boron geochemistry from some typical tibetan hydrothermal systems origin and isotopic fractionation the tibetan plateau is characterized by intense hydrothermal activity and abnormal enrichment of trace elements in geothermal waters hydrochemistry and b isotope samples from geothermal waters in tibet were systematically measured to describe the fractionation mechanisms and provide constraints on potential b reservoirs b concentrations range from 0 35 to 171 90 mg l and isotopic values vary between 16 57 and 0 52 geothermal fields along the indus yarlung zangbo suture zone and n s rifts are observed with high b concentrations and temperatures the similar hydrochemical compositions of high b geothermal waters with magmatic fluid and consistent modeling of b isotopic compositions with present 11b values imply that the b in high b geothermal waters is mainly contributed by magmatic sources probably through magma degassing in contrast geothermal fields in other regions of the lhasa block have relatively low b concentrations and temperatures after considering the small fractionation factor and representative indicators of na ca cl hco3 na k and si the conformity between modeling results and the isotopic compositions of host rocks suggests that the b in low temperature geothermal fields is mainly sourced from host rocks according to simulated results the b in some shallow geothermal waters not only originated from mixing of cold groundwater with deep thermal waters but it was also contributed by equilibration with marine sedimentary rocks with an estimated proportion of 10 it was anticipated that this study would provide useful insight into the sources and fractionation of b as well as further understanding of the relationships between b rich salt lakes and geothermal activities in the tibetan plateau

shallow creep on the haiyuan fault gansu china revealed by sar interferometry interferometric synthetic aperture radar data are used to map the interseismic velocity field along the haiyuan fault system hfs at the north eastern boundary of the tibetan plateau two m 8 earthquakes ruptured the hfs in 1920 and 1927 but its 260 km long central section known as the tianzhu seismic gap remains unbroken since 1000 years the envisat sar data spanning the 2003 2009 period cover about 200 300 km2 along three descending and two ascending tracks interferograms are processed using an adapted version of roi pac the signal due to stratified atmospheric phase delay is empirically corrected together with orbital residuals mean line of sight velocity maps are computed using a constrained time series analysis after selection of interferograms with low atmospheric noise these maps show a dominant left lateral motion across the hfs and reveal a narrow 35 km long zone of high velocity gradient across the fault in between the tianzhu gap and the 1920 rupture we model the observed velocity field using a discretized fault creeping at shallow depth and a least squares inversion the inferred shallow slip rate distribution reveals aseismic slip in between two fully locked segments the average creep rate is 5 mm yr 1 comparable in magnitude with the estimated loading rate at depth suggesting no strain accumulation on this segment the modeled creep rate locally exceeds the long term rate reaching 8 mm yr 1 suggesting transient creep episodes the present study emphasizes the need for continuous monitoring of the surface velocity in the vicinity of major seismic gaps in terms of seismic hazard assessment

replenishment crystal accumulation and floor aggradation in the megacrystic kameruka suite australia detailed field evidence indicates that the kameruka suite plutons of the bega batholith eastern australia grew by crystal accumulation on the floor of a magma chamber depositional features in the plutons including mafic enclave channels asymmetric enclave pillows and exotic rafts load casts and flame structures and graded and trough cross beds indicate that the pluton built progressively upward the general eastward dip of depositional features in the main pluton implies a lower western and upper eastern contact consistent with a basal granite migmatite contact in the west and a sharp hornfelsic sidewall contact in the east mafic felsic and composite dykes most common near and below the basal western contact are interpreted as conduits for magma chamber replenishment and imply open system behaviour during pluton construction textural relations are also consistent with an open system cumulate origin typically centimetre scale grains of quartz plagioclase and megacrystic alkali feldspar form a touching framework with interstices filled with smaller biotite flakes and smaller intercumulus quartz and feldspar crystals alkali feldspar megacrysts vary from euhedral and unzoned to mantled and partially replaced by plagioclase to ovoid and completely pseudomorphed by quartz albite aggregates the common occurrence of mantled and pseudomorphed alkali feldspar in mafic enclaves and in hybrid tonalitic rocks forming the matrix to enclave swarms suggests that replacement or resorption of granitic primocrysts was associated with mafic replenishments the occurrence of all megacryst types at outcrop scale implies extended alkali feldspar crystallization in different parts of the chamber thorough stirring during or after periodic replenishment and final settling in a cumulate mush the bulk composition of the cumulate mush represented by granodiorite cannot represent the emplaced magma compositional variation can be modelled by variable degrees of crystal accumulation from a parental silica rich melt represented by the silicic dykes as dykes periodically fed the magma chamber crystals accumulated on the floor and more evolved melts probably erupted from its roof thus the average composition of the magma and the cumulus minerals may have remained relatively constant and the sublinear chemical trends that typify the kameruka suite simply reflect differing proportions of melt and cumulate material sublinear chemical trends can also be explained by a restite model however the distinctive ba light rare earth element and zr spikes at high silica can be explained only by a cumulate model which also explains why the low silica granites of the suite share the same chemical characteristics as the high silica granites

the origin of rapakivi texture by sub isothermal decompression abstract the rapakivi texture plagioclase mantled k feldspar ovoids rounded quartz megacrysts and euhedral plagioclase megacrysts in a more fine grained granitic matrix has been studied in five proterozoic 1 64 1 55 ga anorogenic rapakivi granite batholiths in the fennoscandian shield with emphasis on mineral stability and inherited cores k feldspar ovoids and rounded quartz megacrysts with deep embayments consist principally of a core zone and an outer melted and recrystallized zone when the k feldspar ovoids are mantled by plagioclase the outermost part of the mantle is homogeneous but towards the k feldspar a skeletal texture develops intensive parameters obtained from different textural positions show that mineral inclusions in cores of the k feldspar ovoids and quartz megacrysts were formed at low t 680 720 c and high p 5 6 kbar conditions while inclusions in the periphery of ovoids and the plagioclase mantles display high t 780 c and intermediate to low p 3 5 1 kbar the lowest p is comparable to that during solidification of the matrix the total water equivalent of the volatile content in the magma has been calculated as 2 5 the amount of solids in the magma at 1 kbar has been estimated as 40 theoretical calculations and experimental data for mineral stabilities in granitic systems suggest that the texture formed when a crystal saturated kfsp qtz pl 60 and volatile undersaturated a type granite magma was transported under approximately constant temperature 760 780 c from the lower middle crust 5 6 kbar to upper crustal levels according to phase stabilities in the eutectoid granite system quartz and k feldspar were resorbed but plagioclase remained stable and precipitated during this sub isothermal rise of magma textural presence of disequilibrium textures and mineralogical presence of different mineral assemblages including relics evidence of a sub isothermal rise of the rapakivi magmas is better preserved in subvolcanic and contact varieties of rapakivi granites than in the more deep seated rapakivi granites formed by slow cooling

plagioclase mantles on sanidine in silicic lavas clear lake california implications for the origin of rapakivi texture at clear lake california mixed dacite lavas contain sanidine mantled by oligoclase that closely resemble rapakivi feldspars in granites resorption and mantling of sanidine by plagioclase is one of many disequilibrium textures in these lavas resulting from maficfelsic magma interaction mantling of sanidine by plagioclase may occur directly in mixed magmas due to shifts in composition and temperature or indirectly in crystal rich silicic magmas influenced by thermal under plating or mafic felsic hybridization in adjacent regions of the magmatic system other silicic laves containing mantled sanidine also show evidence for mafic felsic magma interaction textural and compositional similarities between rapakivi texture in extrusive and intrusive rocks suggest that they have a common origin moreover modification of early formed textures due to protracted crystallization subsolidus reactions and metasomatic hydrothermal alteration in the plutonic environment accounts for most of the observed differences between extrusive and intrusive examples the association of coeval mafic rocks and evidence for mafic felsic magma interaction in many plutons containing rapakivi exture confirm that magma mixing plays a key role in its formation in some intrusive texamples evidence for a compositional control and multiple episodes of mantle formation are also compatible with repeated cycles of recharge and mixing regardless of the exact cause of k feldspar instability textural evidence from volcanic rocks and experiments indicates that development of rapakivi texture is controlled by cation diffusion in a dissolution boundary layer developed on k feldspar mantles appear to form in a two stage process that involves initial epitaxial nucleation of plagioclase on sanidine followed by simultaneous dissolution of sanidine and inward growth of plagioclase

volcanology history and myths of the lake albano maar colli albani volcano italy abstract the polygenetic albano maar is the most recent centre of the colli albani volcano located just few kilometres to the south east of roma presently the maar hosts a 167 5 m deep crater lake the deepest in europe the maar is to be considered quiescent as phreatic activity is documented throughout the holocene this paper illustrates the close relationships between the activity of the maar and the history of settlement in the roman region as recorded in the geology archaeology history and legends of the area severe fluctuations of the groundwater table and catastrophic overflows of the lake albano from the maar rim had occurred prior to and after the early prehistoric settlements dated in the maar area at the eneolithic times ca iii millennium b c repeated lahars occurred along the northwestern slope of the maar filling in the paleodrainage network and forming a vast plain paleohydraulic analyses on fluvial and lahar deposits originated from the holocene phreatic activity of the albano maar indicate sediment water flows in excess of hundreds of cubic metres per second absolute age determinations of the paleosoil underlying one of the most recent deposits of the lahar succession at 5800 100 yr b p 14 c cal are in perfect agreement with the age of the overlying eneolithic age settlements the last catastrophic overflow is described in the roman literature as a consequence of the anger of poseidon against the romans in 398 b c for their war against the etruscans in 394 b c the romans decided to prevent the repetition of such events by the excavation through the maar crater wall of a 1 5 km long drain tunnel which is still operational keeping the lake 70 m below the lowest point of the maar rim this tunnel drain may be regarded as the first prevention device for volcanic hazard in history and shows an unprecedented development of the engineering technology under the pressure of hazard perception the surprising and still largely unknown results of this study are very important to redefine the hazard of the roman region

geochemistry and origin of early proterozoic dongargarh rapakivi granite complex central india an example for magma mixing and differentiation abstract early proterozoic dongargarh granite complex of central india intruding the tonalitic to granodioritic amgaon gneisses and the nandgaon group bimodal volcanic suite comprises three different textural and compositional types viz porphyritic granodiorite pg coarse equigranular granite eg and microgranite mg synplutonic mafic dykes are common in the granite complex the pg is characterised by rapakivi texture and the eg is the dominant facies and exhibits sporadically developed rapakivi texture microgranular enclaves are common in the eg while they are rare in pg major and trace element geochemistry of pg shows marked i type and some occasional a type granite characters unusual for a rapakivi granite while the eg shows a type granite signatures the field petrographic chemical and isotopic data of these granites suggest their derivation by mixing of mantle derived basic magma with a crustal derived partly crystalline granitic magma episodic mafic magma underplating caused the anatexis of the archaean lower continental crust in a continental margin tectonic setting resulting first in the formation of the i type granodiorite followed by a type granite the i type granodiorite is mixed with the basic magma synplutonic dykes while the eg is formed by mingling of a type granite magma and the intruding basic magma

coherence and amplitude based analysis of seismogenic damage in bam iran using envisat asar data the sensitivity of synthetic aperture radar sar and interferometric sar insar to surface properties especially changes in height and roughness combined with an all weather capability makes radar remote sensing a potential tool for mapping urban damage caused by earthquakes with insar surface displacement has been mapped successfully and in detail but for urban damage mapping results have so far been less conclusive envisat advanced sar images of bam iran that were acquired before and after the 2003 earthquake were used between preseismic and coseismic image pairs coherence decreased with increasing damage levels however contrary to previous studies earthquake damage caused both increases and decreases in amplitude therefore its absolute value which correlated with damage level was used individually coherence difference led to better results than absolute amplitude change although still with limited accuracy the combination of both resulted in an overall accuracy of 52 since vegetation causes decorrelation a predisaster advanced spaceborne thermal emission and reflection radiometer image was used to mask out vegetated areas which improved the accuracy by 4 the ground truth map showed damage levels per district instead of per pixel therefore the ratio of pixels classified as damage and nondamage was calculated for each damage class of the map and a clear relation was found this shows that the aggregation level of the map partly explains the low accuracy figures of the pixel based evaluation although improvement was made insar techniques for urban damage mapping do not yet provide the accuracy levels needed for disaster mitigation however substantial improvements can be expected from instruments with higher spatial resolution such as the recently launched phased array type l band sar and terra sar x

fluid geochemistry and geothermometry in the unexploited geothermal field of the vicano cimino volcanic district central italy abstract the vicano cimino volcanic district vcvd is related to the post orogenic magmatic activity of the peri tyrrhenian sector of central italy the chemical and isotopic compositions of 333 water discharges and 25 gas emissions indicate the occurrence of two main sources 1 cold ca hco 3 to ca na k hco 3 type waters from relatively shallow aquifers hosted in volcanic and sedimentary formations and 2 thermal ca so 4 hco 3 type waters located in a deep co 2 pressurized reservoir hosted in carbonate evaporite rocks and separated from the shallow aquifers by thick sequences of low permeability formations carbon dioxide is mainly produced by thermal metamorphic decarbonation within the deepest and hottest parts of the carbonate evaporite reservoir 13 c co 2 from 3 1 to 2 2 vs vpdb likely affected by a mantle rooted co 2 release of co 2 rich gases from the deep aquifer into the overlying shallow aquifers produces high co 2 springs and bubbling pools the spatial distribution of thermal waters and co 2 rich cold discharges is strongly controlled by fractures and faults located in correspondence with buried structural highs stable isotopes d and 18 o suggest that meteoric water feeds both the shallow and deep reservoirs the relatively low r r a values 0 27 1 19 indicate that he is mainly deriving from a crustal source with minor component from the mantle affected by crustal contamination related to the subduction of the adriatic plate consistently relatively high n 2 ar and n 2 3 he ratios and positive 15 n n 2 values from 0 91 to 5 7 vs air characterize the vcvd gas discharges suggesting the occurrence of a significant excess nitrogen isotopic compositions of ch 4 13 c ch 4 and d ch 4 values from 28 9 to 22 1 vs vpdb and from 176 to 138 vs vsmow respectively and composition of light alkanes are indicative of prevalent thermogenic ch 4 although the occurrence of abiogenic ch 4 production cannot be excluded the 34 s h 2 s values from 9 3 to 11 4 vs vcdt are consistent with the hypothesis of h 2 s production from thermogenic reduction of triassic anhydrites gas geothermometry in the h 2 o h 2 ar h 2 s system suggests that the vcvd gases equilibrated in a liquid phase at redox conditions controlled by interactions of fluids with the local mineral assemblage at temperatures lower 2000 m geothermal wells this confirms that secondary processes i e steam condensation gas dissolution in shallow aquifers re equilibration at lower temperature and microbial activity significantly affect the chemistry of the uprising fluids thermal water chemistry supports the occurrence in this area of an anomalous heat flow that coupled with the recent demographic growth makes this site suitable for direct and indirect exploitation of the geothermal resource in agreement with the preliminary surveys carried out in the 1970 s 1990 s for geothermal exploration purposes

origin and hazard of co2 and h2s emissions in the lavinio tor caldara zone metropolitan city of rome capital italy abstract gas hazard was evaluated at lavinio tor caldara the southernmost gas discharging zone of the quiescent albani hills volcano in central italy also this zone like the other gas discharges of this volcanic complex is located above a structural high of the buried mesozoic carbonate basement which represents the main reservoir for gas rising from depth all extensional faults affecting the carbonates are leaking pathways along which gas may rise to the surface creating hazardous conditions gas is dominated by co2 90 vol and the second component at lavinio tor caldara is h2s that displays the highest content 4 0 6 3 vol of all gas manifestations of the rome region this h2s enrichment corresponds to a marked decrease in 3he 4he r ra isotopic ratio suggesting that gas was contaminated in an upper crustal environment the main gas discharge occurs at the natural reserve of tor caldara in zones where past sulphur mining excavations removed the surficial impervious cover or along a ditch comparison of the results of four soil co2 flux surveys carried out in 2005 2018 at miniera grande within tor caldara indicates that the highest soil co2 release occurs shortly after local earthquakes continuous monitoring of co2 and h2s air concentration and of wind speed has been carried out for four months in twelve anomalous gas realising sites of tor caldara results indicate that only h2s reaches lethal concentration 250 ppm near the soil in no wind nights explaining the presence of small dead animals at lavinio the main soil gas release occurs near old water wells that likely produced a gas blowout during drilling a total release of over 20 tons day from 2 93 km2 of gas of endogenous origin has been estimated for the lavinio tor caldara area by a detailed soil co2 flux survey 2572 measurement points over an area of 3 65 km2 the main structural lineaments of the area have n s and w e directions but also ne sw and nw se directions are well represented some sectors of the investigated area are exposed to a severe gas hazard for people and animals and precautionary measures should be adopted

quartz and feldspar zoning in the eastern erzgebirge volcano plutonic complex germany czech republic evidence of multiple magma mixing abstract zoned quartz and feldspar phenocrysts of the upper carboniferous eastern erzgebirge volcano plutonic complex were studied by cathodoluminescence and minor and trace element profiling the results verify the suitability of quartz and feldspar phenocrysts as recorders of differentiation trends magma mixing and recharge events and suggest that much heterogeneity in plutonic systems may be overlooked on a whole rock scale multiple resorption surfaces and zones element concentration steps in zoned quartz ti and feldspar phenocrysts anorthite content ba sr and plagioclase mantled k feldspars etc indicate mixing of silicic magma with a more mafic magma for several magmatic phases of the eastern erzgebirge volcano plutonic complex generally feldspar appears to be sensitive to the physicochemical changes of the melt whereas quartz phenocrysts are more stable and can survive a longer period of evolution and final effusion of silicic magmas the regional distribution of mixing compatible textures suggests that magma mingling and mixing was a major process in the evolution of these late variscan granites and associated volcanic rocks quartz phenocrysts from 14 magmatic phases of the eastern erzgebirge volcano plutonic complex provide information on the relative timing of different mixing processes storage and recharge allowing a model for the distribution of magma reservoirs in space and time at least two levels of magma storage are envisioned deep reservoirs between 24 and 17 km the crystallisation level of quartz phenocrysts and subvolcanic reservoirs between 13 and 6 km deflation of the shallow reservoirs during the extrusion of the teplice rhyolites triggered the formation of the altenberg teplice caldera above the eastern erzgebirge volcano plutonic complex the deep magma reservoir of the teplice rhyolite also has a genetic relationship to the younger mineralised a type granites as indicated by quartz phenocryst populations the pre caldera biotite granites and the rhyodacitic schonfeld volcanic rocks represent temporally and spatially separate magma sources however the deep magma reservoir of both is assumed to have been at a depth of 24 17 km the drastic chemical contrast between the pre caldera schonfeld westfalian b c and the syn caldera teplice westfalian c d volcanic rocks is related to the change from late orogenic geotectonic environment to post orogenic faulting and is considered an important chronostratigraphic marker

geochemistry of water and gas discharges from the mt amiata silicic complex and surrounding areas central italy abstract the mt amiata volcano in central italy is intimately related to the post orogenic magmatic activity which started in pliocene times major trace elements and isotopic composition of thermal and cold spring waters and gas manifestations indicate the occurrence of three main reservoir of the thermal and cold waters in the mt amiata region the deepest one is located in an extensive carbonate reservoir buried by thick sequences of low permeability allochthonous and neo autochthonous formations thermal spring waters discharging from this aquifer have a neutral ca so4 composition due to the presence of anhydrite layers at the base of the carbonate series and possibly to absorption of deep derived h2s with subsequent oxidation to so42 in a system where ph is buffered by the calcite anhydrite pair marini and chiodini 1994 isotopic signature of these springs and n2 rich composition of associated gas phases suggest a clear local meteoric origin of the feeding waters and atmospheric o2 may be responsible for the oxidation of h2s the two shallower aquifers have different chemical features one is ca hco3 in composition and located in several sedimentary formations above the mesozoic carbonates the other one has a na cl composition and is hosted in marine sediments filling many post orogenic nw se trending basins strontium ba f and br contents have been used to group waters associated with each aquifer although circulating to some extent in the same carbonate reservoir the deep geothermal fluids at latera and mt amiata and thermal springs discharging from their outcropping areas have different composition na cl and ca so4 type respectively considering the high permeability of the reservoir rock the meteoric origin of thermal springs and the two different composition of the thermal waters self sealed barriers must be present at the boundaries of the geothermal systems the complex hydrology of the reservoir rocks greatly affects the reliability of geothermometers in liquid phase which understimate the real temperatures of the discovered geothermal fields more reliable temperatures are envisaged by using gas composition based geothermometers bulk composition of the 67 gas samples studied seems to be the result of a continuous mixing between a n2 rich component of meteoric origin related to the ca so4 aquifer and a deep co2 rich component rising largely along the boundaries of the geothermal systems nitrogen rich gas samples have nearly atmospheric n2 ar 83 and 15 n 14 n 0 ratios whereas co2 rich samples show anomalously high 15n values up to 6 13 likely related to n2 from metamorphic schists lying below the carbonate formations on the basis of average 13 c 12 c isotopic ratio 13c around 0 co2 seems to originate mainly from thermometamorphic reactions in the carbonate reservoir and or in carbonate layers embedded in the underlying metamorphic basement distribution of 3 he 4 he isotopic ratios indicates a radiogenic origin of helium in a tectonic environment that in spite of the presence of many post orogenic basins and mantle derived magmatics can presently be considered in a compressive phase

hydrogeochemistry and strontium isotopes in the arno river basin tuscany italy constraints on natural controls by statistical modeling summary in this paper the chemistry of major and trace elements and for the first time strontium isotopic ratios measured in running waters from the arno river basin tuscany central northern italy and thermal springs discharging in the same hydrographic system are presented and discussed classical graphical methods e g mixing diagrams have here been improved to identify in a correct statistical sample space extreme chemical compositions attributable to the action of geochemical processes and or inherited from specific lithologies namely contributions or components 1 2 and 3 to be used in inverse modeling procedures due to the absence of clear end members a linear least squares problem with non negativity constraints and distances as required for compositional data convex linear mixing was solved by considering the contribution of the most discriminant variables given by the 87 sr 86 sr isotopic ratios and the concentration of ca 2 mg 2 sr and rb following such approach it can be assumed p 2 mg 2 hco 3 radiogenic rich 87 sr 86 sr 0 71274 rb sr 0 039 represents a dominant feature at basin scale with a weight ranging from 69 to 100 much lower percentages are related to component 2 represented by a ca 2 mg 2 so 4 2 facies with intermediate 87 sr 86 sr 0 70874 and low rb sr 2 8 10 4 ratios and component 3 identified by ca 2 hco 3 facies with less radiogenic 87 sr 86 sr 0 70827 and low mg 2 ca 2 0 011 ratios these components are mainly dominated by the dissolution of evaporitic rocks and or mixing with thermal waters in the southern part of the arno river basin and by dissolution of the carbonatic fraction kinetically favored with respect to that of the silicatic minerals in the upper reaches of the main course and its tributaries respectively

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

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

fluid geochemical transect in the northern apennines central northern italy fluid genesis and migration and tectonic implications chemical and isotopic characteristics of natural gas and thermal water discharges from the western back arc tyrrhenian sea across the apennine thrust belt to the po valley and adriatic coast foredeep basins in the northern apennines central northern italy reveal a large scale fluid motion in the upper crust both vertically and horizontally on the basis of gas compositions two different domains of rising fluids have been distinguished 1 co2 rich he poor 3he 4he high domain in the western peri tyrrhenian extensional sector 2 ch4 rich he rich 3he 4he low domain in the eastern adriatic compressional sector such gases rising from various depths are crossed by a huge lateral n2 rich water flow in the peri tyrrhenian sector of ca so4 hco3 meteoric derived waters that move in a regional wide aquifer hosted in a quite thick mesozoic carbonate series morphologically the co2 vents consist of mud basins with high gas rate emission where the rising fluids move upwards through diatremes on the other hand ch4 emissions seep out from typical mud volcanoes with a reduced gas flow rate where the fluid motion is likely related to saline diapir extrusions and the methane is mostly carried to the surface by the associated mud the two rising mechanisms described locate southwest and northeast of the apennine watershed respectively from a seismic point of view the ch4 domain in the thrust belt and foredeep areas is characterized by a large number of earthquakes indirectly pointing to a different rheological behavior of the terrains with respect to the more internal peri tyrrhenian area owing to the quite high thermal gradient of the latter the boundary of the brittle ductile crust in the peri tyrrhenian sector can be located at a 10 km shallow depth although the presence of several post orogenic basins would suggest widespread extensional tectonics in all areas west of the apennine watershed those located in the easternmost part display gas vents with typical crustal 3he 4he ratios as this ratio is very sensitive to deep fluids rising from the mantle we hypothesize that such basins at the foot of the apennines are not due to tensive stress as suggested by their morphological shape they are piggy back thrust top basins developed and evolved in a still acting compressive tectonic regime

regional differences in pb isotopic compositions of feldspars in plutonic rocks of the northern appalachian mountains u s a and canada a geochemical method of terrane correlation feldspar pb isotopic compositions from paleozoic tonalitic to leucogranitic caledonian plutons from the northern appalachian mountains of the u s a and canada range from nonradiogenic to radiogenic relative to the evolution curve of stacey and kramers 1975 pb isotopic values in the feldspars are generally independent of modal and major and trace element contents of the plutons plutons with the least radiogenic pb isotopic signatures northern group have intruded allochthonous rocks closest to the north american craton and plutons with the most radiogenic pb southern group have intruded avalonian basement feldspars from plutons in the central group have intermediate pb isotopic compositions between the northern and southern groups and do not define an isotopically unique group the predominant source of the felsic magmas was the continental lithosphere as indicated by the general pb isotopic similarity of the plutonic feldspars with either grenville or chain lakes basement in the case of the northern group and with avalonian basement rocks in the case of the southern group the source region for plutons in the central group may have contained a mixture of grenvillian and avalonian components plutons in the northern appalachians are as a group more evolved in their pb isotopic compositions relative to caledonian plutons in the british isles

gas geochemistry of natural analogues for the studies of geological co2 sequestration geological sequestration of anthropogenic co2 appears to be a promising method for reducing the amount of greenhouse gases released to the atmosphere geochemical modelling of the storage capacity for co2 in saline aquifers sandstones and or carbonates should be based on natural analogues both in situ and in the laboratory the main focus of this paper has been to study natural gas emissions representing extremely attractive surrogates for the study and prediction of the possible consequences of leakage from geological sequestration sites of anthropogenic co2 i e the return to surface potentially causing localised environmental problems these include a comparison among three different italian case histories i the solfatara crater phlegraean fields caldera southern italy is an ancient roman spa the area is characterised by intense and diffuse hydrothermal activity testified by hot acidic mud pools thermal springs and a large fumarolic field soil gas flux measurements show that the entire area discharges between 1200 and 1500 tons of co2 per day ii the panarea island aeolian islands southern italy where a huge submarine volcanic hydrothermal gas burst occurred in november 2002 the submarine gas emissions chemically modified seawater causing a strong modification of the marine ecosystem all of the collected gases are co2 dominant maximum value 98 43 vol iii the tor caldara area central italy located in a peripheral sector of the quiescent alban hills volcano along the faults of the ardea basin transfer structure the area is characterised by huge co2 degassing both from water and soil although the above mentioned areas do not represent a storage scenario these sites do provide many opportunities to study near surface processes and to test monitoring methodologies

hydrogeochemistry of the campania region in southern italy abstract a geochemical study of thermal springs cold springs stream waters and natural gas emissions has been carried out in the campania region of southern italy this region hosts four quaternary volcanic areas and thermal springs and gas emissions occur in three of them most thermal springs discharge na cl composition waters of connate origin derived from post orogenic volcanic and sedimentary formations although high enthalpy systems are present in two of the four volcanic areas there appear to be no magmatic contributions to the thermal springs solute geothermometers are unreliable as spring waters are strongly affected by mixing with shallow brines before discharging thermal springs and gas emissions also occur in non volcanic areas where an extensive carbonate unit acts as a regional aquifer for cold low salinity bicarbonate waters thermal features in these areas occur in fractured zones associated with active faults their compositions are determined only by the type of rock encountered by solutions before surface discharge as in other areas of north central italy the widespread occurrence of hot and cold co2 rich springs and gas emissions in both volcanic and non volcanic zones suggests a deep origin for the co2

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

evolution of the latera geothermal system ii metamorphic hydrothermal mineral assemblages and fluid chemistry abstract the latera field vulsini volcanic complex latium italy is one of the geothermal areas of the peri tyrrhenian belt along which a regional high thermal anomaly has been detected so far nine deep wells have been drilled within the latera caldera and four of them have been productive the geothermal reservoir is located within the fractured carbonatic rocks of the tuscan nappe the overlying volcanic units sealed by hydrothermal minerals mainly calcite and anhydrite act as an impervious cover the fluid produced by the wells comes from a deep aquifer about 1000 1500 m depth which at present is not connected with the shallow aquifer in the volcanoclastic units fluid temperatures range between 200 and 230 c in hole temperatures as high as 343 c at 2775 m depth have been measured in dry wells the study of the newly formed mineral assemblages from both volcanic and sedimentary units as sampled from the geothermal wells can be used to reconstruct the thermal evolution of the geothermal field the intrusion of a syenitic melt up to a depth of about 2000 m dated 0 86 ma represents the major thermal event for the units in the area and is assumed to represent the first step in the geothermal evolution of the latera system the above mentioned newly formed mineral assemblages can be divided into three groups a contact metasomatic calcite anhydrite diopsidic pyroxene grossularitic garnet phlogopite wollastonite or monticellite b high temperature hydrothermal calcite anhydrite k feldspar vesuvianite melanitic garnet tourmaline amphibole epidote sulphides c low temperature hydrothermal calcite anhydrite k feldspar clay minerals sulphides group a minerals are now relics part of b and all of c group are still in equilibrium with the existing conditions in different parts of the geothermal system thermodynamic calculations on the observed mineral assemblages permitted estimates of the p t conditions and gas fugacities

the magma mixing origin of mantled feldspars the key to mantled feldspar genesis is epitaxial nucleation of plagioclase on k feldspar or k feldspar on plagioclase once this nucleation takes place there is a relatively straightforward process of crystal growth yielding rapakivi and antirapikivi textures the most common mantling is plagioclase on k feldspar which occurs in both volcanic and plutonic environments in the volcanic environment the morphology of the plagioclase overgrowth typically is dendritic though in subvolcanic and shallow plutonic environments dendritic growth is followed by a more or less continuous non cellular shell of plagioclase in the plutonic environment early stages of plagioclase overgrowth also tend to be dendritic although with coarser grained characteristics dendritic morphology is thus a common denominator in rapakivi genesis since growth of dendritic plagioclase is clearly related to marked undercooling in silicate melt systems its occurrence in many volcanic rocks is to be expected equivalent quenching in the plutonic environment requires a cooling mechanism independent of conductive heat transfer to wallrock and also independent of effective cooling related to sudden loss of volatile phases that could only occur late in the crystallization of most magmas and therefore after much dendritic plagioclase had already formed internal quenching of portions of magma systems must occur if mafic magma is abruptly mixed with felsic magma such magma mixing yields a heterogeneous system at first one that is in a drastic state of disequilibrium and tending to force nucleation of one feldspar type on the surface of another resulting in epitaxial crystallization of dendritic plagioclase on k feldspar mantling of one feldspar type by another during magma mixing is paralleled by dendritic growth zones in coexisting plagioclase crystals

interaction between shallow and deep aquifers in the tivoli plain central italy enhanced by groundwater extraction a multi isotope approach and geochemical modeling abstract in the tivoli plain rome central italy the interaction between shallow and deep groundwater flow systems enhanced by groundwater extraction has been investigated using isotopic and chemical tracers a conceptual model of the groundwater flowpaths has been developed and verified by geochemical modeling a combined hydrogeochemical and isotopic investigation using ion relationships such as dic cl ca ca mg so 4 so 4 hco 3 and environmental isotopes 18 o 2 h 87 sr 86 sr 34 s and 13 c was carried out in order to determine the sources of recharge of the aquifer the origin of solutes and the mixing processes in groundwater of tivoli plain multivariate statistical methods such as principal component analysis and cluster analyses have confirmed the existence of different geochemical facies and the role of mixing in the chemical composition of the groundwater results indicate that the hydrochemistry of groundwater is characterized by mixing between end members coming directly from carbonate recharge areas and to groundwater circulating in a deeply buried meso cenozoic carbonate sequence the travertine aquifer is fed by both flow systems but a local contribution by direct input in the plain has also been recognized the stable isotope data 18 o 2 h 13 c and 34 s supports the flow system conceptual model inferred from the geochemical data and represents key data to quantify the geochemical mixing in the different groundwaters of the plain the results of numerical modeling phreeqc are consistent with the flowpaths derived from the hydrogeochemical conceptual model the inverse models performed generated the main geochemical processes occurring in the groundwater flow system which also included mixing geochemical and isotope modeling demonstrate an increasing influence of groundwater from the deeply buried aquifer in the travertine aquifer enhanced by lowering of the travertine aquifer water table due to quarry pumping

fluid mixing in carbonate aquifers near rapolano central italy chemical and isotopic constraints chemical major and trace elements and isotopic compositions dd and d 18 o in waters and d 13 ci n co 2 and 3 he 4 he in gases of natural thermal 11 and cold 39 fluids spring waters and gases discharging from a tectonic window of mesozoic limestones in central italy have proved to be the result of mixing processes inside the limestone formations the limestones provide a preferential route for subsurface fluid migration and they gather both descending cold ca hco3 b depleted groundwaters and rising convective ca so4 hco3 co2 saturated b rich thermal waters atmospherically derived descending gas components n2 ne he dissolved in rainfall that infiltrates the limestone system mix with n2 ne he depleted hot rising waters boron in the liquid phase and n2 and ne in the gas phase are the most useful elements to trace the mixing process the deeper gas samples recognised in the area are associated with the hotter waters emerging in the area in spite of being depleted in ne and he and light hydrocarbons they have the higher measured 3 he 4 he ratios suggesting a contribution of mantle 3 he to the gas phase this contrasts with deep circulation in the crust which would lead to increased concentration of 4 he in the deeper gases paradoxically there is more relative concentration of 4 he in the more air contaminated gas samples than in the deeper gas samples a similar paradox exists when the d 13 co f co 2 in the deeper gas samples is considered the shallower air contaminated gas samples although they should be affected by the addition of soil 13 c depleted organic c have d 13 ci n co 2 more positive than the deeper gas samples recognized since any deep hydrothermal source of co2 should generate co2 with more positive values of d 13 c than those measured at surface a multiple single calcite precipitation process from hydrothermal solutions with c isotopic fractionation along the rising path inside the mesozoic limestone formations is proposed 2002 elsevier science ltd all rights reserved

looking into a volcanic area an overview on the 350 m scientific drilling at colli albani rome italy abstract a 350 m deep borehole was drilled in the colli albani volcanic district central italy in order to understand the shallow crust structure beneath the volcanic complex characterize the rock physical properties especially through in situ measurements and afterward laboratory experiments assess the local present day stress field install a broad band seismometer at depth the borehole is located adjacent to the western rim of the tuscolano artemisio caldera where several phenomena of unrest recently occurred in 1989 90 a seismic swarm affected this area and a related uplift was recognized in addition high gas concentrations mainly co 2 and h 2 s in aquifers and soils caused illnesses and casualties among inhabitants and animals in the past we describe the investigations carried out at the drill site and the results achieved from data analysis wire line drilling produced a complete stratigraphic record of the quaternary volcanic units down to the plio pleistocene sedimentary sequence and geophysical logs allowed a characterization of the rock physical properties from a tectonic point of view data provided by dipmeter and borehole televiewer were used for investigations on the recent and present day stress field and the results are compared to those available in the literature in the volcanic units we recognized two main fracture systems sw and nw dipping several faults intersecting the borehole show planes with oblique striae indicating a prevalent strike slip component of the movement finally borehole breakout analysis defined an active stress field with a e w oriented minimum horizontal component at the end of the drilling a blow out occurred due to pressurized fluids trapped into the sandy unit drilled in the last few meters of the hole sampling these fluids gave an additional value to the borehole providing information about the deep volcanic circulation and its possible connection to a deep seated magma chamber the main results show water with a na hco 3 chemistry and the highest salinity ever recognised in the area electrical conductivity 10 12 ms cm stable o and h isotopes reveal a meteoric origin of water and the absence of tritium points out a long residence time in the aquifer emitted gas is co 2 dominated with n 2 as second most important component helium isotopic composition of the gas allows us to estimate a magmatic component ranging in the interval 40 50 one of the highest in the colli albani carbon isotopes of co 2 0 53 vs pdb suggest that it could derive partly from a magmatic source and partly by the thermal decarbonation of the carbonatic basement

magma chambers emplaced in carbonate substrate petrogenesis of skarn and cumulate rocks and implications for co2 degassing in volcanic areas crystal rich lithic clasts occurring in volcanic deposits are key tools to understand processes of storage cooling and fractionation of magmas in pre eruptive volcanic systems these clasts represent snapshots of the magma chamber host rock interface before eruption and provide information on crystallization differentiation and degrees of interaction between magma and wall rock in this study we have focused on the petrology of clasts of cumulate and skarn rocks from the colli albani volcanic district with the aim of shedding light on magma carbonate interaction and co2 emission in volcanic areas by means of phase relations bulk rock chemistry mineral compositions and isotope data we have identified different types of cumulates and skarns cumulates containing either clinopyrox

titaniq a titanium in quartz geothermometer titanium is one of many trace elements to substitute for silicon in the mineral quartz here we describe the temperature dependence of that substitution in the form of a new geothermometer to calibrate the titaniq thermometer we synthesized quartz in the presence of rutile and either aqueous fluid or hydrous silicate melt at temperatures ranging from 600 to 1 000 c at 1 0 gpa the ti contents of quartz in ppm by weight from 13 experiments increase exponentially with reciprocal t as described by text log left x text qtz text ti right 5 69 pm 0 02 frac 3765 pm 24 t k application of this thermometer is straightforward typically requiring analysis of only one phase quartz this can be accomplished either by epma for crystallization temperatures above 600 c or by sims for temperatures down to at least 400 resulting temperature estimates are very precise usually better than 5 c potentially allowing detailed characterization of thermal histories within individual quartz grains although calibrated for quartz crystallized in the presence of rutile the thermometer can also be applied to rutile absent systems if tio2 activity is constrained

chemical composition of thermal springs cold springs streams and gas vents in the mt amiata geothermal region tuscany italy abstract a geochemical study of thermal and cold springs stream waters and gas emissions has been carried out in the mt amiata geothermal region the cold springs and stream waters do not seem to have received significant contribution from hot deep fluids on the contrary the thermal springs present complex and not clearly quantifiable interactions with the hot fluids of the main geothermal reservoir the liquid dominated systems in the mt amiata area like most of the high enthalpy geothermal fields in the world are characterized by saline nacl fluids the nature of the reservoir rock carbonatic and anhydritic and its widespread occurrence in central italy favor a regional circulation of ca sulfate thermal waters which discharge from its outcrop areas waters of this kind which have been considered recharge waters of the known geothermal fields dilute disperse and react with the deep geothermal fluids in the mt amiata area preventing the use of the main chemical geothermometers for prospecting purposes the temperatures obtained from the chemical geothermometers vary widely and are generally cooler than temperatures measured in producing wells other thermal anomalies in central italy apart from those already known might be masked by the above mentioned circulation a better knowledge of deep fluid chemistry could contribute to the calibration of specific geothermometers for waters from reservoirs in carbonatic rocks

fluid geochemistry and geothermometry in the western sector of the sabatini volcanic district and the tolfa mountains central italy abstract a geochemical survey of 197 fluid discharges cold and thermal waters and bubbling pools and 15 gas emissions from the western sector of the sabatini volcanic district and the tolfa mountains latium central italy was carried out in 2007 2008 the chemical and isotopic compositions of the fluid discharges indicate the occurrence of two main sources 1 relatively shallow aquifers with ca na k hco 3 and ca mg hco 3 compositions when trapped in volcanic and sedimentary formations respectively and 2 a deep reservoir which is hosted in the mesozoic carbonate sequence rich in co 2 and having a ca so 4 hco 3 composition dissolution of a co 2 rich gas phase into the shallow aquifers produces high tds and high pco 2 cold waters while oxidation of deep derived h 2 s to so 4 2 generates low ph the 13 c co 2 values for gas emissions from 2 8 to 2 7 vs vpdb suggest that the origin of co 2 associated with the deep fluids is mainly related to thermo metamorphic reactions within the carbonate reservoir although significant mantle contribution may also occur however r r a values 0 37 0 62 indicate that he is mainly produced by a crustal source with a minor component from a crust contaminated mantle on the basis of the 13 c ch 4 and d ch 4 values from 25 7 to 19 5 vs vpdb and from 152 to 93 4 vs vsmow respectively ch 4 production is associated with thermogenic processes possibly related to abiogenic co 2 reduction within the carbonate reservoir the 34 s h 2 s values from 9 3 to 10 4 vs vcdt are consistent with the hypothesis of a sedimentary source of sulfur from thermogenic reduction of triassic sulfates geothermometric evaluations based on chemical equilibria co 2 ch 4 and separately h 2 s suggest that the reservoir equilibrium temperature is up to 300 c the d and 18 o data indicate that water recharging both the shallow and deep aquifers has a meteoric origin fluid geochemistry coupled with gravimetric data and tectonic lineaments supports the idea that significant contributions from a deep seated geothermal brine are present in the stigliano thermal fluid discharges exploration surveys investigated this area during 70 s 90 s for geothermal purposes nevertheless presently the area is still under exploited the presence of thermal waters and anomalous heat flow together with the demographic growth of the last years makes this site a suitable location for direct applications of the geothermal resource

limestone assimilation and the origin of co2 emissions at the alban hills central italy constraints from experimental petrology abstract the alban hills volcanic region 20 km south of rome in the roman province emitted a large volume of potassic magmas 280 km 3 during the quaternary chemical interactions between ascending magmas and the 7000 8000 m thick sedimentary carbonate basement are documented by abundant high temperature skarn xenoliths in the eruptive products and have been frequently corroborated by geochemical surveys in this paper we characterize the effect of carbonate assimilation on phase relationships at 200 mpa and 1150 1050 c by experimental petrology calcite and dolomite addition promotes the crystallization of ca rich pyroxene and mg rich olivine respectively and addition of both carbonates results in the desilication of the melt furthermore carbonate assimilation liberates a large quantity of co 2 rich fluid a comparison of experimental versus natural mineral glass and bulk rock compositions suggests large variations in the degree of carbonate assimilation for the different alban hills eruptions a maximum of 15 wt assimilation is suggested by some melt inclusion and clinopyroxene compositions however most of the natural data indicate assimilation of between 3 and 12 wt carbonate current high co 2 emissions in this area most likely indicate that such an assimilation process still occurs at depth we calculate that a magma intruding into the carbonate basement with a rate of 1 2 10 6 m 3 year estimated by geophysical studies and assimilating 3 12 wt of host rocks would release an amount of co 2 matching the current yearly emissions at the alban hills our results strongly suggest that current co 2 emissions in this region are the shallow manifestation of hot mafic magma intrusion in the carbonate hosted reservoir at 5 6 km depth with important consequences for the present day volcanic hazard evaluation in this densely populated and historical area

geothermal resources within carbonate reservoirs in western sicily italy a review abstract low to medium temperature fluid reservoirs hosted in carbonate rocks are some of the most promising and unknown geothermal systems western sicily is considered a key exploration area this paper illustrate a multidisciplinary and integrated review of the existing geological geochemical and geophysical data mainly acquired during oil and gas explorations since the 1950s specifically re analyzed for geothermal purposes has led to understanding the western sicily geothermal system as a whole and to reconstructing the modalities and particular features of the deep fluid circulation within the regional reservoir the data review suggests the presence of wide groundwater flow systems in the reservoir beneath impervious cap rocks we identified the main recharge areas reconstructed the temperature distribution at depth recognized zones of convective geothermal flow and depicted the main geothermal fluid flow paths within the reservoir we believe that our reconstruction of geothermal fluid circulation is an example of the general behavior of low to medium enthalpy geothermal systems hosted in carbonate units on a regional scale due to the recent technological developments of binary plants these systems have become more profitable not only for geothermal direct uses but also for power production

surface deformation detected by alos palsar small baseline sar interferometry over permafrost environment of beiluhe section tibet plateau china abstract the evolution of permafrost and the active layer is highly related to biological diversity and climate change because of its feedback effects involving water and carbon storage in this study we firstly examined the relationship of active layer variation geomorphological processes and anthropogenic activities by means of small baseline synthetic aperture radar interferometry in beiluhe hoh xil natural reserve in tibet plateau tp china 3 5 yr observation span of l band alos palsar data june 2007 to december 2010 was used the estimated surface displacements primarily in the range of 20 mm yr 1 to 20 mm yr 1 and time series implied evolution of the active layer and permafrost beneath the motion trend along slopes was complicated due to the geomorphological processes and thus interdisciplinary interpretations were needed anthropogenic influences on this frail permafrost environment were significant as evident from the remarkable surface settlement along the embankment of qinghai tibet railway it is crucial and necessary to monitor this permafrost plateau owing to the consequences arising from a combination of factors related to climate change geo hazard prediction nature conservation and regional sustainable development

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

assessing short and long time displacements in the venice coastland by synthetic aperture radar interferometric point target analysis 1 the venice lagoon in italy is a unique environment vulnerable to loss in surface elevation relative to the mean sea level we present detailed synthetic aperture radar sar interferometric analyses on persistent point targets for the historical center of venice the tourist area of sottomarina and the zennare farmland close to the southern lagoon edge the selected areas are characterized by different degrees of development and our analyses show the remarkable capability of sar interferometric point target analysis ipta to map land displacement rates in densely urbanized zones and to detect movement information on isolated structures with a mm year accuracy a detailed analysis of the time series from 1992 to 2000 provided by ipta shows that the vertical component of the measured displacements are the superposition of a short timescale generally seasonal movement on the order of 1 cm that is likely related to the fluctuation of environmental variables temperature piezometric head in the aquifer system underlying the lagoon sea lagoon water level and a long term ground deformation associated with building construction the geomorphology of the area and the human development of natural resources if venice is confirmed to be generally stable significant long term subsidence on the order of 4 mm year is detected at the sottomarina coastland the highest displacement rates of up to 8 10 mm year are recorded in the farmland bounding the lagoon margin where the movements are found to be highly site specific

hydrogeochemistry of the volcanic district in the tolfa and sabatini mountains in central italy abstract a geochemical study on 26 thermal springs and 5 samples from thermal wells t 20 c 19 cold springs 11 cold gas pools and 14 stream samples from the tolfa and sabatini mountains volcanic district about 1300 km2 has clarified their genesis and evolution meteoric waters infiltrate the more permeable exposed rocks carbonates and or volcanites and percolate down into two main aquifers one is deep and located in mesozoic anhydritic carbonate formations and is the regional geothermal reservoir that feeds springs that emerge at the margins of the carbonate series either exposed or barely covered its waters display typical bicarbonate sulfate alkaline earth composition the other aquifer s is shallower consisting of waters that circulate primarily in volcanic deposits the chemical characteristics of these shallow waters are heavily influenced by lithology and by a gas phase mainly co2 originating at depth temperature estimates obtained with sio2 and gas geothermometers which seem to be the most reliable under these conditions indicate the widespread occurrence of deep fluids at temperatures higher than 110 c under the area covered by the sabatini volcanites in some areas manziana trevignano nepi and cesano the subsurface waters reach temperatures within the range characteristic of medium to high enthalpy systems 120 160 c

p t conditions of crystallization and origin of plagioclase mantled alkali feldspar megacrysts in the mesozoic granitoids in the qinling orogen china abstract the qinling orogen between the north china and south china cratons was intruded at 211 217 ma by calc alkaline quartz monzonitic to monzogranitic plutons characterized by i to a type geochemistry and in many places contain plagioclase mantled alkali feldspar megacrysts rapakivi texture sensu lato the felsic rocks contain mafic to intermediate magmatic enclaves suggestive of mingling and mixing of mafic and felsic magmas the p t conditions of crystallization have been determined for early mineral assemblages inner parts of alkali feldspar megacrysts and their plagioclase quartz amphibole and biotite inclusions and late assemblages matrix minerals of the rapakivi textured granitoids al contents in amphibole from the early and late mineral assemblages yield pressures of 1 2 3 0 and 0 7 3 0 kbar respectively and indicate only minor pressure change between the crystallization of the early and late assemblages amphibole plagioclase thermometry gives temperatures mainly of the order of 900 to 1000 c for both the early and late assemblages indicating nearly isothermal conditions feldspar thermometers yield lower temperatures relative abundances of minerals and their chemical compositions indicate that the late mineral assemblages tend to be richer in mgo na 2 o and cao than the early assemblages rapakivi texture is interpreted in this case mainly as a result of compositional changes related to the hybridization between granitic and more mafic magmas small release of pressure during crystallization of the magmas may have contributed to the origin of the mantled alkali feldspar megacrysts

the chemistry and isotopic composition of waters in the low enthalpy geothermal system of cimino vico volcanic district italy abstract geothermal energy exploration is based in part on interpretation of the chemistry temperature and discharge rate of thermal springs here we present the major element chemistry and the d 18o 87sr 86sr and 11b isotopic ratio of groundwater from the low enthalpy geothermal system near the city of viterbo in the cimino vico volcanic district of west central italy the geothermal system hosts many thermal springs and gas vents but the resource is still unexploited water chemistry is controlled by mixing between low salinity hco3 rich fresh waters

stable isotope and noble gas isotope compositions of inclusion fluids from larderello geothermal field italy constraints to fluid origin and mixing processes noble gas and n 2 compositions have been determined in paleofluids of core samples from geothermal wells in the larderello area italy the results were coupled with hydrogen and carbon isotope compositions of similar fluids from an independent batch of samples to provide constraints on the origin of the fluids the fluids trapped during early stage hydrothermal circulation are characterized by relatively high 4 0 ar 3 6 ar and n 2 ar ratios 332 4 0 ar 3 6 ar 564 and 248 n 2 ar 4197 respectively and indicate the presence of radiogenic 4 0 ar and excess n 2 when compared to air asw air saturated water the fluid inclusions related to late stage hydrothermal activity show low n 2 ar and 4 0 ar 3 6 ar ratios 309 4 0 ar 3 6 ar 354 and 47 n2 ar 66 respectively similar to present day geothermal fluids the 6d values of the inclusion fluids range from 53 to 85 indicating that the fluids were derived from mixing of water rich components probably from a shallow reservoir similar in composition to present day meteoric waters and fluids from a deeper reservoir the r r a ratios up to 3 2 of the paleofluids and present day fluids suggest a deep he contribution at larderello the 1 3 c values for co 2 trapped during early stage activity 3 8 o to 0 5 o were produced by carbonate country rock volatilisation 1 3 c values as low as 17 were measured in inclusion fluids related to late stage circulation and were likely produced by oxidation of organic matter at shallow depths

land cover classification using multitemporal ers 1 2 insar data in this study the potential of ers 1 2 tandem insar data for land cover classification was investigated at a 2500 km sup 2 study area around the helsinki metropolitan area in southern finland a time series of 14 ers 1 2 sar tandem image pairs was processed into 28 five look intensity images 14 tandem coherence images and two coherence images with a longer temporal baseline 36 and 246 days all image data was coregistered and orthorectified into map coordinates using an insar dem a two stage hybrid classifier method was employed where the water class was classified separately in the first classifier stage and the remaining classes were classified with an isodata classifier temporal averaging and principal components transformation pct were used to reduce the number of images fed into isodata classification accuracy was assessed using high resolution aerial orthophotos digital base maps and the finnish national forest inventory nfi the overall accuracy for six classes field open land dense forest sparse forest mixed urban dense urban water was found to be 90 with kappa coefficient of 0 86 interferometric coherence carries more land cover related information than the backscattered intensity this study confirms that the ers 1 2 tandem archives could be exploited for land cover classification

hydrothermal hydrocarbon gases 1 genesis and geothermometry various sources for hydrothermal ch4 have been proposed over the years while c isotope studies have narrowed the possibilities enough higher hydrocarbon gas data now exist both to supplement the isotopic data and to permit additional deductions regarding origins comparison of typical c1 c6 data for gases of various origins from sedimentary and crystalline rocks and hydrothermal systems reveals certain characteristics apart from isotopic differences hydrothermal hydrocarbons differ from sedimentary hydrocarbons mainly in possessing tendencies towards a relative excess of ch4 higher normal iso ratios for butane and pentane and relatively high amounts of c6 gases despite these differences consideration of the evidence indicates that hydrothermal hydrocarbon gases in most cases originate like sedimentary basin gases by thermal degradation of organic matter in the relatively shallow subsurface the principal characteristic of these hydrothermal gases excess ch4 appears to have a geothermometric function the following empirical relationship has been derived t c 57 8 log ch4 c2h6 96 8 which fits moderately well a range of geothermal fields worldwide this gas geothermometer may be particularly applicable during geothermal exploration in areas where there is little direct knowledge of subsurface conditions

origin of mantle rapakivi feldspars experimental evidence of a dissolution and diffusion controlled mechanism experiments designed to simulate the dissolution of alkali feldspar during magma mixing produced plagioclase mantles that are texturally and compositionally similar to those in some hybrid volcanic rocks in hydrous dacite melt 69 sio2 at 0 8 gpa 850 c orthoclase or93 and sanidine or30 partially dissolved and were mantled by sodic plagioclase an25 30 although plagioclase nucleated epitaxially as a thin shell on the alkali feldspar surface near the time of initial resorption plagioclase subsequently grew inward mostly in the form of parallel blades toaard the receding dissolution surface orthoclase dissolved at a rate approximately proportional to the square root of run duration indicating diffusional control plagioclase grew inward within a static boundary zone of melt that formed between the original crystal dacite interface and the dissolution surface during orthoclase dissolution this boundary zone rapidly and simultancously gained na by diffusion from dacite and lost k by diffusion into dacite ca diffused more slowly into this zone from which non feldspar species were mostly excluded plagioclase was stable where sufficient ca had diffused in that the boundary zone melt intersected the plagioclase saturation liquidus plagioclase subsequently grew toward the receding dissolution surface as the ca compositional gradient and hence the site of plagioclase saturation stepped inward crystallization of plagioclase in the form of parallel blades allowed continued diffusive exchange of melt components between the dissolution surface and the host melt bladed growth also served to maintain at blade tips proximity of plagioclase to the dissolution surface thereby apparently preserving locally a thin zone of low variance melt in natural systems mantling of alkali feldspar by plagioclase will occur in a similar manner when a p t or x are changed to induce alkali feldspar dissolution b sufficient ca is available in the host melt to drive by diffusion boundary zone melt compositions to plagioclase saturation and c temperatures are low enough to stabilize sodic plagioclase and to maintain a coherent boundary zone these reqjirements are satisfied in volcanic systems when alkali feldspar is juxtaposed during mixing with hybrid melts of dacitic composition mantled feldspars in some intrusive systems i e rapakivi granites may form by a similar dissolution and diffusion controlled mechanism textural evidence of a similar origin may be obscurred in intrusive rocks however by products of late stage magmatic and subsolidus processes

on the derivation of coseismic displacement fields using differential radar interferometry the landers earthquake we present a map of the coseismic displacement field resulting from the landers california june 28 1992 earthquake derived using data acquired from an orbiting high resolution radar system we achieve results more accurate than previous space studies and similar in accuracy to those obtained by conventional field survey techniques data from the ers 1 synthetic aperture radar instrument acquired in april july and august 1992 are used to generate a high resolution wide area map of the displacements the data represent the motion in the direction of the radar line of sight to centimeter level precision of each 30 m resolution element in a 113 km by 90 km image our coseismic displacement contour map gives a lobed pattern consistent with theoretical models of the displacement field from the earthquake fine structure observed as displacement tiling in regions several kilometers from the fault appears to be the result of local surface fracturing comparison of these data with global positioning system and electronic distance measurement survey data yield a correlation of 0 96 thus the radar measurements are a means to extend the point measurements acquired by traditional techniques to an area map format the technique we use is 1 more automatic 2 more precise and 3 better validated than previous similar applications of differential radar interferometry since we require only remotely sensed satellite data with no additional requirements for ancillary information the technique is well suited for global seismic monitoring and analysis

geothermometry on fluids circulating in a carbonate reservoir in north central italy the peri tyrrhenian belt of north central italy is a site of large scale fluid circulation in mesozoic carbonate anhydritic formations of thermal waters with ca sulfate composition these carbonate formations are the principal geothermal reservoir of the known italian geothermal fields owing to differences in the regional structure these carbonate rocks may have an intrinsic high or low hydraulic continuity the ca sulfate springs that surface at the periphery of these formations have circulated in the unconfined parts of the carbonate aquifer the high salinity na chloride geothermal fluids discharge from the confined parts of the same reservoir rocks these fluids are somewhat separated from fluids generated in the unconfined parts by possible barriers of low permeability they are also diluted with the ca sulfate waters and have re equilibrated at lower temperature because of these conditions the assessment of the deep reservoir temperatures cannot be made using rapidly re equilibrating geothermometers such as the sio2 geothermometer the latter reveals the temperature of the unconfined aquifer at best the study of the geohydrological nature of the reservoir rocks the composition of liquid and gas phases and the statistical behavior of the main chemical geothermometers applied to the shallow cold waters of the principal italian geothermal areas has shown that the geothermometer based on nali ratio seems to be the most reliable to evaluate the deep temperatures inside the confined parts of the carbonate reservoir

geochemical study on natural gas and water discharges in the southern latium italy circulation evolution of fluids and geothermal potential in the region abstract the waters discharged in southern latium south of rome are mainly meteoric in origin two types of circulation occur in the region one infiltrates the carbonate sediments outcropping in the area and emerges from fractures along their borders the other consists of waters that infiltrate and circulate essentially within the albani volcanic rocks the first type produces either alkaline earth bicarbonate sulfate waters or if they mix with fossil marine waters or interact with recent marine sediments alkaline chloride waters on the pontina plain the chemistry of the waters produced by the second type of circulation alkaline earth bicarbonate or alkaline bicarbonate is strictly related to their gaseous phases which consist for the most part of the co 2 produced at depth silica and gas geothermometers whose results correlate well indicate that low enthalpy fluids 80 c are present throughout the study area with the exception of the northwestern part where medium enthalpy fluids 150 c also appear

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

theoretical geothermometers andpco2 indicators for aqueous solutions coming from hydrothermal systems of medium low temperature hosted in carbonate evaporite rocks application to the thermal springs of the etruscan swell italy in order to derivet pco2 geoindicators suitable for thermal waters coming from the hydrothermal systems of medium low temperature which are hosted in carbonate evaporite rocks the theoretical concentration of ca mg hco3 so4 f and their complexes in aqueous solutions in equilibrium with a mineral assemblage made up of calcite dolomite anhydrite and fluorite has been calculated at temperatures between 0 and 150 c atpco2 in the 0 1 100 bar interval and for total molality of mobile species na and ci ranging between 0 0001 and 0 3 the results of such calculations indicated that 1 the ca mg s04 and f contents and thes04 f 2 andcamg ratios are potential geothermometers 2 the hc03 2so4 ratio is a pco indicator 3 thehc03f ratio and the hc03 content arc indicators of bothpco2 andt a first geothermometric and geobarometric evaluation of the thermal springs of the etruscan swell generally shows equilibrium temperatures in the interval 50 100 c and pco from about 1 bar to bars these estimations are consistent with the general knowledge of the hydrothermal systems of medium low temperature present in the region

hydrogeochemical and hydrogeological investigations of thermal waters in the emet area kutahya turkey metamorphic rocks host the majority of the thermal waters of the emet area only dereli springs are hosted by nonmetamorphic carbonates and ophiolitic rocks the carbonated rocks of the lower parts of the neogene sequence are also secondary reservoir rocks the measured surface temperatures of thermal waters are between 33 and 54 c most of the thermal waters are characterized as ca mg so4 hco3 type although there are a few ca na hco3 na ca so4 and ca mg hco3 waters calcium concentrations in the thermal waters are 89 354 mg kg high so4 contents of the thermal waters up to 1309 mg kg are related to rocks and minerals in the red unit below the emet borate deposits although the so4 concentrations are high and so4 is the major anion gypsum and anhydrite are undersaturated for all of the thermal waters indicating that dissolution of so4 is still taking place in the reservoir thermal waters are oversaturated at outlet conditions with respect to calcite chalcedony dolomite and quartz according to the activity diagrams thermal waters are likely to form illite as an alteration product in the reservoir and ca and mg contents are controlled by exchange with smectite reservoir temperatures obtained by silica geothermometers and assessments of the saturation states of minerals are more appropriate for emet geothermal waters assessments of the various geothermometers suggest that reservoir temperature is around 75 87 c

temperature pressure and redox conditions governing the composition of the cold co2 gases discharged in north latium central italy abstract gases rich in co2 are produced over the northern latium area by metamorphic reactions involving carbonate formations or by magma degassing the gas migrates towards the surface and accumulates in sedimentary permeable structures which act as gas traps in that environment the pco2 is a variable externally fixed and the redox conditions at which the gases equilibrate are governed by the c co2 buffer temperature in the interval 100 180 c and pco2 from few bar to tens of bar have been estimated by means of the ratios between the redox sensitive gas species and co2 the composition of gases from two geothermal wells located in the study area and of other hydrothermal fluids suggest that the redox potential of low medium temperature carbonate hosted hydrothermal systems may be fixed by the c co2 buffer

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

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

tracing deep fluid source contribution to groundwater in an active seismic area central italy a combined geothermometric and isotopic δ13c perspective abstract an understanding of the origin and migration pathways of geofluids in an active seismic area is of paramount importance in terms of societal challenges such as mitigation of seismic hazards this study investigates the relationship between the stable isotope ratio 13c 12c of deep co2 and geothermometry in selected groundwater samples located close to extensional faults in central italy the temperature range is inferred from an equation based on the na li ratio and chemical geothermal modelling 113 130 c globally the calculated temperature range agrees with that resulting from deep boreholes in the northern apennines an alternative method is also included to better evaluate the difference in isotopic composition between the aqueous and gaseous 13c co2 at deep condition a review of previously published data shows that monitoring of the isotopic composition of the dissolved inorganic carbon dic in springs fed by meteoric origin located in seismically active areas must take into account mass and isotopic balance to correctly evaluate the component and the role of deep fluid during seismic events in particular the coupled and corrected isotope and geothermometrical monitoring of the springs could help to distinguish between deep gas or deep fluid contributions to shallow aquifers the results of this study indicate that faults play a crucial role in controlling the migration of crustal fluids in addition they reveal that possible evaluation of potential seismic precursors mandatorily requires a long period of monthly monitoring

geothermal mineral equilibria the dominant reaction determining the chemistry of fluids in a geothermal system of the new zealand type consists of the conversion of primary plagioclase by co2 to calcite and clays with log pco2 15 26 7850 t 273 2 temperature t in c subsequent reactions involving secondary minerals control relative co2 h2s contents the distribution of mineral phases throughout a geothermal system reflects the stepwise conversion of thermodynamically unstable primary phases through a series of intermediate metastable phases to a thermodynamically stable secondary assemblage the relative stabilities of these phases was evaluated on the basis of their solubilities the least soluble aluminiumsilicate representing the thermodynamically most stable phase under a given set of conditions observed assemblages of secondary minerals in geothermal systems represent indicators allowing mineral fluidinteraction conditions to be evaluated on the basis of multi component mineral stability diagrams

geochemistry of quaternary travertines in the region north of rome italy structural hydrologic and paleoclimatic implications in the tyrrhenian region of central italy late quaternary fossil travertines are widespread along two major regional structures the tiber valley and the ancona anzio line the origin and transport of spring waters from which travertines precipitate are elucidated by chemical and isotopic studies of the travertines and associated thermal springs and gas vents there are consistent differences in the geochemical and isotopic signatures of thermal spring waters gas vents and present and fossil travertines between east and west of the tiber valley west of the tiber valley 13c of co2 discharged from gas vents and 13c of fossil travertines are higher than those to the east to the west the travertines have higher strontium contents and gases emitted from vents have higher 3he 4he ratios and lower n2 contents than to the east fossil travertines to the west have characteristics typical of thermogene thermal spring origin whereas those to the east have meteogene low temperature characteristics including abundant plant casts and organic impurities the regional geochemical differences in travertines and fluid compositions across the tiber valley are interpreted with a model of regional fluid flow the regional mesozoic limestone aquifer is recharged in the main axis of the apennine chain and the groundwater flows westward and is discharged at springs the travertine precipitating waters east of the tiber valley have shallower flow paths than those to the west because of the comparatively short fluid flow paths and low normal heat flow the groundwaters to the east of the tiber valley are cold and have co2 isotopic signatures indicating a significant biogenic contribution acquired from soils in the recharge area and limited deeply derived co2 in contrast spring waters west of the tiber valley have been conductively heated during transit in these high heat flow areas and have incorporated a comparatively large quantity of co2 derived from decarbonation of limestone the elevated strontium content of the thermal spring water west of the tiber valley is attributed to deep circulation and dissolution of a triassic evaporite unit that is stratigraphically beneath the mesozoic limestone u series age dates of fossil travertines indicate three main periods of travertine formation ka 220 240 120 140 and 60 70 based on the regional flow model correlating travertine deposition at thermal springs and precipitation in the recharge area we suggest that pluvial activity was enhanced during these periods our study suggests that travertines preserve a valuable record of paleofluid composition and paleoprecipitation and are thus useful for reconstructing paleohydrology and paleoclimate

insights into magmatic evolution and recharge history in capraia volcano italy from chemical and isotopic zoning in plagioclase phenocrysts plagioclase phenocrysts in dacites from the high k calc alkaline capraia volcano were investigated for major trace element and sr isotope variations in order to gain better insight into the proposed open system behaviour of the volcano repeated dissolution zones in plagioclases from the early erupted monte castello mc and later monte rucitello mr dacitic units are associated with a sharp increase in an content and variation in isotopic compositions 87sr 86sr 0 70872 0 71004 which argue for repeated magma mixing in particular petrographic and mineralogical evidence suggest that recharge with hot basaltic magma occurred repeatedly during the lifetime of the capraia volcanic system we attempted to correlate shared crystallization and resorption histories using chemical mol an fe and sr isotopic zoning in plagioclase in this correlation framework the observed mismatch between chemical and isotopic data in some phenocrysts is interpreted to reflect either growth of phenocrysts in a separate magma chamber or compositional zoning within a single magma chamber a minor role of crustal contamination is inferred instead the intra crystal variations in isotopic composition in plagioclase reflect the existence of distinct components that may have thoroughly mixed at the end of the mc plagioclase growth history the dominant radiogenic component is similar to lamproites occurring in tuscany recharge with this component occurred throughout the genesis of the mr dacites but was restricted to the early growth history of the mc dacites the mr plagioclases are inferred to have crystallized from separate more differentiated batches of magma that were likely to have evolved at the top of a zoned magma reservoir decrease in the an content after most dissolution zones in all phenocrysts and low temperature estimates from zircon saturation thermometry 800 c also emphasize the importance of crystal fractionation during the evolution of the volcano in agreement with the occurrence of a significant amount of rhyolitic material thus it is inferred that a rather large magma chamber may have existed during the first cycle of eruptive activity

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

textural analyses of classical rapakivi granites texture formation through coarsening size selective replacement and stirring abstract the well known rapakivi texture has been extensively studied through a geochemical lens presented here is a detailed textural analysis of two classical rapakivi granites from the proterozoic the wiborg batholith finland and the wolf river batholith usa crystal size distributions csds of mantled and unmantled ovoid populations indicate that protracted textural coarsening was important prior to mantling an analysis of mantle thicknesses coupled with a model replicating slices through mantled feldspars indicates that mantling occurred in a semi selective manner mantle thickness on smaller k feldspar ovoids range from 0 to 100 of the ovoid and the variability of mantling decreases with increasing size selective mantling could be accomplished within a replacement front operating over a thermal gradient whereby melting augments the ovoid population and generates the mantles but with partial overlap of these two processes csds of mantled and unmantled feldspars are exceptionally similar between randomly selected samples suggesting stirring post mantling and prior to emplacement was an efficient process results indicate that classical rapakivi granites are texturally complex and cannot be generated through a single down temperature process it is suggested that coarsening of ovoids followed by mantling and homogenization may be efficiently generated in the sub caldera setting where there are repeated pulses of mantle derived magmas or high temperature anatectic melts acting as an intermediary for mantle heat

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

a karst hydrology model for the geomorphic evolution of grand canyon arizona usa abstract the evolution of grand canyon started 85 ma when the southwestern hualapai plateau section of the colorado plateau began uplifting this uplift initiated a northeast trending drainage canyon system laramide paleo grand canyon that was to constrain all later routes including that of the colorado river this drainage proceeded down dip but up the stratigraphic section so that northward incision intersected progressively younger paleozoic to mesozoic rock we propose a capture of groundwater by the karstic redwall limestone at rm 197 that shifted the drainage direction of this early canyon along a n60 e trending section to rm 130 uplift of the kaibab arch at 80 65 ma forced coconino plateau drainage to divert around the west side of the arch rather than northeast across it in the mid tertiary an arizona river in the western grand canyon transported shinumo clasts to the california sespe formation and a magmatism tectonic volcanism episode occurred on and south of the hualapai plateau by 17 ma basin and range down faulting furthered earlier miocene canyon headward erosion eastward and then northward into utah causing a complete regional drainage reversal southward this miocene western paleo grand canyon river incised into the redwall muav karst aquifer so as to supply the 12 6 ma hualapai limestone with high 87sr 86sr carbonate spring water a 6 0 5 5 ma final connection between the east and west sides of the kaibab arch was accomplished by karst piracy drainage traversing under the arch this complexity of origin separate canyon sections joined drainage reversals and a final karst connection is why grand canyon remains enigmatic to geologists

mineral deposits in the rotokawa geothermal pipelines new zealand abstract at the point of flashing at 224 c and 25 bar absolute black silica scales enriched in cu 5 6 ag 4 0 te 3 0 zn 1 5 pb 0 6 and au 0 2 form in the wellhead of production well rk 9 silver pb cu and au are deposited as tellurides cu pb and zn as sulfides and au as a native element these elements decrease rapidly downstream of the wellhead to other parts of the surface geothermal pipeline mercury b as se sb and reduced s are partially transported in the gas phase and largely deposited at a distance from the wellhead total s and b occur primarily in the steam line where b is stabilised by silica deposited from carry over brine and s by sulfide mineralisation arsenic and se are mainly found in scales from the steam and mixing reinjection lines hg in the condensate and mixing reinjection lines and sb in the mixing reinjection line where 80 105 c low salinity condensate mixes with 140 170 c brine a decrease in the solubility of minerals in solution is the primary cause for deposition of opal a and increased concentrations of base and precious metal concentrations in scales scale deposition is thus induced by flashing at the wellhead of the production wells attached to the ormat binary plant phase separation dilution cooling and mixing of cooled brine and condensate the reaction of steel with circulating solutions and gases results in a corrosion mineral assemblage reflecting local oxidation potentials and variations in h2s partial pressures along the pipeline corrosion of steel introduces and augments trace elements such as p cr mn ni and mo in the pipeline solutions selective incorporation or sorption of elements onto opal a and opal ct or corrosion products such as goethite and pyrite may increase concentrations of li b cl and p in opal cr mn ni cu zn and mo in goethite and cu zn as hg sb and se in pyrite wherever water circulates in the pipeline system silica precipitates initially from solution as a gel which later solidifies to opal a and subsequently crystallises to opal ct then quartz aggregates the transformation of opal a to more ordered and stable silica polymorphs in the pipelines is a kinetically induced dissolution reprecipitation crystal growth process that is accelerated at temperatures 200 224 c

karst springs as natural pluviometers constraints on the isotopic composition of rainfall in the apennines of central italy abstract this paper describes an indirect method to calculate the isotopic composition of rainfall by using the isotopic composition of karst springs fed by waters circulating in the most important regional aquifer of central italy i e the mesozoic limestone sequence that forms the backbone of the apennines by using 18o and d data and the 18o and or d average gradient for elevation evaluated through the use of literature rainfall data and new measurements from a typical alpine valley in northern italy the altitude of precipitation of their parent water has been re calculated vertical descents of more than 2000 m from recharge to discharge have been assessed in some high flow rate cold springs in the morphologically steep adriatic sector of central italy a clear correlation between the vertical descents and more negative isotopic compositions at their relative emergence elevations is highlighted in contrast in the tyrrhenian sector lower karstic drops generally lower than 500 m correlate with less negative isotopic composition of recharge areas the 18o iso contour map of the recalculated parent rainfall in central italy is more detailed than any possible isotopic map of rainfall made using pluviometers unless large number of rainfall collectors were deployed on mountaintops the data also show that the isotopic composition of rainfall depends on the source of the storm water in particular precipitation is isotopically heavier when originating in the mediterranean sea and lighter when formed in the atlantic ocean consequently the collision between air masses with such a different isotopic signature results in a relatively small latitudinal fractionation effect the peninsular part of central italy is very narrow with several mountains and massifs more that 2000 m high and any latitudinal variation in the isotopic composition between rainfall sourced in the atlantic ocean and in the mediterranean sea is much lower than that due to the isotopic fractionation due to elevation

geochemical characteristics of greek thermal springs abstract a systematic sampling of all known thermal springs and gas emissions of continental greece has been carried out the main gas and water composition and some trace elements in liquid phase sio 2 h 3 bo 3 nh 4 and li have been determined the chemical composition of most thermal springs analyzed is typical of deep na hco 3 rising hot waters which circulate in co 2 rich silicic formations and which acquire progressively a na cl composition by admixing of colder shallower saline connate waters housed in the rock matrix of marine post orogenic tertiary quaternary sediments on the whole the thermal manifestations of continental greece can be fitted in a tectonic framework where high hydraulic gradients enable waters in hot deep aquifers to reach the surface rapidly along fault systems at the boundary of n s and e w trending tertiary basins equilibration temperatures of 80 120 c in the main storage zone 130 150 c max in the nestos xanthi basin have been assessed for most of the study area high n 2 and low h 2 and h 2 s content in gas emissions associated to water samples are consistent with temperatures assessed by using geothermometers in liquid phase

systematic review of geochemical data from thermal springs gas vents and fumaroles of southern italy for geothermal favourability mapping abstract in recent years two research projects specifically conceived by italian institutions of research to promote the implementation of the use of geothermal energy in southern italy has allowed the review of most data on chemical and isotopic compositions of natural thermal manifestations in the territory of italy two large databases one for thermal springs and co2 rich springs and a second one for fumarolic condensates and associated gas phase have been produced and are available on line with data spanning in time from the early 70 s to the present we have used those data after careful evaluation of the quality and reliability of them to produce correlation diagrams and isodistribution maps of some relevant geochemical geothermal parameters such as pco2 in thermal springs co2 and 13c in co2 of gas phases 3he 4he ratio and he in this way we have been able to delimit the areal patterns of thermal anomalies potentially related with geothermal reservoirs the cross correlation among the many parameters 40 selected has allowed the overview on the circulation of fluids at shallow crust in one of the most active tectonic boundary of the earth between the african and the eurasian continents shallow circulation of hot fluids is particularly active in the roman comagmatic province the neapolitan area and sicily both at etna aeolian archipelago and pantelleria island in the sicily channel where active geothermal systems are already known whose areal extension is probably much larger than what envisaged at present the geothermometric evaluation of data has not allowed to clearly identity new areas apart from those already known but nevertheless some areas in the inner apennines as well as sicily and sardinia have shown anomalous 3he 4he values that point to the presence of mantle fluids located inside the crust being most of active volcanic islands likely much smaller than the thermal anomaly they are associated with a futuristic perspective of utilizing geothermal fluids off shore is suggested moreover the database and the proposed maps can be a useful tool both scientific community and stakeholders to perform geothermal favourability maps and to identify potential new areas interesting from a geothermal perspective

sar interferometry on a very long time scale a study of the interferometric characteristics of man made features anthropogenic features show up as highly coherent objects even in heavily decorrelated interferograms in order to assess whether the information from such features is still usable the stability of their phase and coherence is analyzed through a series of interferograms the results indicate that these features can remain interferometrically stable over several years

mapping regional land displacements in the venice coastland by an integrated monitoring system abstract an original integrated monitoring method is designed to infer an accurate and reliable figure of regional land displacements in coastal areas where the presence of internal waters wetlands farmlands urban and industrial centers usually reduces the efficiency of single ground based and satellite based measuring techniques five different methods i e spirit leveling differential global positioning system dgps continuous gps cgps interferometric synthetic aperture radar insar and interferometric point target analysis ipta are integrated into a subsidence integrated monitoring system sims to overcome the limits characterizing each technique the sims has been used over the past decade to provide a new image of the land displacements in the venice region the result exhibits a resolution never obtained before the central lagoon including the city of venice shows a general stability while the northern and southern lagoon extremities and their related catchment sectors sink with serious rates averaging 3 to 5 mm year the sinking rates increase up to 10 15 mm year in the coastland south of the lagoon relatively small uplifts less than 1 mm year are observed at the alpine foothills and in a wide area comprised between the euganean hills and the lagoon the observed land displacements have been associated to the geological features of the study region i e tectonics seismicity differential consolidation of the middle upper pleistocene and holocene deposits and to anthropogenic activities such as land reclamation and groundwater withdrawal

hydrothermal hydrocarbon gases 2 application in the east african rift system hydrocarbon gases are ubiquitous in the hydrothermal systems of the east african rift system ears though often found at very low concentrations in the volcanic eastern branch as compared to the sedimentary western branch study of the chemical and isotopic compositions of these hydrocarbons from sites in kenya ethiopia djibouti and uganda reveals considerable homogeneity over hundreds of km of the various rift units consideration of c and he isotopic evidence points to a predominantly crustal thermogenic origin for the hydrocarbons there being no evidence of mantle inputs in either the morb or hotspot sectors of the ears temperature information from geothermal wells has been utilised to investigate the relationship between reservoir temperatures and ratios of ch4 to c2h6 the general c1 c2 geothermometric relationship proposed in part 1 of this study holds reasonably well and is shown to give results equal to or better than the inorganic gas geothermometers presently in use both in the wellfields and undeveloped high enthalpy geothermal areas results from low enthalpy hot spring systems are less well correlated with apparent deep temperatures but consistent with data from similar systems elsewhere in the world

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

formation of rapakivi feldspar in the deer isle granite complex coastal maine in situ lead isotope and trace element analysis rapakivi and alkali feldspar phenocrysts from the devonian deer isle granite complex maine were investigated to see if magma mixing or isothermal decompression was responsible for their formation pb isotope and trace element analyses of alkali feldspar ovoids and their plagioclase inclusions were obtained by la icp ms to determine the characteristics of the initial magma these were compared with the plagioclase mantles rapakivi grains show a decrease in pb isotopic values and an increase in ba la and ce concentrations from the ovoids and inclusions to the innermost plagioclase mantles adjacent to the ovoids these variations along with cl imagery of quartz phenocrysts indicate an open system with compositional changes in the magma chamber occurring during rapakivi feldspar growth repeated episodes of magma mixing replenishment by ba and lree enriched magmas with lower pb isotopic ratios along with hybridized variations with the host magma created localized dissolution of alkali feldspar and quartz alkali feldspar phenocrysts proximal to these zones of thermal perturbation were first resorbed and then mantled by plagioclase that records the more primitive signature of the more mafic melt pb isotopic values and ba la and ce concentrations trend back to the initial magma composition at the mantle rims as the effects of the mixing event dissipated for grains that were somewhat more distal to these zones of mixing resorption of the alkali feldspar crystals did not occur yet the fresh supply of ba resulted in ba rich alkali feldspar mantles over ba poor alkali feldspar cores other alkali feldspar crystals were too far from the site of mixing hence they lack any evidence of open system crystallization as crystallization of the chamber continued along solidification fronts batches of cooler crystal rich magmas settled en masse to the floor disaggregation of these batches during settling and subsequent accumulation on the reservoir floor brought grains with disparate crystallization histories together filter pressing of the cumulate pile flushed highly evolved melts fluids out from interstitial pores to the high silica upper portions of the chamber the crystallization transportation and juxtaposition of disparate types of feldspar phenocrysts suggest that a relatively large and active magma chamber periodically recharged by localized batches of melt must have existed in this case it is clear that rapakivi mantled feldspars are the result of magma mixing such interpretations may apply to many other occurrences as well

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

a combined geochemical and isotopic study of the fluids discharged from the montecatini thermal system nw tuscany italy abstract the thermo mineral fluids discharges of montecatini terme northern apennines tuscany italy have been exploited since the roman times and despite the fact that this thermal complex is one of the biggest in europe the most recent geochemical investigations were published almost 40 years ago to fill this gap in this paper a detailed geochemical and isotopic investigation on the main thermal springs and wells from the montecatini thermal system mts is presented the chemical and isotopic features of the montecatini waters suggested that they are mainly controlled by water rock interaction processes between meteoric water permeating at depth from the surrounding reliefs up to 800 m a s l and the triassic evaporites burano formation belonging to the tuscan sedimentary series the local stratigraphic and tectonic framework favors an efficient recharge of the hydrothermal reservoir by the meteoric precipitation from a large catchment area and this aspect plays a fundamental role for the longevity of the montecatini thermal spas notwithstanding the huge amount of thermal water exploited the 3h values indicated that the thermal waters are likely related to a relatively long 50 years fluid circulation pattern approaching the surface thermal and saline waters mix with cold and low tds total dissolved solids waters hosted in short shallow aquifer s whose chemistry is dictated by the interaction of rain waters with silico clastic rocks of low solubility geothermometric estimations in the f so42 hco3 system suggested the occurrence of a main fluid reservoir at t 80 95 c and pco2 0 5 bars such co2 pressure is consistent with values estimated for other thermal springs from central southern tuscany being co2 basically supplied by a deep source nevertheless 13c co2 and 13c tdic values were lower than those expected for a mantle thermometamorphic co2 source this can be explained by i isotopic fractionation occurring during calcite precipitation and or ii mixing with biogenically derived gases occurring at relatively shallow depth

chemistry of thermal springs in the larderello travale geothermal region southern tuscany italy abstract thirty two thermal spring eleven cold spring and six steam condensates in the larderello travale geothermal region have been studied from a geochemical point of view the aim of this work was to delineate the relation between the chemical composition of the natural thermal manifestations and the thermal anomaly which is among the best known in the world the larderello spring both hot and cold are characterized by low salinity total dissolved solids generally lower than 1000 mg kg and alkaline earth bicarbonate composition in contrast an alkaline earth sulfate composition characterizes the thermal springs of the travale area this difference is due to the fact that the underground pathways of the larderello hot springs are only in shallow flyschoid caprock formations whereas at travale the paths are longer and in carbonate anhydritic mesozoic rocks which constitute the main reservoir formations in both the larderello and travale areas the thermal character of larderello springs is therefore mainly due to rock conduction whereas in travale it is mostly due to inflows of hot fluid phases from the geothermal reservoir comparison between ammonia li and b in fluid phases both steam condensates and hot springs in the larderello area suggests that in some of them their temperatures might be partly due to direct vapor inflows