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This paper presents new chemical and isotopic data on gases from deep oil and gas fields, bubbling gases, dissolved gases in groundwaters and dry seeps of the Southern Po River Basin (Emilia-Romagna, Italy), aiming to (i) characterize and differentiate the various types of deep natural gases; (ii) identify the source(s) of methane and light hydrocarbons in shallow aquifers and surface gas-rich emissions; (iii) propose a conceptual model of natural fluid migration pathways in the sedimentary prism of the Southern Po River Basin. Based on the isotopic composition of CH4 and C2–C4 n-alkanes, CH4/(C2H6+C3H8) ratio, relative proportion of the C7 hydrocarbons and relative concentration of cyclic compounds with respect to the total cyclic abundance, three main deep reservoirs of hydrocarbons are identified in the subsurface of the Southern Po River Basin: (1) microbial gas hosted in Pliocene-Pleistocene marine sediments, (2) thermogenic gas hosted in Miocene deposits and (3) thermogenic gas produced in Triassic carbonates. Helium isotopes of these deep fluids indicate an almost pure crustal origin (Rc/Ra values = 0.014–0.04), with negligible contributions from mantle-derived helium. A variable contribution of atmosphere-derived fluids is highlighted by low 4He/20Ne (down to 5.42) and 40Ar/36Ar (≤319.5) values. Comparison of chemical and isotopic signatures of deep and surficial hydrocarbon occurrences suggests that methane in shallow groundwaters or gas seeps is sourced by microbial gas migrating upward from deep Plio-Pleistocene reservoirs, with no detectable contributions of Triassic or Miocene thermogenic hydrocarbons. At shallow depths (roughly around 20–50 m.b.g.l.), Plio-Pleistocene microbial methane appears to be mainly stored in anoxic aquifers. However, where CH4 further migrates upwards and reaches aerobic environments (e.g., aquifers or soils), it readily undergoes a process of exothermic microbial oxidation mediated by methanotrophic bacteria. Where the structu

Panarea seafloor hydrothermal system is associated with a range of mafic to felsic volcanic rocks. The hydrothermal system is active at present and discharges magmatic-hydrothermal fluids and precipitates massive sulfides. The sulfides exhibit multi-stage deposition, evident in the alternation of several mineral generations that follow a general temporal precipitation sequence: marcasite → alunite → opal. Sr-Nd-Pb isotope data indicate that most of the metals in the sulfides are derived predominantly from the Panarea volcanic rocks with some contribution from ambient seawater and/or local sediments. A remarkable feature of these sulfides is their chondrite-normalized rare earth element (REEN) distribution pattern with a pronounced negative Eu anomaly, which has not been observed previously. Our study demonstrates that this REEN pattern reflects the REE fractionation during sulfide deposition. The ionic radius mismatch between Eu2+ (the main form of Eu in reduced, high-temperature hydrothermal fluids) and the only possible site for REE substitution in the marcasite, that of Fe2+, suggests a crystallographic control on the REEN pattern. Apparently, marcasite precipitation can generate a sulfide deposit with a negative Eu anomaly due to discrimination against Eu2+ relative to REE3+ in the Fe2+ crystallographic site.

This preliminary report provides a detailed description of several stratigraphie sequenees of the Early Miocene Bükkalja Ignimbrite Field, summarizing the main volcanosedimentological eharacters. Many volcanological features suggest that most of the deposits can be classified as high volume pyroclastie flows (ignimbrite). Two major ignimbritie units have been distinguished, which may belong to two different stages of the vo1canism and form a SW-NE orientated belt. The first (lower) unit is eharaeterized predominantly by non-welded ignimbrites, whereas the second (upper) unit, usually found south of the first unit, shows variable degrees of welding. Hydrovolcanic deposits also occur in different stratigraphie horizons. The final phases of volcanism could have been contemporancous with lacustrine sedimentation.

This preliminary report provides a detailed description of several stratigraphie sequenees of the Early Miocene Bükkalja Ignimbrite Field, summarizing the main volcanosedimentological eharacters. Many volcanological features suggest that most of the deposits can be classified as high volume pyroclastie flows (ignimbrite). Two major ignimbritie units have been distinguished, which may belong to two different stages of the vo1canism and form a SW-NE orientated belt. The first (lower) unit is eharaeterized predominantly by non-welded ignimbrites, whereas the second (upper) unit, usually found south of the first unit, shows variable degrees of welding. Hydrovolcanic deposits also occur in different stratigraphie horizons. The final phases of volcanism could have been contemporancous with lacustrine sedimentation.

The Dallol volcano and its associated hydrothermal field are located in a remote area of the northern Danakil Depression in Ethiopia, a region only recently appraised after decades of inaccessibility due to severe political instability and the absence of infrastructure. The region is notable for hosting environments at the very edge of natural physical-chemical extremities. It is surrounded by a wide, hyperarid salt plain and is one of the hottest (average annual temperatureDallol: 36–38°C) and most acidic natural system (pHDallol ≈0) on Earth. Spectacular geomorphologies and mineral deposits produced by supersaturated hydrothermal waters and brines are the result of complex interactions between active and inactive hydrothermal alteration of the bedrock, sulfuric hot springs and pools, fumaroles and geysers, and recrystallization processes driven by hydrothermal waters, degassing, and rapid evaporation. The study of planetary field analog environments plays a crucial role in characterizing the physical and chemical boundaries within which life can exist on Earth and other planets. It is essential for the definition and assessment of the conditions of habitability on other planets, including the possibility for biosignature preservation and in situ testing of technologies for life detection. The Dallol area represents an excellent Mars analog environment given that the active volcanic environment, the associated diffuse hydrothermalism and hydrothermal alteration, and the vast acidic sulfate deposits are reminiscent of past hydrothermal activity on Mars. The work presented in this paper is an overview of the Dallol volcanic area and its hydrothermal field that integrates previous literature with observations and results obtained from field surveys and monitoring coupled with sample characterization. In so doing, we highlight its exceptional potential as a planetary field analog as well as a site for future astrobiologica

The Dallol volcano and its associated hydrothermal field are located in a remote area of the northern Danakil Depression in Ethiopia, a region only recently appraised after decades of inaccessibility due to severe political instability and the absence of infrastructure. The region is notable for hosting environments at the very edge of natural physical-chemical extremities. It is surrounded by a wide, hyperarid salt plain and is one of the hottest (average annual temperatureDallol: 36–38°C) and most acidic natural system (pHDallol ≈0) on Earth. Spectacular geomorphologies and mineral deposits produced by supersaturated hydrothermal waters and brines are the result of complex interactions between active and inactive hydrothermal alteration of the bedrock, sulfuric hot springs and pools, fumaroles and geysers, and recrystallization processes driven by hydrothermal waters, degassing, and rapid evaporation. The study of planetary field analog environments plays a crucial role in characterizing the physical and chemical boundaries within which life can exist on Earth and other planets. It is essential for the definition and assessment of the conditions of habitability on other planets, including the possibility for biosignature preservation and in situ testing of technologies for life detection. The Dallol area represents an excellent Mars analog environment given that the active volcanic environment, the associated diffuse hydrothermalism and hydrothermal alteration, and the vast acidic sulfate deposits are reminiscent of past hydrothermal activity on Mars. The work presented in this paper is an overview of the Dallol volcanic area and its hydrothermal field that integrates previous literature with observations and results obtained from field surveys and monitoring coupled with sample characterization. In so doing, we highlight its exceptional potential as a planetary field analog as well as a site for future astrobiologica