applications of geophysical techniques to improve a groundwater conceptual model in an outcrop area of the guarani aquifer system in brazil the comprehension of groundwater flow depends on the knowledge of hydrogeological features and water cycle especially the recharge process geophysical techniques can provide useful hydrogeological information e g water table and base aquifer toward improving the water balance in groundwater models this study conducted in an outcrop area of the guarani aquifer system gas in sao paulo state brazil applied ground penetrating radar gpr and geoelectrical techniques for structuring a conceptual groundwater model a gpr with 200 mhz antenna 4 vertical electrical soundings ves with schlumberger array and 12 electrical resistivity tomographies ert with dipole dipole array were used geophysical techniques soil samples and water level from monitoring wells helped the definition of two different hydraulic conductivity regions and a flux boundary condition for the groundwater flow model

the effect of hydrogeological conditions on variability and dynamic of groundwater recharge in a carbonate aquifer at local scale summary groundwater recharge in fractured karstic aquifers is particularly difficult to quantify due to the rock mass s heterogeneity and complexity that include preferential flow paths along karst conduits the present study s major goals were to assess how the changes in lithology as well as the fractured karst systems influence the flow mechanism in the unsaturated zone and to define the spatial variation of the groundwater recharge at local scale the study area is located within the fractured carbonate western mountain aquifer yarkon taninim west of the city of jerusalem at the ein karem ek production well field field monitoring included groundwater level observations in nine locations in the study area during years 1990 2014 the measured groundwater level series were analyzed with the aid of one dimensional dual permeability numerical model of water flow in variably saturated fractured porous media which was calibrated and used to estimate groundwater recharge at nine locations the recharge values exhibit significant spatial and temporal variation with mean and standard deviation values of 216 and 113 mm year respectively based on simulations relationships were established between precipitation and groundwater recharge in each of the nine studied sites and compared with similar ones obtained in earlier regional studies simulations show that fast and slow flow paths conditions also influence annual cumulative groundwater recharge dynamic in areas where fast flow paths exist most of the groundwater recharge occurs during the rainy season 60 80 from the total recharge for the tested years while in locations with slow flow path conditions the recharge rate stays relatively constant with a close to linear pattern and continues during summer

petrofabrics of high pressure rocks exhumed at the slab mantle interface from the point of no return in a subduction zone sivrihisar turkey the highest pressure recorded by metamorphic rocks exhumed from oceanic subduction zones is 2 5 gpa corresponding to the maximum decoupling depth mdd 80 10 km identified in active subduction zones beyond the mdd the point of no return exhumation is unlikely the sivrihisar massif turkey is a coherent terrane of lawsonite eclogite and blueschist facies rocks in which assemblages and fabrics record p t fluid deformation conditions during exhumation from 80 to 45 km crystallographic fabrics and other features of high pressure metasedimentary and metabasaltic rocks record transitions during exhumation in quartzite microstructures and crystallographic fabrics record deformation in the dislocation creep regime including dynamic recrystallization during decompression and a transition from prism slip to activation of rhomb and basal slip that may be related to a decrease in water fugacity during decompression 2 5 to 1 5 gpa phengite lawsonite and omphacite or glaucophane in quartzite and metabasalt remained stable during deformation and omphacite developed an l type crystallographic fabric in marble aragonite developed columnar textures with strong crystallographic fabrics that persisted during partial to complete dynamic recrystallization that was likely achieved in the stability field of aragonite p 1 2 gpa results of kinematic vorticity analysis based on lawsonite shape fabrics are consistent with shear criteria in quartzite and metabasalt and indicate a large component of coaxial deformation in the exhuming channel beneath a simple shear dominated interface this large coaxial component may have multiplied the exhuming power of the subduction channel and forced deeply subducted rocks to flow back from the point of no return

a potential method to confirm the previous existence of lawsonite in eclogite the mass imbalance of sr and lrees in multistage epidote ganghe dabie uhp terrane lawsonite is an important hydrous mineral that is stable at low temperature lt and high to ultrahigh pressure hp uhp conditions in subducted slabs the occurrence absence of lawsonite in eclogite is a significant constraint for the construction of the metamorphic tectonic and fluid melt evolution histories of an hp uhp terrane however lawsonite is very rarely preserved in natural eclogites and accurate judgment of its former existence is a significant challenge for petrologists at present whether lawsonite has ever existed in lawsonite absent eclogite is mainly judged by i pseudomorphs after lawsonite and ii phase equilibria modelling in this study major element and trace element distributions in multistage minerals were examined in the ganghe lawsonite absent uhp eclogite in the dabie uhp terrane eastern china this work demonstrates that the whole rock sr and light rare earth elements lrees are mainly dominated by epidote other minerals garnet omphacite quartz kyanite barroisite phengite and accessory minerals play a very limited role in the sr and lrees budgets two stages of epidote which have noticeably different sr and lrees contents were recognized in the eclogite i epidote porphyroblasts ep p core which are suspected to be the pseudomorphic mineral after lawsonite contain significantly high sr 7200 10 300 ppm and lrees 160 1300 ppm for la ii an earlier stage epidote ep in core occurs as inclusions in matrix omphacite or in omphacite inclusions in the suspected pseudomorphic minerals after lawsonite spmal this early epidote has significantly lower sr 990 1890 ppm average 1495 ppm n 17 and lrees contents 60 110 ppm for la average 91 ppm n 17 all of the existing early stage minerals predating the spmal have very low contents of sr and lrees and the total amounts of these elements in the early stage minerals do not balance those in the spmal this indicates that a missing ca al sr and lree rich mineral which was previously in equilibrium with the early stage minerals likely existed in the ganghe eclogite on the basis of the mineral geochemistry and phase equilibria modelling we confirm that the missing mineral cannot be anything but lawsonite this study indicates that examining the mass im balance of sr and lrees between multistage hp uhp epidote can be used as a potential method to confirm the previous existence of lawsonite in lawsonite absent eclogite

tectonics of the syros blueschists cyclades greece from subduction to aegean extension 1 on syros high pressure metamorphism affects a lithological pile that is composed of from base to top 1 the komito vari granitic basement 2 a margin sedimentary sequence that is predominantly made of marbles and schists the pyrgos and kastri units and 3 the kambos metaophiolitic melange the tectonic history occurred in three main stages during the first stage in the mid eocene the kambos oceanic unit was thrust southward on top of the sedimentary pile top to the south southwest ductile senses of shear are synchronous with prograde high pressure metamorphism and associated with this thrusting event the second stage corresponds to a top to the northeast ductile shear that affects the whole metamorphic pile and is synchronous with the metamorphic retrogression from eclogite to greenschist facies however the kambos oceanic unit remained partly undeformed as shown by significant volumes containing undeformed lawsonite pseudomorphs no major extensional detachment related to this exhumation event outcrops on the island the localized semibrittle to brittle deformation of the third stage is associated with the postmetamorphic development of 1 a ramp flat extensional system at the island scale whose southward minimum displacement is estimated at approximately 7 km and 2 two sets of steeply dipping strike slip faults with a normal component trending either east west or around north south indicating that the mean stretching and shortening directions are trending nne ssw and ese wnw respectively this sequence of major tectonic events and their relationship to metamorphism are interpreted within the framework of the subduction of the pindos ocean and then of the adria continental passive margin

groundwater flow modeling of two levels perched karstic leaking aquifers as a tool for estimating recharge and hydraulic parameters summary perched springs in nature emerge from aquifers laying on aquitards within the unsaturated zone some of which emerge one above the other a finite element model was introduced using the feflow code for simulating the groundwater flow regime in each of these aquifers for quantifying the fraction of rain that recharges the aquifers and for estimating the hydrogeological parameters of the aquifers and aquitards many of the perched springs in israel are found in the judea group aquifer a stratified carbonate rock unit characterised by a well developed karst system the batir and jamia springs exemplifies such a system where batir is the upper spring discharging at the contact between aminadav and moza formations and jamia is the lower one discharging at the contact between kesalon and sorek formations the 25 year long measured spring s hydrographs were used to calibrate the spring s coefficients the hydraulic conductivities of the different layers the karst features and the yearly amount of rain recharging the spring

blueschist metamorphism in an active subduction zone the high pressure low temperature metamorphic rocks known as blueschists have long been considered to form in subduction zones where the descent of a relatively cold slab leads to the occurrence of unusually low temperatures at mantle pressures until now however the link between blueschist facies rocks and subduction zones has been indirect relying on a spatial association of blueschists with old subduction complexes and estimates of the geothermal gradients likely to exist in subduction zones here we strengthen this link by reporting the discovery of blueschist facies minerals lawsonite aragonite sodic pyroxene and blue amphibole in clasts from a serpentinite seamount in the forearc of the active mariana subduction zone the metamorphic conditions estimated from the mineral compositions are 150 250 c and 5 6 kbar 16 20 km depth the rocks must have been entrained in rising serpentine mud diapirs and extruded from mud volcanoes onto the sea floor further study of these rocks may provide new insight into the tectonics of trench forearc systems and in particular the processes by which blueschist facies clasts come to be associated with forearc sediments in ancient subduction complexes

lawsonite composition and zoning as tracers of subduction processes a global review abstract lawsonite is an abundant hydrous mineral in oceanic crust sediments and metasomatic rocks at depths of 45 to 300 km in most subduction zones but it is rarely preserved in the geologic record because it commonly transforms to epidote and other minerals during prograde or retrograde metamorphism owing to the significance of lawsonite for water and element cycling in subduction zones occurrences of fresh lawsonite in blueschist and more rarely eclogite provide important opportunities to determine lawsonite composition zoning and inclusion suites and to use this information to reconstruct reaction history during subduction and exhumation in this review we use new and published data to document lawsonite composition in eight of the nine known lawsonite eclogite localities in which fresh lawsonite coexists with garnet omphacite in the rock matrix as well as the composition of lawsonite inclusions in six of seven known sites in which lawsonite occurs only as inclusions in garnet in eclogite facies rocks that lack matrix lawsonite as lawsonite blueschist is much more common than lawsonite eclogite we survey the composition of lawsonite in representative localities of blueschist including blueschist associated with eclogite lawsonite bearing epidote bearing and blueschist not associated with eclogite at current exposure levels included in this review are metabasaltic rocks silica and carbonate rich metasedimentary rocks metasomatic rocks and lawsonite rich veins this dataset demonstrates that lawsonite composition is a sensitive indicator of reaction history during subduction and exhumation and specifically of fluid rock interaction with implications for element cycling in subduction zones furthermore most exhumed lawsonite eclogite records slab surface conditions that correspond to the location where the slab mantle interface transitions from decoupled to coupled and therefore provides key insights into the thermal history and dynamics of subduction zones

effects of karst and geological structure on groundwater flow the case of yarqon taninim aquifer israel summary this study demonstrates the significant influences of the geological structure especially folding and lithology and the karst system on groundwater flow regime folds divert groundwater flow from the general hydraulic gradient marly layers sustain several perched sub aquifers above the regional aquifer and karstification increases the hydraulic conductivity by several orders of magnitude these phenomena are quantitatively demonstrated within the yarqon taninim yt basin israel which is a complex groundwater system combining several extremely opposite characteristics humid and arid recharge zones phreatic and confined parts shallow and deep sub aquifers stratified and relatively homogeneous sub basins saline and fresh water bodies as well as stagnant and fast flowing groundwater regions we have introduced a 3d geological based grid for the basin for the first time it was implemented into a numerical code feflow which was used thereafter to analyze quantitatively the flow regime the groundwater mass balance and the aquifer hydraulic properties we present up to date conceptual understanding and numerical modeling of the yt flow field especially at its mountainous parts based on the calibration procedure and the sensitivity analyses we obtained the best fitted hydraulic conductivity values for the aquifer mesh the general phenomenon observed is that as groundwater flow quantity increases the hydraulic conductivity also increases we interpret this result by the karstification mechanism including paleo karst thus where groundwater flow lines converge and where groundwater discharge amount increases the karstification process intensifies and permeability increases consequently at the mountainous region along the syncline axes where groundwater flow lines converge higher conductivities are found modeling results also exhibit that at the lowland confined area the geological structure does not play a major role in directing groundwater flow rather the flow field is controlled by the well developed karst system and the relatively homogenous carbonate section it is hypothesizes that the extensive karstification took place at the messinian salinity crises 5 5 ma during which groundwater heads as well as sea level were lowered by several 100 m

modeling the hydraulical behavior of a fissured karstic aquifer in exploitation conditions abstract a 5 year daily measurement of the dynamic level in a borehole was plotted versus cumulative yield since the beginning of exploitation eighty percent of the experimental curve is explained by a linear function h aqc h0 by intervals only floods which follow heavy storms and non pumping cannot be taken into account the slopes of the straight lines are spread around two constant values of the slope a r 0 35 10 3 m m 3 which characterizes the part which is controlled by recharge and a p 0 14 10 3 m m 3 which characterizes the draining part of the aquifer fractures this linear fitting demonstrates that the borehole aquifer system can be considered as an equivalent continuous medium where the linear relationship between dynamic head and pumped yield are defined by the values of ar and ap thus the hydraulic behavior of the aquifer differs according to the pumping rate equivalent continuous medium for a low rate dual permeability for a high one this work demonstrates that the long term behavior of an exploited fissured aquifer can be described by a simple model if the duration of the aquifer test is long enough 1 3 months it also shows that the production phase must include repetitive head measurements in order to refine the exploitation yield and the management conditions

analytical 1d dual porosity equivalent solutions to 3d discrete single continuum models application to karstic spring hydrograph modelling abstract one dimensional analytical porosity weighted solutions of the dual porosity model are derived providing insights on how to relate exchange and storage coefficients to the volumetric density of the high permeability medium it is shown that porosity weighted storage and exchange coefficients are needed when handling highly heterogeneous systems such as karstic aquifers using equivalent dual porosity models the sensitivity of these coefficients is illustrated by means of numerical experiments with theoretical karst systems the presented 1d dual porosity analytical model is used to reproduce the hydraulic responses of reference 3d karst aquifers modelled by a discrete single continuum approach under various stress conditions simulation results show the relations between the dual porosity model coefficients and the structural features of the discrete single continuum model the calibration of the equivalent 1d analytical dual porosity model on reference hydraulic responses confirms the dependence of the exchange coefficient with the karstic network density the use of the analytical model could also point out some fundamental structural properties of the karstic network that rule the shape of the hydraulic responses such as density and connectivity

phase relations of epidote blueschists phase diagrams have been computed for minerals in the system ncmash using the optimised thermodynamic data base of berman 1988 augmented by data on glaucophane and pumpellyite to illustrate the relationships between rocks containing epidote and sodic amphibole and those containing assemblages characteristic of neighbouring metamorphic facies the stoichiometries of stable bounding equilibria yield a simple list of mineral parageneses that serves to define an epidote blueschist facies and surrounding metamorphic facies the calculations suggest that when iron free the pairs zoisite glaucophane and clinozoisite glaucophane do not possess a stability field the natural fe bearing paragenesis of epidote sodic amphibole occupies a closed field in the pt diagram whose size increases dramatically as the ratio fe3 al in the minerals is increased where garnet is involved in bounding reactions such as with respect to eclogite and garnet bearing albite epidote amphibolite the epidote blueschist field decreases in size as the ratio fe2 mg is increased the classic blueschist to greenschist transition reaction is best developed in rocks with large fe3 and fe2 contents and is possibly metastable in mgal rich rocks in the latter a wedge of albite epidote actinolite barroisite amphibolite separates the epidote blueschist from the greenschits paragenesis field a first occurrence of garnet divides the epidote blueschist field into a lower temperature garnet free zone and a higher temperature garnet bearing zone although the temperatures calculated for this garnet isograd seem high the locations of all the facies boundaries are influenced by h2o activity however even minor amounts of co2 in the fluid phase x co2 0 005 render the epidote sodic amphibole paragenesis metastable so that facies boundaries cannot be shifted by varying the co2 content of the fluid phase below 600 c no mutual boundaries exist between the amphibolite facies and the epidote blueschist and eclogite facies respectively the calculated low pressure limit for the eclogite paragenesis pyralspite omphacite jd 50 quartz typical metabasite compositions is 12 to 14 kbars with h2o activity 0 9 or 1 5 to 2 kbar lower for jd 30

incipient blueschist metamorphism and metasomatism in the tavsanli region northwest turkey volcano sedimentary rocks in an imbricate tectonic zone around a peridotite massif have been studied northeast of the town of tavsanli in northwest turkey basic volcanic rocks which are the dominant rock type in this zone show incipient blueschist metamorphism and associated metasomatism while the igneous textures of the volcanic rocks are retained augites are partially to completely replaced by sodic pyroxene and plagioclase is albitised resulting in rocks with 6 8 wt na2o the volcanic rocks are cross cut by numerous veins of calcite aragonite quartz pumpellyite albite lawsonite and sodic pyroxene pelagic limestones which are interbedded with the basic volcanic rocks consist of coarse aragonite grains showing partial replacement by calcite the occurrence of aragonite lawsonite and albite indicates conditions of metamorphism for the whole zone in the range of 5 8 kb and 150 200 c metasomatism probably related to high pressure serpentinization has occurred contemporaneously with the incipient high pressure metamorphism

fluid flow modeling of a coastal fractured karstic aquifer by means of a lumped parameter approach fluid flow and solute transport phenomena in fractured and karstic aquifers remain an open issue that calls the attention of numerous researchers belonging to different disciplinary fields as far as the aspects linked both to shallow and to deep phenomena are concerned the hydrogeologic knowledge of these phenomena proves to be of high importance especially if considered in relationship with water resource exploitation with the problems linked to contamination and the ones linked to urban and industrial development of the territory in the examined area characterized by a dismissed contaminated site the realization of the landfill has required the development of a 3d flow model supported by a detailed local scale geologic model in order to evaluate the effects on groundwater flow and subsequently on contaminant propagation the results of the flow model prove to be coherent with the fractured and karstic nature of the site in that they show at higher depths the presence of a subterranean stream channel that would speed up pollutant propagation the obtained results represent the fundamental basis to implement a transport model that will permit to achieve a more in depth knowledge of the subsoil transport phenomena and therefore to optimize any anthropic intervention that can involve the site

dehydration melting of ultrahigh pressure eclogite in the dabie orogen evidence from multiphase solid inclusions in garnet several types of multiphase solid ms inclusions are identified in garnet from ultrahigh pressure uhp eclogite in the dabie orogen the mineralogy of ms inclusions ranges from pure k feldspar to pure quartz with predominance of intermediate types consisting of k feldspar quartz silicate plagioclase or epidote barite the typical ms inclusions are usually surrounded with radial cracks in the host garnet similar to where garnet contains relict coesite barite aggregates display significant heterogeneity in major element composition with total contents of only 57 73 and highly variable sio2 contents of 0 32 25 85 that are positively correlated with bao and so3 contents the occurrence of ms inclusions provides petrographic evidence for partial melting in the uhp metamorphic rock the occurrence of barite aggregates with variably high sio2 contents suggests the coexistence of aqueous fluid with hydrous melt under hp eclogite facies conditions thus local dehydration melting is inferred to take place inside the uhp metamorphic slice during continental collision this is ascribed to phengite breakdown during hot exhumation of the deeply subducted continental crust as a consequence the aqueous fluid is internally buffered in chemical composition and its local sink is a basic trigger to the partial melting during the continental subduction zone metamorphism

p t evolution of glaucophane omphacite bearing hp lt rocks in the western tianshan orogen nw china new evidence for alpine type tectonics the late palaeozoic western tianshan high pressure low temperature belt extends for about 200 km along the south central tianshan suture zone and is composed mainly of blueschist eclogite and epidote amphibolite greenschist facies rocks p t conditions of mafic garnet omphacite and garnet omphacite blueschist which are interlayered with eclogite were investigated in order to establish an exhumation path for these high pressure rocks maximum pressure conditions are represented by the assemblage garnet omphacite paragonite phengite glaucophane quartz rutile estimated maximum pressures range between 18 and 21 kbar at temperatures between 490 and 570 c decompression caused the destabilization of omphacite garnet and glaucophane to albite ca amphibole and chlorite the post eclogite facies metamorphic conditions between 9 and 14 kbar at 480 570 c suggest an almost isothermal decompression from eclogite to epidote amphibolite facies conditions prograde growth zoning and mineral inclusions in garnet as well as post eclogite facies conditions are evidence for a clockwise p t path analysis of phase diagrams constrains the p t path to more or less isothermal cooling which is well corroborated by the results of geothermobarometry and mineral textures this implies that the high pressure rocks from the western tianshan orogen formed in a tectonic regime similar to alpine type tectonics this contradicts previous models which favour franciscan type tectonics for the southern tianshan high pressure rocks

modelling karst vadose zone hydrology and its relevance for paleoclimate reconstruction abstract understanding past climatic changes allows us to better understand how our planet will evolve in the future one important source of information on paleoclimate is the analysis of speleothems that develop in karst caves and conduits due to the dissolution and precipitation of calcite however there are many uncertainties in paleoclimatic reconstruction with speleothems one of them being hydrological variability up to now only few studies have considered the impact of hydrological variability on speleothem formation and composition this review paper will provide an introduction to hydrological processes that have the potential to affect speleothem composition and the hydrological modelling approaches that are able to account for them it presents the current state of knowledge on paleoclimatic reconstruction using speleothems and shows that many important flow and transport processes have not yet been included in the interpretation of these archives mostly due to a lack of field information to parametrize them possible directions of future research efforts therefore include a better exploration of karst vadose zone processes and new approaches to incorporate this information into simulation models finally we foresee the exciting advances in reconstructing paleohydrology using karst hydrology models combined with speleothem growth rate and geochemical composition to understand how past climate changes affected the hydrological cycle and water availability

analysis of water level response to rainfall and implications for recharge pathways in the chalk aquifer se england summary water table response to rainfall was investigated at six sites in the upper middle and lower chalk of southern england daily time series of rainfall and borehole water level were cross correlated to investigate seasonal variations in groundwater level response times based on periods of 3 month duration the time lags in days yielding significant correlations were compared with the average unsaturated zone thickness during each 3 month period in general for cases when the unsaturated zone was greater than 18 m thick the time lag for a significant water level response increased rapidly once the depth to the water table exceeded a critical value which varied from site to site for shallower water tables a linear relationship between the depth to the water table and the water level response time was evident the observed variations in response time can only be partially accounted for using a diffusive model for propagation through the unsaturated matrix suggesting that some fissure flow was occurring the majority of rapid responses were observed during the winter spring recharge period when the unsaturated zone is thinnest and the unsaturated zone moisture content is highest and were more likely to occur when the rainfall intensity exceeded 5 mm day at some sites a very rapid response within 24 h of rainfall was observed in addition to the longer term responses even when the unsaturated zone was up to 64 m thick this response was generally associated with the autumn period the results of the cross correlation analysis provide statistical support for the presence of fissure flow and for the contribution of multiple pathways through the unsaturated zone to groundwater recharge

evolution of the conceptual model of unsaturated zone hydrology at yucca mountain nevada abstract yucca mountain is an arid site proposed for consideration as the united states first underground high level radioactive waste repository low rainfall approximately 170 mm yr and a thick unsaturated zone 500 1000 m are important physical attributes of the site because the quantity of water likely to reach the waste and the paths and rates of movement of the water to the saturated zone under future climates would be major factors in controlling the concentrations and times of arrival of radionuclides at the surrounding accessible environment the framework for understanding the hydrologic processes that occur at this site and that control how quickly water will penetrate through the unsaturated zone to the water table has evolved during the past 15 yr early conceptual models assumed that very small volumes of water infiltrated into the bedrock 0 5 4 5 mm yr or 2 3 percent of rainfall that much of the infiltrated water flowed laterally within the upper nonwelded units because of capillary barrier effects and that the remaining water flowed down faults with a small amount flowing through the matrix of the lower welded fractured rocks it was believed that the matrix had to be saturated for fractures to flow however accumulating evidence indicated that infiltration rates were higher than initially estimated such as infiltration modeling based on neutron borehole data bomb pulse isotopes deep in the mountain perched water analyses and thermal analyses mechanisms supporting lateral diversion did not apply at these higher fluxes and the flux calculated in the lower welded unit exceeded the conductivity of the matrix implying vertical flow of water in the high permeability fractures of the potential repository host rock and disequilibrium between matrix and fracture water potentials the development of numerical modeling methods and parameter values evolved concurrently with the conceptual model in order to account for the observed field data particularly fracture flow deep in the unsaturated zone this paper presents the history of the evolution of conceptual models of hydrology and numerical models of unsaturated zone flow at yucca mountain nevada flint a l flint l e kwicklis e m bodvarsson g s fabryka martin j m 2001 hydrology of yucca mountain reviews of geophysics in press this retrospective is the basis for recommendations for optimizing the efficiency with which a viable and robust conceptual model can be developed for a complex site

response of a fractured bedrock aquifer to recharge from heavy rainfall events abstract climate change is predicted to lead to an increased frequency of high intensity rainfall events the impact on groundwater resources particularly in areas of fractured bedrock aquifer systems requires knowledge of how recharge is affected in this study the response of a fractured bedrock aquifer to heavy rainfall events is characterized the study area is the gulf islands a temperate region in british columbia canada of the 14 provincial observation wells with hourly groundwater level data only three showed pronounced responses to heavy rain events and were analyzed in detail a detailed analysis at one well suggests rises in groundwater level were better correlated to all rain events than exclusively heavy rain during summer the strength of the correlation decreased as the rainfall intensity increased solution of the green ampt equation for rainfall events of varying magnitude indicated that an increase in rainfall intensity leads to more surface ponding and overland flow thus the occurrence of more frequent heavy rain events in the future may result in lower net recharge thermal infrared images in seepage areas and the 18 o and 2 h composition for precipitation and seepage suggest rapid seepage responses to heavy rain events and rapid seepage dissipation rates the overall rapid response of the fractured bedrock was advantageous for studying the response of the system to heavy rain events

intraoceanic subduction of heterogeneous oceanic lithosphere in narrow basins 2d numerical modeling abstract we provide 2d thermomechanical numerical models to constrain the subduction process of narrow 600 km wide oceanic basins resulting in formation and exhumation of serpentinite bearing high pressure hp and ultrahigh pressure uhp complexes presently exposed as dismembered massifs in orogenic belts we simulated subduction of heterogeneous i e non layered oceanic lithosphere testing different serpentinite rheologies and varying other major parameters initial slab dip convergence rate age and structure of oceanic lithosphere distance subduction zone continental margin weak zone geometry we show that serpentinite rheology is the most important parameter affecting both the geometry and behavior of serpentinite channels that form in the mantle wedge as the result of upward migration of slab fluids a strong serpentinite power law rheology is responsible for the continuous accretion and underthrusting of slab slices at the base of mantle wedge to form planar or wedge shape serpentinitic channels the great part of sediments is buried only during continental crust subduction but is never exhumed moreover slab slices do not mix with mantle wedge rocks exhumation of mafic ultramafic rocks occurs from pressure not exceeding 15 kbar on the other hand a weak newtonian behavior of serpentine best describes subduction and exhumation dynamics this rheology produces channels that usually widen to depth slab and sediment slices are easily incorporated in mantle wedge serpentinite during ongoing convergence in this case slab and mantle wedge serpentinite are mixed together and can be closely associated in the channel the models running a newtonian rheology highlight that slices of the oceanic overriding plate can be eroded and dragged in the channel till great depth a weak power law serpentinite rheology produces a transitional behavior between that of strong power law and newtonian rheology the serpentinitic melange produced using a newtonian rheology is finally exhumed from pressure 20 kbar during the final stages of continental crust subduction and collision the rise to shallow depth of the hp melange is driven by concurrent serpentinite buoyancy slab roll back and asthenospheric mantle upwelling moreover we propose that the subduction exhumation dynamics observed in the model acted during closure of the narrow alpine tethys ocean in particular we suggest that some slices presently outcropping in hp ophiolitic massifs of the western alps voltri and monviso massifs were tectonically coupled at slab mantle interface and exhumed during collision in a soft low viscosity serpentinite channel we finally investigated intensity and dynamics of magmatic processes during subduction our numerical experiments suggest that even subduction of narrow oceanic basins may indeed allow the development of a magmatic arc in such relatively small short living arcs steeper faster and younger slabs produce earlier onset of the volcanism after the beginning of subduction

evidence of a southward eddy corridor in the south west indian ocean mesoscale eddies and meanders have been shown to be one of the dominant sources of flow variability in the world s ocean one example of an isolated eddy hotspot is the south west indian ridge swir several investigations have shown that the swir and the corresponding planetary potential vorticity field f h exert a strong influence on the location and dynamics of the antarctic circumpolar current acc resulting in substantial fragmentation of the jets downstream of the ridge the easterly extension of this eddy corridor appears to be restricted to the deep channel separating the conrad rise from the del cano and crozet plateau however while the fate of eddies formed at the swir has been widely investigated and the frontal character of this eastward extension is well known the zone of diminishing variability that extends southwards to approximately 60 s remains poorly sampled using a combination of argo aviso and ncep ncar datasets the character of this eddy corridor as a conduit for warm core eddies to move across the acc into the antarctic zone is investigated in this study we track a single warm core eddy as it moves southwards from an original position of 31 e 50 20 s to where it dissipates 10 months later in the enderby basin at 56 20 s an argo float entrained within the eddy confirms that its water masses are consistent with water found within the antarctic polar frontal zone north of the apf latent and sensible heat fluxes are on average 8w m2 and 10w m2 greater over the eddy than directly east of this feature it is estimated that the eddy lost an average of 5w m2 of latent heat and 5w m2 of sensible heat over a 1 year period an amount capable of melting approximately 0 92m of sea ice in addition using an eddy tracking algorithm a total of 28 eddies are identified propagating southwards 25 of which are anti cyclonic in rotation based on the new argo float data combined with aviso and ncep ncar datasets these results suggest that the southward passage of warm core eddies act as vehicles transporting heat salt and biota southwards across the acc and into the eastern boundary of the weddell gyre

early paleozoic blueschist from the schist of skookum gulch eastern klamath mountains northern california late ordovician blueschist from the schist of skookum gulch eastern klamath mountains california is the oldest known blueschist in california and one of the oldest in north america lawsonite bearing glaucophane schist occurs as lenses intimately interlayered with chlorite schist quartz albite schist and dolomite marble detailed investigation of a portion of the skookum gulch schist demonstrates that these rock types share a common deformational and metamorphic history the first deformation occurred during blueschist metamorphism and produced similar style isoclinal folds and an axial planar foliation during subsequent deformations parallel style open to tight folds and local kink bands deformed foliation but produced no recognizable recrystallization major and selected trace elements analyzed by xrf for 12 samples of mafic schist show that the protoliths were broadly basaltic in composition sio 2 mostly ranges from 46 to 53 wt and that ocean floor basalt affinities are suggested by

double porosity models for a fissured groundwater reservoir with fracture skin theories of flow to a well in a double porosity groundwater reservoir are modified to incorporate effects of a thin layer of low permeability material or fracture skin that may be present at fracture block interfaces as a result of mineral deposition or alteration the commonly used theory for flow in double porosity formations that is based upon the assumption of pseudo steady state block to fissure flow is shown to be a special case of the theory presented in this paper the latter is based on the assumption of transient block to fissure flow with fracture skin under conditions where fracture skin has a hydraulic conductivity that is less than that of the matrix rock it may be assumed to impede the interchange of fluid between the fissures and blocks resistance to flow at fracture block interfaces tends to reduce spatial variation of hydraulic head gradients within the blocks this provides theoretical justification for neglecting the divergence of flow in the blocks as required by the pseudo steady state flow model coupled boundary value problems for flow to a well discharging at a constant rate were solved in the laplace domain both slab shaped and sphere shaped blocks were considered as were effects of well bore storage and well bore skin resultsmore obtained by numerical inversion were used to construct dimensionless type curves that were applied to well test data for a pumped well and for an observation well from the fractured volcanic rock terrane of the nevada test site less

groundwater recharge assessment at local and episodic scale in a soil mantled perched karst aquifer in southern italy summary groundwater recharge assessment of karst aquifers at various spatial and temporal scales is a major scientific topic of current importance since these aquifers play an essential role for both socio economic development and fluvial ecosystems in this study groundwater recharge was estimated at local and episodic scales in a representative perched karst aquifer in a region of southern italy with a mediterranean climate the research utilized measurements of precipitation air temperature soil water content and water table depth obtained in 2008 at the acqua della madonna test area terminio mount karst aquifer campania region at this location the aquifer is overlain by ash fall pyroclastic soils the episodic master recession emr method an improved version of the water table fluctuation wtf method was applied to estimate the amount of recharge generated episodically by individual rainfall events the method also quantifies the amount of precipitation generating each recharge episode thus permitting calculation of the recharge to the precipitation ratio rpr on a storm by storm basis depending on the seasonally varying air temperature evapotranspiration and precipitation patterns calculated values of rpr varied between 35 and 97 among the individual episodes a multiple linear correlation of the rpr with both the average intensity of recharging rainfall events and the antecedent soil water content was calculated given the relatively easy measurability of precipitation and soil water content such an empirical model would have great hydrogeological and practical utility it would facilitate short term forecasting of recharge in karst aquifers of the mediterranean region and other aquifers with similar hydrogeological characteristics by establishing relationships between the rpr and climate dependent variables such as average storm intensity it would facilitate prediction of climate change effects on groundwater recharge the emr methodology could further be applied to other aquifers for evaluating the relationship of recharge to various hydrometeorological and hydrogeological processes

reactive transport modeling in fractured rock a state of the science review abstract the field of reactive transport modeling has expanded significantly in the past two decades and has assisted in resolving many issues in earth sciences numerical models allow for detailed examination of coupled transport and reactions or more general investigation of controlling processes over geologic time scales reactive transport models serve to provide guidance in field data collection and in particular enable researchers to link modeling and hydrogeochemical studies in this state of science review the key objectives were to examine the applicability of reactive transport codes for exploring issues of redox stability to depths of several hundreds of meters in sparsely fractured crystalline rock with a focus on the canadian shield setting a conceptual model of oxygen ingress and redox buffering within a shield environment at time and space scales relevant to nuclear waste repository performance is developed through a review of previous research this conceptual model describes geochemical and biological processes and mechanisms materially important to understanding redox buffering capacity and radionuclide mobility in the far field consistent with this model reactive transport codes should ideally be capable of simulating the effects of changing recharge water compositions as a result of long term climate change and fracture matrix interactions that may govern water rock interaction other aspects influencing the suitability of reactive transport codes include the treatment of various reaction and transport time scales the ability to apply equilibrium or kinetic formulations simultaneously the need to capture feedback between water rock interactions and porosity permeability changes and the representation of fractured crystalline rock environments as discrete fracture or dual continuum media a review of modern multicomponent reactive transport codes indicates a relatively high level of maturity within the yucca mountain nuclear waste disposal program reactive transport codes of varying complexity have been applied to investigate the migration of radionuclides and the geochemical evolution of host rock around the planned disposal facility through appropriate near and far field application of dual continuum codes this example demonstrates how reactive transport models have been applied to assist in constraining historic water infiltration rates interpreting the sealing of flow paths due to mineral precipitation and investigating post closure geochemical monitoring strategies natural analogue modeling studies although few in number are also of key importance as they allow the comparison of model results with hydrogeochemical and paleohydrogeological data over geologic time scales

hydrology of yucca mountain nevada yucca mountain located in southern nevada in the mojave desert is being considered as a geologic repository for high level radioactive waste although the site is arid previous studies indicate net infiltration rates of 5 10 mm yr 1 under current climate conditions unsaturated flow of water through the mountain generally is vertical and rapid through the fractures of the welded tuffs and slow through the matrix of the nonwelded tuffs the vitric zeolitic boundary of the nonwelded tuffs below the potential repository where it exists causes perching and substantial lateral flow that eventually flows through faults near the eastern edge of the potential repository and recharges the underlying groundwater system fast pathways are located where water flows relatively quickly through the unsaturated zone to the water table for the bulk of the water a large part of the travel time from land surface to the potential repository horizon 300 m below land surface is through the interlayered low fracture density nonwelded tuff where flow is predominately through the matrix the unsaturated zone at yucca mountain is being modeled using a three dimensional dual continuum numerical model to predict the results of measurements and observations in new boreholes and excavations the interaction between experimentalists and modelers is providing confidence in the conceptual model and the numerical model and is providing researchers with the ability to plan further testing and to evaluate the usefulness or necessity of further data collection