trapped xenon in ordinary chondrites a trapped component of heavy noble gates representing a distinct solar system presumably asteroid belt reservoir is known to be concentrated in carbonaceous carriers of chondritic meteorites the isotopic signature of trapped xe in separates of the h4 chondrite forest vale fv was determined by combusting its carrier phases at 600 c in oxygen discriminating against in situ produced nucleogenic components which are released above 600 c the isotopic abundances of fv combustion xe fvc xe are compared to signatures of bulk trapped xe in chondritic meteorites we conclude that fvc xe represents the predominant trapped component in ordinary chondrites oc for which we adopt the term oc xe its isotopic signature differs from xe in ureilites in average carbonaceous chondrites in earth s atmosphere and in the solar wind additional minor xe components were identified in type 3 chondrites and in the metal phase of chondrites we discuss relationships among solar system xe reservoirs and show that oc xe signature is consistent with a mixture of hl xe with slightly mass fractionated solar type xe

unraveling the evolution of chondrite parent asteroids by precise u pb dating and thermal modeling u th pb isotopic data are reported for mineral fractions individual chondrules and fractions of chondrule fragments from the equilibrated ordinary chondrite richardton h5 chondrules and milligram sized fractions of pyroxene rich chondrule fragments contain highly radiogenic pb and concordant or nearly concordant u th pb isotopic systems and are suitable for precise pb pb age determinations olivine and sulfide have low u concentrations and contain less radiogenic pb the ages of individual chondrules pyroxene rich and phosphate fractions are determined using u pb and pb pb isochron and model date calculations the pb pb isochron date of 4562 7 1 7 ma of the richardton chondrules and chondrule fragments is resolved from the pb pb isochron date of 4550 7 2 6 ma obtained from multiple phosphate fractions possible biases of the isochron dates due to single stage approximation of multi stage evolution contamination with modern common pb and disturbance to the system by reheating are examined and are found to be insignificant the chondrule and phosphate dates are interpreted as the timing of cessation of pb diffusion during cooling following metamorphism in chondrite parent bodies the difference in estimated closure temperatures 950 1150 k for pyroxenes and 700 800 k for phosphates temperature estimates are based on published diffusion rates for pb in pyroxenes and apatite allows evaluation of the average cooling rate at 26 13 k million years for the richardton parent body over the period of 4563 4551 my thermal modeling of the h chondrite parent body which is assumed to be asteroid 6 hebe heated by decay of 26al suggests a scenario in which accretion initiated at 1 7 m y after formation of calcium aluminum rich inclusions and continued for 3 5 m y

the effect of terrain topography on commonly used resistivity arrays in this work a study of the effect of surface topographical variations on several dc resistivity arrays is presented a 2 5 d finite element modeling scheme is used to examine the performance of several arrays over buried features that exist below a range of different topographical terrain contexts such as valleys hills and steep slopes a mesh generating algorithm allows a realistic representation of terrain topography the results confirm that topographical variations can have a significant impact on the field resistivity data values for all resistivity arrays further topographical variations can be treated flexibly using a realistic resistivity forward modeling process thus topographic effects to the degree they can be modeled are predictable and should be taken into account when designing surveys and interpreting data

early solar system events and timescale some recent information on the mn cr and al mg systems is reviewed this information is used to derive constraints on the timing of processes and events which took place in the early solar system using reasonable assumptions a timeline is constructed where the estimated age of the solar system is 4571 ma this age is taken to mark the time when most calcium aluminum rich inclusions cais were starting to form a process that may have lasted for several 105 years almost contemporaneously small planetesimals have accreted that served to store these cais for later dispersal among larger planetesimals by the time large numbers of planetesimals of several tens of kilometers in size had formed the interior of these objects started to melt through the decay of 26al collisional disruption of these planetesimals allowed gases dust and melt to escape into the surrounding space the fine droplets of melt reacted with gas and dust to form chondrules which after rapid cooling were partially re accreted onto the residual rubble pile this process of primary chondrule formation in most cases involving several generations of planetesimals most plausibly lasted only for 2 ma towards the end of this period and during the following 3 to 4 ma planetary objects of several hundred kilometers in size were formed they still stored enough energy to continue melting from the inside to finally differentiate into chemically stratified layers with basaltic volcanism occurring within a few million years

the duration of ordinary chondrite metamorphism inferred from tungsten microdistribution in metal abstract precise ratios of w and re relative to ir determined by laser ablation icp ms reveal that matrix metal in equilibrated ordinary chondrites eoc exhibits a correlated variation of these ratios in unequilibrated ordinary chondrites uoc the w ir ratio varies by over two orders of magnitude w ir 0 003 0 6 and shows no correlation with any other siderophile element most matrix metal in uoc is depleted in w relative to metal in eoc thus w must enter metal during metamorphism the correlation between w ir and re ir is evident in type 4 chondrites this implies that the abundance and isotopic composition of w is set in ordinary chondrite metal by petrologic type 4 and that the reductant must be exhausted to limit further isotopic exchange as indicated by the 182 hf 182 w ages of ordinary chondrite metal lee and halliday science 274 1996 1876 1879 this offers a means of dating the onset of metamorphic heating of oc parent bodies a discrepancy in ages between 182 hf 182 w lee and halliday science 274 1996 1876 1879 and 207 pb 206 pb gopel et al earth planet sci lett 121 1994 153 171 or 129 i 129 xe brazzle et al geochim cosmochim acta 63 1999 739 760 dating is real and measures the interval of metamorphism the time difference between reduction of w during the onset of heating and isotopic closure of pb or xe by cooling e g t m 2 12 myr for h chondrites the 187 re 187 os and 182 hf 182 w ages are set by the same process metamorphic equilibration establishing an important link between an absolute chronometer t 1 2 187 re 41 6 billion years and a short lived radioisotope system t 1 2 182 hf 9 myr

reconstruction of landslide movements by inversion of 4 d electrical resistivity tomography monitoring data reliable tomographic inversion of geoelectrical monitoring data from unstable slopes relies critically on knowing the electrode positions which may move over time we develop and present an innovative inverse method to recover movements in both surface directions from geoelectrical measurements made on a grid of monitoring electrodes for the first time we demonstrate this method using field data from an active landslide to recover sequences of movement over timescales of days to years comparison with gps measurements demonstrated an accuracy of within 10 of the electrode spacing sufficient to correct the majority of artefacts that would occur in subsequent image reconstructions if incorrect positions are used over short timescales where the corresponding subsurface resistivity changes were smaller the constraints could be relaxed and an order of magnitude better accuracy was achievable this enabled the onset and acceleration of landslide activity to be detected with a temporal resolution of a few days

high mg adakitic rocks formed by lower crustal magma differentiation mineralogical and geochemical evidence from garnet bearing diorite porphyries in central tibet

extinct i129 in c3 chondrites abstract eight c3 chondrites were examined by the i129 xe129 dating method to see whether their i xe ages better initial i 129 i 127 ratios r0 correlate with any other properties the r0 s range from 1 60 10 4 to 1 09 10 4 corresponding to i xe ages from 2 0 myr before to 6 7 myr after murchison magnetite three c3o s lance felix ornans have essentially indistinguishable r0 s of 1 41 0 13 to 1 17 0 10 10 4 the fourth c3o warrenton is undatable owing to homogenization of radiogenic and trapped xe four c3v s show a distinct spread vigarano and grosnaja are highest r0 1 60 0 07 and 1 57 0 14 10 4 mokoia is intermediate and kaba is lowest r0 1 38 0 06 and 1 09 0 10 10 4 literature values for allende place it near kaba these r0 s correlate inversely with 4 other properties i br and cd content and olivine composition both percent mean deviation pmd and proportion of iron poor olivine grains 2 fayalite it is difficult to accept the 9 myr spread in r0 as a true age reflecting either nebular or parent body processes this time span is more than an order of magnitude longer than the lifetime of the solar nebula inferred from astronomical evidence nor does the degree of thermal metamorphism which is slight for c3 s anyway correlate with r0 a more plausible interpretation is that the variations in r0 reflect mainly isotopic heterogeneity of iodine the simplest model that accounts for the correlations with r0 involves mixing of two iodine components in the solar nebula associated with gas and grains respectively the second of lower i 129 i 127 ratio predominated at later times and thus became enriched in late formed meteorites along with other volatiles such as cd and br the low fe content and large pmd of olivine may reflect either less metamorphism owing to shallow location in the parent body or greater reduction of fe2 during chondrule formation

assessment of ground based monitoring techniques applied to landslide investigations a landslide complex in the whitby mudstone formation at hollin hill north yorkshire uk is periodically re activated in response to rainfall induced pore water pressure fluctuations this paper compares long term measurements i e 2009 2014 obtained from a combination of monitoring techniques that have been employed together for the first time on an active landslide the results highlight the relative performance of the different techniques and can provide guidance for researchers and practitioners for selecting and installing appropriate monitoring techniques to assess unstable slopes particular attention is given to the spatial and temporal resolutions offered by the different approaches that include real time kinematic gps rtk gps monitoring of a ground surface marker array conventional inclinometers shape acceleration arrays saa tilt meters active waveguides with acoustic emission ae monitoring and piezometers high spatial resolution information has allowed locating areas of stability and instability across a large slope this has enabled identification of areas where further monitoring efforts should be focused high temporal resolution information allowed the capture of s shaped slope displacement time behaviour i e phases of slope acceleration deceleration and stability in response to elevations in pore water pressures this study shows that a well balanced suite of monitoring techniques that provides high temporal and spatial resolutions on both measurement and slope scale is necessary to fully understand failure and movement mechanisms of slopes in the case of the hollin hill landslide it enabled detailed interpretation of the geomorphological processes governing landslide activity it highlights the benefit of regularly surveying a network of gps markers to determine areas for installation of movement monitoring techniques that offer higher resolution both temporally and spatially the small sensitivity of tilt meter measurements to translational movements limited the ability to record characteristic s shaped landslide movements at hollin hill which were identified using saa and ae measurements this high sensitivity to landslide movements indicates the applicability of saa and ae monitoring to be used in early warning systems through detecting and quantifying accelerations of slope movement

collisional modification of the acapulcoite lodranite parent body revealed by the iodine xenon system in lodranites the i xe system of three lodranites has been investigated samples of gibson yielded no isochrons and late model ages are attributed to late addition of iodine two metal and one silicate separate from the transitional lodranite graves nunataks gra 95209 gave ages that are consistent with each other and with the literature i xe age of acapulco feldspar these yield a mean closure age 4 19 0 53 ma after the shallowater enstatite reference age 4562 3 0 4 ma such identical i xe ages from distinct phases imply that the parent material underwent a period of rapid cooling the absolute age of this event being 4558 1 0 7 ma such rapid cooling indicates an increase in the rate at which heat could be conducted away requiring a significant modification of the parent body we suggest the parent body was modified by an impact at or close to the time recorded by the i xe system an age of 10 4 2 3 ma after shallowater has been determined for one whole rock sample of lewis cliff lew 88280 since the release pattern is similar to that of gra 95209 this hints that the larger grain size of this sample may reflect slower cooling due to deeper post impact burial

verification and interpretation of the i xe chronometer abstract comparisons of i xe and pb pb relative ages are made for phosphate and feldspar separates from 12 different meteorites in all cases where i xe ages can be measured in phosphate i xe and pb pb chronometers agree within experimental uncertainty no discordant phosphate samples are observed with the exception of allegan i xe ages for feldspar separates generally agree with pb pb ages for the corresponding phosphate the general concordancy observed between i xe and pb pb chronometers suggests that the i xe system is a reliable and interpretable chronometer when applied to single minerals systems allegan feldspar differs from the other feldspar separates predating its phosphate by 17 ma with an i xe age indistinguishable from those of orgueil and murchison magnetites among the oldest observed

shock metamorphism of ordinary chondrites a revised petrographic classification of progressive stages of shock metamorphism of ordinary chondrites is proposed six stages of shock s1 to s6 are defined based on shock effects in olivine and plagioclase as recognized by thin section microscopy the characteristic shock effects of each shock stage are s1 unshocked sharp optical extinction of olivine s2 very weakly shocked undulatory extinction of olivine s3 weakly shocked planar fractures in olivine s4 moderately shocked mosaicism in olivine s5 strongly shocked isotropization of plagioclase maskelynite and planar deformation features in olivine and s6 very strongly shocked recrystallization of olivine sometimes combined with phase transformations ringwoodite and or phases produced by dissociation reactions s6 effects are always restricted to regions adjacent to melted portions of a sample which is otherwise only strongly shocked in stages s3 to s6 localized melting results from stress and temperature peaks which locally deviate from the equilibration shock pressure due to differences in shock impedance these melting effects are a opaque melt veins shock veins b melt pockets with interconnecting melt veins c melt dikes and d troilite metal deposits in fractures based on a critical evaluation of data from shock recovery experiments a shock pressure calibration for the six shock stages is proposed which defines the s1 s2 s2 s3 s3 s4 s4 s5 and s5 s6 transitions at 5 5 10 15 20 30 35 and 45 55 gpa respectively whole rock melting and formation of impact melt rocks or melt breccias occurs at about 75 90 gpa the symbol for the shock stage may be used in combination with the symbol for the petrologic type to abbreviate the complete classification of a chondrite e g h5 s3 we propose this new shock classification and pressure calibration system to replace previous systems which are out of date with respect to the pressure calibration nominally restricted to l chondrites and based on incomplete and in part illdefined sets of shock effects we have classified seventy six ordinary chondrites using the new classification system and conclude the following 1 1 shock effects and the sequence of progressively increasing degrees of shock metamorphism are very similar in h l and ll groups differences in the frequency distribution of shock stages are relatively minor e g l chondrites appear to have the largest fraction with stages s5 and s6 this suggests that the collisional histories of the h l and ll parent bodies were similar 2 2 petrologic type 3 chondrites are deficient in stages s4 to s6 and with increasing petrologic type the frequency of stages s4 to s6 increases we suggest that the more porous and volatile rich type 3 chondrites are subject to melting at a lower shock pressure than the nonporous chondrites of higher petrologic type volatiles trapped in pores cause shock induced dispersal of the shocked and melted material into small particles which are not expected to survive as meteorites 3 3 stage s3 is the most abundant in nearly all petrologic types 4 4 at shock pressures in excess of about 35 gpa s5 and s6 4he and 40ar are almost completely lost pressures below 10 gpa s1 and s2 do not cause noble gas losses

impacts of permafrost degradation on a road embankment at umiujaq in nunavik quebec canada differential subsidence of as much as 0 85 m is affecting the access road to umiujaq airport in nunavik quebec canada located in the discontinuous permafrost zone a geotechnical and geophysical investigation including piezocone test ground penetrating radar profiling electrical resistivity tomography and numerical modeling of the thermal regime of the road embankment and subgrade is presented to characterize the ground stratigraphy and permafrost conditions and to assess the exact causes and effects of permafrost degradation on the road embankment the subsidence is due to thaw consolidation taking place in a layer of ice rich silt underneath a superficial sand layer while the seasonal freeze thaw cycles were initially restricted to the sand layer the thawing front has now reached the thaw unstable ice rich silt layer according to our numerical modeling the increase in air temperature recently observed in nunavik cannot be the sole cause of the observed subsidence affecting this engineering st

geophysical monitoring of moisture induced landslides a review author s whiteley js chambers je uhlemann s wilkinson pb kendall jm abstract 2018 the authors geophysical monitoring of landslides can provide insights into spatial and temporal variations of subsurface properties associated with slope failure recent improvements in equipment data analysis and field operations have led to a significant increase in the use of such techniques in monitoring geophysical methods complement intrusive approaches which sample only a very small proportion of the subsurface and walk over or remotely sensed data which principally provide information only at the ground surface in particular recent studies show that advances in geophysical instrumentation data processing modeling and interpretation in the context of landslide monitoring are significantly improving the characterization of hillslope hydrology and soil and rock hydrology and strength and their dynamics over time this review appraises the state of the art of geophysical monitoring as applied to moisture induced landslides here we focus on technical and practical uses of time lapse methods in geophysics applied to monitoring moisture induced landslide the case studies identified in this review show that several geophysical techniques are currently used in the monitoring of subsurface landslide processes these geophysical contributions to monitoring and predicting the evolution of landslide processes are currently underrealized hence the further integration of multiple parametric and geotechnically coupled geophysical monitoring systems has considerable potential the complementary nature of certain methods to map the distribution of subsurface moisture and elastic moduli will greatly increase the predictive and monitoring capacity of early warning systems in moisture induced landslide settings

thermal and impact history of the h chondrite parent asteroid during metamorphism constraints from metallic fe ni abstract we have studied cloudy taenite metallographic cooling rates and shock effects in 30 h3 6 chondrites to elucidate the thermal and early impact history of the h chondrite parent body we focused on h chondrites with old ar ar ages 4 4 gyr and unshocked and mildly shocked h chondrites as strongly shocked chondrites with such old ages are very rare cooling rates for most h chondrites at 500 c are 10 50 c myr and do not decrease systematically with increasing petrologic type as predicted by the onion shell model in which types 3 5 are arranged in concentric layers around a type 6 core some type 4 chondrites cooled slower than some type 6 chondrites and type 3 chondrites did not cool faster than other types contrary to the onion shell model cloudy taenite particle sizes which range from 40 to 120 nm are inversely correlated with metallographic cooling rates and show that the latter were not compromised by shock heating the three h4 chondrites that were used to develop the onion shell model ste marguerite beaver creek and forest vale cooled through 500 c at 5000 c myr our thermal modeling shows that these rates are 50 higher than could be achieved in a body that was heated by 26al and cooled without disturbance by impact published ar ar ages do not decrease systematically with increasing petrologic type but do correlate inversely with cloudy taenite particle size suggesting that impact mixing decreased during metamorphism metal and silicate compositions in regolith breccias show that impacts mixed material after metamorphism without causing significant heating impacts during metamorphism created portales valley and two other h6 chondrites with large metallic veins excavated the fast cooled h4 chondrites around 3 4 myr after accretion and mixed petrologic types metallographic data do not require catastrophic disruption by impact during cooling

oxygen isotope and petrological study of silicate inclusions in iie iron meteorites and their relationship with h chondrites abstract the origin of silicate bearing irons especially those in groups iab iiicd and iie is poorly understood as silicate should have separated rapidly from molten metal here we report the results of high precision oxygen isotope analysis of silicate inclusions in eleven group iie meteorites and a petrological study of silicate inclusions in ten iie irons including those in garhi yasin and tarahumara which have not been described in detail before oxygen isotopes have also been analysed in 20 h chondrites to investigate their possible relationship with the iie irons based on petrographic observations and mineral analysis the silicate bearing iie meteorites have been divided into four types according to the nature of their silicate inclusions 1 primitive chondritic 2 evolved chondritic 3 differentiated with 10 vol orthopyroxene and 4 differentiated with 17 o variation a wide range of values is seen in the dataset as a whole group iie irons with differentiated silicates with the exception of colomera have a range of mean 17 o values that is essentially identical to those of the h4 6 chondrites 0 60 0 77 and 0 61 0 76 respectively colomera inclusions which are differentiated with 17 o value and plot 2 away from the next nearest iie iron however in view of the textural similarities to other iie inclusions a separate source for colomera is deemed unlikely three iie irons with primitive chondritic inclusions garhi yasin netschaevo and techado have relatively low mean 17 o values of 0 56 0 57 as well as relatively reduced silicates with fa 15 17 olivine which have been called hh chondrites given the significant overlap in their oxygen isotope compositions a genetic relationship between iie irons and h chondrites is supported by our new data however derivation of both groups from one parent body seems unlikely instead both groups probably sampled similar precursor materials and accreted at a similar nebular location our data suggest that the iie meteorites formed on an internally heated h hh chondrite like body that experienced the initial stages of differentiation in response to radiogenic heating however prior to full differentiation the iie parent body experienced a major hit and run style collision that resulted in silicate metal mixing the initial stages of this event involved a phase of rapid cooling that prevented unmixing of metal and silicates reassembly of the iie parent body produced a large regolith blanket that facilitated subsequent slow cooling the iie parent body has probably experienced numerous subsequent less catastrophic collisions the development of alkali glass textures in some differentiated inclusions is probably the result of one of these later events

pb pb dating of individual chondrules from the cb a chondrite gujba assessment of the impact plume formation model the cb chondrites are metal rich meteorites with characteristics that sharply distinguish them from other chondrite groups their unusual chemical and petrologic features and a young formation age of bulk chondrules dated from the cba chondrite gujba are interpreted to reflect a single stage impact origin here we report high precision internal isochrons for four individual chondrules of the gujba chondrite to probe the formation history of cb chondrites and evaluate the concordancy of relevant short lived radionuclide chronometers all four chondrules define a brief formation interval with a weighted mean age of 4562 49 0 21 myr consistent with its origin from the vapor melt impact plume generated by colliding planetesimals formation in a debris disk mostly devoid of nebular gas and dust sets an upper limit for the solar protoplanetary disk lifetime at 4 8 0 3 myr finally given the well behaved pb pb systematics of all four chondrules a precise formation age and the concordancy of the mn cr hf w and i xe short lived radionuclide relative chronometers we propose that gujba may serve as a suitable time anchor for these systems

modeling the evolution of the parent body of acapulcoites and lodranites a case study for partially differentiated asteroids abstract the acapulcoites and lodranites are rare groups of primitive achondrites that originate from a common parent body and are of particular interest since they experienced only partial melting we calculated thermal evolution and differentiation models of the parent body of the acapulco lodran meteorite clan the models were compared to the maximum metamorphic temperatures differentiation degree and thermo chronological data available an optimized set of parameters which fits to the data was determined a radius of 260 km a formation time of 1 7 ma after cais and an initial temperature of 250 k the burial depths derived are 7 13 km the respective layers experienced minor melting and small scale melt migration matching the differentiation degree of the meteorites the resulting structure has an iron core a silicate mantle a partially differentiated layer and an undifferentiated outer shell our results indicate a larger size an earlier formation time and a formation closer to the sun of the parent body of acapulcoites and lodranites than typical estimates for ordinary chondritic parent bodies consistent with a stronger thermal metamorphism the burial depths support excavation by a single impact the presence of core and mantle indicates that these meteorites could share a common parent body with differentiated stony and iron meteorites

subsurface resistivity changes and triggering influences detected by continuous geoelectric monitoring during a project to analyze the internal structure of landslides and identify and isolate their trig gering factors repeated geoelectric measurements in intervals of 1 2 years showed significant resistivity changes inside landslide prone areas niesner and weidinger 2008 changing water saturation was recognized as the most influential factor on these time lapse resistivity profiles therefore repeated resistivity measurements should be able to observe the internal regime and dynamics of subsurface water and in turn as changing water saturation is in most cases directly correlated with slope stability a major factor influencing slope stability could be deduced from repeated resistivity measurements

application of geophysical measurements for assessing the role of fissures in water infiltration within a clay landslide trieves area french alps rainfall and its consequences are usually considered as the major factor triggering slope instabilities within clay deposits the link between rainfall water infiltration and landslide activity may be complex and comprehensive sets of data are still necessary to understand how water infiltrates in cohesive material on unstable slopes made of fine grained sediments gravitational deformation generates superficial shear ruptures and tension fissures whose continuous opening could be amplified by shrinkage during dry periods this fissure network at the surface can be very dense and strongly controls the water infiltration process however it remains difficult to assess the fissure evolution at depth and its eventual relationship with shallow slip surfaces this work presents the results of a geophysical study which aimed to characterize the fissures that are observed along the unstable clay slopes of the trieves area french alps the site was first investigated combining geomorphological analysis drilling borehole logging geotechnical tests and geophysical experiments this investigation evidenced the presence of at least three rupture surfaces at 5 10 15 and 42 m with a water flow at the second one in a second step permanent instruments were installed piezometers and soil water content probes results indicate high water infiltration velocities down to the water table located at 2 5 m depth that are likely to be linked with sub vertical preferential paths such as fissures geophysical parameters electrical resistivity s wave velocities and rayleigh waves attenuation were monitored geophysical results suggest that fissures are permanently open that they serve as preferential infiltration paths and that they can reach at least a depth of 2 m the methods employed in this research put forward that the system of imbricated fissures drains water from the surface down to the shallow slip surfaces at 5 and 10 15 m this work highlights the role of fissures network in water infiltration in the numerous clay landslides of the trieves area copyright 2011 john wiley sons ltd

characterizing landslides through geophysical data fusion example of the la valette landslide france many studies show that certain geophysical methods such as seismic and electrical resistivity imaging appear to be well adapted for investigating the internal structures of landslides and understanding the related hydro mechanical mechanisms these are methods that allow the direct and non intrusive measurement of acoustic p and shear s wave velocities and electrical resistivity which are three physical parameters considered as essential for estimating the mechanical properties of moving reworked material we applied these techniques to the la valette landslide southern french alps a typical example of an intra material landslide carrying out measurements simultaneously along two profiles 400 m and 300 m long and respectively perpendicular to and along the slide direction we then used suitable inversion algorithms to estimate both the p and s wave velocity fields and the electrical resistivity field from the recorded data the results aided by field surface observations show that a correlation exists between the state of the material and the seismic velocity and or electrical resistivity data thus confirming that the simultaneous use of the two methods provides complementary information on the geomechanical behavior of the landslide more particularly the seismic data provide information on fissure density variations and the presence of shear bent material whereas the electrical resistivity data provide information on the groundwater content to enable a more integrated petrophysical interpretation we applied a data fusion strategy based on fuzzy subsets to the geophysical datasets through combining the tomograms we identified a surface layer of soft material along the two profiles the bottom of this layer was also recognized in a borehole from a methodological point of view the results show the applicability of adopting geomechanical hypotheses as inputs of geophysical data fusion for identifying areas where sediment mobilization could occur

in situ determination of iodine content and iodine xenon systematics in silicates and troilite phases in chondrules from the ll3 chondrite semarkona iodine concentrations in small domains 10 m of silicates and troilite fes phases in three chondrules from the semarkona ll3 meteorite were determined by an ion microprobe independent determination of i content in some of these phases was accomplished by in situ laser probe mass spectrometric analysis of i derived 128 xe in one of these neutron irradiated chondrules the ion microprobe data suggest low i content for olivines 20 45 ppb and relatively higher values for pyroxene and glass mesostasis 40 160 ppb the broad similarity in the measured i contents in pyroxenes in a porphyritic pyroxene chondrule by ion microprobe 42 138 ppb and by laser probe 37 76 ppb demonstrate the feasibility of in situ determination of i content in silicate phases via ion microprobe the i contents in troilite measured by ion microprobe however are prone to uncertainty because of the lack of a sulfide standard the ion microprobe data suggest i content of 1 ppm in troilite if the calibration from our silicate standard is used however the noble gas data suggest that the i content in troilite is comparable to that in silicates we attribute this apparent discrepancy to an enhanced sputter ion yield of i from sulfides iodine derived 129 xe excesses were observed in both pyroxene and troilite within this chondrule the i xe model ages of these selected phases are consistent with the i xe studies of the bulk chondrule the individual data points fall on or near the isochron obtained from the bulk chondrule although all except the most radiogenic data point contain evidence of low temperature uncorrelated iodine

the i xe chronometer and the early solar system we review the development of the i xe technique and how its data are interpreted and specify the best current practices individual mineral phases or components can yield interpretable trends in initial 129i 127i ratio whereas whole rock i xe ages are often hard to interpret because of the diversity of host phases many of which are secondary varying standardizations in early work require caution only samples calibrated against shallowater enstatite or bjurble can contribute reliably to the emerging i xe chronology of the early solar system although sparse data for which i xe and mn cr can be compared suggest that the two systems are concordant among ordinary chondrite samples we derive a new age for the closure of the shallowater enstatite standard of 4563 3 0 4 myr from the relationship between the i xe and pb pb systems this yields absolute i xe ages and allows data from this and other systems to be tested by attempting to construct a common chronology of events in the early solar system absolute i xe dates for aqueous and igneous processes are consistent with other systems consideration of the i xe host phases in cais and dark inclusions demonstrates that here the chronometer records aqueous alteration of pre existing material the ranges of chondrule ages deduced from the al mg and i xe systems in semarkona ll3 0 and chainpur ll3 4 are consistent chainpur i xe data exhibit a greater range of ages than semarkona possibly reflecting a greater degree of parent body processing however individual chondrules show little or no evidence of such processing determining the host phase s responsible for high temperature correlations may resolve the issue

resistivity imaging survey to delineate subsurface seepage of hydrocarbon contaminated water at karbala governorate iraq this research is an attempt to accomplish a 3 d resistivity imaging survey which was carried out near a water well contaminated with hydrocarbon materials in karbala governorate two dimensional resistivity imaging measurements were collected along four parallel profiles using a wenner array with electrode spacing of 1 m the res3dinv program was used to invert the apparent resistivity data the results displayed a resistivity distribution of the subsurface in a three dimensional volume thus both the horizontal and vertical extents of the contaminated zone were displayed this technique revealed a low resistivity zone at depth ranges from 3 to 6 m in the investigation area but the seepage starts at depth ranges between 2 and 3 m and continues down depth may be to the groundwater level this low resistivity zone is the most likely location for a subsurface seepage of contaminated water it is clear that the sufficient measurement points along 2 d lines in a small area can increase the 3 d imaging resolution and nearly real 3 d imaging can be achieved when the size of subsurface anomaly compared with the electrode spacing a of the wenner array is taken into consideration

upb systematics of phosphates from equilibrated ordinary chondrites u pb systematics were determined from fifteen phosphate separates from equilibrated ordinary chondrites and from small bulk fragments of the same meteorites the high 238u204pb ratios of thirteen of these phosphate separates lead to extremely radiogenic pb whose 206pb204pb ratios range from 250 up to 3500 the pb pb model ages for these phosphates range from 4 563 to 4 502 ga with an analytical precision of 106 y and the u pb system is apparently concordant the time interval observed 60 106 y reflects the thermal processing of the equilibrated chondrites and is consistent with that previously derived from the rb sr k ar and pu chronologies the pb pb ages of the phosphates from the seven h chondrites show a negative correlation versus their metamorphic grade this is the first clear relationship ever observed between a long lived chronometer and the intensity of metamorphism as reflected by metamorphic grade assuming that the pb pb age indicates the accurate u pb closure time in phosphates the pb pb chronology is compatible with the model of a layered h chondrite parent body however this interpretation of the u pb systematics is not unique it postulates a slow cooling of the equilibrated materials at high temperature in apparent conflict with petrological observations except for the h chondrites which agree rather well with pu systematics comparison of the pb pb chronology with published radiochronometric data does not reveal simple correlations in the present debate concerning the thermal history of chondrites the chronometric information derived from each isotope system is interpreted as the time of its thermal closure however this basic assumption may not be correct for all the radiochronologies and must be evaluated before the radiochronometric data can be applied as compelling time constraints for the period of 4 56 4 4 ga of proto planetary history

i xe ages of enstatite chondrites abstract in order to elucidate the early thermal history of enstatite chondrite parent bodies we determined 129i 129xe whole rock ages of enstatite chondrites 5 eh 2 el one eh impact melt relative to the shallowater reference meteorite 4562 3 0 4 ma all errors are 1 i xe ages of both el6 chondrites lon 94100 4 38 0 60 ma and neuschwanstein 3 87 0 73 ma negative sign indicates ages younger than shallowater agree well with data of other el6 chondrites lon 94100 displayed a second isochron at lower temperatures equivalent to a younger age of 5 25 1 17 ma perhaps reflecting different retention temperatures of respective carrier phases during sequential cooling the enstatite chondrites abee eh4 indarch eh4 eet 96135 eh4 5 and st marks eh5 encompass a i xe age range of 0 57 1 05 ma eet 96135 1 to 0 45 0 72 ma abee again in agreement with previously reported ages of eh chondrites only the age of st marks differs strongly from previously reported younger ages now being more in accordance with other members of the eh clan the eh3 chondrite sahara 97096 showed the youngest i xe age of 7 87 0 46 ma distinctly younger than other i xe ages of eh chondrites including other eh3s due to the apparent high retention temperature of the i xe system in enstatite estimated 800 c this young age implies a later resetting of the i xe system by a severe thermal likely impact induced event the eh impact melt lap 02225 records a similarly young thermal event though no isochron relationship could be established the data fall within an apparent i xe age range of 5 to 15 ma similar to sahara 97096 overall eh chondrite parent body experienced a thermal history determined by a complex interplay between impact disturbances and parent body metamorphism

129i 127i variations among enstatite chondrites abstract this paper presents the 129i 127i composition for 11 different enstatite chondrites there is a well defined hiatus in iodine isotopic compositions separating the enstatite chondrites the hiatus correlates with a similar hiatus defined by variations in chemical composition both major and minor elements eh 4 5 chondrites have 129i 127i ratios 20 higher 4 m y older than el 6 chondrites the enstatite chondrites are the third meteorite group joining silicates in iab irons and c3v carbonaceous chondrites in which 129i 127i correlates with chemical composition within each enstatite chondrite group the variations in initial iodine isotopic composition is less than 4 comparable to the experimental resolution the 20 difference between eh and el may indicate a maximum iodine isotopic heterogeneity between the eh and el nebular reservoirs alternatively if eh and el chondrites evolved from a homogeneous iodine isotopic reservoir then the el group must have evolved 4 0 m y longer than the eh group and either in an environment with a much lower i xe ratio than presently observed or one which was open to the loss of radiogenic 129xe the latter case may imply a nebular environment and would therefore be consistent with the open system evolution required to produce the chemical hiatus the duration of subsequent evolution in the high i xe environment must have been 1 m y and probably represents thermal metamorphism in two different parent bodies

testing an integrated chronology i xe analysis of enstatite meteorites and a eucrite we have determined initial 129i 127i ratios for mineral concentrates of four enstatite meteorites and a eucrite in the case of the enstatite meteorites the inferred ages are associated with the pyroxene rich separates giving pyroxene closure ages relative to the shallowater standard of indarch eh4 0 04 0 67 ma khairpur el6 4 22 0 67 ma khor temiki aubrite 0 06 ma and itqiy enstatite achondrite 2 6 2 6 ma negative ages indicate closure after shallowater no separate from the cumulate eucrite asuka a 881394 yielded a consistent ratio though excess 129xe was observed in a feldspar separate suggesting disturbance by thermal metamorphism within 25 ma of closure in shallowater iodine 129 ages are mapped to the absolute pb pb time scale using the calibration proposed by gilmour et al 2006 who place the closure age of shallowater at 4563 3 0 4 ma comparison of the combined 129i pb data with associated 53mn ages for objects that have been dated by both systems indicates that all three chronometers evolved concordantly in the early solar system the enstatite chondrites are offset from the linear array described by asteroid belt objects when 53mn ages are plotted against combined 129i pb data supporting the suggestion that 53mn was radially heterogeneous in the early solar system

four dimensional imaging of moisture dynamics during landslide reactivation landslides pose significant risks to communities and infrastructure and mitigating these risks relies on understanding landslide causes and triggering processes it has been shown that geophysical surveys can significantly contribute to the characterization of unstable slopes however hydrological processes can be temporally and spatially heterogeneous requiring their related properties to be monitored over time geoelectrical monitoring can provide temporal and volumetric distributions of electrical resistivity which are directly related to moisture content to date studies demonstrating this capability have been restricted to 2d sections which are insufficient to capture the full degree of spatial heterogeneity this study is the first to employ 4d i e 3d time lapse resistivity imaging on an active landslide providing long term data three years highlighting the evolution of moisture content prior to landslide reactivation and showing its decline post reactivation crucially the time lapse inversion methodology employed here incorporates movements of the electrodes on the unstable surface although seasonal characteristics dominate the shallow moisture dynamics during the first two years with surficial drying in summer and wetting in winter in the months preceding reactivation moisture content increased by more than 45 throughout the slope this is in agreement with independent data showing a significant rise in piezometric heads and shallow soil moisture contents as a result of prolonged and intense rainfall based on these results remediation measures could be designed and early warning systems implemented thus resistivity monitoring that can allow for moving electrodes provides a new means for the effective mitigation of landslide risk

landslides triggered factors analysed by time lapse electrical survey and multidimensional statistical approach abstract a temporal imagery of water circulation in a landslide by electrical resistivity tomography ert was conducted to identify spatially and temporally the coupling between rainfalls consecutive water inflows in a sliding mass and induced resistivity variations this work is based on a multi scale experimental approach applied on the vence landslide south eastern france which is characterised by a sandy clay sliding mass on a marly limestone substratum mostly controlled by high rainfall events at the landslide scale historical geological and geotechnical data combined with field investigations and the interpretation of three ert allowed the definition of a geometrical model of the landslide and the calibration of the resistivity values on the basis of these results a permanent time lapse ert survey was designed on a specific part of the landslide coupled with water level acquisition piezometric levels and rain fall events results covering a three month period are showed the statistical analyses of all the physical parameters measured during the three months of investigation show that the matrix of correlations highlighted strong correlations between the rainfall piezometric elevation and the resistivity these first results show an accurate answer resistivity piezometric elevation that can be associated as a precursor of the reactivation of the landslide

old formation ages of igneous clasts on the l chondrite parent body reflect an early generation of planetesimals or chondrule formation abstract the barwell meteorite contains large abundant clasts that are igneous in nature we report iodine xenon ages of five clasts and one sample of host chondrite material the fragment of host chondrite material yielded the oldest age determined 4567 8 1 2 ma two clasts produced old well defined ages of 4564 96 0 33 ma and 4565 60 0 33 ma these and a third clast having a less precise old age of 4566 0 3 2 ma are interpreted as recording the timing of crystallisation of the samples they were incorporated into the barwell parent body before it underwent thermal metamorphism but the i xe ages survived secondary processing on the parent body and were not reset by metamorphism metasomatism or shock two further clasts record younger ages of 4560 96 0 45 ma and 4554 22 0 38 ma these samples contain a high abundance of albitic mesostasis and the most likely explanation of the ages is that they record the timing of metasomatism on the parent body we also analysed four host chondrite samples that do not give i xe ages in these samples the system appears to have been disturbed by shock it has been suggested previously that the igneous clasts are derived from an early generation of partially melted asteroids we do not have direct evidence that the clasts we examined were necessarily derived from a partially differentiated body only that they were derived from cooling of a silicate melt the clasts could thus be the products of any one of several proposed models for chondrule formation our results indicate that processes akin to chondrule formation in that they involve rapid cooling of a silicate melt were ongoing at the same time as cai formation lending support to the suggestion that al mg chondrule ages indicate either heterogeneous distribution of 26 al or resetting of the al mg system after chondrule formation

extreme sensitivity of crosshole electrical resistivity tomography measurements to geometric errors summary the effects of geometric errors on crosshole resistivity data are investigated using analytical methods geometric errors are systematic and can occur due to uncertainties in the individual electrode positions the vertical spacing between electrodes in the same borehole or the vertical offset between electrodes in opposite boreholes an estimate of the sensitivity to geometric error is calculated for each of two generic types of four electrode crosshole configuration current flow and potential difference crosshole xh and in hole ih it is found that xh configurations are not particularly sensitive to geometric error unless the boreholes are closely spaced on the scale of the vertical separation of the current and potential electrodes however extremely sensitive ih configurations are shown to exist for any borehole separation therefore it is recommended that xh configurations be used in preference to ih schemes the effects of geometric error are demonstrated using real xh data from a closely spaced line of boreholes designed to monitor bioremediation of chlorinated solvents at an industrial site a small fraction of the data had physically unrealistic apparent resistivities which were either negative or unexpectedly large however by filtering out configurations with high sensitivities to geometric error all of the suspect data were removed this filtering also significantly improved the convergence between the predicted and the measured resistivities when the data were inverted in addition to systematic geometric errors the measured data also exhibit a high level of random noise despite this the resulting inverted images correspond reasonably closely with the known geology and nearby cone penetrometer resistivity profiles

salty old rocks small grains of halite in meteorites are generally interpreted as a sign of the former presence of water in his perspective ott 1 discusses the unexpected discovery of halites in relatively highly metamorphosed meteorites according to the age determined by whitby et al 2 for halite crystals in one of these meteorites they are among the oldest known materials in the solar system 1 http www sciencemag org cgi content full 288 5472 1761 2 http www sciencemag org cgi content short 288 5472 1819

three dimensional geophysical anatomy of an active landslide in lias group mudrocks cleveland basin uk a geoelectrical investigation of a slow moving earth slide earth flow in lower jurassic lias group rocks of the cleveland basin uk is described these mudrock slopes are particularly prone to failure and are a major source of lowland landslides in the uk but few attempts have been made to spatially or volumetrically characterise the subsurface form of these slides the primary aim of this study was to consider the efficacy of fully three dimensional geoelectrical imaging for landslide investigation with reference to a geological setting typical of lias group escarpments the approach described here included a reconnaissance survey phase using two dimensional electrical resistivity tomography ert resistivity mapping self potential sp profiling and mapping followed by a detailed investigation of an area of the landslide using three dimensional 3d ert and self potential tomography spt interpretation of the geophysical data sets was supported by surface observations aerial lidar and differential gps geomorphological surveys and intrusive investigations boreholes and auger holes the initial phase of the study revealed the existence of a strong sp signature at the site consistent with a streaming potential source and established the relationships between the main geological units the geomorphologic expression of the landslide and the resistivity of the materials in and around the study area the 3d spt model generated during the second phase of the study indicated drainage patterns across the landslide and preferential flow from the low permeability mud rocks into the underlying more permeable sandstone formation because of favourable resistivity contrasts between the clay rich whitby mudstone formation landslide material and the underlying staithes sandstone formation the volumetric 3d ert image allowed a number of surface and subsurface landslide features to be identified and spatially located these included the lateral extent of slipped material and zones of depletion and accumulation the surface of separation and the thickness of individual earth flow lobes and the dipping in situ geological boundary between the whitby mudstone and staithes sandstone bedrock formations