scholarly journals Chemical and isotopic composition of fumarolic gases at Iwate volcano, Japan, during and after seismic activity in 1998: implications for the modification of ascending volcanic gases

2011 ◽  
Vol 54 (2) ◽  
Author(s):  
Takeshi Ohba ◽  
Kenji Nogami ◽  
Jun-ichi Hirabayashi ◽  
Takeshi Sawa ◽  
Kohei Kazahaya ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Seismic Activity ◽  
Volcanic Gases ◽  
Fumarolic Gases

Hydrogeochemical temporal variations related to changes of seismic activity at Tenerife, Canary Islands

2021 ◽  
Author(s):  
Cecilia Amonte ◽  
María Asensio-Ramos ◽  
Gladys V. Melián ◽  
Nemesio M. Pérez ◽  
Eleazar Padrón ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Seismic Activity ◽  
Temporal Variations ◽  
Total Alkalinity ◽  
Molar Ratio ◽  
Sampling Point ◽  
Volcanic System ◽  
Mean Values ◽  
Isotopic Analyses ◽  
San Fernando

<p>The oceanic active volcanic island of Tenerife (2034 km<sup>2</sup>) is the largest of the Canarian archipelago. There are more than 1,000 galleries (horizontal drillings) in the island, which are used for groundwater exploitation and allow reaching the aquifer at different depths and elevations. During a two-year period (July 2016 to July 2018), a hydrogeochemical study was carried out in two galleries on Tenerife (Fuente del Valle and San Fernando) for volcanic monitoring purposes with weekly sampling. Physicochemical parameter of water, such us temperature (ºC), pH and electrical conductivity (E.C., µS·cm<sup>-1</sup>), were measured in-situ at each sampling point and chemical/isotopic composition of the water determined later in the laboratory.</p><p>Temperature values showed mean values of 28.1 ºC and 19.0 ºC for Fuente del Valle and San Fernando galleries, respectively. According to the average pH values, which were 6.30 for Fuente del Valle and 7.13 for San Fernando, and based on the chemical composition, both galleries are sodium-bicarbonate (Na-HCO<sub>3</sub>) type. E.C. values in both galleries presented high ranges, with mean values of 975 and 1648 µS·cm<sup>-1</sup> for Fuente del Valle and San Fernando, respectively. The total alkalinity mean value of groundwater from Fuente del Valle gallery was 11.3 mEq·L<sup>-1</sup> HCO<sub>3</sub><sup>-</sup>, while that from San Fernando was 17.3 mEq·L<sup>-1</sup> HCO<sub>3</sub><sup>-</sup>. The SO<sub>4</sub><sup>2-</sup>/Cl molar ratio was 0.59 and 3.4 for the samples from Fuente del Valle and San Fernando galleries, respectively.</p><p>The δ<sup>18</sup>O and δD isotopic analyses showed a meteoric origin of groundwaters, with mean values of -6.2‰ and -26‰ vs. VSMOW for Fuente del Valle and -6.2‰ and -21 ‰ vs. VSMOW for San Fernando. The isotopic data showed a strong interaction with endogenous gases such as CO<sub>2</sub>, H<sub>2</sub>S, H<sub>2</sub>, etc. Regarding the isotopic composition of total dissolved carbon species, expressed as δ<sup>13</sup>C<sub>TDIC</sub>, average values of -0.17‰ and 0.26‰ were obtained for Fuente del Valle and San Fernando galleries, respectively. These results show an endogenous origin CO<sub>2</sub> signature, heavier for Fuente del Valle gallery groundwater compared to that of San Fernando.</p><p>Groundwater physicochemical parameters exhibited stable values throughout the study period, while significant temporal variations were observed in the total alkalinity, SO<sub>4</sub><sup>2-</sup>/Cl<sup>-</sup> molar ratio, δ<sup>18</sup>O and δD. Changes in isotopic ratios coincided with variations observed in the alkalinity and the SO<sub>4</sub><sup>2-</sup>/Cl<sup>-</sup> molar ratio. On October 2, 2016, a seismic swarm of long-period events was recorded on Tenerife followed by a general increase of the seismic activity in and around the island. A correlation was observed between some hydrogeochemical parameters in the groundwaters of the galleries, related to observed changes of the seismic activity. This study demonstrates the suitability of monitoring the chemical and isotopic composition of groundwater from Fuente del Valle and San Fernando galleries, as they are sensitive to changes in volcanic activity on Tenerife island. The study of groundwaters associated to a volcanic system can provide information about the magmatic gas input in the aquifer, modelling how the groundwaters flow through the edifice, and offer important geochemical information that could herald a future eruption.</p>

Soil carbon dioxide efflux weekly monitoring network for the volcanic surveillance of Tenerife, Canary Islands

2020 ◽  
Author(s):  
Violeta T. Albertos ◽  
Conor M. Graham ◽  
Leopoldo Cabassa ◽  
Teresa Borges da Cruz ◽  
Gladys V. Melián ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Isotopic Composition ◽  
Rift Zone ◽  
Monitoring Network ◽  
Volcanic Gases ◽  
Average Value ◽  
Volcanic Surveillance ◽  
Head Space ◽  
Closed Chambers ◽  
Ne Rift

<p>Carbon dioxide (CO<sub>2</sub>) is one of the first gases to escape from the magmatic environment due to its low solubility in basaltic magmas at low pressures. Monitoring of volcanic gases in Tenerife Island (2,304 km<sup>2</sup>) has been focused mainly on diffuse CO<sub>2</sub> degassing and other volatiles due to the absence of visible gas manifestations except fumaroles at the summit of Teide volcano. An inexpensive method to determine CO<sub>2</sub> fluxes based in the absorption of CO<sub>2</sub> through an alkaline medium followed by titration analysis has been used with the aim of contributing to the volcanic surveillance of Tenerife. During summer 2016, a network of 31 closed alkaline traps was deployed along the three volcanic rifts of Tenerife (NE, NW and NS) and at Cañadas Caldera. To do so, an aliquot of 50 mL of 0.1N KOH solution is placed inside the chamber at each station to absorb the CO<sub>2</sub> released from the soil. The solution is replaced in a weekly basis and the trapped CO<sub>2</sub> is later analyzed at the laboratory by titration. Values are expressed as weekly integrated CO<sub>2 </sub>efflux. We present herein the results of one year CO<sub>2 </sub>efflux estimated by closed alkaline traps. The CO<sub>2</sub> efflux values ranged from 1.0 to 14.5 g·m<sup>-2</sup>·d<sup>-1</sup>, with average values of 8.5 g·m<sup>-2</sup>·d<sup>-1</sup> for the NE rift-zone, 5.2 g·m<sup>-2</sup>·d<sup>-1 </sup>for Cañadas Caldera, 6.4 g·m<sup>-2</sup>·d<sup>-1</sup> for NW rift-zone and 6.1 g·m<sup>-2</sup>·d<sup>-1</sup> for NS rift-zone. The estimated CO<sub>2 </sub>efflux values were of the same order than the observed ones in 2016. Relatively high CO<sub>2</sub> efflux values were observed at the NE rift-zone, where maximum values were measured. The temporal evolution of CO<sub>2 </sub>efflux estimated by closed alkaline traps did not show significant variations during 2019. However, small seasonal variations are observed during the period 2016 – 2019. To investigate the origin of the soil CO<sub>2</sub>, soil gas samples were weekly sampled on the head space of the closed chambers. Chemical and isotopic composition of C in the CO<sub>2</sub> were analysed in the gas samples. The concentration of CO<sub>2</sub> on the head space of the closed chambers showed a range of 355-50,464 ppm, with an average value of 1,850 ppmV, while the isotopic composition expressed as d<sup>13</sup>C-CO<sub>2</sub> showed a range from -5.03 to -30.44 ‰, with an average value of -15.9 ‰. The heaviest values of d<sup>13</sup>C-CO<sub>2</sub> are in the NW rift-zone. The systematics of closed static chambers alkaline traps can be a simple and economical tool with volcanic surveillance purposes in system where visible volcanic gases manifestations are absence.</p>

The chemical and isotopic composition of fumarolic gases and spring discharges from Galeras Volcano, Colombia

1997 ◽  
Vol 77 (1-4) ◽  
pp. 229-253 ◽  
Author(s):  
Tobias P. Fischer ◽  
Neil C. Sturchio ◽  
John Stix ◽  
Greg B. Arehart ◽  
Dale Counce ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Fumarolic Gases

scholarly journals GEOCHEMICAL CHARACTERIZATION OF NATURAL GAS MANIFESTATIONS IN GREECE

2017 ◽  
Vol 43 (5) ◽  
pp. 2327 ◽  
Author(s):  
W. D’Alessandro ◽  
L. Brusca ◽  
M. Martelli ◽  
A. Rizzo ◽  
K. Kyriakopoulos
Keyword(s):  
Isotopic Composition ◽  
Isotope Composition ◽  
Tectonic Activity ◽  
Helium Isotope ◽  
Air Contamination ◽  
Fumarolic Gases ◽  
Crustal Contribution ◽  
Total Composition ◽  
Definition Of

The Greek region is characterized by intense geodynamic activity with widespread volcanic, geothermal and seismic activity. Its complex geology is reflected in the large variety of chemical and isotopic composition of its gas manifestations. Basing on their chemical composition the gases can be subdivided in three groups, respectively CO2, CH4 or N2-dominated. On oxygen-free basis these three gases make up more than 97% of the total composition. The only exceptions are fumarolic gases of Nisyros that contain substantial amounts of H2S (up to more than 20%) and one sample of Milos that contains 15% of H2. CO2-dominated gases with clear mantle contribution in their He isotopic composition (R/Ra corrected for air contamination ranging from 0.5 to 5.7) are found along the subduction-related south Aegean active volcanic arc and on the Greek mainland close to recent (upper Miocene to Pleistocene) volcanic centers. These areas are generally characterized by active or recent extensive tectonic activity and high geothermal gradients. On the contrary, gases sampled in the more external nappes of the Hellenide orogen have generally a CH4- or N2-rich compositions and helium isotope composition with a dominant crustal contribution (R/Ra corr < 0.2). The chemical and isotopic characteristics of the emitted gas display therefore a clear relationshipwith the different geodynamic sectors of the region. Gas geochemistry of the area contributes to a better definition of the crust-mantle setting of the Hellenic region.

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