strontium and carbon isotope constraints on carbonate solution interactions and inter aquifer mixing in groundwaters of the semi arid murray basin australia abstract strontium and carbon isotopes are used to study the effect of carbonate mineral dissolution and inter aquifer mixing on the chemical evolution of groundwater from the murray group limestone aquifer in semi arid se australia the 87 sr 86 sr ratio of groundwater evolves from 0 7097 at the basin margin to a less radiogenic value of 0 7084 about 250 km down gradient which is similar to the 87 sr 86 sr ratio of the aquifer carbonate matrix the concomitant increase in 13 c dic sr ca and mg ca ratios in the groundwater along a 250 km transect suggests that incongruent dissolution of high mg calcite controls the carbonate geochemistry in this aquifer further down gradient the groundwater is characterized by a relatively more radiogenic 87 sr 86 sr ratio caused by upward leakage and mixing with more radiogenic groundwater from the renmark group sand aquifer a mixing model using 87 sr 86 sr ratio suggests that the fraction of water that contribute to the murray group aquifer through upward leakage from underlying renmark group aquifer ranges from 15 to 85

arid zone groundwater recharge and salinisation processes an example from the lake eyre basin australia in arid central australia the 1 14 m km2 endorheic lake eyre basin leb experiences sporadic floods and contains saline shallow groundwater in this basin where on ground physical and chemical data are very sparse new observations of major ion chemistry stable isotopes 2h 18o 13c radiogenic isotopes 3h 14c and remote sensing modis data were used to investigate groundwater recharge and salinisation processes in 2006 2007 in january 2007 there was a large and intense local rainfall event followed by flooding to the normally dry lake eyre resulting from heavy rainfall in the northern leb that took 2 months to arrive at lake eyre groundwater chemistry from this study show no evidence of recharge from the floodwaters or the local rainfall however this does not preclude the process low transit times and low infiltrating volumes may mean that the recharge event has not yet been detected over the longer term the stable isotope chemistry indicates that groundwater is predominantly diffusely recharged during heavy local rainfall events 100 150 mm month and radiogenic isotopes reflect an older shallow groundwater efficiently mixing with recent decadal recharge the high total dissolved solids tds of regional shallow groundwater up to 52 5 g l is intrinsically linked with these recharge processes where infiltrating diffuse rainfall is evaporated and heavy rainfall events transport saline pore water saline due to evaporation in the unsaturated zone to the groundwater system the high tds of shallow groundwater beneath the dry lake eyre bed up to 322 g l is also controlled by evaporation however although evaporite minerals are prolific in the lake area the non conservative behaviour of br in pore water limits analysis of the role of halite mineral dissolution and precipitation reactions controlling groundwater salinity evaporation driven salinisation of shallow groundwater in arid central australia is distinct from the transpiration driven salinisation of groundwater in the australian murray basin located in a semi arid climate and results in relatively high groundwater salinity values compared with many other large arid zone endorheic basins across the world

transport of soluble salts in a large semiarid basin river murray australia median annual concentrations of cl so4 hco3 na k mg and ca increase greatly downstream in the river murray along its 2500 km route to the sea chloride increases from less than 2 mg l 1 near the headwaters to about 170 mg l 1 near the downstream end of the main channel water near the head of the river has hco3 balanced by similar equivalents of na ca and mg while higher salinity water in the downstream half of the river is dominated by na and cl sources of these dissolved ions include a sea derived airborne salts contributing essentially all of the cl br and 80 of the na and b rock derived ions from weathering of sedimentary rock and soil minerals contributing most of the observed hco3 80 of the ca and 20 25 of the mg and so4 much of the change in chemistry along the axis of the murray is due to influx of saline groundwater which has a major ion composition similar to sea water inflows of irrigation drainage water also enhance downstream transport of salts especially hco3 the stable isotope composition of the river murray 2h and 18o begins with relatively depleted heavy isotope abundances 47 8 in the uplands of the southeastern margin of the murray darling basin increasing steadily by 30 and 6 respectively due to evaporative enrichment from river surfaces and influx of drainage returned from irrigation diversions despite the similarity of groundwater major ion chemistry to that of sea water stable isotope compositions of groundwaters clearly demonstrate that water molecules from past marine incursions have been completely flushed from the system similarly the cl br ratios of groundwaters are not appreciably different from seawater values indicating that dissolution of fossil evaporites does not contribute significant salt to the groundwaters or the river

evaporation rate from a salt pan estimates from chemical profiles in near surface groundwaters evaporation of water from saturated saline soils or sediments induces gradients of the solutes in the remaining interstitial solution these gradients lead to a systematic and predictable solute distribution in the soil solution which may be used in some cases to estimate the rate of evaporation simple one dimensional transport models for the distribution of cl and br indicate net evaporation rates from the salt covered surface of lake eyre south australia of between 0 9 and 2 8 cm yr 1 the former is a minimum estimate averaged over 20 yrs which includes the major 1974 filling event while the latter reflects the most recent summer evaporation period

chloride imbalance in a catchment undergoing hydrological change upper barwon river southeast australia documenting whether surface water catchments are in net chemical mass balance is important to understanding hydrological systems catchments that export significantly greater volumes of solutes than are delivered via rainfall are not in hydrologic equilibrium and indicate a changing hydrological system here an assessment is made of whether a saline catchment in southeast australia is in chemical mass balance based on cl the upper reaches of the barwon river southeast australia has total dissolved solids tds concentrations of up to 5860mg l and cl concentrations of up to 3370mg l the high river tds concentrations are due to the influxes of groundwater with tds concentrations of up to 68 000mg l between 1989 and 2011 the median annual cl flux from the upper barwon catchment was 17 8 106kg 140kg a ha this represents 340 2230 of the annual cl input by rainfall to the catchment major ion and stable isotope geochemistry indicate that the dominant source of solutes in the catchment is evapotranspiration of rainfall precluding mineral dissolution as a source of excess cl the upper barwon catchment is not in chemical mass balance and is a net exporter of solutes the chemical imbalance may reflect the transition within the last 100ka from an endorheic lake system where solutes were recycled producing shallow groundwater with high tds concentrations to a better drained catchment alternatively a rise in the regional water table following land clearing may have increased the input of groundwater with high tds concentrations to the river system

groundwater flow regime within the gambier embayment of the otway basin australia evidence from hydraulics and hydrochemistry a conceptual groundwater flow model for the cainozoic sequence of the gambier embayment of the otway basin south australia is developed using hydraulic head distribution environmental isotopes and hydrochemical data local flow cells occur within the upper sequence of the gambier unconfined aquifer and are recognised by local relief of the water table and as rapid lateral variations in chloride 14c 2h and 18o concentrations indicating that regional flow is not dominant in the upper portion of the unconfined aquifer these localised systems are topographically controlled and have developed in response to undulating stranded coastal dune ridges of the bridgewater formation recharge areas correspond to dune highs while discharge is focused towards the lower lying interdunal regions total dissolved solids concentrations are controlled by evapotranspiration processes during recharge and ion ratios are modified by water rock interactions within the groundwater system groundwaters are more dilute in the southern section of the basin where the surplus of precipitation over evapotranspiration in the winter months is greater than that in the northern section of the basin a regional flow system with interaquifer mixing has developed within the confined dilwyn aquifer system recharge to the dilwyn aquifer has been identified downgradient from the basin margin via downward leakage from an intermediate flow system within the gambier unconfined aquifer to the deeper regional flow system of the confined dilwyn aquifer interaquifer mixing appears to be geologically controlled in the south by the elevated gambier axis and in the north by the kanawinka fault downgradient of the zero head difference line lateral flow appears to be the dominant transport mechanism within the dilwyn aquifer as indicated by constant chloride concentrations monotonic decrease in radiocarbon concentration and more negative 2 and 18 o composition

physical hydrogeology and environmental isotopes to constrain the age origins and stability of a low salinity groundwater lens formed by periodic river recharge murray basin australia summary a low salinity total dissolved solids tds 25 000 mg l is marked by a hectometer to kilometer scale transition in tds concentrations that is not stratigraphically controlled rather this boundary represents a mixing zone with the regional groundwater the position of which is controlled by the rate of recharge from the river the lens is part of an active and dynamic hydrogeological system that responds over years to decades to changes in river levels the lens has shrunk during the drought of the late 1990s to the mid 2000s and it will continue to shrink unless regular high flows in the murray river are re established over longer timescales the rise of the regional water table due to land clearing will increase the hydraulic gradient between the regional groundwater and the groundwater in the lens which will also cause it to degrade replacement of low salinity groundwater in the lens with saline groundwater will ultimately increase the salinity of the murray river reducing its utility for water supply and impacting riverine ecosystems

geochemistry of ground waters from the great artesian basin australia herczeg a l torgersen t chivas a r and habermehl m a 1991 geochemistry of ground waters from the great artesian basin australia j hydrol 126 225 245 ground waters from the confined lower cretaceous jurassic aquifer of the great artesian basin australia gab are characterised by na hco 3 type waters throughout the eastern and central parts of the basin and na sq c1 type waters in the western part sodium and bicarbonate increase in concentration from the northeastern margins to the southwestern discharge areas along the regional groundwater flowlines a mass balance and equilibrium model for major dissolved species and stable carbon isotopes of dissolved inorganic carbon show that the chemical trends observed are caused by mass transfer reactions involving cation exchange of na for ca mg carbonate dissolution and reactions between na and kaolinite to form na smectite the stable carbon isotopic composition of dissolved inorganic carbon dic increases from values of about 15 o near the basin margins to 6 o in the interior of the basin an inverse relationship exists between 6 3c and dic indicating addition of enriched carbon as the ground waters move basinwards a t2c 3c mass balance indicates that the trend toward heavier 6 3c values in the interior of the basin results from bacterial reduction of carbon dioxide to produce methane rather than dissolution of and equilibration with carbonate minerals the gab aquifer system is apparently open to co which is the product of in situ anaerobic fermentation producing co 2 enriched in t3c the chemical evolution of the major dissolved species and carbon isotope distribution in the eastern and central parts of the gab can then be envisaged as an initial pco 2 up to several orders of magnitude above atmospheric level is acquired within the recharge area by plant respiration and oxidation of organic matter in the soil zone initially silicate and carbonate minerals may dissolve at least in some parts of the basin resulting in increased alkalinity higher ca and mg concentrations and a 6 3c concentration of the dic of around 12 0 processes such as cation exchange of na for ca and mg in addition to the removal of some na by reverse weathering which produces a na smectite dominate in the interior of the gab the chemistry of ground waters derived from the western recharge areas is controlled by evaporite dissolution as indicated by very high ci br ratios

using hydrogeochemistry to understand inter aquifer mixing in the on shore part of the gippsland basin southeast australia groundwater in the latrobe valley in the gippsland basin of southeast australia is important for domestic agricultural and industrial uses this sedimentary basin contains a number of aquifers that are used for water supply dewatered for open pit coal mining and which are potentially influenced by off shore oil and gas production major ion chemistry together with stable and sr isotope data imply that the main hydrogeochemical processes are evapotranspiration with minor silicate and carbonate weathering methanogenesis and so4 reduction in reduced groundwater associated with coal deposits have also occurred groundwater has estimated 14c ages of up to 36ka and is largely 3h free carbon 14 ages are irregularly distributed and poorly correlated with depth and distance from the basin margins the observations that the geochemistry of groundwater in aquifers with different mineralogies are similar and the distribution of 14c ages is irregular implies that the aquifers are hydraulically connected and horizontal as well as vertical inter aquifer mixing occurs the connection of shallow and deeper aquifers poses a risk for the groundwater resources in gippsland as contaminants can migrate across aquifers and dewatering of shallow units may impact deeper parts of the groundwater system

geochemistry of halogens in the milk river aquifer alberta canada abstract analytical data are presented for cl br and i on a regional scale for the milk river aquifer the three halides show strikingly similar spatial distributions and are highly correlated concentrations are low in the freshwater portions of the aquifer but increase by as much as two orders of magnitude along the margins however halide ratios reach nearly constant values moving down gradient suggesting the dominance of a common subsurface source for these ions ratios of cl i and cl br are less than those of seawater and fit an origin derived from the diagenesis of organic matter in the sediments halide ratios rule out leakage and or diffusion from the underlying colorado group as a major influence on the chemistry the favored hypothesis is altered connate seawater diffusing from low permeability units within the milk river formation as the primary source of salts this hypothesis of an internal source has important implications for solute sources in other aquifers affected by saline waters because it does not require the importation of a distant fluid the129i i ratio has a meteoric value in groundwater collected near the recharge area but ratios for downflow waters are only 8 70 of this value due to the 16 ma half life of129i these data indicate that most of the increase in dissolved i cannot derive from concentration of a meteoric source by ion filtration but must have a subsurface origin concentrations of129i producedin situ by spontaneous fission of238u attain measurable levels only in the oldest waters sampled ages 105a in which it may account for nearly 90 of the total dissolved129i concentration water ages based upon36cl cl data range up to 2 ma if uncorrected for any dilution by subsurface sources of dead cl if one assumes that the subsurface contributions of cl contribute at least 90 of total cl in the distal portion then the36cl based ages are reduced to 1ma somewhat greater than those estimated by hydrodynamic modeling

quantitative temperature time information from retrograde diffusion zoning in garnet constraints for the p t t history of the central black forest germany garnet from a kinzigite a high grade gneiss from the central black forest germany displays a prominent and regular retrograde diffusion zoning in fe mn and particularly mg the mg diffusion profiles are suitable to derive cooling rates using recent datasets for cation diffusion in garnet this information together with textural relationships thermobarometry and thermochronology is used to constrain the pressure temperature time history of the high grade gneisses the garnet biotite thermometer indicates peak metamorphic temperatures for the garnet cores of 730 810 c the temperatures for the outer rims are 600 650 c garnet al2sio5 plagioclase quartz gasp barometry garnet rutile al2sio5 ilmenite grail and garnet rutile ilmenite plagioclase quartz grips barometry yield pressures from 6 9 kbar u pb ages of monazite of 341 2 ma date the low p high t metamorphism in the central black forest a rb sr biotite whole rock pair defines a cooling age of 321 2 ma the two mineral ages yield a cooling rate of about 15 2 c ma 1 the petrologic cooling rates with particular consideration of the fo2 conditions for modelling retrograde diffusion profiles agree with the geochronological cooling rate the oldest sediments overlying the crystalline basement indicate a minimum cooling rate of 10 c ma 1

transient hydrological conditions implied by chloride mass balance in southeast australian rivers a robust correlation between electrical conductivity ec values and cl concentrations in river water from southeast australia allows detailed cl fluxes to be calculated from continuous ec and river discharge records many victorian rivers export significantly more cl than is delivered to their catchments by rainfall cl is defined as the mass of cl exported in the rivers relative to that input by rainfall over a multi year period cl 100 indicates that the river exports the same mass of cl as is input by rainfall there is a systematic relationship between catchment type and cl rivers draining cleared plains have cl values between 50 and 750 rivers draining volcanic plains have cl values of 770 1600 whereas rivers with large forested upland catchments have cl values of 50 110 these values are minima as they do not account for cl exported by groundwater from the catchments the calculations are based on long term up to 22 year records that span drought and high rainfall periods the magnitude of cl is far higher than can be explained by errors in the calculations or variability in rainfall and runoff and cl br ratios preclude halite dissolution as a source of cl the excess cl reflects hydrological changes in the catchments land clearing on the cleared plains has caused the rise of regional water tables which results in the export of cl from saline groundwater via increased baseflow to the river systems drainage systems on the volcanic plains are re establishing following impoundment by recent 4 5 ma lava flows cl which accumulated in shallow groundwater around saline lakes and marshes developed on these volcanic plains is now being exported via the rivers the upland catchments have undergone less landscape change and may be in chemical balance the methodology outlined here provides a straightforward assessment of whether catchments are in chemical balance that may in turn indicate whether they are undergoing hydrological changes

isotope and minor element geochemistry of high arsenic groundwater from hangjinhouqi the hetao plain inner mongolia abstract high as groundwater is widely distributed in the northwestern hetao plain an arid region with slow groundwater flow arsenic concentration in groundwater ranges from 1 to 1000 g l most water samples have elevated salinities with cl and or hco 3 as the dominant anions and na as the dominant cation high concentrations of as in shallow aquifers are associated with strongly reducing conditions as evidenced by high concentrations of dissolved organic c doc nh 4 dissolved sulfide arsenite and dissolved ch 4 and relatively low concentrations of no 3 and so 4 2 results of the hydrochemical and h and o isotope geochemical studies indicate that evapotranspiration is an important process controlling the enrichment of na and cl as well as trace elements such as as b f and br in groundwater in na hco 3 dominated groundwaters as b and f were enriched decades of irrigation using yellow river water has resulted in elevation of the groundwater level which has accelerated salt accumulation in shallow groundwater and surface soil in addition irrigation is responsible for the release of some components from aquifer materials and mixing with saline groundwaters as indicated by minor element and isotope geochemical data used to trace groundwater flow paths sr isotope composition also indicates that bedrock weathering is one of the primary sources of as in groundwater in the study area

the hydrogeology hydrochemistry and environmental isotopes of the campaspe river aquifer system north central victoria australia the campaspe river hydrogeological system of north central victoria consists of two major units 1 the tertiary deep lead aquifer a combination of the renmark group and calivil formation which forms the major aquifer of the region and 2 the plio pleistocene shepparton formation which forms a complex aquitard aquifer system on top of the deep lead recharge to the deep lead aquifer is twofold 1 a major component of recharge occurs along the southern reaches of the campaspe river where the overlying shepparton formation is thin and becomes more permeable and 2 recharge occurs by vertical downward movement of water from the shepparton formation whose heads are everywhere higher than those of the deep lead natural discharge from the system occurs further to the northwest beyond the murray river salinity gradually increases down gradient in the deep lead with an abrupt increase to greater than 6000 mg l 1 total dissolved solids close to the murray river except in the goornong area in the south which appears to be separated from the main deep lead system this increase is characterised by a certain hydrochemical evolution of the water wherein very fresh recharge with a mnacl 1 0 changes to an oceanic type composition while still in the low salinity range this is due largely to concentration of the original solutes in the system and is the consequence of salt remobilisation within the catchment the shepparton formation waters on the other hand are characterised by disorder namely fresh to saline water juxtaposed both horizontally and vertically heads in both the shepparton formation and the deep lead had been increasing at the rate of about 15 20 cm yr 1 for at least several decades the advent of large scale withdrawal from the deep lead in the early 1980s has arrested this trend in the northern and central portions of the area a decline in aquifer pressures is evident this decline will induce increased leakage from the shepparton formation down into the deeper aquifer and such leakage could possibly result in a degradation of its water quality stable isotope data indicate that under the existing hydrologic regime little irrigation drainage water has penetrated to the deep system

geochemical and 222rn constraints on baseflow to the murray river australia and timescales for the decay of low salinity groundwater lenses the distribution of 222rn activities and major ion concentrations show that during low river flows characteristic of the recent drought conditions the middle reaches of the murray river northern victoria were a predominantly gaining system at low river levels may 2009 may 2010 and were variably gaining and losing at higher river levels november 2009 the location of gaining and losing reaches are partially governed by the position of the river with respect to the edge of its floodplain gaining reaches occur where the floodplain narrows or where the river is adjacent to the steep slopes at the floodplain margin cumulative inflows along this 350km stretch of the river estimated from 222rn activities were 320 1500m 3 day in november 2009 and 560 4300m 3 day in may 2010 the relatively large uncertainty reflects the heterogeneous and poorly constrained groundwater 222rn activities major ion variations notably cl concentrations and na ca ratios correlate with 222rn activities and may be used as indicators of groundwater inflows baseflow contributed 1 of the total water to this part of the river and consequently has little impact on river water quality nevertheless the groundwater inflows remove water from low salinity groundwater lenses that underlie the river and during the drought conditions these lenses were degrading these reaches of the river murray are an example of a system that transitioned from being dominantly losing to being variably gaining due to diminishing surface water flows

delivery of marine chloride in precipitation and removal by rivers in the murray darling basin australia abstract rising groundwater tables and increasing river salinities are major problems in the semi arid murray darling m d drainage basin of se australia chemical data from precipitation rivers and groundwaters are integrated here to estimate chloride fluxes in the context of dramatic alteration of the hydrologic balance in the basin initiated during european settlement approximately 150 years ago our analysis indicates that about half of cl deposition from the atmosphere in the western murray basin is derived from resuspended regional continental dust resulting in high ca na ratios in bulk precipitation samples estimates of recent marine deposition of cl to the m d basin were made by excluding rainfall data from sites having high ca na ratios basin wide budgets for cl delivery from the atmosphere and removal by rivers indicate that the darling basin retains about 90 of current annual input of marine cl whereas the river murray exports two to three times current annual input to the murray basin exclusive of the darling some implications from this study are as follows 1 1 re evaluation of net marine cl input by rain implies that recent model calculations of 36 cl cl inputs from the atmosphere to the murray basin may differ significantly from actual values in particular net 36 cl cl input ratios from the atmosphere to the western murray basin may be a factor of two higher than those derived assuming all cl in rain is of recent marine origin 2 2 the very large inventories of salt within the two catchments especially the saline groundwaters of the murray basin accumulated over very long periods probably of the order of a few million years the current rearrangements of stored salinity as a result at least in part of human perturbations of the hydrologic balance are likely to continue for an extended period because of the massive quantities of salts involved and thus present major limitations on options for long term management of the m d basin

handbook of environmental isotope geochemistry vol 1 the terrestrial environment a p fritz and j ch fontes editors elsevier amsterdam 1980 xii 532 pp u s 90 25 dfl 185 00

the role of soil organic matter in the geochemical cycling of chloride and bromide abstract chloride to bromide ratios were determined for rainfall in western australia and groundwaters and surface waters from a number of catchments in western australia victoria and queensland the ratio in rainfall though showing a large short term scatter on average reflected the ratio in ocean water groundwaters and surface waters often showed characteristic differences in cl br presumably associated with the cycling of bromide through soil organic matter to prove this association it is shown that in the leachate of saturated small columns of soil the cl br ratio is governed by chloride and bromide released from decomposing organic matter on leaching the columns of soil the cl br weight ratio decreased rapidly from a high 300 reflecting rainfall to a low 10 reflecting the ratio of chlorine to bromine bound to soil organic matter

halogens cl br and i geochemistry in middle triassic carbonates implications for salinity and diagenetic alteration of i ca mg ratios abstract as an important family of elements halogens cl br and i have been widely used to study geological processes particularly in high temperature environments showing great prospects either in fundamental or in applied studies however little work has been conducted for sedimentary and low temperature diagenetic environments re construction although these elements have the potential in theory here we perform a pilot study on this issue using a case study of middle triassic marine dolomitization in south china our results show that the average cl concentrations in limestone dolomitic limestone calcitic dolomite and dolomite are 88 3 ppm 114 7 ppm 121 3 ppm and 142 9 ppm respectively and the corresponding br concentrations are 1 15 ppm 1 42 ppm 1 59 ppm and 2 13 ppm respectively both the concentrations of cl and br increased with the increasing dolomitization degree the increasing tendency of cl and br is similar to the seawater evaporation trajectory before halite precipitation indicating that dolomitization occurs in fluids with elevated salinity meanwhile the difference of cl br ratios between our carbonate samples and seawater may be ascribed to the input of terrestrial water which has variable cl br ratios as for the concentration of i the mean values sharply decreased from 0 36 ppm in limestone to 0 13 ppm in dolomitic limestone samples and it further lowered to 0 09 ppm and 0 08 ppm in calcitic dolomite and dolomite samples respectively the calculated i ca mg ratios in limestones vary between 0 05 and 0 58 mol mol with an average value of 0 29 mol mol indicating that limestone formed in open ocean oxygen minimum zone omzs or anoxic basin environment the average i ca mg ratio decreases from 0 29 mol mol in limestone to 0 06 mol mol in dolomite serving as an important case that dolomitization decreases i ca mg ratios of carbonates rocks halogens in carbonates therefore have promising potential for investigating the sedimentary and diagenetic environments of carbonate rocks

contributions to the solute and isotopic groundwater geochemistry antelope island great salt lake utah abstract the 110 km2 antelope island is predominantly composed of precambrian gneiss similar to rocks in the wasatch range 32 km to the east three types of island groundwater systems have been identified on the basis of aquifer composition and dissolved solute content the systems include ground waters which discharge from either crystalline or sedimentary rocks sedimentary groundwater systems contain ground water which is either na cl rich or poor all island ground water has anomalously high na cl or so24 concentrations when compared with ground waters that issue from similar bedrock in nearby areas island groundwater systems may be statistically distinguished from each other and from other ground water in the region the solute chemistry of island ground water cannot be accounted for by the simple dissolution of aquifer minerals and the water does not plot along fault controlled thermal water precipitation or parent aquifer precipitation cl so 2 4 mixing lines discharge elevations and cl so 2 4 also rule out mixing with residual salts from paleo lake bonneville or brines of the great salt lake for most island ground water tritium values 40 tritium units tu suggest that island groundwater systems are primarily recharged from modern meteoric water stable isotopic 2h and 18o data plot along an evaporation line which indicates that recharge water contains a component of evaporated great salt lake water temporal variations in spring discharges tritium concentrations and discharge temperatures of less than 20 c indicate short flow paths and shallow circulation excess cl and so2 4 concentrations are attributed to the deposition of aerosols of wind blown dust from nearby evaporate deposits and sea spray sulfur isotope data suggest contributions to crystalline systems of reduced sulfur from nearby smelter or other industrial plumes

chlorine 36 dating of very old groundwater 1 the great artesian basin australia chlorine 36 has many advantages as a dating tool for very old groundwater these advantages include a suitable half life 3 01 x 10 sup 5 years simple geochemistry conservative behavior in groundwater and a general absence of subsurface sources at levels comparable to the atmospheric input recent advances in tandem accelerator mass spectrometry have permitted the analysis of sup 36 cl at low abundance expected following residence in the subsurface for 10 sup 6 years or more in order to test the suitability of sup 36 cl for dating very old groundwater the sup 36 cl cl ratios of 26 groundwater samples from the great artesian basin of australia have been measured groundwater ages calculated from the sup 36 cl data compare favorably with ages computed independently from hydrodynamic simulations

environmental isotopes as indicators of inter aquifer mixing wimmera region murray basin southeast australia abstract complex groundwater flow systems in confined aquifers that result from geological structures stratigraphic changes or the absence of efficient aquitards are difficult to constrain using physical parameters alone despite a relatively simple aquifer configuration the distribution of groundwater total dissolved solids tds concentrations 13c values 87sr 86sr ratios and 14c activities a14c in groundwater in the wimmera region of the southern murray basin implies that considerable inter aquifer flow has occurred given the presence of both silicate and carbonate aquifers 13c values and 87sr 86sr ratios are the key parameters that demonstrate inter aquifer flow locally between 40 and 95 of water from one aquifer has infiltrated the underlying aquifer homogenising many aspects of the groundwater geochemistry groundwater residence times estimated from a14c range from modern to 30 ka and the distribution of 14c residence times confirm that inter aquifer flow is regional scale and long term recharge of the deepest aquifers occurs across a broad region and not solely at the basin margins vertical leakage rates are 6 10 10 3 m year and long term recharge rates 0 1 0 2 mm year

geological control on the origin of fresh groundwater in the otindag desert china abstract the present study has explored the origin of fresh groundwater in the otindag desert china using environmental tracers the results characterize hydrochemical and isotopic properties of groundwater in this middle latitude desert of arid asia clarifying their spatial distribution and linkage with climatic topographic and geologic settings and interpreting the groundwater source and chemical evolution hydrogeochemical and isotopic signals suggest that groundwater recharge in the desert is isolated from seasonal and regional variations in meteorological forcing stable isotopic data 2h 18o and radioactive isotopic data 3h indicate that the desert aquifer is dominated by high altitude cold water originating from the highland mountains that border the desert to the east and south variography shows that the dip of the main xilamulun fault is a dominant control on the groundwater flow implying that the tectonic settings are more important than climatic and topographical settings to explain the origin of groundwater in the desert this means that the origin of fresh groundwater in the desert is maily controlled by geological structures this study provides a new perspective into the origin and evolution of groundwater resources in the middle latitude deserts of the arid asia

hydrogeochemical and isotopic constraints on the origins of dryland salinity murray basin victoria australia abstract combined hydrogeological and hydrogeochemical data allow flow systems and the origins of solutes in the honeysuckle creek area of the southeastern murray basin which is an area affected by dryland salinity to be constrained recharge occurs both on the uplands that are composed of fractured violet town volcanic rocks and the riverine plain that comprises sediments of the shepparton and coonambidgal formations groundwater from the violet town volcanics has low salinity 20 mmol l groundwater has intermediate cl br ratios 600 1000 which indicate that the high salinities do not simply result from halite dissolution rather mixing of groundwater homogenises cl br ratios and evaporation as a consequence of a shallow water table is the dominant process that increases salinity oxygen and h isotopes also indicate that mixing and evaporation have occurred these results indicate that land use over the whole region not just the uplands needs to be considered in any salinity management plans additionally future development of salinity is controlled by depth to the water table on the plains and the efficiency of recharge rather than by salt stores halite or brines in the unsaturated zone

geochemistry and origin of formation brines from the paris basin france 2 saline solutions associated with oil fields abstract oil fields from the paris basin are located in three geological levels dogger middle jurassic rhaetian and keuper upper triassic the origin of water and dissolved salts in saline solutions associated with oil is investigated using the hypothesis that cl and br are conservative in solution in a diagram of cl br ratios vs cl the points of the dogger and the keuper aquifers lie in the zone of primary brines whereas those of the rhaetian are located in the zone of secondary brines the na cl ratio is very high in all of the saline solutions suggesting either a relatively poorly evolved brine at the beginning of halite deposition or some halite dissolution all of the saline solutions especially those from the dogger aquifer are clearly diluted dilution by meteoric waters would not alter the cl br ratio high concentrations of lithium rubidium and boron are attributed to the presence of an extremely evolved brine of marine origin in mixtures of secondary brines formed by dissolution of halite and small amounts of sylvite and ca sulphate mass balance calculations of the excess of cl with respect to na k allows the fraction x of water derived from the primary brine to be calculated assumptions are that all na and k is derived from the secondary brine and that the cl content of the primary brine is constrained by bischofite saturation at 11 000 mmol kg 1 the typical proportion of water from the primary brine waters is 0 7 in the dogger formation and 2 4 in the keuper values of the concentration factor cf expressed as the ratio of the molal concentration of a conservative ion in the evolved brine to its concentration in seawater have been calculated for lithium solutions from the dogger and keuper aquifers have cfli values of 1 8 103 and of 7 7 103 respectively in the rhaetian aquifer the linear relationship between heavy isotope contents of the brine 2h and 18o and the cl content indicates a mixture of two water sources the first one is meteoric water as defined by the intersection of the formation water line with the global meteoric water line 2 h 65 18 o 9 3 the other end member is enriched in heavy isotopes and in cl and is attributed to seawater that has dissolved evaporites mainly halite however the presence of small amounts of an extremely evolved brine is required to account for the bromide lithium rubidium and boron contents of the formation brine from the rhaetian aquifer as this contribution is very limited in amount it cannot affect the heavy isotope content of the formation water mass balance equations are solved for ternary mixtures of meteoric water seawater and brine the same constraints as above no na and k supplied by the primary brine and clbrine 11 000 mmol kg 1 are applied it is also assumed that the seawater component has the same ionic contents as modern seawater and that the salt content of the meteoric component is negligible the fraction of primary brines is x 1 4 according to the cl balance this estimate agrees with that obtained from the lithium balance assuming that the primary brine component was the same as that of the keuper formation water mass balance calculations also indicate that the so42 content of the rhaetian formation water is exclusively due to the secondary brine component in the three saline solutions the very high ca2 contents and high ca 2 mg 2 ratios may be attributed to reaction of the very evolved brine free of so2 4 with gypsum or anhydrite the result is an exchange of mg2 for ca2 which causes a release of ca2 to the solution and a precipitation of secondary mg sulphate this process can also account for the high strontium contents of the analysed samples values of the ratio 87 sr 86 sr are very high in the keuper formation water due to close contact of the solutions with the granitic basement or with granite derived detrital deposits values in the rhaetian and dogger aquifers equal those of upper triassic marine deposits the stable isotope 34s and 18o content of the dissolved aqueous so2 4 indicates a triassic origin for the bulk of sulphate involved in the evolution of formation waters from the rhaetian and from the dogger all geochemical indicators thus show a vertical migration of triassic brines however aqueous so2 4 from the keuper has a permian isotopic signature suggesting a reworking in solution of salts from this period

geochemical evolution of groundwater flowing through arsenic source sediments in an aquifer system of west bengal india the source of geogenic arsenic as contaminating a shallow aquifer in west bengal was traced to fine grained sediments deposited in an abandoned river channel along with as bearing phases these sediments contain 0 46 co deposited organic carbon the release of as and the geochemistry of groundwater within the channel fill deposits is investigated using a detailed mass balance model supported by aqueous solid phase and mineralogical data the model describes the evolution of groundwater chemistry along a flow path extending from its recharge in an abandoned channel pond through the channel fill to the underlying aquifer variations in groundwater composition are explained in terms of mineral weathering of host sediments driven by organic carbon decay arsenic is released through the reductive dissolution of goethite and the weathering of chlorite concomitantly some as is sequestered in precipitating vivianite these competing processes reach equilibrium deeper in the channel fill sequence as groundwater as concentrations stabilize the model yields estimates of mineral reaction or precipitation rates including rates of organic carbon oxidation 1 15 mmol c l 1 a 1 and net as release 4 57 10 4 mmol l 1 a 1 fine grained slightly permeable deposits such as channel fill containing reactive organic carbon and as bearing goethite and phyllosilicates are centers of intense chemical weathering conducive to as mobilization

chlorine 36 in groundwater as a palaeoclimatic indicator the east midlands triassic sandstone aquifer uk the36cl contents of groundwaters from the east midlands triassic sandstone have been used to deduce rainfall its chloride content and evapotranspiration during the late pleistocene at this time the regional precipitation and evapotranspiration would have been reduced relative to the modern and holocene climate it is estimated that the infiltration was reduced by about 40 mm a 1 the method for evaluation of these palaeoclimatic parameters is dependent upon the major cl source being a marine aerosol fall out this is the general case but groundwater east of the exploited zone of the aquifer contains chloride which is derived from saline formation water with a marinecl br ratio and in equilibrium with the in situ neutron flux the fall out of cosmogenic36cl at the geomagnetic latitude 56 2 n is evaluated as 30 6 atoms m 2s 1 and is significantly greater than that estimated from the theoretical fall out curve of bentley et al 1 the bomb peak of36cl remains entirely within the unconfined zone of the aquifer the assessment of groundwater residence time from the36cl chronometer is shown to be impossible for this aquifer

geochemical and isotopic evidence for palaeo seawater intrusion into the south coast aquifer of laizhou bay china this research aims to improve the current knowledge of groundwater salinisation processes in coastal aquifers using combined hydrochemical and isotopic parameters and inverse hydrochemical modelling field investigations were conducted in laizhou bay which is the area most seriously affected by seawater intrusion in north china during three sampling campaigns along a vertical transect in the changyiliutuan area 95 ground and surface water samples were collected for major ion and isotope analysis

decoupling of solutes and water in regional groundwater systems the murray basin australia documenting the origins residence times and movement of groundwater and the solutes that it contains is critical to understanding hydrogeological systems this study uses cl mass balance to determine the cl accession time i e the time required for cl to accumulate and cl to estimate the residence times of cl in the victorian portion of the murray basin southeast australia much of the murray basin contains saline groundwater with total dissolved solids tds concentrations commonly 14 000 mg l and locally up to 300 000 mg l the total mass of cl stored in the victorian portion of the basin is estimated as between 12 400 and 47 100 mt using present day rainfall totals and cl concentrations in rainfall the cl accession time is 170 to 650 ka aquifer thicknesses and groundwater salinity both increase westwards in this part of the murray basin consequently the cl accession times increase westward from 0 1 0 6 ka to 286 1080 ka by contrast c activities of the majority of the groundwater are 2 pmc and commonly much higher notwithstanding the difficulty in correcting c residence times the widespread occurrence of groundwater with above background c activities implies that groundwater residence times are generally 30 ka which is substantially shorter than the cl accession times rcl the ratio of cl to total cl 10 values of the groundwater are between 20 and 230 and are uncorrelated with cl concentrations while it is difficult to determine precise cl residence times the observation that the rcl values are significantly higher than those that represent secular equilibrium with the aquifer matrix rcl of 5 to 10 indicates that they are up to a few hundred thousand years and similar to the cl accession times the rcl values together with the geology of the aquifers stable isotope ratios and major ion geochemistry precludes halite dissolution incorporation of connate water or the long term diffusion of cl from clays as mechanisms of producing the elevated cl concentrations rather it is most likely that the high cl concentrations result from recycling of solutes in saline lakes and playas or repeated cycles of evapotranspiration in the unsaturated zone

the importance of silicate weathering of a sedimentary aquifer in arid central australia indicated by very high 87sr 86sr ratios with the exception of brine systems and crystalline rock aquifers groundwater 87sr 86sr ratios rarely differ by more than 0 01 from the phanerozoic seawater value of 0 70923 groundwater 87sr 86sr ratios from central australia 0 72562 0 76248 are the highest ever recorded for a low salinity sedimentary aquifer we propose a model for the evolution of these 87sr 86sr ratios and demonstrate how the lowest 87sr 86sr ratios reflect water rock interactions with predominantly carbonate minerals while the highest 87sr 86sr ratios are ultimately controlled by weathering of old primary silicate minerals detailed analysis of aquifer core material identified albite and microcline as the most prevalent primary silicates and where these minerals were abundant relatively high rb concentrations were measured high rb combined with long time scales since deposition has produced very high 87sr 86sr ratios in the rocks and subsequently the groundwater therefore strontium isotopes can provide further constraints for chemical models of arid zone groundwater systems particularly when silicate hydrolysis is believed to significantly contribute to dissolved solute compositions

hydrogeochemistry groundwater ages and sources of salts in a granitic batholith on the canadian shield southeastern manitoba abstract the hydrogeochemistry of the lac du bonnet granitic batholith has been determined for the region of the whiteshell research area wra in southeastern manitoba canada this work forms part of the geosciences studies performed for the canadian nuclear fuel waste management program over the period 1980 1995 by atomic energy of canada limited aecl knowledge of the variation of groundwater chemistry and its causes is useful in assessing the performance and safety of a nuclear fuel waste vault located at depths of up to 1000 m in a crystalline rock formation of the canadian shield groundwaters and matrix pore fluids have been obtained by standard sampling methods from shallow piezometers in clay rich overburden from packer isolated borehole zones intersecting fractures or fault zones in the bedrock and from boreholes in unfractured rock in aecl s underground research laboratory url eighty six individual fracture groundwaters have been sampled and analysed from permeable zones in 53 boreholes drilled to depths of up to 1000 m in the lac du bonnet batholith in addition 28 groundwaters from piezometers in a large wetland area near the url have been sampled and analysed to determine the influence of clay rich overburden on the bedrock hydrogeochemistry analyses have been made for major and minor ions ph eh trace metals and stable and radioactive isotopes to characterise these groundwaters and relate them to their hydrogeologic regimes shallow groundwaters in the fractured bedrock are generally dilute tds 500 m na ca cl so4 waters of increasing salinity up to 50 g l with depth are found and in some fractures the waters have evolved to a ca na cl composition isotopic data indicate that these waters are warm climate and pre glacial in origin with residence times of over 1 ma pore fluids observed to drain from the unfractured rock matrix in the url facility are almost pure ca cl in composition 90 g l salinity and have a 2h 18o composition displaced well to the left of the global meteoric water line about which all other wra groundwaters lie this information indicates that these pore fluids have undergone prolonged water rock interaction and have residence times of 101 103 ma most of the deeper fracture groundwaters and pore fluids have low br cl ratios and moderate to high 34s values of dissolved so4 which indicates that their salinity could be derived from a marine source such as the basinal sedimentary brines and evaporites to the west of the batholith these fluids may have entered the batholith during early paleozoic times when sedimentary rocks were deposited over the granite and were driven by a hydraulic gradient resulting from higher ground in western canada the hydrogeochemical data and interpretations show that below 500 m in the wra fracture hosted groundwaters are very saline reducing and old and are therefore indicative of stagnant conditions over the period of concern for nuclear waste disposal 1 ma the intact rock matrix at these depths is extremely impermeable as indicated by the presence of pore fluids with unusual geochemical and isotopic characteristics the pore fluids may represent basinal brines that have evolved geochemically and isotopically to their current composition over periods as long as 103 ma

factors controlling mechanisms of groundwater salinization and hydrogeochemical processes in the quaternary aquifer of the eastern nile delta egypt in this study combining interpretations of conservative dissolved ions and environmental isotopes in water were used to investigate the main factors and mechanisms controlling groundwater salinization and hydrogeochemical processes in the eastern nile delta egypt hydrogeochemical and isotopic study has been carried out for 61 water samples from the study area total dissolved solid tds contents of groundwater are highly variable rising along flowpath from the south 410 mg l to the north 14 784 mg l implying significant deterioration and salinization of groundwater based on tds and ionic ratios groundwater samples were classified into three groups in low saline groups water chemistry is greatly influenced by cation exchange mineral dissolution precipitation anthropogenic pollutants and mixing with surface water whilst in high saline groups water chemistry is affected by salt water intrusion reverse cation exchange and evaporation the chemical constituents originating from saline water sources reverse ion exchange and mineral dissolution are successfully differentiated using ionic delta and saturation index approaches the 18o 2h relationship plots on a typical evaporation line suggesting potential evaporation of the recharging water prior to infiltration isotope evidence concludes that the groundwater have been considerably formed by mixing between depleted meteoric water recharged under different climatic conditions and recently infiltrating enriched surface water and excess of irrigation water the 18o data in conjunction with chloride concentrations provide firm evidence for impact of dissolution of marine origin evaporite deposits during past geologic periods on groundwater salinity in the northern region moreover the relation between 14c activities and cl concentration confirms this hypothesis

past changes to isotopic and solute balances in a continental playa clues from stable isotopes of lacustrine carbonates in many salt lakes around the world the relative abundance of preserved authigenic minerals is different from that predicted from solute mass balance calculations conventional mass balance models assume that chloride behaves conservatively over long periods of time and fail to take into account the role of diffusion deflation and fractional crystallisation dissolution of salts an alternative approach is to use oxygen isotopes as these reflect directly water molecule rather than solute concentrations and have the added advantage of providing a palaeohydrological record in lacustrine carbonates we present a steady state stable isotope model in conjunction with stable isotopic measurements of sub surface brines regional groundwaters and carbonate deposits from the lake malata lake greenly playa complex in south australia to estimate the apparent leakage and palaeoleakage from these superficially closed playa lakes the steady state model calculations using the present and compositions of the lake brines and inflowing groundwater suggest that the apparent present day leakage for the complex is 75 to 90 of inflow 35 times that calculated from cl and br under such conditions only low magnesian calcite precipitates and the lake water experiences reduced effects of evaporation gas and vapour exchange and consequently reduced isotopic and chemical enrichment further our model shows that calcite becomes increasingly mg rich until leakage is reduced to 55 to 70 of inflow a condition favourable for dolomitisation and of the lacustrine carbonates show excursions on the order of 5 over the length of a 2 3 m core indicating that the lake complex has varied from being throughflow dominated presence of low mg calcite relatively depleted in and to evaporation dominated high mg calcite dolomite relatively enriched in and throughout late quaternary our estimates of leakage fractions are consistent with the observed mineralogical suite but there remains a discrepancy between apparent closure indicated by the presence of the highly saline brine reservoir 1 leakage and high rates of throughflow inferred from stable isotope data we propose that the brine was formed by winter time re solution of a seasonal halite crust which forms during summer dominated evaporative discharge recirculation of the secondary brine and mixing with regional groundwater may decouple the solute cycle from the water cycle in many playa lakes the end result is a partially mixed brine characterised by nearly conserved solutes but with isotopic signatures indicative of brine rainfall groundwater interactions

spatial variations of seismic attenuation and heterogeneity in the pyrenees coda q and peak delay time analysis abstract lateral variations of seismic attenuation in the pyrenees are explored from the analysis of local earthquake records scattering loss and intrinsic absorption both control the propagation of short period s waves through the crust the role of intrinsic and scattering attenuation is analyzed in two steps firstly the coda quality factor q c which quantifies the energy decay of coda waves is estimated at large lapse time in five frequency bands and interpreted as intrinsic absorption next we systematically measure the peak delay time defined as the time lag from the direct s wave onset to the maximum amplitude arrival this parameter quantifies the strength of multiple forward scattering due to random inhomogeneities along the seismic ray path comparison of coda q and peak delay time measurements allows a qualitative interpretation of the origin of seismic attenuation scattering absorption in the pyrenean crust at low frequency coda q variations mainly depend on the tectonic units of the pyrenees with stronger absorption in sedimentary basins and smaller absorption in paleozoic basements at high frequency coda q is low at the location of neogene structures in the eastern pyrenees a more enigmatic low q c anomaly is also observed at the location of the maladeta massif in the central pyrenees in all frequency bands peak delay time measurements systematically show stronger scattering in the western pyrenees in the labourd mauleon area absorption and scattering are both important at low frequency the western pyrenees also correspond to a high velocity density anomaly revealed from tomography and gravity data analysis this suggests that the high level of inhomogeneities and absorption may be related to intrusion of mantle and or lower crustal materials in the eastern pyrenees absorption appears dominant over scattering at high frequency we hypothesize that the strong absorption observed in this area may be related to volcanic structures

addition of aeolian dusts to soils in southeastern australia red silty clay trapped in dunes bordering murrumbidgee river in the wagga wagga region in southeastern australia aeolian dust deposits are very common and have a significant influence on soil properties and soil landscapes however the characteristics of the pure dust materials and the rates of dust fall in the past are unclear because of the low overall rate of dust deposition and mixing with locally derived sediments in the wagga wagga region some dunes have functioned as dust traps thin 1 cm thick red clayey bands and thick up to 2 5 m red clayey layers within the dune sequences are likely to represent illuviated aeolian dust these dust materials are characterised by a bi modal particle size distribution one mode in the clay and another in the coarse medium silt the clay minerals are dominated by kaolinite illite and smectite both 14c and optical dating indicate the most recent period of dune formation was around 3 4 ka in an example of these young dunes there is a total of 2 cm equivalent thickness of dust materials giving a deposition rate of 0 5 0 7 cm ka 1 all three samples from an elevated dune are saturated with respect to environmental radiation dosage and give minimum optical ages in excess of 80 ka in this higher dune the total thickness of dust is 50 80 cm similar to that 50 100 cm of the yarabee parna the youngest aeolian dust deposit in the wagga wagga region this may have been deposited unevenly being more concentrated during the period 25 16 ka which has been identified as a major dust deposition period in the tasman sea if this variation occurred the dust deposition rate indicated by the 50 80 cm dust material in the dune could have been as high as 5 cm ka 1 for the period 25 16 ka

application of isotopic methods to dating of very old groundwaters milk river aquifer alberta canada the aim of this joint project was to evaluate the usefulness of available geochemical and isotope techniques for dating very old groundwater this paper represents a synthesis of an iaea sponsored study for which purpose the milk river aquifer groundwaters were sampled from 16 wells during 1985 and subsequent years for the following measurements 2h 3h 13c 18o 14c 39ar 81kr 85kr noble gases including222rn 36cl 129i and u isotopes the milk river aquifer was selected for this study because several preceding investigations had established that this groundwater system contains waters whose ages range from recent to 1ma the present study has established that the milk river aquifer system is very complex both in terms of groundwater origin and in terms of the evolution of its chemical and isotopic contents however this apparent complexity proved to be an interesting challenge with respect to the use of different and complementary approaches to interpretation of the geochemical and isotope data in terms of groundwater residence time thus the groundwater ages based on the hydrodynamic model should be considered as a lower limit of the average groundwater age in the milk river aquifer 0 25ma while those based on the36cl cl data uncorrected for any dilution by dead cl should be considered as an upper limit 2ma the milk river aquifer international project is an excellent illustration of the variety of insight and increased confidence possible in flow system analysis when multiple independent dating methods are combined with detailed hydrogeological studies the conclusion of the present study is that the potential for dating of very old groundwaters by a variety of isotope techniques is very high provided a combination of methods is applied never a simple method by itself

cl br ratios and environmental isotopes as indicators of recharge variability and groundwater flow an example from the southeast murray basin australia abstract systematic variations in cl br ratios together with r 36 cl values 14 c activities and 18 o values reflect differences in groundwater recharge and define groundwater flow paths in the riverine province of the southeast murray basin in groundwater from the shallowest shepparton formation homogenisation of cl br and 18 o values and a decline in 14 c activities with depth imply that vertical flow dominates the 14 c activities define variations in pre land clearing recharge in the palaeovalleys of present day rivers deep leads which contain sandier sediments higher recharge 0 5 to 1 4 mm year produced relatively fresh groundwater tds 36 cl values in groundwater from the goulburn subcatchment zones of groundwater with variable cl br ratios in the deeper calivil renmark aquifer also allow the detection of rapid leakage from the surface that has the potential to compromise groundwater resources

saline ground waters and brines in the canadian shield geochemical and isotopic evidence for a residual evaporite brine component abstract saline ca na cl type groundwaters and brines sampled in deep mines over an extensive area of the canadian precambrian shield have elevated br cl ratios which may indicate that the chlorinity of these waters was derived from the infiltration of residual evaporitic brines remnants of the great marine incursions of the paleozoic era boron concentrations in these waters are generally low i e 11 b 10 b ratios of these waters are significantly greater than the average value for continental crustal rocks with the highest values 4 19 approaching that of present day seawater 4 20 moreover the boron isotopic ratios generally trend to higher values with increasing chlorinity which supports the conclusion from the br cl relationship that most of the chloride in shield brines is of marine origin rather than a product of water rock interactions if this is correct crystalline rocks must then be sufficiently permeable on a regional scale to have allowed the brine to infiltrate to depths of several kilometers where it now resides

the evaporation path of seawater and the coprecipitation of br and k with halite brines and salt were sampled at the morton bahamas solar salt production facility on great inagua island in the bahamas the brines were analyzed by ion chromatography to define more precisely than heretofore the evaporation path of seawater to the end of the halite facies at inagua calcium carbonate begins to precipitate at a brine concentration factor of 1 8 times that of seawater gypsum begins to precipitate at a brine concentration of 3 8 times seawater and halite at a concentration factor of 10 6 three of the most concentrated brines from inagua 40 times seawater were evaporated further in the laboratory magnesium sulfate first precipitated at brine concentrations about 70 times those of seawater and potassium bearing phases began to precipitate for these brines at concentrations greater than 90 times those of seawater the distribution of coefficients of br and k between brines and halite were determined by combining analytical data for the inagua brines with measurements of the br and k content of halites from inagua and of halite which had precipitated from inagua brines during storage the observed average value of dbr is 0 032 in good agreement with some of the previous measurements the measured values of dk are highly variable 0 001 to 0 021 dk for halite precipitated early in the halite facies is in the vicinity of 0 015

timing of biogenic gas formation in the eastern qaidam basin nw china abstract quaternary biogenic gas from the qaidam basin nw china is regarded as one of the representative examples of early generation biogenic gas gases formed by microbial activity during sedimentation of source rocks however new age determinations of natural gas and formation waters make this generally accepted assumption questionable gas in the qaidam basin is dominantly methane 99 0 and has 13 c ch 4 values in the range of 68 to 65 reflecting the microbial origin carbon and hydrogen isotope values of methane coupled with carbon isotope values of carbon dioxide and dissolved inorganic carbon dic reflect water derived hydrogen in the methane and a dominant co 2 reduction metabolic pathway for the formation of biogenic methane coproduced formation waters have hydrogen and oxygen isotope values similar to surface water from the golmud and ortmuren rivers t test 0 75 but different from the original formation water t test 1 sequence around 1 35 ma bp this corresponds to a regional uplift erosion and water influx event economic accumulations of biogenic gas were thus most likely generated late in the qaidam basin rather than at the same time as sediment deposition fresh water recharge may be critical to enhancing biogenic methane generation by introducing nutrients and or microbes into the reservoir

ancient groundwaters in the amadeus basin central australia evidence from the radio isotope 36cl abstract we report 36 cl determinations for groundwaters in the major confined aquifer the mereenie sandstone in the amadeus basin in arid central australia groundwaters at the synclinal margins of the amadeus basin have 36 cl ratios 36 cl cl averaging about 176 10 15 these groundwaters have radiocarbon contents ranging from 6 to 39 modern carbon suggesting that they might average out episodic recharge processes over the last 30 000 years deep within the basin groundwaters in the mereenie sandstone at palm valley sampled from petroleum exploration drilling have 36 cl ratios ranging from 8 10 15 to 99 10 15 the average chlorinity of the deep groundwater samples is up to double that of the synclinal margin waters indicating some addition of chloride in the aquifer even so the groundwater residence times are implied to be about four hundred thousand years these mereenie sandstone groundwaters are sourced several hundred metres below ground level and their minimum flow path is 40 50 km from the recharge zone at the margin of the basin this gives an average flow rate of 0 1 m a in accord with previous hydraulic flow modelling which indicated that groundwater travel times in the mereenie sandstone are slow and uneven

geochemical and hydrological processes controlling groundwater salinity of a large inland wetland of northwest australia abstract understanding mechanisms of hydrochemical evolution of groundwater under saline and brine wetlands in arid and semiarid regions is necessary to assess how groundwater extraction or injection in large scale basins may affect the natural interface between saline fresh aquifers in those systems we investigated the evolution of groundwater of the fortescue marsh a large inland wetland of northwest australia that is mainly supplied by floodwater from the upper fortescue river catchment the marsh is located in the pilbara region one of the world s major iron ore provinces where mining activities often occur below water tables here we quantified the stable isotope and chemical composition of groundwater surface water and rainfall in and around the marsh to better understand how saline marshes and playa lakes function geochemically hydrologically and ecologically the deep groundwater 50 m depth of the fortescue marsh is highly saline 100 g l 1 whilst shallow groundwater 0 20 m depth and surface water are mainly fresh or brackish currently the marsh is mainly recharged by occasional floodwater consequently salt in the marsh is concentrated by evaporation of rainfall we expected that the hydrochemical composition of surface and groundwater would therefore reflect the chemical composition of rainwater we analysed 206 water samples for stable isotope composition 2 h 18 o and water chemistry including ph dissolved oxygen electrical conductivity ec and total dissolved solids tds as well as na ca mg k si fe hco 3 so 4 cl sr and br we then developed geochemical models and a salt inventory to estimate the geological time of salt accumulation and to decouple geochemical characteristics of salt from modern groundwater we found that groundwater associated with the marsh can be divided into two distinct groups that are characterised by their stable isotope compositions i fresh and brackish groundwater tds 1 18 o 8 0 0 9 and ii saline and brine groundwater tds 10 g l 1 18 o varies from 2 5 to 7 2 fresh groundwater was evaporated by

origin of recharge and salinity and their role on management issues of a large alluvial aquifer system in the semi arid haouz plain morocco the present study has analyzed the origin of recharge and groundwater salinity in the haouz alluvial plain located in central morocco stable isotopic data 18o 2h indicate that the recharge of the alluvial aquifer is dominated by high altitude meteoric water originating from the high atlas mountains that border the plain to the south tritium globally indicates the presence of recent groundwater as well as mixing between old and recent groundwater alluvial groundwater salinity varies from east to west this variability is mainly induced by enrichment in chloride and sulfate salt contents strontium content reveals that sulfate could be related respectively to the influence of the senonian carbonate deposits containing gypsum dissolution of halite is revealed by the plot of 18o vs cl where the most saline samples do not show any changes in 18o br cl ratio varies in a wide range probably due to an orographic effect the nitrate distribution was analyzed using indicator geostatistical techniques resulting in probability maps nitrate contamination is shown to occur particularly in the eastern part of the haouz plain in this paper some aspects of groundwater resources management are addressed different management actions are identified with regard to the current water resources status and to the land and water uses in this framework controlling groundwater abstraction optimizing irrigation and enhancing mountain front recharge constitute the major key management actions that should be carried out

australian dust deposits modern processes and the quaternary record abstract dust raising and transport are common and important processes in australia today the aridity of the australian continent and high climatic variability result in widespread dust raising in the arid and semi arid areas and transport to the humid margins and surrounding oceans the supply of erodible particles appears to be the greatest limitation on total flux of transported dust dust raising is greatest in the lake eyre basin including the simpson desert and murray darling basin where internal drainage renews supplies of fine particles to the arid zone in the west and northwest dust entrainment is low despite considerable aridity the marine record of dust flux shows at least a threefold increase in dust flux compared with the holocene in the last glacial maximum in both tropical and temperate australia driven by weakened australian monsoon rains and drier westerly circulation respectively despite the widespread confirmation of aeolian dust deposits in southeastern and southwestern australia dated or quantified records are extremely rare the dominant model of australian dust deposits the clay rich parna is shown to be poorly substantiated while modern and ancient dust deposits examined in detail are shown to bear a strong similarity to conventional definitions of loess

the origins of the mengye potash deposit in the lanping simao basin yunnan province western china abstract the lanping simao basin lsb is a mesozoic cenozoic continental margin rift basin in western china it formed during the opening and closing of the tethys ocean this basin is also known as a metal belt as it hosts several metal deposits besides the mengye potash deposit however the exact dates of the formation either in the paleocene or the cretaceous and thus the origins of the marine continental or mixed origins of the mengye deposits remain disputed based on the basin s evolution materials of marine origin and or remnant seawater should be present but instead the salt layers of the mengye potash deposit present typically continental lithological features this study examines and reviews evaporative minerals br cl and i cl molar ratios and isotopes of s b and sr i and i cl data for this area has not been previously reported the basin s evaporative minerals are dominated by halite and sylvite the amounts of anhydrite chlorocalcite langbeinite glaserite tachyhydrite and glauberite are small all of these form in both marine and continental environments the values of i and the i cl molar ratios of halite and sylvite are from 0 07 to 0 27 ppm and from 0 03 to 0 11 10 6 respectively dependent on organic substances br and molar br cl values are from 89 08 to 555 45 ppm and from 0 06 10 3 to 0 38 10 3 respectively all of the br cl molar ratios are lower than those of seawater and most of them are 34 s 11 b and 87 sr 86 sr values for evaporative minerals indicate a continental origin for the mengye potash deposit however materials of hydrothermal origin are widely distributed in the basin and may have played an active role for the formation of the potash deposit thus the mengye potash deposit could be of continental origin with a remnant seawater trace