evidence of multiple halogen sources in scapolites from iron oxide copper gold iocg deposits and regional nacl metasomatic alteration norrbotten county sweden abstract scapolites from barren regional na cl metasomatic assemblages rm iron oxide copper gold deposits iocg scapolite altered metabasic rocks iocg m and from iocg proximal alteration na skarns iocg ps from norrbotten county in northern sweden have been analysed for halogen content and cl stable isotope composition the aim of the study was to constrain the source of halogens within alteration assemblages and to investigate the possible fractionation of cl isotopes between scapolite and the hydrothermal fluid scapolite separates were analysed for cl br and major oxide concentrations using electron probe micro analysis epma and micro x ray fluorescence xrfm spectrometry chlorine was extracted from the scapolite separates via pyrohydrolysis and then analysed for their stable cl isotope compositions by isotope ratio mass spectrometry irms all samples of scapolite investigated in this study are marialitic in composition one of the scapolites from the gruvberget deposit iocg ps had a cl br molar ratio of 2363 which is the highest amongst all scapolites reported in the literature to date cl br molar ratios lower than seawater 650 were identified in two iocg ps scapolite samples cl br 554 and 271 as well as in two iocg m scapolites cl br 393 and 565 three rm scapolites had cl br molar ratios very close to or slightly higher than seawater values 639 to 770 samples with cl br molar ratios less than seawater are inferred to have halogens derived from evaporative residual brines whereas samples with molar ratios higher than seawater may have halogens derived from fluids that have dissolved halite and or are from magmatic systems considering the wide variation of the cl br molar ratios in the iocg ps and iocg m scapolites compared to the restricted composition of the regional alteration rm it is proposed that the hydrothermal fluids interacted with several different protoliths to generate the iocg alteration rm alteration scapolites had 37 cl values from 0 1 to 0 3 two iocg m scapolites had values of 0 2 and iocg ps scapolites had 37 cl values from 0 1 to 1 0 using a previously published 37 cl value from fluid inclusion leachates 1 7 from the iocg m mineralisation at pahtohavare and the 37 cl value of co existing scapolite measured in this study 0 2 an empirical fluid scapolite fractionation factor was calculated to be 1 9 this large fractionation factor is not supported by previous predictions for monovalent chlorides and assuming equilibrium indicates that 37 cl was preferentially accommodated in the a site of the scapolite structure this indicates that either the stable cl isotope partitioning between the cacl 2 rich brine and the scapolite may differ from currently available estimates for nacl brines in equilibrium with silicate minerals or that the scapolite and brine are not in isotopic equilibrium overall the data in this study suggest that halogens in early scapolites were derived from residual brines and halite during metamorphism of evaporites linked to the rm alteration later in the history of the norrbotten district components of the rm alteration were recycled and mixed during magmatic and local metasomatic events to varying extents resulting in the brines associated with iocg alteration

signature of ongoing brine reinjection on noble gas isotopes and fluid chemistry at las tres virgenes geothermal field mexico abstract a geochemical survey of the las tres virgenes geothermal field ltvgf baja california sur mexico was carried out to determine the origin and evolution of its fluids along with the influence of injection of local brines and inhibitors intended to manage carbonate scaling issues major and minor cations cl br sr o h and noble gas he ne ar kr and xe isotopes were measured in fluids collected from four production wells two injection wells and one fumarole el azufre in 2016 and 2018 variations in the stable isotopes of water d and 18o and halogens 37cl 81br over the years suggest that local brine reinjection might have started to modify the pristine chemistry of the fluids however relevant information on the original geothermal fluids has been preserved the na br and cl br ratios suggest that ltvgf brines are seawater having leached evaporite deposits halite these deposits are absent in the area but were likely present during the miocene prior to the breakup of the gulf of california suggesting that the saline fluid end member at the ltvgf could be several million years old measured 3he 4he ratios r normalized to the atmospheric ratio ra 1 384 10 6 plotted against the 4he 20ne ratios suggest mixing between a mantle fluid with a r ra of 6 19 typical of the sub continental lithospheric mantle and an atmospheric helium component the r ra versus the 132xe 36ar ratio normalized to air suggests mixing between a mantle rich pre production fluid and air the source of air appears to be linked to local gravity controlled flow reinjection which causes the entrapment of air bubbles leading to a fluid supersaturated in atmospheric noble gases this pattern suggests that reinjection fluids are impacting the production area

hydrochemical and isotopic δ18o δ2h 87sr 86sr δ37cl and δ81br evidence for the origin of saline formation water in a gas reservoir abstract the permo triassic kangan gasfield in southern iran is composed of an aquifer the kangan aquifer ka and an overlying gas reservoir it is located in the kangan and dalan formations and consists predominantly of limestone and dolomite the kangan gasfield is exploited from 36 wells at depths from 2300 to 2860 m the quality of the produced formation waters pfw varies from fresh to saline with salinities of up to 60 000 mg l the present study aims to identify the origin of the salinity of the pfws the concentration of major ions li sr and br as well as 18o d 87sr 86sr 37cl and 81br isotope compositions of the ka water and pfw samples a fresh and a brine spring and the persian gulf water were all measured the suite of isotopic 37cl and 81br and hydrochemical data li cl and br concentrations and cf index in this study indicates that the salinity origin of the pfws is evaporated seawater which could be either the ka water or the intergranular saturated brine in the kangan gas reservoir kgr both derived from permo triassic evaporated seawater 18o and 87sr 86sr data exclude the ka water as the source of the saline pfw leaving the intergranular brine of the kgr as the most likely source although further isotopic and geochemical tests are needed to verify this this work also proposes for the first time the use of a li cl versus br cl diagram to distinguish between evaporate formation water water modified by halite dissolution and fresh water it is recommended to apply these comprehensive methods to deep brine aquifers especially related to gasfields

chlorine isotopic compositions of high temperature hydrothermal vent fluids over ridge axes abstract we present chlorine stable isotope compositions of high temperature hydrothermal vent fluids from two mid oceanic ridges the six hydrothermal fluids come from sites along the slow spreading mid atlantic ridge menez gwen at 37 50 n lucky strike at 37 17 n and rainbow at 36 14 n and the ultrafast spreading east pacific rise from three contiguous segments centered respectively at 17 25 s 18 15 s and 18 26 s these samples exhibit a large range in temperature ph chlorinity and mg content reflecting various geological settings and substrata nature basaltic or ultramafic although showing a large range of chlorinity from 251 to 821 mmol kg the fluids display homogeneous chlorine isotope signatures 37 cl smoc 0 03 0 06 indistinguishable from that of seawater this homogeneity contrasts with the large range of 37 cl previously observed in continental or off axis oceanic fluids this study explores possible processes that may change cl concentration during fluid genesis and discusses their theoretical isotopic effects the 37 cl homogeneity implies that at the p t conditions of the ridge axis the process of phase separation at sub or super critical conditions that explains most of chlorinity variations does not significantly fractionate chlorine isotopes this study shows that the physical and chemical processes that likely alter cl concentrations in ridge axis systems i e transport processes mixing or water rock interaction contribute to minimize the range of 37 cl around the seawater 37 cl value

an integrated modelling approach to reconstruct complex solute transport mechanisms cl and δ37cl in pore water of sediments from a former brackish lagoon in the netherlands abstract a one dimensional transport model was developed to reconstruct historical conservative transport of chloride and 37 cl in pore water of sediments from a former brackish lagoon in the netherlands an area now covered by the freshwater lakes ijssel and marken knowledge of the mechanism of historical solute transport in the sediments and environmental conditions during transport is critical in understanding observed pore water chemistry and will form a basis for simulating effects of changing environmental climate change conditions the model synthesizes present knowledge of geology and historical information on storm surges in the area and takes into account processes such as erosion of sediments mixing of pore water sedimentation and diffusion emsd the chemistry of pore water from one particular boring in the area was found to be mainly controlled by alternating seawater and freshwater diffusion models with a constant averaged porosity 0 55 and tortuosity factor 0 3 showed similar results as models incorporating the measured bulk porosity variations 0 4 0 8 and variable tortuosity factors calculated with archie s law the relatively small tortuosity factor either results from anion exclusion or from the heterogeneous build up of the profile in which a peaty layer in the middle part may obstruct diffusion diffusion of 35 cl was found to be 1 0017 times faster than of 37 cl seawater diffusion into the sediments started at least 400 years ago and refreshening took place since the lagoon was isolated from the sea by a dam in 1932

sources of fluids and gases expelled at cold seeps offshore georgia eastern black sea four seep sites located within an 20 km2 area offshore georgia batumi seep area pechori mound iberia mound and colkheti seep show characteristic differences with respect to element concentrations and oxygen hydrogen strontium and chlorine isotope signatures in pore waters as well as impregnation of sediments with petroleum and hydrocarbon potential all seep sites have active gas seepage near surface authigenic carbonates and gas hydrates cokheti seep iberia mound and pechori mound are characterized by oil stained sediments and gas seepage decoupled from deep fluid advection and bottom water intrusion induced by gas bubble release pechori mound is further characterized by deep fluid advection of lower salinity pore fluids the pechori mound pore fluids are altered by mineral water reactions at elevated temperatures between 60 and 110 c indicated by heavier oxygen and lighter chlorine isotope values distinct li and b enrichment and k depletion strontium isotope ratios indicate that fluids originate from late oligocene strata this finding is supported by the occurrence of hydrocarbon impregnations within the sediments furthermore light hydrocarbons and high molecular weight impregnates indicate a predominant thermogenic origin for the gas and oil at pechori mound iberia mound and colkheti seep c15 hydrocarbons at the oil seeps are allochtonous whereas those at the batumi seep area are autochthonous the presence of oleanane an angiosperm biomarker suggests that the hydrocarbon source rocks belong to the maikopian formation in summary all investigated seep sites show a high hydrocarbon potential and hydrocarbons of iberia mound colkheti seep and pechori mound are predominantly of thermogenic origin however only at the latter seep site advection of deep pore fluids is indicated

the stable isotopic composition 37cl 35cl of dissolved chloride in rainwater abstract the stable isotopic composition of dissolved cl in rainwater was measured from a coastal and an interior location in eastern canada at the interior bonner lake ontario site the 37cl values of dissolved cl in precipitation ranged from 3 5 to 1 2 smoc with an amount weighted annual average of 2 3 at the coastal site bay d espoir newfoundland 37cl values of dissolved cl values ranged from 3 1 to 0 0 with an amount weighted annual average of 1 3 these negative 37cl values provide evidence that atmospheric hcl is 37cl depleted presumably from acidification of sea salt aerosols accordingly dissolved cl in the headwaters of two montane rivers in western canada had similarly depleted 37cl values these results have implications to the interpretation of the isotopic compositions of dissolved cl in surface waters formation fluids and groundwaters

conceptualizing leakage and storage contributions from long open interval wells in regional deep basin flow models deep basin aquifers are increasingly used in water stressed areas though their potential for sustainable development is inhibited by overlying aquitards and limited recharge rates long open interval wells loiws wells uncased through multiple hydrostratigraphic units are present in many confined aquifer systems and can be an important mechanism for deep basin aquifers to receive flow across aquitards loiws are a major control on flow in the deep cambrian ordovician sandstone aquifers of the upper midwest usa providing a source of artificial leakage from shallow bedrock aquifers and equilibrating head within the sandstone aquifers despite differential pumpage conceptualizing and quantifying this anthropogenic flow has long been a challenge for groundwater flow modellers particularly on a regional scale synoptic measurements of active production wells and well completion data for northeast illinois form the basis for a transient head specified modflow model that determines mass balance contributions to the region and estimates loiw leakage to the aquifers using this insight transient loiw leakage was simulated using transiently changing kv zones in a traditional q specified modflow usg model a novel approach that allows the kv in a cell containing a loiw to change transiently by use of the time variant materials tvm package with this modification we achieved a consistent calibration through time averaging 19 9 m root mean squared error this model indicates that artificial leakage via loiws contributed a minimum of 10 13 of total flow to the sandstone aquifers through the entire history of pumping up to 50 of flow around 1930 removal from storage exceeds 40 of flow during peak withdrawals much of this flow sourced from units other than the primary sandstone aquifers via loiws as such understanding the timing and magnitude of loiw leakage is essential for predicting future water availability in deep basin aquifers

chlorine isotope and cl br fractionation in fluids of poas volcano costa rica insight into an active volcanic hydrothermal system abstract halogen rich volcanic fluids issued at the surface carry information on properties and processes operating in shallow hydrothermal systems this paper reports a long term record of cl br concentrations and 37cl signatures of lake water and fumaroles from the active crater of poas volcano costa rica where surface expressions of magmatic hydrothermal activity have shown substantial periodic changes over the last decades both the hyperacid water of its crater lake laguna caliente and subaerial fumaroles show significant temporal variability in cl br concentrations br cl ratios and 37cl reflecting variations in the mode and magnitude of volatile transfer the 37cl signatures of the lake covering the period 1985 2012 show fluctuations between 0 02 0 06 and 1 15 0 09 condensate samples from adjacent fumaroles on the southern shore collected during the interval 2010 2012 with strong changes in gas temperature 107 763 c display a much larger range from 0 43 0 09 to 14 09 0 08 most of the variations in cl isotope br cl and concentration signals can be attributed to interaction between magma derived gas and liquid water in the volcanic hydrothermal system below the crater the 37cl were lowest and closest to magmatic values in 1 fumarolic gas that experienced little or no interaction with subsurface water and followed a relatively dry pathway and 2 water that captured the bulk of magmatic halogen output so that no phase separation could induce fractionation in contrast elevated 37cl can be explained by partial scavenging and fractionation during subsurface gas liquid interaction hence strong cl isotope fractionation leading to very high 37cl in poas fumaroles indicates that they followed a wet pathway highest 37cl values in the lake water were found mostly in periods when it received a significant input from subaqueous fumaroles or when high temperatures and low ph caused hcl evaporation it is concluded that combined monitoring of 37cl and br cl in laguna caliente and adjacent fumaroles provides valuable information on activity in the subsurface hydrothermal system with significant relevance for volcanic surveillance of poas

origin and fate of hydrothermal fluids at piton des neiges volcano reunion island a geochemical and isotopic o h c sr li cl study of thermal springs abstract as many ocean basaltic volcanoes worldwide piton des neiges reunion island hosts a hydrothermal system that represents a potential geothermal resource despite several prospection campaigns over the past decades this potential has never been confirmed because many aspects of fluid supply and circulation remain unclear to track the origin and fate of hydrothermal fluids we analyzed the geochemistry of thermal springs water and gas by combining conventional tracers major trace elements and o h c sr li isotopes with cl isotopes a geochemical tool under development added to literature data our new results allow us to compare the composition of thermal springs with cold waters rocks gas and fumarolic deposits from la reunion and elsewhere and to untwine the complex history of fluid mixing that constitutes the geothermal system of piton des neiges 18oh2o and dh2o values of springs 8 67 to 4 9 and 56 3 to 23 5 vsmow respectively are positioned close to the local meteoric water line showing that thermal waters are of meteoric origin however their depletion in heavy isotopes relative to cold waters suggests a recharge strongly influenced by cyclones with a possible contribution from high altitude 2000 m rainfalls their absence of 18o enrichment relative to the local meteoric water line indicates that the isotopic exchange between rocks and water is very limited and therefore suggests that their deep temperatures are relatively low and or the water rock ratios are high 13c values in thermal waters 8 0 to 3 2 pdb and gases 6 7 to 5 3 pdb confirm that carbon is essentially of magmatic origin which we interpret as supplied by regional degassing of la reunion hotspot major trace elements and 87sr 86sr 0 704142 to 0 704336 7li 2 and 34 8 lsvec and 37cl 0 35 and 0 40 smoc compositions show that three additional processes contribute to the mineralization of thermal waters 1 interaction with basalt at temperatures 50 c 2 very limited seawater contamination the geothermal system of piton des neiges is thus the result of meteoric water interaction with a trachytic heat source as a solidified intrusion or a magma pocket unrelated to the co2 flux we also emphasize that thermal waters at piton des neiges are exceptionally isolated from seawater compared to other geothermal systems in ocean island volcanoes worldwide which implies a heat source located above the seawater freshwater interface these inferences are of critical importance for the future geothermal exploration on the island as they suggest that the geothermal resource is within reach of relatively shallow drilling depths 1000 m

a cross calibration of chlorine isotopic measurements and suitability of seawater as the international reference material abstract a collection of 24 seawaters from various worldwide locations and differing depth was culled to measure their chlorine isotopic composition 37cl these samples cover all the oceans and large seas atlantic pacific indian and antarctic oceans mediterranean and red seas this collection includes nine seawaters from three depth profiles down to 4560 mbsl the standard deviation 2 of the 37cl of this collection is 0 08 which is in fact as large as our precision of measurement 0 10 thus within error oceanic waters seem to be an homogeneous reservoir according to our results any seawater could be representative of standard mean ocean chloride smoc and could be used as a reference standard an extended international cross calibration over a large range of 37cl has been completed for this purpose 13 geological fluid samples of various chemical compositions and a manufactured ch3cl gas sample with 37cl from about 6 to 6 have been compared data were collected by gas source isotope ratio mass spectrometry irms at the paris reading and utrecht laboratories and by thermal ionization mass spectrometry tims at the leeds laboratory comparison of irms values over the range 5 3 to 1 4 plots on the y x line showing a very good agreement between the three laboratories on 11 samples the trend line between paris and reading universities is 37clreading 1 007 0 009 37clparis 0 040 0 025 with a correlation coefficient r2 0 999 tims values from leeds university have been compared to irms values from paris university over the range 3 0 to 6 0 on six samples the agreement between these two laboratories using different techniques is good 37clleeds 1 052 0 038 37clparis 0 058 0 099 with a correlation coefficient r2 0 995 the present study completes a previous cross calibration between the leeds and reading laboratories to compare tims and irms results anal chem 72 2000 2261 both studies allow a comparison of irms and tims techniques between 37cl values from 4 4 to 6 0 and show a good agreement 37cltims 1 039 0 023 37clirms 0 059 0 056 with a correlation coefficient r2 0 996 our study shows that for fluid samples if chlorine isotopic compositions are near 0 their measurements either by irms or tims will give comparable results within less than 0 10 while for 37cl values as far as 10 either positive or negative from smoc both techniques will agree within less than 0 30

isotopic tracing of perchlorate sources in groundwater from pomona california abstract the groundwater of pomona california is contaminated with perchlorate clo 4 this water is treated to reduce the clo 4 concentration to less than 6 g l 1 for compliance with california department of public health drinking water regulations a study of the isotopic composition of oxygen and chlorine in clo 4 has been conducted to determine the source of the contamination isotopic compositions were measured for clo 4 samples extracted from 14 wells yielding ranges of 18 o values from 10 8 to 8 0 17 o values from 4 6 to 7 5 and 37 cl values from 12 8 to 8 9 evaluation of mixing proportions using published isotopic data for three clo 4 end members synthetic atacama and indigenous natural clo 4 indicates that contamination is dominantly 85 89 atacama clo 4 derived from past use of imported chilean nitrate fertilizer in citrus cultivation this interpretation is consistent with 1 aerial photography archives showing extensive citrus fields surrounding pomona in the early to mid 20th century 2 mass balance estimates for clo 4 and 3 numerical hydrologic models yielding travel times for clo 4 from fields to wells that are in the range of 15 to 100 years the hydrologic models predict that clo 4 contamination of pomona groundwater will persist for decades into the future

chlorine isotopes in fluid inclusions determination of the origins of salinity in magmatic fluids abstract thermal ionisation mass spectrometry tims of the cs 2 cl ion has been used to determine the 37 cl value of paleofluids trapped in fluid inclusions modifications to the existing published method have lowered the precision by a factor of 2 0 09 1 thereby allowing real differences to be measured with greater certainty the method has been applied to determine 37 cl of two sets of magmatic fluids trapped in fluid inclusions samples were studied from the capitan pluton in new mexico and the sw england batholith both of which have high temperature fluids whose d and 18 o signatures are distinctly magmatic relative to standard mean ocean chloride smoc the 37 cl values of the capitan samples cluster around 0 whereas those from sw england cluster around 1 8 the br cl ratios of the capitan fluid inclusions are low indicative of halite dissolution and are comparable to local high salinity waters derived from leaching permian evaporites the br cl ratios of the sw england fluid inclusions are much higher and within the range of values normally considered to be magmatic we conclude that the 37 cl value of the capitan magmatic fluids confirms the evidence from br cl ratios that cl was derived from an evaporite source whereas the 37 cl value of the sw england fluids appears to be more representative of a deep magmatic source

earthquakes near albuquerque new mexico 1976 1981 the u s geological survey conducted a 66 month long study of earthquake activity near albuquerque new mexico during 1976 1981 analysis of over 1000 hypocenters with magnitudes as large as 3 2 revealed that most of the seismicity fell into three regions 1 the socorro and albuquerque areas of the rio grande rift 2 the mount taylor area of the jemez lineament and 3 the estancia basin in the rift the hypocenters are shallow and largely confined to regions beneath the basins composite fault plane solutions suggest both normal and strike slip faulting with an average t axis oriented wnw ese most of the young faults of the rift are seemingly inactive and the rift as a whole cannot be delineated on the basis of seismicity

origin and evolution of fluids from mud volcanoes in the barbados accretionary complex a large collection of fluids 54 interstitial fluids and four expelled fluids were sampled at the manon site at the outer edge of the barbados accretionary complex these warm fluids up to 20 c are expelled by sub marine 5000 mbsl mud volcanoes consisting of diapirs unchanneled flow and diatremes channeled chlorine stable isotope ratios of these fluids were measured by irms with a reproducibility of 0 05 1 versus smoc standard mean ocean chloride a large range of 37cl between 5 3 and 0 1 is observed data from each volcanic structure describe a mixing between seawater and a low 37cl fluid the whole set of data is interpreted as the result of a mixing between two deep components and seawater the two deep fluids are chemically distinct e g in ca mg k li sr and br contents and br cl ratio they display low and significantly different 87sr 86sr ratios 0 707790 and 0 707892 respectively and 37cl values 4 51 and 5 24 respectively physicochemical processes such as mineralogical transformation diffusion compaction or ion filtration are known to fractionate chlorine stable isotopes and can produce fluids with negative 37cl values ion filtration due to sediment compaction appears to be the more likely process to explain the negative 37cl values observed at the manon site a model for the generation of these signatures is proposed where a residual negative 37cl fluid reservoir is created at the bottom of the prism or the sediment pile further compaction fracturing and or dewatering of the slab may flush out these fluids and focus them towards the decollement zone mixing between the fluids and ultimately with seawater and water released during gas hydrate destabilizations may explain the data set within the individual cores and between the different structures

microbial perchlorate reduction a precise laboratory determination of the chlorine isotope fractionation and its possible biochemical basis abstract perchlorate reducing bacteria fractionate chlorine stable isotopes giving a powerful approach to monitor the extent of microbial consumption of perchlorate in contaminated sites undergoing remediation or natural perchlorate containing sites this study reports the full experimental data and methodology used to re evaluate the chlorine isotope fractionation of perchlorate reduction in duplicate culture experiments of azospira suillum strain ps at 37 c 37 cl cl clo 4 previously reported without a supporting data set by coleman et al coleman m l ader m chaudhuri s coates j d 2003 microbial isotopic fractionation of perchlorate chlorine appl environ microbiol 69 4997 5000 in a reconnaissance study with the goal of increasing the accuracy and precision of the isotopic fractionation determination the method fully described here for the first time allows the determination of a higher precision 37 cl cl clo 4 value either from accumulated chloride content and isotopic composition or from the residual perchlorate content and isotopic composition the result sets agree perfectly within error giving average 37 cl cl clo 4 14 94 0 15 complementary use of chloride and perchlorate data allowed the identification and rejection of poor quality data by applying mass and isotopic balance checks this precise 37 cl cl clo 4 value can serve as a reference point for comparison with future in situ or microcosm studies but we also note its similarity to the theoretical equilibrium isotopic fractionation between a hypothetical chlorine species of redox state 6 and perchlorate at 37 c and suggest that the first electron transfer during perchlorate reduction may occur at isotopic equilibrium between an enzyme bound chlorine and perchlorate

deep water circulation at the northern pyrenean thrust implication of high temperature water rock interaction process on the mineralization of major spring water in an overthrust area abstract in an overthrust context of the northern pyrenean area groundwater is affected by high mineralization sources a multi isotopic approach was used to track the origin of mineralization in a complex multilayer aquifer system through the study of a major regional spring the oeillal spring water osw which shows a not yet investigated geochemical singularity the aims of this study are to understand the hydrogeochemical evolution and the mineralization mechanisms of groundwater in a large scale aquifer extending over the northern pyrenean overthrust oriental corbieres based on an adequate set of geochemical and isotopic tracers including cosmogenic stable and radiogenic isotopes we have revealed complex hydrogeochemical processes that cannot be tracked with traditional hydrochemical and isotopic tracers the high 87 sr 86 sr ratios of the osw associated with relatively high concentrations in trace elements cs rb sr b li suggest the influence of brine from the triassic deposits containing saliferous clay orsaline fluids from the fractured basement the basement hypothesis may be considered regarding the hydro geochemical fingerprint of the paleozoic basement as demonstrated in previous study and further data would be required to validate the contribution of basement fluids contrasting with marine primary brine and current seawater the relatively high 37 cl 0 22 and 0 39 of osw attests the non marine origin of the chloride ion 36 cl cl shows that the osw is issued from a mixing process between recently recharged water lightly mineralized and significantly marked in 36 cl by the thermonuclear bomb pulse and a saline deep end member at secular equilibrium this indicates that cl in these springs is primarily derived from subsurface non meteoric sources the osw s low br cl molar ratio suggests the influence of simple dissolution of halite and or the contribution of more complex secondary brine the deep saline water may results from meteoric infiltration into the lower jurassic aquifer in contact with triassic deposits or deeper high temperature promotes water rock interaction enhancing leaching of mg k rich saliferous clay this is supported by environmental scanning electron microscopy esem analyses showing that i cl is found in accessory minerals from the kcl mgcl 2 h 2 o system of the triassic deposits and ii cs rb molar ratio is similar to that of osw ranging between 0 13 and 0 7 and from 0 13 to 0 4 respectively laboratory experiments carried out on triassic material show that high temperature water rock interaction is suitable to explain the relatively high 87 sr 86 sr observed in groundwater such process can be investigated to confirm the deep origin of the osw and to explain the signature of deep brines in contact with the triassic deposits under high temperature conditions basement fluid contribution may also be considered regarding the hydro geochemical fingerprint of the paleozoic basement as shown in previous studies further data would be required to validate this hypothesis

chlorine isotope constraints on fluid rock interactions during subduction and exhumation of the zermatt saas ophiolite 1 chlorine isotope compositions of high pressure 2 3 gpa serpentinite rodingite and hydrothermally altered oceanic crust aoc differ significantly from high and ultrahigh pressure 3 2 gpa metasedimentary rocks in the aosta region italy texturally early serpentinites rodingites and aoc have bulk 37cl values indistinguishable from those of modern seafloor analogues 37cl 1 0 to 1 0 in contrast serpentinites and aoc samples that recrystallized during exhumation have low 37cl values 2 7 to 0 5 37cl depletion correlates with progressive changes in bulk chemistry hp uhp metasediments have low 37cl values median 2 5 that differ statistically from modern marine sediments median 0 6 cl in metasedimentary rocks is concentrated in texturally early minerals indicating modification of seafloor compositions early in the subduction history the data constrain fluid sources during both subduction and exhumation related phases of fluid rock interaction 1 marine sediments at the top of the downgoing plate likely interacted with isotopically light pore fluids from the accretionary wedge in the early stages of subduction 2 no pervasive interaction with externally derived fluid occurred during subsequent subduction to the maximum depths of burial 3 localized mixing between serpentinites and fluids released by previously isotopically modified metasediments occurred during exhumation in the subduction channel most samples however preserved protolith signatures during subduction to near arc depths

chlorine isotopes of thermal springs in arc volcanoes for tracing shallow magmatic activity the evaluation of the status of shallow magma body i e from the final intrusion stage to quiescence and back to activity one of the key parameters that trigger and sustain volcanic eruptions has been challenging in modern volcanology among volatile tracers chlorine cl uniquely exsolves at shallow depths and is highly hydrophilic consequently cl enrichment in volcanic gases and thermal springs has been proposed as a sign for shallow magmatic activities however such enrichment could also result from numerous other processes e g water evaporation dissolution of old chloride mineral deposits seawater contamination that are unrelated to magmatic activity here based on stable isotope compositions of chloride and dissolved inorganic carbon as well as previous published 3he 4he data obtained in thermal springs from two recently erupted volcanoes la soufriere in guadeloupe and montagne pelee in martinique in the lesser antilles arc we show that the magmatic cl efficiently trapped in thermal springs displays negative 37cl values 0 65 0 65 consistent with a slab derived origin but distinct from the isotope compositions of chloride in surface reservoirs e g seawater local meteoric waters rivers and cold springs displaying common 37cl values of around 0 using this 37cl difference as an index of magmatic cl we further examined thermal spring samples including a 30 year archive from two thermal springs in guadeloupe covering samples from its last eruption in 1976 1977 to 2008 and an island wide sampling event in martinique in 2008 to trace the evolution of magmatic cl in the volcanic hydrothermal systems over time the results show that magmatic cl can be rapidly flushed out of the hydrothermal systems within 30 to 80 years after the eruption much quicker than other volatile tracers such as co2 and noble gases which can exsolve at greater depths and constantly migrate to the surface because arc volcanoes often have well developed hydrothermal systems where magmatic cl is easily transferred to the surface following its exsolution from shallow magma body we suggest that 37cl has great potential to be a unique proxy to monitor the cessation and revival of infrequent arc volcanoes particularly at centennial time scales

cl br ratios and stable chlorine isotope analysis of magmatic hydrothermal fluid inclusions from butte montana and bingham canyon utah a bulk geochemical study has been carried out on fluid inclusion leachates extracted from quartz veins from porphyry cu deposits in butte montana usa and bingham canyon utah usa the leachates mostly represent low salinity magmatic hydrothermal fluid inclusions their halogen ratios br cl of fluid inclusion leachates were determined by ion chromatography and 37cl values of the leachates were measured by continuous flow isotope ratio mass spectrometry br cl ratios from early pre main stage and later main stage veins at butte range from 0 60 to 1 88 10 3 m ratios are similar in pre main stage veins with sericite bearing selvages and main stage samples ranging from 0 81 to 1 08 10 3 and from 0 92 to 1 88 10 3 m respectively clustering below seawater 1 54 10 3 m and overlapping mantle values 1 2 10 3 m two samples associated with early pre main stage potassic alteration yield distinctly lower br cl ratios of 0 60 and 0 64 10 3 m butte 37cl values range from 0 8 to 2 3 with no significant difference between pre main stage and main stage samples br cl ratios for quartz veins from bingham canyon range from 0 18 to 3 68 10 3 m br cl ratios from bingham range above and below previously reported for porphyry copper deposits in contrast to butte 37cl values for bingham are lower ranging from 0 9 to 4 1 in the absence of any processes which can significantly fractionate chlorine isotopes at high temperatures we suggest that the porphyry system at bingham and to a lesser extent at butte have inherited negative chlorine isotopic signatures from the subducting slab generated at low temperatures

extraction and analysis of hydrosoluble chlorine and its stable isotopic composition in soil using thermal ionization mass spectrometry abstract chlorine is an essential micronutrient for high plant growth the uptake of chlorine by plants is controlled by the hydrosoluble chlorine in soil which can lead to the cycle change of chlorine isotopes in surficial processes in this study a novel method using water extraction coupled with concatenated ion exchange chromatography for the extraction of hydrosoluble chlorine in soil samples is established for the determination of chorine isotopes by thermal ionization mass spectrometry the results show that no loss of cl ion and the fractionation of chlorine isotopes occur in the extraction with recoveries ranging from 96 4 to 106 4 the variations of 37cl values in soil samples range from 2 40 to 1 31 with an average of 0 44 at a standard deviation of 1 08 stepwise linear regression analysis reveals a positive linear relationship between 37cl values and cl amount in ht soil profile which indicates that the diffusion of cl ion along with soil water flow controls the chlorine isotope in the range of less than 2 in soils the correlation in wf soils shows that except the seawater invasion the 37cl value variation is attributable to the mixing of different sources including anthropogenic activities

establishing constraints on groundwater ages with 36cl 14c 3h and noble gases a case study in the eastern paris basin france abstract groundwaters from the tithonian kimmeridgian oxfordian and upper dogger aquifers within the eastern part of the paris basin france were characterised using 3 h 14 c and 36 cl and noble gases tracers to evaluate their residence times and determine their recharge period this information is an important prerequisite to evaluating the confinement properties of the callovo oxfordian clay formation sandwiched between the oxfordian aquifer and the dogger aquifer currently being investigated by the french nuclear waste management agency andra for radioactive waste disposal data presented in this paper are used to test 4 hypotheses 1 the oxfordian limestone is isolated from the overlying tithonian kimmeridgian surface aquifer this first hypothesis is supported by the presence of measurable 3 h activities in groundwaters from the surface aquifer 6 11 tu and by its absence in groundwaters derived from deeper aquifers 2 the callovo oxfordian clay sequence in the vicinity of the url serves as an effective barrier to advective flow and transport between the underlying upper dogger aquifer and the overlying oxfordian limestone aquifer this second hypothesis is supported by relatively low concentrations of cl 3 5 78 mg l 1 na 15 145 mg l 1 br 0 08 0 4 mg l 1 and 4 he rad 0 2 2 3 ccstp g 1 and slightly higher 36 cl cl ratios 2 7 59 10 15 at at 1 in groundwaters from the oxfordian aquifer compared to those from the upper dogger aquifer 345 4027 mgcl l 1 402 2390 mgna l 1 1 8 22 2 mgbr l 1 1 6 37 2 ccstp he g 1 1 5 10 15 at 36 cl at 1 cl 3 groundwaters from the oxfordian aquifer in the vicinity of url are pre holocene with residence times exceeding 10 ka geochemical and isotopic lines of evidence for this hypothesis include a 13 c values measured on oxfordian aquifer waters that are close to 13 c of the aquifer matrix reflecting strong isotopic exchange over several thousand years b noble gas temperatures that indicate recharge temperatures between 3 and 8 6 c lower by 2 7 c than the modern average temperature in this area c radiogenic 4 he concentrations between 0 16 10 5 and 2 3 10 5 ccstp g 1 of water about 2 3 orders of magnitude greater than the 4 he concentration of air equilibrated water 4 groundwater residence time for the upper dogger aquifer in the vicinity of the url probably exceed several hundred thousand years such long residence times are indicated by the accumulation of radiogenic he up to 37 10 5 ccstp g 1 assuming a closed system primary contributors to uncertainties in interpretation of the data presented in this paper are the lack of well defined 36 cl cl input ratio knowledge about the 4 he rad sources for oxfordian and dogger aquifers knowledge about transport processes occurring through the dogger aquifer and the extensive dilution of initial 14 c activities by dissolution exchange with aquifer matrix overall however although the data presented in this paper remain semi quantitative due to inevitable intrinsic limitations of the methods none contradict the hypotheses of long residence times and aquifer isolation in the vicinity of the url

an evaporated seawater origin for the ore forming brines in unconformity related uranium deposits athabasca basin canada cl br and δ37cl analysis of fluid inclusions abstract analyses of halogen concentration and stable chlorine isotope composition of fluid inclusions from hydrothermal quartz and carbonate veins spatially and temporally associated with giant unconformity related uranium deposits from the paleoproterozoic athabasca basin canada were performed in order to determine the origin of chloride in the ore forming brines microthermometric analyses show that samples contain variable amounts of a nacl rich brine cl concentration between 120 000 and 180 000 ppm and a cacl2 rich brine cl concentration between 160 000 and 220 000 ppm molar cl br ratios of fluid inclusion leachates range from 100 to 900 with most values between 150 and 350 cl br ratios below 650 seawater value indicate that the high salinities were acquired by evaporation of seawater most 37cl values are between 0 6 and 0 seawater value which is also compatible with a common evaporated seawater origin for both nacl and cacl2 rich brines slight discrepancies between the cl concentration cl br 37cl data and seawater evaporation trends indicate that the evaporated seawater underwent secondary minor modification of its composition by i mixing with a minor amount of halite dissolution brine or re equilibration with halite during burial ii dilution in a maximum of 30 of connate and or formation waters during its migration towards the base of the athabasca sandstones iii leaching of chloride from biotites within basement rocks and iv water loss by hydration reactions in alteration haloes linked to uranium deposition the chloride in uranium ore forming brines of the athabasca basin has an unambiguous dominantly marine origin and has required large scale seawater evaporation and evaporite deposition although the direct evidence for evaporative environments in the athabasca basin are lacking due to the erosion of 80 of the sedimentary pile cl br ratios and 37cl values of brines have behaved conservatively at the basin scale and throughout basin history

halogens of bushveld complex south africa δ37cl and cl f evidence for hydration melting of the source region in a back arc setting abstract the bushveld complex is one of only a few layered intrusions anomalously enriched in chlorine this study presents the first chlorine stable isotope analyses of bushveld and associated rocks designed to constrain the source of bushveld cl most samples overlap the range of values for pristine morb and altered seafloor samples 37 cl 4 relative to sea water this contrasts with distal metasedimentary floor rocks 37 cl 0 with little evidence of contamination away from the marginal rocks the cl isotope composition and high cl f ratio is therefore a fundamental characteristic of the lower and critical zone magmas and not derived from infiltration from the country rock these results the high cl f ratio and the boninitic arc like character of bushveld magma are consistent with hydration partial melting of a depleted source in a subduction related setting with cl supplied either by the dehydration of a subducted slab with a heavy cl signature or an overridden wet mantle hotspot

stable cl isotopes and origin of high cl magmas of the stillwater complex montana the first cl isotopic determinations on biotite from the ultramafic series and from the j m reef of the lower banded series of the stillwater complex montana have 37 cl values normalized to seawater 95 confidence limit error is 0 2 ranging from 0 27 to 0 93 the average is 0 18 assuming minimal fractionation on incorporation into biotite these data imply an ultimate crustal source for the cl however field petrographic and isotopic evidence suggests that high cl fluids did not infiltrate from the country rocks after emplacement of the stillwater magma nor was the cl isotopic signature the result of assimilation of cl rich crustal rocks stillwater parent magmas have boninitic affinities and can be modeled as second stage melts from a metasomatically enriched depleted mantle we propose that the early melt extraction event depleted the mantle in f and cl subsequent metasomatism by a cl rich agent with a crustal cl isotopic signature probably a fluid produced a source rock with a high cl f ratio in modern magmas high cl f weight ratios are associated with high overall volatile contents suggesting that the stillwater complex and other high cl layered intrusions crystallized from magmas that may have contained in excess of 1 wt water

halogen element and stable chlorine isotope fractionation caused by fluid rock interaction bamble sector se norway pervasive interaction between rock and fluid produces regional scale alteration and or metasomatism of rock units the middle and upper crustal rocks from the bamble sector se norway show a complex history of metamorphic and metasomatic events accompanied by ore deposit formation which provides an excellent context for investigation of regional scale fluid rock interaction halogens are important agents of rock alteration and ore metal transportation in such hydrothermal regimes here we use f cl br and i concentrations and stable chlorine isotope ratios d 37 cl to trace the metasomatic evolution of two gabbroic bodies and understand the interplay between localized and pervasive fluid flow in the upper crust an alteration sequence was sampled from pristine gabbro to an amphibolitic shear zone showing progressive amphibolitization and scapolitization caused by pervasive fluid ingress halogen concentrations and ratios suggest the evolution of a single fluid causing enrichment of cl br and i in samples nearest the shear zone owing to the differences in fluid mineral distribution coefficients fluid mineral interaction resulted in either enrichment or depletion of halogens in the fluid as it reacted pervasively with the gabbro although scapolite formation leads to progressive desalination of the fluid near the shear zone increasing cl concentrations in amphibole near the gabbro reflect an increase in salinity towards the unaltered gabbro owing to desiccation of the fluid the formation of alteration minerals mainly governs changes in the halogen chemistry of the fluid showing that halogens do not behave fully conservatively during fluid rock interaction nevertheless the evolving fluid has a feedback on the stability of alteration minerals such as scapolite and biotite which form only close to the shear zone the br cl and i cl ratios of the most highly altered samples are 3 10 3 and 25 10 6 respectively and overlap with the range of ratios measured for marine pore fluids remobilization of evaporites would have produced distinctly lower halogen ratios and can be ruled out as a fluid source the unaltered gabbro has d 37 cl values near 0 and a similar value is inferred for the infiltrating fluid minimally altered samples noted by the presence of 20 vol amphibole have negative d 37 cl values average 0 6 6 0 1 the d 37 cl values increase up to 1 nearest the shear zone with increasing evidence of fluid rock interaction towards the shear zone mixing of different cl reservoirs i e gabbro and fluid cannot explain the observed changes in the d 37 cl values instead isotopic fractionation owing to rayleigh distillation with a fractionation factor of 1 0010 can explain the observed negative d 37 cl values of the alteration sequence by the evolution of a single fluid

strong impact of ion filtration on the isotopic composition of chlorine in young clay rich oceanic sediment pore fluids abstract a collection of 34 pore fluids from young clay rich sedimentary piles of the shikoku basin on the philippine oceanic plate at the front of the nankai subduction zone southeast of japan were analyzed for their chloride content and chlorine stable isotope composition 35cl and 37cl reported as 37cl these pore fluids are samples from iodp sites c0011 and c0012 which penetrate deeper than 500 meters below the seafloor at both sites the 37cl values display a regular decrease with depth from about 0 seawater value at the seafloor to 8 5 and 6 5 respectively in hydrogeologically isolated low permeability sediment levels at some depths local deviations of up to 6 in 37cl interrupt the overall decreasing trends they may be interpreted as the injection of external fluids into the sedimentary piles as a result of sedimentary levels with higher permeability at the bottom of the sedimentary piles the injected fluids probably originating from the altered oceanic crust systematically have 37cl values closer to seawater literature data indicate the display of downward trends of decreasing 37cl values of the pore fluids in many other young clay rich sedimentary piles nankai trough and the japan trench accretionary prisms black ridge and juan de fuca ridge flank here we use conservation equations to demonstrate that these 37cl depth profiles can be modeled using the effect of the compaction of growing clay rich sedimentary piles on the water and chlorides including 35cl and 37cl isotopes this modeling shows that a small isotope fractionation of chlorine isotopes 37cl 35clexpulsed fluid residual fluid in the range of 1 006 to 1 001 may explain the observed negative 37cl chlorides at the bottom of the sedimentary piles the complementary positive 37cl chlorides must accumulate at the top but are very likely erased by dilution with seawater chlorides across the seafloor interface this range of chlorine isotope fractionation values is in agreement with the theory of ion filtration of phillips and bentley 1987 in which the mobility of chlorides through semi permeable clay membrane is determined by ion repulsion based on this study we show that young pore fluids in clay rich sediments of the oceanic crust are 37cl depleted chloride reservoirs they might be the source of 37cl depleted chloride fluids advected at mud volcanoes on the seafloor but do not seem to contribute largely to subduction zone magmatic tectonic metamorphic products where no such 37cl depleted chlorine is documented this in turn is a strong argument to propose that most of the clay rich sediment s pore waters are released back into the ocean rather than subducted

circulation and seasonal evolution of polar waters south of australia implications for iron fertilization of the southern ocean abstract the southern ocean iron release experiment soiree was carried out in late summer february 1999 south of australia 61 s 140 e this region of the southern antarctic zone az s between the southern branch of the polar front pf and the southern front of the antarctic circumpolar current saacf is characterized by weak currents and is remote from the influence of sea ice or coastal waters the soiree site exhibits high nutrient concentrations year round phosphate nitrate and silicate remain above 10 m low chlorophyll accumulations

the sources and evolution of mineralising fluids in iron oxide copper gold systems norrbotten sweden constraints from br cl ratios and stable cl isotopes of fluid inclusion leachates we have analysed the halogen concentrations and chlorine stable isotope composition of fluid inclusion leachates from three spatially associated fe oxide cu au mineralising systems in norrbotten sweden fluid inclusions in late stage veins in fe oxide apatite deposits contain saline brines and have a wide range of br cl molar ratios from 0 2 to 1 1 10 3 and 37cl values from 3 1 to 1 0 leachates from saline fluid inclusions from the greenstone and porphyry hosted cu au prospects have br cl ratios that range from 0 2 to 0 5 10 3 and 37cl values from 5 6 to 1 3 finally the cu au deposits hosted by the nautanen deformation zone ndz have br cl molar ratios from 0 4 to 1 1 10 3 and 37cl values that range from 2 4 to 0 5 although the bulk of the data fall within 0 0 5 the br cl ratios of leachates are consistent with the derivation of salinity from magmatic sources or from the dissolution of halite most of the isotopic data from the fe oxide apatite and greenstone deposits are consistent with a mantle derived source of the chlorine with the exception of the four samples with the most negative values the origin of the low 37cl values in these samples is unknown but we suggest that there may have been some modification of the cl isotope signature due to fractionation between the mineralising fluids and cl rich silicate assemblages found in the alteration haloes around the deposits if such a process has occurred then a modified crustal source of the chlorine for all the samples cannot be ruled out although the amount of fractionation necessary to generate the low 37cl values would be significantly larger the source of cl in the ndz deposits has a crustal signature which suggests the cl in this system may be derived from meta evaporites or from input from crustal melts such as granitic pegmatites of the lina suite