noble gases and nitrogen mixing and temporal evolution in the fumarolic fluids of vulcano italy abstract since 1979 noble gases he ne ar and n 2 in the medium temperature fumaroles of vulcano crater have been analyzed repeatedly during these 10 years of surveillance variations have been noticed in fluid composition until 1986 40 ar 36 ar ratios up to 2000 were found n 2 ar was 1600 and he ar was 1 9 indicating the presence of a deep component as the result of a mixing between mantle and crustal fluids since 1987 the atmospheric component has increased and the fluid composition has evolved towards an air saturated groundwater asw this change is considered to be the result of mixing between magmatic fluids and meteoric waters that release their atmospheric gases on entering the volcanic system these gases thus mask the magmatic component which has remained more or less constant in the last decade

controls on the distribution of calcareous foraminifera in the lower carboniferous of ireland abstract microfacies analyses of thin sections from over 650 samples of asbian and brigantian late visean platform carbonates from ireland shows that foraminiferal assemblages are controlled by the relative abundance of echinoderms mainly crinoids bryozoans and calcareous algae koninckopora ungdarella and palaeoberesellids archaediscidae valvulinella and tetrataxidae thrived in algal poor crinoid and bryozoan thickets at or below fair weather wavebase late visean algal limestones contain abundant endothyridae and palaeotextulariidae and are interpreted to have been deposited at depths between 5 and 10 m the morphology of the foraminifera studied is related closely to their facies distribution many taxa inhabited high energy shallow marine algal meadow facies these include bibradya cribrospira nevillella and bradyina with cribrate apertures and other specialised test features that protected the protoplasm from damage gigasbia omphalotis globoendothyra and pseudoendothyra with large rotund or keeled multilayered tests and forschiidae with large thick walled tests infaunal taxa such as the lituotubella nevillella gigasbia and the palaeotextulariids are recorded from algal facies and appear to have been unable to survive on bryozoan and crinoidal substrates pseudoammodiscus and earlandia characterized by simple morphologies and single layered walls and endothyranopsis endothyra and eostaffella planispirally coiled with multilayered micritic tests are regarded as the least facies controlled of the taxa studied the encrusting nature of pseudolituotuba and scalebrina ensured survival in a wide range of platformal palaeoenvironments though algal meadows were not generally suitable substrates for the pseudolituotubidae the secondary deposits in the umbilical region of the asteroarchaediscinae may have been an adaptation for survival in the dense crinoidal bryozoan thickets where they lived delicate planoarchaediscus occurs in algal poor wackestone to packstone facies typical of low energy palaeoenvironments possibly at depths below 20 m howchinia which occurs with fasciella a probable alga in intraclastic wackestone facies may also have lived in water deeper than 20 m major changes in foraminiferal assemblages through the asbian and brigantian stages of the late visean are attributed to changes in associated biotic constituents early asbian endothyrid and forschiid dominated assemblages were controlled by the relative abundance of bryozoans koninckopora and palaeoberesellids by the late asbian the foraminiferal assemblages were controlled by the presence or absence of palaeoberesellids ungdarella and to a lesser extent bryozoans asbian assemblages were similar although foraminifers such as bradyinids cribrospira and globoendothyra became abundant in the late asbian a switch to predominantly echinoderm mainly crinoid and bryozoan substrates in the brigantian may have caused the major change from late asbian endothyrid and palaeotextulariid assemblages to archaediscid and tetrataxid dominated assemblages

geochemistry of geothermal waters from the gonghe region northwestern china implications for identification of the heat source the gonghe geothermal region located in the northeastern part of qinghai tibet plateau is the most geothermally active in qinghai province the geothermal waters from three hydrothermal areas qiabuqia guide and xinghai of gonghe are characterized with different hydrochemical types nevertheless their d and 18o data suggest that they are all of meteoric origin most gonghe samples are far away from the full equilibrium line in na k mg triangular diagram implying that na k geothermometer is generally not suitable for calculating the reservoir temperatures in comparison silica geothermometers perform much better and give more accurate temperature estimations the hydrochemistry of the gonghe geothermal waters is distinctively different from that of the hot springs from rehai a well known magmatic hydrothermal area located in the tengchong volcanic region of yunnan province southwestern china indicating that the geothermal anomaly in gonghe is not related to an underlying magma chamber instead the strong hydrothermal manifestation there is more likely to be supported by the intense deep tectonic activities moreover the possible existence of radioactive heat source can not be ruled out at this stage

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

gas and water geochemistry of geothermal systems in dominica lesser antilles island arc abstract four of the nine potentially active volcanoes on the island of dominica in the lesser antilles volcanic island arc have associated active volcanic hydrothermal systems between 2000 and 2006 the gas and thermal waters from these systems were investigated to geochemically characterise the fluids gain insight into the temperature and equilibrium state of the underlying reservoirs and evaluate the feasibility of monitoring geothermal features as a volcano surveillance tool in dominica the geothermal gases are typical of those found in arc type settings with n2 excess and low amounts of he and ar the dry gas is dominated by co2 ranging from 492 to 993 mmol mol and has a hydrothermal signature with hydrogen sulphide as the main sulphurous gas the waters are predominantly acid sulphate so4 100 4200 mg l ph 4 and likely formed as a result of dilution of acidic gases in near surface oxygenated groundwater enrichment in both 18o and d with respect to the global meteoric water line gmwl confirms that the waters are of primarily meteoric origin but have been affected by evaporation processes quartz geothermometers gave equilibrium temperatures of 83 c 203 c these temperatures contrast with the higher equilibrium temperature ranges 170 c 350 c obtained for the gases using the h2 ar ch4 co2 gas ratios plot suggesting that the quartz geothermometers are affected by non attainment of equilibrium this may be a result of precipitation of the dissolved silica and or dilution by relatively cold shallow aquifers of the thermal fluids generally no significant variations in fluid gas chemistry of the hydrothermal systems were observed during the study period and we propose that there were no changes in the state of volcanic activity in this period one exception to this occurred in a feature known as the boiling lake which underwent a month long period of significant compositional temperature and water level fluctuations ascribed to a drastic decrease of hydrothermal input related to a perturbation in the lake probably seismically induced this geochemical study is part of an ongoing monitoring programme of dominica geothermal systems aimed at establishing long term geochemical observations for the purpose of volcano monitoring

chemical and isotopic characteristics of geothermal fluids from sulphur springs saint lucia abstract sulphur springs is a vigorous geothermal field associated with the active soufriere volcanic centre in southern saint lucia lesser antilles island arc the sulphur springs park is an important tourist attraction touted as the world s only drive through volcano with some of the hot pools being developed into recreational pools some 200 000 people visit the park each year since 2001 the hydrothermal fluids of sulphur springs have been sampled as part of an integrated volcanic monitoring programme for the island gas and water samples were analysed to characterise the geochemistry of the hydrothermal system and to assess the equilibrium state and subsurface temperatures of the reservoir this has also enabled us for the first time to establish baseline data for future geochemical monitoring the gases are of typical arc type composition with n2 excess and low he and ar content the dry gas composition is dominated by co2 ranging from 601 993 mmol mol with deeper magmatic sourced h2s rich vapour undergoing boiling and redox changes in the geothermal reservoir to emerge with a hydrothermal signature in the fumarolic gases fluid contributions from magmatic degassing are also evident mainly from the moderate to high contents of hcl and deeply sourced h2s gas respectively sulphur springs hydrothermal waters have acid sulphate type compositions so4 78 4008 mg l ph 3 7 and are of primarily meteoric origin which have been affected by evaporation processes based on the enrichment in both 18o and d 18o 1 to 15 and d 9 to 14 respectively in relation to the global meteoric water line gmwl these waters are steam heated water typically formed by absorption of h2s rich gases in the near surface oxygenated groundwaters reservoir temperatures calculated from the evaluation of gas equilibria in the co2 ch4 h2 system reveal higher temperatures 190 to 300 c than those derived from quartz geothermometry 95 to 169 c which appeared to be affected by dilution with meteoric waters generally no significant variations in fluid geochemistry of the hydrothermal system were observed between 2001 and 2006 and we propose that there were no changes in the state of volcanic activity during this period

new gas geothermometers for geothermal exploration calibration and application calibration of five gas geothermometers is presented three of which used co2 h2s and h2 concentrations in fumarole steam respectively the remaining two use co2h2 and h2sh2 ratios the calibration is based on the relation between gas content of drillhole discharges and measured aquifer temperatures after establishing the gas content in the aquifer gas concentrations were calculated in steam formed by adiabatic boiling of this water to atmospheric pressure to obtain the gas geothermometry functions it is shown that the concentrations of co2 h2s and h2 in geothermal reservoir waters are fixed through equilibria with mineral buffers at temperatures above 230 c epidote prehnite calcite quartz are considered to buffer co2 two buffers are involved for h2s and h2 and two functions are therefore presented for the geothermometers involving these gases for waters containing less than about 500 ppm chloride and in the range 230 300 c pyrite pyrrholite epidote prehnite seem to be involved but pyrite epidote prehnite magnetite or chlorite for waters above 300 c and waters in the range 230 300 c if containing over about 500 ppm the gas geothermometers are useful for predicting subsurface temperatures in high temperature geothermal systems they are applicable to systems in basaltic to acidic rocks and in sediments with similar composition but should be used with reservation for systems located in rocks which differ much in composition from the basaltic to acidic ones the geothermometry results may be used to obtain information on steam condensation in upflow zones or phase separation at elevated pressures measured aquifer temperatures in drillholes and gas geothermometry temperatures based on data from nearby fumaroles compare well in the five fields in iceland considered specifically for the present study as well as in several fields in other countries for which data were inspected the results of the gas geothermometers also compare well with the results of solute geothermometers and mixing models in three undrilled icelandic fields

shear wave birefringence a new tool for evaluating fractured reservoirs propagation characteristics of shear waves make them particularly well suited to exploration for and definition of fractured reservoirs the department of geophysics at colorado school of mines conducted a three component p and s wave seismic survey in order to determine whether shear wave polarization and splitting birefringence caused by fracture induced azimuthal anisotropy could be measured over a naturally fractured reservoir results indicate that surface seismic recordings of shear waves can be used to calculate azimuthal anisotropy and that seismic observation of azimuthal anisotropy can provide information about the location orientation and intensity of subsurface fractures data obtained from this investigation indicate that measurement of shear wave birefringence is a potentially powerful tool for predicting fracture orientation and permeability trends

the nature of mineralizing fluids of the kipushi zn cu deposit katanga democratic repubic of congo quantitative fluid inclusion analysis using laser ablation icp ms and bulk crush leach methods fluid inclusions from the epigenetic zn cu deposit of kipushi central african copper belt katanga democratic republic of congo have been subjected to an integrated microthermometric bulk crush leach and laser ablation inductively coupled plasma mass spectrometric la icp ms study to elucidate the physicochemical conditions of ore formation and the origin of the mineralizing fluids the kipushi deposit is hosted in carbonates and partly in siliciclastic rocks that have undergone regional low grade greenschist facies metamorphism and which were strongly deformed during the lufilian orogeny main deformation phase 550 ma investigation of host rock gangue and ore samples enabled reconstruction of the paragenesis of ore deposition the main zn cu ge pb sulfide mineralization was accompanied by three generations of hydrothermal dolomite and a generation of coarse grained quartz primary and pseudosecondary fluid inclusions in these minerals contain predominantly halite saturated aqueous brines 30 43 wt nacl equiv with locally unidentified trapped solids these inclusions mostly decrepitate upon heating before total homogenization which could suggest that they also trapped excess carbonic vapor they show petrographic and microthermometric evidence for postentrapment reequilibration prohibiting their use as accurate geothermometers and geobarometers previous studies on chlorite and sphalerite geothermometry framed the formation temperature of the kipushi cu zn deposit between 290 to 380 c younger fluids are present as secondary inclusions in the gangue minerals and as primary fluid inclusions in sphalerite from a minor secondary mineralization phase these two phase aqueous inclusions have a slightly lower salinity 23 31 wt nacl equiv and have homogenization temperatures ranging from 170 to 80 c in successive fluid inclusion assemblages sporadically some mixed aqueous carbonic and gaseous co2 ch4 inclusions are present but their genetic position is un clear and they are insignificant with regard to the mineralization process as a whole crush leach bulk analysis of the fluid inclusions show that the mineralizing fluids had a molar cl br ratio close to or somewhat higher than the seawater value which rules out a major contribution from bittern brines and suggests that the fluids gained their salinity primarily by the dissolution of evaporites younger fluids that circulated through the deposit after the main phase of ore formation have cl br and na br signatures indicative of a greater involvement of halite dissolution brines values much higher than that of seawater la icp ms analyses of the mineralizing fluids reveal that they have molar li na ca na mg na mn na and sr na in the range of natural high salinity fluids in metamorphic environments worldwide however they have relatively high molar fe na zn na pb na and especially very high ba na ratios their molar k na is also somewhat higher than for other low grade metamorphic fluids but is nevertheless in agreement with the values predicted by the k na geothermometer at the conditions of ore formation this suggests that the major element composition of the fluids was buffered by fluid mineral equilibria their relatively high metal contents ba zn fe and pb suggest that they interacted with and leached these elements from felsic basement rocks at higher temperatures whatever the origin of the fluids their salinity and the metals their uniformly high ba and ore metal content together with the absence of barite and the occurrence of ba silicates at kipushi indicates that sulfide mineralization occurred when the metal bearing fluids encountered a reducing h2s rich reservoir the ubiquitous presence of preexisting metamorphosed carbonic material shungite in the sulfides and host rock and a sulfur isotope signature of the ores in agreement with thermogenic sulfate reduction suggests that this condition was likely created due to the high initial reduced carbon content of the host rocks at kipushi which seems to be exceptional in the copper belt therefore we postulate that a critical factor in the formation of major vein type zn cu mineralization was the presence of a hydrocarbon rich facies of the lower nguba carbonates at kipushi

four shallow depth shear wave feasibility studies studies using a hammer impact source were made to evaluate the feasibility of using shallow depth seismic shear wave methods to 1 detect earth fissures 2 map an aguiclude 3 locate a bedrock channel and 4 study the fault and fracture system within a highly fractured welded tuff for detecting earth fissures a v v vertical impact vertical geophone recording both p waves and vertically polarized shear waves sv 6 m common offset procedure was used for mapping the aquiclude an r r radial impact radial geophone recording predominantly sv unbalanced split spread procedure and for the bedrock channel search a wide angle t t transverse impact transverse geophone recording horizontally polarized shear waves sh reflection procedure the principal result of these investigations is that it is technically feasible through use of shear wave methods to obtain reasonable solutions to the first three problems for the tuff study wave tests showed phase velocity differences between r r and t

the hydrothermal volcanic system of rincon de la vieja volcano costa rica a combined inorganic and organic geochemical approach to understanding the origin of the fluid discharges and its possible application to volcanic surveillance abstract in the period 1998 2002 thermal spring discharges of rincon de la vieja volcano nw costa rica have been sampled and analyzed for major trace and isotopic 18 o 16 o and d h in waters and 3 he 4 he and 13 c 12 c in co 2 in gases composition the boiling pools hosted inside the summit crater active crater are characterized by high contents of magmatic related compounds so 2 hcl and hf that strongly affect the chemistry of the crater lake these chemical features are not shown by the thermal discharges seeping out in the surrounding area of the volcano here the shallow aquifer apparently masks any possible clues related to the magmatic system this suggests that the fluid vents located inside the active crater are likely to represent the most appropriate sampling sites for geochemical surveillance purposes although the high gas discharge rate from the lake may occasionally prevent any fluid sampling alternatively as already suggested by recent studies on the behavior of light hydrocarbons in different volcanic environments the compositional features of the organic gas fraction in the more accessible outer flank thermal discharges could usefully be utilized at least to assess the thermodynamic conditions of the volcanic hydrothermal system since these compounds are affected by secondary processes only at limited extent

geology and geochemistry of amealco caldera qro mexico amealco caldera located in the central part of the mexican volcanic belt mvb about 130 km nw of mexico city is characterized by a quasi circular 11 km diameter structure whose southern portion is partly truncated by a regional fault the caldera was formed 5 m y ago due to a voluminous eruption of 65 km3 eq magma volume of ignimbrites which covered an area of 1800 km2 this was followed by eruption of 2 km3 of andesitic and dacitic lava flows from the border of the caldera and emplacement of a total of 8 silicic rhyolitic domes 8 km3 inside the caldera finally postcaldera volcanism 4 km3 consisted of extrusion of andesitic and basaltic andesite lavas and scoriae we have analyzed 17 representative rock samples for their major and trace element contents by x ray fluorescence spectrometry and for rare earth elements by high performance liquid chromatography all samples were also analyzed for their sr and nd isotopic compositions which range as follows 87sr 86sr 0 70379 0 70451 143nd 144nd 0 51267 0 51278 the chemical and isotopic data are used to constrain the origin and evolution of magmas in the caldera no combination of altered morb and overlying sediments from the subducted slab cocos plate can produce the sr and nd isotopic compositions observed in rocks from amealco caldera further modelling reveals that the mantle derived primary magmas in amealco caldera may have assimilated up to 10 of a crustal component during their evolution from basaltic andesites to dacites but no further assimilation appears to have taken place during the evolution of the rhyolitic magmas the structure and genesis of the amealco caldera are comparable to some other calderas of the mvb

leakage of active crater lake brine through the north flank at rincon de la vieja volcano northwest costa rica and implications for crater collapse abstract the active crater at rincon de la vieja volcano costa rica reaches an elevation of 1750 m and contains a warm hyper acidic crater lake that probably formed soon after the eruption of the rio blanco tephra deposit approximately 3500 years before present the active crater is buttressed by volcanic ridges and older craters on all sides except the north which dips steeply toward the caribbean coastal plains acidic above ambient temperature streams are found along the active crater s north flank at elevations between 800 and 1000 m a geochemical survey of thermal and non thermal waters at rincon de la vieja was done in 1989 to determine whether hyper acidic fluids are leaking from the active crater through the north flank affecting the composition of north flank streams results of the water chemistry survey reveal that three distinct thermal waters are found on the flanks of rincon de la vieja volcano acid chloride sulfate acs acid sulfate as and neutral chloride nc waters the most extreme acs water was collected from the crater lake that fills the active crater chemical analyses of the lake water reveal a hyper acidic ph 0 chloride sulfate brine with elevated concentrations of calcium magnesium aluminum iron manganese copper zinc fluorine and boron the composition of the brine reflects the combined effects of magmatic degassing from a shallow magma body beneath the active crater dissolution of andesitic volcanic rock and evaporative concentration of dissolved constituents at above ambient temperatures similar cation and anion enrichments are found in the above ambient temperature streams draining the north flank of the active crater the ph of north flank thermal waters range from 3 6 to 4 1 and chloride sulfate ratios 1 2 1 4 that are a factor of two greater than that of the lake brine 0 60 the waters have an acs composition that is quite different from the as and nc thermal waters that occur along the southern flank of rincon de la vieja the distribution of thermal water types at rincon de la vieja strongly indicates that formation of the north flank acs waters is not due to mixing of shallow steam heated as water with deep seated nc water more likely hyper acidic brines formed in the active crater area are migrating through permeable zones in the volcanic strata that make up the active crater s north flank dissolution and shallow subsurface alteration of north flank volcanoclastic material by interaction with acidic lake brine particularly in the more permeable tephra units could weaken the already oversteepened north flank of the active crater sector collapse of the active crater with or without a volcanic eruption represents a potential threat to human lives property and ecosystems at rincon de la vieja volcano

the early carboniferous chondrichthyans of the south urals russia abstract vertebrate remains including chondrichthyans were found in the devonian early carboniferous carbonate beds on the western and eastern slopes of the south urals some of the late devonian forms species of phoebodus acanthodians devononchus placoderms and onychodontid sarcopterygians disappear by the middle siphonodella praesulcata conodont zone the ichthyoassemblages are considerably replenished by the new chondrichthyan taxa in the polygnathus communis carina and gnathodus texanus mestognathus beckmanni conodont zones the chondrichthyans were abundant among the vertebrate faunas of deep water facies a new species of chondrichthyan protacrodus aequalis from the late famennian early tournaisian of the south urals is described

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

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

hydrothermal water rock interaction and the redistribution of li b and cl in the taupo volcanic zone new zealand abstract lithium b and cl occur as trace elements in the dominant protoliths rhyolite andesite and greywacke underlying high temperature hydrothermal systems in the taupo volcanic zone tvz the fluid mobility of li decreases substantially at 200 c 20 c with the pervasive deposition of quartz chlorite regardless of protolith and altering fluid compositions boron and cl are more fluid mobile than li at all temperatures with mobility affected by the rock type composition of circulating aqueous solutions and to a limited extent by incorporation of the trace elements in hydrothermal minerals uptake of b by clays decreases its mobility at 320 c occur compared to volcanic rocks the mobility of b and cl in greywackes is very low and thus the b cl signature of greywacke in hydrothermal aqueous solutions of the tvz is overwhelmed by the effects of rhyolite and andesite dissolution temperature dependent transitions from mg fe clays and phyllosilicates to k bearing illitic clays tend to decrease the mg li ratios in aqueous solutions at 200 c

new improved equations for and sio2 geothermometers by outlier detection and rejection abstract we present new improved equations for three still widely used na k na li and sio 2 geothermometers obtained by statistical treatment of the data and application of outlier detection and rejection as well as theory of error propagation and compare them with those by fournier and others new equations are also developed for estimating errors associated with the use of these new geothermometric equations and comparing them with the performance of the original equations the errors in the use of the new na k equation for temperatures ranging from 80 to 350 c vary from about 19 to 34 which is lower than the corresponding errors 24 43 for the original fournier equation similarly for temperatures ranging from about 50 to 320 c our new equation for na li geothermometer for cl 2 2 geothermometer we have proposed a linear equation for the temperature range of 210 to 310 c sio 2 295 ppm which shows considerably smaller total propagated errors 2 3 than for the original equation 5 29

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

magmatic helium in subduction zone natural gases abstract he isotope ratios provide important constraints on the input of magmatic gases into crustal systems natural gas associated with active continental margins from taiwan r o c new zealand the philippines indonesia thailand and alaska u s a contain a magmatic he component based on measured 3 he 4 he ratios r ranging from 0 5 to 3 8 times the atmospheric value ra the methane helium results can be interpreted as the result of a mixture between a low 3 he 4 he 0 01r a high ch 4 3 he crustal end member and a high 3 he 4 he 0 6 3 9r a low ch 4 3 he 6 magmatic component the presence of mantle he does not require significant amounts of mantle methane a better fit to the data is obtained using a zero methane magmatic end member the worldwide association of 3he and magmatic activity suggests that volcanism plays a role in methane generation by supplying the heat needed to convert organic matter to methane thermogenically only gases from the accretionary prism of barbados west indies appear totally devoid of magmatic he 3 he 4 he ratio 0 02ra the he is completely of crustal origin there is no evidence that faults within the accretionary prism of this fore arc act as conduits for the migration of mantle he many of the gases studied contain significant quantities of co2 which appear to result from two processes 3 he 4 he high co 2 3 he gases 0 01ra 1011 possibly result from decarbonation reactions in the crust while the high 3 he 4 he low co 2 3 he gases 2 4ra

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

a hot spring in granite of the western tianshan china the western tianshan range is a major cenozoic orogenic belt in central asia exposing predominantly paleozoic rocks including granite ongoing deformation is reflected by very rugged topography with peaks over 7000 m high active tectonic deformation is tied to an e w trending fracture and fault system that sections the mountain chain into geologically diverse blocks that extend parallel to the orogen in the muzhaerte valley upwelling hot water follows such a fault system in the muza granite about 20 l min 1 na so4 cl water with a temperature of 55 c having a total mineralization of about 1 g l 1 discharge from the hot spring the water is used in a local spa that is frequented by the people of the upper ili river area its waters are used for balneological purposes and the spa serves as a therapeutic institution the major element composition of the hot water is dominated by na and by so4 and cl ca is a minor component dissolved silica 1 04 mmol l 1 corresponds to a quartz saturation temperature of 116 c and a corresponding depth of the source of the water of about 4600 m this temperature is consistent with na k and na li geothermometry the water is saturated with respect to fluorite and contains 7 5 mg l 1 f as a consequence of the low ca concentration the water is undersaturated with respect to the primary minerals of the reservoir granite at reservoir temperature causing continued irreversible dissolution of granite the waters are oversaturated with respect to ca zeolite minerals such as stilbite and mesolite and it is expected that zeolites precipitate in the fracture pore space and in alteration zones replacing primary granite the stable isotope composition of o and h supports a meteoric origin of the water the cl br mass ratio of 1500 suggests that the salinity results from halite dissolution salts leached from powders of muza granite show the same cl br signature as the hot spring water sodium chloride is stored in fluid and solid inclusions in the granite which have been introduced to quartz by ductile shearing and faulting related to ongoing orogenesis the hot water remobilizes the salt that is continuously liberated by the tectonic deformation water granite interaction contributes a thenardite component na2so4 to the major element composition by albite dissolution in h2so4 the water rock interaction along faults and fractures transforms and alters muza granite to a low temperature epigranite

shear wave seismic reflection studies of unconsolidated sediments in the near surface we have successfully applied of sh wave seismic reflection methods to two different near surface problems targeting unconsolidated sediments at the former fort ord where the water table is approximately 30 m deep we imaged aeolian and marine aquifer and aquitard stratigraphy to a depth of approximately 80 m we identified reflections from sand clay and sand silt interfaces and we mapped these interfaces along our transects at an aggregate study site in indiana where the water table is at a depth of 1 to 2 m we imaged stratigraphy in alluvial sand and gravel and observe a strong reflection from the 32 m deep bedrock surface in both cases we exploited the high resolution potential of sh waves their insensitivity to water content and the possibility of reducing love wave contamination by working along a roadway we accomplished our results using only sledgehammer sources and simple data processing flows

sources and mechanisms of formation of gaseous hydrocarbons in sedimentary rocks abstract accepted concepts of principal stages of hydrocarbon formation fail to satisfactorily explain the accumulation of supergiant gasfields in west siberia u s s r such as for example urengoy which comprise 30 of the proven gas reserves of the world a new mathematical model has been developed which applies the concept of activation energy distribution to the formation of gases characteristic differences in the molecular structure of humic and sapropelic source organic matter are expressed in different activation energy distributions the model allows the calculation of isotope values for different types of organic matter and their dependence on maturity application of the model to west siberia suggests that the supergiant gas accumulations in urengoy are more likely formed from terrestrial organic matter through thermochemical reactions at moderate depths and are not the result of either deep overmature or bacteriogenic processes the new mathematical model suggests that humic organic matter in general has a high methane generating capacity at comparably low maturities of organic matter equivalent to 0 5 0 7 on the vitrinite reflectance scale

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

shallow seismic reflection mapping of the overburden bedrock interface with the engineering seismograph some simple techniques where unconsolidated overburden exceeds 20 m in thickness the reflection method may be efficiently used with a 12 channel engineering seismograph to map topography on the overburden bedrock interface as well as possible structure within the overburden the two techniques we suggest are the simplest forms of reflection profiling which can be applied with a minimum amount of equipment which we suggest is a 12 channel enhancement seismograph a 12 geophone array and a hammer source these techniques require good transmission characteristics of the overburden as well as a sharp velocity discontinuity at the overburden bedrock interface for data processing and display a microcomputer is essential

1980 1990 ten years of geochemical investigation at phlegrean fields italy abstract a systematic geochemical investigation on the thermal manifestations of the volcanic area of phlegrean fields started in 1980 with the aim of obtaining useful information about the changes possibly occurring at the same time of vertical ground movements termed as bradyseismic which frequently interested this area the attention was initially given to the fumaroles and the boiling pools of solfatara and pisciarelli then subsequently extended to thermal springs dug wells and crater lakes analytical data pertaining to a period preceding the last crisis of 1982 1984 were then available as well as other data collected during the previous crisis of 1970 a comprehensive picture of the variations observed before during and after the acceleration of vertical movement has been drawn according to the results obtained the intrusion of a magmatic body as the trigger of the observed ground deformation is considered unrealistic the whole area appears now in a quiet stage and no further perturbation is expected without previous significant tectonic activity chemical precursors appear suitable for an early detection of changes occurring at depth to forecast possible consequences to be expected in the surface environment

lithostratigraphy and biostratigraphy of the lower carboniferous mississippian carbonates of the southern askrigg block north yorkshire uk a rationalized lithostratigraphy for the great scar limestone group of the southeast askrigg block is established the basal chapel house limestone formation assessed from boreholes comprises shallow marine to supratidal carbonates that thin rapidly northwards across the craven fault system onlapping a palaeotopographical high of lower palaeozoic strata the formation is of late arundian age in the silverdale borehole its northernmost development the overlying kilnsey formation represents a southward thickening and upward shoaling carbonate development on a south facing carbonate ramp foraminiferal algal assemblages suggest a late holkerian and early asbian age respectively for the uppermost parts of the lower scaleber force limestone and upper scaleber quarry limestone members significantly younger than previously interpreted the succeeding malham formation comprises the lower cove limestone and upper gordale limestone members foraminiferal algal assemblages indicate a late asbian age for the formation contrasting with the holkerian age previously attributed to the cove limestone the members reflect a change from a partially shallow water lagoon cove limestone to more open marine shelf gordale limestone coincident with the onset of marked sea level fluctuations and formation of palaeokarstic surfaces with palaeosoils in the latter facies variations along the southern flank of the askrigg block including an absence of fenestral lime mudstone in the upper part of the cove limestone and presence of dark grey cherty grainstone packstone in the upper part the gordale limestone are related to enhanced subsidence during late asbian movement on the craven fault system this accounts for the marked thickening of both members towards the greenhow inlier

incised valley fill interpretation for mississippian black hand sandstone appalachian basin usa implications for glacial eustasy at kinderhookian osagean tn2 tn3 boundary abstract lower mississippian strata of east central ohio are predominantly fine grained marine deposits of the cuyahoga and logan formations within these sediments is the black hand sandstone of the cuyahoga formation the black hand sandstone is a multistory crossbedded coarse grained conglomeratic sandstone the contact between the black hand sandstone and the subjacent cuyahoga formation is sharp and scoured with intraclasts of the cuyahoga formation incorporated into the basal black hand sandstone the black hand sandstone was previously thought to represent a distributary channel deposit however the combination of lithofacies and architectural elements indicates deposition in a braided stream setting the cuyahoga formation was deposited in a shallow marine setting the erosional basal contact of the black hand sandstone and the juxtaposition of fluvial and marine sediments suggests a sequence boundary the geographic distribution of the black hand sandstone combined with the evidence for a sequence boundary suggests deposition in an incised valley the age of the black hand sandstone is key to inferring the causes of valley incision the black hand sandstone is nearly devoid of body fossils necessitating a biostratigraphic analysis of the surrounding cuyahoga and logan formations analysis indicates the logan formation is early osagean age data from the cuyahoga formation suggest a kinderhookian age with a possible transition to the osagean in the uppermost cuyahoga formation this constrains the age of the black hand sandstone to the transition at the kinderhookian osagean boundary recent reports indicate late kinderhookian tournaisian tn2 gondwanan glaciation based upon tillites and sharp excursions in stable isotope curves a glacio eustatic fall in sea level is inferred to have caused incision of the cuyahoga formation followed by deposition of the black hand sandstone and logan formation during the subsequent sea level rise the associated unconformity correlates to the sequence boundary at the kinderhookian osagean boundary in the stratotype area of north america and the correlative tn2 tn3 boundary worldwide supporting the hypothesis of a global eustatic event at this time

geochemistry of fluid discharges from peteroa volcano argentina chile in 2010 2015 insights into compositional changes related to the fluid source region s abstract this study presents the first geochemical data of fluid discharges collected from february 2010 to march 2015 from the planchon peteroa azufre volcanic complex ppavc located in the transitional southern volcanic zone tsvz at the border between argentina and chile during the study period from january 2010 to july 2011 peteroa volcano experienced phreatic to phreatomagmatic eruption possibly related to the devastating maule earthquake occurred on february 27 2010 the compositional dataset includes low temperature from 43 2 to 102 c gas discharges from i the summit of peteroa volcano and ii the se flank of azufre volcano both marked by a significant magmatic fluid contribution as well as bubbling gases located at the foothill of the peteroa volcanic edifice which showed a chemical signature typical of hydrothermal fluids in 2012 strong compositional changes affected the peteroa gases from the summit area the acidic gas species especially so 2 increased suggesting an input of fluids from magma degassing nevertheless the r ra and 13 c co 2 values decreased which would imply an enhanced contribution from a meteoric hydrothermal source in 2014 2015 the chemical and isotopic compositions of the 2010 2011 gases were partially restored the anomalous decoupling between the chemical and the isotopic parameters was tentatively interpreted as produced by degassing activity from a small batch of dacitic magma that in 2012 masked the compositional signature of the magmatic fluids released from a basaltic magma that dominated the gas chemistry in 2010 2011 this explanation reliably justifies the observed geochemical data although the mechanisms leading to the change in time of the dominating magmatic fluid source are not clear at this regard a geophysical survey able to provide information on the location of the two magma batches could be useful to clarify the possible relationships between the compositional changes that affected the peteroa fluid discharges and the 2010 2011 eruptive activity

remobilisation of base metals and gold by variscan metamorphic fluids in the south iberian pyrite belt evidence from the tharsis vms deposit the tharsis massive sulphide deposit one of the major vms type deposits in the iberian pyrite belt ipb was severely deformed by the variscan tectono thermal events the question of whether or not these events affected the metal distribution in the deposit has been addressed by simultaneously studying the mineral parageneses tharsis stockwork and the fluid circulation at local and regional scales the results are 1 the early paragenesis in the stockwork q1 quartz pyrite chlorite phengitefcobaltitefankerite was strongly overprinted by a late post kinematic mineral deposition including new quartz veins q3 quartz and base metal sulphides chalcopyrite sphalerite bi and te minerals pyrite and galena and gold 2 at a regional scale fluids accompanying the peak metamorphism conditions ca 300 mpa ca 300 jc were of c o h n nacl type co2 dominated with ch4 and n2 and are considered to be metamorphic on the basis of microthermometry and geochemistry the late to post kinematic evolution retrograde stage was characterised by a pressure drop down to 40 mpa lithostatic to hydrostatic transition and a heat input leading to temperatures z430 jc then decreasing to temperature around 170 jc fluids of the retrograde type exhibit both dilution of the c o h n nacl fluid by a low salinity meteoric water and progressive loss of volatile components 3 fluids of the retrograde type pervasively percolated through the tharsis stockwork and were responsible for the strong mineral overprint on the early deformed paragenesis all the measurable fluid inclusions f i record these late fluids there are primary fluid inclusions in q1 but they are systematically imploded due to the external overpressure generated by the variscan tectonic events although base metal distribution in the stockwork is basically the result of the

low cost geophysical investigations of a paleochannel aquifer in the eastern goldfields western australia compressional p wave and shear s wave seismic reflection techniques were used to delineate the sand and gravel aquifer within a highly saline clay filled paleochannel in the eastern goldfields of western australia the seismic refraction and gravity methods were also used to investigate the paleochannel the unsaturated loose fine grained sand up to 10 m in depth at the surface is a major factor in degrading subsurface imaging the seismic processing needed to be precise with accurate static corrections and normal moveout corrections deconvolution enhanced the aquifer and other paleochannel reflectors p wave reflection and refraction layer depths had good correlation and showed a total of six boundaries 1 water table 2 change in velocity compaction in the paleochannel sediments 3 sand and gravel aquifer 4 red brown saprolite and green saprolite boundary 5 weathered bedrock and 6 unweathered bedrock p wave explosive and hammer sources were found to have similar signal characteri

extreme alteration in an acid sulphate geothermal field sulphur springs saint lucia abstract sulphur springs is a vigorous geothermal field associated with the soufriere volcanic centre in southern saint lucia intensely altered rocks occur over an area of at least 200 400 m together with bubbling hot pools and fumaroles the pools are sodium calcium sulphate type with phs of 3 7 and temperatures of 41 97 c fumaroles have temperatures up to and at times above 100 c gases collected from both fumaroles and bubbling pools have high contents of co2 601 993 mmol mol and commonly high h2s 3 190 mmol mol least altered host rocks surrounding sulphur springs comprise calc alkaline feldspar quartz porphyritic dacites of near uniform chemical composition these rocks which form massive domes and volcaniclastic units were emplaced 13 30 ka ago lindsay et al 2013 within the geothermal field the dacites have been moderately to highly altered to acid sulphate assemblages of kaolinite illite smectite alunite natroalunite cristobalite opaline silica native sulphur jarosite and amorphous compounds muddy sediments from grey to blackish thermal pools additionally contain iron sulphides despite intense alteration of the volcanic rocks and derived volcaniclastic sediments zr and ti have remained essentially immobile which allows identification of the precursors dacites and calculation of mass changes many of the altered rocks and sediments show major depletions of fe mg ca na extremely altered samples additionally show notable losses of al p k ree and y implying leaching by highly acidic waters a few of the highly altered rocks however have gained al together with p presumably due to neutralization or evaporation of acidic thermal waters also present within the geothermal field are metre scale zones with very high contents of silica and native sulphur and surface thermal waters define a linear trend in a plot of 18o vs d and reach high levels of isotopic enrichment the enrichment trend is ascribed to progressive evaporation in the thermal pools the low slope of the isotopic trend 1 4 is interpreted as being due to surficial mixing between meteoric waters and steam condensates derived at about 230 c from the deep brine that underlies the geothermal field the whole rock o h isotopic composition of four highly altered samples kaolinite smectite opal sulphates can be accounted for if the alteration fluid was a 50 50 mixture of steam and meteoric water and alteration occurred at 50 125 c whole rock 34s values of samples containing variable amounts of sulphates sulphides and native s are all notably negative 5 to 16 consistent with derivation of sulphur from volcanic gases such as so2 and h2s altered rocks and thermal pool sediments in the geothermal field are commonly enriched in hg and se up to 50 mg kg at sulphur springs primary dacitic rocks have been chemically and mineralogically transformed by reaction with acidic waters that formed when uprising volcanic gases condensed into neutral meteoric waters in many cases this has led to substantial mass losses or gains in al p and rees regardless of the degree of alteration however the precursor rocks can still be identified using ti zr relations

mid dinantian waulsortian buildups in the dublin basin ireland abstract the sedimentary history and biostratigraphic setting of waulsortian carbonate buildups of the feltrim limestone formation late courceyan to early chadian within the dublin basin are described there is no unique precursor or successor facies to this formation and the massive waulsortian banks are composed predominantly of peloidal skeletal wackestones and lime mudstones with packstones near the tops of banks these banks form tabular bodies of moderate relief and are interbedded with thin shales and argillaceous crinoidal limestones of inter bank facies in the southwest of the basin inter bank facies are rare and the bank facies have abundant stromatactis cavities and uniquely at roselawn a fauna of rugose corals all buildups in the dublin basin have phase c and or d component assemblages of lees and miller 1985 and are interpreted as accumulating in moderately shallow water depths near or within the photic zone isopachs for the feltrim limestone formation show a ne sw trending axial depocentre where the waulsortian facies is in excess of 400 m thickness deposition appears to have taken place on this double sided ramp in a manner similar to the model of lees 1982 for belgium and southern britain soft sediment deformation such as large scale slumping shale injections and water escape structures not previously recorded from these rocks is widespread the upper surface of the feltrim limestone formation is fissured and displays a prominent erosion surface termination of waulsortian facies deposition and influx of terrigenous sediment was caused by rapid uplift attributed to chadian tectonism however eustatic sea level fall cannot be ruled out as a partial cause of the demise of the waulsortian

galapagos hot spot spreading center system 2 87sr 86 sr and large ion lithophile element variations 85 w 101 w thirty eight samples of basalts dredged from the galapagos spreading center gsc between 85 w and 101 5 w longitudes have been analyzed for k rb cs ba and sr contents as well as for 87sr 86sr ratios basalts between 85 w and 89 w segment of the gsc range from 0 7025 to 0 7028 in 87sr 86sr and those between 95 5 w and 101 5 w range from 0 7026 to 0 7027 these basalts are characterized by lree depleted patterns basalts from 89 w to 95 5 w segment having slightly lree depleted to lree enriched patterns la sm e f between 0 8 and 2 4 range from 0 7027 to 0 7031 in 87sr 86sr the longitudinal 87sr 86sr variation shows a maximum at about 92 w where the gsc is nearest to darwin island the alkali and alkaline earth elements as well as several element ratios also show maxima in their longitudinal profiles but these occur at about 91 w the apparent shift of 87sr 86sr maximum with respect to that of the trace elements may be related to differences in the degree of partial melting the highest 87sr 86sr from the gsc is only slightly lower than the highest 87sr 86sr for tholeiitic basalts from the galapagos archipelago several possible hypotheses have been examined to account for these geochemical and sr isotopic variations in the light of the presently available data the most promising explanation seems to be a binary mixing of hot spot or plume type material with the source of normal mid ocean ridge basalts and resulting rift propagation both end members seem to be heterogeneous and therefore it is at present difficult to put severe constraints on this binary mixing nevertheless the flow pattern of mantle material from the hot spot does not appear to be radial but is preferentially channeled along the 91 w and 92 5 w fracture zones toward the rift

seismic imaging of the shallow subsurface shear wave case histories obtaining high resolution images of the geology and hydrogeology of the subsurface in the depth range from ground level to 50 m is one of the major challenges of modern geophysics the methods which are commonly used such as compressional wave surveys and ground penetrating radar often suffer from adverse effects caused by the near surface conditions changes in water saturation and various sources of noise this paper demonstrates some of the advantages offered by the use of shear wave seismology and by the combination of shear and compressional wave seismic methods in shallow subsurface investigations multicomponent shallow seismic tests were carried out at four different sites to examine the effectiveness of different acquisition geometries under a variety of near surface geological conditions near surface conditions encountered at the sites included thick clays clay sand sequences overlying chalk mudstone overlying granodiorite bedrock and landfill material under all conditions shear wave data acquisition was found to have advantages over compressional wave acquisition for the investigation of the shallow subsurface shear head waves being unaffected by water saturation achieved penetration to greater depths at a site in crewkerne dorset where compressional head wave penetration was limited to the near surface layers better vertical resolution was achieved at shallow depths using shear wave reflection energy at a landfill site shear wave reflections from shallow interfaces were in some cases less affected by noise compared with the equivalent compressional wave reflections combinations of shear and compressional wave data recording allowed the measurement of a poisson s ratio log and gave indications of seismic anisotropy at two sites where dipping clay layers were present

dinantian lower carboniferous biostratigraphy and chronostratigraphy in the british isles vaughan s 1905 zonation of the carboniferous limestone in the bristol district was a pioneer biostratigraphical study which because of its meticulous execution can be reinterpreted in a modern context the replacement of his scheme with a chronostratigraphical one by george et al 1976 had a similar revolutionary affect on british dinantian stratigraphy however it is now time to revise the british dinantian stages so that they more closely correspond to biostratigraphical events dinantian biostratigraphy still requires considerable refinement but it has now achieved a diversity of techniques and resolution far beyond that which was available at the time of these earlier proposals it is the most pragmatic and closest approximation to widespread chronostratigraphical correlation available this paper discusses these and related issues and presents a review and correlation of current biozonations

symmetrical and segmented variation of physical and geochemical characteristics of the central american volcanic front abstract the regional variation of physical and geochemical characteristics of central american volcanoes occurs in two fundamentally different patterns the first pattern is symmetrical about nicaragua crustal thickness silica contents of mafic lavas and volcanic edifice heights are lowest in nicaragua and increase smoothly toward costa rica to the south and guatemala to the north magma density is maximum in nicaragua and decreases smoothly outward the regional variation in crustal thickness is just enough so that magma densities calculated at appropriate moho pressures are the same at the base of the crust throughout the region this is consistent with magma ponding at the base of the crust the bulk compositions of central american basalts show the same symmetrical variation suites of nicaraguan basalts plotted in pseudo ternary cmas projections indicate large olivine and plagioclase primary phase volumes toward costa rica and guatemala the olivine and plagioclase fields inferred from suites of basaltic lavas are smaller which is consistent with fractionation at increasing depth the second pattern is the segmentation of the volcanic front and the plate margin in general the segmentation strongly affects the spacing and size of volcanic centers at segment boundaries volcanic centers are generally small and unusually widely spaced toward segment interiors volcano spacing and size increase systematically the lil element contents of lavas strongly reflect this pattern for lavas with similar silica contents the larger the volcano the higher the lil element contents the relationships between segmentation volcano spacing and volcano size are compatible with diapiric rise of magma accumulated in narrow ribbons near the upper surface of the underthrust slab the relationship between volcano volume and lil element content is qualitatively in agreement with an open system fractionation model

monitoring of volcanic eruptions at yugama crater lake by aqueous sulfur oxyanions abstract variations of polythionates sulfane disulfonates and sulfate in the yugama crater lake japan have been monitored for more than 25 years just before the 1982 eruption at the crater lake polythionate ions decreased to zero from the normal level of about 2000 ppm and sulfate ions increased from 2500 to 5000 ppm during the 1982 eruption polythionate and sulfate ions varied inversely in concentration and the variations exactly coincided with the frequency of volcanic earthquakes and subsequent explosions these observations are interpreted in terms of aqueous reactions of fumarolic so2 h2s gases resulting in precipitation of alunite the behavior of polythionate and sulfate ions strongly suggests that they are useful indicator for prediction of impending volcanic hazards from active crater lakes

the stratigraphy and cyclicity of the late dinantian platform carbonates in parts of southern and western ireland the late dinantian platform carbonate successions of the burren buttevant and callan areas in ireland have been correlated using detailed lithoand biostratigraphy several subdivisions or lithofacies associations la of the asbian to brigantian part of the succession have been recognized in each area lithofacies associations 1 5 holkerian to early asbian ramp carbonates of la 1 underlie the late asbian successions in both the burren and buttevant areas the influx of the bilaminar palaeotextulariid cribrostomum lecomptei coincides with the onset of late asbian shallowmarine cyclic platform sedimentation la 2 in all areas the sediments of la 2 have abundant kamaenella and foraminifera and are characterized by palaeokarstic surfaces and shales that cap a minimum of nine shallowing upward minor cycles in the burren and buttevant areas two new biostratigraphic subdivisions cf6 1 and cf6 2 of the late asbian cf6 subzone are described for the first time in this part of the succession brigantian sedimentation la 3 is typified by amalgamated beds of crinoidal limestone and abundant asteroarchaediscidae thin peloidal limestones with coral thickets cap shallowing upward cycles within this succession these cycles which are thinner and less numerous than those of the underlying late asbian rarely terminated in emergence but most reached shallow subtidal depths prior to the next transgression the change in cyclicity style across the asbian brigantian boundary may be related to the sedimentation rates of the crinoidal limestones due to increases in cyclic oscillation in the brigantian brigantian la 4 is characterized by deep subtidal cherty limestones with abundant algal coated wackestone intraclasts fasciella and howchinia bradyana are typical microfossils no cyclicity is observed probably owing to the deep subtidal nature of this unit la 4 is overlain by another unit of cyclic crinoidal limestones la 5 in the burren which has no correlatives in the other areas studied the succession in all areas is unconformably overlain by namurian siliciclastic rocks the nature and number of minor cycles in the late dinantian of ireland is similar to those of platform successions of the same age elsewhere in the british isles suggesting that eustatic changes were one of the major controls on cyclicity during

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

variety and sustainability of volcanic lakes response to subaqueous thermal activity predicted by a numerical model we use a numerical model to investigate the factors that control the presence or absence of a hot crater lake at an active volcano we find that given a suitable pair of parameters e g the enthalpy of subaqueous fumaroles and the ratio of mass flux of the fluid input at the lake bottom to lake surface area hot crater lakes can be sustained on relatively long timescales neither a high rate of precipitation nor an impermeable layer beneath the lake bottom are always necessary for long term sustainability the two controlling parameters affect various hydrological properties of crater lakes including temperature chemical concentrations and temporal variations in water levels in the case of low temperature crater lakes increases in flux and enthalpy which are a common precursor to phreatic or phreatomagmatic eruptions result in an increase in both temperature and water level in contrast a decrease in water level accompanied by a rise in temperature occurs at high temperature lakes furthermore our model suggests that crater geometry is a key control on water temperature for lakes with a conical topography a perturbation in the water level due to trivial non volcanic activity such as low levels of precipitation can cause persistent increases in water temperature and chemical concentrations and a decrease in the water level even though subaqueous fumarolic activity does not change such changes in hot crater lakes which are not caused by changes in volcanic activity resemble the volcanic unrest that precedes eruptions

stable isotopes evidence of recycled subduction fluids in the hydrothermal volcanic activity across nicaragua and costa rica abstract the central america volcanic front provides a unique opportunity to study hydrothermal inputs and their interaction and mixing with modern meteoric waters the objectives of this study were to a characterize the isotopic composition 18 o 2 h d excess and lc excess of hydrothermal volcanic systems b analyze the influence of kinetic fractionation and meteoric water inputs in the isotopic composition of hydrothermal waters and c estimate the andesitic water contribution recycled subduction fluids within the volcanic front of nicaragua and costa rica hydrothermal evaporation lines are described as 2 h 4 7 18 o 13 0 costa rica and 2 h 2 7 18 o 31 6 nicaragua these regressions are significantly p 2 h 7 6 18 o 7 4 costa rica and 2 h 7 4 18 o 5 2 nicaragua the greater rainfall inputs in costa rica with respect to nicaragua resulted in the attenuation of the evaporative effect as observed in the strong bimodal distribution of the hydrothermal waters which can be divided in fluids a isotopically close to meteoric conditions and b isotopically altered by the interaction with recycled subduction fluids and kinetic fractionation the latter is clearly depicted in the significantly p d excess and lc excess median values between costa rica 5 10 5 25 and nicaragua 2 42 10 65 respectively poor correlations between 18 o 2 h and the elevation gradient emphasize that the contribution of recycled subduction fluids and subsequent surface kinetic fractionation are the main drivers of the isotopic departure from the orographic distillation trend captured in the rainfall isoscapes end member mixing calculations resulted in a significant difference p 2 he contributions across the volcanic front of nicaragua and costa rica

p t x constraints on the koru epithermal base metal au deposit biga peninsula nw turkey abstract the koru deposit is a typical intermediate sulfidation base metal au example of volcanic volcaniclastic hosted mineralization in the biga peninsula and northwestern turkey ore deposition was associated with the collisional and post collisional tectonics related to the closure of the tethys ocean galena baryte and quartz are main minerals accompanied by minor amounts of sphalerite pyrite chalcopyrite covellite and marcasite the homogenization temperature of fluid inclusions indicates two distinct fluid pulses one at a temperature commensurate with epithermal mineralization and boiling near boiling conditions at c 350 c with the second approximately 150 200 c lower salinity in both instances was from 11 0 to 0 2 wt nacl the d and 18o values of water in equilibrium with early quartz and fluid inclusions plot close to the magmatic water box indicating the source of the high temperature fluid was magmatic d and 18o values from early and late baryte trend towards the meteoric water line mwl but this is not due to mixing with meteoric water rather equilibration with alteration assemblages at decreasing temperature la icp ms analyses of fluid inclusions reveal high cu zn pb concentrations in the fluids despite their low salinity transported as chloride complexes the range of temperatures within the early quartz and sphalerite mineralization can be explained by pressure variations during vein and fracture opening

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

hydrochemical evolution and reaction simulation of travertine deposition of the lianchangping hot springs in yunnan china located in western yunnan of china the lianchangping hot springs are of so 4 hco 3 ca na type with total dissolved solids tds ranging from 3560 to 4240 mg l large amounts of travertine are deposited near the hot springs with a variety of travertine morphology including travertine terrace slope and ridge travertine is precipitating along the slope near one of the spring s thresholds chemical compositions of the hot water samples collected along travertine slope show that p co 2 p co 2 tds and contents of hco 3 and ca decrease downstream along the travertine slope due to travertine deposition the initial milliequivalent ratio of ca 2 hco 3 is greater than 1 5 before travertine precipitation and there is an increasing trend in the ratio downstream along the travertine slope high levels of sulphate are probably the result of gypsum dissolution in the sediments widespread in the lianchangping area the spring waters issuing from the land surface are slightly supersaturated with respect to calcite dolomite fluorite kaolinite halite plagioclase and carbon dioxide hydrochemical evolution of the lianchangping spring water along the slope is calculated with the phreeqc interactive 2 12 5 sets of minerals and gases reacted in appropriate amounts are recognized through reaction simulation quantitatively accounting for the variations in chemical compositions especially depositing minerals along the flow path on the travertine slope

some sh wave seismic reflections from depths of less than three metres shallow sh wave reflections are far from routine although their study can provide insights into important properties of near surface materials that cannot be inferred from p wave data alone difficulties in separating sh wave reflections from love waves are generally considered the major obstacle to progress in shallow sh wave seismic reflection this may be the case in surveys undertaken at great depths but it is not necessarily true for reflection data gathered at shallow and ultra shallow depths this paper shows that when sh wave data possess wavelengths greater than the thickness of the superficial layer love waves are not greatly dispersed in this case misinterpretation between parts of reflection hyperbolae and waveguide arrivals is sufficiently limited in a one layer model earth which well approximates typical situations of the near surface underground the most energetic modes the lowermost modes of the dispersed surface waves have a dominant frequency band that falls below the wavelet spectrum of the shallow reflections therefore they can be filtered out in the frequency domain higher modes although their spectral content overlaps that of the reflections exhibit small amplitudes on seismograms and leave strong reflections unaffected we present field examples from three different sites where we were able to obtain ultra shallow reflections 3 m in unconsolidated sediments the high level of resolution vertical resolution up to 15 cm suggests that sh wave reflection imaging has the potential to complement other high resolution techniques such as p wave reflection and ground penetrating radar gpr imaging allowing a better and more complete characterization of the near surface environments

rincon de la vieja volcano guanacaste province costa rica geology of the southwestern flank and hazards implications abstract acid rain and ongoing eruptive activity at rincon de la vieja volcano in northwestern costa rica have created a triangular deeply eroded dead zone west southwest of the active crater the barren steep walled canyons in this area expose one of the best internal stratigraphic profiles of any active or dormant volcano in costa rica geologic mapping along the southwestern flank of the volcano reveals over 300 m of prehistoric volcanic stratigraphy dominated by tephra deposits and two pyroxene andesite lavas dense tropical forests and poor access preclude mapping elsewhere on the volcano in the dead zone four stratigraphic groups are distinguished by their relative proportions of lava and tephra in general early volcanism was dominated by voluminous lava emissions with explosive plinian eruptions becoming increasingly more dominant with time numerous phreatic eruptions have occurred in historic times all emanating from the active crater the stratigraphic sequence is capped by the rio blanco tephra deposit erupted at approximately 3500 yr b p approximately 0 25 km 3 0 1 km 3 dre of tephra was deposited in a highly asymmetrical dispersal pattern west southwest of the source vent indicating strong prevailing winds from the east and east northeast at the time of the eruption grain size studies of the deposit reveal that the eruption was subplinian attaining an estimated column height of 16 km a qualitative hazards assessment at rincon de la vieja indicates that future eruptions are likely to be explosive in style with the zone of greatest hazard extending several kilometers north from the active crater

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

shear wave studies in glacial till within a high resolution shallow reflection survey program in saskatchewan canada s waves were produced using a single seismo electric blasting cap and were found to be distinguishable from surface wave phases the local glacial deposits have average velocities of 450 m s vp vs ratios average 3 6 in these sequences but they vary laterally according to the velocity analyses done in two boreholes drilled along the seismic line vertical resolution for s wave reflections are 0 75 m in the vertical seismic profiling vsp data and 1 5 m in the cdp data yet the s wave cdp results are still better than corresponding p wave data which had a vertical resolution of 2 6 m s wave anisotropy is inferred in the glacial deposits on the basis of particle motion analysis and interpretations of s wave splitting however the amount of observed splitting is small 2 6 ms over 5 10 m and could go undetected for seismic surveys with larger sampling intervals vsps indicate that s wave reflectivity is caused by

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

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

cyclic stratigraphy facies and fauna of the lower carboniferous dinantian of the moscow syneclise and voronezh anteclise

secular variations of helium and carbon isotopes at galeras volcano colombia copyright c 1997 elsevier science b v all rights reserved we have measured 3 he 4 he 4 he 20 ne and co 2 4 he ratios and d 13 c values of co 2 in eighteen samples from crater fumaroles of galeras volcano colombia and seven samples of bubbling gases of the pandiaco mineral spring located about 8 km east of the volcano from april 1988 to july 1995 the 3 he 4 he ratios of crater fumaroles corrected for atmospheric contamination increased significantly from 5 47 r atm in december 1989 to 7 93 r atm in august 1990 and reached a maximum of 8 84 r atm in may 1992 the ratio then decreased gradually until july 1995 overall variation of helium isotopes appears to be related to the current activity of the volcano the 3 he 4 he ratios of pandiaco mineral spring were constant between april 1988 and november 1991 and increased in april 1993 although experimental error is large the d 13 c values of co 2 of crater fumaroles show negative correlation to the helium isotopes while those of pandiaco are relatively constant based on the d 13 c values and co 2 3 he ratios it is possible to estimate fractions of upper mantle carbon in these samples calculated mantle fractions are 3 10 in crater fumaroles while those in pandiaco spring are negligibly small

aquifer heterogeneity from sh wave seismic impedance inversion we collected sh wave seismic reflection data over a shallow aquifer in southwestern british columbia to investigate the use of such data in hydrogeologic applications we used this data set in developing a methodology that uses cone penetrometer data as an integral part of the inversion and interpretation of the seismic data a bayesian inversion technique converts the seismic amplitude variations to velocity variations honoring the probabilities of the priors and adhering to a geologically reasonable sparseness criterion velocity measurements acquired with the cone penetrometer provide velocity profiles and vertical seismic profiling vsp data all of which are valuable in properly constraining the bayesian inversion the differentiation of lithologies in this data set sand and clay is accomplished by first using a normalization procedure to remove the impact of effective stress which dominates the velocity variation in the upper 10 to 20 m the final transformation of seismic velocities to void ratio for the sand dominated regions is made using laboratory derived measurements it provides an image of the heterogeneity of the near surface aquifer

an ultrashallow sh wave seismic reflection experiment on a subsurface ground model an sh wave seismic reflection experiment was conducted to evaluate the feasibility and cost effectiveness of reflection imaging ultrashallow targets commonly encountered in engineering groundwater and environmental investigations it was carried out on a purpose built subsurface ground model consisting of a concrete layer at a depth from 2 85 5 m and a low velocity overburden 80 and 150 m s for s and p waves respectively constituted of filling material with the water table 2 60 m deep high quality cdp data acquired by using a 10 kg sledgehammer and newly designed horizontal detectors allowed us to obtain an extremely detailed stacked section with a minimal amount of processing uncertainty in determining the depth and horizontal dimensions of the concrete model was estimated to be 0 2 and 0 3 m respectively however the dominant frequencies lower than 150 hz the low transmission coefficient at the upper interface and the relatively high velocity 900 m s of the concrete layer prevented

late chadian early arundian high resolution biostratigraphy in the ogmore by sea section south wales mendip shelf and the mid avonian unconformity the study of the foraminiferal fauna in the ogmore section in south wales produced a detailed late chadian early arundian biostratigraphy and sequence stratigraphy with a higher resolution than in the arundian stratotype in hobbyhorse bay the earliest visean late chadian pedogenic horizon close to the gully oolite and caswell bay mudstone boundary mfz9 corresponds to the mid avonian unconformity the entry of primitive archaediscids of mfz10 within the caswell bay mudstone is followed by more advanced archaediscids of mfz11 at the base of the high tor limestone the mid avonian unconformity at the chadian arundian boundary is not confined to the london brabant massif but is also present in central europe the east european platform the urals west siberia and probably also in kuzbass and north america the global extent of the the mid avonian unconformity suggests that it is a consequence of early to mid visean glacioeustacy

seismic investigation of near surface geological structure in the paducah kentucky area application to earthquake hazard evaluation abstract seismics method were used to evaluate shallow geological conditions at 33 sites in the vicinity of paducah kentucky a combined set of p and s wave seismic refraction and reflection soundings were used in addition to local borehole information to produce structure maps of 1 a shallow 160 m deep shear wave velocity contrasts across the shallow unconformity were generally 2 to 1 while the contrast at the top of the paleozoic bedrock exceeds 5 to 1 these seismic boundaries have been determined to be very important in modelling and interpreting earthquake ground motion amplification in the paducah area the quality and accuracy of the data and the cost effective nature of the methods suggest that other communities in areas at risk to damage from seismic activity with foundation conditions comparable to paducah might benefit from similar characterization in order 1 to identify seismically hazardous near surface geological conditions and 2 to develop geological models that could be used in computer simulations of site response

ramp sedimentation in the dinantian limestones of the shannon trough co limerick ireland abstract during the late chadian and arundian lower carboniferous an extensive carbonate ramp limerick ramp developed over county limerick southwest ireland dipping northwestwards three distinct facies can be recognised corresponding to position on this ramp inner mid and outer ramp the inner ramp facies of oolitic and crinoidal grainstones herbertstown limestone formation in east limerick formed a major shoal behind which peritidal limestones were deposited the mid ramp facies of muddy bioclastic limestones and shales cooperhill facies in north limerick formed between fairweather and storm wave bases the outer ramp basinal facies of mudstones and thin graded resedimented limestones rathkeale beds in west limerick developed below storm wave base when fine terrigenous input was high later in the arundian there was progradation of the nearshore oolitic and crinoidal grainstones over the mid ramp facies by the holkerian the deep water basinal facies in west limerick was buried beneath mid ramp facies durnish limestone the initiation of the limerick ramp is closely related to the formation of the shannon trough in the late courceyan accelerated subsidence in the shannon area during deposition of waulsortian facies marked the onset of a sag phase following a quiescent period in early chadian subsidence was renewed in the late chadian and arundian when major facies changes occurred on the ramp comparison of the shannon trough with the dublin basin shows that in the latter tectonic events in the chadian and arundian particularly syn sedimentary faulting created a sharp division between platform and basinal sedimentation such tectonic influence is not recognised in the shannon trough here differential subsidence and eustatic sea level changes led to more permanent ramp existence modified only by westwards progradation

light hydrocarbons in hydrothermal and magmatic fumaroles hints of catalytic and thermal reactions volcanic gaseous mixtures emitted from active volcanoes frequently show variable amounts of saturated alkanes unsaturated alkenes and aromatic volatile hydrocarbons three major patterns of distributions can be recognized apparently related to the chemical physical environment of formation of the gas exhalations alkane rich low temperature gas emissions from recently active volcanic areas aromatic rich hydrothermal manifestations and alkene rich magmatic fumaroles on active volcanoes thermodynamic data together with theoretical and practical findings from the petroleum industry point to two main types of reactions occurring in these volcanic environments cracking and reforming cracking processes mainly caused by thermal effects occur when hydrocarbon bearing hydrothermal fluids enter and mix with a hot and dry rapidly rising magmatic gas phase the most probable products are light alkenes with carbon numbers decreasing with increasing reaction temperatures the presence of aromatic species in hydrothermal fluids can be linked to reforming processes catalysed by several possible agents such as smectites and zeolites generally present in the hydrothermally altered volcanic terranes and facilitated by long residence times in a hydrothermal envelope

early carboniferous extension in east avalonia 350 my record of lithospheric memory abstract despite reactivations during variscan and alpine orogenies and the opening of the northern atlantic avalonia is one of the few regions where the initial mid paleozoic basin structure is still recognisable largely intact and well studied its kinematics and dynamics remain however largely unknown in particular in view of the successive late paleozoic to recent evolution of the basin consequently the importance of the mid palaeozoic tectonic evolution and structural controls are often overlooked and poorly understood in basin studies in this paper we reassess the importance of mid palaeozoic tectonics on subsequent sedimentary basin evolution of north western europe to this end we analyse the dynamics of early variscan extension in avalonia based on the integration and re evaluation of available geophysical and geological data from lithosphere to basin scales based on a revised crustal map of the thor suture zone we present a new paleo tectonic reconstruction and tectonic scenario for the devonian carboniferous rifting these findings are key for a better understanding of long lived tectonic segmentation and post rifting deformation phases our findings indicate that the structural grain of many crustal fault dominated sedimentary basin structures such as the north sea central graben were created in the early carboniferous consequently the main basement structuration of northwest europe was completed before the variscan orogeny and successive post variscan extension and inversion phases reactivated the existing basement structures without creating major new fault groups incorporation of the paleozoic structural grain allows for a consistent tectonic framework for the mesozoic contributing to fundamental understanding of basin evolution from our tectonic framework analysis avalonia therefore stands out as a fine example of long lived lithosphere memory spanning over 350 my of structural control in geodynamic evolution

evolution of hydrothermal waters at mount st helens washington usa abstract hydrothermal water samples at mount st helens collected between 1985 and 1989 and in 1994 are used to identify water types and describe their evolution through time two types of low temperature hydrothermal systems are associated with the 1980 eruptions and were initiated soon after emplacement of shallow magma and pyroclastic flows the loowit hot spring system is located in the breach zone and is associated with the magma conduit and nearby avalanche deposits whereas the pumice plain pp system is associated with pyroclastic flows and avalanche deposits 3 to 5 km north of the volcano the pp waters first discharged at the surface in 1981 whereas the loowit waters began to issue at the surface in 1983 d 18o and 3h indicated all thermal waters are dominantly derived from post 1980 recharge fluids flow through and are restricted to the shallow 1980 avalanche and pyroclastic deposits all water cooled with time up to 43 c on the pp and up to 20 c in loowit in 5 years and chemical compositions have changed rapidly all waters have highly variable and unreliable geothermometer temperatures with maximum indicated temperatures

volatile organic compounds vocs in soil gases from solfatara crater campi flegrei southern italy geogenic source s vs biogeochemical processes the chemical composition of volatile organic compounds vocs in soil gases from the solfatara crater campi flegrei italy was analyzed to investigate the effects of biogeochemical processes on gases discharged from the hydrothermal reservoir and released into the atmosphere through diffuse degassing the chemistry of fluids from fumarolic vents which represent preferential pathways for fluid uprising was also reported for comparison oxidation reduction and hydration dehydration reactions as well as microbial activity strongly affected the composition of c4 c9 alkanes alkenes s bearing compounds and alkylated aromatics especially in those sites where the soil showed relatively low permeability to uprising fluids other endogenous organic compounds such as benzene phenol and hydrofluorocarbons were able to transit through the soil almost undisturbed independently on the gas emission rate products of voc degradation mainly consisted of aldehydes ketones esters ethers and subordinately alcohols cyclic compounds revealed the occurrence of vocs produced within sedimentary formations overlying the hydrothermal reservoir whereas the presence of chlorofluorocarbons cfcs was likely related to air contamination the results of the present study highlighted the strict control of biogeochemical processes on the behavior of hydrothermal vocs that at least at a local scale may have a significant impact on air quality this information could be improved by laboratory experiments conducted at specific chemical physical conditions and in presence of different microbial populations

comparison of standard horizontal geophones and newly designed horizontal detectors to increase the speed and efficiency of shallow seismic sh wave data recording and to decrease acquisition costs we have designed constructed and tested a new velocity tool that detects horizontal movements better than standard horizontal geophones a comparative evaluation of significant characteristics and field performances of this new detector was conducted through laboratory and field tests on two sets of receivers one consisting of 24 prototypes of the new detector and the other consisting of 24 standard horizontal geophones laboratory measurements revealed similar behaviors of impedance curves and geophone responses for the two types of detectors but the impedance amplitudes and the frequency response amplitudes of the new detector were twice those of the standard geophones however comparison of the horizontal to vertical response ratios proved that the new detector better discriminates 6 db on average between the horizontal and vertical excitements field data proved that the energy

boron lithium and nitrogen isotope geochemistry of nh4 illite clays in the fossil hydrothermal system of harghita bai east carpathians romania abstract coarse 2 0 0 2 m and fine boron in nh4 i s clays ranges from 513 to 1457 ppm and reached 1000 ppm in the k i nh4 k i the 11b measured in nh4 i s ranges from 12 6 to 22 4 0 3 and in k i nh4 k i is consistently 5 5 to 5 1 0 3 boron isotopes systematically become lighter in the nh4 i s series as temperature increased from 90 to 270 c low li content 1 to 8 ppm was found in illitic clay fractions the 7li shows negative values ranging from 8 6 to 12 3 0 8 for the coarser 2 0 0 2 m nh4 i s clays and from 4 3 to 14 1 1 for the finer the 11b of k i nh4 k i clays reflect a magmatic source whereas the nh4 i s series is consistent with the influx of isotopically light b waters derived from hydrothermal leaching of continental evaporites and or organic rich sediments the 7li signature measured on k i nh4 k i clays also support a magmatic fluid enriched in heavy li followed by precipitation of coarser nh4 i s from more recent sedimentary contributions of isotopically light li this interpretation is also supported by the 15n which reflect an influx of waters from an organic sediment origin the 15n of 14 6 0 6 measured on nh4 i s could be attributed to the presence of meteoric waters mixed with hydrothermal fluids the isotopic data obtained trace the mobility of magmatic and organic sedimentary components in the upper continental crust

cocos nazca slab window beneath central america abstract integration of petrologic and tectonic data favours a model of slab window formation beneath central america in the pliocene pleistocene central america has been the site of voluminous cenozoic arc volcanism the cocos and nazca plates which are subducting beneath central america are diverging along the east trending cocos nazca spreading ridge since 25 ma the americas have advanced about 1800 km west over the ridge transform system since at least 8 ma plate integrity and the ridge transform configuration have been preserved during convergence resulting in subduction of the spreading ridge and development of a slab window the panama fracture zone an active transform fault is the part of the ridge transform system currently being subducted the ridge transform system formerly adjoining the northern end of the panama fracture zone is likely to have been left stepping we use present day plate motions to design a slab window to fit known variations in igneous composition hypocentre distribution and mantle anisotropy the modeling demonstrates that subduction of ridge segments and resultant slab window development began between 6 and 10 ma cessation of ridge subduction occurred between 1 and 3 ma when subduction of the panama fracture zone is considered to have begun the slab window is continuing to expand and migrate northeastward below the central american volcanic arc the absence of a wadati benioff zone from southeastern costa rica through panama corresponds to the position of the slab window within this region dacitic and rhyolitic volcanic rocks have adakitic compositions and are thought to result from anatexis of the young buoyant crust which forms the trailing edges of the slabs bounding the window basalts in this area were derived from an enriched ocean island type mantle source whereas basalts from the rest of the arc in nicaragua el salvador and guatemala are mainly derived from slab modified depleted mantle characteristic of volcanic arcs the presence of ocean island type mantle beneath southern costa rica and panama is explained by eastward flow of enriched asthenosphere from the galapagos plume head through the slab window and into the volcano source region eastward transfer of asthenosphere is consistent with global plate motion studies and seismic anisotropy in the asthenosphere beneath the nazca and caribbean plates the flow of peridotite is a consequence of progressive shrinkage of the pacific mantle reservoir and concurrent expansion of the atlantic mantle reservoir

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

water chemistry of lakes related to active and inactive mexican volcanoes abstract water chemistry of crater lakes maars and water reservoirs linked to some mexican volcanoes within and outside the mexican volcanic belt has been determined for several years and examined regarding environmental and volcanic factors all the analyzed lakes are relatively small with a maximum depth of 65 m and are located in regions with different climates from semi arid to very humid with altitudes ranging from 100 to more than 4000 m a s l crater lakes in active volcanoes el chichon popocatepetl have very low ph moderate to high temperatures and major ion concentrations varying with the level of volcanic unrest lakes in sub arid and temperate arid regions like maars in puebla and guanajuato states show high alkalinity and ph with bicarbonate carbonate chloride sodium and magnesium as predominant ions lakes located in humid climates central michoacan and veracruz state have low mineralization and near neutral ph values in general conservative dissolved ions and conductivity appear to be mostly controlled by precipitation evaporation and by the ionic concentration of groundwater inputs calcium magnesium sulfate concentrations and ph are strongly influenced by volcanic rock or volcanic gas interactions with water the influence of low level volcanic activity on crater lakes may be obscured by water rock interactions and climatic factors one of the aims of this paper is to define the relative influence of these factors searching for a reference frame to recognize the early volcanic precursors in volcano related lakes