the influence of pore pressure and confining pressure on dynamic elastic properties of berea sandstone compressional and shear wave velocities of watersaturated berea sandstone have been measured as functions of confining and pore pressures to 2 kbar the velocities measured by the pulse transmission technique were obtained at selected pressures for the purpose of evaluating the relative importance of confining pressure and pore pressure on elastic wave velocities and derived dynamic elastic constants changes in berea sandstone velocities resulting from changes in confining pressure are not exactly canceled by equivalent changes in pore pressure for properties that involve significant bulk compression compressional wave velocities and bulk modulus an incremental change in pore pressure does not entirely cancel a similar change in confining pressure on the other hand it is shown that a pore pressure increment more than cancels an equivalent change in confining pressure for properties that depend significantly on rigidity shear wave velocity and poisson s ratio this behavior as well as observed

crustal structure evolution and volcanic unrest of the alban hills central italy the alban hills a quaternary volcanic center lying west of the central apennines 15 25 km southeast of rome last erupted 19 ka and has produced approximately 290 km3 of eruptive deposits since the inception of volcanism at 580 ka earthquakes of moderate intensity have been generated there at least since the roman age modern observations show that intermittent periods of swarm activity originate primarily beneath the youngest features the phreatomagmatic craters on the west side of the volcano results from seismic tomography allow identification of a low velocity region perhaps still hot or partially molten more than 6 km beneath the youngest craters and a high velocity region probably a solidified magma body beneath the older central volcanic construct thirty centimeters of uplift measured by releveling supports the contention that high levels of seismicity during the 1980s and 1990s resulted from accumulation of magma beneath these craters the volume of magma accumulation and the amount of maximum uplift was probably at least 40 106 m3 and 40 cm respectively comparison of newer levelings with those completed in 1891 and 1927 suggests earlier episodes of uplift the magma chamber beneath the western alban hills is probably responsible for much of the past 200 ka of eruptive activity is still receiving intermittent batches of magma and is therefore continuing to generate modest levels of volcanic unrest bending of overburden is the most likely cause of the persistent earthquakes which generally have hypocenters above the 6 km deep top of the magma reservoir in this view the most recent uplift and seismicity are probably characteristic and not precursors of more intense activity

carbon dioxide and radon gas hazard in the alban hills area central italy abstract the sudden and catastrophic or slow and continuous release at surface of naturally occurring toxic gases like co 2 h 2 s and rn poses a serious health risk to people living in geologically active regions in general this problem receives little attention from local governments although public concern is raised periodically when anomalous toxic gas concentrations suddenly kill humans or livestock for example elevated co 2 concentrations have been linked to the death of at least 10 people in the central italian region of lazio over the last 20 years while it was the co 2 asphyxiation of 30 cows in a heavily populated area near rome in 1999 which prompted the present soil gas study into the distribution of the local health risk a detailed geochemical survey was carried out in an area of about 4 km 2 in the ciampino and marino districts whereby a total of 274 soil gas samples were collected and analysed for more than 10 major and trace gas species data were then processed using both statistical and geostatistical methods and the resulting maps were examined in order to highlight areas of elevated risk general trends of elevated co 2 and rn concentrations imply the presence of preferential pathways i e faults and fractures along which deep gases are able to migrate towards the surface the co 2 and rn anomalous trends often correspond to and are usually elongated parallel to the apennine mountain range the controlling structural feature in central italy because of this fundamental anisotropy in the factors controlling the soil gas distribution it was found that a geostatistical approach using variogram analysis allowed for a better interpretation of the data with regard to the health risk to local inhabitants it was found that although some high risk areas had been zoned as parkland others had been heavily developed for residential purposes for example many new houses were found to have been built on ground which has soil gas co 2 concentrations of more than 70 and radon values of more than 250 kbq m 3 it is recommended that land use planners incorporate soil gas and or gas flux measurements in environmental assessments in areas of possible risk i e volcanic or structurally active areas

origin of the lethal gas burst from lake monoun cameroun abstract on 15 august 1984 a lethal gas burst issued from a submerged 96 m deep crater in lake monoun in cameroun western africa killing 37 people the event was associated with a landslide from the eastern crater rim which slumped into deep water waters below 50 m are anoxic dominated by high fe 2 600 mg l and hco 3 1900 mg l anoxic and supersaturated with siderite which is a major component of the crater floor sediments the unusually high fe 2 levels are attributed to reduction of laterite derived ferric iron gradually brought into the lake as loess and in river input sulfur compounds are below detection limits in both water and gas gases effervescing from depressurized deep waters are dominantly co 2 with minor ch 4 having 13 c of 7 18 and 54 8 per mil respectively bacterial decomposition of organic matter may account for the methane but 14 c of lake water indicates that only 10 of the carbon is modern giving an apparent age of 18 000 years the dominant source of carbon is therefore attributed to long term emission of co 2 as volcanic exhalation from vents within the crater which led to gradual build up of hco 3 in the lake the density stratification of the lake may have been upset by an earthquake and underwater landslide on 15 august which triggered overturn of the lake and caused nucleation of co 2 in the deep water the resultant ebullition of co 2 from deep lake waters led to a gas burst at the surface and locally generated a water wave up to 5 m high people travelling through the gas cloud were asphyxiated presumably from co 2 and suffered skin discoloration from unidentified components

trade off of elastic structure and q in interpretations of seismic attenuation the quality factor q is an important phenomenological parameter measured from seismic or laboratory seismic data and representing wave energy dissipation rate however depending on the types of measurements and models or assumptions about the elastic structure several types of qs exist such as intrinsic and scattering qs coda q and apparent qs observed from wavefield fluctuations we consider three general types of elastic structures that are commonly encountered in seismology 1 shapes and dimensions of rock specimens in laboratory studies 2 geometric spreading or scattering in body surface and coda wave studies and 3 reflectivity on fine layering in reflection seismic studies for each of these types the measured q strongly trades off with the inherently limited knowledge about the respective elastic structure for the third of the above types the trade off is examined quantitatively in this paper for a layered sequence of reflectors e g an oil or gas reservoir or a hydrothermal zone reflection amplitudes and phases vary with frequency which is analogous to a reflection from a contrast in attenuation we demonstrate a quantitative equivalence between phase shifted reflections from anelastic zones and reflections from elastic layering reflections from the top of an elastic layer followed by weaker reflections from its bottom can appear as resulting from a low q within or above this layer this apparent q can be frequency independent or dependent according to the pattern of thin layering due to the layering the interpreted q can be positive or negative and it can depend on source receiver offsets therefore estimating q values from frequency dependent or phase shifted reflection amplitudes always requires additional geologic or rock physics constraints such as sparseness and or randomness of reflectors the absence of attenuation in certain layers or specific physical mechanisms of attenuation similar conclusions about the necessity of extremely detailed models of the elastic structure apply to other types of q measurements

modelling the drained undrained transition effect of the measuring method and the boundary conditions abstract the dependence of fluid saturated rocks elastic properties to the measuring frequency is related to fluid flow phenomena at different scales in the frequency range of 10 3 106 hz for fully saturated rocks two phenomena have been experimentally documented i the drained undrained transition i e global flow and ii the relaxed unrelaxed transition i e local flow when investigating experimentally those effects or comparing different measurements in rocks one needs to account for both the boundary conditions involved and the method of measurement used a one dimensional poroelastic model is presented which aims at calculating the expected poroelastic response during an experiment the model is used to test different sets of boundary conditions as well as the role of the measuring setup i e local strain gauges or global linear variable differential transformer strain measurement four properties are predicted and compared with the measurements i e bulk modulus bulk attenuation pseudo skempton coefficient and pore pressure phase shift for the drained undrained transition because fluid pressure may not be homogeneous in the sample local and global measurements are predicted to differ furthermore the existence of a dead volume at both sample s ends is shown to be important due to the existence of the dead volume an interplay between sample s and dead volumes storage capacity determines both the magnitudes and the frequency dependence of the dispersion attenuation measurements the predicted behaviours are shown to be consistent with the measurements recently reported on very compressible and porous sandstone samples

gassmann s fluid substitution and shear modulus variability in carbonates at laboratory seismic and ultrasonic frequencies carbonates have become important targets for rock property research in recent years because they represent many of themajoroilandgasreservoirsintheworld someareundergoing enhanced oil recovery most laboratory studies to understand fluid and pressure effects on reservoir rocks have been performed on sandstones but applying relations developed for sandstones to carbonates is problematic at best we measure in the laboratory nine carbonate samples from the same reservoir at seismic 3 3000 hz and ultrasonic 0 8 mhz frequencies samples are measured dry humidified and saturated with liquid butane and brine our carbonate samples showed typical changes in moduli as a function of porosity andfluid saturation however we explore the applicability of gassmann s theory on limestone and dolomite rocks in the context of shear and bulk modulus dispersion andgassmann stheoryassumptions forourcarbonatesetat high differential pressures and seismic frequencies the bulk modulus of rocks with high aspect ratio pores and dolomite mineralogy is predicted by gassmann s relation we also explore in detail some of the assumptions of gassmann s relation especiallyrock framesensitivitytofluidsaturation our carbonate samples show rock shear modulus change from dry to brine saturation conditions and we investigate several rock fluid mechanisms responsible for this change to our knowledge these are the first controlled laboratory experimentsoncarbonatesintheseismicfrequencyrange

migration of fluid phases and genesis of basalt magmas in subduction zones dehydration and hydration reactions in both the downgoing lithosphere and the overlying mantle wedge have been examined in order to understand the role of h2o in the production of magmas at convergent plate boundaries the subduction of oceanic lithosphere occurring with increasing pressures and rising temperatures causes liberation of h2o from the slab amphibole which can be stable to the highest pt conditions among hydrous phases in the slab decomposes at around 90 km depth it follows that the subducted lithosphere is essentially anhydrous beneath volcanic arcs lying more than 110 km above the slab and that the supply of slab derived h2o is not a direct trigger for the production of arc magmas instead the h2o released from downgoing lithosphere reacts with the forearc mantle wedge to crystallize hydrous minerals serpentine talc amphibole chlorite and phlogopite this hydrated peridotite is dragged downward on the slab toward higher pt regions and releases h2o to shallower potential magma source regions in the mantle wedge combining experimental data on the stability of serpentine and talc with the thermal structure in the mantle wedge it is concluded that those minerals decompose beneath the forearc region on the other hand high pt experimental and thermodynamic data suggest that dehydration of amphibole and chlorite in the downdragged hydrated peridotite can take place just beneath a volcanic front phlogopite in the peridotite decomposes to release h2o at a deeper level about 200 km h2o liberated from the hydrated peridotite causes partial melting of overlying mantle wedge peridotites along with the migration of h2o through the above processes subduction components especially large ion lithophile elements can be overprinted on the magma source region which governs the geochemical characteristics of arc magmas

the transition from calc alkaline to potassic orogenic magmatism in the aeolian islands southern italy the aeolian volcanic arc displays a wide range of magmatic products mafic lavas range from hypersthene normative calc alkaline basalts to silica undersaturated potassic absarokites although the former are spatially and temporally dominant consistent with the subduction zone tectonic setting in addition intermediate and acidic members of the various fractionation series may be recognised large variations in trace element and isotope ratios accompany the rapid calc alkaline to potassic transition and it is argued that these may be largely explained in terms of subduction zone mantle enrichment involving components derived from both basaltic ocean crust and subducted sediments in addition it seems that the mantle wedge itself was substantially heterogeneous prior to the onset of subduction zone processes not only are these subduction components similar to those proposed in a number of island arcs but they also resemble those recognised in the ultra potassic lavas of the roman province supporting recent subduction related petrogenetic models of the roman magmatism although subducted sediment plays an important role in the generation of some potassic magmatism it is not uniquely responsible for k2o rich lavas which are also produced without a large sediment contribution

the holocene of the agro pontino graben recent advances in its palaeogeography palaeoecology and tephrostratigraphy in the past decade 2000 2010 research within the scope of the hidden landscapes project by rug archaeologists provided important information on the holocene history of the agro pontino graben this information complemented earlier studies by dutch universities uva rug and ul the graben was found to hold important tephrochronological palaeoecological and archaeological archives which deserve to be studied in more detail this is demonstrated by the recent robust dating of the avellino pumice layer at 3945 10 cal bp obtained from this archive sevink et al 2011 and by the complex denudation record resulting from early land use in its hinterland an overview is given of the recent knowledge on the bronze age to recent landscape that existed in the graben and of the major early bronze age sites of which most were associated with a large lake doubts have grown about the reliability of the existing chronological framework derived from earlier pollen cores by conventional radiocarbon dating these doubts are discussed in the context of results from recent research with emphasis on the hard water effect that has been largely neglected in the earlier studies the main current research topics are indicated

helium isotope disequilibrium and geochronology of glassy submarine basalts the u th he dating method is the oldest method of geochronology that involves radioactivity but historically it has not been particularly successful even when problems of poor helium retention and loss due to radiation damage are circumvented by analysing suitable mineral phases1 4 problems frequently remain with inherited helium5 6 here we show that isotope disequilibrium in the 3he 4he ratio between helium trapped in vesicles and that dissolved in the glass phase of some young seamount basalts can be used to determine u th he ages for the basalts we use the 3he 4he in vesicles extracted by crushing in vacuo to correct the dissolved phase he by fusion of the remaining powder for the inherited component and compute the radiogenic helium concentration the method is applicable to rocks containing phases with different u th he and the results have implications for dating lavas in the age range of 103 to 106 years thus filling a gap between the limits of the 14c and k ar methods and for reconstructing the geochemical history of young volcanic systems

temporal association of arc continent collision progressive magma contamination in arc volcanism and formation of gold rich massive sulphide deposits on wetar island banda arc whole rock 87sr 86sr and 18o analyses of volcanic rocks and 3he 4he analyses of sulphides and sulphates from mineralized rocks on wetar indonesia indicate a variable contribution of assimilated crustal material or sediment sourced from the subducted australian craton to the south these new data support the idea of progressive source contamination with precisely dated events showing that wetar island hosts the most extreme examples of crustal assimilation in the region the increased continental contamination occurs during the pliocene zanclian to piacenzian during distinct magmatic events between 5 and 4 ma and at 2 4 ma when 87sr 86sr ratios in unaltered lavas with whole rock 18o values between 5 7 and 9 6 increase from 0 707484 to extreme radiogenic values of 0 711656 the earlier of these magmatic events is important in the generation of the hydrothermal systems responsible for the mineralization recorded on wetar samples from this yield radiogenic 3he 4he ratios between 0 5 and 1 4 r ra similar to the data from volcanic rocks on nearby romang the later magmatic event coincides with the arrival of the australian continental margin at the subduction zone along the banda arc progressive incorporation of continental sourced components into the source region below the wetar island edifice coincides with the formation of gold rich volcanogenic massive sulphide deposits hosted within the contaminated volcanic pile

helium and carbon geochemistry of hydrothermal fluids from the mid okinawa trough back arc basin southwest of japan abstract hydrothermal systems located in the okinawa trough back arc basin are considered to be related to rifting activities in the continental margin hydrothermal fluids sampled from two sites jade and clam are significantly enriched in gas species compared to those from mid oceanic ridges a high temperature fluid 320 c from the jade site shows a co 2 concentration of 200 mmol kg 1 which is more than one order of magnitude higher than that of sediment starved ridge crest hydrothermal systems both helium r r a 6 1 6 5 and carbon 13 c co2 5 0 to 4 7 pdb isotopic compositions are typical of island arc magmatic gases also the abundance ratio of co 2 3 he 3 10 10 is within the range of values found in island arcs chemical and isotopic composition of the jade fluid are considered to indicate that both co 2 and helium are derived from a magmatic source beneath the hydrothermal system without significant contamination contrary to these species ch 4 is attributed to a thermogenic origin based on its isotopic composition 13 c ch 4 41 to 36 pdb and high concentration 7 1 mmol kg 1 which values are similar to those observed in sediment hosted hydrothermal systems the clam fluids show gas geochemistry much more affected by fluid sediment interaction lower 3 he 4 he ratios r r a 3 7 3 8 and higher co 2 3 he ratios 10 11 may reflect involvement of gas species introduced during secondary fluid circulation within the sedimentary pile magmatic activity is the main contributor of gas species to the hydrothermal fluids in both the jade and clam sites although fluid sediment interaction modifies their composition the relatively high abundance of co 2 in the mid okinawa trough hydrothermal systems reflects the geochemical nature of island arc magma

accidental gas emission from shallow pressurized aquifers at alban hills volcano rome italy geochemical evidence of magmatic degassing abstract recent studies suggested that alban hills rome is a quiescent and not an extinct volcano as it produced holocene eruptions and several lahars until roman times by water overflow from the albano crater lake alban hills are presently characterized by high p co2 in groundwaters and by several cold gas emissions usually in sites where excavations removed the superficial impervious cover gas consists mostly of co 2 with minor h 2 s and the diffuse co 2 soil flux is locally very high accidental gas blowouts occurred during shallow well drillings tens to hundreds m depth in zones with no surface gas manifestations indicate the presence of gas pressurized aquifers confined underneath impermeable layers within both the volcanic rock pile and the underlying pleistocene loose sediments degassing mostly occurs in correspondence of bordering faults of buried horsts cut in the mesozoic carbonate basement hosting the main aquifer carbon isotopic composition 13 c co2 suggests that co 2 is at least partly originated by thermal decarbonation of these limestones 3 he 4 he isotopic ratio of the gas up to 1 9 ra is the same or even slightly higher than that of olivine and clinopyroxene fluid inclusions of the alban hills volcanic products indicating a possible magmatic source for the gas low r ra values compared to morb and island arc magmas are characteristic of the potassic roman comagmatic province and reflect a deep involvement of crustal material in the magma genesis the lack of high temperature fumaroles can be explained by an efficient meteoric cold water penetration and circulation in the volcano permeable terrains

preliminary geochemical characterization of groundwater drained by the roman emissary of lake albano italy many lakes have been the object of hydraulic works in historical times and the drainage tunnel carved by romans for regulating the level of lake albano central italy can be considered as one of the most important historical hydraulic tunnels in the world we sampled and analysed lake water as well as groundwater samples from the lake albano emissary and another hydraulic work in the area ninfeo which were analysed for their geochemical and isotopic composition in order to extract useful information for a possible reuse of the tunnel for anthropogenic purposes the collected water samples exhibit common chemical features typical of water rock interaction processes in volcanic areas analyses of minor and trace elements confirmed the abovementioned results indicating the presence of an atmospheric pollution source for heavy metals although their concentrations are mostly below the maximum admitted concentrations for drinking water issued by the world health organization the chemical composition of dissolved gases indicated that both lake and groundwater are mainly enriched in co2 isotopic analyses suggested a clear volcanic origin for co2 dissolved in lake water while carbon dioxide in groundwater from the roman emissary is produced by soil respiration as further confirmed by oxygen and deuterium isotopic composition the roman emissary drains local suspended aquifers neither in contact with the lake water body nor influenced by volcanic activity suggesting the opportunity to use the tunnel as a zero condition monitoring site for individuating a possible future renewal of volcanic activity

the 1989 1990 seismic swarm in the alban hills volcanic area central italy abstract a long seismic swarm has been recorded by a digital microseismic network that the istituto nazionale di geo fisica ing deployed from april 1989 to march 1990 in the alban hills quaternary volcanic region about 20 km southeast of rome the network consisted of thirteen digital stations equipped with four six component weak motion and strong motion sensors three three component and six vertical weak motion seismometers including both broad band and short period sensors more than 3000 earthquakes were detected during about one year of operation the data recorded during the sequence provided an unprecedented opportunity to resolve details of the seismogenic features of this area that has experienced earthquakes since the roman age although the temporal distribution of seismicity reveals a volcanic type swarm activity the recorded seismic signals show medium high frequency waveforms and clear s wave arrivals typical of tectonic earthquakes about 1100 earthquakes in a magnitude range between m d 1 5 and md 4 0 have been located the seismicity delineates a 6 12 km 2 nw se elongated region that corresponds to the area where the most recent 0 027 ma phreato magmatic activity took place almost no earthquakes occurred beneath the central cone and the eastern side of the caldera the seismicity is shallow and is mostly concentrated in two clusters that are offset laterally and are at sligthly different depths 3 5 and 4 6 km the fault plane solutions of the strongest earthquakes reveal a ne sw extension consistent with the regional orientation of the stress field along the apenninic chain as obtained by other seismo logical data

the gas cloud of lake nyos cameroon 1986 results of the italian technical mission abstract on august 21 1986 a gas cloud issued from lake nyos in cameroon killed over 1700 people an italian technical mission reached the area seven days later and obtained the first field evidences of the catastrophe on the basis of observations and measurements in the field and of samples collected the origin of the gas outburst is attributed to a phreatic explosion from beneath the bed of the lake this interpretation appears to fit well the observed and reported phenomena and seems perfectly consistent with the geological geothermal conditions of the area

chemical and isotopic signature of old groundwater and magmatic solutes in a costa rican rain forest evidence from carbon helium and chlorine 1 c he and cl concentrations and isotopes in groundwater and surface water in a lowland costa rican rain forest are consistent with the mixing of two distinct groundwaters 1 high solute bedrock groundwater representing interbasin groundwater flow igf into the rain forest and 2 low solute local groundwater recharged in the lowlands in bedrock groundwater high 13c 4 89 low 14c 7 98 pm high r ra for he 6 88 and low 36cl cl 17 10 15 suggest that elevated tracer concentrations are derived from magmatic outgassing and or weathering of volcanic rock beneath nearby volcan barva in local groundwater the magmatic signature is absent and data suggest atmospheric sources for he and cl and a biogenic soil gas co2 source for dissolved inorganic carbon dating of 14c suggests that the age of bedrock groundwater is 2400 4000 years most likely at the lower end of the range local groundwater has 14c 100 pm indicating the presence of bomb carbon and thus ages less than 55 years overall data are consistent with a conceptual hydrologic model originally proposed on the basis of water budget and major ion data 1 large variation in solute concentrations can be explained by mixing of the two distinct groundwaters 2 bedrock groundwater is much older than local groundwater 3 elevated solute concentrations in bedrock groundwater are derived from volcanic fluids and or rock and 4 local groundwater has not interacted with volcanic rock tracers with different capabilities converge on the same hydrologic interpretation also transport of magmatic co2 into the lowland rain forest via igf seems to be significant relative to other large ecosystem level carbon fluxes

a water flow model of the active crater lake at aso volcano japan fluctuations of magmatic gas and groundwater fluxes from the underlying hydrothermal system the first crater of nakadake peak of aso volcano japan contains a hot water lake that shows interesting variations in water level and temperature these variations were discovered by precise continuous observa tions of the lake independent of precipitation we devel oped a numerical model of a hot crater lake and compared with observational data for the period from july 2006 to january 2009 the numerical model revealed seasonal changes in mass flux 75 132 kg s and enthalpy 1 840 3 030 kj kg for the fluid supplied to the lake the relation between the enthalpy and mass flux indicates that the bottom input fluid is a mixture of high and low temperature fluids assuming a mixture of high temperature steam at 800 c and liquid water at 100 c we evaluated the liquid and steam fluxes the liquid water flux shows a seasonal increase lagging behind the rainy season by 2 months suggesting that the liquid water is predominantly groundwater the fluctuation pattern in the flux of the high temperature steam shows a relation with the amplitude of volcanic tremor suggesting that heating of the hydrothermal system drives the tremor consequently precise observations of a hot crater lake represent a potential method of monitoring volcanic hydrothermal systems in the shallow parts of the volcanoes keyword aso volcano hot crater lake hydrothermal system groundwater volcanic tremor

fluorine geochemistry of basaltic rocks from continental and oceanic regions and petrogenetic application fluorine contents in about 300 samples of various types of basalts and related rocks from continental southwestern u s a zaire deccan and south africa and oceanic regions hawaii and mid atlantic ridge between 23 n and 40 n were determined by a selective ion electrode method

an overview of laboratory apparatuses to measure seismic attenuation in reservoir rocks intrinsic wave attenuation at seismic frequencies is strongly dependent on rock permeability fluid properties and saturation however in order to use attenuation as an attribute to extract information on rock fluid properties from seismic data experimental studies on attenuation are necessary for a better understanding of physical mechanisms that are dominant at those frequencies an appropriate laboratory methodology to measure attenuation at seismic frequencies is the forced oscillation method but technical challenges kept this technique from being widely used there is a need for the standardization of devices employing this method and a comparison of existing setups is a step towards it here we summarize the apparatuses based on the forced oscillation method that were built in the last 30 years and were used to measure frequency dependent attenuation in fluid saturated and or dry reservoir rocks under small strains 10 8 10 5 we list and discuss important technical aspects to be taken into account when working with these devices or in the course of designing a new one we also present a summary of the attenuation measurements in reservoir rock samples performed with these apparatuses so far

carbon dioxide degassing from the albani hills volcanic region central italy the albani hills are affected by strong co2 degassing processes the amount of co2 which rises from the depths and subsequently dissolves into shallow groundwater has been estimated to be more than 4 2 109 mol year 1 most of the gas is released in localised anomalous spots lavinio solforata and ciampino albano nemi areas generated by fluid leakage processes from buried pressurized reservoirs hosted by structural highs of the calcareous siliceous marly basement the groundwater circulating in the anomalous areas becomes co2 oversaturated generating observable gas manifestations whose composition is mainly controlled by gas liquid separation processes a gas flow rate of 6 1 108 mol year 1 has been measured from the two larger manifestations using the accumulation chamber technique the presence at shallow level of co2 oversaturated groundwater can explain several episodes of sudden release of gas which was documented by historical chronicles from roman times until now

stable and radiogenic isotopes as tracers for the origin mixing and subsurface history of fluids in submarine shallow water hydrothermal systems the shallow water hydrothermal system in tutum bay on the west side of ambitle island papua new guinea provides us with an exceptional opportunity to study isotope systematics in a near shore setting compared to seawater the hydrothermal fluids in tutum bay have lower values for dd d 18 o d 13 c and 87 sr and higher values for 3 h d 34 s so4 and d 18 o so4 the d 18 o and dd records for vents 1 and 4 indicate that fluid compositions remained stable over an extended period interpretation of isotope data clearly demonstrates the predominantly meteoric origin of tutum bay hydrothermal fluids despite their location in a marine environment d 18 o and dd values are identical to mean average annual precipitation in eastern papua new guinea the hypothesis that these fluids are a simple product of mixing between seawater and onshore hydrothermal fluids from the waramung w 1 and kapkai w 2 thermal areas has been rejected because the observed d 37 cl 3 h d 34 s so4 and d 18 o so4 values cannot be explained by a simple mixing model the application of d 18 o so4 and d 13 c thermometers in combination with 3 h values corroborates the three step model of pichler et al pichler t veizer j hall g e m 1999 the chemical composition of shallow water hydrothermal fluids in tutum bay ambitle island papua new guinea and their effect on ambient seawater marine chemistry 64 3 229 252 where 1 phase separation in the deep reservoir beneath ambitle island produces a high temperature vapor that rises upward and subsequently reacts with cooler ground water to form a low ph co2 rich water of approximately 150 160 8c 2 caused by the steep topography this co2 rich fluid moves laterally towards the margin of the hydrothermal system where it mixes with the marginal upflow of the deep reservoir fluid this produces a dilute chloride water of approximately 165 8c and 3 possibly the entrainment of minor amounts of ground or seawater during its final ascent d 2004 elsevier b v all rights reserved

investigation of elastic weakening in limestone and sandstone samples from moisture adsorption summary elastic and mechanical weakening from water saturation are widely known to occur in sedimentary rocks and particularly in carbonate rocks to improve our understanding of the physics underlying this phenomenon ultrasonic f 0 5 mhz elastic properties are measured on a large suite of clean limestones and sandstones at very low saturations from relative humidity rh variations at ambient conditions measurements clearly highlight an elastic weakening i e decrease in elastic wave velocity from moisture adsorption p and s wave velocities are similarly affected by adsorption but in a different way for limestones and sandstone samples while the elastic properties of limestone samples show almost no rh dependence a large weakening is observed for samples of fontainebleau sandstone that increases with the samples porosity the main elastic weakening effect is likely to result from adsorption of fluid at grain contacts it thus affects particularly granular rocks such as sandstones while well cemented limestones are not affected the granular model from murphy et al accounting for surface energy effects proves to be appropriate applying this model it is shown that i p and s wave velocities have the same dependence on surface energy which is consistent with the measurements and ii surface energy values obtained from the ultrasonic data using this model correlate with rh and are consistent with the expected value for quartz crystals at vapour pressure yet porosity which relates to degree of cementation in the particular case of fontainebleau sandstone appears to be an additional parameter a modified model is thus derived using the cementation model from digby accounting for a bonding radius at grain contact it proves to apply well to the measured data the fundamental difference between limestones and sandstones dependence to rh appears to be related to a microstructural difference saturation variations from rh increase depend on specific surface area which is particularly low in fontainebleau sandstones and large in microporous limestones however elastic weakening from rh is more important in sandstones owing to their granular microstructure

he ne ar and c isotope systematics of geothermal emanations in the lesser antilles islands arc the authors present he ne ar and c isotope analyses of hydrothermal brines and gases from fumaroles hot springs mofettes and hydrothermal exploration drillings on the major islands of the lesser antilles arc the origin of hydrothermal brines which have been analyzed also for o and h isotopes is essentially meteoric hydrothermal air corrected isotope compositions of helium 2 2 rc ra sup 3 he sup 4 he 8 6 rc ra and carbon minus 20 delta sup 13 c sub pdb 0 5 are variable and require a variety of crustal and magmatic sources the diversity of delta sup 13 c sub pdb and sup 3 he co sub 2 ratios within individual volcanic centers suggests that crustal sources e g limestone contaminate magmatic co sub 2 en route from high level magma reservoirs depth 15 km to the surface a similar contamination may be found for magmatic helium on distal springs the sup 3 he sup 4 he signature of summit fumaroles thought to reflect the sup 3 he sup 4 he signature of high level magmas shows a remarkable systematic variation along the arc in addition there is a correlation throughout the arc between published sr pb and nd isotope signatures of lavas and the sup 3 he sup 4 he signatures of summit fumaroles on the northern islands nevis montserrat guadeloupe and dominica summitmore fumaroles have the n morb signature sup 3 he sup 4 he 8 1 r ra and the isotope signature of lavas is not dissimilar from comparable intra oceanic arc tholeiites elsewhere variable enrichments in radiogenic sr and pb have been reported for lavas of individual volcanic centers of the southern islands martinique st lucia and grenada and summit fumaroles on these centers match these variations by variable radiogenic he enrichments i e lower sup 3 he sup 4 he ratios this correlation suggests that radiogenic sr and pb enrichments of lavas and low sup 3 he sup 4 he signatures on summit fumaroles have a common origin i e a terrigenous contaminant derived from the orinoco depositionary fan crustal assimilation is thought to decouple the he isotope system from any other radiogenic isotope system and therefore the authors argue that the observed correlation of he sr pb and nd isotope systems is related to a terrigenous contaminant derived from subducted sediments support for this scenario also comes from the matching of low sup 3 he sup 4 he ratios and tectonic features of the forearc thought to favor the subduction of forearc sediments the present study offers a first clue that under suitable conditions crustal helium from oceanic sediments might be subducted to the depth of arc magma sources and possibly even recycled into the deeper mantle less

frequency and fluid effects on elastic properties of basalt experimental investigations 1 in order to investigate the effects of fluid and frequency on the elastic properties we performed hydrostatic experiments on an icelandic basalt specimen under both dry and saturated conditions this basalt is characterized by a bimodal porosity i e cracks and equant pores the elastic properties bulk moduli in our case were investigated under high pressure through two experimental methods 1 a classical one using ultrasonic p and s waves velocities frequency 106 hz 2 and a new one using oscillation tests frequency 10 2 hz in dry condition experimental data show no significant difference between high hf and low lf frequency bulk moduli however in saturated conditions two effects are highlighted a physico chemical effect emphasized by a difference between drained and dry moduli and a squirt flow effect evidenced by a difference between hf and lf undrained moduli

geochemical and tectonic relationships in the east indonesian arc continent collision region implications for the subduction of the australian passive margin abstract van bergen m j vroon p z and hoogewerff j a 1993 geochemical and tectonic relationships in the east indonesian arc continent collision region implications for the subduction of the australian passive margin in m j r wortel u hansen and r sabadini editors relationships between mantle processes and geological processes at or near the earth s surface tectonophysics 223 97 116 variations in the isotopic signatures of volcanics along the east sunda banda arc reflect changes in the nature and amount of sedimentary material supplied by the northeast indian ocean floor and the adjacent australian passive continental margin which form the two major domains of the indian ocean plate that approach the arc system a compilation of isotopic data for 200 500 km long arc sectors shows that the trend in magmatic signatures follows distinct subduction collision stages reached by the corresponding oceanic and continental margin sections entering the trench system maximum amounts of magma source contamination are inferred for volcanics near an extinct sector north of timor where the australian continent started to collide with the arc first pb nd isotopic source mixing models point to contamination by sediments with variations in composition similar to observed along arc changes in sediments entering the trench the results indicate an increasing contribution of subducted continental material in the direction of the collision region mass balance calculations considering the magmatic output and minimum input of subducted continental material required to generate the composition of the volcanic arc in the collision region are difficult to reconcile with subduction of ocean floor sediments alone thicknesses of sediments presently covering oceanic crust near the margin are close to calculated thicknesses of the sediments fluxed into the trench and magmatically returned to the arc crust but cannot account for the additional volumes of material accreted on the overriding plate in the same period of time it is inferred that leading portions of the australian continental margin have reached magma generation zones in the easternmost sunda arc and western banda arc which implies subduction to depths greater than 100 km

the albano maar lake colli albani volcano italy recent volcanic activity and evidence of pre roman age catastrophic lahar events abstract the evaluation of volcanic hazard in the roman hinterland related to the quiescent colli albani volcano has recently been the subject of renewed attention and several interpretations by many authors however very little was known of the recent history of the volcano making such interpretations rather speculative the most recent activity of colli albani volcano originated from the albano polygenetic maar lake which erupted several phreatomagmatic units the most recent of which the peperino albano ignimbrite has been dated at around 25 ka an area of several square kilometers centered around albano lake is presently the site of shallow and frequent seismic activity and gaseous emission as well as hydrothermal activity and is therefore considered the most prone to geologic hazards this paper presents new stratigraphic and geomorphologic data as well as age determinations that allow rejuvenation of the most recent activity of the colli albani volcano and particularly the albano maar lake to the holocene this study allows for the first time to identify a potential hazard related to the albano maar lake withdrawal interpreted to be related to endogenous causes namely co 2 emission the main results of the study are 1 the peperino albano is not as is generally believed the last phreatomagmatic eruption from the colli albani volcano a previously unrecognized phreatomagmatic surge deposit has been identified overlying the paleosol at the top of the peperino albano and related lahar deposits 2 two lahar deposits separated by paleosols top the stratigraphic succession and are dispersed only to the nw corresponding to the lowest point of the maar rim indicating that catastrophic hydrologic events occurred at the albano lake in recent times rapid and substantial lake level variations and lake withdrawal are reported by roman historians and recorded by the stratigraphy of the albano lake lacustrine sediments 3 microfracturing related to seismic energy release is linked to sudden variation of co 2 flow and upwelling of hydrothermal fluids these occurrences across the lake are the likely causes that triggered during holocene several episodes of lake withdrawal rising the water table and probably triggering convective rollover of the lake water

chemical and isotopic compositions of volcanic gases from the east sunda and banda arcs indonesia the easternmost sunda arc and the banda arc represent a continent arc collision zone where magma genesis is influenced by subducted continent derived material chemical and isotopic studies of volcanic gas samples from this environment provide information on the sources of volatiles in arc magmas these volcanic gases some of which last equilibrated at magmatic temperatures are characterized by anomalous low sup 3 he sup 4 he values but by common arc values of c s approx 2 4 delta sup 13 c approx minus 3 per thousand and delta sup 34 s sub tot approx 5 per thousand abundant helium and high he ar ratios are consistent with the subduction of terrigenous components in local sediments or slivers of continental crust although individual concentration and isotope ratios of volatile components may be explicable by complex fractionation in the recycling process the combined data are in agreement with an important role of subducted sedimentary source components comparison of the authors results with volcanic gas data from other arcs indicates that the carbon and sulfur signals in arc gases are relatively insensitive to the amount and nature of sediment on the subsiding plate hence a contribution to arc volcanic gases from subducted altered oceanic crust cannot be excluded

upper mantle domains beneath central southern italy petrological geochemical and geophysical constraints the italian peninsula shows high complexity of the mantle crust system and of the plio quaternary magmatism the lithospheric thickness has remarkable lateral variations from about 110 km to about 30 km intermediate and deep focus earthquakes indicate the presence of a lithospheric slab under the aeolian calabrian area and at the southern end of campania much less extensive intermediate depth seismicity characterizes the roman tuscany region where the existence of a relic slab has been hypothesized the deep seismicity in the southern tyrrhenian sea is associated with active calcalkaline to shoshonitic volcanism in the aeolian arc alkaline potassic volcanism occurs in central italy and potassic lamproitic magmatism coexists with crustal anatectic and various types of hybrid rocks in the tuscany area the parallelism between changing magmatism and variation of the structure of the crust mantle system makes central southern italy a key place where petrological and geophysical data can be used to work out an integrated model of the structure and composition of the upper mantle beneath tuscany the upper mantle has been affected by intensive subduction related metasomatism this caused the formation of phlogopite rich veins that cut through residual spinel harzburgite and dunite these veins possibly partially molten may explain the unusually soft mechanical properties that are detected just below the moho in the roman province the upper mantle is formed by a relatively thin lid the mantle part of the lithosphere and by metasomatic fertile peridotite probably connected with the upraise of an asthenospheric mantle wedge above the apennines subduction zone geochemical data indicate that metasomatism though still related to subduction had different characteristics and age than in tuscany in the eastern sector of the aeolian arc and in the neapolitan area the upper mantle appears to be distinct from the roman and tuscany areas and is probably formed by fertile peridotite contaminated by the presently active subduction of the ionian sea floor the overall picture is that of a mosaic of various mantle domains that have undergone different evolutionary history in terms of both metasomatism and pre metasomatic events the coexistence side by side of these sectors is a key factor that has to be considered by models of the geodynamic evolution of the central mediterranean area

geochemistry of the albano and nemi crater lakes in the volcanic district of alban hills rome italy abstract lake albano located 20 km to the se of rome is hosted within the most recent crater of the quiescent alban hills volcanic complex that produced hydromagmatic eruptions in holocene times stratigraphic archaeological and historical evidence indicates that the lake level underwent important variations in the bronze age before the iv century b c several lahars were generated by water overflows from the lake and in the iv century b c romans excavated a drainage tunnel the lake is located above a buried carbonate horst that contains a pressurized medium enthalpy geothermal reservoir from which fluids escape to the surface to produce many important gas manifestations of mostly co2 previous studies recognized the presence of gas emissions also from the crater bottom in 1997 the possibility of a nyos type event triggered by a lake rollover was considered very low because the co2 water concentration at depth was found to be far from saturation however considering the high population density nearby the italian civil protection department recommended that periodical monitoring be carried out to this scope we initiated in 2001 a systematic geochemical study of the lake thirteen vertical profiles have been repeatedly carried out in 2001 2006 especially in the deepest part of the lake 167 m in 2006 measuring t ph dissolved o2 and electrical conductivity water samples were collected from various depths and chemically and isotopically analysed two similar profiles have been measured also in the nearby nemi crater lake results indicate that in the 4 5 years of monitoring the pressure of gas dissolved in the lake albano deep waters remained much lower than the hydrostatic pressure a co2 soil survey carried out on the borders of the two lakes indicates the presence of some zones of anomalous degassing of likely magmatic origin a water overturn or a heavy mixing of deep and shallow waters likely occurred in winter 2003 2004 when cold rainfall cooled the surface water below 8 5 c such overturns cause only a limited gas exsolution from the lake when the deep water is brought to a few meters depth but can explain the observed decrease with time of dissolved co2 at depth and related water ph increase a gas hazard could occur in the case of a sudden injection through the lake bottom of a huge quantity of co2 rich fluids which might be caused by earthquake induced fracturing of the rock pile beneath the lake a limnic gas eruption might also occur should co2 concentration build up within the lake for a long time

helium and argon from an atlantic morb glass concentration distribution and isotopic composition data are reported for detailed he and ar measurements on a single morb glass from the atlantic ch 98 dr 11 30 41 n 41 49 w depth 3500 m grain size fractions prepared under ambient conditions are strongly affected by diffusive loss of he from grains and by adsorption of atmospheric argon on grain surfaces both effects could be controlled by crushing gram sized chunks of glass under vacuum and analyzing the powder without any further handling in particular without its exposure to the atmosphere gases from vesicles released upon crushing are characterized by a4he 40ar ratio of6 1 and a40ar 36ar ratio of up to 22 600 in dissolved gases the4he 40ar ratio was found to be 7 2 1 6 times higher and the40ar 36ar ratio to be about ten times lower than in vesicles the difference of theelemental ratio he ar is as anticipated from the ratio of the solubilities ca nine in the investigated basalt of he and ar thus whileelemental abundance ratios are compatible with equilibrium between vesicles and basalt the grossly different argonisotopic ratios are not it is proposed that two basalts chemically very similar but with different40ar 36ar ratios were mixed shortly before eruption the overall4he 40ar ratio in the vesiculated basalt is12 2 so that for the ratio in the primary magma we find6 4he 40ar 12 which is considerably higher than the radiogenic production ratio in all conceivable sources of morb preferential removal from a melt of argon via vesicles is suggested to be the most likely explanation whereas any metasomatic transfer seems unrealistic

hydraulic and acoustic properties as a function of porosity in fontainebleau sandstone laboratory measurements have been made of the permeability k free porosity l compressional velocities vp or ve and compressional attenuations qp or qe in fontainebleau sandstone over a continuous range of porosities from 3 to 28 this large variation was achieved without any composition change fontainebleau sandstone is made of fine quartz grains with regular grain size 250 m permeability was measured with a falling head permeameter velocities and attenuations were obtained either through an ultrasonic experiment for frequencies around 500 khz or through a resonant bar technique experiment for frequencies around 5 khz and in both cases with varying water saturation the results show an excellent correlation between permeability k and total porosity for all our samples for low porosities 3 to 9 permeability in millidarcies is 2 75 10 5 7 33 while for high porosities 9 to 28 permeability k in millidarcies is given by 0 303 3 05 the correlation is also excellent between free porosity and total porosity on the other hand the correlation between acoustic properties and total porosity is not as clear as for hydraulic properties whatever the frequency 500 khz or 5 khz or the water saturation on the average velocity decreases and attenuation roughly increases with increasing total porosity velocity and attenuation values are related to the variation of grain contact structure and two samples with the same porosity and permeability may exhibit different velocities and attenuations the clear correlation between hydraulic properties and porosity is related to constant grain size while the lack of correlation for acoustic properties emphasizes the importance of the microstructure

transfer of sulfur in subduction settings an example from batan island luzon volcanic arc philippines sulfur abundances have been determined in silicic and basaltic melt inclusions in olivines from harzburgitic xenoliths and a basaltic lava sample all from batan island in mantle xenoliths olivines fo80 91 are present as neoblasts or in finely recrystallized patches the most magnesian olivines fo89 7 91 cao 85 cao 0 25 wt and their melt inclusions cao al2o3 from 0 8 to 1 15 have recorded early stages of crystallization the sulfur concentrations for these calc alkaline basaltic melts are estimated between 1720 and 3200 ppm with a mean value at 2550 ppm 1 390 and s cl ratio at nearly 1 this is in agreement with the idea that arc basaltic melts may contain high concentrations of sulfur s 2000 ppm at 1200 c however the heterogeneous distribution of s and its partitioning between silicate melts h2o rich vapor and s bearing solid phases as illustrated by the batan mantle xenoliths would result in highly variable sulfur concentrations in island arc basaltic magmas mostly controlled by fo2 and fs2

shear modulus and internal friction of calcite rocks at seismic frequencies pressure frequency and grain size dependence abstract the shear modulus g and associated internal friction q 1 have been measured at seismic frequencies for a suite of four essentially monomineralic calcite rocks with grain sizes ranging from 4 to 1000 m the measurements are based on a previously described technique for the observation of forced torsional oscillations of a series combination of a rock cylinder and a steel standard under high confining pressure at room temperature the behaviour of each rock has been studied as a function of strain amplitude 10 8 10 6 maximum at surface pressure 0 300 mpa and oscillation period 1 300 s no evidence is found of any departure from linearity in the range of strain amplitudes studied corrections which are significant only at the shortest periods 1 3 s have been applied to the raw data to account for the influence of torques exerted on the specimen assembly by the gas pressure medium up to about 100 mpa increase in pressure results in a marked increase in g and decrease in q 1 attributable to the closure of crack porosity except in the fine grained solnhofen limestone in which both g and q 1 are insensitive to change in pressure indicative of the virtual absence of crack porosity at higher pressures g is much less pressure sensitive and q 1 is essentially pressure independent with values less than 0 001 in all four rocks since the rock specimens were jacketted under conditions of normal humidity these relatively low values of q 1 indicate a diminished role for adsorbed water in the anelasticity of rocks at high effective pressures within the pressure independent regime q 1 is essentially independent of frequency for periods of 3 100 s and increases by only 30 as the grain size decreases from 1000 to 4 m thus within this regime it is concluded that the observed value of q 1 results to a large degree from an intracrystalline mechanism with a broad range of relaxation times the possibility of significant dislocation damping will be discussed

gas composition of the january 1983 eruption of kilauea volcano hawaii abstract gas collections were made from a 900 c vent both by conventional evacuated bottle wet chemical techniques and by manual pumping of flowthrough bottles the complete analyses suggest an equilibrium assemblage quenched at 1 010 c about midway between fountain and vent temperatures i suggest that the very low c s ratio is due to degassing of co2 during storage of the magma in a shallow reservoir before eruption the two sampling techniques yielded analytical data in mutual agreement

isotopic constraints on the role of subducted sialic material in indonesian island arc magmatism the island arcs of indonesia exhibit a range of subduction related tectonic environments and consequently are of particular interest in studying the relationship between the nature of the subducted plate and volcanism the sunda arc in java manifests the underthrusting of oceanic lithosphere beneath the newly accreted margin of asia in the banda arc continental material appears to be subducting beneath a volcanic arc that is underlain by oceanic crust 87sr 86sr ratios 0 7040 to 0 7059 in holocene andesitic lavas from java are higher than those from other volcanic arcs except those arcs where sialic contamination has been inferred a group of anomalous calc alkaline lavas characterized by high 87sr 86sr ratios 0 7054 to 0 7059 and relatively high abundances of k and related elements appear to be the result of sialic contamination of a mantle derived melt high 87sr 86sr ratios as large as 0 7095 together with values of 18o as large as 9 2 smow in lavas from the banda arc imply mixing of mantle derived and sialic components because of the tectonic peculiarities of the region the most likely source of contamination is from subduction of terrigenous material derived from the northwest continental shelf of australia lead isotopic ratios in lavas from java are generally transitional to the trends defined by other arc lavas and are characterized by higher 207pb 206pb ratios than oceanic basalts the anomalous calc alkaline lavas in particular are characterized by relatively high 207pb 206pb ratios interpreted to result from subduction and melting of sediments derived from the precambrian shields of australia and india during the opening of the indian ocean neodymium isotope ratios lie within the range defined from other volcanic arcs in terms of 143nd 144nd and 87sr 86sr the banda arc samples lie on a mixing line between compositions typical of the mantle and the upper continental crust that subducted sediments appear as a component in at least some of the holocene indonesian lavas implies melting at the top of the subducted lithospheric slab and provides constraints on the thermal structure of the descending plate

recent terrestrial and satellite observations to model deformations at colli albani volcano central italy the colli albani volcanic complex rome italy has been dominated by episodic eruptions commencing around 561 ka and ending with the most recent activity of the albano maar phase 70 ka earthquakes of moderate intensity gas emissions and significant ground deformations are the recent evidences of a residual activity former geodetic data from leveling surveys gps stations and insar observations tracked ongoing significant uplift of the order of few mm year near the colli albani western flank different uplift rates were detected by each technique in different time spans suggesting also the possibility of sporadic recharge of the hydrothermal system the renewed high precision leveling data from igmi survey carried out in 1997 1999 and the last leveling survey carried out in 2006 show that the uplift along the route is currently significant at an average rate of 3 mm year radar interferograms from alos satellite show uplift rate of 6 mm year southwest of the central sector of the leveling route we have undertaken a joint inversion of the various geodetic data vertical rates from leveling surveys gps site velocities and insar observations acquired by alos satellite using a nonlinear inversion technique to estimate the parameters of a point pressure source possibly capable of explaining the ongoing deformation at colli albani volcano

geochemistry of the acid kawah putih lake patuha volcano west java indonesia abstract kawah putih is a summit crater of patuha volcano west java indonesia which contains a shallow 300 m wide lake with strongly mineralized acid sulfate chloride water the lake water has a temperature of 26 34 c ph s tot 2500 4600 ppm and cl 5300 12 600 ppm and floating sulfur globules with sulfide inclusions are common sulfur oxyanion concentrations are unusually high with s 4 o 6 2 s 5 o 6 2 s 6 o 6 2 2400 4200 ppm subaerial fumaroles thermodynamic modeling of the lake fluids indicates that the lake water is saturated with silica phases barite pyrite and various pb sb cu as bi bearing sulfides when sulfur saturation is assumed precipitating phases predicted by the model calculations are consistent with the bulk chemistry of the sulfur rich bottom sediments and their identified mineral phases much of the lake water chemistry can be explained by congruent rock dissolution in combination with preferential enrichments from entering fumarolic gases or brines and element removal by precipitating mineral phases as indicated by a comparison of the fluids volcanic rocks and lake bed sediment flank springs on the mountain at different elevations vary in composition and are consistent with local rock dissolution as a dominant factor and ph dependent element mobility discharges of warm sulfate and chloride rich water at the highest elevation and a near neutral spring at lower level may contain a small contribution of crater lake water the acid fluid induced processes at patuha have led to the accumulation of elements that are commonly associated with volcano hosted epithermal ore deposits the dispersal of heavy metals and other potentially toxic elements from the volcano via the local drainage system is a matter of serious environmental concern

a preliminary stable isotope study of volcanic ashes discharged by the 1979 eruption of ontake volcano nagano japan sulphur isotopic compositions of pyrite anhydrite and native sulphur in volcanic ashes discharged by the 1979 eruption of ontake volcano nagano japan were determined the isotopic data indicate that sulphate in anhydrite and a part of native sulphur were produced by the disproportionation reaction of sulphite formed by dissolution of so2 in volcanic gases into water which filled a mud reservoir probably located just below the crater zone some part of h2s in volcanic gases was fixed as pyrite and some was oxidised to form native sulphur hydrothermal alteration of country rocks to form pyrite anhydrite and clay minerals had proceeded in the mud reservoir before eruption at temperatures ranging from 110 to 185 c which were estimated by oxygen isotopic fractionation between anhydrite and water

the sirung volcanic boiling spring an extreme chloride rich acid brine on pantar lesser sunda islands indonesia abstract the sirung volcano with a history of phreatomagmatic outbreaks has its present active center within a 1000 m wide subsidence crater the sirung crater lake scl has 15 g l 1 cl and 19 g l 1 so4 ph 0 75 temperature 40 c a highly saline brine sirung boiling spring sbs boils to the surface beside the lake it contains 116 g l 1 cl ph 1 4 chemical geothermometers indicate a reservoir temperature of 240 c the maximum depth of this reservoir is estimated to be 400 m the stable isotope composition is d 12 and 18o 5 0 to 6 0 tritium in the sbs is 0 0 tu in the scl 4 6 tu evidence against invading seawater as a source is the negative d value in addition to the six times higher cl concentration of the sbs evaporites are rejected as a source of the cl because of the geologic setting the average cl h 2 o ratio in sirung volcanic glasses as estimated by microprobe is very close to the cl h 2 o ratio of 0 047 for the sbs the zero tritium level in the sbs its high cl concentration and the acid character are other evidences for magmatic water as source for the sbs the acid sbs is poor in sulphur which may have been precipitated at depth as sulphides theories on porphyry cu formation in volcanic arc environments invoke highly saline brines as the transporting agent the acid saline brines from the sirung and white island new zealand craters and cl rich crater lakes associated with andesitic volcanism in subduction zones indicate that such fluids occur more frequently at the surface than has been possibly realized hitherto

effect of the volume of the drainage system on the measurement of undrained thermo poro elastic parameters abstract for evaluation of the undrained thermo poro elastic properties of saturated porous materials in conventional triaxial cells it is important to take into account the effect of the dead volume of the drainage system the compressibility and the thermal expansion of the drainage system along with the dead volume of the fluid filling this system influence the measured pore pressure and volumetric strain during an undrained thermal or mechanical loading in a triaxial cell the correction methods previously presented by wissa pore pressure measurement in saturated stiff soils asce j soil mech found div 1969 95 sm 4 1063 73 bishop influence of system compressibility on observed pore pressure response to an undrained change in stress in saturated rock geotechnique 1976 26 2 371 5 and ghabezloo and sulem stress dependent thermal pressurization of a fluid saturated rock rock mech rock eng 2009 42 1 1 24 only permit one to correct the measured pore pressures during an undrained isotropic compression test or an undrained heating test an extension of these methods is presented in this paper to correct the measured volumetric strain and consequently the measured undrained bulk compressibility and undrained thermal expansion coefficients during these tests two examples of application of the proposed correction method are presented for an undrained isotropic compression test and an undrained heating test performed on a fluid saturated granular rock a parametric study has demonstrated that the porosity and the drained compressibility of the tested material and the ratio of the volume of the drainage system to the one of the tested sample are the key parameters that most influence the error induced by the drainage system

rollover in volcanic crater lakes a possible cause for lake nyos type disasters abstract seemingly stably stratified fluids that is a heavier layer of fluid underlying an upper layer of lighter fluid can overturn if there is a heat flux through the system such events are termed rollover in the engineering literature occurring for instance in liquid natural gas tanks they take place as well in lakes and ponds in all such cases the stratification starts off with the heavier more dense fluid underlying lighter convection driven mixing at the stratification interface due to the heat flux as well as other processes serves to minimize with time the stabilizing density differences which may eventually cause the stratification to invert if gas has been contained under pressure in the lower layer this gas may explosively vent from the fluid as it suddenly rises to the top such as occurs in liquid natural gas tanks where rollover is a hazard these processes are quantifiable and are applied here to various scenarios that might refer to volcanic crater lakes whose lower layers are charged with volatiles provided herein are some examples of calculated conditions and calculated time of evolution leading to rollover with attendant release of gases from supersaturated ascending fluids these calculations suggest rollover could occur in volcanic lakes the august 1986 gas release at lake nyos is employed as an example these estimates were made taking note that water is commonly supersaturated in co2

hydrothermal vent waters at 13 n on the east pacific rise isotopic composition and gas concentration abstract gas concentrations and isotopic compositions of water have been measured in hydrothermal waters from 13 n on the east pacific rise in the most mg depleted samples 5 10 3 moles kg the gas concentrations are 3 4 5 10 5 cm 3 stp kg helium 0 62 1 24 cm 3 stp kg ch 4 10 80 16 71 10 3 moles kg co 2 the samples contain large quantities 95 126 cm 3 kg of h 2 and some carbon monoxide 0 26 0 36 cm 3 kg which result from reaction with the titanium sampling bottles 13 c in methane and co 2 16 6 to 19 5 and 4 1 to 5 5 respectively indicate temperatures between 475 and 550 c whereas 13 c co is compatible with formation by reduction of co 2 on ti at 350 c close to the sampling temperature 3 he 4 he are very homogeneous at 7 5 0 1 r a 3 he 4 he 1 0 10 5 and very similar to already published data as well as ch 4 3 he ratios between 1 4 and 2 1 10 6 18 o and d in water show enrichments from 0 39 to 0 69 and from 0 62 to 1 49 respectively these values correspond to w r ratios of 0 4 7 the distinct 18 o enrichments indicate that the isotopic composition of the oceans is not completely buffered by the hydrothermal circulations the 3 he enthalpy relationship is discussed in terms of both hydrothermal heat flux and 3 he mantle flux

postcollision extension in arc continent collision zones eastern indonesia postcollisional extension superimposed on arc continent collision complexes is a common feature in the orogenic belts of eastern indonesia in the southern banda arc the arc continent collision event is essentially a pliocene and younger feature but already an element of extension is being superimposed on the compressional structures of the collision complex it is thus likely that the extension commences within a very short period 5 m y after the initiation of collision related compressional deformation a similar history of fold belt development immediately followed by extension can be inferred for the lengguru fold belt and the adjacent wandamen wondiwoi terranes of irian jaya and for the gulf of bone in sulawesi it is suggested that the extension results from decoupling of the subducting oceanic lithosphere from the unsubductable continental lithosphere and that the superimposition of extension is a virtually unavoidable consequence of the arc continent collision

a new seismic wave attenuation module to experimentally measure low frequency attenuation in extensional mode abstract a seismic wave attenuation module is developed to experimentally measure the attenuation in extensional mode qe 1 and the young s modulus of copper jacketed 60 mm long and 25 4 mm in diameter samples in a gas medium paterson rig the new module is suitable for natural rock samples and was tested under confining pressure up to 50 mpa and room temperature the module is designed to operate at a strain 10 6 for which rocks behave linearly to calculate attenuation both the applied force and the bulk shortening of the sample are measured employing linear variable differential transformers this technique allows measuring samples with a high degree of heterogeneity attenuation at low seismic frequencies 10 2 102 hz is obtained for rocks at dry and various saturation conditions we present a series of measurements on berea sandstone in a room dry condition and saturated with different fluids water and glycerine solutions with viscosities of 10 cp and 22 cp respectively at a confining pressure of 10 mpa and with a pore pressure of 1 mpa the accuracy of the attenuation data expressed as a phase shift is 0 0019 rad

medium temperature fumarolic gas sampling in order to sample medium temperature fumaroles gases are collected by means of iron or glass tubings and conveyed to the condensation system through glass dewar tubes one type of condenser was designed for condensate measurement and gas sampling for radon activity determination the other with naoh absorbing solution for the s cl ratio measurement and the sampling of rare gases with this method it is possible to obtain precise gas vapour measurements as well as air free gas samples

the stable isotope geochemistry of volcanic lakes with examples from indonesia abstract stable isotope compositions d 18o and 34s of volcanic lake waters gas condensates and spring waters from indonesia italy japan and russia were measured the spring fluids and gas samples plot in a broad array between meteoric waters and local high temperature volcanic gas compositions the d and 18o data from volcanic lakes in east indonesia plot in a concave band ranging from local meteoric waters to evaporated fluids to waters heavier than local high temperature volcanic gases we investigated isotopic fractionation processes in volcanic lakes at elevated temperatures with simultaneous mixing of meteoric waters and volcanic gases an elevated lake water temperature gives enhanced kinetic isotope fractionation and changes in equilibrium fractionation factors providing relatively flat isotope evolution curves in 18o d diagrams a numerical simulation model is used to derive the timescales of isotopic evolution of crater lakes as a function of atmospheric parameters lake water temperature and fluxes of meteoric water volcanic gas input evaporation and seepage losses the same model is used to derive the flux magnitude of the keli mutu lakes in indonesia the calculated volcanic gas fluxes are of the same order as those derived from energy budget models or direct gas flux measurements in open craters several 100 m3 volcanic water day and indicate a water residence time of 1 2 decades the 34s data from the keli mutu lakes show a much wider range than those from gases and springs which is probably related to the precipitation of sulfur in these acid brine lakes the isotopic mass balance and s cl values suggest that about half of the sulfur input in the hottest keli mutu lake is converted into native sulfur

a deep search for the release of volcanic gases on mars using ground based high resolution infrared and submillimeter spectroscopy sensitive upper limits for ocs and so2 abstract recent volcanic activity has long been considered a distinct possibility that would place major constraints on the evolution of mars interior volcanic activity would result in the outgassing of sulfur bearing species as part of our multi band search for active release of volcanic gases on mars we looked for carbonyl sulfide ocs at its combination band 1 3 at 3 42 m 2924 cm 1 and sulfur dioxide so 2 at 346 652 ghz in two successive mars years during its late northern spring and mid northern summer seasons l s 43 144 the targeted volcanic districts tharsis and syrtis major were observed during the two intervals 15 dec 2011 to 6 jan 2012 in the first year and 23 may 2014 to 12 june 2014 in the second year using the high resolution infrared spectrometer cshell on the nasa infrared telescope facility and the high resolution heterodyne receiver harp at the james clerk maxwell telescope atop maunakea hawaii no active release of such gases was detected and we report 2 upper limits of 1 8 ppbv and 3 1 ppbv for ocs and so 2 respectively compared to 0 3 ppbv for so 2 encrenaz t et al 2011 astron astrophys 530 a37 krasnopolsky v a 2012 icarus 217 144 152 over the disk of mars our retrieved upper limit on the so 2 outgassing rate of 156 tons day 1 8 kg s corresponds to a mass rate of magma that is able to degas the so 2 of 104 kilotons day 1200 kg s or 40 000 m 3 day 0 46 m 3 s our campaign places stringent limits on the concentration of sulfur bearing species into the atmosphere of mars

linear pressurization method for determining hydraulic permeability and specific storage of a rock sample summary we studied the methodology and applicability of linear pressurization for determining simultaneously hydraulic permeability and specific storage of a rock sample we analytically solved the governing equation for 1 d pressure diffusion through a homogenous isotropic cylindrical rock specimen located between a downstream and an upstream reservoir considering linear pressurization of the upstream fluid as the boundary condition the solution consists of a transient and a steady state for which both differential pressure between the two reservoirs and injection rate at the upstream reservoir assume constant values since the steady state differential pressure is linearly proportional to the compressive storage of the downstream reservoir tests conducted with a systematic variation of the size of the downstream reservoir permit determining permeability and specific storage from the intercept and slope of the linear relationship alternatively simultaneous measurement of differential pressure and fluid injection rate at steady state conditions provides a basis for calculation of the hydraulic properties as previously presented for linear injection experiments were performed on fontainebleau sandstone samples to document the feasibility of the method the determined storage capacity value is used to calculate various poroelastic parameters such as bulk and pore space compressibility skempton and the effective pressure coefficient

fluid mobility and frequency dependent seismic velocity direct measurements the influence of fluid mobility on seismic velocity dispersion is directly observed in laboratory measurements from seismic to ultrasonic frequencies a forceddeformation system is used in conjunction with pulse transmission to obtain elastic properties at seismic strain amplitude 10 7 from 5 hz to 800 khz varying fluid types and saturations document the influence of pore fluids the ratio of rock permeability to fluid viscosity defines mobility which largely controls pore fluid motion and pore pressure in a porous medium high fluid mobility permits pore pressure equilibrium either between pores or between heterogeneous regions resulting in a low frequency domain where gassmann s equations are valid in contrast low fluid mobility can produce strong dispersion even within the seismic band here the low frequency assumption fails since most rocks in the general sedimentary section have very low permeability and fluid mobility shales siltstones tight limestones etc most rocks are not in the lowfrequency domain even at seismic frequencies only those rocks with high permeability porous sands and carbonates will remain in the low frequency domain in the seismic or sonic band

gas hazard assessment in a densely inhabited area of colli albani volcano cava dei selci roma the northwestern flank of the colli albani a quaternary volcanic complex near rome is characterised by high pco2 values and rn activities in the groundwater and by the presence of zones with strong emission of gas from the soil the most significant of these zones is cava dei selci where many houses are located very near to the gas emission site the emitted gas consists mainly of co2 up to 98 vol with an appreciable content of h2s 0 8 2 the he and c isotopic composition indicates as for all fluids associated with the quaternary roman and tuscany volcanic provinces the presence of an upper mantle component contaminated by crustal fluids associated with subducted sediments and carbonates an advective co2 flux of 37 tons day has been estimated from the gas bubbles rising to the surface in a small drainage ditch and through a stagnant water pool present in the rainy season in a topographically low central part of the area a co2 soil flux survey with an accumulation chamber carried out in february march 2000 over a 12 000 m2 surface with 242 measurement points gave a total mostly conductive flux of 61 tons day co2 soil flux values vary by four orders of magnitude over a 160 m distance and by one order of magnitude over several metres a fixed network of 114 points over 6350 m2 has been installed in order to investigate temporal flux variations six surveys carried out from may 2000 to june 2001 have shown large variations of the total co2 soil flux 8 25 tons day the strong emission of co2 and h2s which are gases denser than air produces dangerous accumulations in low areas which have caused a series of lethal accidents to animals and one to a man the gas hazard near the houses has been assessed by continuously monitoring the co2 and h2s concentration in the air at 75 cm from the ground by means of two automatic stations certain environmental parameters wind direction and speed atm p t humidity and rainfall were also continuously recorded at both stations h2s and co2 exceeded by several times the recommended concentration thresholds the highest co2 and h2s values were recorded always with wind speeds less than 1 5 m s mostly in the night hours our results indicate that there is a severe gas hazard for people living near the gas emission site of cava dei selci and appropriate precautionary and prevention measures have been recommended both to residents and local authorities

a laboratory study of low frequency wave dispersion and attenuation in water saturated sandstones abstract laboratory measurements of elastic and anelastic parameters of dry and water saturated sandstones with low 0 7 and 1 1 md and high 425 md permeability have been conducted at seismic frequencies 0 1 to 120 hz the experiments were performed with a laboratory apparatus that measures the stress strain relationship in the linear regime the extensional attenuation in water saturated low permeability sandstones exhibits prominent peaks in the seismic band accompanied by considerable dispersion variations in attenuation and dispersion in the high permeability sandstone are below the measurement error as is the moduli dispersion in all the sandstones in dry condition the experiments demonstrate that for low permeability rocks seismic frequencies do not necessarily correspond to the low frequency limit relaxed pore fluid pressures of acoustic wave dispersion

helium strontium isotope constraints on mantle evolution beneath the roman comagmatic province italy european social fund scottish universities carnegie trust for the universities of scotland

neodymium isotopic composition of quaternary island arc lavas from indonesia abstract 143 nd 144 nd ratios measured in quaternary lavas from java and the banda arc of indonesia range from 0 51242 to 0 51280 and exhibit an inverse correlation with 87 sr 86 sr isotopically the indonesian samples resemble andean rather than island arc lavas the samples from java plot either within or adjacent to the mantle array towards higher 87 sr 86 sr ratios samples from the banda arc and the anomalous calc alkaline volcano papandajan are characterized by relatively low 143 nd 144 nd and high 87 sr 86 sr ratios these characteristics are consistent with the interpretation that subducted terrigenous material was involved in the genesis of these lavas furthermore the banda arc samples appear to lie on a mixing line between isotopic compositions characteristic of the mantle and upper continental crust a high k trachyte from the alkaline volcano muriah java has isotopic characteristics of the mantle 143 nd 144 nd 0 51270 87 sr 86 sr 0 70424 which implies that the extreme enrichment in large ion lithophile elements in its source must have occurred only shortly before its formation the inferred 143 nd 144 nd ratio of the unmodified mantle beneath java and the banda arc is lower than that observed in mid ocean ridge basalt which may have important implications for a better understanding of the geochemical structure of the mantle

an evaluation of the solubility of sulfide sulfur in silicate melts from experimental data and natural samples abstract an evaluation of the solubility of sulfur in silicate melts from experimental data obtained under a wide variety of experimental conditions has been undertaken under reducing conditions fo2 below qfm sulfur is present as sulfide ii oxidation state and precipitates as pyrrhotite or an fe s o sulfide phase when the sulfur concentration in the silicate melt is sufficiently high the basic solubility reaction is 1 2 s 2 g o 2 silicate melt 1 2 o 2 g s 2 silicate melt for silicate melts with high feo contents 10 wt feo sulfur dissolves as an fe3so2 or 2feo fes species when saturated with pyrrhotite fes sulfide melt 2feo silicate melt fe 3 so 2 silicate melt log k log x s 21ogx feo 0 8 at 1200 c 1 bar under saturated and unsaturated conditions 1 2 s 2 g 3feo silicate melt fe 3 so 2 silicate melt 1 2 o 2 g log k log x s 1 2 1og o 2 3 log x feo 1 2 log s 2 4 1 at 1200 c 1 bar log k also shows a positive pressure dependence 0 1 per kbar for silicate melts with low feo contents fes sulfide melt o 2 silicate melt feo silicate melt s 2 silicate melt log k log x s log x feo 5 8 9007ndash 1000 c 1 6 kbar for silicate melts with intermediate feo contents 1 10 wt feo the behavior of sulfur is more complex with sulfur probably present as an fes species fes sulfide melt fes silicate melt log k log x s 1 05 3000 t k 850 1200 c 1 bar 2 2 kbar the effects of temperature pressure melt composition and other experimental conditions have been assessed the ability to predict the solubility of sulfur in silicate melts has implications for the formation of ore deposits associated with igneous systems application of the results to natural systems shows that some samples have a concentration of sulfur higher than that which could have been dissolved in the silicate melt indicating that the magma carried excess sulfur and or sulfur has been added after crystallization of the magma

mapping magma sources in the east sunda banda arcs indonesia constraints from helium isotopes abstract we report new helium isotope analyses of olivine and clinopyroxene separates from recent lavas for eleven volcanoes from flores in the east sunda arc through the inactive segment between the arcs to banda island at the extreme of the contiguous banda arc in the east sunda arc 3 he 4 he ratios r vary between 4 5 ra r a air 3 he 4 he for the leucitic batu tara volcano to a remarkable low of pure radiogenic helium 0 0075 ra for werung at the southern tip of lomblen island lavas from the inactive zone which represents the locus of collision of the australian continent with the arc have a narrower range in r r a from 3 9 for kisu in the straits of pantar to 1 0 for romang island our one locality banda island in the banda arc gives the highest r r a ratio 3 1 observed along this arc to date the results are consistent with the involvement of crustal material in magma genesis throughout the east sunda banda arcs as far west as iya in central flores we combine these helium isotope results with published and on going strontium isotope studies and show that the source of the helium in the crustal component is unlikely to be terrigenous sediments derived from the australian continent rather degassing of australian continental crust appears to be the dominant process controlling the helium budget the he sr isotope systematics also provide a framework to account for the areal pattern of 3 he 4 he in this part of the arcs the radiogenic crustal component is diluted with mantle helium both in a down dip direction and with increasing lateral distance from the collision zone these factors result in an excellent first order relationship between the 3 he 4 he ratio degree of he sr enrichment relative to the postulated mantle endmember and alkalinity of the erupted lavas such a relationship has a direct bearing on models of the tectonic evolution of the collision zone and on the observation that helium isotopes are decoupled from strontium and other geochemical signatures along the banda arc

peculiar features of suiyo seamount hydrothermal fluids izu bonin arc differences from subaerial volcanism abstract this is the first report of the dissolved gas composition of a deep sea venting hydrothermal system originating from arc volcanism the origin of dissolved gases in hydrothermal fluids from the suiyo seamount in the southern izu bonin ogasawara arc is discussed on the basis of chemical and isotopic compositions twelve high temperature up to 310 c fluid samples were collected from three vents of the hydrothermal system using the submersible shinkai 2000 the average 3 he 4 he ratio of the dissolved he is 8 1 r r atm which is within the range of values reported for n morb the co 2 3 he ratio is 12 109 which is within the range of arc volcanic gas values the 13c values of co2 and ch4 are 1 and 8 5 respectively which is quite high compared with other subaerial arc volcanic gases and those from mid ocean ridges these results which do not accord with those from subaerial volcanism are unlikely to result from fractionation or addition of carbon sources during the fluid circulation but are regarded as characteristic of the magma source of suiyo seamount a simple mixing of 97 morb mantle with 3 subducting slab explains well the composition of the helium and carbon in the parent magma

volcanic unrest of the colli albani central italy detected by gps monitoring test this work has been partially supported by the dept of civil protection project dpc115 v3 colli albani

active tectonics of the eastern sunda and banda arcs the tectonics of the eastern sunda and banda arcs of eastern indonesia are inferred from the centroid depths seismic moments and fault plane solutions of 63 large earthquakes that occurred between 1962 and 1984 source parameters are estimated by inverting long period teleseismic p and sh waves earthquakes show that the collision of the australian continent with the banda arc shortens the upper plate beneath the forearc and back arc basin over the broad area between the timor and seram troughs along the eastern end of the sunda arc and along the southern banda arc earthquakes reveal that the arc and forearc respond to collision by shortening in the direction of convergence by elongating in the direction perpendicular to convergence and by thrusting over the back arc basin shallow thrust and strike slip earthquakes beneath the banda basin the back arc basin demonstrate that deformation within the back arc accommodates some of the northward motion of the australian continent the rate of north south shortening of the entire upper plate at the longitude of timor calculated from the seismic moments of the earthquakes over the 22 year period is roughly 20 of the predicted convergence rate between australia and southeast asia strike slip faulting within the banda basin results also in eastward motion of the banda arc with respect to western indonesia and australia eastward extrusion of the banda arc results in thrusting at the aru trough earthquakes due to thrusting of the back arc basin beneath the volcanic arc are too shallow to corroborate that the arc s polarity has reversed although the wetar back arc thrust zone at present has a high seismic slip rate earthquakes and their mechanisms provide evidence that the lithosphere of the weber basin a 7500 m deep forearc basin rests on the subducting lithosphere without intervening asthenosphere so that the weber basin subsides in response to sinking of the subducting lithosphere closure of the banda basin is geometrically incompatible with the australian plate subducting simultaneously beneath both the timor and seram troughs instead the bird s head which subducts beneath seram is decoupled from the australian plate in western new guinea and probably moves west or southwest with respect to australia in the eastern indonesian example strike slip faulting plays a major role in the evolution of the collision zone and clearly demonstrates the complexity in three dimensions of continental accretion and mountain building by arc continent collision

effect of fluids and frequencies on poisson s ratio of sandstone samples abstractpoisson s ratio is an important parameter when interpreting measured geophysical and seismic data for an isotropic medium it directly relates to the ratio of p and s wave velocities we have measured as a function of pressure and frequency in fluid saturated sandstones the method of measuring was first tested as a function of pressure and frequency using standard samples the phase shift between radial and axial strains was also measured for all standard samples such as the linear viscoelastic plexiglas the data indicated that tan correlated with and related to a dissipation on then and tan were measured as a function of pressure and frequency for two dry and fluid saturated fontainebleau sandstone samples under dry conditions no frequency dependence and very small pressure dependence were observed unusual behaviors were observed under fluid saturated conditions in particular of one sample indicated a frequency dependent bell shaped dispersion under water and gl

carbon sources in arc volcanism with implications for the carbon cycle new co2 3 he data from the east sunda arc indonesia confirm earlier observations that arc volcanic gases have higher co2 3 he ratios than mor environments on average 80 of arc volcanic co2 is recycled exogene carbon addition of a few percent of carbonate bearing sediments to the mantle wedge explains much of the carbon abundance andcarbon isotopic data of arc gases but can not explain the he isotope observations the co2 3he in arc volcanoes is not strongly dependent on the composition of modem trough sediments e g deep sea clays vs carbonate rich sequences and calcite veins in the hydrothermally altered subducted slab may provide a contribution to the recycled carbon flux of arcs the sum of globally deep subducted sediment and slab carbon exceeds the estimated arc co2 flux and approximately 3 5 teramole of carbon may return annually to the mantle in convergent zones the modem combined processes of mor volcanism slab alteration and subduction volcanism do not produce a substantial carbon flux into the exosphere and rate changes in ocean floor spreading are unlikely to cause major changes in atmospheric co2 as a result of changes in the volcanic co2 fluxes intense pulses of flood basalt volcanism however may alter the co2 contents of the atmosphere over the course of a millenium or so and influence global climate

the origin of the potassic rock suite from batu tara volcano east sunda arc indonesia abstract atu tara is an active potassic volcano in the eastern sunda arc its leucite bearing rock suite can be subdivided into two groups one less evolved with th 20 ppm 87sr 86sr 18o and trace element systematics in the less evolved group suggests that existence of parental magmas with different mantle origins the mantle below batu tara is most likely heterogeneous and several source components are involved in magma genesis trace element and isotopic compositions of batu tara and adjacent volcanoes are consistent with the involvement of a subducted sedimentary crustal component as well as morb and oib mantle the latter with geochemical characteristics comparable to the mantle underlying muriah java melt extraction from this complex mixture is envisioned as a two stage process partial melts of the crust contaminated morb mantle mix in the mantle wedge with partial melts of oib domains different mixtures of these two melts provide the parental magmas that enter the volcanic plumbing system where crystallization hybridization and refilling processes occur the calcalkaline volcanoes in the arc segment show stronger signatures for a subducted crustal component than batu tara which displays a greater influence from the oib mantle source the potassium enrichment can therefore be attributed to contributions both from the enriched mantle and from subducted crustal material mantle type 18o values of the batu tara magmas indicate that the mantle wedge below potassic orogenic volcanoes is not necessarily strongly enriched in 18o

new method for measuring compressibility and poroelasticity coefficients in porous and permeable rocks over the last decades a large understanding has been gained on the elastic properties of rocks rocks are however porous materials which properties depend on both response of the bulk material and of the pores because in that case both the applied external pressure and the fluid pressure play a role different poroelasticity coefficients exist while theoretical relations exist measuring precisely those different coefficients remains an experimental challenge accounting for the different experimental complexities a new methodology is designed that allows attaining accurately a large set of compressibility and poroelasticity coefficients in porous and permeable rocks this new method relies on the use of forced confining or pore fluid pressure oscillations in total seven independent coefficients have been measured using three different boundary conditions because the usual theories predict only four independent coefficients this overdetermined set of data can be checked against existing thermodynamic relations measurements have been performed on a bentheim sandstone under water and glycerine saturated conditions for different values of confining and pore fluid pressure consistently with the poroelasticity theory the effect of the fluid bulk modulus is observed under undrained conditions but not under drained ones using thermodynamic relations i the unjacketed quartz and skeleton zimmerman s relation bulk moduli fit ii the drained and undrained properties fit and iii it is directly inferred from the measurements that the pore skeleton compressibility c phi is expected to be constant with pressure and to be exceedingly near the bulk skeleton c s and mineral c m compressibility coefficients plain language summary poroelastic properties of rocks are a major information for a large variety of applications linked to rupture processes in saturated media theories exist to link the properties to measurable parameters yet only little measurements exist to confront those theories this article aims at providing a method for accurately measuring those properties moreover for one particular rock a large amount of compressibility and poroelastic coefficients is measured and used to confront those theories

water chemistry of lake albano italy abstract lake albano was stratified at the time of our survey in december 1997 in agreement with previous observations martini et al geochem j 28 1994 173 184 cioni et al report for the civil protection department 1995 pedreschi accad lucch sci lett arti 1995 39 in the absence of phenomena induced by seismic activity either local or regional lake stratification may be perturbed by cooling of shallow waters below 8 5 c circulation is expected to homogenize lake waters and eventually to trigger gas exsolution when total gas pressure exceeds hydrostatic pressure in december 1997 total gas pressure in lake water was very close to atmospheric pressure 0 9 1 3 bar at all depths possibly due to the occurrence of a recent episode of circulation and presumed gas exsolution the state of saturation of lake albano waters and the similarity of the relative concentrations of na k mg and ca in lake waters local groundwaters and local volcanic rocks indicate that na k mg and ca concentrations in lake albano waters are mainly governed by incongruent dissolution of local volcanic rocks coupled with minor calcite precipitation at shallow depths

major and rare gases at white island volcano new zealand origin and flux of volatiles analyses of fumarolic gases at white island new zealand are reported with special emphasis on rare gases he ne ar kr and xe normalization of major species to rare gases have lead to the identification of several sources air saturated meteoric or marine water a magma body the crust and or sediments when compared to mid ocean ridge discharges the white island gas discharge represents about 3 0 7 0 1 and 0 05 of the global water carbon sulfur and helium 3 discharges respectively this balance shows that except for 3he which derives from the mantle practically all rare gases water and carbon and part of sulfur derive from originally superficial sources

isotopic composition of precipitation in italy a first overall map abstract composite monthly samples of atmospheric precipitation were collected over different periods of time ranging from one to seven years at 77 different locations throughout italy these samples were measured for their oxygen and hydrogen isotopic composition to obtain basic information for hydrological and meteorological studies in this area on the basis of the results obtained a first map of the isotopic composition of precipitations in italy has been drawn up the main features of this map are the following 1 no isotopic latitudinal gradient has been found along the tyrrhenian coast from sicily to the italian french border despite the considerable range of latitude 2 a minor latitudinal gradient is found in the southeasternmost section of the country apulia partially favored by the local morphology 3 a marked shadow effect of the apennines is apparent along the southern section of the po valley and along the central section of the adriatic coast 4 the contribution of water vapor from the northernmost section of the adriatic sea affects the eastern and central sections of the po plain 5 the shadow effect of the alps is considerably smaller than expected 6 the isotopic vertical gradients calculated in nine different areas and based on groups of two to five different stations vary but are essentially close to about 0 2 100 m 7 when mean monthly temperature values were available their relationship with the isotopic composition of precipitation was found to be on average very poor 8 the relationship between mean 18o and mean d calculated for the collection locations shows shifts of both the slope and the deuterium excess when compared to the global meteoric water line these shifts are different for northern central and southern italy 9 in a few cases anomalously low monthly values suggest the existence of pronounced amount effects

hazardous gas emissions from the flanks of the quiescent colli albani volcano rome italy abstract gas hazard was evaluated in the three most important cold gas emission zones on the flanks of the quiescent colli albani volcano these zones are located above structural highs of the buried carbonate basement which represents the main regional aquifer and the main reservoir for gas rising from depth all extensional faults affecting the limestone reservoir represent leaking pathways along which gas rises to the surface and locally accumulates in shallow permeable horizons forming pressurized pockets that may produce gas blowout when reached by wells the gas mainly composed of co 2 90 vol contains appreciable quantities of h 2 s 0 35 6 vol and both represent a potentially high local hazard both gases are denser than air and accumulate near ground where they may reach hazardous concentrations and lethal accidents frequently occur to animals watering at local ponds in order to evaluate the rate of degassing and the related hazard co 2 and h 2 s diffuse soil flux surveys have been repeatedly carried out using an accumulation chamber the viscous gas flux of some important discrete emissions has been evaluated and the co 2 and h 2 s air concentration measured by portable devices and by tunable diode laser profiles the minimum potential lethal concentration of the two gases 250 ppm for h 2 s and 8 vol for co 2 is 320 times higher for co 2 whereas the co 2 h 2 s concentration ratio in the emitted natural gas is significantly lower 15 159 this explains why h 2 s reaches hazardous even lethal concentrations more frequently than co 2 a relevant hazard exists for both gases in the depressed zones channels excavations particularly in the non windy early hours of the day

evidence of active crustal deformation of the colli albani volcanic area central italy by gps surveys abstract colli albani is a volcanic complex located in central italy very close to the city of rome its last eruption is dated at 0 03 0 02 ma now it displays a recurrent seismicity sporadic gas emissions from soils wells and springs and post volcanic hydrothermal circulation moreover an uplift of about 30 cm over the last 43 years was recently detected by comparing the height differences between some vertices of repeated leveling surveys thus suggesting a recent active magmatic process beneath the volcano in 1995 a first epoch gps campaign was carried out with last generation receivers the repetition campaign was performed in 1996 data coming from the two repeated surveys were carefully processed and analyzed a statistical analysis rigorously applied between the 1995 and 1996 adjusted coordinates shows significant coordinate differences some sites of the network in particular the sites of vivaro vvr cava di ciampino cva and istituto nazionale di geofisica ingr display a significant subsidence of 2 6 0 7 2 7 0 8 and 2 0 0 8 cm respectively with a confidence interval at 95 percent level this subsidence seems to be induced by a water table level lowering in vivaro while in the area where the sites of cava di ciampino and ingr are located this motion is also confirmed by historical levelling data that show a subsidence of 2 cm yr during the last 45 years and could be due to local tectonics moreover significant planimetric deformations are exhibited by the site of castel romano csr it is remarkable that the stations of cva ingr and csr are located in the area that was struck by the june 12 1995 m d 3 8 earthquake although the displacement vectors are quite small the motion of the capranica prenestina cpr station which shows an uplift of 2 7 0 7 cm must be considered separately being located outside the volcanic structure and placed over the carbonatic outcrops of the prenestini mts furthermore the accuracy obtained in height determinations does not allow us to confirm if the central part of the gps network corresponding to the area investigated by amato and chiarabba is uplifting within the analyzed time span