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Lithium is one of the most important critical minerals required for our concerted effort to curb carbon dioxide, methane, and other greenhouse gas emissions necessary for decarbonizing energy systems. Lithium is needed in a big way to build batteries for electric vehicles and super energy storage systems in addition to several other high-tech industrial applications. This paper focuses on different important aspects of lithium, such as its occurrence, mineralogy, and different forms of ore deposits, such as brine deposits, magmatic deposits, sedimentary deposits, and alternative lithium resources, with a major focus on sedimentary deposits of both land and marine deposits. Several studies indicated that marine mineral deposits such as ferromanganese nodules and ferromanganese crusts also contain significant lithium concentrations, and can provide a new solution to the demand for lithium. Currently, sedimentary deposits on the land and deep oceans are receiving increasing attention due to their large size and potential for future lithium resources. While land sedimentary deposits showed a high value of lithium up to 7250 μg/g, the marine sedimentary deposits recorded a high of 781 µg/g. In addition, there are a minor component of unconventional lithium deposits such as lithium in borate deposits, lithium-enriched coal deposits, geothermal waste, lithium-rich industrial wastes such as red mud, acid mine drainage, and recycling which show a large potential. Here, an attempt is made to provide an account of global lithium sedimentary deposits including marine deposits and their potential for large-scale and long-term production of lithium. Exploration studies in different sedimentary basins are also briefly discussed based on geological, geophysical, remote sensing, mineralogical, and geochemical techniques. This cumulative information on sedimentary lithium deposits can trigger many future studies in unexplored and underexplored terrains around the world. [ABSTRACT FROM AUTHOR]

The Lower Kura Depression (LKD) in Azerbaijan is a unique place on Earth where enormous oil and oil–gas-condensate deposits coexist with mud volcanoes. Large mud volcanoes developed in this area as a result of favorable tectonic processes, depositional settings, and subsurface pressure conditions. Disequilibrium compaction leading to overpressurization of mudrocks, as well as gas generation, have been previously proposed as the main factors that cause overpressure and trigger mud volcanism. To assess the mechanisms contributing to mudrock overpressure, we conducted a 2D basin modeling work to simulate the burial, temperature, maturation, and pressure histories of the sedimentary pile along a 120-km-long geological cross-section in the ENE‒WSW direction perpendicular to major structures in the LKD. The results of the calibrated model suggest that the main petroleum source rocks of the LKD, namely the Oligocene–Middle Miocene Maykop and the Eocene Middle Koun mudrock formations, are still in the oil generation zone. Therefore, previously speculated gas generation effect on overpressurization is insignificant in the LKD. Modeling also predicts overpressure of varying magnitude in the potential hydrocarbon source rocks of dominantly mudstone lithology. We have verified that disequilibrium compaction caused by rapid sedimentation in the last 3 million years has led to mudrock overpressurization that exceeded rock strength. We take model-predicted fracturing as a proxy indicator of mud ascent and suggest that fracturing of the mudrocks enabled ascend of the mud via fault-associated weakness zones. [ABSTRACT FROM AUTHOR]

Terrestrial mud volcanoes represent surface features of channels for subsurface methane transport and, therefore, constitute an important source of methane emission from natural environments. How microbial processes regulate methane emissions in terrestrial mud volcanoes has yet to be fully addressed. This study demonstrated the geochemical characteristics and microbial communities of four mud volcano and seep sites in two geological settings of Sicily, Italy. At sites within the accretionary wedge that exhibited higher methane and sulfate concentrations, the communities were dominated by members capable of catalyzing methane and sulfate metabolisms and organic degradation. In particular, both anaerobic and aerobic methanotrophs were abundant and their abundance distribution coincided with the geochemical transition. In contrast, the sites near Mount Etna were characterized by high fluid salinity, CO2, and low methane and sulfate concentrations, with communities consisting of halophilic organic degraders and sulfur metabolizers, along with a minor presence of aerobic methanotrophs. Substantial variations in community composition and geochemistry across spatial and vertical redox gradients suggest that physicochemical contexts imposed by the geology, fluid path, and source characteristics play a vital role in shaping community composition and cycling of methane, sulfur and organic carbon in Sicily mud volcanoes. [ABSTRACT FROM AUTHOR]

Situated between the petroliferous Cenozoic Zhujiang (Pearl) River Mouth Basin and the mud volcano-rich Mesozoic Dongsha Basin in the middle sector of the northern South China Sea, the Weitan Banks area has been previously mapped as a basement high that is composed of Mesozoic magmatic rocks. In this study, we present several favorable indicators for petroleum geology that were detected from geophysical profiling and benthic sampling in the area. A conspicuous hill was discovered, named "Zhongwei Hill", ∼80 m high above the ∼340 m deep seafloor and ∼1 km broad, in a depression with more than 7 km thick sedimentary strata. The Zhongwei Hill was seismically imaged with a mushroom-shaped structure and containing a cake-like crown, fluid flow pipes, and an ∼10 km broad anticline at depth. Thus, the hill represents a source-plumbing-eruption system. Shallow gas zones linked to deep fracture were found at or near the hill. Stratigraphic correlation indicates that the deep strata comprise the Jurassic and Paleogene strata, the major hosts of hydrocarbon source rocks. In addition to the hill, there are number of mounds from which three bottom water samples were collected and the samples are rich in dissolved methane with concentrations high up to ∼900 nmol/L, much higher than the background level (0.5–2 nmol/L). The benthic samples are rich in coarse sediment clastics, authigenic carbonate nodules, and deep-water habitats likely feeding on methanotrophic community. Given these observations and the context, we propose that the Zhongwei Hill represents a mud volcano, likely thermally driven, that seeps methane from Jurassic and Paleogene source layers, thus poses a favorable clue for significant hydrocarbon generation capacity in transitional zone of the Zhujiang River Mouth Basin and the Dongsha Basin. [ABSTRACT FROM AUTHOR]

Deep‐sea chemosynthetic ecosystems are 'oases' of life powered by reducing geofluids, of which serpentinite‐hosted seeps are among the least studied. South Chamorro Seamount, a serpentine mud volcano on the Mariana Arc, has been known to host chemosynthesis‐based assemblages since 1996, but no detailed information on the fauna was published. Here, we revisited South Chamorro to characterise its biodiversity. We located two regions of chemosynthetic communities dominated by bathymodioline mussels, vesicomyid clams, and chaetopterid parchment worms: one on the northwestern flank ('Fryer Site') and one on the southern summit ('Summit Site'). We sampled a total of 20 species including 13 molluscs, five annelids, and two crustaceans – all present on the more active Summit Site but only a subset being found at Fryer Site. A mussel bed surrounding the Fryer Site was drilled by the Ocean Drilling Program in 2001 resulting in six holes, the deepest being 266 m (Hole 1200C). Cuttings ~50 cm deep still cover an approximately 60 m radius around Hole 1200C even 22 years later, and there is no sign of recovery. Low geofluid supply in serpentinite‐hosted seamounts may not allow decadal recovery of animal colonies, unlike a previous drilling site in an Okinawa Trough vent. [ABSTRACT FROM AUTHOR]

Diversity of extremophilic microorganisms in mud volcanoes is largely unexplored. Here we report the isolation of a novel alkaliphilic, mesophilic, fermentative bacterium (strain FN5sucT) from a terrestrial mud volcano located at the Taman Peninsula, Russia. Cells of strain FN5sucT are gram-stain-positive, non-sporeforming, motile rods. The temperature range for growth is 10–37°C, with an optimum at 30°C. The pH range for growth is 7.5–10.0, with an optimum at pH 9.0. The isolate utilizes various organic polymeric substances, organic acids, carbohydrates, and proteinaceous compounds. The end products of carbohydrates fermentation are acetate, CO2 and trace amounts of H2 and formate. The major cellular fatty acid compounds are C16:0, C16:1 ω7c, and monounsaturated dimethyl acetal C14:1. Phylogenetic analysis reveals that strain FN5sucT is most closely related to Petrocella atlantisensis = DSM 105309T (98.4% 16S rRNA gene identity). The total size of the genome of strain FN5sucT is 3.35 Mb, and a genomic DNA G+C content is 37.0 mol %. The genome contains complete glycolisis/glyconeogenesis pathway. We propose to assign strain FN5sucT to the genus Petrocella, as a new species, Petrocella pelovolcani sp. nov. The type strain is FN5sucT (=DSM 113898T = UQM 41591T). [ABSTRACT FROM AUTHOR]

Geothermal features, such as hot springs and mud volcanoes, host diverse microbial life, including many extremophile organisms. The physicochemical parameters of the geothermal feature, such as temperature, pH, and heavy metal concentration, can influence the alpha and beta diversity of microbial life in these environments, as can spatiotemporal differences between sites and sampling. In this study, water and sediment samples were collected and analyzed from eight geothermal sites at Yellowstone National Park, including six hot springs, a mud volcano, and an acidic lake within the same week in July 2019, and these geothermal sites varied greatly in their temperature, pH, and chemical composition. All samples were processed and analyzed with the same methodology and taxonomic profiles and alpha and beta diversity metrics determined with 16S rRNA sequencing. These microbial diversity results were then analyzed with respect to pH, temperature, and chemical composition of the geothermal features. Results indicated that predominant microbial species varied greatly depending on the physicochemical composition of the geothermal site, with decreases in pH and increases in dissolved heavy metals in the water corresponding to decreases in alpha diversity, especially in the sediment samples. Similarly, sites with acidic pH values had more similar microbial populations (beta diversity) to one another than to relatively neutral or alkaline pH geothermal sites. This study suggests that pH and/or heavy metal concentration is a more important driver for microbial diversity and population profile than the temperature for these sites and is also the first reported microbial diversity study for multiple geothermal sites in Yellowstone National Park, including the relatively new mud volcano Black Dragon’s Caldron, which erupted in 1948. [ABSTRACT FROM AUTHOR]

Microbial communities of terrestrial mud volcanoes are involved in aerobic and anaerobic methane oxidation, but the biological mechanisms of these processes are still understudied. We have investigated the taxonomic composition, rates of methane oxidation, and metabolic potential of microbial communities in five mud volcanoes of the Taman Peninsula, Russia. Methane oxidation rates measured by the radiotracer technique varied from 2.0 to 460 nmol CH4 cm−3 day−1 in different mud samples. This is the first measurement of high activity of microbial methane oxidation in terrestrial mud volcanos. 16S rRNA gene amplicon sequencing has shown that Bacteria accounted for 65–99% of prokaryotic diversity in all samples. The most abundant phyla were Pseudomonadota, Desulfobacterota, and Halobacterota. A total of 32 prokaryotic genera, which include methanotrophs, sulfur or iron reducers, and facultative anaerobes with broad metabolic capabilities, were detected in relative abundance >5%. The most highly represented genus of aerobic methanotrophs was Methyloprofundus reaching 36%. The most numerous group of anaerobic methanotrophs was ANME-2a-b (Ca. Methanocomedenaceae), identified in 60% of the samples and attaining relative abundance of 54%. The analysis of the metagenome-assembled genomes of a community with high methane oxidation rate indicates the importance of CO2 fixation, Fe(III) and nitrate reduction, and sulfide oxidation. This study expands current knowledge on the occurrence, distribution, and activity of microorganisms associated with methane cycle in terrestrial mud volcanoes. [ABSTRACT FROM AUTHOR]

Featured Application: Deep geoelectrical mapping of subsurface objectives. This work presents a case study of a geoelectrical exploration of understudied mud volcanoes in Romania, specifically the Pâclele Mici mud volcano from Buzău County. Using a geoelectrical technique facilitated by the distributed network of V-FullWaver equipment, we present, to our knowledge, the first deep 3D case study of a mud volcano in the country. The findings indicate that while geoelectrical surveys in such environments are met with important challenges in terms of soil conductivity, they nonetheless provide a viable approach to uncovering the complex structures and processes of mud volcanoes. We map a part of the mud volcano, showing that the active subsurface part corresponds only partly with what is visible on the surface, and suggest a framework for an in-depth analysis of the extensive mud volcano area. [ABSTRACT FROM AUTHOR]

We identified 27 new mud volcanoes, including potential ones, in a part of the Hyuga-nada area, southwest offshore Japan, at the northern end of the Ryukyu Trench, based on subseafloor geological structures using geophysical investigations. These mud volcanoes exhibited high density and breadth and were likely connected to other mud volcano fields in the south. Acoustic investigations indicated subseafloor structures. Multiple acoustically transparent bodies were interpreted as a region containing gas. They were likely to appear along faults and below the bottom of valleys and sometimes reached the seafloor, expressing mud volcanoes onto the seafloor. They also indicated the wide distribution of subseafloor free-gas throughout the area. These acoustic investigations suggested that a swarm of mud volcanoes exists over the Hyuga-nada area, heterogeneously distributed along a series of plate convergent margins, the Nankai Trough, and the northern part of the Ryukyu Trench. [ABSTRACT FROM AUTHOR]

Mud volcanoes (MVs) are surface structures typically created by episodic discharge of fluids and solids, often associated to onshore and offshore accretionary prisms on convergent plate boundaries. Detailed investigations of ongoing activity and its associated morphological changes, as well as a better understanding of the temporal evolution of these highly dynamic systems, may improve the estimations of material fluxes from MVs drastically. Until today, approximately 70 individual MVs were discovered in the northern Ionian Sea in the Calabrian Arc (Central Mediterranean Sea), but only a few have been analyzed and described in detail. In this study, new evidence for recent recurring eruptive activity of the ~45 m-high and 1 km-wide Sartori MV situated in the clastic wedge of the Calabrian Arc is presented. High-resolution seafloor mapping as well as sediment temperature, geochemical, and sedimentological data received from two research cruises in 2016 and 2020 are used. Bathymetric and seafloor backscatter data (1 m scale) indicate the presence of two active eruption centers at the flat-topped Sartori MV. Elevated sediment temperature gradients at both eruption centers show that currently heat is transferred to the surface sediments. Pore water analyses indicate that fluids rising below the eruption centers are CH4-rich, Cl--poor, and SO42--free. Stable C and H isotopic compositions of methane suggest that it originates from a mix of primary microbial, secondary microbial, and/or thermogenic sources. A relatively shallow position of the sulfate-methane interface at both eruption centers also indicates the presence of upward fluid migration in recent times. Pore water modeling suggests that seawater has penetrated the surface sediments to a greater extent within the last few years. In contrast, centimeter-thick layers of hemipelagic sediments overlying mud breccia in sediment cores taken from both eruption centers show that no solid material has been ejected in recent times. Sediment core analyses combined with high-resolution seafloor mapping show an absence of rim-passing mudflows over the past ~10 ka. It is concluded that Sartori MV is an episodically active MV from which fluids with a comparatively low flux were released into the bottom water in recent times. [ABSTRACT FROM AUTHOR]

Mud volcanoes are geological structures observed throughout the world that arise from the upwelling of deep fluids along discontinuities in the subsoil. The detection of mud fluid migration pathways can be challenging, even when using Electrical Resistivity Tomography (ERT) as detectability issues may arise from complex geological settings. This paper presents new results from 2D and 3D ERT synthetic modelling for the investigation of the shallow, internal structure of terrestrial mud volcanoes. This study revealed the internal structure of the 'Cenerone-Pineto' mud volcano (Central Italy) and provided further clues as to its internal structure. The main results of the study are: the presence of a mud chamber, which represents the last phase of mud accumulation before final emission, not located beneath the crater but laterally offset, as well as the presence of a narrow, shallow feeder channel; these findings represent evidence of a much more complex structure than one would expect. This means that the mud volcano is not supplied with mud fluids directly from below as would be the case with an uprising of deep fluid along a near-vertical open fracture and that the shallow mud fluid reservoir is not correlated to the distribution of any mud volcano observed on the surface. Findings from this study are consistent with the observed structural features already noted in ERT and seismic field data collected at the 'Cenerone-Pineto' mud volcano and may be helpful in explaining the mechanisms and processes involved in mud volcanism in similar geological settings. [ABSTRACT FROM AUTHOR]

The debate about the conceptual model of mud volcanoes functioning is still alive in the literature. A large part of the literature focuses on the characterization of the deep reservoir where expelled fluids are expected to originate. Another part of literature is focused on the study of the shallow system of mud volcanoes, which could influence the short‐term variations in mud volcanoes activity. We present and analyze a new data set of micro‐gravimetric data to study the area of the Nirano Salse, Italy. Unlike what is commonly assumed for the study area, our results suggest that the geomorphology of the Nirano Salse is not related to a caldera collapse above a shallow mud chamber, but to the surface expression of slip distribution of a fault termination along which the fluids ascended to the surface. We believe that gravimetric data can significantly improve the study of hydrocarbon seeps and mud volcanism. Plain Language Summary: Mud volcanoes are broadly distributed throughout the globe, both on‐and off‐shore. They are formed by the episodic eruption of mud and rock fragments. The eruptions are mainly driven by of gravitative instability, due to the overall low density of clay on surrounding soil types and fluid overpressures. To date, a physical conceptual model of the area of Nirano Salse (Northern Italy), ascribes the mud eruptions to the presence of over‐pressurized fluids that are expelled from a main deep reservoir. The latter is put into communication with the surface due to the episodical reactivation of pre‐existing faults or pipes. The debate about this conceptual model is still open. To improve it, a new data set of gravimetric data was acquired during 2022. Our results suggest that the morphology of the study area is due to the presence of an almost vertical fault, which acts as a preferential route for the ascent of deep fluids. Key Points: A microgravimetric survey coupled with laboratory density measurements allows to image the shallow to medium subsurface below mud volcanoesGravimetric data allow to distinguish between morphologies due to caldera collapse and the surface expression of slip along a faultFor the first time the attenuation volume caused by mud intrusion is imaged by gravimetry along a fault [ABSTRACT FROM AUTHOR]

Chemosynthetic ecosystems powered by microbial primary production are rare 'hot spots' of biological activity in the deep‐sea characterized by dense aggregations of specially adapted animal species. Among settings where such systems have been found, serpentinite‐hosted seep systems supported by alkaline geofluid are particularly understudied with just a few known sites worldwide. Mariana Forearc hosts the world's only series of active serpentinite mud volcanoes, but seep communities have only been reported from South Chamorro Seamount where large bathymodioline mussels dominate. Here, we report the discovery of a serpentinite‐hosted seep on the conical summit of Asùt Tesoru Seamount, Mariana Forearc. Named the 'Big Blue Seep', this field features white, likely carbonate crusts inhabited by animals, under which fluid seepage could be seen. We confirm 16 animal species, including typical seep‐associated fauna such as Desbruyeresia gastropods and Acharax awning‐clams. This is surprising as previous research expeditions did not notice any sign of chemosynthesis‐based ecosystems on this seamount, although the community is indeed difficult to spot due to the lack of large‐bodied epifauna such as mussels. The Big Blue Seep is adjacent to three drill holes made by the International Ocean Discovery Program expedition 366 (Holes U1496A‐C), which may have impact on seepage. Our findings represent the second chemosynthesis‐based ecosystem associated with serpentinite mud volcanism, suggestive of further such communities on other Mariana Forearc mud volcanoes. [ABSTRACT FROM AUTHOR]

Identification of methane origins remains a challenging work as current diagnostic signals are often not sufficient to resolve individual formation and post‐formation processes. To address such a knowledge gap in a tectonically active and fragmented terrain, samples from mud volcanoes, gas seeps, and springs distributed along structural features onshore and offshore of Taiwan were analyzed for their isotopic compositions of methane, nitrogen, helium, dissolved inorganic carbon, CO2, and water. Our analyses yielded Δ13CH3D and Δ12CH2D2 values ranging between +1.9‰ and +7.8‰ and between +3.0‰ and +19.9‰, respectively. A portion of the samples were characterized by values that represent the thermodynamic equilibrium at temperatures of 99°–260°C. These temperature estimates, together with the bulk isotopic compositions and local geothermal gradients (25°–30°C/km), suggest that methane was formed by thermal maturation of organic matter at depths of 2–9 km below the land surface and channeled upward along faults. Other samples were found to deviate from equilibrium by varying degrees. Considering the geological background, helium isotopic ratios, and nitrogen isotopologue compositions, and methanogens detected at some sites, these gases are either abiotic in origin or a mixture of microbial and thermogenic sources. Regardless of whether the equilibrium of methane isotopologues was reached, few sites hosted by sedimentary formations were characterized by mantle‐like helium signatures, indicating decoupled origins and potential degassing of helium from the relic igneous source. Overall, these results suggest the extraction of methane and other gases from multiple depths from strata fragmented by fault displacement in an active orogenic belt. Plain Language Summary: Mud volcanoes and gas seeps are distributed primarily in active tectonic regimes and represent the surface expression of subsurface fracture networks. They provide rapid access to probing subsurface characteristics for the generations of methane, other gases, and water. Identifying the exact mechanisms of methane formation remains a challenging work due to the lack of diagnostic signals with sufficient resolving power. This study employed a wide range of isotopic tools to constrain the origins of gases and water from mud volcanoes and seeps in Taiwan, where dual subductions and associated arc‐continent collision between the Philippine Sea and Eurasian plates have enabled the plumbing of gases and water in accordance with structure development and stratum deformation. Our results reveal a spectrum of geochemical characteristics that point to diverse formation mechanisms and conditions. In particular, deeply sourced thermogenic methane (from depths of 2–9 km) appears to constitute a major gas component at most sites, and is mixed by various degrees with abiotic methane pertinent to igneous bodies emplaced during subduction/collision, or microbial methane generated at shallow depths. Overall, the results address the temporal and spatial variations in gas origins prone to terrain fragmentation and dynamic structural control associated with mountain building. Key Points: Mud volcanoes and gas seeps provide rapid access to probing subsurface fluid characteristics in tectonically active regionsThermogenic methane constitutes a major component of hydrocarbons and forms at temperatures of 99°–260°CA wide spectrum of geochemical characteristics indicates diverse formation mechanisms and conditions that constrain gas and water origins [ABSTRACT FROM AUTHOR]

An alkaliphilic, sulfate-reducing, anaerobic bacterium (strain H1T) was isolated from a terrestrial mud volcano at the Taman Peninsula, Russia. The cells of the isolate were gram-negative motile vibrios, 1 µm in diameter and 2.0–2.5 µm in length. Strain H1T grew at 14–42°C (optimum at 37°C), pH 8.5–10.5 (optimum at pH 9.5), and NaCl concentrations of 0.5–6% (wt/vol) (optimum at 0.5–1.5%); pyruvate, lactate, butyrate, caproate, or pelargonate were used as electron donors, and elemental sulfur, sulfite, or sulfate were used as electron acceptors. Pyruvate and lactate were fermented. No growth occurred in the presence of oxygen. Thiosulfate, DMSO, fumarate, nitrate, nitrite, arsenate, selenite, and Fe(III) were not used as electron acceptors. Elemental sulfur, thiosulfate, and sulfite were not disproportionated. Glucose, fructose, sucrose, trehalose, galactose, xylose, fumarate, citrate, yeast extract, and peptone were not fermented. Predominant fatty acids were C20:0 (54.2%), C22:0 (24.6%), and C18:0 (11.1%). The genome of strain H1T was 3.66 Mb in size and had G + C DNA content of 51.1%. The genome contained the genes encoding the enzymes of dissimilatory sulfate reduction and β-oxidation of fatty acids. According to the results of analysis of the 16S rRNA gene sequence, Desulfobotulus mexicanus was the organism most closely related to strain Н1Т (98.3% similarity). Based on its phenotypic characteristics and the data of phylogenetic analysis, affiliation of the isolate as member of a novel Desulfobotulus species, Desulfobotulus pelophilus sp. nov., is proposed, with the type strain H1T (=DSM 112796T = VKM B-3697Т =UQM 41590T). [ABSTRACT FROM AUTHOR]

The violent eruption of Karabetova Gora mud volcano on 6 May 2000 (Taman Peninsula, 45°12′16″ N; 36°47′05″ E) triggered gas ignition as a giant straight-flow vertical gas flare. The 400 m high, short-lived (~15 min) gas flare left no thermal halo on the ground surface, but the thermal shock caused melting or annealing of mud masses which became dispersed in ≤2 m3 blocks to distances within 30 m around the volcano conduit. The flare reached the maximum temperatures (~1400–1540 °C) at heights from 75 to 250 m, as estimated by a numerical simulation in SigmaFlow. Bulk melting of dehydrated mud masses was mostly limited to <1.5 cm near the surface of the blocks. Porous paralavas at the site consisted of low- and high-silica K-Al glasses (70%–80%) with residual unmolten grains of detrital quartz and fine (<30 µm) new phases: main intermediate members of the magnetite–ulvöspinel solid solutions and plagioclase (An45-61Ab37-44Or2-11 to An73-90Ab10-27Or0.5-1), minor cordierite (XFe = 26%–46%), pigeonite (XFe = 42%–60%), tridymite, cristobalite, and rare mullite. The metapelitic rocks affected by combustion metamorphism were heterogeneous in terms of phase composition and texture. They failed to attain homogeneity due to the high viscosity of anhydrous silicate melts and brevity of the thermal impact. The revealed features of rocks altered by a giant gas fire may serve as a proxy for phase transformation patterns in highly disequilibrium conditions of a thermal shock, far from the formation conditions of ordinary metamorphic rocks. [ABSTRACT FROM AUTHOR]

The key microbial group involved in anaerobic methane oxidation is anaerobic methanotrophic archaea (ANME). From a terrestrial mud volcano, we enriched a microbial community containing ANME-2a, using methane as an electron donor, Fe(III) oxide (ferrihydrite) as an electron acceptor, and anthraquinone-2,6-disulfonate as an electron shuttle. Ferrihydrite reduction led to the formation of a black, highly magnetic precipitate. A significant relative abundance of ANME-2a in batch cultures was observed over five subsequent transfers. Phylogenetic analysis revealed that, in addition to ANME-2a, two bacterial taxa belonging to uncultured Desulfobulbaceae and Anaerolineaceae were constantly present in all enrichments. Metagenome-assembled genomes (MAGs) of ANME-2a contained a complete set of genes for methanogenesis and numerous genes of multiheme c-type cytochromes (MHC), indicating the capability of methanotrophs to transfer electrons to metal oxides or to a bacterial partner. One of the ANME MAGs encoded respiratory arsenate reductase (Arr), suggesting the potential for a direct coupling of methane oxidation with As(V) reduction in the single microorganism. The same MAG also encoded uptake [NiFe] hydrogenase, which is uncommon for ANME-2. The MAG of uncultured Desulfobulbaceae contained genes of dissimilatory sulfate reduction, a Wood–Ljungdahl pathway for autotrophic CO2 fixation, hydrogenases, and 43 MHC. We hypothesize that uncultured Desulfobulbaceae is a bacterial partner of ANME-2a, which mediates extracellular electron transfer to Fe(III) oxide. [ABSTRACT FROM AUTHOR]

Mud volcanoes (MVs) are geological structures that episodically eject mud breccias composed of fluids and solids from the Earth's interior. MVs are predominantly associated to converging plate boundaries such as the African-European collision zone in the Mediterranean Sea. Although many investigations have been conducted on the global distribution, morphology and current activity of MVs, studies on the eruptive history and episodic activity of MVs are limited. This study presents a comprehensive analysis of the chronology of mud eruptions from the submarine Sartori MV located in the Calabrian Accretionary Prism in the central Mediterranean Sea at a water depth of about 1900 m. Seafloor bathymetry and backscatter mapping combined with multi-proxy sediment analysis of 16 sediment cores collected in the area of the MV indicate mud breccia deposits from six distinct eruptive phases. Radiocarbon ages of planktonic foraminifera, ages of interbedded tephra layers, identification of the Holocene sapropel marker horizon S1, and correlation with calculated sedimentation rates of hemipelagic sediments revealed that these six phases occurred during the last ∼56 ka. The mudflow deposits of the individual mud eruption phases differ slightly in their bulk organic carbon and nitrogen content, suggesting that the mud breccia composition varied between each eruptive phase. The duration of the quiescent phases between each eruption varied from ∼1.4 ka to ∼12.2 ka. The backscatter data from the seafloor indicate that only the mudflows that were mobilized between ∼56 and 22 ka cover the surroundings of Sartori MV over a wide area. Mudflows generated during more recent eruptive phases remained confined to the central area and the immediate vicinity of the MV, suggesting that MV activity was attenuated during the post-glacial sea level rise and Holocene sea level highstand. Eruptive phases of Sartori MV did not coincide with the eruptions of magmatic volcanoes in the region, and a correlation with earthquake events is also not evident due to the sparse documentation of (pre-)historical events. Internal processes such as pressure release from over-pressured mud chambers are believed to be important drivers of the episodic activity of Sartori MV. This study documents the episodic activity of a MV, and shows the interplay between internal driving processes and external influencing factors over geological time. • Multi-proxy study revealed eruption history of Sartori Mud Volcano, Calabrian Arc. • Seafloor backscatter and sediment cores show six eruption phases in the last ∼56 ka. • Mudflows spread in different directions and covered up to 4.4 km2 of seabed. • Dating individual mudflows based on ages of foraminifera and marker horizons. • Periodic activity could have been triggered mainly by internal processes. [ABSTRACT FROM AUTHOR]

Microfaunal analyses were conducted near Scoglio d'Affrica in the Tuscan Archipelago (Northern Tyrrhenian Sea), to study the response of benthic foraminifera to methane (CH 4) venting activity that occurs in this shallow water environment. Our data show that sedimentary processes linked to the CH 4 emissions exert a strong influence on foraminiferal assemblages, resulting in a very patchy spatial distribution linked to complex abiotic and biotic interactions. Methane emissions and mud represent the two main stressor factors for the benthic foraminiferal assemblages, although at present it is not possible to determine which impact dominates. Five different morphological settings, controlled by venting activity, were defined on and off the mud volcanoes (MVs). Each of these settings has distinct assemblages: 1) areas with strong emission activity at the top of the MVs, locally associated with gryphons and mudflows, where the environmental conditions are clearly prohibitive for foraminiferal life; 2) mud flows along the MV flanks, where overlapping mudflows likely limit foraminiferal colonization; 3) muddy sediments associated with weak emissions where the development of foraminiferal community is favored, although with differences in terms of density, diversity and compositional features linked to the timing of colonization by each species; 4) intermatte zones with scarce or absent emissions, characterized by typical shallow water taxa indicative of well-oxygenated and highly hydrodynamic conditions; and 5) Posidonia oceanica substrates, characterized by higher foraminiferal content on the leaves compared to the rhizomes and surrounding sediments; indeed, sediments and rhizomes were more impacted by emissions, whereas Posidonia leaves offer "refugia" and a more mitigated environment. Although it is difficult to define a pattern of biota response and to identify seep-exclusive taxa, foraminifera can represent good environmental proxies for both monitoring the variability of recent venting activity and detecting stressed conditions occurring in the geological record. The seafloor around Scoglio d'Affrica represents a very promising study site for multidisciplinary marine research regarding venting activity, geochemistry of cold seep fluids and their effects on benthic organisms. • Relationships and influence of CH 4 on shallow water benthonic associations. • Methane emissions and mud emplacement represent the two main stressor factors for the benthic foraminiferal assemblages. • Five different morphological settings, controlled by venting activity, associated with distinct microfaunal assemblages. • Benthonic foraminifera represent good proxies for both monitoring and detecting recent and past venting activity. • Scoglio d'Affrica represents a very promising study site for multidisciplinary marine research regarding venting activity. [ABSTRACT FROM AUTHOR]

An alkaliphilic, facultatively anaerobic bacterium (strain T05bT) was isolated from a terrestrial mud volcano on the Taman Peninsula, Russia. The cells of the isolate were motile spirilla 0.5 µm in diameter and 1.5–2.5 µm long. Strain T05bT grew at 6–42°C (optimum at 30°C), pH 8.0–11.0 (optimum at 9.0), and 0–14% NaCl (wt/vol). Lactate, formate, malate, pyruvate, H2, elemental sulfur, sulfite, thiosulfate, and sulfide were used as electron donors; nitrate, fumarate, elemental sulfur, sulfite, thiosulfate, dimethyl sulfoxide, arsenate, and oxygen could be used as electron acceptors. Nitrate was reduced to ammonium. Malate, pyruvate, and fumarate were fermented. Microaerobic growth was possible at up to 3% О2 (vol/vol). Strain T05bT did not use sulfate and Fe(III) as electron acceptors, was unable of elemental sulfur, sulfite or thiosulfate disproportionation, and did not ferment glucose, fructose, sucrose, lactate, formate, maleate, yeast extract, or peptone. The predominant fatty acids were C16:1 ω7 (45.9%), C16:0 (25.8%), and C18:1 ω7 (20.9%). The genome of strain T05bT was 2.46 Mb in size and had the G + C DNA content of 45.5%. It contained the genes encoding the following enzymes of energy metabolism: Nap nitrate reductase periplasmic complex, Phs/Psr thiosulfate/polysulfide reductase, Sqr sulfide:quinone oxidoreductase, and Arr respiratory arsenate reductase. According to analysis of the 16S rRNA gene nucleotide sequence, strain T05bT exhibited 98.61% similarity to the type strain of Sulfurospirillum alkalitolerans (phylum "Campylobacterota"). Based on its phenotypic characteristics and the results of phylogenetic analysis, assignment of the isolate to a new Sulfurospirillum species, Sulfurospirillum tamanensis sp. nov., is proposed, with the type strain T05bT (=DSM 112596T = VKM B-3538T). [ABSTRACT FROM AUTHOR]

Mud volcano (MV) is one of the most important channels for deep seated volatile materials to migrate to Earth's surface in the sedimentary basins at subduction zones. It plays a meaningful role of elemental budget in hydrosphere. Waters of MV fluid emitted from 46 mud pools in MV Lei-Gong-Huo (LGH) in eastern Taiwan were sampled from October 2015 to July 2016 monthly. Previous research indicates that the chemical characteristic of fluid expelled by MV LGH is dominated by two-end-member mixing of water--rock interaction with sedimentary and igneous rocks (Chao et al., Front Earth Sci 9:750436, 2022). Trace elements of 165 mud pool samples, including Al, Co, Ni, Cu, Zn, As, Br, Rb, Mo, Sb, I, Cs, Pb and U, were measured. The results show that waters of MV LGH reveal similar chemical characteristics to low-temperature ridge-flank hydrothermal spring and marine pore water in anoxic conditions coupled with the addition of clay dehydration. Principle component analysis (PCA) with previous published variables (Chao et al., Front Earth Sci 9:750436, 2022) indicates the important factors are the source of water--rock interaction, the surface ion exchange, the redox condition of mud pool, and the evaporation. In summary, the concentration of trace elements in the waters expelled by MV LGH is in the range of nM to pM. Their behaviors are dominated by secondary factors during and after migration such as surface ion exchange in response to changes in pressure and temperature, redox state of the mud pool, and evaporation. Trace elements in MV water are not suitable for fluid source or provenance studies. [ABSTRACT FROM AUTHOR]

Low-chlorinity springs sampled from ten sites on nine serpentinite mud volcanoes show systematic chemical gradients across the outer Mariana forearc that result from progressive devolatilization of the subducting Pacific plate. Sites range from 50 to 90 km from the trench axis corresponding to depths to the top of the plate of ∼15–29 km. Dissolved sulfate, Na/Cl, K, Rb, Cs, and B in the springs all increase regularly with distance from the trench, leached from subducting sediment and altered basalt in response to increasing temperature at depth from ∼80 to 350 °C. Sites nearer the trench have high Ca (up to 76 mmol/kg) and Sr, low alkalinity, and pH 10.7, whereas sites farther from the trench have almost no Ca and Sr, alkalinity (some carbonate but mostly hydroxyl) as high as 69 meq/kg, and pH 12.5. Springs with high alkalinity also have high methane (>44 mmol/kg) that feeds sulfate-reducing archaeal communities in the shallow subsurface and macrofauna at the seafloor. These distal springs form chimneys and crusts of CaCO 3 , whereas the proximal springs form chimneys of brucite. High alkalinity at the distal sites apparently results from carbonate dissolution at the top of the subducting plate; because serpentinization during ascent generates both high pH and H 2 , the resulting dissolved carbonate is reduced to methane such that carbonate alkalinity is replaced by hydroxyl alkalinity: 4H 2 + HCO 3 – → CH 4 + 2H 2 O + OH–. This reaction can account for the much higher pH of the distal springs. Chlorinity of the springs varies from 234 to 546 mmol/kg and is related to latitude N S rather than distance from the trench. Distal springs have otherwise similar compositions over this entire range of chlorinity, implying that chloride derives from depth rather than from mixing with seawater within the seamounts themselves. The range in chlorinity can readily be explained by serpentinization at reasonable water/rock mass ratios of 0.2–1.0 if 30–40% of the spring water originates as residual pore water in subducted sediment and basalt rather than as H 2 O+ of dehydration. The pH, alkalinity, and methane content of the springs increase abruptly, while Ca and Sr decrease, because carbonate dissolution joins dehydration as a major process at the top of the subducting plate at ∼70 km from the trench, where metabasites recovered from the serpentinite mud indicate the transition from lawsonite blueschist facies to epidote blueschist facies also occurs. Replacement of lawsonite by epidote drastically depletes the solution in Ca and shifts the equilibrium toward massive dissolution of subducted carbonate. Fluxes of sulfate, C, Na, K, Rb, Cs, B, Ca, and Sr in the forearc springs represent only a few percent of the amounts subducted, consistent with continued supply at greater depth. [ABSTRACT FROM AUTHOR]

The continental subsurface harbors microbial populations highly enriched in uncultured taxa. OPB41 is an uncultured order-level phylogenetic lineage within the actinobacterial class Coriobacteriia. OPB41 bacteria have a wide geographical distribution, but the physiology and metabolic traits of this cosmopolitan group remain elusive. From two contrasting subsurface environments, a terrestrial mud volcano and a deep subsurface aquifer, located in the central part of Eurasia, within the Caucasus petroleum region, we have isolated two pure cultures of anaerobic actinobacteria belonging to OPB41. The cells of both strains are small non-motile rods forming numerous pili-like appendages. Strain M08DHBT is mesophilic, while strain Es71-Z0120T is a true thermophile having a broad temperature range for growth (25-77°C). Strain M08DHBT anaerobically reduces sulfur compounds and utilizes an aromatic compound 3,4-dihydroxybenzoic acid. Strain Es71-Z0120T is an obligate dissimilatory Fe(III) reducer that is unable to utilize aromatic compounds. Both isolates grow lithotrophically and consume molecular hydrogen or formate using either thiosulfate, elemental sulfur, or Fe(III) as an electron acceptor. Genomes of the strains encode the putative reductive glycine pathway for autotrophic CO2 fixation, Ni-Fe hydrogenases, putative thiosulfate/polysulfide reductases, and multiheme c-type cytochromes presumably involved in dissimilatory Fe(III) reduction. We propose to assign the isolated strains to the novel taxa of the species-order levels and describe strain M08DHBT as Anaerosoma tenue gen. nov., sp. nov., and strain Es71-Z0120T as Parvivirga hydrogeniphila gen. nov., sp. nov., being members of Anaerosomatales ord. nov. This work expands the knowledge of the diversity, metabolic functions, and ecological role of the phylum Actinomycetota. [ABSTRACT FROM AUTHOR]

Compared with the deeply buried marine gas hydrate deposits, gas hydrates in the shallow subsurface, close to and at the seafloor, have attracted more attention owing to their concentrated distribution, high saturation, and easy access. They accumulate at relatively shallow depths <100–120 m and occur as gas hydrate-bearing mounds (also known as hydrate outcrops, pingoes) at the seafloor derived from the growth of hydrates in the shallow subsurface or as pure hydrate chunks formed by gas leakage. This paper reviews and summarizes such gas hydrate systems globally from the perspective of gas sources, migration pathways, and accumulation processes. Here, we divided them into four categories: fault-chimney-controlled, diapir-fault-controlled, fault-controlled, and submarine mud volcano-controlled deposits. Gas chimneys originate immediately above the restricted regions, mostly affected by faults where high gas concentrations trigger elevated pore fluid pressures. Diapirism derives a dendritic network of growth faults facilitating focused gas discharge and hydrate formation near the seafloor. Furthermore, pre-existing faults or fractures created by overpressured gas from greater depths in accretionary tectonics at convergent margins act as preferential pathways channeling free gas upwards to the seafloor. Gas flux rates decrease from the submarine mud volcano center to its margins, creating a concentric pattern of distributing temperature, gas concentrations, and hydrate contents in shallow sediments around the mud volcano. Hydrate-bound hydrocarbons are commonly of thermogenic origin and correspond to high-background geothermal conditions, whereas microbial gas is dominant in a few cases. The presence of heavier hydrocarbons mitigates the inhibition of hydrate formation by salt or heat. Fluid migration and pathways could be compared to the "blood" and "bones" in an organic system, respectively. The root of a pathway serves as the "heart" that gathers and provides considerable free gas concentrations in a restricted area, thereby triggering pore fluid pressures as one important drive force for focused fluid flow in impermeable sediments (the organic system). Besides the suitable temperature and pressure conditions, a prerequisite for the formation and stability of hydrate deposits in the shallow subsurface and at the seafloor is the sufficient supply of gas-rich fluids through the hydrate stability zone. Thus, the proportion of gas migrating from deep sources is significantly larger than that trapped in hydrates. As such, such marine hydrate deposits seem more like temporary carbon storage rather than the main culprit for climate warming at least in a short period. [ABSTRACT FROM AUTHOR]

The genus Roseovarius , a member of the ecologically important Roseobacter -clade, is widespread throughout the world. A facultatively anaerobic lithoautotrophic bacterium (strain SHN287T), belonging to the genus Roseovarius , was isolated with molecular hydrogen as an electron donor and nitrate as an electron acceptor from a terrestrial mud volcano. Strain SHN287T possessed metabolic features not reported for Roseovarius such as chemolithoautotrophic growth with oxidation of molecular hydrogen or sulfur compounds, anaerobic growth and denitrification. Based on the phenotypic and phylogenetic characteristics, the new isolate is considered to represent a novel species of the genus Roseovarius , for which the name Roseovarius autotrophicus sp. nov. is proposed. The type strain is SHN287T (= KCTC 15916T = VKM B-3404T). An amended description of the genus Roseovarius is provided. Comparison of 46 Roseovarius genomes revealed that (i) a full set of genes for the Calvin-Benson cycle is present only in two strains: SHN287T and Roseovarius salinarum ; (ii) respiratory H2-uptake [NiFe] hydrogenases are specific for a phylogenetically distinct group, including SHN287T-related strains; (iii) the Sox enzymatic complex is encoded in most of the studied genomes; and (iv) denitrification genes are widespread and randomly distributed among the genus. The metabolic characteristics found in R. autotrophicus sp. nov. expand the ecological role of the genus Roseovarius. [ABSTRACT FROM AUTHOR]

Gas hydrates stored in the continental margins of the world's oceans represent the largest global reservoirs of methane. Determining the source and history of methane from gas hydrate deposits informs the viability of sites as energy resources, and potential hazards from hydrate dissociation or intense methane degassing from ocean warming. Stable isotope ratios of methane (13C/12C, D/H) and the molecular ratio of methane over ethane plus propane (C 1 /C 2+3) have traditionally been applied to infer methane sources, but often yield ambiguous results when two or more sources are mixed, or when compositions were altered by physical (e.g., diffusion) or microbial (e.g., methanotrophy) processes. We measured the abundance of clumped methane isotopologue (13CH 3 D) alongside 13C/12C and D/H of methane, and C 1 /C 2+3 for 46 submarine gas hydrate specimens and associated vent gases from 11 regions of the world's oceans. These samples are associated with different seafloor seepage features (oil seeps, pockmarks, mud volcanoes, and other cold seeps). The average apparent equilibration temperatures of methane from the Δ13CH 3 D (the excess abundance of 13CH 3 D relative to the stochastic distribution) geothermometer increase from cold seeps (15–65 °C) and pockmarks (36–54 °C), to oil-associated gas hydrates (48–120 °C). These apparent temperatures are consistent with, or a few tens of degrees higher than, the temperature expected for putative microbial methane sources. Apparent methane generation depths were derived for cold seep, pockmark, and oil seep methane from isotopologue-based temperatures and the local geothermal gradients. Estimated methane generation depths ranged from 0.2 to 5.3 kmbsf, and are largely consistent with source rock information, and other chemical geothermometers based on clay mineralogy and fluid chemistry (e.g., Cl, B, and Li). Methane associated with mud volcanoes yielded a wide range of apparent temperatures (15–313 °C). Gas hydrates from mud volcanoes the Kumano Basin and Mediterranean Sea yielded δ13C-CH 4 values from −36.9 to −51.0‰, typical for thermogenic sources. Δ13CH 3 D values (3.8–6.0‰) from these sites, however, are consistent with prevailing microbial sources. These mud volcanoes are located at active convergent plate margins, where hydrogen may be supplied from basement rocks, and fuel methanogenesis to the point of substrate depletion. In contrast, gas hydrate from mud volcanoes located on km-thick sediments in tectonically less active or passive settings (Black Sea, North Atlantic) yielded microbial-like δ13C-CH 4 and C 1 /C 2+3 values, and low Δ13CH 3 D values (1.6–3.3‰), which may be due to kinetic isotope effects. Additionally, using samples from two sites, we found that Δ13CH 3 D values of hydrate-bound gas and vent gas agree within measurement error. This study is the first to document the link between methane isotopologue-based temperature estimates and key submarine gas hydrate seepage features, and validate previous models about their geologic driving forces. [ABSTRACT FROM AUTHOR]

The upwelling of fluids, subject to overpressure, along with discontinuities in the subsoil, causes the formation of geological structures known as mud volcanoes. These structures, very widespread in the world and in some cases located near inhabited centers, can represent a considerable risk factor for the population, as they can give rise to paroxysmal eruptions, even very violent. The assessment of the characteristics and structure of the subsoil of the areas affected by this phenomenon can prove to be a useful tool for risk mitigation. Non-invasive geophysical surveys were carried out in the area of the active cone of the Santa Barbara mud volcano in order to obtain a 3D characterization of the subsoil. Through the processing and integration of data derived from active and passive seismic surveys was obtained, a 3D model showing the seismostratigraphic subsoil structure. The electrical resistivity tomography surveys provided results comparable to those obtained from seismic surveys and supplied information on the perimetral areas of the mud volcano. The information obtained is useful to study the boundary conditions that influence short-scale activity. Furthermore, this study seeks to evaluate the possibility of using the proposed methodological approach for monitoring the variations that occur over time in the areas affected by mud volcanoes phenomenon. [ABSTRACT FROM AUTHOR]

On 15 May 2021, the Zhurong rover of China's first Mars mission, Tianwen-1 (TW-1), successfully landed in southern Utopia Planitia on Mars. Various landforms were present in the landing area, and this area recorded a complex geological history. Cones are one of the typical landforms in the landing area and Utopia Planitia, and they have a great significance to the local geological processes due to the diversity of their origins. Using High-Resolution Imaging Camera (HiRIC) images collected by the TW-1 orbiter, we identified a total of 272 well-preserved circular cones in the landing area. Detailed surveys of their spatial distribution, morphological characteristics, and morphometric parameters were conducted. A preliminary analysis of the surface characteristics of these cones also provides additional information to strengthen our understanding of them. The results of the high-resolution topographic analysis show that the cone heights are in the range of 10.5–90.8 m and their basal diameters range from 178.9–1206.6 m. We compared the morphometric parameters of the cones in the landing area with terrestrial and Martian analogous features and found that our measured cones are consistent with the ranges of mud volcanoes and also a small subset of igneous origin cones. However, the result of spatial analysis is more favorable to mud volcanoes, and the lower thermal inertia of the cones in the landing area compared to their surrounding materials is also a typical characteristic of mud volcanoes. Based on current evidence and analysis, we favor interpreting the cones in the TW-1 landing area as mud volcanoes. [ABSTRACT FROM AUTHOR]

Mud volcanoes and other fluid seepage pathways usually transport sufficient gas for the formation of gas reservoirs and are beneficial to the accumulation of gas hydrate. On the other hand, the fluid thermal effects of mud volcanoes can constrain the occurrence of gas hydrates. Current field measurements indicate that fluid thermal anomalies impact the distribution of gas hydrates associated with mud volcanoes. However, due to the lack of quantitative analysis of the mud volcano fluid flow and thermal evolution, it is difficult to effectively reveal the occurrence of gas hydrates in mud volcano development areas and estimate their resource potential. This study took the Håkon Mosby Mud Volcano (HMMV) in the southwestern Barents Sea as the research object and comprehensively used seismic, well logging, drilling and heat flow survey data, combining the principles and methods of fluid dynamics and thermodynamics to study the fluid flow and heat transfer of a mud volcanic pathway. The space framework of the mud volcanic fluid temperature field thermal structure was established, the influence of the HMMV fluid thermal effect on gas hydrate occurrence was analyzed and the distribution and resource potential of gas hydrates in mud volcano development areas were revealed from the perspective of thermodynamics. This study provides a thermodynamic theoretical basis for gas hydrate accumulation research, exploration and exploitation under a fluid seepage tectonic environment. [ABSTRACT FROM AUTHOR]

The South Caspian Basin (SCB), located within the Alpine-Himalayan mobile belt, is known for its intensive modern fluid dynamics, a quantitative and qualitative analysis of which makes it possible to solve many problems of oil and gas ontogenesis, including the development of diapirism and mud volcanism. In this paper, using example of basic mud volcanoes (MVs) and gas condensate fields, the main features of modern fluid dynamics in the SCB are considered in order to quantify the volumetric velocity of their focused flows. These assessments are carried out using both conventional and new (based on the concept of renewable gas resources in the reservoir and in the focus of MVs) methodological approaches. The estimates made for the volumetric rate of periodic replenishment of the MV chamber with gas (0.44 × 103 m3/day) are in good agreement with the estimates of the rate of natural replenishment of the gas reservoir (0.42 × 103 m3/day) at the Lokbatan structure affected by the MV of the same name. The estimates of the volume of gas emitted into the atmosphere during an MV eruption are 1–2 orders of magnitude less than the earlier estimates. The forecast and analysis of the dynamics of fluid pressure in the MV chamber is recommended as an additional criterion for assessing the volume of explosive gas. [ABSTRACT FROM AUTHOR]

The Sidoardjo Mud Volcano in East Java, Indonesia, started on May 29, 2006. The average daily discharge of the mud volcano is 50,000 m3/day , with a 35% average concentration of sand, silt, and clay. Since 2017, the finer fractions have been diverted to the Madura Strait through the Porong River. The Ginonjo Outlet serves as a point source with a constant discharge of 45 m3/s and an average sediment concentration of 57,000 mg/L. The settling and transport of fine sediments were studied through field measurements at 106 cross sections over 16 km of the Porong River. At low flow, maximum concentrations decreased from 4,200 to 90 mg/L in the study reach. The two-dimensional mixing and settling model with flocculation resulted in better agreement with the observed data than did models without flocculation. Flocculation tests showed an increase in settling velocity from 0.013 to 0.028 mm/s. Flocculation affected settling of approximately 38% of the total sediment load. The fractions coarser than 92 μm settled within the first 4 km from the point source. [ABSTRACT FROM AUTHOR]

Mud volcanoes (MVs) are naturally occurring hydrocarbon hotbeds with continuous methane discharge, contributing to global warming. They host microbial communities adapted to hydrocarbon oxidation. Given their research value, MVs still represent a niche topic in microbiology and are neglected by hydrocarbon-oriented research. All the data regarding MVs is sporadic and decentralized. To mitigate this problem, we built a custom Natural Language Processing pipeline (muddy_mine), and collected all the available MV data from open-access articles. Based on this data, we built the muddy_db database. The muddy_db represents the first biologically oriented database rendered as a user-friendly web app. This database includes all the relevant MV data, ranging from microbial taxonomy to hydrocarbon occurrence and geology. The muddy_mine and muddy_db tools are licensed under the GPLv3. muddy_db R Shiny web app: https://muddy-db.shinyapps.io/muddy_db/ muddy_db R package: https://github.com/TracyRage/muddy_db muddy_mine Conda package: https://github. com/TracyRage/muddy_mine. [ABSTRACT FROM AUTHOR]

The mineralogical studies of clay from the onshore mud volcanoes discovered in parts of the Upper Benue Trough of Nigeria provide a clue about the geological formation from which the extruded mud originates. The study area is a part of the Cretaceous Upper Benue Trough filled with Early Cretaceous continental deposits and Late Cretaceous marine deposits, having a history of magmatism dating from the Albian to the Pleistocene. The study approach involves integrated inorganic geochemical analysis of the samples to reveal their composition and origin. The results of XRD analysis of the fresh clays from the mud volcano revealed the presence of quartz, kaolinite, and other clay minerals (illite-smectite), feldspars, and in a much lower quantities, other accessory minerals including muscovite, evaporites, calcite and dolomite, trona, barite, goethite. The saprolite samples are composed mainly of quartz, kaolinite, smectite-illite associations, and feldspars, traces of goethite, calcite, and evaporate minerals (sylvite, halite). The presence of calcite, dolomite, sylvite, and halite suggests the marine origin of the rocks, while trona mineral is a non-marine evaporate. The coexistence of these minerals in some of the analyzed samples suggests the deposition of sediments in a transitional environment of deposition. Traces of marine minerals are present in some of the samples but completely absent in others collected from another site. This suggests that the source rock formations from which the material originated are within the Upper Bima Sandstone interpreted as being deposited in a non-marine environment or the Yolde Formation, which is known as a transitional unit (transitional between the outcropping continental Upper Bima Sandstone and marine Pindiga Formation). [ABSTRACT FROM AUTHOR]

Diversity of extremophilic microorganisms in mud volcanoes is largely unexplored. Here, we report the isolation of a novel alkaliphilic, mesophilic, fermentative bacterium (strain F-3apT) from a terrestrial mud volcano located at the Taman peninsula, Russia. Cells of strain F-3apT are Gram-stain-positive non-motile rods. The formation of endospores is not observed. The temperature range for growth is 14–42 °C, with an optimum at 37 °C. The pH range for growth is 7.5–11.0, with an optimum at pH 9.0. The isolate utilizes various organic polymeric substances, organic acids, carbohydrates, and proteinaceous compounds. The end products of glucose fermentation are ethanol, CO2, and H2. The major cellular fatty acids of strain F-3apT are C16:0, C16:1, and C14:0. Phylogenetic analysis reveals that strain F-3apT belongs to the order Clostridiales, with less than 91% of 16S rRNA gene sequence similarity to any species with a validly published name. The total size of the genome of strain F-3apT is 2.98 Mb, and a genomic DNA G + C content is 56.78 mol%. The whole-genome phylogenetic analysis confirms that strain F-3apT forms a distinct lineage within Clostridia. We propose to assign strain F-3apT to a new species of a novel genus Anaerotalea alkaliphila gen. nov., sp. nov. The type strain is F-3apT (= KCTC 15917 T = VKM B-3406 T). [ABSTRACT FROM AUTHOR]

The main purpose of this study is to investigate the North Anatolian Fault (NAF) entrance into Izmit Bay. Upper Quaternary submarine features (gas seeps, gas bearing sediments, pockmarks, mud volcanos, sediment structures and faults) and alongation of the NAF from land to İzmit Bay are investigated by using water depth data, high-resolution shallow seismic profiles, side scan sonar images, and borehole logs. The presence of acoustic anomalies in the Late Quaternary sequences was observed intensely and these anomalies were interpreted as gas bearing sediments. As a result of earthquakes and / or mass movements, the amount of buried gas accumulated along the sediment column may have increased or displaced. In this study, five different gas bearing layers are classified and their distribution patterns are mapped. It has been determined that the active faults in the region that shaped the coastal zone and sea floor morphology of the İzmit Bay are in two different groups. The first group consists of right-lateral strike-slip faults that run along the north and south slopes of the east depression and are in the east-west direction. The secondary group of faults have normal fault characteristics. These secondary faults are parallel to the depth contour lines of the deltas. [ABSTRACT FROM AUTHOR]

Submarine mud volcanoes (MVs) are one of the most spectacular methane expulsion features at the seafloor and they represent a significant geohazard worldwide. In this work, we focus on the physical processes controlling the initiation and early evolution of the Absheron mud volcano (AMV). Our analyses were carried out based on basin modeling calibrated thanks to existing seismic interpretation of the AMV, analysis of sediment samples from seabed, and data from two exploration wells. Acquired laboratory geotechnical data allowed us to derive laws considering the impact of gas exsolution on host sediment behaviors. In this study, we identified key geological and physical conditions that led to MV formation: by coupling diffusion processes with hydrofracturing and fluid advection, we were able to simulate the conditions required to generate mud 3.5 km below the AMV. Mud remobilization up to the seabed was reproduced by using Navier‐Stokes equations modified to account for the impact of gas expansion on mud density. Considering density inversion only, simulations indicate that mud would be extruded at the seabed 100 years after its generation, an ascent rate similar to extrusion rates measured at the active Kotyrdag MV in Azerbaijan. Plain Language Summary: Mud volcanoes (MVs) build‐up at the Earth surface from liquidized sediments remobilized from depths reaching several kilometers. They are distributed globally, onshore and offshore, in different geological backgrounds and represent serious geohazards for people and infrastructures. Moreover, they are also among the most spectacular methane expulsion features at the surface, participating to the global budget of green‐house gases emissions. Their understanding is thus paramount to prevent natural catastrophes such as Lusi eruption in Indonesia in 2006 and to quantify the human impact on global warming. If MVs are known for centuries (Pline the Elder) and studied for decades, little is known about the processes controlling mud generation from stiff deep sediments and its vertical migration toward the surface. The methane is often considered as being a driving element in this geological process and bubble formation in compacted sediments during laboratory testing led to strong damage of sediment properties. Here we develop two independent numerical models, based on simple physical processes and relying on in situ observations of the Absheron mud volcano (AMV, South Caspian Basin) and laboratory testing. They allow to simulate mud generation at depth and its remobilization to the surface. Our research work provides reliable information to describe the initiation and early evolution of an active MV. Key Points: Simulation of mud generation is possible through 2D basin modeling including the effect of gasMud ascent through gas‐expansion‐driven density inversion is possibleA semi‐quantitative formation model for the AMV is derived from modeling results [ABSTRACT FROM AUTHOR]

We conducted 2D resistivity survey along nine survey lines and inverted them to 3D model by combining 2D data in the Gunshuiping mud volcano in order to understand: (1) the relationship between the resistivity image and the mud-fluid distribution, and (2) the influences of earthquakes and typhoon on mud volcanoes. The three long survey lines passed through the four craters, out of which one was active during the survey period; and the six short networked lines surrounded the crater 2 (C2). The results reveal that a vertical structure is present beneath crater 3 (C3), whom we interpret a conduit transporting the mud-fluid onto the near surface. Also, an area with low resistivity (less than 4 ohm-m) is found at a certain depth suggesting to be the mud-fluid chamber. The high resistivity (more than 4 ohm-m) distribution is found near the surface, and we suggest that the mud volcano craters communicate with each other by the 3D model. Moreover, after the Meinong earthquake of 6 February 2016, the resistivity rose obviously within about 10 m under the surface; while the resistivity of the mud-fluid conduits declined. We also found that after the earthquake, the original active crater (C3) had stopped and was replaced by another crater (C1). We inferred that when the earthquake happened, the gases escaped to the surroundings and caused the gas content of the shallow surface to increase. Besides, as the original crater collapsed, the gases needed another crack to release, which made another crater re-activate. The data also shows that after the typhoon, the resistivity of mud-fluid conduits rose with the active crater changed again from C1 to C4. [ABSTRACT FROM AUTHOR]

The southern Junggar Basin in NW China is a world‐class location for the study of oil and gas seeps, with widely distributed, highly variable oil and gas seeps including gaseous mud volcanoes, liquid oil seeps, and solid bitumen deposits. However, the sources and origins of these seeps are poorly understood, as there are many potential source sequences of Permian to Paleogene age. The uncertainty surrounding the seeps means that it has not been possible to address their significance for oil and gas exploration in the area, and they are not understood in the context of the tectono‐sedimentary evolution of the basin within the piedmont region of the northern Tian Shan Mountains (in the eastern part of the Central Asian Orogenic Belt, CAOB). In the present study, these issues were addressed using combined geological and geochemical methods. Results show that there are five main types of seeps in the region from west to east. Type A seeps originate from Jurassic source rocks and are best represented by the A'erqingou mud volcano. Type B seeps originate mainly from Paleogene source rocks but also contain a Jurassic‐sourced component; they are best represented by the Dushanzi mud volcano. Type C seeps originate from a Cretaceous source and are best represented by the South Anjihai and Horgos oil sands. Type D seeps originate mainly from Jurassic source rocks but also contain a Triassic‐sourced component; they are best represented by the Qigu oil seep. Type E seeps originate from Permian source rocks and are best represented by the Dalongkou bituminous deposit. The primary controls on seep distribution are both sedimentological (deposition of source rock) and tectonic (faulting). The position and burial history of sedimentary centres controlled the distribution and maturation of source rocks. Tectonic faults provided migration pathways and traps for the oil and gas. The results of this study will help to reduce uncertainty during exploration for oil and gas in the area. The findings also have general implications for petroleum systems and exploration in the piedmont areas of foreland basins worldwide. [ABSTRACT FROM AUTHOR]

This study explores the electrical anisotropy effects in a vertical electrical sounding dataset acquired from the Lokbatan mud volcano in Azerbaijan. Vertical electrical sounding is a fundamental geophysical technique for mapping subsurface resistivity distributions; however, electrical anisotropy is a factor often ignored, can significantly influence field measurements, especially with respect to layer thicknesses. This study investigates electrical anisotropy effects on vertical electrical sounding data using generalized regression neural networks for estimating parameters of layered subsurface. Schlumberger electrode arrays were employed for these purposes with a 22-sounding dataset. In general, a classical approach for estimating electrical anisotropy coefficient fails. Vertical and horizontal resistivity values cannot be estimated using vertical electrical sounding data. Thus, generalized regression neural networks are considered. The generalized regression neural networks for appraising parameters of electrical anisotropy can be used with keeping vertical resistivity higher than horizontal resistivity in each layer as an assumption. Further, the proposed method applied how the surrounding clay-rich geological material and layered structure influence electrical properties of the Lokbatan mud volcano in Azerbaijan. As a conclusion, without considering electrical anisotropy makes interpretation erroneous especially with respect to layer thicknesses. • Without considering electrical anisotropy makes interpretation erroneous in geoelectrical methods. • The classical approach fails to estimate electrical anisotropy coefficient using vertical electrical sounding data. • Generalized Regression Neural Network can be used to estimate electrical anisotropy. [ABSTRACT FROM AUTHOR]

Natural fluids with a pH (25 °C) up to 12.3 were collected from a sub-seafloor borehole observatory (Ocean Drilling Program (ODP) Hole 1200C) on South Chamorro Seamount, a serpentinite mud volcano in the Mariana forearc. We used systematic differences in the chemical compositions of pore waters from drilling operations during ODP Leg 195 and borehole fluids collected subsequently from Hole 1200C to define two endmember solutions, one of which was a sulfate-rich fluid with a methane concentration of 50 mM that ascends from the subduction channel and the other was a low-sulfate fluid. The sequence of sample collection and fluid compositions constrain subsurface hydrologic conditions. Deep-sourced, sulfate- and methane-rich, sterile fluids from the subduction channel can reach the seafloor unchanged within the central conduit, whereas other fluid pathways likely intersect the pelagic sediment that underlies the serpentinite mud volcano, providing potentially suitable conditions and inoculum for microbial anaerobic oxidation of methane (AOM). These AOM-affected, low-sulfate fluids also make it to the seafloor where they discharge. The source of the sulfate- and methane-rich fluid in the subduction channel is attributed to abiotic methane production fueled by hydrogen production from serpentinization and carbonate dissolution. This methane production includes a mechanism to raise the pH above values from serpentinization alone. Results from South Chamorro Seamount represent an end member along a transect defined by the distance from the trench. Results from this site are applied to other serpentinite mud volcanoes along this transect to speculate on likely chemical conditions within shallower and cooler portions of the subduction channel. [ABSTRACT FROM AUTHOR]

Multibeam echo‐sounding and seismic data were obtained during three geophysical surveys by Guangzhou Marine Geological Survey (GMGS) on the north‐eastern slope of the South China Sea (SCS). Nineteen seafloor domes and numerous elongated pockmarks were distinguished in the study area. The seafloor domes vary on number of summits, shape, and spatial interrelation, based on which they were classified into four types which are single‐summit, double‐summits, elongated, and connected. Bottom simulating reflectors and blanking zone underneath were observed in the seismic profiles, indicating the potential existence of gas hydrate and free gas. Multiple faults and diapirs exist beneath the seafloor domes and pockmarks, which were inferred to provide efficient pathways for fluid migrating from deep subsurface. The seafloor domes exhibits high backscatter feature, which is potentially associated with the seep‐related gas hydrate and authigenic carbonate in the shallow sediment. It is speculated that fault and diapir activity, fault sliding caused by region extension and the interaction between neighbour domes control and affect the activity and formation of the domes. However, further investigations, including geological sampling and seafloor observation, are still needed to confirm whether they are mud volcanoes. [ABSTRACT FROM AUTHOR]

Introduction: A geoelectric and microsismological study was motivated by the increase of sismic activity as an energy source associated with volcanic muderuptions in Urabá (May 2017), Cartagena (June 2017) and in Canalete, Córdoba (December 2017). Thisseeks to evaluate the dynamics of the El Totumo volcano which is in the limits of the departments of Bolívar and Atlántico in the Caribbean region of Colombia. Objective: The aim of this work is to present the results of a geophysical study to determine anomalies related to the dynamics of the volcano. The rising mudflows towards the surface are expected to be detected by analyzing thetomographies; this situation generate risks for tourism in the region. Methodology: Two geophysical methods were applied here: Geoelectric Prospecting and Seismic Monitoring, with the aim of detecting the distribution of lithological materials in depth, as well as the most important structural features related to the distribution and mud ascent. All of the above was achieved through the analysis of tomographs that clearly reveal the danger generated by the ascending fine mud flows, plus the application of the SPAC (Spatial Autocorrelation) method that allowed the correlation of signal speeds with sedimentary strata, and clearly identify the alteration of the structural support of El Totumo volcano due to the pressure exerted by the surface rising mud. In both mentioned cases, a normal lithological distribution characteristic of the subsoil resistivities is observed by the Geophysical data processing. Results: However, neither anomalies or structural changes in the electrical tomographs nor traces of seismic nor seismological activity that would have altered the profile of shear wave velocities are observed. Conclusions: From the above can be drawn that there are no anomalies related to the dynamic behavior of the volcano in this period. The application of the same methodology for future studies of this type of phenomenon not only to the El Totumo volcano but also to any mud volcano is suggested for generating early alerts about the risks that its activity implies in of the people who live nearby. [ABSTRACT FROM AUTHOR]

Using 3D seismic data, we document the subsurface architecture of a cluster of 3 mud volcanoes located on the upper continental slope offshore Nigeria. In a background of gently dipping stratified sediments, the subsurface of the cluster contains 8 seismic sequences made of one subcircular syncline, 1–3 km in diameter, and adjoining unstratified units. Synclines flatten out upward through intercalation of unstratified concave-up lenses between stratified units and are eventually filled by a convex-up unstratified lens onlapped by background sediments. The lower boundary of each sequence is a 0.5–1.5 km-deep bowl-shaped unconformity across which high-dip strata rest above truncated low-dip series. We interpret each seismic sequence as a mud volcano system (MVS) sourced from a connected region and evolving through episodes of roof collapse. Three are associated with the surface mud volcanoes and another 4 to fossil ones. Mud volcano systems are dynamic features that record the evolution of: 1) the material extruded from one single connected source region (depletion zone) as it grows downwards and stepwise becomes depleted; 2) the basal unconformity, which joins strata originally separated by material evacuated in the remobilization process; by analogy with salt tectonics, we propose to call it a "mud weld"; 3) the conduits; and 4) the successive collapsed roofs of the depletion zone. The evolution of each mud volcano system in this interpretation records progressive growth of the depletion zone by downbuilding, punctuated by episodes of roof collapse and extrusion. The geometry and evolution of this type of MVS can be interpreted in the light of analogue models of magmatic caldera development: in early stages, the thin roof experiences downsagging while remobilized material is extruded through an axial pipe-like conduit; in later stages the thickened roof undergoes piston-like subsidence, and mud extrusion occurs along the peripheral fault. • 3D seismic is used to characterize the subsurface architecture of mud volcanoes. • The basic architectural motif includes 1 subcircular syncline and unstratified units. • Each of these is interpreted as a multiphase mud volcano system (MVS). • An MVS records remobilization and extrusion from one connected depletion zone. • Convergence of top and base of depletion zone upon extrusion form a "mud weld". [ABSTRACT FROM AUTHOR]

Seismic imaging techniques are widely used to determine fluid migration pathways in the subsurface. Understanding the timing and distribution of focused fluid migration pathways is important for assessing reservoir seal quality and hydrocarbon exploration risk, as well as seafloor biogeochemical processes in the case of fluid venting from the seafloor. The frontier Canterbury Basin southeast of New Zealand is well studied, but questions remain regarding the dynamic movement of fluids through the basin. Using 3D seismic data combined with high-resolution boomer seismic data, we characterise focused fluid migration and sediment remobilisation events in the Canterbury Basin. We show how polygonal fault formation and nucleation is affected in the vicinity of vertically ascending fluids and sediments. A cylindrical region devoid of polygonal faulting around the feeder system of a buried sediment volcano points to the possible existence of an axisymmetrical stress field induced by upward migrating fluids and sediments. Sediment remobilisation and intrusions of permeable stingers (i.e. sand injectites) could enable dewatering of their host strata and thereby prevent polygonal faults from nucleating. Amplitude variations with angle (AVA) and a detailed analysis of two tiers of polygonal faults reveal three phases of fluid migration and sediment remobilisation and intrusion through, and into, low permeability sediments. Our integrated conceptual model provides insights into vertical fluid migration mechanisms and the implications for polygonal fault formation. • Cylindrical faults surround a fluid conduit in a 2 km radius. • Polygonal faults don't nucleate within a cylindrical region around a fluid conduit. • Buried pockmarks formed on the upper tips of polygonal faults. • Shallow bright spots form beneath present day seafloor pockmarks. • Radial faults within a polygonal fault system form around buried Mounds. [ABSTRACT FROM AUTHOR]

• Blueschist from serpentine mud volcano in Mariana forearc is ca. 50 Ma old. • The mineral assemblage records warm metamorphic conditions during IBM subduction initiation. • Blueschist rocks have resided in the subduction channel for at least 46 Ma. From ca. 50 Ma to present, the western Pacific plate has been subducting under the Philippine Sea plate, forming the oceanic Izu-Bonin-Mariana (IBM) subduction system. It is the only known location where subduction zone products are presently being transported to the surface by serpentinite-mud volcanoes. A large serpentine mud "volcano" forms the South Chamorro Seamount and was successfully drilled by ODP during Leg 195. This returned mostly partially serpentinized harzburgites enclosed in serpentinite muds. In addition, limited numbers of small (1 mm–1 cm) fragments of rare blueschists were also discovered. U–Pb dating of zircon and rutile from one of these blueschist clasts give ages of 51.1 ± 1.2 Ma and 47.5 ± 2.0 Ma, respectively. These are interpreted to date prograde high-pressure metamorphism. Mineral equilibria modelling of the blueschist clast suggests the mineral assemblage formed at conditions of ∼1.6 GPa and ∼590 °C. We interpret that this high-pressure assemblage formed at a depth of ∼50 km within the subduction channel and was subsequently exhumed and entrained into the South Chamorro serpentinite volcano system at depths of ∼27 km. Consequently, we propose that the material erupted from the South Chamarro Seamount may be sampling far greater depths within the Mariana subduction system than previously thought. The apparent thermal gradient implied by the pressure–temperature modelling (∼370 °C/GPa) is slightly warmer than that predicted by typical subduction channel numerical models and other blueschists worldwide. The age of the blueschist suggests it formed during the arc initiation stages of the proto-Izu-Bonin-Mariana arc, with the P – T conditions recording thermally elevated conditions during initial stages of western Pacific plate subduction. This indicates the blueschist had prolonged residence time in the stable forearc as the system underwent east-directed rollback. The Mariana blueschist shows that subduction products can remain entrained in subduction channels for many millions of years prior to exhumation. [ABSTRACT FROM AUTHOR]

Submarine mud volcanoes (MVs) along continental margins emit mud breccia and globally significant amounts of hydrocarbon-rich fluids from the subsurface, and host distinct chemosynthetic communities of microbes and macrofauna. Venere MV lies at 1,600 m water depth in the Ionian Sea offshore Italy and is located in a forearc basin of the Calabrian accretionary prism. Porewaters of recently extruded mud breccia flowing from its west summit are considerably fresher than seawater (10 PSU), high in Li+ and B (up to 300 and 8,000 μM, respectively), and strongly depleted in K+ (<1 mM) at depths as shallow as 20 cm below seafloor. These properties document upward transport of fluids sourced from >3 km below seafloor. 16S rRNA gene and metagenomic sequencing were used to characterize microbial community composition and gene content within deep-sourced mud breccia flow deposits as they become exposed to seawater along a downslope transect of Venere MV. Summit samples showed consistency in microbial community composition. However, beta-diversity increased markedly in communities from downslope cores, which were dominated by methyl- and methanotrophic genera of Gammaproteobacteria. Methane, sulfate, and chloride concentrations were minor but significant contributors to variation in community composition. Metagenomic analyses revealed differences in relative abundances of predicted protein categories between Venere MV and other subsurface microbial communities, characterizing MVs as windows into distinct deep biosphere habitats. [ABSTRACT FROM AUTHOR]

Among natural hazards, mud volcanoes can damage property and infrastructures and affect hillslope evolution at different spatial and temporal scales. The results of 10-year-long multidisciplinary investigations performed on a Roman-age archaeological site, La Rovina di Montegibbio, are presented, showing a peculiar example of mutual interplay between human settlement and geological forcing in the mud-volcanic environment. The site (350 m a.s.l.) lies at the termination of the upper Secchia River catchment, near the town of Sassuolo (Modena Province). Here, a 4-km-long mud volcano belt borders the Apennines chain front, comprising one of the most prominent mud volcanoes of Italy (Salsa di Montegibbio), and the still-active chain hinge tectonics gives origin to gas and oil seeps. Based on geological, geoarchaeological, palaeobotanical, geochemical, geophysical records and analytical data, we unravel the onset, the evolution and the abandonment of the settlement in relation to the existence of a previously unknown mud volcano, belonging to the larger Montegibbio mud volcano system. The damages affecting the Roman-age buildings record the ground deformations in the context of mud volcano tectonics. In particular, the pattern of faults set buried under the archaeological site is shown and compared with that of the main mud volcano conduit. At least two Roman-age eruptive episodes have been recorded, whose ejected muds are geochemically characterized. The first recorded eruption must be regarded as the reason for the initial location and function of the sacred ancient settlement. The final site abandonment was because of subsequent severe ground deformations affecting the hillslope as a consequence of mud volcano activity. [ABSTRACT FROM AUTHOR]

Mud volcanoes are significant indicators of neotectonic activity and have important research significance. Mud volcanoes can not only be used as an important index for the long‐term evaluation of oil and gas fields but are also an important symbol for locating gas hydrates in the seabed. Additionally, the eruption of mud volcanoes will affect drilling, pipe laying, and other projects, and the eruption of large amounts of methane gas can also cause greenhouse effects and climate change. The trigger mechanisms of mud volcanoes have always been a focus of debate among geologists. In recent years, many scholars have argued that mud volcanoes are triggered by earthquake activity. However, the stress and strain caused by earthquakes and their control mechanisms on the eruption of mud volcanoes still require further study. This paper is based on the calculated results of static stresses caused by the M5.5 Wusu earthquake of May 2, 1995, the M5.4 Shawan earthquake of January 9, 1996, the M5.3 Shihezi earthquake of February 14, 2003, and the M6.3 Xinyuan–Hejing earthquake of June 30, 2012, on the Horgos, Dushanzi, Aiqigou, and Baiyanggou mud volcanoes distributed in the southern margin of the Junggar Basin, NW China. The calculated static stresses, the earthquake response characteristics of these four groups of mud volcanoes, and the continuous observational data of the Horgos mud volcanoes showed that static stresses from these earthquakes did not reach the triggering threshold, though the mud volcanoes exhibited a good relationship with earthquakes. We speculate that static stress may not be the main triggering mechanism for the mud volcanoes and that the mechanisms of earthquake triggering may be divided into two types: (a) For a mud volcano in a critical state before an earthquake, dynamic stress changes may trigger eruption of the mud volcano by increasing permeability and mobilizing magma; (b) for mud volcanoes that have not yet reached the critical eruption state before an earthquake, both static and dynamic stresses play roles in their activities. [ABSTRACT FROM AUTHOR]

Mud volcanoes (MVs) are potential conduit migration pathways for deep thermogenic DOM. In this study, we investigated the dissolved organic matter (DOM) of porewater in a MV in the Canadian Beaufort Sea and compared dissolved organic carbon (DOC) and fluorescent DOM (FDOM) between the MV and a reference site (RS). The chemical and isotopic compositions (Cl−, δ18O and δD) of porewater from the MVs indicated that these fluids are derived from a mixture of seawater, meteoric water, and clay dehydration, causing a freshening of the porewaters. Interestingly, the porewaters in the MV exhibited DOC concentrations up to 14 times higher than those in the RS. This high DOC concentration was attributed to a higher concentration in the deep fluid moving upwards through the MV, and in minor part to processes such as particulate organic matter sulfate reduction, anaerobic oxidation of methane and higher biological activity in the MV sediments. The fluorescence results showed the presence of four components in both MV and RS sites, which included two humic-like, one microbial humic-like, and a protein-like component. All the four fluorescent components increased with depth, showing a good linear relationship with DOC. However, the DOC-normalized fluorescence in the porewater DOM was on average 3 to 7 times lower in the MV, suggesting that the DOM molecules have undergone thermogenic processes in the deep sediments, and that shallow processes do not affect significantly the FDOM composition. Our results highlight that fluids migrating from the deep sediment through the MV can be an important source of thermogenically altered DOM to the shallow sediments and overlaying water column. • Sources of mud volcano porewaters were identified by Cl−, δD, and δ18O • Porewaters in mud volcano sites had much higher DOC than those of reference site • Deep fluids and biological activity explain the high DOC in the mud volcano • Fluorescence results suggest that DOM has undergone thermogenic processes • DOC flux from mud volcano needs to be considered for deep water carbon cycles [ABSTRACT FROM AUTHOR]