Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione Palermo, Palermo, Italia

Studying spatial and temporal trends in volcanic gas compositions and fluxes is crucial both to volcano monitoring and to constrain the origin and recycling efficiency of volatiles at active convergent margins. New volcanic gas compositions and volatile fluxes are here reported for Nevado del Ruiz, Galeras, and Purace, three of the most persistently degassing volcanoes located in the Colombian Arc Segment of the Northern Volcanic Zone. At Nevado del Ruiz, from 2014 to 2017, plume emissions showed an average molar CO2/ST ratio of 3.9 ± 1.6 (ST is total sulfur, S). Contemporary, fumarolic chemistry at Galeras progressively shifted toward low‐temperature, S‐depleted fumarolic gas discharges with an average CO2/ST ratio in excess of 10 (6.0–46.0, 2014–2017). This shift in volcanic gas compositions was accompanied by a concurrent decrease in SO2 emissions, confirmed on 21 March 2017 by high‐resolution ultraviolet camera‐based SO2 fluxes of ~2.5 kg/s (~213 t/day). For comparison, SO2 emissions remained high at Nevado del Ruiz (weighted average of 8 kg/s) between 2014 and 2017, while Puracé maintained rather low emission levels (<1 kg/s of SO2, CO2/SO2 ≈ 14). We here estimate carbon dioxide fluxes for Nevado del Ruiz, Galeras, and Puracé of ~23, 30, and 1 kg/s, respectively. These, combined with recent CO2 flux estimates for Nevado del Huila of ~10 kg/s (~860 t/day), imply that this arc segment contributes about 50% to the total subaerial CO2 budget of the Andean Volcanic Belt. Furthermore, our work highlights the northward increase in carbon‐rich sediment input into the mantle wedge via slab fluids and melts that is reflected in magmatic CO2/ST values far higher than those reported for Southern Volcanic Zone and Central Volcanic Zone volcanoes. We estimate that about 20% (~1.3 Mt C/year) of the C being subducted (~6.19 Mt C/year) gets resurfaced through subaerial volcanic gas emissions in Colombia (Nevado del Ruiz ~0.7 Mt C/year). As global volcanic volatile fluxes continue to be quantified and refined, the contribution from this arc segment should not be underestimated.

the characterization of triggering dynamics and remobilized volumes is crucial to the assessment of associated lahar hazards. We propose an innovative treatment of the cascading effect between tephra fallout and lahar hazards based on probabilistic modelling that also accounts for a detailed description of source sediments. As an example, we have estimated the volumes of tephra fallout deposit that could be remobilized by rainfall-triggered lahars in association with two eruptive scenarios that have characterized the activity of the La Fossa cone (Vulcano, Italy) in the last 1000 years: a long-lasting Vulcanian cycle and a subplinian eruption. The spatial distribution and volume of deposits that could potentially trigger lahars were analysed based on a combination of tephra fallout probabilistic modelling (with TEPHRA2), slope-stability modelling (with TRIGRS), field observations, and geotechnical tests. Model input data were obtained from both geotechnical tests and field measurements (e.g. hydraulic conductivity, friction angle, cohesion, total unit weight of the soil, and saturated and residual water content). TRIGRS simulations show how shallow landsliding is an effective process for eroding pyroclastic deposits on Vulcano. Nonetheless, the remobilized volumes and the deposit thickness threshold for lahar initiation strongly depend on slope angle, rainfall intensity, grain size, friction angle, hydraulic conductivity, and the cohesion of the source deposit.

The understanding of the relationship between the geochemistry of fluids circulating during travertine deposition and the presence of active faults is crucial for evaluating the seismogenetic potential of an area. Here we investigate travertines from Pamukkale and Reşadiye (Turkey), sited in seismic regions and next to thermal springs. These travertines formed ~24,500–50,000 (Pamukkale) and ~240–14,600 years (Reşadiye) BP. We characterize fluid inclusions (FIs) and studied concentration of H2O, CO2, O2 + N2, and 3He, 4He, 20Ne, and 40Ar, and bulk composition (trace elements and δ13C‐δ18O). FIs from both localities are mainly primary with low salinity and homogenization temperature around 136–140 °C. H2O is the major component followed by CO2, with the highest gas content measured in Pamukkale travertines. Concentrations of Ne‐Ar together with O2 + N2 indicate that travertines from both areas precipitated from atmosphere‐derived fluids. The 3He/4He is 0.5–1.3 Ra in Pamukkale and 0.9–4.4 Ra in Reşadiye. Samples with R/Ra > 1 are modified by cosmogenic 3He addition during exposure to cosmic rays. Excluding these data, FIs of Reşadiye are mostly atmosphere‐derived. This implies a shallow formation where the circulation was dominated by meteoric waters, which is consistent with their young age. Instead, FIs of Pamukkale show mixing of mantle‐, crustal‐, and atmosphere‐derived He, indicating that these travertines formed in lithospheric fractures. Based on the δ13CCO2 and δ18O of bulk rocks, we infer that travertines formed involving crustal‐ (mechanochemical rather than organic) and mantle‐derived CO2. Trace elements of Pamukkale and Reşadiye show comparable rare earth element patterns. We conclude that travertines formed in response of seismogenetic activity.

The report contains the following tables: - Table R1. Results of soil CO2 concentration and of soil CO2 flux measurements carried out in July-September 2011 at Lavinio. - Table R2. Results of soil CO2 and H2S flux measurements carried out on 6 September 2011 at Lavinio Country Club with 10-13m spacing. - Table R3. Results of soil CO2 and H2S flux measurements carried out on 8 September 2011 at Lavinio Country Club with 1m spacing. - Table R4. Average concentration (every 10’ from 12 to 19 September 2011) of CO2, O2 and H2S indoor the balance tank of Lavinio Country Club where a lethal accident occurred on 5 September 2011. - Table R5. Average values (every 30’ from 12 to 19 September 2011) of atmospheric pressure near Lavinio Country Club.

The geothermal field of Torre Alfina is located in central Italy at the northern edge of the Vulsini Volcanic District, the northernmost area of the so-called Quaternary Roman Co-Magmatic Province. In the framework of a medium-enthalpy geothermal exploitation project, INGV installed a local seismic network close to the future geothermal production site for monitoring natural local seismicity. In this paper, we show the results of a study of the microseismicity recorded from June 2014 to May 2016 in a small area of about 10 km2 around Torre Alfina. Analyzing seismic signals recorded by a local temporary network of ten short-period stations and by four permanent stations of the INGV national seismic network, we detected 846 local earthquakes. Then, we accurately relocated 799 events using HypoDD code. Our results show that the region of Torre Alfina is characterized by intense microseismicity, with hypocentral depths between 3 and 7 km and with moderate magnitudes between Md = 0.1 and ML = 2.8. Moreover, more than half of the earthquakes are grouped into six main swarm-like clusters each lasting few days. Furthermore, we computed 36 well-constrained fault plane solutions, which show a clear transtensional deformation regime in the whole study area. Three main tectonic directions have been evidenced from the focal mechanisms analysis: E-W, WSW-ENE, and NW-SE. The understanding of the seismogenic structural setting of the Torre Alfina geothermal field, and the study of its background natural seismicity can be of great importance in recognizing any possible future seismicity induced by the exploitation of the field.

The noble gas isotope composition of the mantle can provide unique insights into the origin and evolution of volatile elements on Earth. Xenon isotopes combine primordial signatures with contributions from extinct and extant radionuclides, therefore offering the potential to set constraints on both the nature of Earth’s planetary precursor(s) and the timing of their contributions. However, measuring the Xe isotope composition of mantle-derived samples to sufficiently high-precision has proven difficult due to (i) large occurrence of a modern-like atmospheric component in the mantle, and (ii) contribution from shallow and post-eruptive atmospheric contamination. Mantle-derived samples therefore exhibit only small deviations from the modern atmospheric composition, making the identification and deconvolution of mantle-derived Xe signals challenging. Here, we use the Giggenbach sampling method to concentrate magmatic noble gases from the Eifel volcanic area (Germany) into glass bottles in order to conduct high-precision analyses of Ne, Ar and Xe isotopes. The three samples collected from Victoriaquelle and Schwefelquelle wells (South East Eifel) show variable contributions from atmospheric contamination, with the least contaminated sample reaching 40Ar/36Ar ∼8,300. Our data indicate that the mantle beneath the Eifel volcanic area, and by extension the Central European Volcanic Province, resembles the convective upper mantle reservoir with limited evidence for an OIB-like deep plume source contribution. It has a geochemical signature that is similar (e.g. in Ne isotopic composition, 40Ar/36Ar, 129Xe/130Xe and 129Xe/136Xe) to the mantle source of the so-called popping rocks (thought to best represent the upper mantle), with an additional source of 238U-derived Xe and low 3He/4He that we attribute to the influence of an ancient subducted component (HIMU). A dichotomy exists between the main sources of fissiogenic xenon isotopes measured in popping rocks and Eifel gas, which appear to be mainly derived from 244Pu and 238U, respectively. According to their respective ratios of 244Pu-to 238U-derived Xe, the mantle sources for Eifel volcanism and popping rocks would have experienced extensive and limited degassing, respectively. In this regard, high Pu–Xe/(Pu+U)–Xe may no longer be considered as being indicative of a mantle deep origin, therefore calling for the geochemical differences between plume and MORB sources to be redefined, with the possibility that volatile signatures within the solid Earth may be more heterogeneously distributed than previously thought.

In recent decades, the percentage increase in water use on a the global scale has exceeded twice that of population growth. This has led to more, and larger, regions in the world being subject to water stress where the current restricted rates of water use and consumption, let alone the desired rates, are unsustainable [1, 2]. In the Mediterranean area, water availability is a main economic and social target for most countries since most of them share several features including, for instance, similar water and land resources, agricultural development, demographic pressure coupled with tourism increase and, last but not least, a climate change evolving toward semiarid to arid conditions [3–5]. This precious resource, widely exploited, is not distributed, at a regional level and within each country, in a homogeneous fashion. The increase in groundwater exploitation poses a severe risk for the availability of water resources, and the resulting resource scarcity is a major concern in most countries of the Mediterranean region. Groundwater paucity often occurs in combination with poor groundwater quality, not only in areas heavily conditioned by human activities [6] or in the often highly saline coastal aquifers [7–9] but also in zones characterized by geogenic contamination sources. In such areas, although human pressure is absent, water-rock interaction processes, as those promoting, for instance, geogenic Cr(VI) water contamination [10], may cause pollution with critical effects on the public health

The Tertiary back‐arc sedimentary basin in East Java (Indonesia) hosts a large variety of piercement structures and hydrocarbon fields. Some of the latter (Wunut, Tanggulangin, Carat, Watudakon) are located a few kilometers away from the Arjuno‐Welirang volcanic complex and neighboring Lusi, the largest active sediment‐hosted hydrothermal system on Earth. In order to investigate interactions between volcanic and sedimentary settings, we performed gas sampling on these four shallow (200‐ to 1,000‐m depth) petroleum fields. The fields around Lusi are dominated by thermogenic gas that was altered during biodegradation processes. The helium isotope ratios 3He/4He) are as high as 6.7 RA, which is remarkably similar to those measured at the fumaroles of the adjacent volcanic complex (R = 7.3 RA) and at the Lusi site (up to 6.5 RA). This highlights the pervasive outgassing of mantle‐derived fluids in the sedimentary basin. Despite these two systems sharing the same mantle‐derived helium source, their hydrocarbons have two different genetic histories: Lusi hydrocarbon gas has been more recently generated and is less molecularly and isotopically fractionated, while the gas trapped in the reservoirs is older and more altered. Unlike Lusi, the hydrocarbon fields contain small amounts of CO2 resulting from biodegradation processes. The Watukosek fault system, originating from the Arjuno‐Welirang volcanic complex and extending toward the northeast of Java, intersects Lusi and the hydrocarbon fields. This network of faults controls the migration of mantle‐derived fluids within the sedimentary basin, feeding the focused venting at the Lusi site and promoting the slower and pervasive migration in the reservoirs.

After a period of mild eruptive activity, Stromboli showed between 2017 and 2018 a reawakening phase, with an increase in the eruptive activity starting in May 2017. The alert level of the volcano was raised from “green” (base) to “yellow” (attention) on 7 December 2017, and a small lava overflowed the crater rim on 15 December 2017. Between July 2017 and August 2018 the monitoring networks recorded nine major explosions, which are a serious hazard for Stromboli because they affect the summit area, crowded by tourists. We studied the 2017–2018 eruptive phase through the analysis of multidisciplinary data comprising thermal video-camera images, seismic, geodetic and geochemical data. We focused on the major explosion mechanism analyzing the well-recorded 1 December 2017 major explosion as a case study. We found that the 2017–2018 eruptive phase is consistent with a greater gas-rich magma supply in the shallow system. Furthermore, through the analysis of the case study major explosion, we identified precursory phases in the strainmeter and seismic data occurring 77 and 38 s before the explosive jet reached the eruptive vent, respectively. On the basis of these short-term precursors, we propose an automatic timely alarm system for major explosions at Stromboli volcano.

In this study we applied petrochemical methods (SEM-EDS; FT-IR) in order to characterize a group of obsidian flakes collected at Ustica island (Sicily). Despite the absence of obsidian geological outcrops, a lot of obsidian fragments still emerging from the lands of Ustica testify that the island was a major import center of obsidian during the prehistory. On this island, there are some prehistoric settlements, dated from the Neolithic to the Middle Bronze Age (6000- 1200 BC), in which the use of obsidian continued until the beginning of metals age. Our study includes: i) Macroscopic and microscopic optical observations, which allowed selecting 18 obsidian flakes (starting from 50 obsidian flakes) on the base of their morphological characteristics. ii) Density measurements (hydrostatic balance). iii) Scanning electron microscope determination (SEM-EDS) of major elements of the obsidian glasses and minerals. Results of our analyses were compared with 12 geological samples collected in obsidian sources from Monte Arci (Sardinia), Palmarola, Lipari and Pantelleria, i.e. the four most exploited obsidian sources of the ancient world in the Western-Central Mediterranean. This study confirms the presence of the Lipari and Pantelleria sources (Sicily) in our obsidian set. iv) We also determined (by FT-IR) the hydration degree of some obsidian flakes in order to detect a possible hydration gradient between the rim and the core of the flake sample. The width of the hydration rim, if any, can be used for an approximate evaluation of the age of the tool.