origin and significance of clay coated fractures in mudrock fragments of the safod borehole parkfield california 1 the clay mineralogy and texture of rock fragments from the safod borehole at 3067 m and 3436 m measured depth md was investigated by electron microscopy sem tem and x ray diffraction xrd the washed and ultrasonically cleaned samples show slickenfiber striations and thin films of ca k bearing smectite that are formed on polished fault surfaces along freshly opened fractures and within adjacent mineralized veins the cation composition and hydration behavior of these films differ from the na montmorillonite of the fresh bentonite drilling mud although there is more similarity with circulated mud recovered from 3479 m md we propose that these thin film smectite precipitates formed by natural nucleation and crystal growth during fault creep probably associated with the shallow circulation of low temperature aqueous fluids along this shallow portion of the san andreas fault

fault zone architecture of the san jacinto fault zone in horse canyon southern california a model for focused post seismic fluid flow and heat transfer in the shallow crust abstract we report results of a new study of the architecture of the san jacinto fault zone in horse canyon california where stream incision has exposed a nearly continuous outcrop of the fault zone at 0 4 km depth the fault zone at this location consists of a fault core transition zone damage zone and tonalitic wall rocks we collected and analyzed samples for their bulk and grain density geochemical data clay mineralogy and textural and modal mineralogy progressive deformation within the fault zone is characterized by mode i cracking subsequent shearing of already fractured rock and cataclastic flow grain comminution advances towards the strongly indurated cataclasite fault core damage progression towards the core is accompanied by a decrease in bulk and grain density and an increase in porosity and dilational volumetric strain palygorskite and mixed layer illite smectite clay minerals are present in the damage and transition zones and are the result of hydrolysis reactions the estimated percentage of illite in illite smectite increases towards the fault core where the illite smectite to illite conversion is complete suggesting elevated temperatures that may have reached 150 c chemical alteration and elemental mass changes are observed throughout the fault zone and are most pronounced in the fault core we conclude that the observed chemical and mineralogical changes can only be produced by the interaction of fractured wall rocks and chemically active fluids that are mobilized through the fault zone by thermo pressurization during and after seismic events based on the high element mobility and absence of illite smectite in the fault core we expect that the greatest water rock ratios occur within the fault core these results indicate that hot pore fluids circulate upwards through the fractured fault core and into the surrounding damage zone though difficult to constrain we speculate that the site studied during this investigation may represent the top of a narrow ephemeral hydrothermal circulation cell that dissipates heat generated from rupture events at deeper levels 4 km

mineralogical characterization of protolith and fault rocks from the safod main hole 1 washed cuttings provide a continuous record of the rocks encountered during drilling of the main hole of the san andreas fault observatory at depth safod both protolith and fault rocks exhibit a wide variety of mineral assemblages that reflect variations in some combination of lithology p t conditions deformation mechanisms and fluid composition and abundance regions of distinct neomineralization bounded by faults may record alteration associated with fluid reservoirs confined by faults in addition both smectites occurring as mixed layer phases and serpentine minerals are found in association with active strands of the san andreas fault that were intersected during drilling although their rheological influence is not yet fully known faults containing these mineralogical phases are prime candidates for continuous coring during phase 3 of safod drilling in the summer of 2007

draining viscous gravity currents in a vertical fracture we consider the flow of instantaneous releases of a finite volume of viscous fluid in a narrow vertical fracture or hele shaw cell when there is a still narrower vertical crack in the horizontal base of the cell the predominant motion is over the horizontal surface but fluid also drains through the crack progressively diminishing the volume of the current in the fracture when the crack is shallow on the scale of the current it saturates immediately with the draining fluid in this case we obtain an exact analytical solution for the motion when the crack is deeper and does not saturate immediately we calculate numerically the motion of the fluid in both the fracture and the crack in each case the current advances to a finite run out length and then retreats we describe both phases of the motion and characterize the run out length in terms of the controlling parameters

modeling leakage pathways in subsurface formations fluid drainage through multiple fractures in porous media insights from hele shaw cell experiments abstract arresting the recent observed warming of the earth s climate is a challenge requiring the reduction of anthropogenic emissions of carbon dioxide one option for reducing emissions into the atmosphere is to capture and sequester the released carbon dioxide in geological formations however potential geological storage first requires a risk assessment of carbon dioxide escaping to overlying layers and back to the atmosphere through leakage pathways in the formation this in turn requires an understanding of fluid flow through the leakage pathways in this study the effect of leakage pathways on the flow of a gravity current was investigated using an analogue system a hele shaw cell fluid was introduced through the top edge of the cell and flowed out through one or more holes in its impermeable base the height of the accumulated fluid above the base of the cell at various points along its length and the outflow rate of fluid through the holes was measured this measurement was conducted with varying conditions of the location number and strength of source as well as the location and number of holes at steady state the fluid motion was in accordance with darcy s law for horizontal flow in a long thin current in another set of experiments in which inflow was stopped and the fluid was allowed to drain out of a single open hole the outflow rate was in accordance with darcy s law for one dimensional flow in the vertical direction until the fluid height above the hole fell below a certain limit this threshold height was found to be 1 3 cm which was similar in magnitude to the length of the hole a time series of photographs tracked the flow of colored dye the photographs demonstrated that at steady state the fluid traveled for some distance beyond the hole before draining through it this implies that contaminants may be transported in a formation even beyond an outlet before finally draining out through it the photographs also documented the shape of the interface between the newly introduced dye and the ambient fluid in the cell these shapes were found to be different in a cell placed horizontally versus one placed on an incline suggesting that the geometry and flow conditions in a formation affecting the transport of an injected fluid these findings may be used as a basis for predicting behavior of a fluid injected into a fractured formation in the subsurface

buoyant dispersal of co2 during geological storage carbon capture and storage is currently the only technology that may allow significant reductions in co2 emissions from large point sources seismic images of geological co2 storage show the rise of co2 is influenced by horizontal shales the buoyant co2 spreads beneath impermeable barriers until a gap allows its upward migration the large number and small scale of these barriers makes the prediction of the co2 migration path and hence the magnitude of co2 trapping very challenging we show that steady buoyancy dominated flows in complex geometries can be modeled as a cascade of flux partitioning events this approach allows the analysis of two dimensional plume dispersal from a horizontal injection well we show that the plume spreads laterally with height y above the source according to y h 1 2 l where l is the width of the shales and h is their vertical separation the fluid volume below successive shale layers and therefore the magnitude of trapped co2 increase as y h 5 4 above the source so that every additional layer of barriers traps more co2 than the one below upscaling small scale flow barriers by reducing the vertical permeability common in numerical simulations of co2 storage does not capture the dispersion and trapping of the co2 plume by the flow barriers

fault rocks and past to recent fluid characteristics from the borehole survey of the nojima fault ruptured in the 1995 kobe earthquake southwest japan the mineralogy fluid inclusions and distribution of fault rocks of the nojima fault were examined in the core recovered from a borehole drilled by the geological survey of japan gsj 12 months after the 1995 kobe hyogo ken nanbu earthquake mjma 7 2 in southwest japan the borehole was drilled across a slipped portion of the fault to a depth of 746 7 m nearly continuous coring between 152 2 and 746 7 m recovered granodiorite protolith porphyry dikes and fault related rocks the fault zone was intersected at 426 2 m and is characterized by a greater intensity of brittle deformation and or hydrothermal alteration than typical host granodiorite the fault core consists of three types of fault gouge and occurs at the depth range of 623 1 to 625 3 m the fault normal thicknesses of the fault core and the fault zone are 0 3 m and 46 5 m respectively three types of hydrothermal alteration are recorded by mineral assemblages and fluid inclusions the first type is characterized by chloritization of mafic minerals at 200 c and occurred prior to the fault activity during the intrusion and cooling of the granodiorite the second type occurred during faulting and is recorded by zeolite mineralization at 200 c the third type is recorded by carbonate mineralization related to recent fluid flow although most of the second type of alteration occurred prior to the third type repeated mineralization is recorded by mutually crosscutting relationships between zeolite and carbonate veins and between zeolite vein and carbonate precipitated fault gouge this may record repeated changes in fluid chemistry within the fault zone in connection with the seismic cycle although the nojima fault slipped in the 1995 earthquake ancient fault related textures and mineral alteration are well preserved in the fault rocks

the effect of a fissure on storage in a porous medium we consider the two dimensional buoyancy driven flow of a fluid injected into a saturated semi infinite porous medium bounded by a horizontal barrier in which a single line sink representing a fissure some distance from the point of injection allows leakage of buoyant fluid our studies are motivated by the geological sequestration of carbon dioxide co2 and the possibility that fissures in the cap rock may compromise the safe long term storage of co2 a theoretical model is presented that accounts for leakage through the fissure using two parameters which characterize leakage driven both by the hydrostatic pressure within the overriding fluid and by the buoyancy of the fluid within the fissure we determine numerical solutions for the evolution of both the gravity current within the porous medium and the volume of fluid that has escaped through the fissure as a function of time a quantity of considerable practical interest is the efficiency of storage which we define as the amount of fluid remaining in the porous medium relative to the amount injected this efficiency scales like t 1 2 at late times indicating that the efficiency of storage ultimately tends to zero we confirm the results of our model by comparison with an analogue laboratory experiment and discuss the implications of our two dimensional model of leakage from a fissure for the geological sequestration of co2

converging gravity currents over a permeable substrate we study the propagation of viscous gravity currents along a thin permeable substrate where slow vertical drainage is allowed from the boundary in particular we report the effect of this vertical fluid drainage on the second kind self similar solutions for the shape of the fluid fluid interface in three contexts i viscous axisymmetric gravity currents converging towards the centre of a cylindrical container ii viscous gravity currents moving towards the origin in a horizontal hele shaw channel with a power law varying gap thickness in the horizontal direction and iii viscous gravity currents propagating towards the origin of a porous medium with horizontal permeability and porosity gradients in power law forms for each of these cases with vertical leakage we identify a regime diagram that characterizes whether the front reaches the origin or not in particular when the front does not reach the origin we calculate the final location of the front we have also conducted laboratory experiments with a cylindrical lock gate to generate a converging viscous gravity current where vertical fluid drainage is allowed from various perforated horizontal substrates the time dependent position of the propagating front is captured from the experiments and the front position is found to agree well with the theoretical and numerical predictions when surface tension effects can be neglected

modelling carbon dioxide sequestration in layered strata motivated by the geological sequestration of carbon dioxide co2 we study the propagation of gravity currents in a porous medium bounded by a thin layer of much lower permeability we formulate a model for drainage assuming that the fluid remains simply connected throughout using this model we examine the propagation of both two dimensional and axisymmetric currents numerically we find that for the fixed flux situation solutions approach a steady state which is described analytically the approach to this final solution depends on both the permeability contrast and thickness of the thin layer and in many cases the current first overshoots before relaxing back to its ultimate steady state finally we examine propagation along multiple thin lower permeability layers as a reduced order model of the plume of co2 currently being injected at sleipner in the north sea

nanoscale porosity in safod core samples san andreas fault article i nfo with transmission electron microscopy tem we observed nanometer sized pores in four ultracataclastic and fractured core samples recovered from different depths of the main bore hole of the san andreas fault observatory at depth safod cutting of foils with a focused ion beam technique fib allowed identifying porosity down to the nm scale between 40 and 50 of all pores could be identified as in situ pores without any damage related to sample preparation the total porosity estimated from tem micrographs 1 5 is comparable to the connected fault rock porosity 2 8 6 7 estimated by pressure induced injection of mercury permeability estimates for cataclastic fault rocks are 10 21 10 19 m 2 and 10 17 m 2 for the fractured fault rock porosity and permeability are independent of sample depth tem images reveal that the porosity is intimately linked to fault rock composition and associated with deformation the tem estimated porosity of the samples increases with increasing clay content the highest porosity was estimated in the vicinity of an active fault trace the largest pores with an equivalent radiusn 200 nm occur around large quartz and feldspar grains or grain fragments while the smallest pores equivalent radiusb 50 nm are typically observed in the extremely fine grained matrix grain sizeb 1 m based on pore morphology we distinguish different pore types varying with fault rock fabric and alteration the pores were probably filled with formation water and or hydrothermal fluids at elevated pore fluid pressure preventing pore collapse the pore geometry derived from tem observations and bet brunauer emmett and teller gas adsorption desorption hysteresis curves indicates pore blocking effects in the fine grained matrix observations of isolated pores in tem micrographs and high pore body to pore throat ratios inferred from mercury injection suggest elevated pore fluid pressure in the low permeability cataclasites reducing shear strength of the fault 2010 elsevier b v all rights reserved

fluid rock interactions in seismic faults implications from the structures and mineralogical and geochemical compositions of drilling cores from the rupture of the 2008 wenchuan earthquake china we describe the structural features and mineralogical and geochemical compositions of the fault rocks recovered from boreholes at the golden river site on the yingxiu beichuan fault which activated and slipped along a 240 km long main surface rupture zone during the 2008 wenchuan earthquake the fault which accommodated co seismic slip cuts granitic rocks from the pengguan complex in which this earthquake most likely nucleated fault rocks including cohesive cataclasite unconsolidated breccia and three fault gouges with distinct colors were identified from the drilling cores on going uplift and erosion in the area means that the fault rocks formed at different depth were exhumed to the shallow surface during the uplift history of the longmenshan fault zone a clear change from fracturing and comminution in the cataclasites and breccia to more pervasive shear formation of fine grained materials in the gouges has been observed the gouges are distinct and have accommodated significant displacement in multiple increments of shear furthermore fault rocks recovered from the boreholes display numerous features indicative of fluid infiltration and fluid rock interaction toward the fault core clay minerals have replaced feldspars the element enrichment depletion patterns of the fault rocks show general fluid infiltration trends such as 1 mobile elements are generally depleted in the fault rocks 2 the microstructural mineralogical and geochemical results of the fault rocks consistently indicate that pervasive fluid infiltration and fluid rock interactions altered feldspars and mafic minerals to clay minerals the fluid was mg2 and fe2 rich facilitating formation of chlorite isocon analyses further reveal that a large rock volume has been lost which is attributed to the removal of mobile elements associated with fluid infiltration and perhaps enhanced by pressure solution these results reflect the accumulated effects of cataclasis and fluid infiltration fluid rock interaction during the long evolution history of the longmenshan fault zone fluid rock interactions in seismic faults implications from the structures and mineralogical and geochemical compositions of drilling cores from the rupture of the 2008 wenchuan earthquake china

similarity solutions for fluid injection into confined aquifers fluid injection into the deep subsurface such as injection of carbon dioxide co 2 into deep saline aquifers often involves two fluid flow in confined geological formations similarity solutions may be derived for these problems by assuming that a sharp interface separates the two fluids by imposing a suitable no flow condition along both the top and bottom boundaries and by including an explicit solution for the pressure distribution in both fluids when the injected fluid is less dense and less viscous than the resident fluid as is the case for co 2 injection into a resident brine gravity override produces a fluid flow system that is captured well by the similarity solutions the similarity solutions may be extended to include slight miscibility between the two fluids as well as compressibility in both of the fluid phases the solutions provide the location of the interface between the two fluids as well as drying fronts that develop within the injected fluid applications to cases of supercritical co 2 injection into deep saline aquifers demonstrate the utility of the solutions and comparisons to solutions from full numerical simulations show the ability to predict the system behaviour

on the slow draining of a gravity current moving through a layered permeable medium we examine the gravitational dispersal of dense fluid through a horizontal permeable layer which is separated from a second underlying layer by a narrow band of much lower permeability we derive a series of analytical solutions which describe the propagation of the fluid through the upper layer and the draining of the fluid into the underlying region the model predicts that the current initially spreads according to a self similar solution however as the drainage becomes established the spreading slows and in fact the fluid only spreads a finite distance before it has fully drained into the underlying layer we examine the sensitivity of the results to the initial conditions through numerical solution of the governing equations we find that for sources of sufficiently large initial aspect ratio defined as the ratio of height to length the solution converges rapidly to the initially self similar regime for longer and shallower initial source conditions this convergence does not occur but we derive estimates for the run out length of the current which compare favourably with our numerical data we also present some preliminary laboratory experiments which support the model

on the origin of mixed layered clay minerals from the san andreas fault at 2 5 3 km vertical depth safod drillhole at parkfield california a detailed mineralogical study is presented of the matrix of mudrocks sampled from spot coring at three key locations along the san andreas fault observatory at depth safod drill hole the characteristics of authigenic illite smectite i s and chlorite smectite c s mixed layer mineral clays indicate a deep diagenetic origin a randomly ordered i s mineral with ca 20 25 smectite layers is one of the dominant authigenic clay species across the san andreas fault zone sampled at 3 066 and 3 436 m measured depths md whereas an authigenic illite with ca 2 5 smectite layers is the dominant phase beneath the fault sampled at 3 992 m md the most smectite rich mixed layered assemblage with the highest water content occurs in the actively deforming creep zone at ca 3 300 3 353 m true vertical depth of ca 2 7 km with i s 70 30 and c s 50 50 the matrix of all mudrock sam ples show extensive quartz and feldspar both plagioclase and k feldspar dissolution associated with the crystalli zation of pore filling clay minerals however the effect of rock deformation in the matrix appears only minor with weak flattening fabrics defined largely by kinked and fractured mica grains adopting available kinetic models for the crystallization of i s in burial sedimentary envi ronments and the current borehole depths and thermal structure the conditions and timing of i s growth can be evaluated assuming a typical k concentration of 100 200 ppm for sedimentary brines a present day geothermal gradient of 35c km and a borehole temperature of ca 112c for the sampled depths most of the i s minerals can be predicted to have formed over the last 4 11 ma and are probably still in equilibrium with circulating fluids the exception to this simple burial pattern is the occurrence of the mixed layered phases with higher smectite content than predicted by the burial model these minerals which characterize the actively creeping section of the fault and local thin film clay coating on polished brittle slip surfaces can be explained by the influence of either cooler fluids circulating along this segment of the fault or the flow of k depleted brines

constraints on mineralization fluid rock interaction and mass transfer during faulting at 2 3 km depth from the safod drill hole 1 mineralogical and geochemical changes in mudrock cuttings from two segments of the san andreas fault observatory at depth safod drill hole 3066 3169 and 3292 3368 m measured depth are analyzed in this study bulk rock samples and hand picked fault related grains characterized by polished surfaces and slickensides were investigated by x ray diffraction electron microscopy and geochemical analysis the elemental changes in fault related grains along the sampled san andreas fault are attributed to dissolution of detrital grains particularly feldspar and quartz and local precipitation of illite smectite and or chlorite smectite mixed layers in fractures and veins assuming zro2 and tio2 to be immobile elements systematic differences in element concentrations show that most of the elements are depleted in the fault related grains compared to the wall rock lithology calculated mass loss between the bulk rock and picked fault rock ranges from 17 to 58 with a greater mass transport in the shallow trace of the sampled fault that marks the upper limit the fault core the relatively large amount of element transport at temperatures of 110 114 c recorded throughout the core requires extensive fluid circulation during faulting whereas dissolution precipitation may be partly induced by the disequilibrium between fluids and rocks during diagenetic processes stress induced dissolution at grain contacts is proposed as the main mechanism for extensive mineral transformation in the fault rocks and localization of neomineralization along grain interface slip surfaces

spatial variability in microscopic deformation and composition of the punchbowl fault southern california implications for mechanisms fluid rock interaction and fault morphology abstract we examine the distribution and nature of microstructures geochemistry and mineralogy along two traverses across the punchbowl fault southern california to determine the morphology and deformation mechanisms of the fault zone in schistose rocks the punchbowl fault is an exhumed fault that has two main strands of slip localization and has a total of 44 km of right slip protolith in the study area consists of the pelona schist which is primarily a quartz albite muscovite actinolite schist with thin to medium banding and rare metabasalts the traverses are 1 3 km apart and were conducted at a site with a single fault strand and a site where both principal strands of the fault are exposed the fault zone thickness is a function of the type of measurement that is used to define it for the single strand site analysis of the distribution of microfractures shows that the fault zone consists of a roughly 40 m thick damaged zone adjacent to the fault core the damaged zone is marked by an increase in veins thin cataclasite bands inter and intragranular fracturing and alteration relative to the country rock brittle grain size reduction occurs in a zone 10 m thick as measured from the fault core which consists of a continuous 10 cm thick very fine grained cataclasite that experienced repeated alteration vein injection and grain size reduction whole rock geochemical analyses of the fault related rocks suggest that the geochemically defined fault zone is less than 10 m thick volume loss at the site with one fault strand appears to have been small the dominant alteration reactions associated with the fault core are the hydration of hornblende and actinolite accompanied by the alteration of muscovite to produce a quartz chlorite albite epidote ultracataclasite the composition of the fault core is variable and locally influenced by one of the adjacent protoliths the examination of the two fault strand sites shows that two damaged zone fault core structures are present the region between the two strands experienced a greater degree of deformation than the protolith but the total deformation is much less than immediately adjacent to the fault cores the total thickness of the damaged zone around the two strands is less than 200 m the fault core enveloped by a damaged zone morphology as well as the textures of the fault core rocks are similar to rocks associated with the north branch san gabriel fault which formed in crystalline rocks with a total displacement of 22 km fault thickness is less in the pelona schist than in the crystalline rocks perhaps owing to more efficient strain localization in the schists thus the faults of the san andreas system may be thinner in regions where schists or franciscan rocks are the protolith but the main fault core may be a constant feature of the fault zone transformation induced weakening is less important in this part of the punchbowl fault since the protolith has a large amount of mica the structure of the fault zone with two principal slip surfaces is marked by both chemical changes and microstructures and indicates that some parts of the san andreas fault system may consist of multiple slip surfaces each with a damaged zone that together may create a fault zone 100 m thick and in which slip is localized to zones meters to decimeters thick

capillary entry pressure and the leakage of gravity currents through a sloping layered permeable rock we examine the motion of a buoyant fluid injected into a water saturated porous rock as it spreads along a thin inclined low permeability barrier we account for leakage of the fluid across the barrier once the current is sufficiently deep so that the pressure exceeds the capillary threshold we show that at some distance from the source the pressure decreases below this threshold and all the remaining flux spreads laterally along the barrier we examine the controls on the partitioning of the flow between the draining flux and the laterally spreading flux and also the controls on the lateral extent of the draining region for the case of an instantaneous release and a maintained release of fluid we consider the implications of our work for the dispersal of co 2 plumes which may be sequestered in deep saline aquifers

the effect of drainage on the capillary retention of co2 in a layered permeable rock buoyant plumes of co 2 spreading through water saturated permeable rock bounded by layers of lower permeability tend to spread laterally as they advance they may gradually leak through fractures or discontinuities in the lower permeability boundary leading to a gradual waning of the original plume and dispersal of co 2 higher in the formation with a finite release of co 2 the trailing edge of the plume recedes with time and capillary forces tend to trap a fraction of this co 2 within the pore space this also leads to a gradual waning of the plume with time and limits the mass of co 2 which can leak through the boundary and rise higher into the formation we explore the balance between these two effects and calculate some of the controls on the fraction of the co 2 plume which becomes trapped within the original layer of rock

fluid drainage from the edge of a porous reservoir we report theoretical and experimental studies to describe buoyancy driven fluid drainage from a porous medium for configurations where the fluid drains from an edge we first study homogeneous porous systems to investigate the influence of heterogeneities we consider the case where the permeability varies transverse to the flow direction exemplified by a v shaped hele shaw cell finally we analyse a model where both the permeability and the porosity vary transverse to the flow direction in each case a self similar solution for the shape of these gravity currents is found and a power law behaviour in time is derived for the mass remaining in the system laboratory experiments are conducted in homogeneous and v shaped hele shaw cells and the measured profile shapes and the mass remaining in the cells agree well with our model predictions our study provides new insights into drainage processes such as may occur in a variety of natural and industrial activities including the geological storage of carbon dioxide

flow and instability of a viscous current down a slope if viscous fluid is released on a horizontal surface it rapidly takes up a circular plan form as it spreads this form is observed1 2 to be stable to any small disturbances which are initiated on the front due for example to irregularities in the horizontal surface or to chance perturbations alternatively if some fluid is released onto a sloping surface for example some liquid detergent on a slanted plate a quite different plan form occurs one two or more extended regions of fluid develop downslope as shown in fig 1a b a situation intermediate between these two is now discussed consider a broad band of viscous fluid uniform in depth across a slope released so as to flow down a constant slope by following the motion which is initially independent of the cross slope coordinate the speed of advance and the depth of the flow before it breaks up into a series of waves of ever increasing amplitude can be determined i present an expression for the wavelength of the front which is determined by surface tension and is independent of the coefficient of viscosity

speleothems and pine trees as sensitive indicators of environmental pollution a case study of the effect of uranium ore mining in hungary abstract four decades of u ore production in hungary provides an opportunity to study the possible environmental effects of mining the study reveals significant changes in chemical composition of a stalagmite cave deposit the good fit between u content changes in the studied deposit and the u ore production rate support the assumption of the relationship with mining activity an independent chemoenviromental archive living pine pinus sylvestis trees were also investigated data on pine tree cores collected from the same region show different levels of pollution cu zn mn u after the 1950s and 1960s linked to the opening of mines and subsequent dust fallout around the site elevated concentrations of detritally derived elements si al th coupled with a rise in u concentration and change in 234 u values of the stalagmite suggest increasing amounts of mine derived dust from 1 to 3 km distance that settled and washed into the karst system the combined usage of different proxies not only provides historic records for the anthropogenic impact in the environment but also allows the timing of u concentration increases within the stalagmite and the identification of elemental behavior from the pollution this study shows that complementary geochemical archives such as stalagmites and tree rings used together can enhance understanding of past environmental contamination

quantification of fabrics in clay gouge from the carboneras fault spain and implications for fault behavior abstract clays in fault rocks have the potential to control fault behavior the formation of frictionally weak clays in fault rocks can lead to fault zone weakening and the development of fabrics through authigenesis and mechanical rotation in clay rich fault rocks can influence fault zone permeability structures the left lateral carboneras fault of southwestern spain is a ca 1 km wide fault zone with anastomosing layers of clay rich gouge up to 50 m thick the gouge derived largely from mica schist is composed of neoformed illite and chlorite anisotropy of magnetic susceptibility 201 measurements and x ray pole figures 144 measurements show comparable oblate clay fabrics with the axis of maximum anisotropy sub parallel to strike this dimensional fabric contrasts with previously published maximum permeability results that are sub vertical this observation coupled with the generally poor clay fabric measured in the samples indicates that the orientation of clays is not likely to be the primary control of the permeability anisotropy of clay rich fault gouge becoming important only when gouge zones are 10s of meters thick which is very unusual even in a fault zone like that of the carboneras fault with thick very clay rich gouge zones with a visible foliations and slip surfaces the degree of clay preferred orientation is low above the millimeter scale showing that any strong clay fabric associated with the foliation are extremely localized phenomena this suggests that processes operating below the millimeter scale may significantly influence fault behavior a result compatible with earlier characterizations of faults in a variety of geologic settings highlighting the importance of understanding how the formation and fabric of fault related authigenic clays influence fault behavior

leakage from gravity currents in a porous medium part 2 a line sink we consider the propagation of a buoyancy driven gravity current in a porous medium bounded by a horizontal impermeable boundary the current is fed by a constant flux injected at a point and leaks through a line sink at a distance from the injection point this is an idealized model of how a fault in a cap rock might compromise the geological sequestration of carbon dioxide the temporal evolution of the efficiency of storage defined as the instantaneous ratio of the rate at which fluid is stored without leaking to the rate at which it is injected is of particular interest we show that the efficiency of storage decays like t 2 5 for times t that are long compared with the time taken for the current to reach the fault this algebraic decay is in contrast to the case of leakage through a circular sink neufeld et al j fluid mech vol 2010 where the efficiency of storage decays more slowly like 1 ln t the implications of the predicted decay in the efficiency of storage are discussed in the context of geological sequestration of carbon dioxide using parameter values typical of the demonstration project at sleipner norway we show that the efficiency of storage should remain greater than 90 on a time scale of millennia provided that there are no significant faults in the cap rock within about 12 km of the injection site

phyllosilicate mineral assemblages of the safod pilot hole and comparison with an exhumed segment of the san andreas fault system 1 this paper establishes a reference phyllosilicate data set from the safod pilot hole for future safod drilling and presents an application of these data for studies of exhumed fault segments the chlorite assemblages in cuttings from two intervals of the safod pilot hole are separated into two populations based on x ray diffraction characteristics the first population is found in granite in both the deeper and shallower interval whereas the second population occurs only in clastic sedimentary rocks in the shallower interval the characteristics of the first population match those for protolith and cataclasite of the exhumed punchbowl fault whereas samples from intensely deformed ultracataclasite are most similar to the second this supports previous findings that the mineral assemblages in the ultracataclasite formed after the cessation of motion along the fault above a depth of 2 km and that mineral assemblages in these exhumed fault rocks have been overprinted by post faulting alteration

implications for mechanical properties of brittle faults from observations of the punchbowl fault zone california field observations of the punchbowl fault zone an inactive trace of the san andreas are integrated with results from experimental deformation of naturally deformed punchbowl fault rocks for a qualitative description of the mechanical properties of the fault and additional information for conceptual models of crustal faulting the punchbowl fault zone consists of a single continuous gouge layer bounded by zones of extensively damaged host rock fault displacements were not only localized to the gouge layer but also to discrete shear surfaces within the gouge deformation in the exposure studied probably occurred at depths of 2 to 4 km and was dominated by cataclastic mechanisms textural data also suggest that significant amounts of pore fluids were present during faulting and that fluid assisted mechanisms such as dissolution diffusion and precipitation were operative the experimental data on specimens collected from the fault zone suggest that there is a gradual decrease in strength and elastic modulus and an increase in relative ductility and permeability toward the main gouge zone the gouge layer has fairly uniform mechanical properites and it has significantly lower strength elastic modulus and permeability than both the damaged and the undeformed host rock for the punchbowl fault and possibly other brittle faults the variations in loading of the gouge zone with time are primarily governed by the morphology of the fault and the mechanical properties of the damaged host rock in addition the damaged zone acts as the permeable unit of the fault zone and surrounding rock it appears that the gouge primarily governs whether displacements are localized and it therefore may have a significant influence on the mode of slip

determination of volume loss and element mobility patterns associated with the development of the copper basin fault picacho state recreation area se california usa abstract the fault zone architectural elements of the copper basin fault include a fault core inner damage zone and outer damage zone utilizing yb as a reference frame element significant elemental mass changes were documented across all three architectural zones with the greatest change in the fault core porosity and volumetric strain both increase toward the principal slip surface reaching a maximum in the inner damage zone and then dropping significantly in the fault core in the damage zone and unaffected wall rocks smectite is the most prominent clay species whereas illite dominates the fault core suggesting that temperatures may have reached 100 150 c or more during the production of the fault core a number of studies have interpreted similar mass changes and clay mineral reactions to indicate high water rock ratios such interpretations imply that during rupture permeability increased within the fault core allowing it to act as a pathway for hot chemically reactive fluids then during and after rupture co 2 and sio 2 rich fluids moved into the inner and outer damage zones where calcite and quartz precipitation healed the fractured and permeable rock

the influence of capillary effects on the drainage of a viscous gravity current into a deep porous medium the drainage of a viscous gravity current into a deep porous medium driven by both the gravitational and capillary forces is considered in two steps we first study the one dimensional case where a layer of fluid drains vertically into an infinitely deep porous medium we determine a transition from the capillary driven regime to the gravity driven regime as time proceeds second we solve the coupled spreading and drainage problem there are no self similar solutions of the problem for the entire time period so asymptotic analyses are developed for the height depth and front location in both the early time and the late time periods in addition we present numerical results of the governing partial differential equations which agree well with the self similar solutions in the appropriate asymptotic limits

origin and behavior of clay minerals in the bogd fault gouge mongolia we analyzed twelve fault gouge samples from the bogd fault in south western mongolia to understand the origin and behavior of clay minerals the investigation relies on x ray powder diffraction xrd scanning electron microscopy sem transmission electron microscopy tem and high energy synchrotron x ray diffraction methods to investigate microstructure and preferred orientation smectite montmorillonite illite smectite mixed layers illite mica and kaolinite are the major clay components in addition to quartz and feldspars which are present in all samples the observations suggest that the protoliths and the fault rocks were highly altered by fluids the fluid rock interactions allow clay minerals to form as well as alter feldspars to precipitate kaolinite and montmorillonite thus newly formed clay minerals are heterogeneously distributed in the fault zone the decrease of montmorillonite component of some of the highly deformed samples also suggests that dehydration processes during deformation were leading to illite precipitation based on synchrotron x ray diffraction data the degree of preferred orientation of constituent clay minerals is weak with maxima for 001 ranging from 1 3 to 2 6 multiples of a random distribution m r d co existing quartz and feldspars have random orientation distributions microstructure and texture observations of the gouges from the foliated microscopic zone alternating with micrometric isotropic clay rich area also indicate that the bogd fault experienced brittle and ductile deformation episodes the clay minerals may contribute to a slip weakening behavior of the fault

leakage from inclined porous reservoirs we investigate the effect of localized leakage on the storage of buoyant fluids in inclined porous reservoirs with application to the geological storage of co 2 we find that once the current has propagated some distance beyond the point of leakage its profile becomes steady in time save for the nose which advances at a constant speed crucially this steady state implies that the efficiency of storage defined as the instantaneous proportion of the injected fluid that does not leak tends to a finite value this contrasts with previous studies of localized leakage in horizontal reservoirs which found that the efficiency of storage tends to zero at late times we analyse the steady state efficiency and the time scales of evolution for a leakage point located either upslope or downslope of the injection point using analytical and numerical methods these findings are verified by model laboratory experiments finally we consider the implications of our results for the geological storage of co 2 under sloping cap rocks compromised by a fracture or fissure