application of zn isotopes in environmental impact assessment of zn pb metallurgical industries a mini review abstract zn and pb smelters are the major contributors to zn and pb emissions among all anthropogenic sources thus it is essential to understand zn isotopic variations within the context of metallurgical industries as well as its fractionation in different environments impacted by smelting activities this mini review outlines the current state of knowledge on zn isotopic fractionation during the high temperature roasting process in zn and pb refineries 66 zn values variations in air emissions slags and effluents from the smelters in comparison to the geogenic zn isotopic signature of ores formation and weathering in order to assess the environmental impact of these smelters the available and measured 66 zn values are compiled for smelter impacted natural water bodies groundwater stream and river water sediments lake and reservoir and soils peat bog soil inland soil finally the discussion is extended to the fractionation induced during numerous physicochemical reactions and transformations i e adsorption precipitation as well as both inorganic and organic surface complexation

relationships between heavy metals distribution and organic matter cycling in mangrove sediments conception bay new caledonia mangroves of new caledonia act as a buffer between a lagoon of more than 20 000 km2 and the island which suffers intense processes of erosion resulting from urbanization and natural resources exploitation this preliminary study aims at determining how heavy metals are distributed in mangrove sediments and pore waters in relationship with their organic content to reach our goal a series of 50 cm deep cores were collected in the mangrove of conception bay the various coring sites are representative of live forests avicennia marina rhizophora stylosa dead forest and intertidal unvegetated area the ranges of concentrations in sediments were the following mol g 1 cu 0 08 to 0 51 co 0 01 to 0 38 ni 0 03 to 3 55 cr 0 36 to 3 11 zn 0 68 to 2 36 mn 1 13 to 5 0 and fe 22 64 to 721 69 heavy metals distribution within sediments and pore water appear to result from diagenetic processes linked to om decomposition beneath the dead avicennia forest and in the unvegetated sediments the higher the organic content the higher the metal concentration in the solid phase beneath living mangrove stands despite a higher organic content as well as higher sulphur content heavy metals concentrations were not higher than those measured in the other sampling sites beneath these forests redox conditions were mainly controlled by the length of waterlogging and the activity of root system we suggest that because of the specificity of the avicennia root system and its position in the intertidal zone heavy metals are more bioavailable and potentially more mobile than beneath rhizophora stand

thermal response of a moving lithosphere over a mantle heat source the mid ocean bathymetric swells observed around some volcanic island chains can be modeled using the thermal conduction equations of an oceanic lithosphere moving over a heat source located at the base of the plate some previous studies of this problem have suggested that the heat source must lie well within the lithosphere in order to explain the observed bathymetry and surface heat flow these conclusions are based on an isothermal boundary condition at the base of the lithosphere but this choice requires that the heat source is maintained above this boundary and can actually lead to a flux of heat back into the mantle particularly in the vicinity of the heat source if the lower boundary is insulated insofar as the anomalous temperature field is concerned flux from the heat source back into the mantle is prevented resulting in a more rapid uplift of and in an increased heat flow across the seafloor previous solutions have considered only the steady state solutions whereas the present model also evaluates transient solutions for rapidly moving oceanic plates the transient effects can be neglected provided that the heat source has been active for at least 107 years and that the direction of motion and the intensity of the heat source have remained constant in this interval solutions with the heat source located near the base of the conductive layer of the conduction equations for heat flow bathymetry and geoid heights in the spatial domain reproduce the principal observational characteristics of the hawaiian swell at distances away from the immediate origin of the swell and this part of the swell can be used to estimate the thermal conduction model parameters the model does not wholly explain the observations near the origin and the mismatch may reflect a dynamic component in the support of the swell

early diagenesis in differing depositional environments the response of transition metals in pore water the cycling of fe mn ni co cu cr v and mo during early diagenesis was investigated in sediments from five different depositional environments in the california borderland dissolved o2 no3 no2 and so4 were also measured at each site to establish the position of redox boundaries pertinent to this study sites were chosen to allow the comparison of several parameters of potential importance to the cycling of these metals bottom water o2 concentration sediment redox conditions cycling of metal oxide carrier phases and the relative contribution of biogenic and terrigenous material to the detrital metal flux at 10 m oxygen and above the sequence of terminal electron acceptor utilization was typical of pelagic sediments differing only in scale under these conditions the recycling of mn oxides resulted in an enriched layer near the interface at bottom water 02 concentrations 5 m mn oxides are not recycled under these conditions fe oxides and so42 are important oxidants the depth of the zone of manganese oxidation with respect to the interface affects the efficiency of metal scavenging by manganese oxides trapping and recycling of ni and co with mn oxides results in remobilization from reducing sediments and enrichment in oxic sediments scavenging of these metals is favored by a deep oxic zone in the sediments in contrast cr v and mo appear to be transported to the sediments as reduced species and are released from the sediments by oxidation the source of the reduced species is assumed to be biogenic material the accumulation of these metals is favored by reducing conditions in the sediments cu is enriched in the sediments by transport with detrital biogenic material followed by adsorption onto sediment solids cu is released at the interface and rapidly removed onto the solids at all sites except the one pelagic site at the base of the slope the magnitude of cu released in the slowly accumulating pelagic sediment exceeds the cu binding capacity of the solids resulting in pore water cu concentrations in excess of 100 nm in general metal cycling associated with the early diagenesis of sediments was observed to decouple transport processes from burial processes for the transition metals measured in this study

the estuarine geochemical reactivity of zn isotopes and its relevance for the biomonitoring of anthropogenic zn and cd contaminations from metallurgical activities example of the gironde fluvial estuarine system france abstract zinc stable isotopes measurements by mc icp ms validated by laboratory intercalibrations were performed on wild oysters suspended particles and filtered river estuarine water samples to provide new constraints for the use of zn isotopes as environmental tracers the samples selected were representative of the long range 400 km transport of metal zn cd etc contamination from former zn refining activities at decazeville i e 66 zn 1 and its phasing out recorded during 30 years in wild oysters from the gironde estuary mouth rno rocch sample bank the study also addresses additional anthropogenic sources urban and viticulture and focuses on geochemical reactivity of zn in the turbidity gradient and the maximum turbidity zone mtz of the fluvial gironde estuary in this area dissolved zn showed a strong removal onto suspended particulate matter spm and progressive enrichment in heavy isotopes with increasing spm concentrations varying from 66 zn 0 02 at 2 mg l to 0 90 at 1310 mg l these signatures were attributed to kinetically driven adsorption due to strongly increasing sorption sites in the turbidity gradient and mtz of the estuary oysters from the estuary mouth contaminated sediments from the lot river and spm entering the estuary showed parallel historical evolutions 1979 2010 for zn cd ratios but not for 66 zn values oysters had signatures varying from 66 zn 1 43 in 1983 to 1 18 in 2010 and were offset by 66 zn 0 6 0 7 compared to past 1988 and present spm from the salinity gradient isotopic signatures in river borne particles entering the gironde estuary under contrasting freshwater discharge regimes during 2003 2011 showed similar values 66 zn 0 35 0 03 1sd n 15 i e they were neither related to former metal refining activities at least for the past decade nor clearly affected by other anthropogenic sources therefore the zn isotopic signatures in gironde oysters reflect the geochemical reactivity of zn in the estuary rather than signatures of past metallurgical contaminations in the watershed as recorded in contaminated river sediments the study also shows that the isotopic composition of zn is strongly fractionated by its geochemical reactivity in the gironde estuary representative of meso macrotidal estuarine systems

atmospheric deposition and isotope biogeochemistry of zinc in ombrotrophic peat abstract zinc isotope ratios were measured in the top sections of dated ombrotrophic peat cores in finland to investigate their potential as proxies for atmospheric sources and to constrain post depositional processes affecting the geochemical record the peat deposits were located in hietajarvi a background site well away from any point pollution source and representing background conditions in outokumpu next to a mining site and in harjavalta next to a smelter measured total concentrations calculated excess concentrations and mass balance considerations suggest that zinc is subjected to important biogeochemical cycling within the peat significant isotopic variability was found in all three peat bogs with heavier zinc in the deeper and lighter zinc in the upper sections isotope ratios and concentrations correlated in the two peats located next to dominant point sources i e the smelting and mining site suggesting that zinc isotopes trace pollution sources concentration and isotope peaks were offset from the period of mining and smelting activity supporting migration of zinc down the profile the 66znjmc where 66zn 66zn 64zn sample 66zn 64zn jmc standard 1 103 of the top section sample at the remote hietajarvi site was 0 9 and we suggest this represents the regional background isotope signature of atmospheric zinc the deeper sections of the peat cores show isotopically heavier zinc than any potential atmospheric source indicating that post depositional processes affected the isotopic records the large variations encountered up to 1 05 for 66zn and rayleigh modelling imply that multiple fractionation of zinc during diagenetic alterations occurs and nutrient recycling alone cannot explain the fractionation pattern we propose that zinc isotopes are amenable to identify different atmospheric zinc sources including zinc derived from anthropogenic activities such as mining and smelting but multiple biogeochemical processes seriously affect the record and they need to be evaluated and assessed carefully if zinc isotopes are used in terrestrial paleorecords

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

volatilization induced by impacts recorded in zn isotope composition of ureilites ureilites are ultramafic achondrites formed by igneous processes early in the history of the solar system ureilites are heavily depleted in volatile elements probably by evaporation at the surface of the ureilite parent body however the moderately volatile element zn is an exception and its abundance is similar to cl volatilization can fractionate isotopes in a mass dependent manner therefore comparing the isotope composition of volatile elements in ureilites may better constrain the physical conditions during ureilite formation and the mechanism of origin of the variation of zn content for this study we measured the zn isotopic composition of 11 ureilites with a large range of zn content the elemental abundance of zn is negatively correlated with delta zn 66 which may reflect that isotopic fractionation occurred by evaporation during the heating event on the ureilite parent body simple rayleigh distillation predicts isotopic fractionations much larger than what is actually observed therefore such a model cannot account for the observed zn isotope fractionation in ureilites we propose that the observed isotopic fractionation can be produced by evaporation in a diffusion limited regime in addition the isotopic composition of zn is shown to be correlated with the shock grade of the ureilites this may indicate that the heating events responsible for the depletion in light isotopes in some ureilites were impacts c 2010 elsevier b v all rights reserved

tracing of anthropogenic zinc sources in coastal environments using stable isotope composition abstract the use of zinc isotopes to trace anthropogenic sources in coastal areas has been tested in this study we determined the stable isotopic composition of zinc in sediment cores suspended particulate matter spm and rocks collected at the sepetiba bay southeastern brazil an estuarine lagoon heavily impacted by metallurgic activities these isotopic signatures were compared with those from willemite ore which represent the main mineral refined by the major industrial source of zinc the aim was to test if this tracer system enables to identify sources and sinks of anthropogenic zinc and to reconstruct the temporal and spatial evolution of zinc contamination the zinc isotopic compositions expressed using the 66zn notation relative to the jmc 3 0749 l solution showed significant variations in the sediment cores the spm and willemite ore minerals ranging between 0 01 and 1 15 spatial and temporal analysis of sediments samples fit well in a model of mixing involving three main end members i terrestrial background 66znjmc 0 28 0 12 2 ii marine detrital material 66znjmc 0 45 0 03 2 and iii a major anthropogenic source associated with electroplating wastes released into the bay 66znjmc 0 86 0 15 2 sediment cores collected in the mud flats showed high correlation between 66zn and zinc enrichment factors suggesting good preservation of the isotopic records of natural and anthropogenic sources the sediment core sampled from a mangrove wetland located in a zone impacted by the metallurgy presented levels of zinc up to 4 sediment dry weight and preserved the isotopic signatures of electroplating wastes despite evidences that post depositional processes slightly changed the isotopic signatures in some layers from this core toward heavier 66znjmc values above 1 0 a two component mixing model suggests contributions of this major anthropogenic zn source up to nearly 80 during periods of electroplating activities our work suggests that zn isotope compositions of sediments are reliable tracers of anthropogenic sources and therefore can be useful to improve environmental monitoring efforts in coastal systems

reviewing the configuration and extent of the midcontinent rift system abstract uncertainty exists in the configuration and extent of the midcontinent rift system mrs because of deficiencies in geophysical data and limited information from outcrops and basement drill holes additional ambiguity is caused by misunderstanding the definition of continental rifts six principal problematic regions in mapping the mrs are described gravity and magnetic data supported by drill hole and seismic reflection data show that the eastern lake superior rift segment of the mrs continues south from lake superior and connects to a much narrower rift in northern lake michigan the eastern margin of this transition is ill defined because of the lack of definitive anomalies and supporting seismic and drill hole data but is interpreted to occur near the u s canada border the rift segment in southeastern michigan intersects the grenville front and likely continues eastwards in modified form to near the boundary with canada cross cutting gravity and magnetic signatures may reflect grenvillian overthrusts near the terminus of the mrs in michigan the proposed southerly extensions of both branches of the rift system into oklahoma and ohio are based primarily on positive gravity anomalies but neither postulated extension appears to be associated with rifted troughs rather the gravity anomalies of the western branch are related to intrusive mafic rocks and those of the eastern branch are most likely related to deep crustal metamorphic rocks thrust into juxtaposition with less dense crust by grenville orogenesis recent paleomagnetic investigations in conjunction with high resolution radiometric dating imply that the mrs developed during the rapid southward movement of laurentia during a quiescent period along its eastern continental margin massive magmatic activity accompanying the rifting was likely due to rising mantle material that was displaced by subducted lithosphere along the southern margin the heated crust was made more ductile fostering rifting due to extensional stresses the nipigon embayment remains as a possible candidate for an early third branch of the mrs but current evidence is insufficient to include the fort wayne rift as part of the mrs future studies of the mrs would be well served by new age dating and high resolution seismic studies of the lithosphere

a cocorp deep reflection profile across the buried reelfoot rift south central united states abstract a cocorp deep reflection survey across the northern mississippi embayment reveals essential features of the late precambrian early paleozoic reelfoot rift stratified reflections delineating the sedimentary fill of the rift basin are of variable thickness the base ranging from 2 0 to a maximum of 3 5 s twt 4 to 8 km depth in contrast the base of phanerozoic the sedimentary section immediately east of the rift is at 1 4 s 2 8 km depth correlation with a basement penetrating well indicates that the base of the upper cretaceous holocene mississippi embayment supergroup base of the cambrian ordovician knox group and the lower upper cambrian bonneterre formation are basin wide seismic stratigraphic markers clastic sedimentary strata of the lamotte formation which immediately overlie precambrian basement show clear angular discordance with the overlying subhorizontal bonneterre formation indicating that the base of the bonneterre marks the transition from active extension to passive subsidence within the reelfoot rift palinspastic restoration of the basement suggests relatively modest extension associated with rift formation 17 the blytheville arch an axial antiformal feature as well as a number of lesser structures indicative of multiple episodes of fault reactivation are also evident on the cocorp profile the crystalline basement beneath the reelfoot rift is relatively devoid of reflections down to 5 0 s 12 15 km depth beyond which it passes gradationally into a complexly reflective diffractive middle and lower crust the lower crust however does not exhibit the distinctly laminated character commonly observed in mesozoic cenozoic extensional provinces the crust mantle transition beneath the rift is characterized by a gradational downward cessation of crustal reflectivity at 12 13 s 40 km depth followed by an unreflective zone which in turn is followed by a distinct horizontal reflection at 14 5 s the latter is not observed on existing profiles outside the rift at present it is not possible to determine strictly whether the deep horizon represents moho or alternatively a discrete feature sill within the uppermost mantle however its spatial association with the reelfoot rift suggests that the two are genetically related regional relations together with the existence of dipping fabric in the deep crust beneath the rift suggest the possibility that the reelfoot rift formed along the southern extension of the circa 1 ga grenville front

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

sediment origin and budget in sepetiba bay brazil an approach based on multielemental analysis sediment origin and transport were de termined in a shallow 447 km 2 coastal lagoon in brazil using the distribution of major elements in bottom and suspended sediments applying multi variate analysis the sum of normalized concentra tions of ti fe and al in sediments was selected to trace the terrigenous influence in bottom sedi ments whereas ca si and k were used as indica tors of marine influence sepetiba bay bottom sedi ments are dominated by up to 80 terrigenous in puts the open bay sediments are enriched in p mg k and ca because of the intensive water co lumn primary production the inner bay forms an independent circulation cell with a predominance of terrigenous sediments the results suggest a long residence time for particles in the bay demon strated by the magnitude of resuspension flux com pared to the total sediment input to the bay

structure and tectonic evolution of the transitional region between the central appalachian foreland and interior cratonic basins abstract the transitional region between the central appalachian foreland basin and michigan and illinois interior cratonic basins is characterized by first and second order structures related to plate convergent processes at the laurentian plate margin the first order structures are the waverly and cincinnati arches believed to be forebulges associated with the taconic and alleghanian orogenies respectively the second order structures are basement faults that exhibit a protracted history of recurrent displacements first and second order structures are linked in that the basement faults have had a major effect in controlling the location and uplift history of the arches the waverly and cincinnati arches share many similarities that suggest a common process of arch development the waverly arch developed over the low density rocks in the central metasedimentary belt of the grenville province near its structural contact with the central gneiss belt uplift on the arch commenced during passive margin development in the cambrian but reached its maximum development at the end of the middle ordovician taconic orogeny reactivation of faults along the arch continued as late as the pennsylvanian the cincinnati arch as expressed in the precambrian basement surface is coincident with the underlying grenville front on a regional scale the front is a major crustal suture which served to localize and control the history of the cincinnati arch local deviations between the location of the arch and front are explained by the presence of proterozoic rift basins filled with low density sedimentary rocks by interactions between the developing appalachian michigan and illinois basins and by a northward decrease in alleghanian tectonic loading in a pattern similar to the waverly arch the cincinnati arch began its history with a period of regional uplift as early as the middle to late ordovician followed by maximum arch development in the pennsylvanian in response to the alleghanian orogeny neither arch showed significant migration following initial development as predicted by general models of forebulge development we attribute this to the effect of preexisting basement anisotropies such as lithotectonic boundaries which served to control the initial location of the forebulge and affect its subsequent history a third major arch the kankakee arch occurs in the western part of the transitional region and is oriented at right angles to the other arches unlike the waverly and cincinnati arches this arch owes its development to subsidence in the adjacent michigan and illinois basins rather than orogenic activity in the appalachians

pyritization of trace metals in anoxic marine sediments the pyritization of reactive trace elements in different anoxic marine sediments was investigated to determine the importance of factors such as h2s reactive fe pyrite content and salinity in controlling this process the areas studied included anoxic sulfidic sediments baffin bay a hypersaline coastal lagoon from texas and green canyon a hemipelagic oil seepage area anoxic nonsulfidic sediments with high sedimentation rates atchafalaya bay mississippi delta system hemipelagic anoxic nonsulfidic sediments with low sedimentation rates gulf of mexico shelf and slope and orca basin an euxinic hypersaline basin and organic rich marsh sediments atchafalaya bay results indicate that the degree of trace metal pyritization dtmp of all trace metals except cd increased with increasing degree of pyritization dop irrespective of the type of sedimentary environment involved however for as hg and mo the dtmpdop values were generally above the 1 1 ratio line whereas the transition metals co cu mn and ni displayed a close to linear increase in dtmp with dop and moderate incorporation into pyrite chromium and the class b metals pb and zn were also gradually incorporated into the pyrite phase but without reaching the dtmp levels exhibited by the transition metals cadmium was not incorporated to a significant extent these results are consistent with the chemical attributes of these different classes of trace elements availability of dissolved trace metals and organic matter content are apparently important factors controlling the incorporation of co cr cu and ni into pyrite in anoxicsulfidic fe poor and h2s rich environments

pyritization of trace metals in mangrove sediments the present study investigates the levels of mn zn ni and co pyritization in mangrove sediments along distinct sedimentary zones in enseada das gracas a lagoon type estuary located on the southeastern coast of brazil the coastal geology is characterized by intense interactions of trace metals forming pyrite minerals specific orders of dop degree of pyritization and dtmp degree of trace metal pyritization are shown supratidal flat mangrove forest mud flat distinct changes in content along the sediment profiles are noted where a supratidal flat presented low levels of dop and dtmp with little variance along the sedimentary depths the mangrove forest showed relatively high values of dop and dtmp in the lower depths while the mud flat showed the highest levels of dop and dtmp

redox stratification and heavy metal partitioning in avicennia dominated mangrove sediments a geochemical model abstract mangrove forest sediments can provide a sink for trace metals because the mangroves create a baffle that promotes the accumulation of fine grained organic matter rich sediment which is usually sulphidic due to the presence of sulphate reducing bacteria direct adsorption complexing with organic matter and the formation of insoluble sulphides all contribute to the trapping of metals the concentration and chemical speciation of the metals are influenced by the distribution of geochemically distinct horizons within the sediment in horizons with a ph 7 and an eh 100 mv oxidation horizons most metals are present as exchangeable or oxide bound species in most cores two oxidation and two reduction horizons can be recognised but dark mottles of low eh 100 mv sediment can be found around mangrove roots and burrows in the reduction horizons the depth to each horizon differs between cores and can change in response to seasonal shifts in the position of the water table a model is presented that accounts for the development of the oxidation and reduction horizons within the avicennia dominated mangrove forest sediment and describes the major controls on metal cycling within the sediment

crustal structure interpreted from magnetic anomalies this review discusses publications during the last quadrennium 1987 1990 that used aeromagnetic data marine magnetic data satellite magnetic data and rock magnetic and petrologic data to provide information on the sources of magnetic anomalies the publications reviewed reflect increased integration of rock magnetic property and petrologic studies with magnetic anomaly interpretation studies particularly in deep crustal magnetization exploration for hydrocarbons and inversion of marine magnetic anomalies interpretations of aeromagnetic data featuring image display techniques and using the horizontal gradient method for locating magnetization boundaries became standard

zinc isotope variations in deep sea carbonates from the eastern equatorial pacific over the last 175 ka the carbonate fraction of sediment core odp 849 leg 138 located in the eastern equatorial pacific mostly consisting of coccoliths was separated and analyzed for its zn isotopic composition the overall variation in zn isotopic composition as determined by multiple collector magnetic sector inductively coupled plasma mass spectrometry was found to be on the order of 1 expressed in 66zn where xzn xzn 64zn sample xzn 64zn standard 1 103 and x 66 67 or 68 over the last 175 ka the analytical precision was 0 04 and the overall reproducibility was usually better than 0 07 the zn isotopic composition signal exhibits several marked peaks and a high frequency variability a periodogram of the 66zn signal showed two periodicities of 35 2 and 21 2 ka we suggest that the latter is caused by the precession of the earth s axis of rotation the periodogram exhibits a minimum at 41 1 ka thus showing that the zn isotopic composition is independent of the obliquity in the eastern equatorial pacific the range of 66zn values observed for the carbonate fraction of odp 849 overlaps with the range observed for fe mn nodules in the world s oceans which suggests that seawater carbonate zn isotope fractionation is weak we therefore assume that most of the zn isotope variability is a result of the selective entrainment of the light isotopes by organic matter in the surface ocean the odp 849 66zn record seems to follow the changes in the insolation cycles changes in the late summer fall equatorial insolation modulate the intensity of the equatorial upwelling hence the mixing between deep and surface waters we propose that during decreased summer fall equatorial insolation when a steep thermocline can develop el nino like conditions the surface waters cannot be replenished by deep waters and become depleted in the lighter zn isotopes by biological activity thus resulting in the progressive increase of the 66zn values of the carbonate shells presumably in equilibrium with surface seawater

zinc isotopes in sphalerite from base metal deposits in the red dog district northern alaska analyses of sphalerite samples from shale hosted massive sulfide and stratigraphically underlying vein breccia deposits in the red dog district in northern alaska show a range of 66zn values from zero to 0 60 per mil the lowest values are observed in the vein breccia deposits and the stratigraphically overlying but structurally displaced shale hosted massive sulfide deposits show a systematic trend of increasing 66zn values from south to north main aqqaluk paalaaq anarraaq the 66zn values are inversely correlated with sphalerite fe mn ratio and also tend to be higher in low cu sphalerite consistent with precipitation of lower 66zn sphalerite closer to the principal hydrothermal fluid conduits the most likely control on isotopic variation is rayleigh fractionation during sulfide precipitation with lighter zinc isotopes preferentially incorporated in the earliest sphalerite to precipitate from ore fluids at deeper levels vein breccias and close to the principal fluid conduits in the orebodies followed by precipitation of sulfides with higher 66zn values in shallower and or more distal parts of the flow path there is no systematic variation among the paragenetic stages of sphalerite from a single deposit suggesting an isotopically homogeneous zinc source and consistent transport deposition conditions and or dissolution reprecipitation of earlier sphalerite without significant fractionation decoupled zn and s isotope compositions are best explained by mixing of separate metal and sulfur bearing fluids at the depositional site the results confirm that zn isotopes may be a useful tracer for distinguishing between the central and distal parts of large hydrothermal systems as previously suggested and could therefore be of use in exploration

abundance of zinc isotopes as a marine biogeochemical tracer 1 the zn isotopic compositions of ferromanganese nodules sediment trap samples sediments and organic reference samples have been analyzed by multiple collector inductively coupled plasma mass spectrometry icp ms the range of isotopic variations 1 for 66zn 64zn is significant with respect to the analytical precision 0 04 at the 95 confidence level marine argillaceous sediments show rather constant values consistent with those of continental shales and loess and with the value of a basalt from reunion island we infer that the depletion of the light zn isotopes in marine particles and in ferromanganese nodules presumably equilibrated with seawater results from biological activity in the upper water column the 66zn values of sediment trap samples collected near the upwelling off the coast of mauritania central atlantic show a seasonal isotopic fluctuation consistent with biological pumping during the high productivity period higher values of 66zn in nodules appear to be associated with the amplitude of seasonal variations rather than with the mean values of the biological productivity

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

the isotopic composition of some common forms of anthropogenic zinc abstract anthropogenic sources account for much of the zinc zn in the environment constraining the isotopic composition of anthropogenic zn is therefore essential to understanding the environmental biogeochemical cycling of zn isotopes this study examines the isotopic variability in several different categories of anthropogenic zn pure zn metal and zn dust are the raw materials used in many zn containing products we have measured 66 zn for zn dust purified by thermal distillation electrochemically purified zn metal and us pennies which are made from the most common grade of zn metal special high grade zn in galvanized steel and electroplated hardware was studied because this is a common use of zn and zn in these products may be easily released into the environment through corrosion vitamins were studied because they are more highly purified than typical zn metals and are made from processed chemical compounds such as zn oxide or zn gluconate the isotopic composition of samples measured in this study are as follows reported as 66 zn compared to lyon jmc zn laboratory standards seven samples 9 15 to 0 17 zn metal dust purified by thermal distillation three samples 0 09 to 0 19 zn metal shot purified by electrochemically one sample 0 22 special high grade zn as represented in us pennies six samples 0 14 to 0 31 galvanized steel three samples 0 12 to 0 58 electroplated hardware three samples 0 56 to 0 20 and health products five samples 0 09 to 0 24 based on these results we suggest that the isotopic composition of common anthropogenic zn products ranges from 0 1 to 0 3 all samples studied here had 66 zn values within this range except four laboratory standards all electroplated hardware samples and a single galvanized steel sample the isotopic range for common anthropogenic zn is much smaller than the total 66 zn range found in zn ore field hydrothermal samples demonstrating the effects of zn isotope homogenization during ore processing and purification laboratory standards may have anomalously light 66 zn values because they undergo extra purification steps and zn recovery during these steps is not quantitative electroplated hardware was also isotopically light consistent with previous studies showing that lighter isotopes are electroplated more quickly than heavy isotopes our results suggest that isotopically heavy zn may be incorporated into the waste stream during the electroplating process by defining the range of 66 zn values that is typical for some common zn products and discovering some kinds of products that fall outside this range we will be better able to use zn isotopes to trace different anthropogenic zn sources

zn isotope evidence for immediate resumption of primary productivity after snowball earth the ediacaran period began with the deglaciation of the ca 635 ma marinoan snowball earth and the deposition of cap dolostones on continental shelves worldwide during post glacial sea level rise these carbonates sharply overlie glacial sediments deposited at low paleolatitudes and preserve negative carbon isotope excursions the snowball earth hypothesis invokes an almost complete cessation of primary productivity in the surface ocean because assimilatory uptake of zn appears to fractionate its isotopes zn isotope ratios measured in carbonate precipitated in the surface ocean should track fluctuations in primary productivity here we report the first zn isotopic data together with carbon and oxygen isotopic profiles from a neoproterozoic cap dolostone the nuccaleena formation in the flinders ranges south australia we interpret the zn isotopic data in terms of a two stage evolution of the deglacial ocean slightly 66 zn enriched values at the base of the cap dolostone indicate immediate resumption of the biological pump upon melting of the surface ocean but this signal was diluted by intense surface runoff that drove 66 zn 66 zn 64 zn versus the jmc lyon reference values down to the composition of continentally derived zn a subsequent rise in 66 zn records a vigorous increase in primary production and export from a nutrient laden surface ocean

zinc stable isotopes in seafloor hydrothermal vent fluids and chimneys many of the heaviest and lightest natural zinc zn isotope ratios have been discovered in hydrothermal ore deposits however the processes responsible for fractionating zn isotopes in hydrothermal systems are poorly understood in order to better assess the total range of zn isotopes in hydrothermal systems and to understand the factors which are responsible for this isotopic fractionation we have measured zn isotopes in seafloor hydrothermal fluids from numerous vents at 9 10 n and 21 n on the east pacific rise epr the tag hydrothermal field on the mid atlantic ridge and in the guaymas basin fluid 66zn values measured at these sites range from 0 00 to 1 04 of the many physical and chemical parameters examined only temperature was found to correlate with fluid 66zn values lower temperature fluids 250 c had both heavier and more variable 66zn values compared to higher temperature fluids from the same hydrothermal fields we suggest that subsurface cooling of hydrothermal fluids leads to precipitation of isotopically light sphalerite zn sulfide and that this process is a primary cause of zn isotope variation in hydrothermal fluids thermodynamic calculations carried out to determine saturation state of sphalerite in the vent fluids support this hypothesis with isotopically heaviest zn found in fluids that were calculated to be saturated with respect to sphalerite we have also measured zn isotopes in chimney sulfides recovered from a high temperature 383 c and a low temperature 203 c vent at 9 10 n on the epr and in both cases found that the 66zn of chimney minerals was lighter or similar to the fluid 66zn the first measurements of zn isotopes in hydrothermal fluids have revealed large variations in hydrothermal fluid 66zn and suggest that subsurface zn sulfide precipitation is a primary factor in causing variations in fluid 66zn by understanding how chemical processes that occur beneath the seafloor affect hydrothermal fluid 66zn zn isotopes may be used as a tracer for studying hydrothermal processes

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

widespread buried precambrian layered sequences in the u s mid continent evidence for large proterozoic depositional basins large regions of the north american mid continent are underlain by precambrian layered rocks buried beneath phanerozoic sedimentary strata south of the wichita mountains published seismic reflection profiles show a precambrian layered assemblage extending for at least 40 km in both the north south and east west directions and industry data show that it may continue 150 km to the southeast seismic reflection data in the illinois region show a precambrian layered assemblage extending 320 km in an east west direction and 200 km in a north south direction in both cases the layered rocks are as much as 12 km thick apparent sequence boundaries onlap downlap within these assemblages suggest they are parts of large depositional basins with diffractions and dipping strat due to faulting the layered sequences correlate with regions of relatively long wavelength and low amplitude magnetic anomalies the extent of this magnetic signature suggests that about 200 000 km 2 of illinois indiana and western ohio about 50 000 km 2 of southernmost oklahoma and north central texas and about 32 000 km 2 of southern missouri and northern arkansas may be underlain by similar precambrian strata drill holes indicate that the top of the mid continent precambrian basement is composed largely of silicic igneous rocks such material may comprise a large part of the layered sequences alternatively these igneous rocks could be intermixed with or underlain by nonvolcanic meta sedimentary strata the strong reflectivity of some layers suggest that minor mafic flows and or sills may also be present analysis of u pb and nd sm isotopes within the granites and rhyolites imply that the layered sequences postdate crustal formation at 1 7 2 0 ga and predate or are contemporaneous with the 1 3 1 5 ga crystallization ages of the granites and rhyolites though these layered rocks have a spatial association with igneous rocks and thus have likely been metamorphosed the possibility tha they contain precambrian hydrocarbons that escaped heating is as yet untested

strontium lead and zinc isotopes in marine cores as tracers of sedimentary provenance a case study around taiwan orogen abstract the active collision zone around taiwan orogen receives a variety of sedimentary inputs including terrigenous flux from taiwan and chinese rivers oceanic currents and atmospheric dust in order to determine the present day respective contributions of these different sources we analysed the pb and sr isotopic compositions of late quaternary sediments accumulated offshore east taiwan samples from the taiwan coastal range andesites sandstones conglomerate and peinan river terraces and suspended loads have also been analysed to constrain the mean taiwan isotopic signature mixing lines between the different sources of material indicate that the core located in the okinawa trough represents a mixture of about 60 of taiwan 30 of chinese loess and 10 of yangtze river contributions the southernmost core located close to luzon arc is influenced by taiwan 60 and volcanic material 40 the sr and pb isotopic compositions of samples cored in the manila trench and in the huatung basin are strongly influenced by the taiwan signature while the ryukyu trench core samples point to significant but variable contributions of chinese loess and yangtze river this work also reports zn isotopic variations in the silicate fraction of these marine core samples the overall variation in zn isotopic compositions expressed as 66zn is greater than 0 3 per mil for an analytical precision of 0 05 the zn isotopic signal for most of the marine core samples is similar to the literature data measured on sedimentary material except for the manila trench core samples and the older sample from the huatung basin they present values heavier by 0 2 0 3 close to those obtained on all taiwan rocks and peinan river particulates these results show 1 the particular characteristics of taiwan zn isotopic compositions on a large scale and 2 the possible use of zn isotopes as a tracer of material sources

possible extension of the midcontinent rift in west texas and eastern new mexico the midcontinent rift system forms one of the most prominent gravity features in north america the recognized geophysical anomaly extends in an arc from southern oklahoma to lake superior and then into southern michigan the midcontinent rift system was active between 1185 1010 ma as indicated in the lake superior region by age determinations on intrusive igneous rocks we suggest that the period of formation of the midcontinent rift was also a time of extensive igneous activity in texas and new mexico this activity is represented by intrusions beneath the central basin platform texas and new mexico intrusions which crop out at the pajarito mountain in the sacramento mountains new mexico a basaltic debris flow in the franklin mountains texas basalt flows at van horn texas and the crosbyton geophysical anomaly east of lubbock texas these bodies and other bodies located by geophysical anomalies and wells drilled into mafic precambrian rocks may be related to the midcontinent rift system

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

use of isotope ratios to assess sources of pb and zn dispersed in the environment during mining and ore processing within the orlovka spokoinoe mining site russia element concentrations element ratios and pb and zn isotope data are reported for different geologic samples barren and ore bearing granites and host rocks technogenic products ore concentrates and tailings and biologic samples lichens and birch leaves from the orlovka spokoinoe mining district eastern transbaikalia russia with the aim to trace the sources of pb and zn at a local level within the mining site lichens and birch leaves were used as receptors of contamination within the mining site pb zr and zn zr values indicated pb and zn enrichment relative to host rocks zn isotope data of 15 geologic and 11 lichen samples showed different zn isotopic signatures with the total range for the geologic suite of 0 4 to 1 2 and for lichens of 0 4 to 1 4 in 66zn relative to lyon jmc zn standard the source of isotopically heavy zn within the orlovka spokoinoe mining site could be potentially associated with long range atmospheric aerosols that also contributed pb to the studied mining site our results demonstrated that zn isotopes might be used as new tools for zn source assessment

aeromagnetic and gravity anomaly constraints on the crustal geology of ohio the u s geological survey and the ohio geological survey recently compiled aero magnetic anomaly maps and revised gravity anomaly data for crustal studies of ohio updated structural and lithologic maps of the precambrian basement surface provide additional constraints to limit interpretational ambiguities of the geopotential anomaly data the combined modeling of five east west gravity and magnetic anomaly profiles supports a generalized crustal model for ohio involving a lower zone of intermediate composition a more felsic and relatively homogeneous middle zone and an upper zone consisting of intrusive and extrusive igneous rock in the western third of the state and medium grade grenville metamorphic rocks to the east modeling of the geopotential field anomalies indicates the presence of large dense lower crustal bodies in western and south central ohio that may be related to a paleo rift system large possibly anorthositic masses in southern ohio post tectonic granitization in northwestern ohio and a volcanic source for igneous rocks in southwestern ohio may also be interpreted from the combined anomaly analysis