ophiolite melange zone records exhumation in a fossil subduction channel recent models propose that the exhumation of high pressure rocks occurs by means of return flow inside a low viscosity channel of serpentinite situated between the plates to test this hypothesis we investigated a serpentinite melange in the western alps which contains exotic mafic and metasedimentary tectonic blocks recording heterogeneous metamorphic evolutions and variable high pressure ages the peak metamorphic conditions range from eclogite to garnet blueschist facies the structural evidence and the pressure temperature paths of the different blocks suggest coupling between blocks and matrix at least in the blue schist facies 39 ar 40 ar dating indicates eclogite facies peak at ca 43 ma and blueschist facies peak at ca 43 and 40 ma in different blocks respectively these data point to diachronous metamorphic paths resulting from independent tectonic evolutions of the different slices we therefore propose that this melange formed during exhumation of subducted rocks equilibrated at different depths inside a subduction channel this mechanism can be extended to other serpentinite melanges in the alps and other orogens e g the cyclades the coast ranges of california for which a growing heterogeneity in the timing of metamorphic equilibration and of pressure temperature paths can be expected with further investigations

a study of oxygen isotopic fractionation during bio induced calcite precipitation in eutrophic baldeggersee switzerland in order to better understand environmental factors controlling oxygen isotope shifts in autochthonous lacustrine carbonate sequences we undertook an extensive one year study march 1995 to february 1996 of water column chemistry and daily sediment trap material from a small lake in central switzerland comparisons between calculated equilibrium isotope values using the fractionation equation of friedman and o neil 1977 and measured oxygen isotope ratios of calcite in the sediment traps reveal that oxygen isotopic values of autochthonous calcite 18o are in isotopic equilibrium with ambient water during most of the spring and summer when the majority of the calcite precipitates in contrast small amounts of calcite precipitated in early spring and again in late autumn are isotopically depleted in 18o relative to the calculated equilibrium values by as much as 0 8 this seasonally occurring apparent isotopic nonequilibrium is associated with times of high phosphorous concentrations elevated ph 8 6 and increased co32 50 mol l in the surface waters the resulting weighted average 18o value for the studied period is 9 6 compared with a calculated equilibrium 18o value of 9 4 these data convincingly demonstrate that 18o of calcite are for the most part a very reliable proxy for temperature and 18o of the water

effect of calcite precipitation on stable strontium isotopic compositions insights from riverine and pool waters in a karst cave abstract radiogenic and stable sr isotope ratios 87 sr 86 sr 88 86 sr serve as potential tracers for evaluation of weathering sources and associated physicochemical processes in terrestrial environments despite carbonate weathering sourcing two thirds of the total continental sr flux to the ocean however few attempts have been aimed at studying stable sr isotope fractionation in carbonate dominated aquifers here we present a monthly resolved monitoring dataset of major ion concentrations and sr isotope ratios for karst riverine and pool waters at the luofang cave in the central china to understand the potential controls responsible for water 88 86 sr compositions under various climatic conditions with the exception of some pool waters in the dry period significantly heavier 88 86 sr were detected in the riverine and pool waters 0 20 to 0 42 compared to bedrock 88 86 sr 0 24 to 0 28 which can t be interpreted solely by lithology a sequential leaching experiment of the local soils suggests limited stable sr isotope fractionation during incongruent silicate mineral dissolution local plant utilization and biological activity in the soil overlying the cave are possible processes for causing the observed heavier 88 86 sr in cave water however air partial pressure of co 2 in cave monitoring water ph and sr isotopic mass balance calculations suggest that plant utilization is unlikely to be the primary control on the heavier water 88 86 sr on the other hand significant stable sr isotope fractionation was found between the cave dripping waters and calcite precipitates and the 88 86 sr car aq was estimated to be 0 15 0 07 2sd precipitation of secondary calcites might be a potential process responsible for the heavier 88 86 sr in the waters the negative correlation between 88 86 sr and sr na ratios in the cave waters is consistent with a scenario of preferential incorporation of the light sr isotope by solid phase furthermore by combining the calcite saturation states and water ph our results suggest that calcite precipitation is the most likely process controlling 88 86 sr compositions in cave water we demonstrate that secondary calcite precipitation in carbonate dominated catchments could be important in controlling the riverine water 88 86 sr compositions

stable sr isotope sr ca mg ca li ca and mg li ratios in the scleractinian cold water coral lophelia pertusa the aragonitic skeletons of scleractinian cold water corals can serve as valuable archives in paleoceanographic studies the potential of 88 86sr sr ca mg ca li ca and mg li ratios of the cold water coral lophelia pertusa to record intermediate water mass properties has been investigated here we used samples from several locations along the european continental margin spanning a large temperature range from 6 to 14 c stable strontium isotope measurements were carried out with the recently developed double spike tims technique and our results differ from those obtained with less precise methods in contrast to the strong positive relationship with temperature of previous studies our results suggest that 88 86sr measured in scleractinian cold water corals is not controlled by seawater temperature but reflects the sr isotopic composition of seawater with an offset of 88 86sr 0 196 as found in previous studies the elemental ratios sr ca li ca and mg li measured in corals are significantly related to water temperature and do not correlate with salinity moreover sr ca ratios in l pertusa display the expected inverse correlation with temperature however the variance in the sr ca data severely limits the accuracy of paleotemperature estimates the li ca and mg ca ratios reveal other influences besides temperature such as ph and or growth or calcification rate however corresponding mg li ratios in l pertusa are more tightly related to temperature as they remove these secondary effects in particular the mg li ratio in l pertusa may serve as a new promising paleotemperature proxy for intermediate water masses our dataset represents the most extensive geochemical examination of l pertusa to date revealing a temperature sensitivity of 0 015 mol mmol c for mg li however using this temperature dependence and the precision of 5 3 2sd only temperature variations larger than 1 5 c can be resolved with 95 confidence

high salinity fluid inclusions formed from recycled seawater in deeply subducted alpine serpentinite abstract the origin of high pressure brines has been investigated in the erro tobbio peridotite western alps a mantle slice that was exposed to the seafloor of the mesozoic ligurian piedmontese tethys and was later involved in alpine subduction hydrothermal alteration by seawater derived fluids led to replacement of the mantle assemblage by cl bearing serpentine 0 35 wt cl brucite 0 2 wt cl and alkali bearing phyllosilicates 0 2 wt cl 0 2 0 55 wt na2o 1 5 wt k2o relics of these hydrous phases occur in olivine titanian clinohumite antigorite assemblages formed at 2 5 gpa and 550 600 c during partial devolatilization and veining of the hydrothermally altered peridotite the high pressure phases lack chlorine and alkalis and are coeval with fluid inclusions trapped in the syn eclogitic veins the inclusions are salt saturated and contain up to 50 wt cl na k mg and fe high fluid chlorinity was probably achieved during rehydration of relict mantle minerals and deposition of hydrous phases in the veins the data presented suggest that the seafloor hydrothermal signature was inherited by the eclogitic fluid due to partitioning of chlorine and alkalis into the fluid phase the presence of salty brines in eclogitized hydrous peridotites can indicate deep recycling of seawater derived fluids hydrous ultramafic systems can therefore act as large scale carriers of seawater into the mantle

aragonite pseudomorphs in high pressure marbles of syros greece numerous rod shaped calcite crystals occur in the blueschist to eclogite facies marbles of syros greece the rods show a shape preferred orientation and the long axes of the rods are oriented at a large angle to foliation the crystals also have a crystallographic preferred orientation calcite c axes are oriented parallel to the long axes of the rods based on their chemical composition shape and occurrence in high pressure marbles these calcite crystals are interpreted as topotactic pseudomorphs after aragonite that developed a crystallographic preferred orientation during peak metamorphism this interpretation is consistent with deformation of aragonite by dislocation creep which has been observed in laboratory experiments but has not been previously reported on the basis of field evidence subsequent to the high pressure deformation of the aragonite marbles the aragonite recrystallized statically into coarse rod shaped crystals maintaining the crystallographic orientation developed during deformation during later exhumation aragonite reverted to calcite and the marbles experienced little further deformation at least in the pseudomorph rich layers some shearing of pseudomorph bearing marble layers did occur and is indicated by twinning of calcite and by a variable inclination of the pseudomorphs relative to foliation

paleoclimate of the past 4000 years at lake turkana kenya based on the isotopic composition of authigenic calcite abstract authigenic calcite was analyzed for 13 c and 18 o in a 12 m long core from lake turkana that spans the last 4200 yr the 18 o record is interpreted to reflect lake level history and indicates high stands prior to 4000 yr b p from 1800 to 2000 yr b p and within the last century this coincides better with the history of lake level change reported for other lakes in africa than did the previous lake level curve for lake turkana based on 14 c dates of exposed shoreline deposits the 13 c curve roughly parallels the 18 o curve and may reflect the influence of the omo river plume both of the isotope records are strongly cyclic with periodicites common to both at 80 120 150 and 225 yr other somewhat longer periodicites are nearly equal in the two records and there is close agreement with previously published cycles based on carbonate and lamination thickness analyses in the same turkana core

88sr 86sr fractionation in inorganic aragonite and in corals conflicting results have been reported for the stable sr isotope fractionation specifically with respect to the influence of temperature in an experimental study we have investigated the stable sr isotope systematics for inorganically precipitated and biogenic coral aragonite natural and laboratory cultured inorganic aragonite precipitation experiments were performed from natural seawater using the co2 diffusion technique the experiments were performed at different temperatures and different carbonate ion concentrations 88sr 86sr of the inorganic aragonite precipitated in the experiments are 0 2 lighter than seawater but showed no correlation to the water temperature or to co32 concentration similar observations are made in different coral species cladocora caespitosa porites sp and acropora sp with identical fractionation from the bulk solution and no correlation to temperature or co32 concentration the lack of 88sr 86sr variability in corals at different environmental parameters and the similarity to the 88sr 86sr fractionation in inorganic aragonite may indicate a similar sr incorporation mechanism in corals skeleton and inorganic aragonite and therefore the previously proposed rayleigh based multi element model gaetani et al 2011 cannot explain the process of sr incorporation in the coral skeletal material it is proposed that the relatively constant 88sr 86sr fractionation in aragonite can be used for paleo reconstruction of seawater 88sr 86sr composition the seawater 88sr 86sr ratio reconstruction can be further used in calcite samples to reconstruct paleo precipitation rates

evidence for stable sr isotope fractionation by silicate weathering in a small sedimentary watershed in southwestern taiwan abstract radiogenic sr isotopes 87 sr 86 sr are robust for provenance identification in hydrology affected mainly by the age of background lithologies and the degree of chemical weathering however there is limited knowledge concerning the fractionation mechanism of stable sr isotopes 88 sr 86 sr in rivers in this study river water was collected on a weekly to monthly basis throughout dry and wet seasons furthermore to study the variations of radiogenic and stable sr isotopes during intense weathering a major flooding event 2000 mm precipitation in three days typhoon morakot water was captured within a small drainage catchment system 161 km 2 along the hou ku river in southwestern taiwan for a better constraint on the end member compositions bedload sediments suspended particles and several host rocks were sampled for a systematic investigation the carbonate and silicate phases of these solids were chemically separated dissolved major elements indicate that the watersheds were predominated by silicate weathering stable sr isotopes show no significant variation 88 sr 0 24 0 31 temporally and spatially with an average of 0 28 additionally all solids showed lower 88 sr values than the river water while the host rocks had higher 88 sr values 88 sr 0 20 0 26 than the residual weathering products 88 sr 0 08 0 22 indicating preferential leaching of heavy sr into the hydrosphere and leaving light sr in the residual solids results of laboratory acid leaching experiments reveal that dissolution of high 88 sr value minerals occurred at an early stage of weathering the variation of weathering intensity does not alter stable sr isotopes in silicate weathering dominated river water which contains higher stable sr isotopes than the associated sediments the silicatic sedimentary rocks preferentially released higher stable sr isotopes into the hydrosphere during chemical weathering thus leaving lower stable sr isotopes in the residual solids

the origin and migration of mud volcano fluids in taiwan evidence from hydrogen oxygen and strontium isotopic compositions abstract mud volcanoes are important gateways for deep fluids to migrate upward and provide windows for studying fluid sediment interaction at depth fluids emitted from 40 terrestrial mud volcanoes were collected in southern and eastern taiwan to study their chemical compositions including h o and sr isotopes 87sr 86sr and 88 86sr relative to seawater the mud volcano fluids are depleted in cl mg so42 and d and are elevated in b ba li and 18o possibly due to water rock interaction and clay dehydration mainly smectite to illite transformation in the source region the distribution of sr in mud volcano fluids shows patterns associated with their localities and geological settings most fluids have higher 87sr 86s than seawater indicating water rock interaction at depth the low na 87sr 86s and high ca fluids emitted from eastern taiwan imply intense interaction with igneous basement most fluids have higher sr cl and lower 88sr than seawater except mud volcanoes in the northern chu kou fault which emit low sr cl and extremely high 88sr up to 0 82 fluids we performed laboratory carbonate precipitation experiments that indicate that these high sr isotope ratios are caused by co precipitation of carbonates from high alkalinity fluids mud volcano fluids in taiwan originate at depth and their chemical compositions are controlled by the host rock degrees of water rock interaction and clay dehydration but also are masked by retrograde progresses such as carbonate precipitation during migration our results show that an approach combining water isotopes d and 18o and strontium isotopes 87sr 86sr and 88 86sr provides a robust tool for tracing fluid sources and migration pathways in accretionary prisms

a new view of ridge segmentation and near axis volcanism at the east pacific rise 8 12 n from em300 multibeam bathymetry 1 new high resolution bathymetry for the east pacific rise between 8 n and 12 n was collected over a 6 km wide swath centered on the ridge axis using the 30 khz simrad em300 multibeam system the coverage area corresponds latitudinally to the designated ridge2000 integrated studies site iss for fast spreading ridges the em300 data gridded at 30 m latitude by 50 m longitude represent a greater than 4x improvement in horizontal resolution over previously available multibeam data and a 2x improvement in depth resolution the new bathymetry was used to update the locations and hierarchy of ridge offsets for this area among the many applications for this data it enables us to tabulate volcanoes half the size that could be previously detected the distribution of near axis volcanic cones 25 m high suggests that this population of small near axis cones results from low effusion rate eruptions of the ridge axis

dust transport and synoptic conditions over the sahara arabia deserts during the mis6 5 and 2 1 transitions from grain size chemical and isotopic properties of red sea cores abstract the red sea situated between the sahara and arabia deserts is a natural trap for fine grained particles transported by winds and floods from weathered materials in these deserts derived from the proterozoic crustal granitic and basaltic terrains and phanerozoic carbonates the accumulated fine particles provide valuable information on the climate conditions in the source regions and modes of atmospheric circulation over the red sea region here we report on the grain size mineralogy chemical composition and nd and sr isotope ratios of fine grained insoluble residues ir from acid leaching that were recovered from two deep sea cores kl23 and kl11 drilled in the northern and central red sea respectively we focus on the mis6 5 and mis2 1 transitions kl23 samples are closer to the sahara granitoids field and display significant variations during the mis6 5 transition between end of 7 to 2 and 87sr 86sr of 0 7096 to 0 7114 smaller variations occurred during the mis2 1 transition between end of 5 to 6 and 87sr 86sr of 0 7104 to 0 7118 the kl11 values are closer to the blue nile field which comprises mixtures of granitoid and basalt derived particles during the mis6 5 transition their end varies from 4 to 1 and in 87sr 86sr from 0 7059 to 0 7091 during periods equivalent to sapropels s5 and s1 both cores appear to converge to similar isotope ratios of e nd 2 and 87sr 86sr 0 7095 indicating derivation from the granitoid terrains of the arabian nubian shield occurring adjacent to the red sea and possibly distributed by runoff in terms of synoptic conditions the data indicate that during glacials dust was blown to the northern red sea from the northern sahara desert in association with the mediterranean winter cyclones and to the central red sea from the ethiopian plateau by southern winds that are associated with monsoonal circulation during interglacials especially sapropel intervals monsoonal rains caused erosion and flooding at the arabian nubian shield margins of the red sea during the heinrich events associated with the studied intervals h11 and h1 dust from mixed basaltic granitic terrains was blown from all of the regional sources in the red sea region reflecting severe regional aridity and transport of dust by regional winds when monsoonal activity and mediterranean cyclone activity were weak

tectonic framework of the indus and shyok suture zones in eastern ladakh northwest himalaya abstract three different phases of plutonic volcanic activity viz 1 1 cretaceous volcanics of the dras and luzarmu formations 2 2 early tertiary granitoids of the ladakh plutonic complex 3 3 oligocene acid volcanics and dykes of the khardung formation have been recognised in the ladakh magmatic arc the dras formation of the indus suture zone and the luzarmu formation of the shyok suture zone were one stratigraphic unit into which granitoids of the ladakh plutonic complex intruded the rocks of the shyok suture zone are interpreted to represent the tectonised remainder of a marginal back arc basin the closure of the marginal basin occurred at the eocene oligocene time boundary and crustal shortening was responsible for generation of neogene 2 mica granites of the karakoram plutonic complex and regional metamorphism of the pangong tso group

determination of temperature dependent stable strontium isotope 88sr 86sr fractionation via bracketing standard mc icp ms stable strontium isotopes here 88sr 86sr are introduced as a new member of the nontraditional stable isotopes we have developed a bracketing standard method for the determination of 88 86sr using an axiom mc icp ms and normalizing to strontium srm nbs987 for individual measurements the external reproducibility is better than about 25 ppm 1 rsd for the iapso seawater standard a 88 86sr value of 0 381 0 010 2sem was determined for the first time a temperature dependent strontium isotope fractionation during calcium carbonate precipitation could be shown aragonite samples inorganically precipitated under temperature control between 10 and 50 c revealed a 88 86sr temperature dependency of 0 0054 5 c r2 0 987 in contrast for natural coral samples pavona clavus from a proxy calibration study 23 to 27 c we did determine 0 033 5 c r2 0 955 the processes causing this sixfold stronger temperature dependency for the natural coral samples have to be studied in more detail in future studies in a first approach the different slopes can be interpreted as effects of kinetic fractionation of strontium ions with or without a hydrate shell of 22 to 29 water molecules

chromium fluxes and speciation in ultramafic catchments and global rivers abstract the role of ultramafic rock weathering in global chromium cr budgets and how these may be linked to changes in earth s climate over geological time was investigated by compiling dissolved cr speciation and fluxes in i 73 of the worlds large rivers representing 35 of global river discharge to oceans and in ii an ultramafic catchment putah creek watershed in the california coast range mountains usa weathering of ultramafic rocks creates ideal conditions for cr release and redox cycling alkaline river water draining ultramafic catchments is naturally enriched in cr up to 582 nmol l chromium concentrations increase with the extent of rock water interaction as indicated by correlations with mg and hco3 concentrations and ph whereas cr cycling depends on the availability of electron donors and acceptors e g fe ii organics mn iii iv oxides thus dissolved cr is exported from ultramafic watersheds as both the soluble hexavalent cr vi species mgcro4 cro42 and also as trivalent cr iii species croh co3 22 cr oh 3 the latter cr iii species were previously thought to have low solubility ultramafic catchments have higher area normalized cr and major ion fluxes for a given runoff when compared to global rivers and may thus have a disproportional impact on global cr budgets long term carbon cycling and moderation of the earth s climate over million year timescales riverine export fluxes of cr are linearly correlated with fluxes of ca mg and alkalinity in both ultramafic catchments and global rivers this suggests that silicate weathering is a key control on cr fluxes and that major element weathering fluxes may be a useful proxy for estimating cr and other trace element fluxes globally present day riverine dissolved cr fluxes to oceans are spatially variable and estimated to be 1 7 109 mol yr three times higher than previously reported however when geochemical reactions in estuaries are considered riverine cr fluxes may be lower throughout earth history cr weathering fluxes also may have varied with changes in the global distribution of ultramafic rocks cr concentrations in continental rocks or climactic conditions e g atmospheric co2 levels or runoff such variation should be considered when interpreting both modern and past cr seawater isotopic compositions and residence times

88 sr 86 sr fractionation and calcite accumulation rate in the sea of galilee abstract this study used the sea of galilee lake kinneret northern israel as a natural laboratory to investigate the fractionation of the stable sr isotope ratio 88 sr 86 sr during precipitation of inorganic primary calcite from the lake s water it was found that the absolute value of the 88 sr 86 sr fractionation factor 88 86 sr increases as a function of calcite accumulation rate 88 86 sr 0 05 to 0 042 log r mol m 2 d 1 where r is the accumulation rate furthermore the 87 sr 86 sr and 88 sr 86 sr ratios in the freshwater and brines that enter the lake were used to calculate the contributions of these sources to the lake sr budget the 87 sr 86 sr and 88 sr 86 sr ratios were measured in primary calcite aragonite shells of live melanopsis lake water and various water sources to the lake while the lake s 87 sr 86 sr ratios are determined by the mixture of freshwater of the jordan river and saline springs the 88 sr 86 sr ratios of the lake reflect a more complex mass balance that includes the effect of isotopic fractionation associated with the precipitation of primary calcite data analysis suggests that long term accumulation of inorganic calcite depleted in the heavy isotope 88 sr results in an increase of the 88 86 sr value of the lake water by 0 05 in contrast to the primary inorganic calcite biogenic aragonite of the melanopsis shells show a rather constant 88 sr 86 sr water caco 3 fractionation of 88 86 sr 0 21 similar 88 86 sr values were reported for the precipitation of coralline and inorganic aragonite from seawater and the precipitation of inorganic calcite from various continental waters the 88 86 sr value of inorganic calcite is modulated by the rate of carbonate precipitation as noted above and shown by precipitation experiments massive precipitation of primary calcite with a wide spread of accumulation rates occurs during the spring phytoplankton bloom in lake kinneret the bloom dictates the degree of calcite saturation in the lake and hence the stable sr isotopic composition of the precipitating calcite the correlation between 88 sr 86 sr and the calcite accumulation rate can be therefore used as a tool to reconstruct environmental and ecological variations in the historical lake by analyzing the 88 sr 86 sr ratio in the primary caco 3 recovered from the lake s sedimentary archives

partitioning of strontium between calcite and fluid the sr ca ratio of biogenic carbonate is widely used as a proxy for paleotemperature this application is supported by empirical calibrations of sr ca as a function of temperature but it is also known that sr uptake in calcite gauged by kdsr is affected by other variables including bulk precipitation rate kdsr increases with increasing precipitation rate there are no data from controlled experiments specifically addressing the effect of radial growth rate of individual crystals on kdsr for this reason we conducted two series of experiments to explore sr partitioning at varying growth rates 1 growth from a cacl2 nh4cl srcl2 solution by diffusion of co2 from an ammonium carbonate source drift experiments and 2 drip precipitation of calcite on a substrate using a steady flow of cacl2 srcl2 and na2co3 solutions mixed just before passage through a tube and dripped onto a glass slide precoated with calcite cave type experiments the growth rates of individual crystals were determined by periodic monitoring of crystal size through time or roughly by comparison of the final size with the duration of the experiment electron microprobe analyses across sectioned crystals grown in the drift experiments show that the concentration of sr is high in the center where radial growth rates are highest and decreases systematically toward the edge the center to edge drop in sr concentration is a consequence of the slowing radial growth rate as individual crystals become larger in general high crystal growth rate v enhances sr uptake in calcite due to a type of kinetic disequilibrium we refer to as growth entrapment the apparent kdsr ranges from 0 12 to 0 35 as v increases from 0 01 nm s to 1 m s at 25 c

mapping and defining sources of variability in bioavailable strontium isotope ratios in the eastern mediterranean abstract the relative contributions of bedrock and atmospheric sources to bioavailable strontium sr pools in local soils was studied in northern israel and the golan regions through intensive systematic sampling of modern plants and invertebrates to produce a map of modern bioavailable strontium isotope ratios 87 sr 86 sr for regional reconstructions of human and animal mobility patterns the study investigates sources of variability in bioavailable 87 sr 86 sr ratios in particular the intra and inter site range of variation in plant 87 sr 86 sr ratios the range of 87 sr 86 sr ratios of plants growing on marine sedimentary versus volcanic geologies the differences between ligneous and non ligneous plants with varying growth and water utilization strategies and the relative contribution of atmospheric sr sources from different soil and vegetation types and climatic zones results indicate predictable variation in 87 sr 86 sr ratios inter and intra site differences in bioavailable 87 sr 86 sr ratios average of 0 00025 while the range of 87 sr 86 sr ratios measured regionally in plants and invertebrates is 0 7090 in pleistocene calcareous sandstone and 0 7074 in mid pleistocene volcanic pyroclast the 87 sr 86 sr ratios measured in plants growing on volcanic bedrock show time dependent increases in atmospheric deposition relative to bedrock weathering the 87 sr 86 sr ratios measured in plants growing on renzina soils depends on precipitation the spacing between bedrock 87 sr 86 sr ratios and plants is highest in wet conditions and decreases in dry conditions the 87 sr 86 sr ratios measured in plants growing on terra rossa soils is relatively constant 0 7085 regardless of precipitation ligneous plants are typically closer to bedrock 87 sr 86 sr ratios than non ligneous plants since the bioavailable 87 sr 86 sr ratios currently measured in the region reflect a mix of both exogenous and endogenous sources changes in the relative contribution of exogenous sources can cause variation over time precipitation the age of the bedrock and the overall sr concentration must to be taken into consideration when interpreting geographical variation in strontium isotopes throughout a region because these factors can change through time we recommend that sr data from time periods older than the holocene be interpreted with caution

biologically induced calcite and its isotopic composition in lake ontario we studied water sediment trap and core samples from eastern lake ontario to reconstruct the factors controlling the biologically induced production and sedimentation of calcite during so called whiting events calcite accumulation and its isotopic composition are controlled by a complex set of interrelated factors including temperature primary productivity and the abundance of pica cyanobacteria during the stratified period calcite precipitation is highly correlated to lake temperature because physical and biological factors interact to produce conditions favorable for whitings during warm years when the lake stratifies early in the seasonal cycle carbonate stratigraphies in multiple cores from eastern lake ontario revealed similar patterns of historical variation in percent carbonate an exponential rise in carbonate accumulation occurred in nine cores after 1930 culminating in peak values in the early 1980s this rise was related to historic increases in primary productivity resulting from increased phosphorus loading to lake ontario superimposed upon this rise were four peaks centered on 1940 1942 1957 1961 1971 1977 and 1983 that correlate with maxima in summer air temperature anomalies from the great lakes region and with strong el niiio events these peaks are also associated with maxima in s c values and minima in s180 values of carbonate lending support to our model that more calcite is precipitated with higher 6 c values during warm years when thermal stratitication occurs early in the seasonal cycle beginning in the mid 1980s calcite accumulation and its 6 c ratio began to decrease suggesting a reduction in primary productivity in surface waters probably related to lower phosphate concentrations in epilimnetic waters of lake ontario during the stratified period reduced summer p loading may be explained either by a lagged response to p abatement measures that began in the late 1970s or by decreased p loading from upstream lake erie beginning in the late 1980s as a result of the establishment of filter feeding zebra mussels

the phanerozoic δ88 86sr record of seawater new constraints on past changes in oceanic carbonate fluxes the isotopic composition of phanerozoic marine sediments provides important information about changes in seawater chemistry in particular the radiogenic strontium isotope 87sr 86sr system is a powerful tool for constraining plate tectonic processes and their influence on atmospheric co2 concentrations however the 87sr 86sr isotope ratio of seawater is not sensitive to temporal changes in the marine strontium sr output flux which is primarily controlled by the burial of calcium carbonate caco3 at the ocean floor the sr budget of the phanerozoic ocean including the associated changes in the amount of caco3 burial is therefore only poorly constrained here we present the first stable isotope record of sr for phanerozoic skeletal carbonates and by inference for phanerozoic seawater 88 86srsw which we find to be sensitive to imbalances in the sr input and output fluxes this 88 86srsw record varies from 0 25 to 0 60 vs srm987 with a mean of 0 37 the fractionation factor between modern seawater and skeletal calcite 88 86srcc sw based on the analysis of 13 modern brachiopods mean 88 86sr of 0 176 0 016 2 standard deviations s d is 0 21 and was found to be independent of species water temperature and habitat location overall the phanerozoic 88 86srsw record is positively correlated with the ca isotope record 44 40casw but not with the radiogenic sr isotope record 87sr 86sr sw a new numerical modeling approach which considers both 88 86srsw and 87sr 86sr sw yields improved estimates for phanerozoic fluxes and concentrations for seawater sr the oceanic net carbonate flux of sr f sr carb varied between an output of 4 7x1010mol myr and an input of 2 3x1010mol myr with a mean of 1 6x1010mol myr on time scales in excess of 100myrs the f sr carb is proposed to have been controlled by the relative importance of calcium carbonate precipitates during the aragonite and calcite sea episodes on time scales less than 20myrs the f sr carb seems to be controlled by variable combinations of carbonate burial rate shelf carbonate weathering and recrystallization ocean acidification and ocean anoxia in particular the permian triassic transition is marked by a prominent positive 88 86srsw peak that reflects a significantly enhanced burial flux of sr and carbonate likely driven by bacterial sulfate reduction bsr and the related alkalinity production in deeper anoxic waters we also argue that the residence time of sr in the phanerozoic ocean ranged from 1myrs to 20myrs

lake kinneret the sea of galilee the effects of diversion of external salinity sources and the probable chemical composition of the internal salinity sources this paper investigates the chemical variations and evolution of lake kinneret lk the sea of galilee after the diversion of onshore saline springs through the salinity diversion channel sdc which reduced the salinity of the lake water the mass balance approach enables to determine the average chemical composition of the unknown internal lake sources of salinity that in addition to other known sources contribute salts and control the chemistry of the lake water this study reveals for the first time the average chemical composition of the internal lake salinity sources mass balances show that the water discharge of the lake internal sources is 61 106 m3 year 1 and that these sources contribute 72 000 tons of chloride annually the sdc operation caused a long term decrease in the concentrations of cl mg na k ca so4 and br in lake water concomitantly the ionic ratios of na cl mg cl ca cl k cl and so4 cl have increased and br cl ratio has decreased the average chemical composition of the lake internal sources is characterized by na cl and mg cl ionic ratios which closely resemble those measured in the two well known submerged saline springs of fulyia a and fulyia b and in water of a deep observation well located north of the lake referred to as kin 8 the decrease in br cl ionic ratio from 3 58 10 3 prior to the sdc operation to 3 29 0 11 10 3 in mid 1990s implies that the major internal sources of cl and br to the lake are characterized by br cl ratios 3 29 10 3 br cl ionic ratios somewhat lower than 3 29 10 3 were found only in fulyia a and fulyia b springs and in kin 8 water it is therefore suggested that fulyia like water is the internal saline source which supplies most of the na cl and br to the lake sulphate however is contributed to the lake mainly over 80 through freshwater streams calcium and alkalinity originate mainly from freshwater sources including internal lake flow of groundwater lower in salinity but saturated with caco3 thus internal sources of solutes are mostly composed of the saline end member of fulyia like water and of fresher groundwater these conclusions have practical implications for lake water management

bimodal stable isotope signatures of zildat ophiolitic melange indus suture zone himalaya implications for emplacement of an ophiolitic melange in a convergent setup zildat ophiolitic melange zom of the indus suture zone himalaya represents tectonic blocks of the fragmented oceanic metasediments and ophiolite remnants the zom is sandwiched between the zildat fault adjacent to a gneissic dome known as tso morari crystalline tmc and thin sliver of an ophiolite called as the nidar ophiolitic complex the zom contain chaotic low density lithologies of metamorphosed oceanic sediments and hydrated mantle rocks in which carbonates are present as mega clasts ranging from 100 meters to few centimeters in size in this work calcite microstructures fluid inclusion petrography and stable isotope analyses of carbonates were carried out to envisage the emplacement history of the zom calcite microstructure varies with decreasing temperature and increasing intensity of deformation intense shearing is seen at the marginal part of the melange near zildat fault these observations are consistent with the melange as a tectonically dismembered block formed at a plate boundary in convergent setup the 18o and 13c isotope values of carbonates show bimodal nature from deeper interior to the shallower marginal near the zildat fault part of the melange carbonate blocks from deeper part of the melange reflect marine isotopic signature with limited fluid rock interaction which later on provide a mixing zone of oceanic metasediments and or hydrated ultramafic rocks carbonates at shallower depths of the melange show dominance of syn deformation hydrous fluids and this has later been modified by metamorphism of the adjacent tmc gneisses above observations reveal that the melange was emplaced over the subducting indian plate and later on synchronously deformed with the tmc gneissic dome

characterizing nutrient pathways in quebec canada vineyards insight from stable and radiogenic strontium isotopes abstract soils are a crucial interface of earth s critical zone responsible for the biogeochemical cycling of mineral nutrients while the sources of essential nutrients such as ca and sr in plants have been widely studied the processes by which these nutrients are transferred from the soil to the plants is less clear we present new evidence for systematic nutrient fractionation between soils grapes and wines from five vineyards from the quebec terroir canada using the novel stable sr 88 86sr isotope system we coupled this approach with traditional radiogenic 87sr 86sr measurements on the same samples bulk soils labile fraction of these soils whole grapes and wines from five vineyards from the quebec terroir canada to ensure that variations in 88 86sr values were provoked by processes involved in sr transfer instead of mixing between different sources the 88 86sr values generally decrease from the bulk to the labile fractions of the soils to the grapes a decrease in the difference between the soil fractions 88 86srbulk labile with increasing 88 86sr values in the labile fraction is interpreted to reflect increasing pedogenic mineral precipitation and higher soil fertility the depleted 88 86sr values of the grapes are consistent with a preferential uptake of lighter isotopes by plants this effect is magnified in soils showing higher secondary mineral precipitation an increase in the 88 86sr values from the grapes to the wines reflects the separation of the skin seeds and the juice pulp enriched in 88sr in the winemaking process this mixing relationship is supported by a correlation between the sr concentrations and the 88 86sr values of the wines and grapes these findings suggest promising new applications of stable sr isotopes values for studying soil fertility and the impact of nutrient availability for plant growth in agricultural ecosystems as well as the impact of the maceration processes in the production of wine the overall similarity of 87sr 86sr ratios of the labile soil fractions grapes and wines from the same vineyard support the hypothesis of a same sr source from the soil solution to its transfer to the grape and wine and confirm the potential of the 87sr 86sr ratios as a proxy for geographic provenance of wine however slightly lower 87sr 86sr ratios in the grape pulps by 0 00040 on average compared to the skins and seeds suggest that the sources of nutrients available for plant uptake vary during the vegetative cycle the grape seeds and skins formed in the early growth cycle are characterized by rapid growth due to enhanced rhizosphere activity enhanced mineral dissolution providing higher nutrient levels the enhanced mineral solubility results in higher 87sr 86sr ratios in the skin and seeds derived from enhanced dissolution of 87sr enriched silicate minerals in contrast the pulp develops later in the growth cycle when rhizosphere activity and mineral solubility is reduced resulting in a lesser contribution from silicate minerals and thus reflect a higher proportion of dissolved carbonate contributing to the lower 87sr 86sr ratios of the pulps

the reconstruction of quaternary freshwater lakes from the chemical and isotopic composition of gastropod shells the dead sea rift israel abstract sr ca ba ca and 87sr 86sr ratios in fossil freshwater aragonitic gastropods melanopsis praemorsum and melanoides tuberculata have been used to reconstruct the water sources of quaternary lakes in the jordan river rift valley the reconstruction is based on the assumption that the same waurces which supply freshwater into the rift valley in the present i e carbonate water basaltic water and rift brines were active throughout the quaternary the distribution coefficients for sr and ba were obtained from live gastropods which were collected from modern water bodies in the region by using these distribution coefficients the composition of the ancient waters could be derived from the fossil shells chemistry altogether four ancient sites were sampled of which mishmar ha yarden and gesher benot ya akov formations are located in the upper jordan valley and erq el ahmar and ubeidiya formations are in its central part low salinity carbonate waters 300 mg l comprised the main h2o source into the hula basin in the upper jordan valley these solutions display a 87sr 86sr ratio of 0 7082 0 0002 which is significantly higher than the corresponding modern ratio 0 7070 suggesting that the ancient drainage system was initially fed by upper eocene carbonate aquifers and shifted later to a jurassic carbonate system the erq el ahmar lake in the central jordan valley was supplied by approximately equal proportions of carbonate and basaltic waters resulting in a water body of low salinity 300 mg l the water source of lake ubeidiya also in the central jordan valley was predominantly basaltic yet its chemistry bears a strong rift brine signature resulting in a salinity of about 1000 1300 mg l the values obtained are in good accord with the biological evaluation of the fossil biota

relicts of an intra oceanic arc in the sapi shergol melange zone ladakh nw himalaya india implications for the closure of the neo tethys ocean in the ladakh zanskar area relicts of both ophiolites and paleo accretionary prism have been preserved in the sapi shergol me lange zone the paleo accretionary prism related to the northward subduction of the northern neo tethys beneath the ladakh asian margin mainly consists of tectonic intercalations of sedimentary and blueschist facies rocks whole rock chemical composition data provide new constraints on the origin of both the ophiolitic and the blueschist facies rocks the ophiolitic rocks are interpreted as relicts of the south ladakh intra oceanic arc that were incorporated in the accretionary prism during imbrication of the arc the blueschist facies rocks were previously interpreted as oceanic island basalts oib but our new data suggest that the protolith of some of the blueschists is a calc alkaline igneous rock that formed in an arc environment these blueschists most likely originated from the south ladakh intra oceanic arc this arc was accreted to the southern margin of asia during the late cretaceous and the buried portion was metamorphosed under blueschist facies conditions following oceanic subduction the external part of the arc was obducted to form the south ladakh ophiolites or was incorporated into the sapi shergol me lange zone the incorporation of the south ladakh arc into the accretionary prism implies that the complete closure of the neo tethys likely occurred by eocene time

strontium stable isotopes fractionate in the soil environments abstract this study shows that the stable isotopic composition of strontium the 88sr 86sr ratio expressed as 88 86sr value relative to the nbs987 standard varies significantly in sedimentary terrestrial environments the abundances of 86sr 88sr isotopes were analyzed by mc icp ms nu plasma all studied rocks and waters show 88 86sr values that are distinctly different from the measured nbs987 standard yielding 0 01 0 05 all errors are reported as 2 modern corals from the northern gulf of aqaba red sea yielded significantly different value than seawater 88 86sr 0 22 0 07 compared to 0 35 0 06 respectively in an excellent correlation with the 88 86sr analyses reported by fietzke and eisenhauer fietzke j eisenhauer a 2006 determination of temperature dependent stable strontium isotopes 88sr 86sr fractionation via bracketing standard mc icp ms geochm geophys geosyst 7 no 8 on other coral samples all carbonate samples that originated in the marine environment corals porites and acropora from the northern gulf of aqaba cretaceous limestone and runoff from the judea mountains as well as lacustrine evaporitic aragonite dead sea and red sea and atlantic seawater yield an average 88 86sr value of 0 26 0 1 on the other hand secondary materials products of chemical weathering from the terrestrial environment of the judea mountain such as terra rossa soil and speleothem calcite that derives its sr from the above lying soil yielded significantly lower 88 86sr value of 0 17 0 06 this indicates that strontium isotopes fractionate in the soil environment calling for a possible development of strontium isotopes as a tracer for processes of chemical weathering and pedogenesis

enrichment of 88 sr in continental waters due to calcium carbonate precipitation abstract 88 86sr data published over the last few years suggest that continental waters are enriched with 88sr as compared to the rocks in their drainage basins in an attempt to understand this phenomenon this study established the fractionation in the 88sr 86sr ratio during precipitation of continental carbonates i e carbonates precipitated on land from surface pedogenic or ground waters and evaluated the contribution of this process to the 88sr enrichment in rivers for this stable and radiogenic sr isotopes 88sr 87sr and 86sr were measured in calcite samples and their precipitating waters collected in various continental environments such as soil cave streams and groundwater the results indicate that continental carbonates are 88sr depleted relative to their precipitating waters placing them as one of the most 88sr depleted reservoirs on earth the average difference in 88 86sr values between waters and solid caco3 tufas or speleothems that they precipitate is carb water 0 218 0 014 1sd an even larger fractionation e carb water 0 285 0 02 was measured in groundwater with particularly high carbonate alkalinity and high carbonate precipitation rate that depleted 65 of the sr in the groundwater resulting in substantial 88sr enrichment in the residual dissolved sr sr 88 86 0 656 results also suggest that pedogenic carbonate precipitation in soil profile removes 50 85 of the sr from the recharging soil water thereby increasing the 88 86sr value of the soil water from 0 18 to 0 3 0 6 similar 88sr enrichment was observed in drip water from a karst cave a maximum removal flux of sr into continental carbonates of about 20 gmol sr y 1 is required to yield the reported 88sr enrichment in global rivers sr 88 86 0 32 relative to their rock sources when using the fractionation factor derived in this study carb water 0 218 and the published 88 86sr composition of marine carbonates of 0 16 this surprisingly large flux requires that 40 of the originally weathered sr should co precipitate with continental carbonates this calculation may suggest that caco3 precipitation is a significant mechanism in the continental sr cycle it is possible however that other mechanisms such as sr uptake by plants or incongruent weathering of silicates could also contribute to the riverine 88sr enrichment alternatively the average 88 86sr value of marine carbonate rock sections undergoing weathering is higher than suggested in current literature it is concluded that additional 88 86sr data on marine carbonate rock sections should be collected to resolve the enigma of the high value of riverine 88 86sr

cold seep systems in the south china sea an overview abstract three decades after the discovery of cold seep systems various sites of hydrocarbon seepage have been found in the south china sea scs over the past decade these sites have become model systems for understanding the variability of hydrocarbon seepage and associated biogeochemical processes in this review we describe the cold seep systems of the scs with an emphasis on seafloor manifestations fluid sources biogeochemical processes and macroecology seafloor features associated with seeps include mud volcanoes pockmarks and carbonate deposits a common characteristic of cold seeps is the occurrence of authigenic i e in situ precipitated carbonate minerals these carbonates commonly exhibit low 13c and high 18o values suggesting the incorporation of methane derived carbon and oxygen derived from gas hydrate water biogeochemical processes such as sulfate driven anaerobic oxidation of methane sd aom the key process at seeps have been studied in detail with the aim of establishing geochemical proxies to trace these processes into the geological past we also detail the features characterizing seep ecosystems understanding the impact of decomposing methane hydrate on the marine carbon budget remains challenging and requires additional seafloor observations as well as models predicting how gas hydrate responds to changing conditions such as temperature increase sea level rise and episodic mass wasting

transient groundwater lake interactions in a continental rift sea of galilee israel the sea of galilee located in the northern part of the dead sea rift is currently an intermediate fresh water lake it is postulated that during a short highstand phase of former lake lisan in the late pleistocene saline water percolated into the subsurface since its recession from the kinarot basin and the instantaneous formation of the fresh water lake the sea of galilee the previously intruded brine has been flushed backward toward the lake numerical simulations solving the coupled equations of fluid flow and of solute and heat transport are applied to examine the feasibility of this hypothesis a sensitivity analysis shows that the major parameters controlling basin hydrodynamics are lake water salinity aquifer permeability and aquifer anisotropy results show that a highstand period of 3000 yr in lake lisan was sufficient for saline water to percolate deep into the subsurface because of different aquifer permeabilities on both sides of the rift brine percolated into aquifers on the western margin whereas percolation was negligible on the eastern side in the simulation after the occupation of the basin by the sea of galilee the invading saline water was leached backward by a topographydriven flow it is suggested that the percolating brine on the western side reacted with limestone at depth to form epigenetic dolomite at elevated temperatures therefore groundwater discharging along the western shores of the sea of galilee has a higher calcium to magnesium ratio than groundwater on the eastern side

calcium magnesium and strontium cycling in stratified hardwater lakes lake kinneret sea of galilee israel abstract in stratified hardwater lakes calcite crystallization in the epilimnion and partial dissolution in the hypolimnion play important roles in the cycling of ca2 in the water column mg2 and sr2 coprecipitate with this mineral to be released together with ca2 upon its dissolution here we focus on lake kinneret sea of galilee israel a stratified warm hardwater lake searching for an interpretable high resolution picture of the processes that drive ca2 mg2 and sr2 cycling in this and similar lakes elsewhere in total 1428 water samples were collected from the lake and another 81 samples were collected from the jordan river and two small streams discharging into it covering a full monomictic cycle from december 2001 through march 2003 particulate material was retrieved from sediment traps in the hypolimnion the water samples were analyzed for na k mg2 ca2 sr2 cl so42 hco3 and br and the trapped particulates were examined under sem and analyzed for their ca mg and sr content individual calcite crystals within the particulate material underwent la icp ms analysis for ca mg and sr downward transport of ca2 involves crystallization of calcite in the epilimnion followed by its settling through the water column followed by its partial dissolution in the hypolimnion magnesium and sr2 follow ca2 by coprecipitation in calcite and are released upon its dissolution in the hypolimnion upward cycling of the three solutes occurs through an admixture of the hypolimnetic water into the epilimnion during thermocline deepening terminated by overturn of the lake removal rates of mg2 and sr2 from the lake relative to that of ca2 and the water calcite distribution coefficients dmg and dsr were calculated from the analyses using 1 epilimnion water and bulk particulates 2 epilimnion water only and 3 epilimnion water and calcite crystals in the particulates the dsr values obtained were internally consistent 0 194 5 9 0 22 0 28 and 0 204 0 232 respectively however the dmg value for the bulk particulates 0 0477 was 6 times higher than that corresponding to calcite crystals included therein 0 00841 this difference is attributed to phytoplankton debris in the bulk particulates and should be of concern to geochemists using mg ca ratios in limestone to reconstruct ancient aquatic environments the cycling of ca2 mg2 and sr2 in the stratified lake is monitored by mg ca vs sr ca regression diagrams where each line represents the water column composition on a specific date the distance of the data points from the initial mixed lake coordinates reflects the fractionation of ca2 mg2 and sr2 after the onset of stratification the regression lines rotate in an orderly anticlockwise direction in response to the high calcite flux from the epilimnion in spring and the higher rate of mg2 replenishment than that of sr2 compensating for their loss in calcite the release of mg2 and sr2 from dissolving calcite in the hypolimnion at an mg sr ratio 7 5 eq eq much lower than that in the surrounding water 160 eq eq lends additional support to the anticlockwise rotation reversal of rotation occurs in summer when calcite crystallization and the freshwater supply slow down and brackish and saline water sources take control over the mg sr ratio in the lake subsequent turnover and mixing of the lake in winter reset the mg ca and sr ca ratios to their original values before the next stratification

strontium isotopic chemical and sedimentological evidence for the evolution of lake lisan and the dead sea precise strontium isotope ratios combined with chemical analyses and sedimentological information are used to monitor the water sources and the evolution of the dead sea and its late pleistocene precursor lake lisan 70 18 kyr b p the materials analyzed include bulk aragonite water leached soluble salts and residual aragonite and gypsum from the lisan formation in the perazim valley near the sw shore of the dead sea the residual aragonite and the associated soluble salts display systematic fluctuations in 17sr86sr ratios between 0 70803 and 0 70806 and from 0 70805 to 0 70807 respectively in individual soluble salt residual aragonite pairs the soluble salt displays a higher 87sr86sr ratio gypsum samples yield 17sr86sr ratios similar to the soluble salts from adjacent layers in the section this shows that in individual samples the source of sr in aragonite was distinct from that in soluble salts and the gypsum the sterility of the lisan sediments their strictly nonbioturbated fine lamination and their high content of chloride salts indicate that lake lisan was a saline or even hypersaline water body in the absence of alternative sources of hco3 and s042 the abundance of primary aragonite and gypsum in the lisan column reflects an import of very large volumes of freshwater into the otherwise saline lake resulting in a density stratification of this water body the history of the upper water layer and that of the lower brine is reflected in the chemical and strontium isotope composition of the aragonite and in that of the associated soluble salts and in the gypsum samples respectively whereas the bicarbonate and much of the ca2 required for aragonite crystallization were supplied by the freshwater the complementary ca2 and sr 2 were added by the lower brine the upper water layer of lake lisan acted as a so42 capacitor during the lake s rise periods it was removed therefrom as prominent gypsum beds upon climatic induced drier period mixing or even complete overturn of the lake the evolution of lake lisan took place between two distinct modes the first was characterized by an extensive supply of freshwater and resulted in a rise of the lake s level a density layered structure and precipitation of aragonite the second mode was marked by a diminishing freshwater input resulting in mixing or complete overturn of its water and precipitation of gypsum these two modes reflect the climatic evolution of the region in the late pleistocene which fluctuated between drier and wetter periods the transition to the holocene is accompanied by the dry up of lake lisan and its contraction to the present dead sea

crystal growth rate effect on mg ca and sr ca partitioning between calcite and fluid an in situ approach abstract partition coefficients of mg and sr kmg and ksr between calcite and fluid were determined in crystals grown under different rates v where v is defined as the crystal extension per unit of time nm s addition of rare earth elements ree into the fluid leads to ree preservation in the calcite this preservation allows for a direct determination of the values of v by measuring the widths of the ree spiked zones the edge to edge spot analyses of mg ca sr ca and ree ca in the individual crystals were conducted using secondary ion mass spectrometry sims the mg ca and sr ca ratios in the fluids from which calcites precipitated were also measured with inductively coupled plasma atomic emission spectroscopy icp oes this allowed for the first time to evaluate kmg in situ in the individual crystals without averaging the data from the multiple calcite crystals results show that ksr increases by a factor of six with increasing calcite growth rate from 0 001 to 4 nm s kmg decreases by a factor of three with the same increase of v values these ksr and kmg behaviors were described quantitatively using a growth entrapment model gem according to the gem simulations sr is enriched and mg is depleted in the near surface layer of calcite relative to the bulk lattice this distinct outermost region of the crystal may be fully or partially captured by its lattice during rapid growth this process causes disequilibrium partitioning of sr and mg through growth entrapment

calcite precipitation in lake constance chemical equilibrium sedimentation and nucleation by algae1 seasonal shifts in calcium carbonate solution equilibria in the limnetic zone of lake constance were documented between 1981 and 1983 except during mixing times lake water was supersaturated with respect to calcite epilimnetic supersaturation maxima were closely related to changes in ph sedimentation of calcium from the lower boundary of the euphotic zone to the lake bottom was also assessed the daily sedimentation flux for calcium during the season varied over three orders of magnitude differences in the calcium content of sediments trapped at various depths were insignificant sedimentation rates of titanium were used as tracers for the fluxes of calcium bound on allochthonous elastic material lacustrine calcite precipitation 39 49 of the total sedimentation rate was obtained by subtracting fluxes of allochthonous ca from the rates of total ca sedimentation calcium supersaturation maxima were not in phase seasonally with maximum fluxes of autochthonous ca instead calcite precipitation was associated with the occurrence of stephanodiscus hantzschii fragilaria crotonensis asterionella formosa chlorella sp pandorina morum and mougeotia thylespora indicating that calcite formation was triggered by heterogeneous nucleation induced by certain algal species autochthonous formation and subsequent precipitation of calcium carbonate is an important process in the carbon and calcium cycling in many hard waters through coprecipitation calcium carbonates affect nutrient budgets rossmann 1980 rossknecht 1980 murphy et al 1983 and by adsorption they remove dissolved organic carbon doc from the water suess 1970 chave and suess 1970 otsuki and wetzel 1972 hence several studies have focused on the formation reactions settling processes and deposition of caco in lakes cf

eclogitic metasediments from the tso morari area ladakh himalaya evidence for continental subduction during india asia convergence metasediments in the tso morari area ladakh himalaya provide new insights into the higher himalayan metamorphism in the northwestern part of the himalayan belt whole rock analyses and petrologic observations show that the metasediments correspond to fe rich metapelites mg rich metapelites intermediate metapelites and metagreywackes of the indian continental margin jadeite chloritoid paragonite garnet in the fe rich metapelites indicate pressures of 20 2 kbar at temperatures of 550 50 c according to major element partitioning thermobarometry stability fields of minerals and thermocalc p t estimates these results are consistent with p t estimates on other metasediments and with the occurrence of eclogites subsequent retrogression at the eclogite blueschist facies transition from 18 to 13 kbar and 540 50 c was followed by an increase in temperature to 630 30 c at amphibolite facies conditions the metamorphic evolution is related to subduction of the indian continental margin beneath the southern asian margin at the onset of the indian eurasian collision

reassessing the stable δ88 86sr and radiogenic 87sr 86sr strontium isotopic composition of marine inputs the stable strontium isotope system 88 86sr has recently been suggested to be a suitable proxy for determining variations in the strength of the marine carbonate system the principal output flux of oceanic sr however in order to be able to interpret carbonate driven variations in 88 86srseawater a robust understanding of 88 86srinput is required surprisingly only a limited amount of 88 86sr data currently exists for rivers and hydrothermal fluids thus this study assesses the variability of 88 86sr and 87sr 86sr in global rivers hydrothermal fluids and porewaters as well as minor marine sr sources such as continental dust rainwater and glacial ice our analyses broadly confirm the findings of krabbenhoft et al 2010 and reveal flux weighted 88 86srriverine and 87sr 86srriverine compositions of 0 32 and 0 71299 respectively the hydrothermal fluids analysed in this study are consistent with an end member 88 86srhydrothermal composition that is the same as the oceanic crust at 0 24 although three samples that display 88 86sr compositions offset from the seawater hydrothermal mixing trend suggest that the precipitation of alteration phases such as anhydrite may drive 88 86srhydrothermal to higher values porewater fluids obtained from sediment cores in the atlantic and pacific oceans have 88 86sr compositions within error of seawater 0 39 implying that the diagenetic flux of sr may not significantly affect the 88 86sr composition of seawater continental loess samples have 88 86sr compositions that are consistently lighter than or equal to terrestrial silicates with their tendency to lower values thought to reflect the preferential removal of heavier sr isotopes into solution during weathering finally rainwater and glacial ice samples have 88 86sr compositions that are also isotopically lighter than their associated water sources a factor that may be attributed to interaction with isotopically light loess and additional sr contributions from the bedrock together the principal marine inputs define flux weighted oceanic 88 86srinput and 87sr 86srinput compositions of 0 32 and 0 71161 these values are consistent with an elevated supply of riverine sr to the oceans due to increased post glacial weathering but require the enhanced weathering of exposed carbonate shelves during glacial periods or significant changes in the rate of carbonate burial to match observed changes in the 87sr 86sr ratio of seawater our results confirm that providing a diagenetically robust proxy can be found the 88 86sr and 87sr 86sr isotope systems should provide a useful proxy for investigating changes in the marine carbonate system through time

exhumation of the ultrahigh pressure tso morari unit in eastern ladakh nw himalaya a case study exhumation processes of the ultra high pressure uhp tso morari dome nw himalaya are investigated using structural petrological and geochronological data the uhp tso morari unit is bounded by the low grade metamorphic indus suture zone to the ne and mata unit to the sw three deformation phases d1 d2 and d3 are observed only d3 is common to the uhp unit and the surrounding units in the uhp unit the first deformation phase d1 produced upright folds under eclogitic conditions 20 kbar 580 60 c d1 is overprinted by d2 structures related to a nw se trending open anticline this phase is characterized by blueschist mineral associations and corresponds to the quasi isothermal decompression from a depth of 90 km eclogitic conditions up to 30 40 km the final exhumation phase of the tso morari unit is dominated by tectonic denudation and erosion d3 associated with a slight temperature increase radiochronological analyses indicate that the uhp exhumation process began during the eocene exhumation was fast during d1 d2 and slowed down through d3 in oligocene time the change in the deformation style from d1 d2 to d3 in the tso morari unit coincides with changes in the exhumation rates and in the metamorphic conditions these changes may reflect the transition from an exhumation along the subduction plane in a serpentinized wedge to the vertical uplift of the tso morari unit across the upper crust

primary fluids entrapped at blueschist to eclogite transition evidence from the tianshan meta subduction complex in northwestern china the tianshan is the first locality worldwide where primary fluids at blueschist to eclogite transition have been documented veins containing high pressure minerals in massive host eclogites transitional to blueschists or eclogite boudins surrounded by blueschists indicate that a free fluid phase was present at the time of eclogitization the high pressure veins are predominantly composed of omphacite fibers with minor quartz or calcite the transition from blueschist to eclogite facies parageneses occurs as dehydration halos around these veins clinozoisite paragonite glaucophane and omphacite inclusions preserved in garnet porphyroblasts in wall eclogites document the transformation of blueschist to eclogite c axis parallel non planar populations of fluid inclusions were trapped during the growth of omphacite in high pressure veins and dehydrated wall rocks low salinity h2o nacl solid bearing inclusions are preserved in omphacite fibers in veins and matrix omphacite of wall rocks none of the isochores of these low salinity aqueous fluid inclusions intersect peak eclogite facies metamorphic conditions suggesting that although the textural evidence constrains the entrapment of fluid inclusions to peak metamorphic conditions their densities must have been modified during exhumation the fluids are interpreted to have been derived from the host blueschist as a result of dehydration reactions such as 13 gln 5 czo 9 prp 26 jd 12 di 19 qtz 15 h2o and gln pg prp 3 jd 2 otz 2 h2o the similarity of vein and wall rock mineral compositions fluid inclusion characteristics and o isotope data also favor an internal source for the fluids the major element composition of veins indicate that si na and ca rich aqueous fluids were released during dehydration at a depth of 50 10 km within a paleozoic subduction zone

chemical tracing of salinity sources in lake kinneret sea of galilee israel lake kinneret is a freshwater lake in northern israel that receives a major part of its salt input from unmonitored springs that discharge through the lake s bottom we attempt to characterize the nature of these springs by estimating their chemical composition while the springs around lake kinneret are subject to wide spatial and temporal variations in their ionic concentrations specific sodium na potassium magnesium mg strontium bromine and lithium to chlorine cl ion ratios are almost constant within individual springs and spring groups the radium cl ratio and the d 18 o cl relationship confirm the notion that the spring waters result from recent mixing between saline brines and freshwater available compositional data from past years along with new analyses of the lake and its known springs allow identification of the salinity source that causes the observed deficit in the lake s salt budget e g 91 93 chloride the relative contributions from these saline springs are different for different ions this contribution is highest for bromide 95 decreases to 84 for na and is less than 50 for mg two independent approaches have been used for balancing the salts in the lake and they are as follows 1 an annual mass balance between salt removal and supply of the different ions assuming a steady state lake and 2 simulation of the lake s evolution from 1964 the beginning of salt removal from the lake via the salinity diversion channel until the present both methods predict very similar ionic ratios for the yet unknown average saline spring s testifying to the reliability of both approaches the ionic ratios so obtained closely resemble fuliya 6 tabgha type waters excluding the tiberias and eastern shore springs as significant salt sources this inferred composition of the average unmonitored springs depends strongly on present day diversion of saline springs this diversion thus prevents their flow into the lake the different ionic ratios that identify the various spring groups reflect the respective compositions of the brine pockets that feed them our simulation also shows that the layered structure of lake kinneret enhanced the evolution rate of the lake after the implementation of the salt diversion program in 1964 lake kinneret lk lake tiberias or the sea of galilee is a lake of immense historical and religious significance it is also the only freshwater lake in israel and the main water reservoir for the national water carrier nwc the water supply system that transfers freshwater to central and southern israel about 30 of the country s water supply was pumped from lk in 1995 furthermore with the water shortage in the middle east becoming more and more acute lk is also a waterbody of great political significance the lake is monomictic it is stratified between mid march and december the mixing of a fully stratified to a fully mixed lake takes about 4 5 months though it is a flowthrough lake it is significantly saltier than the jordan river which is its major water source table 1 the composition

thermally induced grain growth of calcite marbles on naxos island greece the island of naxos is composed of an elliptically shaped structural and thermal dome of miocene age peak metamorphic temperatures within the central migmatite complex exceeded 700 c decreasing to about 300 c at the most distant exposures on the island equigranular calcite marbles which outcrop together with metapelites and metabasites over the whole island show a systematic pattern of increasing grain size towards the central migmatite complex with a significant discontinuity in the pattern corresponding approximately with the 500 c isotherm the microstructures and grain size distributions in the marbles are consistent with normal grain growth the variation of grain size with peak temperature attained can be explained equally well by the assumptions that a a maximum grainsize had developed particularly at higher temperatures or that b the grain size had been frozen in by a combination of cooling and coarsening both of which combine to reduce the rate of grain growth

strontium isotope fractionation of planktic foraminifera and inorganic calcite we have investigated the strontium isotope fractionation 88 86srcarb aq between inorganic calcite and aqueous sr2 ions by precipitation experiments at a constant temperature of 25 c and precipitation rates r ranging from 102 3 to 104 2 mol m2 h strontium isotope ratios were measured using the 87sr 84sr double spike technique it was found that strontium isotope fractionation in these calcites is strongly dependent on the precipitation rate view the mathml source the measured 88 86sr values are significantly correlated with previously measured 44 40ca and sr ca values of the same calcite samples 88 86srcarb aq 0 18 44 40cacarb aq 0 01 view the mathml source the slope of 88sr 86sr versus 44ca 40ca fractionation is 0 18 0 04 and compatible with a kinetic fractionation during dehydration of the strontium and calcium ions but not with isotope fractionation in a diffusive boundary layer using published equilibrium 44 40cacarb aq and view the mathml source values we estimate the equilibrium isotope fractionation of strontium to be very close to zero 88 86sreq carb aq 0 01 0 06 this estimate is confirmed by strontium isotope values of natural inorganic calcites that precipitated very slowly in basalts of the ocean crust the results from the inorganic calcites are used to explain strontium isotope fractionation of planktic foraminifera specimens of two warm water species globigerinoides ruber and globigerinoides sacculifer were picked from the holocene section of a caribbean sediment core we found no significant difference in 88 86sr between the two species in addition g ruber specimens from marine isotope stage 2 in the same core show 88 86sr values identical to the holocene specimens the strontium isotopes of both foraminifera species are strongly fractionated 88 86srcarb aq 0 248 0 005 when compared to published data of other major marine calcifiers applying the results from the inorganic precipitation experiments we find that the strong foraminiferal strontium isotope fractionation can be explained by calcification in a largely open system at high precipitation rates comparable in magnitude to rates known from scleractinian reef corals this interpretation is in good agreement with the kinetic calcification model for planktic foraminifera by kisakurek et al 2011 which was based on calcium isotopes and elemental sr ca ratios

carbon isotope anomaly and other geochemical changes at the triassic jurassic boundary from a marine section in hungary most mass extinctions are linked with carbon isotope excursions implying that biotic crises are coupled with changes in the global carbon cycle the isotopic evolution during the end triassic extinction is far less documented than that for the other major phanerozoic extinctions here we report a sharp and short lived 23 5 excursion in carbon isotope values for carbonate d 13 ccarb corresponding to a 22 excursion in the isotopic composition of marine organic matter d 13 corg and other geochemical

internal sources and sinks of water p n ca and cl in lake kinneret israel mass balance budgets linked among several materials are used to infer rates of processes affecting lake kinneret comparisons among budgets reveal the magnitudes of internal sources and sinks that cannot be directly inferred from individual budgets a water budget indicates that 180 x 1 o6 m3 of sublacustrine spring water plus ungauged surface flow enters the lake annually about a fifth the total inflow and two thirds as much water as is lost to evaporation this total ungauged inflow delivers about 90 000 t of cl yr i nine times the stream input ca input from total ungauged flow is about a third the stream input and the net internal ca sink in the system is sufficient to precipitate 60 000 t of caco yr i stream delivery of p mainly as particulate material is largely sequestered in the sediments 100 t yr i at least 1 100 t yr i of n primarily as n03 delivered by streams are apparently lost to denitrification while only 200 t yr 1 are sedimented cycling of n and p within the lake dominates over throughput in controlling standing stocks vertical mixing within the lake may play a dominating role in this cycling cycling of p in the lake can be regarded as closed a sediment water column turnover of materials with only minor hydrographic loss from the system by contrast n cycling is open with an important net loss to the atmosphere aquatic ecosystems for which hydrographic constraints are well defined provide an opportunity for mass balance analysis of reactive materials biogeochemical patterns deduced in well defined systems should have general application in this paper mass balance analyses are derived for water cl p n and ca in lake kinneret israel most mass balance analyses of lakes treat individual elemental budgets independently of one another we deliberately compare budgets to ask the following two questions what

constraining the marine strontium budget with natural strontium isotope fractionations 87sr 86sr δ88 86sr of carbonates hydrothermal solutions and river waters we present strontium sr isotope ratios that unlike traditional 87sr 86sr data are not normalized to a fixed 88sr 86sr ratio of 8 375209 defined as 88 86sr 0 relative to nist srm 987 instead we correct for isotope fractionation during mass spectrometry with a 87sr 84sr double spike this technique yields two independent ratios for 87sr 86sr and 88sr 86sr that are reported as 87sr 86sr and 88 86sr respectively the difference between the traditional radiogenic 87sr 86sr normalized to 88sr 86sr 8 375209 and the new 87sr 86sr values reflect natural mass dependent isotope fractionation in order to constrain glacial interglacial changes in the marine sr budget we compare the isotope composition of modern seawater 87sr 86sr 88 86sr seawater and modern marine biogenic carbonates 87sr 86sr 88 86sr carbonates with the corresponding values of river waters 87sr 86sr 88 86sr river and hydrothermal solutions 87sr 86sr 88 86sr hydend in a triple isotope plot the measured 87sr 86sr 88 86sr river values of selected rivers that together account for not vert similar18 of the global sr discharge yield a sr flux weighted mean of 0 7114 8 0 315 8 the average 87sr 86sr 88 86sr hydend values for hydrothermal solutions from the atlantic ocean are 0 7045 5 0 27 3 in contrast the 87sr 86sr 88 86sr carbonates values representing the marine sr output are 0 70926 2 0 21 2 we estimate the modern sr isotope composition of the sources at 0 7106 8 0 310 8 the difference between the estimated 87sr 86sr 88 86sr input and 87sr 86sr 88 86sr output values reflects isotope disequilibrium with respect to sr inputs and outputs in contrast to the modern ocean isotope equilibrium between inputs and outputs during the last glacial maximum 10 30 ka before present can be explained by invoking three times higher sr inputs from a uniquely glacial source weathering of shelf carbonates exposed at low sea levels our data are also consistent with the weathering peak hypothesis that invokes enhanced sr inputs resulting from weathering of post glacial exposure of abundant fine grained material

sources and transport routes of fine detritus material to the late quaternary dead sea basin abstract the sources and routes of transport of fine detritus material fdm to the lakes filling the late quaternary dead sea basin were studied by petrographic mineralogical grain size chemical and sr nd isotope analyses on sediments of the late quaternary lacustrine formations including river flood material dust and loess from the lake watershed the lacustrine formations comprise two sedimentary facies one that consists of alternating laminae of primary aragonite and silty detritus material aad facies and another that consists mainly of laminated detritus particles and generally lacks aragonite ld facies the aad facies characterizes the glacial intervals e g mis2 and 4 when lake levels were high while the ld facies characterizes interglacials e g mis1 5 and warmer glacial intervals e g mis3 when lake levels were low the detritus of both aad and ld facies show similar mineralogy mainly quartz and calcite grains with minor feldspars and clays but distinct grain sizes 8 10 m and 50 60 m respectively and distinct 87 sr 86 sr and end 0 711 0 712 and 7 to 8 versus 0 709 0 710 and 5 respectively the aad and ld fdm comprise desert dust of mixed granitic basaltic composition that was blown from the sahara desert and from the nile delta to the northern negev desert e g the loess deposits and the judean mountains bordering the dead sea basin mainly during glacial intervals along with enhanced mediterranean rain fronts the aad fdm reflects an enhanced transport of saharan granitic dust to the vicinity of the lake mainly during glacials the ld fdm was recycled from the loess surface cover of the negev desert mainly during interglacials and warm glacial intervals

estimating the viscosity and prandtl number of the tso morari crystalline gneiss dome indian western himalaya the tso morari crystalline tmc gneiss dome in the indian himalaya extruded from a depth of 120 km through an inclined subduction channel of sub elliptical cross section at the leading edge of the indian plate the velocity profile of this gneiss dome is derived after 1 presuming its incompressible newtonian rheology 2 finding the best fit of the outcrop of the gneiss dome to an ellipse 3 taking into account different lithologies to have existed at the top of the extruding gneiss body 4 considering the extrusion to have been driven by the buoyant push of the denser mantle beneath the lighter gneiss and 5 assigning a range of plausible densities for different litho units fitting the known rates of extrusion from a few centimetres up to about one hundredth of a millimetre per year from 53 ma onwards of this gneiss dome to its velocity profile constrains its maximum possible viscosity to 7 5 1022 pa s this magnitude is 102 104 times higher than previous estimates for gneisses and granites alternative explanations of our data are the following 1 there was a fall in extrusion rates of the tmc gneiss from 53 to 30 ma because of an increase in the estimated maximum viscosity from 6 2 1020 to 7 5 1022 pa s possibly indicating a fall in temperature and or compositional change of the tmc gneiss 2 lower the extrusion rates higher are the estimated viscosities 3 the tmc gneiss was more viscous probably due to its eclogite content 4 the estimated maximum viscosity is 102 times higher than that in collision zones and 102 104 times than that in the tibetan lower crust but broadly conforms to that for the crustal channel and average lithospheric and asthenospheric values the high magnitude of maximum possible prandtl number of 1028 of the tmc gneiss might be related to isothermal decompression of the gneiss during its extrusion

controls on stable strontium isotope fractionation in coccolithophores with implications for the marine sr cycle abstract the controls on stable sr isotope fractionation into the calcite produced by the coccolithophore species emiliania huxleyi coccolithus pelagicus spp braarudii and gephyrocapsa oceanica are investigated each species has been cultured under controlled laboratory conditions at a range of temperatures 10 25 c to test the potential of 88 86 sr as a proxy for growth rate and or sea surface temperature coccolithophores are one of the most abundant pelagic calcifiers since sr substitutes to some degree for ca in their calcite coccoliths coccolithophores represent a significant output of sr from seawater potentially influencing the 88 86 sr mass balance in the modern oceans the coccoliths are investigated for their 88 86 sr sr ca and 18 o measured as function of temperature as temperature is increased all species show a negative stable sr isotopic fractionation related to a temperature controlled growth rate we infer the shift of 88 86 sr to lighter values as indicative of a kinetic control on the isotope fractionation revealing the potential of 88 86 sr as a proxy for growth rate which in these experiments is primarily dictated by temperature the results from these experiments indicate that coccolithophore calcite incorporates sr with a very light 88 86 sr isotope composition as low as 0

calcite precipitation rates in the field measurement and prediction for a travertine depositing stream abstract rates of calcite precipitation from a travertine depositing stream were determined from changes in stream composition between consecutive sampling points and were compared with rates predicted from a laboratory derived rate law plummer et al 1978 the agreement in rates was generally within an order of magnitude and routinely within a factor of 3 least agreement between measured and predicted rates was obtained for sections of flowpath where relatively little change in bulk chemical composition occurred which were the sections with the greatest mass transfer calculation error and for the stream segment including a waterfall which was the section with the greatest error in estimated surface area reaction rate obtained from the mass of calcite precipitated onto seed crystals placed in the stream significantly underestimated the mass transfer rate for the travertine depositing stream of warm river cave and falling spring creek virginia the coupling of equilibrium speciation models with mass balance calculations and simple field measurements allowed successful field based quantification of reaction rates

sedimentary geochemical and hydrological history of lake kinneret during the past 28 000 years abstract the sedimentary geochemical and hydrological history of lake kinneret sea of galilee is reconstructed for the past 28 kyrs based on three sedimentary cores drilled at the lake and a trench dug at the shore of the prehistorical ohalo ii site during the past 28 kyrs either laminated or massive fine grained sediments were deposited in the lake comprising primary calcites and fine grain detritus sr ca mg ca 87sr 86sr ratios and 18o values of live and fossil ostracod shells cyprideis torosa and primary calcites together with xrd grain size and carbonate content analyses indicate contribution of the following types of waters to the lake 1 jordan river 2 regional runoff and 3 ca chloride brines currently comprises the tiberias spa brine during the last glacial period 28 24 ka the lake rose to its highest stand of 170 m below sea level bsl expanding over the kinnarot basin and converging with the southern hypersaline lake lisan at that time waters were mainly supplied to the lake by the jordan river and regional runoff with enhanced contribution of the dead sea ca chloride brine primary calcites were precipitated from the lake s solution forming sequences of laminated sediments on the lake s floor at 24 22 ka coinciding with heinrich event h2 at the north atlantic the lake retreated below the modern level of 214 m bsl depositing mainly flood related sediments at its margins the lake slightly rose during the younger dryas and subsequently declined towards the modern level with decreasing contributions of the jordan river waters brines and regional runoff reflecting a continuous aridification of the region during the holocene

tectonics and structural zonation of southern tibet china the yarlung zangbo suture zone is composed of several thrust sheets with distinct stratigraphies states of deformation and metamorphic grades successive deformations have been produced by persistent north south shortening since obduction of the ophiolites by late cretaceous palaeocene times a possible decoupling of the crust may be associated with the intracontinental thrust system which has formed in the subducted indian plate this article emphasizes the role of shear deformations in the building of a collision belt

salinization and dilution history of ground water discharging into the sea of galilee the dead sea transform israel abstract the mechanism governing salinization of ground water discharging into the sea of galilee in israel has been the subject of debate for several decades because the lake provides 25 of the water consumed annually in israel correct identification of the salt sources is essential for the establishment of suitable water management strategies for the lake and the ground water in the surrounding aquifers existing salinization models were evaluated in light of available and newly acquired data including general chemistry and o h c and cl isotopes based on the chemical and isotopic observations the proposed salt source is an ancient intensively evaporated brine 21 to 33 fold seawater which percolated through the valley formations from a lake which had formed in the rift valley following seawater intrusion during the late miocene low na cl and high br cl values support the extensive evaporation whereas high ca cl and low mg cl values indicate the impact of dolomitization of the carbonate host rock on the residual solution based on radiocarbon and other isotope data the dilution of the original brine occurred in two stages the first took place 30 000 a ago by slightly evaporated fresh to brackish lake water to form the sea of galilee brine the second dilution phase is associated with the current hydrological regime as the sea of galilee brine migrates upward along the rift faults and mixes with the actively circulating fresh ground water to form the saline springs the spatially variable chemical and isotopic features of the saline springs suggest not only differential dilution by fresh meteoric water but also differential percolation timing of the original brine into the tectonically disconnected blocks registering different evaporation stages in the original brine consequently various operations to reduce the brine contribution to the lake may be differentially effective in the various areas

efficiency of natural calcite precipitation compared to lake marl application used for water quality improvement in an eutrophic lake abstract since the 1980s several in lake restoration methods for eutrophied lakes have been developed based on artificially induced calcite precipitation and lime additions the aim of these measures is to improve water quality and reduce the incidence of cyanobacterial blooms by increasing p adsorption and removal through natural calcite precipitation the authors compared the relative efficiencies of lake marl application and natural calcite precipitation in immobilizing p mn and fe in lake arendsee northeastern germany and their subsequent value as a tool for managing eutrophication microprobe investigations of element distributions in calcite minerals of laminae precipitated annually during several years before and two years following the restoration suggest that recently grown biogenic calcites were more efficient at the co precipitation and immobilization of p fe and mn the lake marl applied as 16 calcite water mixture proved unsuitable as a restoration tool because of its coarse grain size mainly in the range of 20 1000 m and associated organic matter which reduced its suspension time and sorption reaction rates in the water column in lake arendsee or in similar eutrophic hardwater lakes with fast internal p recycling by rapid degradation of autochthonous organic matter in the water column and at the sediment surface sedimentary toc tp ratios of 200 or more biogenic calcites provide almost permanent p fe and mn retention in the sediments the study shows that epilimnetic additions of pure caco 3 seed crystals comparable to natural calcite precipitation are the most effective for improving water quality small caco 3 crystals exhibit a larger reactive surface and thus incorporate adsorbed dissolved nutrients and trace metals more rapidly during growth however in lake water quality management strategies work best only if external point and non point nutrient sources are reduced or diverted

evidence for mass dependent isotopic fractionation of strontium in a glaciated granitic watershed abstract the stable isotope composition of strontium expressed as 88 86sr may provide important constraints on the global exogenic strontium cycle here we present 88 86sr values and 87sr 86sr ratios for granitoid rocks a 150 yr soil chronosequence formed from these rocks surface waters and plants in a small glaciated watershed in the central swiss alps incipient chemical weathering in this young system whether of inorganic or biological origin has no resolvable effect on the 87sr 86sr ratios and 88 86sr values of bulk soils which remain indistinguishable from bedrock in terms of sr isotopic composition although due in part to the chemical heterogeneity of the forefield the lack of a resolvable difference between soil and bedrock isotopic composition indicates that these soils have thus far witnessed minimal net loss of sr a low degree of chemical weathering is also implied by bulk soil chemistry the isotopic composition of sr in streamwater is more radiogenic than median soil reflecting the preferential weathering of biotite in the catchment streamwater 88 86sr values however are indistinguishable from bulk soil 88 86sr values implying that no resolvable fractionation of sr isotopes takes place during release to the weathering flux in the damma forefield analyses of plant tissue reveal that plants rhododendron and vaccinium preferentially assimilate the lighter isotopes of sr such that their 88 86sr values are significantly lower than those of the soils in which they grow additionally 88 86sr values of foliar and floral tissues are lower than those of roots contrary to observations for ca for which sr is often used as an analogue in weathering studies we suggest that processes that discriminate against sr in favour of ca due to the different nutritional requirement of plants for these two elements are responsible for the observed contrast

spatial characteristics and controlling factors of chemical weathering of loess in the dry season in the middle loess plateau china hydrochemistry methods were used to decipher the weathering and geochemical processes controlling solute acquisition of river waters in the dry season in the middle loess plateau mlp one of the most severely eroded areas and turbid riverine systems in the world river waters were neutral to slightly alkaline with ph varying from 7 6 to 9 6 the total dissolved solids decreased from northwest to southeast with a mean value of 804 mg l much higher than the global average and other large rivers in china ternary diagram showed that river waters were dominated by na hco3 and cl with the main water type of hco3 cl na saturation index values mg2 ca2 and hco3 analyses indicated the preferential ca2 removal by calcite precipitation gibbs plots and stoichiometry plots indicated that the dissolved solutes were mainly derived from rock weathering with minor anthropogenic and atmospheric inputs samples in the northwestern basin are also influenced by evaporation a forward model of mass budget calculation showed that owing to high soluble characteristics evaporite dissolution was a major feature of river waters and contributed 41 to the total dissolved cations on average while carbonate and silicate weathering contributed 28 and 25 on average respectively besides evaporite dissolution cation exchange is also responsible for the high concentrations of na in river water spatial variations showed that evaporite dissolution and silicate weathering were higher in the northern basin whereas carbonate weathering was higher in the southern basin different from most rivers in the world the physical erosion rates varying from 117 7 to 4116 6 t km2y are much higher than the chemical weathering rates varying from 3 54 to 6 76 t km2y in the mlp because of the loose structure of loess and poor vegetation in the basin in the future studies on comparison of water geochemistry in different seasons and on influence of different types of land use and soil salinization on water geochemistry denudation rates and water quality should be strengthened in the mlp these results shed some lights on processes responsible for modern loess weathering and also indicate the importance of time series sampling strategy for river water chemistry copyright 2016 john wiley sons ltd

calcite twin morphology a low temperature deformation geothermometer abstract twinning of the e plane is the dominant crystal plastic deformation mechanism in calcite deformed below about 400 c calcite in a twin domain has a different crystallographic orientation from the host calcite grain so called thin twins appear as thin black lines when viewed parallel to the twin plane at 200 320 magnification under a petrographic microscope thick twins viewed in the same way have a microscopically visible width of twinned material between black lines calcite e twin width and morphology has been correlated with temperature of deformation in naturally deformed coarse grained calcite in this paper we present a compilation and analysis of data from limestones of the frontal alps france and switzerland and the appalachian valley and ridge and plateau provinces eastern united states to document this temperature dependence mean calcite twin width correlates directly with temperature of deformation such that thin twins dominate below 170 c and thick twins dominate above 200 c above 250 c dynamic recrystallization is an important deformation mechanism in calcite mean twin intensity twin planes mm correlates negatively with temperature and a cross plot of twin intensity with twin width can yield information about both strain and temperature of deformation these relationships provide a deformation geothermometer for rocks that might otherwise yield little or no paleotemperature data