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

isotopic and chemical assessment of geothermal potential of the colli albani area latium region italy abstract the chemical and isotopic compositions of low temperature mineral waters discharged over the colli albani region south of rome italy are those of highly immature waters of essentially meteoric origin formed through absorption of gases emanating from greater depth followed by cation leaching of country rock at shallow levels the composition of the gases discharged points to the presence at depth of a co2 producing high temperature system in its waning stage low h2 and unsaturated hydrocarbon contents as well as relative he ar and n2 contents indicate long residence time for the rising gas phase of the order of 1 ma on the basis of these findings temperatures higher than 120 c appear unlikely to exist at shallow depth

roman comagmatic province central italy evidence for subduction related magma genesis geochemical data on mafic volcanics show that important affinities exist between the roman and the calc alkaline rocks from the aeolian arc south tyrrhenian sea these affinities together with the close association of calc alkaline and k rich volcanics in the aeolian arc and in the naples area the continuity in the variation of abundances of incompatible elements from calc alkaline to potassic suites and the similarity in terms of major element geochemistry support a genetic relationship of the roman magmatism and the subduction processes that affected the apennines in tertiary time and are still active under the aeolian arc in the genetic model presented here both calc alkaline and k rich magmas were generated within a mantle heterogenously enriched in lil elements composition of the mantle was modified by addition of material probably sediments dragged down by the undergoing slab the geochemical and petrological differences displayed by the calc alkaline and k rich volcanics are accounted for by the different conditions of melting as well as by chemical and isotopic heterogeneities of the source 26 references 3 figures 1 table

flux measurements of nonvolcanic co2 emission from some vents in central italy in central italy nonvolcanic co2 is discharged from many areas of focused degassing vents and associated strong diffuse emission and from high pco2 groundwater we estimate that there are at least 100 co2 vents in central italy many of which have a history of lethality to animals and humans the gas vents are extremely efficient pathways for transporting large amounts of deeply derived co2 from gas reservoirs to the surface as co2 fluxes from these vents were heretofore unmeasured several complementary methods were developed to measure the co2 flux from seven of these vents which cumulatively discharge 3 1 109 mol yr 1 co2 472 t d 1 considering all of the vents in central italy the total co2 flux from vents alone may be similar to the co2 emission from the taupo volcanic zone in new zealand 1010 mol yr 1 1200 t d 1 and other areas of high heat flow summing the co2 discharged from vents areas of diffuse co2 degassing and degassing of high pco2 groundwater we provisionally estimate that the total nonvolcanic co2 flux to the atmosphere in central italy may be 1011 mol yr 1 12 000 t d 1

rate of diffuse carbon dioxide earth degassing estimated from carbon balance of regional aquifers the case of central apennine italy central italy is characterized by an anomalous flux of deeply derived co2 in the western tyrrhenian sector of central italy co2 degassing occurs mainly from focused emissions vents and strong diffuse degassing and thermal springs whereas in the eastern apennine area deep co2 is dissolved in cold groundwaters of regional aquifers hosted by mesozoic carbonate evaporite formations influx of deep co2 into 12 carbonate aquifers 12 500 km2 of the central apennine is computed through a carbon mass balance that couples aquifer geochemistry with isotopic and hydrogeological data mass balance calculations estimate that 6 5 1010 mol yr 1 of inorganic carbon are dissolved in the studied aquifers approximately 23 of this amount derives from biological sources active during the infiltration of the recharge waters 36 comes from carbonate dissolution while 41 is representative of deep carbon sources characterized by a common isotopic signature 13c 3 the calculated deep co2 influx rate ranges from 105 to 107 mol yr 1 km 2 increasing regionally from east to west in the study area

thermal springs in italy their relation to recent tectonics the large scale circulation of thermal waters in italy is reviewed from both a chemical and an isotopic point of view two main areas are recognized one in the alpine region and the other in the central southern apennine region the alps are an area of very high hydraulic heads and low thermal gradients where hot deep seated waters of meteoric origin rapidly reach the surface along active boundary fault systems the apennines in contrast are characterized by lower hydraulic heads and higher thermal gradients all thermal springs in italy including those in active volcanic areas originate essentially from meteoric waters and most follow long pathways in mesozoic carbonate anhydritic aquifers before emerging as indicated by relations among present hydrothermal activity in central southern italy deep crustal structures and pco2 content in thermal waters

helium 3 anomalies and crust mantle interaction in italy abstract the distribution of primordial 3he in the crust of italy has been investigated through a survey of groundwaters hot springs exploration and production geothermal wells the mantle derived component varies from 0 to 60 and reaches a maximum at vulcano in the eolian islands 3he anomalies occur where the conductive heat flow is relatively high but the relationships between heat flow and anomaly are uncertain the distribution of 3he in the main reservoir and cap rock to the larderello geothermal system shows that the mantle derived 3he varies from 5 to 40 of total he and reaches a maximum in fluids extracted from a depth of ca 3 km within the basement bomb produced tritiogenic 3he appears to make a near negligible contribution well 107 at larderello has been monitored over a period of 17 months and the 3 he 4 he ratio r varies from 1 4 to 1 6 times the atmospheric ratio ra whilst he ne varies from 9 to 160 a model is proposed for the larderello geothermal system whereby mantle derived heat and volatiles are advected to shallow 6 8 km depths in association with melts and released into the main geothermal reservoir at larderello in a non uniform manner possibly associated with fracturing isotopic and elemental equilibrium of gaseous species c o h appears to have taken place in the basement to the main reservoir from where fluid with r ra 3 2 has been extracted

gas blowout from shallow boreholes near fiumicino international airport rome gas origin and hazard assessment abstract in summer 2013 a toxic and polluting gas blowout 19 tonnes day 1 co2 95 kg day 1 ch4 occurred from two shallow boreholes drilled at only 50 m from the international airport of rome italy in the town of fiumicino another gas blowout occurred in the same period from a borehole located offshore 2 km away also generating sea water acidification it lasted only a couple of days onshore co2 was also diffusing from holes within the soil particularly toward the airport generating a soil flux up to 1 8 tonnes day 1 in 3 5 months 1500 tonnes of co2 and 5 4 tonnes of ch4 were emitted in the atmosphere temporal monitoring of gas geochemistry indicates that in this area a mixing occurs between shallow and pressurized gas pockets co2 dominated but with different chemical i e he ch4 ratio and isotopic 3he 4he 13c dch4 characteristics numerical simulation of co2 dispersion in the atmosphere showed that dangerous air co2 concentrations up to lethal values were only found near the vents at a height of 0 2 m fiumicino is a high blowout risk area as co2 rising through deep reaching faults pressurizes the shallow aquifer contained in gravels confined underneath shales of the tiber delta deposits the fiumicino blowout is a typical example of dangerous phenomenon that may occur in urban context lying nearby active or recent volcanoes and requires quick response on hazard assessment by scientists to be addressed to civil protection and administrators

accounting for the marine reservoir effect in radiocarbon calibration abstract the radiocarbon dating method is supported by highly refined calibration data empirically obtained from environmental archives nevertheless marine calibration remains problematic due to the spatiotemporally variable marine reservoir effect mre the currently accepted curve for radiocarbon calibration in the ocean is a global curve partly derived by numerical modelling from its atmospheric counterpart as such this curve cannot account for the effects of local phenomena strongly correlated with 14c signatures in seawater e g ocean dynamics and continental input although the radiocarbon community has suggested the use of regional calibration curves that would better represent the heterogeneous ocean reservoir a reasonable method for their construction has not yet been proposed we directly address this longstanding issue in radiocarbon research by exploring the output of a model for the temporal evolution of the mre the limitations of this model are inherited by our method and this hinders the use of the regional curves derived here in many regions of the world ocean nevertheless the approach described in this paper remains valid regardless of the chosen model and our preliminary results show that with the future development of accurate and highly resolved models for the mre this method may be a promising alternative to the use of r values in the process of marine calibration

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

economic geology hidden gold how the giant sediment hosted gold deposits of nevada were formed is disputed a model linking regional tectonics with magma emplacement and fluid generation at depth suggests that these deposits result from an optimal coincidence of processes

fluxes of deep co2 in the volcanic areas of central southern italy abstract both the shallow organic derived and deep mantellic magmatic metamorphic fluxes of co 2 co 2 mass time 1 and specific fluxes of co 2 co 2 mass time 1 surface 1 dissolving in the shallow groundwaters of the volcanic areas of amiata vulsini vico sabatini albani roccamonfina vesuvio vulture and etna were evaluated by partitioning the composed population of total dissolved inorganic carbon in two individual populations and subsequent subtraction of local background population the flux of deep co 2 released from the geothermal fields of piancastagnaio amiata torre alfina latera marta bracciano south cesano and mofete and from the overall northern latium hydrothermal reservoir were also evaluated by means of the total surface heat flux and the enthalpy and co 2 molality of the single liquid phase circulating in each geothermal reservoir these data suggest that the co 2 released to the atmosphere varies from 9 5 10 6 to 3 0 10 6 mol year 1 km 2 over the geothermal fields of bracciano south and cesano respectively and that a total co 2 of 3 8 10 8 mol year 1 is cumulatively released from the geothermal fields of torre alfina latera and cesano extending over an area of only 66 km 2 in addition a flux of 2 2 10 11 to 3 8 10 11 mol year 1 of gaseous co 2 entering the atmosphere is obtained for the entire anomalous area of central italy extending from the tyrrhenian coastline to the apennine chain 45 000 km 2 thus terrestrial co 2 emission in central southern italy appears to be a significant carbon source

multiple mantle metasomatism in central southern italy geochemical effects timing and geodynamic implications the regional petrological and geochemical variations observed in the recent magmatism along the italian peninsula are interpreted to testify to the coexistence of distinct sectors of upper mantle these are suggested to result from at least three compositionally and temporally distinct metasomatic events that affected petrologically different premetasomatic mantle sources geological and geochemical evidence suggests that metasomatism in the northern sector occurred during the alpine subduction by introduction of a composition similar to the deeply subducted dora maira metagranites into a residual lithospheric mantle of upper crustal material metasomatic events beneath the roman and neapolitan areas are younger these are related to the addition of melts and fluids into a fertile asthenospheric mantle during the latest stage of the west directed apennine subduction of the adria plate and during the current northwest subduction of the ionian sea floor

gas blowout from shallow boreholes at fiumicino rome induced hazard and evidence of deep co2 degassing on the tyrrhenian margin of central italy abstract a borehole drilled at fiumicino rome down to only 27 m depth in a zone where no gas emission at the surface was known caused a gas blowout from a pressurized gas pocket confined beneath a clay cover gas slowly diffused from the borehole within superficial permeable sand seven persons living in three ground floor flats of a near building had to be hospitalized due to co2 exposure all the houses in the proximity were evacuated at the request of the fire brigade two additional boreholes were drilled nearby hoping that this could rapidly exhaust the gas stored underground to the contrary the soil gas flux near houses increased and indoor co2 air concentration rapidly rose to lethal values 15 to 30 vol as a remediation we suggested to restore the continuity of the impervious gas cover by squeezing quick setting cement into the formation through new boreholes to be drilled near the existing ones although the first cement squeeze reduced drastically the co2 soil flux and indoor concentration six additional squeezes had to be carried out in order to lower the gas emission below the gas hazard threshold the gas was mostly made of co2 98 vol with minor n2 and ch4 its chemical and isotopic composition 13cco2 1 55 3he 4he 0 314 ra is similar to that of the gas manifestations of mts sabatini and alban hills volcanic areas though being somewhat contaminated by crustal and shallow organic volatiles these gases likely have a component originated in the mantle that beneath the volcanic roman comagmatic province is probably deeply contaminated with crustal material the fiumicino gas blowout indicates that the area of central italy characterized by strong co2 degassing extends westerly to include the tyrrhenian coast

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

physical stratigraphy and sedimentology of the late pleistocene holocene tiber delta depositional sequence the tiber delta lies on the passive continental margin of central western italy the tiber delta is a late pleistocene holocene sedimentary succession and constitutes an incomplete high frequency depositional sequence 4th or 5th order which developed from the last post glacial rise in sea level to the present stillstand it is bound by a type 1 basal unconformity which cuts pleistocene deposits five depositional systems have been identified 1 coastal barrier lagoon 2 shelf transition 3 fluvial braided 4 tiber lagoonal deltas t1 t2 t3 and 5 tiber wave dominated delta the first four systems constitute the transgressive system tract tst which is characterized by a retrogradational parasequences set while the fifth system represents the highstand system tract hst characterized by only one parasequence progradational the evolution of these depositional systems has been mostly controlled by sea level rise which was not continuous but punctuated by eight minor stillstands and rapid rises this mechanism of sea level change led to the formation of parasequences that developed within the depositional systems from a palaeogeographical point of view the present tiber delta area was mainly characterized by a coastal barrier lagoon and tiber lagoonal deltas t1 t2 t3 which migrated landwards during the sea level rise throughout the time of the present stillstand the t3 lagoonal delta prograded rapidly into the lagoon reaching the coastal barrier and the lagoon was replaced first by marshes and then by the alluvial plain finally the tiber river overcame the littoral barrier supplying the coast giving rise to the present wave dominated delta

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

carbon dioxide earth degassing and seismogenesis in central and southern italy 1 we present the first regional map of co2 earth degassing from a large area most of central and south italy derived from the carbon of deep provenance dissolved in the main springs of the region the investigation shows that a globally significant amount of deeply derived co2 10 of the estimated global co2 emitted from subaerial volcanoes is released by two large areas located in western italy the anomalous flux of co2 suddenly disappears in the apennine in correspondence to a narrow band where most of seismicity concentrates here at depth the gas accumulates in crustal traps generating co2 overpressurized reservoirs which induce seismicity