groundwater dating with 3h and sf6 in relation to mixing patterns transport modelling and hydrochemistry a comprehensive study of a sandy aquifer of deltaic origin in southern poland included water chemistry isotopes dissolved trace gases and transport modelling tritium sulphur hexafluoride sf6 and freons f 11 f 12 and f 113 showed the presence of modern waters in the recharge areas and shallow confined parts of the aquifer the presence of older holocene waters farther from the recharge areas was indicated by lack of 3h sf6 contents 0 02 fmol l 1 and relatively low 14c values the discharge from the system is by upward seepage in the valley of a major river pre holocene waters of a cooler climate identified on the basis of 18o 2h 14c ne and ar data were found in some distant wells concentrations of n2 ne and ar determined by gas chromatography were used for calculating the noble gas temperatures air excess needed for correction of sf6 and nitrogen content released by denitrification process the time series of 3h content available for some wells supplied quantitative information on age distributions and the total mean ages of flow through the unsaturated and saturated zones the derived 3h age distributions turned out to be very wide with mean values in the range of about 30 to 160 years for each well with determined 3h age the sf6 data showed either a lower age range or the possibility of a lower age as expected due to shorter travel times of sf6 through the unsaturated zone which most probably also resulted in different types of age distributions of these tracers freons appeared to be of little use for individual age determinations a quantitative estimation of two component mixing from sf63h relations is not possible unless the travel time of 3h through the unsaturated zone is comparable to that of sf6 the ratio of integrals of the response function over the age range with tracer and the whole response function yields the ratio of water with tracer to total flow of water that ratio is a tracer dependent function of time transport modelling of sf6 tracer done with mt3d code yielded initially large discrepancies between calculated and measured tracer concentrations some discrepancies remained even after calibration of the transport model with sf6 simulation of tritium contents with a calibrated transport model yielded reasonable agreement with measured contents in some wells and indicated a need for further investigations particularly in the eastern part of the aquifer the existence of distinct hydrochemical zones is consistent with the tracer data young waters with measurable 3h and sf6 contents are aerobic and of hco3ca or hco3so4ca types slightly elevated na and cl contents as well as the highest concentrations of so4 and no3 within this zone are due to anthropogenic influences anaerobic conditions prevail in the far field under the confining cover where pre bomb era holocene waters dominate in that zone dissolved oxygen no3 and u contents are reduced and fe mn and nh4 contents increase in the third zone early holocene and glacial waters occur they are of hco3cana or hco3na types with tds values higher than 1 g l 1 and na content higher than 200 mg l 1 due to either small admixtures of ascending or diffusing older water or freshening of marine sediments a process that is probably occurring till the present time copyright 2005 john wiley sons ltd

organic metamorphism as a key for reconstructing tectonic processes a case study from the austroalpine unit eastern alps at the northwestern margin of the gurktal alps eastern alps eoalpine cretaceous thrusting of carbonaceous material cm bearing metasediments formed a very low to low grade metamorphic nappe stack above higher grade metamorphic basement nappes sedimentary burial as well as progressive metamorphism transformed the enclosed cm to anthracite metaanthracite and semigraphite in a kinematically well constrained section at the northwestern frontal margin of the nappe stack this transformation has been investigated by vitrinite reflectance measurements and raman spectroscopy of carbonaceous materials rscm automated interactive fitting of raman spectra estimates the metamorphic peak temperatures in a complete section through the upper part of the upper austroalpine unit a rscm trend indicates a temperature profile of ca 250 600 c the top part of the gradient is reconstructed by one dimensional thermal modeling the certainty of ca 25 c at a confidence level of 0 9 resembles the data variability within a sample location due to the large calibration range the method is able to reconstruct a thermal crustal profile in space and time the study highlights the versatility of rscm which characterizes almost 250 ma of a complex and polyphase tectonic history rscm data characterize the variscan metamorphic grade in nappes now imbricated in the eoalpine nappe stack they additionally constrain a numerical model which emphasizes the significance of an increased thermal gradient in a continental margin towards the western neotethyan ocean during permo triassic lithospheric extension it finally characterizes the eoalpine metamorphic gradient during nappe stacking and a significant metamorphic jump related to exhumation and normal faulting

a quaternary solution model for white micas based on natural coexisting phengite paragonite pairs a thermodynamic model for the quaternary white mica solid solution with end members muscovite mg celadonite paragonite feceladonite ms mgcel pg fecel is presented the interaction energies for the mgcel pg join the fecel pg join and the ternary interactions were obtained from natural coexisting phengite paragonite pairs phengite paragonite pairs were selected based on the criteria that their chemical compositions may be represented as a linear combination of the model end member compositions and that the respective formation conditions 350 650 c 4 21kbar are accurately known previously published excess free energy expressions were used for the ms pg ms mgcel and ms fecel binaries the suggested mixing model was tested by calculating multicomponent equilibrium phase diagrams this proved to be particularly well suited to reproduce compositional variations of white micas from amphibolite facies metapelites

mixing properties of phengitic micas and revised garnet phengite thermobarometers mixing properties for muscovite celadonite ferroceladonite solid solutions are derived from combining available experimental phase equilibrium data with tabulated thermodynamic data for mineral end members when a partially ordered solution model is assumed the enthalpy of mixing among the end members muscovite celadonite ferroceladonite is nearly ideal although the gibbs energies of muscovite celadonite and muscovite ferroceladonite solutions are asymmetric due to an asymmetry in the entropy of mixing thermodynamic consistency is achieved for data on phengite compositions inassemblages with a pyrope kyanite quartz coesite b almandine kyanite quartz coesite c talc kyanite quartz coesite and d garnet phengite pairs equilibrated both experimentally at high temperatures and natural pairs from low grade schists the muscovite paragonite solvus has been reanalysed using the asymmetric van laar model and the effects of the phengite substitution into muscovite have been quantitatively addressed in order to complete the simple thermodynamic mixing model for the solid solution among the mica end members results are applied to a natural pyrope coesite phengite talc rock from the western alps and to investigate the conditions under which biotite bearing mica schists transform to whiteschist like biotite absent assemblages for average pelite bulk compositions

preconditioning an ensemble kalman filter for groundwater flow using environmental tracer observations abstract groundwater resources management requires operational regional scale groundwater models accounting for dominant spatial variability of aquifer properties and spatiotemporal variability of groundwater recharge we test the ensemble kalman filter enkf to estimate transient hydraulic heads and groundwater recharge as well as the hydraulic conductivity and specific yield distributions of a virtual phreatic aquifer to speed up computation time we use a coarsened spatial grid in the filter simulations and reconstruct head measurements at observation points by a local model in the vicinity of the piezometer as part of the observation operator we show that the enkf can adequately estimate both the mean and spatial patterns of hydraulic conductivity when assimilating daily values of hydraulic heads from a highly variable initial sample the filter can also estimate temporally variable recharge to a satisfactory level as long as the ensemble size is large enough constraining the parameters on concentrations of groundwater age tracers here tritium and transient hydraulic head observations cannot reasonably be done by the enkf because the concentrations depend on the recharge history over longer times while the head observations have much shorter temporal support we thus use a different method the kalman ensemble generator keg to precondition the initial ensemble of the enkf on the groundwater age tracer data and time averaged hydraulic head values the preconditioned initial ensemble exhibits a smaller spread as well as improved means and spatial patterns the preconditioning improves the enkf particularly for smaller ensemble sizes allowing operational data assimilation with reduced computational effort in a validation scenario of delineating groundwater protection zones the preconditioned filter performs clearly better than the filter using the original initial ensemble

p t d histories from quartz a case study of the application of the titaniq thermobarometer to progressive fabric development in metapelites 1 this study investigates the ability of quartz to record segments of the pressure temperature deformation p t d path in poly deformed metamorphic terranes and the associated application of the ti in quartz thermobarometer titaniq metapelites from the strafford dome eastern vermont were selected for this study because they record progressive fabric development during prograde metamorphism and have well constrained p t d histories from previous work results of this investigation are in agreement with previous studies and demonstrate that quartz in these samples records additional distinct intervals of the p t d path six preserved quartz equilibration events include 1 early prograde growth during burial 2 kyanite in quartz producing reactions 3 prenappe emplacement equilibration during isobaric heating 4 precipitation of quartz in quartz feldspar domains during crenulation cleavage development due to solution transfer 5 quartz producing chlorite out reactions during heating postnappe emplacement and 6 retrograde quartz overgrowths from an influx of siliceous fluids modeling quartz volume allows for the identification of quartz producing reactions in p t space the same may be done for ti phases to better constrain activities during reequilibration events an integration of cathodoluminescence imaging microstructural and petrographic investigation isochemical forward stability modeling and thermobarometry allows identification and interpretation of zoning patterns in quartz to unravel histories that would otherwise not be obtainable

an investigation about natural radioactivity hydrochemistry and metal pollution in groundwater from calabrian selected areas southern italy the increasing interest in radioactivity has brought about the need for an assessment of human exposure to radiation it is therefore necessary to examine naturally occurring radioactivity in the environment especially its occurrence in groundwater the aim of this work was then to study the levels and behavior of the most significant natural radionuclides also in order to improve the knowledge of the hydrochemical processes involved in the selected groundwater systems natural radioactivity in fifteen calabrian groundwaters for human use was investigated through high resolution gamma spectrometry with a negative biased ortec hpge detector and liquid scintillation measurements particular attention was given on those radionuclides 3h 238u 226ra and 228ra which contribute in a significant way to the overall effective dose received by members of the public due to the intake of drinking water originating from groundwater systems the activity concentration of 238u varied from 1 to 51 mbq l as a result of the geology of the investigated area and of the oxidizing conditions that favored u dissolution 226ra presented a broad range of activity concentrations 0 011 0 14 mbq l lower than uranium ones because radium occurs in groundwater under reducing conditions some heavy metals cd pb be hg ag as tl sb se and ni were also investigated through icp ms measurements and compared with the limits set by the italian legislation metals are released into the environment by both natural and anthropogenic sources they leach into underground waters moving along water pathways and eventually depositing in the aquifer

quantification of electron microprobe compositional maps of rock thin sections an optimized method and examples quantification of discrete pressure temperature domains in deformed chlorite white mica bearing metapelites was undertaken on mineral compositions derived by two dimensional microprobe compositional mapping of selected areas of rock thin sections in order to achieve compositional information at sufficient analytical precision spatial resolution and sample coverage within a typical analysis time of 1 day an optimization of measurement methods was necessary the method presented here allows collection of raw counts for eight different element concentrations at an analytical precision of 1 2 wt x ray intensity multiplane maps one map per measured chemical element are translated into concentration multiplane maps utilizing selected conventionally measured spot analyses combined with the castaing approximation for each mineral as this step requires identification of the different minerals present in the mapped area a statistical clustering technique to identify different groups of composition was developed guided by simple petrographic inspection of the thin section to delineate the important minerals in the mapped area finally the compositions of each pixel are translated into a mineral structural formula thus yielding a new kind of image with a high content of petrological information the reliability of the mineral composition images was emphasized by carrying out precision tests on the analytical data the possible use of chemical maps to infer the p t deformation history of metamorphic rocks is illustrated with two samples from the spitzbergen and the sambagawa blueschist facies belts in both samples a strong correlation between structures and chemistry is observed qualitative estimates of p t conditions from the si content of mica and chlorite are in good agreement with their location in microstructures that formed at different times therefore the combination of chemical maps with microstructural observations is a very powerful approach to understand both the evolution of complex metamorphic rocks and the control by deformation of mineral reactivity

underground renewal time and mixing of the main mineral waters of tunisia a multi tracer study bottled waters are increasingly popular in tunisia most of them come from groundwaters thus raising the question of the long term availability of the mineral groundwater resources water collected from production springs or wells of eleven mineral waters of tunisia among the main commercial brands were analyzed for tritium 3h helium 3 sf6 cfcs and carbon 14 tracer tracer plots indicate that all of the groundwaters of our data set are a mixture of modern rainwater with older groundwater flow waters that are beyond the time scale of the transient tracers 14c data suggest that the age of these old waters which constitute the main water reservoir is of the order of radiocarbon half life or more most of the studied sites have groundwater renewal times in the range 50 150 years for the sites where tracer concentrations are the most diluted by old waters this value logically increase to several centuries

noble gases dissolved in groundwater in a volcanic aquifer helium isotopes in the kumamoto plain this study investigates a tracing method using dissolved noble gases to survey the groundwater flow in a large groundwater basin the tracing method is based on measuring the concentrations of noble gases and the ratio of helium isotopes in groundwater samples since it is very difficult to detect trace amounts of noble gases and helium with high accuracy in a 15 ml groundwater sample dissolved gases were extracted and purified then a high resolution mass spectrometer was used for measurement and comparison with standard samples we used this method with samples from a confined aquifer formed by the deposition of pyroclastic flow in the kumamoto plain on the west side of mt aso in central kyushu japan the groundwater basin under the plain is divided into four small basins based on the helium concentrations and isotope ratios with two major groundwater flows one flow is buried by the aso pyroclastic flow along the old kase river the other is along the tsuboi river valley these two groundwater flows were identified from the different helium isotope ratios the helium component from the deep mantle is mixed into the groundwater under the kumamoto plain finally data on the concentrations and ratios of3he to4he in groundwater samples were used to determine the location of faults in the volcanic aquifer

exhumation of the high pressure tsakkok lens swedish caledonides insights from the structural and white mica 40ar 39ar geochronological record

groundwater transit time distribution and mean from streambed sampling in an agricultural coastal plain watershed north carolina usa we measured groundwater apparent age and seepage rate v in a sandy streambed using point scale sampling and seepage blankets a novel seepage meter we found very similar mtt estimates from streambed point sampling in a 58 m reach 29 years and a 2 5 km reach 31 years the ttd for groundwater discharging to the stream was best fit by a gamma distribution model and was very similar for streambed point sampling in both reaches between adjacent point scale and seepage blanket samples water from the seepage blankets was generally younger largely because blanket samples contained a fraction of young stream water correcting blanket data for the stream water fraction brought estimates for most blanket samples closer to those for adjacent point samples the mtt estimates from corrected blanket data were in good agreement with those from sampling streambed points adjacent to the blankets collectively agreement among age dating tracers general accord between tracer data and piston flow model curves and large groundwater age gradients in the streambed suggested that the piston flow apparent ages were reasonable estimates of the groundwater transit times for most samples overall our results from two field campaigns suggest that groundwater collected in the streambed can provide reasonable estimates of apparent age of groundwater discharge and that mtt can be determined from different age dating tracers and by sampling with different groundwater collection devices coupled streambed point measurements of groundwater age and groundwater seepage rate represent a novel reproducible and effective approach to estimating aquifer ttd and mtt

metamorphic evolution and 40ar 39ar geochronology of the wuguan complex eastern qinling area china implications for the late paleozoic tectonic evolution of the qinling orogen abstract the late paleozoic tectonic evolution of the qinling orogen is poorly constrained the wuguan complex which lies between the north qinling and south qinling tectonic belts represents a late paleozoic metamorphic belt of the qinling orogen in this contribution we report new metamorphic pressure temperature p t constraints and 40ar 39ar ages of garnet amphibolites and garnet bearing metapelites from the wuguan complex textural observations and mineral compositions especially garnets with two stages of growth indicate the wuguan complex experienced two distinct metamorphic events conventional geothermobarometry and phase equilibria modelling indicate that the earlier metamorphism had peak p t conditions of 660 725 c and 8 0 12 0 kbar with a clockwise p t path whereas the later metamorphic overprint records p t conditions of 560 610 c and 7 5 9 0 kbar hornblendes from amphibolites yield 40ar 39ar ages of 306 299 ma whereas muscovites from garnet bearing metapelites yield 40ar 39ar ages of 252 251 ma the two groups of 40ar 39ar ages correspond to the cooling time of the two distinct metamorphic events respectively combining with previously published zircon u pb ages from the wuguan complex and two groups of metamorphic ages from the guishan complex and the xiongdian eclogite belt we infer that the earlier metamorphism probably occurred at the hangingwall of a subduction zone during carboniferous subduction of oceanic crust the later metamorphic overprint might have been related to the initial collision between the sino korean and yangtze cratons during the late permain

use of tritium and helium to define groundwater flow conditions in everglades national park the concentrations of tritium 3 h and helium isotopes 3 he and 4 he were used as tracers of groundwater flow in the surficial aquifer system sas beneath everglades national park enp south florida from ages determined by 3 h 3 he dating techniques groundwater within the upper 28 m originated within the last 30 years below 28 m waters originated prior to 30 years before present with evidence of mixing at the interface interannual variation of the 3 h 3 he ages within the upper 28 m was significant throughout the 3 year investigation corresponding with varying hydrologic conditions in the region of taylor slough bridge younger groundwater was consistently detected below older groundwater in the biscayne aquifer suggesting preferential flow to the lower part of the aquifer an increase in he with depth in the sas indicated that radiogenic 4 he produced in the underlying hawthorn group migrates into the sas by diffusion higher 4 he values in brackish groundwaters compared to fresh waters from similar depths suggested a possible enhanced vertical transport of 4 he in the seawater mixing zone groundwater salinity measurements indicated the presence of a wide 6 28 km seawater mixing zone comparison of groundwater levels with surface water levels in this zone indicated the potential for brackish groundwater discharge to the overlying everglades surface water

petrology of hp metamorphic veins in coesite bearing eclogite from western tianshan china fluid processes and elemental mobility during exhumation in a cold subduction zone abstract a petrological study was carried out for high pressure hp veins which cut through the host coesite bearing eclogites at habutengsu kebuerte in western tianshan china the results place constraints on the origin and property of metamorphic fluids during subduction zone metamorphism omphacite clinozoisite and quartz dominated veins occur on centimeter to meter scales within lens shaped and layered eclogites or cutting into the country rocks of garnet phengite schists coesite bearing eclogites mainly consist of fibrous fine grained omphacite and porphyroblastic garnet with minor amounts of amphibole mainly barroisite clinozoisite white mica mainly paragonite and rutile the veins are pronouncedly coarse grained compared to the host eclogites and commonly consist of quartz clinozosite rutile white mica phengite and paragonite and garnet with or without omphacite titanite apatite carbonate mainly dolomite and glaucophane fluid inclusions are abundant in vein omphacite titanite and apatite but are rare in the equivalent minerals of host eclogites rounded vein garnets usually occur close to the sharp interface of vein and host eclogite omphacite in the veins is characterized by its euhedral form surrounded by quartz or coarse bladed aggregates in contrast to the fibrous or patchy one suggesting dynamic recrystallization in the host rocks omphacite in both veins and host eclogites has similar jadeite contents jd 40 50 indicating formation at eclogite facies metamorphic conditions vein phengite uniformly contains certain amounts of ba with maximum bao content of 3 16 4 25 wt suggesting that ba was mobilized during the exhumation of uhp rocks specific textures of vein minerals such as the enclosure of magnesite or calcite in dolomite rutile in titanite and the occurrence of zoned ba rich phengite indicate the chemical variability of channelized fluids over time based on zr content in rutile and the presence of paragonite omphacite phengite glaucophane as well as the little deformed textures of hp veins it is estimated that the vein forming fluids would flow at about 1 3 2 1 gpa and 540 580 c corresponding to the stage of retrograde eclogite facies recrystallization during exhumation of the uhp eclogites that formed at peak p t conditions of 2 7 gpa and 460 520 c the hp veins occur as a consequence of a regional tectonothermal event triggering breakdown of lawsonite within the uhp eclogites based on the petrology of vein minerals it is inferred that the hp fluids were enriched in si ca na al and ba this suggests that these elements could be mobilized during the retrograde metamorphism of uhp eclogites in a cold subduction zone coeval pervasive flow of hp metamorphic fluids through the uhp eclogites at this stage may be an important process to eliminate most mineralogical evidence of the uhp metamorphism

recalibration of the garnet muscovite gm geothermometer and the garnet muscovite plagioclase quartz gmpq geobarometer for metapelitic assemblages the garnet muscovite gm geothermometer and the garnet muscovite plagioclase quartz gmpq geobarometer have been simultaneously calibrated under conditions of t 1 4 450 760 c and p 1 4 0 8 11 1 kbar using a large number of metapelitic samples in the compositional ranges x grt fe 1 4 0 53 0 81 x grt mg 1 4 0 05 0 24 x grt ca 1 4 0 03 0 23 in garnet x pl ca 1 4 0 17 0 74 in plagioclase and fe 1 4 0 04 0 16 mg 1 4 0 04 0 13 al 1 4 1 74 1 96 in muscovite on the basis of 11 oxygens the resulting gm thermometer yielded similar temperature estimates mostly within 50 c to that of the garnet biotite thermometer and successfully discerned the expected systematic temperature change of prograde sequences thermal contact zones and an inverted metamorphic zone the resulting gmpq barometer yielded similar pressure estimates mostly within 1 0 kbar to the garnet aluminum silicate plagioclase quartz gasp barometer and placed the aluminosilicate bearing samples in the appropriate aluminosilicate stability fields application of the gmpq barometer to thermal contact aureoles or rocks within limited geographical areas confirmed the expected constant pressures that should exist in these settings the random errors of the gm thermometer and the gmpq barometer are estimated to be 16 c and 1 5 kbar respectively when biotite or aluminosilicate is absent in metapelites metamorphic p t conditions may be determined by simultaneously applying the gm thermometer and the gmpq barometer

trace metals distribution pattern in floodplain sediments of a lowland river in relation to contemporary valley bottom morphodynamics the distribution of trace metals in alluvial sediments depends on their natural background concentrations and on the dynamics of contemporary depositional and erosional mainly flood induced processes geological and geochemical investigations were carried out in the valley of vistula river near magnuszew central poland sediment samples were collected from a depth of 35 cm and comprise sediments of all defined geomorphological features identification and geological interpretation of the morphodynamic sediment features was supported by aerial photographs and high resolution satellite images these studies revealed that the distribution of trace metals is closely linked to the morphogenesis of the alluvial floodplain the highest concentrations of cu co zn v cr and ni were observed in crevasse splays deposits by contrast sr pb and as were concentrated in deposits which fill oxbow lakes partly infilled with organic deposits the lowest concentrations of trace metals were detected in flood sediments deposited within erosional troughs the geomorphological and sedimentological history of the fluvial features explains the pattern of heavy metal distribution on the current floodplain surface copyright 2014 john wiley sons ltd

flow of river water into a karstic limestone aquifer 2 dating the young fraction in groundwater mixtures in the upper floridan aquifer near valdosta georgia abstract tritium helium 3 3h 3he and chlorofluorocarbon cfcs cfc 11 cfc 12 cfc 113 data are used to date the young fraction in groundwater mixtures from a karstic limestone aquifer near valdosta georgia where regional paleowater in the upper floridan aquifer receives recharge from two young sources the flow of withlacoochee river water through sinkholes in the river bed and leakage of infiltration water through post eocene semi confining beds above the upper floridan aquifer in dating the young fraction of mixtures using cfcs it is necessary to reconstruct the cfc concentration that was in the young fraction prior to mixing the 3h 3he age is independent of the extent of dilution with older 3h free and 3hetrit free water the groundwater mixtures are designated as type 1 for mixtures of regional paleowater and regional infiltration water and type 2 for mixtures containing more than approximately 4 of river water the fractions of regional paleowater regional infiltration water and withlacoochee river water in the groundwater mixtures were determined from cl and 18o data for water from the upper floridan aquifer at valdosta georgia the chlorofluorocarbons cfc 11 and cfc 113 are removed by microbial degradation and or sorption processes in most anaerobic type 2 groundwater at valdosta but are present in some aerobic type 1 water cfc 12 persists in both so4 reducing and methanogenic water the very low detection limits for cfcs approximately 0 3 pg kg 1 permitted cfc 11 and cfc 12 dating of the fraction of regional infiltration water in type 1 mixtures and cfc 12 dating of the river water fraction in type 2 mixtures overall approximately 50 of the 85 water samples obtained from the upper floridan aquifer have cfc 12 based ages of the young fraction that are consistent with the 3h concentration of the groundwater because of uncertainties associated with very low 3h and 3he content in dilute mixtures 3h 3he dating is limited to the river water fraction in type 2 mixtures containing more than about 10 river water of the 41 water samples measured for 3h 3he dating dilution of 3h and low 3he concentration limited 3h 3he dating to 16 mixtures in which 3h 3he ages are defined with errors ranging from 2 to 7 5 a 1 after correction for dilution with assumed cfc free regional infiltration water and regional paleowater in the upper floridan aquifer adjusted cfc 12 ages agree with 3h 3he ages within 5 a or less in 7 of the 9 co dated type 2 mixtures tritium data and dating based on both cfc 11 and cfc 12 in type 1 mixtures indicate that travel times of infiltration water through the overlying post eocene semi confining beds exceed 35 a the cfc and 3h 3he dating indicate that the river fraction in most groundwater entered the groundwater reservoir in the past 20 to 30 a few domestic and municipal supply wells sampled intercept water younger than 5 a calculated velocities of river water in the upper floridan aquifer downgradient of the sinkhole area range from 0 4 to 8 2 m d radiocarbon data indicate that ages of the regional paleowater are on the 10 000 a time scale an average lag time of approximately 10 to 25 a is determined for discharge of groundwater from the surficial and intermediate aquifers above the upper floridan aquifer to the withlacoochee river

dissolved gases in groundwater and groundwater dating methods how useful for hydrogeological modeling foreword to the special issue one of the major challenges in hydrogeology is the basic spatial lack of continuous data as this is restricted to available boreholes basic information is provided by the measurements of physical parameters e g porosity and permeability at the well scale information related to a larger part of the aquifer are provided for example by continuous measurement of piezometric levels or spring flow temporal information is extremely powerful in order to characterize aquifer functioning globally groundwater dating has thus been developed in order to provide time constraints in aquifer studies

microdiamond on areskutan confirms regional uhp metamorphism in the seve nappe complex of the scandinavian caledonides metamorphic diamond in crustal rocks provides important information on the deep subduction of continental crust here we present a new occurrence of diamond within the seve nappe complex snc of the scandinavian caledonides on areskutan in jamtland county sweden microdiamond is found in situ as single and composite diamond carbonate inclusions within garnet in kyanite bearing paragneisses the rocks preserve the primary peak pressure assemblage of ca mg rich garnet phengite kyanite rutile with polycrystalline quartz surrounded by radial cracks indicating breakdown of coesite calculated p t conditions for this stage are 830 840 c and 4 1 4 2 gpa in the diamond stability field the ultrahigh pressure uhp assemblage has been variably overprinted under granulite facies conditions of 850 860 c and 1 0 1 1 gpa leading to formation of ca mg poor garnet biotite plagioclase k feldspar sillimanite ilmenite quartz this overprint was the result of nearly isothermal decompression which is corroborated by ti in quartz thermometry chemical th u pb dating of monazite yields ages between 445 and 435 ma which are interpreted to record post uhp exhumation of the diamond bearing rocks the new discovery of microdiamond on areskutan together with other evidence of ultrahigh pressure metamorphism uhpm within gneisses eclogites and peridotites elsewhere in the snc provide compelling arguments for regional at least 200 km along strike of the unit uhpm of substantial parts of this far travelled allochthon the occurrence of uhpm in both rheologically weak gneisses and strong lithologies eclogites peridotites speaks against the presence of large tectonic overpressure during metamorphism

low pressure temperature stability of pyrope quartz relative to orthopyroxene kyanite a new model for aluminous orthopyroxene with vacancies determination of the stability of pyrope with quartz could provide theoretical pressure temperature p t constraints on silica saturated eclogites as well as near end member pyrope bearing terrains the lower p t stability of pyrope in the presence of quartz in the system mgo al2o3 sio2 can be modeled by the reaction 3 enstatite 2 kyanite 2 pyrope 2 quartz reaction reversals were experimentally obtained using a in diameter piston cylinder press and a 1000 t multi anvil press besides natural quartz all other starting materials including orthopyroxene pyrope and kyanite were synthesized the reaction has been bracketed at 1 50 gpa at 1040 1080 c 1 69 1 79 gpa at 1000 c 2 26 gpa at 920 940 c 2 90 gpa at 840 860 c the bracketed boundary is higher in temperature and pressure than that calculated using the newest dataset of holland et al j petrol 59 881 900 https doi org 10 1093 petrology egy048 2018 particularly at higher pressures aluminum is usually thought to be taken into orthopyroxene in the form of mg tschermak s pyroxene mgts mgal2sio6 under these experimental p t conditions in contrast the observed orthopyroxene composition indicated the involvement of a non stoichiometric component mg eskola pyroxene mges mg0 5 0 5alsi2o6 an aluminous orthopyroxene with octahedral vacancies end member thermodynamic properties for mges as well as a mixing model for the ternary enstatite mgts mges solid solution have been derived the thermodynamic calculations employing the mixing model are in good agreement with the experimental brackets the new model has potential applications to constrain p t conditions of tectonic settings such as ultrahigh pressure and ultrahigh temperature metamorphisms

parameter estimation using groundwater age and head data cape cod massachusetts a practical inversion procedure is used to parametrize an unconfined aquifer on cape cod massachusetts using groundwater age and hydraulic head data the inversion resulted in estimates of the recharge flux homogeneous but anisotropic hydraulic conductivity porosity boundary hydraulic heads and the aquifer thickness the range of estimated values agreed well with independent measurements at the site by themselves hydraulic heads are sensitive to the ratio of recharge flux to hydraulic conductivity the age data are sensitive to the ratio of recharge to porosity together age and head data provide a constraint on both boundary values and material properties however a sensitivity analysis shows that porosity hydraulic conductivity and recharge are all correlated and thus a unique inverse solution requires an independent constraint on one of these parameters simulations also show that groundwater ages at a given point on a streamline are sensitive to the recharge flux at the point where the streamline begins at the water table this implies that a vertical profile of age data will be sensitive to the upstream recharge flux suggesting that spatial patterns in recharge can be estimated using vertical profiles from multilevel monitoring wells because measurements of groundwater age can be made in many shallow aquifers this approach may be applicable to other sites

groundwater residence time downgradient of trench no 22 at the chernobyl pilot site constraints on hydrogeological aquifer functioning following the explosion of reactor 4 at the chernobyl power plant in northern ukraine in 1986 contaminated soil and vegetation were buried in shallow trenches dug directly on site in an aeolian sand deposit these trenches are sources of radionuclide rn pollution the objective of the present study is to provide constraints for the chernobyl flow and rn transport models by characterising groundwater residence time a radiochronometer 3h 3he method t1 2 12 3 a and anthropogenic tracers including cfc and sf6 are investigated along with the water mass natural tracers na cl 18o and 2h the groundwater is stratified as evidenced by na and cl concentrations and stable isotopes 18o 2h in the upper aeolian layer the na cl relationship corresponds to evapotranspiration of precipitation while in the underlying alluvial layer an increase in na and cl with depth suggests both water rock interactions and mixing processes the 3h 3he and cfc apparent groundwater ages increase with depth ranging from recent 1 3 a at a 2 m depth below the groundwater table to much higher apparent ages of 50 60 a at 27 m depth below the groundwater table discrepancies in 3h 3he and cfc apparent ages 20 25 a and 3 10 a respectively were observed during the 2008 campaign at an intermediate depth immediately below the aeolian alluvial sand limit which were attributed to the complex water transfer processes extremely high sf6 concentrations well above equilibrium with the atmosphere and up to 1112 pptv are attributed to significant contamination of the soils following the nuclear reactor explosion in 1986 the sf6 concentration vs the apparent groundwater ages agrees with this interpretation as the high sf6 concentrations are all more recent than 1985 the persistence of the sf6 concentration suggests that sf6 was introduced in the soil atmosphere and slowly integrated in the groundwater moving along the hydraulic gradient the apparent age distribution in the lumped parameter models suggests an exponential or piston flow model in the upper geological section followed by more pronounced mixing processes in the lower section

inverted oligo miocene metamorphism in the lesser himalaya sequence arunachal pradesh india age and grade relationships the lesser himalaya sequence in the siyom valley eastern arunachal pradesh exposes a telescoped and inverted greenschist upper amphibolite facies sequence over 20 km tectonically overlain by an upright grade decreasing upward granulite to lower amphibolite facies sequence over 30 km such grade relationships would normally attribute the boundary to a main central thrust mct structure and predict a change from underlying lesser himalaya sequence lhs to greater himalaya sequence rocks across the boundary however all pelitic and psammitic samples have similar detrital zircon age spectra involving c 2500 1750 1500 1200 and 1000 ma gondwanan populations correlated with the lhs isograds are broadly parallel to a penetrative nw dipping s2 foliation developed contemporaneously with the inversion garnet growth in garnet staurolite and kyanite zone schists beneath the thrust commenced at 8 kbar and 550 c before syn to post s2 heating of staurolite and kyanite zone rocks to 640 c at 8 5 kbar most probably at c 18 5 ma kyanite rutile garnet migmatite immediately above the thrust records peak conditions of 10 kbar and 750 c and c 21 5 ma monazite ages slip on a se propagating thrust was likely contemporaneous with early miocene metamorphism based on the distribution of structure metamorphic textures and overlap of age relationships it is inferred to have initially controlled the uplift of granulite to mid crustal levels between 22 and 19 ma thermal relaxation within a disrupted lhs metamorphic profile inducing a post s2 thermal peak in lower grade footwall rocks

geochemical study of arsenic release mechanisms in the bengal basin groundwater 1 to investigate arsenic mobility in the bengal basin groundwater we sampled water wells and sediments throughout the region there are strong correlations among high levels of dissolved arsenic and iron ammonia and methane especially in samples from a single site laxmipur no linkage is seen between as and agricultural tracers such as phosphate the association of as and fe occurs because arsenic strongly adsorbs onto feooh particles in river water they flocculate with other fine grained particles at the freshwater saltwater transition zone subsequent bacterially mediated reduction of feooh in the clay releases the adsorbed arsenic weathering of as bearing mica plays a significant role in the as budget the correlated presence of as ch4 and nh4 in water supply wells is the result of diffusion out of organic rich clay into the more permeable zones arsenic is mainly released from recent sediments at 50 m depth deposited in the gbr floodplain as sea level rose throughout the holocene

steady annual and monthly recharge implied by deep unconfined aquifer flow abstract we consider the response of a deep unconfined horizontal aquifer to steady annual and monthly recharge a groundwater divide and a zero head reservoir constrain the aquifer so that sinusoidal monthly and aperiodic annual recharge fluctuations create transient specific discharge near the reservoir and an unsteady water table elevation inland one existing and two new long term data sets from the plymouth carver aquifer in southeastern massachusetts calibrate and confirm hydraulic properties in a set of analytical models geohydrology and simulated groundwater flow 1992 data and a new power law for tritiugenic helium to tritium ratios calibrate the steady recharge that drives the classical parabolic model of steady hydraulics applied hydrogeology 2001 observed water table and gradient fluctuations calibrate the transient recharge models in the latter regard monitoring wells within 1 km of buttermilk bay exhibit appreciable specific discharge and reduced water table fluctuations we apply trans am geophys union 32 1951 238 periodic model to the monthly hydraulics and a recharge convolution integral j hydrol 126 1991 315 to annual flow an infiltration fraction of 0 79 and a consumptive use coefficient of 1 08 10 8 m s c relate recharge to precipitation and daylight weighted temperature across all three time scales errors associated with this recharge relation decrease with increasing time scale

factors affecting the movement and persistence of nitrate and pesticides in the surficial and upper floridan aquifers in two agricultural areas in the southeastern united states differences in the degree of confinement redox conditions and dissolved organic carbon doc are the main factors that control the persistence of nitrate and pesticides in the upper floridan aquifer ufa and overlying surficial aquifer beneath two agricultural areas in the southeastern us groundwater samples were collected multiple times from 66 wells during 1993 2007 in a study area in southwestern georgia acfb and from 48 wells in 1997 98 and 2007 08 in a study area in south carolina sant as part of the us geological survey national water quality assessment program in the acfb study area where karst features are prevalent elevated nitrate n concentrations in the oxic unconfined ufa median 2 5 mg l were significantly p 0 03 higher than those in the overlying oxic surficial aquifer median 1 5 mg l concentrations of atrazine and deethylatrazine dea the most frequently detected pesticide and degradate were higher in more recent groundwater samples from the acfb study area than in samples collected prior to 2000 conversely in the sant study area nitrate n concentrations in the ufa were mostly 0 06 mg l resulting from anoxic conditions and elevated doc concentrations that favored denitrification although most parts of the partially confined ufa in the sant study area were anoxic or had mixed redox conditions water from 28 of the sampled wells was oxic and had low doc concentrations based on the groundwater age information nitrate concentrations reflect historic fertilizer n usage in both the study areas but with a lag time of about 15 20 years simulated responses to future management scenarios of fertilizer n inputs indicated that elevated nitrate n concentrations would likely persist in oxic parts of the surficial aquifer and ufa for decades even with substantial decreases in fertilizer n inputs over the next 40 years

hydraulic controls on the entrapment of heavy metal polluted sediments on a floodplain of variable width the upper vistula river southern poland distribution of heavy metal polluted overbank sediments deposited by a major flood in july 2001 in three gauging sections of different width on the vistula river southern poland was investigated and related to reconstructed pattern of flow velocity during the event the mean velocity of the flow over the floodplain was low and showed a marked contrast with mean velocity in the channel zone in the smolice and the sieroslawice cross sections 4 5 and 9 times wider than the respective channel widths high rates of lateral thinning and fining of overbank deposits were observed at sieroslawice the heavy metal concentrations first rapidly increased with distance from the channel and then remained high over most of the floodplain at smolice concentrations were relatively low within the levee deposits and high over the rest of the floodplain in both cross sections the loads of heavy metals were highest close to the channel margins and decreased exponentially with increasing distance from the channel due to the rapid lateral thinning of the flood deposits the mean velocity of the flow over the floodplain was high in the bielany cross section only 2 6 times wider than the channel width sediments deposited on the narrow floodplain were mostly sand slowly thinning laterally while the concentrations of various heavy metals increased gradually with increasing distance from the channel their loads varied across the floodplain the highest load of some metals occurred near the channel margin and that of others away from the channel this study indicates that floodplain width and the resultant flow hydraulics exert a significant influence on the lateral distribution of floodplain sediments and entrapped heavy metals in wider floodplain sections the largest amounts of heavy metals accumulate near the channel margin and may be remobilized in the future due to bank erosion

calculated phase relations in high pressure metapelites in the system nkfmash na2o k2o feo mgo al2o3 sio2 h2o using an internally consistent thermodynamic dataset and updated models of activity composition relation for solid solutions petrogenetic grids in the system nkfmash na2o k2o feo mgo al2o3 sio2 h2o and the subsystems nkmash and nkfash have been calculated with the software thermocalc 3 1 in the p t range 5 36 kbar and 400 810 c involving garnet chloritoid biotite carpholite talc chlorite kyanite sillimanite staurolite phengite paragonite albite glaucophane jadeite with quartz coesite and h2o in excess these grids together with calculated afm compatibility diagrams and p t pseudosections are shown to be powerful tools for delineating the phase equilibria and p t conditions of na bearing pelitic assemblages for a variety of bulk compositions from high p terranes around the world these calculated equilibria are in good agreement with petrological studies moreover contours of the calculated phengite si isopleths in p t pseudosections for different bulk compositions confirm that phengite barometry is highly dependent on mineral assemblage

physical and chemical characteristics of a metal contaminated overbank deposit west central south dakota u s a a metal contaminated overbank deposit in west central south dakota resulted from the discharge of a large volume of mine tailings into a river system between the late 1800s and 1977 the deposit along the belle fourche river is typically up to 2 m thick and extends about 90 m away from the channel along the insides of meander bends the sediments contain above background levels of copper iron manganese zinc and particularly arsenic which is commonly two orders of magnitude above background level in the contaminated sediments carbonate minerals in the deposit limit the desorption of arsenic by preventing acid formation arsenic concentrations provide a measure of the dilution of mine tailings by uncontaminated sediment the arsenic appears to have been transported and deposited as arsenopyrite but is now at least partially associated with iron oxides and hydroxides within individual samples arsenic concentration has an inverse relation with grain size that results from the more efficient accumulation of arsenic on the greater surface area of the smaller particles arsenic concentration is inversely related to the sample weight percent finer than 16 m however as a consequence of the dilution of the contaminated sediments by uncontaminated sediment with a finer grain size distribution dilution by uncontaminated sediment from tributaries cause arsenic concentrations to decrease by a factor of 3 along 100 km of floodplain an influx at high streamflow of uncontaminated sediment from terraces and the premining floodplain as well as from tributaries causes arsenic concentrations in parts of the contaminated deposit that are farthest away from the channel to be two to three times less than arsenic concentrations in overbank sediment that is immediately adjacent to the channel

the study of the interactions between groundwater and sava river water in the ljubljansko polje aquifer system slovenia abstract river basin aquifers are common sites for drinking water wells as bank filtration can be a cost effective pretreatment technology a groundwater vulnerability to pollution depends on a groundwater mean residence time and on a relative contribution of river water versus local precipitation to groundwater environmental isotopes of oxygen and hydrogen 18o and 2h tritium 3h and concentrations of nitrate no3 were used to investigate hydrological pathways mean residence time and interactions between surface water and groundwater in the ljubljansko polje aquifer system in slovenia 18o and 2h values indicate a spatial variability of the influence of individual groundwater sources inside the aquifer local precipitation and the sava river water fractions of river water in groundwater depend on the depth of perforated screens in the pumping wells and their distance from the sava river it was estimated that groundwater at wells klece 11 hrastje 3 and hrastje 8 is mostly composed of recently infiltrated local precipitation while the sava river is the dominant source of groundwater at the well jarski prod 1 groundwater at wells klece 8 klece 12 and jarski prod 3 contains on average between 41 and 48 of the sava river water the 3h and 3h 3he methods indicate short mean residence time of groundwater present at jarski prod 2 7 years and hrastje 7 8 years a small fraction

dating degassed groundwater with 3h 3he the production of gases in groundwater under contaminated locations by geochemical and biological processes is not uncommon degassing of these gases from groundwater and repartitioning of noble gases between water and gas phase distorts groundwater dating by 3h 3he we observed noble gas concentrations below atmospheric equilibrium in 20 out of 34 groundwater samples from agriculturally polluted sandy areas in the netherlands from the absence of nitrate in degassed samples we conclude that denitrification causes degassing the 22ne 20ne ratios show that degassing had attained solubility equilibrium and had not caused isotopic fractionation by diffusion to correct for the loss of tritiogenic 3he due to degassing we present a single step equilibrium degassing model we use the total dissolved gas pressure at the monitoring screen to estimate the depth and timing of degassing which is essential to estimate travel times from degassed samples by propagating the uncertainties in the underlying measurements and assumptions through the travel time calculations we found a travel time uncertainty of 3 years a we therefore conclude that 3h 3he dating can produce valuable information on groundwater flow even at sites with strong degassing copyright 2007 by the american geophysical union

tritium and helium isotopes as hydrologic tracers in a shallow unconfined aquifer measurements of tritium and 3he in groundwater can be used to calculate the age of tritium in groundwater such combined measurements on water samples thus provide a powerful tool towards understanding fluid flow in the near surface saturated zone we report tritium and helium isotope measurements on waters from an unconfined aquifer associated with a low level nuclear waste storage area these values are used to calculate ages of tritium in groundwater from 0 1 to 6 years from the groundwater ages and a three dimensional flow net hydraulic conductivities of 3 3 10 6 to 5 5 10 6 ms 1 for five wells and extreme values from a single well of 18 10 6 and 97 10 6ms 1 are calculated these values agree with hydraulic conductivities obtained from conventional aquifer tests the high conductivity value may indicate an area of preferred fluid flow

empirical garnet muscovite plagioclase quartz geobarometry in medium to high grade metapelites abstract based on the net transfer reactions among garnet muscovite plagioclase and quartz for both mg and fe end member models the garnet muscovite plagioclase quartz gmpq geobarometry was empirically calibrated under the physical conditions of p 1 0 11 4 kbar and t 505 745 c for 128 natural metapelitic rock samples collected from the literature the input temperatures and pressures were simultaneously determined by the garnet biotite thermometer and the garnet aluminosilicate plagioclase quartz gasp barometer the gmpq calibrations adopted the same asymmetric quaternary solid solution model of garnet and the same al avoidance asymmetric ternary model of plagioclase as the calibrations of the garnet biotite geothermometer and the gasp geobarometer a symmetric fe mg al vi ternary solid solution model of muscovite was adopted and the margules parameters of muscovite were obtained through regression the mg and fe model reactions along with the assumption of whether the ferric iron content in muscovite is 0 or 50 resulted in four gmpq barometry formulae the gmpq barometry formulae reproduce the input gasp pressures well within 1 0 kbar mostly within 0 5 kbar for both aluminosilicate bearing and aluminosilicate absent samples the gmpq barometry formulae yield identical pressures for every sample whether the sample was included or not in calibrating the barometers for each of the mg or fe model reaction the formulae gave identical pressures within 40 bars the random error of the gmpq barometry may be expected as 1 4 kbar the d p d t slopes of these gmpq formulae are close to that of the gasp barometer in the p t space applications of the gmpq barometry to aluminosilicate absent metapelites within a limited geographic area without postmetamorphic structural discontinuity generally show no pressure difference it may be concluded that the gmpq barometry formulae derived in this work may be used as practical tools for metamorphic pelites under the conditions of 505 745 c and 1 11 4 kbar in the composition range of x gros 3 in garnet and x an 17 in plagioclase

the groundwater geochemistry of the bengal basin weathering chemsorption and trace metal flux to the oceans sixty eight groundwater samples from the ganges brahmaputra floodplain in the bengal basin were analyzed to assess the groundwater geochemistry the subsurface hydrology the buffering effects of sediments on trace metal concentrations and their isotopic compositions and the magnitude of the subsurface trace element flux to the bay of bengal and to the global ocean samples obtained from depths of 10 to 350 m were measured for major and trace elements dissolved gas and tritium on the basis of the 3he 3h ages the groundwater at depth 30 150 m appears to be continually replenished indicating that this recharge of groundwater to depth must ultimately be balanced by a significant quantity of submarine discharge into the bay of bengal using the 3he 3h groundwater age depth relationship to calculate a recharge rate of 60 20 cm yr we estimate a subsurface discharge into the bay of bengal of 1 5 0 5 1011 m3 yr or 15 of the surface ganges brahmaputra river gbr flux several trace elements especially sr and ba display elevated concentrations averaging 7 to 9 times the surface gbr water values the submarine groundwater fluxes of sr and ba to the oceans are 8 2 2 108 and 1 5 0 3 108 mol yr or 3 3 and 1 2 respectively of the world total or equal to the surface gbr sr and ba estimated fluxes our groundwater flux for ba agrees with the estimate of moore 1997 3 108 3 109 mol yr on the basis of measured ba and ra excesses in the bay of bengal other trace metals such as u and mo are at low but measurable levels and are not major contributors to the global flux in this river system a comparison of the sr and ba concentrations plus 87sr 86sr ratios in groundwater to the oxalate extractable fractions of a coastal sediment core suggests that weathering of carbonates and minor silicates coupled with cation exchange plus adsorption and desorption reactions controls the trace element concentrations and 87sr 86sr isotopic compositions in both the groundwater and river water our data also imply that other coastal floodplains e g the mekong and the irrawaddy rivers that have high precipitation rates and rapid accumulation of immature sediments are likely to make significant contributions to the global oceanic trace metal budgets and have an impact on the sr isotopic evolution in seawater

tritium helium 3 dating under complex conditions in hydraulically stressed areas of a buried valley aquifer the 3h 3he dating method is applied in a buried valley aquifer near dayton ohio the study area is large not all sampling locations lie along well defined flow paths and existing wells with variable screen lengths and diameters are used reliable use of the method at this site requires addressing several complications 1 the flow system is disturbed because of high pumping rates and induced infiltration 2 tritium contamination is present in several areas of the aquifer and 3 radiogenic helium concentrations are elevated in a significant number of the wells the 3h 3he ages are examined for self consistency by comparing the reconstructed tritium evolution to the annual weighted tritium measured in precipitation deviations result from dispersion tritium contamination and mixing 3h 3he ages are next examined for consistency with chlorofluorocarbon ages the agreement is poor because of degradation of cfcs finally the 3h 3he ages are examined for consistency with the current understanding of local hydrologic processes the ages are generally supported by hydrogeologic data and the results of groundwater flow modeling coupled with particle tracking analyses

application of mineral equilibria modeling to constrain t and x co2 conditions during the evolution of the magdala gold deposit stawell victoria australia mineral equilibria modeling involving solid solution calculations has been combined with mineral assemblage information from the alteration zones associated with gold mineralization to determine the t and xco2 conditions for the formation of the magdala gold deposit at stawell victoria australia economic gold mineralization is primarily hosted within the stilpnomelane alteration zone of the stawell facies that is adjacent to the magdala basalt evolution of the magdala gold deposit involved at least three fluid infiltration events 1 a co2 bearing fluid during the d2 deformation event produced carbonate spots throughout the chlorite zone 2 a co2 s k bearing fluid accompanied the d3 4ab deformation and produced a muscovite zone and siderite rims on ankerite and 3 a co2 k s au bearing fluid during the d4c deformation event produced the stilpnomelane zone of the stawell facies the proximal and distal alteration zones within the magdala basalt and the main economic gold mineralization mineral equilibria modeling constrains the temperature of formation of the magdala deposit to t 345 390 c at 3kbar substantially lower than indicated by other previous classical thermobarometry methods furthermore this method has allowed the characterization of the mineralizing fluid and constrained its composition to xco2 0 08 at 3kbar the timing and composition of the mineralizing fluids are similar to that of metamorphic fluid generated from devolatilization of a greenstone pile with peak of metamorphism occurring earlier and at deeper levels in the crust

groundwater age distributions at a public drinking water supply well field derived from multiple age tracers 85kr 3h 3he and 39ar 1 groundwater age is a key aspect of production well vulnerability public drinking water supply wells typically have long screens and are expected to produce a mixture of groundwater ages the groundwater age distributions of seven production wells of the holten well field netherlands were estimated from tritium helium 3h 3he krypton 85 85kr and argon 39 39ar using a new application of a discrete age distribution model and existing mathematical models by minimizing the uncertainty weighted squared differences of modeled and measured tracer concentrations the observed tracer concentrations fitted well to a 4 bin discrete age distribution model or a dispersion model with a fraction of old groundwater our results show that more than 75 of the water pumped by four shallow production wells has a groundwater age of less than 20 years and these wells are very vulnerable to recent surface contamination more than 50 of the water pumped by three deep production wells is older than 60 years 3h 3he samples from short screened monitoring wells surrounding the well field constrained the age stratification in the aquifer the discrepancy between the age stratification with depth and the groundwater age distribution of the production wells showed that the well field preferentially pumps from the shallow part of the aquifer the discrete groundwater age distribution model appears to be a suitable approach in settings where the shape of the age distribution cannot be assumed to follow a simple mathematical model such as a production well field where wells compete for capture area

ion exchange and trace element surface complexation reactions associated with applied recharge of low tds water in the san joaquin valley california abstract stable isotope data a dissolved gas tracer study groundwater age dating and geochemical modeling were used to identify and characterize the effects of introducing low tds recharge water in a shallow aerobic aquifer affected by a managed aquifer recharge project in california s san joaquin valley the data all consistently point to a substantial degree of mixing of recharge water from surface ponds with ambient groundwater in a number of nearby wells screened at depths above 60 m below ground surface groundwater age data indicate that the wells near the recharge ponds sample recently recharged water as delineated by stable o and c isotope data as well as total dissolved solids in addition to much older groundwater in various mixing proportions where the recharge water signature is present the specific geochemical interactions between the recharge water and the aquifer material appear to include ion exchange reactions comparative enrichment of affected groundwater with na and k at the expense of ca and mg and the desorption of oxyanion forming trace elements as v and mo possibly in response to the elevated ph of the recharge water

dehydration of dioctahedral aluminous phyllosilicates thermodynamic modelling and implications for thermobarometric estimates we propose a solid solution model for dioctahedral aluminous phyllosilicates accounting for the main compositional variations including hydration observed in natural smectites interlayered illite smectite illites and phengites from diagenetic to high grade metamorphic conditions the suggested formalism involves dehydrated micas and hydrated pyrophyllite like thermodynamic end members with these end members the equilibrium conditions of quartz water k bearing mica like phyllosilicates of fixed 2 1 composition are represented by a line in p t space along which the interlayer water content varies the relevant thermodynamic properties required for the calculation of equilibrium conditions were derived using a set of 250 natural data of known maximal temperature and pressure conditions which covers a range between 25 c and few mpa to 800 c and 5 gpa the temperatures calculated at fixed pressure with our model are in fair agreement with those reported in the literature for the 250 natural data at low temperature and pressure the amount of interlayer water in k deficient phengite and illite is predicted to reach 100 of the apparent vacancies which is consistent with previous values reported in the literature although the amount of interlayer water is predicted to decrease with pressure and temperature it is calculated to be significant in k deficient phengite from lt hp pelites metamorphosed at about 350 c 10 kbar the presence of molecular water in the interlayer site of such phengites has been confirmed by ftir mapping its implications for p t estimates are discussed

structural controls of fluid flow and gold mineralization in the easternmost parts of the karagwe ankole belt of north western tanzania abstract gold mineralization in the biharamulo region of western tanzania is confined to the sheared low angle basement cover contact between archaean basement gneisses of the tanzania craton and the structurally overlying low grade metamorphic metasediments of the mesoproterozoic karagwe ankole belt regional scale fluid flow along this detachment is indicated by the pervasive silicification and retrogression of wall rocks to pervasively foliated phyllonites and pyritization of particularly metasediments commonly graphite rich in the hanging wall of the shear zone gold mining centres on specific structural sites along the detachment but also in stratigraphically higher sections in the structurally overlying metasediments zones of gold mineralization along the detachment correlate with ne trending ramp structures dip angles 20 35 that are most ideally orientated for slip and reactivation within the low angle phyllonitic detachment repeatedly overprinted auriferous quartz vein stockworks in quartzofeldspathic gneisses immediately below the detachment indicate brittle fracturing of the competent footwall lithotypes during slip along the weaker detachment in cases of massive silicification up to 50 m thick quartz blows are formed along the contacts between detachment phyllonites and footwall gneisses the multiple overprinting relationships of successive quartz vein generations in these zones of massive silicification suggests that the quartz blows acted as competent blocks in the weak detachment causing the repeated overprint of earlier silicification by later fracturing and quartz veining events gold mineralization above the detachment and in stratigraphically higher metasediments is closely associated with fold structures that form part of the low grade metamorphic fold and thrust belt veining is particularly abundant in competent lithotypes such as quartzite and chemically reactive ferruginous mafic sills overprinting relationships between quartz vein sets illustrate fluid flow during fold amplification and importantly the final lock up stage of folds during which much of the mineralization was introduced oxygen isotope values for quartz veins indicate fluids were likely derived from clastic mainly metapelitic sedimentary sequences of the karagwe ankole fold belt the data also implies that the partially reworked archaean granitoid greenstone basement of the tanzania craton has not contributed to the fluid evolution and possibly gold mineralization the extent 100 km of the basement cover detachment and associated alteration is indicative for a regional scale fluid system gold mineralization is however controlled by local structures and lithological contrasts that require the detailed mapping and sampling of the regional structure

hydrological control of as concentrations in bangladesh groundwater 1 the elevated arsenic as content of groundwater from wells across bangladesh and several other south asian countries is estimated to slowly poison at least 100 million people the heterogeneous distribution of dissolved arsenic in the subsurface complicates understanding of its release from the sediment matrix into the groundwater as well as the design of mitigation strategies using the tritium helium 3h 3he groundwater dating technique we show that there is a linear correlation between groundwater age at depths 20 m and dissolved as concentration with an average slope of 19 g l 1 yr 1 monitoring wells only we propose that either the kinetics of as mobilization or the removal of as by groundwater flushing is the mechanism underlying this relationship in either case the spatial variability of as concentrations in the top 20 m of the shallow aquifers can to a large extent be attributed to groundwater age controlled by the hydrogeological heterogeneity in the local groundwater flow system

on modelling hillslope water flow paths and travel times abstract this paper considers a darcian representation of hillslope water flow to derive flow paths and particle travel times under transient conditions of varying degrees of saturation a finite element solution of a porous medium flow equation is used to derive specific discharge fields interpolation within these fields in relation to prevailing water content allows water particles to be tracked within the slope material according to mean pore water velocities and allows the times of such hillslope travel to be determined examples of specific discharge fields particle tracks and slope base arrival times are discussed

intercomparison of tritium and noble gases analyses 3h 3he ages and derived parameters excess air and recharge temperature abstract groundwater age dating with the tritium helium 3 h 3 he method has become a powerful tool for hydrogeologists the uncertainty of the apparent 3 h 3 he age depends on the analytical precision of the 3 h measurement and the uncertainty of the tritiogenic 3 he component the goal of this study as part of the groundwater age dating interlaboratory comparison exercise was to quantify the analytical uncertainty of the 3 h and noble gas measurements and to assess whether they meet the requirements for 3 h 3 he dating and noble gas paleotemperature reconstruction samples for the groundwater dating intercomparison exercise were collected on 1 february 2012 from three previously studied wells in the paris basin france fourteen laboratories participated in the intercomparison for tritium analyses and ten laboratories participated in the noble gas intercomparison not all laboratories analyzed samples from every borehole the reproducibility of the tritium measurements was 13 5 the reproducibility of the 3 he 4 he ratio and 4 he ne ar kr and xe concentrations was 1 4 1 8 1 5 2 2 2 9 and 2 4 respectively the uncertainty of the tritium and noble gas measurements results in a typical 3 h 3 he age precision of better than 2 5 years in this case however the measurement uncertainties for the noble gas concentrations are insufficient to distinguish the appropriate excess air model if the measured helium concentration is not included while the analytical uncertainty introduces an unavoidable source of uncertainty in the 3 h 3 he apparent age estimate other sources of uncertainty are often much greater and less well defined than the analytical uncertainty

inverse ductile thinning via lower crustal flow and fold induced doming in the west carpathian eo alpine collisional wedge 1 continental core complexes are generally interpreted to result from extensional doming due to gravity driven upflow of lower crust in contrast the vepor dome is characterized by the lack of inverted density profile and relatively cold metamorphic field gradient which precludes an activation of rayleigh taylor instability instead the crustal structure of the vepor unit is marked by dense and weak metapelitic lower crust and light and strong granitoid upper crust inherited from variscan nappe stacking it is shown that the cretaceous eo alpine tectonic evolution of the vepor dome is controlled by the dynamics of two neighboring mechanically strong continental blocks i e the overthrusting of the suprastructural gemer unit from the south and the underthrusting of the fatric basement from the north structural metamorphic and geochronological data from the vepor unit imply two main phases of the convergent process 1 lower cretaceous crustal thickening due to overthrusting and internal deformation of the gemer unit together with upper crustal folding in the vepor unit led to the progressive development of the orogenic front parallel pressure gradient the instantaneous response of the lower crustal and low viscosity metapelites led to an along strike lower crustal flow accompanied by prograde barrovian type metamorphism 2 as the south vergent underthrusting of the fatric basement propagated to greater depths during the upper cretaceous the convergent process switched from top driven to bottom driven and the exhumation of the lower crust occurred via polyharmonic folding overall doming of the vepor unit induced upper crustal detachment faulting and eastward unroofing of the dome

the variability of heavy metals in floodplain sediments a case study from mid wales abstract a series of vertical alluvial profiles from the upper river severn floodplain at welshpool ranging in age from late pleistocene to the present have been examined for their ni cu zn cd ba and pb concentrations the floodplain deposits have been variably contaminated with heavy metals following extensive metalliferous mining in the upper catchment during the mid 19th century the data are used to establish whether vertical increases in concentrations can be used to indicate a younging upwards of the sediments the data show that grain size and organic content do not influence heavy metal concentrations although some of the most recent alluvial profiles contain the highest levels of contamination a great deal of variation exists not only between the general vertical distribution of individual metals but also between the absolute values themselves there was no consistent age concentration relationship in the vertical profiles pb displays the least complex picture with predominantly increasing values towards the top of the alluvial profiles in the historically sedimented sites indicating a younging upwards rapid sedimentation and post depositional processes such as leaching particle translocation or the lateral migration of groundwaters enriched in heavy metals result in different vertical heavy metal distributions at superficially similar sites it is recommended that sampling strategies for contaminated floodplain sediments utilise a multiple profile approach including the whole range of sediment types ages and depositional forms that are known to exist at a study site

concentration and spatial variability of mercury and other heavy metals in surface soil samples of periurban waste mine tailing along a transect in the almaden mining district spain mercury hg is one of the elements with increasing environmental significance a total of 22 samples soils rocks and gels were collected along a 6km transect around the valdeazogues river valley in the southwest of the iberian peninsula almaden spain samples were characterized by different soil types of depositional sequences associated with mining tailings type and system tracts 15 surface soil samples included in the transect 3 of a haploxerept soil profile developed on slates 2 of quartzite and slates rocks reference rocks in the area moreover two of a gel substance in the lower tract of the river soil samples were analyzed for hg cu ni cr v pb cd and as as well as for organic matter ph abrasion and calcium carbonate content all samples were collected from the almaden mining district the level of occurrence of the elements especially hg and the effect of some properties on its concentration distributions were investigated the total mercury contents varied in the range 7 315 3 44mgkg 1 the mean concentration of total mercury in soils and rocks was 477 03mgkg 1dry mass this value is very high compared to the regional background value of other areas only rarely is it higher than 1 in one sample 7 315mgkg 1 it was almost eight times in comparison with the affected zones with a high value of 1 000mgkg 1 significant differences between samples were found in the total content of mercury a large percentage of the samples registered detectable levels of v cr ni pb as and cu cd readings were below the detectable range for all samples tested cr mean concentration was 216 95mgkg 1 minimun concentration 86 maximun 358 v mean concentration was 119 09mgkg 1 minimun concentration 69 maximun 1 209 as mean concentration was 51 24mgkg 1 minimun 13 3 and maximun 319 4 ni mean concentration was 45 64mgkg 1 minimun concentration 21 2 and maximun 125 6 cu mean concentration was 33 25mgkg 1 minimun concentration 19 3 and maximun 135 pb mean concentration was 15 19mgkg 1 minimun 1 12 and maximun 1013 metal distribution generally showed spatial variability ascribed to significant anthropogenic perturbation by mining tailing type hg showed vertical profile characterized by surface enrichment with concentrations in the upper layer 93 7 82 2mgkg 1 in front of 3 4 of the rock value exceeding in several occasions the background value the results obtained denote a potential toxicity of some heavy metals in some of the studied samples water soluble mercury could enter the aquatic system and accumulate in sediments mercury and other heavy metals contamination depended on the duration and intensity of mining activities

refining the timing of eclogite metamorphism a geochemical petrological sm nd and u pb case study from the pohorje mountains slovenia eastern alps high pressure metamorphism in the pohorje mountains of slovenia austroalpine unit eastern alps affected n morb type metabasic and metapelitic lithologies thermodynamic calculations and equilibrium phase diagrams of kyanite phengite bearing eclogites reveal pt conditions of 2 1 gpa at t 750 c but within the stability field of quartz metapelitic eclogite country rocks contain the assemblage garnet phengite kyanite quartz for which calculated peak pressure conditions are in good agreement with results obtained from eclogite samples the eclogites contain a single population of spherical zircon with a low th u ratio combined constraints on the age of metamorphism come from u pb zircon as well as garnet whole rock and mineral mineral sm nd analyses from eclogites a coherent cluster of single zircon analyses yields a 206pb 238u age of 90 7 1 0 ma that is in good agreement with results from sm nd garnet whole rock regression of 90 7 3 9 and 90 1 2 0 ma end 8 for two eclogite samples the agreement between u pb and sm nd age data strongly suggests an age of approximately 90 ma for the pressure peak of the eclogites in the pohorje mountains the presence of garnet omphacite and quartz inclusions in unfractured zircon indicates high pressure rather than ultrahigh pressure conditions the analysed metapelite sample yields a sm nd garnet whole rock scatterchron age of 97 15 ma these data probably support a single p t loop for mafic and pelitic lithologies of the pohorje area and a late cretaceous high pressure event that affected the entire easternmost austroalpine basement including the koralpe and saualpe eclogite type locality in the course of the complex collision of the apulian microplate and europe