localization of a coal seam fire using combined self potential and resistivity data abstract the remediation of coal seam fires requires as a first step the precise localization of the burning front various geophysical methods can be employed for this purpose but not all of them can provide an unambiguous localization of this type of target we propose a combined inversion of self potential and resistivity data and the use of joint attributes characterizing the target to localize the burning front of a coal seam fire this new methodology is applied to the 3d reconstruction of a shallow coal seam fire in boulder colorado the coal seam fire is located in the gorham subbituminous coal formation at a depth comprised between 10 and 15 m the self potential survey comprises 160 stations 5 profiles and 32 stations per profile located at the ground surface with self potential anomalies amounting 70 to 50 mv with respect to an arbitrary reference located further away from the burning front the resistivity survey comprises 5 resistivity profiles with 118 measurements per profile 590 measurements in total the burning front is associated with very low value of the electrical resistivity

twenty years of groundwater evolution in the triassic sandstone aquifer of lorraine impacts on baseline water quality abstract the lorraine triassic sandstone aquifer ltsa which has already been the subject of a chemical and radioisotopic study 1979 is used to investigate the impacts of 20 a of large scale pumping on baseline water quality in parallel new sampling of the aquifer 2001 provides new inorganic geochemical data including trace elements that allow improving the knowledge of baseline conditions and hydrochemical functioning of a major sandstone aquifer the good correlation between 14 c activities temperature and depth along the main flow line indicate regular downgradient trends and possible water stratification unreactive tracers mainly stable isotope ratios 18 o and 2 h as well as c isotopes are used to define a timescale for the aquifer showing two groups of groundwater namely of modern and holocene age and late pleistocene age with a mixing zone baseline quality is then represented by a wide range of concentrations mainly the result of time dependent water rock interaction as already observed elsewhere in triassic sandstone aquifers some trace elements such as li rb cs which are not limited by solubility constraints show linear trends during saturated flow downgradient the chemistry is also specifically characterised by a regular increase in na and cl and locally so 4 as a result of evaporite dissolution related to overlying or basement limits the aquifer is mostly oxidising with a redox boundary marked by u decrease some 40 km from outcrop groundwater abstraction since the 1970s has created a strong lowering 10 150 m of the water table especially from 1970 to 1980 based on nine boreholes previously sampled in 1979 a decreasing evolution in radiocarbon content of the tdic together with significant evolution of 18 o content indicate that old groundwater has moved upgradient the major difference in terms of baseline evolution is observed using cl and na concentration and locally so 4 indicating an increasing influence of water circulation involving overlying or basement formations or of mixing with permian waters from the point of view of aquifer management the perceptible no 3 increase could provide information on the progress of any contamination under the aerobic conditions in addition the few key elements indicators of disequilibrium related to overlying or deep waters should be included in regular monitoring programmes

regional framework structural and petroleum aspects of rift basins in niger chad and the central african republic c a r abstract this paper overviews the regional framework tectonic structural and petroleum aspects of rifts in niger chad and the c a r the data base is from mainly proprietary exploration work consisting of some 50 000 kilometres of seismic profiles 50 exploration wells one million square kilometres of aeromagnetics coverage and extensive gravity surveys there have been 13 oil and two oil and gas discoveries a five phased tectonic history dating from the pan african orogeny 750 550 my b p to the present suggests that the western central african rift system wcas with its component west african rift subsystem was and central african subsystem cas formed mainly by the mechanical separation of african crustal blocks during the early cretaceous among the resulting rift basins in niger chad and the c a r seven are in the was grein kafra tenere tefidet termit bongor and n dgel edgi and three doba doseo and salamat are in the cas the was basins in niger and chad are all extensional and contain more than 14 000 m of continental to marine early cretaceous to recent clastic sediments and minor amounts of volcanics medium to light oil 20 api 46 api and gas have been discovered in the termit basin in reservoir source and seal beds of late cretaceous and palaeogene age the most common structural styles are extensional normal fault blocks and transtensional synthetic and antithetic normal fault blocks the cas doba doseo and salamat are extensional to transtensional rift basins containing up to 7500 m of terrestrial mainly early cretaceous clastics heavy to light oil 15 39 api and gas have been discovered in doba and doseo basins source rocks are early cretaceous lacustrine shales whereas reservoirs and seals are both early and late cretaceous dominant structural styles are extensional and transtensional fault blocks transpressional anticlines and flower structures the existence of a total rift basin sediment volume of more than one million cubic kilometres with structured reservoir source and seal rocks favours the generation migration and entrapment of additional significant volumes of hydrocarbons in many of these basins

the abundance of seafloor massive sulfide deposits the possibility of mining seafl oor massive sulfide deposits has stirred debate about the sustainable use of this new resource and whether commercial development is worth the risk among the outstanding questions is how many deposits might be accessible to deep sea mining more than 300 sites of high temperature hydrothermal venting have been identifi ed since the discovery of black smokers but signifi cant massive sulfide accumulation has been found at only 165 of these sites estimates of the total number of vent fields and associated mineral deposits based on plume studies and deposit occurrence models range from 500 to 5000 we have used new deposit occurrence data from 10 000 km of ridge arc and backarc spreading centers to estimate the amount of massive sulfide in the easily accessible neovolcanic zones of the global oceans the total accumulation in these areas is estimated to be on the order of 6 108 tonnes containing 3 107 tonnes of copper and zinc this is similar to the total discovered copper and zinc in cenozoic massive sulfi de deposits mined on land but is insuffi cient to satisfy a growing global demand for these metals

the use of 36cl and chloride bromide ratios in discerning salinity sources and fluid mixing patterns a case study at saratoga springs abstract the well known saratoga springs of new york state are low temperature 10 19 c mildly acidic highly carbonated mineral springs which discharge along the many normal faults in the saratoga mcgregor fault system of eastern north america fifteen saline and moderately saline fluids collected from the saratoga springs system and its surroundings were measured for 36 cl cl ratios chloride concentrations and cl br ratios to determine the sources of salinity fluid mixing patterns and history of these waters the springs have total chloride concentrations between 300 and 6500 mg l far in excess of local freshwater and cl br ratios typically in the range of 100 140 36 cl cl ratios for these waters range from 3 22 10 15 markedly below both the modern rainwater 36 cl cl ratio of above 1500 10 15 and the expected pre nuclear rainwater 36 cl cl ratio for the region of 400 10 15 indicating that cl and 36 cl in these springs are primarily derived from subsurface non meteoric sources 36 cl concentrations and cl br ratios can be effectively used to eliminate the possibility of magmatic ancient marine porefluid and evaporite contributions to the springs 36 cl production rates and secular equilibrium 36 cl cl ratios were derived for different subsurface lithologies in the region based on estimated subsurface neutron fluxes for different rock types a comparison of 36 cl cl ratios and cl br ratios in the saratoga springs with secular equilibrium 36 cl cl ratios and with cl br ratios in potential host formations indicates water rock interactions in the subsurface to be the main source of 36 cl to the springs especially from the ordovician carbonates which make up the aquifer and the underlying cambrian clastic rocks the more dilute springs appear to be a mix of saline springs and a meteoric component probably due to the addition of rainwater as the springs rose to the surface along the fault zone the use of chloride bromide ratios was found to be an effective way to support and clarify the information yielded by 36 cl cl ratios and chloride concentrations in the study of brine history

hydrogeochemical and isotopic characterization of the groundwater in the chari baguirmi depression republic of chad the chari baguirmi groundwater in the republic of chad is undergoing a steady deterioration both qualitative and quantitative due to climatic severe droughts and anthropogenic overexploitation constraints however this major water resource has not been to date the object of any comprehensive scientific investigation to fill this gap and consider a sustainable exploitation a hydrodynamic and hydrochemical study was undertaken this aquifer is located south of lake chad and displays a significant natural piezometric depression piezometric campaign on an area of 70 000 km2 bounded by lake chad the chari river the mountains of guera and the dunes of harr was conducted to understand the hydrodynamics of the groundwater water samples were collected on 124 points scattered over the study area hydrochemical and isotopic analyses 18o and 2h were achieved on all samples the interpretation of hydrochemical data was done using the piper diagram the multivariate analysis hierarchical ascending classification the index of base exchanges and ratios of na cl na so4 cl so4 br cl sr ca the hydrochemical results coupled with groundwater isotopes data allowed to understand the processes that govern the mineralization and the origin of groundwater salinity these investigations allowed on the one hand to differentiate between two poles of water mixing and second to demonstrate that the mineralization process and origin of salinity in the center of depression are both related to the lithology of the geological formations crossed by groundwater flow and climatic events causing evaporation of water from the aquifer

geoelectrical measurements at the tag hydrothermal mound direct current electrical experiments with electrode arrays deployed by a submersible alvin were used to determine the resistivity structure of the seafloor below and vertical potential gradients in sea water above the hydrothermally active tag mound apparent resistivities of the sulfides at shallow depths 10 m below seafloor over the mound ranged between 0 18 0 21 ohm m compared to nearby basalt pillow apparent resistivities of 2 1 2 4 ohm m the potential differences between heights of about 18 to 27 m above the mound averaged 3 7 mv voltage increasing with height with variations between about 2 9 and 12 7 mv

a self potential investigation of submarine massive sulfides palinuro seamount tyrrhenian sea the self potential sp method detects naturally occurring electric fields which may be produced by electrically conductive mineral deposits such as massive sulfides recently there has been increasing interest in applying this method in a marine environment to explore for seafloor massive sulfide sms deposits which may contain economic resources of base and precious metals while sms sites that are associated with active venting and are not buried under sediment cover are known to produce an sp signal the effectiveness of the method at detecting inactive and sediment covered deposits remained an outstanding question we built an instrument capable of recording sp data in a marine setting we carried out a test of the instrument at the palinuro seamount in the tyrrhenian sea palinuro is one of only a few known sites containing an sms occurrence which is buried under sediment and not associated with active hydrothermal venting although diffuse seepage of hydrothermal fluids is known to occur at the site elevated electric field strengths recorded in and near the site of previously drilled massive sulfide samples are on the order of 1 3 mv m a second zone of high field strengths was detected by us to the north of the drilling area where gravity coring later confirmed the existence of massive sulfides our observations indicate that an sp signal can be observed at the site of sms mineralization even when the mineralized zone is shallowly buried and active hydrothermal venting is not present these observations could aid in the planning of future marine research expeditions which use the sp method in the exploration of seafloor massive sulfides

geological fate of seafloor massive sulphides at the tag hydrothermal field mid atlantic ridge deep sea mineral deposits potentially represent vast metal resources that could make a major contribution to future global raw material supply increasing demand for these metals many of which are

combined effect of carbonate and biotite dissolution in landslides biases silicate weathering proxies abstract long term estimates of the dissolution of silicate rock are generally derived from a range of isotopic proxies such as the radiogenic strontium isotope ratio 87 sr 86 sr which are preserved in sediment archives for these systems to fairly represent silicate weathering the changes in isotopic ratios in terrestrial surface waters should correspond to changes in the overall silicate dissolution this assumes that the silicate mineral phases that act as sources of a given isotope dissolve at a rate that is proportional to the overall silicate weathering bedrock landsliding exhumes large quantities of fresh rock for weathering in transient storage and rapid weathering in these deposits is controlled primarily by dissolution of the most reactive phases in this study we test the hypothesis that preferential weathering of these labile minerals can decouple the dissolution of strontium sources from the actual silicate weathering rates in the rapidly eroding western southern alps wsa of new zealand we find that rapid dissolution of relatively radiogenic calcite and biotite in landslides leads to high local fluxes in strontium with isotopic ratios that offer no clear discrimination between sources these higher fluxes of radiogenic strontium are in contrast to silicate weathering rates in landslides that are not systematically elevated on a mountain belt scale radiogenic strontium fluxes are not coupled to volumes of recent landslides in large 100 km 2 catchments but silicate weathering fluxes are such decoupling is likely due first to the broad variability in the strontium content of carbonate minerals and second to the combination of radiogenic strontium released from both biotite and carbonate in recent landslides this study supports previous work suggesting the limited utility of strontium isotopes as a system to study silicate weathering in the wsa crucially however in settings where bedrock landsliding is a dominant erosive process there is potential for both random and systematic bias in isotope proxies if the most reactive phases exposed for dissolution by landslides disproportionately contribute to the proxy of choice this clearly suggests that the isotopic composition of marine sr is a proxy for periods of rapid mountain uplift and erosion rather than for the associated enhanced silicate weathering

marine dipole dipole controlled source electromagnetic and coincident loop transient electromagnetic experiments to detect seafloor massive sulphides effects of three dimensional bathymetry seafloor massive sulphides smss are regarded as a potential future resource to satisfy the growing global demand of metals including copper zinc and gold aside from mining and retrieving profitable amounts of massive sulphides from the seafloor the present challenge is to detect and delineate significant sms accumulations which are generally located near mid ocean ridges and along submarine volcanic arc and backarc spreading centres currently several geophysical technologies are being developed to detect and quantify sms occurrences that often exhibit measurable contrasts in their physical parameters compared to the surrounding host rock here we use a short fixed offset controlled source electromagnetic csem system and a coincident loop transient electromagnetic tem system which in theory allow the detection of sms in the shallow seafloor due to a significant electrical conductivity contrast to their surroundings in 2016 csem and tem experiments were carried out at several locations near the trans atlantic geotraverse hydrothermal field to investigate shallow occurrences of massive sulphides below the seafloor measurements were conducted in an area that contains distinct sms sites located several kilometres off axis from the mid atlantic ridge some of which are still connected to hydrothermal activity and others where hydrothermal activity has ceased based on the quality of the acquired data both experiments were operationally successful however the data analysis indicates bias caused by three dimensional 3d effects of the rough bathymetry in the study area and thus data interpretation remains challenging therefore we study the influence of 3d bathymetry for marine csem and tem experiments focusing on shallow 3d conductors located beneath mound like structures we analyse synthetic inversion models for attributes associated with 3d distortions of csem and tem data that are not sufficiently accounted for in conventional 1d tem and 2d csem interpretation schemes before an adequate quantification of sms in the region is feasible these 3d effects need to be studied to avoid over underestimation of sms using the acquired em data the sensitivity of csem and tem to bathymetry is investigated by means of 3d forward modelling followed by 1d tem and 2d csem inversion of the synthetic data using realistic error conditions subsequently inversion models of the synthetic 3d data are analysed and compared to models derived from the measured data to illustrate that 3d distortions are evident in the recorded data sets

caracterisation des eaux de l aquifere turonien du bassin du tadla maroc par le rapport des concentrations molaires sr2 ca2 resume l analyse des variations de la concentration du strontium dissous dans les eaux souterraines de la nappe des calcaires cretaces du bassin marocain du tadla qui s etend sur 10 000 km2 nous conduit a en proposer une explication les formations geologiques du turonien qui affleurent sur la peripherie du bassin sauf sur la bordure sud est chevauchee par le haut atlas peuvent etre environnees par des evaporites au toit ou a la base des contaminations de l eau par dissolution et par melange d eaux sulfatees et d eaux carbonatees de l aquifere sont decelees nous demontrons que le rapport sr 2 ca 2 est un moyen de distinguer la nature du reservoir aquifere ainsi que les origines des relations hydrodynamiques quatre groupes geographiques ont ete individualises selon la valeur du rapport sr 2 ca 2 un groupe septentrional en affleurement 0 8 1 un autre en regime captif 1 2 1 7 avec des anhydrites associees aux calcaires un groupe avec une nappe a facies sulfate 3 24 subdivise en deux sous groupes l un au ne influence par le cenomanien gypseux 7 24 et l autre au s marque a la fois par le senonien lagunaire toit de l aquifere et par le cenomanien substratum un cinquieme groupe distinct 2 84 correspond aux eaux superficielles sulfatees de l oued oum er rbia alimente par les eaux sulfatees issues des horizons evaporitiques triasiques de l atlas

self potential signals generated by the corrosion of buried metallic objects with application to contaminant plumes abstractlarge amplitude 100 mv negative electric self potential anomalies are often observed in the vicinity of buried metallic objects and ore bodies or over groundwater plumes associated with organic contaminants to explain the physical and chemical mechanisms that generate such electrical signals a controlled laboratory experiment was carried out involving two metallic cylinders buried with vertical and horizontal orientations and centered through and in the capillary fringe within a sandbox the 2d and 3d self potential sp data were collected at several time steps along with collocated ph and redox potential measurements large dipolar sp and redox potential anomalies developed in association with the progressive corrosion of the vertical pipe although no anomalies were observed in the vicinity of the horizontal pipe this discrepancy was due to the orientation of the pipes with the vertical pipe subjected to a significantly larger eh gradient accounting for the electrical conductivity dis

chemical characteristics of groundwater in parts of mountainous region alvand hamadan iran eighty seven groundwater samples have been collected from a mountainous region alvand iran for hydrochemical investigations to understand the sources of dissolved ions and assess the chemical quality of the groundwater most water quality parameters are within world health organization acceptable limits set for drinking water the least mineralized water is found closest to the main recharge zones and the salinity of water increased towards the north of the basin the most prevalent water type is ca hco3 followed by water types ca no3 ca cl ca so4 and mg hco3 the ca no3 water type is associated with high nitrate pollution agricultural and industrial activities were associated with elevated level of no3 mineral dissolution weathering of evaporites dominates the major element hydrochemistry of the area chemical properties of groundwater in alvand region are controlled both by natural geochemical processes and anthropogenic activities

piceance basin mesaverde anomalous self potential response identification of capillary seals in a basin centered gas accumulation wells in the piceance basin show anomalous large magnitude up to 200 mv large interval 2000 ft 610 m self potential sp log responses in the mesaverde gas producing interval that can be best explained by electrokinetic potential resulting from water flow toward producing mesaverde wells water flow is compartmentalized by capillary seals that are formed when gas generated from coals saturates adjacent thinly bedded sandstones and shales capillary seals can be identified by shifts in the sp baseline the first wells drilled in an area with no previous mesaverde production have very little sp response as is expected in tight sandstones with single to double digit microdarcy permeability after mesaverde production is established in a new area the sp log begins to show stepwise changes to more negative values beginning in the upper mesaverde and becoming increasingly more negative with increased depth the magnitude of the change to more negative values increases with time in an area of active mesaverde production some of the more recent sp logs have negative deflections of over 200 mv this type of sp anomaly has not been reported before and these anomalies can be used to identify large scale water movement within a reservoir

pattern of shallow ground water flow at mount princeton hot springs colorado using geoelectrical methods abstract in geothermal fields open faults and fractures often act as high permeability pathways bringing hydrothermal fluids to the surface from deep reservoirs the mount princeton area in south central colorado is an area that has an active geothermal system related to faulting and is therefore a suitable natural laboratory to test geophysical methods the sawatch range front normal fault bordering the half graben of the upper arkansas valley is characterized by a right lateral offset at mount princeton hot springs this offset is associated with the chalk cliffs of hydrothermally altered quartz monzonite because fault identification in this area is complicated by quaternary deposits including glacial and fluvial deposits we use dc electrical resistivity tomography and self potential mapping to identify preferential fluid flow pathways the geophysical data over 5600 resistivity and 2700 self potential measurements provide evidence of the existence of a dextral strike slip fault zone fault b responsible for the offset of the sawatch fault a segment of this dextral strike slip fault termed u1 is acting as the dominant vertical flow path bringing thermal waters to a shallow unconfined aquifer upwelling of the thermal waters is also observed at two zones u2 and u3 of an open fracture called fault a this fault is located at the tip of the sawatch fault and is likely associated with an extensional strain regime in this area self potential measurements are used to estimate the flux of upwelling thermal water the upflow estimate 4 1 10 3 m 3 day for the open segment of the fault b and 2 1 10 3 m 3 day for fault a from the geophysical data is remarkably consistent with the downstream mt princeton hot water production 4 3 4 9 10 3 m 3 day at approximately 60 86 c a temperature map indicates that a third upwelling zone termed u4 may exist at the southern tip of the sawatch fault

using hydrochemical and isotopic data to determine sources of recharge and groundwater evolution in an arid region a case study in the upper middle reaches of the shule river basin northwestern china understanding sources of recharge and mechanisms for hydrogeochemical evolution of groundwater in the shule river basin an arid inland river basin in northwestern china is essential for successful water resource management sources of water and associated groundwater recharge processes were investigated using hydrogeological hydrogeochemical and isotopic methods the study area was divided into three parts changma the shule valley and the beishan area the hydrogeochemical and isotopic analysis results show that groundwater in changma mainly originated from precipitation in the qilian mountains lateral flow from changma is the primary recharge mechanism while direct recharge by infiltration of precipitation can be neglected in the shule valley minerals within the aquifer material e g halite calcite dolomite and gypsum dissolve into water that recharges the groundwater system therefore strong linear relationships were found between na and cl and between ca2 mg2 and so42 hco3 with stoichiometry ratios of approximately 1 1 in both cases groundwater quality in the region is generally good with low salinity and hardness local precipitation is the only source of recharge for groundwater in the beishan area low groundwater velocity and dry climatic conditions suggest that dissolution of minerals from the aquifer material controls hydrogeochemical evolution water rarely travels from the beishan area to the shule valley therefore almost all the groundwater in the shule valley originates from changma global climate change and loss of glaciers in the qilian mountains may lead to a reduction of recharge therefore the groundwater resources of the shule valley must be managed to sustain water supply

oxidative dissolution of hydrothermal mixed sulphide ore an assessment of current knowledge in relation to seafloor massive sulphide mining highlights seafloor massive sulphides vary in mineralogy and oxidise at different rates galvanic cells play a role in increasing dissolution rates sms deposits that have been inactive for some time may have lost economic value the geochemistry of oxidation products has potential to be an exploration tool potential for anthropogenic release of heavy metals during seafloor mining any risk needs addressing by the isa prior to the formation of mining regulations the weathering process of seafloor massive sulphide sms deposits can be considered analogous to weathering of terrestrial volcanogenic massive sulphides vms deposits however in the context of sms deposits the process occurs in chemically buffered waters of near neutral ph resulting in the formation of insoluble fe oxy hydroxide minerals including goethite and hematite as well as sulphates such as jarosite as a result of this precipitation it is commonly assumed that any sms deposit is unlikely to exhibit a significant loss of metals dissolution and release of heavy metals into the water column however galvanic interactions have never been considered in this seafloor context whilst they have already been shown to have the ability to increase dissolution significantly in terrestrial deposits if heavy metal release is not temporally balanced by precipitation of oxide phases there is the potential that these metal occurrences lose economic value this is specifically significant if there is an industrial focus on exploiting deposits associated with hydrothermal vents that have been inactive for some time not only this but the geochemistry of weathering products gossans that are formed have the potential to be used as tools for exploration furthermore it is unknown what impact galvanic coupling may have with regards to anthropogenic release of heavy metals during seafloor mining of deposits associated with either active or inactive vents disturbance of sediment plume generation and dewatering process this environmental impact needs to be addressed prior to the formulation of regulations for deep sea mining by the international seabed authority the present review examines our current understanding of oxidation and dissolution of a mixed sulphide ore bringing together lines of evidence from a range of literature sources based on this review different seafloor sulphide ore deposits will dissolve by oxidation and release a variety of different metals economic and or toxic all at different rates with galvanic cells playing a role by increasing dissolution rates while precipitation of oxide and oxy hydroxide phases will occur it is unknown in both a natural weathering and anthropogenic mining context whether heavy metal release including economic and toxic metals is temporally balanced by this precipitation and any subsequent adsorption based on our current understanding certain sites will be more predisposed to oxidation as a result of their mineralogy those containing significant pyrrhotite marcasite galena and secondary copper sulphides and or environment higher temperatures and oxygen concentrations lower ph s furthermore certain sites pose more of an environmental risk in terms of toxicity than others with arc related sms deposits associated with higher concentrations of as pb sb cd and hg and ultra mafic hosted sms deposits associated with high concentrations of co and ni the review highlights the need for subsequent studies that investigate the natural weathering process of seafloor sulphide ore deposits including how this process impacts their economic value and consequent geochemical signature of oxides that are produced over time moreover this review underlines the necessity for experiments to elucidate the oxidative dissolution of ore throughout any mining process

marine self potential gradient exploration of the continental margin the self potential sp method for mineral exploration is seldom used on land primarily because of electrode noise problems and nonunique interpretations marine measurements of the horizontal gradient of the sp field on the other hand are relatively simple to make with an array of electrodes towed behind a ship with low ship speeds of 5 to 10 km hour dense spatial sampling 1 m can be obtained with resolution of better than 1 v m in this paper we report on gradient sp data recorded on the continental shelf of south australia by a horizontal array of towed electrodes approximately 20 m above the seafloor ocean waves and swells with periods of 5 to 15 s yielded large amplitude signals 20 v m but subseafloor mineralization produced sp gradient anomalies of 50 v m and widths of 2 km or more in a number of parallel traverses integrating the observed sp gradients along each line delineated sp anomalies of amplitude up to 100 mv self potential and magnetic anomaly data show limited spatial cor

geochemistry characterization of groundwater in an agricultural area of razan hamadan iran this study was conducted to evaluate factors regulating groundwater quality in an area with agriculture as main use thirty groundwater samples have been collected from razan area hamadan iran for hydrochemical investigations to understand the sources of dissolved ions and assess the chemical quality of the groundwater the chemical compositions of the groundwater are dominated by na ca2 hco3 cl and so42 which have been derived largely from natural chemical weathering of carbonate gypsum and anthropogenic activities of fertilizer s source the production of so42 has multiple origins mainly from dissolution of sulphate minerals oxidation of sulphide minerals and anthropogenic sources the major anthropogenic components in the groundwater include na cl so42 and no3 with cl and no3 being the main contributors to groundwater pollution in razan area

hydrogeochemical assessment of the upper cheliff groundwater north west algeria the quality of the upper cheliff groundwater located in north west algeria has in recent years undergone serious deterioration due to uncontrolled discharge of urban wastewaters intensive use of chemical fertilizers in agriculture as well as to overexploitation this study aims at analyzing the flow pattern of the upper cheliff groundwater determining its current hydrochemical status and understanding the mineralization processes involved in its chemical quality two piezometric and sampling campaigns were carried out in 2008 in high water april and low water october periods the major chemical ions ca2 mg2 na k cl hco3 no3 so4 2 were analyzed in all samples the piezometric data were mapped and allowed to analyze the groundwater flow conditions in particular at the boundaries of the aquifer the interpretation of hydrochemical data was made using various methods piper diagram stabler classification base exchanges index bi elements scatter diagrams saturation indices mapping and multivariate principal component analysis the results provide a better understanding of this aquifer hydrogeology and hydrochemistry several hydrochemical types chloride calcium chloride sodium and bicarbonate calcium characterize the groundwater mineralization processes and the origin of salinity are determined by the lithology of the aquifer dissolution base exchanges and by climatic evaporation and anthropogenic factors agricultural and urban wastes the groundwater in the upper cheliff is currently of poor quality this status is worrying as this groundwater is an important natural resource for the socio economic development of this region urgent measures must be taken to preserve this resource

using cl br ratios and other indicators to assess potential impacts on groundwater quality from septic systems a review and examples from principal aquifers in the united states summary a detailed review was made of chemical indicators used to identify impacts from septic tanks on groundwater quality potential impacts from septic tank leachate on groundwater quality were assessed using the mass ratio of chloride bromide cl br concentrations of selected chemical constituents and ancillary information land use census data well depth soil characteristics for wells in principal aquifers of the united states chemical data were evaluated from 1848 domestic wells in 19 aquifers 121 public supply wells in 6 aquifers and associated monitoring wells in four aquifers and their overlying hydrogeologic units based on previously reported cl br ratios statistical comparisons between targeted wells where cl br ratios range from 400 to 1100 and cl concentrations range from 20 to 100 mg l and non targeted wells indicated that shallow targeted monitoring and domestic wells 0 5 mg l shallow groundwater from target domestic wells relative to non target wells 1 5 mg l corresponded to significantly higher potassium boron chloride dissolved organic carbon and sulfate concentrations which may also indicate the influence of septic tank effluent impacts on groundwater quality from septic systems were most evident for the eastern glacial deposits aquifer and the northern high plains aquifer that were associated with the number of housing units using septic tanks high permeability of overlying sediments mostly oxic conditions and shallow wells overall little or no influence from septic systems were found for water samples from the deeper public supply wells the cl br ratio is a useful first level screening tool for assessing possible septic tank influence in water from shallow wells

electric potential source localization reveals a borehole leak during hydraulic fracturing abstracta laboratory experiment was performed to see if passively recorded electric signals can be inverted to retrieve the position of fluid leakages along a well during an attempt to hydraulically fracture a porous block in the laboratory the cubic block was instrumented with 32 nonpolarizing sintered ag agcl electrodes during the test several events were detected corresponding to fluid leakoff along the seal of the well each event showed a quick burst in the electric field followed by an exponential type relaxation of the potential distribution over time the occurrence of these electric events was always correlated with a burst in the acoustic emissions and a change in the fluid pressure these self potential data were inverted in two steps 1 using a deterministic least square algorithm with focusing to retrieve the position of the source current density in the block for a given snapshot in the electric potential distribution and 2 using a genetic algorithm to refine the position of the sou

hydrochemical geophysical and multivariate statistical investigation of the seawater intrusion in the coastal aquifer at phetchaburi province thailand abstract seawater intrusion in coastal regions is an imperative ecological issues and results in an undesirable consequence on future groundwater resources to assess and mitigate seawater intrusion the affected aquifers need to be characterized by integrating geophysical investigation and multivariate statistical analysis of hydrochemical data seawater intrusion into coastal aquifers at cha am district in phetchaburi province thailand as a model area that is adversely affected by this problem was evaluated the vertical electrical sounding ves survey study was conducted at 80 locations and then 47 ves locations were used to create four pseudo cross section lines in a west east direction the geophysical results were described together with the hydrochemical analysis of 57 groundwater samples revealed that seawater intrusion occurred in the quarternary colluvial sediment aquifer at an average depth of 50 60 m a resistivity value of

thermoelectric self potential and resistivity data localize the burning front of underground coal fires abstractself potential signals and resistivity data can be jointly inverted or analyzed to track the position of the burning front of an underground coal seam fire we first investigate the magnitude of the thermoelectric coupling associated with the presence of a thermal anomaly thermoelectric current associated with a thermal gradient a sandbox experiment is developed and modeled to show that in presence of a heat source a negative self potential anomaly is expected at the ground surface the expected sensitivity coefficient is typically on the order of 0 5 mv c 1 in a silica sand saturated by demineralized water geophysical field measurements gathered at marshall near boulder co show clearly the position of the burning front in the electrical resistivity tomogram and in the self potential data gathered at the ground surface with a negative self potential anomaly of about 50 mv to localize more accurately the position of the burning front we developed a strategy based on two steps 1 we

induced polarization tomography applied to the detection and the monitoring of leaks in embankments abstract during an induced polarization survey both electrical conductivity and chargeability can be imaged recent petrophysical models have been developed to provide a consistent picture of these two parameters in terms of water and clay contents of soils we test the ability of this method at a test site in which a controlled artificial leakage can be generated in an embankment surrounding an experimental basin 3d tomography of the conductivity and normalized chargeability are performed during such a controlled leakage conductivity and induced polarization measurements were also performed on a core sample from the site the sample was also characterized in terms of porosity and cation exchange capacity combining the 3d survey and these laboratory measurements a 3d tomogram of the relative variation in water content before leakage and during leakage was estimated it clearly exhibits the ground water flow path through the embankment from the outlet of the tube used to generate the leak to the bottom of the embankment in addition a self potential survey was performed over the zone of leakage this survey evidences also the projection of the ground water flow path over the ground surface both methods are found to provide a consistent picture a 2 5d time lapse tomography of the electrical conductivity and normalized chargeability was also performed and evidences the position of the preferential flow paths below the profile these results confirm the ability and efficiency of induced polarization to provide reliable information pertaining to the detection of leakages in dams and embankments

marine mineral exploration with controlled source electromagnetics at the tag hydrothermal field 26 n mid atlantic ridge seafloor massive sulphide sms deposits are of increasing economic interest in order to satisfy the relentless growth in worldwide metal demand the trans atlantic geotraverse tag hydrothermal field at 26 n on the mid atlantic ridge hosts several such deposits this study presents new controlled source electromagnetic csem bathymetric and magnetic results from the tag field potential sms targets were selected based on their surface expressions in high resolution bathymetric data high resolution reduced to the pole magnetic data show negative anomalies beneath and surrounding the sms deposits revealing large areas of hydrothermal alteration csem data sensitive to the electrical conductivity of sms mineralization further reveal a maximum thickness of up to 80 m and conductivities of up to 5 s m sms samples have conductivities of up to a few thousand s m suggesting that remotely inferred conductivities represent an average of metal sulphide ores combined with silicified and altered host basalt that likely dominates at greater depths

geochemistry of groundwater burdwan district west bengal india hydrogeochemical investigations are carried out in the different blocks of burdwan district west bengal india in order to assess its suitability for drinking as well as irrigation water purpose altogether 49 representative groundwater samples are collected from bore wells and the water chemistry of various ions viz ca2 mg2 na k co32 hco3 cl so42 and no3 are carried out the chemical relationships in piper and gibbs diagram suggest that the groundwater mainly belongs to alkali type and cl group and are controlled by rock dominance a comparison of groundwater quality in relation to drinking water quality standards proves that most of the water samples are suitable for drinking water purpose whereas groundwater in some areas of the district has high salinity and high sodium adsorption ratio sar indicating unsuitability for irrigation water and needs adequate drainage

first active hydrothermal vents on an ultraslow spreading center southwest indian ridge the ultraslow spreading southwest indian ridge is a major tectonic province representing one of the important end member mid ocean ridge types for its very slow and oblique spreading and providing the only known route for migration of chemosynthetic deep sea vent fauna between the atlantic and indian oceans we report the investigation of the first active high temperature hydrothermal field found on any ultraslow mid ocean ridge worldwide located on southwest indian ridge at 37 47 s 49 39 e it consists of three zones extending 1000 m laterally and it is one of four recently discovered active and inactive vent sites within a 250 km long magmatically robust section our results provide the first direct evidence for potentially widespread distribution of hydrothermal activity along ultraslow spreading ridges at least along magmatically robust segments this implies that the segment sections with excess heat from enhanced magmatism and suitable crustal permeability along slow and ultraslow ridges might be the most promising areas for searching for hydrothermal activities it is surprising that the special vent fauna appear to indicate some complex affinity to those on the central indian ridge southern mid atlantic ridge and the southwest pacific ocean

hydrochemistry of a complex volcano sedimentary aquifer using major ions and environmental isotopes data dalha basalts aquifer southwest of republic of djibouti in the republic of djibouti horn of africa fractured volcanic aquifers are the main water resources the country undergoes an arid climate alluvial aquifers exist in the wadis intermittent streams valleys and in relation with volcanic aquifers form complex volcano sedimentary systems due to increasing water demands groundwater resources are overexploited and require a rigorous management this paper is focused on the dalha basalts aquifer located in the dikhil area southwest of djibouti this aquifer is of vital importance for this area hydrochemical data and isotopic tracers 18o and 2h were used to identify factors and phenomena governing the groundwater s mineralization the piper diagram shows complex water types results from multivariate statistical analyses highlight three water families according to their locations 1 groundwater characterized by low ionic concentrations located at the wadis zones 2 groundwater characterized by moderate salinity and 3 highly mineralized waters mainly flowing in the eastern and central part of the study area in volcanic aquifers results from scatter plots especially na versus cl and br versus cl suggest that the origin of more saline waters is not from dissolution of halite the 18o and 2h data indicate that the groundwater flowing in the alluvial aquifer is of meteoric origin and fast percolation of rainwater occurs in the volcanic aquifers these findings provide a preliminary understanding of the overall functioning of this complex volcano sedimentary system additional investigations pumping tests numerical modeling are in progress to achieve a more comprehensive understanding of this system

hydrochemical characteristics of aquifers near sutherland in the western karoo south africa the western karoo depends entirely on groundwater for domestic and agricultural use an understanding of the chemical evolution of the groundwater provides insight into the interaction of water with the environment and contributes to better resource management descriptive statistics correlation matrices and factor analysis together with stable isotope data were used to gain an understanding of the hydrochemical processes of the groundwaters in the fractured rocks around sutherland in the western karoo the main processes influencing the groundwater chemistry are salinisation mineral precipitation and dissolution cation exchange and human activity the stable isotope data indicate that the infiltration of evaporated water is partly responsible for the occurrence of saline subsurface waters the ionic oxygen and hydrogen stable isotope composition of the groundwaters suggests that the effects of localised topography are one of the overriding factors controlling the groundwater chemistry in higher lying areas ca hco3 2 type waters are prevalent while in topographical flat areas nacl type waters dominate in areas where water collects close to or at the surface saline soils are formed from these areas salts are leached to the subsurface during significant recharge periods these findings are important in that they contribute to the identification of suitable locations for developing groundwater resources that could yield a relatively better quality water q 2001 elsevier science b v all rights reserved

bulk geochemistry sulfur isotope characteristics of the yuhuang 1 hydrothermal field on the ultraslow spreading southwest indian ridge abstract the yuhuang 1 hydrothermal field hf was discovered recently on the ultraslow spreading southwest indian ridge segment 29 this field comprises two main sulfide deposition areas including the southwest sulfide area sws and the northeast sulfide area nes all of which are about 500 m in diameter sulfide rich samples collected on the seafloor consist of zinc rich iron rich and silicified samples the zn rich samples contain up to 60 sphalerite and 5 chalcopyrite while iron rich samples primarily contain pyrite and marcasite and silicified sulfide rich samples primarily consist of amorphous silicon 70 pyrite 15 20 and minor sphalerite sulfide rich samples generally show mound features with similar mineral assemblages except that the nes contains pyrrhotite indicating precipitation under relatively reduced conditions bulk geochemistry of the sws and nes massive sulfide samples display similar au co ni and si contents and ni co ratios similar to mafic related hfs while the sn content and the cd zn ratio are comparable to ultramafic related hfs which probably indicates a multi stage origin sulfides rich samples from the sws have 34s values ranging from 1 37 to 6 02 with a median value of 0 83 currently the 34s value of 1 37 is the lowest sulfur isotope composition observed in hfs on ultraslow spreading ridges bacteria derived sulfur which is calculated to be 10 25 of the total sulfur component is likely the cause of the negative sulfur isotope composition conversely the 34s values of the seafloor sulfides rich samples in the nes ranges from 3 75 to 8 73 with a median value of 4 74 which is distinctly heavier than that of the sws this study suggests that the sws and nes of the yuhuang 1 hf probably formed during different mineralization stages

three dimensional inversion of self potential data used to constrain the pattern of groundwater flow in geothermal fields 1 we propose an algorithm to invert self potential signals measured at the ground surface of the earth to localize hydromechanical disturbances or to the pattern of groundwater flow in geothermal systems the self potential signals result from the divergence of the streaming current density groundwater flow can be either driven by topography of the water table free convection or deformation of the medium the algorithm includes the electrical resistivity distribution of the medium obtained independently by dc resistance tomography or electromagnetic methods or by coding the assumed geology in terms of distribution of the electrical resistivity accounting for the effect of the temperature and salinity distributions and possibly constraints from borehole measurements inversion of the distribution of the source current density from ground surface and borehole self potential measurements is achieved by solving the inverse problem using tikhonov regularization solutions that are compatible with the physics of the primary flow problem by introducing assumptions regarding the smoothness or the compactness of the source and the three dimensional distribution of the electrical resistivity of the system the inverse problem can be solved in obtaining the three dimensional distribution of the current source density in the ground however an annihilator can be added to the inverted source geometry without affecting the measured self potential field annihilators can be obtained from boundary conditions synthetic models and a sandbox experiment are discussed to demonstrate the validity of the algorithm an application is presented to the geothermal field of cerro prieto baja california mexico using literature data inversion of the self potential and resistivity data allows observing a plume of hot groundwater rising to the ground surface in the central part of the investigated area and discharging to the ground surface in the southwest part the temperature anomaly associated with the existence of this plume is independently observed by interpolating borehole temperature measurements we found a good agreement between the distribution of the temperature and the inverted source current density the proposed method appears therefore as a noninvasive method for remote detection and three dimensional mapping of subsurface groundwater flow

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

using the cl br ratio as a tracer to identify the origin of salinity in aquifers in spain and portugal summary a study on the applicability of the cl br molar ratio for identifying the origin of groundwater salinity is presented according to the experience gained in spain and portugal cl br ratios in atmospheric bulk deposition have helped to distinguish groundwater in which cl derives only from atmospheric sources from groundwater in which cl is contributed by endogenous lithological or anthropogenic sources considering the seawater cl br ratio of 655 4 cl br ratios may be increased up to 1500 in groundwater by the addition of wastewater loaded with nacl or leaching of solid waste and decreased to 300 by the use of br based pesticides or leaching farm animal or septic waste leaching and dissolution of natural and industrial nacl and of gypsum rich formations containing some nacl may yield cl br ratios between one thousand and several thousand although leaching of potassium halides near salt mines produces cl br ratios below the seawater ratio when cl content in groundwater is not affected by extreme evaporation up to halite saturation at 6 2 mol l 1 of nacl and if there are no other cl sources recharge by rainfall can be estimated by relating cl in atmospheric bulk deposition to derived groundwater the cl br ratio appears to be a good tracer for discriminating non atmospheric cl contributions to groundwater provided chemical analyses are accurate since its variability is not wide data have been collected from different areas of spain and portugal and are explained and illustrated by two cases described in detail the donana aquifer in southwest spain and the canary islands both showing the mixing paths