modelling of the evolution of ground waters in a granite system at low temperature the stripa ground waters sweden abstract from chemical data collected by nordstrom and his colleagues on stripa ground waterswe have tried to model the evolution of the chemical composition of a ground water in a granitic system at low temperature the existence of two end member ground water compositions made it possible first to test the conventional model of a geothermal system according to which an overall equilibrium between the waters and a given mineral assemblage can be defined and then to show that such a model could be extended to low temperatures 10 c conversely if we know the mineral assemblage the equilibration temperature and the charge of the mobile ions in this case cl the composition of the solution is entirely fixed in our model of the stripa ground waters the existence of two end member ground water compositions can be explained by an evolution from a kaolinite albite laumontite equilibrium to a prehnite albite laumontite equilibium the latter requiring less al than the former we have also emphasized the importance of the cl ion concentrions ofof the ground waters because they cab be considered as indicators of the degree of reaction progress between rock and water thus determining the degree of equilibration of the system

linking soil element mass transfer to microscale mineral weathering across a semiarid environmental gradient abstract understanding controls on silicate weathering is critical to characterizing critical zone evolution the objective of this study was to investigate how climate vegetation and landscape position control feldspar transformations across a semiarid environmental gradient granitic surface soil and saprock samples were collected from desert scrub and mixed conifer sites within the santa catalina mountain critical zone observatory where mean annual temperature ranges from 24 c to 10 c and mean annual precipitation from 25 to 85 cm quantitative x ray diffraction x ray fluorescence and electron microprobe analyses were employed to quantify elemental changes in bulk soils and across plagioclase grains the chemical depletion of na in bulk soils ranged from 5 4 15 in the desert scrub sites relative to 16 33 in the mixed conifer sites plagioclase grain alteration was classified into unaltered edge and altered sections to compare microscale weathering and elemental variation the na al and si al ratios decreased from unaltered to edge to altered grain sections in the mixed conifer sites whereas the element ratios of the desert scrub system were similar between unaltered and edge grain sections and only exhibited significant decreases in na al and si al ratios between edge and altered materials the microscale depletion of na and si suggested increased silicate weathering in the cooler wetter and more biologically productive mixed conifer system compared to the hot dry desert scrub system the results also demonstrated a topographic control on mineral transformation where increased plagioclase weathering occurred in convergent footslope landscapes with little change in elemental depletion of soils in divergent summit sites

block model of earthquake sequence abstract a model of interaction of lithospheric blocks is suggested dynamics of the lithosphere is described as an alternation of slow deformations and ruptures earthquakes the model is used to produce an artificial catalog of seismicity and the properties of this catalog are compared with and contrasted to the properties of real seismicity catalogs by this means it is possible to determine which properties of earthquake sequences can be derived from simple assumptions about the processes that occur in the lithosphere we consider both the instability of the process and possibility that large earthquakes might be predicted

u sr isotopic speedometer fluid flow and chemical weathering rates in aquifers abstract both chemical weathering rates and fluid flow are difficult to measure in natural systems however these parameters are critical for understanding the hydrochemical evolution of aquifers predicting the fate and transport of contaminants and for water resources water quality considerations 87 sr 86 sr and 234 u 238 u activity ratios are sensitive indicators of water rock interaction and thus provide a means of quantifying both flow and reactivity the 87 sr 86 sr values in ground waters are controlled by the ratio of the dissolution rate to the flow rate similarly the 234 u 238 u ratio of natural ground waters is a balance between the flow rate and the dissolution of solids and recoil loss of 234 u from the solids by coupling these two isotope systems it is possible to constrain both the long term ca 100 s to 1000 s of years flow rate and bulk dissolution rate along the flow path previous estimates of the ratio of the dissolution rate to the infiltration flux from sr isotopes 87 sr 86 sr are combined with a model for 234 u 238 u to constrain the infiltration flux and dissolution rate for a 70 m deep vadose zone core from hanford washington the coupled model for both 234 u 238 u ratios and the 87 sr 86 sr data suggests an infiltration flux of 5 2 mm yr and bulk silicate dissolution rates between 10 15 7 and 10 16 5 mol m 2 s the process of recoil enrichment while primarily responsible for the observed variation in 234 u 238 u of natural systems is difficult to quantify however the rate of this process in natural systems affects the interpretation of most u series data models for quantifying the recoil loss fraction based on geometric predictions surface area constraints and chemical methods are also presented the agreement between the chemical and theoretical methods such as direct measurement of 234 u 238 u of the small grain size fraction and geometric calculations for that size fraction is quite good

oxygen diffusion in quartz diffusional oxygen exchange between quartz and water was studied by determining 18o profiles in the quartz using an ion microprobe inverse error function plots of the data are linear as required for a diffusion mechanism one natural and two synthetic samples were used and although they had different impurity concentrations oh na and al per 106 si atoms are 7 4000 35 835 and 67 127 respectively the d values were the same within experimental uncertainty diffusion parallel to c is about 2 orders of magnitude faster than that normal to c at 700 c and diffusion normal to the rhombohedron is intermediate the data indicate a change in slope on an arrhenius plot at the boundary at 100 mpa 1 kbar water pressure the preexponential factors do in square centimeters per second and activation energies q in kilojoules per mole for quartz 500 550 c are as follows do 190 and q 284 parallel to c and do 8 10 2 and q 238 normal to the rhombohedron for quartz 600 800 c do 4 10 7 and q 142 parallel to c do 9 10 7 and q 155 normal to the rhombohedron and do 1 10 4 and q 234 normal to c d increases with ph 2 o and between 25 and 350 mpa log d versus log h 2 o has a slope of approximately 1 1 these d values are all several orders of magnitude larger than previously reported values for oxygen diffusion in water free systems

silicate weathering mechanisms determined using soil solutions held at high matric potential abstract we present evidence of surface controlled and proton promoted chemical weathering of primary silicates in a brown acidic soil vauxrenard rhone france we used aqueous silica si in soil solutions held at high matric potential 180 1600 kpa which are representative of solutions reacting with soil solids si concentration was well correlated with h concentration and to a lesser extent with dissolved organic carbon doc which showed a significant affect p 0 05 geochemical modelling showed that primary silicates dissolved under far from equilibrium conditions and that organic ligands modelled with a triprotic analogue may have a weak but significant effect on the variations in log si at the profile scale and at both 15 30 and 30 45 cm depths comparison of si al ratios to literature data and observed soil mineralogy demonstrated that significant linear relationships found in the activity diagram between log al3 3ph and log h4sio4 may not have been caused by the reversible formation of secondary al si phases in the soil instead the apparent trends may arise from relationships between log si and ph and the control of al mobility by the reversible formation of al hydroxides in the vermiculite interlayer all these results indicated that active in situ chemical weathering of silicates may be surface controlled and mostly proton promoted mineralogy suggested that k feldspar weathered much faster than albite and white mica in contrast to the weathering gradient inferred from the mass balance between unweathered and soil material this was certainly caused by differential changes in mineral reactive surfaces with time

constancy of silicate mineral weathering rate ratios between natural and experimental weathering implications for hydrologic control of differences in absolute rates abstract inverse models which apportion watershed effluxes geochemical mass balance over estimated mineral surface area give weathering rates for individual silicate minerals e g feldspar 1 3 orders of magnitude slower than laboratory rates comparisons of rates calculated from several recent watershed geochemical mass balance studies with experimentally determined rates reveal that the ratio of mineral weathering rates for a given silicate mineral pair determined in an internally consistent field study equals the ratio of rates for the same minerals in any internally consistent set of laboratory experimental data thus the coefficient which corrects the weathering rate for any mineral from a laboratory data set to a field setting is identical to the corresponding coefficient for any other mineral in the same data sets the correction factor linking experimental and natural rates must be independent of composition physical e g hydrologic controls rather than compositional or chemical controls cause the difference between weathering rates in nature and the laboratory because flow in natural weathering profiles is spatially heterogeneous not all of the potentially available surface in natural systems actually participates in reactions with pore fluids

possible creep related tilt precursors obtained in the central apennines italy and in the southern caucasus georgia daily averaged tilt component data from two sites of the central apennines italy and of the southern caucasus georgia respectively revealed intermediate term tilts as possible precursors to earthquakes m 3 0 4 7 which occurred in the above mentioned seismic areas within a distance of 50 km from the sites a good temporal correlation as well as a fair spatial correspondence between these residual tilts with amplitude and duration of some microradians and months respectively and main shocks were pointed out by removing both secular trends and seasonal thermoelastic effects from the raw tilts an attempt was made to justify the above mentioned results based on the assumption that the observed intermediate term preseismic tilts are the manifestation of aseismic creep episodes of comparable duration in the fault materials of thrust faults close to the tilt sites the mechanism refers to a strain field slowly propagating from the preparation focal area to the tilt site through crustal blocks separated by weak transition zones this propagation is thought to be the cause of the local aseismic fault slip recorded by the tiltmeters previously both discrete structures and strain propagation effects were revealed in the central apennines and are thought also to exist in the southern caucasus as in the past the rheological properties of fault materials are revealed as viscoelastic ones in fact creep equations obtained by applying several viscoelastic models on our data proved to fit quite well some of the observed tilt precursors producing viscosity and rigidity values very similar to those reported in literature

late pleistocene and holocene environmental changes recorded in deposits of the bukovynka cave the east carpathian foreland ukraine abstract a study of pollen fossil mammals and lithology including grain size analysis of the terrigenous deposits in the bukovynka cave enables the reconstruction of the environments of several geochronologic subdivisions of the middle pleniglacial late glacial and holocene a comparison of pollen assemblages in surface samples from the cave deposits and from the soils prove the importance of cave palynology for palaeovegetation reconstruction the same patterns were shown by a comparison of pollen from hyaena coprolites in the cave and their enclosing sediments in the trapeznyi chamber record the two interstadials and one stadial identified are correlated with those of the moershoofd interval and the following stadial after 41 000 yrs bp is compared with the hosselo stadial of western europe in the sukhyi chamber record late glacial times around 10 700 yrs bp differed from the holocene in having a much harsher climate with the spread of boreal forest during the holocene a relatively wet phase transitional from atlantic to early subboreal was separated from the similar phase of the late subboreal 2800 yrs bp by a drier middle subboreal with the disappearance of water loving trees and the existence of steppe rodents the subatlantic was the wettest time with culmination of a broad leaved flora in the roman 2300 1800 yrs bp and medieval 1000 yrs bp warm periods the cultivation of cerealia started from 2800 yrs bp and forest clearances increased after the medieval warm period

microenvironments of ph in biofilms grown on dissolving silicate surfaces abstract differences in ph between silicate biofilm interfaces and bulk medium ph ph interface ph bulk were detectable with commercial microelectrodes in cultures grown in unbuffered medium ph 0 27 1 08 for an arthrobacter species but were generally beneath detection ph arthrobacter ranged from 1 2 to 11 5 mm and were highly variable even for replicates in buffered medium neither bacterium produced a measurable ph across the biofilms grown on silicates the silicates consisted of polished hornblende synthetic fe rich glass similar to hornblende in bulk composition and two commercially available float glasses one low fe and one high fe the two species of soil bacteria investigated are both known to accelerate release of fe from hornblende for the arthrobacter values of ph developed on hornblende crystal or glass substrates were generally larger than those developed on either float glass differences in ph developed on different substrates could not be related simply to relative rates of dissolution of substrates differences between the two bacterial species are probably related to differences in 1 rates of growth 2 production of low molecular weight organic acids 3 physical characteristics of polysaccharide slimes excreted and or 4 production of siderophores although values of ph developed at mineral water interfaces in natural systems may not be as large as those measured here except for water saturated systems it is probable that significant values of ph ph unit develop where fast growing acid producing microbes colonize slow dissolving phases in the presence of unbuffered solutions

seismomagnetic observation during the 8 july 1986 magnitude 5 9 north palm springs earthquake a differentially connected array of 24 proton magnetometers has operated along the san andreas fault since 1976 seismomagnetic offsets of 1 2 and 0 3 nanotesla were observed at epicentral distances of 3 and 9 kilometers respectively after the 8 july 1986 magnitude 5 9 north palm springs earthquake these seismomagnetic observation are the first obtained of this elusive but long anticipated effect the data are consistent with a seismomagnetic model of the earthquake for which right lateral rupture of 20 centimeters is assumed on a 16 kilometer segment of the banning fault between the depths of 3 and 10 kilometers in a region with average magnetization of 1 ampere per meter alternative explanations in terms of electrokinetic effects and earthquake generated electrostatic charge redistribution seem unlikely because the changes are permanent and complete within a 20 minute period

a late pleistocene palaeoclimate record based on mineral magnetic properties of the entrance facies sediments of kulna cave czech republic summary kulna cave is located in the moravian karst a well developed karstic region formed in devonian limestones in the eastern part of the czech republic the entrance facies sediments in the cave consist of interbedded layers of silts loess and clay rich silts loam that were either directly blown into the cave entrance or redeposited in the cave by slope processes during the last glacial stage the layers of loess and loam overlie fluvial sands and gravels deposited during the last interglacial previous research at kulna concentrated on the archaeology palaeontology and dendrology of these entrance facies sediments from these data palaeoenvironmental conditions in the vicinity of the cave were reconstructed our results suggest that susceptibility variations and in particular variations in pedogenic susceptibility yield a more detailed record of the palaeoenvironmental conditions at the cave during the last glacial stage magnetic susceptibility was measured on approximately 700 samples collected throughout three well studied profiles in the cave entrance the record is well defined and correlates from one profile to another mineral magnetic measurements fd arm sirm s ratio t suggest that variations in the kulna sediments from the last glacial stage are controlled by the concentration of magnetite and or maghemite formed during pedogenesis after the removal of the effects of fine carbonate debris and detrital ferromagnetic minerals on the bulk record we obtained a record of pedogenic susceptibility p that serves to quantify the concentration of magnetic minerals formed during pedogenesis therefore p can be thought of as a proxy reflecting the intensity of pedogenesis which in turn is controlled by climate our p record is also in good agreement with the median grain size record of the kulna sediments another proxy for climatic change we suggest that in the case of kulna p is more sensitive to climate change than bulk the kulna pedogenic susceptibility record shows variations on both long and short timescales the long term trends are in good agreement with the deep sea specmap record while the short term oscillations correlate well with rapid changes in the north atlantic sea surface temperatures our results suggest that central european climate during the last glacial stage was strongly controlled by the sea surface temperatures in the north atlantic short term warmer events and perhaps higher precipitation over the mid continent increased the intensity of pedogenesis given the number of independent climate proxies determined from the entrance facies of the cave and their high resolution kulna is an extremely important site for studying late pleistocene climate

modal mineralogy of cm2 chondrites by x ray diffraction psd xrd part 1 total phyllosilicate abundance and the degree of aqueous alteration abstract cm carbonaceous chondrites are samples of incompletely serpentinized primitive asteroids using position sensitive detector x ray diffraction psd xrd and a pattern stripping technique we quantify the modal mineralogy of cm2 chondrites mighei murray murchison nogoya and cold bokkeveld there is a narrow range in the combined modal volume vol of the most abundant phases mg serpentine 25 33 and fe cronstedtite 43 50 cold bokkeveld is anomalous in containing more mg serpentine 49 59 than fe cronstedtite 19 27 even including cold bokkeveld the range in modal total phyllosilicate is 73 79 average 75 total phyllosilicate abundance provides a non ambiguous measure of the degree of aqueous alteration and indicates that these meteorites have all experienced essentially the same degree of aqueous alteration this reflects pervasive hydration of matrix across cm2 samples apparent differences in the alteration of chondrules observed in petrographic studies represent various stages in the progression towards complete hydration of all components but are not manifest in significant differences in modal mineralogy for all samples there is a limited range in olivine 6 9 and pyroxene 5 abundances modal abundances of the remaining identified phases also show a limited range calcite 0 1 3 gypsum 0 1 6 magnetite 1 1 2 4 pentlandite 0 2 1 and pyrrhotite 1 3 8 as expected we observe a strong negative correlation in the modal abundance of anhydrous fe mg silicates olivine pyroxene and total phyllosilicate mg serpentine fe cronstedtite consistent with the idea that phyllosilicate is forming by aqueous alteration of the anhydrous components the negative correlation in the modal abundance between mg serpentine and fe cronstedtite indicates a mineralogic transformation of fe cronstedtite to mg serpentine by fluid driven recrystallisation or b that these meteorites had different initial abundances of olivine and pyroxene the observed positive correlation in the relative proportion of mg serpentine with increasing total phyllosilicate abundance reflects the evolution of increasingly mg rich phyllosilicate during aqueous alteration fe cronstedtite is the dominant phyllosilicate while cm chondrule olivines are forsteritic and will form mg serpentine during aqueous alteration this implies that matrix olivine was more fe rich than chondrule olivine prior to aqueous alteration

numerical modeling of preseismic slow movements of crustal blocks caused by quasi horizontal tectonic forces abstract a 2d model is proposed for slow crustal movements caused by subhorizontal forces applied to a system of rigid blocks separated by transition zones faults filled with viscoelastic material the aim of the modeling is to explain the main features of tilt anomalies observed prior to earthquakes it is assumed that an earthquake is prepared within the fault zone where macroproperties of the fault gouge material are changed due to the increase of microfractures the fault zones are inclined and the blocks are allowed to move in both vertical and horizontal directions as well as to rotate numerical experiments were performed for systems of two and seven blocks with different viscosity and rigidity of the fault material the shape of the anomalies as well as the time delay and decay of the anomaly amplitude with distance from the earthquake preparation zone are explained by the model

magnetic and electric fields associated with changes in high pore pressure in fault zones application to the loma prieta ulf emissions we determined the electric and magnetic fields generated during failure of faults containing sealed compartments with pore pressures ranging from hydrostatic to lithostatic levels exhumed fault studies and strain measurement data limit the possible size of these compartments to less than 1 km in extent rupture of seals between compartments produces rapid pore pressure changes and fluid flow and may create fractures that propagate away from the high pressure compartment along the fault face nonuniform fluid flow results from pressure decrease in the fracture from crack generated dilatancy partial blockage by silica deposition and clearing as pressure increases a direct consequence of this unsteady fluid flow may be associated transient magnetic signals caused by electrokinetic piezomagnetic and magnetohydrodynamic effects models of these processes for fault geometries with 1 km high pressure compartments show that electrokinetic effects are several orders of magnitude larger than the other mechanisms the electrokinetic signals produced by this unsteady flow are comparable in magnitude and frequency to the magnetic signals observed prior to the ml 7 1 loma prieta earthquake of october 18 1989 provided fracture lengths are less than 200 m

detection of ultra low frequency emissions connected with the spitak earthquake and its aftershock activity based on geomagnetic pulsations data at dusheti and vardzia observatories abstract ulf electromagnetic emissions from the spitak armenia earthquake site have been detected observations were carried out at the dusheti and vardzia georgia observatories at distances 120 200 km from the epicentre in a frequency range 0 005 1 hz it is shown that the emission appears several hours before the main shock and some of the powerful aftershocks and is not connected with geomagnetic pulsations of magnetospheric sources

can we use pyroxene weathering textures to interpret aqueous alteration conditions yes and no pyroxene minerals are a significant component of shergottite nakhlite chassignite snc meteorites e g velbel 2012 and detected across large areas of mars surface e g mustard et al 2005 these minerals are associated with chloride sulfate and perchlorate salts that may represent briny waters present in mars history previous textural analyses by velbel and losiak 2010 comparing pyroxenes and amphiboles from various natural weathering environments showed no correlation between apparent apical angles describing the morphology of denticular weathering textures and mineralogy or aqueous alteration history in relatively dilute solutions however high salinity brines preferentially dissolve surface species potentially leading to different textures dependent on the brine chemistry in this study we performed controlled pyroxene dissolution experiments in the laboratory on a well characterized diopside to determine if aqueous alteration in different high salinity brines representative of potential weathering fluids on mars produce unique textural signatures following two months of dissolution in batch reactors we observed denticles on etch pit margins and pyroxene chip boundaries in all of the solutions investigated ultrapure water 18 m cm 1 a h 2 o 1 low salinity solutions containing 0 35 m nacl a h 2 o 0 99 0 35 m na 2 so 4 a h 2 o 0 98 and 2 m naclo 4 a h 2 o 0 9 and near saturated brines containing 1 7 m na 2 so 4 a h 2 o 0 95 3 m nacl a h 2 o 0 75 and 4 5 m cacl 2 a h 2 o 0 35 no systematic change in denticle length or apical angle was observed between any of the solutions investigated even when altered in brines with significantly different salinity activity of water and anion composition based on these and previous results from natural systems apical angle measurements are not a useful proxy for determining the extent or nature of aqueous alteration however since denticles form relatively slowly during weathering at circum neutral ph denticle length may be a useful proxy for chemical weathering duration all of the experimental solutions produced median denticle lengths 1 m likely due to the brief weathering experiments however perchlorate brines produced a significantly wider range of denticle lengths than those observed in all the other experimental solutions tested since perchlorate is likely a common constituent in martian soils glotch et al 2016 denticle length measurements should be used cautiously as proxies for extent of aqueous alteration on mars particularly in samples that also contain perchlorate

deformation of the mitaka rhombus strain buildup following the 1923 kanto earthquake central honshu japan frequently repeated surveys of a local network near tokyo provide considerable detail on the horizontal strain changes immediately adjacent to the rupture zone of the m 8 1 kanto earthquake changes in the three independent tensor strain components are determined for 35 epochs during 1916 1980 to a precision of about 1 5 strain no significant shear or elongational strain changes preceded the earthquake a change in dilational strain is marginally significant postseismic movements are large accumulating to 40 or more of the coseismic strain drop they have at least two time scales a distinct short term transient lasting less than a year is explained well by slip or localized deformation that occurs downdip of the coseismic rupture plane and has a time constant of about 3 months more complex longer period postseismic movements continue for at least another 10 years their precise duration as well as the transition to presumably steadier interseismic deformation is obscured by notable irregularities in the strain buildup at mitaka as a result neither the interseismic strain rate nor the occurrence time of the next kanto earthquake can be reliably estimated from these observations

conditions of subaerial weathering of basalts in the neoarchean and paleoproterozoic abstract precambrian weathering profiles or regoliths were formed on the earth s surface in contact with meteoritic water this signifies that their mineral and bulk composition should reflect the environmental conditions at the time of weathering the aim of this study is to reconstruct the main mineralogical and chemical trends involved in the formation of precambrian weathering regoliths by means of geochemical modeling verified through laboratory experimentation we have demonstrated that in a wide range of modeling conditions weathering profiles of basalts consist mostly of clay minerals smectites and illite carbonate minerals may also be deposited within the profile at the initial stage of weathering which are later dissolved during a further process the time necessary for complete dissolution of primary minerals and crystallization of authigenic minerals is between 100 and 140 kyr modeling results indicate that neoarchean and paleoproterozoic 2 8 2 0 ga weathering profiles were formed under an atmosphere with pco2 not much higher than 25 pal and climatic conditions close to those found in modern times weathering under co2 rich pco2 1 and 10 bar and ch4 rich atmospheres as well as high temperature 50 c and 75 c conditions do not produce compounds corresponding to the analyzed samples

theory of electrokinetic effects occurring at the final stage in the preparation of a tectonic earthquake crustal deformation processes occur with relative rapidity when short term precursors appear at the final preparatory stage of a tectonic earthquake this paper contains calculations of crustal bulk strain before an earthquake based on the model of a rigid inclusion the data give initial conditions for the problem of fluid percolation in a two phase medium accompanied by electrokinetic effects the solution provides a description of systems of currents arising in the vicinity of the source region an analysis of this theoretical evidence yields information on the behaviour of short term precursors in telluric currents and the geomagnetic field

transmission electron microscopy of muscovite alteration of tourmaline partially sericitized tourmaline from a pegmatite was investigated using high resolution transmission electron microscopy hrtem fine grained muscovite crystals form extensive narrow veinlets preferentially developed along the 110 and 100 cleavages of tourmaline indicating that a cleavage controlled alteration mechanism was dominant hrtem images show that tourmaline muscovite interfaces parallel well defined 110 and 100 of tourmaline in general 001 of muscovite parallels the c axis of tourmaline but otherwise tourmaline and replacing muscovite lack crystallographically oriented relation

the role of microorganisms and biofilms in the breakdown and dissolution of quartz and glass three different types of silica 1 quartz sand 2 crystalline scepter quartz and 3 commercial glass subjected to biological growth were investigated for evidence of biologically induced breakdown the results of laboratory experiments with biofilms on quartz sand and glass were compared with material from the field microscopic optical and sem analysis of quartz sand weathered in vitro by a microbial community of cyanobacteria diatoms and heterotrophic bacteria demonstrate grain diminution of a sand fraction of north sea sediment the microbial community changes the minerals in the vicinity of the living cells which leave their mark on the quartz surface in form of imprints depressions and pits subsequently microbial growth on the surface brought about a general decrease of the grain size in the layer beneath a biofilm imprints of diatoms on glass surfaces colonized by diatoms and heterotrophic bacteria confirm the chemical etching activity of these organisms mixed cultures of diatoms and bacteria show depressions corresponding to the shape of individual cells our experiments confirm that diatoms heterotrophic bacteria and cyanobacteria from natural biofilms can actively attack quartz and glass microscopic analysis of an idiomorphic scepter quartz crystal from a tepui weathering environment reveals that the associated biofilms can create a local shift in the ph from 3 4 ph of water on the tepui to evidently higher than 9 necessary for quartz dissolution the quartz covered with a biofilm is partially perforated to a depth of more than 4 mm we conclude that biofilm growth in marine sub aquatic and terrestrial sub aerial conditions can significantly increase the breakdown of silica in the amorphous glass sub crystalline chert crystalline and granular forms of quartz microbial growth may therefore substantially modify the processes of transformation of a major rock forming mineral of great chemical and physical resistance

deleterious reactions of aggregate with alkalis in concrete concrete in the built environment the word concrete is derived from the latin concretus compact condensed representing a conjunction of con together and the past participle of cresco to grow compare crescendo thus concrete could be liberally translated as grown solid together alluding to the consolidation of a particulate aggregate material with a cement binder of some sort concrete containing aggregate has been used in construction by the ancient greek and romans possibly as a further development of clay initially used by the assyrians and babylonians as a binder later superseded by burnt lime and gypsum by the egyptians as a construction material concrete allows architects and engineers to design a structure with only minimal constraints to its form a complicated shape requiring great effort to chisel out from a piece of stone can simply be poured in a mold and reproduced as often as desired also ex situ both the invention of ordinary portland cement opc first patented by british bricklayer joseph aspdin in 1824 and of reinforced concrete first patented by parisian gardener joseph monier in 1867 for making durable flower pots contributed to the development of mechanically stronger concrete allowing yet slimmer and taller structures to be built today concrete is the most popular building and construction material with an annual production volume exceeding 7 5 km3 or about 20 billion tonne concrete is the prime ingredient in the world s largest and most prominent structures and landmark edifices including hydropower dams e g three gorges dam yichang cn also see charlwood and solymar 1995 coastal defense works e g delta works nl telecommunication e g cn tower toronto ca office skyscrapers e g burj khalifa dubai uae theatres e g opera house sydney au hotels and casinos e g marina bay area singapore sg nuclear power plants oil and gas drilling and productions rigs e g sakhalin ru sea ports and harbors e g

an updated and homogeneous world secular variation data base 1 smoothing of the archaeomagnetic results the available original archaeomagnetic world data on intensity and direction have been compiled and sorted according to geographical region then after correcting them to correspond to a single site associated with each region called a world site they have been processed using the gaussian statistic for the intensity f data and bivariate statistic for the declination d and inclination i data to obtain smoothed values at regular time intervals we include a discussion of the statistical methods used we have limited the data to the last 20 centuries because the archaeomagnetic data alone do not allow us to go back further in the past we have also excluded archaeomagnetic studies at world sites where the number of data is not sufficient to perform a statistical analysis we obtained results at nine world sites for which the values of at least two of the three above quoted parameters have been calculated at 25 year intervals from the beginning of our era the results for each world site with their associated errors are given and discussed the potential of this new set of world data for improving our knowledge of the global terrestrial magnetic field tmf during the past 20 centuries is sketched these results will be completed in a second paper by analysing in the same way the data supplied for volcanic rocks and lake sediments

the heights of sporadic e layer simultaneously observed by the vhf radar and ionosondes in chung li ionosondes and vhf radars have been employed to simultaneously observe the sporadic e es layer in previous studies an absence of correlation was found between the height of field aligned irregularities fai observed by the radars and the virtual height of the es layer h es by their colocated ionosondes a careful study shows that the low correlation results from the beam broadening effect of the ionosonde in this paper the investigation shows a better correlation between the heights of the fai bottom side hfaib observed by the vhf radar and the h es by ionosondes in chung li it is found that the h es is greater than the hfaib by about 5 10 km meanwhile we demonstrate that h es observed by two nearby ionosondes and or radars can be employed to evaluate the velocity of waves in the es layer

granite hydrothermal interaction a simultaneous estimation of the mineral dissolution rate based on the isotopic doping technique we propose an experimental evaluation of the simultaneous dissolution rate of k feldspar biotite and plagioclase during the interaction between a granite and a fluid artificially enriched in the less abundant strontium and potassium isotopes experiments were carried out at 453 k and 10 bars for a time of 6 months putting powered granite in contact with fluids spiked in 39k and 84sr and saturated with respect to kaolinite low temperature albite prehnite calcite adularia and quartz the evolution of the rb 39k sol vs 41k 39k sol and 87sr 86sr sol vs 84sr 86sr sol ratios allows us to identify a single rock end member from the first month of interaction this indicates that the dissolving mineral assemblage remains constant during the remaining 5 months of interaction associating the mass conservation law to the isotopic mixing equations for both sr and k we evaluate that the mass of dissolved plagioclase is 3 4 times higher the mass of dissolved biotite and 10 20 times higher the mass of dissolved sanidine the rate of potassium dissolution is estimated assuming that the 41k 39k sol ratio is continuously in equilibrium with the ratio in neogenic phases coupling the proportion of dissolved minerals to the overall rate of potassium dissolution and normalising to the mineral surface area we finally estimate that in our experimental conditions plagioclase and biotite dissolve with a rate of respectively 3 1 10 12 and 6 2 10 13 mol m 2 s 1 while the k feldspar dissolution rate is 4 2 10 13 mol m 2 s 1

environmental magnetism principles and applications 1 in environmental magnetism rock and mineral magnetic techniques are used to investigate the formation transportation deposition and postdepositional alterations of magnetic minerals under the influences of a wide range of environmental processes all materials respond in some way to an applied magnetic field and iron bearing minerals are sensitive to a range of environmental processes which makes magnetic measurements extremely useful for detecting signals associated with environmental processes environmental magnetism has grown considerably since the mid 1970s and now contributes to research in the geosciences and in branches of physics chemistry and biology and environmental science including research on climate change pollution iron biomineralization and depositional and diagenetic processes in sediments to name a few applications magnetic parameters are used to routinely scan sediments but interpretation is often difficult and requires understanding of the underlying physics and chemistry thorough examination of magnetic properties and of the environmental processes that give rise to the measured magnetic signal is needed to avoid ambiguities complexities and limitations to interpretations in this review we evaluate environmental magnetic parameters based on theory and empirical results we describe how ambiguities can be resolved by use of combined techniques and demonstrate the power of environmental magnetism in enabling quantitative environmental interpretations we also review recent developments that demonstrate the mutual benefit of environmental magnetism from close collaborations with biology chemistry and physics finally we discuss directions in which environmental magnetism is likely to develop in the future

effects of parent material and weathering on feldspar content in different particle size fractions from forest soils in nw germany abstract the feldspar content of three soils developed from pleistocene calcareous till glacial sand and loess in nw germany was investigated in order to characterize the stores of feldspar in detailed particle split as well as changes as a function of soil depth feldspars are present in all fractions

historical climatic record from flood sediments deposited in the interior of spiralka cave czech republic abstract magnetic susceptibility was measured on more than four hundred samples collected from a 5 m high section of fine grained sediments deposited during flood events in the interior of spiralka cave spiralka cave is located in the northeastern portion of the moravian karst czech republic in the upper 1 5 m of this profile mineral magnetic fe arm sirm s ratio t and other non magnetic measurements heavy mineral concentration loss on ignition and particle grain size indicate that variations are controlled by the concentration of magnetite and by magnetic grain size i e increased magnetic susceptibility results from increased concentration of coarse grained magnetite a positive correlation with ti and zr concentrations in this part of the profile with our magnetic susceptibility record is a detrital signal responding to changing environmental conditions in the catchment area furthermore a comparison of our susceptibility record to the record of winter temperature anomalies constructed from both instrumental and historical records collected at the klementinum observatory in prague shows a remarkable correlation the most probable explanation of these correlations is that during years with warmer winters positive winter temperature anomalies and less snow cover the floods were less intensive but probably had access to larger tracts of cultivated land as agriculture tended to expand during these warmer periods cultivation of the land provided flood waters with greater access to coarser grained magnetite like materials exposed by tilling of soils lower in the profile interpreting the environmental significance of magnetic susceptibility variations is more complex as remobilization of iron has occurred nevertheless the magnetic susceptibility record when coupled with non magnetic measurements can be shown to correlate to known environmental conditions present in central europe during the deposition of the lower portion of the profile

diffusive transport of water in porous feldspars from granitic saprolites in situ experiments using ftir spectroscopy abstract a novel experimental cell was developed for in situ measurements of transport phenomena in porous media using fourier transform infrared ftir spectroscopy the technique was employed at ambient pressure in the temperatures range of 11 44 c to study the h 2 o d 2 o exchange between water saturated weathered feldspars bulk porosity of 5 19 vol for feldspar from granitic saprolites and a surrounding aqueous liquid such measurements are an important step for understanding internal weathering reactions of feldspars in soils and aquifers effective diffusion coefficients d eff for water in water saturated porous feldspars were determined assuming one dimensional diffusion in a quasi homogeneous medium the values of d eff vary from 7 2 10 10 to 1 9 10 11 m 2 s and are 1 2 orders of magnitude lower than the diffusion coefficients d of protons and molecular h 2 o in liquid water the activation energy for the h 2 o d 2 o exchange process in porous feldspars ranges from 7 8 to 18 8 kj mol the results imply that the effective diffusivity of water is mainly controlled by physical properties of the feldspars like porosity pore connectivity pore geometry and distribution perthitic feldspars with homogeneous pore distribution in the albitic lamellas have diffusional tortuosity factors x d d eff between 3 and 10 while alkali feldspars with inhomogeneously distributed and disconnected pores have much higher x values up to 129 diffusion anisotropy has been verified for a vein perthite with diffusion perpendicular to the lamellas being faster by 0 3 0 5 log units than within the lamellas it has to be emphasized that the study is based only on few selected feldspars including perthitic feldspar and additional work on samples with different weathering stages is needed to test the importance of the different parameters controlling diffusive transport in the pore system

metal sources of the navan carbonate hosted base metal deposit ireland nd and sr isotope evidence for deep hydrothermal convection nd and sr isotope analyses are presented for gangue mineral samples from the giant carbonate hosted navan zn pb deposit ireland and for rocks from which navan metals may have been derived analysis of gangue minerals spanning the navan paragenetic sequence reveals systematic evolution in the composition of the mineralising fluid early fluid represented by replacive dolomite exhibits the lowest initial 87sr 86sr ratio 0 7083 0 7086 closest to that of the host limestone and to lower carboniferous seawater and the highest 143nd 144nd ratio 0 51161 0 51176 later generations of dolomite barite and calcite which encompass sulphide precipitation have higher initial 87sr 86sr ratios maximum 0 7105 and lower initial 143nd 144nd ratios minimum 0 51157 all samples have initial nd isotope ratios that are too low to have been acquired only from the host limestone drill core samples of presumed ordovician volcanic and sedimentary rocks from beneath the navan orebody have 143nd 144nd and 87sr 86sr ratios at the time of mineralisation of 0 51184 0 51217 and 0 7086 0 7138 respectively the data are interpreted to indicate mixing of sulphide rich limestone buffered brine with a metal bearing hydrothermal fluid which had passed through sub carboniferous rocks consistent with published fluid inclusion and s isotope data the 143nd 144nd ratio of this basement derived fluid is too low to have been imparted by flow through the devonian old red sandstone as required in models of regional fluid flow in response to hercynian uplift irrespective of whether such regional fluid flow occurred the hydrothermal nd must have been derived from sub devonian rocks these conclusions broadly support the hydrothermal convection cell model in which brines ultimately of surface origin penetrated to a depth of several kilometres leaching metals from the rocks through which they passed the data also support increasing depth of penetration of convection cells with time metals were subsequently precipitated in carbonate rocks at sites of mixing with cooler sulphide rich fluids however comparison of the navan hydrothermal gangue nd sr isotope data with data from lower palaeozoic rocks strongly suggests that the latter cannot alone account for the basement signature as the navan deposit lies immediately north of the iapetus suture this suggests that the laurentian margin includes precambrian basement

glaciers show direct linkage between erosion rate and chemical weathering fluxes field studies suggest a linkage between high physical erosion rates and rates of chemical denudation mechanical erosion by temperate glaciers is commonly an order of magnitude higher than in mountainous fluvial catchments leading to an expectation that chemical weathering fluxes should also be high from glacierized basins yet solute fluxes from glaciers are not found to be higher than non glacierized catchments application of a model of silicate weathering from glaciers based on mineral surface area production and mineralogy shows that solute fluxes are consistent with the low temperatures dilute water chemistry and high mineral surface area production in these environments low temperatures reduce silicate weathering rates this effect explains the difference between silica fluxes from glaciers and from non glacierized basins as in laboratory flow through reactors glacial solute flux should depend on surface area production and mineral weathering rate constants the surface area production is significant a typical glacial erosion rate and grain size distribution produces on the order of 104 km2 of mineral surface area per square kilometer per year this new surface area is highly reactive because mineral weathering rates decline with surface age application of the reactor model yields results largely consistent with measured solute fluxes for the example of bench glacier alaska the model underpredicts potassium fluxes probably due to accelerated initial dissolution of biotite strained by abrasion the success of the model in predicting other silicate weathering fluxes reflects the far from equilibrium conditions in glacial runoff such that mineral weathering rate constants are not limited by saturation state in a small data set from glacial catchments both annual silica fluxes and mean concentrations increase with water discharge this suggests that mineral surface area increases with water discharge from glaciers an effect plausibly linked to erosion rates those glaciers for which both erosion rate and silica flux data are available support the idea that production of new reactive mineral surface area by glacial erosion drives silicate weathering fluxes

diffusion effects on oxygen isotope temperatures of slowly cooled igneous and metamorphic rocks recently obtained data on oxygen diffusion in feldspars quartz and hornblende permit the prediction of the apparent18o16o temperatures that would be measured in a rock that consisted only of those three minerals and cooled slowly from high temperature the computed temperatures would be based on the differences in the18o16o ratios between coexisting pairs of minerals the present calculation takes into account the diffusion rates for oxygen as a function of temperature the cooling rate of the rock the mineral grain sizes and the mode of the rock for mineral grains 1 mm in radius and a cooling rate of 10 c m y the minimum difference in apparent temperature between quartz feldspar and feldspar hornblende pairs will be 115 c despite the assumption of a normal uneventful slow cooling history to room temperature further the apparent quartz hornblende temperature will range over 30 c 590 620 c depending on the mode of the rock for a cooling rate of 1000 c m y the apparent difference in temperature can be as much as 400 c consequently consistency in temperatures obtained by oxygen isotope analysis should not be expected in most high grade metamorphic rocks or igneous rocks which are cooled slowly departures from the pattern of temperatures obtained in this model would imply a very rapid quench from high temperature or a complex history for the rock for some minerals including hornblende the relation between temperature and the equilibrium fractionation of oxygen isotopes between coexisting phases has been derived from observed relations in natural specimens the choice of the specimens used for such calibrations needs to be re evaluated in light of these findings this may result in a change in the equilibrium equation constants an example from the literature the san jose tonalite baja california mexico was modelled and yields 18o concentrations in the minerals that correspond closely with the measured values this suggests that the model used is appropriate that the rock has had a simple thermal history and that it cooled at 100 200 c m y over the temperature range 800 500 c the set of paleotemperatures obtained for a rock will in general yield neither the mineral closure temperatures nor the formation or crystallization temperatures on the other hand the cooling rate of the rock may be derived from the data this in turn may have important tectonic implications with regard to denudation and uplift rates

characterization of mineral surfaces using fib and tem a case study of naturally weathered alkali feldspars using a focused ion beam fib instrument electron transparent samples termed foils have been cut from the naturally weathered surfaces of perthitic alkali feldspars recovered from soils overlying the shap granite northwest england characterization of these foils by transmission electron microscopy tem has enabled determination of the crystallinity and chemical composition of near surface regions of the feldspar and an assessment of the influence of intragranular microtextures on the microtopography of grain surfaces and development of etch pits damage accompanying implantation of the 30 kv ga ions used for imaging and deposition of protective platinum prior to ion milling creates amorphous layers beneath outer grain surfaces but can be overcome by coating grains with 85 nm of gold before fib work the sidewalls of the foil and feldspar surrounding original voids are also partially amorphized during later stages of ion milling no evidence was found for the presence of amorphous or crystalline weathering products or amorphous leached layers immediately beneath outer grain surfaces the absence of a leached layer indicates that chemical weathering of feldspar in the shap soils is stoichiometric or if non stoichiometric either the layer is too thin to resolve by the tem techniques used i e similar to 2 5 nm or an insufficient proportion of ions have been leached from near surface regions so that feldspar crystallinity is maintained no evidence was found for any difference in the mechanisms of weathering where a microbial filament rests on the feldspar surface sub micrometer sized steps on the grain surface have formed where subgrains and exsolution lamellae have influenced the propagation of fractures during physical weathering whereas finer scale corrugations form due to compositional or strain related differences in dissolution rates of albite platelets and enclosing tweed orthoclase with progressive weathering etch pits that initiated at the grain surface extend into grain interiors as etch tubes by exploiting preexisting networks of nanopores that formed during the igneous history of the grain the combination of fib and tem techniques is an especially powerful way of exploring mechanisms of weathering within the internal zone beneath outer grain surfaces but results must be interpreted with caution owing to the ease with which artifacts can be created by the high energy ion and electron beams used in the preparation and characterization of the foils

anomalies in geophysical and geochemical parameters revealed on the occasion of the paravani m 5 6 and spitak m 6 9 earthquakes caucasus abstract on the occasion of the paravani may 13 1986 and spitak december 7 1988 earthquakes which occurred in the caucasus irregularities in several geophysical and geochemical parameters were revealed in this paper data on anomalies in the water level in deep wells in the helium content in thermal waters in electromagnetic signals revealed by surface and underground antennae and in an f gt function based on traveltimes of p and s waves are presented data were collected from sites located in the georgian s s r in the case of the spitak earthquake the anomalies in all the presented parameters can be attributed to the processes that preceded and accompanied the earthquake for the paravani earthquake no significant precursory phase seems to have been reflected in the helium content in thermal waters though this phase can be observed in the other parameters in general it would appear that the magnitude of the earthquake and the distance from the epicentre exert a significant control on the appearance of the anomalies

radio emission associated with rock fracture possible application to the great chilean earthquake of may 22 1960 stress induced piezoelectric fields produce freely propagating electromagnetic radiation when microscopic rock fractures occur in quartz bearing rocks a laboratory study is presented which shows that electromagnetic emissions are produced when microfractures occur in westerly granite a detailed model is presented for the emission process which allows an estimate of the total radiated power from an individual microfracture on the basis of these results a case is presented that an unusual radio emission seen on several widely separated radio astronomy receivers in the northern hemisphere on may 16 1960 was due to a stress induced microfracture along the chilean fault this radio event occurred 6 days prior to the great chilean earthquake of may 22 1960 and may have been a precursor to one of the largest earthquakes of this century

on the mechanisms and kinetics of oxygen isotope exchange in quartz and feldspars at elevated temperatures and pressures stereological and scanning electron microscope sem analyses of quartz water and plagioclase feldspar water interactions have been combined with 18o 17o and 17o 16o measurements of the associated isotope exchange in an attempt to develop an understanding of mineral water interactions at elevated temperatures and pressures the quartz water exchange t 250 to 600 c ph2o 1 to 22 kbar is dominated by an ostwald ripening recrystallization mechanism in which reprecipitated quartz develops as faceted overgrowths on original grains that have been rounded by initial solution processes correspondingly there is a linear decrease in specific surface area s as a function of fractional extent of exchange f the unrecrystallized quartz cores exchange through diffusional mechanisms that also become dominant in later stages when recrystallization becomes retarded and increasingly ineffective as a mechanism of isotopic exchange this transition from solution precipitation to diffusional mechanisms accounts for a plateau pressure effect on exchange rate observed in later stages of exchange substantial recrystallization does not occur in feldspar water exchange at 500 and 600 c ph2o 2 to 15 kbar the feldspar grains rapidly degrade into smaller fragments and become incoherently coated by a small amount of fine precipitated crystals subsequently isotopic exchange occurs without further textural change and at constant s these observations the preservation of al si order in albite throughout exchange the high calculated values of oxygen diffusion coefficients and possible dependence of these coefficients on ph2o indicate inhibition of feldspar recrystallization and are consistent with diffusional mechanisms for penetration of water into the feldspar and exchange with shared oxygen atoms in alumino silica tetrahedra equilibrium 18o 16o fractionation factors for both quartz water and albite water agree well with those measured previously in this laboratory

some statistical results on very low frequency radiowave emissions in the upper ionosphere over earthquake zones abstract an anomalous increase in the intensity of low frequency 0 1 16 khz radiowave emissions was detected using intercosmos 19 data when the satellite was nearly over the epicentre of an earthquake zone ample statistical data are the basis for a determination of the probable spatial temporal dimensions of the region of the upper ionosphere in justify which elf vlf emissions were detected the reliability of the detected phenomenon is 0 8 0 9 the ionospheric regions with the low frequency emissions observed by intercosmos 19 have been found to be formations noise belts extended along 60 of geographic longitude and 2 of geographic latitude the spectral characteristics of elf vlf emissions near seismic areas are specified the earthquake depth and location under a continent or under an ocean has an effect on the results of the satellite observations of earthquakes possible mechanisms of the phenomenon are discussed

protective mineral layers formed from granite dry steam interaction abstract this work focuses on interaction between granite stainless steel sus pipe dry steam in the presence of cu three types of hydrothermal experiments were conducted 1 sus cu granite 2 sus cu 3 sus granite it was found that a high protective amorphous alsi 1 6 o 4 layer thickness about 5 m was formed on the supporting pipe surface only in the case of sus cu granite interaction the al silicate layer formed during the experiment was characterized by x ray diffraction xrd techniques and scanning electron microscopy sem with edx according to kinetic data this layer has high protective properties

some relationship between van seismic electric signals ses and earthquake parameters abstract a possible correlation between ses seismic electric signals of the van method characteristics and earthquake parameters is investigated for the period january 1 1983 december 31 1994 for western greece during this period there were total of 55 earthquakes of mb 5 0 in the region of the so called selectivity maps of the ioannina ioa and pirgos pir van stations cmt solutions are available for 29 of these earthquakes eighteen were preceded by ses at ioa and eleven at pir none of them was preceded by simultaneous ses at both stations the main results are as follows 1 the direction of the ses vector at ioa is correlated with the focal position of predicted earthquakes although nearby earthquakes often have ses with dissimilar vector directions 2 the ses of all nine thrust events of the 29 earthquakes were observed at ioa but their vector direction was not unique 3 eleven earthquakes in the zone west of kefallinia to peloponese preceded by ses at pir were of the strike slip type with varying degrees of normal component the vector direction of ses at pir for these earthquakes was predominantly westward 4 the source mechanism changed from largely strike slip type to thrust type in the above zone at the end of 1987 and this coincided with a shift in the sensitive site from pir to ioa indicating a possible correlation between the source mechanism and selectivity characteristics of van stations

geomechanical and geochemical changes during early stages of weathering of karamu basalt new zealand abstract variations in geochemical and geomechanical characteristics were measured through a basalt weathering sequence exposed at an abandoned quarry at karamu near hamilton new zealand geochemical measurements show that at the early stages of weathering fresh to slightly weathered reductions in the concentrations cao and mgo are rapid although they are not accompanied by major mineralogical change during later stages of weathering secondary clay minerals form following well described mineralogical changes fresh basalt is strong uniaxial compressive strength 262 mn m 2 point load index 5 59 with well developed closely spaced columnar jointing slightly weathered material is distinguished in the field only by slight discolouration along joint planes but laboratory tests show a dramatic loss of strength in slightly weathered rock point load index 0 41 cbr 43 a causal relationship between the loss of cations and loss of strength in the early stages of weathering is suggested this stage of weathering is diffusion controlled whereby cations are lost from the constituent primary minerals and replaced by h this process disrupts the lattice structure and causes a marked loss of strength implications are that slightly weathered rock which appears competent in the field is likely to have much lower strength and durability than assumed from field evidence

preseismic creep strains revealed by ground tilt measurements in central italy on the occasion of the 1997 umbria marche apennines earthquake sequence daily averaged tilt component data from four sites of the central apennines italy revealed intermediate term tilts of a few months as possible precursors of the seismic sequence occurred in the umbria marche region during 1997 a change was also observed in the secular tectonic trend recorded at one site and referred to the same seismic sequence the observed intermediate term preseismic tilts are considered as the manifestation of aseismic creep episodes in the fault materials close to the tilt sites the mechanism refers to a strain field slowly propagating from the dilatancy focal area to the tiltmeters through rigid crustal blocks separated by weak transition zones with viscoelastic rheology this propagation is thought to be the cause of the local aseismic fault slip recorded by tiltmeters in one case such creep strains revealed to have larger amplitude and higher frequency content than those accepted for fault materials and this was attributed to an amplified response of the heterogeneous ground surface at the site the existence of a propagating strain field is confirmed by the different onset time delays in the preseismic tilt signals recorded at different distances from the same earthquake in particular the onset time delays observed at each tilt site appear to increase with increasing distance of such site from the epicentral area at greatest distances where the preseismic strain becomes negligible the characteristic intermediate term ground tilts vanish completely

differences between geothermal and experimentally derived fluids how well do hydrothermal experiments model the composition of geothermal reservoir fluids fluid parameters from a diverse set of dilute water rock experiments 80 degree 300 degree c were compared with reservoir data from several geothermal fields the comparisons show that experiments of this type can reproduce many properties of geothermal reservoir fluids compositional parameters for most species in experimentally derived fluids are temperature dependent but are relatively independent of rock type initial fluid composition and water rock mass ratio at lower temperatures le 250 degree c many experimental parameter temperature trends agree with geothermal trends however at higher temperatures ge 250 degree c the geothermal fluids have calculated high temperature ph values 1 to 2 ph units lower than do the experimentally derived fluids this produces a consistent offset between values of experimental and natural cation proton activity ratios two possible experimental reasons for offsets are pervasive metastable mineral formation in experiments and absence in experiments of the equivalent of a magmatic or metamorphic gas input results from current experiments suggest that while metastability may be partially responsible for offsets observed geothermal fluid parameters can be duplicated by addition of co sub 2 furthermore maintenance of high line integral co sub 2 low ph conditions requires a co sub 2 flux finally in geothermal fields addition of exotic co sub 2 or other acid gases during upflow or samplingmore of wet steam discharges may also contribute to such offsets by producing lower than actual reservoir ph values thus the offsets could suggest that some geothermal fluid ph values are more basic than commonly calculated and closer to those ph values produced during dilute water rock experiments less

aqueous alteration without a pronounced oxygen isotopic shift implications for the asteroidal processing of chondritic materials primitive meteorites exhibit certain features that are consistent with aqueous and thermal alteration on asteroids but o isotopic analyses show only a modest heavy isotope shift interpreted as indicating modification in the nebula to understand the isotopic effects of asteroidal alteration we take the l group ordinary chondrites weathered in antarctica as an analogue the data show that alteration is a two stage process with an initial phase producing only a negligible isotopic effect although surprising a possible explanation is found when we consider the alteration of terrestrial silicates numerous studies report pervasive development of channels a few to a few tens of nanometer wide in the incipient alteration of silicates we observe a similar texture alteration involves a restructuring of clay minerals along these narrow channels in which access of water is restricted the clay shows a topotactic relationship to the primary grain which suggests either epitaxial growth of the clay using the silicate as a substrate or inheritance of the original o structure by the clay our data suggests the latter with extensive inheritance of structural polymers by the weathering product the bulk o isotopic composition is comparatively unaffected this offers an explanation for the lack of an isotopic effect in the weathering of the l chondrites if substantial modification of chondritic materials may occur without a pronounced isotopic effect it also reconciles existing o analyses of cv chondrites with an asteroidal model of aqueous alteration

electromagnetic precursors to earthquakes in the ulf band a review of observations and mechanisms despite over 2 decades of international and national monitoring of electrical signals with the hope of detecting precursors to earthquakes the scientific community is no closer to understanding why precursors are observed only in some cases laboratory measurements have demonstrated conclusively that self potentials develop owing to fluid flow and that both resistivity and magnetization change when rocks are stressed however field experiments have had much less success many purported observations of low frequency electrical precursors are much larger than expectations based on laboratory results in some cases no precursors occurred prior to earthquakes or precursory signals were reported with no corresponding coseismic signals nonetheless the field experiments are in approximate agreement with laboratory measurements maximum resistivity changes of a few percent have been observed prior to some earthquakes in china but the mechanism causing those changes is still unknown anomalous electric and magnetic fields associated with fluid flow prior to earthquakes may have been observed finally piezomagnetic signals associated with stress release in earthquakes have been documented in measurements of magnetic fields

deep water circulation at the northern pyrenean thrust implication of high temperature water rock interaction process on the mineralization of major spring water in an overthrust area abstract in an overthrust context of the northern pyrenean area groundwater is affected by high mineralization sources a multi isotopic approach was used to track the origin of mineralization in a complex multilayer aquifer system through the study of a major regional spring the oeillal spring water osw which shows a not yet investigated geochemical singularity the aims of this study are to understand the hydrogeochemical evolution and the mineralization mechanisms of groundwater in a large scale aquifer extending over the northern pyrenean overthrust oriental corbieres based on an adequate set of geochemical and isotopic tracers including cosmogenic stable and radiogenic isotopes we have revealed complex hydrogeochemical processes that cannot be tracked with traditional hydrochemical and isotopic tracers the high 87 sr 86 sr ratios of the osw associated with relatively high concentrations in trace elements cs rb sr b li suggest the influence of brine from the triassic deposits containing saliferous clay orsaline fluids from the fractured basement the basement hypothesis may be considered regarding the hydro geochemical fingerprint of the paleozoic basement as demonstrated in previous study and further data would be required to validate the contribution of basement fluids contrasting with marine primary brine and current seawater the relatively high 37 cl 0 22 and 0 39 of osw attests the non marine origin of the chloride ion 36 cl cl shows that the osw is issued from a mixing process between recently recharged water lightly mineralized and significantly marked in 36 cl by the thermonuclear bomb pulse and a saline deep end member at secular equilibrium this indicates that cl in these springs is primarily derived from subsurface non meteoric sources the osw s low br cl molar ratio suggests the influence of simple dissolution of halite and or the contribution of more complex secondary brine the deep saline water may results from meteoric infiltration into the lower jurassic aquifer in contact with triassic deposits or deeper high temperature promotes water rock interaction enhancing leaching of mg k rich saliferous clay this is supported by environmental scanning electron microscopy esem analyses showing that i cl is found in accessory minerals from the kcl mgcl 2 h 2 o system of the triassic deposits and ii cs rb molar ratio is similar to that of osw ranging between 0 13 and 0 7 and from 0 13 to 0 4 respectively laboratory experiments carried out on triassic material show that high temperature water rock interaction is suitable to explain the relatively high 87 sr 86 sr observed in groundwater such process can be investigated to confirm the deep origin of the osw and to explain the signature of deep brines in contact with the triassic deposits under high temperature conditions basement fluid contribution may also be considered regarding the hydro geochemical fingerprint of the paleozoic basement as shown in previous studies further data would be required to validate this hypothesis

earthquake predictions issued in greece by seismic electric signals since february 6 1990 abstract the present paper describes the results of all official predictions that were issued on the basis of seismic electric signals recorded in greece during the period feb 6 1990 may 31 1991 they amount to four cases of activities multiple events in two cases the predictions were also submitted for publication to tectonophysics before the beginning of the corresponding seismic activities while in a third case the prediction was announced during an international conference held in japan also before the occurrence of the earthquake after the submission of the manuscript a number of earthquakes occurred during the period up to may 31 1992 they are summarized along with their predictions in appendix 1

piezoelectric effects in quartz rich rocks abstract piezoelectricity a polarization of charge produced by an applied stress occurs in many minerals it is particularly strong in quartz aggregates of piezoelectric grains are themselves piezoelectric if the grains are suitably aligned such aggregates may be said to have a piezoelectric fabric thus quartz rich rocks may possess a piezoelectric fabric and this paper discusses the various possible fabrics to test whether a piezoelectric fabric might be detected in a quartz rich rock apparatus was built that hydraulically applied a sinusoidal stress to cubic specimens the three resulting orthogonal polarizations of charge were measured via a charge amplifier a specimen of pure quartz was used to verify the experimental method and to ensure that absolute piezoelectric moduli were being measured rocks with and without preferred orientation were tested of the latter types those containing little or no free quartz marble basalt did not exhibit measurable piezoelectric effects however all quartz rich rocks quartzites granites gneisses mylonites did show piezoelectric effects when stressed these effects were in two categories 1 1 effects due to piezoelectric fabrics called true piezoelectric effects 2 2 effects due to random distributions of the piezoelectric vectors called statistical effects to distinguish between these two effects three criteria were used firstly the measured effects were compared with the expected statistical effect for a rock of that grain size and composition secondly where possible multiple specimens were cut from the one rock sample all specimens with the same orientation specimens from a rock with a piezoelectric fabric should show similar results thirdly the optically observed c axis distribution and orientation was compared with the piezoelectrically predicted fabric and orientation this paper shows that while most rocks gave results consistent with statistical effects from a non polar or random distribution some rocks exhibited a true piezoelectric effect due to fabric this effect may be used with some imprecision to locate the a axes and c axes of quartz in the aggregate the polarities of the a axes are also obtained

experimental constraints on energy partitioning during stick slip and stable sliding within analog fault gouge abstract the lack of substantial frictional heat anomalies across major fault zones has been a key observation suggesting that faults support low shear stress during slip some studies have suggested that the lack of large thermal anomalies across faults may be a result of considerably less energy going to frictional heat than generally thought and that a large fraction of energy is dissipated by other processes such as the creation of new surface area we evaluate this hypothesis through the analysis of laboratory shear experiments for both stick slip seismic and stably sliding aseismic analog fault gouges these experiments differ from previous laboratory studies in that they 1 provide independent constraints on frictional heat generation and energy consumed generating new surface area 2 cover a broader range of shear stresses 2 20 mpa than most previous studies and 3 evaluate both stick slip and stable sliding within granular material based on the analysis of high precision temperature measurements and comparisons with numerical model simulations 90 of the total energy appears to go to frictional heat generation e h for all of our experiments we also show based on grain size analysis that 1 of total work is consumed generating new surface area e sa these results are consistent with assumptions allowing frictional resistance to be inferred from thermal data furthermore we observe no resolvable difference in the fraction of energy going to fracturing or frictional heat between stick slip and stable sliding experiments

simulating loss of primary silicate minerals from soil due to long term weathering using allogen comparison with soil chronosequence lake sediment and river solute flux data this paper presents allogen a process model of soil mineral chemical weathering though designed principally to aid interpretation of lake sediment geochemical records by providing mass balance constraints for competing interpretations the model is also applicable to more general questions about long term weathering and soil development the model is constructed around a generalised version of the mineral weathering submodel of profile modified to minimise the need for site specific data and to optimise performance for long term change comparison with observed weathering rate data river flux studies chronosequences and lake sediment chemical stratigraphy suggests that soil mineral depletion can be usefully simulated over timescales applicable to quaternary and holocene studies to illustrate this the plausibility of a weathering interpretation is demonstrated for sediment records at lake hope simpson and moraine lake and the lake chronosequence at glacier bay while long term soil mineral depletion appears predictable reliable simulation of past runoff quality is hampered by lack of a suitable long term model for soil carbon

the role of intragranular microtextures and microstructures in chemical and mechanical weathering direct comparisons of experimentally and naturally weathered alkali feldspars abstract electron microscopic observations of alkali feldspars from soils show that intragranular microtextures such as exsolution lamellae and microstructures primarily dislocations are both highly significant determinants of the weathering behaviour of these minerals in particular strained structure around intersecting edge dislocations in the plane of exsolution lamellae 6 01 dissolves at a rate which is orders of magnitude greater than unstrained feldspar producing a mesh of intersecting etch tubes extending 5 10 3 cm into the crystal as a result dissolution at dislocations is the major source of solutes during initial stages of chemical weathering in the field with progressive chemical weathering the most highly reactive feldspar is consumed by growth and coalescence of etch tubes but outer parts of the grain are physically weakened leading to mechanical flaking that increases available surface area and exposes further reactive sites in contrast previous dissolution experiments and microscopy of reacted surfaces have shown little or no correlation between dissolution rate and dislocation density and few visible signs of dissolution at particularly reactive sites to resolve the apparent discrepancy between field and laboratory behaviour we have carried out flow through dissolution experiments using ph 2 hcl at 25 c on three alkali feldspars with carefully characterized intragranular microtextures and microstructures these alkali feldspars were 1 eifel sanidine an alkali feldspar that has no microtextures at the tem scale and a low dislocation density 2 3 108 cm 2 and 3 naturally weathered alkali feldspars also from the shap granite which have the same microtextures as unweathered shap granite alkali feldspars but because they have been weathered have a lower density of dissolution reactive dislocations exposed on grain surfaces

naturally weathered feldspar surfaces in the navajo sandstone aquifer black mesa arizona electron microscopic characterization abstract naturally weathered feldspar surfaces in the jurassic navajo sandstone at black mesa arizona was characterized with high resolution transmission and analytical electron microscope hrtem aem and field emission gun scanning electron microscope feg sem here we report the first hrtem observation of a 10 nm thick amorphous layer on naturally weathered k feldspar in currently slightly alkaline groundwater the amorphous layer is probably deficient in k and enriched in si in addition to the amorphous layer the feldspar surfaces are also partially coated with tightly adhered kaolin platelets outside of the kaolin coatings feldspar grains are covered with a continuous 3 5 m thick layer of authigenic smectite which also coats quartz and other sediment grains authigenic k feldspar overgrowth and etch pits were also found on feldspar grains these characteristics of the aged feldspar surfaces accentuate the differences in reactivity between the freshly ground feldspar powders used in laboratory experiments and feldspar grains in natural systems and may partially contribute to the commonly observed apparent laboratory field dissolution rate discrepancy at black mesa feldspars in the navajo sandstone are dissolving at 10 5 times slower than laboratory rate at comparable temperature and ph under far from equilibrium condition the tightly adhered kaolin platelets reduce the feldspar reactive surface area and the authigenic k feldspar overgrowth reduces the feldspar reactivity however the continuous smectite coating layer does not appear to constitute a diffusion barrier the exact role of the amorphous layer on feldspar dissolution kinetics depends on the origin of the layer leached layer versus re precipitated silica which is uncertain at present however the nanometer thin layer can be detected only with hrtem and thus our study raises the possibility of its wide occurrence in geological systems rate laws and proposed mechanisms should consider the possibility of this amorphous layer on feldspar surface

electromagnetic elf radiation from earthquake regions as observed by low altitude satellites seismo electromagnetic sem waves observed by low altitude satellites passing over seismic regions were studied the data of the cosmos 1809 satellite were analysed over the earthquake region in armenia during the period from january 20 to february 17 1989 intense em radiation at frequencies below 450 hz was observed at the l shells of the earthquake during 12 orbits out of the 13 that passed within 6 in longitude from the epicenter and during 1 out of 6 in the range of 6 8 longitude away from this region the other orbits which passed 10 12 from the epicentre showed no effect to complete this study we used the emissions observed by another low altitude satellite aureol 3 it is shown that during the event the seismic region is permanently radiating the intensity and the envelope shape of the wave depend on its time relatively to the time of the earthquake their frequency spectra are compared to the average spectrum recorded in the same geomagnetic regions similar wave intensities and spectral distributions were observed on the two satellites during the seismic periods

seismo induced effects in the near earth space combined ground and space investigations as a contribution to earthquake prediction abstract the paper aims at giving a few methodological suggestions in deterministic earthquake prediction studies based on combined ground based and space observations of earthquake precursors up to now what is lacking is the demonstration of a causal relationship with explained physical processes and looking for a correlation between data gathered simultaneously and continuously by space observations and ground based measurements coordinated space and ground based observations imply available test sites on the earth surface to correlate ground data collected by appropriate networks of instruments with space ones detected on board of leo satellites at this purpose a new result reported in the paper is an original and specific space mission project esperia and two instruments of its payload the esperia space project has been performed for the italian space agency and three esperia instruments arina and lazio particle detectors and egle search coil magnetometer have been built and tested in space the egle experiment started last april 15 2005 on board the iss within the eneide mission the launch of arina occurred on june 15 2006 on board the resurs dk 1 russian leo satellite as an introduction and justification to these experiments the paper clarifies some basic concepts and critical methodological aspects concerning deterministic and statistic approaches and their use in earthquake prediction we also take the liberty of giving the scientific community a few critical hints based on our personal experience in the field and propose a joint study devoted to earthquake prediction and warning

rockmagnetic and palaeomagnetic studies of unconsolidated sediments of bukovynka cave chernivtsi region ukraine rockmagnetic palaeomagnetic and paleontological studies of loamy non consolidated sediments of the bukovynka cave chernivtsi region ukraine have been carried out the sections include three main types of deposits 1 fluvial deposits containing travertine grus derived from the karst massif 2 fluvial deposits derived from temporary waterflows from outside the cave 3 aeolian deposits deposits of type 2 and 3 were examined in sections 1 and 2 in the trapeznyi chamber their low field magnetic susceptibility r eflects climatic conditions in the late pleistocene the layer with cave hyena bones has higher magnetic susceptibility and appeared to indicate warmer climate deposits of type 1 and 2 were investigated in the section 3 in the dry chamber of the cave low field magnetic susceptibility of fluvial deposits derived from inside of the karst massif is much higher than for deposits derived from outside the cave deposits in section 3 sharply differ in nrm intensity and keonigsberger ratio the fluvial strata of type 1 in section 3 dated using paleontological remains as holocene contains the record of palaeosecular variations of the geomagnetic field the etrussia excursion dated 2 8 ka bp was found at 1 m depth in section 3 the lowest layer has anomalous polarity

comments on stable isotope geothermometry the system quartz water we show that the results of quartz water partial oxygen exchange experiments under hydrothermal conditions are determined primarily by exchange between water and dissolved silica species and not by diffusion in the solid hence these experiments do not provide an accurate value of the variation of fractionation with temperature but only a rough indication of it we conclude that the bottinga and javoy 1 equation relying on this type of information and on the precise calculation of the coefficient a 3 7 in the thermometric equation 1000 ln a b 106 t2 is not seriously questioned by these17o 18o partial exchange experiments

intermediate term earthquake prediction an earthquake of magnitude m and linear source dimension l m is preceded within a few years by certain patterns of seismicity in the magnitude range down to about m 3 in an area of linear dimension about 5l 10l prediction algorithms based on such patterns may allow one to predict approximately 80 of strong earthquakes with alarms occupying altogether 20 30 of the time space considered an area of alarm can be narrowed down to 2l 3l when observations include lower magnitudes down to about m 4 in spite of their limited accuracy such predictions open a possibility to prevent considerable damage the following findings may provide for further development of prediction methods i long range correlations in fault system dynamics and accordingly large size of the areas over which different observed fields could be averaged and analyzed jointly ii specific symptoms of an approaching strong earthquake iii the partial similarity of these symptoms worldwide iv the fact that some of them are not earth specific we probably encountered in seismicity the symptoms of instability common for a wide class of nonlinear systems

very slow moving crustal strain disturbances abstract a model of discrete crustal blocks separated by a thin weak transition zone whose stress strain relations contain derivatives of real order implying a memory mechanism in the medium seems to give a good explanation for the low velocity values 0 03 15 cm s of slow moving crustal strain disturbances tilt and strain anomalies observed before moderate and large earthquakes are thought to be generated in the focal zone of the forthcoming earthquake due to the spatial and temporal redistribution of the physical processes that occur during the preparation time of the earthquake on the basis of experimental results it has been assumed that these anomalies propagate from the hypocentral area in addition post seismic deformations show the effects of propagation the anomalies observed have a duration and a velocity ranging from minutes to months and from o o5 cm s to 10 cm s respectively the velocity of migration of post seismic deformation also lies in this range the velocity of propagating strain disturbances is obtained as a function of the frequency and of the linear dimension of the oscillating blocks the velocity values calculated using this model range from 0 1 cm s to 10 cm s for viscosities of 10 9 10 11 g cm 1 s 2 z 0 1 z 0 5 and blocksizes 1 4 10 6 cm at frequencies of 10 5 10 8 s 1

gypsum facies transitions in basin marginal evaporites middle miocene badenian of west ukraine in the middle miocene badenian gypsum basin of the carpathian foredeep west ukraine three main zones of gypsum development occur in the peripheral parts of the basin zone i consists entirely of stromatolitic gypsum formed in a nearshore zone zone ii is located more basinward and is characterized by stromatolitic gypsum in the lower part of the section overlain by a sabre gypsum unit zone iii occurs in still more basinward areas and is characterized by giant gypsum intergrowths or secondary nodular gypsum pseudomorphs of these in the lowermost part overlain by stromatolitic gypsum sabre gypsum and then by clastic gypsum units correlation between these facies and zones has been achieved using lithological marker beds and surfaces of particular importance for correlation is a characteristic marker bed usually 20 40 cm thick of cryptocrystalline massive gypsum occurring in zones ii and iii the marker was not distinguished in zone i possibly because this bed is older than the entire gypsum section of that zone these new results strongly suggest that the deposition of giant gypsum intergrowth facies and stromatolitic gypsum facies was coeval in some sections of zones i and ii limestone intercalations have been recorded within the upper part of the gypsum sections considerable scatter of the 18o and 13c values of these limestones indicates variable diagenetic overprints of marine carbonates but a marine provenance of the limestones is confirmed by microfacies analysis some of the limestones are coeval with an intercalation of gypsarenitic mostly laminated gypsum occurring in the sabre gypsum unit of zones ii and iii badenian gypsum formed in extremely shallow water to subaerial environments on broad very low relief areas of negligible brine depth which could be affected by rapid transgressions stable isotope 34s 18o studies of the gypsum demonstrate that the sulphate was of sea water origin or was derived from dissolution of miocene marine evaporites investigations of individual inclusions in the gypsum indicate decreased water salinity when compared with modern marine derived calcium sulphate saturated water groundwater influences are indicated by high calcium sulphate contents of the brines in the evaporite basin the chemical composition of badenian waters was thus a mixture of relic sea water depleted in nacl groundwater enriched in calcium sulphate and surface run off

high frequency seismo electromagnetic effects abstract electromagnetic perturbations caused by natural geophysical activity such as earthquakes and volcanic eruptions have been studied since the great alaskan earthquake in 1964 in recent years interest has been increasing because when a precursor event occurs it normally does so less than a few hours before the shock this paper presents a review of the high frequency seismo electromagnetic phenomena already observed and occurring before as well as after the shock the term high frequency is to be taken in the seismic sense i e larger than a few hertz mechanisms that might produce these seismo electromagnetic emissions will be described it is shown that at the moment a causal relationship between electromagnetic signals and seismic activity still remains to be demonstrated theoretical as well as intensive experimental studies are necessary to understand the physical processes responsible for seismo or volcano electric variations electrical resistivity variations electromagnetic effects associated with dilatance as well as electromagnetic fields generated during laboratory experiments or ionospheric disturbances

experimental study of igneous and sedimentary apatite dissolution control of ph distance from equilibrium and temperature on dissolution rates apatite dissolution experiments were conducted using both a fluidized bed and stirred tank reactor over a range of ph temperature solution saturation state and on non carbonated and carbonated apatite compositions igneous fluorapatite fap and sedimentary carbonate fluorapatite cfa respectively from 2 8 5 were not possible due to detection limits of the analytical techniques used in this study and the high insolubility of fap for the cfa compositions studied the dissolution rate decreased with increasing ph from 4 ph 7 during early stages of the dissolution reaction for both fap and cfa mineral components were released in non stoichiometric ratios with reacted solution ratios of dissolved ca p and ca f being greater than mineral stoichiometric ratios suggesting that ca was preferentially released compared to p and f from the mineral structure during the early stages of dissolution an increase in reacted solution ph accompanies this early elevated release of ca as the dissolution reaction proceeded to steady state dissolution became congruent when normalized to bet measured surface area fap dissolved faster from 4 ph 7 compared to cfa the apparent arrhenius activation energy ea of fap dissolution over the temperature range of 25 55 c at ph 3 0 i 0 1 and pco2 0 is 8 3 0 2 kcal mol 1 both the apparent exchange of solution h for solid bound ca at low ph in the early stage of dissolution and the ea of dissolution suggest a surface and not a diffusion controlled dissolution reaction for fap and cfa the degree of undersaturation of the solution gr with respect to fap was important in determining the dissolution rate at ph 3 0 i 0 1 and pco2 0 the dissolution rate of fap was 5 greater in the far from equilibrium region compared to the near equilibrium slope region a simple apatite weathering model incorporating the experimental results from this study was constructed and numerical calculations suggest that during the phanerozoic both the surface area of igneous rock available for weathering and the average global temperature were important factors in determining the p weathering flux from apatite dissolution it is possible that elevated global temperatures coupled with relatively high surface area of igneous rock during the early to mid paleozoic resulted in elevated p weathering fluxes which along with climatic evolutionary pressures of the neoproterozoic facilitated the radiation of multicellular organisms large scale phosphorite deposition and abundance of calcium phosphate shelled organisms during the early cambrian

development of a fracture network in crystalline rocks during weathering study of bishop creek chronosequence using x ray computed tomography and 14c pmma impregnation method the progressive development of porosity during subsoil weathering of granodiorite clasts was studied at the bishop creek moraine chronosequence in east central california fractures and other pores were examined using two complementary imaging techniques x ray computed tomography xrct and a 14c pmma 14c polymethylmethacrylate method the well known xrct method allows the investigation of three dimensional 3 d pore space 14c pmma is a less known method based on the complete impregnation of pore space with 14c doped pmma and subsequent autoradiograph of a rock section these imaging methods allow us to decipher the evolution of pore space in the granodiorite during the 120 k y weathering period the 14c pmma imaging technique was found to be more suitable for following the evolution of the whole sequence from intact bedrock to saprock in terms of crack density porosity and aperture working with hand specimens this method was adapted to detect both the low aperture fractures microcracks and macrocracks only a slight and progressive increase in total fracture density was observed during the whole weathering period however this trend does not hold if macrocracks and microcracks are separated microcrack density slightly decreases whereas macrocrack density increases due to a progressive expansion of microcracks the total porosity of the rock increases during weathering and is correlated to the progressive aperture increase of all types of cracks this evolution is accompanied by a change of crack morphology and connectivity and an overall increase in intragranular porosity of biotite and plagioclase aggregates

current denudation rates in dolostone karst from central spain implications for the formation of unroofed caves abstract rock tablets of known weight were buried in the soil of a karst region in central spain to evaluate the carbonate weathering during a period of a year the experiment was conducted at two different soil depths 5 10 and 50 55 cm from the surface the parental rock used in the experiment is composed of dolomite and magnesite with variable proportion of accessory minerals and minor elements soil mineral and chemical composition as well as its texture was also characterized meteorological conditions at the site together with temperature and co2 in both soil levels were monitored sets of tablets were retrieved after 6 and 12 months of the start of the experiment to account for seasonal weathering different lithologies do not exhibit significant differences in weathering although a large inter sample variability is attributed to variable size and distribution of the porosity results show an enhanced weathering during the wet and cold season that accounts for 78 1 of the total annual weathering rock tablets examined under scanning electron microscopy prior and after exposure to natural environment show that most of the material lost occurred along cracks edges or large pores although dissolution is a common process most of the weathering is due to crystal detachment rock tablets at the depth of 5 10 cm were weathered 68 1 more than those set at 50 55 cm from the surface higher soil moisture and concentration of co2 were found deeper in the soil which likely enhanced the dissolution of carbonate however physical weathering dominated weight loss of rock tablets at both soil depths especially at the 5 10 cm level where soil thermal and moisture cycles were more frequent and greater denudation rate calculated from the 12 months set provides values of 2 48 1 07 m yr and 1 75 0 66 m yr at the depths of 5 10 and 50 55 cm respectively since the conditions at the average contact between soil and bedrock are similar to those at the 50 55 cm depth we consider that this is a more reliable denudation rate for the studied location during the studied period the calculated weathering rate suggests that denudation has a limited contribution to the thinning of bedrock over caves at this site therefore we consider that the formation of unroofed caves in this region most likely results from the thinning of bedrock cover over caves due to collapse of blocks from their ceilings

vlf emissions associated with earthquakes and observed in the ionosphere and the magnetosphere abstract several electromagnetic phenomena recorded at the time of earthquakes were recorded independently by the geostationary satellite geos 2 above africa longitude 37 e and the polar orbiting satellite aureol 3 apogee 2012 km perigee 408 km inclination 82 5 period 109 5 min the observations were made with magnetic and electric antennae in the frequency range 10 hz 15 khz characteristics of the emissions and differences between low and high altitude observations are presented some geos 2 very low frequency data can be correlated with ionospheric measurements made on ground at the djibouti station latitude 11 n longitude 42 e where increases of the critical frequency f 0 e s of the sporadic e s layer are observed when earthquakes occur nearby time differences between disturbance at ionospheric level and at the height of geos 2 seem to indicate that earthquakes cause two distinct types of electromagnetic disturbance an electromagnetic wave in the ionosphere and a density increase of the e s layer

fault mechanics and the kinematics of block rotations in many strike slip tectonic settings large rotations up to 100 of crustal blocks have been inferred from paleomagnetic data these blocks are bounded by sets of parallel faults which accommodate the relative motion between the blocks as regional deformation progresses simple geometrical considerations require that the faults must also rotate in this paper we show that on the basis of mechanical considerations the amount of fault rotation permissible under a stationary stress field is limited to 20 to 45 consequently block rotations that are larger than 40 or 45 require more than one set of accompanying faults to accommodate the block rotation examples of such multiple sets with 40 to 45 between them as predicted by the model were recognized in sistan iran in yerington the lake mead area nevada and in southern california

87sr 86sr of brines from the fennoscandian shield a synthesis of groundwater isotopic data from the baltic sea region high salinity ca na cl brines occur in sweden and finland the complex geological history of the fennoscandian shield is reflected by the wide range of saline waters whose chemical compositions have been explained by local water rock interaction simple evolution of relict sea water or freezing of sea water during glacial periods this study deals with the present knowledge of sr isotopes in groundwater from the fennoscandian shield to better constrain the origin of their deep saline component two different mixing trends are seen between aspo island groundwater and the baltic sea the first trend links the north sea to rivers through various dilution levels in the baltic the second trend is a simple linear relationship through aspo groundwaters agreeing with a binary mixing between a baltic end member and a highly sr concentrated fluid strontium isotope compositions are presented for precipitation in finland and sweden the baltic sea and the river waters draining the fennoscandian shield and for g

a mossbauer spectroscopy and x ray diffraction study of ordinary chondrites quantification of modal mineralogy and implications for redox conditions during metamorphism we present a method that combines mssbauer spectroscopy and x ray diffraction to quantify the modal mineralogy of unequilibrated ordinary chondrites uocs despite being a fundamental tool in the interpretation of geological systems there are no modal mineralogical data available for these meteorites this is due to their fine grained nature highly heterogeneous silicate mineralogy and the presence of poorly characterized phases consequently it has not been possible to obtain accurate modal mineralogy by conventional techniques such as point counting here we use mssbauer spectroscopy as a preliminary identification technique and x ray diffraction provides the quantification for a suite of recent uoc falls we find the most primitive uocs to contain a significant amount of phyllosilicate material that was converted during metamorphism to form ferromagnesian silicates a complete suite of antarctic samples is analyzed by each method to observe mineralogical trends and these are compared with trends shown by recent falls the fact that mineralogical relationships shown by finds and falls are in agreement allows us to be confident that we are observing the products of pre terrestrial alteration mssbauer spectroscopy reveals evidence of steadily increasing reduction with metamorphism in the uocs because this technique allows comparisons to be made between uocs and eocs our reduction sequence can be combined with other evidence showing progressive oxidation in the eocs this yields an integrated model of changing redox conditions on equilibrating ordinary chondrite parent bodies

chrysotile dissolution rates implications for carbon sequestration abstract serpentine minerals e g chrysotile are a potentially important medium for sequestration of co2 via carbonation reactions the goals of this study are to report a steady state far from equilibrium chrysotile dissolution rate law and to better define what role serpentine dissolution kinetics will have in constraining rates of carbon sequestration via serpentine carbonation the steady state dissolution rate of chrysotile in 0 1 m nacl solutions was measured at 22 c and ph ranging from 2 to 8 dissolution experiments were performed in a continuously stirred flow through reactor with the input solutions pre equilibrated with atmospheric co2 both mg and si steady state fluxes from the chrysotile surface and the overall chrysotile flux were regressed and the following empirical relationships were obtained f mg 0 22 ph 10 02 f si 0 19 ph 10 37 f chrysotile 0 21 ph 10 57 where fmg fsi and fchrysotile are the log10 mg si and molar chrysotile fluxes in mol m2 s respectively element fluxes were used in reaction path calculations to constrain the rate of co2 sequestration in two geological environments that have been proposed as potential sinks for anthropogenic co2 carbon sequestration in chrysotile tailings at 10 c is approximately an order of magnitude faster than carbon sequestration in a serpentinite hosted aquifer at 60 c on a per kilogram of water basis a serpentinite hosted aquifer however provides a larger sequestration capacity the chrysotile dissolution rate law determined in this study has important implications for constraining potential rates of sequestration in serpentinite hosted aquifers and under accelerated sequestration scenarios in mine tailings

isotopic identification of natural vs anthropogenic sources of pb in laramie basin groundwaters wyoming usa water well samples precipitation and leachates of aquifer rock samples from the laramie basin wyoming were analyzed to test the suitability of pb isotopes for tracing hydrologic processes in a basin where sr isotopes had proven effective leachable pb from host rocks to aquifers in this basin have isotopically distinct compositions and isotopic tracing would be effective in differentiating natural sources of pb however in almost all cases this natural signal is apparently swamped by anthropogenic pb sources in drilled water wells the isotopic compositions of these samples cannot be produced by any combination of pb in precipitation and leached pb from the aquifers alone but are consistent with mixtures of anthropogenic pb thorogenic 208pb vs uranogenic 206pb 207pb pb was especially useful for discriminating natural from anthropogenic sources for these samples it is strongly recommended that all four pb isotopes be reported in hydrologic and environmental studies that employ this approach

water rock interaction in the bisagno valley genoa italy application of an inverse approach to model spring water chemistry abstract the chemical evolution of the bisagno valley spring waters ranging from initial ca hco3 towards final na hco3 composition is reconstructed with a reaction progress scheme defined by a fractional degree of advancement of the irreversible mass transfer process and attaining the continuum limit during water rock interaction the system is solved in terms of a transposed reaction rate vector introducing the experimental kinetic rate constants and solving for the surface areas of dissolving albite and k feldspar and precipitating carbonates this is also done by considering the activities of dissolved silica and al3 ion as constrained by the instantaneous equilibrium with quartz and kaolinite respectively the results of this inverse geochemical model are fully consistent with those obtained using the eq3nr eq6 forward code provided this last is run in iterative way changing progressively the surface areas of solid reactants and fco2 values accounting for the compositional dependence of the kinetic rate constants of plagioclase and alkali feldspar allows explanation of the progressive albitization of the mt antola formation through a kinetic phenomenon involving nowadays circulating fluids the comparison of computed surface areas with estimates based on the modal mineralogy grainsize and intergranular porosity of the arenitic siliciclastic beds outlines the importance of fracture driven flow in agreement with available lugeon flow tests

age and origin of base and precious metal veins of the coeur d alene mining district idaho ore bearing quartz carbonate veins of the coeur d alene mining district yield 87sr 86sr ratios of 0 74 to 1 60 for low rb sr carbonate gangue minerals similar to current ranges measured in middle proterozoic high rb sr rocks of the belt supergroup stable isotope and fluid inclusion studies establish a genetic relationship between vein formation and metamorphic hydrothermal systems of the region these extraordinary 87sr 86sr ratios require accumulation of radiogenic 87sr in a high rb sr system over an extended period prior to incorporation of sr into the hydrothermal veins evaluation of the age and composition of potential sources of highly radiogenic sr indicates that the ore bearing veins of the coeur d alene district formed during the cretaceous from components scavenged from rocks of the belt supergroup the primary host rocks of the district proterozoic pb isotope ratios observed in galena from many coeur d alene veins were established when pb separated from uranium during deposition or diagenesis of the belt supergroup at 1400 to 1500 ma possibly as disseminated syngenetic deposits k ar and rb sr apparent ages and 18o values of belt supergroup rocks decrease from the coeur d alene district toward the idaho and kaniksu batholiths approximately normal to the trends of metamorphic isograds fold axes foliation and the major reverse faults of the district isoclinal folding thrust faulting high temperature metamorphism granitic plutonism and regional scale metamorphic hydrothermal activity is documented in the region between 140 and 45 ma representing the only such combination of events in the coeur d alene region subsequent to about 1300 ma the sr and oxygen results and geologic evidence favor formation of the ore bearing carbonate veins by fluids related to a complex metamorphic hydrothermal system during the cretaceous pb with proterozoic isotopic compositions was probably mobilized and incorporated like other metals into the hydrothermal veins during this event the ore bearing veins were sheared and displaced during early tertiary northwest trending dextral strike slip faulting along the osburn fault and related structures of the lewis and clark line

ultra low frequency magnetic field measurements in southern california during the northridge earthquake of 17 january 1994 measurements of ultra low frequency ulf magnetic field fluctuations by two independent monitoring systems in southern california were in progress during january 1994 when the moderately large m6 7 northridge earthquake occurred on 17 january our two measuring systems are located at table mountain on the other side of the san gabriel mountains and at a distance of 81 km from the epicenter and at pinon flat south of palm springs and at a distance of 206 km from the epicenter both systems operated well throughout the month and without interruption due to the earthquake as a result of the occurrence of a moderate magnetic storm on 11 january which was followed by a period of enhanced ulf magnetic activity that persisted until after the time of the earthquake the sensitivity of our measurements throughout california was reduced for roughly a week before the earthquake took place nevertheless no large signals that could be associated with the earthquake were evident at any time except for the usual co seismic shaking response of the detectors subsequent removal of the upper atmosphere signals from the table mountain measurements using the measurements from the more distant pinon flat location as reference essentially left no significant residual thus assuming that ulf magnetic fields were produced by the earthquake their amplitudes were too small to produce obvious increases in the ulf background noise at 81 km from the epicenter which is in agreement with our earlier estimate of a range of about 100 km for the ulf magnetic field fluctuations observed prior to the m7 1 loma prieta earthquake these results imply that a network of conventional magnetic field detectors spaced less than 100 km apart would be required to detect ulf magnetic field fluctuations prior to earthquakes with magnitudes greater than 7 under the same conditions superconducting magnetic field gradiometers could offer greater sensitivity and range