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Annette E. Götz - One of the best experts on this subject based on the ideXlab platform.
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outcrop analogue study of permocarboniferous geothermal sandstone Reservoir formations northern upper rhine graben germany impact of mineral content depositional environment and diagenesis on petrophysical properties
International Journal of Earth Sciences, 2016Co-Authors: Anke Aretz, Annette E. Götz, Ingo SassAbstract:The Permocarboniferous siliciclastic formations represent the largest Hydrothermal Reservoir in the northern Upper Rhine Graben in SW Germany and have so far been investigated in large-scale studies only. The Cenozoic Upper Rhine Graben crosses the Permocarboniferous Saar–Nahe Basin, a Variscan intramontane molasse basin. Due to the subsidence in this graben structure, the top of the up to 2-km-thick Permocarboniferous is located at a depth of 600–2900 m and is overlain by Tertiary and Quaternary sediments. At this depth, the Reservoir temperatures exceed 150 °C, which are sufficient for geothermal electricity generation with binary power plants. To further assess the potential of this geothermal Reservoir, detailed information on thermophysical and hydraulic properties of the different lithostratigraphical units and their depositional environment is essential. Here, we present an integrated study of outcrop analogues and drill core material. In total, 850 outcrop samples were analyzed, measuring porosity, permeability, thermal conductivity and thermal diffusivity. Furthermore, 62 plugs were taken from drillings that encountered or intersected the Permocarboniferous at depths between 1800 and 2900 m. Petrographic analysis of 155 thin sections of outcrop samples and samples taken from Reservoir depth was conducted to quantify the mineral composition, sorting and rounding of grains and the kind of cementation. Its influence on porosity, permeability, the degree of compaction and illitization was quantified. Three parameters influencing the Reservoir properties of the Permocarboniferous were detected. The strongest and most destructive influence on Reservoir quality is related to late diagenetic processes. An illitic and kaolinitic cementation and impregnation of bitumina document CO2- and CH4-rich acidic pore water conditions, which are interpreted as fluids that migrated along a hydraulic contact from an underlying Carboniferous hydrocarbon source rock. Migrating oil and acidic waters led to the dissolution of haematite cements in the lower Permocarboniferous formations. During the Eocene, subsidence of the Upper Rhine Graben porosities and permeabilities of the sandstones of these formations were strongly reduced to 2.5 % and 3.2 × 10−18 m2. The second important influence on Reservoir quality is the distinct depositional environment and its influence on early diagenetic processes. In early stage diagenesis, the best influence on Reservoir properties exhibits a haematite cementation. It typically occurs in eolian sandstones of the Kreuznach Formation (Upper Permocarboniferous) and is characterized by grain covering haematite coatings, which are interpreted to inhibit cementation, compaction and illitization of pore space during burial. Eolian sandstones taken from outcrops and Reservoir depths exhibit the highest porosities (16.4; 12.3 %) and permeabilities (2.0 × 10−15; 8.4 × 10−16 m2). A third important influence on Reservoir quality is the general mineral composition and the quartz content which is the highest in the Kreuznach Formation with 73.8 %. Based on the integrated study of depositional environments and diagenetic processes, Reservoir properties of the different Permocarboniferous formations within the northern Upper Rhine Graben and their changes with burial depth can be predicted with satisfactory accuracy. This leads to a better understanding of the Reservoir quality and enables an appropriate well design for exploration and exploitation of these geothermal resources.
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lithofacies and depth dependency of thermo and petrophysical rock parameters of the upper jurassic geothermal carbonate Reservoirs of the molasse basin
Zeitschrift Der Deutschen Gesellschaft Fur Geowissenschaften, 2014Co-Authors: S Homuth, Annette E. Götz, I SassAbstract:In the early stages of Hydrothermal Reservoir exploration, the thermo-physical characterisation of the Reservoir is accomplished by evaluating drilling data and seismic surveys. Especially in carbonate Reservoirs, the distinction of different facies zones and heterogeneities in general is very complex. For economic reasons a sufficiently high flow rate toward the production well and an according high fluid temperature is necessary. For Reservoir predictions and modelling, geothermal parameters such as permeability, thermal conductivity/diffusivity, and specific heat capacity have to be quantified. The thermophysical parameters are facies related. The application of a thermofacies classification to Upper Jurassic limestones serves to understand the heterogeneities and to identify production zones. Outcrop analogue studies enable the determination and correlation of facies related thermophysical parameters and structural geology data and thus the geothermal exploration concept becomes more precise and quantitative. The analogue outcrops of the Swabian and Franconian Alb represent the target formations of Upper Jurassic carbonate Reservoirs in the adjacent Molasse Basin. These limestone formations contain the main flow paths through fractures, faults, and characteristic of limestone formations also through karstification. The type and grade of karstification is also facies related. In general, the matrix permeability has only a minor effect on the Reservoir’s sustainability except for some grainstones and dolomitised zones with higher porosities and permeabilities. Permeabilities range from 10-18 to 10-13 m2 (0.001 mD to 100 mD). The permeability range of mudand wackestones is about the same. A high variation of thermophysical parameters is recognised within individual facies zones or stratigraphic units. Mudand wackestones show thermal conductivities around 2 W/(mK), whilst mudstones have lower thermal conductivities than wackestones. The thermal conductivities of massive reefal limestones show values of 1.8 to 3.9 W/(mK). Secondarily silicified reefal limestones and dolomites show the highest values of thermal conductivity. These parameters determined on ovendried samples have to be corrected for water-saturated rocks under the according temperature and pressure conditions using transfer models. A comparison of calculated Reservoir properties with measurements from deep drill cores confirms a good correlation. Based on the investigation of the matrix parameters in combination with Reservoir transfer models, the Reservoir prognosis and numerical simulation can be improved. The facies related characterisation and prediction of Reservoir formations is a powerful tool for the exploration, operation, extension and quality management of geothermal Reservoirs in the Molasse Basin. Kurzfassung: In der Planungsphase einer Hydrothermalen Reservoirerkundung erfolgt die thermophysikalische Charakterisierung des Reservoirs durch die Auswertung von Bohrungsdaten und seismischen Erkundungen. Im Falle von KarbonatReservoiren ist die Differenzierung von verschiedenen Faziesbereichen bzw. Heterogenitaten im Allgemeinen sehr komplex. Aus wirtschaftlichen Grunden ist eine hohe Forderrate der Produktionsbohrung und eine entsprechend hohe Fluidtemperatur notwendig. Fur eine Reservoirprognose und -modellierung mussen die geothermischen Kennwerte wie Permeabilitat, Warmeleitfahigkeit, Temperaturleitfahigkeit und spezifische Warmekapazitat im Reservoir quantifiziert werden. Diese thermound petrophysikalischen Kennwerte sind faziesabhangig. Die Anwendung einer thermofaziellen Klassifikation auf die Karbonate des Oberen Jura dient hierbei zum besseren Verstandnis der Heterogenitaten und zur Identifikation von Produktionszonen. Aufschlussanalogstudien ermoglichen hierbei die Bestimmung faziesabhangiger thermophysikalischer Kennwerte und deren Korrelation mit strukturgeologischen Daten, wodurch die geothermische Erkundung praziser und quantitativer wird. Die analogen Aufschlusse der Schwabischen und Frankischen Alb reprasentieren die Zielformation der © 2014 E. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, Germany DOI: 10.1127/1860-1804/2014/0074 www.schweizerbart.de 1860-1804/0074 $ 8.10 Z. Dt. Ges. Geowiss. (German J. Geosci.), 165 (3), p. 469–486, 15 figs., 2 tables Article Published online August 2014
Ingo Sass - One of the best experts on this subject based on the ideXlab platform.
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outcrop analogue study of permocarboniferous geothermal sandstone Reservoir formations northern upper rhine graben germany impact of mineral content depositional environment and diagenesis on petrophysical properties
International Journal of Earth Sciences, 2016Co-Authors: Anke Aretz, Annette E. Götz, Ingo SassAbstract:The Permocarboniferous siliciclastic formations represent the largest Hydrothermal Reservoir in the northern Upper Rhine Graben in SW Germany and have so far been investigated in large-scale studies only. The Cenozoic Upper Rhine Graben crosses the Permocarboniferous Saar–Nahe Basin, a Variscan intramontane molasse basin. Due to the subsidence in this graben structure, the top of the up to 2-km-thick Permocarboniferous is located at a depth of 600–2900 m and is overlain by Tertiary and Quaternary sediments. At this depth, the Reservoir temperatures exceed 150 °C, which are sufficient for geothermal electricity generation with binary power plants. To further assess the potential of this geothermal Reservoir, detailed information on thermophysical and hydraulic properties of the different lithostratigraphical units and their depositional environment is essential. Here, we present an integrated study of outcrop analogues and drill core material. In total, 850 outcrop samples were analyzed, measuring porosity, permeability, thermal conductivity and thermal diffusivity. Furthermore, 62 plugs were taken from drillings that encountered or intersected the Permocarboniferous at depths between 1800 and 2900 m. Petrographic analysis of 155 thin sections of outcrop samples and samples taken from Reservoir depth was conducted to quantify the mineral composition, sorting and rounding of grains and the kind of cementation. Its influence on porosity, permeability, the degree of compaction and illitization was quantified. Three parameters influencing the Reservoir properties of the Permocarboniferous were detected. The strongest and most destructive influence on Reservoir quality is related to late diagenetic processes. An illitic and kaolinitic cementation and impregnation of bitumina document CO2- and CH4-rich acidic pore water conditions, which are interpreted as fluids that migrated along a hydraulic contact from an underlying Carboniferous hydrocarbon source rock. Migrating oil and acidic waters led to the dissolution of haematite cements in the lower Permocarboniferous formations. During the Eocene, subsidence of the Upper Rhine Graben porosities and permeabilities of the sandstones of these formations were strongly reduced to 2.5 % and 3.2 × 10−18 m2. The second important influence on Reservoir quality is the distinct depositional environment and its influence on early diagenetic processes. In early stage diagenesis, the best influence on Reservoir properties exhibits a haematite cementation. It typically occurs in eolian sandstones of the Kreuznach Formation (Upper Permocarboniferous) and is characterized by grain covering haematite coatings, which are interpreted to inhibit cementation, compaction and illitization of pore space during burial. Eolian sandstones taken from outcrops and Reservoir depths exhibit the highest porosities (16.4; 12.3 %) and permeabilities (2.0 × 10−15; 8.4 × 10−16 m2). A third important influence on Reservoir quality is the general mineral composition and the quartz content which is the highest in the Kreuznach Formation with 73.8 %. Based on the integrated study of depositional environments and diagenetic processes, Reservoir properties of the different Permocarboniferous formations within the northern Upper Rhine Graben and their changes with burial depth can be predicted with satisfactory accuracy. This leads to a better understanding of the Reservoir quality and enables an appropriate well design for exploration and exploitation of these geothermal resources.
Anke Aretz - One of the best experts on this subject based on the ideXlab platform.
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outcrop analogue study of permocarboniferous geothermal sandstone Reservoir formations northern upper rhine graben germany impact of mineral content depositional environment and diagenesis on petrophysical properties
International Journal of Earth Sciences, 2016Co-Authors: Anke Aretz, Annette E. Götz, Ingo SassAbstract:The Permocarboniferous siliciclastic formations represent the largest Hydrothermal Reservoir in the northern Upper Rhine Graben in SW Germany and have so far been investigated in large-scale studies only. The Cenozoic Upper Rhine Graben crosses the Permocarboniferous Saar–Nahe Basin, a Variscan intramontane molasse basin. Due to the subsidence in this graben structure, the top of the up to 2-km-thick Permocarboniferous is located at a depth of 600–2900 m and is overlain by Tertiary and Quaternary sediments. At this depth, the Reservoir temperatures exceed 150 °C, which are sufficient for geothermal electricity generation with binary power plants. To further assess the potential of this geothermal Reservoir, detailed information on thermophysical and hydraulic properties of the different lithostratigraphical units and their depositional environment is essential. Here, we present an integrated study of outcrop analogues and drill core material. In total, 850 outcrop samples were analyzed, measuring porosity, permeability, thermal conductivity and thermal diffusivity. Furthermore, 62 plugs were taken from drillings that encountered or intersected the Permocarboniferous at depths between 1800 and 2900 m. Petrographic analysis of 155 thin sections of outcrop samples and samples taken from Reservoir depth was conducted to quantify the mineral composition, sorting and rounding of grains and the kind of cementation. Its influence on porosity, permeability, the degree of compaction and illitization was quantified. Three parameters influencing the Reservoir properties of the Permocarboniferous were detected. The strongest and most destructive influence on Reservoir quality is related to late diagenetic processes. An illitic and kaolinitic cementation and impregnation of bitumina document CO2- and CH4-rich acidic pore water conditions, which are interpreted as fluids that migrated along a hydraulic contact from an underlying Carboniferous hydrocarbon source rock. Migrating oil and acidic waters led to the dissolution of haematite cements in the lower Permocarboniferous formations. During the Eocene, subsidence of the Upper Rhine Graben porosities and permeabilities of the sandstones of these formations were strongly reduced to 2.5 % and 3.2 × 10−18 m2. The second important influence on Reservoir quality is the distinct depositional environment and its influence on early diagenetic processes. In early stage diagenesis, the best influence on Reservoir properties exhibits a haematite cementation. It typically occurs in eolian sandstones of the Kreuznach Formation (Upper Permocarboniferous) and is characterized by grain covering haematite coatings, which are interpreted to inhibit cementation, compaction and illitization of pore space during burial. Eolian sandstones taken from outcrops and Reservoir depths exhibit the highest porosities (16.4; 12.3 %) and permeabilities (2.0 × 10−15; 8.4 × 10−16 m2). A third important influence on Reservoir quality is the general mineral composition and the quartz content which is the highest in the Kreuznach Formation with 73.8 %. Based on the integrated study of depositional environments and diagenetic processes, Reservoir properties of the different Permocarboniferous formations within the northern Upper Rhine Graben and their changes with burial depth can be predicted with satisfactory accuracy. This leads to a better understanding of the Reservoir quality and enables an appropriate well design for exploration and exploitation of these geothermal resources.
Orlando Vaselli - One of the best experts on this subject based on the ideXlab platform.
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anomalous concentrations of arsenic fluoride and radon in volcanic sedimentary aquifers from central italy quality indexes for management of the water resource
Environmental Pollution, 2019Co-Authors: D Cinti, Orlando Vaselli, Pier Paolo Poncia, L Brusca, Fausto Grassa, M Procesi, Franco TassiAbstract:Abstract 659 water samples from springs and wells in the Sabatini and Vicano-Cimino Volcanic Districts (central Italy) were analyzed for arsenic (As), fluoride (F−) and radon (222Rn) concentrations. Waters mostly sourced from a shallow and cold aquifer hosted within volcanic rocks, which represents the main public drinking water supply. Cold waters from perched aquifers within sedimentary formations and thermal waters related to a deep Hydrothermal Reservoir were also analyzed. The highest concentrations of As and F− were measured in the thermal waters and attributed to their enhanced mobility during water-rock interaction processes at Hydrothermal temperatures. Relatively high concentrations of As and F− were also recorded in those springs and wells discharging from the volcanic aquifer, whereas waters hosted in the sedimentary units showed significantly lower contents. About 60% (As) and 25% (F−) of cold waters from the volcanic aquifer exceeded the maximum allowable concentrations for human consumption. Such anomalously high levels of geogenic pollutants were caused by mixing with fluids upwelling through faulted zones from the Hydrothermal Reservoir. Chemical weathering of volcanic rocks and groundwater flow path were also considered to contribute to the observed concentrations. Cold waters from the volcanic aquifer showed the highest 222Rn concentrations, resulting from the high contents of Rn-generating radionuclides in the volcanic units. Approximately 22% of these waters exceeded the recommended value for human consumption. A specific Quality Index (QI), comprised between 1 (very low) and 4 (very high), was computed for each water on the basis of As, F− and 222Rn concentrations and visualized through a spatial distribution map processed by means of geostatistical techniques. This map and the specific As, F− and 222Rn maps can be regarded as useful tools for water management by local authorities to both improve intervention plans in contaminated sectors and identify new water resources suitable for human consumption.
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fluid geochemistry of a deep seated geothermal resource in the puna plateau jujuy province argentina
Journal of Volcanology and Geothermal Research, 2017Co-Authors: Peralta Y Arnold, Franco Tassi, Jacopo Cabassi, Pablo J Caffe, Orlando VaselliAbstract:Abstract This study focused on the geochemical and isotopic features of thermal fluids discharged from five zones located in the high altitude Puna plateau (Jujuy Province between S 22°20′–23°20′ and W 66°–67°), i.e. Granada, Vilama, Pairique, Coranzuli and Olaroz. Partially mature waters with a Na + -Cl − composition were recognized in all the investigated zones, suggesting that a deep Hydrothermal Reservoir hosted within the Paleozoic crystalline basement represents the main Hydrothermal fluid source. The Hydrothermal Reservoirs are mainly recharged by meteoric water, although based on the δ 18 O-H 2 O and δD-H 2 O values, some contribution of andesitic water cannot be completely ruled out. Regional S-oriented faulting systems, which generated a horst and graben tectonics, and NE-, NW- and WE-oriented transverse structures, likely act as preferentially uprising pathways for the deep-originated fluids, as also supported by the Rc/Ra values (up to 1.39) indicating the occurrence of significant amounts of mantle He (up to 16%). Carbon dioxide, the most abundant compound in the gas phase associated with the thermal waters, mostly originated from a crustal source, although the occurrence of CO 2 from a mantle source, contaminated by organic-rich material due to the subduction process, is also possible. Relatively small and cold Na + -HCO 3 − -type aquifers were produced by the interaction between meteoric water and Cretaceous, Palaeogene to Miocene sediments. Dissolution of evaporitic surficial deposits strongly affected the chemistry of the thermal springs in the peripheral zones of the study area. Geothermometry in the Na-K-Ca-Mg system suggested equilibrium temperatures up to 200 °C for the deep aquifer, whereas lower temperatures (from 105 to 155 °C) were inferred by applying the H 2 geothermometer, likely due to re-equilibrium processes during the thermal fluid uprising within relatively shallow Na-HCO 3 aquifers. The great depth of the geothermal resource (possibly > 5000 m b.g.l.) is likely preventing further studies aimed to evaluate possible exploitation, although the occurrence of Li- and Ba-rich deposits associated may attract financial investments, giving a pulse for the development of this remote region.
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volatile organic compounds vocs in soil gases from solfatara crater campi flegrei southern italy geogenic source s vs biogeochemical processes
Applied Geochemistry, 2015Co-Authors: Franco Tassi, Barbara Nisi, Jacopo Cabassi, Francesco Capecchiacci, Stefania Venturi, Orlando VaselliAbstract:The chemical composition of volatile organic compounds (VOCs) in soil gases from the Solfatara crater (Campi Flegrei, Italy) was analyzed to investigate the effects of biogeochemical processes on gases discharged from the Hydrothermal Reservoir and released into the atmosphere through diffuse degassing. The chemistry of fluids from fumarolic vents, which represent preferential pathways for fluid uprising, was also reported for comparison. Oxidation–reduction and hydration–dehydration reactions, as well as microbial activity, strongly affected the composition of C4–C9 alkanes, alkenes, S-bearing compounds and alkylated aromatics, especially in those sites where the soil showed relatively low permeability to uprising fluids. Other endogenous organic compounds, such as benzene, phenol and hydrofluorocarbons were able to transit through the soil almost undisturbed, independently on the gas emission rate. Products of VOC degradation mainly consisted of aldehydes, ketones, esters, ethers and, subordinately, alcohols. Cyclic compounds revealed the occurrence of VOCs produced within sedimentary formations overlying the Hydrothermal Reservoir, whereas the presence of chlorofluorocarbons (CFCs) was likely related to air contamination. The results of the present study highlighted the strict control of biogeochemical processes on the behavior of Hydrothermal VOCs that, at least at a local scale, may have a significant impact on air quality. This information could be improved by laboratory experiments conducted at specific chemical–physical conditions and in presence of different microbial populations.
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new geochemical and isotopic insights to evaluate the geothermal resource of the Hydrothermal system of rosario de la frontera salta northern argentina
Journal of Volcanology and Geothermal Research, 2015Co-Authors: A Chiodi, Orlando Vaselli, Franco Tassi, Walter Baez, R Maffucci, C Invernizzi, Guido Giordano, Sveva Corrado, Gabriele Bicocchi, J ViramonteAbstract:Abstract In this study, the chemical and isotopic composition of thermo-mineral springs from the Rosario de la Frontera Hydrothermal system was used to construct a conceptual model describing the source regions the thermal fluids and the chemical–physical processes controlling the chemistry of waters and dissolved gases during their underground circulation. The main Hydrothermal Reservoir, hosted within the Cretaceous Pirgua Subgroup deposits, is fed by meteoric water and shows a Na–HCO 3 composition produced by water–rock interactions involving sedimentary formations mostly consisting of conglomerates and sandstones, which are interbedded with alkaline volcanic rocks and shales and limestone deposits. This aquifer also receives significant contributions of crustal CO 2 and He from mantle degassing, the latter being likely favored by the regional tectonic assessment that is characterized by a deep detachment (at about 10 km depth) in the basement of the Santa Barbara thick-skinned thrust system and a thinned lithosphere. The uprising thermal fluids mix with a relatively high salinity Na–Cl dominated aquifer produced by the interaction of meteoric water with the Tertiary Anta Formation evaporite. The temperatures of the Hydrothermal Reservoir, estimated with water geothermometers, are up to 130 °C, which are consistent with the thickness of the Hydrothermal circuit (2700–3000 m) and the relatively high local geothermal gradient (~ 40 °C/km). These results suggest that the heat stored in the fluid phase of RFHS is up to ~ 1 × 10 18 J, a value significantly higher (20%) than that previously estimated assuming an average Reservoir temperature of 90 °C.
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gas geochemistry of the magmatic Hydrothermal fluid Reservoir in the copahue caviahue volcanic complex argentina
Journal of Volcanology and Geothermal Research, 2013Co-Authors: Mariano Agusto, Orlando Vaselli, Franco Tassi, Bruno Capaccioni, Alberto Tomas Caselli, Dmitri Rouwet, Stefano Caliro, Giovanni ChiodiniAbstract:Abstract Copahue volcano is part of the Caviahue–Copahue Volcanic Complex (CCVC), which is located in the southwestern sector of the Caviahue volcano-tectonic depression (Argentina–Chile). This depression is a pull-apart basin accommodating stresses between the southern Liquine–Ofqui strike slip and the northern Copahue–Antinir compressive fault systems, in a back-arc setting with respect to the Southern Andean Volcanic Zone. In this study, we present chemical (inorganic and organic) and isotope compositions (δ13C-CO2, δ15N, 3He/4He, 40Ar/36Ar, δ13C-CH4, δD-CH4, and δD-H2O and δ18O-H2O) of fumaroles and bubbling gases of thermal springs located at the foot of Copahue volcano sampled in 2006, 2007 and 2012. Helium isotope ratios, the highest observed for a Southern American volcano (R/Ra up to 7.94), indicate a non-classic arc-like setting, but rather an extensional regime subdued to asthenospheric thinning. δ13C-CO2 values (from − 8.8‰ to − 6.8‰ vs. V-PDB), δ15N values (+ 5.3‰ to + 5.5‰ vs. Air) and CO2/3He ratios (from 1.4 to 8.8 × 109) suggest that the magmatic source is significantly affected by contamination of subducted sediments. Gases discharged from the northern sector of the CCVC show contribution of 3He-poor fluids likely permeating through local fault systems. Despite the clear mantle isotope signature in the CCVC gases, the acidic gas species have suffered scrubbing processes by a Hydrothermal system mainly recharged by meteoric water. Gas geothermometry in the H2O-CO2-CH4-CO-H2 system suggests that CO and H2 re-equilibrate in a separated vapor phase at 200°–220 °C. On the contrary, rock–fluid interactions controlling CO2, CH4 production from Sabatier reaction and C3H8 dehydrogenation seem to occur within the Hydrothermal Reservoir at temperatures ranging from 250° to 300 °C. Fumarole gases sampled in 2006–2007 show relatively low N2/He and N2/Ar ratios and high R/Ra values with respect to those measured in 2012. Such compositional and isotope variations were likely related to injection of mafic magma that likely triggered the 2000 eruption. Therefore, changes affecting the magmatic system had a delayed effect on the chemistry of the CCVC gases due to the presence of the Hydrothermal Reservoir. However, geochemical monitoring activities mainly focused on the behavior of inert gas compounds (N2 and He), should be increased to investigate the mechanism at the origin of the unrest started in 2011.
Franco Tassi - One of the best experts on this subject based on the ideXlab platform.
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anomalous concentrations of arsenic fluoride and radon in volcanic sedimentary aquifers from central italy quality indexes for management of the water resource
Environmental Pollution, 2019Co-Authors: D Cinti, Orlando Vaselli, Pier Paolo Poncia, L Brusca, Fausto Grassa, M Procesi, Franco TassiAbstract:Abstract 659 water samples from springs and wells in the Sabatini and Vicano-Cimino Volcanic Districts (central Italy) were analyzed for arsenic (As), fluoride (F−) and radon (222Rn) concentrations. Waters mostly sourced from a shallow and cold aquifer hosted within volcanic rocks, which represents the main public drinking water supply. Cold waters from perched aquifers within sedimentary formations and thermal waters related to a deep Hydrothermal Reservoir were also analyzed. The highest concentrations of As and F− were measured in the thermal waters and attributed to their enhanced mobility during water-rock interaction processes at Hydrothermal temperatures. Relatively high concentrations of As and F− were also recorded in those springs and wells discharging from the volcanic aquifer, whereas waters hosted in the sedimentary units showed significantly lower contents. About 60% (As) and 25% (F−) of cold waters from the volcanic aquifer exceeded the maximum allowable concentrations for human consumption. Such anomalously high levels of geogenic pollutants were caused by mixing with fluids upwelling through faulted zones from the Hydrothermal Reservoir. Chemical weathering of volcanic rocks and groundwater flow path were also considered to contribute to the observed concentrations. Cold waters from the volcanic aquifer showed the highest 222Rn concentrations, resulting from the high contents of Rn-generating radionuclides in the volcanic units. Approximately 22% of these waters exceeded the recommended value for human consumption. A specific Quality Index (QI), comprised between 1 (very low) and 4 (very high), was computed for each water on the basis of As, F− and 222Rn concentrations and visualized through a spatial distribution map processed by means of geostatistical techniques. This map and the specific As, F− and 222Rn maps can be regarded as useful tools for water management by local authorities to both improve intervention plans in contaminated sectors and identify new water resources suitable for human consumption.
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fluid geochemistry of a deep seated geothermal resource in the puna plateau jujuy province argentina
Journal of Volcanology and Geothermal Research, 2017Co-Authors: Peralta Y Arnold, Franco Tassi, Jacopo Cabassi, Pablo J Caffe, Orlando VaselliAbstract:Abstract This study focused on the geochemical and isotopic features of thermal fluids discharged from five zones located in the high altitude Puna plateau (Jujuy Province between S 22°20′–23°20′ and W 66°–67°), i.e. Granada, Vilama, Pairique, Coranzuli and Olaroz. Partially mature waters with a Na + -Cl − composition were recognized in all the investigated zones, suggesting that a deep Hydrothermal Reservoir hosted within the Paleozoic crystalline basement represents the main Hydrothermal fluid source. The Hydrothermal Reservoirs are mainly recharged by meteoric water, although based on the δ 18 O-H 2 O and δD-H 2 O values, some contribution of andesitic water cannot be completely ruled out. Regional S-oriented faulting systems, which generated a horst and graben tectonics, and NE-, NW- and WE-oriented transverse structures, likely act as preferentially uprising pathways for the deep-originated fluids, as also supported by the Rc/Ra values (up to 1.39) indicating the occurrence of significant amounts of mantle He (up to 16%). Carbon dioxide, the most abundant compound in the gas phase associated with the thermal waters, mostly originated from a crustal source, although the occurrence of CO 2 from a mantle source, contaminated by organic-rich material due to the subduction process, is also possible. Relatively small and cold Na + -HCO 3 − -type aquifers were produced by the interaction between meteoric water and Cretaceous, Palaeogene to Miocene sediments. Dissolution of evaporitic surficial deposits strongly affected the chemistry of the thermal springs in the peripheral zones of the study area. Geothermometry in the Na-K-Ca-Mg system suggested equilibrium temperatures up to 200 °C for the deep aquifer, whereas lower temperatures (from 105 to 155 °C) were inferred by applying the H 2 geothermometer, likely due to re-equilibrium processes during the thermal fluid uprising within relatively shallow Na-HCO 3 aquifers. The great depth of the geothermal resource (possibly > 5000 m b.g.l.) is likely preventing further studies aimed to evaluate possible exploitation, although the occurrence of Li- and Ba-rich deposits associated may attract financial investments, giving a pulse for the development of this remote region.
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volatile organic compounds vocs in soil gases from solfatara crater campi flegrei southern italy geogenic source s vs biogeochemical processes
Applied Geochemistry, 2015Co-Authors: Franco Tassi, Barbara Nisi, Jacopo Cabassi, Francesco Capecchiacci, Stefania Venturi, Orlando VaselliAbstract:The chemical composition of volatile organic compounds (VOCs) in soil gases from the Solfatara crater (Campi Flegrei, Italy) was analyzed to investigate the effects of biogeochemical processes on gases discharged from the Hydrothermal Reservoir and released into the atmosphere through diffuse degassing. The chemistry of fluids from fumarolic vents, which represent preferential pathways for fluid uprising, was also reported for comparison. Oxidation–reduction and hydration–dehydration reactions, as well as microbial activity, strongly affected the composition of C4–C9 alkanes, alkenes, S-bearing compounds and alkylated aromatics, especially in those sites where the soil showed relatively low permeability to uprising fluids. Other endogenous organic compounds, such as benzene, phenol and hydrofluorocarbons were able to transit through the soil almost undisturbed, independently on the gas emission rate. Products of VOC degradation mainly consisted of aldehydes, ketones, esters, ethers and, subordinately, alcohols. Cyclic compounds revealed the occurrence of VOCs produced within sedimentary formations overlying the Hydrothermal Reservoir, whereas the presence of chlorofluorocarbons (CFCs) was likely related to air contamination. The results of the present study highlighted the strict control of biogeochemical processes on the behavior of Hydrothermal VOCs that, at least at a local scale, may have a significant impact on air quality. This information could be improved by laboratory experiments conducted at specific chemical–physical conditions and in presence of different microbial populations.
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new geochemical and isotopic insights to evaluate the geothermal resource of the Hydrothermal system of rosario de la frontera salta northern argentina
Journal of Volcanology and Geothermal Research, 2015Co-Authors: A Chiodi, Orlando Vaselli, Franco Tassi, Walter Baez, R Maffucci, C Invernizzi, Guido Giordano, Sveva Corrado, Gabriele Bicocchi, J ViramonteAbstract:Abstract In this study, the chemical and isotopic composition of thermo-mineral springs from the Rosario de la Frontera Hydrothermal system was used to construct a conceptual model describing the source regions the thermal fluids and the chemical–physical processes controlling the chemistry of waters and dissolved gases during their underground circulation. The main Hydrothermal Reservoir, hosted within the Cretaceous Pirgua Subgroup deposits, is fed by meteoric water and shows a Na–HCO 3 composition produced by water–rock interactions involving sedimentary formations mostly consisting of conglomerates and sandstones, which are interbedded with alkaline volcanic rocks and shales and limestone deposits. This aquifer also receives significant contributions of crustal CO 2 and He from mantle degassing, the latter being likely favored by the regional tectonic assessment that is characterized by a deep detachment (at about 10 km depth) in the basement of the Santa Barbara thick-skinned thrust system and a thinned lithosphere. The uprising thermal fluids mix with a relatively high salinity Na–Cl dominated aquifer produced by the interaction of meteoric water with the Tertiary Anta Formation evaporite. The temperatures of the Hydrothermal Reservoir, estimated with water geothermometers, are up to 130 °C, which are consistent with the thickness of the Hydrothermal circuit (2700–3000 m) and the relatively high local geothermal gradient (~ 40 °C/km). These results suggest that the heat stored in the fluid phase of RFHS is up to ~ 1 × 10 18 J, a value significantly higher (20%) than that previously estimated assuming an average Reservoir temperature of 90 °C.
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gas geochemistry of the magmatic Hydrothermal fluid Reservoir in the copahue caviahue volcanic complex argentina
Journal of Volcanology and Geothermal Research, 2013Co-Authors: Mariano Agusto, Orlando Vaselli, Franco Tassi, Bruno Capaccioni, Alberto Tomas Caselli, Dmitri Rouwet, Stefano Caliro, Giovanni ChiodiniAbstract:Abstract Copahue volcano is part of the Caviahue–Copahue Volcanic Complex (CCVC), which is located in the southwestern sector of the Caviahue volcano-tectonic depression (Argentina–Chile). This depression is a pull-apart basin accommodating stresses between the southern Liquine–Ofqui strike slip and the northern Copahue–Antinir compressive fault systems, in a back-arc setting with respect to the Southern Andean Volcanic Zone. In this study, we present chemical (inorganic and organic) and isotope compositions (δ13C-CO2, δ15N, 3He/4He, 40Ar/36Ar, δ13C-CH4, δD-CH4, and δD-H2O and δ18O-H2O) of fumaroles and bubbling gases of thermal springs located at the foot of Copahue volcano sampled in 2006, 2007 and 2012. Helium isotope ratios, the highest observed for a Southern American volcano (R/Ra up to 7.94), indicate a non-classic arc-like setting, but rather an extensional regime subdued to asthenospheric thinning. δ13C-CO2 values (from − 8.8‰ to − 6.8‰ vs. V-PDB), δ15N values (+ 5.3‰ to + 5.5‰ vs. Air) and CO2/3He ratios (from 1.4 to 8.8 × 109) suggest that the magmatic source is significantly affected by contamination of subducted sediments. Gases discharged from the northern sector of the CCVC show contribution of 3He-poor fluids likely permeating through local fault systems. Despite the clear mantle isotope signature in the CCVC gases, the acidic gas species have suffered scrubbing processes by a Hydrothermal system mainly recharged by meteoric water. Gas geothermometry in the H2O-CO2-CH4-CO-H2 system suggests that CO and H2 re-equilibrate in a separated vapor phase at 200°–220 °C. On the contrary, rock–fluid interactions controlling CO2, CH4 production from Sabatier reaction and C3H8 dehydrogenation seem to occur within the Hydrothermal Reservoir at temperatures ranging from 250° to 300 °C. Fumarole gases sampled in 2006–2007 show relatively low N2/He and N2/Ar ratios and high R/Ra values with respect to those measured in 2012. Such compositional and isotope variations were likely related to injection of mafic magma that likely triggered the 2000 eruption. Therefore, changes affecting the magmatic system had a delayed effect on the chemistry of the CCVC gases due to the presence of the Hydrothermal Reservoir. However, geochemical monitoring activities mainly focused on the behavior of inert gas compounds (N2 and He), should be increased to investigate the mechanism at the origin of the unrest started in 2011.
