effect of partial melting on rock deformation experimental and natural evidences on rocks of granitic compositions abstract deformation tests at constant strain rate 10 5 s 1 at 210 250 mpa confining pressure and at 560 900 c are performed on an aplite with varying water contents the mechanical behaviour is correlated with the microstructure after a stage of plastification depending on the temperature and on the water content the rock strength falls dramatically under such confining pressures before melting and before straining the pores of the wet rocks burst as the thermal expansion of water develops a local high pore pressure which causes cracking and fracturing in our opinion this pore bursting will increase the effects of thermal cracking due to the differential expansion of the minerals the rocks exhibit a uniform crack network with increasing temperature melting occurs in the cataclased rock the crack development and melting depend on the initial water content the loss of cohesion obtained either by cracking or by cracking and melting provokes a dramatic weakening axial shortening induces cracking parallel to 1 and melt transfer into extensional regions deformation is concentrated in dilatant shear bands at the highest temperature 900 c a melt film network is rapidly established and induces a very low flow stress melt effects in naturally deformed gneisses suggest that biotite breakdown furnishes a silicate fluid which induces hydraulic fracture and melt dispersion

on the rheology of partially molten synthetic granite abstract in an attempt to obviate some of the difficulties inherent in using natural rocks to study experimentally the rheology of partially molten granitic rocks we report some preliminary experiments using hot pressed synthetic aggregates with quartz as the solid phase and a quartz albite glass to form the melt phase undrained constant displacement rate and stress relaxation experiments were performed at 1100 c and 300 mpa total confining pressure using nominally 16 and 28 wt anhydrous melt and at 980 c with 12 wt of water saturated melt strain rate varies non linearly with stress corresponding to a stress exponent of 3 6 for the anhydrous melt tests and 1 9 with the wet melt strain rate is enhanced about 160 fold through doubling the melt fraction from 16 wt intracrystalline plasticity appears to contribute insignificantly to the observed deformation and the preservation of relatively equant grains implies a granular flow process microcracking occurs during isostatic hot pressing and also contributes to subsequent non isostatic deformation at high stresses and strain rates models of flow of partially molten rock that assume diffusive transfer accommodation of granular flow predict linear viscosity but only at lower strain rates than accessed experimentally it is suggested that the non linear granular flow observed in these experiments involved the episodic unsticking of sintered contacts between grains by a rate dependent cracking and or dislocation accommodation process

cross hole fracture connectivity assessed using hydraulic responses during liner installations in crystalline bedrock boreholes abstract in order to continually improve the current understanding of flow and transport in crystalline bedrock environments developing and improving fracture system characterization techniques is an important area of study the presented research examines the installation of flexible impermeable flute liners as a means for assessing cross hole fracture connectivity flute liners are used to generate a new style of hydraulic pulse with pressure response monitored in a nearby network of open boreholes drilled in gneissic rock of the canadian shield in eastern ontario canada borehole liners were installed in six existing 10 15 cm diameter boreholes located 10 35 m apart and drilled to depths ranging between 25 45 m liner installation tests were completed consecutively with the number of observation wells available for each test ranging between one and six the collected pressure response data have been analyzed to identify significant groundwater flow paths between source and observation boreholes as well as to estimate inter well transmissivity and storativity using a conventional type curve analysis while the applied solution relies on a number of general assumptions it has been found that reasonable comparison can be made to previously completed pulse interference and pumping tests results of this research indicate areas where method refinement is necessary but nonetheless highlight the potential for use in crystalline bedrock environments this method may provide value to future site characterization efforts given that it is complementary to and can be used in conjunction with other currently employed borehole liner applications such as the removal of cross connection at contaminated sites and the assessment of discrete fracture distributions when boreholes are sealed recreating natural hydraulic gradient conditions

very low frequency subionospheric remote sensing of thunderstorm driven acoustic waves in the lower ionosphere we present observations of narrowband subionospheric vlf transmitter signals on 20 march 2001 exhibiting coherent fluctuations of over 1 db peak to peak spectral analysis shows that the fluctuations have periods of 1 4 min and are largely coherent the subionospheric propagation path of the signal from puerto rico to colorado passes over two regions of convective and lightning activity as observed by goes satellite imagery and national lightning detection network lightning data we suggest that these fluctuations are evidence of acoustic waves launched by the convective activity below observed in the 80 90 km altitude range to which nighttime vlf subionospheric remote sensing is sensitive these observations show that vlf subionospheric remote sensing may provide a unique 24 h remote sensing technique for acoustic and gravity wave activity we reproduce this event in simulations using a fluid model of gravity and acoustic wave propagation to calculate the ionospheric disturbance followed by an electromagnetic propagation model to calculate the perturbation amplitude at the location of the vlf receiver simulation results show that a very large and coherent convective source is required to produce these amplitude perturbations

deformation of incompletely crystallized magma systems granitic gneisses and their tectonic implications certain textures in two feldspar calc alkaline granitic gneisses have been identified as indicators of the presence of intercrystalline melt during deformation of crystal melt mushes fluid relocation or fracting is to be expected in an incompletely crystallized magmatic system as deviatoric stresses are applied to it relocation of late stage fluids capable of crystallizing k feldspar quartz microaplite and myrmekite to low pressure zones such as the pressure shadow region around earlier crystals occurs within some developing mylonitic gneiss fabrics and results in a distinctive assemblage of textures strain in these rocks is expressed by various brittle and ductile features and by fluid relocation textures the petrogenesis of these particular gneisses is therefore both magmatic and metamorphic contrasting with gneiss forming processes that had no participating magmatic component migmatitic complexes evolving by partial anatexis of non magmatic rocks in a tectonically active environment are not

grain boundary migration of quartz during annealing experiments at high temperatures and pressures with implications for metamorphic geology annealing experiments on agate quartz schist and metachert at 800 1000 c confining pressures of 400 and 800 mpa and annealing times of 6 0 10 3 6 105s revealed normal grain growth of quartz in the agate grain size increasing with time but the rate of grain growth decreasing with increasing grain size the boundaries of agate with quartz schist and metachert migrated into the agate at the expense of fine grained quartz in the agate the driving force for the migration appears to be the reduction of surface energy associated with removal of fine grained quartz in the agate assuming the activation energy as qm 11 kcal mol 1 a general expression for the relationship between velocity of boundary migration v and driving force p is where is the specific surface energy of quartz r is the gas constant and t is the absolute temperature the velocity is relatively fast at high temperatures on a geological time scale the expression assists a quantitative understanding of the microstructural development of quartz at metamorphic conditions

flowmetering of drainage wells in kuwait city kuwait a heat pulse flowmeter was used in six drainage wells in kuwait city for flow profiling under both ambient and pumping conditions the data collected were used in a estimating the cross flow among the screened intervals under ambient conditions b estimating the relative transmissivity adjacent to the individual screen zones and c determination of the hydraulic heads at the far boundaries of the large scale aquifer zones these inferences were cross checked against known hydrogeology of the aquifer aquitard system in the study area and the calibration results of numerical flow modeling the major conclusions derived from the flow measurements were a the presence of natural downward cross flow under ambient condition supported the hypothesis that the upper part of the kuwait group aquifer in the study area was divided into a series of permeable units aquifers separated by confining or semi confining beds aquitards b the head differences between the different screened zones derived through modeling of the flowmeter data of the wells provided additional confirmation for the division of the upper part of the kuwait group aquifer into compartments in the study area c flowmeter data indicated that the second and third aquifers were contributing most of the water to the well bores compared with the uppermost first and the lowermost fourth aquifers and d inflow to the wells during pumping was associated with discrete sub intervals in the screened zones controlled by local aquifer heterogeneity and possibly clogging of screens and gravel pack

hydrogeological characterization of seawater intrusion in tidally forced coastal fractured bedrock aquifer summary hydrogeological investigation was carried out to characterize seawater intrusion in a tidally forced coastal fractured bedrock aquifer in the west coast of korea peninsular which was also subject to heavy groundwater extraction times series analysis using the data of electrical conductivity ec groundwater level and tidal oscillation showed that intensive groundwater extraction from the wells near the shore caused a severe seawater intrusion the geophysical loggings and hydraulic tests indicated that the tidally forced coastal fractured aquifer in the study area was characterized by the shallow fresh groundwater transition zone and deep high saline water zone the extent of seawater intrusion highly depended on conductive fractures and their hydraulic connectivity in the deep saline water layer progressive seawater intrusion took place mainly by persistent intensive pumping and in part by tidal activity the conductive fractures acted as a pathway for saline water flow from the deep saline water zone to the transition zone when groundwater was extracted the extent of transition zone depended on the change of groundwater level by groundwater pumping or recharge this study indicated that a persistent intensive extraction of groundwater would intensify seawater intrusion in tidally forced coastal fractured aquifer and proper measures would be required to prevent it

magnetic fabric and microstructural evidence for a tectono thermal overprint of the early proterozoic murray pluton central ontario canada abstract the 2 38 ga old murray granite pluton intruded the southern footwall of the sudbury igneous complex and was subjected to repeated ductile deformation its nw and se domains display differences in strain state ams signature and the nature and distribution of fe oxide minerals the magnetic foliation is parallel to the visible foliation in the nw domain but discordant to it in the se domain microstructural data show that the magnetic fabric in the nw domain coincides with a foliation formed at high temperature probably in response to thermal softening during the emplacement of the adjacent sudbury igneous complex this tectono thermal overprint affected pre existing shape fabrics and was facilitated by incipient melting of the granite near the intrusive contact with the sudbury igneous complex rocks of the se domain are only partially overprinted and two mineral subfabrics are preserved prolate susceptibility ellipsoids and clusters of maximum susceptibility directions at the intersections of the two planar fabrics suggest oblique superposition of strain increments increases in bulk magnetic susceptibility and magnetic anisotropy degree towards the intrusive contact with the sudbury igneous complex can be explained by respective increases in the proportion of magnetite over ilmenite and strain intensity in the murray pluton

flowing fluid electric conductivity logging for a deep artesian well in fractured rock with regional flow the flowing fluid electric conductivity ffec logging method is a well logging technique that may be used to estimate flow rate salinity transmissivity and hydraulic head of individual fractures or high permeability zones intersected by a wellbore wellbore fluid is first replaced with fluid of a contrasting electric conductivity then repeated fec logging is done while the well is pumped zones where fluid flows into the wellbore show peaks in the fec logs which may be analyzed to infer inflow rate and salinity of the individual fractures conducting the procedure with two or more pumping rates multi rate ffec logging enables individual fracture transmissivity and hydraulic head to be determined here we describe the first application of the multi rate ffec logging method to an artesian well using a 500 m well in fractured rock at horonobe japan an additional new factor at the site is the presence of regional groundwater flow which heretofore has only been studied with synthetic data ffec logging was conducted for two different pumping rates several analysis techniques had to be adapted to account for the artesian nature of the well the results were subsequently compared with independent salinity measurements and transmissivity and hydraulic head values obtained from packer tests in the same well despite non ideal operating conditions multi rate ffec logging successfully determined flow rate salinity and transmissivity of 17 conducting fractures intercepted by the logged section of the borehole including two fractures with regional groundwater flow predictions of hydraulic head were less accurate a not unexpected result in light of operational problems and the form of the equation for hydraulic head which involves the difference between two uncertain quantities this study illustrates the strengths and weaknesses of the multi rate ffec logging method applied to artesian wells in conjunction with previous studies it demonstrates the usefulness of the method for a broad range of conditions encountered in subsurface fractured rock

aquifer heterogeneity characterization with oscillatory pumping sensitivity analysis and imaging potential 1 periodic pumping tests in which a fluid is extracted during half a period then reinjected have been used historically to estimate effective aquifer properties in this work we suggest a modified approach to periodic pumping test analysis in which one uses several periodic pumping signals of different frequencies as stimulation and responses are analyzed through inverse modeling using a steady periodic model formulation we refer to this strategy as multifrequency oscillatory hydraulic imaging oscillating pumping tests have several advantages that have been noted including no net water extraction during testing and robust signal measurement through signal processing through numerical experiments we demonstrate additional distinct advantages that multifrequency stimulations have including 1 drastically reduced computational cost through use of a steady periodic numerical model and 2 full utilization of the aquifer heterogeneity information provided by responses at different frequencies we first perform fully transient numerical modeling for heterogeneous aquifers and show that equivalent results are obtained using a faster steady periodic heterogeneous numerical model of the wave phasor the sensitivities of observed signal response to aquifer heterogeneities are derived using an adjoint state based approach which shows that different frequency stimulations provide complementary information finally we present an example 2 d application in which sinusoidal signals at multiple frequencies are used as a data source and are inverted to obtain estimates of aquifer heterogeneity these analyses show the different heterogeneity information that can be obtained from different stimulation frequencies and that data from several sinusoidal pumping tests can be rapidly inverted using the steady periodic framework

inferring transport characteristics in a fractured rock aquifer by combining single hole ground penetrating radar reflection monitoring and tracer test data 1 investigations of solute transport in fractured rock aquifers often rely on tracer test data acquired at a limited number of observation points such data do not by themselves allow detailed assessments of the spreading of the injected tracer plume to better understand the transport behavior in a granitic aquifer we combine tracer test data with single hole ground penetrating radar gpr reflection monitoring data five successful tracer tests were performed under various experimental conditions between two boreholes 6 m apart for each experiment saline tracer was injected into a previously identified packed off transmissive fracture while repeatedly acquiring single hole gpr reflection profiles together with electrical conductivity logs in the pumping borehole by analyzing depth migrated gpr difference images together with tracer breakthrough curves and associated simplified flow and transport modeling we estimate 1 the number the connectivity and the geometry of fractures that contribute to tracer transport 2 the velocity and the mass of tracer that was carried along each flow path and 3 the effective transport parameters of the identified flow paths we find a qualitative agreement when comparing the time evolution of gpr reflectivity strengths at strategic locations in the formation with those arising from simulated transport the discrepancies are on the same order as those between observed and simulated breakthrough curves at the outflow locations the rather subtle and repeatable gpr signals provide useful and complementary information to tracer test data acquired at the outflow locations and may help us to characterize transport phenomena in fractured rock aquifers

a multidisciplinary fractured rock characterization study at raymond field site raymond ca abstract a dedicated field site was developed and a suite of experiments were conducted in the sierra nevada foothills near the town of raymond ca to develop and test a multi disciplinary approach to the characterization of groundwater flow and transport in fractured rocks a wealth of geologic hydrologic and geophysical data was collected at the site using a variety of unique tools a cluster of nine approximately 90 m deep boreholes were drilled at the site in a v shaped pattern with an angle of 60 the boreholes are spaced 7 5 15 30 and 60 m from the central borehole various geophysical and hydrologic tests were conducted in and between these boreholes integration of cross hole radar and seismic tomography borehole flow surveys and images from a new digital borehole scanner indicated that groundwater flow is mainly confined to a few sub horizontal fracture zones a unique suite of hydraulic tests were conducted in which three to four intervals in each of the nine boreholes were isolated using pneumatic packers some 130 injection tests were conducted and more than 4100 cross hole transient pressure measurements were obtained a computer algorithm was developed to analyze such massive interference data systematically as a result of the analysis an image of the fracture connections emerged which is consistent with the geophysical data high precision tiltmeters were effective in remotely characterizing the preferential flow path several radial convergent tracer tests were conducted by injecting a mixture of several conservative tracers and one sorbing tracer deuterium fluorescein lithium bromide and polystyrene micro spheres some differences between the breakthrough curves are observed which may be due to possible differences among so called conservative tracers some characterization tools were found to be more effective than others in locating flowing fractures however no single tool was almighty characterization of fractured rock is extremely challenging and requires a stepwise and well thought approach which is basically a good old scientific approach prediction of transport based on the characterization results is even more challenging and one should always bear in mind that it is virtually impossible to uniquely characterize a fractured rock

microstructures of melt bearing regional metamorphic rocks the most reliable microstructural criterion for the former presence of felsic melt in regional migmatites is a three mineral quartz k feldspar and sodic plagioclase aggregate in veinlets several other criteria are potentially reliable namely 1 euhedral crystals of feldspar precipitated from liquid or peritectic minerals e g garnet cordierite orthopyroxene k feldspar lining felsic protoleucosomes 2 inclusionfree euhedral overgrowths of feldspar precipitated from liquid or peritectic minerals e g garnet cordierite orthopyroxene k feldspar on residual grains of the same minerals with abundant inclusions in the mesosome 3 aligned euhedral feldspar crystals 4 simple twinning in k feldspar 5 dihedral angles of 60 subtended where a grain of feldspar and or quartz inferred to have pseudomorphed former melt meets two grains of other minerals 6 cuspate volumes of quartz k feldspar or sodic plagioclase especially where surrounded by grains inferred to have been residual during melting 7 veinlets of inferred former melt now mineral pseudomorphs consisting of one of quartz k feldspar or sodic plagioclase preferably though less commonly involving two or three of these minerals along grain boundaries or along inferred former intragranular fractures 8 biotite pseudomorphed by feldspar 9 veinlets of plagioclase that is more sodic than plagioclase grains in the adjacent rock 10 plagioclase with oscillatory zoning 11 microgranophyric intergrowths of quartz and alkali feldspar in patches or veinlets between primary grains 12 symplectic replacement aggregates that can be explained by reactions between peritectic grains and cooling melt and 13 melanosome patches and layers from which leucosome has been extracted however all these criteria must be interpreted with care some other proposed criteria are questionable for example 1 random mineral distributions 2 grain size increase 3 interstitial grains 4 corroded relics of inferred reactant mineral grains surrounded by areas of quartz k feldspar or sodic plagioclase 5 projections into a mineral grain 6 lobes of myrmekite and 7 plagioclase rims with a constant sodic composition occurring on plagioclase cores that are more calcic and or of variable composition

numerical evaluation of flowmeter test interpretation methodologies we evaluate systematic errors inherent in two flowmeter test interpretation methodologies a physically consistent two dimensional groundwater flow model is used to numerically simulate the single flowmeter test and the double flowmeter test in 25 different two layer confined aquifers of a priori known horizontal hydraulic conductivities kt specific storativities ssi and hydraulic diffusivities vt ktissi9 in each layer i 1 2 values selected for the layer hydraulic parameters span those encountered in natural sandy formations with the ratios of the corresponding parameters in the two layers falling in the following ranges 1 kl k2 100 0 0001 ssl ss2 100 and 1 vjv2 10 000 we find that the size of the hydraulic diffusivity contrast rather than the hydraulic conductivity ratio is the dominating factor for the parameter estimation accuracy in the two flowmeter methodologies for the single flowmeter test methodology the ratio of the estimate over the corresponding true value falls within the range 0 97 kjkt 1 55 whereas for the double flowmeter test it falls within 0 99 kjkt 3 40 the double flowmeter test also provides estimates of layer specific storativity ssi these are accurate only for the special case of equal layer hydraulic diffusivities the test yields order of magnitude estimates of ssi for layer hydraulic diffusivities differing from each other by up to an order of magnitude for larger differences the estimation errors are much larger hydraulic parameters of a given layer are better estimated when the flowmeter is placed either exactly at the interlayer boundaries or ideally at two different points within each layer away from the boundaries the results from simulated flowmeter tests in a five layer system are consistent with those for the two layer aquifers this implies that the presented results most likely apply to flowmeter tests in arbitrary multilayer aquifers existence of significant errors in aquifer parameters estimated from synthetic flowmeter data demonstrate that the theis 1935 model which is assumed to be valid in each layer by the two considered interpretation methodologies does not fully capture the flow dynamics in layered aquifers this is illustrated by numerically calculated examples of simultaneousl y nonuniform and transient well face flux distributions in a layered aquifer a model more sophisticated than that of theis 1935 needs to be found

inferring the heterogeneity transmissivity and hydraulic conductivity of crystalline aquifers from a detailed water table map abstract estimating the transmissivity or hydraulic conductivity field to characterize the heterogeneity of a crystalline aquifer is particularly difficult because of the wide variations of the parameters we developed a new approach based on the analysis of a dense network of water table data it is based on the concept that large scale variations in hydraulic head may give information on large scale aquifer parameters the method assumes that flux into the aquifer is mainly sub horizontal and that the water table is mostly controlled by topography rather than recharge it is based on an empirical statistical relationship between field data on transmissivity and the inverse slope values of a topography reduced water table map this relationship is used to compute a transmissivity map that must be validated with field measurements the proposed approach can provide a general pattern of transmissivity or hydraulic conductivity but cannot correctly reproduce strong variations at very local scale less than10 m and will face of some uncertainties where vertical flows cannot be neglected the method was tested on a peridotite ultramafic rock aquifer of 3 5 km 2 in area located in new caledonia the resulting map shows transmissivity variations over about 5 orders of magnitude average logt 5 2 0 7 comparison with a map based on measured water level data n 475 shows that the comparison between logt computed values and logt data deduced from 28 hydraulic tests is estimated with an error less than 20 in 71 of cases logt 0 4 and with an error less than 10 logt 0 2 on average in 39 of cases from this map a hydraulic conductivity map has been computed showing values ranging over 8 orders of magnitude the repeatability of the approach was tested on a second data set of hydraulic head measurements n 543 the mean deviation between both logt maps is about 11 these encouraging results show that the method can give valuable parameter estimates and can characterize aquifer heterogeneity the computed logt and logk maps highlight the spatial distribution of parameters that show a pattern clearly controlled by the fault network of this ultramafic massif however the faults are mainly characterized by low permeability zones this differs from results on other crystalline aquifers and may be due to the fact that weathering products of peridotite are clay like materials the resulting transmissivity map can be used as a starting point for modelling or to direct additional fieldwork

on the pseudomorphing of melt filled pores during the crystallization of migmatites pseudomorphs of melt filled pores recognized by their generally cuspate shape are used as diagnostic for the former presence of partial melt they are commonly observed in migmatites from the mid to deep crust although they occur in the smaller pores in migmatites from shallower levels 1 2 kbar the pseudomorphing of meltfilled pores is controlled by the kinetics of nucleation and is a consequence of the greater supersaturation required for nucleation in a small pore compared with a larger one we examine three migmatites in detail a contact metamorphosed cherty band from an iron formation an archaean regional granulite from an accretionary prism and an amphibolite facies sample from the roots of an archaean mountain chain the greater undercooling required for nucleation in progressively smaller pores is recorded by the composition of plagioclase pseudomorphs a study of dihedral angles at the corners of pseudomorphed pores demonstrates that melt solid textural equilibrium was probably attained only in the contact aureole the regional granulite preserves an almost unmodified reaction controlled melt distribution with little evidence for either melt solid textural equilibration or solid solid re equilibration whereas the reactioncontrolled melt distribution in the regional amphibolite facies example has been modified by a partial approach to solid solid textural equilibrium it is not clear whether the differences in dihedral angle population are due to differences in uplift and exhumation rates or due to the presence of h2o on grain boundaries

transition from dislocation creep to melt enhanced diffusion creep in fine grained granitic aggregates abstract sintered aggregates composed of quartz albite and microcline of two different grain sizes 2 10 and 10 50 m each with two different melt contents

combined use of straddle packer testing and flute profiling for hydraulic testing in fractured rock boreholes summary a combination of high resolution hydraulic tests using straddle packers and transmissivity t profiling using the flute flexible liner method liner profiling in densely fractured rock boreholes is shown to be efficient for the determination of the vertical distribution of t along the entire hole the liner t profiling method takes a few hours or less to scan the entire borehole length resulting in a t profile under favorable conditions this method has good reliability for identifying the highest t zones identified by distinct decreases in liner velocity when these zones are covered by the descending liner in contrast for one short test interval e g 1 2 m the multiple test straddle packer method takes a few hours to measure t with good precision and accuracy using a combination of steady state and transient tests e g constant head step tests slug tests and constant rate pumping tests because of the time consuming aspect of this multiple test method it is most efficient in each borehole to conduct straddle packer testing only in priority zones selected after assessment of other borehole data collected prior to packer testing the t profile from the liner method is instrumental in selecting high permeable zones for application of the multiple test method using straddle packers which in turn refines the t estimation from the liner profile results from three boreholes in densely fractured sandstone demonstrate this approach showing the synergistic use of the methods with emphasis on information important for determining hydraulic apertures

identifying hydraulically conductive fractures with a slow velocity borehole flowmeter the u s geological survey used a recently developed heat pulse flowmeter to measure very slow borehole axial water velocities in granitic rock at a site near lac du bonnet manitoba canada the flowmeter was used with other geophysical measurements to locate and identify hydraulically conducting fractures contributing to the very slow vertical water flow in the two boreholes selected for study the heat pulse flowmeter has no moving parts and operates on the tag trace principle it is an improved version of the flowmeter developed by the water research centre in england in 1975 the u s geological survey s heat pulse flowmeter has a flow measuring range in water of 0 06 6 m min and can resolve velocity differences as slow as 0 01 m min this is an order of magnitude slower than the stall speed of spinner flowmeters the flowmeter is 1 16 m long and 44 mm in diameter it was calibrated in columns of 76 and 152 mm diameter to correspond to the boreholes studied the heat pulse flowmeter system is evalu

melt organisation and strain partitioning in the lower crust abstract partial melts can form as a result of crustal thickening due to orogenesis even small melt fractions weaken the crust so that partially molten volumes should accumulate significant amounts of strain however relatively little is known of how strain partitions in partial melts and how effective the melt expulsion processes from the partially molten crust are using examples from the western gneiss region wgr norway we consider a case of co existing migmatites and shear zones field image analysis and microanalytical methods allow semi quantification of melt volume rock mineralogy and mineral chemistry and microstructures integration of these analyses implies effective syn melt strain partitioning and subsequent freezing of both the shear zone and migmatite texture we propose a mechanism that allows i syn melt strain localisation at an outcrop scale through stress driven melt organisation resulting in significant relative competence differences in a partially molten rock volume and ii formation of fine grained rocks at outcrop that is entirely or mostly syn melt without subsequent mylonitic shearing in the solid state syn melt shear zones that have not acted as effective melt transport channels and or that have not accumulated post melt deformation may be more common than conventionally assumed

melt assisted interior to margin switch from dislocation to diffusion creep in coarse grained plagioclase evidence from a deformed anorthosite pluton abstract at bolangir eastern india massive anorthosites in the pluton interior grade into anorthosites with outward dipping margin parallel foliation neighboring the pluton margin sheets and veins of ferrodiorites residual melts of anorthosite crystallization concordant and discordant to the margin parallel foliation suggest pluton deformation at near magmatic conditions t 950 c and p 6 12 kbar in the pluton interior the larger than centimeter sized magmatic plagioclase grains are replaced by aggregates of smaller 100 600 m dynamically recrystallized internally strained grains with un equilibrated boundaries neighboring the pluton margin poly sized 200 2500 m plagioclase grains in anorthosites are of two types strain free rectangular shaped plagioclase grains with high energy an richer margins indenting neighboring plagioclase grains formed by diffusion creep whereas unstrained end to end touching euhedral plagioclase grains showing tilling represent magmatic flow textures the pluton interior to margin switch in plagioclase deformation from grain boundary migration accommodated dislocation creep to grain boundary diffusion creep is attributed to the increasing melt fraction melt crystal ratio during syn deformation pluton emplacement plagioclase grains in the bolangir pluton are significantly coarser compared to plagioclase aggregates

fracture characterization using earth tide analysis summary wells tapping confined aquifer systems are known to commonly produce water level fluctuations caused by strain induced earth tides in this investigation a straightforward methodology is presented for quantifying the specific storage and secondary porosity of a fractured fault zone aquifer system using earth tides water level and barometric pressure head data are smoothed and then filtered to remove low frequency responses the resulting tidal signals are used in the program baytap g to yield amplitude and phase shifts of all the major tidal groups the resulting tidal parameters can be used to compute the time dependent volumetric strain caused by the m 2 and o 1 tides stress strain hysteresis loops are produced when the reduced water levels are compared to the volumetric strain induced by these tides for amplification factors near unity representing the ratio of pressure response to tidal loading in the fracture to water level response in the well the slopes of the loops represent the specific storage of the fracture the barometric efficiency and specific storage can then be used to estimate a secondary porosity and other parameters of the aquifer system this analysis was carried out at the fractured rock research site frs in the blue ridge physiographic province in floyd county virginia

melt generation and fluid flow in the thermal aureole of the bushveld complex granite sheets emplaced into the migmatite zone of the eastern contact aureole of the bushveld complex resulted from fluid enhanced incongruent biotite melting of the underlying silverton formation shales during prograde metamorphism ba concentrations are extreme in both the sheets 1000 ppm and the hornfels 800 ppm into which they have been emplaced we conclude that a ba rich hydrothermal fluid induced melting in the aureole and that fluid transport of ba2 and to a lesser extent sr2 and eu2 persisted in the melt zones under subsolidus conditions sr isotope systematics from high ba localities define an errorchron of 2161 106 ma with an initial 87sr 86sr ratio of 0 705 0 001 metasedimentary rocks unaffected by fluid infiltration were homogenized at the same time but with an increased initial ratio suggesting that whereas isotope homogenization was achieved between outcrops permeated by fluids there is no evidence of regional homogenization oxygen isotope compositions of psammitic metasediments in the aureole are uncorrelated with distance from the contact suggesting the infiltrating fluid equilibrated isotopically with the metasediments their elevated 18o values 11 3 12 1 are consistent with a fluid source from devolatilization of the sedimentary lithologies textural analysis at both outcrop and thin section scale of arkose and psammites in the aureole lakenvalei and magaliesberg formations shows that the extent of melting was highly heterogeneous even on the grain scale and resulted from heterogeneously distributed infiltration of aqueous fluid on dilatant cracks and grain boundaries cathodoluminescence imaging of quartz shows a marked difference in the amount of fine structure with that in the melted rocks having uniform luminescence in contrast to that in rocks containing little or no melt which preserve textures inherited from the regionally metamorphosed protolith simple finite difference thermal modelling of the aureole suggests that the width of the melt zone 500 m is inconsistent with conductive heat transfer and hence that the thermal structure has been modified by fluid advection

quartz fabric transition in a cooling syntectonic granite hermitage massif france abstract the hermitage granite situated in the northwest massif central france is a syntectonic hercynian leucogranite emplaced along an active transcurrent shear zone during emplacement and cooling the progressive deformation is marked by the development of a primary homogeneous foliation gradually affected by ductile shear bands c s mylonites increase in strain heterogeneity during cooling corresponds to a change of dominant deformation mechanism of the quartz phase from grain growth and migration recrystallization to intracrystalline a slip and rotation recrystallization migration recrystallization is characterized by preferred orientations of c axes close to the principal extension direction we discuss relevant deformation mechanisms and rheological implications for syntectonic plutons in particular we argue that the transitions between homogeneous and heterogeneous accumulation of strain cannot generally be correlated with transition between magmatic and solid state flow

borehole flowmeters field application and data analysis abstract this paper reviews application of borehole flowmeters in granular and fractured rocks basic data obtained in the field are the ambient flow log and the pumping induced flow log these basic logs may then be used to calculate other quantities of interest the paper describes the applications of the tennessee valley authority tva electromagnetic em flowmeter in a granular medium in an attempt to ascertain the effect of formation disturbance on flowmeter readings test wells were subjected to repeated periods of development using air lifting between the development periods flowmeter tests were run the results indicated that flowmeter data are not highly sensitive to formation disturbance in the near vicinity of a test well evidence of changes in the natural ambient flow in the test well was attributed to high variable rates of pumping by nearby chemical plants in fractured media flowmeters may be used to detect flow to or from individual fractures or fracture zones in these applications additional information in the form of caliper televiewer and resistivity logs are useful further studies of the type described herein are warranted

mechanical stratigraphic controls on fracture patterns within carbonates and implications for groundwater flow abstract groundwater flow in low matrix permeability carbonate rocks is largely controlled by fracture networks the stratigraphic features that control fracture initiation and termination within a sequence of sedimentary rock strata define the mechanical stratigraphy of the sequence we investigate the effectiveness of various types of stratigraphic horizons in terminating opening mode fractures in two different carbonate rock sequences a relatively homogeneous dolomite sequence in door county wi and an interbedded chalk and marl sequence within the austin chalk tx additionally we present analog and numerical modeling results that delineate the specific mechanisms that facilitate fracture termination the combination of model results and empirical relationships between observed sedimentary features and mechanical stratigraphy shows 1 fractures terminate at weak contacts e g thin organic layers shallowly buried contacts or thick fine grained units adjacent to thin fractured beds 2 fractures propagate across strong contacts e g intracycle contacts between different lithology and thin fine grained units adjacent to thick fractured beds and 3 fractures step over at moderate strength contacts we use these guidelines to predict fracture network from sedimentary stratigraphy by qualitatively assessing the mechanical stratigraphy of a portion of the relatively complex cretaceous shelf margin sequence at sant corneli spain this predictive demonstration illustrates the utility of assessing the mechanical stratigraphy of subsurface strata within which fractures are not directly observable we conclude that for a variety of carbonate mechanical stratigraphic sequences dominant fluid flow characteristics such as horizontal high flow zones and flow compartmentalization can be evaluated using fracture spacing and connectivity within fracture networks that is predicted from sedimentary stratigraphy although the resulting heterogeneous flow networks do not rely on every fracture present they are highly dependent on the mechanical stratigraphy

diffusion creep and partial melting in high temperature mylonitic gneisses hope valley shear zone new england appalachians usa field petrographic microstructural and isotopic studies of mylonitic gneisses and associated pegmatites along the hope valley shear zone in southern rhode island indicate that late palaeozoic deformation c 275 ma in this zone occurred at very high temperatures 650 c high energy cuspate lobate phase boundary microstructures a predominance of equant to sub equant grains with low internal lattice strain and mixed phase distributions indicate that diffusion creep was an important and possibly predominant deformation mechanism field and petrographic evidence are consistent with the presence of an intergranular melt phase during deformation some of which collected into syntectonic pegmatites rb sr isotopic analyses of tightly sampled pegmatites and wall rocks confirm that the pegmatites were derived as partial melts of the immediately adjacent isotopically heterogeneous mylonitic gneisses the presence of syntectonic interstitial melts is inferred to have permitted a switch from dislocation creep to melt enhanced diffusion creep as the dominant mechanism in these relatively coarse grained mylonitic gneisses 200 500 lm syn deformational grain size a switch to diffusion creep would lead to significant weakening and may explain why the hope valley shear zone evolved into a major regional tectonic boundary this work identifies conditions under which diffusion creep operates in naturally deformed granitic rocks and illuminates the deformation processes involved in the development of a tectonic boundary between two distinct late proterozoic avalonian basement terranes

syn exhumation partial melting and melt segregation in the sulu uhp terrane evidences from leucosome and pegmatitic vein of migmatite abstract in order to investigate partial melting and melt evolution during exhumation of deeply subducted continental crust we carried out a combined study on layered leucosomes and pegmatitic veins from the weihai rongcheng migmatites in the sulu ultra high pressure uhp metamorphic terrane eastern china the leucosomes are millimetric to centimetric in thickness and mainly consists of k feldspar quartz plagioclase the pegmatitic veins emplace along the compositional layers or crosscut them and are mainly composed of k feldspar quartz cl images show that most zircon grains of the leucosomes have a core rim zoning structure whereas zircons of the pegmatitic veins are mostly new growth grains with rarely preserved relict domains the inherited zircon domains ca 750 ma are of a magmatic origin with zircon ehf t values between 5 7 and 5 3 mean 0 8 1 5 suggesting that the protolith rock is a mid neoproterozoic juvenile crust the zircon overgrowth rims 223 3 ma of the leucosomes and the new zircon grains 217 2 ma of the pegmatitic veins formed in equilibrium with melt and are similar to magmatic zircons in terms of their cl images and trace element compositions e g heavy enriched ree patterns i e very low gd lu n ratios with positive ce and variably negative eu anomalies high y contents and low hf y ratios compared with the inherited protolith zircon domains the triassic zircon domains of the leucosomes and the pegmatitic veins have obviously high u but low th contents resulting in very low th u ratios

field study of dispersion in a heterogeneous aquifer 3 geostatistical analysis of hydraulic conductivity observations of the spatial variability of hydraulic conductivity at a tracer test site located at columbus air force base in mississippi are presented direct measurements of hydraulic conductivity of the heterogeneous alluvial aquifer at the site were made using borehole flowmeter logging slug tests and a laboratory permeameter to test undisturbed soil cores indirect methods estimating hydraulic conductivity were also evaluated including soil grain size analyses surface geophysical surveys and mapping of sediment facies the spatial covariance of the 2187 hydraulic conductivity values obtained with the borehole flowmeter method was examined the log hydraulic conductivity variance ln2k and the horizontal and vertical correlation scales h and v of 4 5 12 8 m and 1 6 m respectively were estimated assuming second order stationarity of the conductivity field the covariance parameters are uncertain with bounding values that are 24 76 above or below the estimate covariance parameters estimated with more limited nonflowmeter data were within the same magnitude as those obtained using the extensive flowmeter data suggesting that data from a variety of methods may be used to provide approximate values of the autocovariance parameters nonstationarity of the ln k field was examined by removing three dimensional polynomial trend surfaces and calculating variograms of the residuals significantly lower estimates for ln2k h and v of 2 7 4 8 m and 0 8 m respectively were obtained from the third order log conductivity residuals after trend removal the bounding parameter values differ 15 44 from the estimated values accounting for unsteady flow and the uncertainty in the covariance parameters of the third order log conductivity residuals the calculated longitudinal and horizontal transverse macrodispersivities ranged from 1 5 m to 1 8 m and 0 3 m to 0 6 m respectively

textural immaturity of cumulates as an indicator of magma chamber processes infiltration and crystal accumulation in the rum eastern layered intrusion textural maturity describes the extent to which rocks have approached textural equilibrium for igneous rocks this is a function of the time integrated thermal history in the sub solidus which for cumulate rocks generally translates to the cooling history via the rate of solidification of the accumulating crystal mush the most straightforward way to quantify the textural maturity of orthocumulates sensu lato is to measure the angle subtended at the corners of interstitial grains texturally mature cumulates have angle populations with median values of c 120 whereas texturally immature cumulates have lower medians inherited by the interstitial phase which infills either an impingement texture in the accumulating mush or a texturally equilibrated pore topology textural observations of allivalites from the rum layered suite demonstrate that stratigraphically localized excursions towards textural immaturity are the result of either transient relatively rapid solidification rates perhaps a result of the arrival of cold crystal laden bodies of fluid on the chamber floor or late stage infiltration of fully solidified cumulates by evolved liquids expelled upwards by compaction of underlying horizons these two processes have distinct textural and compositional signatures

the impeller meter for measuring aquifer permeability variations evaluation and comparison with other tests a knowledge of the variation of horizontal hydraulic conductivity with vertical position k z is important in understanding the transport and dispersive properties of aquifers using an impeller meter to measure the discharge distribution in a screened well while pumping at a constant rate is a promising technique for obtaining the k z function such an application is described herein and the resulting k z functions are compared with those obtained previously using tracer tests and multilevel slug tests impeller meter data were the most convenient to obtain and tracer data the most difficult the k z functions obtained by the three methods were not identical but quite similar overall this similarity between both borehole tests and the larger scale tracer test showed that nonstationary hydraulic conductivity trends in a stochastic hydrologic sense exist in the test aquifer the impeller meter method was better able to detect the higher k layers than was the multilevel slug approach overall the results suggest that a practical strategy for fitting impeller meter tracer or multilevel slug test data to a given aquifer is to use the selected testing procedure to obtain a dimensionless distribution and then a standard pumping test to measure combining both types of information enables dimensional values for k z to be calculated in low permeability aquifers or near the bottom of a test well the fluid velocity due to pumping may be below the stall velocity of an impeller thus there is a definite need for the commercial development of more sensitive flow measuring devices such as heat pulse flowmeters hess 1986 which will extend the resolution of this field method

upscaling and regionalizing hydraulic conductivity and effective porosity at watershed scale in deeply weathered crystalline aquifers two innovative approaches for upscaling and regionalizing hydraulic conductivity and effective porosity at watershed scale are proposed they are based on the concept that large scale variations in hydraulic head may characterize large scale properties and were tested on an unconfined granitic aquifer exposed to deep weathering located in south india maheshwaram watershed 53 km2 both methods are based on field data such as water levels discharge rates of irrigation wells geological observations and the results of small scale hydraulic tests the resulting hydraulic conductivity map uses the statistical empirical relationship between log normal distributions of hydraulic conductivity from small scale tests and linear discharge rates from exploited wells i e the ratio between discharge rate and the saturated aquifer thickness the empirical relationship agrees with thiem dupuit s assumption for unconfined aquifers the performance of the method was compared to the values of local hydraulic conductivity estimates deduced from small scale tests not used for drawing the map about 90 of simulated values varies less than 20 from local measurements logk 0 4 on average which is reasonable considering the complexity of the studied fractured aquifer the regionalization of the effective porosity was based on a method that combines both water table fluctuation and groundwater budget techniques in the absence of recharge from rainfall however the use of these techniques at cell scale requires a good knowledge of groundwater flux to and from the cells which here is unknown to avoid this difficulty a coarse graining method was used assuming that increasing the cell size for such computations leads to a negligible contribution of these flux compared to net groundwater abstraction from the cell our results show that cell sizes over 520 520 m achieve a negligible balance in addition porosity maps provide average values of around 1 5 that are almost identical to the ones previously found at watershed scale the proposed methods for regionalizing hydraulic conductivity and porosity fields provide access not only to the average large scale values but also to their spatial distribution which is of prime interest in terms of flux and contaminant transport in a hard rock environment the uncertainty introduced by field data the choice of the computation scale as the impact of cell size on the calculated effective porosity value and the possible meaning of their spatial variations are also discussed

laboratory studies on a new laser doppler velocimeter system for horizontal groundwater velocity measurements in a borehole this paper introduces a new instrument for measuring groundwater velocity in a borehole using a laser doppler velocimeter ldv technique the major improvement of the proposed ldv system is that the probe can be inserted into a borehole that has a minimum diameter of 10 cm and that a disk type rotating grating is used as a frequency shifter for low velocities in order to determine the velocity sign the speed of the glass plate passing through the ldv measurement point is calibrated to demonstrate the accuracy of the new ldv system from a comparison with the true constant speed of the glass plate we confirm that the new ldv system can measure low speeds in the range from 10 5 to 10 2 cm s at a measurement error of less than 8 laboratory experiments were carried out to investigate the performance of the new ldv system for the horizontal velocity measurement of groundwater in a borehole the result obtained by the proposed ldv system shows that the horizontal velocity at the center of an unscreened borehole is 3 times larger than the seepage velocity in a confined aquifer this result agrees with the theoretical solution for groundwater flow in a borehole derived by sano 1983 the validity of the theoretical solution is experimentally verified in the laboratory using the current ldv system although the detectable minimum velocity in a borehole is limited by the velocity fluctuations due to the brownian motion of scattering particles results obtained in the experiments using 0 804 m polystyrene particles show that the ldv system described in this paper can measure with a sufficient accuracy both the magnitude and the direction of groundwater velocity down to 10 4 cm s in a borehole

conceptualization of flow and transport in a limestone aquifer by multiple dedicated hydraulic and tracer tests abstract limestone aquifers are of great interest as a drinking water resource in many countries they often have a complex crushed and fractured geology which makes the analysis and description of flow and transport processes in such aquifers a challenging task in this study the solute transport behavior including fracture matrix interaction in hydrogeological units of a limestone aquifer in eastern denmark was characterized by designing conducting and interpreting six depth specific tracer tests involving natural and forced gradient conditions with multiple tracers representing different diffusion properties to determine flow parameters the tracer tests were complemented by a comprehensive set of depth specific borehole and hydraulic tests based on the tests a new and stronger conceptual understanding was developed for the different aquifer units the investigated limestone aquifer is composed of a glacially crushed unit and two fractured units with calcarenitic and bryozoan limestone of similar hydraulic properties hydraulic tests revealed that the crushed unit has a lower hydraulic conductivity than the fractured limestone units likely due to the crushed conditions with small limestone clusters and small aperture fractures potentially filled with fine material in the fractured limestone units a distinct preferential flow and primary transport along major horizontal fractures was inferred from the tracer tests under forced gradient conditions the dominant horizontal fractures were identified on impeller flow logs and appear connected between wells having an extent of up to several hundred meters connectivity between the aquifer units was investigated with a long term pumping test and tracer tests revealing restricted vertical flow and transport a very pronounced hydraulic conductivity contrast between major fractures and matrix could also be inferred from the borehole and hydraulic tests which is consistent with the findings from the tracer tests the difference in the matrix diffusion behavior of the simultaneously injected tracers and a long tailing in the breakthrough curves revealed that matrix diffusion has a strong influence on the solute transport in the fractured limestone

partial melt topology in statically and dynamically recrystallized granite microstructures of the murray granite pluton central ontario canada show evidence of both static and dynamic crystallization subsequent to partial melting backscattered electron analyses reveal interstitial k feldspar and plagioclase at triple junctions of strain free isometric quartz grains the geometry of the quartz feldspar boundaries mimics the original topology of the quartz melt contacts during crystallization this conclusion is suggested by the occurrence of both rounded and planar faces of quartz grains and by low 27 dihedral angles of quartz quartz feldspar boundaries similar to dihedral angles in experimentally crystallized quartz quartz silicic melt systems in contrast feldspar seams in deformed granites have high axial ratios are usually elongated perpendicular to the foliation plane and are located preferentially along individual grain boundaries quartz grains are dynamically recrystallized and occasionally transected by feldspar seams indicating that fracturing occurred in the presence of melt during crystal plastic deformation of quartz the subparallel orientation in quartz grains of intragranular feldspar bearing fractures and interstitial feldspar seams suggests that these features originated as intragranular and intergranular fractures respectively partial melt topology was therefore controlled by intergranular and occasionally by intragranular fracturing

spatial constraints on magma chamber replenishment events from textural observations of cumulates the rum layered intrusion scotland the eastern layered series of the rum layered suite is formed of 16 macro units each comprising a lower peridotite and an overlying feldspar rich layer the local term is allivalite the origin of the peridotite layers is unresolved with two contrasting models the earlier of the two is based on repeated replenishment of an opensystem magma chamber with deposition of fractionated material on the chamber floor the second is based on the early formation of a troctolitic complex which is then repeatedly intruded by sills of replenishing picritic magma to form the peridotite horizons the lack of resolution of this fundamental problem is a consequence of the reliance of previously published studies on field observations i present evidence to show that the clinopyroxene in the allivalites preserves information about the distribution of the last melt to solidify permitting determination of not only the extent of supersolidus textural equilibration but also the sub solidus history of the allivalite horizons comparison of profiles of clinopyroxene plagioclase plagioclase median dihedral angle across allivalite units demonstrates that it is possible to distinguish between those that were intruded by later picrite sills and those adjacent to peridotite horizons formed by replenishment and subsequent deposition of fractionated crystals above the pre existing pile in the region studied only the main peridotite body of unit 9 was intruded into a pre existing allivalitic mush

comparison of alternative methodologies for identifying and characterizing preferential flow paths in heterogeneous aquifers one of the main difficulties encountered when characterizing the hydrodynamic properties of a fractured aquifer is to identify the preferential flow paths within it different methods may be applied to determine the variability of the permeability at the borehole scale and to image the structure of the main flow zones between boreholes in this paper we compare the information obtained from different measurement techniques performed in a set of three 100 m depth wells well to well spacing 5 10 m in a fractured crystalline rock setting geophysical logging and borehole wall imaging are used to identify open and closed fractures intersecting the boreholes and their orientation the comparison with flowmeter and single packer tests shows that few of the fractures interpreted as open from geophysical logs are significantly transmissive cross borehole connectivity is first investigated from single packer tests with pressure monitoring in adjacent boreholes to determine fracture zone connectivity we propose a methodology simply based on the variation with packer depth of the ratio of the drawdown in the observation well and the drawdown in the pumping well the results are compared to the analysis of cross borehole flowmeter tests we show that both methods provide consistent results with a similar level of information on connectivity

analysis of flow in an observation well intersecting a single fracture abstract a semi analytical model is developed to determine transmissivity and storativity from the interpretation of transient flow in an observation well due to pumping in a source well where the two wells are connected by a single fracture flow rate can be determined using a heat pulse flowmeter located above the intersection of the fracture in the observation well the results of a field experiment were interpreted using the new model and compared with drawdown data from the same test good agreement between the transmissivity estimates was observed whereas estimates of storativity were found to be better determined from the analysis of flow rate

a methodology for regionalizing 3 d effective porosity at watershed scale in crystalline aquifers 13 an innovative approach for regionalizing the 3 d effective porosity field is presented and 14 applied to two large overexploited and deeply weathered crystalline aquifers located in 15 southern india the method derives from earlier work on regionalizing a 2 d effective 16 porosity field in that part of an aquifer where the water table fluctuates which is now 17 extended over the entire aquifer using a 3 d approach a method based on geological and 18 geophysical surveys has also been developed for mapping the weathering profile layers 19 saprolite and fractured layers the method for regionalizing 3 d effective porosity 20 combines water table fluctuation and groundwater budget techniques at various cell sizes 21 with the use of satellite based data for groundwater abstraction the structure of the 22 weathering profile and geostatistical techniques the approach is presented in detail for the 23 kudaliar watershed 983 km 2 and tested on the 730 km 2 anantapur watershed at watershed 24 scale the effective porosity of the aquifer ranges from 0 5 to 2 in kudaliar and between 25 0 3 and 1 in anantapur which agrees with earlier works results show that i depending 26 on the geology and on the structure of the weathering profile the vertical distribution of 27 effective porosity can be very different and that the fractured layers in crystalline aquifers are 28 not necessarily characterized by a rapid decrease in effective porosity and ii that the lateral 29 variations in effective porosity can be larger than the vertical ones these variations suggest 30 that within a same weathering profile the density of open fractures and or degree of 31 weathering in the fractured zone may significantly varies from a place to another 32 the proposed method provides information on the spatial distribution of effective porosity 33 which is of prime interest in terms of flux and contaminant transport in crystalline aquifers 34 implications for mapping groundwater storage and scarcity are also discussed which should 35 help in improving groundwater resource management strategies 36 37

groundwater flows in weathered crystalline rocks impact of piezometric variations and depth dependent fracture connectivity summary groundwater in shallow weathered and fractured crystalline rock aquifers is often the only perennial water resource especially in semi arid region such as southern india understanding groundwater flows in such a context is of prime importance for sustainable aquifer management here we describe a detailed study of fracture properties and relate the hydraulic connectivity of fractures to groundwater flows at local and watershed scales investigations were carried out at a dedicated experimental hydrogeological park in andhra pradesh southern india where a large network of observation boreholes has been set up twenty height boreholes have been drilled in a small area of about 18 000 m 2 in which borehole loggings and hydraulic tests were carried out to locate the main flowing fractured zones and investigate fractures connectivity several hydraulic tests nineteen slug tests and three pumping tests performed under two water level conditions revealed contrasting behavior under high water level conditions the interface including the bottom of the saprolite and the first flowing fractured zone in the upper part of the granite controls groundwater flows at the watershed scale under low water level conditions the aquifer is characterized by lateral compartmentalization due to a decrease in the number of flowing fractures with depth depending on the water level conditions the aquifer shifts from a watershed flow system to independent local flow systems a conceptual groundwater flow model which includes depth dependent fracture connectivity is proposed to illustrate this contrasting hydrological behavior implications for watershed hydrology groundwater chemistry and aquifer vulnerability are also discussed

primary crustal melt compositions insights into the controls mechanisms and timing of generation from kinetics experiments and melt inclusions abstract we explore the controls mechanisms and timing of generation of primary melts and their compositions and show that the novel studies of melt inclusions in migmatites can provide important insights into the processes of crustal anatexis of a particular rock partial melting in the source region of granites is dependent on five main processes i supply of heat ii mineral melt interface reactions associated with the detachment and supply of mineral components to the melt iii diffusion in the melt iv diffusion in minerals and v recrystallization of minerals as the kinetics of these several processes vary over several orders of magnitude it is essential to evaluate in nature which of these processes control the rate of melting the composition of melts and the extent to which residue melt chemical equilibrium is attained under different circumstances to shed light on these issues we combine data from experimental and melt inclusion studies first data from an extensive experimental program on the kinetics of melting of crustal protoliths and diffusion in granite melt are used to set up the necessary framework that describes how primary melt compositions are established during crustal anatexis then we use this reference frame and compare compositional trends from experiments with the composition of melt inclusions analyzed in particular migmatites we show that for the case of el hoyazo anatectic enclaves in lavas the composition of glassy melt inclusions provides important information on the nature and mechanisms of anatexis during the prograde suprasolidus history of these rocks including melting temperatures and reactions and extent of melt interconnection melt homogenization and melt residue equilibrium compositional trends in several of the rehomogenized melt inclusions in garnet from migmatites granulites in anatectic terranes are consistent with diffusion in melt controlled melting though trace element compositions of melt inclusions and coexisting minerals are necessary to provide further clues on the nature of anatexis in these particular rocks

the role of subgrain boundaries in partial melting abstract evidence for partial melting along subgrain boundaries in quartz and plagioclase is documented for rocks from the lost creek gneiss of the llano uplift central texas the wet mountains of central colorado and the albany fraser orogen southwestern australia domains of quartz or plagioclase crystals along subgrain boundaries are preferentially involved in partial melting over unstrained domains of these minerals material along subgrain boundaries in quartz and plagioclase has the same morphology as melt pseudomorphs present along grain boundaries and is commonly laterally continuous with this former grain boundary melt indicating the material along subgrain boundaries can also be categorized as a melt pseudomorph subgrain boundaries consist of arrays of dislocations within a crystal lattice and unlike fractures would not act as conduits for melt migration instead the presence of former melt along subgrain boundaries requires that partial melting occurred in these locations because it is kinetically more favorable for melting reactions to occur there preferential melting in high strain locations may be attributed to strain energy which provides a minor energetic contribution to the reaction and leads to preferential melting in locations with weakened bonds and or the presence of small quantities of water associated with dislocations which may enhance diffusion rates or locally lower the temperature needed for partial melting

submagmatic microfractures in granites microstructures in hercynian granite plutons of the pyrenees indicate fracturing of plagioclase crystals in the presence of melt this is represented mainly by quartz and or feldspar that fills fractures electron microprobe analyses demonstrate that in compositional agreement with the rims of the zoned plagioclase the feldspar infillings are more sodic with decreasing melt fraction fracturing resulted from concentration of stress at contacts between grains while the granite was submagmatic i e when the melt was below the critical fraction for magmatic flow material compositionally far from eutectic is petrologically the best candictate to develop submagmatic fractures because during cooling the volume fraction of melt remains low for a large temperature range a strong tendency for microfractures to be oblique to flow foliation may constitute a new criterion for shear sense in magmas

characterizing groundwater flow and heat transport in fractured rock using fiber optic distributed temperature sensing 1 we show how fully distributed space time measurements with fiber optic distributed temperature sensing fo dts can be used to investigate groundwater flow and heat transport in fractured media heat injection experiments are combined with temperature measurements along fiber optic cables installed in boreholes thermal dilution tests are shown to enable detection of cross flowing fractures and quantification of the cross flow rate a cross borehole thermal tracer test is then analyzed to identify fracture zones that are in hydraulic connection between boreholes and to estimate spatially distributed temperature breakthrough in each fracture zone this provides a significant improvement compared to classical tracer tests for which concentration data are usually integrated over the whole abstraction borehole however despite providing some complementary results we find that the main contributive fracture for heat transport is different to that for a solute tracer

origin of large volume pseudotachylite in terrestrial impact structures large volume pseudotachylite bodies in impact structures are dike like and consist of angular and rounded wall rock fragments enveloped by a microcrystalline and sporadically glassy matrix that crystallized from a melt knowledge of the formation of pseudotachylite bodies is important for understanding mechanics of complex crater formation most current hypotheses of pseudotachylite formation inherently assume that fragmentation and melt generation occur during a single process based on the structure of pseudotachylite bodies at sudbury canada and vredefort south africa we show that these processes differ in time and space we demonstrate that the centimeter to kilometer scale bodies are effectively fragment and melt fi lled tension fractures that formed by differential rotation of target rock during cratering highly variable pseudotachylite characteristics can be accounted for by a single process i e drainage of initially superheated impact melt into tension fractures of the crater fl oor

advanced aquifer characterization for optimization of managed aquifer recharge managed aquifer recharge mar will play an increasingly important role in solving water scarcity the performance of mar systems depends primarily upon local hydrogeology greatest opportunities for improvement in the implementation of mar systems lie in the targeted application of conventional and advanced technologies to improve aquifer characterization surface geophysics e g ves tdem and seismic reflection and refraction generally provide low resolution but areal extensive data on subsurface hydrogeology times series of relative microgravity measurements have been used to map changes in both vadose and phreatic zone storage and to augment monitoring well systems surface nuclear magnetic resonance nmr has the potential to provide quantitative data on water filled porosity and pore size distribution and in turn an estimate of hydraulic conductivity standard borehole geophysical logging techniques can provide coarse scale data on aquifer heterogeneity advanced borehole logging techniques such as nmr microresistivity imaging and gamma ray spectroscopy have been used in mar projects in the usa and uae to provide fine scale petrophysical data e g porosity porosity types and pore size distribution groundwater modeling is used in mar investigations to evaluate system feasibility and to optimize system design and operation opportunities to improve groundwater modeling exist through the application of advanced reservoir simulation platforms that allow for the processing and integration of available lithological geophysical and aquifer testing data and their subsequent incorporation into groundwater flow models advanced groundwater modeling programs are available that allow for the simulation of complex aquifers such as dual porosity systems and variable density

hydrogeologic controls imposed by mechanical stratigraphy in layered rocks of the châteauguay river basin a u s canada transborder aquifer 1 the ch teauguay river basin delineates a transborder watershed with roughly half of its surface area located in northern new york state and half in southern quebec province canada as part of a multidisciplinary study designed to characterize the hydrogeologic properties of this basin geophysical logs were obtained in 12 wells strategically located to penetrate the four major sedimentary rock formations that constitute the regional aquifers the layered rocks were classified according to their elastic properties into three primary units soft sandstone hard sandstone and dolostone downhole measurements were analyzed to identify fracture patterns associated with each unit and to evaluate their role in controlling groundwater flow fracture networks are composed of orthogonal sets of laterally extensive subhorizontal bedding plane partings and bed delimited subvertical joints with spacings that are consistent with rock mechanics principles and stress models the vertical distribution of transmissive zones is confined to a few select bedding plane fractures with soft sandstone having the fewest one per 70 m depth and hard sandstone the most five per 70 m depth bed normal permeability is examined using a probabilistic model that considers the lengths of flow paths winding along joints and bedding plane fractures soft sandstone has the smallest bed normal permeability primarily because of its wide geomechanically undersaturated joint spacing results indicate that the three formations have similar values of bulk transmissivity within roughly an order of magnitude but that each rock unit has its own unique system of groundwater flow paths that constitute that transmissivity

interpretation of transient borehole flow metering data in a fissured granite formation summary heat pulse flowmeter hpf data obtained in a fractured granite formation under transient pumping conditions are interpreted using a borehole flow model the phraeatic formation is modeled using cylindrically symmetric layers composed of thick low permeability intervals between thin layers of much higher permeability corresponding to fracture zones the inflow to the borehole at fracture zones generates sharp increases in the flow profiles obtained during pumping heat pulse flowmeter measurements are given as a function of depth and time drawdown and pumping rate are also recorded during the measurement period the numerical flow model is used to calculate the drawdown and evolving profile of borehole flow as a function of time during the pumping period the model allows for vertical flow across the horizontal interfaces between layers and accounts for borehole storage effects the model is also designed to allow for changes in fracture zone permeability with distance from the borehole bi zonal flow by allowing for changes in permeability with radial distance the model uses a finite difference technique to compute borehole flow and drawdown during pumping the accuracy of the finite difference code was checked against available analytical and semi analytical solutions derived by integral transform techniques the model was calibrated using estimates of formation properties and distance to lateral boundaries derived from short medium and long term packer tests results of two borehole flow experiments are evaluated for experiments in boreholes with 7 and 4 discrete fracture zones distributed over 59 50 and 121 16 m of open borehole interval

cross borehole flow profiling delineating subsurface flow paths within a geophysically defined aquifer framework an extensive geophysical tool box is available with which to construct models of subsurface flow paths in complex aquifers using a combination of surface and borehole methods these methods include electromagnetic and seismic sounding from the surface and downhole imaging methods based on acoustic optical and electrical properties of rocks surrounding the borehole however such methods are inherently limited in hydrogeophysics because of the need to measure properties such as rock alteration or local fracture density that are indirectly related to subsurface flow rather than directly sampling the hydraulic parameters permeability storage coefficient and hydraulic head of subsurface flow paths high resolution borehole flow profiles provide an opportunity to relate geophysical characterization to hydraulic properties as an integral part of the standard geophysical logging program single borehole flow analysis provides information on the hydraulic properties of flow paths in the limited region immediately adjacent to the borehole cross borehole methods where flow is measured in one borehole while an adjacent borehole is stressed characterize the large scale flow paths that connect the individual flow zones identified in individual boreholes

large scale natural gradient tracer test in sand and gravel cape cod massachusetts 3 hydraulic conductivity variability and calculated macrodispersivities hydraulic conductivity k variability in a sand and gravel aquifer on cape cod massachusetts was measured and subsequently used in stochastic transport theories to estimate macrodispersivities nearly 1500 k measurements were obtained by borehole flowmeter tests and permeameter analyses of cores the geometric mean for the flowmeter tests 0 11 cm s is similar to that estimated from other field tests the mean for the permeameter tests 0 035 cm s is significantly lower possibly because of compaction of the cores the variance for the flowmeter 0 24 is also greater than that for the permeameter 0 14 geostatistical analyses applying negative exponential models with and without nuggets reveal similar spatial correlation structures for the two data sets estimated correlation scales range from 2 9 to 8 m in the horizontal and from 0 18 to 0 38 m in the vertical estimates of asymptotic longitudinal dispersivity b 35 0 78 m are similar in magnitude to that observed in the natural gradient tracer test 0 96 m previously conducted at this site

analysis of 6 year fluid electric conductivity logs to evaluate the hydraulic structure of the deep drill hole at outokumpu finland over the last two decades the flowing fluid electric conductivity ffec logging method has been applied in boreholes in the well testing mode to evaluate the transmissivity hydraulic head and formation water electrical conductivity as a function of depth with a resolution of about 10 20 cm ffec profiles along the borehole are obtained under both shut in and pumping conditions in a logging procedure that lasts only 3 or 4 days a method for analyzing these ffec logs has been developed and successfully employed to obtain formation parameters in a number of field studies the present paper concerns the analysis of a unique set of ffec logs that were taken from a deep borehole reaching down to 2 5 km at outokumpu finland over a 6 year time period the borehole intersects paleoproterozoic metasedimentary granitoid and ophiolite derived rocks after the well was drilled completed and cleaned up ffec logs were obtained after 7 433 597 948 and 2036 days in analyzing these five profiles we discovered the need to account for salinity diffusion from water in the formation to the borehole analysis results include the identification of 15 hydraulically conducting zones along the borehole the calculation of flow rates associated with these 15 zones as well as the estimation of the variation of formation water electrical conductivity as a function of depth the calculated flow rates were used to obtain the tentative hydraulic conductivity values at these 15 depth levels

application of direct fitting mass integral and multirate methods to analysis of flowing fluid electric conductivity logs from horonobe japan 1 the flowing fluid electric conductivity ffec logging method is an efficient way to provide information on the depths salinities and inflow strengths of individual conductive features intercepted by a borehole without the use of specialized probes using it in a multiple flow rate mode allows in addition an estimate of the transmissivities and inherent far field hydraulic heads in each of the conductive features the multirate method was successfully applied to a 500 m borehole in a granitic formation and reported recently the present paper describes the application of the method to two zones within a 1000 m borehole in sedimentary rock which produced for each zone three sets of logs at different pumping rates each set measured over a period of about 1 day the data sets involve several complications such as variable well diameter gradual water level decline in the well during logging possible fluid flow through the unfractured rock matrix and effects of drilling mud various techniques were applied to analyze the ffec logs direct fitting mass integral and the multirate method mentioned above in spite of complications associated with the tests analysis was able to identify 44 hydraulically conducting fractures distributed over the depth interval 150 775 m below ground surface the salinities in fec and transmissivities and hydraulic heads in dimensionless form of these 44 features were obtained and found to vary significantly among one another these results were compared with transmissivity and head values inferred from eight packer tests that were conducted in this borehole over the same depth interval ffec results were found to be consistent with packer test results thus demonstrating the robustness of the ffec logging method under nonideal conditions

deep confined karst detection analysis and paleo hydrology reconstruction at a basin wide scale using new geophysical interpretation of borehole logs summary deep karst voids can be identified by a new method of geophysical interpretation of commonly used borehole logs in deeply confined carbonate aquifers we show that deep buried karst voids can be characterized by combining this geophysical interpretation together with geological and hydrological data and with known speleological constraints we demonstrate how this characterization can reveal past hydrological regimes and allow mapping of karst distribution on a basin wide scale a combined analysis of geophysical geological hydrological and speleological data in the confined yarkon taninim aquifer israel led us to reconstruct past groundwater levels at different relief and sea levels with the karst voids as a marker for long term flow close to the water table paleo canyons along the mediterranean sea shoreline strongly affected the region s paleo hydrology by serving as major outlets of the aquifer during most of the cenozoic we conclude that intensive karstification was promoted by flow periods of longer duration and or higher flux and flow velocities close to the aquifer s past and present outlets in addition we suggest that karst voids found under shallow confinement were developed by renewed aggressivity due to hypogene water rising in cross formational flow becoming mixed with fresh lateral water flow from the east

experimental deformation of partially melted granitic aggregates abstract the effects of varying amounts of partial melt on the deformation of granitic aggregates have been tested experimentally at conditions 900 c 1500 mpa 10 4 to 10 6 s where melt free samples deform by dislocation creep with microstructures approximately equivalent to those of upper greenschist facies experiments were performed on samples of various grain sizes including an aplite 150 m and sintered aggregates of quartz albitemicrocline 10 50 and 2 10 m water was added to the samples to obtain various amounts of melt 1 15 in the aplite 1 5 in the sintered aggregates optical and tem observations of the melt distribution in hydrostatically annealed samples show that the melt in the sintered aggregates is homogeneously distributed along an interconnected network of triple junction channels while the melt in the aplites is inhomogeneously distributed the effect of partial melt on deformation depends an melt amount and distribution grain size and strain rate for samples deformed with 1 melt all grain sizes exhibit microstructures indicative of dislocation creep for samples deformed with 3 5 melt the 150 m and 10 50 m grain size samples also exhibit dislocation creep microstructures but the 2 10 m grain size samples exhibit abundant tem scale evidence of dissolution precipitation and little evidence of dislocation activity suggesting a switch in deformation mechanism to predominantly melt enhanced diffusion creep at natural strain rates melt enhanced diffusion creep would predominate at larger grain sizes although probably not for most coarse grained granites the effects of melt percentage and strain rate have been studied for the 150 m aplites for samples with 5 and 10 melt deformation at 10 6 s squeezes excess melt out of the central compressed region allowing predominantly dislocation creep conversely deformation at 10 5 s produces considerable cataclasis presumably because the excess melt cannot flow laterally fast enough and a high pore fluid pressure results for samples with 15 melt deformation at both strain rates produces cataclasis presumably because the inhomogeneous melt distribution resulted in regions of decoupled grains which would produce high stress concentrations at point contacts at natural strain rates there should be little or no cataclasis if an equilibrium melt texture exists and if the melt can flow as fast as the imposed strain rate however if the melt is confined and cannot migrate a high pore fluid pressure should promote brittle deformation

groundwater sources and geochemical processes in a crystalline fault aquifer the origin of water flowing in faults and fractures at great depth is poorly known in crystalline media this paper describes a field study designed to characterize the geochemical compartmentalization of adeep aquifer system constituted by a graben structure where a permeable fault zone was identified analysesof the major chemical elements trace elements dissolved gases and stable water isotopes reveal theorigin of dissolved components for each permeable domain and provide information on various watersources involved during different seasonal regimes the geochemical response induced by performinga pumping test in the fault zone is examined in order to quantify mixing processes and contributionof different permeable domains to the flow reactive processes enhanced by the pumped fluxes are alsoidentified and discussed the fault zone presents different geochemical responses related to changes in hydraulic regime theyare interpreted as different water sources related to various permeable structures within the aquifer during the low water regime results suggest mixing of recent water with a clear contribution of olderwater of inter glacial origin recharge temperature around 7 c suggesting the involvement of watertrapped in a local low permeability matrix domain or the contribution of large scale circulation loops during the high water level period due to inversion of the hydraulic gradient between the major permeablefault zone and its surrounding domains modern water predominantly flows down to the deep bedrockand ensures recharge at a local scale within the graben pumping in a permeable fault zone induces hydraulic connections with storage reservoirs the overlaidregolith domain ensures part of the flow rate for long term pumping around 20 in the present case during late time pumping orthogonal fluxes coming from the fractured domains surrounding the majorfault zone are dominant storage in the connected fracture network within the graben structure mainlyensures the main part of the flow rate 80 in the present case reactive processes are induced by mixingof water from different sources and transfer conditions a specific approach is applied to quantify thereaction rate involved along the pumping time autotrophic denitrification coupled with iron mineralsoxidation is highlighted and water rock interaction is clearly enhanced by the flux changes induced bypumping

flow modeling and permeability estimation using borehole flow logs in heterogeneous fractured formations a numerical model of flow in the vicinity of a borehole is used to analyze flowmeter data obtained with high resolution flowmeters the model is designed to 1 precisely compute flow in a borehole 2 approximate the effects of flow in surrounding aquifers on the measured borehole flow 3 allow for an arbitrary number n of entry exit points connected to m n far field aquifers and 4 be consistent with the practical limitations of flowmeter measurements such as limits of resolution typical measurement error and finite measurement periods the model is used in three modes 1 a quasi steady pumping mode where there is no ambient flow 2 a steady flow mode where ambient differences in far field water levels drive flow between fracture zones in the borehole and 3 a cross borehole test mode where pumping in an adjacent borehole drives flow in the observation borehole the model gives estimates of transmissivity for any number of fractures in steady or quasi steady flow experiments that agree with straddle packer test data field examples show how these cross borehole type curves can be used to estimate the storage coefficient of fractures and bedding planes and to determine whether fractures intersecting a borehole at different locations are hydraulically connected in the surrounding rock mass

using flowmeter pulse tests to define hydraulic connections in the subsurface a fractured shale example cross borehole flowmeter pulse tests define subsurface connections between discrete fractures using short stress periods to monitor the propagation of the pulse through the flow system this technique is an improvement over other cross borehole techniques because measurements can be made in open boreholes without packers or previous identification of water producing intervals the method is based on the concept of monitoring the propagation of pulses rather than steady flow through the fracture network in this method a hydraulic stress is applied to a borehole connected to a single permeable fracture and the distribution of flow induced by that stress monitored in adjacent boreholes the transient flow responses are compared to type curves computed for several different types of fracture connections the shape of the transient flow response indicates the type of fracture connection and the fit of the data to the type curve yields an estimate of its transmissivity and storage coefficient the flowmeter pulse test technique was applied in fractured shale at a volatile organic contaminant plume in watervliet new york flowmeter and other geophysical logs were used to identify permeable fractures in eight boreholes in and near the contaminant plume using single borehole flow measurements flowmeter cross hole pulse tests were used to identify connections between fractures detected in the boreholes the results indicated a permeable fracture network connecting many of the individual boreholes and demonstrated the presence of an ambient upward hydraulic head gradient throughout the site

temporal and spatial scaling of hydraulic response to recharge in fractured aquifers insights from a frequency domain analysis quantification of the recharge in fractured aquifers is particularly challenging because of the multiscale heterogeneity and the range of temporal scales involved here we investigate the hydraulic response to recharge of a fractured aquifer using a frequency domain approach transfer functions are calculated in a range of temporal scales from 1 day up to a few years for a fractured crystalline rock aquifer located in ploemeur s brittany france using recharge and groundwater level fluctuations as input and output respectively the spatial variability of the response to recharge characteristic response time amplitude temporal scaling is analyzed for 10 wells sampling the different compartments of the aquifer some of the transfer functions follow the linear reservoir model behavior on the contrary others display a temporal scaling at high frequency that cannot be represented by classic models large scale hydraulic parameters estimated from the low frequency response are compared with those estimated from hydraulic tests at different scales the variability of transmissivity and storage coefficient tends to decrease with scale and the average estimates converge toward the highest values at large scale the small scale variability of diffusivities which implies the existence of a range of characteristic temporal scales associated with different pathways is suggested to be at the origin of the unconventional temporal scaling of the hydraulic response to recharge at high frequency

high temperature crustal scale shear zone at the western margin of the eastern ghats granulite belt india implications for rapid exhumation abstract a mylonitic shear zone occurs along the western margin of the eastern ghats granulite belt india in the northern sector it separates metapelitic and mafic granulites from the granite gneisses of the bastar craton while in the southern sector it separates charnockitic gneisses and mafic granulites from the granite gneisses of the bastar craton this boundary shear zone is characterized by a mylonitic foliation and a stretching lineation microstructures characterize high grade conditions and quartz c axis patterns show strong point maxima close to the long axes of the strain ellipsoids indicating dominant prism c slip in quartz commonly interpreted in terms of ductile deformation at high temperatures quartz c axis patterns in the recrystallized and unrecrystallized domains also imply grain boundary migration as the principal mechanism of dynamic recrystallization at high temperature conditions a rapid exhumation during shearing in this marginal part of the convergent eastern ghats orogen is indicated by decompression reaction textures and retrograde hydration reactions presumably due to hydrous fluid ingress in the shear zone rocks