd between 0 and 2 5 at mg 0 53 suggesting that the bulk of the sfbp was derived from a mantle source with near chondritic ndisotopic signature our data and six previously published analyses define a hyperbolic array near the mantle correlation line in 87sr86sr t nd t space however the majority 70 of the volumetrically significant putorana basalts fall in the ranges of 0 to 2 5 and 0 7046 to 0 7052 for the initial nd and 87sr86sr respectively in nd and sr isotopic space most of the siberian basalts also fall within the field defined by the ocean island basalts data implying common mantle sources it is concluded that the sfbp originated by hotspot volcanism due to the rise of a large and relatively primitive lower mantle derived plume beneath the siberian continent

remobilisation of the continental lithosphere by a mantle plume major trace element and sr nd and pb isotope evidence from picritic and tholeiitic lavas of the noril sk district siberian trap russia the late permian to early triassic siberian traps have been sampled by drill core core sg 9 and from surface exposure section 1f in the noril sk region of the siberian platform russia combined major trace element and nd sr and pb isotope data on selected samples through the siberia trap offer new chemostratigraphic criteria for the identification and characterisation of two fundamentally different magma types and 9 of the 11 formations of lava developed near noril sk a lower sequence of sub alkalic basalts tholeiites and picritic basalts upwards these are the ivakinsky syverminsky and gudchichinsky formations are overlain by an upper sequence of picritic basalts and tholeiites interbedded with tuffs upwards these are the khakanchansky tuklonsky nadezhdinsky morongovsky mokulaevsky and kharayelakhsky formations the gudchichinsky and tuklonsky formations contain both picritic and tholeiitic lavas the tuklonsky formation tholeiites and picrites have moderate gd yb 1 6 1 8 low tio2 0 45 0 95 wt a significant negative ta and nb anomaly nb la 0 42 0 57 and unradiogenic nd nd chur to 4 6 in contrast both the gudchichinsky formation tholeiites and picrites have high gd yb 2 3 3 1 and tio2 1 2 2 3 wt no significant nb or ta anomaly nb la 0 8 1 1 and radiogenic nd nd chur to 7 3 the low ti and nb la high la sm and unradiogenic nd isotope signatures of the picritic tuklonsky formation lavas and the tholeiitic lavas of the upper sequence are characteristic of magmas strongly influenced by material from the continental lithosphere whereas the high ti and nb la low la sm and radiogenic nd isotope signatures of the lower sequence are more comparable to deeper asthenospheric mantle plume generated lavas similar to oceanic island basalts the lavas overlying the tuklonsky formation have mg numbers of 0 63 to 0 68 and are more evolved than the tuklonsky mg number 0 62 and have more radiogenic nd chur tuklonsky 0 03 to 4 66 mokulaevsky 0 60 to 1 61 but have many of the incompatible trace element features of the tuklonsky sky type magma these lavas show a progressive upwards decline in sio2 55 49 wt la sm 4 6 2 0 and ur sr 67 to 13 which has previously been attributed to a decrease in the proportion of crustal material contributed to the magma this paper explores and alternative model where a component of the crustal contribution might be derived from within an ancient region of the mantle lithosphere as recycled sediment rather than from the overlying continental crust

high 3he plume origin and temporal spatial evolution of the siberian flood basalts an olivine nephelinite from the lower part of a thick alkalic ultrabasic and mafic sequence of volcanic rocks of the northeastern part of the siberian flood basalt province sfbp yielded a 40ar 39ar plateau age of 253 3 2 6 million years distinctly older than the main tholeiitic pulse of the sfbp at 250 0 million years olivine phenocrysts of this rock showed 3he 4he ratios up to 12 7 times the atmospheric ratio these values suggest a lower mantle plume origin the neodymium and strontium isotopes rare earth element concentration patterns and cerium lead ratios of the associated rocks were also consistent with their derivation from a near chondritic primitive plume geochemical data from the 250 million year old volcanic rocks higher up in the sequence indicate interaction of this high 3he sfbp plume with a suboceanic type upper mantle beneath siberia

petrogenesis and alteration of tuffs associated with continental flood basalts from putorana northern siberia in the putorana region of the siberian continental flood basalt province tuffs form thin layers or small bodies between single basaltic lava flows based on our fieldwork these ash fall deposits have relatively small volumes 100 000 m 3 compared with the associated basaltic flows and the tuffs of the adjacent noril sk region in the north six tuff units with different degrees and modes of alteration were analysed by xrd sem and xrf in order to determine mineralogical and chemical changes which occurred during progressive alteration pyroxene compositions and immobile element ratios suggest that the tuffs were derived from a basaltic lava like the flood basalts post eruptive low temperature alteration processes have significantly changed the primary composition of the tuffs therefore the different tuffs have variable petrography mineralogy and geochemistry mgo 5 2 9 2 wt sio 2 33 6 69 1 wt and tio 2 0 6 1 6 wt compared to the tholeiitic basalts in which they are interbedded crystallization of secondary minerals such as carbonate clay minerals zeolites and analcime occurred from circulating fluids the results show that the fluid compositions varied significantly between the different tuffs this implies that the elements behaved differently depending on the circulating agent which led to the formation of different minerals in addition two samples show an input of quartz derived either by wind from terrigenous sediments or generated by magma sediment interaction and one sample was deposited in a subaqueous possibly lacustrine environment these results indicate that the conditions during alteration varied despite the close spatial relationship of the tuffs and that a generalization about the alteration processes cannot be made in the putorana region the analyses of the clay minerals show alteration of chlorite to vermiculite interestingly corrensite a regularly stacked 50 50 mixed layered clay mineral composed of chlorite and vermiculite is still preserved in two samples this indicates different alteration stages in the different tuff outcrops the state of alteration deduced from immobile element ratios plagioclase compositions and mineral assemblages shows contradictory results this suggests that the state of alteration is best deduced from clay minerals as one can follow this process step by step

historical variations in the isotopic composition of atmospheric zinc deposition from a zinc smelter abstract in order to test the usefulness of stable zinc isotopes as an atmospheric source tracer we analyzed the zinc isotopic composition of two sediment cores taken at 1 km distance of the former zinc smelter in lommel belgium the peat bog lake sediments accumulate mainly atmospheric particles have high organic matter contents 12 60 wt are anoxic and highly contaminated with heavy metals up to 4 7 wt zn and 1 1 wt pb with a sulfide mineralogical control on mobility down core variations in 66 zn relative to the jmc 3 0749l standard were small ranging from 0 07 to 0 39 but are nevertheless eight times the external reproducibility of 0 04 good agreement was found between the two cores and despite 30 zn mobilization to deeper layers no evidence of associated diagenetic zn isotope fractionation was found sediments deposited in the early 20th century have 66 zn of 0 30 0 05 2sd n 5 and a shift takes place between 1945 and 1950 to 66 zn values of 0 14 0 09 2sd n 7 in the 2nd half of the century in order to understand this shift in 66 zn we analyzed 32 ore grade sphalerite zns samples from african australian and european origin together with 29 published 66 zn values for ore grade zns we find remarkably homogeneous isotopic compositions which when averaged for mining location gives 66 zn of 0 16 0 20 2sd n 10 mines n 61 analyses early 20th century zn deposition with 66 zn of 0 30 is significantly different p 66 zn of 0 16 we suggest that this reflects the presence of an atmospheric smelting residue slag component enriched in the heavy zn isotopes due to rayleigh type fractionation during zn refining

the chemical compositions and abundances of volatiles in the siberian large igneous province constraints on magmatic co2 and so2 emissions into the atmosphere abstract the siberian large igneous province slip is known to be synchronous with the most severe mass extinction on the earth at the end of permian the viability of the slip as a trigger for the mass extinction depends crucially on the total amounts of important volatiles such as co 2 and so 2 emitted from the slip into the atmosphere the chemical compositions and abundances of volatiles in picrite and gabbroic rocks of the slip have been determined by a vacuum stepwise heating mass spectrometer system the volatiles released at temperatures 2 o with high contents of co 2 so 2 and h 2 plus detectable he the total amounts of primary volatiles in the picrite are 19 991 mm 3 stp g stp standard temperature and pressure h 2 o 331 co 2 202 h 2 28 co 13 so 2 and 2 h 2 s the total amounts of primary volatiles in the gabbroic rocks are 2869 mm 3 stp g h 2 o 131 so 2 120 h 2 85 co 2 79 h 2 s and 16 co these data together with other important constraints from literatures are used to calculate the total amounts of volatiles emitted from the slip into the atmosphere in our mass balance calculations we used the abundances of co 2 and so 2 in melt inclusions in olivine phenocrysts from the slip determined previously by other researchers to represent their initial concentrations in magma before degassing and our new data for the slip picrite to represent the volatile compositions of magma basalt after eruption our results for the gabbroic rocks are used to estimate the proportions of volatiles that are still retained in the subvolcanic intrusions of the slip the results reveal that the total amounts of important volatiles emitted from the slip are 8 5 10 7 tg co 2 4 4 10 6 tg co 7 0 10 6 tg h 2 s and 6 8 10 7 tg so 2 tg trillion grams these values are similar to the previous estimates using different methods by other researchers our data support a popular notion that the end permian mass extinction on the earth was caused by the emission of enormous amounts of volatiles from the slip into the atmosphere

cadmium isotope fractionation within the soil profile complicates source identification in relation to pb zn mining and smelting processes abstract many cadmium species are among the most toxic of environmental contaminants because cd in many forms is mobile in the environment identifying its sources is a crucial aspect of remedial intervention data from the literature suggest that cd isotopes could be a useful tool for such identification but no data about cd isotopes through entire soil profiles has yet been published we compared in this paper the cd isotope composition of three forest and two meadow soil profiles affected by different contamination sources near the olkusz pb zn smelter in southern poland together with the main industrial source of possible contamination at that location in the contaminated forest soil profile the upper soils reflected the heaviest cd isotope compositions while the deeper soil humus layer had the lightest cd isotope compositions we found that the overall cd isotope heterogeneity in industrial wastes was overlapped by the overall cd isotope fractionation within the forest soil profile near the smelter e 114 110 cd nist3108 values of 5 14 compared to 11 8 respectively both meadow soil profiles had approximately a cd isotope composition corresponding to the processed ore olkusz sphalerite

40ar 39ar ages of flood basalt provinces in russia and china and their possible link to global faunal extinction events a cautionary tale regarding alteration and loss of 40ar abstract the hypothesis that the permo triassic boundary ptb mass extinctions were caused by flood basalt volcanism in russia siberian traps and or china the emeishan traps is investigated from the point of view of time of occurrence 40 ar 39 ar ages numerous published ages in the literature are rejected as good estimates of the time of crystallization the filters applied in this respect are a statistical reliability of plateau isochron sections of stepheating data and b the alteration state of the material that was dated alteration appears to be ubiquitous unsurprising since most of the material dated was used without acid leaching a procedure that is effective in yielding fresh er samples of 70 ages in the literature for the main pulse of siberian trap volcanism less than ten prove to be reliable ages similar techniques applied to 40 ar 39 ar for the emeishan traps leaves only a single reliable age for the magmatic episode these ages are compared to both published and new 40 ar 39 ar ages for the ptb as based on analysis of minerals from critical ash beds in china there is good overlap in the ages ptb 250 0 0 1 ma siberian trap lavas 250 1 0 4 ma lending credence to a genetic link between the formation of the siberian traps and the faunal extinction event at the ptb a similar link for the formation of the viluy traps russia and the late devonian extinction event is investigated only a single reliable 40 ar 39 ar age is available for the viluy traps and falls close to the interpolated age for the frasnian fammenian boundary the use of the unspiked k ar technique to yield accurate ages for such altered samples is questioned a review of u pb data pertinent to these problems suggests a close temporal link between the formation of the siberian traps and the ptb comparison of u pb and 40 ar 39 ar ages for the ptb raises questions about the accuracy of high precision sanidine ages possibly resulting from very slow leakage of 40 ar from this mineral

on models of mars interior and amplitudes of forced nutations 2 the effects of liquid core and mantle elasticity abstract the numerical modeling of mars forced nutation of the real mars model with a radially heterogeneous compressible self gravitating liquid core and elastic mantle is performed effects of three axiality of mars figure are taken into account to compute values for the periods of free core nutation fcn and the amplitudes of forced nutations the effects of the liquid core for different models are of the order of few percents for the prograde semi annual component and of the order of 10 15 for the semi annual retrograde component the absolute values of these effects are of the order of 5 20 ms of arc mas and 1 3 mas respectively taking into account that the modern accuracy of vlbi measurements for the case of the earth is of the order of 0 02 mas we see that important results about mars internal structure may be obtained even if the accuracy of mars nutational measurements 1 2 order of magnitude less than accuracy for the earth the effects of the shear stress relaxation during long time intervals are studied the corrections to the nutational amplitudes for prograde semi annual component are between 8 93 and 9 8 for retrograde semi annual component are between 4 81 and 8 2 ms of arc and the period of free core nutation is varied in the limits between 257 2 and 295 8 earth s solar days the differences exceed significantly the errors of mars nutational components measurements and consequently these measurements can give new important information about martian mantle rheology the possibilities of inferring properties of the interior structure of mars based on the measurements of its rotation are discussed

diagenesis and quartz cement distribution of low permeability upper triassic middle jurassic reservoir sandstones longyearbyen co2 lab well site in svalbard norway reservoir properties of upper triassic middle jurassic sandstones spitsbergen are studied as part of a co2 storage pilot project in longyearbyen the reservoir formations show large contrasts in sandstone compositions with unexpected low permeability despite moderate porosity values petrographic analyses were performed to investigate the influence and distribution of diagenesis it is concluded that because of various compaction cementation and dissolution processes the sandstone porosity is mainly isolated molds and micropores and associated with fibrous illite and chamosite explaining the low permeability diagenesis and the distribution of quartz cement is influenced by lithofacies and detrital compositions mineralogically immature sandstones de geerdalen formation show a homogeneous distribution of quartz cement overgrowths on quartz grains distributed interstitial to labile grains and other cements e g late calcite the main silica source was from the dissolution of adjacent feldspar and labile grains as part of the chemical compaction in contrast quartz dominated sandstones knorringfjellet formation show a heterogeneous patchy distribution of quartz cement influenced by the sedimentary bioturbation pattern with silica sourced also from dissolution at clay rich microstylolites phosphatic beds at the base and top of the formation are strongly influenced by marine eogenesis and reworking processes and associated with concentration of iron rich authigenic minerals the highest porosity appears in sand supported conglomerate where moldic clay mineral ooids contributed to reduce quartz cementation the stratigraphic change from mineralogical immature triassic to mature uppermost triassic jurassic sandstone compositions is detected in wide areas of the barents shelf and has considerable implications for the distribution of sandstone reservoir properties

nickel isotope fractionation during laterite ni ore smelting and refining implications for tracing the sources of ni in smelter affected soils abstract nickel isotope ratios were measured in ores fly ash slags and feni samples from two metallurgical plants located in the goias state brazil barro alto niquel ndia this allowed investigating the mass dependent fractionation of ni isotopes during the ni laterite ore smelting and refining feeding material exhibits a large range of 60 ni values from 0 02 0 10 to 0 20 0 05 n 7 explained by the diversity of ni bearing phases and the average of 60 ni feeding materials was found equal to 0 08 0 08 2sd n 7 both 60 ni values of fly ash 60 ni 0 07 0 07 n 10 and final feni produced 0 05 0 02 n 2 were not significantly different from the feeding materials ones these values are consistent with the very high production yield of the factories however smelting slags present the heaviest 60 ni values of all the smelter samples with 60 ni ranging from 0 11 0 05 to 0 27 0 05 n 8 soils were also collected near and far from the niquel ndia metallurgical plant to evaluate the potential of ni isotopes for tracing the natural vs anthropogenic ni in soils the ni isotopic composition of the non impacted topsoils developed on ultramafic rocks ranges from 0 26 0 09 to 0 04 0 05 n 20 on the contrary the ni isotopic composition of the non ultramafic topsoils collected close to the plant exhibit a large variation of 60 ni ranging from 0 19 0 13 up to 0 10 0 05 n 4 this slight but significant enrichment in heavy isotopes highlights the potential impact of smelting activity in the surrounding area as well as the potential of ni isotopes for discerning anthropogenic samples heavier 60 ni values from natural ones lighter 60 ni values however given the global range of published 60 ni values from 1 03 to 2 5 and more particularly those associated to natural weathering of ultramafic rocks from 0 61 to 0 32 the use of ni isotopes for tracing environmental contamination from smelters will remain challenging

a conodont based revision of the 87 sr 86 sr seawater curve across the permian triassic boundary abstract based on analyses of 565 conodonts from meishan liangfengya and daijiagou south china and abadeh central iran we propose a revision of the seawater 87 sr 86 sr curve for the time period spanning 200 kyr prior to the permian triassic boundary ptb to 330 kyr after the ptb with carefully designed sample cleaning conodonts faithfully record seawater 87 sr 86 sr seawater 87 sr 86 sr was 0 707030 10 200 kyr prior to the ptb rose to 0 707070 10 approximately 39 kyr prior to the ptb at the marine extinction horizon the top of bed 24e at meishan to 0 707080 10 at the ptb and to 0 707120 20 at 330 kyr after the ptb the rate of change of seawater 87 sr 86 sr was 0 0000185 myr from the capitanian minimum to 100 kyr before the ptb and was 0 00020 7 5 myr between 100 kyr before and 330 kyr after the ptb over 6 myr this rate of change would result in a maximum 87 sr 86 sr of 0 70825 at the end of the early triassic compared with a model value of 0 7080 the sr data are consistent with the interpretation that the rise in marine 87 sr 86 sr was due primarily to an increase in the continental weathering and erosional flux and that soil binding vegetation was not re established during most of the early triassic the rapid rise in seawater 87 sr 86 sr began at least 30 kyr prior to the marine extinction at meishan indicating that the terrestrial extinction preceded that in the oceans

cadmium isotope fractionation in seawater a signature of biological activity investigations of cadmium isotope variations in the oceans may provide new insights into the factors that control the marine distribution and cycling of this element here we present the results of cd isotope and concentration analyses for 22 seawater samples from the atlantic southern pacific and arctic oceans the results reveal for the first time large and well resolved cd isotope fractionations in the marine environment the majority of the seawater samples display an inverse relationship between dissolved cd contents and isotope compositions which range from e114 110cd 3 0 5 for cd rich waters 0 8 1 0 nmol kg to e114 110cd 38 6 for surface water with a cd concentration of only 0 003 nmol kg all e114 110cd data are reported relative to the jmc cd munster standard this suggests that the cd isotope variations reflect kinetic isotope effects that are generated during closed system uptake of dissolved seawater cd by phytoplankton a few samples do not follow this trend as they exhibit extremely low cd contents 0 008 nmol kg and nearly un fractionated cd isotope compositions such complexities which are not revealed by concentration data alone require that the cd distribution at the respective sites was affected by additional processes such as water mass mixing atmospheric inputs of cd and or adsorption uniform isotope compositions of e114 110cd 3 3 0 5 1 s d were determined for seawater from 900 m depth despite of cd concentrations that display the expected increase along the global deep water pathway from the atlantic 0 3 nmol kg to the pacific ocean 0 9 nmol kg this indicates that the biomass which is remineralized in the deeper ocean is also characterized by a very constant cd isotope composition this observation is in accord with the interpretation that the cd distribution in surface waters is primarily governed by rayleigh fractionation during near quantitative uptake of dissolved seawater cd

nd sr isotopic provenance and trace element geochemistry of amazonian foreland basin fluvial sands bolivia and peru implications for ensialic andean orogeny nd and sr isotopes and the trace element contents including the rare earths were determined for fluvial sands of lithic arenite composition from the madre de dios foreland basin of bolivia and peru on standard petrologic ternary diagrams the sands fall in the recycled orogen provenance field and thus are similar to typical ancient foreland basin composition the average rare earth elemental pattern of the sands is identical to the upper continental crustal average as estimated from post archean composite shales of different continents ratios ofth u co th la sc and th sc of the fluvial sands are intermediate between an average magmatic arc and an upper crustal average compositions the dispersion of some trace elemental patterns in the sands can be attributed to fractionation of dense minerals including zircon during the sedimentation process the variations of nd isotopes in conjunction with the petrographic parameters of lithic metamorphic lm and volcanic lv fragments allow a two fold classification of the sands these two sand types can be interpreted in terms of mixing among three different provenances one volcanic rock suite with less negativeend o parameter than the other volcanic suite and a third metasedimentary source withend o value of around 12 which is considered to be similar to the average western brazilian shield composition thus the overall compositions of the sands has been modeled as mechanical mixtures of two components an andean magmatic arc and the brazilian shield derived metasediments the model is strongly supported by a plot ofend o versusesr o of the sands in this plot the type 1 and 2 sands define two coherent hyperbolic trends contiguous with two different portions of the andean magmatic trend this relationship has been interpreted to indicate that the observed andean magmatic trend in anesr o end o diagram is the result of varying degrees of contamination of a primitive arc type magma by the precambrian continental crust of the western brazilian shield the depleted mantle average nd model age of 1 46 ga for the fluvial sands reflects the average age of the brazilian continental crustal source the development of the andean orogenic belt has been discussed schematically with the isotopic data of the sands the model describes a trailing edge prism of sediments derived from the brazilian shield during the late paleozoic early mesozoic the prism becomes part of the fold thrust belt during the andean orogeny in the neogene when the foreland basin develops with the basin fill partly derived from the fold thrust belt the sedimentary rocks in the fold thrust belt are also a major source of contaminants for the andean magmas the contiguous nature of the andean magmatic trend and the fluvial sand data in theesr o end o diagram suggests that the ensialic andean magmatic arc has remained connected to its parent continent the western brazilian shield throughout the development of the andean orogeny

zn isotopes as tracers of anthropogenic pollution from zn ore smelters the riou mort lot river system article i nfo zn values up to 1 49 zn extraction yields for these samples were calculated using presumable conservative elements fe ca mg k na and mn and vary from 95 4 to 99 4 extraction yields are related to the intensity of zn isotopic fractionation different rayleigh isotope fractionation scenarios for zn refining yielded ore tailings ranging from 1 00012 to 1 00062 the 66 zn of the riou mort sediments downstream from

mass dependent cadmium isotopic variations in nature with emphasis on the marine environment abstract we report a survey of natural mass dependent cadmium isotope fractionation measured by thermal ionization mass spectrometry using a double spike technique ds tims over sixty samples of natural terrestrial cd from diverse environments including morb oib continental loess hydrogenic and hydrothermal ferromanganese deposits and sphalerites both oceanic and from major continental ore deposits were analysed our results are expressed in terms of e 112 110 cd which are deviations in 112 cd 110 cd from our in house jmc cd standard in parts per 10 4 the total e 112 110 cd variation is relatively small with a range of only 5 e units and is one to two orders of magnitude smaller than that previously found in meteorites the morb oib and loess e 112 110 cd values are similar and provide a good estimate for the bulk silicate earth bse value which is 0 95 0 12 relative to our cd standard e 112 110 cd 0 16 relative to munster jmc cd taken together these data suggest little cd isotope fractionation takes place during crust mantle segregation cd isotopic compositions of continental sphalerite zns deposits worldwide and high temperature oceanic hydrothermal sulphides show remarkably similar e 112 110 cd values consistent with our estimate for the bse in contrast mid temperature oceanic sulphides from a single extinct hydrothermal chimney display over 4 e units variation along with the most negative values these variations are most probably caused by precipitation redissolution of sulphide phases en route within the hydrothermal system the e 112 110 cd variability found in worldwide marine fe mn deposits reflects the seawater cd isotope signal upon precipitation from ambient seawater a decrease in e 112 110 cd is observed in passing from shallow water fe mn deposits to those from deeper waters 2000 m depth this shift is explained by biological fractionation related to the uptake of dissolved seawater cd by phytoplankton in the upper water column the relatively uniform e 112 110 cd values close to zero at great depths are consistent with regeneration and remineralization of cd at depth our data suggest that cd isotopes much like the cd ca ratio in foraminifera could potentially serve as a proxy for past changes in biological productivity the temporal cd isotope record in a fe mn crust archive at 2000 m depth from the ne atlantic suggests no gross long term changes in cd cycling took place over the past 8 ma

a mesosiderite rock from northern siberia russia not a meteorite a possible mesosiderite meteorite was found in the area of the putorana plateau noril sk district siberia russia although this rock resembles a mesosiderite in its hand sample aspect and in having ni bearing iron metal it is not a meteorite this inference is based on the lack of a fusion crust the lack of cosmogenic nuclides oxygen with terrestrial isotope ratios and several mineral chemical criteria most likely the rock is from the iron metal bearing basalts of the siberian trap basalt sequence which are mined for their base and platinum group metals mesosiderite imposters like this may be recognized by 1 the presence of cu metal in hand sample or as microscopic blebs in the low ni metal kamacite 2 the absence of high ni metal taenite and 3 the presence of iron carbide cohenite enclosing the kamacite even if these macroscopic tests are inconclusive isotopic and mineral chemical tests will also distinguish rocks like this from mesosiderites

calcium isotopes in the global biogeochemical ca cycle implications for development of a ca isotope proxy abstract at the earth s surface calcium ca is a critical element at a variety of scales it is soluble in natural waters a biological nutrient and a major constituent of the dominant mineral sink for carbon in the ocean caco3 there is a 4 variation in the ca isotopic composition 44ca 40ca expressed as 44ca of various ca reservoirs on earth suggesting ca isotopes as a promising tracer of ca cycling in both the present and the past fifteen years of high precision ca isotope measurements has revealed much about the behavior of ca isotopes in the earth surface environment but there remain fundamental questions concerning how ca isotopes are used to elucidate the marine and terrestrial ca cycles the current work presents a data compilation of over 70 published ca isotope studies totaling over 2600 measurements presented on a common delta scale that includes data on rivers and groundwater dust soils and soil pore fluids vegetation rainwater silicate minerals rocks and authigenic marine minerals carbonates sulfates and phosphates both modern and ancient the data compilation suggests that 1 there is a significant difference between carbonate 0 60 and silicate 44ca 0 94 2 riverine 44ca 0 88 does not simply reflect the compiled carbonate 44ca and 3 terrestrial vegetation exhibits the largest range of ca isotopic compositions 3 5 in the terrestrial setting we discuss these observations in the context of the global ca cycle exploring the extent to which seawater 44ca variability is feasible and how we can achieve accurate reconstructions of seawater 44ca over geologic time scales the current study presents simple mass balance models that quantify the leverage of inputs to change the ca isotopic composition of the ocean as this directly impacts the manner in which ca isotopes are interpreted although ca fractionates isotopically in the modern system during continental cycling the 44ca range of riverine inputs to the ocean is considerably smaller than the variability observed in putative seawater proxies such as nannofossil ooze and marine barite in the terrestrial realm plants exhibit a wide 44ca range and there is evidence that ca fluxes via biomass degradation are significant at the catchment scale we therefore assess the ability of the continental biosphere to influence riverine and consequently seawater 44ca a steady state biosphere has little leverage to alter riverine 44ca except in cases where the 44ca of the recycling flux is isotopically distinct from the 44ca of the uptake flux a non steady state biosphere can substantially impact both soil and riverine 44ca driving exchangeable ca either heavier or lighter depending on the magnitude of the recycling flux relative to the uptake flux based on estimates of the size of the global biosphere 1 5 1015 mol ca we suggest a decaying biosphere has the potential to impact riverine 44ca by tenths of a permil over time scales in the marine realm we evaluate the effect of a variable fractionation factor accompanying global removal of ca from the ocean on seawater 44ca and suggest methods by which such a mechanism can be recognized in the rock record experimental data suggest that there is considerable leverage