mineral and gas chemistry of hydrothermal fluids on an ultrafast spreading ridge east pacific rise 17 to 19 s naudur cruise 1993 phase separation processes controlled by volcanic and tectonic activity during the naudur cruise in december 1993 23 dives using the french submersible nautile were conducted on the axis of the east pacific rise between 17 and 19 s where the spreading rate is among the fastest in the ocean 14 to 16 cm yr twenty hydrothermal fluids located at the topographic high of each segment in the axial domain were collected between 2573 and 2669 m depth on three segments centered respectively at 17 25 s 18 15 s and 18 26 s the fluids exhibit a very wide range of temperature chemical and gas compositions on the 17 25 s and 18 26 s segments fluids have quite uniform compositions low chlorinities are gas enriched and are low in dissolved metals relative to fluids from the 18 15 s segment which show high chlorinities are less gas enriched and show high metal concentrations chloride and metal depletion associated with gas enrichment is consistent with phase separation whereas ch 4 end members show large variations between sites the 13 ch 4 data are very similar with 13 c values in a narrow range 22 0 to 23 9 versus pee dee belemnite pdb 13 co 2 measured in fluids within the 18 15 s and 18 26 s segments are respectively 7 9 and 5 8 versus pdb similar to 13 c of co 2 trapped in mid oceanic ridge basalts suggesting a magmatic origin the variability in fluid composition is linked to the variability of the accretion process observed on the three segments the uniform venting of low chlorinity fluids in the 17 25 s and 18 26 s segments is connected with volcanic activity which causes boiling with preferential venting of vapor enriched fluids high salinity fluids are emitted on the 18 15 s segment where the ridge is tectonics dominated and subseafloor circulation controlled by faults phase separated effluents induced by volcanic and tectonic activity are delivered to the deep ocean in this area as previously observed on the juan de fuca ridge or in the north fiji basin ridge

h2 generation in wet grinding of granite and single crystal powders and implications for h2 concentration on active faults 1 granite and single crystals of quartz alkali feldspar biotite and muscovite are ground in ph controlled and pure water solutions using a ball mill at ambient condition to examine the production of h2 the amount of h2 generated by grinding is linearly related with the surface area of ground samples the slope of the straight line indicates h2 productivity of each mineral 3 9 10 3 mol m2 quartz 1 0 10 3 mol m2 alkali feldspar 3 6 10 2 mol m2 biotite 2 2 10 2 mol m2 muscovite 4 5 10 3 mol m2 granite high productivity of biotite and muscovite is probably related to the existence of hydroxyls in their crystal structures interestingly h2 production did not depend on the ph of the solution in the case of biotite and granite while comparisons between fluid acidity and h2 concentration on several active faults suggest that anomalously high h2 is commonly observed at relatively acidic water springs this correlation may be explained by locally high abundance of phyllosilicates

fault controlled soil co2 degassing and shallow magma bodies summit and lower east rift of kilauea volcano hawaii 1997 soil co2 flux measurements were carried out along traverses across mapped faults and eruptive fissures on the summit and the lower east rift zone of kilauea volcano anomalous levels of soil degassing were found for 44 of the tectonic structures and 47 of the eruptive fissures intercepted by the surveyed profiles this result contrasts with what was recently observed on mt etna where most of the surveyed faults were associated with anomalous soil degassing the difference is probably related to the differences in the state of activity at the time when soil gas measurements were made kilauea was erupting whereas mt etna was quiescent although in a pre eruptive stage unlike mt etna flank degassing on kilauea is restricted to the tectonic and volcanic structures directly connected to the magma reservoir feeding the ongoing east rift eruption or in areas of the lower east rift where other shallow likely independent reservoirs are postulated anomalous soil degassing was also found in areas without surface evidence of faults thus suggesting the possibility of previously unknown structures

geophysical and geochemical methods applied to investigate fissure related hydrothermal systems on the summit area of mt etna volcano italy abstract a multidisciplinary approach integrating self potential soil temperature heat flux co 2 efflux and gravity gradiometry signals was used to investigate a relatively small fissure related hydrothermal system near the summit of mt etna volcano italy measurements were performed through two different surveys carried out at the beginning and at the end of july 2009 right after the end of the long lived 2008 2009 flank eruption and in coincidence with an increase in diffuse flank degassing related to a reactivation of the volcano leading to the opening of a new summit vent nsec the main goal was to use a multidisciplinary approach to the detection of hidden fractures in an area of evident near surface hydrothermal activity despite the different methodologies used and the different geometry of the sampling grid between the surveys all parameters concurred in confirming that the study area is crossed by faults related with the main fracture systems of the south flank of the volcano where a continuous hydrothermal circulation is established results also highlighted that hydrothermal activity in this area changed both in space and in time these changes were a clear response to variations in the magmatic system notably to migration of magma at various depth within the main feeder system of the volcano the results suggest that this specific area initially chosen as the optimal test site for the proposed approach can be useful in order to get information on the potential reactivation of the summit craters of mt etna

soil gas survey for tracing seismogenic faults a case study in the fucino basin central italy soil gas he rn co2 and ch4 surveys were performed to test their sensitivity for locating fault or fracture systems when masked by unconsolidated lithologies and to investigate the gas bearing properties of seismogenic faults the fucino basin central italy was chosen as a test site because it displays a network of surface and shallow buried active faults within the valley floor which were partially reactivated during the 1915 avezzano earthquake ms 7 0 the highest radon values were found aligned along the most important faults especially along the san benedetto gioia dei marsi fault sbgmf to the east and in the northwestern sector where the avezzano celano fault acf meets the northwestern prolongation of the 1915 coseismic rupture moderately anomalous values of radon occur along the faults located in the depression of the historical lake trasacco fault tf and ortucchio fault of anomalous values of co2 rn and he were detected north of borgo ottomila in a zone where coseismic scarps and liquefaction phenomena were responsible for a pervasive brittle deformation during the 1915 earthquake highest helium values prevail in the western part of the plain in correspondence with a horst structure bounded by the tf and considered to be the extension of the vallelonga trasacco ridge results of this research confirm the possible usefulness of soil gas methods for locating some tectonic faults when covered by unconsolidated deposits the study provides some clues on the spatial influence of tectonics and geology on deeply seated gas migration toward the surface

preseismic hydrogen gas anomalies caused by stress corrosion process preceding earthquakes simultaneous monitoring of he h2 ar n2 ch4 and rn in gas bubbles of groundwater from the 1 500 m deep nagashima well in the active yoro fault zone central japan reveals that three microearthquakes with m 1 6 2 6 in the fault zone are accompanied and preceded by increases of h2 as is a moderately large event with m 5 4 in the same fault zone all the focal distances of the earthquakes are within 25 km no comparable anomalies were seen in the gas species other than h2 we suggest that the selective and preseimic increases of h2 in groundwater gas bubbles are geochemical signals of the earthquake nucleation process of stress corrosion mechanism aseismic slips preceding earthquakes in the active fault zone are likely to have enhanced h2 production by mechanochemical reaction of fractured rock surface with water in pre existing fault planes as groundwater conduits

soil co2 degassing along tectonic structures of mount etna sicily the pernicana fault abstract carbon dioxide emissions from the soil have been investigated along lines of equally spaced sampling points perpendicular to the pernicana fault on mt etna anomalous values of soil co2 have been found not only along the fault plane but also along directions parallel to it both to the n and to the s of the main fault the acquired data seem to reveal a shallow step like geometry of the pernicana fault system with parallel faults being generally not deeper than the interface between etna s volcanic cover and its sedimentary basement a few hundred meters the distribution of the anomalous co2 emissions has also revealed that the pernicana fault continues at least as far as the ionian sea in an area where only sedimentary rocks crop out this finding would suggest that the main structure is deeper than the base of the volcanic cover thus cutting at least the uppermost portion of etna s sedimentary basement isotopic analyses of c carried out in samples from locations of high co2 seem to indicate that the emitted co2 is a mixture of an organic shallow component and a minor deeper magmatic one both chemical and isotopic data on soil gases emitted in the easternmost part of the studied area distinguished another tectonic structure which seems to be much deeper than the pernicana fault and is roughly directed nne ssw this direction being coincident with an important structural trend of eastern sicily

gas geochemical changes at mineral springs associated with the 1995 southern hyogo earthquake m 7 2 japan abstract gas concentrations monitored at a mineral spring in central japan over the past 15 years showed similar changes before and after two large earthquakes september 1984 m 6 9 50 km distant and january 1995 m 7 2 220 km distant namely a concurrent and abrupt drop in all three gas ratios he ar n 2 ar and ch 4 ar several months before the events improved measurements of gas compositions since 1991 and the addition of gas discharge rate monitoring since 1993 disclosed the following features for anomalies in response to small earthquakes as well as the large 1995 event 1 the gas ratios increased for both large and small earthquakes but they did not return to the preseismic values for the large event as they did within a few hours for the small events 2 at the 1995 event the gas discharge rate decreased remarkably 3 h before the event and then increased to higher than preseismic level for several months in contrast coseismic rates at small events generally increased for less than 15 min 3 during a seismically quiet period from january 1993 to december 1994 the variation in the he ar ratio was well correlated with that of gas discharge rate such correlation disappeared in august and september 1994 when the three gas ratios dropped before the large event 4 gas compositions at an auxiliary monitoring site revealed a coseismic change similar to that described above for the 1995 event these lines of evidence show that subsurface fluids may habitually respond to changes in physical conditions relating to earthquake occurrences and thus suggest the usefulness of monitoring subsurface fluids for earthquake prediction

distal degassing of radon and carbon dioxide on galeras volcano colombia abstract diffuse degassing at galeras volcano colombia was studied during three consecutive field seasons from 1993 to 1995 measurements of222rn and co2 were made at 30 stations which were distributed on the volcano and on regional faults intersecting the edifice time series data show a decline of radon soil gas of up to 50 prior to a m 2 8 earthquake on 12 august 1993 at stations located near the epicenter and on the volcano near the location of earthquake swarms which occurred in april 1993 november december 1993 and march 1995 the onset of volcanic seismic activity tornillos on 9 august 1994 was preceded by anomalous soil gas increases at six stations located on the flanks of the volcano on the southwestern flank radon increased from 51 to 130 pci 1 between 7 and 14 august while on the northern flank radon concentrations began to increase 19 days before the appearance of tornillos in general stations close to the crater showed the largest radon increases soil gas distributions and carbon isotope data suggest that diffuse degassing on the volcano is structurally controlled and that the abundance of co2 in soil gas on the edifice cannot be taken as an indicator for the presence of magmatic gases radon soil gas concentrations and the222rn emanating226ra concentration increase near faults whereas co2 concentrations are more variable but commonly are higher on the volcano than near faults 13c values in soil co2 vary between 8 5 and 23 2 with 13c values more enriched than 15 found only in the vicinity of faults or sites prone to earthquake swarms this suggests a magmatic origin of co2 soil gas only near faults and an almost impermeable edifice in unfractured areas the observed correlations between seismic activity and soil degassing provide further evidence that soil gas studies especially when correlated to other methods of volcano surveillance such as seismicity and deformation may be useful in forecasting volcanic and seismic events

continuous chemical monitoring of volcanic gas in izu oshima volcano japan abstract a new continuous monitoring system has been developed for the measurement of volcanic gas from the steam well located 3 km north from the summit of izu oshima volcano japan after removing the water vapor using three sequential dehydration methods co 2 and so 2 contents are measured using ir sensors and o 2 and h 2 using a zirconia sensor and a semiconductor sensor respectively this system has been in operation without any significant trouble for 3 years the dehydrated volcanic gas from the well consists of a mixture of co 2 o 2 and n 2 a decreasing trend of the co 2 content was observed from 1995 to 1998 together with a decrease of volcanic activity seasonal changes have also been observed in co 2 and o 2 contents co 2 being higher and o 2 lower in summer which suggests larger contribution of magmatic components in summer while changes in short term variation in co 2 and o 2 are influenced by atmospheric pressure changes the co 2 content correlates inversely with atmospheric pressure unlike o 2 with some hours delay in contrast the h 2 content increased intermittently up to 1200 ppm one to several hours after a sudden drop in the atmospheric pressure and without any apparent correlation with seasonal changes this system allows us to study temporal variation in chemical composition of volcanic gas during quiescent periods of volcanic activity of izu oshima volcano and might help us detect anomalous changes before future eruptive events

a multidisciplinary approach to detect active pathways for magma migration and eruption at mt etna sicily italy before the 2001 and 2002 2003 eruptions two strong flank eruptions occurred in july august 2001 and from late october 2002 to late january 2003 at mt etna volcano the two eruptions mainly involved the upper southern flank of the volcano a particularly active area during the last 30 years damaging several tourist facilities and threatening some villages the composite eruptive activity on the upper southern flank of mt etna during 2001 2003 has confirmed a posteriori the results of a multidisciplinary study started well before its occurrence by combining geological seismic and geochemical data gathered in this part of the volcano we were able in fact to highlight fractured zones likely to be re activated in the near future in this area where the largest majority of eruptive fissures in the recent past opened along n120 to n180 ranging directions the spatial distribution of earthquake epicentres during the period june 30th 2000 june 30th 2001 showed the greatest frequency in a sector compatible with both the direction of the main fissures of the pre 2001 period and that of the 2001 and 2002 lateral eruptions soil co2 and soil temperature surveys carried out in the studied area during the last 3 years have revealed anomalous release of magmatic fluids mainly co2 and water vapour along some nnw sse trending volcano tectonic structures of the area even during inter eruptive periods indicating persistent convective hydrothermal systems at shallow depth connected with the main feeder conduits of etna the temporal changes in both seismic and geochemical data from june 30th 2000 to june 30th 2001 were compared with the evolution of volcanic activity the comparison allowed to recognize at least two sequences of anomalous signals august to december 2000 and april to june 2001 likely related to episodes of step like magma ascent towards the surface as indicated by the following eruptive episodes the n120 to n180 structural directions are in accord with one of the main structural lines affecting eastern sicily they would be important pathways for magma uprise to the surface that will keep on feeding the eruptive activity of etna in the near future this study also pointed out the high instability of the southern slope of etna a sector where the potential hazard by lava flow invasion will remain high also in the near future

intense ch4 plumes generated by serpentinization of ultramafic rocks at the intersection of the 15 20 n fracture zone and the mid atlantic ridge abstract as part of the fara french us program designed to study the mid atlantic ridge mar between 15 n and the azores twenty three dives with the submersible nautile were conducted during the french us faranaut 15n cruise on the eastern and western parts of the 15 20 n fracture zone ridge axis intersection south of the eastern ridge transform fault intersection nine nautile dives were made within the rift valley and along the western rift valley wall ch4 concentrations in the bottom waters reach 53 2 nmol kg along faulted zones on top and on the east flank of the ultramafic inner corner high 15 05 n 44 59 w where serpentinized rocks outcrop no 3he anomaly is associated with methane ruling out any primary mantle component fourteen dives were also made in the rift valley to the north close to the western intersection of the 15 20 n transform high ch4 anomalies up to 22 nmol kg are also present in the bottom waters of the rift valley northern segment on both the western and eastern valley walls and on the inner high adjacent to the eastern wall where ultramafic rocks outcrop seven vertical hydrocasts carried out in the axial valley 4500 m deep show an intense ch4 anomaly with a maximum 35 8 nmol kg at 3200 m depth this ch4 concentration is among the highest found along the mid atlantic ridge charlou and donval 1993 charlou et al 1997 ch4 concentrations of 9 9 14 9 nmol kg are also present on the western wall along the 3200 m isobath the high ch4 concentrations correspond to only weak 3he anomalies this ch4 rich plume is also associated with active fault zones that expose peridotite rocks ch4 output from ultramafic outcrops on the western and eastern intersections of the 15 20 n fracture zone with the mar is believed to reflect ongoing serpentinization these results associated with many other ch4 anomalies measured in the water column above ultramafic outcrops found between 12 n and the azores most likely reflect serpentinization processes extending along the whole slow spreading mid atlantic ridge

sampling procedure for small scale heterogeneities crossbedding for reservoir modelling sampling permeability from individual laminae in crossbedded rocks is very well possible by making use of a so called probe permeameter the methodology and calculation of permeabilities from the output of this instrument are fairly well established however what is hardly established is a sampling strategy that guarantees adequate representation of permeability contrast between laminae especially so because finer foreset and bottomset are difficult to sample yet their permeabilities are critical to fluid flow through a crossbed therefore we propose to systematically sample laminae to this end we suggest a sampling strategy that is adapted to the heterogeneity under study namely to the thickness of the finer foreset

the detection and interpretation of hydrogen in fault gases hydrogen gas can be released by chemical and mechanical changes in crustal rocks once released it is highly mobile buoyant and almost insoluble in groundwater a fault system may act as a conduit allowing hydrogen to accumulate in soil gases near a surface expression since hydrogen is scarce in ambient air its presence at elevated levels in soil gases may be a tool for fault mapping in order to evaluate this tool we surveyed eleven different faults by measuring the concentration of hydrogen and methane in 2 to 21 soil gas samples that were collected near each of them the sense of motion at four of those faults is normal western united states greece at five it is strike slip or dip slip california colorado japan and at two it is thrusting california at four of these faults hebgen lake yellowstone yamasaki burro mountain maximum concentrations of hydrogen ranged from 80 ppm to 70 and methane from 300 ppm to 5 all other sites showed ambient levels of both gases except for one sample taken at mt borah idaho that was 2 methane from this preliminary study it is not clear whether the presence of hydrogen is correlated uniquely to the location of faults or whether it occurs randomly the conditions required to produced and accumulate hydrogen are also not clear excess hydrogen may well be produced by different mechanisms in different geological regimes for example if ferrous hydroxide is present in local rocks it may react to produce hydrogen detailed and extensive studies are needed to clarify the connection between hydrogen and tectonic faulting

soil gas prospection of he 222rn and co2 vulcano porto area aeolian islands italy abstract in march 1994 soil gases were sampled in the area of vulcano porto on the island of vulcano using a grid of about 200 points km 2 analysed gases were co 2 he and 222 rn and over a smaller area h 2 s some of the samples were also analysed for the isotope composition of co 2 c three anomalous co 2 degassing areas were identified grotta dei palizzi the area near the telephone exchange and the area near the beach fumaroles the behaviour of he and 222 rn is different in these 3 areas the concentration of he is much lower than that of atmospheric he down to 3950 ppb in the isthmus and only in the area near grotta dei palizzi does it have values significantly higher than atmospheric ones up to 1900 ppb the activity of 222 rn always significantly positively related to co 2 concentrations peaked in the 2 fumarole areas isthmus telephone exchange

origin and spatial distribution of gas at seismogenic depths of the san andreas fault from drill mud gas analysis abstract data are presented on the molecular composition of drill mud gas from the lower sedimentary section 1800 3987 m of the safod san andreas fault observatory at depth main hole measured on line during drilling as well as c and h isotope data from off line mud gas samples hydrocarbons h 2 and co 2 are the most abundant non atmospheric gases in drill mud when drilling seismogenic zones gas influx into the well at depth is related to the lithology and permeability of the drilled strata larger formation gas influx was detected when drilling through organic rich shales and permeable sandstones the saf san andreas fault encountered between approximately 3100 m and 3450 m borehole depth is generally low in gas but is encompassed by two gas rich zones 2700 2900 m and below 3550 m at the fault margins with enhanced 222 rn activities and distinct gas compositions within the fault two interstratified gas rich lenses 3150 3200 m and 3310 3340 m consist of co 2 and hydrocarbons upper zone but almost exclusively of hydrocarbons lower zone the isotopic composition indicates an organic source of hydrocarbons and co 2 in the entire sedimentary section of the well hydrocarbons in sedimentary strata are partly of microbial origin down to 2500 m borehole depth the contribution of thermogenic gas increases between 2500 m and 3200 m below 3200 m hydrocarbons fully derive from thermal degradation of organic matter the lack of h 2 in the center of the fault and the high concentration of h 2 in the fractured zones at the fault margins are consistent with h 2 formation by interaction of water with fresh silica mineral surfaces generated by tectonic activities however this needs to be verified by laboratory experiments based on these studies it is concluded that the fault zone margins consist of strata with enhanced permeability separated by a low permeability fault center

different tdm ch4 hydrothermal plume signatures tag site at 26 n and serpentinized ultrabasic diapir at 15 05 n on the mid atlantic ridge as a part of the 1988 noaa vents program ch4 and mn tracers were used to identify and compare hydrothermal plumes found above the tag field 26 n and in the rift valley at 15 n close to the eastern intersection of the ridge axis with the 15 20 n fracture zone at the mid atlantic ridge mar active hydrothermal venting was confirmed at tag based on elevated concentrations of total dissolved mn tdm up to 30 nmol kg high ch4 concentrations up to 200 nl l and elevated nephelometry signals plumes of a different composition were identified at 15 n with high ch4 concentrations up to 400 nl l low total dissolved mn concentrations tdm 1 nmol kg and no significant nephelometry signal the different properties of these tracers and the different tracer ratios can be used to deduce vent fluid characteristics and compare one hydrothermal area to another tdm ch4 and nephel ch4 ratios at tag are of the same order of magnitude as those observed at other spreading axis hydrothermal fields at 15 n the low tdm ch4 ratio provides evidence of fluid circulation into ultrabasic rocks and offers a potentially useful and single method of exploring for hydrothermal activity associated with serpentinization mantle degassing through hydrothermal activity associated with serpentinization is an important process with respect to chemical and thermal exchanges between the upper mantle and the ocean different ratios of hydrothermal tracers i e tdm ch4 provide a useful framework for identifying subseafloor processes along mid oceanic ridges

new evidence for the form and extent of the pernicana fault system mt etna from structural and soil gas surveying a multidisciplinary study based on structural and soil gas surveys was carried out in order to investigate the relationship between soil co2 degassing and the tectonic setting of the lower northeastern flank of mt etna volcano the results show that anomalous soil co2 emissions occur mainly along faults trending wnw ese and also where these faults intersect the other main fault set trending ne sw that displaces the study area in particular anomalies in co2 degassing were revealed both along the pernicana fault and along another fault fiumefreddo fault which may represent the prolongation of the former towards the ionian sea coast in the areas where these structures show evident surface faulting they are all characterised by left lateral displacements and aseismic creep behaviour furthermore the geochemical survey revealed that these faults join in an area devoid of geological evidence of surface faulting and continue underneath an apparently unfaulted alluvial cover near the coastline in the light of these findings we suggest that the pernicana and fiumefreddo faults are discrete segments of a near continuous left lateral shear zone affecting the whole north eastern flank of mt etna as far as the ionian coast

origin and coseismic behavior of mineral spring gas at byakko japan studied by automated gas chromatographic analyses abstract the origin and coseismic behavior of mineral spring gas were examined on the basis of continual monitoring data for several gas species the automatic monitoring system used in this study consists of two gas chromatographs and a personal computer several gas species can simultaneously be analyzed with these analyzers the system was so stable and sensitive that minute coseismic anomalies in these species could be detected a positive correlation between n 2 ar and ch 4 ar implies that the mineral spring gas is a mixture of atmospheric air and lithospheric gas the lithospheric gas is mainly composed of n 2 and ch 4 and also contains trace amounts of he it is inferred from isotopic data that lithospheric n 2 and ch 4 are thermogenic and he is mostly radiogenic in contrast o 2 and h 2 in trace amounts show large diurnal fluctuations suggesting that these species should be mostly biogenic ten earthquakes felt around the station occurred during the monitoring period and four of them coincided with coseismic anomalies in the he ar ratio the anomalies may be interpreted as follows by the ground motion at these felt quakes he accumulated in the ground was additionally released into the spring water the continual monitoring of these gas species enables us to discuss in detail the origin and behavior of the spring gas and to evaluate background noise of the data

late pleistocene granodiorite source for recycled zircon and phenocrysts in rhyodacite lava at crater lake oregon abstract rhyodacite tephra and three lavas erupted 27 ka interpreted to be early leaks from the climactic magma chamber of mount mazama contain ubiquitous resorbed crystals antecrysts that were recycled from young granodiorite and related plutonic rocks of the same magmatic system the shallow composite pluton is represented by blocks ejected in the 7 7 ka climactic eruption that formed crater lake caldera plagioclase crystals in both rhyodacite and granodiorites commonly have cores with crystallographically oriented fe oxide needles exsolved at subsolidus conditions at least 80 of plagioclase crystals in the rhyodacite are antecrysts derived from plutonic rocks other crystals in the rhyodacite notably zircon also were recycled sims 238 u 230 th dating indicates that zircons in 4 granodiorite blocks crystallized at various times between 20 ka and 300 ka with concentrations of analyses near 50 70 110 and 200 ka that correspond to periods of dacitic volcanism dated by k ar u th ages of zircon from a rhyodacite sample yield similar results no analyzed zircons from the granodiorite or rhyodacite are pre quaternary zircon minimum ages in blocks from different locations around the caldera reflect ages of nearby volcanic vents and may map the distribution of intrusions within a composite pluton survival of zircon in zircon undersaturated hydrous magma and of fe oxide needles in plagioclase suggests that little time elapsed from entrainment of antecrysts to the 27 ka eruption of the rhyodacite the 27 ka rhyodacite is an example of young silicic magma that preserved unstable antecrysts from a known source early during growth of a large high level magma chamber in contrast the voluminous 7 7 ka climactic rhyodacite pumice is virtually lacking in zircon indicating dissolution of any granodioritic debris in the intervening period mineralogical evidence of assimilation may be destroyed in hot vigorously growing silicic magma bodies such as ultimately produced the climactic eruption of mount mazama

monitoring of hydrogen along the san andreas and calaveras faults in central california in 1980 1984 hydrogen h2 has been monitored continuously at 1 5 m depth at nine sites along the san andreas and calaveras faults in central california since december 1980 site characteristic small noninstrumental diurnal variations were recorded during quiescent periods at most sites abrupt h2 changes were observed concurrently at two sites on the calaveras fault some of these were correlated with oscillatory fault slips large 1000 4000 ppm h2 increases were recorded at some sites on the san andreas fault between july 1982 and november 1983 which may be correlated with eleven m 5 earthquakes that occurred near coalinga during this period we attribute both the h2 increases and the triggering of the earthquakes to a large scale compressive stress field within the ductile mafic crust near the plate boundary the stress perhaps caused bulging of the base of the brittle upper crust and thus caused dilation of the san andreas fault zone allowing the escape of pent up h2 generated by hydration reaction of the mafic crust at the same time mobile serpentinites may have squeezed into the seismogenic fault beneath the coalinga area triggering the earthquakes

fluid circulation at stromboli volcano aeolian islands italy from self potential and co2 surveys this work addresses the study of fluid circulation of the stromboli island using a dense coverage of self potential sp and soil co2 data a marked difference exists between the northern flank and the other flanks of the island the northern flank exhibits 1 a typical negative sp altitude gradient not observed on the other flanks and 2 higher levels of co2 the general sp pattern suggests that the northern flank is composed of porous layers through which vadose water flows down to a basal water table in contrast to the other flanks where impermeable layers impede the vertical flow of vadose water in the sciara del fuoco and rina grande le schicciole landslide complexes breccias of shallow gliding planes may constitute such impermeable layers whereas elsewhere poorly permeable fine grained pyroclastites or altered lava flows may be present this general model of the flanks also explains the main co2 patterns concentration of co2 at the surface is high on the porous north flank and lower on the other flanks where impermeable layers can block the upward co2 flux the active upper part of the island is underlain by a well defined hydrothermal system bounded by short wavelength negative sp anomalies and high peaks of co2 these boundaries coincide with faults limiting ancient collapses of calderas craters and flank landslides the hydrothermal system is not homogeneous but composed of three main subsystems and of a fourth minor one and is not centered on the active craters the latter are located near its border this divergence between the location of the active craters and the extent of the hydrothermal system suggests that the internal heat sources may not be limited to sources below the active craters if the heat source strictly corresponds to intrusions at depth around the active conduits the geometry of the hydrothermal subsystems must be strongly controlled by heterogeneities within the edifice such as craters caldera walls or gliding planes of flank collapse as suggested by the correspondence between sp co2 anomalies and structural limits the inner zone of the hydrothermal subsystems is characterized by positive sp anomalies indicating upward movements of fluids and by very low values of co2 emanation this pattern suggests that the hydrothermal zone becomes self sealed at depth thus creating a barrier to the co2 flux in this hypothesis the observed hydrothermal system is a shallow one and it involves mostly convection of infiltrated meteoric water above the sealed zone finally on the base of co2 degassing measurements we present evidence for the presence of two regional faults oriented n41 and n64 and decoupled from the volcanic structures

episodic growth and homogenization of plutonic roots in arc volcanoes from combined u th and u th he zircon dating abstract tracing the fate of unerupted magma is challenging because plutonic roots of young volcanoes are largely inaccessible here we develop the use of zircon age spectra to determine crystal provenance and source rocks for volcanic products in analogy to detrital crystals in sediments u th zircon crystallization ages for the soufriere volcanic complex saint lucia lesser antilles frequently predate their eruption as determined from combined u th and u th he zircon dating the oldest dated eruptions are 273 15 ka and 264 8 ka 1 uncertainty for morne bonin dacite and bellevue pumice deposit respectively the most recent eruptions formed morphologically pristine domes in the center of the qualibou depression belfond 13 6 0 4 ka terre blanche 15 3 0 4 ka u th u pb zircon crystallization ages determined for crystal rims and interiors range between near eruption ages to 600 ka older xenocrysts are absent zircon crystallization age distributions are complex yet systematic crystal rim ages in the most recently erupted volcanic rocks match those of co erupted plutonic inclusions whereas crystal interiors are equivalent to the cumulative distribution of zircon ages from older eruptions this is evidence that silicic lava domes and pyroclastic flows share a common source that is located underneath the qualibou depression where the intrusive roots of this long lived arc volcanic system became homogenized through thermal and mechanical reprocessing of individual batches of unerupted magma from earlier volcanic episodes within timescales of

a comparison of plug derived and probe derived permeability in cross bedded sandstones of the virgelle member alberta canada the influence of flow directions on probe permeametry in this article we compare permeability measured on radially confined cylindrical plugs to permeabilities measured using a millimeter scale probe tip on unconfined end faces of the same plugs our investigation focuses on directional attributes of probe permeametry data as a means to understand the differences between plug scale and probe scale permeability magnitudes horizontal and vertical plug and probe flow tests were carried out on fine to medium grained three dimensional 3 d cross bedded sandstones collected from estuarine channel successions within the cretaceous age virgelle member at writing on stone provincial park southern alberta canada the sandstones are heterogeneous in that they contain thin discontinuous micaceous carbonaceous laminae and apparent bedding parallel grain scale fabric the resulting probe derived permeabilities 0 4 3 5 d are mostly higher than corresponding plug permeabilities 0 5 1 6 d and mean probe derived permeability anisotropy is significantly lower than that derived from plug scale measurements that is plug k v k h is less than probe derived k v k h the results can be understood as a consequence of the model flow geometry of probe flow tests goggin et al 1988 namely that flow is preferentially directed parallel to the sample surface radially outward from the probe tip on end faces of vertical plugs the bedding parallel fabric further enhances flow parallel to the sample surface and probe measurements yield reliable estimates of horizontal permeability having magnitudes comparable to the permeability of equivalent horizontal plugs for probe measurements on end faces of horizontal plugs flow paths appear to be variably confined parallel to bedding as a function of grain scale and laminae scale fabric systematically yielding an overestimate of horizontal permeability k prh k plh interpretation of probe data in this orientation however is very uncertain due to partitioning of flow paths parallel to and at angle to bedding significantly almost all probe permeameter core and outcrop studies are based on measurements of this type

hydrogen gas of organic origin in shales and metapelites abstract the changes in inorganic and organic gases retained in shales and metapelites with increasing heating temperature are not fully understood the compositional and isotopic changes of residual gases such as h 2 ch 4 and co 2 in marine shales and metapelites during burial diagenesis and metamorphism were investigated in the present study shale rocks and metapelites which experienced paleo temperatures in the range of 100 600 c were collected from the borehole cores in niigata sedimentary basin and outcrops exposed in kochi district japan gases released from shale or metapelite fragments during pulverization in the laboratory were analyzed as the residual gas the major residual gas in shales and metapelites changes from co 2 ch 4 to h 2 in this order with increasing temperature drastic decrease of co 2 derived from decarboxylation of sedimentary organic matter is due to the expulsion of pore fluids with dissolved co 2 the ch 4 concentration in residual gas subsequently increases with organic maturation and reaches the maximum at paleo temperature of ca 250 c the ch 4 concentration decreases during late metagenesis to metamorphism probably due to the formation of h 2 gas and graphite the h 2 starts to increase at paleo temperature of ca 200 c the h 2 gas is the most abundant gas in residual gas of metapelite the 2 value of h 2 in shales and metapelites is quite low to be in the range of ca 850 to 650 the change of major residual gas from ch 4 to h 2 with increasing paleo temperature and the significantly low 2 h values of h 2 suggest that h 2 gas in shales and metapelites is largely derived from liberation of hydrogen in organic matter

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

analysis of co2 leakage through low permeability faults from natural reservoirs in the colorado plateau east central utah the numerous co 2 reservoirs in the colorado plateau region of the united states are natural analogues for potential geologic co 2 sequestration repositories to better understand the risk of leakage from reservoirs used for long term underground co 2 storage we examine evidence for co 2 migration along two normal faults from a reservoir in east central utah co 2 charged springs geysers and a hydrocarbon seep are localised along these faults these include natural springs that have been active for long periods of time and springs that were induced by recent drilling the co 2 charged spring waters have deposited travertine mounds and carbonate veins the faults cut siltstones shales and sandstones and the fault rocks are fine grained clay rich gouge generally thought to be barriers to fluid flow the geologic and geochemical data are consistent with these faults being conduits for co 2 to the surface consequently the injection of co 2 into faulted geologic reservoirs including faults with clay gouge must be carefully designed and monitored to avoid slow seepage or fast rupture to the biosphere

alteration and mass transfer in cataclasites and mylonites in 6 6 km of granitic crust at the siljan impact structure central sweden granitic rocks deformed by cataclasis and mylonitization on macro a few meters and micro thin section scales are found at depths down to 6 6km in the siljan impact structure in central sweden granites near fault planes exhibit 1 fracturing kinking fragmentation and recrystallization of feldspars into pure k and na endmember varieties 2 fragmentation polygonization and development of undulose extinction in quartz and 3 kinking appearance of wavy extinction and alteration of biotite chlorite amphibole and alteration of ilmenite and magnetite whole rock chemical analyses of deformed and undeformed rocks show that deformed rocks are enriched in sio2 by about 5 wt and depleted in other oxides by variable percentages apart from rb and co the concentrations of other trace elements including ba sr zn zr pb cd cu cr ni v u th la and li are lower in deformed relative to undeformed rocks mass balance calculations for a 1000 cm3 model granite which were based on modal mineralogy whole rock chemistry and mineral analyses suggest that the break down of primary biotite chlorite and amphibole in deformed zones released elements to circulating fluids these calculations also indicate liberation of water and a doubling of porosity from 1 to 2 during the deformation episodes later precipitation of minerals in shear and tension fractures reduced this porosity within the upper 2000 m of the gravberg 1 well the formation of fracture filling minerals smectite calcite hematite chlorite and albite is impact related and was favored by active circulation of meteoric water fracture filling minerals in the upper 2000 m of the borehole formed at temperatures of 70 to 200 c between depths of 2000 and 3500 m fracture filling mineral assemblages dominated by fe mg chlorite sphene and epidote suggest formation temperatures in the range of 150 to 300 c occurrence of pumpellyite and prehnite in some altered biotite and chlorite of the deformed zones between 3500 and 5500 m suggest preimpact metamorphism and formation temperature above 150 c below 5500 m the mineral assemblages in the fractures are dominated by quartz sphene epidote and some muscovite and chlorite indicating a temperature range between 300 and 450 c one of the possible origins for the ch4 and h2 gases detected in the gravberg 1 well is a combination of hydrogen ions released by decomposition of hydrated silicates biotite chlorite hornblende with carbon the presence of iron in the deformed granitic rocks prevented the resulting ch4 from being oxidized

natural h2 in kansas deep or shallow origin a geochemical study of gas coming from three wells in northeastern kansas supplements previous studies from the 1980s and points to a persistent regional phenomenon of h2 production in 2008 a new well showed just after drilling a free gas phase with more than 80 mole of h2 followed by water production associated with gas this gas is mainly composed of n2 he h2 and occasionally ch4 with changing proportions through time a drastic decrease in h2 at the well was observed since the aquifer is produced along with occasional recharges in h2 evidenced notably in the early phases of gas sampling we demonstrate that this evolution of gas composition is closely associated to the well completion story accordingly two distinct origins of h2 are proposed 1 deep crustal h2 water reduction associated to iron oxidation in the precambrian basement 2 reactions occurring in the tubing primarily attributed to high contents of reduced iron and or dissolved organic carbon doc 4 1 mg l 1 in the water the low d values averaging 760 are attributed to a low temperature process possibly a re equilibration with water furthermore the suggested origins are supported by the observed gas associations a deep crustal h2 with radiogenic gases 4he and 40ar and metamorphic n2 15n averaging 2 5 b surficial h2 with methane produced in the sedimentary aquifer and the tubing by methanogenic organisms

anomalous hydrogen emissions from the san andreas fault observed at the cienega winery central california we began continuous monitoring of h2 concentration in soil along the san andreas and calaveras faults in central california in december 1980 using small h2 o2 fuel cell sensors ten monitoring stations deployed to date have shown that anomalous h2 emissions take place occasionally in addition to diurnal changes among the ten sites the cienega winery site has produced data that are characterized by very small diurnal changes a stable baseline and remarkably distinct spike like h2 anomalies since its installation in july 1982 a major peak appeared on 1 10 november 1982 and another on 3 april 1983 and a medium peak on 1 november 1983 the occurrences of these peaks coincided with periods of very low seismicity within a radius of 50 km from the site in order to methodically assess how these peaks are related to earthquakes three h2 degassing models were examined a plausible correlational pattern was obtained by using a model that 1 adopts a hemicircular spreading pattern of h2 along an incipient fracture plane from the hypocenter of an earthquake 2 relies on the feo h2o reaction for h2 generation and 3 relates the accumulated amount of h2 to the mass of serpentinization of underlying ophiolitic rocks the mass was tentatively assumed to be proportional to the seismic energy of the earthquake

geogas transport in fractured hard rock correlations with mining seismicity at 3 54 km depth tautona gold mine south africa abstract an on site gas monitoring study has been conducted in the framework of an earthquake laboratory the international nelsam dafgas projects at the tautona gold mine south africa five boreholes up to 60 m long were drilled at 3 54 km depth into the highly fractured pretorius fault zone and instruments for chemical and seismic monitoring installed therein over the span of 4 years sensitive gas monitoring devices were continuously improved to enable the direct observation of geogas concentration variations in the dafgas borehole the major gas concentrations are constant and air like with about 78 n 2 21 o 2 1 ar the geogas components co 2 ch 4 he and h 2 show the most interesting trends and variations on the minute by minute basis and significantly correlate with seismic data while the 222 rn activity remains constant time series and cross correlation analysis allow the identification of different gas components geogas and tunnel air and the identification of two processes influencing the borehole gas composition 1 pumping induced tunnel air breakthrough through networks of initially water saturated fault fractures and 2 seismicity induced permeability enhancement of fault fractures to above 5 10 10 m 2 the current set up of the gas monitoring system is sensitive enough to quantify the resulting geogas transport during periods of intense blasting activities including recorded blasts with seismic moment 1 10 9 nm located within 1000 m of the cubby and it is suggested also during induced earthquakes a final goal of the project

statistical approach for the geochemical signature of two active normal faults in the western corinth gulf rift greece abstract soil gas measurements of different gas species were performed in two distinct areas of the corinth gulf rift greece the aigion neos erineos lambiri anel fault zone and the rion patras fault zone both zones lie in one of the most seismically active areas of the euro mediterranean region where a fast opening continental rift is located in particular the geochemical investigations were focused on fault segments and fracture systems previously inferred by geomorphological lithological and structural studies in this work the applicability of soil gas geochemistry surveys for the exploration of buried hidden faults was tested by using various statistical methods moreover a comprehensive geostatistical treatment of the collected data provided new insights into the control exerted by active structures on deep seated gas migration towards the surface in both investigated areas the highest 222rn and co2 concentration peaks correspond with zones where the interaction among fracture and fault segments was inferred by structural and morphological methods this indicates a clear correlation between the shape and orientation of the anomalies and the different attitude and kinematic behavior of the faults recognized in the two areas furthermore obtained results show that gases migrate preferentially through zones of brittle deformation by advective processes as suggested by the relatively high rate of migration needed to obtain anomalies of short lived 222rn in the soil pores

zircon growth and recycling during the assembly of large composite arc plutons abstract concordant u pb zircon dates have been interpreted traditionally to date the crystallization ages of plutons because until recently analytical uncertainties have generally been large enough to encompass the anticipated duration of pluton growth advances in zircon tims analysis and geochronological studies by sims on zircon from young volcanic rocks along with evolving views of the evolution of magmatic systems makes it necessary to revaluate this interpretation assignment of unique pluton crystallization ages based on zircon dating is complicated by the propensity of zircon to survive multiple intrusive events that culminate in a large pluton distinctions must be made between true inherited zircon xenocrystic zircon derived from host rocks during magma ascent and or emplacement and multi stage growth of zircon during waxing and waning of magma reservoirs that solidify to form large plutons these complications are exemplified by recent high precision u pb zircon age dating from the cretaceous tuolumne and mt stuart batholiths which clearly show that the timeframe of pluton assembly was long 5 ma for mt stuart and 8 ma for tuolumne zircon crystals from samples from both batholiths exhibit appreciable concordant age dispersion for zircon several 10 5 yr up to 2 10 6 yr and assignment of statistically valid rock solidification ages is not possible from these data low zr in the rocks of each batholith indicates that magmas were initially strongly undersaturated in zircon when emplaced and inherited zircon is rare or absent recycling of zircon antecrysts during successive magmatic injections is the primary cause of the modest age dispersion of concordant zircon ages and is compatible with progressive growth of a large long lived crystal mush body because eruption of magma requires low to moderate crystal fraction and high temperatures relative to stored crystal mushes zircon crystals are more likely to be eradicated during thermal rejuvenation preceding major eruptions

geochemical precursors to seismic activity studies of earthquake precursory phenomena during the last several decades have found that significant geophysical and geochemical changes can occur prior to intermediate and large earthquakes among the more intensely investigated geochemical phenomena have been 1 changes in the concentrations of dissolved ions and gases in groundwaters and 2 variations in the concentrations of crustal and mantle volatiles in ground gases the concentration changes have typically showed no conanomalies trend either increasing or decreasing and the spatial and temporal distribution of the observed anomalies have been highly variable as a result there is little agreement on the physical or chemical processes responsible for the observed anomalies mechanisms proposed to account for precursory groundwater anomalies include ultrasonic vibration pressure sensitive solubility pore volume collapse fracture induced increases in reactive surfaces and aquifer breaching fluid mixing precursory changes in soil gas composition have been suggested to result from pore volume collapse micro fracture induced exposure of fresh reactive silicate surfaces and breaching of buried gas rich horizons an analysis of the available field and laboratory data suggests that the aquifer breaching fluid mixing ab fm model can best account for many of the reported changes in temperature dissolved ion and dissolved gas concentrations in groundwater ultrasonic vibration and pressure sensitive solubility models cannot reasonably account for the geochemical variations observed and although the pore collapse model could explain some of the observed chemical changes in groundwater and ground gas uncertainties remain regarding its ability to generate anomalies of the magnitude observed other geochemical anomalies in particular those associated with hydrogen and radon seem best accounted for by increases in reactive surface areas irsa model that may accompany precursory deformation around the epicenter of an impending earthquake analysis of the probable response of these models to the earthquake preparation process as well as to other environmental factors suggests that geochemical monitoring programs can provide information that may be valuable in forecasting the probability of an earthquake however because of the complexity of the earthquake preparation process the absolute prediction of seismic events using geochemical methods alone does not presently appear to be feasible

rock comminution as a source of hydrogen for subglacial ecosystems microbes live under glaciers that have persisted for millions of years without a clear energy supply analyses of crushed rocks suggest that interactions of glaciers with the rocks beneath can produce enough h2 to support methanogenic bacteria substantial parts of the beds of glaciers ice sheets and ice caps are at the pressure melting point1 the resulting water harbours diverse subglacial microbial ecosystems2 3 capable of affecting global biogeochemical cycles4 5 such subglacial habitats may have acted as refugia during neoproterozoic glaciations6 however it is unclear how life in subglacial environments could be supported during glaciations lasting millions of years because energy from overridden organic carbon would become increasingly depleted7 8 here we investigate the potential for abiogenic h2 produced during rock comminution to provide a continual source of energy to support subglacial life we collected a range of silicate rocks representative of subglacial environments in greenland canada norway and antarctica and crushed them with a sledgehammer and ball mill to varying surface areas under an inert atmosphere in the laboratory we added water and measured h2 production with time h2 was produced at 0 c in all silicate water experiments probably through the reaction of water with mineral surface silica radicals formed during rock comminution h2 production increased with increasing temperature or decreasing silicate rock grain size sufficient h2 was produced to support previously measured rates of methanogenesis under a greenland glacier we conclude that abiogenic h2 generation from glacial bedrock comminution could have supported life and biodiversity in subglacial refugia during past extended global glaciations

resistivity structure of a seismic gap along the atotsugawa fault japan abstract seismicity along the atotsugawa fault located in central japan shows a clear heterogeneity the central segment of the fault with low seismicity is recognized as a seismic gap although a lot of micro earthquakes occur along this fault in order to elucidate the cause of the heterogeneity in seismicity the electrical resistivity structure was investigated around the atotsugawa fault by using the magnetotelluric mt method the regional geoelectrical strikes are approximately parallel to the fault in a low frequency range we constructed two dimensional resistivity models across the fault using tm mode mt responses to minimize three dimensional effects on the modeling process a smooth inversion algorithm was used and the static shifts on the apparent resistivity were corrected in the inversion process a shallow low resistivity zone along the fault is found from the surface to a depth of 1 2 km in the best fit model across the high seismicity segment of the fault on the other hand the corresponding low resistivity zone along the low seismicity segment is limited to a shallower depth less than 1 km the low resistivity zone along the atotsugawa fault is possibly due to fluid in the fracture zone the segment with higher levels of seismicity may have higher fluid content in the fault zone compared with the lower seismicity segment on a view of the crustal structure a lateral resistivity variation in a depth range of 3 12 km is found below the fault trace in the high seismicity segment while a resistive layer of wide extent is found at a depth of about 5 km below the fault trace in the low seismicity segment the resistive layer is explained by less fluid condition and possibly characterized as high rigidity differences in the resistivity structures between low and high seismicity segments of the fault suggest that the seismic gap in the central part of the atotsugawa fault may be interpreted as a locked segment thus mt is an effective method in evaluating a cause and future activity of seismic gaps along active faults the lower crust appears as a conductive zone beneath the low seismicity segment less conductive beneath the high seismicity segment fluid is inferred as a preferable cause of the conductive zone in this study it is suggested that the conductive lower crust beneath the low seismicity segment is recognized where fluid is trapped by an impermeable layer in the upper crust on the other hand fluid in the lower crust may upwell to the surface along the high seismicity segment of the fault

vertical and horizontal permeability variation within a sandstone reservoir based on minipermeameter measurements abstract the drilling and coring through the entire reservoir interval in two wells separated by 570 m presented the opportunity to carry out mini probe permeametry measurements on comparable reservoir zones the reservoir sandstones were deposited in a shallow marine tidally influenced environment and consist of alternating fine grained micaceous wackes to coarser grained high permeable subarkosic arenites statistical analysis of the data had three main objectives 1 correlation between lithofacies and permeability 2 characterization of vertical and horizontal permeability variation at the reservoir and reservoir zone scale and 3 to study relationships between core plug and minipermeameter measurements nine lithofacies types are recognized in the cores ranging from massive homogeneous sandstones through to fine grained micaceous sandstones with varying degrees of bioturbation a good correlation is found between minipermeameter measurements and lithofacies variograms at the reservoir and reservoir zone scales show similar trends vertically and horizontally between wells variance in core plug data is greater than that for minipermeametry data permeability as measured by minipermeametry is significantly higher than core plug measurements although overall trends are similar in the two data sets there is generally better agreement between plug and minipermeameter measurements for the highly permeable homogeneous sandstones than for the fine grained micaceous sandstones with relatively low permeability

hydrocarbon gases in the crystalline rocks of the gravberg 1 well swedish deep gas project abstract desorbed gas analyses of cuttings from the gravberg 1 well the culmination of the swedish deep gas project were undertaken every 100 m from 219 to 5907 m a sample at 6517 m from sidetrack 2 was also included the desorbed gas method performed by hot acid treatment in an evacuated system was superior to both ball mill crushing and thermodesorption methods two types of hydrocarbon gases were found in trace quantities one type associated with the dolerite sills was an isotopically heavy 13 c 1 11 to 15 dry gas with a methane content up to 98 the other type occurring throughout the granitic rocks was an isotopically lighter gas 13 c 1 21 to 39 containing 30 45 of c 2 c 4 olefins and paraffins were present in almost equal amounts in the second type of gas the dry gas observed in the dolerites is assumed to be abiogenic gas existing in inclusions of basic minerals which react with acid during the analytical procedure the other type of hydrocarbon gas is thought to be formed from h 2 and co 2 by a catalytic reaction since it is mainly associated with the magnetic fraction of the rock a fischer tropsch reaction over a magnetite catalyst is the most likely reaction since it produces both paraffins and olefins studies on thin sections of cores and coarse cuttings suggest that the wet gas is not isolated in inclusions and the changes with time observed for a few thin sections indicate that it diffuses quite freely the potential risks of contamination from drilling fluids and bit metamorphism were examined by comparing the hydrocarbon results with changes in the mud system rate of penetration and bit life hydrocarbon analyses of a few mud additives were included as well the result of these examinations plus the results of hydrocarbon analyses of cores from pilot core holes in the siljan crater suggest that the hydrocarbons observed in the cuttings are indigeneous comparing the results of the present study with other hydrocarbon occurrences outside of the siljan crater indicates that the hydrocarbons found in the gravberg 1 well occur widespread in crustal rocks

chemical signature detection of groundwater and geothermal waters for evidence of crustal deformation along fault zones abstract common crustal igneous and high grade metamorphic rocks contain peroxy defects which remain dormant until the rock experiences stress upon deformation stress activated peroxy defects form highly reactive oxygen species ros at the rock water interface observed in both terrestrial and extraterrestrial rock samples the ros complex is formed upon rock fluid interaction when groundwater combines with the ros to produce hydrogen peroxide giving an indirect measure of the underlying rock stress and crustal deformation along active faults the average concentration of hydrogen peroxide from the sohna thermal spring water falling along the active sohna fault and geothermal field was measured to be 0 53 0 014 mg l similar average concentration was also recorded from borewell sample north of the spring 0 56 0 017 mg l within the same geothermal field lower concentration of hydrogen peroxide was recorded within samples collected from hard rock aquifers outside the geothermal field and the active fault zone 0 138 0 095 mg l the detailed analysis suggests that the presence of hydrogen peroxide is largely dependent on the circulation pattern through the interconnected fractures joints within the quartzite bedrock lying adjacent to the fault plane laboratory analysis results also show high hydrogen peroxide concentration within two borewell samples falling adjacent to the epicentre of a shallow microtremor event within the hard rock region falling alongside a lineament along the delhi hard rock mega fold rock water interaction post stress activation of peroxy defects and formation of ros has therefore been inferred to be responsible for the formation of hydrogen peroxide at the rock water interface within these zones this pilot study provides scientific field evidence that hydrogen peroxide concentrations within groundwaters might offer prospects for seismic stress estimation and crustal deformation along seismically active zones

gases and helium isotopes in high temperature solutions sampled before and after odp leg 158 drilling at tag hydrothermal field 26 n mar hydrothermal fluids were sampled for dissolved gases at tag 26 n mar during two alvin dive series in april may 1993 and march 1995 respectively 17 months before and 4 months after ocean drilling program leg 158 total gas volumes extracted from the 1993 and 1995 samples are of the same order of magnitude even if some increase in h2s c02 and ch4 was noticeable in the 1995 samples no significant difference was observed in helium concentration and helium isotopic ratio 3 he 4 he 8 2 0 1 ra the ch4 3 he ratio found in black smokers sampled in 1993 is around 9 x 10 6 close to ratio found in mar basalts in 1995 this ratio is around 4 times higher due to the ch4 increase the 13 c in c02 measured on two black smokers sampled in 1993 is uniform at 8 4 to 8 8 versus pdb while a 13 c value of 13 is measured at a new site sampled in 1995 located 40 meters east of the main black smokers complex bsc ch4 3 he and 13 c values both point to a mainly magmatic abiogenic origin of the carbon species in the system overall comparison of the 1993 and 1995 data suggests that the hydrothermal circulation is continuing through the basaltic layer carrying helium c02 and ch4 of magmatic origin even if some thermogenic ch4 contribution seems likely in the 1995 samples collected in the new active area we can speculate that the 1994 drilling may have modified the previously steady state hydrothermal circulation in the tag mound and temporarily enhanced the hydrothermal circulation by opening new pathways favouring transient input of ch4 rich fluids before coming back to a new steady state

origin of hydrogen and carbon dioxide in fault gases and its relation to fault activity gases occluded in fracture zones of active faults are characterized by a high concentration of h 2 and or co 2 a predominant gas species h 2 or co 2 is related to the lithofacies which the fault cuts carbon dioxide concentration in sediments fluctuates with temperature this evidence and sigma 13 c of co 2 about 20 suggests that co 2 originates from organic materials carbon dioxide with sigma 13 c of 5 to 17 in brecciated gneiss containing marble may have been produced by interaction between organically derived co 2 and the marble or alternatively may have been magmatically derived hydrogen usually occurs in sheared silicate rocks and its concentration fluctuates a great deal the concentration of h 2 from active faults associated with historical earthquakes usually amounts to as high as several percent in maximum whereas the concentration of h 2 from quaternary faults not associated with historical earthquakes is at most 1

petrogenesis of the basalt andesite dacite association of grenada lesser antilles island arc revisited the basalt andesite dacite association of grenada is produced by fractional crystallization of primary magmas that contain about 15 weight percent mgo and 1 2 weight percent h2o the compositions of primary magmas indicate that they were last in equilibrium with the mantle at depths greater than about 65 km indicating that they must ascend rapidly after they segregate from residual mantle it is inferred that mantle wedge diapirism typically leads to moderately large degrees of batch partial melting in the formation of primary arc magmas 10 30 the trace element geochemical diversity of primary magmas mainly reflects variable degrees of source region enrichment by fluids derived from the subducted slab the degree to which source regions are enriched is likely related to mantle wedge dynamics water pressure suppresses plagioclase crystallization in derivative magmas leading to development of the calc alkaline rather than tholeiitic differentiation trend amphibole crystallization typically occurs only after melt mgo content decreases below about 4 weight percent the island arc crust acts as a density filter as arc crust thickens parental basaltic magmas will have a greater tendency to stagnate at mid crustal levels the observation that basalts predominate in young island arcs while andesites and dacites predominate in more mature arcs is explained by this hydrostatic control the thicker the arc crust the more magmas must differentiate by crystal segregation to become buoyant enough to erupt at the surface

first hydroacoustic evidence of marine active fluid vents in the naples bay continental shelf southern italy abstract we present the first results of a multidisciplinary research aimed at the detection and mapping of active fluid vents afvs at the seafloor of the naples bay italy this segment of the campania continental margin is characterised by severe quaternary extension and intense volcanism at ischia and procida islands the campi flegrei and somma vesuvius volcanic complexes high resolution hydroacoustic profilers were used to identify and localize fluid emission from the seafloor rov direct observation showed that each emission centre is generally composed by the coalescence of several emitting points ctd probes showed that there are no significant gradients in temperature profiles the results of this study include the detection and mapping of 54 fluid emission points all located in the 71 158 m depth range and spatially distributed into four main clusters three of the described clusters are located along the margin of a complex toe shaped seafloor morphology southwest of the somma vesuvius representing the shallow expression of partly buried coalesced depositional features namely two flank collapses and one pyroclastic flow associated with the late pleistocene activity of the volcano the fourth afv cluster was detected at the morphological high located about 8 km south of naples banco della montagna represented by a field of volcaniclastic diapirs composed of massive pumiceous deposits originated from the campi flegrei intruding rising through the latest quaternary holocene marine deposits our study suggests that the occurrence of afv in this area could be genetically linked to the interaction between volcanic related seafloor morphologies and the main ne striking faults present in the area i e the magnaghi sebeto line and the vesuvian fault

gas geochemistry and seismotectonics a review abstract publications on soil and spring gases have been examined regarding their relationships with both tectonic and seismic activities the main sources behaviours and uses of species detected in soils and springs are displayed and their mode of sampling and analysing briefly described the main patterns of degassing in soils are described and we outline the wide range of geochemical signatures as the result of both permeability and mineralogical contrasts because thermomineral waters have been in contact with great volumes of crustal rocks at various depths spring gases might be more representative of the local environment than soil gases moreover gas signature comparisons show that spring gases are much more enriched with deep gases and slightly contaminated by atmospheric gases therefore they can be considered as better samples for identifying precursors of earthquakes environmental perturbations are examined and it is shown from divergent cases that pressure temperature soil moisture or earth tides may generate very high perturbations of the degassing process such effects demonstrate that no systematic correction law can be proposed and that removing external contributions from gas concentrations must be performed case by case this demonstrates therefore the need for the simultaneous measurement of external parameters during gas monitoring a qualitative examination of about 150 claimed precursors proposed in the literature has been reviewed as noted by previous authors anomalies appear at distances sometimes much greater than typical source dimensions and occur in the field of strain higher than 10 9 most of them being in the field of strain higher than 10 8 taking into account the very high heterogeneity of such a set of data we can suggest that amplitudes of gas anomalies are independent of both magnitudes and epicentral distances of related earthquakes suggesting local conditions to control amplitudes on the contrary precursory time and duration of anomalies seem to increase both with magnitudes and epicentral distances abundant evidence demonstrates the major role of crustal fluids in the earthquake cycle many works have outlined the fact that crustal instabilities can appear as the result of low stress strain perturbations during loading it has been suggested that motion of fluids may occur at various scales from microcrack fluid transfer up to changes of hydraulic levels of water tables the study of subsequent anomalies is expected to supply a tool for earthquake prediction following previous authors we outline the need for further methodological improvements including the setting up of multiparameter station networks and the simultaneous recording of the main external parameters atmospheric pressure water and air temperature soil moisture for signal processing

discharge of h2 from the atotsugawa and ushikubi faults japan and its relation to earthquakes the concentration of h2 in soil gases has been measured weekly at five stations on the atotsugawa and ushikubi faults in northern central main island japan since 1981 in search of possible relationship with earthquakes the observed h2 concentration varies from lower than 1 ppm to 7 8 in time and place when a large earthquake m 7 7 epicenter distance 486 km occurred on 26 may 1983 an outstanding discharge of h2 was observed at all five stations preseismically at three of them and coseismically at the other two simultaneous h2 emission was also observed at some stations in seven other occasions these periods of unusual h2 discharge nearly coincided with occurrences of major earthquakes in japan but not of local minor earthquakes along the atotsugawa fault this fault being a deep fracture zone may be sensitive to large scale crustal stress changes which incidentally cause the major earthquakes increased h2 may be produced by rock fracture caused by the increased stresses on the fault and by the earthquakes themselves local minor earthquakes along atotsugawa fault with magnitude lower than 3 may be unable to cause sufficient rock fracture to produce significant h2

continuous monitoring of hydrogen and carbon dioxide at mt etna article i nfo this study assessed the use of an h2 fuel cell as an h2 selective sensor for volcano monitoring the resolution repeatability and cross sensitivity of the sensor were investigated and evaluated under known laboratory conditions a tailor made device was developed and used for continuously monitoring h2 and co2 at mt etna throughout 2009 and 2010 the temporal variations of both parameters were strongly correlated with the evolution of the volcanic activity during the monitoring period in particular the co2 flux exhibited long term variations while h2 exhibited pulses immediately before the explosive activity that occurred at mt etna during 2010

cluster analysis of soil co2 data from mt etna italy reveals volcanic influences on temporal and spatial patterns of degassing soil co2 concentration data were collected periodically from july 2001 to june 2005 from sampling site grids in two areas located on the lower flanks of mt etna volcano paterno and zafferana etnea santa venerina cluster analysis was performed on the acquired data in order to identify possible groups of sites where soil degassing could be fed by different sources in both areas three clusters were recognised whose average co2 concentration values throughout the whole study period remained significantly different from one another the clusters with the lowest co2 concentrations showed time averaged values ranging from 980 to 1 170 ppm vol whereas those with intermediate co2 concentrations showed time averaged values ranging from 1 400 to 2 320 ppm vol and those with the highest concentrations showed time averaged values between 1 960 and 55 430 ppm vol we attribute the lowest co2 concentrations largely to a biogenic source of co2 conversely the highest co2 concentrations are attributed to a magmatic source whereas the intermediate values are due to a variable mixing of the two sources described above the spatial distribution of the co2 values related to the magmatic source define a clear direction of anomalous degassing in the zafferana etnea santa venerina area which we attribute to the presence of a hidden fault whereas in the paterno area no such oriented anomalies were observed probably because of the lower permeability of local soil time series analysis shows that most of the variations observed in the soil co2 data from both areas were related to changes in the volcanic activity of mt etna seasonal influences were only observed in the time patterns of the clusters characterised by low co2 concentrations and no significant interdependence was found between soil co2 concentrations and meteorological parameters the largest observed temporal anomalies are interpreted as release of co2 from magma batches that migrated from deeper to shallower portions of etna s feeder system the pattern of occurrence of such episodes of anomalous gas release during the observation period was quite different between the two studied areas this pattern highlighted an evident change in the mechanism of magma transport and storage within the volcano s feeder system after june 2003 interpreted as magma accumulation into a shallow 8 km depth reservoir

behavior and origin of helium neon argon and nitrogen from active faults compositional variations of gas species occluded in fracture zones type i within active faults are essentially the same as those in bubble gases type ii separating from mineral springs along faults the variation in type ii is hydrogeochemically interpreted as a result of dissolving and degassing of atmospheric air in groundwater at various temperatures the comparison of these variations in both types of gases suggests that ne ar and n2 in the type i gases are of atmospheric origin and their fluctuation is strongly controlled by the circulation of groundwater which recharges and discharges atmospheric air at various temperatures further hydrogeochemical evaluation shows that a part of he observed in fault zones is of radiogenic origin but its proportion is very small in active faults in these zones juvenile he emission related to the tectonic stresses causing earthquake may be substantially modified by the compositional fluctuation of gases controlled by the water circulation within the fault system accordingly monitoring of rare gases except for h2 from historically active faults may be less effective for earthquake prediction in contrast gas bubbles of high he content issuing from mineral springs which usually occur along prehistorically active faults are less contaminated by air and may provide some general precursory information concerning regional stresses at depth prior to an earthquake

anomalous soil co2 degassing in relation to faults and eruptive fissures on mount etna sicily italy the relationships between soil gas emissions and both tectonic and volcano tectonic structures on mt etna have been studied the investigation consisted of soil co2 flux measurements along traverses orthogonal to the main faults and eruptive fissures of the volcano anomalous levels of soil degassing were found mainly in coincidence with faults whereas only 49 of the eruptive fissures were found to produce elevated co2 soil fluxes this result suggests that only zones of strain are able to channel deep gases to the surface according to this hypothesis several previously unknown structures are suggested based on our geochemical data new structural maps of different areas of etna are proposed the soil co2 fluxes observed in this study are higher than those measured in a 1987 study and they are consistent with the higher level of volcanic unrest during the current study

serpentinization and the origin of hydrogen gas in kansas hydrogen gas occurs in ten kansas wells near the mid continent rift system since 1982 two wells have yielded small amounts of gases containing an average of 29 37 mole h2 the remainder being chiefly n2 with only traces of hydrocarbons isotopic compositions for hydrogen dgrd 740 to 836 pmil imply near ambient about 10 c equilibration temperatures for the gases which are among the most deuterium depleted in nature and resemble the h2 rich gases described from ophiolites in oman isotopic values for the kansas n2 differ slightly from those of the atmosphere but not enough to rule out an atmospheric origin because they are low in ch4 and co2 expected byproducts of biogenic activity the gases are probably abiogenic in origin the existence of such gases near a major rift system containing mafic rocks and not far from known kimberlites is consistent with an origin from reactions involving fe 2 oxidation for example during serpentinization because the gases may be associated with kimberlites and deep seated rifting mantle outgassing is possible but such an origin would be difficult to reconcile with the low isotopic temperatures the h2 gases from kansas and elsewhere seem to be too low in pressure to have commercial value however neither the kansas gases nor those from other h2 occurrences have been adequately examined to assess their importance as potential resources

calderas or gravity slide structures in the lesser antilles island arc abstract large arcuate depressions up to about 10 km in diameter on the back arc side of st lucia dominica and st vincent in the lesser antilles arc are discussed the qualibou depression on st lucia has been previously described as a caldera partly because it was believed to be the source of ignimbrites on the island remapping and stratigraphic studies of these ignimbrites show they were not erupted from the depression but from central vents in the highland rainforests and are much younger dominica is geologically similar and has two scarped depressions at the southern end of the island soufriere volcano st vincent has a prominent arcuate scarp opening to the west the southern half of which has been buried under the youngest volcanic products of the volcano we interpret these structures as the root zones of gravity slides perhaps eruption related and triggered by magmatic inflation post slide activity lava domes and fumaroles has occurred within them due to reduction in lithostatic load and pressure release on the flanks of these island volcanic complexes the presence of these structures only on the western coasts is correlated with the steeper 9 slopes into the grenada basin in contrast to the 1 submarine slopes of the atlantic side

co2 and radon measurements in the vogtland area germany a contribution to earthquake prediction research the interpretation of long term radon measure ments in a spring located in vogtland shows a significant relationship to the seismicity of a region close to the sampling point a statistical check was performed in order to identify the anomaly generating area the cause for this relation is emission of mantle originated gases including co2 influenced by tectonic processes in the crust

soil h2 and co2 surveys at several active faults in japan soil h2 and co2 surveys were carried out along seven active faults and around the aftershock region of the 2000 tottori ken seibu earthquake in japan diffuse co2 effluxes were also measured along one fault and around the 2000 aftershock region the results show highly variable h2 concentration in space and time and it seems that the maximum h2 concentration at each active fault correlates with fault activity as exemplified by the time of the latest big earthquakes even though observed h2 concentrations in four faults were markedly lower than those collected previously in the latter half of the 1970s it is evident that the higher h2 concentrations in this study are due to the addition of the fault gases comparing the chemical composition of trapped gases h2 5 20 and co2 h2 0 5 12 in fractured rocks of drill cores bored at the nojima fault a soil gas sample with the highest h2 concentration showed large amounts of the trapped fault gas diluted with atmospheric component the profile experiment across a fracture zone at the yamasaki fault showed higher h2 concentrations and lower co2 h2 ratios as was observed in soil gas from the fracture zone a few days after the 2000 tottori kei seibu earthquake no co2 effluxes related to the occurrence of earthquakes were observed at the aftershock region however only above the epicenter zone relatively high h2 concentrations in soil gases were observed

rn he and co2 soil gas geochemistry for the study of active and inactive faults abstract two italian areas characterized by different seismological histories were investigated to enhance the basic knowledge of gas migration mechanisms during earthquakes sharp variations occur in the movement and concentration of some gaseous species due to the evolution of the local stress regime the first area colpasquale is located in the central italian region of marche and provided a good location to study gas migration in a seismically active region the area was devastated by a sequence of shallow earthquakes over a 3 month long period september december 1997 the occurrence of this catastrophic event as well as the long duration of the seismic sequence presented a unique opportunity to study gas migration in a zone undergoing active displacement soil gas surveys were performed 1 day 1 week 1 year and 2 years after the main shock ms 5 6 in the colpasquale area in particular results highlight a change in the rn distribution during the three monitoring years indicating a variation of gas migration that may be linked to the evolution of the stress regime the second study area is located in the campidano graben southern part of sardinia island this area is characterized by seismic quiescence displaying an almost complete lack of historical earthquakes and instrumentally recorded seismicity the consistently low values observed for all analyzed gases suggest that the studied area is likely characterized by sealed non active faults that prevent significant gas migration the comparison of data from both studied areas indicate that soil gas geochemistry is useful to locate tectonic discontinuities even when they intersect non cohesive clastic rocks near the surface and thus are not visible i e blind faults

soil co2 degassing on mt etna sicily during the period 1989 1993 discrimination between climatic and volcanic influences wide variations were measured in the diffuse co2 flux through the soils in three selected areas of mt etna between august 1989 and march 1993 degassing of co2 from the area of zafferana etnea s venerina on the eastern slope of the volcano has been determined to be more strongly influenced by meteorological parameters than the other areas the seasonal component found in the data from this area has been excluded using a filtering algorithm based on the best fitting equation calculated from the correlation between co2 flux values and those of air temperature the filtered data appear to have variations temporally coincident with those from the other areas thus suggesting a common and probably deep source of gas the highest fluxes measured in the two most peripheral areas may correlate well with other geophysical and volcanological anomalous signals that preceded the strong eruption of 1991 1993 and that were interpreted as deep pressure increases anomalous decreases in co2 fluxes accompanied the onset and the evolution of that eruption and have been interpreted as a sign of upward migration of the gas source the variations of co2 flux at the 1989 se fracture have also given interesting information on the timing of the magmatic intrusion that has then fed the 1991 1993 eruption

geochemical investigations applied to active fault detection in a volcanic area the north east rift on mt etna sicily italy geochemical investigations were performed on the northeast rift of mt etna a prominent volcanic structure of this volcano low temperature fumaroles were found on the upper part of this area and the isotopic compositions of c co2 and he suggest a likely magmatic origin of the emitted gases on the contrary very low degassing was found in the lower part of the ne rift with co2 concentrations generally very close to those in air this pattern is probably due to sealing of the eruptive fissures by the repeated injections of magma solidified into dikes and by consequent shallow hydrothermal alteration of the fissured rocks due to residual magma degassing high soil co2 concentrations were also found in an elongated area parallel to the ne rift and located immediately to the east of it the geometry of these anomalies suggests the existence of several hidden faults sub parallel to the ne rift and likely connected to the pernicana fault system this latter structure seems to merge with the ne rift at the altitude where the fumarole emissions are located the hidden structures together with the pernicana system and the ne rift represent the western and northern boundaries of a large eastward collapsing sector of mt etna

gas geochemistry applied to earthquake prediction an overview terrestrial gases in groundwater and soil air have been extensively studied in recent years in seismically active areas especially in ussr china japan and united states in search of premonitory changes that might be useful for earthquake prediction concentrations of radon helium hydrogen mercury carbon dioxide and several other volatiles have been found generally to be anomalously high along active faults suggesting that the faults may be paths of least resistance for the terrestrial gases generated or stored in the earth to escape to the atmosphere temporal gas concentration changes with durations of a few hours to many months have been observed before many large earthquakes at a relatively small number of favorably situated stations at epicentral distances of up to several hundreds of kilometers these sensitive stations are generally located along active faults especially at intersections or bends of faults or some other structurally weak zones possibly because of tectonic strain concentration at such places however gas concentrations especially those measured at or near the ground surface may also be significantly affected by meteorological hydrological and other nontectonic changes in the environment the nontectonically induced variations must be carefully eliminated or recognized in the search of true earthquake related anomalies

investigation of the 1867 lesbos ne aegean earthquake fault pattern based on soil gas geochemical data abstract in this work the soil gas method is being used to compare geochemical data with the geological and structural information on lesbos island ne aegean in particular in the aghia paraskevi kalloni region the epicentral area of an earthquake in 1867 the island belongs to an seismically active zone part of the right lateral and normal fault systems of north anatolia and north and central aegean field observations aerial photo interpretation and microearthquake distribution show two main fault systems trending ne sw to nne ssw and nw se the strongest known destructive earthquake hit the island in 1867 with its epicentral area in the central part of lesbos estimated intensity ix x for the most central and eastern part of the island and vi vii for the rest the soil gas sampling was performed in august 1996 in the aghia paraskevi area by this soil gas survey an attempt was made for the recognition of active faults using the soil gases as fault tracers high values of all the investigated gases he 222rn co2 and ch4 characterize the central and southern sector of the area the soil gas anomalous concentrations are probably linked to the very active extensional tectonic structures that cause the characteristic seismicity of lesbos especially those of 222rn and co2 after statistical processing of the data and the use of contour and dot maps of each investigated gas an important accordance was found between the interpreted linear gas anomalies and the observed faults which possibly generated the 1867 shock

relation between hydrogen emission and seismic activities measurements of chemical composition of bubbles from a mineral spring at yuya spa situated close to the median tectonic line the longest active fault in japan showed that the periods of increased h2 emission coincided with occurrences of the ohno earthquake swarm nearby four cases of the coincidence without exception were observed in the last three years the fluctuation of h2 concentration ranges between 0 5 and 200 ppm whereas other gases such as he ar n2 and ch4 do not fluctuate much the h2 concentration is correlated with the energy released by the seismic activity this field evidence together with the results of laboratory experiments conducted bysugisakiet al 1983 leads to the conclusion that h2 observed at the mineral spring was produced by the reaction between groundwater and rock fractured in the seismic activities the observation that h2 in the mineral spring tends to appear prior to an earthquake suggests that microcracks may occur in rocks prior to earthquakes the precursory emission of h2 may be useful for earthquake prediction

gas anomalies at three mineral springs and a fumarole before an inland earthquake central japan conspicuous anomalies in gas compositions were observed at a fumarole and three mineral springs about 1 3 months prior to an inland earthquake of 6 8 magnitude in central japan on september 14 1984 the epicentral distances are 9 km for the fumarole and 50 71 and 95 km for the springs the anomalies in he ar n2 ar and ch4 ar ratios of bubble gases from the springs can be attributed to fluctuations in the emission rate of some deep seated gas due to change in pore pressure which is subjected to crustal stress resulting in the earthquake the anomaly at the fumarole showed an increase in discharge rate of deep volcanic gas under a compressional stress near the focal region since the behavior of subsurface fluids represented by he ar and other ratios is presumably controlled by the change of pore pressure temporal variations in the fluids can be used as a strain gauge for the crust on the other hand the precursory emissions of h2 which were observed after changes in he ar and other ratios had occurred may have resulted from a reaction between groundwater and the surface of newly formed cracks the timing and amplitude of the geochemical anomalies are compatible with the result predicted by a dilatancy model without fluid diffusion although h2 emission may be related to groundwater permeation into newly formed cracks monitoring of several gases with automatic gas chromatographs at several stations may be useful for unraveling earthquake mechanisms and for predicting earthquakes

spatial radon anomalies on active faults in california abstract radon emanation has been observed to be anomalously high along active faults in many parts of the world we tested this relationship by conducting and repeating soil air radon surveys with a portable radon meter across several faults in california the results confirm the existence of fault associated radon anomalies which show characteristic features that may be related to fault structures but vary in time due to other environmental changes such as rainfall across two creeping faults in san juan bautista and hollister the radon anomalies showed prominent double peaks straddling the fault gouge zone during dry summers but the peak to background ratios diminished after significant rain fall during winter across a locked segment of the san andreas fault near olema the anomaly has a single peak located several meters southwest of the slip zone associated with the 1906 san francisco earthquake across two fault segments that ruptured during the magnitude 7 5 landers earthquake in 1992 anomalously high radon concentration was found in the fractures three weeks after the earthquake we attribute the fault related anomalies to a slow vertical gas flow in or near the fault zones radon generated locally in subsurface soil has a concentration profile that increases three orders of magnitude from the surface to a depth of several meters thus an upward flow that brings up deeper and radon richer soil air to the detection level can cause a significantly higher concentration reading this explanation is consistent with concentrations of carbon dioxide and oxygen measured in soil air samples collected during one of the surveys

soil gas co 2 ch 4 and h 2 distribution in and around las canadas caldera tenerife canary islands spain abstract diffuse degassing of co 2 ch 4 and h 2 was investigated at the surface environment of canadas caldera canary islands during the gas survey carried out in the summer of 1995 soil co 2 concentration varied significantly from atmospheric levels to 30 while soil ch 4 and h 2 contents ranged from 5 to 851 ppm and from 0 5 to 620 ppm respectively soil co 2 ch 4 and h 2 distribution suggests that high diffuse degassing at canadas caldera is volcanic structurally controlled anomalous soil h 2 concentrations were identified at the summit of teide and outside caldera boundaries where the most recent eruption of tenerife island occurred 13 c co 2 data showed a magmatic mixed magmatic biogenic and biogenic origin while a biogenic origin is suggested for soil ch 4 at canadas caldera and its surroundings by coupling the co 2 3 he ratio with the 3 he 4 he ratio of fumarolic gas samples from the summit of teide we propose three possible sources for carbon morb type organic carbon and carbonate

spatial domain analysis of carbon dioxide from soils on vulcano island implications for co2 output evaluation abstract the carbon dioxide emissions of volcanoes have been targeted as effective contributors of co 2 to the atmosphere however different sources can be effective and active at the same time in the generation and release of co 2 in volcanic zones since isotopic fingerprinting of co 2 allows the precise identification of different sources coupling carbon isotope and co 2 flux measurements enables the evaluation of the mass contribution of each source to the carbon dioxide emissions this paper accounts for the first extensive spatial analysis of coupled measurements of carbon isotopologues of co 2 in the soil gases and co 2 fluxes discharged by soils on vulcano island an innovative method has been designed tested and fine tuned in the laboratory to measure 13 c co 2 values directly in field using a new type of laser based isotopologues analyzer namely a deltaray thermo fisher scientific the method can be used to determine the carbon isotope composition across the full range of co 2 concentrations in the soil gases 0 100 vol these data have been combined with measurements of the co 2 contents in the soil gases to distinguish co 2 from deep origins from co 2 of biogenic origin in the inhabited area of vulcano porto the method of evaluating the amount of deep origin co 2 in the soil gases is widely applicable in volcanic and geothermal zones for evaluation and monitoring purposes for both gas and volcanic hazards

the contribution of fluid geochemistry to the volcano monitoring of stromboli abstract the persistent open vent mild explosive activity of stromboli volcano is episodically interrupted by more violent and dangerous explosive events major explosions and paroxysms according to the nature of erupted products paroxysms can be related either to the explosion of overpressured gas pockets located in the proximity of the magma column or to the sudden uprise of hot gas rich magma from a deep part of the plumbing system in both cases these more energetic explosive events should be preceded by an escape or a preferential uprise of the highly mobile volatiles which in turn should produce gas leakage anomalies at the surface in sites of high vertical permeability such as deep reaching faults in order to identify such gas leaking sites a systematic co2 soil flux survey has been carried out on the island using an accumulation chamber four hundred sixty one points have been measured with a high density in the summit crater area where high flux values have been found 10 3 10 2 cm s anomalous points are concentrated along the main ne sw axial feeding system of the volcano co2 soil flux decreases from the crater zone to the base of the volcanic cone where however an interesting gas leakage anomaly occurs pizzillo mofette in the pizzillo area thermal water wells also occur whose chemistry indicates an origin by sea water heated by hot gas soil gases have been sampled in the sites with the highest co2 flux in the crater area and at the base of the cone chemical and isotopic analyses indicate the presence of a deep gas component especially in the crater zone samples high co2 appreciable contents of he and h2 3he 4he values up to 3 55 13c of co2 2 the sc5 low flux fumarole on the crater rim has shown during six years a remarkable persistence of temperature 93 95 c with only minor fluctuations of chemistry appearance of anomalous peaks of h2 in correspondence with strombolian explosions was observed during a 2 h 30 min experiment of continuous recording of hydrogen content of the fumarole together with previous data on h2o co2 and he this experiment confirms that strombolian blasts produce rapid fluctuations in the fumarolic gas composition in the light of this study sc5 fumarole and pizzillo mofette look promising sites for the testing of a continuous geochemical monitoring system of stromboli volcano

the detection of concealed faults in the ofanto basin using the correlation between soil gas fracture surveys abstract an integrated geochemical morphological and structural analysis was applied to a basin filled with clayey sediments in southern italy ofanto valley to delineate tectonic features more than 100 soil gas samples were collected and analysed for co2 rn and he and the resulting distribution was compared with the location and orientation of field observed brittle deformations faults and fractures and air photo interpreted morphotectonic features the results show that the highest helium radon and co2 values occur preferentially along elongated zones similar to the most representative trends obtained by geomorphological and mesostructural analyses i e anti apennine apennine and secondarily n s orientations furthermore the development of geostatistical techniques has allowed the semi quantitative evaluation of the anisotropic soil gas distribution the gas distribution pattern is considered to result from the combination of the anisotropic distribution of fracture traces and the randomly distributed background field the correspondence between soil gas distribution and geomorphological mesostructural features as well as the results from the geostatistical analysis suggest that gas leakage towards the surface is controlled by the same structural pattern which also created some morphological features this technique has been shown to be a useful tool for neotectonic studies this is especially true in basins filled with clayey sediments as soil gas is even able to define the leakage of deep seated gases along tectonic discontinuities which have no surface expression

adjacent releases of mantle helium and soil co2 from active faults observations from the marmara region of the north anatolian fault zone turkey volatile releases in terms of co2 efflux and noble gas of mantle origin are investigated in the marmara region of the seismically active north anatolian fault naf zone a total of 180 co2 efflux measurements 1 to 309 g m 2d 1 were carried out along four transects across the naf spatial variability of surface co2 effluxes was higher at faulted sites relative to comparable background areas the 13c values of soil co2 are 24 0 to 15 6 without correlation with co2 efflux values which suggest that co2 efflux anomaly is caused by fault related biogenic gas flow furthermore 36 gas and water samples from spring sites were investigated for 3he 4he ratios which resulted in a range from 0 26 r ra to 4 22 r ra large mantle helium contributions were observed from several sources along the naf the high co2 efflux sector on the gazikoy saros fault along the naf coincides with the area of high mantle helium flux this shows that fault zones play an important role both in transferring mantle helium to the surface and in causing fault related biogenic gas flow

probe permeametry an overview and bibliography applications of probe permeameters in both laboratory and outcrop studies of permeability heterogeneity are common we present an overview of the current status of probe permeameter data acquisition analysis and application the multidisciplinary nature of probe permeameter studies has led to their publication in diverse scientific journals we present a bibliography that includes literature covering both the technology and the application of probe permeametry

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

the qualibou caldera st lucia west indies abstract recent geological geophysical and hydrogeochemical studies conducted in the qualibou area of st lucia west indies provide new data for reevaluation of the geothermal resource and recommendation of sites for renewed drilling activities this work supports the original hypothesis of tomblin that the qualibou depression is a caldera precaldera volcanic activity was concentrated along faults associated with regional ne and nw trending structures basaltic lavas dated at 5 5 ma crop out along the western coast and are overlain by andesitic composite cones dated at 1 2 and 0 9 ma which form the highest ridges of the island superimposed upon the andesitic cones are dacitic domes 0 25 ma the eroded plugs of two of these form the spectacular pitons the major event in this volcanic field was the intermittent eruption of the choiseul pumice concurrent with the formation of the qualibou caldera 32 000 to 39 000 yrs ago about 6 km3 dense rock equivalent of lithic crystal andesitic tephra was erupted mainly as nonwelded to welded pyroclastic flows and surges some of these tuffs have been identified in geothermal drill holes within the 12 km2 caldera postcaldera eruption of dacitic tephra and dome lava 20 000 to 32 000 yrs ago occurred from vents within the caldera and appear to be a result of magmatic resurgence a 5 2 km long dipole dipole dc resistivity survey measured along a north south trending line through the caldera gave apparent resistivity results similar to those obtained in previous studies these results are compatible with a caldera substructure where low apparent resistivities analysis and interpretation of hydrogeochemical data from the qualibou caldera indicate that a geothermal reservoir underlies the sulphur springs area and consists of three layers 1 an upper steam condensate zone 2 an intermediate two phase vapor zone and 3 a lower brine zone measured temperatures at depth of 212 c are complemented by estimated temperatures of 250 c in the brine layer the water chemistry of various thermal springs indicates upwelling primarily near the caldera center at sulphur springs which feeds steam to steamcondensate hot springs along the northern caldera wall

identification of pathways for hydrogen gas migration in fault zones with a discontinuous heterogeneous permeability structure and the relationship to particle size distribution of fault materials previous studies have reported that high concentrations of h2 gas are released from active fault zones experimental studies suggest that the h2 gas is derived from the reaction of water with free radicals formed when silicate minerals are fractured at hypocenter depths during fault activities however the pathways for migration of deep seated fluids to surface are still unknown in this study we performed quick multipoint h2 gas measurements across a fault zone using a portable gas monitor and a hand drill the fault zone studied includes a smectite rich fault core dividing two clearly distinguishable damage zones granite cataclasite and welded tuff fault breccia the measurements show that h2 gas emissions collected in 2 3 h sampling periods from start of measurement range from 320 3 to 446 2 ppm min in the granite cataclasite and 60 5 to 137 8 ppm min in the welded tuff fault breccias negligible quantities of h2 gas could be collected from the fault core particle size distribution analyses of fault rocks indicate that the granite cataclasite tends to be rich in particles that are finer i e less cohesive and easy to disaggregate which leads to the inference that the granite cataclasite has high permeability based on the h2 gas measurements and the particle size distribution analyses the h2 gas is considered to have migrated in permeable damage zones mostly by advection with groundwater multipoint h2 gas measurement will be effective in qualitative delineation of variations in permeability of regional structures

a multidisciplinary approach to the evaluation of the mechanism that triggered the cerda landslide sicily italy abstract the present paper describes a multidisciplinary approach to the evaluation of a seismically triggered landslide that occurred in the cerda area italy on september 6 2002 about 1 h after an earthquake took place in the south tyrrhenian sea the study was focused on an analysis of the role of the seismic input in triggering the landslide in view of the evidence that no other mass movement was recorded in the adjacent areas despite geological and geomorphological spatial homogeneity the studied area is located on a slope of the western flank of the fiume imera settentrionale northern sicily which is made up of clayey arenitic rocks the slope inclines gently but is not uniform due to fluvial gravitative and rainwash processes field data dealing with global positioning system gps geology geomorphology geophysics vertical electrical sounding or ves and geochemistry soil gas fluxes and composition were acquired and analysed in order to investigate the cause effect relationships between the earthquake and the mass movement the gps survey allowed us to map the ground failures that have also been classified on the basis of their kinematical meaning i e compressive distensive or transcurrent structures the geological analysis revealed outcropping rocks and tectonic structures the geomorphologic survey highlighted the presence of preexisting landslide bodies the geophysical survey detected a buried surface located at a depth of about 100 m finally the geochemical survey showed that the gas released from the displaced mass came from a shallow depth and was not related to any active fault system the abovementioned information allowed us to interpret the landslide event as a partial reactivation of a preexisting landslide body that was triggered by the earthquake

variability in the gas phase composition of fluids discharged from los azufres geothermal field mexico abstract studies related to hydrological structure of the los azufres geothermal field and its effects on the exploitation of the field for generation of electrical energy have included a program of sampling and chemical analysis of fluids discharged by a number of deep wells in continuous production chemical analysis of the gaseous phase includes monitoring of co 2 h 2 s nh 3 h 2 he n 2 ch 4 and 222 rn five wells in los azufres field were periodically sampled during 1983 1988 the monitoring program has shown considerable variability in the gas concentrations of fluids before mid 1985 the base line concentrations of the gases showed standard deviations between 8 and 28 during the later period the average concentrations of different gases ranged from 37 to much higher values above the base line the largest variations are observed in he co 2 and 222 rn this variability is interpreted in terms of 1 addition of excess steam 2 a possible relationship with earthquake events that occurred in mexico during september 19 21 1985 and early may to early june of 1987 and 3 more recent variations after mid 1987 increased exploitation of the field