a field study of hydraulic geochemical and stable isotope relationships in a coastal wetlands system both chemical and stable isotope data provide important supplemental information to more traditional hydraulic data and unravel the processes that underpin the large variations in chemical and stable isotopic composition within a coastal wetland system the system studied was the lake warden wetlands located in esperance in south coast of western australia the spatial and temporal variations of chemical and isotopic composition of the individual water bodies within the system were measured for an annual cycle in broad terms the groundwater levels appear to follow the topography but the distinct higher chloride and isotopic concentrations observed within the wetlands were not reflected in the low lying coastal plain groundwater the hydraulic analysis of the region surrounding the wetlands suggest that the wetlands are flow through bodies however the chemical and isotope information indicates the lakes almost invariably act as discharge points for the surface water flows and the north south groundwater flow the northeast southwest groundwater flow is along an observed paleochannel within the wetlands system and in this case the chemical and isotopic evidence are complimentary with the hydraulic study the study highlighted the importance of correcting the isotopic values for the salt effect in highly saline water the isotopic activity ratios of 2h 2ha of some samples were up to 15 higher than the uncorrected values the high salinity of the terminal lake in the wetlands chain also required implementation of a theoretical evaporative model to explain the lower enrichment of the isotopic results as compared to expectations for a shallow and ephemeral lake the inter lake variation in the theoretical evaporative model parameters coupled with a significant variation in the hydrochemistry and isotope composition suggests that the lakes within the wetlands system cannot be treated as single water body as is implied by the bathymetry survey

spectrum of pore types and networks in mudrocks and a descriptive classification for matrix related mudrock pores matrix related pore networks in mudrocks are composed of nanometer to micrometer size pores in shale gas systems these pores along with natural fractures form the flow path permeability network that allows flow of gas from the mudrock to induced fractures during production a pore classification consisting of three major matrix related pore types is presented that can be used to quantify matrix related pores and relate them to pore networks two pore types are associated with the mineral matrix the third pore type is associated with organic matter om fracture pores are not controlled by individual matrix particles and are not part of this classification pores associated with mineral particles can be subdivided into interparticle interp pores that are found between particles and crystals and intraparticle intrap pores that are located within particles organic matter pores are intrap pores located within om interparticle mineral pores have a higher probability of being part of an effective pore network than intrap mineral pores because they are more likely to be interconnected although they are intrap om pores are also likely to be part of an interconnected network because of the interconnectivity of om particles in unlithifed near surface muds pores consist of interp and intrap pores and as the muds are buried they compact and lithify during the compaction process a large number of interp and intrap pores are destroyed especially in ductile grain rich muds compaction can decrease the pore volume up to 88 by several kilometers of burial at the onset of hydrocarbon thermal maturation om pores are created in kerogen at depth dissolution of chemically unstable particles can create additional moldic intrap pores

hydrogeochemical and isotope evidence of groundwater evolution and recharge in minqin basin northwest china a hydrochemical investigation was conducted in the minqin basin to identify the groundwater evolution and recharge in the aquifer the mbr cl ratio is strongly depleted average 0 000451 compared with sea water 0 0035 indicating an evaporite origin the ionic ration plot saturation index si and chloro alkaline indices cai suggest that the dissolution of halite the glauberite gypsum dolomite and calcite determine na cl ca2 mg2 so42 and hco3 chemistry but other processes such as na exchange for ca2 and mg2 and calcite precipitation also contribute to the water composition the 6180 and 62 h in precipitation near the study area are linearly correlated similar to that for the world meteoric water line wmwl with an equation of delta h 2 7 49 delta o 18 5 11 r 2 0 97 according to radiocarbon residence time estimates the deep groundwater is approximatety 40 ka old and was recharged during a period when the climate was wetter and colder the radiocarbon content of shallow groundwater shows a clear evolution along the groundwater flow path from the beginning of the groundwater flow path to similar to 31 km the radiocarbon values are 73 6 pmc whereas beyond this point the values are 42 9 pmc based on radiocarbon content the shallow groundwater is older than 1 ka and represents pataeowaters mixed with a limited quality of modern recharge the rain fed groundwater direct recharge was estimated by chloride mass balance cmb method to range from 1 55 to 1 64 mm yr 1 with a mean value of 1 6 mm yr 1 this value represents about 1 5 of local rainfall the direct recharge volumes is about 0 666 x 10 8 m 3 yr 1 indirect recharge volumes by the surface water is about 0 945 x 10 8 m 3 yr 1 the total natural recharge in the minqin basin is 1 6 x 10 8 m 3 yr 1 whereas the groundwater abstraction has reached 11 6 x 10 8 m 3 yr 1 far exceeding the groundwater natural recharge c 2006 elsevier b v all rights reserved

shale gas transport model in 3d fractal porous media with variable pore sizes abstract a model for gas transport in shale is proposed by accounting for three major fluid flow mechanisms in shale stratum which is modeled as a 3d fractal media the proposed apparent permeability of shale is an analytical expression that also accounts for heterogeneous pore sizes in shale stratum and is verified using experimental datasets for methane and helium flow in shale results of sensitivity analysis indicate that surface diffusion of adsorbed gas plays an important role specifically in smaller pores while surface diffusion would be negligible in larger pores further the proposed model shows that flow due to surface diffusion decreases moderately with the increase of isosteric adsorption heat while it increases significantly with the increase of the maximum adsorption capacity one of the key novelties of the proposed permeability model is that it accounts for pore size distribution to reveal novel insights on gas transport in shale that can be used to optimize gas production by operational controls e g controlling reservoir pressure as flow regimes change with time

seasonal water use patterns of juniperus ashei on the edwards plateau texas based on stable isotopes in water summary naturally occurring stable isotopes of oxygen and hydrogen were used to determine the seasonal water sources of juniperus ashei and its relationship with soil water content on the edwards plateau of central texas honey creek state natural area the patchy nature of juniper stands rooting in the thin soils over karstified carbonate bedrock imparts large spatial heterogeneity in soil water content and isotopic composition largely by differential shading but also by canopy interception there is a seasonal decrease in the oxygen isotope composition of juniper xylem water by 2 during the transition from hot dry summer conditions to the cool moist winter prior to this shift the xylem water isotope composition is similar to local springs presumed to represent local groundwater after this shift the xylem water composition is similar to soil water below 10 cm these results suggest a change in juniper water use from a dominantly deep water source during the summer to a dominantly soil source during the winter over the study period but the timing of this transition will likely vary from year to year

zr bearing minerals as indicators for the polymetamorphic evolution of the eastern lower austroalpine nappes stubenberg granite contact aureole styria eastern alps austria abstract contact metamorphism during emplacement of the permian stubenberg granite has led to the formation of the assemblage forsterite calcite titanian clinohumite phlogopite chlorite in the adjacent marbles during intrusion of the granite veins rich in ti zr ree and actinides u th formed these veins show a distinct mineralogical zoning sequence with four zones going from the center of the vein to the margin these zones include the assemblages 1 geikielite baddeleyite zirconolite apatite calcite chlorite magnetite pyrrhotite assemblage 2 calcite chlorite 3 forsterite titanian clinohumite chlorite calcite phlogopite and 4 calcite forsterite baddeleyite is always replaced by zirconolite possibly via the model reaction baddeleyite 2 geikielite 3 calcite co 2 zirconolite 2 dolomite zirconolite zirc i shows a strong internal oscillatory zoning and distinct overgrowths zirc ii which have a different chemical composition the chemical variation between the cores zirc i and the rims zirc ii can be explained by using the substitutions me 5 me 2 ti 4 me 3 and ree 3 me 5 me 2 ca 2 2ti 4 in contrast to zirconolite from metacarbonates associated with contact aureoles these analyses show elevated nb contents of up to 4 5 wt nb 2 o 5 and unusually high w contents of 1 2 wt wo 3 a strong eo alpine metamorphic overprint led locally to the formation of the assemblage chlorite dolomite calcite ilmenite zirconolite ii geikielite fe sulfides late zircon grew locally presumably as the last zr bearing mineral in the carbonates which formed during permian contact metamorphism the zr mineral sequence baddeleyite zirconolite zircon implies an increasing a sio 2 and f co 2 during the growth of these minerals electron microprobe dating of zirconolite zirc i yields a weighted average age of 263 16 ma and indicates that the hfse and ree rich assemblages formed during the permian emplacement of the stubenberg granite as a result of the subsequent high p eo alpine metamorphic overprint 111 15 ma hfse and ree were locally re mobilized leading to dissolution of zirc i and reprecipitation of the ree and nb rich overgrowths of zirc ii

assessment of grain scale homogeneity and equilibration of carbon and oxygen isotope compositions of minerals in carbonate bearing metamorphic rocks by ion microprobe abstract nineteen samples of metamorphosed carbonate bearing rocks were analyzed for carbon and oxygen isotope ratios by ion microprobe with a 5 15 m spot three from a regional terrain and 16 from five different contact aureoles contact metamorphic rocks further represent four groups calc silicate marble and hornfels 6 brucite marble 2 samples that contain a reaction front 4 and samples with a pervasive distribution of reactants and products of a decarbonation reaction 4 the average spot to spot reproducibility of standard calcite analyses is 0 37 2 standard deviations sd for 18 o and 0 71 for 13 c ten or more measurements of a mineral in a sample that has uniform isotope composition within error of measurement can routinely return a weighted mean with a 95 confidence interval of 0 09 0 16 for 18 o and 0 10 0 29 for 13 c using a difference of 6sd as the criterion only four of 19 analyzed samples exhibit significant intracrystalline and or intercrystalline inhomogeneity in 13 c at the 100 500 m scale with differences within individual grains up to 3 7 measurements are consistent with carbon isotope exchange equilibrium between calcite and dolomite in five of six analyzed samples at the same scale because of relatively slow carbon isotope diffusion in calcite and dolomite differences in 13 c can survive intracrystalline homogenization by diffusion during cooling after peak metamorphism and likely represent the effects of prograde decarbonation and infiltration all but 2 of 11 analyzed samples exhibit intracrystalline differences in 18 o up to 9 4 intercrystalline inhomogeneity in 18 o up to 12 5 and or disequilibrium oxygen isotope fractionations among calcite dolomite calcite quartz and calcite forsterite pairs at the 100 500 m scale inhomogeneities in 18 o and 13 c are poorly correlated with only a single mineral dolomite in a single sample exhibiting both because of relatively rapid oxygen isotope diffusion in calcite intracrystalline inhomogeneities in 18 o likely represent partial equilibration between calcite and fluid during retrograde metamorphism calcite is in oxygen isotope exchange equilibrium with forsterite in one of four analyzed samples in equilibrium with dolomite in none of six analyzed samples and in equilibrium with quartz in neither of two analyzed samples there are no samples of contact metamorphic rock with analyzed reactants and products of an arrested metamorphic reaction that are in oxygen isotope equilibrium with each other the degree of departure from equilibrium in analyzed samples is variable and is often related at least in part to alteration of 18 o of calcite during retrograde fluid rock reaction in situ sub grain scale carbon and oxygen isotope analyses of minerals are advisable in the common applications of stable isotope geochemistry to metamorphic petrology correlation of sub mm scale stable isotope data with imaging will lead to improved understanding of reaction kinetics reactive fluid flow and thermal histories during metamorphism

high resolution holocene environmental changes in the thar desert northwestern india sediments from lunkaransar dry lake in northwestern india reveal regional water table and lake level fluctuations over decades to centuries during the holocene that are attributed to changes in the southwestern indian monsoon rains the lake levels were very shallow and fluctuated often in the early holocene and then rose abruptly around 6300 carbon 14 years before the present 14c yr b p the lake completely desiccated around 4800 14c yr b p the end of this 1500 year wet period coincided with a period of intense dune destabilization the major harrapan indus civilization began and flourished in this region 1000 years after desiccation of the lake during arid climate and was not synchronous with the lacustral phase

stable isotope ratios of carbon in phytoliths as a quantitative method of monitoring vegetation and climate change the 13c 12c ratios of occluded carbon within opal phytoliths from the northern great plains show potential as a basis for paleoclimatic reconstruction a significant correlation exists between the carbon isotopic composition of a host plant and that of the organic matter in its phytoliths the 13c 12c ratios for phytoliths from surface layers of soils along climatic gradients reflect the current proportions of c3 and c4 plants variations in the 13c values of phytoliths with soil depth are caused by a variety of processes burial of soil surface by dust bioturbation and possible illuviation by percolating water also contributions of phytoliths by dust and roots have unknown isotopic effects the 13c values of phytoliths from soils increase with decreasing 14c age suggesting that the proportion of c4 plants in this region has increased during the holocene phytoliths of apparent mid holocene age suggest exclusive dominance by c4 plants which agrees with paleoclimatic interpretations of an arid middle holocene climate

multiscale modeling of shale samples based on low and high resolution images abstract accurate modeling of shale samples is very crucial for evaluating and predicting the physical properties however obtaining large scale and high resolution images of shales using a single imaging tool such as x ray computed tomography or scanning electron microscopy machine might not be plausible as there is always a trade off between the resolution and field of view on the other hand relying on small scale images may jeopardize the accuracy of porous media modeling one solution scheme for addressing these issues is to fuse the spatial information from the multiscale and multiresolution images into a multiscale high resolution image as such a novel multiscale modeling algorithm based on template matching for complex rocks is proposed in this study this algorithm can fuse multiscale and multiresolution structural patterns from the images with different scales resolution and phases into one single image the accuracy of the presented algorithm is tested using two heterogeneous shale samples and the results are compared with the actual large and high resolution images we found that the algorithm can generate an accurate image after comparing the geometrical properties of pore systems correlation functions and image similarity indicators of the generated image and reference image

crystal size distribution of periclase in contact metamorphic dolomite marbles from the southern adamello massif italy crystal size distributions csd of periclase in contact metamorphic dolomite marbles are presented for two profiles near the cima uzza summit in the southern adamello massif italy the database was combined with geochemical and petrological information to deduce the controls on the periclase forming reaction the contact metamorphic dolomite marbles are exposed at the contact of mafic intrusive rocks and are partially surrounded by them brucite is retrograde and pseudomorphs spherical periclase crystals prograde periclase growth is the consequence of limited infiltration of waterrich fluid at t near 6058c stable isotope data show depletion in 13 c and 18 o over a narrow region 40 cm near the magmatic contact whereas the periclase forming reaction front extends up to 4 m from the contact csd analyses along the two profiles show that the median grain size of the periclase crystals does not change but that there is a progressively greater distribution of grain sizes including a greater proportion of larger grains with increasing distance from the contact a qualitative model based on the textural and geochemical data attributes these variations in grain size to changing reaction affinities along a kinetically dispersed infiltration front this study highlights the need to invoke disequilibrium processes for metamorphic mineral growth and expands the use of csds to systems of mineral formation driven by fluid infiltration

carbon 14 dating of ground water in the palouse basin of the columbia river basalts summary delineation of the spatial distribution of ground water that is several thousands of years old can provide an important piece of the puzzle in the evaluation of long term ground water resource sustainability under pumping conditions ground water for municipal and local water supplies within the palouse basin of eastern washington and northern idaho are derived almost entirely from two basalt aquifer systems decades of continual water level declines in the deeper aquifer system in response to interstate pumping have suggested that this high transmissivity low storativity aquifer system is being mined average water level declines in the deeper aquifer system have been on the order of 0 46 m 1 5 ft per year for the past 40 plus years carbon isotopic measurements on dissolved inorganic carbon were used to provide information on the relative ages of the ground water pumped from various locations within the basin mass balance modeling of hydrochemical reactions together with steep downward vertical gradients throughout the basin suggest that the ground water being withdrawn currently required several thousand years to traverse spatially variable sequences of loess fluvial sediments and basalt flows with associated sedimentary interbeds that overlie the primary producing zones in the basin restrictions to the vertical movement of recharge water such as low permeability overburden deposits well developed fragipans and thick low permeability sedimentary interbeds increase in the eastern portion of the palouse basin compared to the western portion this has resulted in accumulation of the oldest ground water in the topographically highest areas of the basin adjacent to the basin divide

prograde and retrograde fluid flow during contact metamorphism of siliceous carbonate rocks from the ballachulish aureole scotland siliceous dolomites and limestones contain abundant retrograde minerals produced by hydration carbonation reactions as the aureole cooled marbles that contained periclase at the peak of metamorphism bear secondary brucite dolomite and serpentine forsterite dolomite marbles have retrograde tremolite and serpentine wollastonite limestones contain secondary calcite and quartz and wollastonite free limestones have retrograde tremolite secondary tremolite never appears in marbles where brucite has replaced periclase or in wollastonite bearing limestones a model for infiltration of siliceous carbonates by co2 h2o fluid that assumes a vertical upwardly directed flow b fluid flux proportional to cooling rate and c flow and reaction under conditions of local equilibrium between peak temperatures and 400 c reproduces the modes of altered carbonate rocks observed reaction textures and the incompatibility between tremolite and brucite and between tremolite and wollastonite except for samples from a dolomite xenolith retrograde time integrated flux recorded by reaction progress is on the order of 1000 mol fluid cm2 rock local focusing of flow near the contact is indicated by samples from the xenolith that record values an order of magnitude greater formation of periclase forsterite and wollastonite at the peak of metamorphism also required infiltration with prograde time integrated flux approximately 100 1000 mol cm2 the comparatively small values of prograde and retrograde time integrated flux are consistent with lack of stable isotope alteration of the carbonates and with the success of conductive thermal models in reproducing peak metamorphic temperatures recorded by mineral equilibria although isobaric univariant assemblages are ubiquitous in the carbonates most formed during retrograde metamorphism isobaric univariant assemblages observed in metacarbonates from contact aureoles may not record physical conditions at the peak of metamorphism as is commonly assumed

estimating permeability of shale gas reservoirs from porosity and rock compositions it is challenges for effectively estimating the permeability of shale gas reservoirs by traditional models however the study on this area is lacked and deficient we proposed a method for predicting permeability of shale gas reservoirs from porosity and rock compositions including mineralogy and organic matter content which is applicable to laboratory data and downhole measurements first two sets including 38 samples from the longmaxi formations were tested for porosity permeability grain density total organic carbon toc content mineralogical compositions and low temperature nitrogen adsorption we used the kozeny s equation to calculate the specific surface area which was viewed as the effective specific surface in shale formations through comparing with the specific surface from low temperature nitrogen adsorption further the effective specific surface was found to be positively correlated with clays pyrite and toc contents while negatively with quartz feldspar and carbonates then an

geikielite exsolution in spinel euhedral crystals of purple spinel are associated with calcite and forsterite in the central zone of composite metasomatic veins of the adamello contact aureole northern italy in thin section spinel is generally colorless but exhibits concentric zones of dark brown color these zones are aligned parallel to prominent crystal faces and contain abundant anisotropic lath shaped inclusions with their long axis oriented in the six directions of spinel this orientation results from the alignment of 001 geik and the 111 sp crystallographic planes the small up to approximately 20 1 m inclusions were identified as geikielite by means of element distribution maps micro raman spectroscopy and transmission electron microscopy electron microprobe data revealed that spinel consists mainly of mgal2o4 with only minor amounts of other components the overall chemical variation within individual crystals is characterized by a continuous increase in feotot and zno from center to rim 0 6 2 1 wt and 0 1 1 0 wt respectively whereas v2o3 is relatively constant 0 15 wt the bulk tio2 concentration analysis spot 20 m diameter increases in general from center 0 12 wt to rim 1 2 wt this variation however is marked by several discontinuities that correspond to the zones containing geikielite inclusions where geikielite occurs the spinel matrix is depleted in ti relative to the inclusion free zones geikielite was analyzed by analytical electron microscopy and has the formula mg0 83fe0 15mn0 02 ti0 99fe0 01 o3 the textural relationships between geikielite inclusions and spinel matrix combined with the analytical data suggest that geikielite laths represent exsolution features thus a miscibility gap exists between mg al spinel and geikielite the purple color results from scattering of light by the geikielite inclusions spinel with similar features was also observed in metasomatic veins of the bergell contact aureole italy and in granulite facies marbles of southern india

regional groundwater flow paths in trans pecos texas inferred from oxygen hydrogen and strontium isotopes summary stable isotopes radiogenic isotopes and major ion chemistry are used to constrain flow paths in a fracture controlled regional groundwater flow system in far west texas the flow system occurs in permian and cretaceous sedimentary rocks and cenozoic alluvial basin fill samples from springs and wells in the study area were analyzed for major ions and hydrogen oxygen and strontium isotopes d and 18o values fall close to the global meteoric water line indicating that these values have not been significantly affected by evaporation or mineral water reactions 18o values from samples along the regional flow path are lower by as much as 3 relative to local recharge values the distribution of stable isotope values throughout the study area suggests that lower 18o values represent recharge during cooler climatic conditions rather than latitude or altitude effects 87sr 86sr values for water samples from along the regional flow path range from 0 7093 to 0 7148 with the highest values at the upgradient end of the flow system these values are significantly higher than expected for groundwaters dominated by dissolution of permian and cretaceous marine carbonates and evaporites the high 87sr 86sr values reflect dissolution of minerals of precambrian and early paleozoic origin in the crystalline rocks of the carrizo and baylor mountains and alluvial basin fill at the upgradient end of the flow system contours of 87sr 86sr values indicate a zone of high 87sr 86sr water that corresponds to the regional groundwater flow paths mass balance mixing models and mineral reactions models indicate a three end member mixing system modified by dissolution of strontium bearing minerals in the alluvial fill at the upgradient end of the flow system

precipitation origin and evaporation of lakes in semi arid patagonia argentina inferred from stable isotopes δ18o δ2h stable isotope approaches are often used for estimating water balances of lakes such studies require regional background information about hydrogen and oxygen isotope variability of lakes and their potential inflows here a stable isotope database 2h and 18o is presented for estimating evaporation to inflow ratios e i of lakes in semi arid southern patagonia water samples of 23 lakes and ponds located in the patagonian steppe at about 52 s were sampled during three subsequent austral summers two deep crater lakes laguna azul and laguna potrok aike were studied in more detail during a two years monitoring furthermore precipitation groundwater and atmospheric water vapor were sampled for isotope analyses presented data imply that the isotopic composition of rainfall in southeastern patagonia is predominantly determined by precipitation amount and moisture source area for the investigated area the first meteoric water and evaporation lines in 2h vs 18o space are presented the database was further used to estimate the water balances of the two crater lakes laguna azul and laguna potrok aike which are in the focus of recent paleoclimatic investigations according to that approach about 50 and 60 respectively of the water entering laguna azul and laguna potrok aike via surface and subsurface inflow evaporates these results testify a considerable flow of lake waters into the groundwater

experimental investigation of matrix permeability of gas shales predicting long term production from gas shale reservoirs has been a major challenge for the petroleum industry to better understand how production profiles are likely to evolve with time we have conducted laboratory experiments examining the effects of confining stress and pore pressure on permeability experiments were conducted on intact core samples from the barnett eagle ford marcellus and montney shale reservoirs the methodology used to measure permeability allows us to separate the reduction of permeability with depletion because of the resultant increase in effective confining stress and the increase in permeability associated with knudsen diffusion and molecular slippage also known as klinkenberg effects at very low pore pressure by separating these effects we are able to estimate the relative contribution of both darcy and diffusive fluxes to total flow in depleted reservoirs our data show that the effective permeability of the rock is significantly enhanced at very low pore pressures because of the slippage effects we use the magnitude of the klinkenberg effect to estimate the effective aperture of the flow paths within the samples and compare these estimates to scanning electron microscopy image observations our results suggest effective flow paths to be on the order from tens of nanometers in most samples to 100 200 nm in a relatively high permeability eagle ford sample finally to gain insight on the scale dependence of permeability measurements the same core plugs were crushed and permeability was again measured at the particle scale using the so called gas research institute method the results show much lower permeability than the intact core samples with very little correlation to the measurements on the larger scale cores

a mid to late holocene record of palaeoclimatic changes from nal sarovar a palaeodesert margin lake in western india with a view to obtain palaeoclimatic data from a climatically sensitive region we have studied core samples from nal sarovar a large shallow lake lying within the palaeodesert margin of thar in western india a combination of c n ratios and 13c on a radiocarbon dated core section have been used as climatic proxies a high resolution record extending back to ca 6 6 ka bp has been reconstructed the data indicate that in the past climate has varied from drier to wetter than present on time scales of few hundreds to few thousands of years there are however significant differences on the timing of these wet and dry periods when compared with the available data from lakes farther north in rajasthan further it looks unlikely that during the 6 6 ka the catchment areas of nal sarovar experienced such a significant increase in rainfall as has been suggested for the rajasthan lakes interestingly drier periods in nal sarovar data appear to correlate well with periods of glacier expansion in eurasia indicating that the palaeoclimatic variations recorded in nal sarovar are a regional feature 1997 john wiley sons ltd

late pleistocene precipitation δ18o interpolated across the global landmass global water cycles ecosystem assemblages and weathering rates were impacted by the 4 c of global warming that took place over the course of the last glacial termination fossil groundwaters can be useful indicators of late pleistocene precipitation isotope compositions which in turn can help to test hypotheses about the drivers and impacts of glacial interglacial climate changes here a global catalog of 126 fossil groundwater records is used to interpolate late pleistocene precipitation 18o across the global landmass the interpolated data show that extratropical late pleistocene terrestrial precipitation was near uniformly depleted in 18o relative to the late holocene by contrast tropical 18o responses to deglacial warming diverged late pleistocene 18o was higher than modern across india and south china but lower than modern throughout much of northern and southern africa groundwaters that recharged beneath large northern hemisphere ice sheets have different holocene pleistocene 18o relationships than paleowaters that recharged subaerially potentially aiding reconstructions of englacial transport in paleo ice sheets global terrestrial late pleistocene precipitation 18o maps may help to determine 3 d groundwater age distributions constrain pleistocene mammal movements and better understand glacial climate dynamics

strontium isotope characterization and major ion geochemistry of karst water flow shentou northern china summary karst water is the most important source of water supply for shanxi province northern china the shentou springs are representative of the 19 major karst springs at shanxi the total area of the shentou karst water system is 5316 km 2 the middle ordovician limestone being its major karst aquifer in this study data about the strontium isotope geochemistry and major ion hydrochemistry were analyzed to understand the flow patterns and hydrogeochemical processes of karst water at shentou the contour map of tds value of karst water and that of sr concentration are similar showing the general tendency of increase from the northern western and southern boundary to the discharge area the average values of 87 sr 86 sr ratios of karst water decrease from recharge 0 7107 to discharge area 0 7102 evolving towards those of limestone hostrocks comparison of 87 sr 86 sr ratios with sr content suggests that isotopic compositions of some karst water samples from the recharge and flow through area should be the result of interaction between aquifer limestone matrix and strontium poor recharge waters of meteoric origin however for samples from the discharge area that are plotted above the mixing line mixing with groundwater in the quaternary aquifers with high 87 sr 86 sr ratios may be another factor controlling sr isotope chemistry two major groundwater flow paths were discerned from hydrogeological and geochemical data along both flow paths the 87 sr 86 sr ratios of karst water show a general tendency of decrease geochemical modeling of the major ion geochemistry of karst water using phreeqc also indicates that the chemistry of springs should be affected by the incorporation of groundwater in quaternary aquifer the effect of the mixing action on the spring hydrochemistry in flow path 1 is more remarkable than that in flow path 2 according to different mixing ratios in both paths 30 in flow path 1 and 5 in flow path 2

three novel isograds in metamorphosed siliceous dolomites from the ballachulish aureole scotland isograds were mapped in siliceous dolomites from the ballachulish aureole on the basis of the formation of geikielite mgti03 baddeleyite zr02 and qandilite mg2ti04 by the following model reactions rutile dolomite geikielite calcite c02 zircon 2 dolomite baddeleyite forsterite 2 calcite 2 c02 and geikielite periclase qandilite the t xco conditions of reaction inferred from 1 mineral equilibria in pelitic rocks 2 calcite dolomite thermometry and 3 the diopside dolomite forsterite calcite tremolite and dolomite periclase calcite equilibria are geikielite isograd 640 655 c 0 76 0 80 baddeleyite isograd 660 710 c 0 76 0 95 qandilite isograd 725 755 c 0 08 these t xco2 conditions for the geikielite and baddeleyite isograds are the same within error of those independently estimated from rutile dolomite geikielite calcite and zircon dolomite baddeleyite forsterite calcite equilibria using berman s thermodynamic data base rutile zircon geikielite and baddeleyite are common in dolomites from at least two other contact aureoles in scotland and montana although the minerals occur in concentrations 0 01 they appear to have been in local equilibrium during metamorphism both with each other and with coexisting carbonates and silicates and are potentially useful but currently unexploited records of the physical conditions of metamorphism

environmental isotopes investigation on recharge processes and hydrodynamics of the coastal sedimentary aquifers of tiruvadanai tamilnadu state india summary environmental isotopes 2 h 18 o 3 h 13 c 14 c 34 s in conjunction with hydro geological and hydro chemical data were employed to understand the groundwater recharge processes and hydrodynamics of the tiruvadanai aquifers in the tamilnadu state in southern india hydro chemical characterisation of the groundwater indicated that the tertiary aquifers depth 50 200 m un confined semi confined confined contain no dominant ca mg hco 3 cl to brackish na cl type of waters and the deeper 350 500 m cretaceous aquifer confined contains freshwater the concentration of various chemical species along the general groundwater flow direction northwest to east showed a trend with decrease in mg 2 and ca 2 and an increase in na and k in both tertiary and cretaceous aquifers which is also indicated by decreasing saturation index values for dolomite along the flow path this could be attributed to ion exchange processes a higher ph value of cretaceous aquifer samples 7 4 8 6 could also be responsible for the lowering of mg 2 and ca 2 concentrations by facilitating precipitation of carbonates in them on the 2 h 18 o plot the tertiary aquifers samples fall on an evaporation line their 3 h values near the ephemeral rivers range from 2 to 5 tu while those away from the rivers have 14 c dic model ages range from 1 to 13 ka bp the cretaceous aquifer samples measured 3 h values 14 c dic model ages are 20 ka bp indicating palaeo waters based on 14 c model ages the groundwater velocity was estimated tertiary aquifers 10 2 10 3 m d 1 cretaceous aquifer 10 3 m d 1 dissolution of carbonate bearing minerals in the tertiary aquifer and oxidation of organic matter in the cretaceous aquifers seems to be the dominant processes and thus resulting in the corresponding enrichment and depletion in 13 c dic along the flowpaths the values of 34 s aq so 4 2 showed enrichment in the cretaceous aquifer samples compared to that of the tertiary aquifers samples the 34 s aq so 4 2 enrichment could be due to bacterial reduction of sulphate from the investigation three types of recharge processes to the aquifer system are discerned with the overall modern recharge component being low the cretaceous aquifer contains fossil groundwaters and hence the resources may be finite and their exploitation is mining deeper coastal groundwater isotopic evidence of palaeo climatic excursions between arid and humid phases during the holocene and late pleistocene in the southern india has been obtained for the first time

multivariate statistical analysis and environmental isotopes of amman wadi sir b2 a7 groundwater yarmouk river basin jordan multivariate statistical techniques cluster and factor analyses were applied on the amman wadi sir groundwater chemistry yarmouk river basin north jordan the main objective was to investigate the main processes affecting the groundwater chemical quality and its evolution the k means cluster analysis yields three groups with distinct ionic concentrations cluster 1 comprises the vast majority of the sampled wells and the water that belongs to this cluster can be classified as freshwater cluster 2 comprises only 2 of the sampled wells it has the highest ionic concentration the water of this cluster can be classified as brackish water cluster 3 involves 23 of the sampled wells and it has total ionic concentration intermediate to that of clusters 1 and 2 factor analysis yields a three factor model which explains 76 77 of the groundwater quality variation factor 1 salinity factor involves ec na cl so4 2 k and mg 2 and reflects groundwater salinization because of overpumping factor 2 hardness factor includes ca 2 hco3 and the ph value and signifies soil water rock interaction factor 3 nitrate factor involves only no3 and points to groundwater contamination because of human activities mainly untreated wastewater and crops and animal cultivation in the unconfined portion of the aquifer factors 1 and 3 can be described as human induced factors whereas factor 2 can be described as geogenic factor factors scores were mapped to deduce the controlling processes on the groundwater chemistry stable isotope composition of 18o and 2h has revealed that the groundwater is a mixture of two water types the radioactive isotopes tritium and 14 c were used to evaluate present day recharge to the aquifer and to estimate the groundwater age respectively present day recharge to the groundwater is taking place in the unconfined portion of the aquifer as it is indicated by the measurable tritium content and low groundwater age copyright 2012 john wiley sons ltd

patterns of mineral occurrence in metamorphic rocks patterns in the occurrence of minerals in metamorphic rocks suggest additional opportunities for investigating chemical and physical processes during metamorphism three such patterns are reviewed first trace minerals in metamorphic rocks commonly occur with regular distributions indicating their participation in prograde reactions that can be mapped as isograds examples include the distribution of allanite and monazite in pelitic rocks and of zircon and baddeleyite in siliceous dolomites recognition of these isograds points to the potential for developing a chronology of specific chemical reactions during metamorphism and for defining the p t conditions of those reactions second the mineralogical products of retrograde metamorphism in many cases occur in distinctive associations that are consistent with partial mineral fluid equilibrium examples include the distribution of retrograde calcite quartz and tremolite in siliceous limestones and of retrograde tremolite dolomite brucite and serpentine in siliceous dolomites from contact aureoles among other things application of partial equilibrium to retrograde metamorphic rocks leads to constraints on the amount and direction of fluid flow in contact aureoles as they cool third pseudomorphs are typically absent from prograde metamorphic rocks but are common in retrograde metamorphic rocks the distribution may be explained by the effect of force of crystallization the pattern of occurrence of pseudomorphs thus suggests novel phenomena during metamorphism that develop from an interplay between chemical and mechanical processes

differentiation of palaeomarine and modern seawater intruded salinities in coastal groundwaters of karaikal and tanjavur india based on inorganic chemistry organic biomarker fingerprints and radiocarbon dating abstract hydrosalinity evolution is examined in the karaikal and tanjavur coastal aquifers situated about 300 km south of madras tamil nadu india ancient and modern sources of solutes in groundwaters have been differentiated using hydro geochemical data environmental radioisotope dates and organic biomarkers results from different techniques show consistently that the pliocene aquifer possesses characteristic palmitoleic and oleic acid biomarkers apparent 14 c ages of more than 20 000 years and high i cl ratio the modern marine estuarine intruded groundwaters in the alluvial aquifer display relatively younger apparent 14 c ages modern to 3000 years enriched potassium ion low i cl ratio and contain vaccenic and hopanoic acid biomarkers and they also tend to display transient changes in chemical characteristics these results have practical importance with regard to identifying and controlling seawater intrusion in coastal areas

application of multiple isotopic and geochemical tracers for investigation of recharge salinization and residence time of water in the souss massa aquifer southwest of morocco summary groundwater and surface water in souss massa basin in the west southern part of morocco is characterized by a large variation in salinity up to levels of 37 g l 1 the high salinity coupled with groundwater level decline pose serious problems for current irrigation and domestic water supplies as well as future exploitation a combined hydrogeologic and isotopic investigation using several chemical and isotopic tracers such as br cl 18 o 2 h 3 h 87 sr 86 sr 11 b and 14 c was carried out in order to determine the sources of water recharge to the aquifer the origin of salinity and the residence time of water stable isotope 3 h and 14 c data indicate that the high atlas mountains in the northern margin of the souss massa basin with high rainfall and low 18 o and 2 h values 6 to 8 and 36 to 50 is currently constitute the major source of recharge to the souss massa shallow aquifer particularly along the eastern part of the basin localized stable isotope enrichments offset meteoric isotopic signature and are associated with high nitrate concentrations which infer water recycling via water agricultural return flows the 3 h and 14 c data suggest that the residence time of water in the western part of the basin is in the order of several thousands of years hence old water is mined particularly in the coastal areas the multiple isotope analyses and chemical tracing of groundwater from the basin reveal that seawater intrusion is just one of multiple salinity sources that affect the quality of groundwater in the souss massa aquifer we differentiate between modern seawater intrusion salinization by remnants of seawater entrapped in the middle souss plains recharge of nitrate rich agricultural return flow and dissolution of evaporate rocks gypsum and halite minerals along the outcrops of the high atlas mountains the data generated in this study provide the framework for a comprehensive management plan in which water exploitation should shift toward the eastern part of the basin where current recharge occurs with young and high quality groundwater in contrast we argued that the heavily exploited aquifer along the coastal areas is more vulnerable given the relatively longer residence time of the water and salinization processes in this part of the aquifer

regional scale stable isotopic signatures of recharge and deep groundwater in the arsenic affected areas of west bengal india summary samples of deep groundwater river water and rainwater were collected for 18o and 2h analyses from an area of 22 000 km2 in the arsenic affected districts of west bengal india in order to examine groundwater recharge a plot of 18o versus 2h of groundwater falls subparallel to the constructed local meteoric water line 2h 7 2 18o 7 7 suggesting a predominance of meteoric recharge with some evaporation the stable isotopic signature of groundwater from the deeper part of the semiconfined main aquifer is similar to that of shallower groundwater which suggests that deeper groundwater has been recharged in the present day climatic regime mostly from monsoonal rainfall groundwater in deeper isolated aquifers falls within the isotopic range observed for the main aquifer a trend of isotopic depletion of groundwater that extends northward and westward from the bay of bengal the monsoonal moisture source area indicates a rain out process following rayleigh type distillation some recharge may have taken place from the rivers ganges and bhagirathi hoogly with minimal inflow from other rivers jalangi and ichamati

the effect of fluid salinity on infiltration driven contact metamorphism of carbonate rocks calculated phase equilibria involving minerals and h2o co2 nacl fluid lead to predictions of how infiltration of rock by h2o nacl fluids with xnacl in the range 0 0 3 0 58 wt nacl drives the reactions calcite quartz wollastonite co2 and dolomite periclase calcite co2 calculations focus on metamorphism in four aureoles that together are representative of the normal p t conditions and processes of infiltration driven contact metamorphic reactions the effect of salinity on the spatial extent of oxygen isotope alteration was also computed the time integrated input fluid flux q that displaces the mineral reaction front an increment of distance along the flow path always increases with increasing xnacl for input fluids with salinity up to approximately five times that of seawater xnacl 0 05 values of q required to explain the spatial extent of decarbonation reaction are no more than 1 1 1 5 times that computed assuming the input fluid was pure h2o for more saline fluids values of q may be up to 1 4 7 9 times that for pure h2o except for reaction in the presence of halite and vapor v infiltration of h2o nacl fluids expands the region of oxygen isotope alteration relative to the size of the region of mineral reaction the expansion is significant only for saline fluids with xnacl 0 1 immiscible fluid phase separation and differential loss of the liquid l or v phase from the mineral reaction site increases the amount of reactive fluid required to advance the mineral reaction front compared to conditions under which equilibration of minerals and fluid is attained with no loss of l or v decarbonation reactions driven by infiltration of fluids with even modest seawater like salinity can explain the occurrence of salt saturated fluid and solid halide inclusions in contact metamorphosed carbonate rocks

hydrogeochemical and isotopic evidence of groundwater salinization in a coastal aquifer a case study in jeju volcanic island korea abstract in order to identify the origin of saline groundwater in the eastern part of jeju volcanic island korea a hydrogeochemical and isotopic study has been carried out for 18 observation wells located in east and southeast coastal regions the total dissolved solid contents of groundwaters are highly variable 77 21 782 mg l oxygen hydrogen sulfur and strontium isotopic data clearly show that the saline water results from mixing of groundwater with seawater strontium isotopic compositions and br cl and i cl ratios strongly suggest that the source of salinity is modern seawater intrusion hydrogeochemical characteristics based on bivariate diagrams of major and minor ions show that changes in the chemical composition of groundwater are mainly controlled by the salinization process followed by cation exchange reactions the highly permeable aquifers at the east coastal region are characterized by low hydraulic gradient and discharge rate and high hydraulic conductivity as compared with other regions these properties enhance the salinization of groundwater observed in the study area based on the cl br and 18 o data seawater was determined to have intruded inland some 2 5 km from the coastline considering the poor correlation of sampling depth and cl concentrations observed the position of seawater freshwater interface is not uniformly distributed in the study area due to heterogeneities of the basaltic aquifers

distribution of oxygen and hydrogen isotopes in shallow groundwaters from southern india influence of a dual monsoon system oxygen and hydrogen isotopic investigation of groundwater and river water samples from the southern indian peninsula was undertaken to characterise the isotopic nature of the near surface water sources and provide basic framework for future hydrological studies it is assumed that the shallow groundwater retains the isotopic signature of the local precipitation averaged over a few tens of years except in a few cases where the same gets modified by post precipitation evaporation and or recharge contribution from surface water bodies therefore isotopic character of the groundwater can in principle be used to determine the relative influence of the different vapour sources contributing to the local regional precipitation and to characterise the modifications before groundwater recharge in the present context vapour sources for two rainy seasons namely southwest sw and northeast ne monsoon are respectively the indian ocean arabian sea and the asian continental sources together with the bay of bengal this study shows that i the regions dominated by ne monsoon have distinctly depleted isotopic composition compared to those dominated by sw monsoon ii the 18o d regression line slope of 6 in the east coast region is lower than that expected for local precipitation suggesting secondary evaporation iii the orography of the western ghats hill ranges plays a significant role in controlling the isotopic distribution along the west coast region iv the low d excess values in most part of study area indicate secondary evaporation v the high d excess values over the deccan plateau region in the nw part of the study area suggest admixture of recycled moisture with the inflowing oceanic vapour

groundwater δ18o and δd from central indian peninsula influence of the arabian sea and the bay of bengal branches of the summer monsoon abstract results of oxygen and hydrogen isotopic investigations of shallow groundwater and river water samples from the central indian peninsula are reported the study was undertaken to isotopically characterise the near surface water sources and identify the influence of the two branches of the indian summer monsoon june september in this region the western part of the study area receives vapour flux largely from the arabian sea branch whereas the eastern part receives significant vapour flux from the bay of bengal branch no significant rainfall occurs in the study area during northeast winter monsoon period of october december or the remaining part of the year therefore the isotopic character of shallow groundwater from this region could be used to study the relative influence of the vapour sources from the arabian sea and the bay of bengal the study shows that i the northeast part receiving significant rainfall from the bay of bengal branch has a distinctly depleted isotopic composition 18 o 5 2 compared to areas receiving dominant rain from the arabian sea branch 18 o 1 1 ii in the west coastal belt the average 18 o in groundwater is close to the average 18 o of precipitation at bombay 1 4 1 1 but groundwater samples in the entire deccan plateau region show signatures of evaporative enrichment in the form of a low slope 6 5 of 18 o d regression line b low d excess 0 5 and c slightly enriched 18 o values 1 1 compared to those expected from the limited precipitation data from stations in maner basin approximately in the middle of the study area iii depleted ground waters along the central indian east coast could arise due to continental rainout of the arabian sea vapour source as the moisture laden monsoon winds crossover to the bay of bengal alternatively it is necessary to postulate that the surface waters of the bay of bengal contributing to inland vapour flux are significantly more depleted during the monsoon period than the known depletion of 1 it is also possible that both factors are operative

elemental dispersion and stable isotope fractionation during reactive fluid flow and fluid immiscibility in the bufa del diente aureole ne mexico evidence from radiographies and li b sr nd and pb isotope systematics the 31 6 0 3 ma old bufa del diente alkali syenite ne mexico intruded a sequence of cretaceous limestones with intercalated sub horizontal chert layers the cherts acted as aquifers that facilitated transport of brines and pegmatitic melts within the shallow level 1 kbar contact metamorphic aureole fluid driven reactions between chert and marble wallrock and the influx of late melts and various fluids gave rise to distinct chemical and isotopic signatures within the aquifer and across the zones of infiltration and fluid driven reaction aqueous brines of magmatic origin produced thick wollastonite mantles around the chert layers wollastonite formation occurred at the expense of limestone and chert and generated co2 this co2 induced fluid unmixing into an aqueous brine and a low density co2 rich fluid which was lost to the overlying marble where it oxidized organic matter and caused 13c and 18o shifts in a zone some 5 10 cm wide after wollastonite formation the chert aquifers were locally intruded by pegmatite veins carrying alkali feldspar quartz aegirine augite eudialyte zircon and apatite aqueous fluids that exsolved during crystallization of the pegmatite veins escaped along late cross fractures and migrated along the inner and outer borders of the wollastonite margins chemical dispersion patterns of u al na k p s fe and ree across the chert to marble boundary and its metasomatic rims are shown by autoradiography and neutron induced radiography scavenging of cations at mineralogical contacts and cation transport into the marbles occurred only on the mm to cm scale isotopic data for pb and sr across a simple metachert marble boundary and for pb sr nd b and li across a metachert pegmatite marble sequence demonstrate the following 1 the pb and sr isotopic signature of early fluids was buffered by the carbonate wallrock only late fluids shielded from wallrock interaction by a wollastonite mantle variably preserved a memory of their initial magmatic signature 2 since the nd isotope signature of marble and chert is bound to calcite and clay minerals systematic shifts to unradiogenic nd in marble reflect loss of carbonate bound nd as the wollastonite margin is approached nd in the wollastonite margin is dominated by nd originally bound to clay minerals the later emplacement of the pegmatite which carried the nd isotope signature of its alkali syenite source had little effect on the nd isotopic composition of the wollastonite rim 3 although the li and b isotopic compositions reflect the alkali syenite source they are also affected by isotopic fractionation and partitioning between melt fluid and solids

ree bearing minerals in a ti rich vein from the adamello contact aureole italy zirconolite aeschynite ce titanite and apatite have been found as minor or accessory minerals in a ti rich tio2 2 1 4 5 wt hydrothermal vein occurring in dolomite marbles at the contact with a tonalite intrusion of the tertiary adamello batholith northern italy the vein consists of four distinct mineral zones comprising from margin to center 1 forsterite calcite 2 pargasite calcite titanite sulfides 3 phlogopite calcite titanite sulfides and 4 titanian clinohumite spinel calcite sulfides zirconolite occurs in two vein zones only in the phlogopite zone it is invariably anhedral often corroded and exhibits complex chemical zonation patterns in the titanian clinohumite zone zirconolite is idiomorphic and characterized by a pronounced discontinous chemical zoning but shows no evidence of corrosion the considerable compositional variation observed for zirconolite in wt ree2o3 0 74 16 8 uo2 0 59 24 0 tho2 0 67 17 1 is due to the zoning and may be attributed to four major substitutions described by the exchange vectors 1 th u mg fe2 ca 1 ti 1 2 ree al ca 1 ti 1 3 ree fe2 nb ta ca 1 ti 1 4 hf zr 1

paleoclimatic investigations using isotopic signatures of the late pleistocene holocene groundwater of the stratified aquifers in kuwait abstract the study attempts to determine paleo recharge sources for two major aquifer units of kuwait namely kuwait group aquifer kga and dammam formation dfm were collected and analyzed for major ions and isotopes the obtained results of 14c ages indicated that the groundwater samples ranged from 31 9 ky to 3 9 ky in dfm and 23 3 ky to 0 8 ky in kga the variations in 18o signatures with respect to age reflected that there were two major sources of rainwater such as enriched southern indian ocean monsoon and the depleted northwesterly mediterranean vapor source the samples found to show variations during the three marine isotopic stages mis 1 3 heinrich events bolling allerod and dryas time periods in both aquifers a shift in the intertropical convergence zone itcz was witnessed in the groundwater of both aquifers from 7 8 ky to 4 9 ky the variation in the holocene climate is mainly due to the influence of tropospheric easterly jet governed by the swing in itcz as a result of holocene volcanism the mean 18o values of dfm samples 3 81 reflect depletion than kga samples 2 31 and the d excess values were 0 95 and 2 05 respectively thus it could be inferred that the dfm was predominantly recharged during late pleistocene period and it was in a relatively cooler climate than recharge environment of kga the study infers that kga was recharged between 26on and 26 8on latitudes and that of the dfm was noted to be recharged south west of kuwait in two different patches between 25 8on and 26 2on and 26 7on 27 4on latitudes during late pleistocene the kga was concluded to be recharged between 25 5on and 27 5on latitudes south of kuwait during holocene

ion microprobe survey of the grain scale oxygen isotope geochemistry of minerals in metamorphic rocks abstract the oxygen isotope compositions of calcite diopside dolomite forsterite garnet k feldspar kyanite plagioclase quartz and wollastonite were analyzed in suites of contact and regional metamorphic rocks using an ion microprobe spatial resolution was 10 m precision measured as the standard deviation of working standards averaged over the entire project was 0 13 0 18 for three carbonate standards and 0 11 0 12 for two silicate standards a total of 1176 analyses excluding standards were made of 73 minerals in 23 samples both intercrystalline and intracrystalline variability in 18 o is greater in contact than in regional metamorphic rocks of 27 minerals analyzed in contact metamorphosed rocks 70 exhibit statistically significant grain to grain variability in 18 o over areas 1 41 cm 2 with the largest range in silicates and carbonates in a single sample of 7 4 forsterite and 10 6 dolomite of 88 grains analyzed in two or more places in contact metamorphosed rocks 32 exhibit statistically significant intracrystalline variability in 18 o with the largest range in a single silicate and carbonate grain of 3 1 forsterite and 10 1 dolomite in contrast 44 of 45 minerals in regional metamorphic rocks exhibit significant grain to grain variability in 18 o over areas 1 17 cm 2 with the largest range in silicates and carbonates in a single sample of only 1 1 plagioclase and 0 9 calcite only 6 of 144 grains analyzed in two or more places in regional metamorphic rocks exhibit significant intracrystalline variability in 18 o with the largest range in a single silicate and carbonate grain of only 1 5 diopside and 0 7 calcite the difference in intercrystalline and intracrystalline variability in 18 o between contact and region metamorphic rocks is explained by the longer duration and slower reaction rates of regional metamorphism rather than to differences in temperature there is no significant difference in intercrystalline and intracrystalline variability in 18 o in regional metamorphic rocks among samples from the biotite garnet and kyanite zones calcite inclusions in forsterite and calcite and quartz inclusions in garnet either have 18 o that is statistically indistinguishable from 18 o of the same mineral occurring as nearby matrix grains or have statistically significant lower 18 o no reversed isotope fractionations were measured between coexisting mineral pairs minerals in individual samples however exhibit a wide range in the degree to which they attained and preserve oxygen isotope fractionations consistent with metamorphic temperatures recorded by mineral equilibria processes that account for grain scale departures from isotope exchange equilibrium include a overstepping of prograde mineral reactions b growth zoning in low diffusivity minerals c interaction of rocks with fluids at the peak of metamorphism and or during cooling d retrograde mineral reactions and e closed system isotope exchange between coexisting minerals during cooling this study provides new information about 1 the degree to which a variety of textural changes experienced by rocks during metamorphism are associated with changes in 18 o 2 oxygen isotope homogenization at the outcrop scale among contrasting lithologies 3 changes in 18 o with increasing grade of regional metamorphism and 4 time scales of metamorphic process

multi variable mixing cell model as a calibration and validation tool for hydrogeologic groundwater modeling abstract agricultural irrigation can make substantial changes to groundwater systems this study focuses on an arid area in northern nevada where 100 yr of extensive irrigation has occurred in particular the impacts of long term agricultural activities on the groundwater fluid balance geochemistry and potential changes to the water quality of a nearby river were investigated the study conducted in the fernley basin in western nevada utilized two different modeling approaches to construct a conceptual model that honors both the chemical and physical aspects of the basin groundwater flow regime a multi variable mixing cell model was constructed to represent the hydrochemical approach while a modflow model was constructed to represent the hydrogeological model a geochemical and isotopic analysis of the basin and its margin groundwater was conducted to identify all of the water sources that potentially flow through the basin and all water bodies within the basin those water bodies and sources were incorporated into a mixing cell model that allowed delineation of the general flow lines connecting the different water bodies within the basin with their sources the mixing cell model results were used to calibrate the hydrogeological model until a general agreement between the flow lines of both models was achieved the calibration of the hydrogeologic model included adjustments of the hydraulic conductivities and the use of various interpolation methods the study showed that parallel application of two different modeling approaches the mixing cell model along with a hydrogeological model provides an excellent tool for the validation of the conceptual model moreover it allowed calibration of the hydrogeologic model not only to the water heads as usually done in hydrogeological models but also to the general flow lines that honors the basin geochemistry

contact metamorphism of layered carbonate shale sequences in the oslo rift ii migration of isotopic and reaction fronts around cooling plutons abstract intrusion of felsic plutons of permian age into lower paleozoic shale carbonate sequences caused extensive contact metamorphism in the oslo rift oxygen and carbon isotope data from both carbonates and shales are presented to demonstrate that the progress of metamorphic reactions in the contact aureole around the drammen granite was to a large extent controlled by the infiltration of water rich fluids of a magmatic oxygen and with a carbon isotope signature highly integrated fluid fluxes were confined to shale rich lithologies massive limestones were relatively impermeable to fluid flow the spatial distribution of isotopic and reaction fronts in the aureole and coupled 18 o 13 c isotope variations of carbonates from interlayered shale carbonate units fits well to a 1 d transport model with fluid flow away from the intrusive contact whereas the same isotope variations in limestones containing thin shale intercalations do not the high fluid fluxes estimated from 1 d models 2000 m 3 m 2 require either focused flow of magmatic fluids in the study area or large scale convective flow possibly involving fluids of meteoric origin limited kinetic broadening of the oxygen isotopic front indicates fluid fluxes of 8 m s fluid flow must have persisted for 10 4 yr to have moved the oxygen front 1000 m from the intrusive contact simple 2 d transport models involving dominant fluid flow along aquifers or fractures and involving diffusion as well as advection explain most of the coupled 18 o 13 c trends reported for carbonates from contact aureoles

mineralogical evidence for fluid rock interaction accompanying prograde contact metamorphism of siliceous dolomites alta stock aureole utah usa contact metamorphism of siliceous dolomite in the southern part of agrees well with the q m tiff 3 4 10 7 mol m 2 determined by the metamorphic aureole of the alta stock utah usa produced numerical simulation of the temperature and 18 o depletion profiles the prograde isograd sequence talc tc tremolite tr forsterite preserved in the southern aureole the estimates of q m tiff for the fo and periclase per calcite cc dolomite do ge forsterite and tremolite zones have much greater uncertainty but othermometry and phase equilibria define a general prograde t may indicate that fluid flux was considerably lower in these zones x co2 path of decreasing x co2 with rising temperature for than in the periclase zone given the outward down temperature the dolomite high variance assemblages typify the aureole per subhorizontal flow geometry indicated by a variety of petrologic cc and fo cc do characterize the inner aureole per and geochemical and geothermometry evidence presented here and elsefo zones and tr do cc and tc do cc are where this decrease implies that fluid has leaked from the flow widespread in the outer aureole tr and tc zones low variance system between the periclase and tremolite zones assemblages are rare and the thickness of reaction zones coexisting reactant and product minerals at the isogradic reaction fronts are narrow tens of metres or less the mineral assemblages calculated progress of isograd reactions and the prograde t x co2 path all key words alta fluid flow infiltration marble mineralogical indicate that massive dolomite was infiltrated by significant fluxes of water rich fluids during prograde metamorphism and that the fluid flow was down temperature and laterally away from the igneous contact fluid infiltration continued through at least the initial retrograde cooling of the periclase zone down t fluid flow introduction is also consistent with the results of cc do geothermometry and both mineral assemblages and stable isotopes have been patterns of 18 o depletion in this area the close spatial association

implications of geochemical fronts in the notch peak contact metamorphic aureole utah usa abstract the geochemistry of the notch peak contact metamorphic aureole was examined to determine the dominant source of fluid attendant on metamorphism and to estimate fluid fluxes progressive metamorphism of calc silicate rocks is defined by phlogopite diopside and wollastonite isograds mineral assemblages at wollastonite and diopside grades indicate water rich conditions during decarbonation reactions near the intrusion the rocks are highly fractured in both the horizontal and the vertical direction the 18o values of most unmetamorphosed through diopside grade rocks range from 16 3 to 20 2 whereas in the wollastonite zone and near a pre intrusion fault the values approach the 9 5 value of the granitic stock coincident with the zone of18o depletion are zones of ba and zn enrichment consideration of solubilities of these elements in magmatic fluids and of published mineral water distribution coefficients indicates that these elements were advected from the magma model 18o profiles for up temperature flow of formation water assuming variable damko hler numbers and both static and variable thermal gradients fit poorly most data and do not reproduce the broadened front in the observed profile in contrast model profiles for radial one dimensional flow of magmatic water with variable damko hler number under static or variable thermal gradients fit the data well although the model isotopic front remains less distended that the one observed the integrated radial flux of magmatic water indicated by the position of the isotopic front is 1 8 107 mol m 2 additional broadening of the observed front and the scatter of the data suggest diffusion or hydrodynamic dispersion of oxygen regression of the data indicates an effective porosity of 12 in the inner aureole during fluid flow the porosity was largely fracture controlled and resulted from decarbonation sustained exsolution of water from the magma and up to 30 reaction produced volume loss in the high grade rocks the coincidence of the ba zn and 18o fronts suggests that bulk of the magmatic water flow was confined to the wollastontie zone the exception is the proximity of the fault where fluids emanating from an underlying part of the intrusion may also have flowed upward through lower grade rocks

effect of tortuosity on the stress dependent permeability of tight sandstones analytical modelling and experimentation abstract accurately modelling stress dependent permeability is of great significance to predicting the oil gas production of unconventional tight sandstone reservoirs with time dependent pressure depletion the classic theory indicates that the porosity exponents of the capillary tube model and the fracture model are 2 and 3 respectively however experimental results demonstrate that the value of the porosity exponent usually varies greatly the effect of the nonuniform distribution of tortuosity on stress dependent permeability is rarely studied assuming that tight sandstones with natural microfractures can be represented by a bundle of tortuous capillary tubes and parallel plate fractures a new stress dependent permeability model of tight sandstones is proposed based on fractal theory considering the tortuosity effect the research results show that the porosity exponents of the tortuous capillary tube model and the tortuous plate fracture model are 3 d t 2 and 2 d t respectively here d t is the tortuosity fractal dimension for the capillary tube model and the plate fracture model without tortuosity d t 1 their porosity exponents can be simplified to 2 and 3 respectively the tortuosity fractal dimension is one of the reasons causing the porosity exponent to deviate from the classic theoretical value the newly developed stress dependent permeability model is verified with experimental data determined using tight sandstone core samples from the yanchang formation in the ordos basin china the average error of the permeability prediction under different effective stresses is only 3 78 thus the newly developed model can accurately predict the stress dependent permeability of tight sandstones

formation and destruction of periclase by fluid flow in two contact aureoles periclase formed in steeply dipping marbles from the beinn an dubhaich aureole scotland and the silver star aureole montana by the reaction dolomite periclase calcite co2 equilibrium between rock and fluids with x co 2 1 requires that reaction was infiltration driven brucite pseudomorphs after periclase occur in the beinn an dubhaich aureole either as bed by bed replacement of dolomite or in a lens along the contact between dolomite and a pre metamorphic dike transport theory predicts that infiltration drove both periclase reaction and 18o depletion fronts which moved at significantly different velocities along the flow path the distributions of brucite and 18o depleted rocks are identical in surface exposures thus indicating upward flow time integrated flux q was 500 mol cm2 and the fluid source was magmatic because periclase and its hydrated equivalent brucite are unaltered to dolomite by retrograde reactions the exposure of brucite marbles accurately images the flow paths of peak metamorphic fluids in the silver star aureole brucite pseudomorphs after periclase exclusively occur in tabular bodies that are beds with elevated mg ca the spatial pattern of 18o depletion requires upward vertical fluid flow estimated prograde q 103 104 mol cm2 and the fluid source was magmatic low mg ca 18o depleted brucite free rocks pose a dilemma because the periclase reaction front should have traveled 18 times further through them than the isotope alteration front the dilemma is resolved by reaction textures that indicate periclase and brucite were destroyed in low mg ca rocks by infiltration driven retrograde carbonation reactions values of retrograde q were 103 104 mol cm2 brucite after periclase was preserved only in high mg ca layers where periclase developed in greater abundance the geometry of brucite marbles at silver star thus reflects the location of high mg ca beds rather than the geometry of fluid flow retrograde reactions must be considered before the mineralogical record of prograde fluid flow can correctly be interpreted in both aureoles fluid flow mineral reaction and isotope depletion were structurally controlled by bedding and lithologic contacts

isotopic characteristics of indian precipitation 1 hydrogen 2h 1h and oxygen 18o 16o isotopic ratios were measured in precipitation 900 samples collected from several locations in india during the period 2003 2006 12 locations in 2003 and 18 locations in 2004 2006 the amount of rainfall along with air temperature and humidity were also measured the meteoric water line developed for india using isotopic data of precipitation samples namely 2h 7 93 0 06 18o 9 94 0 51 n 272 r2 0 98 differs slightly from the global meteoric water line regional meteoric water lines were developed for several indian regions i e northern and southern regions of india western himalayas and found to be different from each other southern indian meteoric water line slope is 7 82 intercept or d excess is 10 23 northern indian meteoric water line slope is 8 15 intercept is 9 55 which is attributed to differences in their geographic and meteorological conditions and their associated atmospheric processes i e ambient temperature humidity organ and source of vapor masses the local meteoric water lines developed for a number of locations show wide variations in the slope and intercept these variations are due to different vapor sources such as the northeast ne monsoon that originates in the bay of bengal the southwest monsoon sw that originates in the arabian sea a mixture of ne and sw monsoons retreat of ne and sw monsoons and western disturbances that originate in the mediterranean sea the altitude effect in the isotopic composition of precipitation estimated for western himalayan region also varies from month to month

investigation of a dynamic seawater intrusion event using strontium isotopes 87sr 86sr summary a seawater intrusion experiment was carried out in a shallow coastal unconfined aquifer at skansehage denmark the aquifer consists of 6 10 m of postglacial holocene eolian and marine sands and gravels resting on pleistocene glacial sequence of tills and glacio fluviatile sediments on a basement of palaeocene danian limestone stable isotopes 18 o and 2 h strontium isotopes 87 sr 86 sr and the elements sr and cl were measured to delineate the mixing of seawater and groundwater in the shallow aquifer and to determine the contribution from different water sources along the flow paths the stable isotopes reflect recharge conditions and mixing between groundwater and seawater the 87 sr 86 sr isotope ratios are controlled by aquifer matrix chemistry the 87 sr 86 sr ratio distribution and sr content reveal a ternary mixing system in the shallow aquifer encompassing brackish seawater fresh shallow groundwater and deep groundwater from the underlying limestone aquifer as end members a mixing analysis is performed using the cl contents and the 87 sr 86 sr ratios the mixing analysis indicates a zone with leakage of deep groundwater from the limestone aquifer into the lower part of the shallow sandy aquifer through the pleistocene sedimentary sequence the upper part of the sandy aquifer is thoroughly dominated by mixing processes between infiltrating fresh groundwater and brackish seawater from isefjord prior to the intrusion experiment there appeared to be limited mixing between the upper and lower part of the water body in the shallow sandy aquifer the leakage of deep groundwater increased during the intrusion experiment as a result of the large abstraction of groundwater following the ceasing of the groundwater pumping the interface went from being vertical to being predominantly horizontal due to density flow as a consequence the deep groundwater from the limestone aquifer was pushed by the seawater into the upper part of the aquifer to mix with the upper fresh groundwater

fluid flow patterns and infiltration isograds in melilite marbles from the bufa del diente contact metamorphic aureole north east mexico in the inner aureole of the bufa del diente alkali syenite north east mexico thin calcareous argillite bands horizontally embedded in impure marbles acted as contact metamorphic aquifers for hypersaline brines of magmatic origin thick bedded marbles were largely impervious from 180 m up to the intrusion contact argillites were completely decarbonated resulting in melilite wollastonite phlogopite perovskite bearing parageneses in marbles this assemblage is confined to a narrow 7 12 m wide infiltration zone adjacent to the contact up to this distance calcite wollastonite diopside alkali feldspar titanite was stable indicating that the fluid evolution in these marbles was internally buffered brine infiltration from the metaargillite aquifer into the marbles occurred perpendicular to the marble metaargillite boundaries and was confined to a zone 4 6 cm wide above the boundaries this is documented by the three reactions cc di mel co2 1 cc kfs di h2o phl wo co2 2 cc ttn prv wo co2 3 melilites ak32 45gh13 32sm32 40 to ak52 72gh0 1sm28 48 occur as rims around diopsides and become continuously thicker towards the metaargillite beds fluid inclusion observations suggest that the infiltrating brine was hypersaline nacl kclcq 65 wt and that the reactions took place at the water rich side of the h2o co2 salts immiscibility field at about 600d c 2 3 and 660 to 680d c 1 at p 1200 bar and xco2 0 02 mass balance calculations show that the amount of brine infiltrated from the aquifer into the marble was very low and decreased continuously with increasing distance from the boundary the maximum width of brine infiltration was about 6 cm this confirms that brine flow was largely parallel to the aquifer not perpendicular to it the co2 produced by the decarbonation reactions probably escaped as an immiscible low density h2o co2 fluid of xco2 0 5 into overlying marble via grain edge flow the metaargillite marble boundary acted as a semipermeable membrane 6 cm in thickness keeping back the brine in the aquifer and losing the in situ produced low density co2 rich fluid

characterizing the pore structure of low permeability eocene liushagang formation reservoir rocks from beibuwan basin in northern south china sea abstract the hydrocarbon exploration from low permeability 50 nm mainly contribute to the total pore spaces for most samples with lower shale content mesopores 2 50 nm dominate the pore spaces of samples with higher shale content which leads to the relatively large surface area of these samples permeability of these low permeability rocks is positively related with average pore throat radius and negatively related with relative sorting coefficient while no such a close relationship exists between permeability and porosity fractal dimension has a negative relationship with average pore throat radius and permeability in summary this work comprehensively investigates the pore structure characteristics of low permeability liushagang formation reservoir rocks from beibuwan basin using multiple complementary approaches which helps to further understand the hydrocarbon migration and accumulation mechanism of these low permeability reservoirs

2d and 3d nanopore characterization of gas shale in longmaxi formation based on fib sem abstract studying complex pore structures is the key to understanding the mechanism of shale gas accumulation fib sem focused ion beam scanning electron microscope is the mainstream and effective instrument for imaging nanopores in gas shales based on this technology 2d and 3d characteristics of shale samples from lower silurian longmaxi formation in southern sichuan basin were investigated 2d experimental results show that the pores in shale are nanometer sized and the structure of those nanopores can be classified into three types organic pores inorganic pores and micro fractures among the three types organic pores are dominantly developed in the om organic matter with three patterns such as continuous distributed om om between clay minerals and om between pyrite particles and the size of organic pores range from 5 nm to 200 nm inveresly inorganic pores and micro fractures are less developed in the longmaxi shales 3d digital rocks were reconstructed and segmented by 600 continuous images by fib cutting and sem imaging simultaneously the pore size distribution and porosity can be calculated by this 3d digital core showing that its average value is 32 nm and porosity is 3 62 the 3d digital porosity is higher than its helium porosity which can be regarded as one important parameter for evaluation of shale gas reserves the 2d and 3d characterized results suggest that the nanometer sized pores in organic matter take up the fundamental storage space for the longmaxi shale these characteristics have contributed to the preservation of shale gas in this complex tectonic area

helium 4 characteristics of groundwaters from central australia comparative chronology with chlorine 36 and carbon 14 dating techniques summary helium isotope and concentration characteristics were determined for a suite of groundwater samples from the amadeus basin in central australia two study areas include a wellfield south of alice springs and the dune plains and mututjulu aquifers near uluru measurements of 36cl cl and 14c on the same sample suite enable us to assess the relative applicability of the three groundwater chronometers over a range of anticipated groundwater residence times ages and to investigate possible causes of discordant ages derived from the different groundwater dating techniques results from the analyses of 39 groundwater samples reveal helium 4 4he concentrations that range from 0 80 to 98 8 10 7 cm3 stp g 1 h2o in the alice springs samples and from 0 47 to 65 6 10 7 cm3 stp g 1 h2o in the uluru samples 4he concentrations yield uncorrected groundwater residence times i e time since recharge of between modern to 2500 ka near alice springs and modern to 1600 ka near uluru assuming an effective porosity of 20 and uranium and thorium contents of 1 7 and 6 1 ppm respectively 36cl cl ratios on the same samples range from 93 to 158 10 15 near alice springs and from 80 to 335 10 15 near uluru representing groundwater residence times near alice springs from modern to 200 ka and from modern to 300 ka near uluru percent modern carbon pmc on the same samples ranged from 64 9 to 12 5 pmc near alice springs and from 93 5 to 30 ka for the amadeus basin groundwater samples the 4he method uncorrected over estimates groundwater residence time compared to 36cl and 14c techniques this implies the presence of an extraneous he component or basal flux of he j0 to reconcile groundwater 4he and 14c residence times it is necessary to adopt j0 values between 0 and 30 10 8 cm3 stp he cm 2 a 1 which supplements in situ produced he within the aquifer adoption of j0 values over this range lowers 4he residence times relative to 36cl and produces closer agreement between the 4he and 14c chronometers the extraneous he component basal flux in amadeus basin samples is dominated by radiogenic crustal 4he without a detectable amount of mantle derived 3he we conclude that the stable tectonic regime albeit with the presence of major faults within the basin inhibits the input of mantle volatiles to the groundwater system so that in this region diffusion is the dominant transport mechanism for he in the crust

stable isotope evidence of heterogeneous fluid infiltration at the ubehebe peak contact aureole death valley national park california stable isotope ratios of carbon and oxygen are used to define quantitatively the effects of magmatic fluid infiltration in marbles contact meta morphosed by the 173 ma ubehebe peak quartz monzonite death valley national park california in previous studies of fluid infiltration quantitative interpretation of aureole wide isotopic data has been difficult due to small data sets for this study sampling strategies were developed to obtain a data set that was large and unbiased enough to be statistically representative of the carbonates north of the ubehebe peak intrusion a total of 357 samples of marble were analyzed for bulk carbonate isotopic ratios separate analyses of coexisting calcite and dolomite were also obtained for an additional 31 samples unmetamorphosed samples 1900 3000 m from the intrusion have 18 o permil smow values of 25 5 0 8 1 and 13 c permil pdb values of 0 4 0 6 1 samples in the tremolite zone 750 1900 m have 18 o values ranging from 19 4 to 27 7 permil with a median value of 25 2 permil and 13 c ranges from 5 1 to 0 5 permil with a median value of 0 9 permil forsterite zone samples 0 750 m have isotopic ratios shifted to values as low as 11 1 permil 18 o and 9 1 permil 13 c despite this shift most forsterite zone samples retain sedimentary isotopic compositions with median 18 o values of 25 0 permil and 13c values of 1 2 permil 18o values for igneous minerals show no evidence for interaction with heated meteoric or metamorphic fluids the shifts in isotopic compositions within the marbles are interpreted to be the result of magmatic infiltration the effects of this infiltration were quantified by identifying samples with isotopic alteration that can only be attributed to infiltration the results show that magmatic fluid infiltration was limited in extent and very heterogeneous there is no evidence for infiltration of isotopically reactive fluids beyond 850 m from the intrusive contact and within this 850 m zone only 28 percent of the samples have been infiltratively altered with respect to 18 o and 20 percent are depleted in 13 c compositions the isotopic data when evaluated in conjunction with geostatistical and petrologic data indicate that the geometry of the hydrothermal flow system was mainly vertical and away from the pluton infiltration was restricted to large nearly vertical tube like zones of increased permeability these higher permeability zones likely reflect an initial heterogeneity of the host rocks and show no significant evidence for reaction enhanced permeability given the heterogeneity of the system and a lack of knowledge about many basic parameters controlling fluid infiltration it is shown that the best method of calculating the amount and composition of the infiltrating fluid may be a mass balance approach fluid rock ratio the application of mass balance models is discussed and shown to be valid only under limited conditions since infiltration at ubehebe peak was largely vertical the observed isotope alteration patterns represent an infiltration side and not a front because this precludes the use of traditional mass balance calculations a new infiltration side inside model is proposed that allows the isotopic data to be evaluated the inside model uses the ratio of the areal amounts of infiltrative alteration to calculate a fluid composi tion fluid amounts cannot be obtained from this model results for the ubehebe

isotopic fingerprints of paleoclimates during the last 30 000 years in deep confined groundwaters of southern india isotopic and geochemical evidence of paleoclimates especially for the last glaciation has been obtained from deep confined groundwaters of southern india the 13c 18o chloride and deuterium analyses of groundwaters show distinct excursions inferred to be related to climatic variations the arid climatic episode associated with the last glaciation 18 000 2000 yr b p is conspicuously identified by signatures of relatively enriched 13c 10 to 12 pdb and 18o 5 3 to 4 8 smow values and high chloride concentration 80 to 160 mg l the transition from an arid to humid period ca 12 000 8000 yr b p is shown by a decreasing trend in the 13c 9 5 to 17 and 18o 4 5 to 6 3 contents of groundwaters the late holocene since 4000 yr b p marked by a more humid but unstable climate is identified by further depletion of 13c 13 to 20 and 18o 5 2 to 6 3 similar variation between 18o and chloride values in confined groundwaters further demonstrates two distinct climatic excursions arid and humid governed by the amount effect this is the first time that isotopic and geochemical signatures related to changing paleoclimates have been identified in the confined groundwaters of the southern indian landmass

stable isotope ratios in meteoric recharge and groundwater at mt vulture volcano southern italy summary a rain gauge network consisting of five sites located at different altitudes ranging from 320 to 1285 m a s l was installed at mt vulture volcano southern italy rain water samples were collected monthly over a two year period and their isotopic composition 18o and d was analyzed during the same period circulating groundwater was sampled from 24 springs and wells distributed throughout the study area monthly isotopic composition values were used to determine the local meteoric water line lmwl its slope is slightly lower than the relationship defined by longinelli and selmo longinelli a selmo e 2003 isotopic composition of precipitation in italy a first overall map j hydrol 270 75 88 for southern italy the groundwater samples analyzed were distributed essentially along the lmwl the weighted local meteoric water line wlmwl defined through the mean values weighted by the rainfall amount however may define in a short range the meteoric end member in the local hydrological cycle more precisely since most of the groundwater sampling locations do not show seasonal variations in their stable isotope values the flow system appears to be relatively homogeneous the mean altitude of the recharge by rainfall infiltration was estimated on the basis of the local vertical isotopic gradient 18o a few springs which show anomalous isotopic values reveal more regional circulation systems associated with tectonic structures responsible for the ascent of deeper water

numerical simulation of unsaturated flow along preferential pathways implications for the use of mass balance calculations for isotope storm hydrograph separation an objective common to many watershed studies is to separate storm hydrographs into two components water that was present in the watershed prior to a storm event soil moisture and groundwater and water which fell on the watershed during the storm to use this approach a number of assumptions must be made including that the composition of water in the soil moisture and groundwater reservoirs are constant and known the objective of this paper is to show that in settings where flow and transport are dominated by preferential pathways for flow steady state mass balance calculations for quantitative hydrograph separation may be in error we present field data from a site where flow and transport are dominated by preferential pathways relict fractures in saprolite of sedimentary rocks which indicate that the 18o content of the water in the unsaturated and shallow saturated zones is not constant over the course of a storm event we use a numerical model to further explore the interactions between the fractures and surrounding matrix both the field data and modeling results indicate that the 18o of the previous storm event s has a strong influence on water in the fractures on the time scale of a storm event only the water in the matrix immediately surrounding the fracture mixes with water in the fracture while the bulk of the matrix is isolated from fracture flow the spatial and temporal heterogeneity of the 18o in the subsurface and the isolation of the most of the matrix water from flow in fractures make the measurement of a singular 18o value for subsurface reservoirs problematic and the assumption of a constant value doubtful since most near surface geologic materials have preferential flow paths we suggest that quantitative hydrograph separation using mass balance techniques is not possible in most situations future field and modeling investigations using the approach outlined here could be designed to explore the important temporal and spatial scales of variability in watersheds and lead to a more quantitative approach to storm hydrograph separation

calcite inclusions in forsterite forsterite in metamorphosed siliceous dolomites commonly contains calcite inclusions that are significantly more magnesian than even the most magnesian calcite grains in the matrix of the same rock calcite inclusions in forsterite from dolomite bearing rocks therefore have an unexploited potential for providing more accurate estimates of the peak t of metamorphism than do matrix calcite grains some consequences for estimating fluid pressure and for the development of models of heat and fluid transport during contact metamorphism are reviewed measured compositions of calcite inclusions in forsterite from five contact aureoles indicate that significant growth of forsterite grains continues over a 50 200 c range in t after the initial nucleation and growth of the mineral during heterogeneous mineral fluid reaction the continued growth may occur by an annealing mechanism driven by reduction in interfacial free energy

geochemical and isotopic investigations on groundwater residence time and flow in the independence basin mexico abstract the independence basin in the semi arid guanajuato state of central mexico is facing serious groundwater resources deficiency due to an increasing demand linked to a rapid population growth and agricultural development this problem is aggravated by an inadequate evaluation of groundwater resources in the region geochemistry and isotopic tracers were used in order to investigate the groundwater flow system and estimate the groundwater residence time the groundwater is characterized by low salinity with some exceptions associated to a contribution of more saline groundwater from deep formations the predominant reactions are co 2 gas dissolution carbonate dissolution albite weathering kaolinite and chalcedony precipitation six principal hydrochemical zones were recognized which provided information on plausible recharge sources and groundwater chemical evolution the 14 c concentration varies between 19 and 94 pmc the high 14 c values indicating recent recharge are observed at the basin margins and a trend to lower 14 c values is observed along the modern groundwater flow paths the groundwater residence time according to radiocarbon estimations ranges between recent and 11 ka the residence time distribution matches the regional important discharge zones west in the basin center from dolores hidalgo and southwest from doctor mora hydrochemical tracers are in general agreement with the predeveloped and current hydraulic head configuration however show some inconsistencies with the predeveloped head in the downgradient areas which means that the impact by gradually increasing groundwater extraction during the last decades is reflected on radiocarbon age distribution geochemical evidences imply that the recharge input from the northern basin area is insignificant

formation of wollastonite by chemically reactive fluid flow during contact metamorphism mt morrison pendant sierra nevada california usa quartz calcite sandstones experienced the reaction calcite introduction quartz wollastonite co2 during prograde contact metaflow of chemically reactive fluid may control the minmorphism at p 1500 bars and t 560 c rocks were in eralogy stable isotope composition and trace element equilibrium during reaction with a co2 h2o fluid with xco2 chemistry of rocks during contact metamorphism e g 0 14 the transition from calcite bearing wollastonite free to labotka et al 1988 jamtveit et al 1992a 1992b nabelek wollastonite bearing calcite free rocks across the wollastonite isograd labotka 1993 bowman et al 1994 roselle et al is only several millimeters wide the wollastonite forming reaction 1999 a number of aspects of metamorphic fluid flow was driven by infiltration of quartz calcite sandstone by chemically however remain the subject of debate including the reactive h2o rich fluids and the distribution of wollastonite directly direction of flow labotka et al 1988 ferry dipple images the flow paths of reactive fluids during metamorphism the 1992 ferry 1995a hanson 1995a whether numerical mapped distribution of wollastonite and modeling of an o isotope models that assume uniform rock properties adequately profile across a lithologic contact indicate that the principal direction predict the geometry of fluid flow in aureoles that contain of flow was layer parallel directed upward with any cross layer a variety of anisotropic structural features hanson 1992 component of flow 0 1 of the layer parallel component fluid 1995b cook et al 1997 and the degree to which local flow was channeled at a scale of 1 100 m by pre metamorphic mineral fluid equilibrium is attained lasaga rye dikes thrust and strike slip faults fold hinges bedding and 1993 bolton et al 1999 lasaga et al 2000 these and stratigraphic contacts limits on the amount of fluid based on related questions were addressed in an investigation of minimum and maximum estimates for the displacement of the contact metamorphism in the mt morrison pendant wollastonite reaction front from the fluid source are 0 7 1 9 eastern sierra nevada california the location is an 10 cm fluid cm rock the sharpness of the wollastonite isograd exceptional site for the study of metamorphic fluid flow the consistency of mineral thermobarometry the uniform measured for several reasons first the mt morrison sandstone o o fractionations between quartz and calcite and model the focus of this study is ideal for application of concalculations all argue for a close approach to local mineral fluid tinuum models of coupled fluid flow and reaction because equilibrium during the wollastonite forming reaction it is unusually homogeneous in mineralogy and texture

titanian clinohumite and geikielite in marbles from the bergell contact aureole the assemblage titanian clinohumite forsterite spinel calcite is widespread in marbles from the eastern bergell contact aureole switzerland italy the bergell titanian clinohumites vary considerably in composition tio2 0 19 to 2 05 wt f 2 2 to 3 4 wt electron microprobe analyses show that the titanian clinohumites contain less than detectable amounts of co cu ni zn al cr and cl no trace of ferric iron could be detected by moessbauer spectroscopy moreover the moessbauer spectra indicate that fe2 occurs only in one of the five octahedral positions in the crystal structure of the studied titanian clinohumite under the conditions of the contact metamorphism 600 650 c 3 kb total pressure the compositional variation along the exchange vector tio2m 1 oh f 2 takes place at constantxoh which is fixed by the pore fluid titanian clinohumite sometimes contains geikielite inclusions which strongly fractionate fe and mn relative to titanian clinohumite the geikielites from the bergell marbles are poor in cr2o3 fe2o3 and mno and thus different from those found in carbonatites kimberlites and serpentinized ultramafic rocks

determining the direction of contact metamorphic fluid flow an assessment of mineralogical and stable isotope criteria one dimensional fluid advection dispersion models predict differences in the patterns of mineralogical and oxygen isotope resetting during up and down temperature metamorphic fluid flow that may in theory be used to determine the fluid flow direction with respect to the palaeotemperature gradient under equilibrium conditions down temperature fluid flow is predicted to produce sharp reaction fronts that separate rocks with isobarically divariant mineral assemblages in contrast up temperature fluid flow may produce extensive zones of isobarically univariant mineral assemblages without sharp reaction fronts however during contact metamorphism mineral reaction rates are probably relatively slow compared with fluid velocities and distended reaction fronts may also form during down temperature fluid flow in addition uncertainties in the timing of fluid flow with respect to the thermal peak of metamorphism and the increase in the variance of mineral assemblages due to solid solutions introduce uncertainties in determining fluid flow directions equilibrium down temperature flow of magmatic fluids in contact aureoles is also predicted to produce sharp 18o fronts whereas up temperature flow of fluids derived by metamorphic devolatilization may produce gradational 18o vs distance profiles however if fluids are channelled significant kinematic dispersion occurs or isotopic equilibrium is not maintained the patterns of isotopic resetting may be difficult to interpret the one dimensional models provide a framework in which to study fluid rock interaction however when some of the complexities inherent in fluid flow systems are taken into account they may not uniquely distinguish between up and down temperature fluid flow it is probably not possible to determine the fluid flow direction using any single criterion and a range of data is required

ionic and isotopic ratios for identification of salinity sources and missing data in the gaza aquifer abstract groundwater is the only source of fresh water in the gaza strip however it is severely polluted and requires immediate effort to improve its quality and increase its usable quantity intensive exploitation of groundwater in the gaza strip over the past 40 years has disturbed the natural equilibrium between fresh and saline water and has resulted in increased salinity in most areas salinization in the coastal aquifer may be caused by a single process or a combination of different processes including seawater intrusion upconing of brines from the deeper parts of the aquifer flow of saline water from the adjacent eocene aquifer return flow from irrigation water and leakage of wastewater each of these sources is characterized by a distinguishable chemistry and well known isotopic ratios in this paper na cl so4 cl br cl ca hco3 so4 and mg ca ionic ratios were used to distinguish different salinization sources 11b and 87sr 86sr isotopic composition were also included in the model to study their importance in this monitoring task the task of monitoring and the associated decision making process are characterized by a high degree of uncertainty with respect to input data and accuracy of models for this reason probabilistic expert systems and more specifically bayesian belief networks bbns are used to identify salinization origins the bbn model incorporates the theoretical background of salinity sources area specific monitoring data that are characteristically incomplete in their coverage expert judgment and common sense reasoning to produce a geographic distribution for the most probable sources of salinization the model is also designed to show areas where additional data on chemical and isotopic parameters are needed

delineation of the coastal aquifer of israel based on repetitive analysis of 14c and tritium summary repetitive sampling for radioactive isotope analysis can be used to more accurately estimate the age of groundwater groundwater was sampled in wells along the coastal aquifer of israel for tritium 14 c and 13 c analysis in the 1970s as well as the 1990s examination of the tritium values from two sampling periods on the tritium bomb curve enabled us to overcome the ambiguity of tritium data in which a single value could yield two ages and allowed a better age estimate therefore repetitive sampling over an extended time interval was found to be effective in assisting calculations of groundwater ages through the use of the tritium curve over the 20 year period the age obtained by repetitive sampling can be used to determine the dilution factor q of the initial 14 c value in the aquifer this corrected initial value can thus be utilized for better age determination of older samples in the deeper sub aquifers in most cases based on the presence of detectable levels of tritium throughout most of the aquifer the groundwater in the coastal aquifer was determined to contain a young component with a transit time of less than forty years however the 14 c levels of most of the same groundwater samples were found to be lower than atmospheric levels 34 102 vs 100 pmc probably due to water rock interactions rather than decay due to old age some older waters exist in the lower sub aquifers of the deeper wells 120 140 m where both lower 14 c values 42 69 pmc and very low levels of tritium were found 0 1 0 7 tu

morphology genesis and distribution of nanometer scale pores in siliceous mudstones of the mississippian barnett shale research on mudrock attributes has increased dramatically since shale gas systems have become commercial hydrocarbon production targets one of the most significant research questions now being asked focuses on the nature of the pore system in these mudrocks our work on siliceous mudstones from the mississippian barnett shale of the fort worth basin texas shows that the pores in these rocks are dominantly nanometer in scale nanopores we used scanning electron microscopy to characterize barnett pores from a number of cores and have imaged pores as small as 5 nm key to our success in imaging these nanopores is the use of ar ion beam milling this methodology provides flat surfaces that lack topography related to differential hardness and are fundamental for high magnification imaging nanopores are observed in three main modes of occurrence most pores are found in grains of organic matter as intraparticle pores many of these grains contain hundreds of pores intraparticle organic nanopores most commonly have irregular bubblelike elliptical cross sections and range between 5 and 750 nm with the median nanopore size for all grains being approximately 100 nm internal porosities of up to 20 2 have been measured for whole grains of organic matter based on point count data from scanning electron microscopy analysis these nanopores in the organic matter are the predominant pore type in the barnett mudstones and they are related to thermal maturation nanopores are also found in bedding parallel wispy organic rich laminae as intraparticle pores in organic grains and as interparticle pores between organic matter but this mode is not common although less abundant nanopores are also locally present in fine grained matrix areas unassociated with organic matter and as nano to microintercrystalline pores in pyrite framboids intraparticle organic nanopores and pyrite framboid intercrystalline pores contribute to gas storage in barnett mudstones we postulate that permeability pathways within the barnett mudstones are along bedding parallel layers of organic matter or a mesh network of organic matter flakes because this material contains the most pores

application of isotopic tracers as a tool for understanding hydrodynamic behavior of the highly exploited diass aquifer system senegal summary the diass horst aquifer system located 50 km east of dakar senegal is exploited in two main aquifers covered by a sandy superficial aquifer the confined unconfined palaeocene karstic limestone and the confined maastrichtian sandstone aquifer underneath this system has experienced intensive groundwater abstraction during the last 50 years to supply increasing water demand agricultural and industrial needs the high abstraction rate from 1989 to 2009 about 109 000 m 3 d has caused a continuous groundwater level decline up to 30 m a modification of the groundwater flow and salinization in parts of the aquifers the objective of the study is to improve our understanding of the system functioning with regards to high pumping identify the geochemical reactions that take place in the system infer origin and timing of recharge by using mainly stable 18 o 2 h 13 c and radioactive 3 h and 14 c isotopes water types defined in the piper diagram vary in order of abundance from ca hco 3 65 ca na cl 20 na hco 3 3 and na cl 12 values of 18 o and 2 h for the superficial aquifer range between 5 8 and 4 2 and between 42 and 31 respectively for the palaeocene aquifer they range from 5 8 to 5 0 and from 38 to 31 respectively values in the maastrichtian aquifer are between 5 9 and 4 3 for 18 o and 38 to 26 for 2 h plotted against the conventional 18 o vs 2 h diagram data from the upper aquifer exhibit a dispersed distribution with respect to isotopic fractionation while those of the palaeocene and maastrichtian aquifers are aligned parallel and slightly below or on the global meteoric water line gmwl evidencing ancient waters which had evaporated during infiltration the low tritium generally 14 c 0 7 57 2 pmc contents indicate predominance of older water being recharged during the pleistocene and holocene periods however few boreholes which exhibit high tritium 1 2 4 3 tu and 14 c 65 7 70 8 pmc values indicate some mixture with recent water likely through faulting and vertical drainage from the upper to deeper aquifers as well as lateral flow along flow paths to the piezometric depressions created by pumping