application of stochastic simulation to co2 flux from soil mapping and quantification of gas release 1 conditional sequential gaussian simulations sgs have been applied for the first time to the study of soil diffuse degassing from different volcanic and nonvolcanic systems the application regards five data sets of soil co2 fluxes measured with the accumulation chamber methodology at the volcanic areas of solfatara of pozzuoli italy vesuvio cone italy nisyros greece and horseshoe lake california and at the nonvolcanic degassing area of poggio dell olivo italy the sgs algorithm was used to generate 100 realizations of co2 flux for each area probabilistic summaries of these simulations together with the information given by probability plots were used 1 to draw maps of the probability that co2 fluxes exceed thresholds specific for a background flux i e to define the probable extension of the degassing structures 2 to calculate the total co2 output and 3 to quantify the uncertainty of the estimation the results show that the sgs is a suitable tool to model soil diffuse degassing producing realistic images of the distribution of the co2 fluxes that honor the histogram and variogram of the original data moreover the relation between the sample design and the uncertainty of estimation was investigated leading to an empirical relation between uncertainty and the sampling density that can be useful for the planning of future co2 flux surveys

dynamics of carbon dioxide emission at mammoth mountain california mammoth mountain a dormant volcano in the eastern sierra nevada california has been passively degassing large quantities of cold magmatic co2 since 1990 following a 6 month long earthquake swarm associated with a shallow magmatic intrusion in 1989 a search for any link between gas discharge and volcanic hazard at this popular recreation area led us to initiate a detailed study of the degassing process in 1997 our continuous monitoring results elucidate some of the physical controls that influence dynamics in flank co2 degassing at this volcano high coherence between variations in co2 efflux and variations in atmospheric pressure and wind speed imply that meteorological parameters account for much if not all of the variability in co2 efflux rates our results help explain differences among previously published estimates of co2 efflux at mammoth mountain and indicate that the long term annual co2 degassing rate has in fact remained constant since 1997 discounting the possibility of large meteorologically driven temporal variations in gas efflux at other volcanoes may result in spurious interpretations of transients that do not reflect actual geologic processes

diffuse emission of co2 from showa shinzan hokkaido japan a sign of volcanic dome degassing two soil co2 efflux surveys were carried out in september 1999 and june 2002 to study the spatial distribution of diffuse co2 degassing and estimate the total co2 output from showa shinzan volcanic dome japan seventy six and 81 measurements of co2 efflux were performed in 1999 and 2002 respectively covering most of showa shinzan volcano soil co2 efflux data showed a wide range of values up to 552 g m 2 d 1 carbon isotope signatures of the soil co2 ranged from 0 9 to 30 9 suggesting a mixing between different carbon reservoirs most of the study area showed co2 efflux background values during the 1999 and 2002 surveys b 8 2 and 4 4 g m 2 d 1 respectively the spatial distribution of co2 efflux anomalies for both surveys showed a good correlation with the soil temperature indicating a similar origin for the extensive soil degassing generated by condensation processes and fluids discharged by the fumarolic system of showa shinzan the total diffuse co2 output of showa shinzan was estimated to be about 14 0 15 6 t d 1 of co2 for an area of 0 53 km2

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

diffuse carbon dioxide emissions from hidden subsurface structures at asama volcano japan we measured diffuse carbon dioxide co2 flux and soil temperature around the summit of asama volcano japan to assess the diffuse degassing structure around the summit area soil co2 flux was measured using an accumulation chamber method and the spatial distributions of co2 flux and soil temperature were derived from the mean of 100 sequential gaussian simulations results show that soil co2 flux was high on the eastern flank of kamayama cone and the eastern rim of maekake crater the outer cone these areas mostly correspond to high temperature anomalies the average emission rate of diffuse co2 was calculated to be 12 6 t day 1 12 2 14 6 t day 1 such diffuse emissions account for 12 of the total diffuse and plume co2 emissions from the summit area the diffuse co2 anomalies probably reflect permeable zones controlled by local topography and hidden fractures bordering maekake crater the permeable zones are connected to the low electrical resistivity zone inferred to indicate both a hydrothermal fluid layer and an upper sealed layer made of clay minerals magmatic gas from the main conduit ascends to the volcano surface through this fluid layer and the permeable zones these insights emphasize that the pathways and the connection between the pathways and the source of diffuse co2 combine to create the pattern of heterogeneous diffuse co2 emission seen at the surface only by using a combination of gas measurements and geophysical tools can we begin to understand the dynamics of this system as a whole

correlated increase in co2 fumarolic content and diffuse emission from la fossa crater vulcano italy evidence of volcanic unrest or increasing gas release from a stationary deep magma body 1 the peculiarity of the quiescent la fossa volcano is the occurrence of crises characterized by strong increases of fumarole t and output and by chemical changes indicative of an increasing input of magmatic fluids several surveys carried out during a new crisis began in november 2004 indicate that the total diffuse co2 emission for the crater area increases by one order of magnitude during crises up to 1600 ton d 1 in december 2005 concern exists on the possibility that these crises be related to an unrest process leading to eruption the repetition along decades of the same gas compositional variations during crises their temporal coincidence with increases of the local shallow seismicity and the lack of any significant ground motion rather suggest that they correspond to moments of increasing volatile release from a stationary magma system

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

structure and evolution of the hengill grensdalur volcanic complex iceland geology geophysics and seismic tomography recent geological and geophysical research indicates the presence of three volcanic systems in the hengill grensdalur area and progressive westerly migration of the accretionary plate boundary the hengill system comprises the active hengill central volcano and a nne trending fissure swarm that is the present locus of crustal accretion in the area extinct volcanic systems are identified with the mountain hromundartindur and the grensdalur area and associated nne trending zones the grensdalur system was formerly the locus of accretion in the area a widespread geothermal area encompasses the whole area and is fueled by at least three distinct heat sources associated with the three volcanic systems a tomographic study of the upper 5 km of crust using local earthquakes imaged three bodies with velocities up to 15 higher than the average background velocities and volumes of several tens of cubic kilometers one of these underlies the grensdalur volcano and a second underlies the olkelduhals area within the hromundartindur system these are interpreted as intrusions that are the solidified magma reservoirs of their respective volcanic systems and the heat sources of those parts of the geothermal area above them the third high velocity body underlies the extinct basalt shield husmuli which is not associated with geothermal resources that body is interpreted as a cold intrusion that is the frozen magma conduit that fed the surface eruptive site a low velocity body with a volume of a few cubic kilometers was imaged in the depth range 2 4 km beneath the northern part of the presently active hengill central volcano this volume may contain partial melt and represent the heat source or part of the heat source fueling the hengill field heat balance calculations show that subsurface magmatism continued in the extinct grensdalur volcano long after volcanic activity and crustal accretion migrated from it to the hengill system

the hengill geothermal area iceland variation of temperature gradients deduced from the maximum depth of seismogenesis abstract given a uniform lithology and strain rate and a full seismic data set the maximum depth of earthquakes may be viewed to a first order as an isotherm these conditions are approached at the hengill geothermal area s iceland a dominantly basaltic area the likely strain rate calculated from thermal and tectonic considerations is 10 15 s 1 and temperature measurements from four drill sites within the area indicate average near surface geothermal gradients of up to 150 c km 1 throughout the upper 2 km the temperature at which seismic failure ceases for the strain rates likely at the hengill geothermal area is determined by analogy with oceanic crust and is about 650 50 c the topographies of the top and bottom of the seismogenic layer were mapped using 617 earthquakes located highly accurately by performing a simultaneous inversion for three dimensional structure and hypocentral parameters the thickness of the seismogenic layer is roughly constant and about 3 km a shallow aseismic low velocity volume within the spreading plate boundary that crosses the area occurs above the top of the seismogenic layer and is interpreted as an isolated body of partial melt the base of the seismogenic layer has a maximum depth of about 6 5 km beneath the spreading axis and deepens to about 7 km beneath a transform zone in the south of the area beneath the high temperature part of the geothermal area the maximum depth of earthquakes may be as shallow as 4 km the geothermal gradient below drilling depths in various parts of the area ranges from 84 9 ckm 1 within the low temperature geothermal area of the transform zone to 138 15 ckm 1 below the centre of the high temperature geothermal area shallow maximum depths of earthquakes and therefore high average geothermal gradients tend to correlate with the intensity of the geothermal area and not with the location of the currently active spreading axis

diffuse volcanic gas emission and thermal energy release from the summit crater of pico do fogo cape verde we report the first detailed study of diffuse emission of carbon dioxide co2 hydrogen sulfide h2s helium he and hydrogen h2 from the summit crater of pico do fogo volcano cape verde diffuse co2 h2s he and h2 gas fluxes were measured at 57 sampling sites and ranged up to 12 800 13 1 and 6 g m 2 day 1 respectively soil temperature measurements at each sampling site were used to evaluate the heat flux most of the summit crater shows relatively high co2 efflux with highest values close to the fumarolic area suggesting a structural control of the degassing process in contrast h2s effluxes were negligible or very low at the summit crater except close to the fumarolic area where anomalously high co2 efflux and soil temperatures were also measured we estimate total co2 h2s he and h2 diffuse gas fluxes of 219 t day 1 25 4 and 33 kg day 1 respectively based on a h2o co2 mass ratio of 1 52 measured at the fumaroles we estimate a diffuse steam flux from the summit crater of approximately 330 t day 1 the enthalpy of this steam is equivalent to a heat flux of about 10 3 mw the diffuse gas emission and thermal energy released from the summit crater of pico do fogo volcano are comparable to those observed at other volcanoes sustained surveillance of pico do fogo using these methods will be valuable for monitoring the activity of one of the most active volcanoes in the atlantic ocean

mapping of h2s fluxes from the ground using copper passive samplers an application study at the zolforata di pomezia degassing area alban hills central italy abstract a new method for measuring h2s mass flux from the ground based on the digital analysis of the interference colours produced by the sulphidation of copper passive samplers cps is proposed and discussed in this article cps sulphidation has a wide range of linear responses to h2s doses and can be used together the accumulation chamber method to estimate gas fluxes from natural degassing areas these are often characterized by the presence of vent centred degassing areas vcdas which are recognizable from the absence or rarefaction of vegetation due to high acid gas concentrations in the soil pores and in the air at ground level a reference emission curve accounting for the advective and diffusive components of the flux can be modelled and used to estimate the total h2s mass released from each vcda the application of this method can be supported by remote sensing analysis that helps identify vcdas in the field in perivolcanic h2s degassing areas as an illustrative application h2s gas fluxes from the ground were measured in spring 2007 at the zolforata di pomezia degassing area zpda alban hills central italy using an accumulation chamber internally equipped with cps h2s peak fluxes were measured over the vents after remote sensing assisted identification of the vcdas further measurements were carried out in two ponds and one artificial channel bordering the study area the total atmospheric flux released at the zpda estimated to be about 1207 6 kg day 1 was calculated as the summation of the fluxes from all the h2s sources the background flux being negligible

gas emissions and crustal deformation from the krýsuvik high temperature geothermal system iceland abstract the kr suvik volcanic system is located on the oblique spreading reykjanes peninsula sw iceland since early 2009 the region has been undergoing episodes of localized ground uplift and subsidence from april november 2013 we operated near real time monitoring of gas emissions in kr suvik using a multi component gas analyzer system multi gas collecting data on gas composition from a fumarole h2o co2 so2 h2s the dataset in this study comprises a near continuous gas composition time series the quantification of diffuse co2 gas flux analytical results for direct samples of dry gas seismic records and gps data gas emissions from the kr suvik geothermal system were examined and compared with crustal deformation and seismicity the gas emissions from the kr suvik system are h2o dominated with co2 as the most abundant dry gas species followed by smaller concentrations of h2s the average subsurface equilibrium temperature was calculated as 278 c this is consistent with previous observations made through sporadic spot sampling campaigns in addition the semi continuous multi gas dataset reveals higher variations in gas composition than previously reported by spot sampling the diffuse soil co2 flux is found to be variable between the three studied degassing areas in kr suvik ranging from 10 9 70 9 t day with the highest flux in hveradalir where the multi gas station is located the total flux is estimated as 101 t day comparison between multi gas and geophysical data shows that peaks of h2o rich emissions appears to follow crustal movements coinciding with the h2o rich peaks so2 is detected in minor amounts 0 6 ppmv allowing for calculations of h2o so2 co2 so2 and h2s so2 ratios this is the first time so2 has been detected in the kr suvik area the large variations in h2o co2 and h2o h2s ratios are considered to reflect variable degassing activity in the fumarole the activity of the fumarole appears less intense during intervals of low or no recorded seismic events the h2o co2 and h2o h2s ratios are lower presumably due to h2o condensation affecting the steam jet before reaching the multi gas inlet tube

continuous monitoring of distal gas emanations at vulcano southern italy the increasing activity of vulcano island italy since 1985 led to the initiation of continuous geochemical monitoring of the lateral soil gas emissions on the basis both of their relative geochemical characteristics and of local considerations three gaseous components were selected for monitoring namely co2 he and 222rn monitoring has been performed by means of specific analysers gases extracted from a water well located at the foot of the active cone were selected for monitoring on the basis of their geochemical and isotopic characters that indicate their genetic link with central high temperature fumarolic gases emitted at the crater very strong variations of gas composition can be observed within one day from 1 to about 94 for co2 some variations display a daily character and can be correlated with that of atmospheric pressure the three monitored gases are highly correlated suggesting very high kinetics of gas transfer in the system because of these considerable variations of chemical composition bulk concentrations obviously are not suitable for monitoring at vulcano however the evolution with time of ratios such as 222rn co2 and he co2 the latter being corrected for atmospheric contamination supplies numerical parameters that the expected to characterize the intensity of the degassing process a new input of magmatic gases that would lead to an increase in the 222rn co2 and he co2 ratios should therefore be detected by such a monitoring station

diffuse volcanic degassing and thermal energy release from hengill volcanic system iceland we report the first detailed study of spatial variations on the diffuse emission of carbon dioxide co2 and hydrogen sulfide h2s from hengill volcanic system iceland soil co2 and h2s efflux measurements were performed at 752 sampling sites and ranged from nondetectable to 17 666 and 722 g m 2 day 1 respectively the soil temperature was measured at each sampling site and used to evaluate the heat flow the chemical composition of soil gases sampled at selected sampling sites during this study shows they result from a mixing process between deep volcanic hydrothermal component and air most of the diffuse co2 degassing is observed close to areas where active thermal manifestations occur northeast flank of the hengill central volcano close to the nesjavellir power plant suggesting a diffuse degassing structure with a ssw nne trend overlapping main fissure zone and indicating a structural control of the degassing process on the other hand h2s efflux values are in general very low or negligible along the study area except those observed at the northeast flank of the hengill central volcano where anomalously high co2 efflux and soil temperatures were also measured the total diffuse co2 emission estimated for this volcanic system was about 1 526 160 t day 1 of which 453 t day 1 29 7 are of volcanic hydrothermal origin to calculate the steam discharge associated with the volcanic hydrothermal co2 output we used the average h2o co2 mass ratio from 12 fumarole samples equal to 88 6 range 9 4 240 2 as a representative value of the h2o co2 mass ratios for hengill fumarole steam the resulting estimate of the steam flow associated with the gas flux is equal to 40 154 t day 1 the condensation of this steam results in thermal energy release for helgill volcanic system of 1 07 1014 j day 1 or to a total heat flow of 1 237 mwt

heat flux from magmatic hydrothermal systems related to availability of fluid recharge abstract magmatic hydrothermal systems are of increasing interest as a renewable energy source surface heat flux indicates system resource potential and can be inferred from soil co 2 flux measurements and fumarole gas chemistry here we compile and reanalyze results from previous co 2 flux surveys worldwide to compare heat flux from a variety of magma hydrothermal areas we infer that availability of water to recharge magmatic hydrothermal systems is correlated with heat flux recharge availability is in turn governed by permeability structure lithology rainfall topography and perhaps unsurprisingly proximity to a large supply of water such as the ocean the relationship between recharge and heat flux interpreted by this study is consistent with recent numerical modeling that relates hydrothermal system heat output to rainfall catchment area this result highlights the importance of recharge as a consideration when evaluating hydrothermal systems for electricity generation and the utility of co 2 flux as a resource evaluation tool

seismic signature of the lake mien impact structure southern sweden the eugeno s seismic profile iv in southern sweden crossed lake mien a confirmed heavily eroded 121 ma impact structure the lake mien structure has a pre erosion rim diameter of about 9 km it is

changes in the diffuse co2 emission and relation to seismic activity in and around el hierro canary islands significant changes in the diffuse emission of carbon dioxide were recorded in a geochemical station located at el hierro canary islands before the occurrence of several seismic events during 2004 two precursory co2 efflux increases started thirteen and nine days before two seismic events of magnitude 2 3 and 1 7 which took place near el hierro island canary islands on march 23 and april 15 reaching a maximun value of 51 1 and 46 2 g m 2 d 1 respectively five and eight days before the two seismic events other similar increases started thirteen and five days before the occurrence of two seismic events of magnitude 1 3 and 1 5 which took place on october 15 and 21 respectively reaching the maximum values four and one day before the earthquakes these changes were not related to variations in atmospheric or soil parameters the material failure forecast method ffm which analyzes the rate of precursory phenomena was successfully applied to forecast the first seismic event that took place in el hierro island in 2004

carbon dioxide emissions from soils at hakkoda north japan 1 a soil gas and co2 efflux survey was carried out at hakkoda north japan to investigate the spatial distribution and origin of the gas which caused the accidental death of three japanese soldiers on 12 july 1997 in the study area no fumarolic and or thermal activity is observed chemical composition of the gas from areas with high co2 effluxes 5 000 g m 2 d 1 and high co2 contents 15 vol indicate a strong deep sourced contribution for co2 whereas air and or air saturated water is suggested for the rest of the discharged gases which are mainly released from a shallow aquifer isotopic analysis of soil gas and hot spring discharges suggests a combination of magmatic degassing and thermal decarbonation with magmatic degassing being the main contributior to the high co2 emission approximately 74 t d 1 of deep seated magmatic plus thermal decarbonation origin co2 were estimated to contribute to the total output of co2 from this area

diffuse co2 emission rate from pululahua and the lake filled cuicocha calderas ecuador abstract we report herein the first results of two soil co 2 efflux surveys carried out at cuicocha lake filled and pululahua caldera volcanic systems ecuador a total of 172 and 217 soil co 2 efflux measurements were taken at the surface environment of pululahua and cuicocha calderas respectively by means of the accumulation chamber method during the summer of 2006 to constrain the total co 2 output from the studied area soil co 2 efflux values ranged from non detectable up to 48 5 and 141 7 g m 2 d 1 for cuicocha and pululahua calderas respectively in addition probability graphs were used to distinguish the existence of different geochemical populations sequential gaussian simulation was used to construct an average map for 100 simulations and to compute the total co 2 emission at each studied area 106 and 270 t d 1 metric tons per day for cuicocha 13 3 km 2 and pululahua 27 6 km 2 volcanoes respectively

dynamics of diffuse carbon dioxide emissions from cumbre vieja volcano la palma canary islands we report herein the results of 13 soil co2 efflux surveys at cumbre vieja volcano la palma island the most active basaltic volcano in the canary islands the co2 efflux measurements were undertaken using the accumulation chamber method between 2001 and 2013 to constrain the total co2 output from the studied area and to evaluate occasional co2 efflux surveys as a volcanic surveillance tool for cumbre vieja soil co2 efflux values ranged from non detectable up to 2442 g m 2 days 1 with the highest values observed in the south where the last volcanic eruption took place teneguia 1971 isotopic analyses of soil gas carbon dioxide suggest an organic origin as the main contribution to the co2 efflux with a very small magmatic gas component observed at the southern part of the volcano total biogenic and magmatic combined co2 emission rates showed a high temporal variability ranging between 320 and 1544 t days 1 and averaging 1147 t days 1 over the 220 km2 region two significant increases in the co2 emission observed in 2011 and 2013 were likely caused by an enhanced magmatic endogenous contribution revealed by significant changes in the 3he 4he ratio in a co2 rich cold spring the relatively stable emission rate presented in this work defines the background co2 emission range for cumbre vieja during a volcanic quiescence period

diffuse emission of carbon dioxide from cerro negro volcano nicaragua central america we report the first detailed soil co2 efflux survey carried out at cerro negro volcano nicaragua central america soil co2 efflux values ranged from 0 5 to 35 000 g m 2 d 1 spatial distribution of co2 efflux shows that volcanic gas is mainly released from the summit crater and the fissures opened during the august 1999 eruption the total co2 output of cerro negro is conservatively estimated to be 2 800 t d 1 based on a study area of 0 58 km contour maps of soil co2 efflux ground temperature and 13c co2 distributions support an important magmatic contribution for the total output of co2 at cerro negro volcano

anomalous diffuse co2 emission prior to the january 2002 short term unrest at san miguel volcano el salvador central america on january 16 2002 short term unrest occurred at san miguel volcano a gas and steamash plume rose a few hundred meters above the summit crater an anomalous microseismicity pattern about 75 events between 7 30 and 10 30 hours was also observed continuous monitoring of co2 efflux on the volcano started on november 24 2001 in the attempt to provide a multidisciplinary approach for its volcanic surveillance the background mean of the diffuse co2 emission is about 16 g m 2 d 1 but a 17 fold increase up to 270 g m 2 d 1 was detected on january 7 nine days before the january 2002 short term unrest at san miguel volcano these observed anomalous changes on diffuse co2 degassing could be related to either a sharp increase of co2 pressure within the volcanic hydrothermal system or degassing from an uprising fresh gas rich magma within the shallow plumbing system of the volcano since meteorological fluctuations cannot explain this observed increase of diffuse co2 emission

pinpointing deep geothermal upflow in zones of complex tectono volcanic degassing new insights from aluto volcano main ethiopian rift the project was financed in the framework of the volkswagen foundation s postdoctoral fellowships for african researchers in the engineering sciences reference 90017

thermal power of grimsvotn iceland from 1998 to 2016 quantifying the effects of volcanic activity and geothermal anomalies abstract grimsvotn lies beneath the centre of the vatnajokull ice cap iceland and has for centuries been one of the most geothermally active calderas in the world as well as being iceland s most active volcano calorimetric studies of its heat output have suggested long term heat release of 2 4 gw we have performed a detailed study of the heat release at grimsvotn over the period 1998 2016 which includes the eruptions of 1998 2004 and 2011 annual mapping of the ice surface is used to monitor ice volume changes combined with results of mass balance monitoring over this same period we estimate an average heat release of 1800 200 mw whereof about 1200 mw is the base geothermal heat flux the remaining 600 mw is an average over the study period composed of peaks above the base flux from melting during eruptions and geothermal anomalies the most intense melting occurred at eruption sites during eruptions less intense signals lasting several months to years were due to increased geothermal melting creating new ice cauldrons and deepening pre existing ones such thermal anomalies were observed both as precursors to the eruptions and in the 2 3 years following the strongest signal followed the 1998 eruption which produced an average of 650 mw in the two years following after the 2004 eruption a thermal anomaly of 500 mw was observed in the following years and an average signal of 450 mw followed the 2011 eruption these thermal signals demonstrate a post eruption link to increased geothermal activity at the caldera walls

soil diffuse degassing and thermal energy fluxes from the southern lakki plain nisyros greece two diffuse soil co2 flux surveys from the southern lakki plain show that co2 is mainly released from the hydrothermal explosion craters the correspondence between high co2 fluxes and elevated soil temperatures suggests that a flux of hot hydrothermal fluids ascends towards the surface steam mostly condenses near the surface and the heat given off is conductively transferred to the atmosphere through the soil accompanied by a large co2 flux it was calculated that 68 t d 1 of hydrothermal co2 are released through the total surveyed area of 1 3 km admitting that a steam flux of 2200 t d 1 accompanies this co2 flux the thermal energy released through steam condensation amounts to 58 mw

carbon dioxide degassing by advective flow from usu volcano japan magmatic carbon dioxide co2 degassing has been documented before the 31 march 2000 eruption of usu volcano hokkaido japan six months before the eruption an increase in co2 flux was detected on the summit caldera from 120 september 1998 to 340 metric tons per day september 1999 followed by a sudden decrease to 39 metric tons per day in june 2000 3 months after the eruption the change in co2 flux and seismic observations suggests that before the eruption advective processes controlled gas migration toward the surface the decrease in flux after the eruption at the summit caldera could be due to a rapid release of co2 during the eruption from ascending dacitic dikes spreading away from the magma chamber beneath the caldera

diffuse co2 efflux from iwojima volcano izu ogasawara arc japan abstract iwojima volcano located on the southernmost part of the izu ogasawara arc is characterized by the extrusion of trachyte or trachy andesite lavas and pyroclastic rocks of holocene and surface thermal manifestations small phreatic explosions have been recorded frequently during the last 100 years with the most recent in 1999 and 2001 in order to elucidate the behavior of volcanic volatiles and to assess the potential activity of this volcano diffuse co 2 efflux co 2 content and 13 c co 2 in soil gas and soil temperature at 30 cm depth were measured at 272 sites in march 2000 112 sites in december 2000 and 40 sites in december 2001 we found that high co 2 efflux values of more than 100 g m 2 day 1 occurred at several locations on motoyama volcano corresponding with high soil temperatures more than 60 c at 30 cm depth region and with areas where co 2 with magmatic 13 c was observed here the magmatic 13 c determined for fumarolic co 2 data ranged from 2 to 3 which is clearly higher than magmatic gas values 8 to 2 typically found in island arc settings around the world however this can be explained in terms of carbon isotope fractionation between calcite and co 2 under subsurface temperature and pressure conditions at iwojima a total efflux of co 2 for iwojima volcano is estimated to be 760 t day 1 with a magmatic contribution of about 450 t day 1 this value is rather high compared with other volcanoes in island arc settings since iwojima has no visible plume almost all volcanic co 2 is released as diffuse efflux through the volcanic edifice

globally significant co2 emissions from katla a subglacial volcano in iceland volcanoes are a key natural source of co2 but global estimates of volcanic co2 flux are predominantly based on measurements from a fraction of world s actively degassing volcanoes we combine high precision airborne measurements from 2016 and 2017 with atmospheric dispersion modeling to quantify co2 emissions from katla a major subglacial volcanic caldera in iceland that last erupted 100 years ago but has been undergoing significant unrest in recent decades katla s sustained co2 flux 12 24 kt d is up to an order of magnitude greater than previous estimates of total co2 release from iceland s natural sources katla is one of the largest volcanic sources of co2 on the planet contributing up to 4 of global emissions from nonerupting volcanoes further measurements on subglacial volcanoes worldwide are urgently required to establish if katla is exceptional or if there is a significant previously unrecognized contribution to global co2 emissions from natural sources we combine high precision airborne measurements from 2016 and 2017 with atmospheric dispersion modelling to quantify co2 emissions from katla a major subglacial volcanic caldera in iceland that last erupted 100 years ago but has been undergoing significant unrest in recent decades katla s sustained co2 flux 12 24 kt d is up to an order of magnitude greater than previous estimates of total co2 release from iceland s natural sources katla is one of the largest volcanic sources of co2 on the planet contributing up to 4 of global emissions from non erupting volcanoes further measurements on subglacial volcanoes world wide are urgently required to establish if katla is exceptional or if there is a significant previously unrecognized contribution to global co2 emissions from natural sources

investigating the deepest part of a volcano plumbing system evidence for an active magma path below the western flank of piton de la fournaise la reunion island abstract peripheral diffuse degassing of co 2 from the soil occurs across the western flank of piton de la fournaise volcano la reunion island indian ocean along a narrow zone in this area carbon isotopic analysis on soil gas samples highlights significant mixing between magmatic and organic end members the zones with the strongest magmatic signature highest 13 c overlap spatial distribution of hypocenters recorded shortly before and during volcano reactivation and allow discriminating a n135 degassing lineament with a minimum length of 11 km and 140 20 m width such orientation is in accordance with that of an old dyke network along the rift zone and with n120 130 and n140 155 lineaments related to the inheritance of oceanic lithosphere structures our findings show that this n135 lineament represents a preferential magmatic pathway for deep magma transfer below the volcano flank moreover spatial distributions of recent eccentric cones indicate a well founded possibility that future eruptions may by pass the shallow plumbing system of the central area of the volcano taking a lateral pathway along this structure our results also confirm that piton de la fournaise activity is linked to a laterally shifted plumbing system and represent a major improvement in identifying the main high risk area on the densely populated western flank of the volcano

magmatic volatiles to assess permeable volcano tectonic structures in the los humeros geothermal field mexico abstract magmatic volatiles can be considered as the surface fingerprint of active volcanic systems both during periods of quiescent and eruptive volcanic activity the spatial variability of gas emissions at earth s surface is a proxy for structural discontinuities in the subsurface of volcanic systems we conducted extensive and regular spaced soil gas surveys within the los humeros geothermal field to improve the understanding of the structural control on fluid flow surveys at different scales were performed with the aim to i identify areas of increased gas emissions reservoir scale ii their relation to un known volcano tectonic structures fault scale favoring fluid flow and iii determine the origin of gas emissions herein we show results from a co2 efflux scouting survey which was performed across the main geothermal production zone 6 km 4 km together with soil temperature measurements we identified five areas with increased co2 emissions where further sampling was performed with denser sampling grids to understand the fault zone architecture and local variations in gas emissions co2 efflux values range from below detection limit of the device to 1464 g m 2 d 1 with a total output of 87 t d 1 across an area of 13 7 km2 furthermore 13cco2 and 3he 4he analyses complemented the dataset in order to assess the origin of soil gases carbon isotopic data cover a broad spectrum from biogenous to endogenous sources determined 3he 4he ratios indicate a mantle component in the samples of up to 65 being most evident in the northwestern and southwestern part of the study area we show that a systematic sampling approach on reservoir scale is necessary for the identification and assessment of major permeable fault segments the combined processing of co2 efflux and 13cco2 facilitated the detection of permeable structural segments with a connection to the deep high temperature geothermal reservoir also in areas with low to intermediate co2 emissions the results of this study complement existing geophysical datasets and define further promising areas for future exploration activities in the north and southwestern sector of the production field

mantle co2 degassing at mt vulture volcano italy relationship between co2 outgassing of volcanoes and the time of their last eruption abstract mantle volatiles are mainly lost from the earth to the atmosphere through subaerial and submarine volcanism recent studies have shown that degassing of mantle volatiles also occurs from inactive volcanic areas and in tectonically active areas a new challenge in earth science is to quantify the mantle derived flux of volatiles e g co2 which is important for understanding such diverse issues as the evolution of the atmosphere the relationships between magma degassing and volcanic activity gas pressure and seismogenic processes and the hazards posed by volcanic lakes here we present a detailed study of mantle derived co2 budget from mt vulture volcano in the apennines italy whose latest eruption occurred 141 11 kyr ago the relationship between 13cco2 and total dissolved carbon at mt vulture volcano indicates that the emitted co2 is a mixture of a biogenic end member with an average 13cco2 of about 17 and a mantle derived co2 end member with 13cco2 values from 3 to 2 these values of mantle derived 13cco2 are in the range of those for gas emitted from active volcanoes in the mediterranean we calculated the contribution of individual components co2 in groundwater in lakes and from main pools to the total co2 budget in the area we used new measurements of water flow combined with literature data to calculate the co2 flux associated with groundwater and measured the gas flux from the main pools on the volcanic edifice finally we calculated the co2 flow in the lakes based on the gradient concentration and eddy diffusivity the total mantle derived co2 budget in the area is 4 85 10 8 mol yr 1 which is more than double previous estimates this is higher than those observed in younger volcanic systems elsewhere thereby supporting the existence of actively degassing mantle melts below mt vulture volcano a structural map highlights the tectonic control on co2 flow across the mt vulture volcanic edifice indeed the tectonic discontinuities that controlled the magma upwelling during the most recent volcanic activity are still the main active degassing structures the new estimate of co2 budget in the mt vulture area together with literature data on co2 budget from historically active and inactive italian volcanoes suggests a power law functional relationship between the age of the most recent volcanic eruption and both total discharged co2 r 2 0 73 and volcano size normalized co2 flux r 2 0 66 this relation is also valid by using data from worldwide volcanoes highlighting that deep degassing can occur over very long time too in turn the highlighted relation provides also an important tool to better evaluate the state of activity of a volcano whose last activity occurred far in time finally our study highlights that in the southern apennines an active degassing of mantle derived volatiles i e he co2 occurs indiscriminately from west to east this is in contrast to the central northern apennine which is characterized by a crustal radiogenic volatile contribution which increases eastward coupled to a decrease in deep co2 flux this difference between the two regions is probably due to lithospheric tears which control the upwelling of mantle melts their degassing and the transport of volatiles through the crust

three dimensional imaging of the p and s wave velocity structure and earthquake locations beneath southwest iceland three dimensional imaging of the p and s wave velocity structure and earthquake locations beneath southwest iceland

diffuse surface emanations as indicator of structural permeability in fault controlled geothermal systems abstract diffuse degassing processes provide valuable information on geothermal reservoir characteristics not only in the context of monitoring but also for exploration purposes areas with increased gas emissions can be indicative of major upflow zones from the reservoir through deep reaching permeable fault zones these fault zones may act as preferential target areas for geothermal production drillings in this study it is successfully demonstrated that diffuse degassing measurements can be used for the detection and characterization of permeable structural elements the combination of following techniques has been applied at the brady s geothermal system in the basin and range province nevada usa accumulation chamber method for carbon dioxide and hydrogen sulfide measurements alpha spectroscopic measurements of radon and thoron activity concentrations and gamma spectroscopic measurements of selected nuclides

carbon dioxide degassing and thermal energy release in the monte amiata volcanic geothermal area italy abstract the quaternary volcanic complex of mount amiata is located in southern tuscany italy and represents the most recent manifestation of the tuscan magmatic province the region is characterised by a large thermal anomaly and by the presence of numerous co2 rich gas emissions and geothermal features mainly located at the periphery of the volcanic complex two geothermal systems are located at increasing depths in the carbonate and metamorphic formations beneath the volcanic complex the shallow volcanic aquifer is separated from the deep geothermal systems by a low permeability unit ligurian unit a measured co2 discharge through soils of 1 8 109 mol a 1 shows that large amounts of co2 move from the deep reservoir to the surface a large range in 13ctdic 21 07 to 3 65 characterises the waters circulating in the aquifers of the region and the mass and isotopic balance of tdic allows distinguishing a discharge of 0 3 109 mol a 1 of deeply sourced co2 in spring waters the total natural co2 discharge 2 1 109 mol a 1 is slightly less than minimum co2 output estimated by an indirect method 2 8 109 mol a 1 but present day release of 5 8 109 mol a 1 co2 from deep geothermal wells may have reduced natural co2 discharge the heat transported by groundwater computed considering the increase in temperature from the infiltration area to the discharge from springs is of the same order of magnitude or higher than the regional conductive heat flow 200 mw m 2 and reaches extremely high values up to 2700 mw m 2 in the north eastern part of the study area heat transfer occurs mainly by conductive heating in the volcanic aquifer and by uprising gas and vapor along fault zones and in those areas where low permeability cover is lacking the comparison of co2 flux heat flow and geological setting shows that near surface geology and hydrogeological setting play a central role in determining co2 degassing and heat transfer patterns

degassing regime of hekla volcano 2012 2013 hekla is a frequently active volcano with an infamously short pre eruptive warning period our project contributes to the ongoing work on improving hekla s monitoring and early warning systems in 2012 we began monitoring gas release at hekla the dataset comprises semi permanent near real time measurements with a multigas system quantification of diffuse gas flux and direct samples analysed for composition and isotopes 13c d and 18o in addition we used reaction path modelling to derive information on the origin and reaction pathways of the gas emissions hekla s quiescent gas composition was co2 dominated 0 8 mol fraction and the 13c signature was consistent with published values for icelandic magmas the gas is poor in h2o and s compared to hydrothermal manifestations and syn eruptive emissions from other active volcanic systems in iceland the total co2 flux from hekla central volcano diffuse soil emissions is at least 44 t d 1 thereof 14 t d 1 are sourced from a small area at the volcano s summit there was no detectable gas flux at other craters even though some of them had higher ground temperatures and had erupted more recently our measurements are consistent with a magma reservoir at depth coupled with a shallow dike beneath the summit in the current quiescent state the composition of the exsolved gas is substantially modified along its pathway to the surface through cooling and interaction with wall rock and groundwater the modification involves both significant h2o condensation and scrubbing of s bearing species leading to a co2 dominated gas emitted at the summit we conclude that a compositional shift towards more s and h2o rich gas compositions if measured in the future by the permanent multigas station should be viewed as sign of imminent volcanic unrest on hekla

diffuse emission of co2 from the fossa crater vulcano island italy numerous measurements of co2 degassing from the soil carried out with the accumulation chamber method indicate that in the period april july 1995 the upper part of the fossa cone released a total output of 200 t d 1 of co2 which corresponds to approximately 1000 t d 1 of steam these large amounts of fluids are of the same order of magnitude as those released by the high temperature fumarolic field located inside the crater the spatial distribution of soil gas fluxes shows that the main structures releasing co2 are the inner slopes of the crater and a nw se line located ne of the crater rim which correspond to the main direction of vulcano island active faults the comparison of the co2 maps with the soil temperature distribution derived from both direct measurements and airborne infrared images indicates the occurrence of extensive condensation of fumarolic steam within the upper part of the fossa cone whose total amount is comparable to the rainfall budget part of the condensate which originates from this process contributes to the recharge of the phreatic aquifer of porto plain modifying the chemical and isotopic composition of the groundwater

geochemical evidences of seismo volcanic unrests at the nw rift zone of tenerife canary islands inferred from diffuse co 2 emission we report the results of 49 soil co2 efflux surveys by the accumulation chamber method at the north west rift nwr zone of tenerife island canary islands the surveys were carried out from 2000 to 2016 to evaluate the temporal and spatial variations of co2 efflux and their relationships with the volcanic and seismic activity at tenerife soil co2 efflux values ranged from non detectable 0 5 g m 2 day 1 up to 141 g m 2 day 1 with the highest values measured in may 2005 whereas total co2 emission rates ranged between 52 and 867 t day 1 metric tons per day isotopic analyses of soil gas in carbon dioxide 13c co2 suggest a mixing between organic and atmospheric co2 with a small contribution of deep seated co2 the main temporal variation in the total co2 output does not seem to be driven by external factors it shows a clear temporal correlation with the onsets of seismic activity subsurface magma degassing affecting the central part of the island is proposed as a cause for the observed changes in the total output of diffuse co2 emission as well as for the spatial distribution of soil co2 efflux

quantification of carbon dioxide emissions of ciomadul the youngest volcano of the carpathian pannonian region eastern central europe romania abstract we provide the first high resolution co 2 flux data for the neogene to quaternary volcanic regions of the entire carpathian pannonian region eastern central europe and estimate the co 2 emission of the seemingly inactive ciomadul volcanic complex the youngest volcano of this area our estimate includes data from focused and diffuse co 2 emissions from soil the co 2 fluxes of focused emissions range between 277 and 8172 g d 1 corresponding to a co 2 output into the atmosphere between 0 1 and 2 98 t per year the investigated areas for diffuse soil gas emissions were characterized by wide range of co 2 flux values at apor baths ranging from 1 7 10 1 to 8 2 10 4 g m 2 d 1 while at l z re ti ranging between 1 43 and 3 8 10 4 g m 2 d 1 the highest co 2 focused gas fluxes at ciomadul were found at the periphery of the youngest volcanic complex which could be explained either by tectonic control across the brittle older volcanic edifices or by degassing from a deeper crustal zone resulting in co 2 flux at the periphery of the supposed melt bearing magma body beneath ciomadul the estimate of the total co 2 output in the area is 8 70 10 3 t y 1 and it is consistent with other long 10 kyr dormant volcanoes with similar age worldwide such as in italy and usa taking into account the isotopic composition of the gases that indicate deep origin of the co 2 emissions this yields further support that ciomadul may be considered indeed a dormant or pams volcano volcano with potentially active magma storage rather than an inactive one furthermore hazard of co 2 outpourings has to be taken into account and it has to be communicated to the visitors finally we suggest that co 2 output of dormant volcanic systems has to be also accounted in the estimation of the global volcanic co 2 budget

diffuse co2 soil degassing and co2 and h2s concentrations in air and related hazards at vulcano island aeolian arc italy ingv dpc programme project v5 diffuse degassing in italy airplane firb project of the italian ministry of the university and research

geochemical precursors of the activity of an open conduit volcano the stromboli 2002 2003 eruptive events 1 marked increases of co2 h2 and he dissolved in thermal waters and changes in the dissolved carbon isotopic composition were observed at stromboli before the 28 december 2002 eruption and before a violent explosive paroxysm occurred on 5 april 2003 high anomalous co2 flux values were recorded at the crater rim since a week before the eruption onset the first anomalies in the thermal waters dissolved co2 amount appeared some months before the eruption when magma column rose at a very high level in the conduit high peaks of dissolved h2 and he were recorded a few days before the paroxysm carbon isotopic composition indicates a magmatic origin of the dissolved co2 whose increase together with those of h2 and he is attributed to an increasing output of deep gases likely produced by depressurization of a rising batch of a deep gas rich magma whose fragments have been emitted during the explosion

the fluid geochemistry of icelandic high temperature geothermal areas abstract icelandic high temperature geothermal systems are considered to number thirty three thereof three are submarine and seven subglacial all are briefly described but the chemistry of fluids from twenty four of them is considered the fluid in the three submarine areas and those four on land that are closest to the sea are relatively saline but to a differing extent mixed with groundwater the rest contain dilute fluids the fluids of the central highland systems are mostly locally derived but may in some instances be quite old whereas those in the northerly krafla area which is inland and the oxarfjor ur area which is close to the sea appear to be a mixture of local and central highland water but those in the inland hengill geysir namafjall and theistareykir areas appear to have travelled relatively long distances from the central highlands the gas observed is magmatic except in the northerly oxarfjordur area close to the sea where it is apparently derived from organic sediments

soil efflux and total emission rates of magmatic co2 at the horseshoe lake tree kill mammoth mountain california 1995 1999 abstract we report the results of eight soil co 2 efflux surveys by the closed circulation chamber method at the horseshoe lake tree kill hltk the largest tree kill on mammoth mountain the surveys were undertaken from 1995 to 1999 to constrain total hltk co 2 emissions and to evaluate occasional efflux surveys as a surveillance tool for the tree kills hltk effluxes range from 1 to 10 000 g m 2 day 1 grams co 2 per square meter per day they are not normally distributed station efflux rates can vary by 7 35 during the course of the 8 to 16 h surveys disturbance of the upper 2 cm of ground surface causes effluxes to almost double semivariograms of efflux spatial covariance fit exponential or spherical models they lack nugget effects efflux contour maps and total co 2 emission rates based on exponential spherical and linear kriging models of survey data are nearly identical similar results are also obtained with triangulation models suggesting that the kriging models are not seriously distorted by the lack of normal efflux distributions in addition model estimates of total co 2 emission rates are relatively insensitive to the measurement precision of the efflux rates and to the efflux value used to separate magmatic from forest soil sources of co 2 surveys since 1997 indicate that contrary to earlier speculations a termination of elevated co 2 emissions at the hltk is unlikely anytime soon the hltk co 2 efflux anomaly fluctuated greatly in size and intensity throughout the 1995 1999 surveys but maintained a n s elongation presumably reflecting fault control of co 2 transport from depth total co 2 emission rates also fluctuated greatly ranging from 46 to 136 t day 1 metric tons co 2 per day and averaging 93 t day 1 the large inter survey variations are caused primarily by external meteorological processes operating on time scales of hours to days the externally caused variations can mask significant changes occurring at depth a striking example is the masking of a degassing event generated at depth and detected by a soil gas sensor network in september 1997 while an efflux survey was in progress thus occasional efflux surveys are not an altogether effective surveillance tool for the hltk and making them effective by greatly increasing their frequency may not be practical

diffuse emission of co2 from miyakejima volcano japan abstract two soil gas surveys were carried out in may and september 1998 at miyakejima volcano in the izu mariana arc japan co 2 flux values for may and september surveys ranged from 0 1 to 18 150 g m 2 day 1 and from 0 1 to 9685 g m 2 day 1 respectively statistical graphical analysis showed three overlapping populations the spatial distribution of these emissions correlated quite closely with the geothermal and geological characteristics of the studied area the structure releasing higher co 2 is the summit cone oyama and surrounding areas where the most obvious geothermal features occur a total output about 100 150 t day 1 is estimated from this area a good correlation was observed between soil co 2 flux and soil temperature at the summit caldera indicating extensive condensation of fumarolic steam within the upper part of miyakejima carbon isotopic analysis of selected samples inside the summit caldera 13 c co 2 0 90 to 5 70 suggests a mixing of carbon derived from marine limestone and magmatic co 2 while a clear biogenic origin 13 c co 2 14 76 to 25 52 is observed for the diffuse degassing of co 2 outside summit caldera

deep co2 release revealed by stable isotope and diffuse degassing surveys at vulcano aeolian islands in 2015 2018 abstract the partitioning of carbon dioxide co2 released by soils at vulcano island aeolian islands italy was performed by combining the co2 flux and the carbon isotope measurements based on this method the amount of co2 of volcanic origin was quantified six times during the period 2015 2018 the data analysis allowed us to establish the correlation between co2 soil degassing and changes in the contribution of volcanic fluids carbon isotope determinations were performed in situ to enhance the coverage of data collection in space and time these data were combined with both the co2 contents in the ground gases and the soil co2 flux the amount of volcanic co2 was distinguished from that of biogenic origin by implementing a three component mixing model the results of this study indicate that the increase in co2 output in september 2018 reflects the increase in volcanic gas emissions the measurement method and analysis presented in this work are sufficiently general to be applicable to the monitoring programs of active volcanoes

hengill triple junction sw iceland 1 tectonic structure and the spatial and temporal distribution of local earthquakes the hengill area is an unstable ridge ridge transform triple junction in sw iceland it contains the active central volcano hengill associated with the present accretionary zone and the extinct grensdalur central volcano associated with an accretionary zone that became inactive at about 0 7 m y when the locus of spreading migrated about 5 km w to the hengill zone the dominant tectonic trend of the area is n25 e parallel to the accretionary zones but transverse tectonic topographic features have also developed in the neighborhood of the two central volcanoes these result from local modification of the regional stress field associated with the spreading by radially symmetric stress fields associated with the volcanoes and the migration of volcanism a double high temperature geothermal system mirrors the double volcanic system the transform branch of the triple junction is represented by an ew striking zone of historic destructive earthquakes in the s of the area a seismological study was conducted with the aims of studying the tectonic structure and evaluating the passive seismic method as a geothermal prospecting tool the seismicity may be broadly divided into two groups first infrequent intense episodes of crustal movement occur that are associated with the release of tectonic stress along the plate boundary second continuous small magnitude activity occurs on a day to day basis this activity is mostly associated with the extinct grensdalur central volcano not the present plate boundary statistically significant temporal variations in b accompanied a swarm in the transform zone the continuous small magnitude activity may be geothermal in origin releasing thermal stress and not associated with plate boundary tectonics

carbon dioxide diffuse emission and thermal energy release from hydrothermal systems at copahue caviahue volcanic complex argentina abstract the north western sector of caviahue caldera argentina close to the active volcanic system of copahue is characterized by the presence of several hydrothermal sites that host numerous fumarolic emissions anomalous soil diffuse degassing of co2 and hot soils in march 2014 measurements of soil co2 fluxes in 5 of these sites namely las maquinas las maquinitas i las maquinitas ii anfiteatro and termas de copahue allowed an estimation that 165 t of deeply derived co2 is daily released the gas source is likely related to a relatively shallow geothermal reservoir containing a single vapor phase as also suggested by both the geochemical data from the 3 deep wells drilled in the 1980s and gas geoindicators applied to the fumarolic discharges gas equilibria within the h c o gas system indicate the presence of a large probably unique single phase vapor zone at 200 210 c feeding the hydrothermal manifestations of las maquinas las maquinitas i and ii and termas de copahue a natural thermal release of 107 mw was computed by using co2 as a tracer of the original vapor phase the magmatic signature of the incondensable fumarolic gases the wide expanse of the hydrothermal areas and the remarkable high amount of gas and heat released by fluid expulsion seem to be compatible with an active magmatic intrusion beneath this portion of the caviahue caldera