scholarly journals FLUID GEOCHEMISTRY INVESTIGATIONS ON THE VOLCANIC SYSTEM OF METHANA

2007 ◽  
Vol 40 (2) ◽  
pp. 712
Author(s):  
W. D'Alessandro ◽  
L. Brusca ◽  
K. Kyriakopoulos ◽  
M. Margaritopoulos ◽  
G. Michas ◽  
...  
Keyword(s):  
Geothermal System ◽  
Volcanic System ◽  
Spatially Correlated ◽  
Co2 Output ◽  
Active Tectonic ◽  
Soil Site ◽  
Gas Hazard ◽  
Tectonic System ◽  
Cold Groundwaters

An extensive geochemical survey on the fluids released by the volcanic/geothermal system of Methana was undertaken. Characterization of the gases was made on the basis of the chemical and isotopie (He and C) analysis of 14 samples. CO2 soil gas concentration and fluxes were measured on the whole peninsula at more than 100 sampling sites. 31 samples of thermal and cold groundwaters were also sampled and analysed to characterize the geochemistry of aquifers. Anomalies referable to the geothermal system, besides at known thermal manifestations, were also recognized at some anomalous degassing soil site and in some cold groundwater. These anomalies were always spatially correlated to the main active tectonic system of the area. The total CO2 output of the volcanic system has been preliminary estimated in about 0.2 kg s~ . Although this value is low compared to other volcanic systems, anomalous C02 degassing at Methana may pose gas hazard problems. Such volcanic risk, although restricted to limited areas, cannot be neglected and further studies have to be undertaken for its better assessment.

scholarly journals Degassing at the Volcanic/Geothermal System of Kos (Greece): Geochemical Characterization of the Released Gases and CO2 Output Estimation

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-16 ◽  
Author(s):  
Kyriaki Daskalopoulou ◽  
Antonina Lisa Gagliano ◽  
Sergio Calabrese ◽  
Lorenza Li Vigni ◽  
Manfredi Longo ◽  
...  
Keyword(s):  
Isotope Composition ◽  
Total Output ◽  
Geothermal System ◽  
Geothermal Systems ◽  
Geochemical Parameters ◽  
Co2 Output ◽  
Before And After ◽  
Flux Measurements ◽  
Of Greece

Forty-five gas samples have been collected from natural gas manifestations at the island of Kos—the majority of which are found underwater along the southern coast of the island. On land, two anomalous degassing areas have been recognized. These areas are mainly characterized by the lack of vegetation and after long dry periods by the presence of sulfate salt efflorescence. Carbon dioxide is the prevailing gas species (ranging from 88 to 99%), while minor amounts of N2 (up to 7.5%) and CH4 (up to 2.1%) are also present. Significant contents of H2 (up to 0.2%) and H2S (up to 0.3%) are found in the on-land manifestations. Only one of the underwater manifestations is generally rich in N2 (up to 98.9%) with CH4 concentrations of up to 11.7% and occasionally extremely low CO2 amounts (down to 0.09%). Isotope composition of He ranges from 0.85 to 6.71 R/RA, indicating a sometimes-strong mantle contribution; the highest values measured are found in the two highly degassing areas of Paradise beach and Volcania. C-isotope composition of CO2 ranges from -20.1 to 0.64‰ vs. V-PDB, with the majority of the values being concentrated at around -1‰ and therefore proposing a mixed mantle—limestone origin. Isotope composition of CH4 ranges from -21.5 to +2.8‰ vs. V-PDB for C and from -143 to +36‰ vs. V-SMOW for H, pointing to a geothermal origin with sometimes-evident secondary oxidation processes. The dataset presented in this work consists of sites that were repeatedly sampled in the last few years, with some of which being also sampled just before and immediately after the magnitude 6.6 earthquake that occurred on the 20th of July 2017 about 15 km ENE of the island of Kos. Changes in the degassing areas along with significant variations in the geochemical parameters of the released gases were observed both before and after the seismic event; however, no coherent model explaining those changes was obtained. CO2 flux measurements showed values of up to about 104 g×m−2×d−1 in both the areas of Volcania and Kokkino Nero, 5×104 g×m−2×d−1 at Paradise beach, and 8×105 g×m−2×d−1 at Therma spring. CO2 output estimations gave values of 24.6, 16.8, 12.7, and 20.6 t×d−1, respectively, for the above four areas. The total output of the island is 74.7 t×d−1 and is comparable to those of the other active volcanic/geothermal systems of Greece (Nisyros, Nea Kameni, Milos, Methana, and Sousaki).

scholarly journals Channel Quantization Based on the Statistical Characterization of Spatially Correlated Fading

2015 ◽  
Vol 64 (9) ◽  
pp. 3931-3943 ◽  
Author(s):  
Fernando Domene ◽  
Gema Pinero ◽  
Maria de Diego ◽  
Alberto Gonzalez
Keyword(s):  
Statistical Characterization ◽  
Spatially Correlated ◽  
Channel Quantization ◽  
Correlated Fading

Characterization of a geothermal system in the Upper Arkansas Valley, CO

2009 ◽  
Author(s):  
Thomas Blum ◽  
Kasper van Wijk ◽  
Lee Liberty ◽  
Michael Batzle ◽  
Richard Krahenbuhl ◽  
...  
Keyword(s):  
Geothermal System

Three-Dimensional interpretation of broadband magnetotelluric data at Fogo Volcano, Azores Islands 

2021 ◽  
Author(s):  
Colin Hogg ◽  
Duygu Kiyan ◽  
Volker Rath ◽  
Andreas Junge ◽  
Philip Hering ◽  
...  
Keyword(s):  
Transfer Functions ◽  
Jacobian Matrix ◽  
Hydrothermal Systems ◽  
Geothermal System ◽  
Matrix Elements ◽  
Renewable Energy Resources ◽  
Magnetotelluric Data ◽  
Volcanic System ◽  
Northern Flank ◽  
Fogo Volcano

<p>The architecture of volcanic systems is essential to know as (1) it yields knowledge on evolution of the volcanic system, thus improving our capability to project future behaviour; (2) as it provides insights regarding geohazards (such as seismic activity, landslides, increased outgassing), crucial for mitigating risk to human population; (3) as it contributes to the assessment of potential for renewable energy resources. High electrical conductivity values are typically associated with volcanic-hydrothermal systems and the magnetotelluric (MT) method has proven to be successful in mapping such conductivity contrasts and constraining volcanic processses.</p><p>The Azores archipelago (Portugal) is formed by nine volcanic islands located in the North Atlantic Ocean where the American, Eurasian, and African plates meet at a triple junction. São Miguel Island is the largest of the archipelago and<span> hosts</span> three trachytic polygenetic volcanoes: Sete Cidades, Fogo (Água de Pau) and Furnas. Following our earlier MT studies at Furnas, 44 high-quality (to ~1000s) broadband MT sites were collected during 2018 across Fogo Volcano and the adjacent Congro region that is prone to seismic swarm activity.</p><p>Our MT studies comprised two avenues: generating geoelectrical models that provided new insights into this unique setting, and investigating and assessing new tools for the MT community.</p><p>(1) Fogo has a resistive core and we do not see a magma chamber beneath.</p><p>(2) Shallow conductive channels are observed beneath Congro and their presence have been tested and validated through forward modelling and additional sensitivity tests.</p><p>(3) The MT results can be used to map clay alteration, with the highly conductive zone on the northern flank of Fogo corresponding to the smectite zone. The alteration temperature distribution is consistent with the formation temperature recorded within the area.</p><p>(4) A potential new geothermal resource has been identified. An area north of Ribeira Cha, on the southern flank of Fogo has very similar characteristics of the Ribeira Grande geothermal system that is located on the northern flank. This area may be key in increasing the energy self-sufficiency of the island. <br><br>Depth slices through the final 3-D MT inversion volume will be presented.</p><p>The new MT processing code of University of Frankfurt was compared against two long-standing codes commonly used in the MT community and it proved to yield superior responses for every site and examples will be presented. See presentation in this session “FFproc - an improved multivariate robust statistical data processing code for the estimation of MT transfer functions” (Castro et al).</p><p>A novel approach exploiting the Jacobian matrix elements for the 3-D MT inversion strategy will be presented. The Jacobian matrix elements map the relationship between the model and model responses, thus portions of the model with low sensitivities infer that the sensitivity structure is algorithmically influenced more strongly by the regularisation term than by the data-fitting term. Our results will show that the computation of the Jacobian matrix (albeit computationally expensive) is a powerful tool in aiding interpretation.</p>

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