helium and carbon fluxes in lake nyos cameroon constraint on next gas burst on 21 august 1986 a lethal gas burst issued from lake nyos in cameroon western africa killing at least 1700 people although the consensus is that the victims died of asphyxiation by co2 of magmatic origin the frequency of such catastrophic degassing events is still unknown the co2 flux at the bottom of lake nyos is estimated based on the measurement of3he4he and4he20ne ratios and the chemical composition of gases exsolved from the lake water the calculated co2 flux at the bottom of lake nyos is 4 4 2 3 1013cm3stp year combined with the estimated release in the august 1986 event of 8 2 1014 cm3 stp the co2 flux suggests that the gas burst may happen about once in18 10 years although the significant uncertainty should be taken into account for the frequency resulting from assumptions such as steady state fluxes in the lake and small fractionization of the c he ratio during the degassing event several yearly measurements of hypolimnetic fluxes and seasonal measurements of epilimnetic fluxes are needed to constrain better the recurrence interval in addition the results of a regional3he4he survey of carbonated mineral springs in northwestern cameroon are discussed in the context of the regional geotectonics

resolving volatile sources along the western sunda arc indonesia we present the chemical and isotope hecn characterization of active fumaroles and hydrothermal gases and waters from the summits and flanks of 19 volcanic centers along the western sunda arc indonesia samples were collected over two field expeditions 1991 and 2010 and cover 13 volcanic centers in sumatra 5 in java and one in bali in addition we present data from three geothermal sites in sumatra associated with active fault systems in between volcanic centers ibvc the overall aim is to resolve volatiles associated with the sub arc mantle subducting slab and mantle wedge from inputs derived from the over riding arc crust the western sunda arc is a prime locality to assess controls on volatile provenance at subduction zones due to changes in composition and thickness of over riding crust and variations in sediment input rates along the strike of the arc the dry gas chemistry of the majority of volcanic samples is dominated by co2 with inert gas variations hearn2 typical of subduction zone gases however there is a strong crustal control on the heco2 isotope and relative abundance systematics on a number of volcanic centers this effect is most clearly observed at flank localities and in water phase samples filtering the entire database for modifications due to air contamination degassing induced fractionation c isotopes and co2 3he ratios and crustal contamination associated with volatile transport within shallow level hydrothermal systems allows recognition of the magmatic volatile signature of individual volcanoes along the arc helium isotopes at all but two volcanic centers talang and dempo on sumatra range from 5 3 ra to 8 1 ra ra air 3he 4he pointing to the mantle wedge as the principal source of he but with a small input of crustal radiogenic he at some localities samples from java and bali span an even more limited range 6 6 to 7 9 ra implying a relatively smaller input of crustal he carbon isotope and co2 3he ratios vary from 1 4 to 6 4 and 4 38 to 150 109 respectively with higher and more variable values to the north of sumatra this latitudinal effect is not apparent in air corrected n isotope values 15nc 3 91 to 5 92 or various elemental ratios such as n2 ar and n2 he the three ibvc sites all located in sumatra have significantly lower 3he 4he ratios 3 6 ra with co2 3he values both higher and lower than volcanic centers their 13c 15nc and gas ratios overlap with the volcanic centers the elemental and isotopic characteristics of carbon and helium have been modified at ibvc sites due to crustal processes however based upon relationships between ch4 and 3he as well as co variations between hecn isotopes the over riding crust and associated sediments add minimal volatiles to volcanic centers throughout the western sunda arc in turn subducted sediment particularly the nicobar fan which supplies himalayan derived sediment to the slab off sumatra exerts a strong control on the magmatic co2 characteristics although it is less influential for n2 in spite of large sections of incoming sedimentary material being off scraped during subduction our data suggest that a significant fraction must enter the trench enhancing fluid melt production in the mantle wedge we propose that subduction related source contamination plays the dominant role over thick old crustal basement in supplying the major volatile output budget of the western sunda arc

temporal variations of gas compositions of fumaroles in the tatun volcano group northern taiwan article i nfo he 4 he geochemical monitoring hydrothermal activity is common in the tatun volcano group of northern taiwan helium isotopic compositions of fumarolic samples show that mantle component occupies more than 60 in the previous study along with recent seismic results a magma reservoir is inferred to have existed beneath the area of da you keng where fumarolic venting is the most active in tatun volcano group progressive increases of hcl concentrations and so2 h2s ratio in fumaroles from da you keng have been observed since august 2004 the hcl concentration changed from almost the detection limit to thousands of ppm even up to 30 000 ppm so2 h2s ratios varied from almost 0 to 3 hence so2 became the dominated s species in this area these variations were accompanied by rising temperature of fumaroles in the tatun volcano group especially in the area of da you keng from boiling point to 131 c meanwhile 3

diffuse emission of carbon dioxide methane and helium 3 from teide volcano tenerife canary islands diffuse emission of co2 ch4 and he was investigated in the summit crater of teide volcano tenerife canary islands the results indicate that teide volcano releases abundant co2 not only from its active crater but also from its flanks as diffuse soil emanations the spatial distribution of these emanations correlates quite closely with that of geothermal anomalies and manifestations our flux measurements indicate a total output of 380 ton day 1 of co2 and 1 6 on day 1 of ch4 by diffuse degassing from the he co2 ratios and the co2 flux we estimate a diffuse he flux of 0 052 mol year 1 isotopic analysis of carbon in soil gas samples from sites of high soil co2 flux indicates a magmatic origin for the co2 also reported by high he 4he ratios of 5 50 and 5 87 ra the origin of methane is more uncertain with low 13c values suggesting a biogenic contribution

helium isotope systematics at nevado del ruiz volcano colombia implications for the volcanic hydrothermal system abstract we have collected 14 water and gas samples from 9 thermal springs and gas vents near nevado del ruiz volcano colombia the 3 he 4 he and 4 he 20 ne ratios vary significantly from 0 98 r atm where r atm is the atmospheric 3 he 4 he ratio of 1 4 10 6 to 6 30 r atm and from 0 37 to 7 0 respectively the 3 he 4 he ratio corrected for air contamination decreases with increasing distance from the central crater of the volcano to the sampling site the trend is very similar to that observed at ontake volcano japan a hydrodynamic porous media dispersion model can explain the 3 he 4 he trend the temporal variations in the 3 he 4 he ratio at four sites provide useful information on the apparent velocity of the magmatic fluid flow brought on by a volcanic eruption the estimated value of several tens m day 1 agrees well with the inferred velocity of flow in oshima volcano japan and is comparable to the largest rate of groundwater movement in a deep sedimentary basin

helium and carbon isotope variations in liaodong peninsula ne china chemical and c he isotopic compositions have been measured for n2 rich hydrothermal gases from the liaodong abbreviation of east liaoning province peninsula from which the oldest crustal rocks in china with 3 8 ga outcrop with the exception of one sample containing tritogenic 3he and atmospheric 4he in liaoyang the observed 3he 4he ratios from 0 1 ra to 0 7 ra indicate 1 8 helium from mantle 92 98 from crust and 0 1 0 8 from atmosphere despite the lack of quaternary volcanism such 3he 4he ratios suggest together with geophysical evidences the existence of intrusive magmas that contain mantle helium and heat within the liaodong middle lower crust the 3he 4he ratios are high along the ne trending jinzhou faults and gradually decrease with the increase of distance from the faults such a spatial distribution suggests that the mantle helium exsolves from magmatic reservoir in the middle lower crust becomes focused into the root zones of jinzhou faults and subsequently traverses the crust via permeable fault zones when transversely migrated by groundwater circulation in near surface mantle helium with high 3he 4he ratio may have been further diluted to the observed values by addition of radiogenic helium produced in the crust this pattern shows strong evidence that the major faults played an important role on mantle derived components transport from mantle upwards

mantle derived helium in two peruvian hydrothermal ore deposits strong differences exist between the helium isotopic compositions of mantle derived magmas1 8 axial vent hotspring fluids9 14 subduction related magmas15 20 and many associated hot springs21 24 and the atmospheric and crustal values fig 1 here we report helium isotope ratios for two late tertiary fossil hydrothermal systems responsible for precious metal base metal and tungsten mineralization and compare them to those of circum pacific hot spring emanations the 3he 4he ratios of inclusion fluids hosted by gangue and sulphide minerals from casapalca and pasto bueno peru all lie between two and three times the atmospheric value indicating the presence of a dilute component of mantle helium consistent with previously reported stable isotope evidence for the presence of magmatic fluids during mineralization25 27 although post trapping modification of the helium isotope composition is possible we suggest that these apparently low values represent the composition of helium inherited from contributing magmas as a tracer of magmatic fluids in hydrothermal systems helium isotopes are decoupled from the factors that govern other stable isotope signatures

helium 3 emission related to volcanic activity the helium 3 helium 4 ratio in bubbling gases from ten hot springs located around mount ontake an active volcano in central japan ranges from 1 71 r sub atm 1 71 times the atmospheric ratio of 1 40 x 10 sup 6 to 6 15 r sub atm the value of the ratio decreases with distance from the central cone of the volcano such a tendency may be a characteristic of helium 3 emission in volcanic areas and suggests more primitive helium 3 is carried with fluid flowing through a conduit during volcanic activity 6 references 1 figure 1 table

noble gas isotopes in hydrothermal volcanic fluids of la soufriere volcano guadeloupe lesser antilles arc article the ascending magmatic component in la soufriere volcano guadeloupe lesser antilles was investigated by measuring noble gas concentrations and isotopic ratios in thermal springs and fumaroles a clear magmat ic helium signal 4 he 3 he 89 000 r ra 8 equivalent to the morb value is recorded in most fluids 3 he fluxes in both fumarole and springs have been estimated and related to 3 he content in the magma chamber in order to explain the 3 he flux measured at the surface we conclude that the magma chamber must be reg ularly fed by fresh magma batches using our new results and data from literature we propose that the his torical activity of la soufriere volcano can be explained by both abnormal energy inputs from new batches of magma in the chamber and cycles of clogging opening of the hydrothermal system we propose a new sce nario for the origin of the 1976 1977 crisis whereby a fresh batch of magma could have been emplaced prior to 1968 possibly between 1959 and 1962 in the magma chamber the resulting heat flux is not stored in the different aquifers but preferentially evacuated through fractures reactivated or created during the 1956 phre atic eruption only when the self sealing of the hydrothermal system is sufficiently developed can pressure and temperature within the aquifers rapidly increase to trigger a crisis

geographical distribution of 3he 4he ratios in japan implications for arc tectonics and incipient magmatism the 3he 4he and 4he 20ne ratios of 115 natural gas samples including various types of gases from volcanoes hot springs mineral springs water wells petroleum fields and natural gas fields were measured using a mass spectrometer the observed 3he 4he and 4he 20ne ratios range from 7 47 10 8 to 9 65 10 6 and from 0 26 to 1100 respectively the 3he 4he ratios reflect well the geotectonic structure of the japanese islands in northeastern ne japan there is a clear geographical difference in the 3he 4he ratios between the frontal arc forearc and volcanic arc back arc regions lower ratios were found in the trench side region and higher ratios in the back arc side this result suggests that the mantle derived helium in the volcanic arc region is associated with the diapiric uprise of a magma lower 3he 4he ratios in the frontal arc region may be due to radiogenic he produced by radioactive decay of u and th in the crustal and sedimentary rocks in southwestern sw japan there is no clear geographical contrast in the 3he 4he ratios some samples in the frontal arc region show quite high 3he 4he ratios the tendency of the 3he 4he ratios agrees with the distribution of terrestrial heat flow data and reflects geotectonic structures different from ne japan the high 3he 4he ratios observed in the frontal arc region in sw japan may be indicative of renewed or incipient magmatism due to a descending young and warm slab

rare gas isotopic compositions in natural gases of japan isotopic and elemental compositions of rare gases in various types of gas samples collected in the japanese islands were investigated excess3he was found in most samples many samples showed a regionally uniform high3he 4he ratio of about 7 times the atmospheric ratio the he concentrations varied from 0 6 to 1800 ppm and they were low in co2 rich gases and high in n2 rich gases ne isotopic deviations from the atmospheric ne were detected in most volcanic gases the deviations and the elemental abundance patterns in volcanic gases can be explained by a mixing between two components one is mass fractionated rare gases and the other is isotopically atmospheric and is enriched in heavy rare gas elements ar was a mixture of mass fractionated ar atmospheric ar and radiogenic ar and the contribution of radiogenic40ar was small in all samples except for he elemental abundance patterns were progressively enriched in the heavier rare gases relative to the atmosphere several samples were highly enriched in kr and xe relative to the abundance pattern of dissolution equilibrium of atmospheric rare gases in water the component which is highly enriched in heavy rare gases may be released from sedimentary materials in the crust

lithium and strontium isotopic systematics of waters around ontake volcano japan implications for deep seated fluids and earthquake swarms abstract since 1976 earthquake swarms have occurred beneath the southeast flank of ontake volcano in central japan electrical conductivity surveys have shown that these earthquake swarms are associated with the upwelling of deep seated fluid to investigate the nature of the deep seated fluid we analyzed 7 li 6 li and 87 sr 86 sr ratios of water samples collected from springs and wells around ontake volcano in 2000 2003 2005 2007 and 2009 the li and sr isotopic compositions of these water samples are largely explained by binary component mixing between near surface meteoric water and non surface fluid at each sampling site on the basis of their cl li and cl sr ratios we singled out water samples whose li and sr isotopic ratios were minimally affected by meteoric water contamination to represent non surface fluids the li and sr isotopic compositions of most ontake non surface fluids except for samples from the earthquake swarm region can be explained as the result of volcanic fluids reacting with basement rocks where they acquired upper crustal signatures we attribute the fluid associated with the region of earthquake swarms to the lower crust beneath the study area

atlantic forcing of western mediterranean winter rain minima during the last 12 000 years abstract the limited availability of high resolution continuous archives insufficient chronological control and complex hydro climatic forcing mechanisms lead to many uncertainties in palaeo hydrological reconstructions for the western mediterranean in this study we present a newly recovered 19 63 m long core from lake sidi ali in the north african middle atlas a transition zone of atlantic western mediterranean and saharan air mass trajectories with a multi proxy approach based on magnetic susceptibility carbonate and total organic c content core scanning and quantitative xrf stable isotopes of ostracod shells charcoal counts cedrus pollen abundance and a first set of diatom data we reconstruct western mediterranean hydro climatic variability seasonality and forcing mechanisms during the last 12 000 yr a robust chronological model based on ams 14 c dated pollen concentrates supports our high resolution multi proxy study long term trends reveal low lake levels at the end of the younger dryas during the mid holocene interval 6 6 to 5 4 cal ka bp and during the last 3000 years in contrast lake levels are mostly high during the early and mid holocene the record also shows sub millennial to centennial scale decreases in western mediterranean winter rain at 11 4 10 3 9 2 8 2 7 2 6 6 6 0 5 4 5 0 4 4 3 5 2 9 2 2 1 9 1 7 1 5 1 0 0 7 and 0 2 cal ka bp early holocene winter rain minima are in phase with cooling events and millennial scale meltwater discharges in the sub polar north atlantic our proxy parameters do not show so far a clear impact of saharan air masses on mediterranean hydro climate in north africa however a significant hydro climatic shift at the end of the african humid period 5 ka indicates a change in climate forcing mechanisms the late holocene climate variability in the middle atlas features a multi centennial scale nao type pattern with atlantic cooling and western mediterranean winter rain maxima generally associated with solar minima

he ar o sr and nd isotope constraints on the origin and evolution of mount etna magmatism abstract the 0 5 ma history of the origin and evolution of mount etna sicily has been investigated by analysing the isotopic composition of he ar o sr and nd in 21 selected lava samples the near constancy of the isotopic compositions of oxygen 18 o 5 4 0 3 and of helium trapped in olivine phenocrysts 6 7 0 4 ra is interpreted as evidence of a single mantle source despite drastic petrological changes during the volcano s history he analyses performed by crushing cogenetic pyroxene and olivine phenocrysts show a tendency to lower 3 he 4 he ratios in pyroxenes this is best explained by crystallization of pyroxenes at a depth shallower than that of olivines and or by exchange of helium trapped in pyroxenes with atmospheric or radiogenic he before eruption 87 sr 86 sr ratios of recent lavas tend to increase with time and to correlate with rb th ratios and for historical lavas these variations are tentatively attributed to shallow selective contamination from underlying sediments based on the similarity of the 3 he 4 he ratios at etna to those of european mantle xenoliths 1 we propose that the baseline geochemical signature of isotopic tracers at etna reflects the composition of the subcontinental mantle comparison to other southern italian active volcanoes etna vulcano ischia campi flegrei vesuvius shows gradual dilution of the predominantly mantle etnean end member by more radiogenic sr and he and material with higher 18o and c 3 he which is reasonably explained by the progressively important influence of subducted continental crust

geologic evidence for a magma chamber beneath newberry volcano oregon at newberry volcano central oregon more than 0 5 m y of magmatic activity including caldera collapse and renewed caldera filling volcanism has created a structural and thermal chimney that channels magma ascent holocene rhyolitic eruptions 1 have been confined mainly within the caldera in an area 5 km in diameter 2 have been very similar in chemical composition phenocryst mineralogy and eruptive style and 3 have occurred as recently as 1300 years ago with repose periods of 2000 3000 years between eruptions holocene basaltic andesite eruptions are widespread on the flanks but are excluded from the area of rhyolitic volcanism basaltic andesite in fissures at the edge of the rhyolite area has silicic inclusions and shows mixed basalt rhyolite magma relations these geologic relations and the high geothermal gradient that characterizes the lower part of a drill hole in the caldera u s geological survey newberry 2 indicate that a rhyolitic magma chamber has existed beneath the caldera throughout the holocene its longevity probably is a result of intermittent underplating by basaltic magma

gas pathways and remotely triggered earthquakes beneath mount fuji japan large earthquakes sometimes trigger local seismicity that is distal to their rupture zones various mechanisms for this triggered seismicity have been proposed based on either the static stress change or ground shaking from seismic waves but local geological structure is rarely studied to discern why this seismicity is remotely induced we present the results of a joint three dimensional resistivity and isotopic analysis of the groundwater system surrounding mount fuji japan where increased seismicity was observed following the a d 2011 tohoku oki megathrust earthquake an electrically conductive zone and high concentrations of magmatic gases he and co2 correspond to the zone of triggered seismicity in contrast a contribution of magmatic water is not suggested from 2h deuterium d and 18o isotope ratios these results suggest that the earthquakes were triggered within a fractured zone through which magmatic gases preferentially migrated we hypothesize that the upwelling of gas rich hydrous fluids and or gas bubbles occurred along this fracture pathway causing an increase in the pore pressure and triggering the resultant earthquake sequence

spatial and temporal variations of gas geochemistry at mt ontake japan abstract this report describes spatial and temporal variations of helium carbon and nitrogen isotopes measured in co2 rich bubbling gases from natural springs associated with mt ontake central honshu japan from november 1981 through september 2015 during the entire period the 3he 4he ratio decreased concomitantly with increasing distance of the sampling site from the central cone in contrast the co2 3he ratios and the 13c values of co2 increased with distance these spatial trends became more pronounced after the september 27 2014 ontake eruption suggesting reactivation of the volcano plumbing system with enhanced emission of magmatic volatiles although the spatial trend of nitrogen isotopes disappeared the 3he 4he ratios of the most proximal site to the central cone remained constant until 2000 apparently increasing from june 2003 through october 2014 they became constant soon after the eruption until september 2015 the ten year 3he enhancement might have been a precursor of the 2014 ontake eruption in contrast 13c values of co2 at the same site remained constant through this period the lack of 13c anomaly might be attributable to 1 negligibly small amounts of magmatic co2 introduced into the source of hot springs compared to ambient co2 in the air saturated aquifer or 2 close resemblance of the carbon signature of magmatic co2 to that of ambient co2 therefore its addition cannot change the overall 13c value of the sampled hot springs at distal sampling sites no measurable change of helium carbon or nitrogen isotopes was observed in relation to the 2014 ontake eruption suggesting that the effect of this eruption on the ontake hydrothermal system was geographically localized

mantle derived helium in foreland basins in xinjiang northwest china abstract hydrocarbon rich natural gases from the tarim junggar turpan hami and santanghu basins in xinjiang northwest china have measured 3he 4he ratios from 0 01 to 0 6 times higher than the atmospheric value indicating 0 7 helium derived from the mantle the mantle derived helium is high in foreland basins associated with the tianshan kunlun and zhayier halalate orogenic mountains but low towards the center of basins this spatial distribution suggests that the mantle derived helium originates either from fluids or small scale melts in the upper asthenospheric or lithospheric mantle which have found pathways into the root zones of the major faults defining these mountains but do not significantly move into the basins themselves during upward transport to near the surface the mantle derived helium is significantly diluted by radiogenic helium produced in the crust despite the lack of recent magmatic activity or extensional tectonics within the basins this pattern shows strong evidence that the major faults play an important role in mantle derived components degassing from the mantle to the surface

high 3he 4he ratios in peridotite xenoliths from sw japan revisited evidence for cosmogenic 3he released by vacuum crushing 1 in isotope studies of magmatic systems magmatic he is preferentially extracted by crushing minerals under vacuum whereas cosmogenic and or radiogenic he isotopes are released by mineral melting as they are produced and remain in the mineral s matrix interpretation of magma source composition or surface residence time depends on the assumption that vacuum crushing releases insignificant cosmogenic 3he we reinvestigated the helium isotopic composition of olivines in xenoliths from takashima and kurose volcanoes japan which were reported to have high 3he 4he interpreted as mantle plume contributions sumino et al 2000 ikeda et al 2001 combining vacuum crushing and heating protocols we show that samples from both localities contain considerable concentrations of cosmogenic 3he significantly up to 25 of the matrix sited helium was extracted by prolonged crushing it seems possible that previous high 3he 4he ratios measured in samples from kurose and takashima were the result of the high cosmogenic 3he concentrations and do not imply a mantle plume beneath japan for kurose lavas sampled about 1 m above present day sea level exposure ages computed from cosmogenic 3he accumulation are similar to k ar eruption ages of 1 13 0 12 ma implying that erosion of the sampling site has been limited and that the samples have not been below sea level for prolonged periods during the last myr helium extraction from the matrix by crushing cannot be explained by volume diffusion because the diffusivity of helium in olivine is slow at the crushing temperature and therefore requires an additional mechanism to enhance the release a fracture related extraction mechanism may be responsible for this phenomenon and a semiquantitative model is developed assuming that the increase in specific surface area during crushing represents newly created fractures according to this model he released from about 10 unit cells of olivine from the fracture results in helium extraction of only 1 but the spallation damage tracks along fractures may provide sufficient pathway for observed helium extraction of up to 25

helium isotopes in the izu peninsula japan relation of magma and crustal activity abstract the relation of magma and crustal activity has been studied from spatial distribution of 3he 4he ratios of gas and or water samples over the izu peninsula where significant crustal deformation associated with seismic swarm activities has been observed since 1970s the air corrected values of 3he 4he ratios ranged from 3 5 to 8 2 ra where ra is the atmospheric 3he 4he ratio 1 4 10 6 indicating that helium is mostly of magmatic origin among the three pressure sources proposed to explain the crustal deformation two inflation sources beneath the inland of northeast and the mid east coast of the izu peninsula locate in the broad distribution of high 3he 4he ratios which supports relation of magma to the crustal uplift in contrast the distribution of 3he 4he ratios around the tensile fault assumed in the area of seismic swarms appears not to indicate existence of significant amount of magma below the tensile fault alternatively the results suggest magma below a point several kilometers south of the tensile fault the seismic swarms are explained either by fluid pressurization of thermal water heated by this magma or by intrusion of magma to the tensile fault moved obliquely from the deep magma reservoir

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

geochemical monitoring system ii prototype gms ii installation at the acqua difesa well within the etna region first data during the 1999 volcanic crisis abstract the geochemical monitoring system ii gms ii prototype was designed assembled tested and installed at the acqua difesa test site near belpasso ct within the etna region in the frame of an ec funded program named automatic geochemical monitoring of volcanoes the easily changeable and versatile configuration of the remote station provides actual data every 10 min recording groundwater temperature electrical conductivity ph redox potential dissolved co 2 he atmospheric pressure and air temperature the radon sensor was assembled despite no jet added to the remote station an automatic sampler collects every 72 h 3 days two bottles of water acidified and not for further laboratory analyses the choice of the acqua difesa test site arises from preliminary volcanological studies deserving special interest i e for the high co 2 degassing for the high he isotopic values exhibiting a direct mantle signature of the volcanic gases and for the peculiar sensitivity to volcanic activity as tested by discrete monitoring in the past and confirmed by the present study during the discussed monitoring period october 1998 june 1999 an enhanced volcanic activity of etna was observed it started on july 1998 with enhanced plume degassing and since september 1998 with periodical lava fountains as well as with episodic low energy earthquakes and seismic swarms m max 3 1 till june 1999 the activity culminated with a summit crater fracture involving a sub terminal eruption on 04 02 1999 the summit crater fracture was not accompanied by enhanced seismicity despite moderate seismic energy release occurring in the succeeding months in that monitoring period the acqua difesa gms ii station recorded a few geochemical anomalies mostly in temperature ph co 2 electrical conductivity and eh as well as in the concentration of some major elements trend mostly in mg and hco 3 the geochemical continuous and discrete data set is discussed in comparison with the available information on the ongoing volcanic and seismic activity tentatively enhancing the comprehension of the aquifers mass heat transport properties of the volcano during crises the experimental observations may be defined at present the forerunners of the etna eruptions affecting the single out acqua difesa well it is nowadays a self consistent site with its own response to the pre eruptive processes defined sensitive to the etna aquifer modifications induced by the volcanic activity in a recurrent way thus we defined the typical answer of this specific test site to the pre eruptive processes and to the associated seismicity further data may modify this statement the station prototype configuration and the results may give hints for future volcanic eruption and seismic activity forecasting

influence of volcanic eruptions on helium isotope ratios in hydrothermal systems induced by volcanic eruptions temporal variations of 3he4he and 4he20ne ratios occur in high temperature gases from a steam well located about 3 km north of the central cone of mt mihara an active volcano in oshima island japan the 3he4he ratio gradually increased from 1 71ratm 1 71 times the atmospheric ratio of 1 40 10 6 in october 1986 to 5 02 ratm in november 1987 taking into account a similar 4he20ne change the magmatic he component in the steam has increased since the violent eruptions of oshima volcano from november 15 to december 18 1986 this confirms a direct relationship between magmatic activity and elevated 3he4he ratios in groundwater hydrothermal systems based on the distance from the craters to the steam well the time lag between the eruptions and the increase of 3he4he we estimate the magmatic component velocity in the fluid flow the calculated value several tens of m per day is significantly higher than typical groundwater flow in deep sedimentary basins of japan