the rotokawa geothermal system new zealand an active epithermal gold depositing environment the rotokawa geothermal system is less than 20 000 yrs old and is situated in a sequence of pleistocene and recent volcanic rocks and underlying mesozoic graywacke basement in the taupo volcanic zone a region dominated by extensional tectonics at lease 12 different hydrothermal explosition breccias are preserved in surface outcrops the largest eruptive site being a crater of 1 5 km in diameter which formed about 6 060 years ago and is presently occupied by an acid lake lake rotokawa with a ph approximately 2 significant bedded sulfur deposits which formed in an earlier crater lake exist beneath the present lake the deep fluids are dilute chloride 0 022 mole kg waters having higher reduced sulfur concentrations h 2 s approximately 7x10 super 3 mole kg than any previously studied active geothermal system a maximum temperature of 320 degrees c has been measured in the system water rock interaction has given rise to a zone of propylitic alteration at depth which is overlain by a region of advanced and intermediate argillic alteration extensive boiling occurs at depth an sulfide minerals such as sphalerite galena chalcopyrite and argentite occur sporadically with ubiquitous pyrite argentiferous alunite occurs in the advanced argillic alteration zone clasts of silicified lake beds in the hydrothermal explosion breccias commonly contain pyrite and carry subeconomic gold values of up to 0 1 g metric ton thermal waters discharging on the northeast shore of the lake are depositing gold ore grade arsenic and antimony sulfide rich muds which also contain high concentrations of tungsten thallium mercury silver and gallium this surface deposit is estimated to contain about 250 kg 8 000 oz of gold and has been deposited during the past 1 800 yrs since the formation 6 060 yrs ago of the large hydrothermal explosion crater in which lake rotokawa is now situated about 12 0 million oz 370 metric tons of gold may have been transported into the environment beneath the crater it is estimated that 1 7 to 3 3 million oz of gold may have been deposited in the upper 300 to 400 m underlying lake rotokawa from hydrothermal fluids initially saturated with gold

environmental arsenopyrite stability and dissolution theory experiment and field observations arsenopyrite has traditionally been considered to be chemically unstable in the surficial environment however field evidence demonstrates that arsenopyrite does not readily decompose under water saturated near surface conditions arsenopyrite occurs in the heavy mineral suite of a variety of thin sediments in southern new zealand with no evidence for chemical corrosion these sediments have been water saturated but within metres of the surface for 10 60 28000 and 2 million years these observations of long term arsenopyrite stability are in accord with geochemical predictions based on recent experimentally determined thermodynamic data for arsenopyrite calculations using the new thermodynamic data suggest that arsenopyrite has similar eh ph stability range to pyrite except under acid conditions ph 4 where arsenopyrite should transform to realgar or orpiment calculated as concentrations in equilibrium with the pyrite arsenopyrite assemblage in the surficial environment are 0 01 0 1 ppm similar to groundwater in arsenopyrite bearing rocks in this study 0 005 0 3 ppm and these waters may be in chemical equilibrium arsenopyrite decomposes in oxidised waters to yield up to 1100 ppm dissolved as in the laboratory and up to 400 ppm dissolved as in mine processing waters these concentrations of dissolved as are several orders of magnitude lower than equilibrium solubility of arsenopyrite because of kinetic effects and development of protective oxide coatings on arsenopyrite grains mine tailings containing arsenopyrite should be chemically stable during longterm storage provided they are kept water saturated and moderately reduced d 2003 elsevier science b v all rights reserved

vertical distribution of as iii and as v in a coastal sandy aquifer factors controlling the concentration and speciation of arsenic in the stuarts point groundwater system northern new south wales australia arsenic species were measured in a bundled piezometer installed in the holocene barrier of the stuarts point coastal sands aquifer northern new south wales australia vertical distribution shows two peaks of elevated as concentration at a depth of 10 11 m concentrations of as tot as v and as iii are in the range of 52 85 38 67 and 14 18 mg l respectively and the ratio of as v as iii is well above 1 at 3 7 2 7 the second peak at a depth of 25 m shows the highest concentrations of as tot as v and as iii with values reaching 337 125 and 212 mg l respectively the as v as iii ratio is below 1 at 0 6 0 7 high as tot and as v concentrations at shallower depths are associated with acidic conditions and very low concentrations of all ions desorption of as from al hydroxides and as enriched feoxyhydroxides are plausible mechanisms releasing as into the groundwater system the elevated concentration of as tot and as iii at 25 m is potentially related to the leaching of the clay surfaces elevated hco3 and alkaline ph conditions at this depth cause desorption of as which is later present as as iii species in the reducing environment the high concentrations of hco3 further reduce the possible extent of as sorption on fe and mn oxyhydroxides the identification of as in a groundwater system associated with the coastal barrier sand dune environment raises serious questions of the suitability of human consumption of untreated groundwater drawn from these aquifer types further investigation both in australia and globally are needed to classified the extent of this hydrogeochemical occurrence near coastal communities that rely on groundwater 2003 elsevier science ltd all rights reserved

asthenospheric structure beneath a neogene basin in southeast hungary abstract beneath one of the subbasins of the pannonian basin formed between the alps carpathians and dinarides the bekes basin in southeast hungary a typical structure of the lithosphere and an upwelling of the asthenosphere can be inferred from seismic reflection geothermal geomagnetic gravity and magnetotelluric investigations in the bekes basin the thickness of neogene sediments reaches 6 7 km i e the basement of the neogene basin sinks 3 4 km over the basin area in the reflection section of the pannonian geotraverse that ends in the bekes basin the crust mantle boundary rises by 5 6 km up to a depth of 22 km in the course of performing and processing seismic reflection measurements particular care was given to the preservation of low frequency 2 10 hz information this explains that data were successfully received even from the upper mantle amplitude distribution of reflection arrivals and the dipping of reflecting surfaces permit to infer an uplift by 15 20 km in the lithosphere asthenosphere boundary which thus is assumed to be at a depth of 40 45 km beneath the bekes basin in geothermal investigations the model was established with seismic results being accounted for assuming an upwelling in the lithosphere asthenosphere boundary the superficial heat flow density corrected for the cooling effect of sediments was in good agreement with the values of model calculations the latest magnetotelluric results support the upwelling position of the lithosphere asthenosphere boundary the geomagnetic anomaly determined over the area of the bekes basin can be explained by the uplifted position of the lower crust the gravity anomaly can be attributed to the combined effect of this and the upwelling in the crust mantle boundary it is hoped that the integrated interpretation of results obtained by various geophysical methods confirms the assumption that said methods permit to investigate the structure of the whole lithosphere and thus the disclosed results may contribute to the completion and precision of basin models studied so far

reaction path modelling in the as s system a case study for geothermal as transport abstract geochemical speciation and reaction path modelling with the geochemists workbench gwb software was used to investigate zonal as sulphide mineral precipitation and as transport in an active geothermal field the uzon caldera kamchatka a new compilation and critical review of published experimental and theoretical thermodynamic data for as phases was used to modify and update a supcrt92 database with important missing phases the equilibrium constants for these as phases were then added or modified in the current gwb database speciation calculations predict that the sampled fluids are undersaturated with respect to as phases and aqueous as is dominantly transported as the complex h3aso3 aq and to a lesser extent the as sulphide complexes as2s3 aq has2s4 and as2s42 modelling the changes in concentration of dissolved as between the samples 0 2 8 6 mg kg indicates a strong dependence on redox log o2 g from 53 to 60 and temperature 95 65 c and illustrates the importance of mixing between the hydrothermal fluid and an oxygenated fluid reaction path models that follow the cooling of a h2s aq dominated as enriched 15 mg kg fluids from 125 to 25 c with sliding redox from log o2 g 55 to 60 predict the mineral paragenesis native as pyrite realgar pyrite orpiment pyrite pyrite this mineral sequence closely resembles the natural layering observed in the uzon caldera although field measurements contain a lower reduced s concentration than the model the error margin in the measured sulphide inherent from in situ oxidation during sampling is enough to account for the discrepancy despite assumptions in fluid parameters and modelling approaches as well as deficiencies in the thermodynamic data and an equilibrium approach this study has shown that acceptable and useful analogues for natural as rich systems can be developed

depth of crustal conducting layer and asthenosphere in the pannonian basin determined by magnetotellurics abstract on the basis of numerical modelling and statistical investigations of the horizontal electrical inhomogeneities narrow fractures change of conductance of the surface sediments min magnetotelluric mt sounding curves were found to be less distorted and therefore they can be used for the determination of deep conducting formations in the crust and upper mantle carefully selected mt curves indicate the crustal conductive layer at depths of 7 13 km and the conductive asthenosphere between 50 and 80 km the relatively shallow position of the asthenosphere corresponds to the high heat flow q 80 mw m 1 in the pannonian basin according to the empirical relation derived by adam 1978

towards a mechanical model for the formation of the pannonian basin abstract new maps showing crustal and lithospheric thickness variations in the pannonian basin and the surrounding east alpine carpathian and dinaric mountains have been prepared on the basis of recent seismic seismologic and electromagnetic data a map presenting miocene faults of regional significance has been also constructed for the same region by using a wealth of recently available national and or more local studies it is suggested that observed crustal and lithospheric structural contrasts have been controlled primarily by neogene kinematic history of the region kinematic history is characterized by the following main patterns 1 1 indentation by adria and large scale backthrusting in the southern alps 2 2 eastward escape and extension of the eastern alps 3 3 extensional collapse in the pannonian basin area 4 4 formation of broad wrench fault systems along strike in the dinarides and southern carpathians and the western carpathians with dextral and sinistral shear respectively 5 5 compression and accretion of the external thrust and fold belt in the eastern carpathians these kinematic patterns are thought to be interrelated and all are manifestations of the late stage evolution of an overthickened orogenic wedge in order to arrive at a better understanding of the mechanism of extension which formed the pannonian basin deep crustal seismic profiles hydrocarbon exploration reflection lines and borehole data have been analyzed in the little hungarian plain this plain represents the transition zone between the alps and the pannonian lowlands and the results are illustrated by eight interpreted cross sections one result of regional importance is the clear recognition that the transdanubian central range at the southeastern flank of the little hungarian plain is composed of alpine pre senonian thrust sheets this finding marks the end of a century of debate the allochthony of the substrata of the pannonian basin can be now considered proven another result of more general interest is that these cross sections document the mode of lithospheric extension preexisting compressional detachment planes reactivate as low angle normal faults and lead to tectonic unroofing of deeply buried metamorphic terranes characterized by ductile flow along subhorizontal lineation

environmental mercury and arsenic sources in fossil hydrothermal systems northland new zealand northland new zealand has been affected by natural hot water spring systems depositing elevated concentrations of mercury and arsenic over the past 5 million years due to the different erosion levels of these hot water systems four principal types of mercury and arsenic occurrences are found active hot springs layered surface deposits sinters deposited by hot springs highly fractured rock zones formed immediately beneath hot springs and chemically altered and mineralized rock from the deeper roots of hot spring systems mercury occurs principally as cinnabar and as a minor impurity 1 wt in phosphate minerals and iron sulfides particularly marcasite mercury is irregularly distributed through limonitic cements formed during oxidation arsenic occurs as a minor impurity 1 wt in phosphate minerals and iron sulfides particularly marcasite arsenic is also variably dispersed through limonite but not necessarily with mercury decomposition of marcasite constitutes the most significant source of mercury and arsenic pollution from the studied sites release of mercury and arsenic into the environment from marcasite phosphates and limonite is enhanced by acidification of the sites down to ph of 2 caused by oxidation of iron sulfides mercury and arsenic concentrations of up to 100 parts per billion should be expected in waters near the deposits these concentrations are in excess of recommended drinking water levels

crustal temperature and mantle heat flow in europe abstract the map of the surface heat flow in europe was supplemented by the crustal thickness pattern and data on crustal radioactivity and transformed to the mantle moho heat flow distribution using a model of radioactivity decreasing exponentially with depth a z a 0 exp z d with a0 2 wm 3 and d 10km we computed generalized one dimensional steady state conductive temperature depth curves for the major tectonic units of europe the available information on the heat flow tectonic age heat flow heat generation and heat flow crustal thickness relationships were summarized and discussed in terms of crustal structure the mohorovicic discontinuity is clearly not an isothermal surface neither is the outflow of heat from the upper mantle constant but both parameters may vary within broad limits the moho temperature can be as low as 280 c in the shield areas however it can exceed 900 c in some young intrarnontane depressions or rift structures regional variations of the moho heat flow can be as large as 30 40 mwm 2 the value of the moho temperature reflects primarily the tectonic stabilization of the crust as a result of the deep seated processes in the upper mantle

imaging pn velocities beneath the pannonian basin abstract the pannonian depression is an extensional back arc basin in central europe and is an integral part of the alpine carpathian orogenic mountain belts it can be characterized by thinned lower crust shallow moho discontinuity high surface heat flow and moho temperature implying recent active tectonic processes imaging the velocity structure of the upper mantle may help us to better understand the structure and formation of the pannonian region in this paper p n traveltimes from regional earthquakes are used to tomographically image the lateral velocity variations in the uppermost mantle beneath the pannonian basin the set of linear tomographic equations built up of the time term equation for each source receiver pair is solved by a truncated singular value decomposition algorithm the explicit computation of the generalized inverse of the tomographic equations makes it possible to deduce both the resolution matrix and the model covariance matrix allowing us to estimate the resolution and reliability of the solution the mean compressional wave velocity in the uppermost mantle beneath the pannonian basin is 7 9 km s substantially lower than the average continental p n velocity of 8 1 km s it is mostly due to the high moho temperature having values on average 400 500 c more than those in the surrounding areas the velocity anomalies range from 0 3 to 0 3 km s relative to the mean velocity of 7 9 km s due to high moho temperature below the north hungarian range low 7 6 7 7 km s velocities can be found high velocity anomalies of around 8 1 km s can be detected along the w sw boundaries of hungary and at the junction of the pannonian basin and the southern carpathians the great hungarian plain shows average 7 9 km s p n velocities

stratospheric global winds on titan at the time of huygens descent 1 measurements of stratospheric zonal winds on titan were made in preparation for and during the time of the descent of the huygens probe into titan s atmosphere on 14 january 2005 fully resolved emission lines from ethane near 11 7 m were measured on the east center and west positions on titan using the nasa gsfc heterodyne instrument for planetary wind and composition hipwac mounted on the national astronomical observatory of japan 8 2 m subaru telescope on mauna kea hawaii analysis of the doppler shifts of the emission line shapes yielded mean prograde gas velocity 60 65 m s at altitudes below 120 km 5 mbar this result is consistent with retrievals from the huygens doppler wind experiment and from other observations near this altitude range current spectral line shapes however differed significantly from those obtained in similar measurements on subaru in 2004 and on the nasa irtf in 1993 1996 which retrieved prograde zonal winds 190 90 m s at 230 km 0 4 mbar the cores of the emission lines which probe the high altitude region could not be fitted as before to retrieve wind directly using the accepted atmospheric model for titan they imply an approximately tenfold increase in ethane mole fraction 1 2 10 4 with strong wind shear above the stratopause providing a potential probe of the lower mesosphere and possible evidence of temporal and spatial variability results contribute to coordinated measurements of winds by various techniques providing information on the altitude distribution of wind velocity in titan s atmosphere from near the surface to the lower mesosphere

bacterial s layer preservation and rare arsenic antimony sulphide bioimmobilization in siliceous sediments from champagne pool hot spring waiotapu new zealand siliceous sinter loose sediments and suspended flocs in champagne pool an anoxic hot 75 c spring at waiotapu new zealand are composed of opaline silica and metal rich sulphides that contain many well preserved mineralized microbes detailed analysis by transmission electron microscopy and energy dispersive spectrometry has shown that bacterial cell wall and capsular material is preserved by the immobilization of high levels of as sb and s in the organic matrix calculation of the probable metal species in the spring water suggests that arsenic and antimony are present in solution as negative and neutrally charged sulphide or hydroxide complexes such as has 2 s 4 h 3 aso 3 and hsb 2 s 4 the early adsorption of these complexes onto reactive groups on the bacterial surface may be paramount in the excellent preservation of cell morphology as biomineralization progresses biomineral composition commonly becomes dominated by the precipitation of a supersaturated al rich amorphous silica phase biomineralization commonly preserves s layers an ordered mosaic of proteins on the outer surface of the cell wall these are the finest ultrastructure details thus far found in microbes preserved by hydrothermal mineralization and can be used as an aid to identify microfossils the s layers preserved here probably belong to clostridium thermohydrosulfuricum or desulfotomaculum nigrifacans

the solubility of as2s3 and speciation of as in dilute and sulphide bearing fluids at 25 and 90 c abstract the solubility of synthetic crystalline as 2 s 3 in o 2 free dilute and sulphide bearing solutions has been determined at temperatures of 25 and 90 c the predominant dissolved as species are h 3 aso 0 3 and h 2 as 3 s 6 orpiment solubility is limited by the reactions 0 5as 2 s 3 3h 2 o h 3 aso 0 3 1 5hs 1 5h pk 25 23 11 0 11 pk 90 18 83 0 05 1 5as 2 s 3 1 5hs 0 5h h 2 as3s 6 pk 25 3 61 09 pk 90 3 42 0 06 a formational free energy for orpiment has been calculated as g 0 f 96 72 kj mol measured concentrations of as in hot springs of the taupo volcanic zone new zealand are consistent with those predicted using the solubility reactions and equilibrium constants of this study in sampled springs ph 2 6 97 100 of the dissolved as is present as h 3 aso 0 3 when h 3 aso 0 3 is the dominant as species orpiment deposition is likely to occur in response to fluid cooling in the sub aerial environment

magnetotelluric and seismological determination of the lithosphere asthenosphere transition in central europe abstract we assembled all available magnetotelluric mt sounding curves that cover characteristic provinces of europe the depths of layers with increased electrical conductivities estimated from mt sounding curves by the respective authors were compared with a model of the lithosphere thickness derived from seismic p residuals regions of a relatively thin and thick lithosphere are characterized by positive and negative p residuals respectively we have found a good correspondence with both sets of results in the central part of the pannonian basin the depth of the lithosphere asthenosphere transition is estimated at 60 80 km and 100 120 km at the flanks the results for the bohemian massif show deeper levels of this transition between 100 and 200 km these depths seem to be typical of the lithosphere base beneath the variscan domain of central europe

consolidation and incipient oxidation of alkaline arsenopyrite bearing mine tailings macraes mine new zealand abstract fine grained ca 15 m arsenopyrite bearing mine tailings have been exposed to drying and oxidation for 4 a pending relocation the tailings are still partly covered by a pond of decanted pore waters the water table in drying tailings has lowered by 1 3 m and desiccation cracks up to 2 cm wide have formed on the 1 m scale extending through the unsaturated zone tailings in the unsaturated zone have similar pore water contents to saturated tailings typically 16 32 wt water saturated tailings retain alkaline ph ca 10 from the mine cyanidation plant but ph lowers progressively towards ca 7 near the surface or near desiccation cracks in the unsaturated zone the redox state of the tailings changes in parallel with ph with an empirical relationship eh mv 55 ph 290 water in the remnant decant pond reflects this relationship also unsaturated tailings have variable but low permeabilities typically 10 3 to 10 4 m day and more permeable horizons have allowed incursion of oxygenated air and or rain water from desiccation cracks sulphide grains in all tailings examined are unaltered sulphides and solutions in the tailings are out of thermodynamic equilibrium predicted from the redox ph conditions due to kinetic constraints incursion of rain water locally facilitates deposition from pore waters of insoluble fe oxide and arsenate minerals thus fixing as in the dry unsaturated tailings

uppermost mantle velocities and anisotropy beneath europe pn data collected within southern europe and the mediterranean are used to tomographically image variations in both seismic velocity and seismic anisotropy seismic anisotropy is an essential part of the inversion and without it several low velocity features within the uppermost mantle could not be properly imaged the technically active mantle of southern europe has much lower seismic velocities 7 6 8 1 km s than the more stable mantle of the sub african plate of the adriatic sea 8 3 km s however the most dramatic features within europe s uppermost mantle relate to the apennine dinaride and hellenide arcs these arcs all have extremely low 5 amounts of arc parallel anisotropy the tyrrhenian and aegean back arc regions also show low velocities 7 7 7 9 km s but less anisotropy the same may be true for the pannonian basin but the tomography has poorer resolution there a model explaining these observations focuses on subducted water metasomatizing the mantle wedge the addition of water causes melting creates arc volcanism lowers the seismic velocity and enhances the formation of anisotropy due to preferential olivine orientation for collisional arcs of the northern mediterranean arc parallel anisotropy has formed in response to compression across them and extension along them within back arc regions water is no longer a major factor instead convection associated with subduction and back arc extension controls the anisotropy

the adsorption behavior of thioarsenite on magnetite and ferrous sulfide abstract thioarsenite tasiii is an important arsenic as species under sulfidic environments adsorption behavior of tasiii on iron fe bearing minerals affects the transformation and the distribution of as at solid liquid interface in this study we investigated the formation of tasiii species in the mixed arsenite and sulfide asiii s ii solutions with different s as ratios and adsorption behavior of tasiii on the surface of magnetite fe3o4 and ferrous sulfide fes it was found that the extent of s substitution of tasiii was enhanced with the increasing s as molar ratio in the asiii s ii solutions the adsorption experiments showed that as in the asiii s ii solutions was adsorbed to a less extent on two fe minerals than that of asiii in circumneutral to alkaline solutions indicating that tasiii has lower affinity to fe3o4 and fes the adsorption of tasiii on the surface of fe3o4 led to hydrolyzation and asiii is the main sorbed species on the surface of fes the extent of s substitution of tasiii was promoted and as sulfide surface precipitate may form overall the formation of tasiii species is the vital factor affecting the redistribution of as between solid and aqueous phase in sulfidic environment

sulfur redox chemistry governs diurnal antimony and arsenic cycles at champagne pool waiotapu new zealand abstract champagne pool a sulfidic hot spring in new zealand exhibits distinct diurnal variations in antimony sb and arsenic as concentrations with daytime high and night time low concentrations to identify the underlying mobilization mechanisms five sites along the drainage channel of champagne pool were sampled every 2 h during a 24 h period temporal variations in elemental concentrations and sb as and sulfur s speciation were monitored in the discharging fluid total trace element concentrations in filtered and unfiltered samples were analyzed using icp ms and sb as and s species were determined by ic icp ms sulfur speciation in the drainage channel was dominated by thiosulfate and sulfide at night while sulfate dominated during the day the distinct diurnal changes suggest that the transformations are caused by phototrophic sulfur oxidizing bacteria these bacteria metabolize thiosulfate and sulfide in daylight to form sulfate and as suggested by modeling with phreeqc elemental sulfur sulfide consumption during the day results in undersaturation of antimony sulfides which triggers the additional release of dissolved sb for as diurnal cycles were much more pronounced in speciation than in total concentrations with di and trithioarsenate forming at night due to excess sulfide and monothioarsenate forming from arsenite and elemental sulfur during the day sulfur speciation was thus found to control sb and as in terms of both solubility and speciation

the behaviour of antimony released from surface geothermal features in new zealand abstract antimony rich geothermal features in the taupo volcanic zone tvz of new zealand s north island drain directly into surface aquatic environments the discharge from champagne pool a mixed alkali chloride sulfate hot spring at wai o tapu geothermal field contains up to 194 g l sb the discharge from frying pan lake a chloride sulfate hot spring at waimangu geothermal field contains up to 21 5 g l sb at champagne pool downstream concentrations of sb show distinct diurnal variations particularly in winter when concentrations in the early morning were less than half those measured mid afternoon changes in sulfide sulfate equilibria and direct stibnite oxidation may explain this phenomenon in the discharge from frying pan lake sb exhibits little diurnal variation most 80 of the dissolved sb released from champagne pool is removed from solution at alum lake an acid sulfate hot pool containing elevated levels of dissolved sulfide therefore relatively little sb is discharged into the freshwater drainage in the area however in the absence of a sulfide rich feature at waimangu most of the sb discharged from frying pan lake remains dissolved and is transported into the freshwater drainage system of lake rotomahana the contrast in sb behaviour between these two sites confirms the importance of dissolved sulfide and low

large scale waveform inversions of surface waves for lateral heterogeneity 2 application to surface waves in europe and the mediterranean linear surface wave scattering theory is used to reconstruct the lateral heterogeneity under europe and the mediterranean using surface wave data recorded with the network of autonomously recording seismographs nars the waveform inversion of the phase and the amplitude of the direct surface wave leads to a variance reduction of approximately 40 and results in phase velocity maps in the period ranges 30 40 s 40 60 s and 60 100 s a resolution analysis is performed in order to establish the lateral resolution of these inversions using the phase velocity perturbations of the three period bands a two layer model for the s velocity under europe and the mediterranean is constructed the s velocity perturbations in the deepest layer 100 200 km are much more pronounced than in the top layer 0 100 km which confirms that the low velocity zone exhibits pronounced lateral variations in both layers the s velocity is low under the western mediterranean while the s velocity is high under the scandinavian shield in the deepest layer a high s velocity region extends from greece under the adriatic to northern italy several interesting smaller features such as the massif central are reconstructed one of the spectacular features of the reconstructed models is a sharp transition in the layer between 100 and 200 km near the tornquist tesseyre zone this would indicate that there is a sharp transition at depth between central europe and the east european platform the waveform inversion of the surface wave coda leads to good waveform fits but the reconstructed models are chaotic this is due both to a lack of sufficient data for a good imaging of the surface wave energy on the heterogeneities and to an appreciable noise component in the surface wave coda

the distribution of arsenic iii and arsenic v in geothermal waters examples from the massif central of france the island of dominica in the leeward islands of the caribbean the valles caldera of new mexico u s a and southwest bulgaria abstract data for as iii as v and total as for various types of geothermal spring water are given the different species of as were separated at the time of sampling after filtration acidification and dilution where necessary using an anion exchange method total as as iii and as v were determined by flameless atomic absorption spectrometry the total as content ranges from 5 to 1800 g l 1 samples from dominica show evidence of different sulfur arsenic oxidation kinetics as iii being the major component 85 99 in fluids from deep levels of the geothermal reservoir and also 99 in oxidized waters of the acid sulfate type the bicarbonate spring water of the valles caldera new mexico contains more as iii than as v but there as v is the major component of the acid sulfate springs as iii proves to be the predominant form 60 100 in the warm alkaline waters from southwest bulgaria a selection of co 2 rich spring waters from the central massif france cezallier is analysed two groups are distinguished on the basis of major element chemistry and total as content oxidized forms are mainly encountered in the first group including a well sample containing 0 5 as iii the as iii content of the second group ranges from 10 to 70 these preliminary results indicate that the fluids directly related to hydrothermal systems contain mainly as iii whereas acid sulfate springs have a variable as iii content bicarbonate waters are generally enriched in oxidized as in the absence of springs or sinks within a geothermal region the total as concentration may display conservative properties but both as iii and as v may be reactive during mixing and cooling

lithospheric thermal regimes in europe abstract the heat flow pattern of europe derived from more than 8000 observations is dominated by a general northeast to southwest increase in geothermal activity which is the consequence of the tectonic evolution of the whole continent this paper reviews the history of the geothermal mapping of europe and describes the recently compiled set of geothermal maps of europe surface heat flow is correlated with the age of the last tectonothermal event with the near surface heat production and with the crustal thickness deep temperature distributions within the crust lithosphere are calculated for 1 d 2 d and simple 3 d models characteristic temperature depth curves are given for some of the major tectonic provinces and the results of various techniques are compared the value of the crustal heat contribution is assessed and a regional moho heat flow pattern is proposed the mohorovicic discontinuity is clearly not an isothermal surface neither is the heat flow from below the crust constant

the european african collision and its effects on the lithosphere asthenosphere system abstract in the european area lateral changes in the shear wave velocities of the lithosphere asthenosphere system are quite pronounced gravity data imply a positive density contrast 0 03 0 07 g cm 3 in the upper mantle related to almost aseismic lithospheric roots which seem to characterize many orogenic belts the analysis of a transect along the longitudinal axis of the alps seems to indicate that relevant lateral variations in density are also present in the lithospheric part of the mantle

geothermal model of the earth s crust in the pannonian basin abstract a geothermal model of the hyperthermal zone of the pannonian basin is constructed on the basis of results of seismic measurements along five deep seismic sounding profiles on the territory of the basin and the surrounding areas and also of measurements of heat flow heat production by radioactive elements and thermal conductivity of rocks the variation of temperature with depth and maps of mono temperatures and heat flux through this surface are calculated and constructed respectively it is shown by numerical model calculations that the heat anomaly of the pannonian basin indicated by a number of surface measurements is mainly of mantle origin inhomogeneities of the heat flow increase with depth down to the upper mantle and the temperature on the moho surface below the hyperthermal zone has values on average 400 500 c more than those in the surrounding areas heat flux through the moho under the pannonian basin is also higher by about 40 50 mw m 2 on the basis of the present calculations it can be suggested that the upper mantle is probably partially molten beneath the annonian basin as a most reasonable source mechanism of formation of this heat anomaly the frictional heating arising in areas of induced secondary convection that probably has proceeded also beneath the basin from the triassic to the miocene is suggested here

three dimensional modelling of deep temperature and heat flow anomalies with applications to geothermics of the pannonian basin abstract on the basis of the solution of the three dimensional stationary equation of heat conduction with variable thermal conductivity and heat generation a geothermal model of the crust and upper mantle beneath the pannonian basin is constructed present calculations indicate that the heat flow in the area investigated has an average positive anomaly of 40 mw m 2 the average temperature anomaly on the moho surface is 500 k increasing with depth the melting temperature is reached at depths of 70 80 km in some particular areas at 65 km the upper boundaries of the high conductivity layer and the low velocity zone in the pannonian basin are also about the same depths as indicated above and contours of the melted region coincide well with the zone of the miocene andesite rhyolite volcanism the thermal state of the crust likewise its structural composition is rather uniform in the upper mantle however significant local temperature inhomogeneities exist additional non radiogenic heating is of primary importance in the formation of temperature anomalies of the pannonian basin it results from part of the crust and upper mantle having been heated in the past up to melting or to temperatures close to melting which is now cooling the nature of this extra heat source is not yet clear the results of this study suggest that the terrestrial heat flow measured in the pannonian basin might have been overestimated

comparison of arsenic and molybdenum geochemistry in meromictic lakes of the mcmurdo dry valleys antarctica implications for oxyanion forming trace element behavior in permanently stratified lakes abstract water samples were collected for arsenic as and molybdenum mo analysis from different depths in lakes hoare and fryxell both of which are located in the taylor valley within the mcmurdo dry valleys of antarctica sampling depths within each lake were chosen to capture variations in as and mo concentrations and as speciation in the oxic mixolimnia and anoxic monimolimnia of these meromictic lakes arsenic concentrations ranged from 0 67 nmol kg 1 to 3 54 nmol kg 1 in lake hoare and from 1 69 nmol kg 1 to 17 5 nmol kg 1 in lake fryxell molybdenum concentrations varied between 5 05 nmol kg 1 and 43 nmol kg 1 in lake hoare and between 3 52 nmol kg 1 and 25 5 nmol kg 1 in lake fryxell concentrations of as and mo generally increased with depth in the mixolimnion of each lake consistent with uptake near the ice water interface by organic particles and or fe mn oxides oxyhydroxides followed by gravitational settling and regeneration remineralization at depth in the vicinity of the redoxcline arsenic concentrations either remained constant hoare or increased with depth fryxell in the anoxic monimolimnia whereas mo exhibited dramatic decreases in concentrations across the redoxcline in both lakes geochemical modeling predicts that as and mo occur as thioanions in the anoxic bottom waters of lakes hoare and fryxell and further that the contrasting behavior of both trace elements reflects the respective reactivity of their thioanions towards fe sulfide minerals such as mackinawite fes and or pyrite fes 2 more specifically the geochemical model suggests that fe sulfide mineral precipitation in the anoxic monimolimnia of both lakes regulates dissolved sulfide concentrations at levels that are too low for as sulfide minerals e g orpiment realgar to precipitate whereas mackinawite and or pyrite react s with particle reactive thiomolybdate anions possibly forming an fe mo s mineral that precipitates and hence leads to mo removal from solution

a preliminary stripped gravity map of the pannonian basin abstract by removing the gravity effects of the known near surface sources from the gravity map we obtain a stripped gravity map that enables a better interpretation of the deep seated geological structures of the earth s crust the total gravity effect of anomalous bodies is acquired by summation of the gravity effects of n sided vertical prisms with horizontal bases the stripping procedure has a more accurate physical foundation than any other mathematical method of gravity field analysis provided that the geometry and density of the disturbing bodies are known with sufficient accuracy this method was applied to the pannonian basin

arsenic retention and remobilization in muddy sediments with high iron and sulfur contents from a heavily contaminated estuary in china the wuli estuary and its offshore area the bay of jinzhou have received large amount of wastewater and smelting slag from a non ferrous smelter for decades we collected three sediment cores from the wuli estuary the middle and the mouth of the bay of jinzhou respectively chemical sequential extraction and x ray absorption near edge structure spectrometry xanes for arsenic as accompanying with fe mn tom s and ca analyses were conducted to investigate as retention and remobilization in this estuary bay system the concentrations of as in the sediment up to 3400 g g and porewater up to 1100 g l have been significantly elevated in the wuli estuary and serious as contamination has been spreading to the bay of jinzhou sequential extraction displayed that adsorbed as was the dominant form of as in sediments from the wuli estuary but in the bay of jinzhou xanes data showed that a portion of as 10 was precipitated as as sulfides correlation analysis showed that total as ast hcl extractable as ashcl in sediment correlated well with total fe fet and hcl extractable fe fehcl in the estuary with fehcl total s st and acid volatile sulfur avs in the middle of the bay and with avs in the mouth of the bay the results indicated that as retention in the wuli estuary is very likely fe controlled region while the impact of s becomes more pronounced in the bay of jinzhou pseudo partition coefficients pseudo kd for ast the ratio of dissolved ast in porewater to ast in sediment decreased systematically from the wuli estuary to the mouth of the bay of jinzhou indicating that mobility of as decreased during the migration and digenetic processes the dominant form of dissolved as in porewater was present in the form of asiii 87 100 in the wuli estuary the reduction of arsenate asv to arsenite asiii 23 91 mediated by microbial activities was the most important cause for as release from solid to aqueous phase whereas the role of reductive dissolution of fe in remobilization of as was likely very limited

as sb bi au mineralization in the baogutu gold deposit xinjiang nw china here we report the occurrence of some uncommon mineral assemblages including paakonenite aurostibite native arsenic native antimony and native bismuth found in the baogutu gold deposit in the western junggar xinjiang nw china the mineralization could be generally subdivided into two types the gold bearing quartz vein type mineralization and disseminated mineralization in the wall rocks the sulfide minerals in gold lodes commonly include pyrite arsenopyrite marcasite and stibnite however the l7 lode in no 4 orebody and the l1 lode in no 11 orebody of the baogutu gold deposit are quite different in terms of their mineral assemblages the l7 lode contains native arsenic quartz veins in shallow levels and stibnite quartz veins at depth gold bearing minerals electrum native gold and rarely aurostibite mainly coexist with paakonenite stibnite native arsenic and native antimony the crystallization of as and sb bearing minerals was likely to have consumed h2s from the hydrothermal fluid which probably triggered the precipitation of native gold the l1 lode consists of several discontinuous sulfide dominated lensoid orebodies the massive sulfide ores that produced most of the gold resource are characterized by an intimate association between native bismuth and native gold mineralization

thiosulphate in surficial geothermal waters north island new zealand abstract thiosulphate is present in hot springs streams and thermal pools of the taupo volcanic zone and ngawha new zealand at concentrations of 1 2 1 3 10 5 m to 7 05 0 12 10 4m formed as a metastable product of sulphide oxidation thiosulphate is buffered in the presence of elemental s according to 0 5 s 8 3 h 2 o s 2 o 3 2 2 h 2 s a q 2 h unless all sulphide present has been bacterially oxidised to sulphate a steady state concentration of thiosulphate is maintained as a soft base thiosulphate is capable of complexing several transition metals the thermodynamically predicted speciation of ag in champagne pool for example indicates a ag s2o3 2 3 activity similar to that of agcl2 though less than that of ag hs 2

travel time tomography of the european mediterranean mantle down to 1400 km abstract the 3 d p wave velocity structure of the mantle below europe the mediterranean region and a part of asia minor is investigated this study is a considerable extension of an earlier tomographic experiment that was limited to imaging upper mantle structure only here the earth s volume under study encompasses the mantle to a depth of 1400 km and we increase the number of international seismological centre isc data for inversion by a factor of four by taking more years of observation and by including data from teleseismic events the most important departure from the earlier study is that we do not use the jeffreys bullen model as a reference model but an improved radially symmetric velocity model the pm2 model which is appropriate for the european mediterranean mantle our inversion procedure consists of two steps first the radial model pm2 is determined from the isc delay times by a nonlinear trial and error inversion of the data as opposed to the jeffreys bullen model the new reference model has a high velocity lithosphere a low velocity zone and seismic discontinuities at depths of 400 and 670 km next the isc data are corrected for effects related to the change in reference model and inverted for 3 d heterogeneity relative to the pm2 model we follow this two step approach to attain a better linearizable tomographic problem in which ray paths computed in the pm2 model provide a better approximation of the actual ray paths than those computed from the jeffreys bullen model hence the two step scheme leads to a more credible application of fermat s principle in linearizing the tomographic equations inversion results for the 3 d heterogeneity are computed for both the uncorrected isc data and for the pm2 data the data fit obtained in the two step approach is slightly better than in the inversion of isc data using the jeffreys bullen reference model a comparison of the tomographic results demonstrates that the pm2 data inversion is to be preferred to assess the spatial resolution an analysis is given of hit count patterns sampling of the mantle by ray paths and results of sensitivity tests with 3 d synthetic velocity models the spatial resolution obtained varies with position in the mantle and is studied both in map view and in cross section in the well sampled regions of the mantle the spatial resolution for larger scale structure can qualitatively be denoted as reasonable to good and at least sufficient to allow interpretation of larger scale anomalies a comparison is made of the results of this study with independent models of s velocity heterogeneity obtained in a number of investigations and with a prediction of the seismic velocity structure of the mantle computed from tectonic reconstructions of the mediterranean region in the context of this comparison interpretations of large scale positive anomalies found in the mediterranean upper mantle in terms of subducted lithosphere are given specifically addressed are subduction below southern spain below the western mediterranean and italy and below the aegean in the last region a slab anomaly is mapped down to depths of 800 km

crustal and upper mantle structure of the mediterranean area derived from surface wave data abstract a summary of results based mainly on the inversion of available surface wave dispersion data is given for the mediterranean area both for crustal and upper mantle structure the results are presented on maps outlining the regionalization of the crust and the lithosphere asthenosphere system in the area it is possible to distinguish several types of crust with average s wave velocities in the range 2 8 3 8 km s 1 and thickness varying from a minimum of about 10 16 km in the western mediterranean to a maximum of about 50 km including a possible transitional layer beneath the ionian sea the average properties of the crust and of the lithospheric part of the mantle indicate a possible continuous structure extending from north africa through the ionian sea to the adriatic sea characterized by the presence of a transitional layer at the crust mantle boundary strong lateral variations are present in the lithosphere asthenosphere system both in thickness from 30 km in the western mediterranean to about 130 km under the alps and in s wave velocity from 4 1 4 2 km s 1 up to 4 7 km s 1 the relatively high position of low resistivity material that seems to characterize the mediterranean area agrees fairly well with the shallower average top of the asthenosphere found in this area from the study of the elastic properties the usefulness of combining seismological and electromagnetic studies is stressed