episodic graben formation and extensional neotectonic regime in west central anatolia and the isparta angle a case study in the aksehir afyon graben turkey

hydrochemical characteristics and salinity of groundwater in the ejina basin northwestern china a hydrochemical investigation was conducted in the ejina basin to identify the hydrochemical characteristics and the salinity of groundwater the results indicate that groundwater in the area is brackish and are significantly zonation in salinity and water types from the recharge area to the discharge area the ionic ration plot and saturation index si calculation suggest that the silicate rock weathering and evaporation deposition are the dominant processes that determine the major ionic composition in the study area most of the stable isotope 18o and d compositions in the groundwater is a meteoric water feature indicating that the groundwater mainly sources from meteoric water and most groundwater undergoes a long history of evaporation based on radioactive isotope tritium 3h analysis the groundwater ages were approximately estimated in different aquifers the groundwater age ranges from less than 5 years between 5 years and 50 years and more than 50 years within 1 km of the river water influence zone the groundwater recharges from recent heihe river water and the groundwater age is about less than 5 years in shallow aquifer from 1 km to 10 km of the river water influence zone the groundwater sources from the mixture waters and the groundwater age is between 5 years and 50 years in shallow aquifer the groundwater age is more than 50 years in deep confined aquifer

evaluation of groundwater quality in the cihanbeyli basin konya central anatolia turkey the cihanbeyli basin is located in the northern part of konya in the central anatolian region turkey and is characterized by semi arid climatic conditions and scarcity in water resources the suitability of groundwater quality for drinking and agricultural purposes in the cihanbeyli basin was assessed by measuring physicochemical parameters including major cation and anion compositions ph total dissolved solid electrical conductivity and total hardness for this purpose 54 samples were collected from different sources viz deep wells shallow wells and springs results from hydrochemical analyses reveal that groundwater is mostly affected by salty and gypsiferous lithologies evaporite minerals such as gypsum anhydrite and chloride salts make high contributions from the recharge areas west northwest and southwest parts toward the discharge area central and eastern parts high values of total dissolved solids in groundwater are associated with high concentrations of all major ions a comparison of groundwater quality in relation to drinking water standards showed that most of the water samples are not suitable for drinking based on sodium absorption ratio values and percent sodium salinity appears to be responsible for the poor groundwater quality rendering most of the samples unsuitable for irrigation usage it is concluded that evaporation and mineral dissolution are the main processes that determine major ion compositions

modelling the link between hillslope water movement and stream flow application to a small mediterranean forest watershed abstract the decomposition of hydrographs by isotopic analysis has already shown that in small mediterranean catchments an important proportion of storm discharge comes from old water by analysing in detail water movement on a hillslope in a sub basin of the real collobrier experimental catchment we can explain how such high proportions arise the hydraulic properties of the hillslope soil were measured intensively and these included the texture porosity and hydraulic conductivity the hydraulic conductivity is found to be very high in the surface layer down to a depth of about 20 cm this essentially represents the macropore ridden portion of at least the root zone underneath the conductivity drops off rapidly we have modelled infiltration into this soil supposing it to comprise two layers in this manner we can simulate the formation of a perched water table at the base of the permeable upper layer in our model groundwater flows are rapidly generated by this perched saturated level by displacement these flows are considered to consist firstly of old water which represents an important contribution to river flow furthermore the sharp peaks observed in the discharge hydrograph are explained by rapid surface and near surface flow from these saturated zones

permian continental basins in the southern alps italy and peri mediterranean correlations the late carboniferous to permian continental successions of the southern alps can be subdivided into two main tectono sedimentary cycles separated by a marked unconformity sealing a middle permian time gap generally estimated at over 10 ma the lower cycle 1 between the variscan crystalline basement and the early permian is mainly characterised by fluvio lacustrine and volcanic deposits of calc alkaline acidic to intermediate composition which range up to a maximum thickness of more than 2 000 m the upper cycle 2 which is devoid of volcanics is mostly dominated through the mid late permian by alluvial sedimentation which covered the previous basins and the surrounding highs giving rise to the subaerial verrucano lombardo val gardena groden red beds up to about 800 m thick the palaeontological record from the terrigenous deposits of both the above cycles consists mainly of macro and microfloras and tetrapod footprints the age of the continental deposits is widely discussed because of the poor chronological significance of a large number of fossils which do not allow reliable datings however some sections are also controlled by radiometric calibrations the comparison with some selected continental successions in southern europe allows to determine their evolution and set up correlations a marked stratigraphic gap shows everywhere between the above mentioned cycles 1 and 2 as in the southern alps the gap reaches the greatest extent during the mid permian near the illawarra reversal geomagnetic event 265 ma in western europe however such as in provence and sardinia the discussed gap persists upwardly to late permian and early triassic or slightly younger times i e to the onset of the alpine sedimentary cycle even though in northeastern spain iberian ranges balearic islands this gap results clearly interrupted by late guadalupian lopingian deposits the above two major tectonosedimentary cycles reflect in our view two main geodynamic events that affected the southern europe after the variscan orogenesis the late carboniferous early permian transformation of the gondwana eurasia collisional margin into a diffuse dextral transform margin and the middle late permian opening of the neotethys ocean with the onset of a generalised extensional tectonic regime and the progressive westward marine ingression

groundwater recharge history and hydrogeochemical evolution in the minqin basin north west china the minqin basin is a type area for examining stress on groundwater resources in the gobi desert and has been investigated here using a combination of isotopic noble gas and chemical indicators the basin is composed of clastic sediments of widely differing grain size and during the past half century over 10 000 boreholes have been drilled with a groundwater decline of around 1 m a 1 modern diffuse recharge is unlikely to exceed 3 mm a 1 as determined using unsaturated zone profiles and cl mass balance a small component of modern 50 a groundwater is identified in parts of the basin from 3h 3he data probably from irrigation returns a clear distinction is found between modern waters with median 18o values of 6 5 0 5 and most groundwaters in the basin with more depleted isotopic signatures radiocarbon values as pmc range from 0 6 to 85 modern but it is difficult to assign absolute ages to these although a value of 20 modern c probably represents the late pleistocene to holocene transition the 13c compositions remain near constant throughout the basin median value of 8 1 13c and indicate that carbonate reactions are unimportant and also that little reaction takes place there is a smooth decrease in 14c activity accompanied by a parallel increase in 4he accumulations from s n across the basin which define the occurrence of a regional flow system noble gas temperatures indicate recharge temperatures of about 5 6 c for late pleistocene samples which is some 2 3 c cooler than the modern mean annual air temperature and the recharge temperature obtained from several holocene samples groundwaters in the minqin basin have salinities generally below 1 g l and are aerobic containing low fe but elevated concentrations of u cr and se mean values of 27 5 5 8 and 5 3 g l 1 respectively nitrate is present at baseline concentrations of around 2 mg l 1 but there is little evidence of impact of high no3 from irrigation returns strontium isotope and major ion ratios suggest that silicate reactions predominate in the aquifer the results have important implications for groundwater management in the minqin and other water stressed basins in nw china a region so far destined for rapid development the large proportion of the water being used at present is in effect being mined and significant changes are urgently needed in water use strategy

major ion chemistry of groundwater in a river basin a study from india groundwater is the prime source in the area of varaha river basin andhra pradesh india groundwater samples collected during pre and post monsoon were analyzed for major ion chemistry to understand the operating mechanism of geochemical processes for variation of groundwater quality low ionic concentration is observed in the groundwater occurring at topographic highs and towards the river compared to the rest of the area this is caused by the influence of recharge water geochemistry of groundwater is observed to be mainly controlled by the rock weathering mineral dissolution leaching ion exchange and evaporation and is subsequently modified by the anthropogenic and marine activities contribution of residual soluble salts below the depth of 5 m from the ground surface is high while it is low beyond the depth of 5 m anthropogenic activities cause an accumulation of excess residual soluble salts in the former depth and the content of this soluble matter is reduced by the clay products beyond the latter depth seasonal ionic concentration of groundwater is greatly influenced by the recharge process with reference to topographical features lithological characteristics and anthropogenic activities groundwater quality is classified as mixed and non carbonate alkali groups due to a combined action of geogenic anthropogenic and marine sources respectively the groundwater quality is above the adequacy level for both drinking and irrigation and appropriate management measures are recommended for sustainable development

post collisional rapid exhumation and erosion during continental sedimentation the example of the late variscan salvan dorenaz basin western alps the salvan dorenaz intramontane basin formed between ca 308 293 ma as an asymmetric graben along crustal scale transtensional fracture zones within the aiguilles rouges crystalline massif western alps and represents a feature of the post collisional evolution of the variscan orogens it contains 1 5 1 7 km of continental clastic deposits which were eroded from granitic volcanic and metamorphic rocks textural and compositional immaturity of the sandstones and the numerous lithic fragments with low chemical and physical stability suggest only short range transport 40ar 39ar analyses of detrital muscovite are interpreted to represent cooling of the crystalline basement below the respective closure temperatures ages from detrital muscovite range between ca 280 330 ma 40ar 39ar white mica plateau ages from granitic boulders range between 301 312 ma and suggest rapid cooling the very short time interval recorded between the 40ar 39ar cooling ages and the stratigraphic age of the host sediment suggests that considerable portions of the upper crust were removed prior to the formation of the basin late variscan granitic boulders document surface exposure and erosion of late carboniferous granites during early stages of the infilling of the basin therefore unroofing of basement units magmatic activity and formation of the fault bounded salvan dorenaz basin were acting concomitantly and are highly suggestive of extensional tectonics when compared with other orogens this situation seems specific to the variscan especially the exclusively young ages of detrital material however modern analogous may exist

hydrochemical processes governing groundwater quality of sedimentary aquifers in central saudi arabia and its environmental implications the present study deals with the interpretation of the major processes governing the groundwater chemistry in parts of qassim and riyadh province of saudi arabia the study area that is dominated by agricultural activities is represented by a multi layered aquifer system with sedimentary formations ranging from cambrian to the quaternary present as outcrops groundwater samples from 97 agricultural bore wells in the area were collected and analyzed for 16 physio chemical parameters the evaluation of the main hydrochemical processes affecting the groundwater quality was carried out by interpreting the ionic relationships and hydrochemical facies analysis the interpretation pointed toward evaporation gypsum dissolution and ion exchange as main factors controlling the major ion groundwater chemistry the piper plot showed so4 cl type of groundwater with majority of the samples falling in the zone of permanent hardness due to the formation of non carbonate salts principal component analysis that helps to understand the underlying natural and anthropogenic factors controlling the groundwater chemistry in an area was used in the present study based on which four principal components pcs were extracted the first pc as expected was dominated by the major ions and was attributed to natural processes whereas the extracted components mainly heavy metals in pc 2 3 and 4 pointed toward anthropogenic activities playing an active role in affecting the trace element hydrochemistry

melt water chemistry and its impact on stream water quality samples of snowpack leachate were collected over a 60 day period of the spring melt season in 1988 and 1989 at a 10 km2 upland catchment in the cairngorm mountains of scotland these were analysed for major ions to assess snowpack chemistry dynamics through the spring and to assess the melt water influence on stream water chemistry the data clearly show preferential elution of sulphate and nitrate over chloride and hydrogen over the other cations during the early melt of 1988 following the addition of ions to the snow surface either as snow or later in the season as rain the elution sequence is reproduced comparison of leachate chemistry with stream chemistry samples taken at the basin outlet indicate that snow pack melt water contributes directly to stream water the stream water chemistry signal is however noisy and the stream concentrations are considerably damped relative to the snowpack leachate this is thought to be a consequence of differential melting within the catchment as the snowpack at lower altitudes is at a more advanced stage of melt and so holds fewer solutes and mixing with groundwater contributions temperature observations at different altitudes within the catchment support this interpretation

assessment of shallow groundwater in lake nyos catchment cameroon central africa implications for hydrogeochemical controls and uses in 1986 carbon dioxide gas exploded from lake nyos and killed about 1 800 people after that disaster various administrative and research activities have been conducted to mitigate subsequent disasters however none of those endeavors have characterized the groundwater chemistry to identify hydrogeochemical processes that control the water chemistry and the quality of the water for domestic and agricultural uses that support the lives of un official resettlers around lake nyos conventional hydrochemical techniques coupled with statistical and graphical analysis were therefore employed to establish the baseline hydrochemical conditions assess processes controlling solutes distribution in shallow groundwater in the lake nyos catchment and explore its usability groundwater samples were analyzed for their physical and chemical properties the wide ranges of electrical conductivity and total dissolved solid values reveal the heterogeneous distribution of groundwater within the watershed the relative abundance of major dissolved species was ca mg na k for cations and hco3 cl so4 no3 for anions piper diagram classified almost all water samples into mixed camg hco3 water type major ion geochemistry reveals that in addition to silicates weathering water rock interaction ion exchange processes regulate the groundwater chemistry principal component analysis supports the occurrence of water rock interaction hierarchical cluster analysis showed that the chemistry of groundwater in the study area is controlled by three main factors and suggests no hydraulic connectivity between deep lake water and groundwater in the catchment the quality assessment of the groundwater showed that groundwater parameters are within the acceptable limit of the world health organization and nigeria guidelines for drinking and domestic uses and water found to be good for irrigation

carbon and isotopic mass balance models of oasis valley fortymile canyon groundwater basin southern nevada environmental isotopes and carbon chemistry provide means of differentiating various recharge areas flow paths and ages of ground water in portions of the nevada test site and vicinity regional delta d delta sup 18 o trends are offset from the present day meteoric line by a deuterium depletion of 5 per thousandth suggesting paleoclimatic changes partial pressures of co sub 2 and the sup 18 o and sup 13 c data indicate solubility and isotopic equilibrium between the gas and water in the soil zone with progressive exchange with underlying ground water in the shallow alluvium of oasis valley application of a closed system co sub 2 model using the eq3nr eq6 reaction path simulator successfully reproduces chemical compositions observed in the alluvium in the amargosa desert and in the deep tuff aquifer beneath pahute mesa and yucca mountain initial p sub co sub 2 input to the soil zone during recharge was calculated to range from 0 03 to 0 10 atm which is comparable to measured soil co sub 2 pressures in oasis valley results are compared for sup 14 c ages using the delta sup 13 c dilution correction and a mass action correction term relating predicted and calculated ionic activity products of caco sub 3 results are generally comparable with discrepancies attributed to anomalous delta supmore 13 c values less

hydrogeochemistry and strontium isotopes in the arno river basin tuscany italy constraints on natural controls by statistical modeling summary in this paper the chemistry of major and trace elements and for the first time strontium isotopic ratios measured in running waters from the arno river basin tuscany central northern italy and thermal springs discharging in the same hydrographic system are presented and discussed classical graphical methods e g mixing diagrams have here been improved to identify in a correct statistical sample space extreme chemical compositions attributable to the action of geochemical processes and or inherited from specific lithologies namely contributions or components 1 2 and 3 to be used in inverse modeling procedures due to the absence of clear end members a linear least squares problem with non negativity constraints and distances as required for compositional data convex linear mixing was solved by considering the contribution of the most discriminant variables given by the 87 sr 86 sr isotopic ratios and the concentration of ca 2 mg 2 sr and rb following such approach it can be assumed p 2 mg 2 hco 3 radiogenic rich 87 sr 86 sr 0 71274 rb sr 0 039 represents a dominant feature at basin scale with a weight ranging from 69 to 100 much lower percentages are related to component 2 represented by a ca 2 mg 2 so 4 2 facies with intermediate 87 sr 86 sr 0 70874 and low rb sr 2 8 10 4 ratios and component 3 identified by ca 2 hco 3 facies with less radiogenic 87 sr 86 sr 0 70827 and low mg 2 ca 2 0 011 ratios these components are mainly dominated by the dissolution of evaporitic rocks and or mixing with thermal waters in the southern part of the arno river basin and by dissolution of the carbonatic fraction kinetically favored with respect to that of the silicatic minerals in the upper reaches of the main course and its tributaries respectively

assessment of geochemistry and hydrogeochemical processes in groundwater of the tefenni plain burdur turkey the tefenni burdur plain is located in the southwest of turkey and is semi closed basin groundwater is densely used as drinking irrigation and domestic water in the tefenni plain hydrogeochemical processes controlling groundwater chemistry and geochemical assessment of groundwater were investigated in the tefenni burdur turkey plain the conceptual hydrogeological model of the plain was prepared for qualitative description of the underground geology and interpretation of hydrogeochemical processes of the study area in this study groundwater samples for two seasons were analyzed and major ion chemistry of groundwater was researched to understand the groundwater geochemistry two major hydrochemical facies ca2 mg2 hco3 and mg2 ca2 hco3 were determined in the area mg2 na so42 and cl concentrations of water samples increased seasonally related to ion exchange of minerals in rocks by rainwater in wet season various graphical plots and multivariate statistical analysis pearson correlation analysis were used for identifying the occurrence of different geochemical processes carbonate weathering in dry season and silicate weathering in wet season were the major hydrogeochemical processes in the study area in addition ion exchange and reverse ion exchange were two possible processes of water rock interaction in the basin the mechanism controlling groundwater chemistry at the tefenni plain is originally regulated by the geogenic process rather than antropogenic activities

major ion chemistry of the ganga brahmaputra river system weathering processes and fluxes to the bay of bengal the ganga brahmaputra one of the world s largest river systems is first in terms of sediment transport and fourth in terms of water discharge a detailed and systematic study of the major ion chemistry of these rivers and their tributaries as well as the clay mineral composition of the bed sediments has been conducted the chemistry of the highland rivers upper reaches of the ganga the yamuna the brahmaputra the gandak and the ghaghra are all dominated by carbonate weathering ca mg and hco3 account for about 80 of the cations and anions in the lowland rivers the chambal the betwa and the ken hco3 excess over ca mg and a relatively high contribution of na k to the total cations indicate that silicate weathering and or contributions from alkaline saline soils and groundwaters could be important sources of major ions to these waters the chemistry of the ganga and the yamuna in the lower reaches is by and large dictated by the chemistry of their tributaries and their mixing proportions illite is the dominant clay mineral about 80 in the bedload sediments of the highland rivers kaolinite and chlorite together constitute the remaining 20 of the clays in the chambal betwa and ken smectite accounts for about 80 of the clays this difference in the clay mineral composition of the bed sediments is a reflection of the differences in the geology of their drainage basins the highland rivers weather acidic rocks whereas the others flow initially through basic effusives the ganga brahmaputra river system transports about 130 million tons of dissolved salts to the bay of bengal which is nearly 3 of the global river flux to the oceans the chemical denudation rates for the ganga and the brahmaputra basins are about 72 and 105 tons km yr 1 respectively which are factors of 2 to 3 higher than the global average the high denudation rate particularly in the brahmaputra is attributable to high relief and heavy rainfall

fluoride incidence in groundwater in an area of peninsular india groundwater samples were collected from anantapur district andhra pradesh india the district is mainly underlain by peninsular gneisses of archaean age the samples were analysed for fluoride f along with other chemical parameters the results suggest that the main sources of f in groundwater in the district are the country rocks in which fluorine is strongly absorbed in soils consisting of clay minerals a strong positive correlation between f and lithogenic sodium reflects weathering activity this is responsible for the leaching of f which is also caused by the semi arid climate and intensive irrigation in the area an alkaline environment of circulating water in the investigated area mainly facilitates leaching of f from the soils contributing to high f containing groundwater a longer residence time of water in the aquifer zone caused by a high rate of evapotranspiration and a weathered zone of low hydraulic conductivity which promotes the dissolution of fluorine bearing minerals is another factor that further increases the f content in groundwater suggestions are made to improve groundwater quality and thus the health status of the population

the transition between the two major permian tectono stratigraphic cycles in the central southern alps results from facies analysis and u pb geochronology the val daone conglomerate vdc is a continental clastic unit that crops out eastwards of the central southern alps from the ne sector of the collio basin to the w as far as the tione basin to the e this significant but as yet relatively unknown formation lies just above the regional unconformity that marks the boundary between the two permian major tectono sedimentary cycles tsu1 and tsu2 and grades upwards paraconformably to the fluvial red beds of verrucano lombardo val gardena sandstone generally associated with late permian times recent palynological investigations on the vdc suggested a guadalupian age late roadian early wordian owing to the remarkable presence of diversified pollen associations therefore this sedimentary unit is to date the first one ascribed on a palaeontological basis to the middle permian in the entire southern alps domain a detailed facies analysis of vdc shows deposition in amalgamated alluvial fan braided and fluvial environments with wide channels and longitudinal bars in its type area and val rendena the vdc rests unconformably above the last volcanic episode of the tsu1 la icp ms u pb dating on zircon from two samples of such topmost lower permian volcanic rocks known as ponte murandin dacitic lava and malga plan rhyodacitic ignimbrites tione basin provided concordia ages of 278 2 ma mswd 0 01 and 279 2 ma mswd 0 16 respectively as well as allowing us to better define the duration of the time gap between the two permian megacycles in the central southern alps in almost 10 ma these radiometric age determinations are also significant because they enable us to regionally link the coeval volcanic bodies which crop out in the collio basin to the sw and in the athesian volcanic group to the ne respectively

environmental geochemistry and quality assessment of mine water of jharia coalfield india a long mining history and unscientific exploitation of jharia coalfield caused many environmental problems including water resource depletion and contamination a geochemical study of mine water in the jharia coalfield has been undertaken to assess its quality and suitability for domestic industrial and irrigation uses for this purpose 92 mine water samples collected from different mining areas of jharia coalfield were analysed for ph electrical conductivity ec major cations ca2 mg2 na k anions f cl hco3 so4 2 no3 dissolved silica h4sio4 and trace metals the ph of the analysed mine water samples varied from 6 2 to 8 6 indicating mildly acidic to alkaline nature concentration of tds varied from 437 to 1 593 mg l 1 and spatial differences in tds values reflect the variation in lithology surface activities and hydrological regime prevailing in the region so4 2 and hco3 are dominant in the anion and mg2 and ca2 in the cation chemistry of mine water high concentrations of so4 2 in the mine water of the area are attributed to the oxidative weathering of pyrites ca mg so4 and ca mg hco3 are the dominant hydrochemical facies the drinking water quality assessment indicates that number of mine water samples have high tds total hardness and so4 2 concentrations and needs treatment before its utilization concentrations of some trace metals fe mn ni pb were also found to be above the desirable levels recommended for drinking water the mine water is good to permissible quality and suitable for irrigation in most cases however higher salinity residual sodium carbonate and mg ratio restrict its suitability for irrigation at some sites

filling sequence in late paleozoic continental basins a chimera of climate change a new light shed given by the graissessac lodeve basin se france abstract the characteristics of sedimentary deposits in continental basins especially those controlled by extension are often used to infer global climatic changes we question the relevance of such an approach because the stratigraphic pattern of those basins are mostly similar whatever their latitudes paleolatitudes i e their general climatic conditions namely the transition from 1 an ancestral drainage network to 2 deep lake with a dominance of black and grey shale deposits 3 shallow oxic lake with a dominance of red pelites deposits and to eventually 4 a new drainage network such transitions observed in late palaeozoic continental basins throughout laurasia and gondwana are generally interpreted as evidence of global change from a wet climate to an arid climate from the sedimentological and structural analysis of a late palaeozoic basin the graissessac lodeve basin in the south of the variscan french massif central we proposed a new tectono stratigraphic sequence of this basin from the late carboniferous to the early trias we estimate the paleo area from 295 450 km 2 to 880 1150 km 2 of the basin and we deduce a subsidence curve from the late carboniferous to the late permian from 600 200 m my to 100 10 m my we conclude that the graissessac lodeve basin stratigraphic pattern corresponds to a classical continental rift sequence controlled by tectonics in order to assess a possible control of the stratigraphic sequence by the climate we have reconstructed the paleo depth of the lake with 1 the morphometric analysis of the wave ripples and 2 with an estimation of the lacustrine slope considering the tectonic origin of the lake we find that the maximum lacustrine depth has evolved from a range of 80 300 m during the late carboniferous to 40 45 m during the late permian from our estimates of the different configurations of the basin we show that the volume of the water in the lake has remained nearly constant between 10 and 30 km 3 from the late carboniferous 300 my to the late permian 250 my eventually we conclude that the sedimentological indicators of shallowing and episodic drying observed from the late carboniferous to late permian in this basin and probably in all the pangea basins of the same type are the consequence of the basin enlargement by tectonics and its sedimentary filling rather than climatic change

zircon growth and recycling during the assembly of large composite arc plutons abstract concordant u pb zircon dates have been interpreted traditionally to date the crystallization ages of plutons because until recently analytical uncertainties have generally been large enough to encompass the anticipated duration of pluton growth advances in zircon tims analysis and geochronological studies by sims on zircon from young volcanic rocks along with evolving views of the evolution of magmatic systems makes it necessary to revaluate this interpretation assignment of unique pluton crystallization ages based on zircon dating is complicated by the propensity of zircon to survive multiple intrusive events that culminate in a large pluton distinctions must be made between true inherited zircon xenocrystic zircon derived from host rocks during magma ascent and or emplacement and multi stage growth of zircon during waxing and waning of magma reservoirs that solidify to form large plutons these complications are exemplified by recent high precision u pb zircon age dating from the cretaceous tuolumne and mt stuart batholiths which clearly show that the timeframe of pluton assembly was long 5 ma for mt stuart and 8 ma for tuolumne zircon crystals from samples from both batholiths exhibit appreciable concordant age dispersion for zircon several 10 5 yr up to 2 10 6 yr and assignment of statistically valid rock solidification ages is not possible from these data low zr in the rocks of each batholith indicates that magmas were initially strongly undersaturated in zircon when emplaced and inherited zircon is rare or absent recycling of zircon antecrysts during successive magmatic injections is the primary cause of the modest age dispersion of concordant zircon ages and is compatible with progressive growth of a large long lived crystal mush body because eruption of magma requires low to moderate crystal fraction and high temperatures relative to stored crystal mushes zircon crystals are more likely to be eradicated during thermal rejuvenation preceding major eruptions

pre mesozoic alpine basements their place in the european paleozoic framework prior to their alpine overprinting most of the pre mesozoic basement areas in alpine orogenic structures shared a complex evolution starting with neoproterozoic sediments that are thought to have received detrital input from both west and east gondwanan cratonic sources a subsequent neoproterozoic cambrian active margin setting at the gondwana margin was followed by a cambrian ordovician rifting period including an ordovician cordillera like active margin setting during the late ordovician and silurian periods the future alpine domains recorded crustal extension along the gondwana margin announcing the future opening of the paleotethys oceanic domain most areas then underwent variscan orogenic events including continental subduction and collisions with avalonian type basement areas along laurussia and the juxtaposition and the duplication of terrane assemblages during strike slip accompanied by contemporaneous crustal shortening and the subduction of paleotethys under laurussia thereafter the final pangea assemblage underwent triassic and jurassic extension followed by tertiary shortening and leading to the buildup of the alpine mountain chain recent plate tectonic reconstructions place the alpine domains in their supposed initial cambrian ordovician positions in the eastern part of the gondwana margin where a stronger interference with the chinese blocks is proposed at least from the ordovician onward for the visean time of the variscan continental collision the distinction of the former tectonic lower plate situation is traceable but becomes blurred through the subsequent oblique subduction of paleotethys under laurussia accompanied by large scale strike slip since the pennsylvanian this global collisional scenario has been replaced by subsequent and ongoing shortening and strike slip under rising geothermal conditions and all of this occurred before all these puzzle elements underwent the complex alpine reorganization

solute and isotopic geochemistry and ground water flow in the central wasatch range utah ground water flow systems in the rugged central wasatch range utah were investigated by solute and isotopic methods six types of ground water systems were identified on the basis of rock type and structure the systems are broadly grouped into four categories 1 granitic systems 2 non granitic systems a unconsolidated alluvial systems b consolidated sedimentary rock systems and c fault controlled systems 3 thermal systems 4 mine drainage systems these ground water systems have distinctive solute and isotopic chemistries based on an analysis of 3h and 14c data all of the ground waters have a component of post 1952 recharge water and most of the ground waters are composed almost entirely of post 1952 recharge water a few of the ground water systems contain some water which is hundreds to perhaps thousands of years old the 18o and 2h data plot on a local meteoric water line and none of the data exhibit a positive 18o shift the absence of a positive 18o shift suggests maximum aquifer temperatures are approximately 100 c granitic terrains are dominated by fracture controlled local ground water flow systems which respond rapidly to recharge events the granitic ground water systems have estimated maximum circulation depths of about 160 m below land surface all the alluvial most of the consolidated sedimentary bedrock and some of the fault controlled ground water systems are shallow circulating local flow systems with short travel times ground water circulation of most of the local flow systems is within 200 m of land surface and is bedding plane controlled some of the consolidated bedrock and many of the fault controlled ground water systems are of the intermediate type and have circulation depths to 500 m four thermal ground water systems have been identified the thermal systems are heated by the geothermal gradient and have not circulated deeper than 2 2 5 km the thermal systems are of the intermediate and regional type the solute chemistry of most of the non granitic ground waters may be attributed to the dissolution of carbonate minerals and minor amounts of gypsum contributions of external co2 g to some of the thermal systems from either metamorphic or silicate hydrolysis processes is suspected

revealing exhumation of the central alps during the early oligocene by detrital zircon u pb age and fission track double dating in the taveyannaz formation

the controls on spatial and temporal variation of hydrochemical facies and major ion chemistry in groundwater of south west district delhi india the existence of freshwater resource is a critical pre requisite for any growing urban center the south west district of delhi is among the most rapidly developing urban areas of delhi region the freshwater requirement of this district is heavily dependent on groundwater due to absence of other sources groundwater availability as well as its quality is controlled primarily by geological features such as older alluvial in the western to central parts and quartzite exposure in the eastern part of the district the groundwater flow direction and the presence of the najafgarh drain in the district impact the groundwater quality as well as hydrochemical facies evolution this article establishes spatial and temporal hydrochemical facies variation in groundwater of the district and its linkages with the geologic and anthropogenic factors

the evolution of the polymetamorphic basement in the central alps unravelled by precise u pb zircon dating the u pb age determinations of zircon and rutile from the aar massif reveal a complex evolution of the central alpine basement the oldest components are found in zircons of metasediments which bear cores of archean age the u pb age of discordant prismatic zircons of the same rocks ranges between 580 and 680 ma an age that is typical for pan african metamorphism the zircons are interpreted as pan african detritus with archean inheritance the provenance region of the pan african zircons is assumed to be a terrane of gondwana affinity i e the w african craton or the pentevrian microplate the caledonian metamorphism left a pervasive structural imprint in amphibolite facies on the rocks of the aar massif it is dated at 456 2 and 445 ma by zircons of a layered migmatitic gneiss and a migmatitic leucosome respectively both occurring in the northernmost zones of the massif hercynian metamorphism never exceeded greenschist facies conditions and is recorded by zircon in a garnet amphibolite and by rutile in a meta psammite that yield an age of 330 ma both zircon and rutile are considered to be products of retrograde mineral reactions and therefore do not date the peak conditions of hercynian metamorphism the gastern granite at the western end of the aar massif is a contaminated granite that intruded at 303 4 ma contemporaneously with the wide spread late hercynian post collisional i type magmatism the study demonstrates the potential of isotope dilution u pb dating of single grains and microfractions in deciphering complex evolutionary histories of polymetamorphic terrains

kinematics and age of syn intrusive detachment faulting in the southern alps evidence for early permian crustal extension and implications for the pangea a versus b controversy permian basin formation and magmatism in the southern alps of italy have been interpreted as expressions of a wsw ene trending dextral megashear zone transforming early permian pangea b into late permian pangea a between 285 and 265 ma in an alternative model basin formation and magmatism resulted from n s crustal extension to characterize permian tectonics we studied the grassi detachment fault a low angle extensional fault in the central southern alps the footwall forms a metamorphic core complex affected by upward increasing top to the southeast mylonitization two granitoid intrusions occur in the core complex the synmylonitic val biandino quartz diorite and the postmylonitic valle san biagio granite u pb zircon dating yielded crystallization ages of 289 1 4 5 ma for the former and 286 8 4 9 ma for the latter consequently detachment related mylonitic shearing took place during the early permian and ended at 288 ma but kinematically coherent brittle faulting continued considering 30 anticlockwise rotation of the southern alps since early permian the extension direction of the grassi detachment fault was originally n s even though a dextral continental wrench system has long been regarded as a viable model at regional scale the local kinematic evidence is inconsistent with this and rather supports n s extensional tectonics based on a compilation of 200 u pb zircon ages we discuss the evolution and tectonic framework of late carboniferous to permian magmatism in the alps

permo carboniferous climate early pennsylvanian to late permian climate development of central europe in a regional and global context a well justified stratigraphical correlation of continental successions and new palaeogeographic reconstruction of pangaea reveal new insights into the northern pangaean climate development influenced by palaeogeography palaeotopography glacio eustatic sealevel changes and ocean currents the overall permo carboniferous aridization trend was interrupted by five wet phases these are linked to the gondwana icecap the aridization and weakening of wet phases over time were not only caused by the drift of northern pangaea to the arid climatic belt but also by the successive closure of the rheic ocean which caused the expansion of arid semi arid environments in the lower middle permian the end of the gondwana glaciation rearranged ocean circulation leading to a cold coast parallel ocean current west of northern pangaea blocking moisture coming with westerly winds the maximum of aridity was reached during the roadian wordian the trans pangaean mountain belt was non existent its single diachronous parts never exceeded an average elevation of 2000 m the maximum elevation shifted during time from east to west the hercynian orogen never acted as an orographic east west barrier and the inter tropical convergence zone was widely displaced causing four seasons dry summer winter wet spring autumn at the equator and a strong monsoon system the climate history of the european realm during the late carboniferous pennsylvanian and permian is stored in many solitary basins fig 1 within the hercynian orogen and the foreland basin the story of westphalian climate is well known because of the numerous investigations of the coal bearing variscan foredeep the younger westphalian is characterized by a slight aridization abbink van kronijnenburgvan cittert 2003 oplustil 2004 which was accompanied by an increase of seasonality nevertheless the environment was strongly influenced by the ocean and epi continental seas with multiple transgression events the last extensive marine ingression was the aegir mansfield band westphalian b c the post westphalian climate development is more differentiated and

post variscan verrucano like deposits in italy and the onset of the alpine tectono sedimentary cycle abstract in the italian regions the stratigraphic successions of the verrucano s l consist essentially of continental alluvial plain to coastal neritic siliciclastic redbeds deposited at different times in the alps mid late permian the northern apennines mid late triassic p p locally in southern tuscany also followed by the jurassic pseudoverrucano complex and the calabro peloritani arc mid late triassic exceptionally reaching earliest jurassic whereas in sardinia the recognition of the verrucano succession is still a topic of discussion the most typical metamorphic lithofacies in the pisan mts of tuscany is represented by the verrucano s s conglomerates and breccias including quartz clasts and minor metamorphic and volcanic lithics grading laterally and vertically to quartzitic sandstones and pelites in the pisa symposium the term verrucano was suggested only for those detrital deposits laid down in the alpine mediterranean areas after the final act of the variscan orogeny and also to use local geographical names consequently the typical terms verrucano toscano the verrucano lombardo the verrucano brianconnais and other similar deposits being linked to the variscan belt were generally accepted the ages of these verrucanos since they are devoid of fossils can only be interpreted indirectly the verrucano lombardo of central southern alps was recently ascribed to a mid late permian interval late guadalupian lopingian p p taking into account that the connected val gardena sandstones of the nearby venetian region are interdigitated with the late permian bellerophon fm the verrucano brianconnais of the maritime alps is again mostly related to late permian being covered by the lower triassic alluvial deltaic quartzites in the easternmost ligurian apennines near la spezia the mesozoic section of punta bianca which begins with a fluvial conglomerate transgressive and unconformable on a metamorphosed paleozoic variscan basement is composed of two main cycles of which the upper one correlates to the typical pisan verrucano s s and the overlying mt serra quartzites the latter yielding carnian pelecypods and vertebrate footprints the verrucano from the mid tuscan ridge to mt leoni and in the argentario promontory is delimited above by the tocchi formation and presumably developed from middle late ladinian up to late triassic carnian times in contrast in calabria e g the longobucco unit of sila grande and in sicily e g the taormina longi unit of peloritani mts the so called pseudo verrucano deposits pertain to mid late triassic and are capped by a basal jurassic succession determined by the discovery of an early hettangian palynoflora all over their distribution areas the above mentioned alpine verrucanos rest through an unconformity marked by a gap of varying and imprecise duration on late paleozoic volcanic sedimentary successions or directly on the underlying variscan metamorphic basement schematically the post variscan succession in italy can be subdivided into three main tectono sedimentary megacycles the first generally ranges from the late carboniferous to or slightly above the early permian the second from mid late permian to middle triassic while the third cycle begins with the mid late triassic p p attaining the jurassic in some parts of southern tuscany and the calabro peloritani arc after the late carboniferous and early permian transtensional tectonics represented by many strike slip continental basins cycle i widespread middle permian geodynamic reorganization mid permian episode auctt led to the development of a dominant extensional regime and the birth of tectonic plates and oceans neotethys meliata maliak etc between africa and europe the erosion of the variscan relief was followed by ingression from s e sectors of shallow marine branches of neotethys cycle ii the major rifting events that led to the jurassic birth of the ligurian piedmont ocean started during the middle late triassic and were related to the eastern opening of the atlantic ocean these rifting events gave rise to the development of the adria and europe corsica sardinia conjugate passive margins characterized by an asymmetric structural and sedimentary evolution in this geological context the verrucano like deposits of italy can be interpreted as a discontinuous and asynchronous tectofacies that marks the final dismantling of the se border of the variscan chain

comparison of hydrograph deconvolutions using residual alkalinity chloride and oxygen 18 as hydrochemical tracers hydrograph deconvolution using geochemical tracers is currently widely used for determining the hydrologic mechanisms occurring in watersheds however few chemical parameters can be used as tracers because their involvement in biogeochemical processes prevents them from behaving in a conservative way the aim of this study was to combine several geochemically controlled parameters into a single tracer residual alkalinity is a combination of several controlled parameters and is conservative in a wide range of natural environments it was used in this study for quantifying the contributions of surface runoff and of groundwater flow during a flood in a mediterranean watershed underlain by sedimentary rock a preliminary geochemical study revealed that interactions with calcite dolomite and the clay humus complex controlled calcium and magnesium concentrations as well as carbonate alkalinity alkc which prevented using them as tracers nevertheless although residual alkalinity alkresidual is a combination of these three parameters alkresidual alkc 2 ca2 t 2 mg2 t it provided results that were highly comparable to those obtained using chloride and 18o contrary to the most cases in the literature the contribution of direct runoff was dominant about 80 at peak discharge accuracy estimates which took into account analytical errors temporal variations in the isotopic signature of rainfall and the spatial variability of chemical elements supported this result and confirmed that residual alkalinity is a useful concept in hydrology

hydrogeochemical assessment of groundwater in isfahan province iran groundwater quality in five catchment areas in isfahan province of iran is assessed by measuring physicochemical parameters including major cation and anion compositions ph total dissolved solid electrical conductivity and total hardness for this purpose 567 piezometric well samples were collected in october 2007 the abundance of major ions in four of the catchment areas including gavkhuni ardestan salt lake and central iran desert basins is similar and follows cl so42 na hco3 ca2 mg2 k co32 trend while in the fifth basin karoon the trend changes into hco3 ca2 cl so42 mg2 na k co32 in general four water facies are determined and it is shown that alkali elements and strong acids are dominating over alkaline earth and weak acids statistical analysis including mann whitney u test indicate that physicochemical parameters in three of the five investigated basins gavkhuni ardestan and central iran desert cid are similar while karoon and salt lake basins display different characteristics the result indicate that groundwater west of the province is suitable for irrigation while in the central and eastern parts of the province the groundwater loses its quality for this purpose it is concluded that mineral dissolution and evapotranspiration are the main processes that determine major ion compositions

geochemical characteristics of groundwater in different climatic zones of sri lanka sri lanka is characterized by well demarcated climatic zones based on the rainfall pattern known as wet zone dry zone and intermediate zone groundwaters in these three zones are extracted mainly for drinking and irrigation from metamorphic hard rock aquifers and saprolite developed on metamorphic rocks detailed hydrogeochemical investigations were carried out covering these three climatic zones in order to characterize the groundwater a total of 166 groundwater samples were collected representing three climatic zones and analyzed for their major and trace element geochemistry the results indicate a clear difference in the geochemistry of groundwater between climatic regions whereas semiarid dry zone groundwater is characterized with higher dissolved mineral contents compared that of the wet and intermediate zones low ph levels were noticed in the wet zone areas while high calcium and fluoride contents were observed in the dry and intermediate terrains remarkably high phosphate contents were observed in all three regions indicating the influence of fertilizer application on groundwater particularly in the dry zone regions the groundwater chemistry is mainly controlled by rock water interactions and ion exchange processes in which high mineral contents are added from underlying metamorphic rocks to the drinking and irrigation water the results indicate that groundwater in the dry zone area is under stress compared to other climate areas but in the wet zone groundwater shows remarkable influence of anthropogenic activities

a paleomagnetic study of tectonically deformed red beds of the lower glarus nappe complex eastern switzerland a paleomagnetic study at 15 sites 315 samples in permo triassic red beds of the helvetic nappes of eastern switzerland isolated stable characteristic and secondary remanent directions thermal demagnetization and isothermal remanent magnetization experiments suggest pigmentary hematite carries the characteristic direction secondary directions are scattered but may have been acquired during the alpine deformation in the oligocene and miocene the characteristic directions also show large between site scatter anisotropy of magnetic susceptibility indicates that the hematite grains are flattened within the slaty cleavage and that there is a north south lineation this anisotropy pattern implies that the magnetic grains were realigned by the alpine deformation it is not possible to explain the characteristic remanent magnetization deviations on a site by site basis but the site mean directions are streaked along a great circle the down dip direction of which is approximately parallel to the regional fold axes 60 20 this spread could be explained by a penetrative simple shear deformation associated with the nappe internal deformation

hydrogeochemical parameters for assessment of groundwater quality in the upper gunjanaeru river basin cuddapah district andhra pradesh south india in the management of water resources quality of water is just as important as its quantity in order to know the quality and or suitability of groundwater for domestic and irrigation in upper gunjanaeru river basin 51 water samples in post monsoon and 46 in pre monsoon seasons were collected and analyzed for various parameters geological units are alluvium shale and quartzite based on the analytical results chemical indices like percent sodium sodium adsorption ratio residual sodium carbonate permeability index pi and chloroalkaline indices were calculated the pre monsoon waters have low sodium hazard as compared to post monsoon season residual sodium carbonate values revealed that one sample is not suitable in both the seasons for irrigation purposes due the occurrence of alkaline white patches and low permeability of the soil pi values of both seasons revealed that the ground waters are generally suitable for irrigation the positive values of chloroalkaline indices in post monsoon 80 and in pre monsoon 59 water samples indicate absence of base exchange reaction chloroalkaline disequilibrium and remaining samples of negative values of the ratios indicate base exchange reaction chloroalkaline equilibrium chadha rectangular diagram for geochemical classification and hydrochemical processes of groundwater for both seasons indicates that most of waters are ca mg hco3 type assessment of water samples from various methods indicated that majority of the water samples in both seasons are suitable for different purposes except at yanadipalle sample no 8 that requires precautionary measures the overall quality of groundwater in post monsoon season in all chemical constituents is on the higher side due to dissolution of surface pollutants during the infiltration and percolation of rainwater and at few places due to agricultural and domestic activities

the role of groundwater in delaying lake acidification models used to study lake acidification generally divide a watershed into several zones or compartments e g soil and groundwater zones through which water and chemicals are routed to date most emphasis has been placed on the buffering of acid inputs by chemical reactions in the soil zone although buffering in the soil zone undoubtedly is important the focus of this paper is the role of the groundwater system in delaying lake acidification in this study a deterministic approach was selected over the standard parametric modeling used in watershed models specifically an advection dispersion model of the groundwater system was linked to a simple groundwater rain lake mixing model which in turn was linked to a geochemical speciation and reaction path model simulations of hypothetical groundwater lake systems utilized chemical data from small lake systems in northern wisconsin an area which is currently experiencing acid rain ph 4 6 and is potentially sensitive to acid rain impacts owing to the absence of carbonate minerals in the underlying glacial tills and bedrock results of the modeling studies demonstrated that even when the effects of chemical reactions are ignored groundwater inflow can mitigate the effects of acid deposition on lakes when chemical reactions in the groundwater system were included in the model using a retardation factor the acidification rate of the lake was significantly decreased when speciation reactions between lake water and net acid additions were simulated using the geochemical model phreeqe parkhurst et al 1980 the depression of lake water ph was markedly reduced indicating that low alkalinity lakes like the ones in northern wisconsin may have appreciable buffering capacity

an isotopic and geochemical study of snowmelt runoff in a small arctic watershed old water contributions to snowmelt runoff in a stream can be defined as water which was stored in the catchment prior to the start of the runoff event in question we used mass balance techniques for natural oxygen 18 and several chemical parameters electrical conductivity ca and mg to estimate the magnitude and timing of old water contributions to snowmelt runoff in the apex river watershed during the 1983 field season the apex river catchment is located in the southern part of baffin island northwest territories canada the watershed has an area of 60 km2 it is in the zone of continuous permafrost and the geology is dominantly precambrian gneiss with sporadic thin glacial overburden the isotopic data indicate that for the snowmelt season of 1983 third highest peak discharge of 11 years of record approximately 50 per cent of the peak stream discharge consisted of old water our data also suggest that about 60 per cent of the entire 1983 hydrograph was old water the chemical parameters give old water contributions which are at least 10 per cent less than the isotopically derived estimate but they are consistent with the isotopic estimate during peak flow

provenance of the silurian elder sandstone north central nevada one of the principal clastic units in the roberts mountains allochthon of north central nevada is the elder sandstone which may have been deposited in or about early silurian time rock fragments in the elder sandstone were derived from paleozoic carbonate rock argillite chert quartzite and intermediate to basic volcanic rock feldspar zircon and quartz probably were derived initially from pre cambrian crystalline rocks and were recycled into the elder sandstone from pre silurian supracrustal deposits u pb isotopic data indicate that detrital zircons were derived initially from a source that may have included rocks 2 2 b y old the location of the source of detritus in the elder sandstone is problematical and there is nothing in the data presented here that precludes the possibility that detritus was derived from a foreign continent

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

the volcano sedimentary evolution of a post variscan intramontane basin in the swiss alps glarus verrucano as revealed by zircon u pb age dating and hf isotope geochemistry the late palaeozoic glarus verrucano basin gvb glarus alps eastern switzerland formed as an intramontane graben in the aftermath of the variscan orogeny its fill the glarus verrucano consists of immature alluvial fan and playa lake deposits with intercalated bimodal volcanics basalts and rhyolites despite its importance for local and regional geology no modern sedimentologic or stratigraphic studies on the gvb exist by means of sedimentologic and geochronologic studies we reconstruct the volcano sedimentary evolution of the gvb it developed at the carboniferous permian boundary and experienced a first bimodal volcanic phase around 285 ma for the same time indications for temporarily humid climate in the otherwise rather arid early permian are demonstrated e g pyrite bearing sandstones during the middle and early late permian increasing aridity is indicated by playa deposits fanglomerates and subaerial ignimbrites which mark a second silicic volcanic phase at 268 ma the detrital zircon age spectra are dominated by late variscan ages and thus demonstrate that older sedimentary and metamorphic rocks once forming the variscan nappe edifice were already mostly eroded at that time finally some larger scale speculations are given which could indicate a causal connection between the widespread tectono magmatic mid permian episode and the local development of the glarus verrucano basin

geochemistry and assessment of hydrogeochemical processes in groundwater in the southern part of bathinda district of punjab northwest india hydrogeochemistry of groundwater is important for sustainable development and effective management of the groundwater resource fifty six groundwater samples were collected from shallow tube wells of the intensively cultivated southern part of district bathinda of punjab india during pre and post monsoon seasons conventional graphical plots were used to define the geochemical evaluation of aquifer system based on the ionic constituents water types hydrochemical facies and factors controlling groundwater quality negative values of chloroalkaline indices suggest the prevalence of reverse ion exchange process irrespective of the seasons a significant effect of monsoon is observed in terms chemical facies as a considerable amount of area with temporary hardness of ca2 mg2 hco3 type in the pre monsoon switched to ca2 mg2 cl type 18 followed by na hco3 type 14 in the post monsoon evaporation is the major geochemical process controlling the chemistry of groundwater process in pre monsoon however in post monsoon ion exchange reaction dominates over evaporation carbonate weathering is the major hydrogeochemical process operating in this part of the district irrespective of the season the abundance of ca2 mg2 in groundwater of bathinda can be attributed mainly to gypsum and carbonate weathering silicate weathering also occurs in a few samples in the post monsoon in addition to the carbonate dissolution water chemistry is deteriorated by land use activities especially irrigation return flow and synthetic fertilisers urea gypsum etc as indicted by concentrations of nitrate sulphate and chlorides overall results indicate that different natural hydrogeochemical processes such as simple dissolution mixing weathering of carbonate minerals locally known as kankar and silicate weathering are the key factors in both seasons

neutralization of acid runoff by groundwater discharge to streams in canadian precambrian shield watersheds abstract application of environmental isotope techniques during storm and snowmelt runoff from the harp lake and turkey lakes watersheds on the precambrian shield of central ontario canada indicates that subsurface pre event water is a major component of the runoff hydrograph storm runoff from two sub basins in the harp lake watershed is comprised of 40 90 groundwater depending on rainfall amount and intensity and antecedent soil moisture conditions and water table depth because the alkalinity of the groundwater is large compared to the acid precipitation ph 3 8 4 5 characteristic of this region groundwater discharge results in significant neutralization of runoff acidity snowmelt runoff studies in the turkey lakes watershed indicate that much of the first meltwater from the acidic ph 4 5 snowpack infiltrates the subsurface displacing higher ph groundwater to the stream since the first meltwater from an ablating snowpack is more acidic than the snow itself meltwater infiltration limits the extent of stream acidification during snowmelt runoff hence the physical displacement of near neutral ph pre event subsurface water during storm and snowmelt runoff periods partially buffers the alkalinity of baseflow as long as the acid neutralization capacity of the geologic materials storing the subsurface water is not exhausted groundwater contributions to runoff will continue to neutralize acid runoff

physical properties governing groundwater flow in a glacial till catchment abstract hydraulic conductivity surface topography and sediment thickness influence the spatial and temporal pattern of groundwater flow and stream discharge in an unconfined aquifer in a 3 7ha headwater catchment in central ontario canada groundwater levels in the soils adjacent to the stream also significantly influence the magnitude and spatial distribution of stream discharge topographic convergence in plan and decreasing sediment thickness along flowpaths result in surface saturation and groundwater discharge hillslope gradients adjacent to discharge areas determination how fluctuating groundwater levels influence the extent of spatial variations in surface saturation and saturation within the soils as a result of spatial differences in hillslope gradients the spatial patterns of both groundwater and stream discharge change with fluctuating groundwater levels unsaturated sediment s in upslope locations store water infiltrating during wet periods such that groundwater flow from upslope sediments maintains high groundwater levels near the stream and supplies baseflow during dry periods the direction of horizontal groundwater flow in harp 4 21 is not perpendicular to topographic contours so that subcatchment boundaries based on topographic divides differ by as much as 57 from their true subcatchment boundaries based on groundwater divides therefore groundwater flow models based on surface topography may incorrectly predict the spatial pattern of stream discharge

u pb zircon ages for post variscan volcanism in the ligurian alps northern italy abstract ages of permian volcanic rocks from the ligurian brianconnais domain western italian alps have been determined by laser ablation inductively coupled plasma mass spectrometry u pb dating of zircon three major volcanic units yielded zircons that were dated calc alkaline rhyolites 285 6 2 6 ma andesites with inherited cores yielded ages c 476 ma and older and voluminous rhyodacites rhyolites 272 7 2 2 ma following an amagmatic sediment starved time gap of c 14 ma alkaline volcanic activity is recorded at the top of the sequence by k alkaline rhyolites dated at 258 5 2 8 ma the ligurian segment of the southern variscan belt records transtensional and then extensional tectonics associated with the volcanic activity the switch from calc alkaline to alkaline activity corresponds to the transition from a post orogenic to an anorogenic setting in the southern variscides it may represent progressive and increasing delamination of the continental lithosphere accompanied by partial melting of the lithospheric mantle supplementary material technical and data acquisition parameters u th pb isotope analyses and calculated ages of zircons from samples and standard and trace element compositions of selected zircons are available at http www geolsoc org uk sup18322

assessment of the hydrogeochemical characteristics of groundwater in two aquifer systems in cumra plain central anatolia located in a semi arid climate cumra konya plain is one of the most important agricultural regions in turkey groundwater is the major source for agricultural domestic and other water related activities due to the insufficiency of surface water as groundwater is the only major source of water in this area it is important to know the effects of geological formations and anthropogenic activities on groundwater chemistry this study was carried out with the objective of identifying the hydrogeochemical characteristics and processes controlling the groundwater chemistry in cumra plain central anatolia turkey the study area is comprised of two main aquifers which are the semi confined aquifer of the neogene age and the unconfined aquifer of the quaternary age to identify the hydrogeochemical characteristics of groundwater in two aquifer systems and to understand the major factors and mechanisms controlling the groundwater chemistry graphical plots mineral saturations and multivariate statistical analysis of chemical constituents in the groundwater were used study results show that groundwater is generally neutral to slightly alkaline in nature with a ph ranging from 6 67 to 8 10 and the dominance of ions is in the order of ca2 mg2 na k for the neogene aquifer and hco3 so4 2 cl no3 mg2 ca2 na k and so4 2 hco3 cl no3 for the quaternary aquifer while the chemical composition of groundwater in the neogene aquifer is mainly controlled by water rock interaction including dissolution of carbonates and gypsum calcite precipitation and de dolomitization the main geochemical processes in the quaternary aquifer are reverse ion exchange evaporation dissolution of carbonates gypsum and soil salts calcite precipitation and silicate weathering the mechanism controlling groundwater chemistry in the neogene aquifer is actually regulated by the geogenic processes water rock interaction rather than by anthropogenic activities however the mechanism controlling groundwater chemistry in the quaternary aquifer is regulated by both geogenic processes and anthropogenic activities in addition anthropogenic nitrogen pollution in the study area is currently not serious but evaporation and leaching of soil salts due to anthropogenic activities increase the concentrations of ions in the quaternary aquifer

application of geochemistry and radioactivity in the hydrogeological investigation of carbonate aquifers sierras blanca and mijas southern spain the chemical characteristics 3 h contents and radioactivity of groundwaters from the sierras blanca and mijas southern spain have been studied in relation to the chemical composition and radioactivity of the aquifer host rocks and the residence time of the water the sierras blanca and mijas are made up of calcitic and dolomitic marbles of triassic age the groundwaters that drain the calcitic marbles which outcrop principally in the western sierra blanca have less mineralization which descreases quickly with recharge as does the 3 h content and the gross alpha and beta activities are below detection limit this is due to the short residence time of water inside the aquifers which are conduit flow systems the waters of the dolomitic marbles eastern sierra blanca and sierra mijas have higher and less variable mineralization and contain greater concentrations of mg 2 sio2 and so 2 4 ions normally associated with slow flows the 3 h contents are more uniform with time indicating an older age and there is detectable natural radioactivity because the waters have a longer residence time in the aquifers which

flow path composition relationships for groundwater entering an acidic lake the relationship of groundwater flow paths to the acid base status and composition of groundwater was examined by directly monitoring groundwater inputs to an acidic adirondack new york lake dart s lake groundwater inputs near the shoreline of the lake were acidic throughout the year ph 40 mu eq l sup minus 1 elevated concentrations of basic cations and alkalinity as well as lower concentrations of organic anions and sulfate were characteristic of deep ground water entering the lake at the study site spatial variability of groundwater chemistry was found to be substantial over a relatively short distance 6 m from the lake shoreline and indicates that input to the lake of components dissolved in groundwater are highly flow path dependent

hydrochemical characteristics of groundwater in the zhangye basin northwestern china the zhangye basin located in arid northwest china is an important agricultural and industrial center in recent years rapid development has created an increased demand for water which is increasingly being fulfilled by groundwater abstraction detailed knowledge of the geochemical evolution of groundwater and water quality can enhance understanding of the hydrochemical system promoting sustainable development and effective management of groundwater resources to this end a hydrochemical investigation was conducted in the zhangye basin types of shallow groundwater in the zhangye basin were found to be hco3 hco3 so4 2 so4 2 hco3 so4 2 cl cl so4 2 and cl the deep aquifer groundwater type was found to be hco 3 so 4 2 throughout the entire area ionic ratio and saturation index calculations suggest that silicate rock weathering and evaporation deposition are the main processes that determine the ionic composition in the study area the suitability of the groundwater for irrigation was assessed based on the us salinity laboratory salinity classification and the wilcox diagram in the study area the compositions of the stable isotopes 18o and d in groundwater samples were found to range from 4 00 to 9 28 and from 34 0 to 65 0 respectively these values indicate that precipitation is the main recharge source for the groundwater system some local values indicate high levels of evaporation tritium analysis was used to estimate the ages of the different groundwaters the tritium values of the groundwater samples varied from 3 13 to 36 62 tu the age of the groundwater at depths of less than 30 m is about 5 10 years the age of the groundwater at depths of 30 50 m is about 10 23 years the age of the groundwater at depths of 50 100 m is about 12 29 years for groundwater samples at depths of greater than 100 m the renewal time is about 40 years

hydrogeochemical characterization and quality assessment of groundwater in parts of southern gangetic plain a comprehensive assessment of groundwater is carried out in parts of the southern gangetic plain to identify the hydrogeochemical processes influencing groundwater geochemistry and to ascertain the suitability of groundwater for drinking and irrigational uses results of detailed chemical analysis reveal that groundwater of the study area is slightly acidic ph values from 6 2 to 7 37 during post monsoon with dominant concentrations of na and ca2 cations and hco3 and cl anions groundwater chemistry is largely controlled by rock weathering and ion exchange processes with secondary contribution from anthropogenic sources in particular values of ec total hardness and concentrations of na and hco3 exceed the prescribed limits of indian and who water quality standards suitability of groundwater for irrigation purposes are evaluated on the basis of sodium adsorption ratio sodium percent na magnesium hazard residual sodium carbonate and kelley s index in this regard nearly 40 50 of the groundwater in the study area is found to be of excellent to good quality in addition principal component analysis performed to identify the dominant geochemical processes shows that the first three components are together account for 80 84 and 78 85 of the total variance in the dataset for post monsoon and pre monsoon periods respectively this analysis also reveals key contributions from hydrogeochemical processes like mineral dissolution silicate and carbonate weathering alongside anthropogenic activities like leaching of fertilizers from agricultural lands

episodic and long lasting paleozoic felsic magmatism in the pre alpine basement of the suretta nappe eastern swiss alps the suretta nappe of eastern switzerland contains a series of meta igneous rocks with the rofna porphyry complex rpc being the most prominent member we present la icp ms u pb zircon data from 12 samples representing a broad spectrum of meta igneous rocks within the suretta nappe in order to unravel the pre alpine magmatic history of this basement unit fine grained porphyries and coarse grained augengneisses from the rpc give crystallization ages between 284 and 271 ma which either represent distinct magma pulses or long lasting magmatic activity in a complex magma chamber there is also evidence for an earlier variscan magmatic event at 320 310 ma mylonites at the base of the suretta nappe are probably derived from either the rpc augengneisses or another unknown carboniferous permian magmatic protolith with a crystallization age between 320 and 290 ma two polymetamorphic orthogneisses from the southern suretta nappe yield crystallization ages of 490 ma inherited zircon cores are mainly of late neoproterozoic age with minor neo to paleoproterozoic sources we interpret the suretta nappe as mainly representing a gondwana derived crustal unit which was subsequently intruded by minor cambrian ordovician and major carboniferous permian magmatic rocks finally the suretta nappe was thrust into its present position during the alpine orogeny which hardly affected the u pb system in zircon

the use of na cl ratios to trace solute sources in a semiarid zone rainwater interaction with soils is a major source of dissolved salts in groundwater the transition zone between the humid and the arid area is characterized by a specific combination of reactions which do not exist elsewhere this combination of caco3 dissolution and base exchange reactions affects the na cl ratio which is the quantitatively most important parameter used for tracing salinity sources of groundwater the increase in the na cl ratio in the coastal plain aquifer of israel from north to south is related to local recharge of na rich water after interaction with soils of loessial origin

facies and basin architecture of the late carboniferous salvan dorenaz continental basin western alps switzerland france the salvan dorenaz basin formed during the late palaeozoic within the aiguilles rouges crystalline basement western alps as an asymmetric intramontane graben elongated in a ne sw direction and bounded by active faults at least 1700 m of fluvial alluvial fan and volcanic deposits provide evidence for a strong tectonic influence on deposition with long term average subsidence rates of 0ae 2m m yr 1 the early basin fill was associated with coarse grained alluvial fans that were dominated by braided channels unit i these issued from the south western margin of the basin the fans then retreated to a marginal position and were overlain by muddy floodplain deposits of an anastomosed fluvial system unit ii that drained towards the ne deposition of thick muds resulted from a reduction in the axial fluvial gradient caused by accelerated tectonic subsidence overlying sand rich meandering river deposits unit iii document a reversal in the drainage direction from the ne to the sw caused by synsedimentary tectonism reflecting large scale topographic reorganization in this part of the variscides with subsidence now preferentially in the w and sw and uplift in the e and ne coarse grained alluvial fan deposits unit iv repeatedly prograded into and retreated from the basin as documented by coarsening upward cycles tens of metres thick reflecting smaller scale tectonic cycles volcanism was active throughout the evolution of the basin and u pb isotopic dating of the volcanic deposits restricts the time of basin development to the late carboniferous 308 295 ma 40 ar 39 ar ages of detrital white mica indicate rapid tectonic movements and exhumation of the nearby basement in unit i youngest ages are close to that of the host sediment but the age spectrum is wide in unit ii high subsidence and or sedimentation rates coincide with very narrow age spectra indicating small homogeneous catchment areas in unit iii age spectra became wider again and indicate growing catchment areas

estimating groundwater exchange with lakes 2 calibration of a three dimensional solute transport model to a stable isotope plume a three dimensional groundwater flow and solute transport model was calibrated to a plume of water described by measurements of 18o and used to calculate groundwater inflow and outflow rates at a lake in northern wisconsin the flow model was calibrated to observed hydraulic gradients and estimated recharge rates calibration of the solute transport submodel to the configuration of a stable isotope 18o plume in the contiguous aquifer on the downgradient side of the lake provides additional data to constrain the model a good match between observed and simulated temporal variations in plume configuration indicates that the model closely simulated the dynamics of the real system the model provides information on natural variations of rates of groundwater inflow lake water outflow and recharge to the water table inflow and outflow estimates compare favorably with estimates derived by the isotope mass balance method krabbenhoft et al this issue model simulations agree with field observations that show groundwater inflow rates are more sensitive to seasonal variations in recharge than outflow

early permian pangea b to late permian pangea a the pre drift wegenerian model of pangea is almost universally accepted but debate exists on its pre jurassic configuration since tedirving introd ucedpangea b by placing gond wana farther to the east by v3000 km with respect to laurasia on the basis of paleomagnetic data new paleomagnetic data from radiometrically dated early permian volcanic rocks from parts of adria that are tectonically coherent with africa gondwana integrated with published coeval data from gondwana and laurasia again only from igneous rocks fully support a pangea b configuration in the early permian the use of paleomagnetic data strictly from igneous rocks excludes artifacts from sedimentary inclination error as a contributing explanation for pangea b the ultimate option to reject pangea b is to abandon the geocentric axial dipole hypothesis by introducing a significant non dipole zonal octupole component in the late paleozoic time averaged geomagnetic field we demonstrate however by using a dataset consisting entirely of paleomagnetic directions with low inclinations from sampling sites confined to one hemisphere from gondwana as well as laurasia that the effects of a zonal octupole field contribution would not explain away the paleomagnetic evidence for pangea b in the early permian we therefore regard the paleomagnetic evidence for an early permian pangea b as robust the transformation from pangea b to pangea a took place during the permian because late permian paleomagnetic data allow a pangea a configuration we therefore review geological evidence from the literature in support of an intra pangea dextral megashear system the transformation occurred after the cooling of the variscan mega suture andlasted v20 myr in this interval the neotethys ocean opened between india arabia and the cimmerian microcontinents in the east while widespread lithospheric wrenching and magmatism took place in the west around the adriatic promontory the general distribution of plate boundaries and resulting driving forces are qualitatively consistent with a right lateral shear couple between gondwana and laurasia during the permian transcurrent plate boundaries associated with the pangea transformation reactivated variscan shear zones andwere subsequently exploitedby the opening of western neotethyan seaways in the jurassic

groundwater s dynamic role in regulating acidity and chemistry in a precipitation dominated lake abstract the role of groundwater in regulating the hydrologic and chemical regime ofan acid susceptible lake situated in a sandy silicate aquifer in northern wisconsin was determined by direct groundwater measurements using a network of 68 piezometers groundwater inputs were compared with precipitation and dryfall components of the hydrologic and chemical budgets for the lake groundwater contributed only 10 of the water to crystal lake in 1982 but was the major source of alkalinity calcium magnesium sodium potassium silicon and chloride precipitation contributed 90 of the water and was the major source of hydrogen and sulfate ions continuing analyses suggest that groundwater consistently supplies the bulk of the inoorganic constituents to the lake on annual basis the flux of groundwater and dissolved solids to the lake is highly seasonal with large pulses of groundwater inflow occuring after spring snowmelt and in the fall for certain nonconservative elements such as silicon the periodic influx of chemically concentrated groundwater can trigger significant changes in the chemical and biological balance in the lake despite the fact that the aquifer contains no carbonate minerals and the area experiences acid precipitation ph 4 6 the alkalinity of the small amount of groundwater entering crystal lake is more than enough to neutralize all of the acidity contributed by precipitation in lake sulfate reduction may generate an equal amount of alkalinity this buffering of ph helps to regulate aluminum concentrations at low levels thus minimizing potential aluminum toxicity in the lake most lakes in the region probably receive even larger amounts of alkalinity rich groundwater than crystal lake because most lie further downgradient in the regional flow system this may help to explain why most lakes in this acid susceptible area are no more acidic today than they were 50 years ago

magmatic flare up at the carboniferous permian boundary in the ne german basin revealed by shrimp zircon ages shrimp ages of 12 volcanic samples indicate intense magmatic activity to have occurred at the carboniferous permian boundary throughout much of the ne german basin rhyolitic crystal rich samples have been taken from quarries in the halle volcanic complex hvc and in the flechtingen ignimbrite and from drill cores of the kotzen mirow friedland and penkun areas ten samples yielded 206pb 238u ages between 302 and 297 ma 3 ma respectively which indicate that the magmatic activity took place concentrated in a relatively short time span throughout much of the ne german basin two hvc samples have ages of 307 and 294 ma this remarkably synchronous magmatic activity occurred during the initial phase of the basin development considering published volume estimates 48 000 km3 extrusion rates during this time period probably were in the order of 0 01 km3 a 1 implying magma production rates of 0 1 km3 a 1 the calc alkaline sio2 rich volcanic rocks originated from magmas that presumably formed during anatexis and subordinate magma mixing in an intra continental transtensional setting the basaltic magma which must have provided the thermal input into the lower crust probably formed during decompressional melting of lithospheric mantle fertilised by previous magmatic processes the dated volcanic rocks occur in three geotectonic provinces namely the a mid german crystalline rise which forms the northern part of the internal variscides the b external variscides and the variscan foreland which is considered as c eastern avalonia many of the old zircons found in the hvc samples reflect the magmatic activity of the mid german crystalline rise 325 400 ma however cadomian 500 650 ma and older gondwanian elements 1674 2373 ma are also present although the flechtingen and kotzen areas are located within the external variscides it seems more likely that the middle to lower crust that experienced anatexis formed part of the eastern avalonia plate overridden by the variscan front thus the old zircons found in flechtingen 350 and 538 ma and kotzen 345 ma but certainly those present in the penkun drill cores 1483 ma represent eastern avalonia tectonic history the anatectic magmas in the friedland area probably formed partly from baltic crust thrusted below eastern avalonia during the caledonian orogeny among the old zircons from the friedland samples in addition to proterozoic ages 1456 ma we found testimony of caledonian 443 ma and of clearly post caledonian 387 ma magmatism