two pulses of mineralization and genesis of the zhaxikang sb pb zn ag deposit in southern tibet constraints from fe zn isotopes abstract zhaxikang is one large sb pb zn ag deposit located in the north himalaya of southern tibet to date the genesis of this deposit still remains controversial here we present new pyrite fe and sphalerite zn isotopic data for the first three stages of mineralization fe zn isotopic data for mn fe carbonate that formed during the first two stages of mineralization and zn isotopic data for the slate wall rocks of the jurassic ridang formation to discuss the genesis of the zhaxikang deposit the overall 56 fe and 66 zn values range from 0 80 to 0 43 and from 0 03 to 0 38 respectively the 56 fe values of mn fe carbonates are lighter than those of associated pyrite in six mineral pairs indicating that the iron carbonates are preferentially enriched in light fe isotopes relative to pyrite the sphalerite has lighter 66 zn values than associated mn fe carbonates in three mineral pairs the 56 fe values of pyrite that formed during the first three stages of mineralization gradually increase from stage 1 0 33 to 0 09 through stage 2 0 30 to 0 19 to stage 3 0 16 0 43 in comparison the sphalerite that formed during these stages has 66 zn values that gradually decrease from stage 1 0 16 0 35 through stage 2 0 09 0 23 to stage 3 0 03 to 0 22 these data in conjunction with the observations of hand specimens and thin sections suggest that the deposit was overprinted by a second pulse of mineralization this overprint would account for these fe zn isotopic variations as well as the kinetic rayleigh fractionation that occurred during mineralization the temporally increasing 56 fe and decreasing 66 zn values recorded in the deposit are also coincident with an increase in alteration again supporting the existence of two pulses of mineralization the 56 fe values of the first pulse of ore forming fluid were calculated using theoretical equations yielding values of 0 54 to 0 34 that overlap with those of submarine hydrothermal solutions 1 to 0 however the 56 fe values of the stage 3 pyrite are heavier than those of typical submarine hydrothermal solutions which suggests that the second pulse of mineralization was probably derived from a magmatic hydrothermal fluid in addition the second pulse of ore forming fluid has brought some fe and taken away parts of zn which results the lighter 66 zn values of sphalerite and heavier 56 fe values of pyrite from the second pulse of mineralization overall the zhaxikang deposit records two pulses of mineralization and the overprint by the second pulse of mineralization causes the lighter 66 zn values and heavier 56 fe values of modified samples

copper isotopic signature of the tiegelongnan high sulfidation copper deposit tibet implications for its origin and mineral exploration we report the copper isotopic composition of cu sulfides in the tiegelongnan high sulfidation hs copper deposit tibet and investigate the possible application of cu isotopes to mineral exploration the copper isotopic values of samples from four drill holes display consistent progressive increase with depth to 400 m below surface with an overall variation of 65cu of up to 7 60 4 76 to 2 84 such a large range is very different from that observed in cu porphyry deposits which commonly exhibit a small 65cu range 1 with decreasing values with depth the large 65cu variation is likely of supergene origin and reflects strong leaching under oxidized conditions the systematic increase of 65cu with depth can be explained by the release of isotopically heavy cu at the top and its transport downward which is supported by the coupling of positive 65cu values with high cu grade and the occurrence of both negative and positive 65cu values in two drill holes mass balance consideration on the basis of cu isotopes can indicate mineralized zones which have been eroded or have not been found yet such mineralized targets if buried at depth could be located using cu isotopes

copper isotope fractionation in sedimentary copper mineralization timna valley israel abstract copper isotopes 65 cu 63 cu are potentially powerful new geochemical proxies for oxidation reduction processes and metallic cycling this research presents a cu isotope study of mineralization in historically mined stratiform sediment hosted copper ssc ore deposits of the precambrian and cambrian rocks of the timna valley southern israel these deposits provide a natural laboratory for studying isotopic fractionations between cu sulphides and cu ii minerals copper carbonates hydroxides and silicates formed during sequential cycles of low temperature alteration of igneous copper porphyries marine sedimentary diagenesis and epigenetic mobilization in sandstones isotopic measurements were made using mc icp ms after ion chromatographic separation of the copper from matrix elements in accord with abiogenic experimental studies showing that there should be a negative isotopic fractionation between reduced and oxidized copper minerals 65 cu values of cu sulphides are significantly lower 3 4 to 1 2 than coexisting cu ii carbonates and hydroxides 1 2 to 0 5 cu ii silicates which should only show a very small isotopic fractionation relative to parent cu ii solutions give average 65 cu values of 0 09 0 24 consistent with the fact that the primary source of sedimentary copper was the precambrian igneous rocks isotopic zoning profiles in cu sulphides of the cambrian dolomites suggest they were formed through the interaction of small disconnected cu solution reservoirs with h 2 s formed by bacterial reduction of sulphate containing pore waters mass balance modeling based on the measured cu isotope compositions and experimental fractionation factors shows that the main copper reservoir is the cambrian sandstone shale sequence and that the cu sulphide reservoirs are relatively small thus most of the copper transport occurred in relatively oxidized conditions the calculated reservoir sizes are in agreement with field observations and confirm that copper isotopes are able to trace both the oxidation reduction cycles and mass transfer during sedimentary copper mineralization

could the conventionally known abu roash g reservoir upper cenomanian be a promising active hydrocarbon source in the extreme northwestern part of egypt palynofacies palaeoenvironmental and organic geochemical answers abstract in different areas of the western desert of egypt the abu roash g member exhibits either a reservoir or source affinity thus thirteen cutting samples covering the abu roash g member were selected from the nest 1a well at matruh basin to investigate its hydrocarbon source potential palynological age dating of the section that is calibrated with foraminifera and ostracodes enabled a proper identification of the g member detailed analysis of the vertical distribution of particulate organic matter of this member shows two palynofacies types pf 1 reflects an outer middle shelf depositional environment of prevailed reducing suboxic anoxic conditions for the organic rich shales of the lower g member samples 1 8 while pf 2 reflects a minor regression that resulted in deposition of another organic rich shales of the upper g member samples 9 13 in an inner middle shelf setting under the same prevailing reducing suboxic anoxic conditions organic geochemical analysis reveals good to very good potential of the g member as a hydrocarbon source rock 1 8 2 41 avg 2 15 total organic content wt it also shows good to very good petroleum potential pp 4 8 11 avg 8 mg hc g rock pyrolsis and palynofacies analyses show kerogen type ii for the lower g member samples 1 8 which is characterized by high hydrogen index hi 396 and 329 mg hc g toc at depths 1500 and 1560 m and very high dominance of oil prone material amorphous organic matter aom marine palynomorphs and sporomorphs and very rare occurrence of gas prone material brown phytoclasts the upper g member samples 9 13 shows kerogen type ii iii which is characterized by a lower hi value of 213 mg hc g toc at depth 1340 m and it contains fewer amounts of gas prone material and relatively lower aom and marine palynomorphs in comparison to the upper g member maturation parameters t max 430 433 c production index pi 0 1 mg hc g rock and thermal alteration index tai 2 indicate the lower g member has already entered the early oil window kitchen and it is expected to produce oil the upper g member is expected to produce only oil with no gas shows because it is marginally mature t max 426 c pi 0 2 tai 2 the source potential index spi 5 3 t hc m 2 of the g member shows it as currently generating moderate quantities of oil in the area of nest 1a well consequently the organic rich shales of the g member are suggested here as a promising active oil source rock in that extreme northwestern part of the western desert of egypt however for commercial oil recovery from the abu roash g member it is highly recommended to explore the depocentre of matruh basin at about 150 km east the nest 1a well

palynological palaeoenvironmental and sequence stratigraphical analyses of a turonian coniacian sequence beni suef basin eastern desert egypt implication of pediastrum rhythmic signature abstract sixteen samples from the e to b members of the abu roash formation encountered in the beni suef basin eastern desert of egypt were palynologically analyzed for palaeoenvironmental and sequence stratigraphic investigations the integrated palynofacies and lithofacies analysis of the studied section indicates deposition of five alternating regressive and transgressive sequences in well oxygenated proximal shelf settings the abu roash e and the upper d to the lower c members were deposited during pronounced regressive phases in oxic shallow marginal marine settings the upper b member was deposited during a recurring regressive phase but of a lower magnitude in oxic shallow inner neritic conditions the lower d member was deposited during a minor transgression phase in dysoxic shallow inner neritic settings while the upper c to the lower b section was deposited during a stronger transgressive episode in a relatively deep inner neritic environment of prominent dysoxic conditions this interchange in the depositional setting was documented by the pronounced and concurrent cyclic nature of the freshwater algae peridinioid dinoflagellate cysts pteridophyte spores and reworked sporomorphs with variable intensities their increasing and conversely their diminishing trends clearly reflect alternating regressive transgressive periods of reduced and relatively normal salinity conditions respectively overall sedimentation of the studied abu roash section indicates a recurring rise in sea level which accentuated during the earliest santonian time the analogous peaking in the pediastrum signals with those of the pteridophyte spores and reworked taxa indicate a good connection between these pediastrum signals and the pronounced fluviatile influxes of terrigenous sediments during regressive phases accordingly this can be used to identify regressive sequence boundaries and hence the clastic reservoirs even with the small counts recorded herein we believe high ratios of peridinioid gonyalulacoid dinocysts are significantly paralleled by peaking signals of freshwater algae and regressive sedimentation phases this must be preliminary documented here probably future palynological studies will be able to fully interpret and address this important pediastrum rhythmic event in different sequence stratigraphic settings the palynological parameters age controlled sporomorph marker taxa lithology and gamma ray data were used to differentiate the abu roash members into three distinctive 3rd order depositional sequences ar sq1 ar sq2 and ar sq3 these sequences match well with the global stratigraphic sequences tu 3 tu 4 and co 1 and connect the local rise in sea level to the global eustatic sea level rise

isotope variations of dissolved zn in the rio grande watershed usa the role of adsorption on zn isotope composition abstract in order to better understand the factors influencing zinc zn isotope composition in hydrological systems we analyzed the 66 zn of dissolved zn in the streams and groundwater of the upper and middle rio grande watershed in colorado and new mexico united states the stream water samples have a wider variation of 66 zn 0 57 to 0 41 relative to the jmc 3 0749 lyon standard than groundwater samples 0 13 to 0 12 and than samples from streams that are in close proximity to abandoned mining sites 0 24 to 0 40 regional changes of bedrock geology from primarily igneous rocks to primarily sedimentary rocks have no resolvable effect on the 66 zn of aqueous samples instead an increase in water ph from 7 5 to 8 5 corresponds to a considerable decrease in the 66 zn of dissolved zn r 2 0 37 p 0 003 n 22 consequently we link the observed zn isotope variations to the process of adsorption of zn onto suspended sediment and bedrock minerals average 66 zn adsorbed dissolved 0 31 our results are in good agreement with previous experimental and empirical studies suggesting that zn adsorption leads to a residual dissolved pool enriched in light zn isotopes given that anthropogenic zn sources can also be responsible for lowering of 66 zn and may overlap with the ph adsorption effect on 66 zn the latter needs to be carefully considered in future studies to differentiate between natural and anthropogenic factors influencing zn isotopes in this and other aquatic systems

palaeoenvironmental analysis of late cretaceous dinoflagellate cyst assemblages using high resolution sample correlation from the western interior basin usa abstract the cretaceous geological record of the western interior seaway of north america is one of the most thoroughly studied in the world extensive work on the lithostratigraphy biostratigraphy and geochemistry has resulted in a high resolution chronostratigraphic framework allowing precise bed by bed correlation between sections hundreds of kilometres apart late cenomanian to early turonian marine strata from five sites along a transect from arizona to kansas have been analysed for their palynological assemblages at the time of deposition the sites are thought to have been palaeoenvironmentally very different in terms of shoreline proximity bathymetry and salinity precise correlation of samples between the sites using the high resolution stratigraphy has provided a valuable testing ground for a comparison of the dinoflagellate cyst assemblages a number of species are determined to have palaeoenvironmental preferences in terms of salinity and shoreline proximity and this is supported by integration with the lithostratigraphy macropalaeontology micropalaeontology and geochemistry previous palaeoenvironmental interpretations suggest that one kansas site had comparatively much higher levels of primary productivity and this is reflected in the high ratio at this site of peridinioid to gonyaulacoid cysts the high resolution correlation also shows that a number of the biostratigraphically useful dinoflagellate cyst taxa had synchronous or near synchronous range tops and bases across the basin this integrated high resolution study with tight chronostratigraphic control supports the use of dinoflagellate cysts not only as biostratigraphic tools but also for palaeoenvironmental and palaeoecological interpretation

copper and zinc isotope systematics of altered oceanic crust at iodp site 1256 in the eastern equatorial pacific this paper presents the first combined cu and zn isotopic study of altered oceanic crust aoc at iodp hole 1256d that penetrates a volcanic section a lava dyke transition zone a sheeted dyke complex and a plutonic complex in the volcanic section all but one rocks have cu and zn isotopic compositions similar to fresh mid ocean ridge basalt morb reflecting restricted seawater circulation and low oxygen fugacity rocks in the transition zone have morb like 65cu and 66zn indicating the dominant influence of basalt derived cu and zn during alteration rocks in the dyke complex have more variable 65cu 0 50 0 90 and 66zn 0 19 0 55 and those in the plutonic complex have 65cu of 0 43 to 0 20 and 66zn of 0 21 to 0 41 the rocks with heavier 66zn and heavier or lighter 65cu relative to morb are characterized by cu zn depletions low li yb 1 0 and low 18o 5 suggesting that hydrothermal extraction during high temperature alteration of oceanic crust can result in significant cu and zn isotope fractionation such large cu and zn isotopic variations are the results of redox transformation of cu as well as cu and zn isotope fractionation between altered basaltic rocks and dissolved cu and zn species in hydrothermal fluids e g cucl3 1 zn hs 42 this work is the first to define the distribution of cu and zn isotopes in an intact oceanic crust with concentration weighted averages of 65cu 0 05 0 03 and 66zn 0 27 0 01 the potential implications of these new observations are discussed

a global assessment of zn isotope fractionation in secondary zn minerals from sulfide and non sulfide ore deposits and model for fractionation control abstract we investigated extent and direction of zn isotope fractionation in secondary zinc minerals formed during low temperature hydrothermal and or supergene oxidation of primary sulfide deposits zinc isotope data have been obtained from non sulfide zinc mineral separates willemite zn2sio4 smithsonite znco3 hemimorphite zn4 si2o7 oh 2 h2o hydrozincite zn5 co3 2 oh 6 and sauconite na0 3zn3 si al 4o10 oh 2 4h2o collected from several zn deposits in ireland belgium poland namibia peru yemen and zambia the data are compared with zn isotope compositions measured on zn sulfides collected in the same areas and or derived from the existing literature to establish the controls of direction and likely extent of any fractionations we find that willemite has the greatest compositional variability with measured 66znjcm lyon values ranging from 0 42 to 1 39 spanning the entire range of terrestrial variation in zn isotopes recorded to date overall significant fractionations in positive and negative directions are recorded relative to the precursor phase primary sphalerite or an earlier secondary phase with primary sphalerite falling in a relatively narrow range of isotopic values approximately 0 1 to 0 4 most of the data observed on willemite hemimorphite and hydrozincite can be explained with a model of isotopic fractionation in which partial dissolution of primary sphalerite is followed by precipitation of an initial secondary phase that preferentially incorporates heavy zn isotopes smithsonite instead preferentially incorporates light zn isotopes this reflects the variation in the zn x bond strengths of these secondary phases with respect to the original sulfides we also observed that isotope compositions do not depend only on the difference between the fractionation factors of the involved phases but also on the amount of the secondary mineral precipitated after dissolution of primary sulfide and that the greatest fractionations occur when only small amounts of secondary mineral are precipitated progressive precipitation from migrating fluids that form phases enriched in heavy zinc isotopes would lead to a gradual decrease in the 66zn values of such phases and the fluids involved in time and space strong negative isotopic shifts are almost only observed for late crystallizing phases such as those in vugs these are interpreted to reflect precipitation from residual isotopically light fluids that are the inevitable highly fractionated product of the above described process where a more complete replacement of primary sulfide has occurred such as in the high grade core of non sulfide zinc orebodies there is limited net isotopic fractionation because dissolved primary zinc is nearly quantitatively reprecipitated locally in addition in only one case yanque peru we observed that the fringes of non sulfide zinc deposit were characterized by isotopically fractionated compositions with highly negative values implying extensive precipitation earlier or elsewhere of isotopically heavy secondary phases the higher grade ore zones where complete breakdown of primary sulfides and quantitative reprecipitation of zinc have occurred show instead less fractionated compositions

iron isotopes in the amazon river system weathering and transport signatures abstract trace metal clean plankton tows river samples aerosol leachates and porewater samples from the amazon river system were measured for their iron isotopic composition the overall isotopic range observed was 1 5 with fe isotopic variability observed between different types of tributaries dissolved fe and suspended load fe from two main channel sites were isotopically similar 0 1 to 0 3 in contrast the dissolved fe and suspended load fe from an organic rich tributary the negro river were isotopically distinct with the dissolved slightly isotopically heavy 0 3 and the suspended load isotopically light 0 9 the isotopically lightest sample from the amazon region was shelf porewater 1 3 in river water seawater mixing experiments the fe isotopic signal of dissolved fe of river water was modified by flocculation of isotopically heavy fe the variability of the fe isotopic composition of natural samples including biological and aqueous samples demonstrates that significant fractionation is associated with fe biogeochemistry in the environment

integrating palynological and geochemical data in a new approach to palaeoecological studies upper cretaceous of the banterwick barn chalk borehole berkshire uk abstract the dinoflagellate cyst record from an upper cretaceous uppermost cenomanian upper coniacian chalk core drilled at banterwick barn berkshire is described and statistically correlated with elemental and stable isotope bulk sediment geochemical data from the same core seventy two dinocyst species and subspecies are recorded and stable carbon and oxygen isotopic 13 c 18 o trends are documented lithostratigraphy and chemostratigraphic correlation of the 13 c curve with an expanded section at dover kent are used to identify stratigraphically significant marls and determine the positions of macrofossil zones and stage boundaries in the banterwick barn core these data indicate that 30 m of chalk at dover are represented by senoniasphaera rotundata alveolata is proposed which has a fad in the lower turonian and last appears lad in the lower coniacian senoniasphaera rotundata rotundata autonym herein has its fad in the middle turonian first common occurrence in the uppermost turonian and lad in the upper coniacian an extremely impoverished assemblage of dinocysts in the highest cenomanian to lowest turonian is considered to be largely a preservational artefact of intraclastic nodular and calcarenitic chalks and is not related directly to the well documented global oceanic anoxic event oae2 occurring at that time 93 5 ma a sharp increase in dinocyst abundance in the lower turonian corresponds with a change in lithology to more marly chalks a gradual decrease in the number of species is observed through the middle turonian to upper coniacian 18 o records show that this was associated with global climatic cooling cluster analysis of the dinocyst abundance record with geochemical data indicates four distinct species groups with characteristic geochemical associations i e groups 1 4 groups 1 and 2 are associated with phases of increased siliciclastic supply a positive correlation with higher 13 c values differentiates the latter group 3 is independent of carbonate and detrital input and group 4 is associated with high carbonate flux and low detrital supply these groupings suggest that cyst forming dinoflagellates exhibited a range of ecological niches in the late cretaceous although the relationship between the encystment process and the geochemical associations is unclear key environmental factors are likely to be sea level and climate related including water depth turbidity nutrient supply sea surface temperature and environmental stability predictability integrated geochemical and palynological studies have great potential for inter regional correlation and palaeoenvironmental interpretation

modern and paleofluid pathways revealed by cu isotope compositions in surface waters and ores of the pebble porphyry cu au mo deposit alaska copper isotope ratios measured in minerals and shallow groundwater and surface waters provide insight into high temperature mineralization and active weathering processes at the pebble porphyry cu au mo deposit alaska the west zone of the deposit contains hypogene mineralization with a supergene overprint and a thin oxide leached capping whereas the contiguous east zone contains only hypogene mineralization sulfide rich rock powders and mineral separates have 65cu values that range from 0 78 to 2 28 hypogene west 0 02 to 1 55 hypogene east 3 49 to 1 88 oxide west and 5 04 to 1 27 supergene west the results from hypogene samples show that there is a systematic increase in 65cu values from deeper to shallower portions of the deposit furthermore the 65cu values correlate with silicate alteration assemblages mostly positive values correspond to quartz illite pyrite sericite and quartz pyrophyllite alteration zones which formed at relatively lower temperatures whereas negative values characterize the higher temperature potassic and sodic potassic domains this empirical evidence could indicate that fractionation of cu isotopes during hypogene alteration is controlled by ph and or temperature variations shallow surface waters proximal to the deposit and which likely interacted with underlying concealed mineralization have heavy 65cu values which contrast with lighter values in waters distal from the deposit patterns measured in the copper isotope ratios of both solids and surface waters demonstrate the potential use of copper isotope distribution as a vectoring tool in mineral exploration and aid in understanding the sources of copper in the surface and near surface environments

contrasting zinc isotopic fractionation in two mafic rock weathering profiles induced by adsorption onto fe hydr oxides abstract zinc isotopes have been increasingly utilized as a proxy for bio geochemical cycles of nutrient zn in the ecosystem like soils but the behavior and mechanism of zn isotope fractionation during weathering and soil formation remain to be constrained here we reported zinc contents and isotope data for saprolites and laterites from two well characterized mafic rock weathering profiles formed under a subtropical climate south carolina usa and a tropical climate hainan island china respectively leaching experiments with basalt and andesite as the starting materials were also performed for comparison the leaching results revealed no resolvable zn isotope fractionation during dissolution of silicate minerals in the absence of organic ligands in solutions the hainan laterites show strong zn depletion and have lower 66znlyon values 0 10 to 0 27 relative to the parent rock 0 31 0 04 which are coupled with light copper isotope compositions in the same samples these observations suggest that zn mobilization was achieved via metal organic complexation and fe colloids transportation by contrast saprolites from the south carolina are extremely zn rich ten fold higher concentration than the parent rock and most samples have higher 66zn values 0 10 to 0 65 compared with the parent rock 0 24 0 04 zinc isotope ratios of the south carolina profile are positively correlated with iron isotope ratios 56fe and fe3 fetotal the latter of which is related to secondary fe hydr oxide formation these relationships link the high zn contents and 66zn values of saprolites from the south carolina profile to the substantial adsorption of zn onto or isomorphic substitution into fe hydr oxides that prefers heavier zn isotopes our study highlights that fe hydr oxides exert a strong influence on the re distribution of nutrient zn in natural soils and the bio geochemical cycling in natural soil systems

iron isotopic fractionation during continental weathering abstract the effect of continental weathering on the iron isotope compositions of natural materials is investigated unweathered igneous rocks pelagic clay and dust fall within the range 56 fe 0 0 3 rivers with large suspended loads also have 56 fe values near zero dilute streams have 56 fe values that trend towards lower 56 fe 1 suggesting that dissolved riverine iron is isotopically light relative to igneous rocks bulk soil and soil leaches display systematically different 56 fe profiles indicating that isotopically distinct fe pools are generated during pedogenesis nannofossil ooze which contains fe scavenged from the ocean water column has 56 fe 0 but is consistent with seawater dissolved fe having negative 56 fe it is inferred that continental weathering under modern oxidizing earth surface conditions preferentially releases dissolved fe with negative 56 fe which is transported in rivers to the ocean a preliminary analysis of the marine fe budget suggests that riverine fe has a substantial role in determining the 56 fe of both the modern and ancient oceans but other inputs particularly that from diagenesis of marine sediments may also be important since the chemical pathways of fe processing during weathering are dependent on oxidation state and biological activity fe isotopes may prove useful for detecting changes in these parameters in the geologic past

patterns in the copper isotope composition of minerals in porphyry copper deposits in southwestern united states cu isotope measurements of minerals from american southwest porphyry cu deposits reveal a positive relationship with the grade of cu and display spatial patterns we measured the cu isotope composition of 87 minerals contained within veins from drill core and hand specimen samples from three deposits the silver bell ray and morenci mines the overall range of cu isotope ratios varies from 13 5 to 8 3 per mil the deposits possess three different cu reservoirs in which each has unique cu isotope signatures where 65cu for leach cap minerals hypogene minerals supergene enrichment minerals the pattern exists in all three deposits and resulted from oxidative weathering of cu at surface and reprecipitation of cu at depth a rayleigh distillation model mimics the cu isotope patterns found in the leach cap and quantifies the degree of leaching a comparison of the isotopic composition of the three reservoirs among the three deposits reveals distinct differences the silver bell mine possesses leach cap minerals that are more depleted in 65cu and enrichment minerals that are more enriched in 65cu than both the morenci and ray mines a possible explanation for the difference among the deposits could indicate that the silver bell deposit experienced a greater degree of leaching than the ray and morenci deposits the comparative analysis of the cu isotope data reveals the exploration potential of using cu isotope fractionation in the supergene environments

integrated palynological organic geochemical and sequence stratigraphic analyses of the middle to upper cenomanian hydrocarbon reservoir source abu roash g member a depositional model in northwestern egypt abstract the current investigation provides further insight into the petroliferous characteristics of the abu roash g member which is regarded as an important rock unit for the egyptian oil industry forty seven samples covering the g member were selected from the bed 14 1 and bed 2 4 wells in the abu gharadig basin and from the abu tunis 1x well in the matruh basin both of which are located in the north western desert an independent dating of the g rocks of bed 2 4 by benthic foraminifera and ostracods in addition to palynological dating suggests a middle late cenomanian age and provides the biochronostratigraphic framework for the sequence stratigraphic analysis analysis of the vertical distribution of particulate organic matter defines three palynofacies types pf pf 1 represents the basal g where shales of the bed wells and calcareous shale of abu tunis 1x were deposited during a relative sea level rise in an outer middle shelf environment that experienced a notable high primary productivity prevailing reducing suboxic anoxic conditions supported preservation of very high amounts of amorphous organic matter aom in pf 1 pf 2 is equated to shales of the middle g of bed 14 1 and bed 2 4 and to calcareous shales and limestone of the upper g in abu tunis 1x pf 2 was deposited during a relative sea level fall in an inner middle shelf setting under better developed suboxic anoxic conditions pf 3 corresponds to the upper g of bed 14 1 and bed 2 4 and represents the shallowest setting where sandy and silty shales were deposited during a pronounced sea level fall in an inner shelf environment the same suboxic anoxic conditions were prevailing during deposition of pf 3 three bioevents were recorded which could be of palaeoecological and or biostratigraphic significance these are senegalinium aenigmaticum dinopterygium cladoides peak dinopterygium cladoides dinopterygium alatum peak and an acme of classopollis brasiliensis sequence stratigraphy of a transect of the four studied sections was carried out to understand the response of the particulate organic matter distribution and depositional system to the sea level changes three third order depositional genetic sequences were recognized and correlated with the global sea level curve kce 2 kce 3 and kce 4 the early highstand systems tract ehst of the genetically related kce 3 in all wells is characterized by relatively rich organic matter where combined remarkably low water circulation and insignificant dilution of organic matter with coarse terrigenous material probably supported good preservation of organic matter spatial distribution of the g rocks shows lateral facies changes this was inferred from sedimentation of an organic poor avg 0 8 toc wt coarse clastic sandy shales facies in the studied area in abu gharadig basin sedimentation changes laterally into a northeast and northwest organic rich finer clastic shale calcareous shales and argillaceous limestone facies in the western matruh basin the robust anoxic conditions and very low dilution of organic matter by terrigenous influx enhanced the organic richness avg 2 4 toc wt of these rocks which resulted in the formation of promising hydrocarbon source rocks thus for a successful hydrocarbon exploration in the north western desert the promising source section of the g member would be associated with shales calcareous shales and argillaceous limestone lithologies its depositional environment is mainly confined to outer middle and inner middle shelf settings that have widespread suboxic anoxic conditions and show ehst pattern in contrast the regressive intervals that are denoted by the lowstand systems tract lst and or the late hst lhst typify the relatively coarse clastics as good quality reservoir rocks that are characterized by poor organic richness due to dilution with terrigenous influx

the use of cyclic stratigraphic pattern of peridinioid and gonyaulacoid dinoflagellate cysts in differentiating potential thick monotonous carbonate reservoirs a possible ecostratigraphic tool under test abstract the current work used the conventional peridinioid gonyaulacoid ratio p g to devise a new concept of dinoflagellate cyst zonation called the dinoflagellate ecological zone dez which is based here on the peridinioid ecological zone pez and gonyaulacoid ecological zone gez the pez and gez were used successfully to further divide the thick monotonous carbonate succession mid cenomanian to campanian in q 72 1x well in the eastern desert of egypt into smaller ecozones pez and gez are practical and easy to use in subdividing large conventional biozones of the carbonate reservoirs into distinguishable smaller ecozones when a finer resolution is necessary on a reservoir scale for production demands this tool is suggested to be used in the hydrocarbon exploration industry with minimum knowledge of the taxonomy of the dinoflagellate cysts the proposed pez and gez are related to local ecological conditions within the basin hydrocarbon field i e can be traced out laterally in an intra basinal scale this tool can be applied to any carbonate reservoirs in any petroliferous basin worldwide moreover the p g ratio the relative abundances of the dinoflagellate cyst assemblages and other palynological parameters were used successfully to reveal the palaeodepositional settings of the identified pez and gez alternating transgressive and regressive phases were identified although a dissimilar species composition is observed in each of these ecozones environments were interchanging between the regressive marginal marine to proximal inner neritic and the transgressive distal inner to middle shelf settings three peridiniacean dinoflagellate cyst peaks were recorded the middle cenomanian subtilisphaera peak the middle coniacian isabelidinium chatangiella and manumiella peak and the middle santonian isabelidinium peak

first evidence of the cretaceous decapod crustacean protocallianassa from sweden an assemblage of the burrowing ghost shrimp protocallianassa faujasi is described providing the first evidence of this decapod species from sweden the fossils occur in successions of the informal earliest late campanian belemnellocamax balsvikensis zone at asen and the latest early campanian b mammillatus zone at ivo klack both in the kristianstad basin of ne skane numerous heavily calcified chelipeds were found within a restricted bed at a sen that was rich in carbonate cemented nodules based on the burrowing lifestyle of modern mud shrimps we interpret these nodules as infilled burrow chambers the low abundance of molluscs within the protocallianassa beds is also consistent with analogous extant communities indicating that a similar ecologically exclusive relationship ruled within the late cretaceous shallowmarine ecosystems less

integrated fe and s isotope study of seafloor hydrothermal vents at east pacific rise 9 10 n abstract in this study we report on coupled fe and s isotope systematics of hydrothermal fluids and sulfide deposits from the east pacific rise at 9 10 n to better constrain processes affecting fe isotope fractionation in hydrothermal environments we aim to address three fundamental questions 1 is there significant fe isotope fractionation during sulfide precipitation 2 is there significant variability of fe isotope composition of the hydrothermal fluids reflecting sulfide precipitation in subsurface environments 3 are there any systematics between fe and s isotopes in sulfide minerals the results show that chalcopyrite precipitating in the interior wall of a hydrothermal chimney displays a limited range of 56fe values and 34s values between 0 11 to 0 33 and 2 2 to 2 6 respectively the 56fe values are on average slightly higher by 0 14 relative to coeval vent fluid composition while 34s values suggest significant s isotope fractionation 0 6 0 2 during chalcopyrite precipitation in contrast systematically lower 56fe and 34s values relative to hydrothermal fluids by up to 0 91 and 2 0 respectively are observed in pyrite and marcasite precipitating in the interior of active chimneys these results suggest isotope disequilibrium in both fe and s isotopes due to s isotopic exchange between hydrothermal h2s and seawater so42 followed by rapid formation of pyrite from fes precursors thus preserving the effects of a strong kinetic fe isotope fractionation during fes precipitation in contrast 56fe and 34s values of pyrite from inactive massive sulfides which show evidence of extensive late stage reworking are essentially similar to the hydrothermal fluids multiple stages of remineralization of ancient chimney deposits at the seafloor appear to produce minimal fe isotope fractionation similar affects are indicated during subsurface sulfide precipitation as demonstrated by the lack of systematic differences between 56fe values in both high temperature fe rich black smokers and lower temperature fe depleted vents

selenium redox cycling during weathering of se rich shales a selenium isotope study abstract selenium isotopes are becoming an important paleoenvironmental proxy however few studies have focused on the behavior of se isotopes during oxidative weathering in this paper a comprehensive set of se isotopic composition and concentration data were collected from the weathering profiles of se rich shales of the permian maokou formation in yutangba and shadi china to investigate se isotopic fractionation and se enrichment during weathering processes the 82 76se in fresh shales 148 118 mg kg se 1sd n 40 from shadi and yutangba drill cores varies from 1 69 to 1 74 with an average of 0 40 0 71 1sd n 40 consistent with the range in other phanerozoic shales suggesting that se isotopes are not strongly fractionated during se sequestration in the primary sedimentary environment however the strongly weathered se rich shales from shadi and yutangba profiles are isotopically lighter with average 82 76se values of 1 96 1 08 1sd n 5 and 1 08 1 83 1sd n 23 respectively these data suggest that se isotopes can be fractionated during oxidation and reduction processes associated with weathering with heavier isotopes removed preferentially during oxidative weathering of shales such a shift if found to be a global phenomenon would have implications for models of the global se cycle and interpretation of se isotope data from past biogeochemical regimes locally altered shales exposed in a quarry at yutangba are extremely enriched in se with 1642 1505 mg kg 1sd n 45 approximately 10 times greater than that in unaltered drill core samples these rocks display very strong variation in 82 76se over short distances with a single 60 cm transect showing the most strongly negative and positive 82 76se values 14 20 to 11 37 observed to date in natural samples this suggests that se has undergone multiple cycles of oxidation mobilization and re reduction resulting in a se rich redox front that has migrated downward through the organic rich shales over time 82 76se values vary sharply over distances as small as 10 cm indicating that se redox conditions change strongly with position and are controlled by fractures and rock layering our data and a simple conceptual model suggest that zones of increased permeability that are accessed first by infiltrating waters are isotopically light whereas less accessible zones are heavy repeated redox cycling accentuates this pattern furthermore the average 82 76se in se rich shales at the yutangba weathering system is 0 45 5 77 1sd n 39 identical with that 0 40 0 71 in fresh shales from same locality implying that se released by weathering accumulates in the redox front with little loss the strong se isotopic fractionation occurring in the redox front implies that se isotopes can be extensively used in tracing geochemical processes of se in groundwater system especially related to fractures

the copper isotope geochemistry of rivers and the oceans abstract we present the first extensive dataset for copper cu isotopes in rivers as well as preliminary data for estuaries and seawater rivers exhibit a range in dissolved 65 cu relative to nist srm 976 of 0 02 to 1 45 per mil the discharge weighted average dissolved 65 cu and cu concentration for the studied rivers representing around 25 of the global riverine water discharge are 0 68 and 18 8 nmol kg 1 respectively isotopic data for the dissolved phase in two small estuaries in se england exhibit relatively minor variation through the salinity gradient 0 42 to 0 94 and are close to both the data for the rivers upstream from the estuaries and a measurement of the coastal sea at their mouths analyses of the particulate phase in the estuaries reveal a complementary light pool 0 24 to 1 02 the isotopic composition of the total cu inventory is however close to that of the crustal source these data along with published constraints suggest that the isotopically heavy dissolved phase of all the rivers originates in an isotopic partitioning of the weathered pool of cu between a light fraction adsorbed to particulates and a heavy dissolved fraction dominated by cu bound to strong organic complexes open ocean seawater samples generally exhibit even heavier dissolved cu isotopic compositions than the riverine input 65 cu 0 9 to 1 5 the heavy isotopic composition of seawater is inferred to originate from intra oceanic processes the small dataset presented here is most consistent with further isotopic partitioning between an isotopically light pool adsorbed to particulates and a heavy dissolved pool strongly bound to organic ligands scavenging appears to have greatest impact in the surface ocean and least in both the oxygen minimum zone and the ocean bottom perhaps reflecting the relative importance of scavenging and thus the sequestration of light cu to particulate material at different depths

sources and ore forming fluid pathways of carbonate hosted pb zn deposits in southwest china implications of pb zn s cd isotopic compositions the sichuan yunnan guizhou metallogenic province of southwest china contains more than 200 mt of pb zn ore in carbonate hosted pb zn deposits representing 27 of the total pb and zn resources of china sources of metals and pathways of ore forming fluids were elucidated through a study of the pb zn s cd isotopic compositions of sphalerite from the tianbaoshan fusheng maozu jinshachang and daliangzi carbonate hosted pb zn deposits 34s values indicate that s in the deposits is derived mainly from evaporites in cambrian to triassic sedimentary strata sulfates coexisting with sulfides and meso neoproterozoic folded basement 66zn values and pb isotopic ratios indicate that these metals originate mainly from sinian to lower permian sedimentary rocks and proterozoic basement there is a trend towards isotopically heavier cd and zn compositions of sphalerite from maozu to daliangzi jinshachang and tianbaoshan which are all hosted in the upper sinian dengying formation previous studies showed that there would be a trend of enrichment in heavier zn and cd isotopes following the migration of fluids and precipitation of minerals the above observations suggest that the ore forming fluids of these deposits are probably derived from the same hydrothermal fluid system the fluids most likely flowed through maozu first migrating along the xiaojiang and anninghe fault belts and their branch faults to daliangzi jinshachang and tianbaoshan respectively zn and cd isotopes could be useful tools in tracing the pathways of ore forming fluids in this district and heavier zn and cd isotopic compositions could provide a geochemical fingerprint for detecting remote orebodies in large hydrothermal fluid systems

copper isotopic zonation in the northparkes porphyry cu au deposit se australia abstract significant systematic cu isotopic variations have been found in the northparkes porphyry cu au deposit nsw australia which is an orthomagmatic porphyry cu deposit copper isotope ratios have been measured in sulfide minerals chalcopyrite and bornite by both solution and laser ablation multi collector inductively coupled plasma mass spectrometry mc icp ms the results from both methods show a variation in 65cu of hypogene sulfide minerals of greater than 1 relative to nist976 significantly the results from four drill holes through two separate ore bodies show strikingly similar patterns of cu isotope variation the patterns are characterized by a sharp down hole decrease from up to 0 8 0 29 0 56 1 n 20 in the low grade peripheral alteration zones phyllic propylitic alteration zone to a low of 0 4 0 25 0 36 1 n 30 at the margins of the most mineralized zones cu grade 1 wt in the high grade cores of the systems the compositions are more consistent at around 0 2 0 19 0 14 1 n 40 the cu isotopic zonation may be explained by isotope fractionation of cu between vapor solution and sulfides at high temperature during boiling and sulfide precipitation processes sulfur isotopes also show an isotopically light shell at the margins of the high grade ore zones but these are displaced from the low 65cu shells such that there is no correlation between the cu and s isotope signatures fe isotope data do not show any discernable variation along the drill core this work demonstrates that cu isotopes show a large response to high temperature porphyry mineralizing processes and that they may act as a vector to buried mineralization

copper and iron isotope fractionation during weathering and pedogenesis insights from saprolite profiles abstract iron and copper isotopes are useful tools to track redox transformation and biogeochemical cycling in natural environment to study the relationships of stable fe and cu isotopic variations with redox regime and biological processes during weathering and pedogenesis we carried out fe and cu isotope analyses for two sets of basalt weathering profiles south carolina usa and hainan island china which formed under different climatic conditions subtropical vs tropical unaltered parent rocks from both profiles have uniform 56 fe and 65 cu values close to the average of global basalts in the south carolina profile 56 fe values of saprolites vary from 0 01 to 0 92 in the lower reduced part and positively correlate with fe 3 fe r 2 0 90 whereas 65 cu values are almost constant by contrast 56 fe values are less variable and negatively correlate with fe 3 fe r 2 0 88 in the upper oxidized part where large 4 85 65 cu variation is observed with most samples enriched in heavy isotopes in the hainan profile formed by extreme weathering under oxidized condition 56 fe values vary little 0 05 0 14 whereas 65 cu values successively decrease from 0 32 to 0 12 with depth below 3 m and increase from 0 17 to 0 02 with depth above 3 m throughout the whole profile 65 cu positively correlate with cu concentration and negatively correlate with the content of total organic carbon toc overall the contrasting fe isotopic patterns under different redox conditions suggest redox states play the key controls on fe mobility and isotope fractionation the negative correlation between 56 fe and fe 3 fe in the oxidized part of the south carolina profile may reflect addition of isotopically light fe this is demonstrated by leaching experiments which show that fe mineral pools extracted by 0 5 n hcl representing poorly crystalline fe hydr oxides are enriched in light fe isotopes the systematic cu isotopic variation in the hainan profile reflects desorption and downward transport of isotopically heavy cu leaving the organically bound cu enriched in light isotope as supported by the negative correlation of 65 cu with toc r 2 0 88 the contrasting mostly positive vs negative cu isotopic signatures in the upper parts of these two profiles can be attributed to the different climatic conditions e g high rainfall at a tropical climate in hainan favors desorption and the development of organism whereas relatively dry climate in south carolina favors cu re precipitation from soil solutions and adsorption onto fe hydr oxides our results highlight the potential applications of fe and cu isotopes as great tracers of redox condition ancient climate and biological cycling during chemical weathering and pedogenic translocation

iron isotope investigation of hydrothermal and sedimentary pyrite and their aqueous dissolution products abstract oxidative dissolution experiments were carried out on pyrite from multiple petrogenetic environments hydrothermal sedimentary and coal related nodules to investigate possible variations in the iron isotopic composition of pyrite and the products of pyrite dissolution the experimental materials were leached under carefully controlled abiotic conditions and a subset of leachates and starting materials from these experiments was analyzed for 56fe 54fe by multicollector icp ms bulk pyrite 56fe values relative to irmm 014 ranged from 0 1 to 1 3 with hydrothermal bulk pyrite values

dinoflagellate cysts paleoproductivity and upwelling systems a late cretaceous example from israel abstract diverse assemblages of dinoflagellate cysts occur in coniacian maastrichtian sedimentary sequences in israel which represent the inner shallower and outer deeper seaward belt of a late cretaceous upwelling system along the margin of the southern tethys the assemblages are composed mainly of peridinioid p and gonyaulacoid g cysts in varying concentrations it is suggested that the observed fluctuations in the numerical peridinioid gonyaulacoid p g cyst ratio reflect mainly changes in upwelling intensity and productivity in the studied area high p g values represent a higher productivity and vice versa thep g curve indicates a generally high productivity during the campanian followed by a decrease during the maastrichtian the inner part of the upwelling region is characterized by higherp g values representing a higher productivity the similarity between thep g ratio curve and the foraminiferal based paleoproductivity curve from the same sections supports the utility of thep g ratio as a reliable productivity indicator applied here for the first time to upper cretaceous sediments

copper isotopic compositions of the zijinshan high sulfidation epithermal cu au deposit south china implications for deposit origin abstract the zijinshan high sulfidation epithermal cu au deposit is located in the zijinshan ore field of south china comprising porphyry epithermal cu au mo ag ore systems the cu ore body is more than 1000 m thick and is characterized by an assemblage of digenite covellite enargite alunite digenite is the dominant cu bearing mineral which makes this deposit unique although the mechanisms of digenite formation remain controversial to elucidate the genesis of digenite this paper presents the cu isotopic compositions of cu sulfides in the zijinshan high sulfidation cu au deposit the cu isotopic values 65cu relative to nist 976 of all samples range from 2 97 to 0 34 and most values fall in a narrow range from 0 49 to 0 34 which is similar to the cu isotopic signature of typical porphyry systems copper isotope ratios of each mineral decrease with increasing depth a trend that is also typical of porphyry deposits the variation tendency of 65cu values between sulfides is consistent with the sequence of mineral formation these observations suggest that the cu sulfides in the zijinshan cu au deposit have a hypogene origin

copper isotope fractionation during sulfide magma differentiation in the tulaergen magmatic ni cu deposit nw china abstract although it has been recently demonstrated that cu isotope fractionation during mantle melting and basaltic magma differentiation is limited the behavior of cu isotopes during magmatic differentiation involving significant sulfide segregation remains unclear magmatic ni cu deposits which formed via sulfide segregation from basaltic or picritic magmas are appropriate targets to address this issue here we report cu isotope data for sulfides chalcopyrite from the tulaergen ni cu sulfide deposit in xinjiang nw china sulfides including sparsely disseminated hosted by hornblende gabbro moderately disseminated hosted by hornblende olivine websterite densely disseminated hosted by hornblende lherzolite and massive sulfides sandwiched between country rocks and mafic ultramafic rocks were collected from adits at 1050 m 1100 m and 1150 m levels the sparsely and moderately disseminated sulfides on 1150 m and 1050 m levels have a restricted range of 65 cu values from 0 38 to 0 15 whereas disseminated and massive sulfides on 1100 m level have 65 cu values ranging widely from 1 98 to 0 04 and from 1 08 to 0 52 respectively the 65 cu values of disseminated sulfides are negatively correlated with whole rock s and cu concentrations and sulfides formed at later stages have heavier 65 cu values these observations suggest significant cu isotope fractionation during sulfide magma differentiation above 600 c during the formation of the tulaergen magmatic ni cu deposit sulfide segregation and crystallization of olivine and pyroxene caused the increase of fe 3 contents in the residual magmas which would move the redox reaction cu fe 3 fe 2 cu 2 toward larger amounts of cu 2 in the melt the presence of cu 2 in melt allowed redox transformation to happen during sulfide segregation the residual magmas are enriched in heavy cu isotopes due to the removal of 65 cu depleted sulfides and sulfides formed at later stages will have heavier 65 cu values accounting for the large and systematic cu isotopic variation as observed our results therefore demonstrate that cu isotopes could be significantly fractionated during high temperature sulfide magma differentiation up to 2 and cu isotopes may be used to trace the mineralization process of ni cu pge deposits and indicate the movement direction of sulfide enriched magmas

fractionation of cu and mo isotopes caused by vapor liquid partitioning evidence from the dahutang w cu mo ore field the study presents 65cu and 97mo isotope values from cogenetic chalcopyrite and molybdenite found in veins and breccias of the dahutang w cu mo ore field in china the samples span a 3 4 km range both isotopes show a significant degree of fractionation cu isotope values in the chalcopyrite range from 0 31 to 1 48 and mo isotope values in the molybdenite range from 0 03 to 1 06 for the cogenetic sulfide veined samples a negative slope relationship exists between 65cu and 97mo values which suggest a similar fluid history rayleigh distillation models the vein samples change in isotope values the breccia samples do not fall on the trend thus indicating a different source mineralization event measured fluid inclusion and d and 18o data from cogenetic quartz indicate changes in temperature and mixing of fluids do not appear to cause the isotopic shifts measure related equilibrium processes associated with the partitioning of metal between the vapor fluid in the hydrothermal system could be the probable cause for the relationship seen between the two isotope systems

dinoflagellate biostratigraphy and sequence stratigraphy of the type maastrichtian upper cretaceous enci quarry the netherlands abstract the upper maastrichtian strata in enci quarry contain rich assemblages of marine palynomorphs especially dinoflagellate cysts a quantitative study shows that a marked change from dinoflagellate dominated assemblages to assemblages dominated by the acritarch genus paralecaniella occurs at the base of the lanaye member indicating a change from open marine to marginal marine conditions a sequence stratigraphic breakdown into systems tracts based on an interpretation of the changes in the palynological assemblages and lithology suggests the presence of parts of four sedimentary cycles in the enci section three of the cycles may be correlated with the third order cycles uza 4 5 ta 1 1 and ta 1 2 of haq et al 1988 the fourth cycle is probably of higher order three dinoflagellate cysts are new laciniadinium aquiloniforme schioler et al sp nov leberidocysta verrucosa schioler et al sp nov and pulchrasphaera minuscula schioler et al gen et sp nov the description of rottnestia wetzelii is emended and the new combination cribroperidinium wilsonii slimani schioler et al comb nov is proposed the triblastula utinensis zone isabelidinium cooksoniae zone and the palynodinium grallator zone with its two subzones tanyosphaeridium magdalium subzone and thalassiphora pelagica subzone can be recognized in the enci section

zn and cu isotopic variability in the alexandrinka volcanic hosted massive sulphide vhms ore deposit urals russia abstract copper and zn isotope ratios of well characterized samples from three ore facies in the devonian alexandrinka volcanic hosted massive sulphide vhms deposit southern urals were measured using multi collector icp ms mc icp ms and show variations linked to depositional environment and mineralogy the samples analysed derived from a hydrothermal metasomatic vein stockwork b a hydrothermal vent chimney and c reworked clastic sulphides as the deposit has not been significantly deformed or metamorphosed after its formation it represents a pristine example of ancient seafloor mineralization variations in 65 cu where 65 cu 65 cu 63 cu sample 65 cu 63 cu standard 1 1000 and 66 zn where 66 zn 66 zn 64 zn sample 66 zn 64 zn standard 1 1000 of 0 63 and 0 66 respectively are significantly greater than analytical uncertainty for both isotope ratios 0 07 2 very limited isotopic fractionation is observed in primary cu minerals from the stockwork and chimney whereas the zn isotopic composition of the stockwork varies significantly with the mineralogy chalcopyrite bearing samples from the stockwork have lighter 66 zn by 0 4 relative to sphalerite dominated samples which may be due to equilibrium partitioning of isotopically light zn into chalcopyrite during its precipitation 66 zn also showed significant variation in the chimney with an enrichment in heavy isotopes toward the chimney rim of 0 26 which may be caused by changing temperature hence fractionation factor or raleigh distillation post depositional seafloor oxidative dissolution and re precipitation in the clastic sediments possibly coupled with leaching led to systematic negative shifts in cu and zn isotope compositions relative to the primary sulphides copper shows the most pronounced fractionation consistent with the reduction of cu ii to cu i during supergene mineralization however the restricted range in 65 cu is unlike modern sulphides at mid oceanic ridges where a large range of cu isotope of up to 3 has been observed rouxel o fouquet y ludden j n 2004 copper isotope systematics of the lucky strike rainbow and logatchev sea floor hydrothermal fields on the mid atlantic ridge econ geol 99 585 600 zhu x k o nions r k guo y belshaw n s rickard d 2000 determination of natural cu isotope variation by plasma source mass spectrometry implications for use as geochemical tracers chem geol 163 139 149

subsurface processes at the lucky strike hydrothermal field mid atlantic ridge evidence from sulfur selenium and iron isotopes at lucky strike near the azores triple junction the seafloor setting of the hydrothermal field in a caldera system with abundant low permeability layers of cemented breccia provides a unique opportunity to study the influence of subsurface geological conditions on the hydrothermal fluid evolution coupled analyses of s isotopes performed in conjunction with se and fe isotopes have been applied for the first time to the study of seafloor hydrothermal systems these data provide a tool for resolving the different abiotic and potential biotic near surface hydrothermal reactions the 34s between 1 5 and 4 6 and se values between 213 and 1640 ppm of chalcopyrite suggest a high temperature end member hydrothermal fluid with a dual source of sulfur sulfur that was leached from basaltic rocks and sulfur derived from the reduction of seawater sulfate in contrast pyrite and marcasite generally have lower 34s within the range of magmatic values 0 1 and are characterized by low concentrations of se 50 ppm for 82se 76se ratios the 82se values range from basaltic values of near 1 5 to 7 the large range and highly negative values of hydrothermal deposits observed cannot be explained by simple mixing between se leached from igneous rock and se derived from seawater we interpret the se isotope signature to be a result of leaching and mixing of a fractionated se source located beneath hydrothermal chimneys in the hydrothermal fluid at lucky strike we consider two sources for s and se 1 the end member hydrothermal fluid with basaltic se isotopic values 1 5 and typical s isotope hydrothermal values of 1 5 2 a fractionated source hosted in subsurface environment with negative 34s values probably from bacterial reduction of seawater sulfate and negative 82se values possibly derived from inorganic reduction of se oxyanions fluid trapped in the subsurface environment is conductively cooled and has restricted mixing and provide favorable conditions for subsurface microbial activity which is potentially recorded by s isotopes fe isotope systematic reveals that se rich high temperature samples have 57fe values close to basaltic values 0 whereas se depleted samples precipitated at medium to low temperature are systematically lighter 57fe values between 1 to 3 an important implication of our finding is that light fe isotope composition down to 3 2 may be explained entirely by abiotic fractionation in which a reservoir effect during sulfide precipitation was able to produce highly fractionated compositions

late cretaceous campanian leaf and palynoflora from southern skane sweden a late cretaceous campanian leaf megaflora from the vomb trough in southern skane sweden has been investigated on the basis of collections held at the swedish museum of natural history the mai

an introduction to the mesozoic biotas of scandinavia and its arctic territories the mesozoic biotas of scandinavia have been studied for nearly two centuries however the last 15 years have witnessed an explosive advance in research most notably on the richly fossiliferous t

application of iron and zinc isotopes to track the sources and mechanisms of metal loading in a mountain watershed abstract here the hydrogeochemical constraints of a tracer dilution study are combined with fe and zn isotopic measurements to pinpoint metal loading sources and attenuation mechanisms in an alpine watershed impacted by acid mine drainage in the tested mountain catchment 56fe and 66zn isotopic signatures of filtered stream water samples varied by 3 5 and 0 4 respectively the inherent differences in the aqueous geochemistry of fe and zn provided complimentary isotopic information for example variations in 56fe were linked to redox and precipitation reactions occurring in the stream while changes in 66zn were indicative of conservative mixing of different zn sources fen environments contributed distinctively light dissolved fe 0 4 acidic drainage from mine wastes contributed heavier dissolved fe 0 5 and lighter zn 0 2 isotopes relative to the fen upwelling of fe rich groundwater near the mouth of the catchment was the major source of fe 56fe 0 leaving the watershed in surface flow while runoff from mining wastes was the major source of zn the results suggest that given a strong framework for interpretation fe and zn isotopes are useful tools for identifying and tracking metal sources and attenuation mechanisms in mountain watersheds

timing and progression of climatic tectonic and glacioeustatic influences on the messinian salinity crisis abstract new palynological analysis of the continuous upper neogene sequence from the rifian corridor at sale morocco permits the deconvolution of climatic tectonic and eustatic control on the messinian salinity crisis via two indices 1 a distance from shore index based on dinoflagellate cyst versus pollen distribution and 2 a land climate index based on detailed pollen analysis this new pollen analysis indicates that the messinian salinity crisis 6 8 ma to 5 3 ma was not associated with major climate change detailed analyses of dinoflagellate cyst ecology at sale correlated to the sale 18o record show that initial shoaling of the rifian corridor after 7 3 ma primarily resulted from tectonic uplift however from 6 5 ma to 5 4 ma the rifian corridor was sufficiently shallow to have experienced significant restriction of atlantic inflow during at least four small amplitude glacioeustatic lowstands at 5 4 ma abrupt increase in the ratio of continental versus marine derived palynomorphs indicates that restriction intensified as tectonic uplift significantly outpaced gradual glacioeustatic rise despite eustatic rise at 5 32 ma the sale palynological data show that the rifian corridor experienced a second major drop in relative sea level tectonic uplift or increased sedimentation therefore termination of the messinian salinity crisis was probably associated with a breach elsewhere along the gibraltar arc

carl wiman and the foundation of mesozoic vertebrate palaeontology in sweden in 1908 carl wiman of uppsala university sweden discovered rich horizons with triassic vertebrate remains in spitsbergen on svalbard norway this marked the beginning of vertebrate palaeontolog

a partial plesiosaurian braincase from the upper cretaceous of sweden a partial exoccipital opisthotic from the uppermost lower campanian upper cretaceous of the asen locality kristianstad basin southernmost sweden is described and illustrated the fossil represents the first braincase element of a plesiosaur found in sweden it includes the chamber for the ampulla and utriculus openings for the caudal vertical and horizontal semicircular canals and four foramina for cranial nerves the incomplete braincase can be referred to an elasmosaurid plesiosaur and closely resembles the exoccipital opisthotic of libonectes morgani and a referred specimen of aristonectes parvidens although we discuss putative postcranial material of the elasmosaurid subfamily aristonectinae in the uppermost lower campanian of southernmost sweden the exoccipital opisthotic from asen most likely belongs to a juvenile individual of a non aristonectine elasmosaur less

cu isotope ratio variations in the dikulushi cu ag deposit drc of primary origin or induced by supergene reworking this study investigates cu isotope ratio variations in the high grade vein type cu ag deposit of dikulushi democratic republic of congo the dikulushi deposit consists of a cu pb zn fe mineralization comprising sphalerite chalcopyrite bornite and chalcocite that precipitated under reducing conditions this mineralization was partly remobilized in more oxidizing conditions into a cu ag mineralization phase which is dominated by ag rich chalcocite the upper part of the deposit is strongly reworked by weathering sulfides from the two types of mineralization and cu carbonates silicates from the weathering zone display significant cu isotope ratio variations chalcopyrite and chalcocite from the cu pb zn fe and cu ag mineralization types are characterized by variable low cu isotope compositions 0 00 to 2 3 65cu the cu isotope composition for some chalcocite from the cu ag mineralization deviates to lower 65cu values relative to that of chalcocite from the cu pb zn fe mineralization this deviation is likely related to remobilization of the cu pb zn fe mineralization in an oxidizing environment the isotopic composition of cu in chalcocite from both mineralization types becomes higher toward the center of the orebody and as a function of depth this variation could be related to physicochemical changes in the precipitation environment as a consequence of interaction of the reduced mineralizing brine with the oxidized host rock or might have been induced by supergene processes afterward the supergene mineralization is composed of malachite azurite and chrysocolla that are enriched in 65cu 1 37 2 65 65cu

zinc and copper behaviour at the soil river interface new insights by zn and cu isotopes in the organic rich rio negro basin abstract the complex behaviour of zn and cu at the soil river interface was investigated in soil and riverine water samples from the rio negro basin a secondary tributary of the rio amazonas using their stable isotope compositions this acidic and organic river drains two types of intensely weathered terrains podzols in its upstream part and lateritic soils downstream bulk soil particles suspended particulate matter spm as well as colloidal fractions were sampled across the whole basin during low and high water stages in the basin zn and cu are mostly exported from lateritic soils and transported by organic colloids where significant losses are observed in the downstream part of the river the use of 66zn and 65cu measurements reveals distinct stories for these two metals in suspended sediments and colloids in the colloids the constant 66zncoll across the basin is induced by the same weak association mode between zn and organic ligands regardless of the origin of the water by contrast in spm the speciation of zn and thus 66znspm differ according to the type of drained soils zn is associated with organic complexes in particles exported with water draining podzol whereas zn2 is incorporated in the structure of the remaining kaolinite clays in lateritic output the stronger reactivity of cu than zn with organic ligands induces its complete complexation copper is controlled by refractory particulate organic matter pom and by reactive colloidal organic matter the latter being enriched in 65cu due to stronger binding interactions than in pom while the cu content remains constant in the upstream part of the rio negro downstream the decrease of spm and colloidal cu fluxes is associated with a constant 65cuspm and with an increase of 65cucoll at the rio negro outlet geochemical mass balance modelling based on spm cu and zn fluxes in spm and their associated isotopic signatures confirms distinct host phases for zn and cu and identifies the most probable places where losses of these two metals occur in colloids the observed cu isotope fractionation from 0 24 to 0 45 superimposed on the significant cucoll loss is assumed to result from a new isotopic equilibrium in a low velocity and high productivity zone cu rich colloids enriched in 63cu aggregate and settle down whereas the remaining heavy cu is partially complexed on strong organic ligands secreted by phytoplankton forming new cu colloids

fe isotope fractionation between chalcopyrite and dissolved fe during hydrothermal recrystallization an experimental study at 350 c and 500 bars abstract equilibrium fe isotope fractionation between chalcopyrite and dissolved fe was determined in acidic chloride bearing fluid at 350 c and 500 bars the study utilized deformable gold cell technology which allowed time series sampling of solution during chalcopyrite recrystallization and isotope exchange a key element of the experimental design involved the addition of anomalous dissolved 57 fe to an on going experiment as a means of determining the degree and rate of isotope exchange taking explicit account of imposed chemical and isotopic mass balance constraints of fe in fluid and mineral chalcopyrite reservoirs these data indicate that no more than 1000 h is required for the isotopically anomalous dissolved fe reservoir to exchange completely with the coexisting chalcopyrite the experimental calibration of the rate of fe isotope exchange for the 57 fe spiked experiment provides critical insight for the time necessary to achieve fe isotope exchange in two non spiked but otherwise identical experiments the fe isotope data indicate that the equilibrium fractionation between chalcopyrite and dissolved fe 56 fe cpy fe aq at 350 c is small 0 09 0 17 2 and is in good agreement with recent theoretical equilibrium predictions owing to the apparent rate of fe isotope exchange at 350 c it is likely that chalcopyrite formed at high temperature deep sea vents black smoker systems achieves isotopic equilibrium and effectively records the fe isotopic composition of the coexisting end member hydrothermal fluid comparison of the experimental mineral fluid equilibrium fractionation factors with conjugate chalcopyrite and dissolved fe pairs sampled from high temperature hydrothermal vent systems at axial caldera and main endeavour field juan de fuca ridge are in agreement with this inference the experimental data were further used to determine the mineral mineral equilibrium fe isotope fractionation between pyrite chalcopyrite 56 fe pyr cpy at 350 c by combining previously determined pyrite fe 2 aq equilibrium fractionation data with chalcopyrite fe 2 aq from this study the empirically determined 56 fe pyr cpy value 0 90 0 34 2 is consistent with theoretical predictions and when coupled with mineral fluid fe isotope fractionation systematics and experimentally determined exchange rates helps to delineate processes of sulfide mineralization in hydrothermal systems

fe isotope variations in the modern and ancient earth and other planetary bodies iron the fourth most abundant element in the earth s crust has four naturally occurring stable isotopes 54fe 5 84 56fe 91 76 57fe 2 12 and 58fe 0 28 and the natural mass dependent isotope variations of fe in the rock record span a range of 4 per mil in 56fe 54fe ratios fig 1 the field of fe isotope geochemistry is relatively new but has received considerable attention because it may allow us to gain a better understanding of how fe is cycled in different environments iron typically occurs as either reduced ferrous fe in oxygen poor environments or as oxidized ferric iron in oxygen rich environments notably only the reduced species is soluble in oxygenated aqueous solutions unless the ph is low in the archean and early proterozoic the earth may have been relatively oxygen poor e g kasting et al 1979 grandstaff 1980 holland 1994 suggesting that there may have been significant quantities of fe 0 9 millimolar dissolved in the oceans as fe ii aq e g ewers 1983 sumner 1997 the extensive iron formations of archean to early proterozoic age may have been deposited from such fe ii rich oceans e g beukes and klein 1992 in the modern oxic oceans however fe contents are exceedingly low 1 nanomolar in the open oceans e g martin and gordon 1988 bruland et al 1991 martin 1992 johnson et al 1997 and it is now recognized that marine productivity is fe limited in parts of the open oceans e g martin and fitzwater 1988 martin et al 1989 1994 the differences in the behavior of fe with redox state and the significant isotope fractionations 1 or more in 56fe 54fe that are associated with redox conditions suggests that fe isotope studies will be extremely useful for tracing

fractionation of cu fe and zn isotopes during the oxidative weathering of sulfide rich rocks abstract we measured the fe cu and zn isotopic compositions of the fluids generated during leaching experiments with pyrite chalcopyrite and sphalerite rich rocks and with a sphalerite mineral separate our study demonstrates that the oxidative weathering of sulfide rich rocks can produce substantial variations in fe 1 75 to 1 0 56 fe solution pyrite rock and cu 0 0 to 2 0 65 cu solution chalcopyrite rock isotopes and small variations in zn isotopes 0 0 to 0 2 66 zn solution sphalerite in the fluid phase relative to the rock for the fe and cu systems we suggest that isotopic fractionation is caused by electron exchange driven e g fe ii fe iii and cu i cu ii redox reactions at the surfaces of the sulfide minerals that occur during air and aqueous chemical reactions under acidic conditions these reactions tend to enrich the fluid phase in the heavier fe and cu isotopes however under circumneutral ph conditions the fe isotopic composition in solution was controlled by the precipitation of fe iii oxide phases which enriched the solution in the lighter fe isotopes this investigation provides a preliminary framework for interpreting the impact of sulfide oxidation reactions on the distributions of stable fe cu and zn isotopes in natural waters

the zinc stable isotope signature of waste rock drainage in the canadian permafrost region leachate from a well instrumented experimental scale waste rock pile test pile at the diavik diamond mine northwest territories was monitored the well characterized waste rock consists of granite pegmatitic granite and biotite schist with an average total sulfur and carbonate carbon concentration of 0 053 and 0 027 wt respectively the leachate emerging from the southern basal drain of the waste rock pile has been monitored since 2007 the zinc stable isotope footprint was characterized alongside standard monitoring parameters during two field seasons may to november 2011 and 2012 the ph ranged between 4 3 and 6 8 and carbonate alkalinity was low or undetectable 35 mg l 1 caco3 the ph was governed by the oxidation of sulfide minerals and the dissolution of primary carbonate minerals and secondary al and fe oxyhydroxysulfates and hydroxides dissolved al and fe concentrations averaged 6 78 mg l 1 and 175 g l 1 respectively the main processes controlling zn concentrations in the range of 0 4 and 4 7 mg l 1 average 2 2 mg l 1 were the oxidative dissolution of sphalerite zns and the attenuation by secondary fe and al hydroxides zinc isotopes were fractionated mass dependently zinc isotope ratios ranging between 0 16 and 0 18 average 0 05 n 43 were consistent with values reported for sphalerite from other deposits the deviations in isotope ratios 0 36 were significant in comparison to analytical uncertainties 0 06 zinc isotope ratios and concentrations were largely uncorrelated suggesting that the processes affecting zn mobility had little or no impact on the zn isotope signature these data suggest that the zn isotope ratios of the waste rock leachate may be used as a fingerprint to track anthropogenic mine derived zn sources in an environment under fluctuating ph temperature and ionic strength

early campanian late cretaceous squatiniform and synechodontiform selachians from the asen locality kristianstad basin sweden

dinoflagellate based sea surface temperature reconstructions across the cretaceous tertiary boundary abstract quantitative analysis of organic walled dinoflagellate cyst dinocyst assemblages from closely spaced samples across the cretaceous tertiary boundary ktb at el kef nw tunisia caravaca se spain and stevns klint e denmark allows for reconstructions of sea surface temperature sst trends the combined dinocyst based sst curves indicate relatively stable warm conditions during the latest maastrichtian in contrast to strongly fluctuating and on average cooler conditions during the earliest danian in detail the results indicate cooling across the ktb immediately followed by an interval of pronounced warming the latter recorded in all studied sections two more cooling pulses may be recognized in the overlying interval followed by a gradual return to stable relatively warm conditions our data furthermore show that these ktb related climatic changes invoked distinct migration among organic walled cyst producing dinoflagellates a group not pushed to extinction at the ktb recordable in both hemispheres recent models predict periods varying between several months to 8 13 yr of global cooling impact winter and reduced solar transmission as a direct result of the chicxulub ktb impact followed by relatively long term excess co 2 related global warming our results are in line with such models but suggest that the impact related cooling phase may have lasted longer and that marked climatic instability continued to some 100 000 yrs following the ktb event s

iron isotope systematics in estuaries the case of north river massachusetts usa abstract recent studies have suggested that rivers may present an isotopically light fe source to the oceans since the input of dissolved iron from river water is generally controlled by flocculation processes that occur during estuarine mixing it is important to investigate potential fractionation of fe isotopes during this process in this study we investigate the influence of the flocculation of fe rich colloids on the iron isotope composition of pristine estuarine waters and suspended particles the samples were collected along a salinity gradient from the fresh water to the ocean in the north river estuary ma usa estuarine samples were filtered at 0 22 m and the iron isotope composition of the two fractions dissolved and particles were analyzed using high resolution mc icp ms after chemical purification dissolved iron results show positive 56 fe values with an average of 0 43 0 04 relative to the irmm 14 standard and do not display any relationships with salinity or with percentage of colloid flocculation the iron isotopic composition of the particles suspended in fresh water is characterized by more negative 56 fe values than for dissolved fe and correlate with the percentage of fe flocculation particulate 56 fe values vary from 0 09 at no flocculation to 0 1 at the flocculation maximum which reflect mixing effects between river borne particles lithogenic particles derived from coastal seawaters and newly precipitated colloids since the process of flocculation produces minimal fe isotope fractionation in the dissolved fe pool we suggest that the pristine iron isotope composition of fresh water is preserved during estuarine mixing and that the value of the global riverine source into the ocean can be identified from the fresh water values however this study also suggests that 56 fe composition of rivers can also be characterized by more positive 56 fe values up to 0 3 relative to the crust than previously reported in order to improve our current understanding of the oceanic iron isotope cycling further work is now required to determine the processes controlling the fractionation of fe isotopes during continental run off

zinc sulfur and lead isotopic variations in carbonate hosted pb zn sulfide deposits southwest china abstract the sichuan yunnan guizhou pb zn metallogenic province in the western yangtze block southwest china contains more than four hundred pb zn deposits with more than 200 million tons of pb zn ores at mean grades of 5 wt pb and 10 wt zn these deposits are hosted in sinian ediacaran to permian carbonate rocks and are structurally controlled by thrust fault fold structures and are spatially associated with the late permian 260 ma emeishan flood basalts two representative low temperature hydrothermal pb zn sulfide deposits the tianqiao and banbanqiao deposits in the southeastern part of the sichuan yunnan guizhou pb zn metallogenic province are selected for zn s pb isotopic analyses sphalerite from the tianqiao deposit has 66 zn values ranging from 0 26 to 0 58 relative to the jmc 3 0749l zinc isotope standard whereas 66 zn values of sphalerite from the banbanqiao deposit range from 0 07 to 0 71 the zinc isotopic composition of sphalerite from both deposits increase from early to final mineralization stage in addition sphalerite from the center near to bottom part of the no 1 ore body in the tianqiao deposit has lower 66 zn values 0 01 to 0 43 than those 0 11 to 0 57 in the periphery near to top sinian to permian sedimentary rocks and permian emeishan flood basalts the potential zinc metal source rocks have 66 zn values range from 0 24 to 0 17 and from 0 32 to 0 44 respectively the majority of the hydrothermal sphalerite has heavier zinc isotope than the country rocks precluding the mixing of multiple zinc sources as the key factor controlling the spatial and temporal variations of zinc isotope therefore the increased 66 zn values from the early to late stage and from the center to top could be due to kinetic raleigh fractionation sphalerite from the tianqiao and banbanqiao deposits has 34 s values ranging from 10 9 to 14 8 and from 3 9 to 9 0 respectively lower than cambrian to permian marine sulfates 15 to 35 and sulfate bearing evaporates 15 to 28 in the devonian to permian carbonate host rocks sulfur of the pb zn ores from both deposits is interpreted as the result of thermal chemical sulfate reduction of evaporates in the sedimentary rocks most likely the host rocks sphalerite from the tianqiao deposit has pb isotope similar to that of age corrected devonian to permian carbonate host rocks whereas sphalerite from the banbanqiao deposit has pb isotope similar to that of age corrected underlying precambrian basement rocks therefore at least lead in the tianqiao and banbanqiao deposits was mainly originated from the host rocks and the underlying basements respectively zn s pb isotopic studies of sphalerite from both deposits indicate that sources of metals and sulfur in the hydrothermal fluid for the tianqiao deposit are the paleozoic carbonate host rocks whereas for the banbanqiao deposit the sources are the precambrian basements and the paleozoic carbonate host rocks respectively

iron isotope fractionation during microbial reduction of iron the importance of adsorption in experiments investigating the causes of fe isotope fractionation the d 56 54 fe value of fe ii remaining in solution fe ii aq after reduction of fe iii goethite by shewanella putrefaciens is 21 2 relative to the goethite in agreement with previous research the addition of an electron shuttle did not affect fractionation suggesting that fe isotope fractionation may not be related to the kinetics of the electron transfer furthermore in abiotic anaerobic fecl2 aq experiments in which approximately one third of fe ii aq is lost from solution due to adsorption of fe ii onto goethite the d 56 54 fe value of fe ii aq remaining in solution is shifted by 20 8 relative to fecl 2 this finding demonstrates that anaerobic nonbiological interaction between fe ii and goethite can generate signif icant fe isotope fractionation acid extraction of sorbed fe ii from goethite in experi ments reveals that heavy fe preferentially sorbs to goethite simple mass balance modeling indicates that the isotopic composition of the sorbed fe ii pool is 11 5 to 12 5 heavier than fe in the goethite 2 7 3 7 heavier than aqueous fe ii mass balance is also consistent with a pool of heavy fe that is not released to solution during acid extraction

iron and aluminum hydroxysulfates from acid sulfate waters acid sulfate waters are produced mostly by the oxidation of common sulfide minerals such as pyrite chalcopyrite pyrrhotite and marcasite in rocks soils sediments and industrial wastes this spontaneous process of mineral weathering plays a fundamental role in the supergene alteration of ore deposits the formation of acid sulfate soils and the mobilization and release of acidity and metals to surface and ground waters the purely natural process of acid rock drainage is often intensified by human activities related to mining mineral processing construction soil drainage and dredging geochemical reaction rates are accelerated because physical disturbance gives greater exposure of mineral surfaces to air and water and to microbes that catalyze the reaction process large quantities of reactive sulfides are also concentrated and exposed to air as a result of mining and mineral processing acid sulfate waters produce a number of fairly insoluble hydroxysulfate and oxyhydroxide minerals that precipitate during oxidation hydrolysis and neutralization the objective of this chapter is to describe the formation properties fate and environmental implications of the nano to microphase hydroxy sulfates of fe and al that are precipitated from acid sulfate waters these minerals are commonly of poor crystallinity and difficult to characterize much remains to be learned about their occurrence formation and properties mine drainage the best known examples of acid sulfate waters are those released from mines where coal and metallic sulfide ores have been exploited ash et al 1951 barton 1978 nordstrom 1982a rose and cravotta 1998 nordstrom and alpers 1999 there may be as many as 500 000 inactive or abandoned mine sites in the united states alone lyon et al 1993 although most of these pose no immediate water quality problem kleinmann 1989 estimated that about 19 300 km of streams and more than 72 000 ha of lakes and reservoirs have been

late cretaceous campanian actinopterygian fishes from the kristianstad basin of southern sweden although a diverse range of aquatic vertebrates are documented from the upper cretaceous mid campanian marine strata of the kristianstad basin in southern sweden only chondrichthyans and marine amniotes have been described in detail to date in contrast coeval actinopterygians are virtually unreported yet their remains are extremely abundant at most sampled localities a comprehensive assessment of these fossils has identified the first late cretaceous actinopterygian fauna from the fennoscandian shield incorporating indeterminate lepisosteids the durophagous pycnodontid anomoeodus subclavatus the predatory pachycormid protosphyraena sp a large ichthyodectid pachyrhizodontids resembling pachyrhizodus the enchodontid enchodus cf gladiolus and indeterminate small teleosts these taxa are diagnosed mainly from isolated teeth and scales implying substantial taphonomic loss prior to burial moreover the prolific recovery of actinopterygian skeletal remnants in recent excavations suggests that historical collecting biases rather than ecological paucity have contributed to their under representation in the swedish cretaceous record palaeobiogeographically the kristianstad basin actinopterygians show compositional resemblance to assemblages from the northern european platform and the western interior seaway of north america advocating distributional communication across the boreal proto atlantic ocean

equilibrium isotopic fractionation between aqueous zn and minerals from first principles calculations abstract theoretical mineral solution equilibrium isotopic fractionation can contribute to the interpretation of zn isotopic compositions in this study we investigate equilibrium isotopic fractionation properties of hexaaquo zinc complex a major zn aqueous species using first principles molecular dynamics fpmd based on density functional theory dft pentaaquo and tetraaquo zinc complexes which can be relevant for specific mechanisms such as adsorption on mineral surfaces are also considered this approach takes into account both configurational and solvation effects that are less easily accounted for in molecular cluster models the logarithmic value of the reduced partition function ratio of aqueous zn ln 66zn 64zn is 2 86 0 04 at 295 k while the same computational approach gave ln 66zn 64zn in the range 2 2 4 1 for various zn bearing minerals for example calculations predict at 295 k equilibrium fractionations between mineral and aqueous zn of 0 46 for primary zinc sulfide sphalerite and of 0 20 and 0 34 for secondary phases gunningite and hydrozincite respectively molecular clusters are also modelled predicting isotopically heavier zn with respect to related fpmd models ln increases by 0 09 to 0 23 these values are small but significant in the zn isotopic system and supports the idea that a proper description of the dynamics of the system and the solvation effect are required for a reliable prediction of the isotopic properties of solvated ions

variability of the copper isotopic composition in soil and grass affected by mining and smelting in tsumeb namibia abstract the tsumeb mining district namibia is affected by prolonged exposure to multisource contamination related to the mining and smelting of copper ores this study was performed to assess the extent of contamination of topsoil and grass shoots on the basis of the copper isotopic composition compared to an uncontaminated area 65cusoil 0 01 to 0 14 65cugrass 0 17 to 0 03 the soil and grass in the contaminated area are enriched in the heavy isotope 65cusoil 0 13 to 0 76 and 65cugrass 0 15 to 0 64 the 65cugrass soil value exhibits small variations 0 06 to 0 17 due to the variable degree of grass surface contamination depending on the grass washing procedure used the enrichment of soil and grass in the contaminated area in 65cu reflects the cu isotopic composition of old flotation tailings 65cu 0 95 to 1 1 slag 0 11 to 0 55 and particles which originate from the smelting and flue gas cleaning processes 0 15 to 0 49 the long history of mining and processing of copper ores in the tsumeb area and the different isotopic composition of ore concentrates smelted in the local metallurgical plant do not allow assessment of whether the smelting process leads to isotope fractionation of copper however the isotopic composition of cu in the sulfidic feed slag and dust particles sampled over several hours showed that the dust collected from the dusthouse of the local smelter is isotopically lighter 65cu 0 15 relative to the isotopic composition of the charge 65cu 0 28 and 0 44 the results of this investigation demonstrate that the isotopic composition of cu in soils and grasses can be used to assess the intensity of contamination in areas where cu ores are mined and processed provided that the isotopic compositions of the ore processing products are different from the isotopic compositions of the uncontaminated soils and vegetation

deflation in the dustiest place on earth the bodele depression chad the bodele depression in chad is the largest single source of dust on earth because of a combination of strong near surface winds and a large reservoir of readily eroded and easily entrained low density sediment during the holocene and late pleistocene the bodele depression was host to a great lake palaeolake megachad that is now completely desiccated leaving the lake bed sediments exposed to deflation deflation in the bodele depression is revealed in erosional remnants of lake bed deposits exposed as yardangs on the lake floor erosional remnants indicate that locally up to 4 m of sediment has been removed by deflation optically stimulated luminescence dating shows that this occurred in less than 2400 years giving a rate of deflation of at least 1 6 mm yr 1 a range of other geomorphological features indicate that in some areas rates of deflation may be greater than or equal to 10 mm yr 1 deflation appears to be greatest in an arc around the northeastern margins of the lake basin where the diatomite deposits have been removed and revealed an underlying network of distributary channels preserved as gravel capped ridges the ridges which are part of an inverted topography are interpreted as deltaic distributary channels from an inland delta similar to the okavango delta examples of barchan dunes exist that were flooded by the palaeolake and which have now been exhumed from beneath layers of diatomite the distribution of extensive deflation around the northeasterly upwind end of the bodele depression probably results from a combination of large wind velocities an upwind source of abrasive sand and thinner diatomite deposits around the lake margin satellite image analysis shows that outcropping diatomite covers 24 049 km2 of the bodele depression furthermore the area from which diatomite has been removed by deflation is around 14 000 km2 combining this information with the ages and rates of deflation mentioned above indicates that some 61 000 km3 of diatomite has been eroded from the bodele depression during the past 1000 years

zinc isotope and transition element dynamics accompanying hydrozincite biomineralization in the rio naracauli sardinia italy abstract the rio naracauli in sw sardinia drains part of the ingurtosu zn pb mining district and contains extreme concentrations of dissolved zn at near neutral ph in the upper reaches of the stream ph alkalinity and zn concentrations are such that hydrozincite zn 5 co 3 2 oh 6 precipitates in a biologically mediated process facilitated by a microalga chlorella sp and a cyanobacterium scytonema sp values of 66 zn in water and solid samples ranged from 0 35 to 0 5 relative to the jmc 3 0749 lyon standard and closely follow a mass dependent fractionation line two composite samples of sphalerite the primary ore mineral in the ingurtosu deposits had an average 66 zn of 0 15 similar to sphalerite measured elsewhere in hydrothermal mineral deposits zinc isotope measurements of the stream water and the hydrozincite forming in the stream show a consistent preference for the heavy isotope 66 zn in the hydrozincite relative to 64 zn synthetic hydrozincites produced without added bacteria have 66 zn identical to the dissolved zn thus suggesting a biologically mediated mineralization process in rio naracauli the average fractionation hdz water is 0 35 the magnitude of which is consistent with other studies and suggests an extracellular mechanism of the biomineralization process zinc concentration and dissolved 66 zn steadily decrease in the reach of the stream where the biomineralization occurs the biomineralization process also leads to the sequestration of pb cu and ni in the hydrozincite lattice and the coeval precipitation of an amorphous cdco 3 solid prompting the suggestion that if optimized the biomineralization process might represent a feasible passive remediation strategy for streams with high zn and other metals and with near neutral ph

the genesis of the liancheng cu mo deposit in the lanping basin of sw china constraints from geology fluid inclusions and cu s h o isotopes abstract liancheng is an important cu mo deposit hosted by red beds in the mesozoic to cenozoic lanping basin located in the sanjiang tethyan orogen of sw china the deposit is fault controlled where it has been affected and enriched by four hydrothermal events indicated by four distinct sets of veins and their cross cutting relationships a detailed cu s h o isotopic study is reported here on the mineralization focusing on the source of the metals and fluid and on the mineralizing processes the first two hydrothermal events are characterised by co 2 and fluid rich inclusions with homogenisation temperatures of 124 446 c and salinities ranging from 0 4 to 24 6 wt nacl equiv the next two hydrothermal events are characterised by liquid rich fluid inclusions that homogenise at 145 256 c with salinities ranging from 1 4 to 22 9 wt nacl equiv the h o isotope values obtain from the fluid inclusions indicate that the first three hydrothermal events relate to mineralizing fluids derived from a metamorphic source but the last event includes a mixed metamorphic and meteoric source chalcopyrite tennantite and bornite from the deposit have 34 s values between 11 5 and 3 the 65 cu values for quartz cu sulfide mineralization associated with the second hydrothermal event range from 0 31 to 0 2 but carbonate cu sulfide mineralization associated with the third hydrothermal event ranges from 1 01 to 1 08 the combination of the cu and s isotopic values and field observations indicate that the controlling factors include structures the temperature of regional metamorphism and the ph of the mineralizing fluid the zation is therefore characteristic of an orogenic type deposit

zinc isotope variation in hydrothermal systems preliminary evidence from the irish midlands ore field little is known about the range or controls on the zinc isotope composition of terrestrial materials and no systematic studies have been carried out on ore forming systems we have obtained zinc isotope data from 19 sphalerite samples formed over a range of well constrained precipitation conditions from the irish zn pb ore field the results reveal variation in 66zn where 66zn 66zn 64zn sample 66zn 64zn standard 1 1000 from 0 17 to 1 33 per mil relative to the lyon jmc 3 0749l zinc standard this variation is significant compared to the external reproducibility 0 12 2 and the data show very good mass dependency with 67zn and 68zn values thus natural variations in the zinc isotope composition of these ore minerals can be resolved our results span the entire range of 66zn values measured on terrestrial geologic samples to date the data suggest that variations in the primary source rock composition or precipitation temperature are unlikely to be important controls on the zinc isotope composition of sphalerite in the ore field we suggest that the variation is most likely due to a kinetic fractionation involving the preferential incorporation of light zinc isotopes in sphalerite precipitated rapidly under disequilibrium conditions however we cannot rule out the possibility of mixing of zinc derived from two isotopically distinct sources the significant variation in zinc isotope compositions we have observed in the irish ore field confirms that such fractionations can provide new insights into mineralizing processes in the earth s crust

the depth dependency of planktonic benthic foraminiferal ratios constraints and applications abstract study of the ratio between planktonic and benthic foraminifera in a great number of areas shows that variation of this ratio with depth can be described using organic matter flux equations essentially the share of benthic foraminifera in the total association is inversely proportional to depth as is the amount of organic matter resulting from primary productivity reaching the sea bottom variation in the p b ratio from area to area appears to be strongly dependent on the amount of inbenthic living foraminifera if the ratios are corrected for this the regressions between the proportion of planktonic foraminifera p and depth appear to be near identical in the gulf of mexico the gulf of california the west coast of the usa and the adriatic sea this regression can be described by depth e 3 58718 0 03534 p a study of the behaviour of this function in nine cores from the adriatic upper quaternary reveals that the palaeodepth reconstructions are not influenced by fluctuations in productivity and temperature but that they are significantly influenced by redeposition of fine grained deposits

copper isotope ratios in magmatic and hydrothermal ore forming environments multi collector inductively coupled plasma mass spectrometry now provides for precise and accurate measurements of cu isotope ratios copper minerals prepared by direct dissolution with and without chromatographic purification yield identical cu isotope ratios within analytic precision of about 0 04x 1r cu isotope ratios have been measured for copper minerals from worldwide magmatic and hydrothermal copper deposits and for several weathered deposits natural variations in d65cu values relative to nbs976 range over 9x chalcopyrite samples from mafic intrusions lie within a narrow range of about 1 5x and most cluster tightly between 0 10xand 0 20x this range lies within the broader black smoker chalcopyrite and iron meteorite ranges and possibly represents a bulk mantle cu isotope ratio most values for hydrothermal native copper from the michigan native copper district also show a narrow range just larger than 0 1xand suggest a common homogeneous source for cu in this large hydrothermal system later copper sulfide and arsenide minerals from this district range to values more than 2x lower than native copper ratios for chalcopyrite and bornite from moderate to high temperature porphyry skarn and replacement deposits as a group and within individual deposits exhibit a broad range of values variations of nearly 1xare observed over distances on the order of 1 m in some cases these variations may result from multiple mineralization events or copper remobilization during retrograde or later hydrothermal activity fractionations between chalcopyrite and bornite where they occur in the same sample or in related samples cluster near 0 4x suggesting equilibrium cu isotope fractionation between them at moderate temperatures in addition weathering of hydrothermal copper minerals produces a wide range of values in secondary copper phases in the supergene environment cuprite typically has higher values than associated native copper therefore redox states appear to exert a significant control over fractionation at low temperatures significant questions remain to be answered before the source of copper in hydrothermal environments can be fully addressed source reservoir cu ratios need to be determined and chemical and physical factors that control cu isotope fractionation must be quantitatively defined d 2003 elsevier b v all rights reserved

did mangrove communities exist in the late cretaceous of the kristianstad basin sweden abstract previous inferences of oyster dominated communities occupying mangrove like depositional settings in the kristianstad basin sweden during the late early campanian are reassessed a significant percentage of oysters acutostrea incurva from the belemnellocamax mammillatus zone in bed 3 at asen bear indentations on their left valves indicating attachment to plant axes many of these axes bear morphological features characteristic of the distal subaerial portions of woody plant branches and appear to have been rafted into the marine environment rather than representing in situ mangrove stems and roots foraminiferal assemblages recovered from sediment within the oyster body cavities differ from modern mangrove community associations by the absence of siliceous agglutinated foraminifera the presence of diverse and relatively abundant lagenida relatively common triserial buliminida and a notable percentage of planktonic taxa chondrichthyan teeth assemblages from the same beds are similarly incompatible with the interpretation of a mangrove depositional environment based on comparisons with the distribution of related extant taxa apart from oyster shells and belemnite rostra these beds are notably depauperate in diversity and abundance of macroinvertebrate remains compared with coeval carbonate shoal and rocky shoreline assemblages from the same basin the collective palaeontological and sedimentological evidence favours an inner neritic sandy substrate setting but not nearshore or mangrove like depositional environment for the oyster rich bed 3 at asen the absence of mangrove like assemblages at asen is consistent with the development of modern mangrove ecosystems much later during the maastrichtian and cenozoic based on the global palynological record

new data on equilibrium iron isotope fractionation among sulfides constraints on mechanisms of sulfide formation in hydrothermal and igneous systems abstract fe s and cu reduced partition function ratios factors allow calculation of equilibrium isotope fractionation factors factors for chalcopyrite are calculated from experimental and theoretical partial phonon densities of state states kobayashi et al 2007 the fe factors for mackinawite are calculated from mossbauer spectroscopy data bertaut et al 1965 excellent agreement exists between fe factors for chalcopyrite calculated from the experimental and theoretical 57fe phonon densities of states supporting the reliability of the fe factors for chalcopyrite the 34s factor for chalcopyrite is consistent with experimental data on equilibrium sulfur isotope fractionation factors among sulfides and theoretical 34s factors except those recently calculated by a dft approach up to date experimental isotope exchange data on equilibrium fe isotope fractionation factors between minerals and aqueous fe were critically reevaluated in conjunction with fe factors for minerals and the following expressions for factors for aqueous fe2 and fe3 were obtained 10 3 ln fe aq 3 1 0063 10 6 t 2 t 273 k 10 3 ln fe aq 2 0 6537 10 6 t 2 t 273 k application of these new factors to fe and s isotope fractionation at seafloor hydrothermal conditions shows that chalcopyrite may precipitate in equilibrium with fe in hydrothermal fluids in contrast fe and s isotope compositions of pyrite are may not be controlled by isotope equilibration with fe in the hydrothermal fluid previously reported data on fe isotope fractionation between pyrite and chalcopyrite in intrusions in the grasberg igneous complex seem to be reasonable and are in general agreement with previous non isotopic estimates fe isotope fractionation between pyrite and chalcopyrite appear to reflect equilibrium in the intrusions of the grasberg igneous complex and fe isotopes may therefore be considered as a potential geothermometer the pyrite chalcopyrite fe isotope geothermometer however cannot be applied to the skarn facies of the grasberg complex where the initial fe isotope compositions may have been disturbed by subsequent processes related to skarn formation

cu isotopes in marine black shales record the great oxidation event the oxygenation of the atmosphere 2 45 2 32 billion years ago ga is one of the most significant geological events to have affected earth s redox history our understanding of the timing and processes surrounding this key transition is largely dependent on the development of redox sensitive proxies many of which remain unexplored here we report a shift from negative to positive copper isotopic compositions 65 cuerm ae633 in organic carbon rich shales spanning the period 2 66 2 08 ga we suggest that before 2 3 ga a muted oxidative supply of weathering derived copper enriched in 65 cu along with the preferential removal of 65 cu by iron oxides left seawater and marine biomass depleted in 65 cu but enriched in 63 cu as banded iron formation deposition waned and continentally sourced cu became more important biomass sampled a dissolved cu reservoir that was progressively less fractionated relative to the continental pool this evolution toward heavy 65 cu values coincides with a shift to negative sedimentary 56 fe values and increased marine sulfate after the great oxidation event goe and is traceable through phanerozoic shales to modern marine settings where marine dissolved and sedimentary 65 cu values are universally positive our finding of an important shift in sedimentary cu isotope compositions across the goe provides new insights into the precambrian marine cycling of this critical micronutrient and demonstrates the proxy potential for sedimentary cu isotope compositions in the study of biogeochemical cycles and oceanic redox balance in the past

fractionation of fe isotopes by soil microbes and organic acids small natural variations in fe isotopes have been attributed to biological cycling however without understanding the mechanisms of fractionation it is impossible to interpret such variations here we show that the d 56 fe of fe dissolved from a silicate soil mineral by siderophore producing bacteria is as much as 0 8 lighter than bulk fe in the mineral a smaller isotopic shift is observed for fe released abiotically by two chelates and the magnitude of the shift increases with affinity of the ligand for fe consistent with a kinetic isotope effect during hydrolysis of fe at the mineral surface fe dissolved abiotically without chelates shows no isotopic shift the d 56 fe of the exchange fraction on soil grains is also lighter by 0 6 1 than fe from both hornblende and iron oxyhydroxides the kinetic isotope effect is therefore preserved in open systems such as soils when recorded in the rock record fe isotopic fractionation could document fe transport by organic molecules or by microbes where such entities were present in the geologic past

kinetic iron stable isotope fractionation between iron ii and iii complexes in solution abstract iron stable isotope fractionation between tris 2 2 bipyridine iron ii fe ii bipy 3 2 and iron iii chloride complexes has been measured using plasma source mass spectrometry the experimental protocol involves complexing fe ii ion with 2 2 bipyridine in a fe ii fe iii chloride solution and then separating the fe ii and fe iii solution species in 6 m hcl on an anion exchange resin large isotopic variations of 57 fe and 56 fe are experimentally measured in the two separated solution fractions with isotopic fractionations increasing from fe ii fe iii 25 to 174 units for 57 fe 54 fe and 17 to 117 units for 56 fe 54 fe the increase in fractionations correlates with a decrease in the mole fraction of fe ii in the solution fe fe ii fe ii fe iii that results from the dissociation and breakdown of fe ii bipy 3 2 complex in 6 m hcl solution the data variations are mainly ascribed to a kinetic fractionation occurring during this dissociation reaction mass balance calculations assuming that a rayleigh law describes the overall isotopic trends suggest a kinetic fractionation of ca 1 010 100 units the magnitude of this fractionation is attributed to the rupturing of the strong covalent bonds between 2 2 bipyridine and fe ii ion the experimental data confirm that the coordination chemistry of iron exhibits a profound control on its isotopic behaviour and that kinetic fractionations may play an important role in its isotope geochemistry as was also found in the pioneering experimental studies of the sulphur isotopic system in solution

extent and isotopic composition of fe and mo release from two pennsylvania shales in the presence of organic ligands and bacteria abstract isotopic fractionation of fe and mo during weathering could contribute toward the isotopic signatures of river and ocean waters to investigate weathering processes batch experiments were carried out at ph 6 under oxygenated conditions to investigate the influence of a nitrogen fixing soil bacterium and organic ligands on the extent and isotopic signature of fe and mo release from two pennsylvania shales with different mineralogies an olive to grey shale rose hill and a black shale marcellus results of these studies showed that fe and mo were mainly released from illite chlorite vermiculite and fe oxides in the rhs and from pyrite in the ms dissolution rates of the clays estimated from our batch experiments are broadly consistent with published estimates release of fe from both shales was only enhanced by the hydroxamate siderophore desferrioxamine b dfam in contrast none of the treatments enhanced release of mo furthermore release of this metal was measurable only for the black shale for both shales fe that was released in the presence of dfam was depleted in 56 fe as compared to the bulk rock in contrast leachate solutions were enriched in the heavier mo isotope as compared to the bulk marcellus in all experiments with and without organic ligands and the bacterium the isotopic fractionations in fe and mo are broadly consistent with previously reported fractionation effects during sorption onto precipitating fe mn oxides the observed mo isotope fractionation is also consistent with all published studies of rivers i e riverine mo is enriched in heavy mo isotopes the observed fe isotope fractionation is likewise consistent with published studies for some rivers i e riverine fe is sometimes depleted in 56 fe our experimental results are consistent with sorption of fe and mo onto fe oxyhydr oxides during weathering as a possible explanation for the isotopic signatures of these metals in many rivers