geochemistry of thermal fluids in nw honduras new perspectives for exploitation of geothermal areas in the southern sula graben abstract the results of a geochemical survey on thermal waters and for the first time for this site gas discharges in five geothermal sites azacualpa la cueva rio ulua rio gualcarque el olivar and laguna de agua caliente in nw honduras are here presented and discussed el olivar and laguna de agua caliente in the southern part of the sula graben are very close to a quaternary basaltic field whereas azacualpa la cueva rio ulua and rio gualcarque located to the southwest of the yojoa lake direcly emerge from the cretaceous limestone deposits the measured temperatures range between 37 5 and 104 8 c mature alkaline na so 4 thermal waters discharge from azacualpa la cueva while those from el olivar and laguna de agua caliente are immature and show a na hco 3 composition chemical equilibria of waters and gases from the azacualpa la cueva thermal springs indicate temperatures ranging from 150 to 200 c conversely gas discharges from el olivar and laguna de agua caliente have attained a partial chemical equilibrium in the liquid phase at slightly higher temperatures 200 250 c although gas gas faster reactions involving co seem to be adjusted in an isothermally separated vapor phase unlike azacualpa sio 2 geothermometer at el olivar and laguna de agua caliente indicates equilibrium temperatures for the liquid phase much lower than those calculated for the gas phase 120 c we conclude that thermal waters from the azacualpa area likely represent the direct emergence of a water dominated reservoir having temperatures 150 200 c by contrast at el olivar and laguna de agua caliente hot springs are supplied by a boiling shallow aquifer fed by a vapor phase rising from a steam dominated zone the above geochemical model is consistent with a geothermal reservoir hosted within the cretaceous carbonate sequences of the yojoa group in the whole investigated sites the reservoir extensively crops out in the azacualpa area whereas the geothermal sites of the southern sula graben laguna de agua caliente and el olivar are covered by the oligocene miocene volcano sedimentary sequences of the matagalpa formation possibly acting as efficient impermeable cap rocks these results significantly differ from those reported by previous studies and emphasize that the southern sula graben in particular the el olivar area can represent among the investigated thermal springs the most promising site for the exploitation of a high enthalpy geothermal field

mantle derived fluids discharged at the bradanic foredeep apulian foreland boundary the maschito geothermal gas emissions southern italy abstract the mephitis of maschito known since historical times as lago fetente smelly lake although the lake is now dry is located 20 km from the mt vulture volcanic edifice southern italy it is placed along the same regional tectonic discontinuity where some maars are located close to the boundary between the foredeep and the apulian foreland about 300 m 2 of surface is lacking in flora while dead animals are frequently found all around it the smelly exhalations are mainly composed of co 2 98 and in lesser amounts of h 2 s n 2 ch 4 and other hydrocarbons he ne and ar occur in trace amounts the co 2 isotopic composition is in the range of that of the main active italian volcanic gases the helium isotopic ratio 4 7 ra fits with the values measured in mt vulture volcano and particularly with the olivine and pyroxene fluid inclusions of mantle xenoliths ejected during its last volcanic activity 140 000 years the 40 ar 36 ar isotopic ratio of 320 supports some minor non atmospheric contributions the c 3 he ratio 2 9 10 9 is in the typical range of magma released fluids while c ch 4 13 and d ch 4 values fall in the field of thermogenic methane the amount of co 2 released is about 3200 tons year the flux of mantle derived helium 7 10 10 atoms m 2 s 1 is at least three orders of magnitude higher than that of a stable continental crust this study strongly supports the possibility that maschito manifestations are fed by a geothermal system which is powered by a degassing melt bearing in mind that the maschito gas emissions fall along the same fault system of the monticchio maars which formed during mt vulture volcano s last activity

gas and aerosol emissions from lascar volcano northern chile insights into the origin of gases and their links with the volcanic activity abstract this study focuses on the chemical compositions of volcanic gases and aerosols emitted by lascar volcano northern chile the sustained volcanic plume was sampled in april 2009 april 2011 and november 2012 through filter packs and analyzed for major gaseous species so 2 hcl and hf and trace elements during fieldwork so 2 flux measurements were also performed by uv spectrometry doas the lascar volcano is a significant and sustained emitter of so 2 between 150 and 940 t d hcl between 170 t d and 210 t d and hf up to 100 t d combining the so 2 normalized trace element concentrations and the so 2 emission rates we evaluate that the quiescent degassing of lascar is an important local source of trace metals to the atmosphere with contributions to global volcanic fluxes generally less than 2 our data were used to infer the origin of the gas emitted at lascar two major degassing sources were identified a deep magmatic reservoir and a shallow hydrothermal system the variable interaction between these two sources is the most likely scenario for explaining the compositional ranges in acid gases but also in a volatile and fluid mobile trace element such as b these variations are related to changes in volcanic activity an extensive interaction between the hot ascending magmatic gases and the shallow aquifer occurred in 2009 possibly due to a long period of quiescence before magmatic activity renewed in 2011 and 2012 our study highlights therefore that filter pack measurements may be used to study changes in subsurface processes that probably play a key role in triggering volcanic eruptions

synchronizing intercontinental seismic networks using the 26 s persistent localized microseismic source accurate instrument clocks are essential for quantitative studies in seismology recent studies demonstrate that ambient seismic noise can be used to detect clock time drift for ocean bottom seismometers obss or inland seismometers with internal hardware or software problems but the short period 20 s interstation rayleigh waves extracted from ambient seismic noise are too weak for intercontinental seismic station pair correlations and thus are less effective for synchronizing sparse global seismic networks the 26 s persistent localized microseismic source in the gulf of guinea radiates strong seismic signals that can be recorded on global stations thus providing an alternative approach for synchronizing seismometers at large interstation distances in this study we test the feasibility of synchronizing seismic stations in africa north america and europe using the 26 s signals in the noise cross correlation functions we find that the clocks at the tam and obn stations are relatively stable during the years from 2002 to 2009 an 1 s time shift occurred at the ccm station from 2006 to 2009 and the clock drift was not constant we also detected about 150 s time shifts at the kowa station in october 2012 and up to 500 s in january 2013 we validate our results via comparison with the ambient noise method by stehly et al 2007 and teleseismic p wave arrival time residuals the method proposed in this study can be used to calibrate the obss in the north atlantic by synchronizing their clocks with the precisely calibrated inland seismometers

monitoring of active but quiescent volcanoes using light hydrocarbon distribution in volcanic gases the results of 4 years of discontinuous monitoring in the campi flegrei italy abstract during the period from january 1991 to january 1994 the 10 yr geochemical monitoring in the campi flegrei southern italy usually performed using the inorganic gas fraction was implemented by discontinuous monitoring of the hydrocarbon gas fraction the measured compositions have revealed the presence of significant amounts of at least 11 hydrocarbon species related to alkane alkene and aromatic classes thermodynamic calculations showed the possible existence of partially independent equilibria within the c1 c2 c3 and c1 c2 c3 c4 alkane systems as well as among alkene alkane pairs at redox conditions controlled by the geothermal feo fe1 5o redox buffer system at temperatures between 200 and 400 c and ph2o controlled by the presence of a saline brine unlike the constancy of the measured and calculated inorganic temperature equilibrium temperature based on organic species has displayed fluctuations and a significant increase starting from the second half of 1993 according to their apparent correlation with other independent observations such as the measured increases of vapor fraction h2s co2 and h2 n2 ratios on the monitored fumarole in addition to a general increase of dissolved co2 in the campi flegrei groundwaters the observed variations of the organic parameters were interpreted as the result of a general increase in acid bearing gas flux throughout the re equilibration zone

hydrothermal hydrocarbon gases in the sediments of the king george basin bransfield strait antarctica thermogenic hydrocarbons formed by the thermal alteration of organic matter are encountered in several piston core stations in the king george basin anatarctica these hemipelagic sediments are being deposited in an area of active hydrothermalism associated with the back arc spreading in the bransfield strait the lateral extent of sediments infiltrated by the hydrothermally influenced interstitial fluids is characterized by basalt diapirix intrusions and is delineated by an acoustically turbid zone in the sediments of the eastern part of the basin iron sulphide bearing veins and fractures cut across the sediment in several cores they appear to be conduits for flow of hydrothermally altered fluids these zones have the highest c2 and ethene contents the thermogenic hydrocarbons have molecular c1 c2 c3 ratios typically 50 and 13ch4 values between 38 and 48 indicating an organic source which has undergone strong thermal stress several sediment cores also have mixed gas signatures which indicate the presence of substantial amounts of bacterial gas predominantly methane hydrocarbon generation in the king george basin is thought to be a local phenomenon resulting from submarine volcanism with temperatures in the range 70 150 c there are no apparent seepages of hydrocarbons into the water column and it is not believed that significant accumulation of thermogenic hydrocarbons reside in the basin

source complexity of the 6 april 2009 l aquila central italy earthquake and its strongest aftershock revealed by elementary seismological analysis 1 seismic recordings are immediately available when an earthquake occurs their analysis allows the reconstruction of the rupture dynamics by means of sophisticated techniques which usually need some tests to provide robust results however immediate information on the source kinematics is required in order to imagine the fault location and extent and quickly reconstruct the areas of stress release and subsequent accumulation very simple analysis may provide useful information giving insight in source complexity right after the 6 april 2009 l aquila earthquake mw 6 3 we analyzed the seismograms recorded at broadband and strong motion stations and provided firm constraints on rupture kinematics slip distribution and static surface deformation also discriminating the actual fault plane the fracture occurred in two stages with initial updip propagation successively proceeding toward se possibly on a different plane we also analyzed the strongest aftershock mw 5 6 showing that useful indications could be retrieved for lower magnitude events

physico chemical and environmental controls on siliceous sinter formation at the high altitude el tatio geothermal field chile abstract el tatio geothermal field is located 4270 m above sea level in the altiplano northern chile siliceous sinter deposits from el tatio were studied to understand the influence of water chemistry and the extreme climatic conditions on their textures and mineralogy the results of this study show that the mineralogy of el tatio sinters include of opal a and accessory minerals such as halite gypsum and cahnite ca 4 b 2 as 2 o 12 4h 2 o which precipitate by full evaporation of high arsenic boron and calcium thermal waters el tatio sinters show a high degree of structural disorder probably linked to cation incorporation into the silica structure and or the occurrence of micro to nano scale accessory minerals the high content of cations in the thermal waters is strongly tied to relatively high silica precipitation rates considering silica concentration in water 147 285 mg l sio 2 precipitation rate reach 2 5 kg m 2 per year based on in situ precipitation experiments the particular environmental conditions of this high altitude geothermal area that produce high water cooling rate and high evaporation rate may also be responsible for the fast silica precipitation low environmental temperatures create freezing related sinter textures i e silica platelets and micro columns ridges silicified microbial filaments are also characteristic of el tatio sinters and they are indicative of water temperature and hydrodynamic conditions at the moment of sinter formation however sinter textural interpretation in a high altitude andean context must be done carefully as specific relationships between microbial and hydrodynamic textures are found

geochemistry of some gases in hydrothermal fluids from the southern juan de fuca ridge five samples of hydrothermal fluids from two vent areas on the southern juan de fuca ridge were analyzed for dissolved gases concentrations in the end member hydrothermal fluid of h2 270 527 mol kg ch4 82 118 mol kg and co2 3920 4460 mol kg are well above values in ambient seawater and are similar to concentrations reported for other ridge crest hydrothermal systems the carbon isotopic ratios of the ch4 13c 17 8 to 20 8 and co2 13c 3 6 to 4 7 suggest that at least some of the ch4 and co2 in the fluids is basalt derived the range of 13c values for the basalt derived co2 is 6 8 to 9 7 calculated by assuming conservation of recharge co2 during hydrothermal circulation apparent temperatures of equilibration between the ch4 and the basalt derived co2 range from 640 c to 750 c small amounts of ethane c2h6 ch4 0 9 10 3 2 2 10 3 propane and butane detected in the samples may also have formed in the basalt one sample of almost pure 95 5 hydrothermal fluid contained a significant fraction up to 63 and 74 respectively of the recharge ar and n2 this suggests that the fluid has not undergone extensive vapor liquid phase separation

evolution of fluid geochemistry at the turrialba volcano costa rica from 1998 to 2008 turrialba 10 02 n 83 45 w is a 3 349 m high stratovolcano belonging to the holocene cordillera central volcanic belt of costa rica the summit consists of three ew oriented craters east central and west since its last eruptive phase 1864 1866 the central and west craters have displayed modest fumarolic activity with outlet temperatures clustering around 90 c in 2001 seismic swarms ground deformation and increasing fumarolic activity occurred from 2005 to 2008 new fumarolic vents opened between and within the central and west craters and along the western and southwestern outer flanks of the volcanic edifice these physical changes were accompanied by a drastic modification in the gas chemistry that can be divided in three stages 1 hydrothermal from 1998 to autumn 2001 characterized by the presence of h2o co2 h2s and to a very minor extent hcl and hf 2 hydrothermal magmatic autumn 2001 2007 with the appearance of so2 and a significant increase of hcl and hf and 3 magmatic dominated 2007 2008 characterized by increased so2 content so2 h2s 100 and temperatures up to 282 c accordingly gas equilibrium in the co2 ch4 h2 system suggests a progressive evolution of the deep fluid reservoir toward higher temperatures and more oxidizing conditions the chemical physical modifications of turrialba in the last decade can be interpreted as part of a cyclic mechanism controlling the balance between the hydrothermal and the magmatic systems nevertheless the risk of rejuvenation of the volcanic activity cannot be excluded and an appropriate seismic ground deformation and geochemical monitoring program is highly recommended turrialba lies at a distance of 35 and 15 km from san jose and cartago respectively the two largest cities in costa rica

geochemical and isotopic evidences of magmatic inputs in the hydrothermal reservoir feeding the fumarolic discharges of tacora volcano northern chile abstract tacora volcano is a nearly unknown and understudied 5980 m high volcano located on the northernmost border between chile and peru tacora is characterized by intense fumarolic activity with extensive white colored hydrothermal areas along the nw and w flanks of the volcanic structure the chemical and isotopic features of gas emissions indicate that the hydrothermal reservoir is significantly affected by contributions from magmatic degassing despite relatively low outlet temperatures 82 93 c water and gas isotopic signatures stem from degassing of andesitic magmas produced from the sediment poor subducting slab isotopic data suggests ch 4 co 2 isotopic equilibration occurs at 400 c likely in the deepest portion of the hydrothermal magmatic fluid reservoir the h 2 h 2 o co co 2 h 2 ar ch 4 co 2 and c 2 c 3 alkenes alkanes pairs tend to approach a chemical equilibrium at temperatures between 200 and 320 c when redox conditions are more oxidizing than those determined by the typical feo feo 1 5 rock buffer system boiling occurs at shallow depth at 85 c within a discontinuous thin aquifer enough as thermal buffer but not able to scrub the uprising magmatic related acidic gases

fluid geochemistry and geothermometry in the unexploited geothermal field of the vicano cimino volcanic district central italy abstract the vicano cimino volcanic district vcvd is related to the post orogenic magmatic activity of the peri tyrrhenian sector of central italy the chemical and isotopic compositions of 333 water discharges and 25 gas emissions indicate the occurrence of two main sources 1 cold ca hco 3 to ca na k hco 3 type waters from relatively shallow aquifers hosted in volcanic and sedimentary formations and 2 thermal ca so 4 hco 3 type waters located in a deep co 2 pressurized reservoir hosted in carbonate evaporite rocks and separated from the shallow aquifers by thick sequences of low permeability formations carbon dioxide is mainly produced by thermal metamorphic decarbonation within the deepest and hottest parts of the carbonate evaporite reservoir 13 c co 2 from 3 1 to 2 2 vs vpdb likely affected by a mantle rooted co 2 release of co 2 rich gases from the deep aquifer into the overlying shallow aquifers produces high co 2 springs and bubbling pools the spatial distribution of thermal waters and co 2 rich cold discharges is strongly controlled by fractures and faults located in correspondence with buried structural highs stable isotopes d and 18 o suggest that meteoric water feeds both the shallow and deep reservoirs the relatively low r r a values 0 27 1 19 indicate that he is mainly deriving from a crustal source with minor component from the mantle affected by crustal contamination related to the subduction of the adriatic plate consistently relatively high n 2 ar and n 2 3 he ratios and positive 15 n n 2 values from 0 91 to 5 7 vs air characterize the vcvd gas discharges suggesting the occurrence of a significant excess nitrogen isotopic compositions of ch 4 13 c ch 4 and d ch 4 values from 28 9 to 22 1 vs vpdb and from 176 to 138 vs vsmow respectively and composition of light alkanes are indicative of prevalent thermogenic ch 4 although the occurrence of abiogenic ch 4 production cannot be excluded the 34 s h 2 s values from 9 3 to 11 4 vs vcdt are consistent with the hypothesis of h 2 s production from thermogenic reduction of triassic anhydrites gas geothermometry in the h 2 o h 2 ar h 2 s system suggests that the vcvd gases equilibrated in a liquid phase at redox conditions controlled by interactions of fluids with the local mineral assemblage at temperatures lower 2000 m geothermal wells this confirms that secondary processes i e steam condensation gas dissolution in shallow aquifers re equilibration at lower temperature and microbial activity significantly affect the chemistry of the uprising fluids thermal water chemistry supports the occurrence in this area of an anomalous heat flow that coupled with the recent demographic growth makes this site suitable for direct and indirect exploitation of the geothermal resource in agreement with the preliminary surveys carried out in the 1970 s 1990 s for geothermal exploration purposes

origin of strontium and calcium in pedogenic needle fibre calcite nfc abstract strontium sr and calcium ca isotopic compositions and sr ca ratios have been analysed in different fractions of pedogenic needle fibre calcite nfc from the swiss jura mountains villiers neuch tel switzerland in order to determine their ca sources and to investigate the potential role of fungi in the origin of nfc 87sr 86sr ratios have been measured to trace the ca trapped within different pedogenic carbonate this ratio was compared for previously identified microscopic morphological groups of nfc the bulk soil fine earth

mineral assisted production of benzene under hydrothermal conditions insights from experimental studies on c6 cyclic hydrocarbons abstract volatile organic compounds vocs are ubiquitously present at low but detectable concentrations in hydrothermal fluids from volcanic and geothermal systems although their behavior is strictly controlled by physical and chemical parameters the mechanisms responsible for the production of most vocs in natural environments are poorly understood among them benzene whose abundances were found to be relatively high in hydrothermal gases can theoretically be originated from reversible catalytic reforming processes i e multi step dehydrogenation reactions involving saturated hydrocarbons however this hypothesis and other hypotheses are difficult to definitively prove on the basis of compositional data obtained by natural gas discharges only in this study therefore laboratory experiments were carried out to investigate the production of benzene from cyclic hydrocarbons at hydrothermal conditions specifically 300 c and 85 bar the results of experiments carried out in the presence of water and selected powdered minerals suggest that cyclohexane undergoes dehydrogenation to form benzene with cyclohexene and cyclohexadiene as by products and also as likely reaction intermediates this reaction is slow when carried out in water alone and competes with isomerization and hydration pathways however benzene formation was increased compared to these competing reactions in the presence of sulfide sphalerite and pyrite and iron oxide magnetite and hematite minerals whereas no enhancement of any reaction products was observed in the presence of quartz the production of thiols was observed in experiments involving sphalerite and pyrite suggesting that sulfide minerals may act both to enhance reactivity and also as reactants after dissolution these experiments demonstrate that benzene can be effectively produced at hydrothermal conditions through dehydrogenation of saturated cyclic organic structures and highlight the crucial role played by minerals in this process

the magmatic and hydrothermal dominated fumarolic system at the active crater of lascar volcano northern chile low to high temperature fumaroles discharging from the active crater of lascar volcano northern chile have been collected in november 2002 may 2005 and october 2006 for chemical and isotopic analysis to provide the first geochemical survey on the magmatic hydrothermal system of this active volcano chemical and isotopic gas composition shows direct addition of high temperature fluids from magmatic degassing mainly testified by the very high contents of so2 hcl and hf up to 87 800 29 500 and 2 900 mol mol and the high r ra values up to 7 29 contributions from a hydrothermal source mainly in gas discharges of the active crater rim has also been detected significant variations in fluid chemistry mainly consisting of a general decrease of magmatic related compounds i e so2 have affected the fumarolic system during the period of observation indicating an increase of the influence of the hydrothermal system surrounding the ascending deep fluids the chemical composition of active crater fumaroles has been used to build up a geochemical model describing the main processes that regulate the fluid circulation system of lascar volcano to be utilized in volcanic surveillance

origin of methane and light hydrocarbons in natural fluid emissions a key study from greece abstract greece a country characterised by intense seismic and volcanic activity has a complex geodynamic and geological setting that favours the occurrence of many gas manifestations in this study we address the origin of ch 4 and light hydrocarbons in cold and thermal emissions discharging along the hellenic territory also we investigate their possible relationship with the main geochemical composition of the gases and the different geological settings of the sampling sites for this purpose we collected 101 new samples that were analysed for their chemical o 2 n 2 ch 4 co 2 he ne ar h 2 h 2 s and c 2 c 6 hydrocarbons and isotopic r r a 13 c co 2 13 c ch 4 and 2 h ch 4 composition results show that ch 4 presents a wide range of concentrations from 13 c ch 4 from 79 8 to 45 0 vs v pdb 2 h ch 4 from 311 to 301 vs v smow greece was subdivided in four geologic units external eh and internal ih hellenides hellenic hinterland hh and active volcanic arc va and a decreasing ch 4 concentration from eh to hh was recognized whereas ch 4 showed intermediate concentrations in va the ch 4 c 2 h 6 c 3 h 8 ratios from 1 5 to 93 200 coupled with ch 4 isotopic features suggest that the light alkanes derive from different primary sources and are affected by secondary processes an almost exclusive biotic mainly microbial origin of ch 4 can be attributed to eh gases cold gases at ih have mainly a thermogenic origin although some gases connected to continental serpentinization may have an abiogenic origin methane in gases bubbling in thermal waters of ih hh and va and fumarolic gases of the va seem to have an abiogenic origin although their chemical and isotopic characteristics may have been produced by secondary oxidation of thermogenic ch 4 a process that in some of the sampled gases causes extremely positive isotopic values 13 c ch 4 up to 45 0 vs v pdb and 2 h ch 4 up to 301 vs v smow

scrubbing process and chemical equilibria controlling the composition of light hydrocarbons in natural gas discharges an example from the geothermal fields of el salvador 1 the compositional features of fluids from both fumarolic discharges and productive geothermal wells of ahuachapan chipilapa berlin chinameca and san vicente geothermal systems el salvador are described and discussed in order to investigate the complex geochemical interactions involving geothermal fluids within the shallowest part of the hydrothermal circulation pathways our results highlight that secondary processes are able to strongly affect and modify the chemical characteristics of geothermal gases once they discharge to the surface as natural manifestations mainly in relation to the chemical physical properties of each gas species the effects of both gas dissolution in shallow aquifers and gas water rock chemical interactions on gas discharge composition make it difficult to get a correct evaluation of the thermodynamic conditions that characterize the geothermal reservoirs by applying the common geoindicators based on the chemical equilibria of the h2o co2 h2 ch4 co system differently the composition of the c1 c2 c3 alkanes and the c3 and c4 alkane alkene pair established within the geothermal reservoirs under the control of chemical reactions remains stable in samples collected from discharging gas vents these results suggest that the relative abundances of hydrocarbons characterized by similar structure and molecular size seem to be mainly regulated by the diffusion velocity of gases through the liquid dominated system therefore the chemical features of the light organic gas fraction of naturally discharging fluids can be successfully utilized for the evaluation of geothermal reservoir temperatures and redox conditions providing useful indications in terms of geothermal exploration and exploitation on this basis the distribution speciation and relative abundances of light hydrocarbons can also be considered highly promising in geochemical monitoring of active volcanic systems

anisotropic shear wave velocity structure of the earth s mantle a global model 1 we combine a new large data set of surface wave phase anomalies long period waveforms and body wave travel times to construct a three dimensional model of the anisotropic shear wave velocity in the earth s mantle our modeling approach is improved and more comprehensive compared to our earlier studies and involves the development and implementation of a new spherically symmetric reference model simultaneous inversion for velocity and anisotropy as well as discontinuity topographies and implementation of nonlinear crustal corrections for waveforms a comparison of our new three dimensional model s362ani with two other models derived from comparable data sets but using different techniques reveals persistent features 1 strong 200 km thick high velocity anomalies beneath cratons likely representing the continental lithosphere underlain by weaker fast anomalies extending below 250 km which may represent continental roots 2 weak velocity heterogeneity between 250 and 400 km depths 3 fast anomalies extending horizontally up to 2000 3000 km in the mantle transition zone beneath subduction zones 4 lack of strong long wavelength heterogeneity below 650 km suggesting inhibiting character of the upper mantle lower mantle boundary and 5 slow velocity superplumes beneath the pacific and africa the shear wave radial anisotropy is strongest at 120 km depth in particular beneath the central pacific lateral anisotropic variations appreciably improve the fit to data that are predominantly sensitive to the uppermost and lowermost mantle but not to the waveforms that control the transition zone and midmantle depths tradeoffs between lateral variations in velocity and anisotropy are negligible in the uppermost mantle but noticeable at the bottom of the mantle

dynamics within geyser conduits and sensitivity to environmental perturbations insights from a periodic geyser in the el tatio geyser field atacama desert chile abstract despite more than 200 years of scientific study the internal dynamics of geyser systems remain poorly characterized as a consequence there remain fundamental questions about what processes initiate and terminate eruptions and where eruptions begin over a one week period in october 2012 we collected down hole measurements of pressure and temperature in the conduit of an exceptionally regular geyser 132 s cycle located in the chilean desert we identified four stages in the geyser cycle 1 recharge of water into the conduit after an eruption driven by the pressure difference between water in the conduit and in a deeper reservoir 2 a pre eruptive stage that follows the recharge and is dominated by addition of steam from below 3 the eruption which occurs by rapid boiling of a large mass of water at the top of the water column and decompression that propagates boiling conditions downward and 4 a relaxation stage during which pressure and temperature decrease until conditions preceding the recharge stage are restored eruptions are triggered by the episodic addition of steam coming from depth suggesting that the dynamics of the eruptions are dominated by geometrical and thermodynamic complexities in the conduit and reservoir further evidence favoring the dominance of internal processes in controlling periodicity is also provided by the absence of responses of the geyser to environmental perturbations air pressure temperature and probably also earth tides

arsenic speciation in sinter mineralization from a hydrothermal channel of el tatio geothermal field chile summary el tatio geothermal field is the principal natural source of arsenic for the loa river the main surface water resource in the hyper arid atacama desert antofagasta region northern chile prior investigations by bulk x ray absorption spectroscopy have identified hydrous ferric oxides as the principal arsenic containing phase in sinter material from el tatio suggesting sorption as the main mechanism for arsenic scavenging by the solid phases of these hot spring environments here we examine siliceous sinter material sampled from a hydrothermal channel using synchrotron based x ray micro probe techniques including as and fe k x ray fluorescence xrf as k edge x ray absorption near edge structure xanes and x ray diffraction xrd least squares linear fitting of xanes spectra shows that arsenic is predominantly present as arsenate sorbed on hydrous ferric oxides 63 molar proportion but we also identify nodular arsenide micro mineralizations 37 molar proportion similar to loellingite feas 2 not previously detected during bulk scale analysis of the sinter material presence of arsenide mineralizations indicates development of anoxic environments on the surface of the siliceous sinter and suggests a more complex biogeochemistry for arsenic than previously observed for circum neutral ph brine hot spring environments

evolution of light hydrocarbon gases in subsurface processes constraints from chemical equilibrium abstract the behaviour of ch 4 c 2 h 6 and c 3 h 8 in subsurface processes such as magma intrusion volcanic gas discharge and natural gas generation have been examined from the viewpoint of chemical equilibrium it seems that equilibrium among these three hydrocarbons is attainable at about 200 c when a system at high temperatures is cooled re equilibration is continued until a low temperature is reached the rate at which re equilibration is achieved however steadily diminishes and below 200 c the reaction between the hydrocarbons stops and the gas composition at this time is frozen in and it remains unchanged in a metastable state for a long period of geological time natural gas compositions from various fields have shown that when a hydrocarbon system out of chemical equilibrium is heated it gradually approaches equilibrium above 150 c on the way towards equilibration compositions of thermogenic gases apparently temporarily show a thermodynamic equilibrium constant at a temperature that is higher than the real equilibrium temperature expected from the ambient temperature of the samples in contrast biogenic gases indicate a lower temperature in lower temperature regions kinetic effects probably control the gas composition the compositions are essentially subjected to genetic processes operating on the gases such as pyrolysis of organic material and bacterial activity and they fluctuate substantially examination of volcanic gases and pyrolysis experimental data however have suggested that the equilibration rate of these hydrocarbons is sluggish in comparison with that of reactive inorganic species such as h 2 s and so 2 the view presented in this study will be helpful in understanding the genetic processes that create oil and gas and the migration of these hydrocarbons and in interpreting the origins of magmatic gases

carbon dioxide in scree slope deposits a pathway from atmosphere to pedogenic carbonate abstract a continuum of carbon from atmospheric co2 to secondary calcium carbonate has been studied in a soil associated with scree slope deposits in the jura mountains of switzerland this approach is based on former studies conducted in other environments this c continuum includes atmospheric co2 soil organic matter som soil co2 dissolved inorganic carbon dic in soil solutions and secondary pedogenic carbonate soil parameters pco2 temperature ph cmin and corg contents soil solution chemistry and isotopic compositions of soil co2 dic carbonate and soil organic matter 13cco2 13cdic 13ccar and 13csom values have been monitored at different depths from 20 to 140 cm over one year results demonstrated that the carbon source in secondary carbonate mainly needle fiber calcite is related to the dissolved inorganic carbon which is strongly dependent on soil respiration the heterotrophic respiration rather than the limestone parent material seems to control the pedogenic carbon cycle the correlation of 13corg values with rock eval hi and oi indices demonstrates that in a soil associated to scree slope deposits the main process responsible for 13c enrichment in som is related to bacterial oxidative decarboxylation finally precipitation of secondary calcium carbonate is enhanced by changes in soil pco2 associated to the convective movement of air masses induced by temperature gradients heat pump effect in the highly porous scree slope deposits the exportation of soil c leachates from systems such as the one studied in this paper could partially explain the gap in the european carbon budget reported by recent studies

cover beds as soil parent materials in midlatitude regions abstract in parts of southern france the russian plain south central turkey the western usa and in germany slopes are covered by deposits cover beds formed by geomorphic processes not limited to linear discharges often loess material is mixed into them cover beds usually form sequences of two or more distinct layers and their distribution depends on the geomorphic climate driven processes of their formation as they influence pedogenesis they contribute to the understanding of soil properties and soil distribution horizon boundaries occur at depths where cover bed properties change where aeolian matter is mixed in podzolisation is buffered but depletion of clay may occur loess rich cover beds may entirely decouple pedogenesis from bedrock influence in humid areas soil water stagnation is often associated with varying cover bed bulk densities particularly upon flat relief in semiarid areas deep soil profiles consist of multiple layer sequences often with argillic and calcic properties within the same horizons they reflect several cycles of cover bed deposition and incorporation of loess alternating with decalcification accompanied and followed by clay translocation this led to the overprinting of buried soils by pedogenic carbonate leached from younger sediments synchronous sediment and or airborne carbonate accretion and pedogenesis which is usually invoked to explain soil profiles with several calcic horizons cannot apply to cover beds

weathering processes in superficial deposits regolith and their influence on pedogenesis a case study in the swiss jura mountains abstract the last glacial period left a mantle of freshly reworked sediments covering the european landscape glacial periglacial fluvio glacial and aeolian dynamics enhanced transportation and mixing of materials generating new superficial deposits in which holocene soils developed these assorted surface sediments often differed from the underlying bedrock in their lithological composition and texture and were delimited by lithological discontinuities in the swiss jura mountains the mesozoic limestone bedrocks are covered by various superficial deposits moraines cover beds loess deposits cryoclasts etc which reduce or even suppress the influence of limestone on present day soil development in this context soils and their underlying bedrock no longer present a genetic continuity the nature and relationships between these deposits is studied within a toposequence of soils in terms of their mineralogical and geochemical compositions three main superficial deposits limestone bedrock clasts loess and non carbonate moraine are used as reference materials in order to characterize the complex mixing of sediments through the toposequence soils with limestone clasts undergo decarbonation and decalcification processes iron rich alpine loess deposits composed of fine silicate particles enhance brunification process in soils a non carbonate alpine moraine displays the most acidic conditions within the toposequence due to enhanced leaching clay and ions processes consequently the reworked surface sediments including limestone cryoclasts moraines and cover beds have a prevailing influence on pedogenesis compared to the hard underlying bedrock

depositional evolution of an extinct sinter mound from source to outflow el tatio chile siliceous sinter deposits from el tatio chile preserve a wide variety of depositional environments and biosignatures from high temperature 85 c vent proximal facies to distal deposits dominated by silicified microbial mats four cores were drilled into an el tatio sinter mound and associated distal apron to investigate changes in hydrothermal environments over geologic timescales sedimentary and geochemical analysis of multiple sinter cores records the initiation and accretion of diverse depositional features still observed today in el tatio facies adjacent to hydrothermal vents are dominated by laminated sinter crusts on the steep margins of a high temperature pool with sparse microbial preservation outer margins of the same pool contain extensive sinter columns up to ten centimeters in length precipitated during repeated cycles of pool overflow and subsequent evaporation low relief hydrothermal pools also form minor deposits within distal debris aprons and analogous pools are still active close to sampling locations debris aprons are dominated by palisade tufted and arborescent microbial fabrics with distinct mat textures revealing well preserved microfossils surficial deposits in all cores feature detrital rich and microbially influenced sinters overlying higher temperature facies indicating a relative decrease in hydrothermal activity over time geochemical proxies for hydrothermal fluids and de trital input match depositional interpretations based on sedimentary structures 14 c ages from core deposits extend the mound s history by 11 000 years recording at least three thousand years of sinter deposition on top of glacial sandstones 13 337 10 232 y cal bp importantly this work provides a detailed depositional model unavailable through surficial sedimentology alone

evolution of the lithosphere in the indian ocean from combined earthquake and ambient noise tomography rayleigh wave dispersion extracted from ambient seismic noise has been widely used to image crustal and uppermost mantle structure applications of this approach in continental settings are abundant but there have been relatively few studies within ocean basins by cross correlating ambient noise recorded at broadband seismic stations around the indian ocean we demonstrate the feasibility of extracting high quality long period 10 30 mhz rayleigh waves that traverse the entire ocean basin high quality rayleigh wave cross correlation functions can be obtained from stacking waveforms over less than two years at land stations and less than four years at island stations we show that adding the dispersion information extracted from ambient noise to a global earthquake data set can improve the resolution of phase velocity maps by about 20 in the northern indian ocean where the station distribution is the best we find that a plate cooling model with a potential temperature of 1450 c and plate thickness of 125 km can fit both the seismic observations and seafloor topography the seychelles mascarene plateau is characterized by anomalously slow velocity at 30 mhz the inclusion of ambient noise data in the tomographic inversion shifts the slow velocity anomaly into better agreement with the topographic relief allowing us to estimate its crustal thickness and confirm that the plateau s elevation is supported by thick crust the 10 and 20 mhz phase velocity maps show a strong asymmetry across the central indian ridge that is best explained by eastward asthenospheric flow emanating from nearby hotspots

a search for the origin of cadmium in the soil of the swiss jura abstract the top soil of a 14 5 km 2 region at la chaux de fonds in the swiss jura is exceptionally rich in cadmium it contains an average of 1 3 mg per kg of soil the spatial distribution of the metal has no simple pattern that could be explained by atmospheric deposition or agricultural practices thin soil contained most of its cd at the surface in thicker soil cd is mainly concentrated between 60 and 80 cm depth no specific minerals or soil fractions could account for these accumulation and the vertical distribution of cd is best explained by leaching from the topsoil and further adsorption within layers of nearly neutral ph the local jurassic sedimentary rocks contained too little cd to account for the cd concentrations in the soil alpine gravels from glacial till were too sparse in soils to explain such a spreading of cd moreover this origin is contradictory with the fact that cd is concentrated in the sand fraction of soils the respective distributions of fe and cd in soils and soil fractions suggested that the spreading of iron nodules accumulated during the siderolithic period eocene was not the main source of cd atmospheric deposition and spreading of fertiliser or waste from septic tanks seem the only plausible explanation for the cd concentrations but at present few factors allow us to differentiate between them

surface wave array tomography in se tibet from ambient seismic noise and two station analysis i phase velocity maps summary empirical green s functions egfs between pairs of seismographs can be estimated from the time derivative of the long time cross correlation of ambient seismic noise these egfs reveal velocity dispersion at relatively short periods which can be used to resolve structures in the crust and uppermost mantle better than with traditional surface wave tomography we combine rayleigh wave dispersion estimates from egfs and from traditional two station ts analysis into a new approach to surface wave array tomography with data from dense receiver arrays we illustrate the methodology with continuous broad band recordings from a temporary seismographic network on the southeastern part of the tibetan plateau in sichuan and yunnan provinces sw china the egfs are robust under temporal changes in regional seismicity and the use of either ambient noise approximated by records without signal from events with magnitude mb 5 or 4 or surface wave coda produces similar results the egfs do not strongly depend on the presence of large earthquakes but they are not reciprocal for stations aligned in the n s direction this directionality reflects the paucity of seismicity to the north of the array using a far field representation of the surface wave green s function and an image transformation technique we infer from the egfs the rayleigh wave phase velocity dispersion in the period band from 10 30 s a classical ts approach is used to determine rayleigh wave phase velocity dispersion between 20 120 s together they constrain phase velocity variations for t 10 120 s which can be used to study the structure from the crust to the upper mantle beneath se tibet short and intermediate period 10 80 s phase velocities are prominently low suggesting that the crust and upper mantle beneath se tibet is characterized by slow shear wave propagation

submersible observations along the southern juan de fuca ridge 1984 alvin program in september 1984 the research submersible alvin provided direct observations of three major hydrothermal vent areas along the southernmost segment of the juan de fuca ridge jfr the submersible operations focused on specific volcanologie structural and hydrothermal problems that had been identified during the preceding 4 years of photographic dredging acoustic imaging and geophysical studies along a 12 km long section of the ridge a continuously maintained from 1981 to the present net of seafloor anchored acoustic transponders allowed the observations from alvin to be directly tied to all previous u s geological survey data sets and national oceanic and atmospheric administration water column surveys from 1984 to the present the three vent areas studied are the largest of at least six areas identified by previous deep towed camera surveys that lie within a deep cleft which marks the axis of symmetry of the jfr in this region the cleft appears to be the locus of eruption for this segment of the jfr the vent areas at least in part are localized near what appear to be previous volcanic eruptive centers marked by extensive lava lake collapse features adjacent to the cleft at these sites each hydrothermal area has several active discharge sites and sulfide deposits occur as clusters 15 100 m2 of small chimneys individual large chimneys or clusters of large branched chimneys we review the dive program and present a brief synthesis of the geology of the vent sites together with sample and track line compilations

fluid geochemistry of hydrothermal systems in the arica parinacota tarapaca and antofagasta regions northern chile we investigate the chemical and isotopic composition of water and gas thermal discharges from six hydrothermal systems in the tarapaca and antofagasta regions northern chile surire puchuldiza tuja pampa lirima pampa apacheta el tatio and torta de tocorpuri to determine the chemical physical conditions at the fluid source the chemical facies of the thermal discharges vary from na cl el tatio puchuldiza tuja and part of surire where so42 rich waters also occur to na ca2 cl so42 pampa lirima ca2 so42 hco3 torta de tocorpuri and ca2 so42 pampa apacheta the gas seeps are characterized by the dominance of co2 h2s and ch4 with n2 ar ratios that occasionally are up to 450 significant amounts of so2 and hcl are present at pampa apacheta water and gas geothermometry suggests that el tatio and puchuldiza tuja fluid reservoirs have relatively high reservoir equilibrium temperature up to 270 c gases from pampa apacheta apparently equilibrated at unusually high temperature for hydrothermal fluids up to 350 c being likely related to an active magmatic system as testified by the presence of highly acidic gas compounds such as so2 and hcl on the contrary low equilibrium temperatures were calculated for the surire fluids 200 c suggesting interactions of deep originated fluids with meteoric water at shallow depth shallow low temperature aquifers mask any signal of deep fluids in the pampa lirima and torta de tocorcupi thermal discharges despite the variations in temperatures he isotopic compositions and redox conditions of the fluid reservoirs consistently indicate a significant contribution from magmatic degassing although geophysical studies are necessary to better constrain the geothermal potential of northern chile the geothermometric estimations carried out in the present study indicate that el tatio pampa apacheta surire and puchuldiza tuja can be regarded as the most promising areas and deserve more detailed geological investigations

speciation and multivariable analyses of geogenic cadmium in soils at le gurnigel swiss jura mountains abstract mineralogical and geochemical analyses were performed on six closely spaced within a perimeter of 300 m soil profiles which are naturally enriched in cadmium cd at le gurnigel swiss jura mountains the soils consist of cambisols and cambic luvisols the latter including an important allochthonous aeolian fraction loess all soils are associated with bedrock composed of middle jurassic bajocian oolithic carbonate a lithology which has been identified as a source of geogenic cd cd concentrations generally increase down the analyzed soil profiles showing maxima up to 16 3 mg kg 1 near the soil bedrock interface a sequential extraction analysis suggests that most cd resides in the carbonate and organic fractions of topsoils whereas the amorphous iron and manganese oxyhydroxide fraction become the most important cd bearing phase in the middle and deeper parts of the soils a principal component analysis shows that cd zn and cr are positively correlated with comparable distributions in the soil profiles suggesting a common bearing phase such as fe oxyhydroxides for these three elements a complex transfer pattern of cd is proposed for the analyzed soil profiles which starts with the release of cd from the underlying bedrock and its transfer into oxide hydroxide carbonate and organic phases additionally the lateral advection of cd rich soils on top of these soils adds cd to them which is transferred from the topsoil towards the deeper horizons by biological and pedological processes the amount of readily exchangeable and therefore potentially bioavailable cd is low in these soils on average 0 2 mg kg 1 provided that the ph remains above 5 under stronger acidic conditions the concentration of bioavailable cd may increase in the topsoils of thin cambisols 3 0 mg kg 1 and cambic luvisols 1 2 mg kg 1 under stronger acidic ph

fugacity concentration relationship of dilute hydrogen in water at elevated temperature and pressure abstract the fugacity vs concentration ratio y of dilute hydrogen dissolved in water was determined at temperatures below 500 c and pressures below 1000 bar by measuring h 2 concentrations in magnetite hematite water and palladium hydride water systems combining these results with reported solubility data of h 2 in water and with the shaw s expression for the activity composition relationship of h 2 h 2 o mixture at higher temperatures the p t y diagram was constructed over the p t range below 900 c and 1000 bar

soils as a useful tool for reconstructing geomorphic dynamics in high mountain environments the case of the buscagna stream hydrographic basin lepontine alps abstract the soil formation its development and its preservation in high mountain environments are largely determined by topography and geomorphological dynamic therefore soil development in alpine areas is often non linear over time and characterized by phases of progressive and regressive evolution the interaction among soil forming factors is preserved in soils as physical chemical properties and pedological features in particular the action of surface geomorphological processes can be observed as stone lines or sequences of buried surfaces in this light exhaustive investigation of soils and paleosols could provide enough information to reconstruct past environmental conditions and spatio temporal changes in denudation deposition processes the main aim of this study is to assess the role of soil as a useful archive for retracing the geomorphological processes that are responsible for the landscape evolution during the late holocene in a typical alpine catchment such as the buscagna stream hydrographic basin veglia devero natural park lepontine alps the asymmetry in valley slopes due to lithology and structural control generates a great variety of geomorphic processes and landforms therefore seven soil profiles were selected along the two slopes in different morphological contexts to reveal the influence of the different active geomorphic processes in soil development soils were investigated by means of field and laboratory analyses and geomorphological maps of the area surrounding the profiles were made on the southeastern slope characterized by calcschist substratum the soil profiles are composed of two superimposed pedological units separated by an instability hiatus on the northwestern slope characterized by gneiss and ultramafic rocks and on the valley bottom the soils record instability phases in different ways fitting well with the geomorphological context in this mountain environment the close relationship between soil development and geomorphic processes allows us to confirm the role of soil as a useful archive to potentially reconstruct the past geomorphological conditions

late glacial and early holocene changes in vegetation and lake level at hauterive rouges terres lake neuchâtel switzerland palynological and sedimentological analyses of a sedimentary sequence sampled at hauterive rouges terres lake neuch tel switzerland provide documentation of changes in vegetation and lake level during the bolling younger dryas and preboreal pollen zones and have allowed a comparison with sequences covering the same period from other sites located in the western part of the swiss plateau the juniperus hippophae zone regional pollen assemblage zone rpaz chb 2 first part of the bolling ca 14 650 14 450 cal yr bp was characterised by a generally low lake level a weak rise occurred during this zone the juniperus hippophae to betula zone transition coincided with a lake level lowering interrupted by a short lived but marked phase of higher lake level recorded at the neighbouring site of hauterive champreveyres but not present at hauterive rouges terres owing to an erosion surface shortly after the beginning of the betula zone rpaz chb 3 second part of the bolling ca 14 450 14 000 cal yr bp a marked rise in lake level occurred it was composed of two successive periods of higher level coinciding with high values of betula separated by a short episode of relatively lower lake level associated with raised values in artemisia and other non arboreal pollen the last part of rpaz chb 3 saw a fall in lake level the lower lake levels during rpaz chb 2 to early rpaz chb 3 can be correlated with the abrupt warming at the beginning of the greenland interstadial gi 1e thermal maximum the successive episodes of higher lake level punctuating the gi 1e might be linked to the so called intra bolling cold oscillations identified from several palaeoclimatic records in the north atlantic area and also documented in oxygen isotope data sets from swiss plateau lakes the hauterive rouges terres lake level record provides evidence for marked climatic drying through the second part of the younger dryas event gs1 during the gs1 preboreal rpaz chb 4b 4c transition except for a rise at ca 11 450 11 400 cal yr bp and at the rpaz chb 4c 5 preboreal boreal transition following the preboreal oscillation after 11 150 cal yr bp the preboreal oscillation coincided with higher lake levels its end being followed by a rapid expansion of corylus quercus ulmus and tilia the hauterive rouges terres lake level record suggests that radiocarbon plateau at 12 600 10 000 and 9500 14c yr bp corresponded to periods of generally lower lake level this suggests that an increase in solar activity may have contributed to both climatic dryness and a decrease in atmospheric radiocarbon content copyright 2002 john wiley sons ltd

bedrock versus superficial deposits in the swiss jura mountains what is the legitimate soil parent material soils are generally considered to be the result of in situ weathered products of geological substrata nevertheless the earth s surface is mainly composed of superficial deposits made of sediments reworked during periods of climate instability glaciation aridification flooding etc but to what extent do these deposits influence present day soil development and or lessen the contribution of the geological substratum in the swiss jura mountains characterization and distribution of superficial deposits along a toposequence are used in order to decipher the polygenic sources of soil parent materials and question the importance of lithodependence in soil development the in situ weathering material and the allochtonous deposits are discriminated through analysis of mineralogical composition grain size distribution of the soil mineral fraction and multivariate statistical treatment as expected calcite is dominant in the autochonous mineral phase leading to high ph values in deep soil layers however the mineralogical composition of the surficial deposits is made of local mineral components mixed with allochtonous aeolian deposits this exogenous material is dominated by quartz and phyllosilicates and is reflected by low ph values in soil surficial horizons the grain size distribution curves of the insoluble residue from bedrocks are unimodal and dominated by fine loam and clays in contrast surficial deposits display polymodal curves demonstrating the contribution of various aeolian episodes and or sources analysis of the surface texture of quartz sand grains shows glacial marks intersected by aeolian shock marks indicating the posteriority of wind transportation loess material originates from alpine moraines of the swiss plateau and is mixed with deposits originating from more proximal jura moraines diluting the alpine signature consequently the soil development does not follow the expected and conventional decalcification process but is directly influenced by the origin of the primary sediments even when present only in small amounts and their evolution copyright 2012 john wiley sons ltd

periglacial cover beds on the swiss plateau indicators of soil climate and landscape evolution during the late quaternary abstract soils and the stratification of their parent materials were studied on the central swiss plateau this area is characterized by glacial deposits varying from late glacial to pre wurmian in age soils of all studied sites are developed within colluvial layers the so called cover beds in relation to the underlying deposits we find a regular spatial distribution of cover bed types a surficial layer upper layer with relatively constant thickness around 50 cm independent of relief position covers pleistocene sediments of any age therefore it was formed mainly by cryoturbation solifluction after the final glacier retreat from the swiss plateau younger dryas or oldest dryas age layers that originate mainly from aeolian processes intermediate layers are restricted to areas outside the recessional moraines of the berne stade bs hence they were formed merely up to the late pleniglacial they frequently consist of two distinct layers outside the glaciation of the last glacial maximum lgm cover beds in places overlie pre lgm palaeosol relics probably of eemian age or even older these are preserved even on higher relief positions indicating that periglacial erosion during the pleniglacial was only marginal the palaeosol relics also occur on till of the so called older wangen stade which is commonly believed to represent the lgm whereas we consider it to be older at least partly eventually the distribution of soil types and their ecological characteristics are influenced considerably by cover beds as these beds reflect distinct phases of the pleistocene colluvial sediments provide a major tool for linking modern landscape characteristics to the late quaternary climate evolution

chemistry of hydrothermal solutions from the southern juan de fuca ridge fluids from three vent fields on the southern juan de fuca ridge were sampled in september 1984 using the dsrv alvin the fluids are uniquely high in both chloride which ranges up to twice the seawater value and in metal content simple vapor liquid phase separation could not have produced both the high chlorinity and gas concentrations observed in these fluids the cause of the elevated chlorinity can not be uniquely identified but may be the result of either or a combination of two processes 1 subsurface formation of a degassed brine and subsequent mixing of a small amount of this brine with a hydrothermal seawater which has not undergone a phase separation and 2 dissolution of a chloride rich phase combined with a possible small loss of gas during sampling procedures although measured temperatures were all less than 300 sup 0 c quartz geothermometry suggests that the fluids have equilibrated at greater than 340 sup 0 c quartz geobarometry is also in agreement with geophysical estimates of depth to the local magma chamber copyright american geophysical union 1987

an improved method to extract very broadband empirical green s functions from ambient seismic noise the extraction of green s functions by cross correlation of continuous seismic records at station pairs is best achieved in a diffuse wave field where energies radiated by random sources have equal power to partially satisfy the diffuse wave field condition original seismic records must be normalized as they are highly nonstationary and may have amplitude variations of orders of magnitude within the cross correlation time window we adapt a frequency time normalization method to obtain seismograms with an even spectrum at all times within the data processing unit compared with the commonly used one bit normalization the new method improves the signal to noise ratio of empirical green s functions by a factor of 2 and increases the effective data recording duration by a factor of 4 assuming random local and instrument noise it yields useful rayleigh waves at periods up to 300 s for program for array seismic studies of the continental lithosphere passcal type deployments and 600 s for permanent stations with very broadband sensors thus the new method makes it possible to extend surface wave signals to frequencies beyond those in traditional earthquake based surface wave tomography at both the high and low frequency ends

hydrothermal hydrocarbon gases 1 genesis and geothermometry various sources for hydrothermal ch4 have been proposed over the years while c isotope studies have narrowed the possibilities enough higher hydrocarbon gas data now exist both to supplement the isotopic data and to permit additional deductions regarding origins comparison of typical c1 c6 data for gases of various origins from sedimentary and crystalline rocks and hydrothermal systems reveals certain characteristics apart from isotopic differences hydrothermal hydrocarbons differ from sedimentary hydrocarbons mainly in possessing tendencies towards a relative excess of ch4 higher normal iso ratios for butane and pentane and relatively high amounts of c6 gases despite these differences consideration of the evidence indicates that hydrothermal hydrocarbon gases in most cases originate like sedimentary basin gases by thermal degradation of organic matter in the relatively shallow subsurface the principal characteristic of these hydrothermal gases excess ch4 appears to have a geothermometric function the following empirical relationship has been derived t c 57 8 log ch4 c2h6 96 8 which fits moderately well a range of geothermal fields worldwide this gas geothermometer may be particularly applicable during geothermal exploration in areas where there is little direct knowledge of subsurface conditions

broadband ambient noise surface wave tomography across the united states 1 this study presents surface wave dispersion maps across the contiguous united states determined using seismic ambient noise two years of ambient noise data are used from march 2003 through february 2005 observed at 203 broadband seismic stations in the us southern canada and northern mexico cross correlations are computed between all station pairs to produce empirical green functions at most azimuths across the us coherent rayleigh wave signals exist in the empirical green functions implying that ambient noise in the frequency band of this study 5 100 s period is sufficiently isotropically distributed in azimuth to yield largely unbiased dispersion measurements rayleigh and love wave group and phase velocity curves are measured together with associated uncertainties determined from the temporal variability of the measurements a sufficient number of measurements 2000 is obtained between 8 and 25 s period for love waves and 8 and 70 s period for rayleigh waves to produce tomographic dispersion maps both phase and group velocity maps are presented in these period bands resolution is estimated to be better than 100 km across much of the us from 8 40 s period for rayleigh waves and 8 20 s period for love waves which is unprecedented in a study at this spatial scale at longer and shorter periods resolution degrades as the number of coherent signals diminishes the dispersion maps agree well with each other and with known geological and tectonic features and in addition provide new information about structures in the crust and uppermost mantle beneath much of the us

phase relations and adiabats in boiling seafloor geothermal systems abstract observations of large salinity variations and vent temperatures in the range of 380 400 c suggest that boiling or two phase separation may be occurring in some seafloor geothermal systems consideration of flow rates and the relatively small differences in density between vapors and liquids at the supercritical pressures at depth in these systems suggests that boiling is occurring under closed system conditions salinity and temperature of boiling vents can be used to estimate the pressure temperature point in the subsurface at which liquid seawater first reached the two phase boundary data are reviewed to construct phase diagrams of coexisting brines and vapors in the two phase region at pressures corresponding to those of the seafloor geothermal systems a method is developed for calculating the enthalpy and entropy of the coexisting mixtures and results are used to construct adiabats from the seafloor to the p t two phase boundary results for seafloor vents discharging at 2300 m below sea level indicate that a 385 c vent is composed of a brine 7 nacl equivalent in equilibrium with a vapor 0 1 nacl brine constitutes 45 by weight of the mixture and the fluid first boiled at approximately 1 km below the seafloor at 415 c 330 bar a 400 c vent is primarily vapor 88 wt 0 044 nacl with a small amount of brine 26 nacl and first boiled at 2 9 km below the seafloor at 500 c 520 bar these results show that adiabatic decompression in the two phase region results in dramatic cooling of the fluid mixture when there is a large fraction of vapor

a magmatic source for fumaroles and diffuse degassing from the summit crater of teide volcano tenerife canary islands a geochemical evidence for the 2004 2005 seismic volcanic crisis the present work reports the results of 15 studies of diffuse co2 degassing performed at teide volcano crater canary island spain and the chemical and isotopic compositions of fluids discharged from a fumarolic field located at the top of the volcano as measured between 1991 and 2010 a higher contribution of magmatic gases accompanied by enhanced total diffuse co2 emissions were observed in relation with a seismic crisis that occurred in tenerife island between 2001 and 2005 with the main peak of seismic activity between april and june 2004 a significant pulse in total diffuse co2 emission was observed at the crater of teide up to 26 3 t day 1 in 2001 in december 2003 the chemical composition of the teide fumarole changed significantly including the appearance of so2 an increase in the hcl and co concentrations and in the c2h6 c2h4 and c3h8 c3h6 ratios and a decrease in the h2s ch4 and c6h6 concentrations and in the gas steam ratio a few months after a drastic decrease in seismic activity the so2 hcl and co concentrations and the c2h6 c2h4 and c3h8 c3h6 ratios strongly decreased whereas the ch4 and c6h6 concentrations and the gas steam ratios increased according to the trends shown by both the geochemical parameters and the seismic signals late in the observation period the risk of a rejuvenation of volcanic activity at teide is considered to be low the associated temporal changes in seismic activity and magmatic degassing indicate that geophysical and fluid geochemistry signals in this system are related future monitoring programs aimed at mitigating volcanic hazard on tenerife island should involve coupled geophysical and geochemical studies

periglacial slope deposits and their pedogenic implications in germany abstract disconformities within soil parent materials are frequently reported from locations throughout the world but they are rarely within the goals of systematic research this article provides an overview of the current state of knowledge on such materials and their pedogenic relevance in germany it intends to encourage further discussion on stratified soils in other parts of the world the slope deposits in germany are divided into 1 the upper layer that is ubiquitously distributed and displays a relatively constant thickness 2 the intermediate layer that is restricted to flat relief to hollows and to lee ward facing slopes and 3 the basal layer that is rather widespread again both the upper and intermediate layer contain intermixed loess while the basal layer is free of loess these layers were mainly formed by periglacial solifluction such deposits are referred to as cover beds the upper layer formed during the younger dryas within a relatively short episode in contrast the lower layers may be diachronous nevertheless they display recurring vertical sequences this is probably due to the fact that loess free layers usually could not deposit as long as there was loess in the environs thus the last phase of surface wash during which older loess was removed determines the age of the lower layers the composition of the layers differs reflecting the varying portions of loess and of rock allocated from upslope in twofold sequences the cover beds influence the formation of the soils as they provide weathered material and as their boundaries where properties such as texture and bulk density abruptly change determine the soil horizon boundaries some pedogenic processes are favored oxidation depletion of clay or hindered podzolization due to the loess content of the upper layer even exceeding this the dominant loess content of an intercalated intermediate layer in threefold sequences may completely decouple pedogenesis from bedrock influence in all soil formation is largely influenced by the constellation of cover beds at any given site

isotopic and chemical composition of water and steam discharges from volcanic magmatic hydrothermal systems of the guanacaste geothermal province costa rica the guanacaste geothermal province encompasses three major geothermal systems each centered on its respective volcanic structure rincon de la vieja to the nw miravalles in the center and tenorioto the se each shows corresponding sets of surface manifestations vapor discharges from fumaroles and steam heated pools at altitudes 500 m lower temperature so4cl springs on the lower slopes of the respective volcano and cooler neutral cl springs to the s of the volcanic chain at altitudes 500 m the production of hco3 rich waters is limited to a narrow belt stretching to the s of miravalles volcano chemical and isotopic evidence suggests that the neutral cl waters also discharged from deep wells are derived from a more primitive clso4 water formed by transfer of readily mobilised originally magmatic constituents to deeply circulating groundwater isotopic evidence suggests that this groundwater is derived largely from areas to the north of the volcanic chain the presence of immature waters within drillable depth is indicated by the incursion of an acid so4 water into a well at miravalles after deepening to 2000 m as the cl waters rise they start to boil the separated vapors feed the fumaroles and steam heated features at the surface the residual water travels underground to be discharged some 5 25 km to the s the uniformity in chemical and isotopic compositions of the neutral cl waters is compatible with the assumption that the individual thermal systems are linked at depth to form large contiguous geothermal reservoirs beneath the guanacaste geothermal province

epicentral location based on rayleigh wave empirical green s functions from ambient seismic noise summary a new method to locate the epicentre of regional seismic events is developed with strengths and limitations complementary to existing location methods this new technique is based on applying empirical green s functions egfs for rayleigh waves between 7 and 15 s period that are determined by cross correlation of ambient noise time series recorded at pairs of seismic receivers the important advantage of this method in comparison with standard procedures based on use of body wave traveltimes is that it does not rely on an earth model rather it is based on interpolating the egfs to arbitrary hypothetical event locations the method is tested by locating well known ground truth crustal events in the western united states magnitude 4 earthquakes in california magnitude 3 earthquakes in utah and a mine collapse as well as locating seismic stations as virtual events in these applications location errors average less than 1 km but are expected to vary with event mechanism and depth numerical simulations show that the method optimizes when source depth is less than 1 km or more than 5 km and when the source mechanism is nearly purely strike slip thrust or normal

thermodynamics of organic transformations in hydrothermal fluids hydrothermal fluids obtain organic compounds through diverse pathways in submarine systems organic compounds are already dissolved in seawater that is heated and transformed into hydrothermal fluids through water rock reactions microbes inhabiting hydrothermal systems produce metabolites that enter the fluids and cells can be carried into the reaction zones by circulating fluids and pyrolyzed analogous sources of organic compounds can be anticipated in continental systems with the possible addition of novel plant and soil derived organic compounds from the surface in addition hydrothermal systems possess large potentials for abiotic organic synthesis that may add a novel suite of compounds when sedimentary rocks are present ancient biogenic organic matter can be mobilized or transformed by hot fluids these transformations accompany the generation of petroleum coal and other fossil fuels suggesting that expectations for hydrothermal transformations can be built on those that occur in sedimentary basins likewise some types of ore deposition are accompanied by transformations of organic compounds and metal organic complexes may be involved in enhancing the transport of metals in ore forming and other crustal fluids with these thoughts in mind this review starts with an inventory of the types of organic compounds found in hydrothermal systems and some ways that hydrothermal organic compounds are transformed methane can be generated biotically and abiotically from organic or inorganic reactants and since it lacks a carbon carbon bond some researchers would not consider it to be an organic compound nevertheless more data exist for methane in hydrothermal fluids than for any organic compound that fits the definition methane has been quantified in continental and submarine hydrothermal fluids fumarolic gases associated with hydrothermal systems oil field brines deep fluids in sedimentary basins and igneous basement rocks fluids associated with active serpentinization and fluid inclusions in minerals from ore deposits sedimentary basins and deep crustal settings recent examples include

gas geochemistry of the magmatic hydrothermal fluid reservoir in the copahue caviahue volcanic complex argentina abstract copahue volcano is part of the caviahue copahue volcanic complex ccvc which is located in the southwestern sector of the caviahue volcano tectonic depression argentina chile this depression is a pull apart basin accommodating stresses between the southern liquine ofqui strike slip and the northern copahue antinir compressive fault systems in a back arc setting with respect to the southern andean volcanic zone in this study we present chemical inorganic and organic and isotope compositions 13c co2 15n 3he 4he 40ar 36ar 13c ch4 d ch4 and d h2o and 18o h2o of fumaroles and bubbling gases of thermal springs located at the foot of copahue volcano sampled in 2006 2007 and 2012 helium isotope ratios the highest observed for a southern american volcano r ra up to 7 94 indicate a non classic arc like setting but rather an extensional regime subdued to asthenospheric thinning 13c co2 values from 8 8 to 6 8 vs v pdb 15n values 5 3 to 5 5 vs air and co2 3he ratios from 1 4 to 8 8 109 suggest that the magmatic source is significantly affected by contamination of subducted sediments gases discharged from the northern sector of the ccvc show contribution of 3he poor fluids likely permeating through local fault systems despite the clear mantle isotope signature in the ccvc gases the acidic gas species have suffered scrubbing processes by a hydrothermal system mainly recharged by meteoric water gas geothermometry in the h2o co2 ch4 co h2 system suggests that co and h2 re equilibrate in a separated vapor phase at 200 220 c on the contrary rock fluid interactions controlling co2 ch4 production from sabatier reaction and c3h8 dehydrogenation seem to occur within the hydrothermal reservoir at temperatures ranging from 250 to 300 c fumarole gases sampled in 2006 2007 show relatively low n2 he and n2 ar ratios and high r ra values with respect to those measured in 2012 such compositional and isotope variations were likely related to injection of mafic magma that likely triggered the 2000 eruption therefore changes affecting the magmatic system had a delayed effect on the chemistry of the ccvc gases due to the presence of the hydrothermal reservoir however geochemical monitoring activities mainly focused on the behavior of inert gas compounds n2 and he should be increased to investigate the mechanism at the origin of the unrest started in 2011

traveltime measurements from noise correlation stability and detection of instrumental time shifts we test the feasibility of using green s functions extracted from records of ambient seismic noise to monitor temporal changes in the earth crust properties by repeated measurements at regional distances we use about 11 yr of continuous recordings to extract surface waves between three pairs of stations in california the correlations are computed in a moving 1 month window and we analyse the temporal evolution of measured interstation traveltimes the comparison of the arrival times in the positive and negative correlation time of rayleigh and love waves allows us to separate time shifts associated with any form of physical change in the medium those resulting from clock drift or other instrumental errors and those due to change in the localization of the noise sources this separation is based on the principle of time symmetry when possible we perform our analysis in two different period bands 5 10 and 10 20 s the results indicate that significant instrumental time errors 0 5 s are present in the data these time shifts can be measured and tested by closure relation and finally corrected independently of any velocity model the traveltime series show a periodic oscillation that we interpret as the signature of the seasonal variation of the region of origin of the seismic noise between 1999 and 2005 the final arrival time fluctuations have a variance of the order of 0 01 s this allows us to measure interstation traveltimes with errors smaller than 0 3 per cent of the interstation traveltime and smaller than 1 per cent of the used wave period this level of accuracy was not sufficient to detect clear physical variation of crustal velocity during the considered 11 yr between the three stations in california such changes may be more easily detectable when considering pairs of stations more closely located to each other and in the vicinity of tectonically active faults or volcanoes

origin of fumarolic fluids from tupungatito volcano central chile interplay between magmatic hydrothermal and shallow meteoric sources tupungatito is a poorly known volcano located about 100 km eastward of santiago chile in the northernmost sector of the south volcanic zone this 5 682 m high volcano shows intense fumarolic activity it hosts three crater lakes within the northwestern portion of the summit area chemical compositions of fumarolic gases and isotopic signatures of noble gases 3he 4he and 40ar 36ar are up to 6 09 ra and 461 respectively and steam 18o and d suggest that they are produced by mixing of fluids from a magmatic source rich in acidic gas compounds so2 hcl and hf and meteoric water the magmatic hydrothermal fluids are affected by steam condensation that controls the outlet fumarolic temperatures 200 c and redox conditions are consistent with those inferred by the presence of the so2 h2s redox pair typical of fluids that have attained equilibrium in magmatic environment a comprehensive conceptual geochemical model describing the circulation pattern of the tupungatito hydrothermal magmatic fluids is proposed it includes fluid source regions and re equilibration processes affecting the different gas species due to changing chemical physical conditions as the magmatic hydrothermal fluids rise up toward the surface

earthquake centroid locations using calibration from ambient seismic noise earthquakes occur in complex geology making it difficult to determine their source parameters and locations because of uncertainty in path effects we can avoid some of these problems by applying the cut and paste cap method which allows for timing shifts between phases assuming a 1d model and determines source parameters if the travel times or lags of the phases due to path effects are known relative to a reference model we can locate the events centroid with surface waves without knowledge of the 3d velocity structure here we use ambient seismic noise for such a calibration we cross correlate the seismic stations near the earthquake with stations 100 300 km away to obtain the 10 100 s surface wave green s functions the new method is tested in southern california to locate the 2008 chino hills earthquake which proves consistent with the epicenter location from p waves it appears possible to use the location offset between the high frequency p wave onset relative to the centroid to provide a fast estimate of directivity

the concept of the pleistocene periglacial cover beds in central europe a review in low mountain areas of central europe pleistocene periglacial conditions and relevant processes have led to the formation of cover beds in general holocene soils are not developed in bedrock but they have formed in periglacial cover beds their occurrence and characteristics control the spatial distribution of soils and thus periglacial sediments are a useful tool for soil mapping and soil survey the concept of periglacial cover beds distinguishes four main layers topmost upper middle and basal periglacial cover bed the upper and middle layers contain loess whereas the basal one consists entirely of bedrock the loess content causes an increase of site specific soil ecological quality in comparison to soils formed directly on bedrock the occurrence and characteristics of the cover beds is reviewed summarizing the present state of the art

rupture history of the 2009 l aquila italy earthquake from non linear joint inversion of strong motion and gps data 1 we image the rupture history of the 2009 l aquila central italy earthquake using a nonlinear joint inversion of strong motion and gps data this earthquake ruptured a normal fault striking along the apennines axis and dipping to the sw the inferred slip distribution is heterogeneous and characterized by a small shallow slip patch located up dip from the hypocenter 9 5 km depth and a large deeper patch located southeastward the rupture velocity is larger in the up dip than in the along strike direction this difference can be partially accounted by the crustal structure which is characterized by a high velocity layer above the hypocenter and a lower velocity below the latter velocity seems to have affected the along strike propagation since the largest slip patch is located at depths between 9 and 14 km the imaged slip distribution correlates well with the on fault aftershock pattern as well as with mapped surface breakages

3 d upper mantle shear velocity model beneath the contiguous united states based on broadband surface wave from ambient seismic noise ambient noise seismic tomography has been widely used to study crustal and upper mantle shear velocity structures most studies however concentrate on short period 50 s surface wave from ambient noise while studies using long period surface wave from ambient noise are limited in this paper we demonstrate the feasibility of using long period surface wave from ambient noise to study the lithospheric structure on a continental scale we use broadband rayleigh wave phase velocities to obtain a 3 d vs structures beneath the contiguous united states at period band of 10 150 s during the inversion 1 d shear wave velocity profile is parameterized using b spline at each grid point and is inverted with nonlinear markov chain monte carlo method then a 3 d shear velocity model is constructed by assembling all the 1 d shear velocity profiles our model is overall consistent with existing models which are based on multiple datasets or data from earthquakes our model along with the other post usarray models reveal lithosphere structures in the upper mantle which are consistent with the geological tectonic background e g the craton root and regional upwelling provinces the model has comparable resolution on lithosphere structures compared with many published results and can be used for future detailed regional or continental studies and analysis

carbon bearing gas geothermometers for volcanic hydrothermal systems abstract the genetic relationship between carbon bearing species co co 2 ch 4 c 2 h 6 c 3 h 8 c 2 h 4 and c 3 h 6 was investigated in volcanic hydrothermal gases emitted from nisyros greece vesuvio la solfatara campi flegrei and pantelleria all italy apparent carbon isotopic temperatures of the ch 4 co 2 system are 360 c at nisyros 420 460 c at vesuvio 450 c at la solfatara and 540 c at pantelleria these temperatures are confirmed by measured propene propane and h 2 h 2 o concentration ratios ch 4 and co 2 equilibrate in the single liquid phase prior to the onset of boiling whereas propene and propane attain equilibrium in the saturated water vapor phase boiling in these high enthalpy hydrothermal systems might occur isothermally once vapor has been extracted from the parental liquid co co 2 responds most sensitively to the temperature gradient encountered by the ascending gases our results imply that the ch 4 co 2 isotopic geothermometer can provide reliable information about temperatures of deep hydrothermal liquids associated with volcanism propene propane and h 2 h 2 o concentration ratios should be measured along with the carbon isotopic composition of co 2 and ch 4 to provide independent constraints on the geological significance of the apparent carbon isotopic temperatures

geochemistry of gas and water discharge from the magmatic hydrothermal system of guallatiri volcano northern chile this work presents the first chemical and isotopic 13c co2 13c ch4 3he 4he 20ne 40ar 36ar 18o and d data for fluid discharges from guallatiri volcano a remote and massive stratovolcano which is considered as the second most active volcano of the central volcanic zone cvz in northern chile fumarolic gases had outlet temperatures of between 80 2 and 265 c and showed a significant magmatic fluid contribution marked by the occurrence of so2 hcl and hf that are partially scrubbed by a hydrothermal aquifer the helium isotope ratios 3 2 were relatively low compared to those of other active volcanoes in cvz possibly due to contamination of the magmatic source by 4he rich crust and or crustal fluid addition to the hydrothermal reservoir geothermometry in the h2o co2 co h2 ch4 system suggests equilibrium temperatures of up to 320 c attained in a vapor phase at redox conditions intermediate between those typical of hydrothermal and magmatic environments thermal springs located 12 km northwest of the volcano s summit had outlet temperatures of up to 50 1 c neutral to slightly basic ph and a sodium bicarbonate composition typical of distal fluid discharges in volcanic systems cold springs at the base of the volcanic edifice showing a calcium sulfate composition were likely produced by interaction of shallow meteoric water with co2 and h2s rich gases a geochemical conceptual model was constructed to graphically represent these results which can be used as an indication for future geochemical monitoring and volcanic hazard assessment

rubefaction post wurmienne en climat montagnard humide jurassien role du pedoclimat et actualite du processus abstract post wurmian soils from a proglacial region nozeroy jura have been studied they have two b horizons which have developed under the same general climatic conditions a reddish horizon overlying a yellowish horizon analysis of the mineral phases leads to the conclusions that 1 the soils have the same aeolian wurmian origin from a nearby source 2 the recent pedogenetic development has involved the formation of hematite essentially from in situ modification of geothite hematite was identified in the argillaceous granulometric fraction by three methods colour x ray diffraction and mossbauer spectroscopy this pedogenetic change of geothite into hematite which may be quite recent is apparently favoured by the extremely fissured nature of the underlying rock and the stony nature of the soil the siting and organization of the soil rock interface lead to repeated cycles of wetting and drying and thus a pedoclimate with periods of desiccation sufficient to induce the formation of hematite the severe limitations associated with the mountain climate precipitation 1700 mm average temperature 6 c are in this case apparently less important than the interactions of climate and rocks the excellent drainage due to the highly fissured rocks results apparently in a pedological environment favourable to rubification in the horizons most subject to cycles of wetting and drying

testing community velocity models for southern california using the ambient seismic field abstract we correlate the vertical component of ambient seismic noise data recorded on 56 broadband stations with dense coverage in the greater los angeles area to determine station to station green s functions these green s functions provide an important test of community velocity models southern california earthquake center scec cvm 4 0 and cvm h 5 2 used for strong ground motion prediction for future scenario earthquakes in southern california comparisons of the ambient noise green s functions for nearly 300 paths with those calculated by the finite element method in the community velocity models reveal a strong waveform similarity for the dominant surface waves between 0 1 and 0 2 hz we find a mean correlation coefficient between the ambient noise and finite element green s functions of 0 62 for the cvm 4 0 and 0 49 for the cvm h 5 2 indicating stronger waveform similarity for cvm 4 0 we also find that for 77 of the paths the surface waves in the finite element green s functions for cvm 4 0 arrive early suggesting that the cvm 4 0 has velocities in the upper 10 km that are too fast along these paths the same bias is evident for cvm h 5 2 but is substantially smaller with only 61 of the paths too fast for 67 of the paths cvm 4 0 has velocities faster than cvm h 5 2 the time lags we obtain between the ambient noise and finite element green s functions provide key information for improving future community velocity models

location and mechanism of the little skull mountain earthquake as constrained by satellite radar interferometry and seismic waveform modeling we use interferometric synthetic aperture radar insar and broadband seismic waveform data to estimate source parameters of the 29 june 1992 m s 5 4 little skull mountain lsm earthquake this event occurred within a geodetic network designed to measure the strain rate across the region around yucca mountain the lsm earthquake complicates interpretation of the existing gps and trilateration data as the earthquake magnitude is sufficiently small that seismic data do not tightly constrain the epicenter but large enough to potentially affect the geodetic observations we model the insar data using a finite dislocation in a layered elastic space we also invert regional seismic waveforms both alone and jointly with the insar data because of limitations in the existing data set insar data alone cannot determine the area of the fault plane independent of magnitude of slip nor the location of the fault plane independent of the earthquake mechanism our seismic waveform data tightly constrain the mechanism of the earthquake but not the location together the two complementary data types can be used to determine the mechanism and location but cannot distinguish between the two potential conjugate fault planes our preferred model has a moment of 3 2 10 17 n m m w 5 6 and predicts a line length change between the wahomie and mile geodetic benchmarks of 5 mm

light hydrocarbons as redox and temperature indicators in the geothermal field of el tatio northern chile abstract el tatio northern chile one of the largest geothermal fields of south america is presently undergoing a new program of geothermal exploration after the failure of the first exploration phase in the early 1970s the geochemical features of the fluid discharges characterizing this system mainly consist of boiling pools and fumaroles and represent the result of a complex mixing process involving 3 main components i hydrothermal ii atmospheric iii magmatic chemical reactions involving light hydrocarbons equilibrate at higher temperature than those directly measured in the geothermal wells and calculated on the basis of the composition of the inorganic gas species this suggests that in the deeper parts of the hydrothermal system temperatures higher than 300 c may be achieved such results can have a strong impact for the evaluation of the potential resources of this geothermal system moreover the chemical characteristics of the organic gas fraction allow the assessment of the chemical physical conditions governing the geochemical processes acting on geothermal fluids at depth

periglacial cover beds and soils in landslide areas of sw germany abstract at the slopes of the jurassic cuesta scarp in sw germany pedological and mineralogical investigations were carried out in landslide areas so far it is possible to distinguish two well defined landslide areas one of them belonging to the pleistocene the other one characterised by holocene movements in general the distribution of soils and sediments is strongly linked to the age of landslide deposits in pleistocene landslide areas the parent material of the studied soils is formed by periglacial cover beds of late pleistocene age consisting of jurassic aeolian and volcanic components the upper periglacial cover bed was recognised as the most important marker horizon in the studied slope areas there the existence of minerals originating from the eruption of the laacher see volcano dated to 12 900 yr bp could be demonstrated for the first time most of the pleistocene landforms are characterised by well developed soils like clayic and vertic cambisols whereas relic soils exclusively occur in the oldest parts of landslide deposits landslide areas affected by holocene slope processes do not exhibit periglacial layers as mass movements removed periglacial sediments and former soils extensively as a consequence the parent material is different from those of pleistocene landslide areas therefore sediments in these areas are characterised by jurassic components and only initial soils are present

an early brunhes 0 78 ma age for the lower paleolithic tool bearing kozarnika cave sediments bulgaria abstract we present a new sedimentological profile and a magnetostratigraphy of the tool bearing kozarnika cave sediments from bulgaria modal analysis of cave infilling sedimentary texture indicates that the tool bearing layers contain a sizable fraction of sediment interpreted as loess we also find evidence for a relatively thick and well defined normal magnetic polarity in the upper middle part of the section interpreted as a record of the brunhes chron followed down section by reverse polarity directions interpreted as a record of the matuyama chron the lowermost levels with lower paleolithic tools layers 13a c lie in the early brunhes at a nominal maximum age of 0 75 ma while the brunhes matuyama boundary 0 78 ma falls in layer 13 lower immediately below this finding represents a conspicuous revision of previous age estimates for the same tool bearing layers

the 2009 l aquila earthquake central italy a source mechanism and implications for seismic hazard an edited version of this paper was published by agu copyright 2009 american geophysical union

volcanic hotspots of the central and southern andes as seen from space by aster and modvolc between the years 2000 and 2010

fumarolic gases at mombacho volcano nicaragua presence of magmatic gas species and implications for volcanic surveillance mombacho is a deeply dissected volcano belonging to the quaternary volcanic chain of nicaragua the southern historic collapse crater el crater currently hosts a fumarolic field with a maximum temperature of 121 c chemical and isotopic data from five gas sampling field campaigns carried out in 2002 2003 and 2005 highlight the presence of high temperature gas components e g so2 hcl and hf which indicate a significant contribution of juvenile magmatic fluids to the hydrothermal system feeding the gas discharges this is strongly supported by the mantle derived helium and carbon isotopic signatures although the latter is partly masked by either a sedimentary subduction related or a shallow carbonate component the observed chemical and isotopic composition of the mombacho fluids seems to indicate that this volcanic system although it has not experienced eruptive events during the last centuries can be considered active and possibly dangerous in agreement with the geophysical data recorded in the region systematic geochemical monitoring of the fumarolic gas discharges coupled with a seismic and ground deformation network is highly recommended in order to monitor a possible new eruptive phase

organic and inorganic geochemistry of low temperature gas discharges at the baia di levante beach vulcano island italy abstract discharge from subaereal and submarine gas vents of the baia di levante beach gases from the vulcano island were sampled for major and trace gas components in may and november 1995 chemical compositions and equilibrium calculations suggest three different groups of co 2 rich gas emissions depending on their distance from the la fossa crater 1 gas vents close to the faraglione area are characterised by high h 2 s contents high calculated equilibrium temperatures based on inorganic species and relatively high proportion of alkene compounds 2 gas vents close to vulcanello are characterised by low calculated equilibrium temperatures and low amounts of alkenes and 3 pontile sample has the highest equilibrium co 2 pressure up to 68 bars which may account for the observed absence of benzene the relative large variability of h 2 s in the baia di levante beach gas discharge may be attributed to either different interactions between iron sulphides and weakly acid waters or catalytic effect of elemental sulphur on the de hydrogenation of cyclo hexane thermodynamic calculations suggest that the main inorganic species and ch 4 may have re equilibrated at relatively shallow depth 10 200 m b s l and 30 600 m b s l for a lithostatic and hydrostatic pressure respectively the slow kinetics of reactions in the c n h 2 n c n h 2 n 2 systems with respect to that of ch 4 co co 2 may explain the observed propene propane ratios which can only be reached at reaction temperatures of 300 350 c this low speed of reactions can also explain the observed disequilibrium of c1 c4 alkanes

comment on post impact event bed tsunamite at the cretaceous palaeogene boundary deposited on a distal carbonate platform interior korbar et al 2017 report a tsunamite triggered by the chicxulub impact on yucatan from the likva cove carbonate platform of the island of brac croatia which is similar to that in an earlier report from the nearby island of hvar korbar et al 2015 if true such deposits in the adriatic sea would be truly anomalous given that no tsunamites are identified in well preserved cretaceous palaeogene k pg sections from the basque cantabric basin bidart zumaia hendaye and sopelana sections which are located more proximal and towards the hypothetical tsunami wave propagation front this article is protected by copyright all rights reserved