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Viveiros F. - One of the best experts on this subject based on the ideXlab platform.
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New insights into the magmatic-Hydrothermal System and volatile budget of Lastarria volcano, Chile: Integrated results from the 2014 IAVCEI CCVG 12th Volcanic Gas Workshop
'Geological Society of America', 2018Co-Authors: Lopez T., Aiuppa A., Aguilera F., Tassi F., Maarten De Moor, J., Bobrowski N., Tamburello G., Rizzo A., Liuzzo M., Viveiros F.Abstract:Recent geophysical evidence for large-scale regional crustal inflation and localized crustal magma intrusion has made Lastarria volcano (northern Chile) the target of numerous geological, geophysical, and geochemical studies. The chemical composition of volcanic gases sampled during discrete campaigns from Lastarria volcano indicated a well-developed Hydrothermal System from direct fumarole samples in A.D. 2006, 2008, and 2009, and shallow magma degassing using measurements from in situ plume sampling techniques in 2012. It is unclear if the differences in measured gas compositions and resulting interpretations were due to artifacts of the different sampling methods employed, short-term excursions from baseline due to localized changes in stress, or a Systematic change in Lastarria's magmatic-Hydrothermal System between 2009 and 2012. Integrated results from a two-day volcanic gas sampling and measurement campaign during the 2014 International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) Commission on the Chemistry of Volcanic Gases (CCVG) 12th Gas Workshop are used here to compare and evaluate current gas sampling and measurement techniques, refine the existing subsurface models for Lastarria volcano, and provide new constraints on its magmatic-Hydrothermal System and total degassing budget. While compositional differences among sampling methods are present, distinct compositional changes are observed, which if representative of longterm trends, indicate a change in Lastarria's overall magmatic-Hydrothermal System. The composition of volcanic gases measured in 2014 contained high proportions of relatively magma- and water-soluble gases consistent with degassing of shallow magma, and in agreement with the 2012 gas composition. When compared with gas compositions measured in 2006-2009, higher relative H2O/CO2 ratios combined with lower relative CO2/St and H2O/St and stable HCl/St ratios (where St is total S [SO2 + H2S]) are observed in 2012 and 2014. These compositional changes suggest variations in the magmatic-Hydrothermal System between 2009 and 2012, with possible scenarios to explain these trends including: (1) decompression-induced degassing due to magma ascent within the shallow crust; (2) crystallization-induced degassing of a stalled magma body; (3) depletion of the Hydrothermal System due to heating, changes in local stress, and/or minimal precipitation; and/or (4) acidification of the Hydrothermal System. These scenarios are evaluated and compared against the geophysical observations of continuous shallow inflation at ~8 km depth between 1997 and 2016, and near-surface ( < 1 km) inflation between 2000 and 2008, to further refine the existing subsurface models. Higher relative H2O/CO2 observed in 2012 and 2014 is not consistent with the depletion or acidification of a Hydrothermal System, while all other observations are consistent with the four proposed models. Based on these observations, we find that scenarios 1 or 2 are the most likely to explain the geochemical and geophysical observations, and propose that targeted shallow interferometric synthetic-aperture radar (InSAR) studies could help discriminate between these two scenarios. Lastly, we use an average SO2 flux of 604 \ub1 296 t/d measured on 22 November 2014, along with the average gas composition and diffuse soil CO2 flux measurements, to estimate a total volatile flux from Lastarria volcano in 2014 of ~12,400 t/d, which is similar to previous estimates from 2012
Thomas Lebourg - One of the best experts on this subject based on the ideXlab platform.
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Three-Dimensional Electrical Resistivity Tomography of the Solfatara Crater (Italy): Implication for the Multiphase Flow Structure of the Shallow Hydrothermal System
Journal of Geophysical Research : Solid Earth, 2017Co-Authors: Marceau Gresse, Giovanni Chiodini, S. Byrdina, Timothy Johnson, Tullio Ricci, Giuseppe Vilardo, Annarita Mangiacapra, Jean Vandemeulebrouck, André Revil, Thomas LebourgAbstract:The Solfatara volcano is the main degassing area of the Campi Flegrei caldera, characterized by 60 years of unrest. Assessing such renewal activity is a challenging task because Hydrothermal interactions with magmatic gases remain poorly understood. In this study, we decipher the complex structure of the shallow Solfatara Hydrothermal System by performing the first 3‐D, high‐resolution, electrical resistivity tomography of the volcano. The 3‐D resistivity model was obtained from the inversion of 43,432 resistance measurements performed on an area of ~0.68 km2. The proposed interpretation of the multiphase Hydrothermal structures is based on the resistivity model, a high‐resolution infrared surface temperature image, and 1,136 soil CO2 flux measurements. In addition, we realized 27 soil cation exchange capacity and pH measurements demonstrating a negligible contribution of surface conductivity to the shallow bulk electrical conductivity. Hence, we show that the resistivity changes are mainly controlled by fluid content and temperature. The high‐resolution tomograms identify for the first time the structure of the gas‐dominated reservoir at 60 m depth that feeds the Bocca Grande fumarole through a ~10 m thick channel. In addition, the resistivity model reveals a channel‐like conductive structure where the liquid produced by steam condensation around the main fumaroles flows down to the Fangaia area within a buried fault. The model delineates the emplacement of the main geological structures: Mount Olibano, Solfatara cryptodome, and tephra deposits. It also reveals the anatomy of the Hydrothermal System, especially two liquid‐dominated plumes, the Fangaia mud pool and the Pisciarelli fumarole, respectively.
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three dimensional electrical resistivity tomography of the solfatara crater italy implication for the multiphase flow structure of the shallow Hydrothermal System
Journal of Geophysical Research, 2017Co-Authors: Marceau Gresse, Giovanni Chiodini, S. Byrdina, Tullio Ricci, Giuseppe Vilardo, Annarita Mangiacapra, Jean Vandemeulebrouck, André Revil, Timothy C Johnson, Thomas LebourgAbstract:The Solfatara volcano is the main degassing area of the Campi Flegrei caldera, characterized by 60 years of unrest. Assessing such renewal activity is a challenging task because Hydrothermal interactions with magmatic gases remain poorly understood. In this study, we decipher the complex structure of the shallow Solfatara Hydrothermal System by performing the first 3-D, high-resolution, Electrical Resistivity Tomography (ERT) of the volcano. The 3-D resistivity model was obtained from the inversion of 43,432 resistance measurements performed on an area of 0.68 km2. The proposed interpretation of the multiphase Hydrothermal structures is based on the resistivity model, a high-resolution infrared surface temperature image, and 1,136 soil CO2 flux measurements. In addition, we realized 27 soil Cation Exchange Capacity (CEC) and pH measurements demonstrating a negligible contribution of surface conductivity to the shallow bulk electrical conductivity. Hence, we show that the resistivity changes are mainly controlled by fluid content and temperature. The high-resolution tomograms identify for the first time the structure of the gas-dominated reservoir at 50 m depth that feeds the Bocca Grande fumarole through a ~10-m-thick channel. In addition, the resistivity model reveals a channel-like conductive structure where the liquid produced by steam condensation around the main fumaroles flows down to the Fangaia area within a buried fault. The model delineates the emplacement of the main geological structures: Mt Olibano, Solfatara crypto-dome, and tephra deposits. It also reveals the anatomy of the Hydrothermal System, especially two liquid-dominated plumes, the Fangaia mud pool and the Pisciarelli fumarole, respectively.
Viveiros Fátima - One of the best experts on this subject based on the ideXlab platform.
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Innovative boat-towed transient electromagnetics - Investigation of the Furnas volcanic lake Hydrothermal System, Azores
'Society of Exploration Geophysicists', 2020Co-Authors: Yogeshwar Pritam, Byrdina Svetlana, Kuepper Mira, Tezkan Buelent, Rath Volker, Kiyan Duygu, Cruz Jose, Andrade Cesar, Viveiros FátimaAbstract:Water-covered areas may lead to gaps in surface electromagnetic surveys, causing reduced resolution and, as a consequence, increased uncertainty in derived subsurface models. We have evaluated a boat-towed floating central loop time-domain electromagnetic technique that mitigates this problem. It facilitates obtaining data with a spatial sampling density, which is rarely possible with standard instrumentation on land, and it only requires moderate logistical effort. A unique field study on a shallow volcanic lake demonstrated that this method is feasible with only a minor loss of accuracy when compared to anchored and land soundings. We found that the noise sources arising from the moving instrument and the boat engine can be neglected. The field survey was performed on the Lagoa das Furnas (Sao Miguel, Azores Islands, Portugal), which is located within an active volcanic area and is characterized by fumarolic fields and CO2 degassing. Thus, the associated Hydrothermal System is expected to extend below the lake. However, the character, geometry, and extent of this System are unknown because of the lack of boreholes and geophysical studies. In total, 600 soundings, combining towed profiles with anchored and land-based soundings, were acquired with an aim of imaging the Hydrothermal System beneath the lake down to 200 m. The results from all three types of measurements compare well and thus led to consistent 1D inversion models. The inversion results delineate a highly conductive, smectite-rich cap layer dipping below the lake away from the main fumarole zone. Near this zone, the extent of the conductor agrees well with an area of intense dispersed CO2 degassing, which appears to be controlled by at least two electrically distinctive fault zones in which the conductor is found at greater depths
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New insights into the magmatic-Hydrothermal System and volatile budget of Lastarria volcano, Chile: Integrated results from the 2014 IAVCEI CCVG 12th Volcanic Gas Workshop
'Geological Society of America', 2018Co-Authors: Lopez Taryn, Aguilera Felipe, Tassi Franco, De Moor J. Maarten, Bobrowski Nicole, Aiuppa Alessandro, Tamburello Giancarlo, Rizzo, Andrea Luca, Liuzzo Marco, Viveiros FátimaAbstract:Recent geophysical evidence for large-scale regional crustal inflation and localized crustal magma intrusion has made Lastarria volcano (northern Chile) the target of numerous geological, geophysical, and geochemical studies. The chemical composition of volcanic gases sampled during discrete campaigns from Lastarria volcano indicated a well-developed Hydrothermal System from direct fumarole samples in A.D. 2006, 2008, and 2009, and shallow magma degassing using measurements from in situ plume sampling techniques in 2012. It is unclear if the differences in measured gas compositions and resulting interpretations were due to artifacts of the different sampling methods employed, short-term excursions from baseline due to localized changes in stress, or a Systematic change in Lastarria’s magmatic-Hydrothermal System between 2009 and 2012. Integrated results from a two-day volcanic gas sampling and measurement campaign during the 2014 International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) Commission on the Chemistry of Volcanic Gases (CCVG) 12th Gas Workshop are used here to compare and evaluate current gas sampling and measurement techniques, refine the existing subsurface models for Lastarria volcano, and provide new constraints on its magmatic-Hydrothermal System and total degassing budget. While compositional differences among sampling methods are present, distinct compositional changes are observed, which if representative of longterm trends, indicate a change in Lastarria’s overall magmatic-Hydrothermal System. The composition of volcanic gases measured in 2014 contained high proportions of relatively magma- and water-soluble gases consistent with degassing of shallow magma, and in agreement with the 2012 gas composition. When compared with gas compositions measured in 2006–2009, higher relative H2O/CO2 ratios combined with lower relative CO2/St and H2O/St and stable HCl/St ratios (where St is total S [SO2 + H2S]) are observed in 2012 and 2014. These compositional changes suggest variations in the magmatic-Hydrothermal System between 2009 and 2012, with possible scenarios to explain these trends including: (1) decompression-induced degassing due to magma ascent within the shallow crust; (2) crystallization-induced degassing of a stalled magma body; (3) depletion of the Hydrothermal System due to heating, changes in local stress, and/or minimal precipitation; and/or (4) acidification of the Hydrothermal System. These scenarios are evaluated and compared against the geophysical observations of continuous shallow inflation at ~8 km depth between 1997 and 2016, and near-surface (
Wolfgang Bach - One of the best experts on this subject based on the ideXlab platform.
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constraints on the source of cu in a submarine magmatic Hydrothermal System brothers volcano kermadec island arc
Contributions to Mineralogy and Petrology, 2018Co-Authors: Manuel Keith, Karsten M Haase, Reiner Klemd, D J Smith, Ulrich Schwarzschampera, Wolfgang BachAbstract:Most magmatic-Hydrothermal Cu deposits are genetically linked to arc magmas. However, most continental or oceanic arc magmas are barren, and hence new methods have to be developed to distinguish between barren and mineralised arc Systems. Source composition, melting conditions, the timing of S saturation and an initial chalcophile element-enrichment represent important parameters that control the potential of a subduction setting to host an economically valuable deposit. Brothers volcano in the Kermadec island arc is one of the best-studied examples of arc-related submarine magmatic-Hydrothermal activity. This study, for the first time, compares the chemical and mineralogical composition of the Brothers seafloor massive sulphides and the associated dacitic to rhyolitic lavas that host the Hydrothermal System. Incompatible trace element ratios, such as La/Sm and Ce/Pb, indicate that the basaltic melts from L’Esperance volcano may represent a parental analogue to the more evolved Brothers lavas. Copper-rich magmatic sulphides (Cu > 2 wt%) identified in fresh volcanic glass and phenocryst phases, such as clinopyroxene, plagioclase and Fe–Ti oxide suggest that the surrounding lavas that host the Brothers Hydrothermal System represent a potential Cu source for the sulphide ores at the seafloor. Thermodynamic calculations reveal that the Brothers melts reached volatile saturation during their evolution. Melt inclusion data and the occurrence of sulphides along vesicle margins indicate that an exsolving volatile phase extracted Cu from the silicate melt and probably contributed it to the overlying Hydrothermal System. Hence, the formation of the Cu-rich seafloor massive sulphides (up to 35.6 wt%) is probably due to the contribution of Cu from a bimodal source including wall rock leaching and magmatic degassing, in a mineralisation style that is hybrid between Cyprus-type volcanic-hosted massive sulphide and subaerial epithermal–porphyry deposits.
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phyllosilicate alteration mineral assemblages in the active subsea floor pacmanus Hydrothermal System papua new guinea odp leg 193
Economic Geology, 2006Co-Authors: Holger Paulick, Wolfgang BachAbstract:Pacmanus is an active submarine Hydrothermal System in the Manus back-arc basin, Papua New Guinea, located at 1,600 to 1,700 m below sea level on the crest of a dacitic volcano. It is inferred to represent a modern analogue of ancient mineralizing sea-floor Hydrothermal Systems that produced volcanogenic polymetallic massive sulfide deposits. Ocean Drilling Program (ODP) Leg 193 drilled the subsea-floor Hydrothermal alteration zone of Pacmanus in a high-temperature discharge area (Roman Ruins) and a low-temperature discharge area (Snowcap), reaching a maximum depth of 380 m below the sea floor. Evidence from short-wavelength infrared (SWIR) spectroscopy, X-ray diffraction (XRD) analyses, calculated normative mineral abundances, and electron microprobe data show that there are substantial variations in the Hydrothermal phyllosilicate assemblages within the Pacmanus Hydrothermal System. The altered dacite at Roman Ruins contains 10 to 25 wt percent normative chlorite + smectite and up to 15 wt percent normative illite. In contrast, altered dacite below Snowcap contains up to 50 wt percent combined normative illite + paragonite + chlorite + smectite + pyrophyllite. SWIR data show that pyrophyllite is particularly abundant between 50 and 120 and between 220 and 270 m below sea floor, indicating localized interaction of dacite with acidic Hydrothermal fluids. Variations in the Na/K ratio of dioctahedral phyllosilicate, determined by electron microprobe and spectral analyses, confirm the presence of a paragonitic component at Snowcap. A model is suggested to explain the differences in the distribution of Hydrothermal phyllosilicate assemblages in the two areas in terms of variations in fluid composition and changes to the subsea-floor hydrology in a dynamically evolving volcanic-Hydrothermal environment.
Lopez T. - One of the best experts on this subject based on the ideXlab platform.
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New insights into the magmatic-Hydrothermal System and volatile budget of Lastarria volcano, Chile: Integrated results from the 2014 IAVCEI CCVG 12th Volcanic Gas Workshop
'Geological Society of America', 2018Co-Authors: Lopez T., Aiuppa A., Aguilera F., Tassi F., Maarten De Moor, J., Bobrowski N., Tamburello G., Rizzo A., Liuzzo M., Viveiros F.Abstract:Recent geophysical evidence for large-scale regional crustal inflation and localized crustal magma intrusion has made Lastarria volcano (northern Chile) the target of numerous geological, geophysical, and geochemical studies. The chemical composition of volcanic gases sampled during discrete campaigns from Lastarria volcano indicated a well-developed Hydrothermal System from direct fumarole samples in A.D. 2006, 2008, and 2009, and shallow magma degassing using measurements from in situ plume sampling techniques in 2012. It is unclear if the differences in measured gas compositions and resulting interpretations were due to artifacts of the different sampling methods employed, short-term excursions from baseline due to localized changes in stress, or a Systematic change in Lastarria's magmatic-Hydrothermal System between 2009 and 2012. Integrated results from a two-day volcanic gas sampling and measurement campaign during the 2014 International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) Commission on the Chemistry of Volcanic Gases (CCVG) 12th Gas Workshop are used here to compare and evaluate current gas sampling and measurement techniques, refine the existing subsurface models for Lastarria volcano, and provide new constraints on its magmatic-Hydrothermal System and total degassing budget. While compositional differences among sampling methods are present, distinct compositional changes are observed, which if representative of longterm trends, indicate a change in Lastarria's overall magmatic-Hydrothermal System. The composition of volcanic gases measured in 2014 contained high proportions of relatively magma- and water-soluble gases consistent with degassing of shallow magma, and in agreement with the 2012 gas composition. When compared with gas compositions measured in 2006-2009, higher relative H2O/CO2 ratios combined with lower relative CO2/St and H2O/St and stable HCl/St ratios (where St is total S [SO2 + H2S]) are observed in 2012 and 2014. These compositional changes suggest variations in the magmatic-Hydrothermal System between 2009 and 2012, with possible scenarios to explain these trends including: (1) decompression-induced degassing due to magma ascent within the shallow crust; (2) crystallization-induced degassing of a stalled magma body; (3) depletion of the Hydrothermal System due to heating, changes in local stress, and/or minimal precipitation; and/or (4) acidification of the Hydrothermal System. These scenarios are evaluated and compared against the geophysical observations of continuous shallow inflation at ~8 km depth between 1997 and 2016, and near-surface ( < 1 km) inflation between 2000 and 2008, to further refine the existing subsurface models. Higher relative H2O/CO2 observed in 2012 and 2014 is not consistent with the depletion or acidification of a Hydrothermal System, while all other observations are consistent with the four proposed models. Based on these observations, we find that scenarios 1 or 2 are the most likely to explain the geochemical and geophysical observations, and propose that targeted shallow interferometric synthetic-aperture radar (InSAR) studies could help discriminate between these two scenarios. Lastly, we use an average SO2 flux of 604 \ub1 296 t/d measured on 22 November 2014, along with the average gas composition and diffuse soil CO2 flux measurements, to estimate a total volatile flux from Lastarria volcano in 2014 of ~12,400 t/d, which is similar to previous estimates from 2012
