electrical impedance variation with water saturation in rock we measured the electrical impedances of 22 sandstone samples during oil driving water tests using the two electrode method experiments show that the imaginary part x of the impedance r ix of rock may respond well to water saturation in the frequency range 100 hz 15 mhz we found that the maximum x values and their corresponding interfacial polarization frequencies are linear with water saturation the lower critical frequency is found to vary with water saturation in an unclear relationship with the characteristic length of rock the dissipation factor at the interfacial polarization frequency remains quite stable and may be an indicator of the pore structure of rock we used an equivalent circuit to explain the dispersive behavior of rock more than one interfacial polarization frequency in the impedance argand plot is predicted and can be observed if the measurement frequency range is wide enough

crosshole ip imaging for engineering and environmental applications induced polarization ip imaging is a promising tool in engineering and environmental studies application of this technique for near surface investigations has previously been limited by incomplete understanding of the physicochemical controls on the ip response together with a lack of appropriate methods for data inversion as laboratory studies have shown description of ip in terms of complex electrical conductivity enables access to various structural characteristics pertinent to practical issues such as subsurface lithology definition hydraulic permeability estimation or hydrocarbon contaminant mapping in particular analysis in terms of real and imaginary conductivity components offers improved lithological characterization since surface polarization effects are separated from electrolytic and surface conduction effects an occam type ip inversion algorithm based on complex algebra is described which accounts for these advances in ip interpretation by directly solving for complex conductivity results from crosshole applications at two case study sites demonstrate the suitability of the ip imaging approach for subsurface characterization in the first case study the imaging results correlate with the observed complex sequence of quaternary sediments at a waste disposal site characterization of the polarizability of these sediments offers significant value in lithological differentiation in the second case study the results of ip imaging at a hydrocarbon contaminated site illustrate the potential of the method in environmental studies the hydrocarbon location is clearly evident from the ip image and a markedly different response is observed at an uncontaminated region of the site by adopting empirical structural electrical relationships images of textural and hydraulic properties are estimated as a step toward improved quantitative characterization the success of the method for these contrasting applications supports further investigation into understanding the physical and chemical processes that control observed ip

high resolution characterization of vadose zone dynamics using cross borehole radar characterization of the dynamics of moisture migration in the unsaturated zone of aquifers is essential if reliable estimates of the transport of pollutants threatening such aquifers are to be made electrical geophysical investigation techniques such as ground penetrating radar offer suitable methods for monitoring moisture content changes in the vadose zone moreover these tools permit relatively large measurement scales appropriate for hydrological models of unsaturated processes and thus they offer a distinct advantage over conventional measurement approaches ground penetrating radar when applied in transmission mode between boreholes can provide high resolution information on lithological and hydrological features the technique may be applied in tomographic mode and in a much simpler vertical profile mode both modes of measurement have been utilized using two boreholes 5 m apart located at a field site in the uk sherwood sandstone aquifer radar transmission measurements have been used to characterize the change in moisture content in unsaturated sandstone due to controlled water tracer injection continual monitoring of cross borehole radar measurements over an 18 month period has also permitted determination of travel times of natural loading to the system and has revealed the impact of subtle contrasts in lithology on changes in moisture content over time the time series of inferred moisture contents show clearly wetting and drying fronts migrating at a rate of approximately 2 m month 1 throughout the sandstone

controls on induced polarization in sandy unconsolidated sediments and application to aquifer characterization resistivity and induced polarization ip measurements 0 1 1000 hz were made on clay free unconsolidated sediments from a sandy alluvial aquifer in the kansas river floodplain the sensitivity of imaginary conductivity a fundamental ip measurement to lithological parameters fluid conductivity and degree of saturation was assessed the previously reported power law dependence of ip on surface area and grain size is clearly observed despite the narrow lithologic range encountered in this unconsolidated sedimentary sequence the grain size relationship is effectively frequency independent between 0 1 and 100 hz but depends on the representative grain diameter used for the sediments examined here d90 the grain diameter of the coarsest sediments in a sample is well correlated with the distribution of the internal surface in the well sorted sandy sediments investigated here is such that most of the sample weight is likely required to account for the majority of the internal surface we fin

highly siderophile element and osmium isotope evidence for postcore formation magmatic and impact processes on the aubrite parent body abstract aubrites exhibit a wide range of highly siderophile element hse re os ir ru rh pt pd au concentrations and 187os 188os compositions their hse concentrations are one to three orders of magnitude less than chondrites with the exception of the shallowater and mt egerton samples while most aubrites show chondritic hse abundance ratios significant enrichments of pd and re relative to os ir and ru are observed in 12 of 16 samples present day 187os 188os ratios range from subchondritic values of 0 1174 to superchondritic values of up to 0 2263 half of the samples have 187os 188os ratios of 0 127 to 0 130 which is in the range of enstatite chondrites along with the brecciated nature of aubrites the hse and re os isotope systematics support a history of extensive postaccretion processing including core formation late addition of chondritic material and or core material and potential breakup and reassembly highly siderophile element signatures for some aubrites are consistent with a mixing of hse rich chondritic fragments with a hse free aubrite matrix the enrichments in incompatible hse such as pd and re observed in some aubrites reminiscent of terrestrial basalts suggest an extensive magmatic and impact history which is supported by both the 187re 187os isotope system and silicate hosted isotope systems rb sr k ar yielding young formation ages of 1 3 3 9 ga for a subset of samples compared with other differentiated achondrites derived from small planetary bodies aubrites show a wide range in hse concentrations and 187os 188os most similar to angrites while similarities exist between the diverse groups of achondrites formed early in solar system history the aubrite parent body ies clearly underwent a distinct evolution different from angrites brachinites ureilites howardites eucrites and diogenites

the shallowater aubrite evidence for origin by planetesimal impacts shallowater is the only known unbrecciated igneous aubrite enstatite achondrite it is a coarse grained orthopyroxenite consisting of in vol poikilitic orthoenstatite crystals 80 up to 4 5 cm in size which contain as inclusions and in the interstices xenoliths of an assemblage of twinned low ca clinoenstatite 1 forsterite 2 9 plagioclase 2 5 metallic fe ni 3 3 troilite 2 9 schreibersite 0 4 weathered opaques 8 and traces of niningerite and oldhamite conclusions 1 shallowater is of igneous origin 2 shallowater could not have formed by internal igneous nor by impact melting processes either on the h or l enstatite chondrite or aubrite parent bodies instead shallowater appears to be a sample of yet a fourth enstatite type asteroid 3 shallowater experienced an extraordinarily complex and unusual three stage cooling history as determined by mineral stability considerations and modelling of micro structural evolution as a function of cooling rate stage 1 very fast cooling from 1 580 c to somewhere above 712 c at a rate of 100 c hour through 1000 c above 1000 c the rate was probably much faster stage 2 very slow cooling annealing from 712 to 680 c at a rate of 7 5 c 106 y stage 3 fast cooling from 680 to 600 c at a rate of 0 5 c day and from 600 to 300 c at a rate of 0 4 c day 4 this complex cooling history suggests an equally unusual origin for shallowater as follows a completely or partly molten asteroid of nearly pure enstatite composition was broken up by low velocity impact with a solid e like object the melt cooled very fast stage 1 due to incorporation of cold 20 projectile debris the xenoliths fragments reassembled into a rubble pile body while t was 712 c and deeply buried materials like the object that is now shallowater cooled very slowly from 712 to 680 c stage 2 the anneal of stage 2 requires burial at a depth of 40 km on a 100 km diameter asteroid excavation from this depth by impact to account for the fast cooling of stage 3 can be accounted for in two scenarios scenario 1 during catastrophic impact the shallowater object could have been by chance near the surface within 10 m of a very large fragment thus accounting for the fast cooling and for surviving for 4 5 109 y scenario 2 the shallowater object may have been excavated by break up and subsequently buried near the surface of a gravitationally reassembled body this would require yet a second break up and reassembly episode 5 the xenoliths represent an enstatite like meteorite type unknown as an individual fall not unexpected for a rock type from an asteroid that appears to have been largely destroyed early in the history of the solar system

integrated method of rs and gpr for monitoring the changes in the soil moisture and groundwater environment due to underground coal mining mining affects the environment in different ways depending on the physical context in which the mining occurs in mining areas with an arid environment mining affects plants growth by changing the amount of available water this paper discusses the effects of mining on two important determinants of plant growth soil moisture and groundwater table gwt which were investigated using an integrated approach involving a field sampling investigation with remote sensing rs and ground penetrating radar gpr to calculate and map the distribution of soil moisture for a target area we initially analyzed four models for regression analysis between soil moisture and apparent thermal inertia and finally selected a linear model for modeling the soil moisture at a depth 10 cm the relative error of the modeled soil moisture was about 6 3 and correlation coefficient 0 7794 a comparison of mined and unmined areas based on the results of limited field sampling tests or rs monitoring of landsat 5 thermatic mapping tm data indicated that soil moisture did not undergo remarkable changes following mining this result indicates that mining does not have an effect on soil moisture in the shendong coal mining area the coverage of vegetation in 2005 was compared with that in 1995 by means of the normalized difference vegetation index ndvi deduced from tm data and the results showed that the coverage of vegetation in shendong coal mining area has improved greatly since 1995 because of policy input rmb 0 4 per ton coal production by shendong coal mining company the factor most affected by coal mining was gwt which dropped from a depth of 35 41 m before mining to a depth of 43 38 m after mining at the bulianta coal mine based on water well measurements ground penetrating radar at frequencies of 25 and 50 mhz revealed that the deepest gwt was at about 43 4 m there was a weak water linkage between the unsaturated zone and groundwater and the decline of water table primarily resulted from the well pumping for mining safety rather than the movement of cracking strata this result is in agreement with the measurements of the water wells the roots of nine typical plants in the study area were investigated populus was found to have the deepest root system with a depth of about 26 m based on an assessment of plant growth demands and the effect of mining on environmental factors we concluded that mining will have less of an effect on plant growth at those sites where the primary gwt depth before mining was deep enough to be unavailable to plants if the primary gwt was available for plant growth before mining especially to those plants with deeper roots mining will have a significant effect on the growth of plants and the mechanism of this effect will include the loss of water to roots and damage to the root system

composition of metal in aubrites constraints on core formation abstract aubrites are differentiated stone meteorites with small amounts of metal study of eight aubrites reveals that fe ni grains occur in a variety of textures from irregular m sized particles to rounded nodules of up to 1 5 cm in diameter the pattern of siderophile element abundances in the silicates is characteristic of igneous metal segregation the more siderophilic elements are more depleted despite large uncertainties in metal silicate distribution coefficients the calculated minimum metal content of the aubrite precursor is not unlike that of enstatite chondrites and suggests that metal segregation was an extensive process in the early magmatic evolution of the aubrite parent body however the lack of appreciable fractionation in the trace element signature of the metal suggests that the metal now observed in aubrites did not undergo fractional crystallization in a core we argue instead that the analyzed metal nodules represent a fraction of the iron nickel that during partial melting was not completely segregated from the silicates

study of automated top coal caving in extra thick coal seams using the continuum discontinuum element method abstract in order to investigate top coal drawing regularity and automated top coal caving technology in extra thick coal seams an approach coupling the particle element and the block element is presented based on the continuum discontinuum element method cdem then the constitutive model of hydraulic support is introduced into the cdem to simulate the top coal drawing process meanwhile the bergmark roos model for coal drawing of single support is extended into the collaborative coal drawing of multiple supports to optimize the automated top coal caving technology finally cdem models of hydraulic support armored face conveyer and coal rock strata are established according to the field conditions of the tongxin coal mine then the top coal drawing mechanism is analyzed and an automated top coal caving technology is proposed the results show that under the interaction between hydraulic support and surrounding rocks the final drawing body of initial top coal drawing appears as an irregular deflected ellipsoid shape during different support moving cycles the coal rock structure affects the coal drawing amount and support resistance a statistical comparison of the coal rock drawing amount based on 100 drawing openings indicates that the standard deviation of the coal drawing amount in automated one round coal caving is 1 83 m2 less than that in traditional coal caving 8 23 m2 and the coal drawing amount from each drawing window is more uniform for multi round coal caving techniques the average recovery rate remains at 79 4 and the rock mixed rate is less than 1 based on a comparison of several coal caving techniques automated four round coal caving technology is the optimal technology in which the change rate of the standard deviation of the coal drawing amount as well as the top coal recovery rate are both largest

radar frequency dielectric dispersion in sandstone implications for determination of moisture and clay content 1 the relationship between dielectric permittivity water saturation and clay content for the sherwood sandstone from ne england was characterized as part of a wider study of the vadose zone moisture dynamics and pollution vulnerability of this aquifer dielectric permittivity was measured over the full range of saturation levels for various lithologies ranging from clean medium grained sandstone to fine grained sandstone containing up to 5 clay using a specially constructed dielectric cell dielectric constant kr is largely independent of frequency between 350 mhz and 1000 mhz below 350 mhz kr of fine grained clay rich sandstone shows frequency dispersion tests on physical models of the sandstone consisting of a fine fraction of ottawa sand and montmorillonite clay indicate that the clay minerals within the sandstone are responsible for its frequency dispersive behavior these tests also show that increasing pore fluid salinity increases dielectric dispersion at the lower end of the frequency range which indicates that this arises from the interfacial maxwell wagner mechanism associated with platy clay particles water saturated sand clay mixtures show very low dielectric constants at high frequencies over 650 mhz this effect is independent of salinity and probably results from the layered geometric arrangement of solids bound and free water within the swelling clay the complex refractive index method crim with a mineral dielectric constant of about 5 provides a good match to the water saturation versus dielectric constant data for all sherwood sandstone lithologies at frequencies between 350 and 1000 mhz and for clay poor sandstone at lower frequencies below 350 mhz the presence of a few percent of clay in some sherwood sandstone lithologies raises their crim best fit mineral dielectric constant substantially

relevance of induced polarization to quantitative formation evaluation abstract the role of electrical induced polarization ip in the petrophysical estimation of shaliness and permeability remains uncertain in the wake of widely varying degrees of optimism within the literature of the past 30 years therefore there is no general agreement on the potential usefulness of ip methods within the framework of formation evaluation a refinement of the broad scatter of data previously indicated by ip shaliness permeability correlations has been accomplished through new empirical relationships involving time domain ip parameters it is demonstrated that chargeability can be related smoothly and definitively to excess conductivity or intergranular permeability these relationships are based upon measurements of water saturated sandstones over a wide range of electrolyte conductivity their field application is viable provided that three formation constants have been determined from laboratory measurement in the light of these developments the possible contribution of induced polarization measurements to petrophysical evaluation is briefly re examined with more confidence than has been justifiable up to now in so doing particular attention is paid to those precautionary procedures of core preparation and data acquisition which must be followed if the ip approach is to be beneficial from a quantitative standpoint

petrogenesis of mesosiderites i origin of mafic lithologies and comparison with basaltic achondrites abstract new petrologic and trace element data on basaltic and gabbroic clasts in mesosiderites and basaltic achondrites combined with existing petrologic and trace element data have served as a basis for interpretation of the petrogenesis of mesosiderite clasts compared with the basaltic achondrites the mesosiderite basaltic and gabbroic clasts contain more abundant modal tridymite and merrillite and more commonly contain augite as a late magmatic phase their pyroxenes tend to be more mgo rich and have lower fe mn ratios which are positively correlated with the fe mg ratio some of the mesosiderite basaltic and gabbroic clasts contain xenocrystic plagioclase the basaltic clasts commonly show super chondritic eu sm ratios and slight lree depletions the cumulate gabbro clasts are extremely depleted in lil have very high eu sm ratios and high lu sm ratios all of these features can be explained by a model in which the mafic lithologies of mesosiderites were formed by remelting of a mixed basalt cumulate gabbro metal source region near the parent body surface reducing agents p c s from the metallic fraction reduce feo out of the silicate melt and result in the positive correlation of fe mn with fe mg observed in pyroxene analyses and the modal abundances of tridymite merrillite and augite xenocrystic plagioclase is a natural consequence of remelting a cumulate gabbro rich source as are the unique ree patterns observed

vadose zone flow model parameterisation using cross borehole radar and resistivity imaging cross borehole geoelectrical imaging in particular electrical resistivity tomography ert and transmission radar tomography can provide high resolution images of hydrogeological structures and in some cases detailed assessment of dynamic processes in the subsurface environment through appropriate petrophysical relationships these tools offer data suitable for parameterising and constraining models of groundwater flow this is demonstrated using cross borehole radar and resistivity measurements collected during a controlled vadose zone tracer test performed at a field site in the uk sherwood sandstone both methods show clearly the vertical migration of the tracer over a 200 h monitoring period by comparing first and second spatial moments of changes in moisture content predicted from a numerical simulation of vadose zone flow with equivalent statistics from two and three dimensional ert and cross borehole radar profiles the effective hydraulic conductivity is estimated to be approximately 0 4 m d such a value is comparable to field estimates from borehole hydraulic tests carried out in the saturated zone at the field site and provides valuable information that may be utilised to parameterise pollutant transport models of the site

estimation of hydraulic parameters of shaly sandstone aquifers from geoelectrical measurements electrical and hydraulic conductivities of shaly sandstones are described using a capillary approach for a granular clay bearing material the clays are assumed to occur as shale shells uniformly coating the insulated sand grains the real and imaginary components of the complex electrical conductivity for this material model are written in terms of a unique solid matrix conductivity treated as a volumetric property above a critical salt concentration the conductive contribution of the shells is independent of the electrolyte salinity under this condition the equation for the bulk conductivity of the sandstone can be expressed in a simplified form however below the critical concentration the matrix conductivity is dependent on the conductivity of the water saturating the shaly component and can be expressed only by the complete equation the hydraulic conductivity for this model is expressed by a modified kozeny carman equation a new semi empirical equation relates the hydraulic conductivity for such rocks to their porosity formation resistivity factor and the electrical conductivity of its solid matrix these combined properties are described as the lithoporosity factor in this new formulation the petrophysical parameters involved are easily determined from the electrical geophysical measurements the performance of this equation is firmly tested with experimental laboratory data available in the literature its application is then extended to estimate the hydraulic parameters of a shaly sandstone aquifer in bahia brazil using either the borehole or the surface geoelectrical data examples are given to emphasize the combined use of electrical resistivity and induced polarization measurements in computing hydraulic properties

high precision sulfur isotope composition of enstatite meteorites and implications of the formation and evolution of their parent bodies abstract in order to better understand the formation and evolution of their parent bodies the three isotope ratios of sulfur were analyzed in 33 enstatite meteorites 24 enstatite chondrites and 9 aubrites the results show that on average all enstatite chondrite groups are enriched in the lightest isotopes compared to other chondrite groups with means of 34 s of 0 28 0 22 for eh3 4 0 16 0 16 for eh5 0 32 0 15 for el3 0 67 0 16 for el6 and 0 64 0 00 for el7 all 1 aubrites show a larger isotope variability in their composition with a 34 s varying from 1 350 to 0 154 contrary to previously published results our data show a distinct composition for el6 compared to other enstatite chondrites this could be related to an impact induced loss of isotopically heavy oldhamite 34 s by 3 62 3 02 1 on the el parent body although the bulk sulfur in both enstatite meteorites and aubrites does not show any significant 33 s and 36 s the oldhamite fraction shows clear evidence of mass independent fractionation on the 36 s 32 s ratio in 3 out of 9 analyzes 36 s up to 2 2 a signal that is not correlated to any 33 s 32 s anomaly in 1 out of 9 analyzes 33 s down to 0 085 though a nebular or photochemical origin cannot be ruled out the most plausible mechanism to produce such isolated non mass dependent 36 s 32 s anomalies would be a contribution of fecl 2 containing excesses of 36 s due to the decay of 36 cl to the leached oldhamite fraction even though the sulfur isotopic composition measured in enstatite meteorites is distinct from the bulk silicate earth bse the isotopically lightest samples of el6 el7 and aubrites are approaching the isotopic composition of the bse and enstatite meteorites remain the meteorites with the sulfur isotopic composition the closest to the terrestrial one

connecting complex conductivity spectra to mercury porosimetry of sedimentary rocks abstractthe measured spectral induced polarization sip response of highly porous granular materials can be modeled by upscaling the nernst planck equation for a single grain and performing a convolution product with the particle size distribution the distribution of relaxation times associated with the polarization of consolidated porous media seems intuitively to be controlled by the pore size distribution because of the radius of curvature of the interface between the solid and the pore water we have explored a mechanistic model connecting the sip response of consolidated media to mercury injection capillary porosimetry micp data first we developed a mechanistic electric double layer edl polarization model for porous media which considered the polarization of the stern layer which was possibly enhanced by the polarization of the diffuse layer and the effect of the pore size distribution the new model revealed that the relaxation time of porous media such as sandstones could be overestimat

estimating permeability of sandstone samples by nuclear magnetic resonance and spectral induced polarization two techniques to estimate permeability are compared in this paper nuclear magnetic resonance nmr and spectral induced polarization sip both methods are based on relaxation processes nmr records the relaxation of hydrogen nuclei after excitation in an external magnetic field the phenomenon of induced polarization can be characterized by a relaxation of ions after excitation by an electric field hydrogen nuclei are concentrated in the pore water the current flow is restricted to the pore space for most reservoir rocks and permeability is related to the pore space geometry based on the similarity between fluid movement and current flow in the pore space different relations have been published linking parameters derived from nmrand sip data to predict permeability nmr sip and permeability data have been acquired on 53 sandstone samples of the cretaceous bahariya formation western desert egypt including 27 samples showing a lamination that causes anisotropy we compare the applicability of k

mapping oil contaminated sand and till with the spectral induced polarization sip method the laboratory and field results from an environmental application of the spectral induced polarization sip method are presented the phase spectra of the resistivity of uncontaminated glacial till silt sand and gravel were measured in the laboratory the effects of waste oil and motor oil on the phase and amplitude spectra of the resistivity were studied using artificially contaminated sand and till samples and mineral soil samples from real waste sites field ip and sip measurements were also made at the waste sites the laboratory phase spectra of sands and tills were straight or slightly concave upwards in a log log plot the phase angle varies between 0 1 and 20 mrad at 1 hz frequency and increases towards higher frequencies with a slope of 0 15 0 25 in laboratory tests motor oil and waste oil changed the phase and amplitude spectra of sand and till at first the amplitude and phase decreased due to oil contamination later during continued maturation both the amplitude and phase increased after a few days or weeks of maturation some of the contaminated samples showed a convexupwards phase spectrum the features observed in artificially contaminated samples were also detected in the sample material from real waste sites furthermore the in situ results from the waste sites were in agreement with the laboratory results in laboratory tests the phase spectra of clean sand and till remained stable with time whereas the phase spectra of oil contaminated samples changed with increasing maturation time this together with the field results suggests that differences between the spectra of clean and polluted soils and also changes occurring in the phase spectra of contaminated soils with time can be indicative of contamination

investigation of non explosive expansion material in roof caving field application abstract effective roof caving plays a significant role in mining safety a spatiotemporal coupling fracturing method using a non explosive expansion material neem is proposed in this paper this method depends on the high fracturing capacity of the neem and a change from vertical charging to inclined charging aimed at producing new free surfaces step by step until the integrity of the entire rock is destroyed from a space time perspective the expansion stress and water adsorption of the neem were studied to determine the optimum stress increase interval and soak time with respect to the space aspect the charging sequence of boreholes was negatively correlated to their incline angles bringing the neem s superiority into full play based on the generation of new free surfaces in steps with respect to the time aspect the charging intervals of the inclined boreholes were designed to obtain the best stress compensation and highest fracturing efficiency a field trial was carried out in pingdingshan no 2 mine the results of which showed that some radial cracks were produced around the charging boreholes and that they propagated to the pilot boreholes moreover four main cracks were formed and were approximately parallel to the direction of the borehole rows in a fracturing group a fracture network was eventually generated which verified the expansion capacity of the neem and the feasibility of the spatiotemporal coupling fracturing method for field application

origin and history of impact melt rocks of enstatite chondrite parentage we have conducted petrologic chemical and isotopic studies of two impact produced rocks of enstatite chondrite parentage ilafegh 009 is a total impact melt rock with no residual lithic clasts formation on the el chondrite parent body is suggested by its mineralogy and mineral compositions cooling of the impact melt was rapid at melt temperatures and decreased at subsolidus temperatures in contrast to previous studies we show that happy canyon is not a new enstatite achondrite but an impactmelt breccia of enstatite chondrite and not aubrite parentage this rock formed by impact melting and incorporation into the melt of clastic material which resulted in relatively rapid cooling at all temperatures mineralogical and bulk compositional data probably biased by the heterogeneous nature of this rock do not allow unequivocal determination of its parent body i e el vs eh although some data such as bulk total fe content seem to favor el parentage both rocks were subjected to post solidification shock which was more severe for ilafegh 009 than for happy canyon it appears that both impact melt rocks could have formed by impact melting 4 57 ga ago as is indicated by the nearly identical ixe closure ages of 1 6 and 1 4 ma before bjurbole for ilafegh 009 and happy canyon respectively an apparently younger 39ar40ar age of 4 53 ga for happy canyon may be due to small biases in the intercalibration of the ixe and 39ar40ar chronometers whereas the much younger 4 34 4 44 ga age for ilafegh 009 reflects thermal resetting during shock metamorphism shallowater which was impact derived from a different enstatite achondrite parent body has an ixe closure age 0 4 ma younger than that for ilafegh 009 and an 39ar40ar age of 4 53 ga the ancient ages of these three rocks attest to the intense early bombardment in this region of the solar system

the complex exposure histories of the pitts and horse creek iron meteorites implications for meteorite delivery models the concentrations of cosmogenic radionuclides and noble gases in pitts iab and horse creek ungrouped provide unambiguous evidence that both irons have a complex exposure history with a first stage irradiation of 100 600 myr under high shielding followed by a second stage exposure of 1 myr as small objects the first stage exposure ages of 100 myr for horse creek and 600 myr for pitts are similar to cosmic ray exposure ages of other iron meteorites and most likely represent the yarkovsky orbital drift times of irons from their parent bodies in the main asteroid belt to one of the nearby chaotic resonance zones the short second stage exposure ages indicate that collisional debris from recent impact events on their precursor objects was quickly delivered to earth the short delivery times suggests that the recent collision events occurred while the precursor objects of horse creek and pitts were either very close to the chaotic resonance zones or already in earthcrossing orbits since the cosmogenic noble gas records of horse creek and pitts indicate a minimum radius of a few meters for the precursor objects but do not exclude km sized objects we conclude that these irons may represent fragments of two near earth asteroids 3103 eger and 1986 da respectively finally we used the cosmogenic nuclide concentrations in horse creek which contains 2 5 wt si to test current model calculations for the production of cosmogenic 10be 26al and neonisotopes from iron nickel and silicon

induced polarization of shaly sands equations have been developed that relate induced polarization ip in shaly sands to measurable petrophysical parameters the induced polarization process has been modeled in terms of two mechanisms clay counterion displacement and membrane blockage the resulting equations can be used to determine shaliness brine conductivity and oil saturation from in phase and out of phase conductivities laboratory measurements have confirmed the ip dependence on these variables as well as on temperature

electrical burst signature of pore scale displacements 1 electric field bursts were passively observed when a nonwetting fluid displaced a wetting fluid in a porous material drainage as well as during imbibition experiments a sandbox experiment was conducted to study these electrical disturbances using a network of very sensitive nonpolarizing electrodes located at the top surface of the tank drainage exhibited many more electrical bursts with a higher magnitude than imbibition these events were only observed during drainage or imbibition not prior to or after the water flowed inside the porous sandbox we point out the possible relationship between the formation of haines jumps and the occurrence of these electrical bursts these bursts show a power law distribution during drainage with a power law exponent of about 1 7 in agreement with a previous published study using acoustic and hydroacoustic events imbibition does not display such a power law relationship

determination of actual limit angles to the surface and their comparison with the empirical values in the upper silesian basin czech republic abstract this study deals with the determination of the actual limit angles in the long term formed subsidence basin in the czech part of the upper silesian basin the remaining part lays in poland here there was the most extensive underground exploitation of black coal in the north east of the czech republic a limit angle is absolutely decisive in the determination of deep mining influences in relation to the current and future utilisation of this territory the two csm and paskov mine localities on the edge of the subsidence basin were selected for this study since they could not have been affected by mining in neighbouring mines on the grounds of the long term levelling monitoring of points on the surface which started prior to mining the horizontal distance between the mined out area and the undisturbed ground surface was identified the impact of limit angle on the surface was calculated by means of the horizontal distance and the established mining depth such identified actual limit angles reached the values of 36 at the csm mine and 25 for the paskov mine the calculated values are significantly lower when compared with the currently applied empirical values of 57 for the csm mine and 56 for the paskov mine this means that the extent of the undermining effects is unambiguously wider by 611 m at the csm mine and by 883 m at the paskov mine this study thus establishes the existence of a significantly vaster area influenced by coal deep mining than previously expected the identified facts lead to the conclusion that regular revisions and follow up updates of the empirically determined parameters are recommended

partial melting of the indarch eh4 meteorite a textural chemical and phase relations view of melting and melt migration to test whether aubrites can be formed by melting of enstatite chondrites and to understand igneous processes at very low o fugacities we have conducted partial melting experiments on the indarch eh4 chondrite at 1000 1500 c silicate melting begins at 1000 c and indarch is completely melted by 1500 c the metal sulfide component melts completely at 1000 c substantial melt migration occurs at 1300 1400 c and metal migrates out of the silicate charge at 1450 c and 50 silicate partial melting as a group our experiments contain three immiscible metallic melts si p and c rich two immiscible sulfide melts fe and femgmnca rich and silicate melt our partial melting experiments on the indarch eh4 enstatite chondrite suggest that igneous processes at low fo2 exhibit several unique features the complete melting of sulfides at 1000 c suggests that aubritic sulfides are not relics aubritic oldhamite may have crystallized from ca and s complexed in the silicate melt significant metal sulfide melt migration might occur at relatively low degrees of silicate partial melting substantial elemental exchange occurred between different melts e g s between sulfide and silicate si between silicate and metal a feature not observed during experiments at higher fo2 this exchange may help explain the formation of aubrites from known enstatite chondrites

electrical properties of partially saturated sandstones novel computational approach with hydrogeophysical applications 1 electric and electromagnetic geophysical tools are suitable methods for investigating moisture content transport and storage properties of the subsoil with noninvasive surveys interpretation of field data is still based on empirical or semiempirical equations which must be calibrated with complex time consuming laboratory measurements in this paper we develop pore scale models suitable for computing the effective electric conductivity and the effective permittivity of partially saturated porous media on the basis of simple structural parameters grain size distribution and porosity we compute the electrical conductivity with three approaches that model the conductivity of the shell of coating clay around solid grains of shaly sandstones using different assumptions we compare the simulated results with experimental data from sherwood sandstone uk and discuss the effect of these assumptions on the effective conductivity simulations performed using a modeling approach that accounts for interaction between volume and surface conduction show an excellent agreement with experimental data we also model the effective permittivity of the same porous medium at several saturation values and obtain a good match with laboratory measurements

itqiy a metal rich enstatite meteorite with achondritic texture itqiy is a unique coarse grained metal rich enstatite meteorite that was found in the western sahara and consists of two rocks together weighing 4 72 kg which are both completely coated with fusion crust we report results from our electron microprobe and instrumental neutron activation analysis techniques itqiy consists of subhedral equigranular millimeter sized enstatite 25 vol of millimeter sized kamacite and a few tiny intergrowths of sulfides and kamacite relic chondrules are absent pyroxene fs0 2 is chemically similar to enstatite in el chondrites but the metal is closer in composition to that in eh chondrites sulfides resemble those in e chondrites but their compositions are distinct from those in both el and eh chondrites itqiy clearly formed under very reducing conditions but it does not appear to have formed from eh or el chondrites two thermal events can be distinguished silicate compositions including rare earth element abundances indicate loss of partial melt and slow cooling heterogeneous sulfides indicate a subsequent reheating and quenching event which may have been due to shock as many enstatite grains show shock stage s3 features

determining pore throat size in permo triassic sandstones from low frequency electrical spectroscopy 1 hydraulic conductivity or permeability a knowledge of which is vital in modelling the movement of hydrocarbons in reservoir rocks and contaminants in aquifers is strongly related to the intergranular pore throat size in sandstones for many years attempts have been made to determine permeability from the electrical properties of rocks but with little success here we have measured the complex electrical conductivity of permo triassic sandstone samples over the frequency range 0 0001 1000 hz and show how parameters determined from the characteristic shape of the spectra correlate closely to pore throat size determined from mercury injection measurements

acoustic measurements of pore scale displacements 1 we describe how experimentally measurable acoustic and hydroacoustic events occur when one fluid displaces another within a porous medium we show that the events are directly related to discrete fluid bursts haines jumps that occur at the pore scale we find that the events show power law statistics with respect to magnitude for drainage air invading but not for imbibition water invading these observations agree with simple conceptual arguments on how the displacements take place the results show that acoustic and hydroacoustic measurements can be an excellent technique for observing haines jumps in situ

pb isotopes in the impact melt breccia 66095 association with the imbrium basin and the isotopic composition of lithologies at the apollo 16 landing site recent in situ secondary ion mass spectrometry sims pb isotope analyses of lunar basalts have provided precise crystallisation ages and initial pb isotopic compositions for these samples in this

que 94204 a primitive enstatite achondrite produced by the partial melting of an e chondrite like protolith abstract queen alexandra range que 94204 an enstatite achondrite is a coarse grained highly recrystallized chondrule free and unbrecciated rock dominated about 70 vol by anhedral equigranular crystals of orthoenstatite of nearly endmember composition fs0 1 0 4 wo0 3 0 4 with interstitial plagioclase kamacite and troilite abundance of approximately 120 triple junctions and the close association of metal sulfide and plagioclase rich melts indicate that que 94204 has undergone limited partial melting with inefficient melt extraction mineral chemistry indicates a high degree of thermal metamorphism kamacite in que 94204 contains between 2 09 and 2 55 wt si similar to highly metamorphosed el chondrites plagioclase has between 4 31 and 6 66 wt cao higher than other e chondrites but closer in composition to plagioclase from metamorphosed el chondrites que 94204 troilite contains up to 2 55 wt ti consistent with extensive thermal metamorphism of an e chondrite like precursor results presented in this study indicate that que 94204 is the result of low degree about 5 20 vol probably toward the lower end of this range partial melting of an e chondrite protolith textural and chemical evidence suggests that during the metamorphism of que 94204 melts formed first at the fe ni fes cotectic near approximately 900 c followed by plagioclase pyroxene silicate partial melts near approximately 1100 c neither the fe ni fes nor the plagioclase pyroxene melts were efficiently segregated or extracted que 94204 belongs to a grouplet of similar primitive enstatite achondrites that are analogous to the acapulcoites lodranites but that have resulted from the partial melting of an e chondrite like protolith

investigation of movement and damage of integral overburden during shallow coal seam mining abstract most prediction methods used to calculate mining induced subsidence are empirical which cannot explain the mechanism of fundamental rock strata movement in this paper based on key stratum theory and the mechanical analysis of overburden a new analytical solution the analogous hyperbola subsidence model ahsm was proposed to describe the movement and damage of inner burden mining induced rock strata movement was verified using the distinct element method udec to assess the performance of the theoretical model three subsidence parameters smax t sgoaf smax d h generally used to describe surface subsidence trough agree with statistical field measurements of the south coalfield in australia the surface subsidence and the movement boundary in the overburden are very close to the theoretical predictions additionally the primary key stratum damages the least in the overlying strata its broken length is the smallest the width of subsidence trough and maximum surface subsidence increase as the primary key stratum drops

an experimental and theoretical study of rare earth element partitioning between sulfides fes cas and silicate and applications to enstatite achondrites abstract partition coefficients of the rare earth elements ree between sulfides fes or cas and silicate melt were determined experimentally at 1200 1300 c the ree sulfide silicate partition coefficients d are 1 under the experimental o and s fugacities which demonstrates that the ree are mainly located in the silicate phase rare earth element partition coefficients in the fes silicate system decrease from light to heavy ree while the opposite behavior is found for the cas silicate system where partition coefficients increase from light to heavy ree in both sulfide systems eu is preferentially incorporated into the sulfide phases as also expected from thermodynamic calculations the eu sulfide silicate partition coefficient is about a factor of ten higher than that of neighboring sm and gd in accordance with thermodynamic predictions of ree sulfide silicate partition coefficients the low sulfide silicate partition coefficients indicate that cas oldhamite in enstatite achondrites aubrites cannot have gained its high ree concentrations during igneous differentiation processes the high ree concentrations and the ree patterns in aubritic oldhamite are more plausibly explained by ree condensation into refractory cas the refractory nature of cas prevented major exchange reactions of the oldhamite with other aubritic minerals during the short differentiation and metamorphism period on the aubrite parent body thus oldhamite in aubrites may be relict condensates altered to different degrees during short heating events as originally suggested by lodders and palme 1990

evaluation of transport and storage properties in the soil and groundwater zone from induced polarization measurements1 spectral induced polarization as well as complex electrical measurements are used to estimate on a non invasive basis hydraulic permeability in aquifers basic laboratory measurements on a variety of shaly sands silts and clays showed that the main feature of their conductivity spectra in the frequency range from 10 3 to 103 hertz is a nearly constant phase angle thus a constant phase angle model of electrical conductivity is applied to interpret quantitatively surface and borehole spectral induced polarization measurements the model allows for the calculation of two independent electrical parameters from only one frequency scan and a simple separation of electrical volume and interface effects the proposed interpretation algorithm yields the true formation factor the cation exchange capacity and the surface area to porosity ratio which corresponds to the inverse hydraulic radius using a kozeny carman like equation the estimation of hydraulic permeability is possible

resistivity of partially saturated triassic sandstone the variation in resistivity with saturation of poorly cemented triassic sandstone samples from a site in the english midlands has been measured the measurements were obtained using an adapted four electrode technique which utilizes conductive gelling agents between electrodes avoiding the need to sputter electrodes directly on to samples a difficult process with such friable samples the measurements provide important information regarding the way in which resistivity varies with saturation in the triassic sandstone the resulting variation in the observed resistivity versus saturation curves indicates the presence of significant pore scale variation between samples measurements have also been conducted on fully saturated samples these indicate significant variation in the matrix conductivity between samples the results have important implications for field scale monitoring of the unsaturated zone

electrical hydraulic relationships observed for unconsolidated sediments in the presence of a cobble framework mechanistic models now exist to predict hydraulic conductivity k from the spectral induced polarization sip response of granular media we examined the predictions of such a model on unconsolidated coarse fluvial sediments and compared them to those obtained with a modified kozeny carman kc model samples were retrieved from the boise hydrogeophysical research site bhrs located on a gravel bar adjacent to the boise river idaho a sample holder 0 102 m diameter and 0 12 m in length was designed to include the cobble framework in reconstituted samples representing the primary stratigraphic units defined based on porosity variation at this site sip 0 001 1000 hz and k from darcy tests measurements were recorded for twelve samples with sip measurements made as a function of pore fluid conductivity 3 300 ms m grain grain size distribution gsd and total porosity k prediction with the kc model was improved after discounting of the cobble framework and multiplying by the tortuosity resulting from matrix capillaries around the cobbles resulting in estimates within 0 5 orders of magnitude of the measurements k prediction with a mechanistic sip model based on stern layer polarization slp model that requires an estimate of the gsd alsoalso required discounting for the cobble framework to obtain estimates within 0 5 orders of magnitude of the measurements similarly the slp model over predicts the measured imaginary conductivity unless the cobble framework is discounted which then results in estimates of within 0 1 orders of magnitude of the measurements this can be explained by the fact that the cobbles polarize at frequencies well below the minimum measurement frequency 0 001 hz the slp model for k prediction parameterized in terms of the formation factor and imaginary conductivity performed well for the ten samples with a cobble framework without modification as the imaginary conductivity directly senses the matrix grain size characteristics whereas the formation factor captures the porosity reduction and tortuosity resulting from the presence of the cobble framework capillary tortuosity our findings suggest that the estimation of contrasts in hydraulic conductivityk in coarse sediments may be achievable through measurements of electrical properties after appropriate consideration of the cobble fraction

oxide bearing and feo rich clasts in aubrites we report the occurrence of an oxide bearing clast and an feo rich clast from aubrites the feo rich clast in pesyanoe is dominated by olivine and pyroxene phenocrysts with mineral compositions slightly less feo rich than is typical for h chondrites in allan hills alh 84008 the oxide bearing clast consists of a single forsterite grain rimmed by an array of sulfides oxides and phosphides we consider a number of possible origins we can exclude formation by melting of oxide bearing chondrules and cais formed in enstatite chondrites the pesyanoe clast may have formed in a more oxidized region of the aubrite parent body or more likely is a foreign clast from a more oxidized parent body the alh 84008 clast likely formed by reaction between sulfides and silicates as a result of cooling oxidation or de sulfidization this clast appears to be the first oxide bearing clast from an aubritic breccia that formed on the aubrite parent body identification of additional oxide bearing clasts in aubrites could shed light on whether this was a widespread phenomenon and the origin of these enigmatic objects

surface stepped subsidence related to top coal caving longwall mining of extremely thick coal seam under shallow cover the surface stepped subsidence had badly affected the public infrastructure safety the formation mechanism of the surface stepped subsidence case was explained the surface subsidence profile after the sequent mining activity was predicted the possible controls of the stepped subsidence were lastly proposed

dielectric spectroscopy of sedimentary rocks a physiochemical model for the complex dielectric response of sedimentary rocks is used to invert broadband dielectric spectra for effective grain size distributions the complex dielectric response of each grain within the water wet granular matrix is obtained by superimposing the polarization of the electrochemical double layer which is assumed to surround each grain with the complex dielectric response of the dry mineral grain the effective complex dielectric response of the water wet matrix grains and surface phase is obtained by volume averaging over the entire distribution of particle sizes the complex dielectric response of the total mixture water wet matrix and bulk pore solution is obtained using the bruggeman hanai sen effective medium theory studies of berea sandstone show that the grain size distribution obtained by inverting the real part of the complex dielectric spectra is similar to the grain size distribution obtained from optical images of the sample in thin section the current model however does not account for surface roughness effects or the polarization of counterions over multiple grain lengths therefore the grain size distribution obtained by dielectric spectroscopy is broader than the image derived distribution the dielectric derived grain size distribution can be fit with two separate power laws that crossover at r 1 m which corresponds to a relaxation frequency of 2 khz the low frequency dielectric response f 2 khz is primarily controlled by the clay size grains and surface roughness which has a fractal dimension of d 2 48 0 07 at very low frequencies f 0 1 hz the dielectric response appears to be controlled by the electrochemical polarization of counterions over multiple grain lengths a more general model should account for the effects of surface roughness and grain interactions on the dielectric response it would also be useful to develop a simplified version of this model perhaps similar in form to the empirically derived cole cole response which could be more easily used to model and interpret electrical geophysical field surveys e g induced polarization ground penetrating radar and time domain reflectometery measurements

magnetometric resistivity a new approach and its application to the detection of preferential flow paths in mine waste rock dumps the injection of a low frequency electrical current in the ground between two electrodes a and b generates a magnetic field that can be measured at the ground surface with sensitive magnetic sensors the map of the magnetic field measured at the frequency of the injected current can be used to determine the paths of the current through the ground when the current is channelled along preferential conductive paths the magnetometric resistivity mmr method can be used to detect these paths conductive current paths can be associated with preferential flow paths of groundwater when the two electrodes a and b are in the direction of the flow and when the flow path is highly electrically conductive with respect to the background we first review the background equations for the magnetic field in mmr then we provide the kernel of the problem using biot and savart law to connect the components of the observed magnetic field to the current density distribution we also develop a simple approach to invert the magnetic field in terms of electrical current paths to illustrate how the method works we develop five synthetic models to test the sensitivity of the method to the properties of the conductive targets channelling the electrical current the targets are characterized by different shapes sizes depths and conductivity contrasts with the background then we proceed with a case study for which the mmr method is used to identify and map preferential groundwater flow paths bypassing a mine waste rock dump drainage collection trench into the tailings pond in this case the conductivity of the flow paths is much stronger than the background conductivity due to the high mineralization of the ground water along these paths the method underlines the 3 d architecture of these flow paths

ground movements over longwall workings in the kamptee coalfield india abstract subsidence investigations were conducted over three superimposed longwall panels in the kamptee coalfield of central india the extracted contiguous seams were lying below a water bearing unconfined aquifer filling of voids with sand hydraulically was practised to avoid a sudden inrush of water into the under ground workings through ground movement induced cracks the non effective width of extraction varied between 0 55 and 0 61 times the thickness of intact rockmass in the overburden the maximum subsidence slope compressive and tensile strains were 9 of extraction thickness 6 1 6 6 and 5 3 mm m 1 respectively the angle of draw was influenced by the presence of a fault and composition of superincumbent strata the ground movements lowered water table by 6 5 m in the unconfined aquifer due to the mining

induced polarization tomography applied to the detection and the monitoring of leaks in embankments abstract during an induced polarization survey both electrical conductivity and chargeability can be imaged recent petrophysical models have been developed to provide a consistent picture of these two parameters in terms of water and clay contents of soils we test the ability of this method at a test site in which a controlled artificial leakage can be generated in an embankment surrounding an experimental basin 3d tomography of the conductivity and normalized chargeability are performed during such a controlled leakage conductivity and induced polarization measurements were also performed on a core sample from the site the sample was also characterized in terms of porosity and cation exchange capacity combining the 3d survey and these laboratory measurements a 3d tomogram of the relative variation in water content before leakage and during leakage was estimated it clearly exhibits the ground water flow path through the embankment from the outlet of the tube used to generate the leak to the bottom of the embankment in addition a self potential survey was performed over the zone of leakage this survey evidences also the projection of the ground water flow path over the ground surface both methods are found to provide a consistent picture a 2 5d time lapse tomography of the electrical conductivity and normalized chargeability was also performed and evidences the position of the preferential flow paths below the profile these results confirm the ability and efficiency of induced polarization to provide reliable information pertaining to the detection of leakages in dams and embankments

characteristics and mechanism of sanyuan ground fissures in the weihe basin china abstract shuanghuaishu ground fissures in sanyuan county ones of over 200 ground fissures developed in the weihe basin are well known for their sudden occurrence which often cause severe damage to the infrastructures after heavy rainfall in order to reveal the origin of their formation the geological background developmental characteristics and genetic mode of the shuanghuaishu ground fissures were investigated in details by surveying mapping trenching geological drilling geophysical prospecting and field water immersion the fissures are almost parallel with a ne50 ne65 strike and the obvious linear length is 800 m these characteristics are well consistent with the secondary faults of the liquan pucheng heyang fault the fissures cause damage to buildings and farmlands in the form of a horizontal tensile crack and subsidence the deeper the stratum is the bigger fault displacement of the stratum it will be so these fissures possess the characteristics of synsedimentary faults regarding their genesis the fissures were generated under the coupling action of multiple factors the regional extension caused secondary faults of the liquan pucheng heyang fault to slip resulting in a fracture system in the surface strata during the period of heavy rainfall large volumes of water seeped into these hidden fissures causing a strong erosion and washout effect on the soil filled in the fissures this process promoted the formation of the current ground fissures

the iron isotope composition of enstatite meteorites implications for their origin and the metal sulfide fe isotopic fractionation factor abstract despite their unusual chemical composition it is often proposed that the enstatite chondrites represent a significant component of earth s building materials based on their terrestrial similarity for numerous isotope systems in order to investigate a possible genetic relationship between the fe isotope composition of enstatite chondrites and the earth we have analyzed 22 samples from different subgroups of the enstatite meteorites including eh and el chondrites aubrites main group and shallowater and the happy canyon impact melt we have also analyzed the fe isotopic compositions of separated magnetic and non magnetic phases from both enstatite chondrites and achondrites on average eh3 5 chondrites 56fe 0 003 0 042 2 standard deviation n 9 including previous literature data as well as el3 chondrites 56fe 0 030 0 038 2 sd n 2 have identical and homogeneous fe isotopic compositions indistinguishable from those of the carbonaceous chondrites and average terrestrial peridotite in contrast el6 chondrites display a larger range of isotopic compositions 0 180 enstatite achondrites aubrites also exhibit a relatively large range of fe isotope compositions all main group aubrites are enriched in the light fe isotopes 56fe 0 170 0 189 2 sd n 6 while shallowater is isotopically relatively heavy 56fe 0 045 0 101 2 sd n 4 number of chips we take this variation to suggest that the main group aubrite parent body formed a discreet heavy fe isotope enriched core whilst the shallowater meteorite is most likely from a different parent body where core and silicate material remixed this could be due to intensive impact induced shearing stress or the ultimate destruction of the shallowater parent body analysis of separated enstatite meteorite mineral phases show that the magnetic phase fe metal is systematically enriched in the heavier fe isotopes when compared to non magnetic phases fe hosted in troilite which agrees with previous experimental observations and theoretical calculations the difference between magnetic and non magnetic phases from enstatite achondrites provides an equilibrium metal sulfide fe isotopic fractionation factor of 56femetal troilite 56femetal 56fetroilite of 0 129 0 060 2 se at 1060 80 k which confirms the predictions of previous theoretical calculations

aubrites and diogenites trace element clues to their origin we have analyzed by rnaa 25 aubrite and 9 diogenite samples for 13 to 29 siderophile volatile and lithophile trace elements both meteorite classes show a typically igneous siderophile element pattern with ir os re ge more depleted than au ni pd sb but aubrites tend to have about 10 higher abundances 10 3 10 4 cl for the first 4 and 10 2 10 3 cl for the last 4 siderophiles apparently reflecting smaller metal silicate distribution coefficients at lowerf o2 or less complete segregation of metal se is surprisingly abundant in aubrites up to 0 4 cl but te is less so sete 5 cl apparently due to its stronger siderophile character other volatiles ag zn in cd bi t1 show depletions intermediate between lunar dunite and the earth s mantle of 7 aubrites analyzed for ree ce nd eu tb yb lu 6 are depleted in ree 0 08 0 5 cl and 5 show negative eu anomalies the exceptions are bishopville and mt egerton silicate this supports an igneous origin as already noted by boynton and schmitt 1972 no samples of the complementary basaltic and feldspathic rocks have been found thus far but one of our samples of khor temiki dark is a candidate for the basalt it is 5 7 enriched in ree and only slightly less so in rb cs and u though shocked and enriched in siderophiles to 0 05 cl it apparently represents a new meteorite class three diogenites analyzed for ree show very diverse patterns from strongly depleted in light ree for tatahouine ce 0 01 cl to flat for garland 2 5 cl the data confirm the trends found by fukuokaet al 1977 as well as their interpretations factor analysis shows several parallel groupings for aubrites and diogenites siderophiles re ir os pd ge chalcophiles se te volatiles ag in tl and incompatibles u ree and cs or rb but there are some differences for elements such as ni sb cd bi au and zn most of which behave more sensibly in aubrites than in diogenites several element pairs that differ greatly in volatility cs u ge ir correlate closely in aubrites in approximately cl chondrite proportions these correlations and other lines of evidence suggest strongly that aubrites originated by igneous processes in their parent body not by direct nebular condensation the source material may have resembled el chondrites in oxidation state and depletion of refractories metal and volatiles

siderophile trace elements in metals and sulfides in enstatite achondrites record planetary differentiation in an enstatite chondritic parent body abstract siderophile element concentrations were measured by la icp ms in metals and sulfides from five aubrite meteorites siderophile element patterns in aubrites are either similar to those in metal from enstatite chondrites or can be derived by crystallization from metallic liquids derived by partial melting of e chondrites some metal grains in mt egerton cumberland falls and aubres show moderate to severe depletion in compatible highly siderophile elements re os ir ru which are consistent with solid metal liquid metal differentiation of enstatite chondrite like metal metals from chondrite inclusions in cumberland falls show more extremely fractionated patterns than those from the aubritic matrix potentially hinting at fractionation and partial melting processes affecting not only the aubrite parent body but the chondrite body from which the inclusions were derived as well models using experimental partition coefficients show that aubrite metal chemically corresponds to solid metal segregated during differentiation of primary metallic liquids of eh el composition that contained both substantial s and c contents this result is consistent with a genetic link between enstatite chondrites and aubrites but as to whether aubrites were derived from the same body ies as enstatite chondrites or have their origin in multiple and potentially separated bodies cannot be answered unequivocally with chemical or isotopic data alone

a composite fe ni fes and enstatite forsterite diopside glass vitrophyre clast in the larkman nunatak 04316 aubrite origin by pyroclastic volcanism we studied the mineralogy petrology and bulk trace element oxygen and noble gas isotopic compositions of a composite clast approximately 20 mm in diameter discovered in the larkman nunatak lar 04316 aubrite regolith breccia the clast consists of two lithologies one is a quench textured intergrowth of troilite with spottily zoned metallic fe ni which forms a dendritic or cellular structure the approximately 30 m spacings between the fe ni arms yield an estimated cooling rate of this lithology of approximately 25 30 c s 1 the other is a quench textured enstatite forsterite diopside glass vitrophyre lithology the composition of the clast suggests that it formed at an exceptionally high degree of partial melting perhaps approaching complete melting and that the melts from which the composite clast crystallized were quenched from a temperature of approximately 1380 1400 c at a rate of approximately 25 30 c s 1 the association of the two lithologies in a composite clast allows for the first time an estimation of the cooling rate of a silicate vitrophyre in an aubrite of approximately 25 30 c s 1 while we cannot completely rule out an impact origin of the clast we present what we consider is very strong evidence that this composite clast is one of the elusive pyroclasts produced during pyroclastic volcanism on the aubrite parent body wilson and keil 1991 we further suggest that this clast was not ejected into space but retained on the aubrite parent body by virtue of the relatively large size of the clast of approximately 20 mm our modeling taking into account the size of the clast suggests that the aubrite parent body must have been between approximately 40 and 100 km in diameter and that the melt from which the clast crystallized must have contained an estimated maximum range of allowed volatile mass fractions between approximately 500 and approximately 4500 ppm

the origin of aubrites evidence from lithophile trace element abundances and oxygen isotope compositions abstract we report the abundances of a selected set of lithophile trace elements including lanthanides actinides and high field strength elements and high precision oxygen isotope analyses of a comprehensive suite of aubrites two distinct groups of aubrites can be distinguished a the main group aubrites display flat or light ree depleted ree patterns with variable eu and y anomalies their pyroxenes are light ree depleted and show marked negative eu anomalies b the mount egerton enstatites and the silicate fraction from larned display distinctive light ree enrichments and high th sm ratios mount egerton pyroxenes have much less pronounced negative eu anomalies than pyroxenes from the main group aubrites leaching experiments were undertaken to investigate the contribution of sulfides to the whole rock budget of the main group aubrites sulfides contain in most cases at least 50 of the rees and of the actinides among the elements we have analyzed those displaying the strongest lithophile behaviors are rb ba sr and sc the homogeneity of the 17 o values obtained for main group aubrite falls 17 o 0 009 0 010 2 suggests that they originated from a single parent body whose differentiation involved an early phase of large scale melting that may have led to the development of a magma ocean this interpretation is at first glance in agreement with the limited variability of the shapes of the ree patterns of these aubrites however the trace element concentrations of their phases cannot be used to discuss this hypothesis because their igneous trace element signatures have been modified by subsolidus exchange finally despite similar o isotopic compositions the marked light ree enrichments displayed by mount egerton and larned suggest that they are unrelated to the main group aubrites and probably originated from a distinct parent body

nature of volatile depletion and genetic relationships in enstatite chondrites and aubrites inferred from zn isotopes enstatite meteorites include the undifferentiated enstatite chondrites and the differentiated enstatite achondrites aubrites they are the most reduced group of all meteorites the oxygen isotope compositions of both enstatite chondrites and aubrites plot along the terrestrial mass fractionation line which suggests some genetic links between these meteorites and the earth as well for this study we measured the zn isotopic composition of 25 samples from the following groups aubrites main group and shallowater el chondrites eh chondrites and happy canyon impact melt breccia we also analyzed the zn isotopic composition and elemental abundance in separated phases metal silicates and sulfides of the eh4 el3 and el6 chondrites the different groups of meteorites are isotopically distinct and give the following values parts per thousand aubrite main group 7 08 delta zn 66 0 37 eh3 chondrites 0 15 delta zn 66 0 31 eh4 chondrites 0 15 delta zn 66 0 27 eh5 chondrites delta zn 66 0 27 0 09 n 1 el3 chondrites 0 01 delta zn 66 0 63 the shallowater aubrite 1 48 delta zn 66 2 36 el6 chondrites 2 26 delta zn 66 7 35 and the impact melt enstatite chondrite happy canyon delta zn 66 0 37 the aubrite pena blanca spring delta zn 66 7 0 parts per thousand and the el6 north west forrest delta zn 66 7 35 are the isotopically lightest and heaviest samples respectively known so far in the solar system in comparison the range of zn isotopic composition of chondrites and terrestrial samples 1 5 delta zn 66 1 parts per thousand is much smaller luck et al 2005 herzog et al 2009 eh and el3 chondrites have the same zn isotopic composition as the earth which is another example of the isotopic similarity between earth and enstatite chondrites the zn isotopic composition and abundance strongly support that the origin of the volatile element depletion between el3 and el6 chondrites is due to volatilization probably during thermal metamorphism aubrites show strong elemental depletion in zn compared to both eh and el chondrites and they are enriched in light isotopes delta zn 66 down to 7 04 parts per thousand this is the opposite of what would be expected if zn elemental depletion was due to evaporation assuming the aubrites started with an enstatite chondrite like zn isotopic composition evaporation is therefore not responsible for volatile loss from aubrites on earth zn isotopes fractionate very little during igneous processes while differentiated meteorites show only minimal zn isotopic variability it is therefore very unlikely that igneous processes can account for the large isotopic fractionation of zn in aubrites condensation of an isotopically light vapor best explains zn depletion and isotopically light zn in these puzzling rocks mass balance suggests that this isotopically light vapor carries zn lost by the el6 parent body during thermal metamorphism and that aubritcs evolved from an el6 like parent body finally zn isotopes suggest that shallowater and aubrites originate from distinct parent bodies

variations of petrophysical properties and spectral induced polarization in response to drainage and imbibition a study on a correlated random tube network we implement a procedure to simulate the drainage and imbibition in random 2 d square networks we compute the resistivity index the relative permeability and the characteristic lengths of a correlated network at various saturation states under the assumption that the surface conductivity can be neglected these parameters exhibit a hysteretic behaviour then we calculate the spectral induced polarization sip response of the medium under the assumption that the electrical impedance of each tube follows a local warburg conductivity model with identical dc conductivity and chargeability for all the tubes we evidence that the shape of the sip spectra depends on the saturation state the analysis of the evolution of the macroscopic cole cole parameters of the spectra in function of the saturation also behaves hysteretically except for the cole cole exponent we also observe a power law relationship between the macroscopic dc conductivity and time constant and the relative permeability we also show that the frequency peak of the phase spectra is directly related to the characteristic length and to the relative permeability underlining the potential interest of sip measurements for the estimation of the permeability of unsaturated media

relationship between spectral induced polarization and hydraulic properties of saturated and unsaturated sandstone there is growing interest in the use of geophysical methods for hydrological model parameterization empirical induced polarization ip hydraulic conductivity k relationships have been developed but these are only applicable to sediments in which the ip response shows limited variation with electrical current frequency here we examine the spectral ip response of samples taken from a uk sandstone aquifer and compare measured parameters with physical and hydraulic properties we demonstrate the limited value of existing ip k models due to the inherent ip frequency dependence of these samples our results show how the mean relaxation time is a more appropriate measure of ip response for these sediments a significant inverse correlation between the surface area to pore volume ratio and is observed suggesting that is a measure of a characteristic hydraulic length scale this is supported by a measured strong positive correlation between log and log k our measurements also reveal evidence of a relationship between and a dominant pore throat size which leads to postulations about the parallelism between the spectral ip behavior and unsaturated hydraulic characteristics additional experiments show how the relaxation time is affected by degree of fluid saturation indicating that saturation levels must be accounted for if our empirical relationships are applied to vadose zone studies our results show clear evidence of the potential value of frequency based ip measurements for parameterization of groundwater flow models

seasonal variation of moisture content in unsaturated sandstone inferred from borehole radar and resistivity profiles understanding the processes controlling recharge to aquifers is critical if accurate predictions are to be made on the fate of contaminants in the subsurface environment in order to understand fully the hydrochemical mechanisms in the vadose zone it is essential that the dynamics of the hydrology can be suitably characterised the correlation between moisture content and both bulk dielectric and resistivity properties of porous media is well established using suitably placed sensors in boreholes detailed depth profiles of dielectric and resistivity behaviour have been monitored over a period of two years at a triassic sherwood sandstone aquifer field site at hatfield england the borehole borehole transmission radar and borehole resistivity profiles show a significant correlation through appropriate petrophysical relationships derived from core samples seasonal dynamics of the vadose zone are seen to illustrate the migration of wetting and drying fronts over the monitoring period at a second field site in eggborough located 17 km from hatfield similar temporal changes in moisture content in the sandstone were observed using borehole radar profiles travel times of seasonal wetting fronts through the sandstone at both sites appear to be approximately 2 m per month the retardation of this front propagation in the top 3 m is also common to both sites suggesting that pollutant transport may be principally controlled by near surface sediments the results have important consequences to existing groundwater modelling programmes that are being utilised to predict transfer of agricultural chemicals through the vadose zone

influence of overburden mass behavioural properties on subsidence limit characteristics abstract an analytical calculation model for the angle of draw is introduced in this paper on the supposition that the roof is considered as an elastic beam this model indicates the importance of the main factors which control the extent of subsidence produced on the surface and also provides some appreciation of the influence of overburden strength on the angle of draw a finite element model has been developed for application to subsidence related rock mechanics problems by the use of this model the authors have investigated the effects rock mass behavioural properties on the limit angle and also the effects of a distinct bed strong or weak in the overburden on the subsidence affected area at the surface relevant u k data from monitored sites for determining the three limit angles variation with the dip of seam are discussed the trend of the limit angle from the north of england to the midland coalfields is also discussed in the paper it has been found that the results from the data are in good agreement with numerical model results

an approach to the identification of fine sediments by induced polarization laboratory measurements time domain induced polarization ip laboratory measurements were performed on about 200 fine sediment samples with varying water content the results permitted an analysis of ip properties of clays loams silts and sands particular emphasis has been given to the analysis of the chargeability m as a function of lithotype and the water content by analyzing decay curves a new parameter was identified it is a statistically specific characteristic of the lithotype and is independent of the water content therefore it provides a diagnostic parameter for lithotype identification in association with the values of chargeability and electrical resistivity this parameter permits a reliable evaluation of water content and yields useful information about the porosity and permeability of the lithotype

intensive parameters of enstatite chondrite metamorphism abstract the enstatite oldhamite geothermometer eog developed by larimer and buseck 1974 makes use of the five phase assemblage kamacite quartz enstatite oldhamite troilite to determine metamorphic temperatures in enstatite chondrites a re evaluation of the thermodynamic foundation of the eog shows that several of the assumptions and approximations can be significantly improved with new thermodynamic data the geothermometer has been modified to reflect among other things the solution behavior of si in kamacite the solution behavior of a calcium silicate component in enstatite and metal sulfide fusion as a function of temperature and composition an analysis of the eog shows that the activity coefficient of si in kamacite and the ca rich component of enstatite are the model s most important parameters for si the activity coefficient data of sakao and elliot 1975 have been used the activity coefficient of a ca rich component of enstatite presents a unique problem since data on this parameter do not exist for one pyroxene systems and two pyroxene solution models do not provide unique activity coefficients in the absence of diopside the model therefore has been formulated using camgsi 2 o 6 as the ca rich component of enstatite and assumes that it behaves as a symmetric regular margules solution the margules interaction parameter w g is then used as an adjustable constant and is varied such that the resulting temperatures fall between minimum and maximum temperatures determined independently temperature minima were determined from the enstatite diopside solvus of carlson 1986 and indicate that the el6 chondrites have been metamorphosed to temperatures exceeding 900 1000 c the temperature of the enstatite plagioclase quartz eutectic 1090 c appropriate for el6 plagioclase compositions was used as the metamorphic maxima with these constraints a w g value of 52 kj mole was estimated as appropriate within the context of the model for el6 metamorphic conditions el6 temperatures determined via this method range from 981 c for yilmia to 1068 c for blithfield temperature estimates of greater than 1000 c for the highly equilibrated el6 chondrites require the formation of a metal sulfide liquid during metamorphism liquid fractionation of this predominantly fe fes liquid could explain the siderophile chalcophile and volatile element depletion in the el6 class relative to ci and eh chondrites liquid fractionation however is not required by the model and is consistent with a moderate cooling rate which is fast enough to lock in high cao contents in enstatite but slow enough to re equilibrate troilite and alabandite to low temperatures the oxygen fugacity determined in this study shows the enstatite chondrites to have equilibrated at extremely low f o 2 this as well as the activity of si that can be extracted from the eog indicates that the enstatite chondrites that contain sinoite si 2 n 2 o equilibrated under high nitrogen fugacities high f n 2 values imply that sinoite bearing e chondrites either formed in a nebula of high pressure f n 2 10 1 at 1050 c or more likely are products of planetary metamorphism

electrical properties of artificial clay bearing sandstone rocks which contain clay minerals often display electrical properties which cannot be predicted by bulk electrical properties of the constituents cohen 1981 interactions between clay minerals and groundwater can produce polarization phenomena decreases in resistivity and supposed nonlinear behavior

subsidence versus natural landslides when dealing with property damage liabilities in underground coal mines abstract this paper presents a case study in the town of boo asturias spain where land subsidence due to underground coal mining has been observed in the past along with landslides and natural ground settling the confluence of these phenomena represents a liability for mining companies any property damage caused by ground movements is considered by those affected to be a direct result of mining induced subsidence this has led to numerous property damage liability claims against mining companies even many years after the mining activities have stopped based on the analysis of geotechnical studies subsidence simulations developed with hundef and 3dec software and ground movement measurements together with research developed within the research fund for the coal and steel merida project the authors investigated the landslide and slope instability phenomena that are occurring in the town of boo moreover they determined the geographical and temporal limits to distinguish damages for which mining activity may be responsible from natural or human induced damages unrelated to mining this research will allow underground coal mining companies to manage property damage liability claims from a clearer perspective and may help researchers reconsider some studies that focused only on mining induced subsidence to explain ground movements within similar environments