comparison of berkeley and calnet magnitude estimates as a means of evaluating temporal consistency of magnitudes in california abstract magnitude estimates have been calculated independently by berkeley and the u s geological survey for a large number of events in central california the berkeley magnitudes have been determined using a stable set of wood anderson seismometers for many decades this relative stability allowed us to compare calnet magnitudes with the berkeley magnitudes in an attempt to evaluate the temporal stability of the calnet magnitudes the comparisons were carried out in six different regions of central california for events with 2 5 m berkeley

the fallacy of the shallow water problem in marine csem exploration the recent explosion of activity in offshore controlled source electromagnetic csem exploration has shown both theoretically and in practice for the time harmonic case that shallow water environments depths less than say 300 m can pose a significant challenge for detection and characterization of thin resistive targets in the subsurface because the weakly attenuated atmospheric response overprints the weaker target response as an alternative the transient csem experiment is considered to explore the nature of the airwave signature when viewed from the perspective of csem time series the signature of a thin isolated resistive horizon is computed by using the quasi analytic solution for a 1d earth in response to excitation by a horizontal electric dipole antenna that signature clearly seen in the transient data generally lies in the time interval between the arrivalof the airwave and the late time seawater response the fact that either decreasing the water depth or increasing the source r

comment on changes of reporting rates in the southern california earthquake catalog introduced by a new definition of ml by thessa tormann stefan wiemer and egill hauksson abstract earthquake catalogs can be inhomogeneous because of changes in the definition of earthquake magnitude provided that a sufficient number of events have magnitudes defined in more than one system it is possible to apply a monte carlo method to the observed joint distribution to convert sets of magnitudes from one system to another improving any statistical analysis of the catalog i demonstrate the method for the southern california catalog in which the definition of local magnitude has recently been changed monte carlo magnitude mapping appears to eliminate temporal changes that are otherwise present

subsurface imaging using magnetotelluric data a linear programming approach is developed to construct a pseudo impulse response for magnetotelluric mt data the constructed time function is made up of discrete pulses whose amplitudes depend upon the electromagnetic reflection and transmission coefficients at various layer interfaces the arrival time of an individual pulse corresponds to the time for a reference signal to travel a particular raypath from the surface to a reflector and back the display of the impulse responses recovered from many stations produces an mt reflectivity section which is analogous to the image ray section regularly interpreted in reflection seismology application of linear programming inversion to one dimensional conductivity models shows the viability of the method and validates the physical interpretation of the pseudo impulse response function using a number of simple two dimensional geologic models we show that a line of mt stations acquired perpendicular to strike produces a reflectivity section which is an imag

changes of reporting rates in the southern california earthquake catalog introduced by a new definition of ml starting january 2008 local magnitudes m l for southern california are determined by a new calibration that provides various improvements for determining m l for small earthquakes magnitudes for the previous years are being recalculated and the catalog continuously updated with the first year of overlapping data now being available recalibrating a magnitude scale can cause a break in homogeneity of reporting and often produces artifacts in the catalog statistics that can influence a wide range of seismicity studies to search for such a break we compare the old m l and the new m l catalogs for 2007 we find 1 the two magnitude values differ for 96 of the m l events and hand determined magnitudes are also revised 2 the magnitude differences are irregular from magnitude increases of up to 1 5 units to reductions by as much as 2 3 units with an average change of 0 13 units 3 the number of events above m 1 8 decreases by 32 for the new magnitude scale 4 the completeness magnitude apparently drops by 0 3 units from 1 6 to 1 3 5 the b value reduces by approximately 0 2 units dropping from 1 16 to 0 95 6 the new magnitude calibration produces a more stable b value estimate and can therefore be regarded as the better scaling we document selected examples of how the change in magnitude calibration may affect seismicity and hazard related analyses that are based on the southern california seismic network scsn catalog especially the change of the b value from 1 1 to 0 9 has potentially major implications for hazard related applications

mineralogical and geochemical characterisation of open air tailing and waste rock dumps from the libiola fe cu sulphide mine eastern liguria italy active acid mine drainage amd processes at the libiola fe cu sulphides mine are mainly triggered by water rock interaction occurring within open air tailing and waste rock dumps these processes are mainly controlled by exposure to weathering agents the grain size of the dumped materials and by the quantity of sulphides the sulphide types and their mode of occurrence due to these factors several paragenetic stages of evolution have been recognised at different depths at different sites and within the same site the dump samples were investigated with mineralogical reflected and transmitted light optical microscopy xrpd and sem eds and geochemical icp aes leco techniques the amd evaluation of the tailing and waste rock samples was performed by calculating the maximum potential acidity the acid neutralising capacity and the net acid producing potential the results allowed us to demonstrate that the open air tailings had already superseded their amd apex and are now practically inert material composed mainly of stable goethite lepidocrocite hematite assemblages on the contrary the sulphide rich waste rocks still have a strong potential to produce long term amd causing the acidification of circulating waters and the release of several hazardous elements

the behavior of trace elements during schwertmannite precipitation and subsequent transformation into goethite and jarosite schwertmannite is a ubiquitous mineral formed from acid rock drainage ard and plays a major role in controlling the water chemistry of many acid streams the formation of schwertmannite was investigated in the acid discharge of the monte romero abandoned mine iberian pyrite belt sw spain schwertmannite precipitated from supersaturated solutions mainly owing to the oxidation of fe ii to fe iii and transformed with time into goethite and jarosite in a few hours schwertmannite precipitation removed more than half of the arsenic load from solution whereas the concentration of divalent trace metals zn cu pb cd ni and co remained almost unchanged in the laboratory natural schwertmannite was kept in contact with its coexisting acid water in a flask with a solid liquid mass ratio of 1 5 for 353 days during this time the ph of the solution dropped from 3 07 to 1 74 and the concentrations of sulfate and fe increased during the first 164 days schwertmannite transformed into goethite plus h3o jarosite but subsequently goethite was the only mineral to form some of the trace elements such as al cu pb and as were depleted in solution during the first stage as schwertmannite transformed into goethite plus h3o jarosite on the contrary the transformation of schwertmannite to goethite with no jarosite during the second stage released al cu and as to the solution despite the variation in their concentrations in solution approximately 80 of the total al and cu inventories and more than 99 as and pb remained in the solid phase throughout the entire aging process

direct observation of heavy metal mineral association from the clark fork river superfund complex implications for metal transport and bioavailability two sets of samples from riverbeds and adjacent floodplains separated by 80 river kilometers were collected from the clark fork river superfund complex montana the largest superfund site in the united states and studied primarily with transmission electron microscopy tem with several supporting techniques to determine heavy metal mineral association seven of the eight samples studied were strongly influenced by material that once resided in mining and smelting dumps and impoundments this material was transported downstream sometime during the last century and a half from the butte anaconda areas the eighth sample was from a deeper floodplain level and dates to premining days the tem observations afford a direct look down to the nanometer level at secondary mineral formation as a result of the breakdown of sulfides and silicates in the acid environment of this massive mine drainage system in the shallow oxic floodplain sediments heavy metals of concern in this system as cu pb and zn are taken up by the formation of sulfates particularly pb in jarosite as well as hydrous metal oxides as cu pb and zn in and on ferrihydrite and a possibly new vernadite like mineral the oxides are long lived in these systems as they were also found in the anoxic riverbeds metals are also taken up by the formation of sulfides in sulfate reducing environments as observed in the formation of nanoclusters of chalcopyrite and sphalerite in all samples clays make up between 5 and 20 of the sediment and carry significant amounts of cu and zn the hydrous oxides secondary sulfides and clays provide several routes for metal transport downstream over long distances besides the potential bioavailability of heavy metals exchanged on and off the hydrous metal oxides and clays nanometer sized sulfides may also be highly reactive in the presence of biologic systems

electromagnetic active source sounding near the east pacific rise an active source electrical conductivity sounding was carried out near the east pacific rise at 21 n the average electrical conductivity from 2 km beneath the seafloor into the upper mantle was found to be about 0 004 s m there is no evidence of fully molten magma at a distance of 7 km from the spreading axis the inferred conductivity with depth of the crustal rock is consistent with brace s model of connected seawater filled pores in rocks heated from beneath

effects of the airwave in time domain marine controlled source electromagnetics in marine time domain controlled source electromagnetics csem there are two different acquisition methods with horizontal sources for fast and simple data acquisition or with vertical sources for minimizing the effects of the airwave illustrations of the electric field as a function of space and time for various source antenna orientations based on analytical formulation of the electric field in two half spaces provide insights into the properties of the airwave and the nature of diffuse electric fields observing the development of the electric field over time and space reveals that diffusive fields exhibit directionality therefore techniques that have thus far mostly been applied to wavefields can be adapted for csem examples range from the well known up down decomposition to beam steering vertical sources have the advantage of not creating an airwave on the other hand it is quite difficult to achieve perfect verticality of the source antenna results using a numerically modeled data set to analyze the impact of the airwave on a signal from a subsurface reservoir in the case of a slightly dipping vertical source indicate that already for a dip of 0 05 the airwave contributes 20 to the complete electric field in our configuration of reservoir depth water thickness and conductivity values

precipitation of fe iii oxyhydroxide deposits from shallow water hydrothermal fluids in tutum bay ambitle island papua new guinea abstract previous research on sea floor fe iii oxyhydroxide deposits has focused primarily on deep sea hydrothermal systems found along volcanically active portions of the mid ocean ridges and on hydrogenetic deposits formed in deep basins and along continental shelves there is however not much known about their formation in shallow water settings associated with volcanic islands the hydrothermal system at ambitle island papua new guinea provides an excellent opportunity to study the formation of fe iii oxyhydroxides in a shallow water setting precipitation from the hydrothermal solution is caused by mixing with seawater based on a 87 sr 86 sr mixing model the calculated minimum and maximum seawater fractions are approximately 11 and 57 respectively thus precipitation of tutum bay fe iii oxyhydroxides takes place at a temperature range between approximately 60 and 93 c the chemical composition shows low mn contents fe mn 600 and elements that are usually enriched in fe iii oxyhydroxides such as co and v are below crustal abundance and well below their concentrations in island arc volcanics arsenic concentrations on the other hand are by two orders of magnitude higher than those in other marine deposits rare earth element ree concentrations reflect their concentration in the hydrothermal fluids rather than seawater the crystallinity of the deposits increases with age as protoferrihydrite is apparently altered to fe smectite and hematite and as bearing minerals are formed contact with seawater and therefore oxidizing conditions seems to be the factor increasing the crystallinity

spatial variability of arsenic in some iron rich deposits generated by acid mine drainage abstract potential contamination of rivers by trace elements can be controlled among others by the precipitation of oxyhydroxides the streambed of the studied area located in la ch taigneraie district lot river basin france is characterised by iron rich ochreous deposits acidic ph 2 7 4 8 and so 4 mg waters beyond the acid mine drainage the presence of as both in the dissolved fraction and in the deposits is also a problem upstream at the gallery outlet as concentrations are high as max 2 6 mol l and up to 5 wt locally respectively in the dissolved and in the solid fractions downstream as concentrations decrease below 0 1 mol l in the dissolved fraction and to 1327 mg kg in the solid fraction this natural attenuation is related to the as retention within ochreous precipitates amorphous to poorly crystalline fe oxyhydroxides schwertmannite and goethite which have great affinities for this metalloid upstream schwertmannite is dominant while downstream goethite becomes the main mineral the transformation of schwertmannite into goethite is observed in the upstream deposits as schwertmannite is unstable relative to goethite furthermore thermodynamic calculations indicate that the downstream goethite is not able to precipitate in situ according to the water chemistry goethite mainly results from the transformation of schwertmannite and its solid transport downstream moreover as highlighted by leaching experiments carried out on the ochreous precipitates this transformation does not seem to affect the as retention in solids as no release of as was observed in the solution arsenic may either be strongly trapped by co precipitation in the present minerals or it may be quickly released and re adsorbed on the precipitate surface

precipitation in pores a geochemical frontier the purpose of this article is to review some of the recent research in which geochemists have examined precipitation of solid phases in porous media particularly in pores a few nanometers in diameter nanopores while this is a review it is actually more forward looking in that the list of things about this phenomenon that we do not know or cannot control at this time is likely longer than what we do know and can control for example there are three directly contradictory theories on how to predict how precipitation proceeds in a medium of varying pore size as will be discussed below the confusion on this subject likely stems from the complexity of the phenomenon itself one can easily clog a porous medium by inducing a rapid homogeneous precipitation directly from solution or have limited precipitation occur that does not affect permeability or even porosity substantially it is more difficult to engineer mineral precipitation in order to obtain a specific outcome such as filling all available pore space over a targeted area for the purposes of contaminant sequestration however breakthrough discoveries could occur in the next five to ten years that enhance our ability to predict robustly and finely control precipitation in porous media by understanding how porosity and permeability evolve in response to system perturbations these discoveries will likely stem at least in part from advances in our ability to 1 perform and interpret x ray neutron scattering experiments that reveal the extent of precipitation and its locales within porous media anovitz and cole 2015 this volume and 2 utilize increasingly powerful simulations to test concepts and models about the evolution of porosity and permeability as precipitation occurs steefel et al 2015 this volume a further important technique to isolate specific phenomena and understand reactivity is also microfluidics cell

splitting marine controlled source electromagnetic responses into sea and subseafloor contributions grounding the air wave abstractwe have found how the effects of the air wave in marine controlled source electromagnetic csem methods gradually vanish in the sea for shallow waters and how at the same time they gradually grow below the seafloor in an effort to comprehend existing detectability definitions the transition from sea to land is smooth because the sea becomes a thin conductive layer when the water depth is smaller than the skin depth in the sea we consider the problem of detecting resistive layers at depth associated with hydrocarbon reservoirs particularly in shallow water explorations and specifically on how the air wave affects detection our analysis is based on an integral representation of the electric field in terms of its sensitivity to changes in the electrical conductivity of a 1d profile two dimensional images of the integrands are obtained by plotting the integrand as a function of depth for different offsets results include the expected growth of the inhibiting effect of the sea as the water d

randomness of megathrust earthquakes implied by rapid stress recovery after the japan earthquake the 2011 tohoku oki earthquake released stress within a subduction zone analysis of seismic data shows that stresses returned to pre quake levels within a few years implying that large quakes could occur more often than previously thought

ten years of marine csem for hydrocarbon exploration marine controlled source electromagnetic csem surveying has been in commercial use for predrill reservoir appraisalandhydrocarbonexplorationfor10 years althougha recent decrease has occurred in the number of surveys and publications associated with this technique the method has become firmly established as an important geophysical tool intheoffshoreenvironment thisisaconsequenceoftwoimportant aspects associated with the physics of the method first it is sensitive to high electrical resistivity which although not an unambiguous indicator of hydrocarbons is an important property of economically viable reservoirs second although the method lacks the resolution of seismic wave propagation it has a much better intrinsic resolution than potential field methods such as gravity and magnetic surveying which until now have been the primary nonseismicdatasetsusedinoffshoreexploration althoughbymany measures marine csem is still in its infancy the reliability and noise floors of the instrument systems have improved significantly over the last decade and interpretation methodology has progressed from simple anomaly detection to 3d anisotropic inversion of multicomponent data using some of theworld sfastestsupercomputers researchdirectionspresently include tackling the airwave problem in shallow water by applying time domain methodology continuous profiling tools and the use of csem for reservoir monitoring during production

asymptotic airwave modeling for marine controlled source electromagnetic surveying marine controlled source electromagnetic csem surveying also called seabed logging is a technique for finding resistive layers in the subsurface which can be hydrocarbon saturated reservoirs the em signal from the horizontal electric dipole source induces an airwave along the air sea surface that interferes with the signal from the subsurface and dominates at larger offsets the airwave commonly denotes the energy that propagates from the source via the atmosphere to the receiver on the seabed the airwave component is especially problematic in shallow waters where it is less attenuated during its up and down propagation in the water column than for deeper waters an asymptotically derived space domain equation that describes the airwavecomponent in a water half space bounded by air is well known from the em literature we demonstrate that by taking into account the reflections and reverberations of the airwave component in the water column between the seabed and the sea surface at both the source

different types of fine grained sediments associated with acid mine drainage in the libiola fe cu mine area ligurian apennines italy abstract different types of fine grained chemical precipitates were characterized in the surroundings of the pyrite chalcopyrite mine of libiola northern italy both water chemistry and sediment composition were used to investigate metal mobility near the mine area local drainage waters were very acidic with a ph as low as 2 5 and were rich in dissolved metals fe al cu zn mn ni sediments associated with low ph water ph

microseisms and its impact on the marine controlled source electromagnetic signal the marine controlled source electromagnetic method mcsem is employed for studying the electrical characteristics and fluid contents of sedimentary reservoirs however the success rate of the method can be improved significantly by finding the sources of electromagnetic noise and addressing the challenge posed by them at larger offsets where the reservoir signal is often weak i have studied the mcsem data and reporting an electromagnetic noise the strength of the noise is observed 1600 times stronger than the seafloor mcsem signal at 0 1 hz moreover the noise and the transmitted mcsem signals are found coherent in interstation recordings these readings suggest the severity of the noise the source investigation presuming the observed noise as an infragravity wave failed to match the response then the role of microseisms is investigated microseism causes oscillation of the seafloor and produces electromagnetic disturbances by the dynamics of water i have used various conditions for a proper discrimination of the noise as microseisms this mechanism is clearly illustrated with the help of a conceptual diagram the role of the directionality is part of the study which is argued for having a significant role in the generation of microseisms in this paper a new algorithm is presented and is used for calculating the coherency the algorithm helps in mapping the coherency value simultaneously in time and frequency domains

carbonate compositions in cm and ci chondrites and implications for aqueous alteration abstract carbonate minerals in fourteen cm chondrites and two ci chondrites have been analyzed by electron microprobe to provide a better understanding of the aqueous processes that affected carbonaceous chondrite parent bodies calcites in cm chondrites and dolomites and magnesites in ci chondrites display the compositions expected of stable phases formed at low temperatures dolomites in cm chondrites identified here for the first time in five members of the group have small amounts of excess ca which may reflect metastable growth the distribution of fe between dolomite and coexisting serpentine differs in the two chondrite groups if the distributions reflect an approach to chemical equilibrium then the difference implies higher alteration temperatures for the ci group than the cm group in agreement with the results of previously published oxygen isotope thermometry and mineral solubility modeling of the alteration process dolomite fe contents are relatively uniform in the two chondrite groups dolomite mn contents by contrast vary widely the variations may reflect transport controlled coprecipitation of mn resulting from a heterogeneous distribution of the element in the anhydrous precursor material if this interpretation is correct then the altering fluids were essentially immobile while hydration reactions proceeded on the meteorite parent bodies the near closed system character of the alteration process long known from bulk chemical analyses of the meteorites is a direct consequence of the limited mobility of dissolved species

seismic and electromagnetic controlled source interferometry in dissipative media abstract seismic interferometry deals with the generation of new seismic responses by crosscorrelating existing ones one of the main assumptions underlying most interferometry methods is that the medium is lossless we develop an interferometry by deconvolution approach which circumvents this assumption the proposed method applies not only to seismic waves but to any type of diffusion and or wave field in a dissipative medium this opens the way to applying interferometry to controlled source electromagnetic csem data interferometry by deconvolution replaces the overburden by a homogeneous half space thereby solving the shallow sea problem for csem applications we demonstrate this at the hand of numerically modeled csem data

decomposition of multicomponent sea floor data into upgoing and downgoing p and s waves a method for decomposing multicomponent sea floor measurements into upgoing and downgoing p and s waves is presented we assume that a marine survey employing a marine source in the water layer is conducted over a plane layered medium from recordings of the pressure just above the sea floor and the particle velocity vector just below the sea floor decomposition filters can be determined by plane wave analysis the decomposition filter coefficients depend on the p and s wave velocities and the density at the sea bottom we show how to decompose the multicomponent measurements into upgoing and downgoing p and s vertical traction components vertical particle velocity components and horizontal particle velocity components the decomposition filters are applied with good results to synthetic data modeled in a plane layered medium

pb2 and zn2 adsorption by a natural aluminum and iron bearing surface coating on an aquifer sand pb2 and zn2 adsorption was studied in batch experiments with material collected from a shallow unconfined aquifer of glacial outwash sand and gravel in falmouth massachusetts usa the aquifer solids contain primarily quartz 95 w w with minor amounts of alkali feldspars and ferromagnetic minerals pb2 and zn2 adsorption experiments with various grain size and mineral fractions of the aquifer solids showed that 1 zn2 adsorption was independent of grain size but pb2 was preferentially adsorbed by the 64 m size fraction and 2 pb2 adsorption decreased after removal of the paramagnetic fe bearing mineral fraction but zn2 adsorption was unaffected pb2 and zn2 adsorption on mineral separates from the aquifer material compared with metal adsorption on a purified quartz powder indicated that adsorption of both metal ions was dominated by coatings on the quartz fraction of the sediment characterization of the coatings by aes sem eds and tof sims demonstrated that the natural quartz grains were extensively coated with al and fe bearing minerals of variable composition thin sections of quartz grains examined by tem showed that the coatings contained both polycrystalline regions and single mineral crystals the coating thickness varied from 10 nm up to 30 m the coatings were mostly resistant to dissolution by an extraction protocol designed to dissolve noncrystalline phases the effect on metal adsorption of dissolving surface coatings from the sediment by chemical extraction was also measured a hydroxylamine hc extraction designed to dissolve crystalline fe oxide phases decreased pb2 and zn2 adsorption relative to untreated sediment extracted fe al 1 but pb2 and zn2 adsorption were not appreciably changed after sediment was extracted with dithionite citrate extracted fe al 5 overall the results suggest that pb2 preferred to form complexes with iron hydroxyl sites while aluminol sites were more important for zn2 adsorption however a definitive understanding of adsorption reactions in groundwaters will require detailed studies of the extensive coatings formed at mineral water interfaces by chemical weathering processes

seasonal variations of ochreous precipitates in mine effluents in finland abstract ochreous precipitate and water samples were collected from the surroundings of seven closed sulphide mines in finland in the hammaslahti zn cu au mine otravaara pyrite mine and paroistenjarvi cu w as mine the collection was repeated in different seasons to study mineralogical and geochemical variations of precipitates the sampling was done in 1999 2002 from the ditches and drainage ponds of the tailings and waste rock piles that are susceptible to seasonal changes mineralogy of the precipitates was evaluated by x ray diffraction xrd and infrared spectroscopy ir and precipitate geochemistry was examined by selective extractions schwertmannite fe 8 o 8 oh 6 so 4 was the most typical fe hydroxide mineral found goethite was almost as common as schwertmannite was often poorly ordered and contained up to 10 wt of so 4 goethite and schwertmannite were commonly found as mixtures and they occurred in similar ph and so 4 concentrations ferrihydrite nominally fe 5 ho 8 4h 2 o was typically found in areas not influenced by acid mine drainage and also in acid mine waters with high organic matter or as content jarosite kfe 3 so 4 2 oh 6 was found only in one site in addition some gypsum caso 4 2h 2 o and aluminous sulphate precipitates presumably basaluminite al 4 so 4 oh 10 5h 2 o were identified selective extractions showed that acid extracts fe tot s tot ratios of schwertmannite and goethite samples were similar but the ratio of oxalate extractable to total fe fe ox fe tot of goethite samples were lower than those of the schwertmannite samples only al si and as were bound to precipitates in substantial amounts up to several wt in schwertmannites and goethites al cu co mn and zn were mostly structural substituting for fe in an fe oxyhydroxide structure or bound to surface adsorption sites in pores limited by diffusion in ferrihydrites heavy metals were also partly bound in adsorbed form dissolving in acid ammonium acetate ferrihydrites and goethites were more enriched in co mn and zn than schwertmannites but schwertmannites and ferrihydrites were more enriched in as than goethites mineralogical and geochemical evidence showed that in the spring after the snowmelt the acid mine drainage precipitates were predominantly schwertmannite and were partly transformed during warm summer months to goethite the phase transformation of precipitates was followed by a decrease in ph values and increase in so 4 concentrations of waters adsorbed as retarded the phase transformation

reply to comments by yavor kamer and stefan hiemer on analysis of the b values before and after the 23 october 2011 mw 7 2 van ercis turkey earthquake

remote sensing of hydrocarbon layers by seabed logging sbl results from a cruise offshore angola detecting and assessing hydrocarbon reservoirs without the need to drill test wells is of major importance to the petroleum industry seismic methods have traditionally been used in this context but the results can be ambiguous another approach is to use electromagnetic sounding methods that exploit the resistivity differences between a reservoir containing highly resistive hydrocarbons and one saturated with conductive saline fluids modeling presented by eidesmo et al 2002 demonstrates that by using seabed logging sbl a special application of frequency domain controlled source electromagnetic csem sounding the existence or otherwise of hydrocarbon bearing layers can be determined and their lateral extent and boundaries can be quantified such information provides valuable complementary constraints on reservoir geometry and characteristics obtained by seismic surveying

combination of statistical methods with modelling mineral water interaction a study of groundwater in the great hungarian plain abstract the chemical composition of groundwater samples from the southern part of the great hungarian plain was determined cluster analysis was used to separate aquifer systems on the basis of water chemistry processes controlling the chemical features of the different aquifers were established by simulation modelling combined with statistical calculations has proved to be an efficient tool to establish reactions between groundwater and minerals concentrations of ca and mg were controlled by dissolution of calcite and dolomite or magnesian calcite and by ion exchange on clay minerals sodium concentration is governed by irreversible albite weathering the influence of dissolution and ion exchange reactions was distinguished for both bivalent and monovalent cations decomposition of organic matter probably yields the co2 its pressure exceeds the atmospheric co2 pressure even in the deepest sediments studied

controlled electromagnetic sources for measuring electrical conductivity beneath the oceans 1 forward problem and model study exact closed form expressions for the electromagnetic induction fields produced by vertical and horizontal current sources in the conducting ocean overlying a one dimensional earth are derived from the maxwell equations numerical methods for the evaluation of the solutions are given including correction for the finite size of real sources simple models of the electrical conductivity structure of the ocean crust and lithosphere are deduced from geologic petrologic and laboratory data and their electromagnetic response is modeled horizontal electric dipole sources produce much larger field amplitudes than their vertical counterparts for a given frequency and range and the horizontal electric field offers superior received signal performance reflections of electromagnetic waves from the sea surface and thermocline must be considered for low enough frequencies or long ranges estimates of the ambient noise level from natural electromagnetic sources in the frequency range 0 01 10 hz are presented the ability of controlled sources to determine features of the conductivity of the ocean crust and upper mantle especially low conductivity zones is demonstrated if the mantle conductivity is low enough horizontal ranges of 50 km and conductivity estimates to over 20 km depth can be achieved

acidic volatiles and the mars soil large portions of mars surface are covered with deposits of fine homogeneous weathered dusty soil material nanophase iron oxides silicate mineraloids and salts prevail in the soil the mode of formation of this somewhat peculiar type of soil is still far from being clear one scenario suggests that weathering took place during early epochs when mars may have been warm and wet the properties of the soil are not easily reconciled with this scenario we propose another possible scenario that attributes in part the peculiar nature of the martian dust and soil to a relatively young weathering product formed during the last few hundreds of millions of years in a process that involves acidic volatiles we tested this hypothesis in an experimental study of the first step of acidolytic weathering of a partly palagonitized volcanic tephra of hawaiitic lava origin using sulfuric hydrochloric and nitric acids and their mixtures the tephra effectively neutralize the added acidity the protonic acidity added to the tephra attacks the primary minerals releasing fe al and mg which control the ph acting as lewis acid species of varying acid strengths the full amount of acidity added to the tephra is stored in it but only a very small fraction is preserved as the original protonic acidity the majority of the added sulfate and chloride were present as salts and easily solubilized minerals well crystallized sulfate salt minerals of aluminum and calcium were detected by powder x ray diffractometry whereas secondary magnesium and iron minerals were not detected due probably to lack of crystallinity the presence of gypsum caso4 2 h2o and alunogen al2 so4 3 17 h2o is probably responsible for the observed increased hygroscopicity of the acidified tephra and their tendency to form hardened crusts we suggest that if this mechanism is of importance on mars then the chemically weathered component of the martian soil consists of a salt rich mineral mixture containing the salts of the anionicligands so4 and cl resulting from volatiles emitted from volcanoes during more recent eruptions up to 109 years b p the lack of liquid water on mars surface during that time slowed or halted mineralogical evolution into highly crystallized minerals having large mineral grains the chemically weathered components are mixed with the products of physical weathering the recently formed soil may cover and coat more evolved hydrothermally modified mineral deposits formed in earlier epochs of mars

the natural attenuation of two acidic effluents in tharsis and la zarza perrunal mines iberian pyrite belt huelva spain the geochemical evolution of two acid mine effluents in tharsis and la zarza perrunal mines iberian pyrite belt huelva spain has been investigated in origin these waters present a low ph 2 2 and 3 1 and high concentrations of dissolved sulphate and metals fe al mn cu zn as cd co cr ni however the natural evolution of these acidic waters which includes the bacterial oxidation of fe ii and the subsequent precipitation of fe iii minerals represents an efficient mechanism of attenuation this self mitigating process is evidenced by the formation of schwertmannite which retains most of the iron load and by sorption toxic trace elements like as the later mixing with pristine waters rises the ph and favours the total precipitation of fe iii at ph 3 5 and subsequently al compounds at ph 4 5 along with the sorption of trace metals mn zn cu cd co ni until chemical equilibrium at circumneutral conditions is achieved

trace metal retention through the schwertmannite to goethite transformation as observed in a field setting alta mine mt abstract solutions draining the alta mine jefferson county mt were contaminated by acid sulfate waters asw generated from anthropogenic exposure of meteoric waters to sulfidic underground mine workings and a waste rock pile in 1999 a remediation effort was initiated in an attempt to improve the quality of water draining the site through removal of the waste rock pile with which these solutions come in contact asw were sampled in the mineshaft prior to entering the waste rock pile and upon discharge from the waste rock pile aquifer near the pile toe asw composition changed as solutions flowed through the waste rock pile due to sulfide and silicate weathering and schwertmannite precipitation schwertmannite and goethite were both sampled in the waste rock pile where a distinct field relation was observed between the two minerals schwertmannite was always in contact with actively flowing asw while goethite was never in direct contact with asw and was generally above the waste rock water table goethite is hypothesized to be re dissolved re precipitated schwertmannite that was deposited under higher flow conditions and subsequently transformed to goethite through exposure to wet dry cycling associated with seasonal fluctuations in the amount of water moving through the hydrogeologic system trace metal concentrations in ammonium oxalate extracts of these minerals provides the first published data on the behavior of multiple trace metals through this phase transformation which has important ramifications for considering schwertmannite as a long term metal sink due to its known metastability with respect to goethite a relative retention scale through this phase transformation of pb zn mn as al cu is potentially applicable to other asw systems

the origin of high sulfate concentrations in a coastal plain aquifer long island new york ion exchange batch experiments were run on cretaceous magothy aquifer clay cores from a nearshore borehole and an inland borehole on long island ny to determine the origin of high so4 concentrations in ground water desorption batch tests indicate that the amounts of so4 released from the core samples are much greater 980 4700 mg g of sediment than the concentrations in ground water samples the locally high so4 concentrations in pore water extracted from cores are consistent with the overall increase in so4 concentrations in ground water along magothy flow paths results of the sorption batch tests indicate that so4 sorption onto clay is small but significant 40 120 mg g of sediment in the low ph 5 pore water of clays and a significant part of the so4 in magothy pore water may result from the oxidation of fes2 by dissolved fe iii the acidic conditions that result from fes2 oxidation in acidic pore water should result in greater sorption of so4 and other anions onto protonated surfaces than in neu

adsorption of rare earth elements onto carrizo sand experimental investigations and modeling with surface complexation rare earth element ree adsorption onto sand from a well characterized aquifer the carrizo sand aquifer of texas has been investigated in the laboratory using a batch method the aim was to improve our understanding of ree adsorption behavior across the ree series and to develop a surface complexation model for the rees which can be applied to real aquifer groundwater systems our batch experiments show that ree adsorption onto carrizo sand increases with increasing atomic number across the ree series for each ree adsorption increases with increasing ph such that when ph 6 0 98 of each ree is adsorbed onto carrizo sand for all experimental solutions including when actual groundwaters from the carrizo sand aquifer are used in the experiments rare earth element adsorption was not sensitive to ionic strength and total initial ree concentrations in our batch experiments it is possible that the differences in experimental ionic strength conditions i e 0 002 0 01 m nacl chosen were insufficient to affect ree adsorption behavior however cation competition e g ca mg and zn did affect ree adsorption onto carrizo sand especially for light rare earth elements lrees at low ph rare earth element adsorption onto carrizo sand can be successfully modeled using a generalized two layer surface complexation model our model calculations suggest that ree complexation with strong surface sites of carrizo sand exceeds the stability of the aqueous complexes lnoh 2 lnso4 and lnco3 but not that of ln co3 2 or lnpo4 in carrizo groundwaters thus at low ph 7 3 where major inorganic ligands did not effectively compete with surface sites for dissolved rees free metal ion ln 3 adsorption was sufficient to describe ree adsorption behavior however at higher ph 7 3 where solution complexation of the dissolved rees was strong rees were adsorbed not only as free metal ion ln 3 but also as aqueous complexes e g as ln co3 2 in carrizo groundwaters because heavy rare earth elements hrees were preferentially adsorbed onto carrizo sand compared to lrees original hree enriched fractionation patterns in carrizo groundwaters from the recharge area flattened along the groundwater flow path in the carrizo sand aquifer due to adsorption of free and solution complexed rees copyright 2005 elsevier ltd

iron rich precipitates in a mine drainage environment influence of ph on mineralogy ochreous precipitates deposited by waters draining a sulfide rich lignite seam exposed in an abandoned mine in the czech republic show marked variations in color and mineralogy as a function of effluent ph when initially formed under acidic ph 3 7 conditions the precipitates are orange in color and their mineralogy is dominated by schwertmannite following confluence with alkaline ph 8 3 waters that have not been affected by mine drainage the effluent ph rises to 7 3 the color changes abruptly to reddish brown and the principal precipitate mineral is a two line ferrihydrite this change in mineralogy and the associated variation in color can thus serve as direct indicators of the genetic environments under which the minerals were formed

enhanced subsurface response for marine csem surveying one of the main challenges of using marine controlled source electromagnetic csem sounding for hydrocarbon detection has been a relatively low resolution and restricted depth penetration in addition the use of csem in shallow waters has been perceived as particularly difficult a new robust method for enhancing marine csem subsurface response is particularly useful in shallow waters the method is designed to reduce acquisition imprints and attenuate the dominant primary airwave contribution synthetic examples show that it is possible to detect thin deeply buried 3d resistive bodies in a shallow water environment with a complex resistivity structure the results highlight the importance of a sufficient signal to noise ratio

environmentally important poorly crystalline fe mn hydrous oxides ferrihydrite and a possibly new vernadite like mineral from the clark fork river superfund complex ferrihydrite and a vernadite like mineral in samples collected from the riverbeds and floodplains of the river draining the largest mining contaminated site in the united states the clark fork river superfund complex have been studied with transmission electron microscopy tem and energy dispersive x ray edx analysis these poorly crystalline minerals are environmentally important in this system because contaminant heavy metals as cu pb and or zn are always associated with them both two and six line ferrihydrite have been identified with selected area electron diffraction for the vernadite like mineral the two d values observed are approximately between 0 1 and 0 2 a larger than those reported for vernadite the mn hydrous oxide that is thought to have a birnessite like structure but which is disordered in the layer stacking direction in several field specimens the ferrihydrite and vernadite like minerals are intimately mixed on the nanoscale but they also occur separately it is suggested that the vernadite like mineral found separately is produced biogenically by mn oxidizing bacteria whereas the same mineral associated with ferrihydrite is produced abiotically via the heterogeneous oxidation of mn 2 a q initially on ferrihydrite surfaces evidence from this study demonstrates that the vernadite like mineral sorbs considerably more toxic metals than does ferrihydrite demonstrating that it may be a good candidate for application to heavy metal sorption in permeable reactive barriers

a numerical comparison of time and frequency domain marine electromagnetic methods for hydrocarbon exploration in shallow water in shallow water the frequency domain controlled source electromagnetic method is subject to airwave saturation that strongly limits the sensitivity to resistive hydrocarbon targets at depth it has been suggested that time domain csem may offer an improved sensitivity and resolution of these deep targets in the presence of the airwave in order to examine and test these claims this work presents a side by side investigation of both methods with a main focus on practical considerations and how these effect the resolution of a hydrocarbon reservoir synthetic noisy data for both time domain and frequency domain methods are simulated using a realistic frequency dependent noise model and frequency dependent scaling for representative source waveforms the synthetic data studied here include the frequency domain response from a compact broadband waveform the time domain step response from a low frequency square wave and the time domain impulse response obtained from pseudo random binary sequences these data are used in a systematic resolution study of each method as a function of water depth relative noise and stacking length the results indicate that the broadband frequency domain data have the best resolution for a given stacking time whereas the time domain data require prohibitively longer stacking times to achieve similar resolution

electromagnetic interferometry in wavenumber and space domains in a layered earth with interferometry applied to controlled source electromagnetic data the direct field and the airwave and all other effects related to the air water interface can be suppressed in a data driven way interferometry allows for retreival of the scattered field green s function of the subsurface or in other words the subsurface reflection response this reflection response can then be further used to invert for the subsurface conductivity distribution to perform interferometry in 3d measurements on an areal grid are necessary we discuss 3d interferometry by multidimensional deconvolution in the frequency wavenumber and in the frequency space domains and provide examples for a layered earth model we use the synthetic aperture source concept to damp the signal at high wavenumbers to allow large receiver sampling distances interferometry indeed increases the detectability of a subsurface reservoir finally we discuss the dependency of the accuracy of the retrieved reflection response on the two crucial parameters the conductivity of the seabed at the receiver location and the stabilization parameter of the least squares inversion

mineralogical and geochemical spatial analyses of a waste rock dump at the libiola fe cu sulphide mine eastern liguria italy in this work we investigated a 3 ha sulphide bearing waste rock dump libiola mine italy using mineralogical geochemical and geostatistical analyses the dumped materials were highly heterogeneous in grain size and lithology and varied both laterally and vertically other than the host rock of the ore basalts and serpentinites the dumped materials contained high amounts of low grade chalcopyrite and pyrite rich mineralisations due to these characteristics and to the absence of minerals able to neutralise acidity this waste rock dump can be classified as an acid mine drainage amd producer the study confirms that amd is still active and in the best scenario can persist for up to 6 17 103 years the consequences of this process are of serious environmental concern as it involves strong acidification of the circulating waters the release of potentially toxic metals into the soil streams and rivers and the precipitation of huge quantities of secondary fe oxides and fe oxyhydroxides

tem observations of particles in groundwater and their prospecting significance in the bofang copper deposit hunan china abstract groundwater is an important medium in geochemical research due to its mobility and low elemental background values currently major ion and isotopic analyses are the methods that are most commonly used to examine elemental contents this paper aims to explore nanoparticles related to deep concealed ore bodies in the bofang deposit through discussions on their classification and origins and ultimately to provide recommendations for prospecting this research takes groundwater as the main medium for tem transmission electron microscope observations all particles in deep and shallow groundwater samples contain cu zn pb as fe and other metal elements that are related to the ore body cu bearing particles which are the focus of this study comprise the following main components cu bearing particles with carriers and those without carriers these two types of particles are discussed and classified then individual particles are selected among these particles the cu bearing particles that originated from concealed ore bodies comprise the following three types 1 cu occurring with and migrated by geochemical carriers 2 cu nanoparticles physically adsorbed and migrated by fe oh 3 3 cu migrating as single cu or cu o nanoparticles these individual particles and the geological information they provide about the bofang copper deposit suggest that metals that are captured by geochemical carriers in groundwater should be analyzed analysis of these particles combined with analyses of other important prospecting geological data could reduce the cost of drilling and narrow areas of interest

behaviors of trace elements in neoarchean and paleoproterozoic paleosols implications for atmospheric oxygen evolution and continental oxidative weathering abstract the behaviors of redox sensitive and or bio essential trace elements in neoarchean and paleoproterozoic paleosols ancient weathering profiles were investigated to better understand atmospheric oxygen evolution the loss or retention of individual trace elements in the paleosols can show how continental oxidative weathering and thus atmospheric oxygen evolution took place against age mainly due to their various redox potentials the v cr ni cu zn and mo concentrations of two paleoproterozoic paleosols were measured by inductively coupled plasma optical emission spectrometry and mass spectrometry and those as well as co w and u concentrations of nine neoarchean and paleoproterozoic paleosols were obtained from the literature the trace element behaviors were constrained by their degrees of loss or retention in the paleosols we applied two methods to the estimation i retention fraction of element m a mass ratio of element m of paleosol to parent rock using immobile elements such as ti and ii element element in particular si element correlations at different profile depths of a paleosol there are two distinct groups in trace element behavior in the neoarchean and paleoproterozoic paleosols co ni zn and w were lost from weathering profiles until the early paleoproterozoic but retained in the middle and late paleoproterozoic while v cr cu mo and u were retained in the profiles until the early paleoproterozoic or slightly later but lost from the profiles in the middle and late paleoproterozoic more precisely the timings of such loss and retention were different between trace elements during the paleoproterozoic the characteristics of these changes from retention to loss or from loss to retention indicate that the changes occurred and lasted throughout the paleoproterozoic the trace element behaviors accordingly suggest that continental weathering became oxidative progressively with age during almost the whole paleoproterozoic and thus atmospheric oxygen increased similarly with age in the same time period but not suddenly in a relatively short term the loss and retention of the trace elements may infer how they were released from the continent to the ocean against age in the neoarchean and paleoproterozoic

unified multi depth level field decomposition wavefield decomposition forms an important ingredient of various geophysical methods an example of wavefield decomposition is the decomposition into upgoing and downgoing wavefields and simultaneous decomposition into different wave field types the multi component field decomposition scheme makes use of the recordings of different field quantities such as particle velocity and pressure in practice different recordings can be obscured by different sensor characteristics requiring calibration with an unknown calibration factor not all field quantities required for multi component field decomposition might be available or they can suffer from different noise levels the multi depth level decomposition approach makes use of field quantities recorded at multiple depth levels e g two horizontal boreholes closely separated from each other a combination of a single receiver array combined with free surface boundary conditions or acquisition geometries with a high density of vertical boreholes we theoretically describe the multi depth level decomposition approach in a unified form showing that it can be applied to different kinds of fields in dissipative inhomogeneous anisotropic media e g acoustic electromagnetic elastodynamic poroelastic and seismoelectric fields we express the one way fields at one depth level in terms of the observed fields at multiple depth levels using extrapolation operators that are dependent on the medium parameters between the two depth levels lateral invariance at the depth level of decomposition allows us to carry out the multi depth level decomposition in the horizontal wavenumber frequency domain we illustrate the multi depth level decomposition scheme using two synthetic elastodynamic examples the first example uses particle velocity recordings at two depth levels whereas the second example combines recordings at one depth level with the dirichlet free surface boundary condition of zero traction comparison with multicomponent decomposed fields shows a perfect match in both amplitude and phase for both cases the multi depth level decomposition scheme is fully customizable to the desired acquisition geometry the decomposition problem is in principle an inverse problem notches may occur at certain frequencies causing the multi depth level composition matrix to become uninvertible requiring additional notch filters we can add multi depth level free surface boundary conditions as extra equations to the multi component composition matrix thereby overdetermining this inverse problem the combined multi component multi depth level decomposition on a land data set clearly shows improvements in the decomposition results compared with the performance of the multi component decomposition scheme

controlled source electromagnetic sounding in shallow water principles and applications the marine controlled source electromagnetic csem method is being applied to the problem of detecting and characterizing hydrocarbons in a variety of settings until recently its use was confined to deepwater water depths greater than approximately 300 m because of the interaction of signals with the atmosphere in shallower water depths the purpose of this study was to investigate using a simple 1d analytical analysis the physics of csem in shallow water this approach demonstrates that it is difficult to simply decouple signals that have interacted with the earth from those that have interacted with the air using either frequency domain or time domain methods stepping away from wavelike approaches which if applied without care can be misleading for the diffusive fields of csem we demonstrate an effective way to mitigate the effect of the air in shallow water surveys by decomposing the em signal into modes and using only the mode least affected by interaction with the atmosphere such decompos

3d inversion of marine csem and mt data an approach to shallow water problem abstractthe application of the marine controlled source electromagnetic csem technique for shallow water hydrocarbon exploration is challenged by the effect of an airwave that masks the response from the reservoir at depth we applied gauss newton based 3d inversion method to synthetic csem and magnetotelluric mt data to demonstrate the capability of 3d inversion to recover thin resistive targets in shallow water environments the experiment on the model with water depth of 300 m shows that the target signals at 0 25 hz are significant enough to resolve the reservoir at a burial depth of 1 km for the given noise level 6 of the electric field amplitude for the 100 m water depth case the high resistivity zone recovered is located much deeper and thicker than the true reservoir suggesting that the airwave component obscures the target signal more seriously however inverting inline and broadside data together or adding inline data at a different frequency 0 1 hz is quite effective in improving t

characterization of geosynthetic clay liner bentonite using micro analytical methods in barrier design familiarity of the structure and composition of the soil material at the micron scale is necessary for delineating the retention mechanisms of introduced metals such as the formation of new mineral phases in this study the mineralogical and chemical makeup of the bentonite from a geosynthetic clay liner gcl was extensively characterized using a combination of conventional benchtop x ray diffraction xrd and micro x ray diffraction mu xrd with synchrotron generated micro x ray fluorescence mu xrf elemental mapping and mu xrd s mu xrd these methods allow for the non destructive in situ investigation of a sample with micro m spatial resolution synchrotron based hard x ray microprobes are specifically advantageous to the study of trace metals due to higher spatial resolution 10 micro m and higher analytical sensitivity femtogram detection than is possible using normal laboratory based instruments minerals comprising less than 5 of the total bentonite sample such as gypsum goethite and pyrite were identified that were not accessible by other conventional methods for the same gcl bentonite two dimensional general area diffraction detector system gadds images proved to be particularly advantageous in differentiating between the microcrystalline clay which appeared as homogeneous debye rings and the spotty or grainy appearance of primary more coarsely crystalline accessory minerals for s mu xrd themore tunability of the synchrotron x rays allowed for efficient distinction of both clay minerals at low scattering angles and in identifying varying fe oxide minerals at higher angles gcl samples permeated with metal bearing mining solutions were also examined in order to consider how mechanisms of metal attenuation may be identified using the same techniques in addition to the cation exchange capacity from the montmorillonite clay tests showed how minerals comprising only 1 2 of the bentonite such as goethite could potentially play a significant role in sequestering a range of metals specifically ni zn and cu less

the marine controlled source electromagnetic method in shallow water we analyzed marine controlled source electromagnetic csem acquisition in shallow water by analytic and numerical calculations the problem at hand was the fact that the amplitude of the airwave due to a horizontal electric dipole becomes larger as the water depth is reduced the amplitude of the scattered field from a buried thin resistor would be difficult to extract from the increased total field if the scattered field amplitude were independent of water depth however we identified and explained a compensating effect where the amplitude of the scattered field increases with reduced water depth this amplification effect makes marine csem surveys in shallow water feasible we derived an approximate expression for the total field for a simple but realistic conductivity model this expression explains why the amplitudes of the term that describes the background field contribution and the term that gives the scattered field from the thin resistor increase when the water depth is reduced our results and sensitivity analysis indicated that the sensitivity of marine csem data acquired in a water depth of 40 m is comparable to the sensitivity of marine csem data acquired in a water depth of 300 m

tem eels study of natural ferrihydrite from geological biological interactions in hydrothermal systems in this study we have investigated the mineralogy present on the scaphognatite of the rimicaris exoculata shrimp collected at a mid atlantic ridge hydrothermal vent the structure morphology and impurities of the minerals were analyzed by transmission electron microscopy tem and electron energy loss spectroscopy eels the main minerals observed were clusters of iron oxides found attached to the bacterial cells present on the setae of the scaphognatite structural investigations based on high resolution electron microscopy and electron diffraction affirm that these clusters are composed of two line ferrihydrite the eels measurements demonstrate that the ferrihydrite is bearing a mixed valence iron distribution and p si ca n and ni ions at impurity levels the stability of this uncommon phase is then discussed based on work previously reported in literature for analogous poorly ordered iron oxides

the effect of mineralogy on the mobility of heavy metals in mine tailings a case study in the samsanjeil mine korea this study examined the chemical speciation and mobility of as and heavy metals in a tailings impoundment in samsanjeil mine located in gosung korea as well as the factors affecting them xrd sem and 5 step sequential extraction were used to examine the samples at two sampling sites nn and sn sites the ph of the tailings decreased with increasing depth at the nn site from 7 2 to 2 8 whereas no significant differences were observed at the sn site 8 1 8 8 the samples at the sn site showed a larger amount of calcite than those at the nn site indicating that calcite plays an important role buffering the ph in the study sites jarosite was found only at the lower part of the nn site where calcite was not found the mineralogical observation of jarosite and calcite was also confirmed by sem the concentrations of as and heavy metals in the tailings were as follows cu as zn pb co cr ni cd the total concentrations of ni zn co and cd were higher at the sn site than those at the nn site on the other hand the concentrations of as and cr existing as oxyanions were higher at the nn site which can be explained by the mobility changes of those elements affected by ph variations at the nn site the fractions of heavy metals bound to the fe mn oxides except for as and cr decreased and cu zn and co showed an increasing fraction of exchangeable metals with increasing depth this suggests that the ph and resulting surface charge of minerals such as goethite and jarosite are the dominant factors controlling the chemical speciation of metals these results highlight the importance of mineralogy in controlling the mobility and possible bioavailability of heavy metals in tailings

optimized 3d synthetic aperture for controlled source electromagnetics locating offshore hydrocarbon reservoirs has become more challenging with smaller deeper or shallow water targets in complicated environments controlled source electromagnetics csem is a geophysical method used to find reservoirs in marine settings the diffusive nature of csem fields means that the signal from the target is only a small part of the total field to reduce the impact of the complicated settings and to improve the detecting capabilities of csem we have applied a synthetic aperture to csem data the synthetic aperture virtually increased the length and width of the csem source by combining the responses from multiple individual sources applying a weight to each source steered or focused the synthetic aperture source array in the inline and crossline directions we have developed an optimization method to find the optimal weights for synthetic aperture arrays that adapted to the information about the reservoirs in the csem data to demonstrate the benefits of a weighted synthetic aperture we have applied a 2d synthetic aperture array and a crossline only synthetic aperture array to noisy simulated electromagnetic fields both synthetic aperture arrays reduced the noise and increased the detectability of the modeled reservoirs when compared with the original csem response the crossline only synthetic aperture array also preserved the structural information within the measurements

second order moment of central california seismicity 1969 1982 the second order moment cross correlation function of earthquakes in the u s geological survey central california catalog between 1969 and 1982 was calculated with respect to a magnitude threshold m 4 0 over interevent distances up to 80 km and interevent times up to 320 days the statistical procedure results in a representation of the spatial temporal structure of the catalog associated with m 4 0 earthquakes and is capable of revealing patterns too weak to be detected in the space time distribution of seismicity for individual earthquake sequences a method is introduced for identifying aftershocks based on a physical two parameter model of the earthquake interaction process the results show that the aftershock process dominates the second order moment and may even obscure the statistical expression of a precursory process a concentration of foreshocks within 15 km and 3 days of m 4 0 main shocks exhibits an apparent migration toward the main shock loci with velocity 2 6 5 3 km d this concentration may be related to an observed tendency for m 4 0 events to cluster auto correlate over this interevent range with the identified aftershocks removed the residual catalog is poissonion in space and time when two m 4 0 earthquakes occur within 80 km and 40 days of each other aftershock productivity appears to be relatively enhanced in the earlier sequence this suggests that aftershock populations are not solely dependent on their main shocks and that unusually productive aftershock sequences may be predictors of future moderate earthquakes

decomposition in upgoing and downgoing fields and inversion of marine csem data abstractwe describe a data driven method to estimate the top formation resistivity using marine controlled source electromagnetic data the procedure exploits the fact that the airwave contributions are traveling up or down with a poynting vector close to the vertical axis the proposed method is based on forming an impedance in the same way as it is done in magnetotelluric processing the top formation resistivity is used to perform up down decomposition of the electric field below the seabed this procedure suppresses the contribution from the airwave in the resulting upgoing electric field and increases the data sensitivity to the subsurface resistivity distribution the upgoing electric field is used in the misfit kernel for an inversion scheme this is a method that is intended for use in shallow water inversion using the upgoing electric field means that the observed electric and magnetic fields contribute to the data misfit the optimization procedure seeks to reduce the misfit between the observe

mineralogical and chemical evolution of ochreous precipitates from the libiola fe cu sulfide mine eastern liguria italy abstract the mineralogical and chemical evolution of ochreous precipitates forming from acid mine drainage amd from the abandoned libiola fe cu sulfide mine eastern liguria italy was followed through a multianalytical approach xrd tem xrf icp applied to surface precipitates and associated waters collected from several mine adits the mineralogy of the precipitates changed significantly as a consequence of the variations of the chemical parameters of the circulating solutions mainly ph eh and sulfate concentrations which in turn were mainly controlled by mixing with unpolluted stream and rill waters of the mining area a progressive transition from jarosite to schwertmannite to goethite to ferrihydrite to amorphous dominated precipitates was observed mainly as a consequence of an increase in the ph of the associated solutions this mineralogical evolution agrees well with the aqueous speciation and eh ph stability calculations performed on the waters associated with the different precipitate types furthermore tem analysis indicated that metastable pristine phases schwertmannite tend to transform progressively to well crystallized more stable species here represented by goethite the comparison of the water chemistry and the crystal chemistry of the different precipitates showed a significant decrease in the zn cu ni co contents in waters where the coexisting precipitates were almost exclusively composed of goethite the distribution of v sr as concentrations within the different precipitates showed that the most efficient scavenging phase for these elements was jarosite whereas ferrihydrite efficiently took up pb ions and schwermannite acted as a natural sink for cr the comparative analysis of the precipitates and waters of the libiola mining area indicated that the authigenic fe oxyhydroxides play an important role in controlling the composition of the highly polluted amd waters but this role as cleaning agents was mostly ephemeral minor ph eh oscillations facilitated quick mineralogical transformations via dissolution reprecipitation or solid state transformation which in turn controlled the trace elements that were mobilized or permanently stored within the solid phases

decomposition of electromagnetic fields into upgoing and downgoing components this paper gives a unified treatment of electromagnetic em field decomposition into upgoing and downgoing components forconductiveandnonconductivemedia wheretheelectromagneticdataaremeasuredonaplaneinwhichtheelectricpermittivity magneticpermeability andelectricalconductivityareknown constants with respect to space and time above and below the plane of measurement the medium can be arbitrarily inhomogeneousandanisotropic in particular the proposed decomposition theory applies to marine em low frequency data acquired for hydrocarbon mapping where the upgoing components of the recordedfield guided and refracted from the reservoir that are of interest for the interpretation the direct source field the refracted airwave induced by the source the reflected field from the sea surface and most magnetotelluric noise traveling downward just below the seabed are field components that are considered to be noise in electromagneticmeasurements the viability and validity of the decomposition method is demonstrated using modeled and real marine em data also termed seabed logging sbl data the synthetic data are simulated in a model that is fairly representative of the geologic area wheretherealsblwerecollected theresultsfromthesynthetic data study therefore are used to assist in the interpretation of the realdatafromanareawith320 mwaterdepthaboveaknowngas province offshore norway the effect of the airwave is seen clearly in measured data after field decomposition just below the seabed the upgoing component of the recorded electric field has almost linear phase indicating that most of the effect of the airwavecomponenthasbeenremoved

seismicity rate variations and systematic changes in magnitudes in teleseismic catalogs abstract seismicity rate variations are commonplace in teleseismic catalogs these changes have two possible causes they could be real or they could be related to changes in the networks used to detect the events it is clearly important to differentiate between these two possibilities we demonstrate a technique for making this differentiation using uniform data generated with known rates and magnitude shifts we then apply this technique to data from large regions of the world all of these regions show significant variations in seismicity rates for sets with magnitude cutoffs of 5 0 and 5 5 we show that most of these changes have distributions in the magnitude domain which are consistent with systematic changes in magnitudes of between 0 1 and 0 2 units these results suggest that most observed rate variations in teleseismic sets with high magnitude cutoffs are related to systematic changes in magnitudes and are therefore not real this result has important implications for earthquake prediction and tectonic studies which interpret these variations

a solution to the airwave removal problem in shallow water marine em a new method is presented for removing the airwave in shallow water electromagnetic em data by using pairs of receivers or pairs of source points along a towline and forming weighted differences of an em field component the airwave is significantly attenuated the weights are related to the geometric spreading of the airwave specifically the horizontal electric and magnetic field components are weighted with the horizontal offset to the power of three before their differences are calculated one can also first calculate difference data without weights in the common source domain to remove correlated noise and then use the resulting data to perform a second order difference with weights in this case the weights should equal the horizontal offset to the power of four moreover the weighted difference data can be integrated to obtain an estimate of the physical field void of the airwave additionally the airwave contribution to the physical field can be estimated the theory behind the method is presented and demonstrated on a real controlled source em csem data set

specific surface area of a crushed welded tuff before and after aqueous dissolution specific surface areas were measured for several reference minerals anorthoclase labradorite and augite welded tuff and stream sediments from snowshoe mountain near creede colorado crushed and sieved tuff had an unexpectedly small variation in specific surface area over a range of size fractions replicate surface area measurements of the largest and smallest tuff particle size fractions examined 1 0 3mm and 0 212mm were 2 3 0 2m2 g for each size fraction reference minerals prepared in the same way as the tuff had smaller specific surface areas than that of the tuff of the same size fraction higher than expected tuff specific surface areas appear to be due to porous matrix tuff reacted in solutions with ph values from 2 to 6 had little change in specific surface area in comparison with unreacted tuff tuff reacted with solutions having high acid concentrations 0 1 m hydrochloric acid or sulfuric hydrofluoric acid exhibited a marked increase in specific surface area compared to unreacted tuff

controlled source electromagnetic three dimensional grid modelling based on a complex resistivity structure of the seafloor effects of acquisition parameters and geometry of multi layered resistors a comprehensive controlled source electromagnetic csem modelling study based on complex resistivity structures in a deep marine geological setting is conducted the study demonstrates the effects of acquisition parameters and multi layered resistors on csem responses three dimensional 3d finite difference time domain fdtd grid modelling is used for csem sensitivity analysis interpolation of normalized csem responses provides attributes representing relative sensitivity of the modelled structures modelling results show that fine grid 1 1 km receiver spacing provides good correlations between csem responses and the modelled structures irrespective of source orientation the resolution of csem attributes decreases for receiver spacing 2 2 km when using only in line data broadside data in the grid geometry increase data density by 100 approximately 200 by filling in in line responses and improve the resolution of csem attributes optimized source orientation i e oblique to the strike of an elongated resistor improves the structural definition of the csem anomalies for coarse grid geometries receiver spacing 3 3 km the study also shows that a multi resistor anomaly is not simply the summation but a cumulative response with mutual interference between constituent resistors the combined response of constituent resistors is approximately 50 higher than the cumulative response of the multi resistor for 0 5 hz at 4000 m offset a gradual inverse variation of offset and frequency allows differentiation of csem anomalies for multi layered resistors similar frequency offset variations for laterally persistent high resistivity facies show visual continuity with varying geometric expressions 3d grid modelling is an effective and adequate tool for csem survey design and sensitivity analysis

a feasibility study of co2 sequestration monitoring using the mcsem method at a deep brine aquifer in a shallow sea reservoir production monitoring using marine controlled source electromagnetic mcsem has been studied recently because it is sensitive to resistivity changes resulting from variations in hydrocarbon saturation however mcsem for co2 sequestration monitoring has scarcely been investigated although the mcsem method is advantageous for monitoring co2 injection and migration to investigate the feasibility of mcsem monitoring for co2 sequestration we conducted numerical experiments of representative co2 injection models at a deep brine aquifer in a shallow sea by using a modified secondary field method we effectively address the airwave problem occurring when mcsem is applied to a target beneath a shallow sea we demonstrate the modified secondary field method can restore high frequency band data which is beneficial for the detection of the movement of injected co2 furthermore using a modified scattered field approach for 2 5d forward modeling we achieve very high accuracy which is essential for t

estimation of seafloor electromagnetic receiver orientation abstractif the orientation of a seafloor electromagnetic em instrument is unknown it has to be estimated afterwards relatively early in the processing here we present a method to estimate the horizontal and vertical orientation of seafloor electromagnetic receivers three component magnetic recordings of the naturally occurring magnetotelluric field are utilized to find the tilt pitch and azimuth angle relative to a given reference estimation of angles is controlled by minimum difference criteria precautionary measures are necessary to eliminate the subsurface response in the recordings of the em field components the proposed method is applied to synthetic and real data demonstrating that even in difficult geologic settings the simple characteristics of the incident natural em field allow us to quickly estimate the orientation of the instruments

geochemistry of iron ochres and mine waters from levant mine cornwall abstract the geochemistry of metal rich mine waters and mineral precipitates from the levant mine cornwall has been examined sulphide oxidation at levant mine has produced a wide range of secondary sulphides oxides chlorides sulphates and carbonates in a gossan environment the mine waters display a wide variation in alkalinity ph chloride sulphate sodium potassium and heavy metal content which can be explained by variable degrees of mixing between acidic metal rich rock drainage waters and neutral to alkaline sea waters transition metals are soluble in the acidic mine waters with concentrations up to 665 mg l cu 41 mg l zn 76 mg l mn 6 mg l co and 2500 mg l total fe the production of acid rock drainage and leaching of metals can be related to sulphide oxidation where these metal rich acidic waters mix with infiltrated sea water neutralization occurs and some metals are precipitated principally cu where pools of mine drainage are stagnant native copper and cuprite are precipitated frequently observed replacing iron pipes and rail tracks and wooden shaft supports due to electrode potential differences in these solutions dissolved copper species are also reduced by interaction with wood derived organic species precipitation of iron oxyhydroxides caused by a ph increase also occurs and leads to coprecipitation of other metals including cd co ph mn ag and zn thus limiting the release of dissolved metals in solution from the mine however the release of suspended metal rich ochres in mine discharge waters with high ph zn cd mn ni sn sb as bi cu co and ag will still present a potential environmental hazard

optimizing em data acquisition for continental shelf exploration the controlled source electromagnetic csem method has been applied to oil and gas exploration and production for more than 10 years during this time most of the focus has been on derisking deep and ultradeep water drilling decisions in this article we will consider how em methods can be optimized for continental shelf applications which represent approximately 80 of offshore discoveries historically applications of em on the continental shelf have been limited for two principal reasons

3d csem modeling and time lapse sensitivity analysis for subsurface co2 storage abstractmonitoring a time lapse geophysical anomaly due to variation in the pore fluid contents of a subsurface reservoir is critical for further development and management however it may be difficult to detect the changes in p wave responses beyond a certain level of saturation a comprehensive 3d finite difference time domain fdtd forward modeling based on idealized subsurface resistivity structures demonstrates the possibility of marine controlled source electromagnetic csem surveying to monitor the movement of subsurface co2 storage we focused on csem sensitivity studies with respect to variations in geometry and or saturation of co2 storage evaluation of the effects of reservoir depths and lithology and detection of co2 leakage from the main storage a 100 lateral expansion from the initial diameter 1500 m of a typical co2 plume with thickness and resistivity of 100 m and 80 m respectively at 850 m below seafloor results in 41 electric field e field magnitude increase at 2500 m s