Structural pattern and CO2–CH4 degassing of Ustica Island, Southern Tyrrhenian basin

Etiope, Giuseppe; Beneduce, Paolo; Calcara, M.; Favali, P.; Frugoni, F.; Schiattarella, Marcello; Smriglio, G.

doi:10.1016/s0377-0273(99)00010-4

Cited by 48 publications

(30 citation statements)

References 36 publications

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“…Etiope et al (1999) find that a general linear relationship exists between concentration and flux. For practical reasons we chose to measure CO 2 concentrations.…”

Section: Data Acquisition and Processingmentioning

confidence: 83%

“…CO 2 anomalies have their origin in the exsolution from magma at depths of several kilometres (Papale 1999). Structural surveys using CO 2 or He, in flux or concentration, in soil gases have succeeded in finding anomalies in zones often corresponding to faults (Aubert and Baubron 1988;D'Alessandro et al 1992; Barberi and Carapezza 1994;Giammanco et al 1997Giammanco et al , 1998Allard et al 1998;Azzaro et al 1998;Etiope et al 1999). T anomalies rely on conductive and convective heat transfers.…”

Section: Introductionmentioning

confidence: 99%

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The summit hydrothermal system of Stromboli. New insights from self-potential, temperature, CO 2 and fumarolic fluid measurements, with structural and monitoring implications

Finizola

Sortino²,

Lénat³

et al. 2003

Bulletin of Volcanology

130

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Accurate and precisely located self-potential (SP), temperature (T) and CO 2 measurements were carried out in the summit area of Stromboli along 72 straight profiles. SP data were acquired every metre and T data every 2.5 m. CO 2 concentrations were acquired with the same density as T, but only along seven profiles. The high density of data and the diversity of the measured parameters allows us to study structures and phenomena at a scale rarely investigated. The shallow summit hydrothermal activity (Pizzo-Fossa area) is indicated by large positive SP, T and CO 2 anomalies. These anomalies are focused on crater faults, suggesting that the fracture zones are more permeable than surrounding rocks at Stromboli. The analysis of the distribution of these linear anomalies, coupled with the examination of the geologic, photographic and topographic data, has led us to propose a new structural interpretation of the summit of Stromboli. This newly defined structural framework comprises (1) a large Pizzo circular crater, about 350 m in diameter;(2) a complex of two concealed craters nested within the Pizzo crater (the Large and the Small Fossa craters), thought to have formed during the eruption of the Pizzo pyroclastites unit; the Small Fossa crater is filled with highly impermeable material that totally impedes the upward flow of hydrothermal fluids; and (3) The present complex of active craters. On the floor of the Fossa, short wavelength SP lows are organized in drainage-like networks diverging from the main thermal anomalies and converging toward the topographic low in the Fossa area, inside the Small Fossa crater. They are interpreted as the subsurface downhill flow of water condensed above the thermal anomalies. We suspect that water accumulates below the Small Fossa crater as a perched water body, representing a high threat of strong phreatic and phreatomagmatic paroxysms. T and CO 2 anomalies are highly correlated. The two types of anomalies have very similar shapes, but the sensitivity of CO 2 measurements seems higher for lowest hydrothermal flux. Above T anomalies, a pronounced high frequency SP signal is observed. Isotopic analyses of the fluids show similar compositions between the gases rising through the faults of the Pizzo and Large Fossa craters. This suggests a common origin for gases emerging along different structural paths within the summit of Stromboli. A site was found along the Large Fossa crater fault where high gas flux and low air contamination made gas monitoring possible near the active vents using the alkaline bottle sampling technique.

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“…Etiope et al (1999) find that a general linear relationship exists between concentration and flux. For practical reasons we chose to measure CO 2 concentrations.…”

Section: Data Acquisition and Processingmentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

The summit hydrothermal system of Stromboli. New insights from self-potential, temperature, CO 2 and fumarolic fluid measurements, with structural and monitoring implications

Finizola

Sortino²,

Lénat³

et al. 2003

Bulletin of Volcanology

130

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show abstract

“…The island, elongated in a NE-SW direction 4 km long and 2.5 km wide (Romano and Sturiale 1971;de Vita et al 1998), is made up of lava flows and pyroclastic products lying over a submarine basal formation formed by pillow lavas and pillow breccias (Cinque et al 1988;Etiope et al 1999). The subaerial activity, which took place from 0.735 to 0.132 Ma (Barberi and Innocenti 1980;de Vita et al 1995), was concentrated along fractures producing small eruptive centers with preferential E-W and NE-SW alignments (Beneduce and Schiattarella 1991).…”

Section: Geological Settingmentioning

confidence: 99%

“…Notwithstanding that the volcanic activity of Ustica is partially coeval (Barberi and Innocenti 1980;Gillot 1987;Cinque et al 1988;de Vita et al 1995) with the nearby (20 km eastwards) calc-alkaline volcanism of the Aeolian Islands, the volcanoes of Ustica show Na-alkaline affinity (Etiope et al 1999;Schiano et al 2004). These products are typical of intraplate magmatism (anorogenic), which is unusual in an area characterized by orogenic volcanism (Peccerillo 2003) and range in composition from alkali basalt to trachyte, showing petrographical and chemical similarities with comparable rocks from Mount Etna (Schiano et al 2004), about 300 km to the southeast.…”

Section: Geological Settingmentioning

confidence: 99%

“…In this part of the Tyrrhenian Sea, the island of Ustica is the only site that shows subaerial evidences of tectonics related to the opening of the Tyrrhenian basin (de Vita et al 1995). Moreover, regarding volcanic activity, the island is characterized by intraplate magmatism (Etiope et al 1999), generally associated with extensional tectonics (Schiano et al 2004), which is rather peculiar in an area where predominantly orogenic magmatism (Aeolian arc) is found (Peccerillo 2003). Because of these characteristics, the island of Ustica plays a key role in the southern Tyrrhenian basin, and the knowledge of its tectonic features could provide a useful contribution to better clarify the geodynamics of the entire region.…”

Section: Introductionmentioning

confidence: 99%

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Internal structure of Ustica volcanic complex (Italy) based on a 3D inversion of magnetic data

2007

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A ground magnetic study of Ustica Island was performed to provide new insights into subsurface tectonic and volcanic structures. The total-intensity anomaly field, obtained after a data-reduction procedure, shows the presence of a W-E-striking magnetic anomaly in the middle of the island and another two intense anomalies, which seem to continue offshore, in the southwestern and the northeastern sides, respectively. The detected anomalies were analyzed by a quadratic programming (QP) algorithm to obtain a 3D subsurface magnetization distribution. The volcano magnetization model reveals the presence of intensely magnetized volumes, interpreted as the feeding systems of the main eruptive centers of the island, which roughly follow the trend of the main regional structural lineaments. These findings highlight how regional tectonics has strongly affected the structural and magmatic evolution of the Ustica volcanic complex producing preferential ways for magma ascent.

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The Syabru‐Bensi hydrothermal system in central Nepal: 1. Characterization of carbon dioxide and radon fluxes

et al. 2014

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The Syabru-Bensi hydrothermal system (SBHS), located at the Main Central Thrust zone in central Nepal, is characterized by hot (30-62°C) water springs and cold (<35°C) carbon dioxide (CO 2 ) degassing areas. From 2007 to 2011, five gas zones (GZ1-GZ5) were studied, with more than 1600 CO 2 and 850 radon flux measurements, with complementary self-potential data, thermal infrared imaging, and effective radium concentration of soils. Measurement uncertainties were evaluated in the field. CO 2 and radon fluxes vary over 5 to 6 orders of magnitude, reaching exceptional maximum values of 236 ± 50 kg m À2 d À1 and 38.5 ± 8.0 Bq m À2 s À1 , with estimated integrated discharges over all gas zones of 5.9 ± 1.6 t d À1 and 140 ± 30 MBq d À1 , respectively. Soil-gas radon concentration is 40 × 10 3 Bq m À3 in GZ1-GZ2 and 70 × 10 3 Bq m À3 in GZ3-GZ4. Strong relationships between CO 2 and radon fluxes in all gas zones (correlation coefficient R = 0.86 ± 0.02) indicate related gas transport mechanisms and demonstrate that radon can be considered as a relevant proxy for CO 2 . CO 2 carbon isotopic ratios (δ 13 C from À1.7 ± 0.1 to À0.5 ± 0.1‰), with the absence of mantle signature (helium isotopic ratios R/R A < 0.05), suggest metamorphic decarbonation at depth. Thus, the SBHS emerges as a unique geosystem with significant deep origin CO 2 discharge located in a seismically active region, where we can test methodological issues and our understanding of transport properties and fluid circulations in the subsurface.

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Structural pattern and CO2–CH4 degassing of Ustica Island, Southern Tyrrhenian basin

Cited by 48 publications

References 36 publications

The summit hydrothermal system of Stromboli. New insights from self-potential, temperature, CO 2 and fumarolic fluid measurements, with structural and monitoring implications

The summit hydrothermal system of Stromboli. New insights from self-potential, temperature, CO 2 and fumarolic fluid measurements, with structural and monitoring implications

Internal structure of Ustica volcanic complex (Italy) based on a 3D inversion of magnetic data

The Syabru‐Bensi hydrothermal system in central Nepal: 1. Characterization of carbon dioxide and radon fluxes

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