flow directions in dikes from anisotropy of magnetic susceptibility data the bootstrap way one of the first applications of anisotropy of magnetic susceptibility ams was an attempt to determine flow directions from mafic dikes khan 1962 since the seminal work of knight and walker 1988 defining the expected behavior of ams in response to magma flow there has been increasing interest in using ams for this purpose here we present a quantitative method for interpretation of ams data from dikes using a parametric bootstrap first dikes must be sampled with at least five and preferrably more samples from within 10 cm of the dike margin the distributions of the eigenvalues and eigenvectors of the ams tensor are delineated by calculating eigenparameters of many bootstrapped paradata sets we generate paradata sets by first selecting a sample at random then calculating a replacement set of data by drawing tensor elements from normal distributions with the mean and standard deviation of the entire site the bounds containing 95 of the eigenparameters of the bootstrapped data serve as confidence limits for the parameter of interest classification of dikes proceeds as follows sites whose maximum and intermediate eigenvalues could not be distinguished are deemed uninterpretable in addition sites with principal eigenvectors with angles 45 away from the dike margin inverse or with markedly different directions on either side of the dike scissored are excluded the remaining dikes are classified as having unique flow direction information if the principal eigenvectors from at least one side are distinct from the dike plane based on the distribution of the bootstrapped principal eigenvectors if neither side has principal eigenvectors distinct from the dike plane the dikes are classified as having lineation information only a study comprising 251 dikes from the troodos ophiolite has 151 sites with directional data 38 sites with lineations only 7 inverse sites 5 scissored sites and 55 sites not fitting into any other category the flow directions interpreted from the data were generally southerly toward a fossil transform zone

magnetic susceptibility of the rock matrix related to magnetic fabric studies non ferromagnetic minerals constitute what is called the rock matrix whose susceptibility k1 is directly accessible using only high magnetic fields measurements on minerals and a wide range of rock types show that k1 is mainly due to paramagnetism and hardly exceeds 10 3 si with an anisotropy degree p less than 1 35 different methods to estimate the role of the matrix component in low field susceptibility k and its anisotropy include petrological and chemical analysis evolution of p vs k low temperature studies and comparison of k with remanent magnetizations

saline tracer visualized with three dimensional electrical resistivity tomography field scale spatial moment analysis 1 cross well electrical resistivity tomography ert was used to monitor the migration of a saline tracer in a two well pumping injection experiment conducted at the massachusetts military reservation in cape cod massachusetts after injecting 2200 mg l of sodium chloride for 9 hours ert data sets were collected from four wells every 6 hours for 20 days more than 180 000 resistance measurements were collected during the tracer test each ert data set was inverted to produce a sequence of 3 d snapshot maps that track the plume in addition to the ert experiment a pumping test and an infiltration test were conducted to estimate horizontal and vertical hydraulic conductivity values using modified moment analysis of the electrical conductivity tomograms the mass center of mass and spatial variance of the imaged tracer plume were estimated although the tomograms provide valuable insights into field scale tracer migration behavior and aquifer heterogeneity standard tomographic inversion and application of archie s law to convert electrical conductivities to solute concentration results in underestimation of tracer mass such underestimation is attributed to 1 reduced measurement sensitivity to electrical conductivity values with distance from the electrodes and 2 spatial smoothing regularization from tomographic inversion the center of mass estimated from the ert inversions coincided with that given by migration of the tracer plume using 3 d advective dispersion simulation the 3 d plumes seen using ert exhibit greater apparent dispersion than the simulated plumes and greater temporal spreading than observed in field data of concentration breakthrough at the pumping well

birth growth and morphologic evolution of the laghetto cinder cone during the 2001 etna eruption we have undertaken detailed observations of the formation of the laghetto cinder cone a new cone that formed during a 2 week period of intense activity in piano del lago on the upper slopes of mount etna in summer 2001 we describe the events leading to the formation of a small graben the formation of pit craters on the base of the graben the onset of phreatomagmatic activity a transition to intense strombolian activity and a return to phreatomagmatic activity as the eruption came to an end we discuss the reasons for these transitions and describe the morphological development of the cone during these events arcuate cracks on the southern part of the cone were related to withdrawal of magma at the end of the eruption other slope instabilities that developed during the eruption include the formation of small radial grain flows on the outer flanks of the cone and the collapse into the crater of part of the crater rim some of the failure planes we observed were first identified using a flir tm 695 thermal infrared camera this is the first time that infrared thermography has been used to detect instability of volcanic structures results obtained during this test case demonstrate that thermal cameras are a very useful tool for studies of volcanic instability

integration of hydrological and geophysical data beyond the local scale application of bayesian sequential simulation to field data from the saint lambert de lauzon site quebec canada adequate characterization of aquifer heterogeneity is critically important for the sustainable use protection and remediation of groundwater resources the combined use of hydrological and geophysical measurements is arguably the most effective means of achieving this objective in this regard significant progress has been made on the quantitative integration of geophysical and hydrological data at the local scale however the extension of such approaches to larger more regional scales remains a major research challenge in this paper we demonstrate the application of a recently developed regional scale hydrogeophysical data integration approach which is based on bayesian sequential simulation to a field database from quebec canada consisting of low resolution surface based geoelectrical measurements as well as high resolution direct push and borehole based measurements of the electrical and hydraulic conductivities the results of our study which involved the integration of data along an approximately 250 m long survey line confirm that this novel methodology with suitable adaptation is fully applicable to field data and has the potential of providing realistic estimates of the spatial distribution of hydraulic target parameters at the regional scale equally importantly through the generation of multiple stochastic realizations the methodology allows for quantitative assessment of the uncertainty associated with the inferred subsurface models which in turn is essential for interpreting subsequent predictions of the flow and transport characteristics of the studied region

shape anisotropy versus magnetic interactions of magnetite grains experiments and application to ams in granitic rocks the magnetic fabric of ferromagnetic granitic rocks results from both the shape preferred orientation of individual magnetite grains and their distribution anisotropy through magnetic interactions between neighbouring grains measurement of the low field magnetic anisotropy of single multi domain magnetite grains shows a linear correlation between their magnetic anisotropy degree and their aspect ratio interactions between two elongated grains were studied experimentally using two types of grain arrangement an aligned configuration and a side by side configuration for a distance between the grain centers equal to approximately twice the average grain size the magnetic susceptibility and its anisotropy are enhanced in both configurations and the direction of kmax the easiest magnetization axis is stable in the aligned configuration whereas it rotates toward an orthogonal direction in the side by side configuration depending on the distribution of the interacting magnetite grains magnetic interactions may therefore either increase the whole rock anisotropy magnitude or reduce it as in the given example of the granitic rocks from madagascar

magma flow directions in dikes of the koolau complex oahu determined from magnetic fabric studies we compared the magnetic fabric with the macroscopic surface lineation direction previously assumed to be parallel with magma flow direction for 35 dikes of the koolau complex oahu anisotropy of magnetic susceptibility ams was determined for 530 samples from 59 dikes including a sill and a pluglike intrusive body and two filled lava tubes and statistically significant ams clusters were found in all but five dikes for the 35 lineated dikes the mean maximum ams direction 1 coincides with the macroscopic lineations to within 25 in 18 and to within 15 in eight the ams ellipsoid shape in about half of the samples is prolate cigar shaped and in about half is oblate pancake shaped we interpret the ams to be determined by shape anisotropy of ferromagnetic grains the mean total anisotropy is 2 2 and total anisotropy h ranges from 0 24 to as high as 14 12 the principal ams axes for samples from a dike are tightly grouped on equal area plots and for most of the dikes the minimum ams axes plot near to the pole of the dike our ams measurements enable us to infer absolute magma flow directions for half the dikes studied the maximum ams axes of samples from one side of the dike form a tight cluster on an equal area plot and those from the other side of the dike form another tight cluster the two clusters are close together separated by 10 30 for narrow dikes 100 cm wide and are farther apart 30 60 for wide dikes and are symmetrically disposed on either side of the plane of the dike we infer that these paired clusters are caused by imbrication of nonequant ferromagnetic crystals against each margin of the dike during deposition in a velocity gradient and hence indicate the flow azimuth i e the absolute magma flow direction nearly half of the dikes measured 25 gave paired ams plots in 12 the magma flowed up at low oblique angles 5 30 from the horizontal in five it flowed down at 5 20 in four it flowed horizontally 5 in three it flowed up at a steep angle 50 75 and in one it flowed down at a steep angle the magma flow in general was rarely vertical or horizontal

lithofacies association and stratigraphy of the paredao volcano trindade island brazil abstract a stratigraphic framework can be constructed through lithofacies description and interpretation the application of this method in volcanic systems is a fundamental tool for understanding their evolution and eruptive dynamics and for establishing hazard assessments in active volcanic areas this work presents and discusses a detailed stratigraphy of the paredao volcano allowing the understanding of the lateral and vertical distribution of volcanic facies and the 3d geometry of the deposits generating a model for the volcanism and discussing the erupting mechanisms the paredao volcano is a scoria cone located in the southeast of trindade island and represents the youngest subaerial volcanic episode pleistocene recorded in brazil its stratigraphic organization indicates nephelinitic flows alternate with lapillistones and lapilli tuffs of same composition at the base and a pyroclastic cone with nearly 200 m high above the sea level through lithofacies description and association 4 stratigraphic columns were constructed in scale 1 50 three of them at the tartarugas beach trv 01 trv 02 trv 03 and the other one at the pyroclastic cone trv 04 the petrographic characterization of facies was carried through conventional optical microscopy the stratigraphic analysis resulted in the distinction of seven lithofacies divided into two coherent and five volcaniclastic one autoclastic and four pyroclastic the coherent lithofacies are of massive npm and vesicular porphyritic nephelinite npv texturally the lavas are holocrystalline and vesicular composed by olivine phenocrysts in a very fine matrix of clinopyroxene nepheline zeolite and titanomagnetite at times with phlogopite the autoclastic lithofacies of nephelinitic breccia nb is composed of fragments 2 mm 15 cm of vesicular nephelinite and the pyroclastic ones are composed mainly of lapillitic scoria fragments with subordinate bombs and volcanic ash the pyroclastic lithofacies are of massive lapillistone lm and lapilli breccia lbm planar stratified lapilli tuff ltp and reverse grading lapillistone lrg the lithofacies associations characterize a a rubbly pahoehoe and pahoehoe flow types distal and proximal pyroclastic deposits the interpretation of the vertical and lateral facies distribution leads to the conclusion that the volcanism occurred with an initial phreatomagmatic stage succeeded by a strombolian stage pyroclastic with primary fragments domain and a final hawaiian stage lava flows domain

use of high resolution geophysical data to characterize heterogeneous aquifers influence of data integration method on hydrological predictions 1 the integration of geophysical data into the subsurface characterization problem has been shown in many cases to significantly improve hydrological knowledge by providing information at spatial scales and locations that is unattainable using conventional hydrological measurement techniques the investigation of exactly how much benefit can be brought by geophysical data in terms of its effect on hydrological predictions however has received considerably less attention in the literature here we examine the potential hydrological benefits brought by a recently introduced simulated annealing sa conditional stochastic simulation method designed for the assimilation of diverse hydrogeophysical data sets we consider the specific case of integrating crosshole ground penetrating radar gpr and borehole porosity log data to characterize the porosity distribution in saturated heterogeneous aquifers in many cases porosity is linked to hydraulic conductivity and thus to flow and transport behavior to perform our evaluation we first generate a number of synthetic porosity fields exhibiting varying degrees of spatial continuity and structural complexity next we simulate the collection of crosshole gpr data between several boreholes in these fields and the collection of porosity log data at the borehole locations the inverted gpr data together with the porosity logs are then used to reconstruct the porosity field using the sa based method along with a number of other more elementary approaches assuming that the grid cell scale relationship between porosity and hydraulic conductivity is unique and known the porosity realizations are then used in groundwater flow and contaminant transport simulations to assess the benefits and limitations of the different approaches

petrographic and stable isotopic evidences of co2 induced alterations in sandstones in the lishui sag east china sea basin china abstract dawsonite bearing sandstones in the lishui sag east china sea basin china have been investigated as a natural occurrence for co2 induced diagenesis using petrography x ray diffraction and stable isotopes the sandstones are predominantly litharenite with the order of cements growth comprising clay coatings and pyrite siderite pyrite quartz overgrowths ankerite kaolinite and microcrystalline quartz dawsonite and late calcite dawsonite which has recently been considered as trapping mineral after massive co2 charging constituted up to 7 of the whole rock volume occurring as pore filling clusters or replacement of detrital grains stable isotopic data suggest that the co2 in equilibrium with dawsonite and calcite display a mantle magmatic origin and is in close proximity to those of the co2 gas now present in the reservoir indicating the same origin for both the elevated co2 concentrations induced by a mass influx of magmatic co2 into host rock was favourable for dawsonite cementation plagioclase was then considered as the precursor of dawsonite k feldspar could also serve as the aluminum source of dawsonite with an external supply of na in a geochemically open system

bayesian method for hydrogeological site characterization using borehole and geophysical survey data theory and application to the lawrence livermore national laboratory superfund site a stochastic bayesian approach for combining well logs and geophysical surveys for enhancing subsurface characterization is presented the main challenge we face is in creating the bridge to link between ambiguously related geophysical surveys and well data the second challenge is imposed by the disparity between the scale of the geophysical survey and the scale of the well logs our approach is intended to integrate and transform the well log data to a form where it can be updated by the geophysical survey and this tends to be a convoluted process our approach starts with generating images of the lithology conditional to well logs each lithology image is then used as the basis for generating a series of shaliness images conditional to well log data shaliness images are converted to resistivity images using a site specific petrophysical model relating between shaliness resistivity and lithology to create the necessary interface with the cross well resistivity survey the lithology and resistivity images are then updated using cross well electromagnetic resistivity surveys we explored the limits of the approach through synthetic surveys of different resolutions and error levels employing the relationships between the geophysical and hydrological attributes which are weak nonlinear or both the synthetic surveys closely mimic the conditions at the llnl superfund site we show that the proposed stochastic bayesian approach improves hydrogeological site characterization even when using low resolution resistivity surveys

characterization of the magnetic fabric of rocks abstract an inextensive system of magnetic susceptibility anisotropy factors is suggested which is sufficient in the majority of practical applications for characterizing the magnetic fabric of rocks the system involves three newly devised factors the corrected anisotropy degree the shape factor and the difference shape factor the first of these characterizes the quantity of anisotropy somewhat better than the commonly used anisotropy degree the shape factor characterizes the quality of anisotropy i e the shape of the susceptibility ellipsoid in a convenient way its definition is based on a certain analogy between the anisotropy ellipsoid and the strain ellipsoid the difference shape factor can replace the shape factor when only the differences between the principal susceptibilities are given while the mean susceptibility is unknown

the magnetic fabric relationship between sedimentary and basement nappes in the high tatra mountains n slovakia abstract in the high tatra mountains n slovakia the magnetic fabrics are deformational in origin in sedimentary rocks of the kri na nappe in sedimentary rocks covering the underlying crystalline complex and in granitoids and metamorphic rocks of this complex the patterns of the principal susceptibilities are similar in all these units their most important feature is a girdle in magnetic foliation poles oriented nnw sse to n s in sedimentary formations the magnetic fabric pattern is compatible with that predicted by mathematical modelling to develop during a complex deformation comprising lateral shortening and simple shear which is characteristic of nappe deformation consequently the magnetic fabric in the high tatra mountains probably resulted from deformation associated with the formation and movement of the nappes during which not only the sedimentary strata but also the crystalline complex were thrust over the north european platform

anisotropy of magnetic susceptibility studies in tertiary ridge parallel dykes iceland tertiary margin normal aishihik dykes yukon and proterozoic kenora kabetogama composite dykes minnesota and ontario abstract mafic dykes of different ages were collected from three different tectonic settings and analyzed using anisotropy of magnetic susceptibility ams as a proxy for magmatic flow during intrusion in iceland ridge parallel basaltic dykes were sampled on each side of the active tectonic boundary the dykes are k max orientation indicating vertical emplacement the eocene aishihik dyke swarm intrudes the yukon tanana terrane in the yukon province canada over an area 200 by 60 km these dykes were intruded normal to the accretionary margin are porphyritic andesites and have an intermediate geochemical signature based on major and trace element analyses ten dykes were sampled and 111 cores analyzed using ams and the dykes preserve a vertical k max orientation indicating intrusion was vertical through 30 km of continental crust the 2 06 ga kenora kabetogama dykes in northern minnesota and western ontario crosscut a variety of archean terranes thickness 50 km in a radiating pattern the unmetamorphosed basaltic dykes are 1 120 m wide 10 110 km in length are vertical in orientation and can be grouped as either being single intrusion or multiple intrusion composite dykes ams data preserve a vertical k max orientation for the southerly locations 2 dykes n 53 and horizontal k max for the remainder to the northwest 15 dykes n 194 maximum magnetic susceptibility axes 4 dykes n 92 for composite dykes are scattered and yield inconsistent flow directions with regard to the dyke margin almost all of our results are normal in that the magnetic foliation the plane containing k max and k int normal to k min is parallel to the dyke planes which gives us confidence that the magnetic lineations i e k max orientations are parallel to magmatic flow

quantitative integration of hydrogeophysical data conditional geostatistical simulation for characterizing heterogeneous alluvial aquifers high resolution geophysical parameter information as it can be provided for example by crosshole georadar and seismic tomography has proven to provide useful spatial information to complement traditional hydrological methods such as core analyses logging techniques and tracer or pumping tests quantitative integration of these diverse database components is one of the major challenges in the field of high resolution hydrogeophysics because of their different scales of measurement and the usually weak petrophysical relations among the measurements in this study we systematically explore the usefulness of a conditional stochastic simulation approach based on simulated annealing for this purpose first we generate a realistic model of an alluvial aquifer consisting of a 2d scale invariant porosity field on the basis of this model we generate synthetic neutron porosity logs and crosshole georadar tomographic surveys we then use the proposed geostatistical simulation approach to integrate this hydr

magnetic and plagioclase linear fabric discrepancy in dykes a new way to define the flow vector using magnetic foliation in basaltic dykes the magnetic lineation k1 maximum magnetic susceptibility axis is generally taken to indicate the flow direction during solidification of the magma this assumption was tested in tertiary basaltic dykes from greenland displaying independent evidence of subhorizontal flow the digital processing of microphotographs from thin sections cut in k1 k2 planes yields the preferred linear orientation of plagioclase which apparently marks the magma flow lineation in up to 60 of cases the angular separation between k1 and the assumed flow direction is greater than 45 this suggests that the uncorroborated use of magnetic lineations in dykes is risky a simple geometrical method is proposed to infer the flow vector from ams in dykes based solely on magnetic foliations

sampling strategies and the anisotropy of magnetic susceptibility of dykes abstract most studies of the anisotropy of magnetic susceptibility ams of dykes have assumed that susceptibility axes should define a unique orientation relative to the dyke walls and magma flow direction theoretical considerations however predict systematic variations of ams as a function of the amount of shear experienced by the flowing magma although this feature of ams might seem undesirable at first sight based in a theoretical model it has been suggested that actually we can take advantage of such variation in the orientation of the ams axes to infer magma flow directions more confidently than until now if proper attention is given to the scheme followed during sample collection in this work we report the results of a pilot study made to test those theoretical predictions we resampled two dykes from the ko olau dyke complex in o ahu and for which magma flow direction was previously inferred albeit with some uncertainty the resampling was made following the guidelines suggested by the theoretical work as closely as possible i e collecting more than one profile parallel to the dyke walls and across the dyke the results of our measurements provide the first empirical evidence supporting the occurrence of a cyclic fabric acquisition during the emplacement of at least some dykes the procedure described in this paper therefore constitutes a self contained approach that can be followed to test in a case by case basis the occurrence of such fabric behavior this in turn should provide enough elements to increase the reliability of the interpretation in the obtained results

inverse magnetic fabric in carbonate bearing rocks abstract the observation of a magnetic susceptibility ellipsoid whose maximum axis corresponds to the minimum axis of petrofabric pole of bedding or schistosity is referred to as an inverse magnetic fabric the investigation of the magnetic properties of some ferroan carbonate monocrystals and paramagnetic limestones demonstrates that c axis preferred orientation of paramagnetic carbonates results in a maximum susceptibility parallel to the flattening direction inverse magnetic fabrics due to magnetite are also encountered in weakly deformed limestones a mineralogical model based on the property of single domain grains to have a zero susceptibility parallel to their long axis is proposed however more complex cases are also encountered

stratigraphy paleomagnetism and magnetic fabric of the toba tuffs constraints on the sources and eruptive styles the toba depression in north central sumatra is a complex of several overlapping calderas resulting from three major ignimbrite forming eruptions within the depression the upland masses of samosir and northern uluan consist of welded ignimbrite capped by coarse breccia and lacustrine sediment hitherto interpreted to be two parts of a single resurgent dome this study has demonstrated that the welded tuffs of samosir and uluan have different magnetic polarities and therefore at least two different ignimbrites are present the samosir uluan massif may consist of parts of two resurgent domes the first ignimbrite eruption occurred at 0 84 ma and produced a very thick 400 m densely welded unit having a reversed polarity anisotropy of magnetic susceptibility ams flow direction and lithic size data indicate that the source lies in the southern part of the toba depression and the thick deposit of uluan is thought to have ponded in a 40 km wide caldera the second ignimbrite is normally magnetized ams flow direction data indicate two separate source vents one to the north in the haranggaol caldera and another to the south the thick deposit at samosir is thought to have ponded in the southern caldera coarse sediments then accumulated over samosir and northern uluan and were capped by lacustrine deposits a renewed episode of resurgence then uplifted samosir island and possibly the northern part of uluan at approximately 0 075 ma the last and apparently largest ignimbrite eruption occurred from calderas in the north and south parts of the toba depression this ignimbrite is mostly nonwelded and normally magnetized part of the uluan dome was destroyed by collapse of the sibandung caldera and latung graben and concomitant with renewed subsidence of the haranggaol and porsea calderas

investigating the magmatic plumbing system of a monogenetic scoria cone a field and laboratory study of the cienega scoria cone cerros del rio volcanic field new mexico

structure coupled joint inversion of geophysical and hydrological data abstractin groundwater hydrology geophysical imaging holds considerable promise for improving parameter estimation due to the generally high resolution and spatial coverage of geophysical data however inversion of geophysical data alone cannot unveil the distribution of hydraulic conductivity jointly inverting geophysical and hydrological data allows us to benefit from the advantages of geophysical imaging and at the same time recover the hydrological parameters of interest we have applied a coupling strategy between geophysical and hydrological models that is based on structural similarity constraints model combinations for which the spatial gradients of the inferred parameter fields are not aligned in parallel are penalized in the inversion this structural coupling does not require introducing a potentially weak unknown and nonstationary petrophysical relation to link the models the method was first tested on synthetic data sets and then applied to two combinations of geophysical hydrolog

upward and downward flow in a camptonite dike as recorded by deformed vesicles and the anisotropy of magnetic susceptibility ams abstract a 1 6 m wide cretaceous camptonite dike on higby mountain connecticut contains deformed vesicles that record an initial brief period of steeply upward intrusion followed by a prolonged vertical downward flow of magma prior to solidification the camptonite is unusual in that it is almost aphyric but it does contain abundant skeletal microphenocrysts 0 3 mm of magnetite which give the rock a strong magnetic susceptibility 127 10 3 si these crystals are slightly elongate and their long axes became preferentially aligned parallel to the dike walls but perpendicular to the magma flow direction which is indicated by the stretched vesicles consequently the rock has a strong anisotropy of magnetic susceptibility ams with the mean value of p being 1 03 the ams ellipsoid is everywhere prolate t 0 9 to 0 02 with the maximum susceptibility axis being almost parallel to the strike of the dike that is parallel to the walls of the dike but perpendicular to the magma flow direction in the outer part of the dike where the deformed imbricate vesicles indicate upward flow at an inclination of 70 75 the maximum susceptibility direction plunges 11 perpendicular to the flow direction in the interior of the dike where the vesicles indicate almost straight downward flow the maximum susceptibility direction is almost horizontal and again is perpendicular to the flow in many but not all samples the sense of flow i e up or down is indicated by imbrication of the intermediate magnetic susceptibility axis although the major magnetic susceptibility axis is commonly assumed to parallel the direction of flow of magma in dikes the present study indicates that at least in this camptonite dike the maximum susceptibility axis is perpendicular to the flow of magma

magnetite grain shape fabric and distribution anisotropy vs rock magnetic fabric a three dimensional case study abstract shape fabric and distribution anisotropy of magnetite grains in a highly ferromagnetic s l syenite are determined for three mutually perpendicular planes on about 600 magnetite grains the grains are lenticular with an average aspect ratio of about 2 0 their preferred orientation determined by the inertia tensor method is consistent with the principal directions of the magnetic susceptibility ellipsoid and the axial ratios of the magnetic fabric ellipses are very close to those of the shape fabric ellipses e g 1 41 and 1 39 in the section plane perpendicular to the magnetic foliation and parallel to the magnetic lineation the anisotropic wavelet transform can detect and quantify the anisotropic distribution of the magnetite grains which are located interstitially along the feldspar grain boundaries this anisotropic distribution has no noticeable effect on the rock s anisotropy of magnetic susceptibility ams since only a few percent of grains are close enough to interact magnetically therefore it is realistic to consider that the ams of ferromagnetic granitic rocks originates mainly from the shape fabric of anisotropic magnetite grains and a close correlation between the magnetic fabric and the magnetite grain shape fabric is expected

reactive transport simulation study of geochemical co2 trapping on the tokyo bay model with focus on the behavior of dawsonite abstract a long term up to 10 ka geochemical change in saline aquifer co 2 storage was studied using the toughreact simulator on a 2 dimensional 2 layered model representing the underground geologic and hydrogeologic conditions of the tokyo bay area that is one of the areas of the largest co 2 emissions in the world in the storage system characterized by low permeability of reservoir and cap rock the dominant storage mechanism is found to be solubility trapping that includes the dissolution and dissociation of injected co 2 in the aqueous phase followed by geochemical reactions to dissolve minerals in the rocks the co 2 water rock interaction in the storage system mainly in the reservoir changes the properties of water in a mushroom like co 2 plume which eventually leads to convective mixing driven by gravitational instability the geochemically evolved aqueous phase precipitates carbonates in the plume front due to a local rise in ph with mixing of unaffected reservoir water the carbonate precipitation occurs extensively within the plume after the end of its enlargement fixing injected co 2 in a long geologic period dawsonite a na al carbonate is initially formed throughout the plume from consumption of plagioclase in the reservoir rock but is found to be a transient phase finally disappearing from most of the co 2 affected part of the system the mineral is unstable relative to more common types of carbonates in the geochemical evolution of the co 2 storage system initially having formation water of relatively low salinity the exception is the reservoir cap rock boundary where co 2 saturation remains very high throughout the simulation period

anisotropy of magnetic susceptibility in natural olivine single crystals mantle flow dynamics can cause preferential alignment of olivine crystals that results in anisotropy of physical properties to interpret anisotropy in mantle rocks it is necessary to understand the anisotropy of olivine single crystals we determined anisotropy of magnetic susceptibility ams for natural olivine crystals high field ams allows for the isolation of the anisotropy due to olivine alone the orientations of the principal susceptibility axes are related to the olivine s crystallographic structure as soon as it contains 3 wt feo the maximum susceptibility is parallel to the c axis both at room temperature rt and at 77 k the orientation of the minimum axis at rt depends on iron content it is generally parallel to the a axis in crystals with 3 5 wt feo and along b in samples with 6 10 wt feo the ams ellipsoid is prolate and the standard deviatoric susceptibility k0 is on the order of 8 10210 m3 kg for the samples with 1wt feo and ranges from 3 1 1029 m3 kg to 5 7 1029 m3 kg for samples with 3 10 wt feo at 77 k the minimum susceptibility is along b independent of iron content the shape of the ams ellipsoid is prolate for samples with 5 wt feo but can be prolate or oblate for higher iron content the degree of anisotropy increases at 77 k with p0 7757 160 5 the results from this study will allow ams fabrics to be used as a proxy for olivine texture in ultramafic rocks with high olivine content

is this magnetic fabric normal a review and case studies in volcanic formations abstract when studying weakly anisotropic rocks non standard relationships between magnetic and expected petrofabric axes are sometimes observed in particular the so called inverse or intermediate fabrics a review of possible explanations for these effects is presented and leads to the conclusion that a majority of abnormal magnetic fabrics often encountered in magnetite rich volcanic rocks are due to abnormal preferred orientations or distributions of magnetite grains through case studies in dikes from skye island yemen and the iberian peninsula and magma and ash flows from the ethiopian traps and southern corsica the various possible origins of such fabrics are examined it is possible to retrieve reliable magma flow directions from these sites provided proper data selection is performed leading to non unique interpretations

dykes cups saucers and sills analogue experiments on magma intrusion into brittle rocks magma is transported in the crust by blade like intrusions such as dykes sills saucers and also collects in thicker laccoliths lopoliths and plutons recently the importance and great number o

syn eruptive morphometric variability of monogenetic scoria cones according to wood s model morphometric parameters such as slope angle can provide valuable information about the age of conical volcanic edifices such as scoria cones assuming that their initial slopes range from 30 to 33 measured manually on topographic maps and assuming that their inner architectures are homogenous this study examines the morphometric variability of nine young a few thousand years old small volume scoria cones from tenerife canary islands using high resolution digital elevation models in order to assess their slope angle variability because of the young age and minimal development of gullies on the flanks their morphometric variability can be interpreted as the result of syn eruptive processes including 1 pre eruptive surface inclination 2 vent migration and lava outflow with associated crater breaching and 3 diversity of pyroclastic rocks accumulated in the flanks of these volcanic edifices results show that slope angles for flank sectors differ by up to 12 among the studied volcanoes which formed over the same period of time this range greatly exceeds the 2 3 indicated by wood the greater than expected original slope range suggests that use of morphometric data in terms of morphometry based relative dating and detection of erosional processes and settings must be done with great care or detailed knowledge about absolute ages and eruption history especially in field scale morphometric investigation

distribution anisotropy the cause of ams in igneous rocks understanding of ams in pristine basic igneous rocks in terms of flow orientation of ellipsoidal magnetite grains is thwarted by the fact that these grains 1 typically are irregularly equant or skeletal rather than distinctly ellipsoidal and 2 usually crystallize interstitially and late after magma flow has ceased however the distribution of such grains will be relatively anisotropic if they grew in residual liquid volumes within a preferredly oriented by flow silicate template this constraint may impose a slight preferred shape orientation to the irregular magnetite grains during their growth but in addition we suggest it is the anisotropic magnetic interaction between the grains which is the basic cause of ams experiments involving the casting of magnetite epoxy mixtures in various foliated or lineated glass templates have yielded samples with the expected ams symmetry i e k3 perpendicular to glass plates or k1 parallel to glass rods slicing of near isotropic synthetic blank and natural rock cores and interleaving with glass slides showed a progressive increase in anisotropy of the blank from 0 4 to 2 and the natural rock from 0 9 to 2 9 in both the k3 axis migrates to be perpendicular to the glass slides

magnetic anisotropy in clinopyroxene and orthopyroxene single crystals pyroxenes constitute an important component in mafic igneous and metamorphic rocks they often possess a prismatic habit and their long axis the crystallographic c axis helps define a lineation in a textured rock anisotropy of magnetic susceptibility ams serves as a fabric indicator in igneous and metamorphic rocks if a rock s ams is carried by pyroxenes it can be related to their crystallographic preferred orientation and degree of alignment this requires knowing the intrinsic ams of pyroxene single crystals this study provides a comprehensive low field and high field ams investigation of chemically diverse orthopyroxene and clinopyroxene crystals in relation to crystal structure chemical composition oxidation state of fe and the possible presence of ferromagnetic inclusions the paramagnetic anisotropy extracted from high field data shows clear relationships to crystallographic directions and fe concentration both in clinopyroxene and orthopyroxene in the diopside augite series the intermediate susceptibility is parallel to b and the maximum is at 45 to the c axis in aegirine the intermediate axis remains parallel to b while the maximum susceptibility is parallel to c the ams of spodumene depends on fe concentration in enstatite the maximum susceptibility aligns with c and the minimum with b and in the case of hypersthene the maximum susceptibility is normal to the exsolution lamellae magnetite inclusions within augite possess a ferromagnetic anisotropy with consistent orientation of the principal susceptibilities which dominates the low field anisotropy these results provide better understanding of magnetic anisotropy in pyroxenes and form a solid basis for interpretation of magnetic fabrics in pyroxene bearing rocks

a model for radial dike emplacement in composite cones based on observations from summer coon volcano colorado usa we mapped the geometry of 13 silicic dikes at summer coon an eroded oligocene stratovolcano in southern colorado to investigate various characteristics of radial dike emplacement in composite volcanoes exposed dikes are up to about 7 km in length and have numerous offset segments along their upper peripheries surprisingly most dikes at summer coon increase in thickness with distance from the center of the volcano magma pressure in a dike is expected to lessen away from the pressurized source region which would encourage a blade like dike to decrease in thickness with distance from the center of the volcano we attribute the observed thickness pattern as evidence of a driving pressure gradient which is caused by decreasing host rock shear modulus and horizontal stress both due to decreasing emplacement depths beneath the sloping flanks of the volcano based on data from summer coon we propose that radial dikes originate at depth below the summit of a host volcano and follow steeply inclined paths towards the surface near the interface between volcanic cone and basement which may represent a neutral buoyancy surface or stress barrier magma is transported subhorizontally and radially away from the center of the volcano in blade like dikes the dikes thicken with increasing radial distance and offset segments and fingers form along the upper peripheries of the intrusions eruptions may occur anywhere along the length of the dikes but the erupted volume will generally be greater for dike fed eruptions far from the center of the host volcano owing to the increase in driving pressure with distance from the source observed eruptive volumes vent locations and vent area intrusions from inferred post glacial dike fed eruptions at mount adams washington usa support the proposed model hazards associated with radial dike emplacement are therefore greater for longer dikes that propagate to the outer flanks of a volcano

factors affecting the relative importance of shape and distribution anisotropy in rocks theory and experiments abstract the effect of magnetic interactions has been commonly neglected in the interpretation of the anisotropy of magnetic susceptibility ams of igneous rocks despite the likely occurrence of magnetic interactions due to their relatively high content of ferromagnetic minerals current models of magnetic interactions apply to highly simplified systems and are not directly applicable to natural rocks on this work a model that includes variables previously neglected is used to assess the relative importance of magnetically interactive and non interactive fractions in a rock results of the model show that a variable proportion of magnetically interactive grains the relative values of the bulk susceptibility degree of anisotropy and orientation of the anisotropies characteristic for each fraction all play an important role in controlling the rock ams experimental evidence illustrating the importance of the distribution of the ferromagnetic grains within a specimen is also reported and supports the model predictions both theory and experiments indicate that if a rock has unequant magnetic grains and clusters of magnetic grains the contribution to the ams of the rock will depend on the relative values of all the model variables and not only on the occurrence of magnetic interactions as previously presumed

effects of magnetic interactions in anisotropy of magnetic susceptibility models experiments and implications for igneous rock fabrics quantification besides granites of the ilmenite series in which the anisotropy of magnetic susceptibility ams is mainly controlled by paramagnetic minerals the ams of igneous rocks is commonly interpreted as the result of the shape preferred orientation of unequant ferromagnetic grains in a few instances the anisotropy due to the distribution of ferromagnetic grains irrespective of their shape has also been proposed as an important ams source former analytical models that consider infinite geometry of identical and uniformly magnetized and coaxial particles confirm that shape fabric may be overcome by dipolar contributions if neighboring grains are close enough to each other to magnetically interact on these bases we present and experimentally validate a two grain macroscopic numerical model in which each grain carries its own magnetic anisotropy volume orientation and location in space compared with analytical predictions and available experiments our results allow to list and quantify the factors that affect the effects of magnetic interactions in particular we discuss the effects of i the infinite geometry used in the analytical models ii the intrinsic shape anisotropy of the grains iii the relative orientation in space of the grains and iv the spatial distribution of grains with a particular focus on the inter grain distance distribution using documented case studies these findings are summarized and discussed in the framework of the generalized total ams tensor recently introduced by canon tapia canon tapia e 2001 factors affecting the relative importance of shape and distribution anisotropy in rocks theory and experiments tectonophysics 340 117 131 the most important result of our work is that analytical models far overestimate the role of magnetic interaction in rock fabric quantification considering natural rocks as an assemblage of interacting and non interacting grains and that the effects of interaction are reduced by i the finite geometry of the interacting clusters ii the relative orientation between interacting grains iii their heterogeneity in orientation shape and bulk susceptibility and iv their inter distance distribution we reconcile analytical models and experiments with real case studies that minimize the role of magnetic interaction onto the measured ams limitations of our results are discussed and guidelines are provided for the use of ams in geological interpretation of igneous rock fabrics where magnetic interactions are likely to occur

anisotropy of magnetic susceptibility ams analysis of basalt dikes at cathedral cliffs wy implications for heart mountain faulting abstract mafic dikes pervade the upper plate of the heart mountain detachment hmd yet the dike concentration in the lower plate is sparse previous workers interpreted that these dikes were emplaced either coeval with or subsequent to the emplacement of the upper plate the magnetic fabrics of 32 mafic dikes at cathedral cliffs were analyzed using low field anisotropy of magnetic susceptibility ams as a proxy for flow these dikes intrude ordovician mississippian carbonate and overlying eocene volcanic rocks and are truncated along the nearly horizontal hmd the dikes trend between n10 w and n20 e are all steeply dipping and range in width between 0 5 and 3 m flow directions for the dikes were determined by the bearing and plunge of the kmax maximum principal susceptibility axes relative to the dike orientation about 66 of the dikes sampled show typical dike ams patterns with kmax and kint in the plane of the dike and kmin normal to the dike plane about 66 of the dikes sampled have kmax inclinations 45 and thus were emplaced upward 16 of the dikes have kmax inclinations of

heterogeneous aquifer characterization from ground penetrating radar tomography and borehole hydrogeophysical data using nonlinear bayesian simulations it is known that the heterogeneity of hydraulic conductivity drives the groundwater flow and the transport of contaminants however in conventional characterization methods the lack of densely sampled hydrological data does not permit us to describe the aquifer heterogeneity at an appropriate scale in this study we integrate ground penetrating radar gpr tomographic data with hydraulic conductivity logs to estimate the hydraulic conductivity of a heterogeneous unconsolidated aquifer at a decimetric scale between two boreholes the integration of these different data sets is achieved using a nonlinear bayesian simulation algorithm the prior hydraulic conductivity distribution is estimated under gaussian hypothesis by simple kriging of the hydraulic well data the likelihood of hydraulic conductivity given the relative permittivity and the electrical conductivity functions is obtained from a kernel probability density function estimator that describes the in situ relationship between the electric and the hydraulic properties measured along boreholes the proposed method is tested on a synthetic heterogeneous model of permeability to validate the methodology we show that permeability realizations obtained from the proposed algorithm present a higher correlation with the synthetic model than other classical simulation methods the method is then applied on data acquired over an unconsolidated aquifer located in saint lambert de lauzon quebec canada the data set consists of measurements from i gpr crosshole acquisition ii cone penetration testing with pressure measurement combined with soil moisture resistivity and iii a borehole electromagnetic flowmeter by using the presented bayesian approach we generated multiple hydraulic conductivity realizations that are in good agreement with the hydrogeological model of the area

hydrogeophysical data integration at larger scales application of bayesian sequential simulation for the characterization of heterogeneous alluvial aquifers knowledge of the spatial distribution of hydraulic conductivity k within an aquifer is critical for reliable predictions of solute transport and the development of effective groundwater management and or remediation strategies while core analyses and hydraulic logging can provide highly detailed information such information is inherently localized around boreholes that tend to be sparsely distributed throughout the aquifer volume conversely larger scale hydraulic experiments like pumping and tracer tests provide relatively low resolution estimates of k in the investigated subsurface region as a result traditional hydrogeological measurement techniques contain a gap in terms of spatial resolution and coverage and they are often alone inadequate for characterizing heterogeneous aquifers geophysical methods have the potential to bridge this gap the recent increased interest in the application of geophysical methods to hydrogeological problems is clearly evidenced by the formation and rapid growth

magma emplacement into the lemptegy scoria cone chaine des puys france explored with structural anisotropy of magnetic susceptibility and paleomagnetic data the lemptegy volcano is a small monogenetic scoria cone located in the chaine des puys auvergne france which erupted about 32 000 years ago a first edifice lemptegy 1 formed during a trachybasalt eruption as a group of satellite vents of the puy de gouttes scoria cone a second trachyandesitic edifice lemptegy 2 formed soon after and completely covered lemptegy 1 with an 80 m high breached cone since 1946 the lemptegy volcano has been quarried for scoria and today offers unprecedented three dimensional exposure of the subvolcanic plumbing system to map the internal flow architecture of the plumbing system and to study the subvolcanic deformation of lemptegy 2 structural mapping petrographic observations anisotropy of magnetic susceptibility ams rock magnetic and paleomagnetic data were collected field structural mapping and thin section study of tension gashes riedel shears striations as well as ductile shear zones and bubbles allow the direction and sense of the magma flow to be determined twenty ams sites were established in ten dikes one to four sites in each dike with 504 specimens analyzed and 479 specimens used to infer magma flow patterns structural data the maximum susceptibility axis k 1 and the imbrication of the magnetic foliation k 1 k 2 planes indicate both upward and downward sense of flow as well as flow toward and away from the central vent rock magnetic experiments reveal that a cubic fe ti oxide phase likely low ti titanomagnetite is the principal magnetic phase carrying both the remanence and anisotropy paleomagnetic data from some sites yield statistically distinct at the 95 confidence level remanence directions while at other sites the data are indistinguishable at the 95 confidence level the paleomagnetic results observed steeply tilted scoria layers internal unconformities and faults show that as each dike was emplaced it displaced earlier dikes evidencing subvolcanic deformation the lemptegy 2 volcano shares similarities in terms of inferred eruption style and structures with other scoria cones such as cerro negro nicaragua and thus provides an excellent field laboratory to investigate active scoria cones world wide

geochemical modelling of co2 water rock interactions in a potential storage formation of the north german sedimentary basin abstract the lower triassic bunter sandstone and lower jurassic rhat formations of the northern germany sedimentary basin constitute feasible reservoirs for the storage of co 2 from combustion of fossil fuels or industrial production processes this study presents analyses of geochemical interactions between co 2 formation fluid and rock of these potential reservoirs using geochemical modelling in order to assess the short and long term impact of co 2 sequestration batch equilibrium modelling was performed first for assessing the consistency of fluid and mineralogy field data and for identifying potential secondary minerals under the influence of injected co 2 inclusion of reaction kinetics in the batch models allowed an observation of reaction paths and to estimate the time frame of geochemical reactions finally one dimensional equilibrium reactive transport modelling was used in order to investigate the direction of reactions under conditions of fluid flow and mass transport and to quantify feedbacks of reactions on transport processes results of the simulations performed show that dawsonite may act as the main co 2 storage mineral in both formations while the carbonates calcite and dolomite dissolve over time also changes in porosity and permeability are significant in the equilibrium reactive transport simulations the time scale of kinetically controlled reactions observed in the kinetic batch modeling however suggests that co 2 mineral trapping in both formations requires very long time frames and hence other mechanisms such as structural or solubility trapping seem to be more relevant within the injection or early post injection phase for the studied formations

using natural co2 reservoir to constrain geochemical models for co2 geological sequestration abstract numerical modeling of geochemical transport processes is necessary to investigate long term co 2 storage in deep saline formations because aluminosilicate mineral alteration is very slow under ambient deep formation conditions and is not amenable to experimental study geochemical transport modeling can solve many problems and answer questions related to co 2 geological sequestration the numerical modeling provides valuable insights regarding the physical and chemical consequences of co 2 injection in the subsurface environment however the reliability and applicability of the models need to be tested and validated if they are applied for co 2 geological sequestration issues on model validations are important if co 2 injection technologies are to be implemented safely efficiently and predictably validation of geochemical transport models could be different from conventional model validation methods for groundwater flow and solute transport for the short term behaviors the models can be validated using laboratory and field experiments for the long term mineral alteration and co 2 sequestration the natural analogue using high pressure co 2 reservoirs could be a best way to validate the model in this paper a natural co 2 reservoir in southern songliao basin of china which is past accumulations of co 2 in geological formation associated with magmatic or volcanic activity was selected although the length of co 2 exposure and hence the rates of reaction for the natural system is not known in detail we have shown that it is indeed possible to use observation data of mineral alteration in the natural co 2 reservoir to constrain thermodynamic and kinetic data of minerals used in the model and to confine conditions of temperature pressure salinity and primary mineral composition

the pretty hill formation as a natural analogue for co2 storage an investigation of mineralogical and isotopic changes associated with sandstones exposed to low intermediate and high co2 concentrations over geological time abstract the pretty hill formation of the otway basin australia has been studied as a natural analogue for geological storage of anthropogenic co2 in order to examine the effects that co2 concentration and reservoir heterogeneity have on co2 related reactions new petrographic data are presented which validate the use of hylogger as a tool to investigate high resolution vertical changes in reservoir mineralogy the integrated data set confirms earlier interpretations showing that chlorite has been altered to kaolinite and siderite ankerite in reservoir facies exposed to moderate and high co2 concentrations while chlorite remains the dominant clay mineral in all parts of the formation where co2 content is low differences have been observed in the degree of co2 related reaction relative to co2 concentration and reservoir heterogeneity where co2 content is very high c 98 mol and associated with high water saturations both chlorite and detrital feldspars have undergone complete reaction in the reservoir facies resulting in quartzose sandstones with a kaolinite matrix and with siderite as the dominant carbonate precipitate conversely where co2 content is moderate c 29 57 mol and within the gas leg of the reservoir chlorite has undergone significant reaction but much of the original feldspar is preserved suggesting relatively minor reaction carbonate cements from the moderate co2 gas leg comprise calcite siderite and ankerite occurring as cemented zones associated with rock heterogeneities and the present day gas water contact heterogeneities within the gas leg are likely to have associated pore fluid contacts whereby relatively high water saturations will be present in the fine grained baffles and seals the most advanced feldspar reaction occurs locally at the contact between baffles and reservoir rock while reactions have been significantly impeded in the finer grained units due to their low permeabilities stable isotope data presented for carbonate cements analysed from wells with low and moderate co2 levels show no clear distinction relatively early formed calcite has 13c values that require an organic carbon source suggesting precipitation unrelated to the reservoir co2 in the otway basin in contrast diagenetically late calcite and siderite samples display two distinct 13c groups dependent on carbonate type where the calculated fluid carbon isotope compositions are similar to documented magmatic co2 reservoired in the nearby caroline field this suggests that magma derived co2 may have been more prevalent through the pretty hill formation than previously thought although the co2 has not been contained over the long term in the low co2 sites it may have caused the local dissolution of carbonate and laumontite cement and also contributed a source of carbon for late stage calcite cements these studies illustrate the importance of understanding both the reservoir composition and vertical heterogeneity of potential storage systems fluid mineral reactions are likely to be advanced within stacked reservoir facies and impeded within siltstone layers while the distribution of carbonate cement may increase the reservoir heterogeneity by the formation of cemented siltstone sandstone layers thereby creating impermeable barriers or baffles to co2

complex plumbing of monogenetic scoria cones new insights from the lunar crater volcanic field nevada usa abstract the complexity of monogenetic basaltic eruptions is largely governed by the shallow plumbing of the volcanoes that develop in the upper hundreds of meters of the crust as well as within the growing edifice during the eruption we present data pertaining to geometry and dynamics of plumbing features associated with two monogenetic volcanoes observed within in the lunar crater volcanic field nevada usa that have been eroded to varying degrees exposing numerous intrusive bodies the majority of the intrusive bodies observed within the eroded scoria cone and cone remnant are radial dikes and dike sets many of which have irregular shapes we infer that the radial patterns of the dikes resulted from magma overpressure in central conduits and from the stresses induced by the topographic load of the cones with the regional tectonic stresses playing a negligible role internally the dikes display textural features such as multiple chilled margins and or distinct bandings of vesicle populations suggesting multiple injections or pulses of magma originating from the vent conduit area were incrementally added to the dikes pressure fluctuations within the magma columns capable of producing such features can be associated with a variety of dynamic processes including the ascent of slugs of gas through the magma column variations in the source pressure of the ascending magma as well as the weight of relatively degassed magma and temporary blockages of the conduit irregular shapes of some dikes are likely related to the interaction between viscous intruding magma and weakly consolidated scoria cone deposits the geometry of the dikes and the relationship to a central magma column have important implications for eruption processes degassing patterns and gas melt coupling associated with monogenetic eruptions

estimating the hydraulic conductivity at the south oyster site from geophysical tomographic data using bayesian techniques based on the normal linear regression model this study explores the use of ground penetrating radar gpr tomographic velocity gpr tomographic attenuation and seismic tomographic velocity for hydraulic conductivity estimation at the south oyster site using a bayesian framework since site specific relations between hydraulic conductivity and geophysical properties are often nonlinear and subject to a large degree of uncertainty such as at this site we developed a normal linear regression model that allows exploring these relationships systematically although the log conductivity displays a small variation s 2 5 0 30 and the geophysical data vary over only a small range results indicate that the geophysical data improve the estimates of the hydraulic conductivity the improvement is the most significant where prior information is limited among the geophysical data gpr and seismic velocity are more useful than gpr attenuation

traveltime inversion for the geometry of aquifer lithologies crosswell traveltime tomography can provide detailed descriptions of the geometry and seismic slowness of lithologic zones in aquifers and reservoirs traditional tomographic inversions that estimate a smooth slowness field to match traveltime data provide limited information about the dominant scale of subsurface heterogeneity we demonstrate an alternative method called the multiple population inversion mpi that co inverts traveltimes between multiple well pairs to identify the spatial distribution of a small number of slowness populations we also compare the mpi with the split inversion method sim that was recently introduced to address the same problem the lithologies and hydraulic parameters for these populations can then be determined from core data and hydraulic testing the mpi iteratively assigns pixels to a small number of slowness populations based on the histogram of slowness residuals by constraining the number of slowness values this method is less susceptible to inversion artifacts such as those related to slight variations in ray coverage and can resolve finer scale sedimentary structures better than methods that smooth the slowness field we demonstrate the mpi in two dimensions with a synthetic aquifer and in three dimensions with the kesterson aquifer in the central valley of california in both cases the constrained inversion algorithm converges to an equal or smaller average traveltime residual than obtained with unconstrained value tomography the mpi accurately images the dominant lithologies of the synthetic aquifer and provides a geologically reasonable image of the kesterson aquifer

anisotropy of magnetic susceptibility in welded tuffs application to a welded tuff dyke in the tertiary trans pecos texas volcanic province usa consideration of published anisotropy of magnetic susceptibility ams studies on welded ignimbrites suggests that ams fabrics are controlled by groundmass microlites distributed within the existing tuff fabric the sum result of directional fabrics imposed by primary flow lineation welding and if relevant rheomorphism ams is a more sensitive indicator of fabric elements within welded tuffs than conventional methods and usually yields primary flow azimuth estimates detailed study of a single densely welded tuff sample demonstrates that the overall ams fabric is insensitive to the relative abundances of fiamme matrix and lithics within individual drilled cores ams determinations on a welded tuff dyke occurring in a choked vent in the trans pecos texas volcanic field reveals a consistent fabric with a prolate element imbricated with respect to one wall of the dyke while total magnetic susceptibility and density exhibit axially symmetric variations across the dyke width the dyke is interpreted to have formed as a result of agglutination of the erupting mixture on a portion of the conduit wall as it failed and slid into the conduit followed by residual squeezing between the failed block and in situ wallrock irrespective of the precise mechanism widespread occurrence of both welded tuff dykes and point welded aggregate pumices in pyroclastic deposits may imply that lining of conduit walls by agglutionation during explosive volcanic eruptions is a common process

predictive modeling of co2 sequestration in deep saline sandstone reservoirs impacts of geochemical kinetics abstract one idea for mitigating the increase in fossil fuel generated co 2 in the atmosphere is to inject co 2 into subsurface saline sandstone reservoirs to decide whether to try such sequestration at a globally significant scale will require the ability to predict the fate of injected co 2 thus models are needed to predict the rates and extents of subsurface rock water gas interactions several reactive transport models for co 2 sequestration created in the last decade predicted sequestration in sandstone reservoirs of 17 to 90 kg co 2 m 3 to build confidence in such models a baseline problem including rock water chemistry is proposed as the basis for future modeling so that both the models and the parameterizations can be compared systematically in addition a reactive diffusion model is used to investigate the fate of injected supercritical co 2 fluid in the proposed baseline reservoir brine system in the baseline problem injected co 2 is redistributed from the supercritical sc free phase by dissolution into pore brine and by formation of carbonates in the sandstone the numerical transport model incorporates a full kinetic description of mineral water reactions under the assumption that transport is by diffusion only sensitivity tests were also run to understand which mineral kinetics reactions are important for co 2 trapping the diffusion transport model shows that for the first 20 years 20 a after co 2 diffusion initiates co 2 is mostly consumed by dissolution into the brine to form co 2 aq solubility trapping from 20 to 200 a both solubility and mineral trapping are important as calcite precipitation is driven by dissolution of oligoclase from 200 to 1000 a mineral trapping is the most important sequestration mechanism as smectite dissolves and calcite precipitates beyond 2000 a most trapping is due to formation of aqueous hco 3 ninety seven percent of the maximum co 2 sequestration 34 5 kg co 2 per m 3 of sandstone is attained by 4000 a even though the system does not achieve chemical equilibrium until 25 000 a this maximum represents about 20 co 2 dissolved as co 2 aq 50 dissolved as hco 3 aq and 30 precipitated as calcite the extent of sequestration as hco 3 at equilibrium can be calculated from equilibrium thermodynamics and is roughly equivalent to the amount of na in the initial sandstone in a soluble mineral here oligoclase similarly the extent of trapping in calcite is determined by the amount of ca 2 in the initial oligoclase and smectite sensitivity analyses show that the rate of co 2 sequestration is sensitive to the mineral water reaction kinetic constants between approximately 10 and 4000 a the sensitivity of co 2 sequestration to the rate constants decreases in magnitude respectively from oligoclase to albite to smectite

single domain particles in rocks and magnetic fabric analysis magnetic susceptibility anisotropy is commonly used as a guide for determining stress and flow axes in rocks and for assessing the suitability of anisotropic rocks for palaeomagnetic purposes we have recently demonstrated however in laboratory produced samples that as theoretically expected susceptibility anisotropy is dependent on particle size multidomain particles of magnetite or similar strongly magnetic particles with shape anisotropy exhibit a maximum susceptibility parallel to their easy remanent magnetization axes whereas uniaxial single domain particles exhibit a maximum susceptibility perpendicular to their easy magnetization axes hence susceptibility anisotropy does not yield an unambiguous determination of particle alignment in rocks independent of domain state by demonstrating uniaxial single domain anisotropy characteristics for the first time in a rock specimen we show here that susceptibility measurements by themselves may not correctly identify the degree or type of alignment of ferro or ferrimagnetic particles in rocks in particular apparently foliated rocks can actually be lineated and vice versa moreover rocks with low anisotropy of susceptibility can have a much higher anisotropy of remanence remanence anisotropy methods are shown to give unambiguous determinations of the degree and type of alignment

field example of data fusion in site characterization application of data fusion to characterization of the fountain and lyons formations at a field site incorporates geologic knowledge geophysical log data cross hole seismic tomography hydraulic test data and observations of head to reduce uncertainty associated with subsurface interpretation these formations consist of channel and overbank deposits that have undergone variable diagenesis resulting in more hydrofacies than would have been encountered in the original unaltered deposits the disparate types of available data are integrated to yield a coherent hydrofacies classification through use of discriminant analysis and soft data techniques this data fusion improves definition of the complex hydrofacies and increases knowledge of their spatial correlation two hundred multiple indicator conditional stochastic simulations of the site are generated 100 with only hard data and 100 with both hard and soft data forward groundwater flow modeling using estimates of hydraulic conductivity from field testing yields smaller head residuals for realizations which include soft data inverse modeling is used to eliminate hydrofacies realizations that do not honor hydraulic data and to estimate hydrofacies hydraulic conductivity ranges for the hard and hard soft data ensembles inverse parameter estimation substantially decreases head residuals for both ensembles standard deviations of hydraulic conductivities estimated through inverse modeling are smaller when both hard and soft data are used to generate the simulations even though head residuals are similar within the two ensembles when these estimated hydraulic conductivities are used

dike intrusion under shear stress effects on magnetic and vesicle fabrics in dikes from rift zones of tenerife canary islands a theoretical model predicting how anisotropy of magnetic susceptibility ams and vesicle fabrics are modified by shear stress resolved on the dike walls prior to the final cooling of magma is developed for vertical dikes the resulting fabrics are asymmetric with respect to initial fabrics assumed to be symmetric application of this model together with collected data on magma flow direction dike propagation direction and mechanism and shear sense allow us to interpret dike fabrics in terms of shear resolved on the dike walls during intrusion en echelon arrangement offsetting and dike curvature the interpretation of ams and vesicle fabrics of the margins of four dikes shows a reasonable agreement with the proposed theoretical models suggesting that asymmetric fabrics can be used to infer magma flow and may provide valuable information on the shear resolved on the dike walls during intrusion

using bayesian simulations to predict reservoir thickness under tuning conditions mapping reservoir thickness from 3 d seismic data is a difficult task when the seismic response is dominated by tuning effects deterministic solutions may be considered when the acoustic properties of the reservoir and the encasing material are nearly constant when the acoustic properties are highly variable the dispersion of points observed in the tuning curves precludes a deterministic approach and a statistical method is preferred in this study we apply a recently developed nonlinear bayesian simulation technique to map the thickness of a reservoir associated with an intrusive rock in contrast to linear geostatistical techniques such as cokriging this method handles complex nonlinear relationships between thickness and multiple seismic attributes

regional scale integration of multiresolution hydrological and geophysical data using a two step bayesian sequential simulation approach significant progress has been made with regard to the quantitative integration of geophysical and hydrological data at the local scale for the purpose of improving predictions of groundwater flow and solute transport however extending corresponding approaches to the regional scale still represents one of the major challenges in the domain of hydrogeophysics to address this problem we have developed a regional scale data integration methodology based on a two step bayesian sequential simulation approach our objective is to generate high resolution stochastic realizations of the regional scale hydraulic conductivity field in the common case where there exist spatially exhaustive but poorly resolved measurements of a related geophysical parameter as well as highly resolved but spatially sparse collocated measurements of this geophysical parameter and the hydraulic conductivity to integrate this multi scale multi parameter database we first link the low and high resolution geophysical data via a stochastic downscaling procedure this is followed by relating the downscaled geophysical data to the high resolution hydraulic conductivity distribution after outlining the general methodology of the approach we demonstrate its application to a realistic synthetic example where we consider as data high resolution measurements of the hydraulic and electrical conductivities at a small number of borehole locations as well as spatially exhaustive low resolution estimates of the electrical conductivity obtained from surface based electrical resistivity tomography the different stochastic realizations of the hydraulic conductivity field obtained using our procedure are validated by comparing their solute transport behaviour with that of the underlying true hydraulic conductivity field we find that even in the presence of strong subsurface heterogeneity our proposed procedure allows for the generation of faithful representations of the regional scale hydraulic conductivity structure and reliable predictions of solute transport over long regional scale distances

integration of diverse physical property models subsurface zonation and petrophysical parameter estimation based on fuzzy c means cluster analyses inversions of an individual geophysical data set can be highly nonunique and it is generally difficult to determine petrophysical parameters from geophysical data we show that both issues can be addressed by adopting a statistical multiparameter approach that requires the acquisition processing and separate inversion of two or more types of geophysical data to combine information contained in the physical property models that result from inverting the individual data sets and to estimate the spatial distribution of petrophysical parameters in regions where they are known at only a few locations we demonstrate the potential of the fuzzy c means fcm clustering technique after testing this new approach on synthetic data we apply it to limited crosshole georadar crosshole seismic gamma log and slug test data acquired within a shallow alluvial aquifer the derived multiparameter model effectively outlines the major sedimentary units observed in numerous boreholes and provides plausible estimates

a field proof of concept of tomographic slug tests in an anisotropic littoral aquifer hydraulic tomography is increasingly recognized as a characterization approach that can image pathways or barriers to flow as well as their connectivity in this study we assess the performance of a transient analysis of tomographic slug test head data in estimating heterogeneity in horizontal hydraulic conductivity kh hydraulic conductivity anisotropy the ratio between vertical and horizontal hydraulic conductivity kv kh and specific storage ss under actual field conditions the tomographic experiment was carried out between two wells in a moderately heterogeneous and highly anisotropic silt and sand littoral aquifer in this field proof of concept the inversion of the two dimensional 2d head dataset was computed with a 2d radial flow algorithm that considers kh kv kh ss and wellbore storage effects this study demonstrated that a transient analysis of tomographic slug tests is able to capture the key features of the littoral environment of the test the vertical profiles of kh and kv are indeed in agreement with those from other field and laboratory tests and ss values exhibit physically plausible profiles furthermore the simulation of independent inter well hydraulic tests slug and pumping tests screened over the entire aquifer using resolved kh kv kh and ss tomograms produce responses very close to field observations this study demonstrates that the effects of fine scale heterogeneity that induces k anisotropy at larger scales can be captured through a transient analysis of tomographic slug tests which are very difficult to quantify otherwise with conventional hydraulic tests thus allowing a better representation of properties controlling flow and transport in aquifer systems