Search

This paper is devoted to study of the issues of the seismic hazard and danger of mud volcanism in the Taman Peninsula in Krasnodar krai. The tectonic structure and the active tectonics directly responsible for strong earthquakes in the region are considered. Ruins of the ancient Greek city of Hermonassa and the city of Tmutarakan located above—the Saltovo–Mayak (Khazar) archaeological section have been studied. Traces of strong seismic events have been found in the ruins of both cities; some of them led to the abandonment of settlements by ancient inhabitants. The study results obtained for some volcanoes of the Taman Peninsula and their relation to certain active tectonic structures are reported. [ABSTRACT FROM AUTHOR]

The article is devoted to the study of the tectonic stress field of Southern Sakhalin on the basis of seismological, geological, tectonophysical, GPS and remote (satellite) methods. The most characteristic type of stress state for the South of Sakhalin is latitudinal — sublatitudinal horizontal compression. The field forming the morphology of the Pugachev and Yuzhno-Sakhalinsk mud volcanoes, as well as the shape of their lithoclastite fields, fully corresponds to the nature of this state, which is confirmed by the analysis of satellite images.The images were used to supplement the results of previous researchers on the study of the directions of the gryphon bands and to measure deformation of volcano lithoclastite fields. The Pugachev volcano lithoclastite fields bend strikes 25°, and that of the Yuzhno-Sakhalinsk mud volcano strikes 30°, which well corresponds to the regional tectonic stress field. The expediency of using remote (satellite) methods as an supplement to geological and geophysical methods, in particular borehole caliper, is shown.

The article in the journal "Frontiers in Earth Science" explores contemporary studies on cold seeps, hydrothermal vents, mud volcanoes, and related seafloor features. These features provide insights into deep processes that are typically inaccessible to scientists. The research emphasizes multidisciplinary approaches to studying seafloor fluid emissions, highlighting the importance of geologic, physical, chemical, and biological processes in these environments. The studies cover a wide range of topics, including microbial processes, fluid dynamics, mineralization, and the role of seafloor emissions in global biogeochemical cycles. [Extracted from the article]

We present new data on mud volcanism accompanied by gas emissions in Lake Baikal. Rupture deformations of the bottom with traces of erupted liquefied sediments were found at depths of 105.0–163.6 m in Malaya Kosa Bay and Goryachinskaya Bay in the North Baikal depression. The deposits, outcropped in the extended scarps and mud craters, are mainly represented by highly porous clays. Scarps of boulder–pebble sediments are occasionally encountered. The areas of mud volcanism are attributed to the zone of the North Baikal fault, indicating its current activity. Clays and the soft sediments covering them are disturbed, which indicates the recent eruption of gas-saturated fluid and mud. Cone-shaped edifices about 5 × 5 cm in size with a crater in a top were found in sediments at depths of 157–162 m in Goryachinskaya Bay. Similar gas plumes were revealed in Solontsovaya Bay along straight-line faults opposite the paleoseismic dislocation of the same name. It is necessary to continue studying the revealed shallow-water manifestations of mud volcanism and rupture deformations of the bottom by integrated geological and geophysical studies. [ABSTRACT FROM AUTHOR]

Sediments deposited into foreland basins can provide valuable insights related to the geological evolution of their hinterlands. Located in the peripheral foreland of the South Sistan Suture Zone (SE Iran), the Karvandar Basin exhibits a several‐kilometer‐thick shallow‐marine to continental clastic sedimentary sequence forming elongated sub‐circular synclines. These synclines overlie a mud‐dominated formation with exotic volcanic blocks that hosts one of Iran's largest mud volcano, known as Pirgel. In this study, we present a ∼3.5‐km‐thick magnetostratigraphic section and U‐Pb zircon ages of interlayered tuffs that constrain a depositional age of the Karvandar Basin of ∼24–17 Ma. Sandstone and microconglomerate framework analyses and paleocurrent directions suggest a first‐cycle active volcanic arc source to the northeast of the basin. We interpret the mud‐dominated lithology with volcanic blocks as an olistostrome originating from a similar source as the overlying clastic sequence. The deposition of the olistostrome is dated at ∼24.5 Ma by a U‐Pb calcite age from a coral block. The absence of large‐scale anticlines and the occurrence of angular unconformities suggest that the sub‐circular synclines in the Karvandar Basin formed by gravity‐driven downbuilding into the unconsolidated fluid‐saturated olistostrome, resembling salt‐related minibasins. Integrated results indicate that a late Oligocene to early Miocene Makran volcanic arc represents the source of the clastic sequence. Hence, our results provide new constraints on the initiation of arc volcanism related to the Makran subduction zone, predating earliest reported ages from the Mirabad pluton (19 Ma) to the northeast of the Karvandar Basin by ∼5 Myr. Key Points: A ∼3.5‐km‐thick section in the Karvandar foreland basin was sampled for magnetostratigraphy and sandstone framework analysisThe shallow‐marine to continental sequence (24–18 Ma) consists of first‐cycle volcanic lithics and overlays an olistostrome depositThe late Oligocene to early Miocene sequence represents the erosion product of a volcanic arc related to the Makran subduction [ABSTRACT FROM AUTHOR]

We present geochemical and mineralogical datasets for five new mud volcanoes in continental Azerbaijan (Hamamdagh and Bendovan) and the adjacent Caspian Sea (Khara-Zire, Garasu and Sangi-Mughan). The fluid ejects have a Na–Cl-type composition and are generated by the mixing of evaporated Caspian seawater and low- to high-salinity pore waters, as indicated by Br–B and Cl–B systematics and Na–K and SiO2 geo-thermometers. The fluids contain high concentrations of As, Ba, Cu, Si, Li, Sr and Zn (60 to 26,300 ppm), which are caused by surface evaporation, pyrite oxidation, ion exchange reactions and hydrocarbon maturation in Oligocene-Miocene 'Maykop' shales. The solid ejects comprise liquid, oily and brecciated mud, mud/claystones and sandstones. The mud heterogeneity of the volcanoes is related to the geological age and different sedimentological strata of the host rocks that the mud volcanoes pass through during their ascent. All ejects show evidence of chemical alterations via water–rock–gas reactions, such as feldspar weathering, smectite illitization and the precipitation of Fe-(hydr)oxides, calcite, calcian dolomite, kaolinite and smectite. The studied localities have petrographic similarities to northern extending mud volcano systems located on Bahar and Zenbil islands, which suggests that mud volcanoes in the Caspian Sea region are sourced from giant shallow mud chambers (~1–4 km depth) located in Productive Series strata. Our results document the complex architecture of the South Caspian Basin—the most prolific hydrocarbon region in the world. [ABSTRACT FROM AUTHOR]

Self‐ignition during the explosive eruption of mud volcanoes can create flames that in some cases reach heights that exceed hundreds of meters. To study the controls on electrical discharge in natural mud, we performed laboratory experiments using a shock‐tube apparatus to simulate explosive eruptions of mud. We vary the water content of the mud and proportions of fine particles. We measure electric discharge within a Faraday cage and we use a high‐speed video camera to image the eruption of mud and some of the electric discharge events. We find that (a) decreasing the proportion of fine particles and (b) increasing water content each suppress the number and magnitude of electric discharge events. Experimentally observed mud volcano lightning occurs where particles exit from the vent and within the jet of erupting particles. Plain Language Summary: Vigorous mud volcano eruptions are often accompanied by large flames, which are the result of the self‐ignition of natural gas blasted with the erupting mud. The mechanisms for this gas ignition are not yet understood. We study a potential self‐ignition mechanism: volcanic lightning. We erupt mud in a laboratory setting and measure the conditions that promote lightning. We find that dry mud and mud with abundant fine particles create more lightning. For safety reasons, we studied mud samples with argon as the carrier gas for the eruption but expect that if a flammable gas was used, the lightning could ignite the gas. Key Points: Laboratory experiments show that jets of erupting mud can create electric dischargeDecreasing the proportion of fine particles and increasing water content suppress number and magnitude of electric discharge eventsElectric discharge is one mechanism that may enable self‐ignition of hydrocarbons during explosive mud volcano eruptions [ABSTRACT FROM AUTHOR]

The Nirano Salse, known since the Roman Times, are one of the most beautiful and scenic mud volcanoes areas of Italy with thousands of visitors every year. In this work, we apply novel (for the context) hydrogeological techniques to characterize mud levels in the Salse by means of GPS-RTK positioning and continuous level logging within mud conduits. This is important to quantify the gas–liquid ratio in the conduits and evaluate the potential for dangerous abrupt mud eruptions. The results presented suggest that different mud levels in mud volcanoes clusters are due to the different gas–liquid ratio in the conduits and not necessarily exclude interconnection at depth, a hypothesis, on the other hand, that seems strengthened by mud level time series correlations. The presence of shallow aquifers at a depth of 5 to 30 m is also supported by our field data and allows us to delineate the boundaries of the shallow mud reservoir—pipes system and its overall shape. The shallow aquifers may provide a temporary storage for the ascending gas and when fluid pressure in these aquifers exceeds the tensional strength of the sedimentary rock, leakage of fluids to the surface would occur. In this case, if the gas–liquid ratio is high, mud volcanoes develop into tall gryphons and tend to have a discontinuous activity with sudden eruptions of mud after long periods of quiescence. This, together with the knowledge of shallow conduits localization has an important implication for site safety in proximity to the mud volcanoes. Our inferences based on mud level relationships to mud extrusion dynamics can be applied to lower risk in other mud volcanoes areas of the world with high geo-tourist visits, such as those of Trinidad, Azerbaijan, and Colombia. [ABSTRACT FROM AUTHOR]

This paper is a review of our work, an experimental study and simulation of seismic fields in volcanic structures using vibrators as sources of elastic waves. We review the results of experimental studies of mud volcanoes carried out by the Institute of Computational Mathematics and Mathematical Geophysics (ICM&MG) of the Siberian Branch (SB), Russian Academy of Sciences (RAS); by the Institute of Physics of the Earth (IPE), RAS; and by the Kuban State University in the Taman mud-volcanic province using vibrators. We have carried out mathematical simulation in heterogeneous geophysical media to refine the information on the structure of the object under investigation, as well as on the distinguishing features of the seismic field. We have developed a mathematical approach to deal with the simulation of vibroseismic probing of mud volcanoes with arbitrary geometries incorporating knowledge of deep-seated faults, overlapping layers, and so on. Numerical techniques were used to solve sets of equations in elasticity theory and to develop parallel algorithms, program packages, as well as carrying out numerical experiments in high-performance computational systems. We present results from calculations of the seismic field for the source zone of the Shugo mud volcano. This paper describes 3D and 2D geophysical models developed for this study and the results of simulation for the seismic field of the Karabetova Gora mud volcano and for the Elbrus magmatic volcano. It is shown that the approach developed here using active vibroseismic techniques can be successfully used in practice to refine the seismic field, the deep structure of geophysical models, and to study the effects exerted by the geometry of a magma chamber and by the presence of erupting channels on data acquired by an observation system on the ground surface. These studies prove that vibroseismic sources with high accuracies of periodic excitation can be used to study volcanic structures and to conduct active monitoring of volcanic activity. [ABSTRACT FROM AUTHOR]

The success of recently developed geological and geophysical methods and technologies for monitoring of mud volcanoes in the Kerch-Taman region is eventually based on the fundamental scientific results accumulated at the turn of the century under the overall leadership of the Academician E.F. Shnyukov. The results of geological and geophysical studies of the Mount Karabetov mud volcano (Taman Peninsula) featuring the passive seismoacoustic sounding method are presented. New data on the spatial configuration of subvertical fluid-saturated structures associated with the volcano's feeding system were obtained. Subsequent common interpretation of the geophysical data and the results of the structural-geomorphologic observations allowed one to formulate a consistent hypothesis on the possible deep mechanism of mud volcanic activity responsible for the mostly paroxysmal nature of eruptions of the Mount Karabetov.

The article discusses the morphology and material composition of seasonal minerals of mud volcanoes in Azerbaijan Mud volcanism is a complex and rather unexplored geological phenomenon. Mud volcanoes are known in Turkmenistan, Dagestan, Georgia, Sakhalin, Taman Peninsula, Crimea, Azerbaijan and many regions of the World. In the geological literature, this phenomenon has been widely reflected. The bibliography of scientific works on mud volcanism has hundreds of titles. One of the classic areas of mud volcano development is Azerbaijan. In the process of geological research in recent decades, a huge geological material has been accumulated on the mud volcanism of Azerbaijan. The described types of mud volcanoes eruptions and the material composition of the mound breccia, it was possible to discover new interesting facts of unusual mineralogical finds. Of particular interest are authigenic minerals formed directly from the water phase of mud volcanoes and are seasonal. Their formation indicates that mineral formation processes are active in these natural sites. The occurrence of seasonal minerals is controlled by several factors, including the climatic conditions of the region. Main part of such minerals crystallizes only in dry and warm weather, which makes their systematic research much more difficult. The sodium hydroxide described in the article, which is very unstable under natural conditions, is a confirmation of this. However, even for a short interval of the existence of seasonal minerals, studying the features of their composition, one can obtain important information for genetic constructions. In addition to exogenous minerals of the weathering zone, the article also describes molybdenite associated with hydrothermal processes. The study of the mineral component of both endogenous and exogenous processes makes it possible to assess their evolution, the direction of the geological development of mud volcanoes in the region.

Most mud volcanoes are located along large tectonic zones within the Alpine and Central Asian folded regions, the Pacific mobile belt and rift regions of the Atlantic and Indian oceans. One of the basic conditions for the functioning of the mobile crust of mud volcanic processes in the earth's crust is the location and creasing into folds of the complex of sedimentary formations. It is these geological conditions that determine the activity of many mud volcanoes within the Kerch-Taman mud volcanic province, including the mud volcano Shugo. Long-term studies of the phenomenon of mud volcanism, carried out under the guidance and with the direct participation of Academician Ye.F. Shnyukov created the fundamental foundations of a geological and geophysical approach to a deeper understanding of the conditions of formation and mechanisms of activity of the volcanoes of the Kerch and Taman Peninsulas. This work is devoted to the results of seismological and geoacoustic studies of the Shugo volcano, expanding our ideas about the features of the deep structure of the studied object and contributing to the further development of the ideas of the outstanding scientist, academician of the National Academy of Sciences of Ukraine Ye.F. Shnyukov.

Recent studies of the stress state of the Earth's crust and rates of plate movement of the Caucasian fold system with respect to the Eurasian continent, analysis of sources of underwater degassing and volcanism, as well as seismological modeling, suggest that combination of these processes has a positive effect on replenishment of hydrocarbon resources in the Black Sea–Caspian Sea region: they activate the fluid–dynamic systems of the region. The replenishment of hydrocarbon resources is associated with restoration of the energy state of hydrocarbon deposits at various stages of their development and physicochemical fluid–dynamic factors. The broad generalization, seismological modeling of mud volcanoes, and analysis of different-scale factual material allow us to argue that current sources of hydrocarbon generation–natural laboratories and technological lines for converting fluid accumulations into industrial energy and chemical raw materials for industrial application are functioning in the depths of the Black Sea–Caspian Sea region. We consider hydrocarbon deposits as a product of the functioning of such natural, technological lines. [ABSTRACT FROM AUTHOR]

It has been determined that the content of dissolved fluorides in waters of 13 mud volcanoes of the Kerch-Taman Region varies within 0.13–2.00 mg/L and averages 0.87 mg/L (n = 37). We have revealed a rather close correlation of the fluorine concentration with pH (r = 0.80) and the absence of its relationship with the mineralization and the content of components of the basic salt composition. It is suggested that the fluorine concentration in mud-volcano waters is controlled by the exchange reaction + OH– = F– + , where and are the contents of adsorbed and structural fluorine (hydroxyl ions) in clay minerals, and F– and OH– are the concentrations of fluorides (hydroxyl ions) in the water phase. [ABSTRACT FROM AUTHOR]

Identifying the mechanism and formation time of a mud volcano is one of the most debatable issues concerning the geological phenomenon of mud volcanism. As of now, the use of 3D seismic data is a unique technique that allows documenting the main formation stages of mud volcanism and revealing the connection of this process with the formation of hydrocarbon deposits in the South Caspian Basin (SCB). It is shown that the formation of mud volcanoes began after the accumulation of the Maikop (Oligocene–Lower Miocene) series stratum and continued in parallel with the deposition of sediments. As the thickness of the sedimentary cover increased, mud volcanoes periodically became active. A paragenetic relationship may perhaps exist between the formation of mud volcanoes and the formation of petroleum hydrocarbons. [ABSTRACT FROM AUTHOR]

This paper presents the results of areal seismic studies in the deep structure of the Dzhau Tepe mud volcano, which is the largest of its kind on the Kerch Peninsula. It is the first time that data has been obtained concerning nearly vertical fluid-conducting structures beneath the volcano that supply material onto the ground during more active periods. A new approach is proposed for interpretation of measured relative amplitudes of microseismic noise based on numerical simulation of plane-stratified media. The results derived in this study are compared with previous geological and geophysical data on the area. [ABSTRACT FROM AUTHOR]

Oblique convergent margins accumulate strike‐slip deformation that controls basin formation and evolution. The Bahia Basin is located offshore, proximal to major strike‐slip fault systems that affect northern Colombia. It lies behind the toe of the modern accretionary prism, where the Caribbean Plate is being subducted obliquely beneath South America. This is the first attempt using 3‐D seismic reflection data to interpret a complex strike‐slip basin at the western end of the southern margin of the Caribbean Plate. Detailed 2‐D and 3‐D seismic mapping of regional unconformities and faults is used to describe the structural geometry, timing, and evolution of extensional and strike‐slip faults, which controlled the formation of the basin. Analysis of the fault zones is coupled with a description of the seismic‐stratigraphic units observed within the Bahia Basin to reconstruct the spatial and temporal evolution of deformation and to evaluate the influence of the pervasive shale tectonics observed in the area. The results, presented as a series of structural‐paleogeographic maps, illustrate an initial stage of transtension that controlled the formation of shale‐withdrawal minibasins from late Oligocene to late Miocene times. The continuous deformation and northward expulsion of the Santa Marta Massif resulted in transpression during Pliocene times, leading to basin inversion and ultimate closure of the basin. Basin evolution along the southern Caribbean oblique, convergent margin, shows the occurrence of a complex interaction between subduction and major‐onshore strike‐slip fault systems and illustrates how strain‐partitioning led to the break‐up and lateral displacement of early accretionary prisms formed along the margin. Key Points: In response to oblique convergence, strike‐slip deformation occurs at the rear of the South Caribbean Deformed Belt and controls the evolution of the Bahia BasinStrike‐slip deformation and sediment loading triggered the movement of overpressured shale, creating mud‐withdrawal minibasinsStrain‐partitioning led to the break‐up and lateral displacement of accretionary prisms formed along the margin, opening the space for depocenters [ABSTRACT FROM AUTHOR]

Abstract An elongated, flat-floored basin, located in the northern part of Terra Sirenum on Mars, holds numerous enigmatic mounds (100 m wide) on the surface of its floor. We investigated their geological context, spatial distribution, morphological characteristics, and morphometric parameters by analyzing a variety of current remote sensing data sets of Mars. Over 700 mounds are identified; mapping of the mounds shows the spatial density of about 21 per 100 km2 and appearances of several clusters, coalescence, and/or alignment. Most of the mounds have smoother surface textures in contrast to the rugged surrounding terrain. Some of the mounds display depressions on their summits, meter-sized boulders on their flanks, and distinct lobate features. We also perform high-resolution topographic analysis on 50 isolated mounds, which reveals that their heights range from 6 to 43 m with a mean of 18 m and average flank slopes of most mounds are below 10°. These characteristics are consistent with the deposition and extension of mud slurries with mud breccia and gases extruded from subsurface, almost equivalent to terrestrial mud volcanism. If so, both abundance of groundwater and abrupt increase in pore fluid pressure are necessary for triggering mud eruption. Absolute crater retention ages suggest that the floor of the basin located among middle Noachian-aged highland terrains has been resurfaced during the Late Hesperian Epoch. Because of cross-cutting relationships with the basin and the mounds superposed on the basin floor, the faults and fissures (part of Memnonia Fossae) are thought to have formed during and/or after the period of mound formation. Compressional stress fields which likely formed Memnonia Fossae and Mangala Valles, expected from the dike emplacement model of Wilson and Head (JGR 107:1-1–1-24, 2002), may have facilitated undercompaction or overpressurization of subsurface fluids, focused pore fluids beneath the basin, and opened conduits along faults for upwelling voluminous sediments and fluids.

Numerous mud volcanoes (MVs) of the Kerch Peninsula emit water and mud with extreme boron enrichment. Boron content correlates with the burial depth of the source Oligo-Miocene Maykop mudrocks yielding the highest boron contents in illite-dominated mud (up to ~900–1500 ppm B) and clay fractions found in the Bulganak MV, which represent the deep endmembers (up to 3.5 km) in the Kerch Peninsula. Smectite-dominated mud and clay fractions from shallow depths (1–1.5 km) at small MVs are poorer in both illite and boron (66–250 ppm). B-enrichment of the parent shale and diagenetically-driven smectite illitization and dewatering may be main prerequisites for boron enrichment in MVs. The majority of both Cl-HCO 3 /Na and HCO 3 -Cl/Na highly evolved saline MV waters sampled in large MVs are enriched in 18O (δ18O = +9.8 to +14.5‰ VSMOW) and D (δD = −30 to −4‰ VSMOW) isotopes being also rich in boron (average 650 ppm). Waters of small MVs with shallow roots are poorer in 18О (δ18O = +3.6 to +6.1‰ VSMOW) and B (average 130 ppm). MV waters are mainly related to diagenetically altered basinal water diluted by 18O-enriched fresh water released during smectite illitization. The fluid generation temperatures inferred to be Т Mg/Li = 34 to 117 °С correspond to source depths of 1.0 to 3.5 km, at 30–35 °C/km regional geothermal gradients. In the hot season, MV waters reach a salinity of 40–70 g/L total dissolved solids and precipitate halite, ulexite, borax and tincalconite. At the Bulganak MV field, there is a unique accumulation of MV-related non-marine borates. Such borate deposits can form at the following essential conditions: venting of B-rich MV waters; environment akin to playa lake; long dry and hot seasons; evaporation and ensuing increased boron concentration in shallow close MV pools; pH of MV water between 8.5 and 9.5; low permeability of clayey mud cover. Unlabelled Image • Mud, clay fractions, and fluids of the Kerch mud volcanoes are rich in boron. • The B content in mud increases proportionally to illite percentage. • Onshore mud volcanism produces Na and Na-Ca borate accumulations. [ABSTRACT FROM AUTHOR]

Studies in paleomagnetism, structural geology, and paleontology (mammals, mollusks, palynology) in the coastal sections of the Taman Peninsula north-western part (2017–18) resulted in definition of three sedimentary sequences. The sandy and clayey lower sequence (I) formed at 2.1–1.7 Ma. It contains a normally magnetised zone within deposits of reversed polarity correlated to the Olduvai Subchron and the Matuyama Chron. The middle sequence (II) is composed of the basal pebbles overlain by sands. The reversely magnetised deposits hosting the Sinyaya Balka site, the type locality of the Tamanian faunal complex, is correlated to the basal bed of the middle sequence II. The overlying sands are normally magnetised (Jaramillo Subchron) in the lower part and show reverse polarity (late Matuyama Chron) in the upper part. The sequence II is dated in the range of 1.3–0.78 Ma. The silty upper sequence (III) represents Middle-Late Pleistocene. The dissimilar displacement degree of the sequences reflect developmental stages of the Quaternary deformation. The sequence I is characterised by dip angles up to 70° is fragmented by faults into blocks. The sequence II filled the relief of the eroded surface of the sequence Member I and also displaced by faults. The faulting separated the bone-bearing body of the Taman faunal complex as a rock land-slide. The attitude of the member III outline an anticline with a gentle south-western and a steeper north-eastern limbs eroded by land-slides and marine abrasion. During its entire life the anticline was affected by mud volcanism. The anticline continues its development at the present stage. [ABSTRACT FROM AUTHOR]

Seismic studies of serpentinite seamounts in the outer forearc of the Mariana subduction zone can provide constraints on the structure and development of these large edifices. We present the seismic velocity structure of the Fantangisña, formerly Celestial, mud volcano obtained by the downward continuation of multichannel seismic reflection data and first arrival tomographic inversion; the P -wave velocity model is well constrained to ∼1.5 km depth below the seafloor with a spatial resolution of 400–800 m. We identify a low velocity, 1720–2500 m s−1, sediment unit which is 500 m thick at the summit, and varies between 200 and 1000 m on the flanks of the volcano. Deeper seismic velocities increase to >3500  m s−1 below the summit and >4000 m s−1 beneath the flanks. The thickest, 1000 m, low velocity sediment, which represents less consolidated rocks occurs below the southeast flank resulting in an asymmetric velocity structure at depth. By integrating the velocity model with the coincident migrated seismic reflection image, we infer that the seamount was probably formed from serpentinite fluid upwelling through a central conduit, as previously proposed, and likely experienced episodic slope failures during its evolution that resulted in debris flows that formed mud mounds adjacent to the volcano. A small nearby dome on the seafloor may also be a mud volcano related to fluid flow along an underlying fault. [ABSTRACT FROM AUTHOR]

Mud volcanism is known to be strictly linked to tectonic structures, since they have the ability to trap hydrocarbon and other fluids, and eventually induce them to migrate from a deep reservoir (e.g. sited into an anticline core, where large overpressures may be generated), to the surface. A central theme is how fluids can migrate upward, and which is the role in this process of near structures (i.e. structures directly controlling the mud volcano system) and far structures (i.e. faults located far away from the mud volcano system). In this study, we investigate the role of both types of structures in the genesis and evolution of mud volcanoes. In particular, we investigate six mud volcano case studies from the Emilia-Romagna and Marche Pede–Apennine margin, in Italy, through integration of fieldwork, interpretation of available seismic reflection profiles and aerial photos. The results of these analyses support an intimate link of the investigated mud volcanoes with anticline structures. We discuss two different fluid migration settings, particularly (i) mud volcanoes emplaced on outcropping anticlines, and (ii) mud volcanoes located on top of buried structures, discerning when fluids are likely to exploit anticline-related fracture sets, or secondary structures and porosity. Finally, we speculate on how far structures, via the seismic triggering, may play a role in the occurrence of historical eruption of some of the investigated mud volcanoes. [ABSTRACT FROM AUTHOR]

The Gulf of Cadiz is characterized by extensive active and inactive fluid escape structures which manifest as mud volcanoes, diapiric ridges, pockmarks and cold seeps. The high methane content and the presence of gas hydrates in the shallow sediments of the most active fluid escape structures indicate that these are areas of preferential migration and escape of fluids enriched in hydrocarbons and methane. Extensive fields of methane-derived authigenic carbonates are found at fluid escape structures along the upper and mid-continental slope, where the Mediterranean Outflow water is in direct contact with the seafloor, at water depths generally <1400 m. These methane-derived authigenic carbonates occur in much higher abundance at these shallower depths than in the fluid escape structures of the deeper (>1400 m) parts of the basin. The estimated U/Th ages of the authigenic carbonates, suggest that they were probably formed during discrete episodes of gas hydrate activity that may have occurred as a result of rapid climatic changes (such as the termination of the last glacial stage.) Numerical modelling indicates that seafloor temperature variations, associated with glacial/interglacial cycles and the changes of the Mediterranean Outflow pathway, could have restricted or eliminated the gas hydrate stability zone at the mud volcanoes shallower than 1400 m, resulting in intense fluxes of methane-rich fluids to the shallow sediments or even the seafloor. This fluid flux was recorded by the microbially mediated precipitation of authigenic carbonates. • Authigenic carbonates are abundant at shallow mud volcanoes in the Gulf of Cadiz. • Mediterranean Outflow water is in direct contact with the seafloor at these sites. • Changes of the Mediterranean Outflow can destabilize gas hydrates at these sites. • Destabilization of gas hydrates promotes higher fluxes of methane-rich fluids. • High methane fluxes promote the precipitation of the authigenic carbonates. [ABSTRACT FROM AUTHOR]

The southern part of the smooth plain of Chryse Planitia on Mars hosts a large population of kilometer‐sized (from ~0.2 to ~20 km) landforms spread over a wide area. Based on the investigation of a small part of this area, Komatsu et al. (2016, https://doi.org/10.1016/j.icarus.2015.12.032) proposed that the edifices may be the result of the subsurface sediment mobilization. We mapped the full extent of these landforms within Chryse Planitia and performed a morphological and spatial analysis in an attempt to further test this hypothesis. We identified a total number of 1,318 of these objects, which we grouped into five different morphological classes. The edifices can be observed over an area of 700,000 km2 near the termini of the large outflow channels, Ares, Simud, and Tiu Valles, with a nonrandom spatial distribution. The features are clustered and anticorrelated to the ancient highlands, which form erosional remnants shaped by the outflow events. This suggests a genetic link between the distribution of the edifices and the presence of the sedimentary deposits on which they are superposed. Such distribution is consistent with the previous notion that subsurface sediment mobilization may be the mechanism for their formation and is less consistent with the alternative igneous volcanic hypothesis. We also propose a scenario in which the large morphologic variability can be explained by variations of the water content within the ascending mud and by variations in the effusion rates. The edifices may represent one of the most prominent fields of sedimentary volcanism detected on Mars. Plain language summary: Ever since the presence of methane in the Martian atmosphere was reported from ground‐based, orbital, and in situ observations, mud volcanism was hypothesized to be a possible release mechanism, and various mud volcano fields have been tentatively identified. Although morphological similarities with Earth sedimentary volcanism have been proposed (e.g., Skinner & Mazzini, 2009, https://doi.org/10.1016/j.marpetgeo.2009.02.006), it is difficult, however, to prove unambiguously the presence of mud volcanism in remote sensing data, and some of the reported mud volcanoes have alternatively been interpreted as igneous volcanoes. A definitive identification of sedimentary volcanoes on Mars is therefore still problematic. A useful candidate area to test the hypothesis of sedimentary volcanism on Mars is a field of kilometer‐sized cone‐ and pie‐like landforms in the southern part of the large ancient Chryse impact basin, part of which was previously studied by Komatsu et al. (2016, https://doi.org/10.1016/j.icarus.2015.12.032). In this study, we searched for those landforms inside Chryse Planitia and determined their full spatial extent. We found that they can be divided into five morphologically different groups and that they occur exclusively on the level sedimentary plains. These findings enable us providing additional evidence to support the hypothesis of subsurface sediment mobilization as a possible mechanism for their formation. Key Points: Southern Chryse Planitia contains a large field of Amazonian‐aged extrusive landforms, which can be grouped into five classesThey are exclusively located in the sedimentary plains between erosional remnants suggesting that they were formed by sedimentary volcanismThe variability in shapes can be explained by properties of the mud and environment [ABSTRACT FROM AUTHOR]

Abstract Mud Volcanism and fluid seepage are widespread phenomena in the Gulf of Cadiz (SW Iberian Margin). In this seismically active region located at the boundary between the African and Eurasian plates, fluid flow is typically focused on deeply rooted active strike-slip faults. The geochemical signature of emanating fluids from various mud volcanoes (MVs) has been interpreted as being largely affected by clay mineral dehydration and recrystallization of Upper Jurassic carbonates. Here we present the results of a novel, fully-coupled 1D basin-scale reactive-transport model capable of simulating major fluid forming processes and related geochemical signatures by considering the growth of the sediment column over time, compaction of sediments, diffusion and advection of fluids, as well as convective and conductive heat flow. The outcome of the model is a realistic approximation to the development of the sediment pore water system over geological time scales in the Gulf of Cadiz. Combined with a geochemical reaction transport model for clay mineral dehydration and calcium carbonate recrystallization, we were able to reproduce measured concentrations of Cl, strontium and 87Sr/86Sr of emanating mud volcano fluids. These results support previously made qualitative interpretations and add further constraints on fluid forming processes, reaction rates and source depths. The geochemical signature at Porto MV posed a specific problem, because of insufficient constraints on non-radiogenic 87Sr/86Sr sources at this location. We favour a scenario of basement-derived fluid injection into basal Upper Jurassic carbonate deposits (Hensen et al., 2015). Although the mechanism behind such basement-derived flow, e.g. along permeable faults, remains speculative at this stage, it provides an additional source of low 87Sr/86Sr fluids and offers an idea on how formation water from the deepest sedimentary strata above the basement can be mobilized and eventually initiate the advection of fluids feeding MVs at the seafloor. The dynamic reactive-transport model presented in this study provides a new tool addressing the combined simulation of complex physical-geochemical processes in sedimentary systems. The model can easily be extended and applied to similar geological settings, and thus help us to provide a fundamental understanding of fluid dynamics and element recycling in sedimentary basins. [ABSTRACT FROM AUTHOR]

Mud volcanoes in the Mediterranean Sea have been subject of scientific research since the 1970s and contributed to the understanding of these seafloor features and their role in the subduction budgets worldwide. Recently, the need to better characterize the connection of these mud volcanoes with the deeper lithologies of the accretionary prism and its implications led to expedition POS410 (2011) and SO278 (2020). During these expeditions, mud volcanoes which had been investigated in ODP Leg 160 (1996) were resampled and complemented with new sites along the Mediterranean Ridge accretionary complex. We present pore water data from six mud volcanoes and two brine pools in and around the Olimpi Mud Volcano Field (OMVF). The data highlight strong depletion in Cl (<200 mM), Na (∼200 mM), Mg and K (with concentrations ∼0 mM) and striking water isotope ratios (δ18O of +9.79‰ V-SMOW and δD of −26.33‰ V-SMOW), indicating dehydration of clay minerals at depth. At five locations, the interstitial waters are characterized by extremely high salinities (Cl > 5000 mM and Na >6500 mM), therefore drastically expanding the previous reports of highly saline pore waters in the OMVF. The measurements further reveal that Gelendzhik mud volcano, located in the western part of the OMVF along a major strike-slip fault, shows an unusual pore water downcore profile and its water isotopes signature differ strongly from the other structures (δ18O of +13.63‰ and δD of +1.83‰). Upon further investigation through XRF scans and hydrates stability calculations we tied the anomalous low salinity values of the Gelendzhik MV pore waters results from the presence of gas hydrates in the sediments. This is the first, indirect evidence of gas hydrates in the OMVF, several years after this hypothesis was formulated by De Lange and Brumsack (1998) and then quickly discarded. • Major- and minor-elements and water-isotopes of pore waters from six MVs and two brine pools of the OMVF have been analysed. • Three fluid sources (seawater, clay mineral dehydration and highly saline fluids) reveal different mixing processes. • First evidence of highly saline fluids from pore waters of Gelendzhik and Heraklion MVs. • Unusual pore water profiles obtained from Gelendzhik MV clearly point to dissociation of gas hydrates in its sediments. [ABSTRACT FROM AUTHOR]

The Dongsha waters of the South China Sea are the location of thick Mesozoic deposits and many mud volcanoes that suggest hydrocarbon accumulation. Knowledge of the mechanism, fluid source and evolution of these mud volcanoes, however, remains inadequate. Ferromanganese nodules have been sampled from several deep-water mud volcanoes in waters around Southeast Dongsha island and provide a unique opportunity to study the fluid origin and evolution of the mud volcanoes in the area. In this contribution, the petrology, geochemistry and C–O isotopes of fluid inclusions in the nodules have been analyzed. The ferromanganese nodules are composed of distinct black Fe–Mn crust layers and light-yellow nucleus that contain quartz that hosts fluid inclusions. The outermost layers mainly consist of iron manganese minerals with high Mn/Fe ratios (0.9∼1.57), whereas the nucleus are dominated by siliceous debris. Positive Ce anomalies (δCe: 1.45∼2.13) and negative Y anomalies in growth layers indicate an anoxic environment, which is conducive to hydromanganite precipitation. In contrast, negative Ce anomalies (δCe: 0.27∼0.96) and positive Y anomalies in the nucleus suggest oxidized conditions. The absence of obvious Eu anomalies may be related to low-temperature hydrothermal conditions. The nucleus is enriched in δ13C (−2.59∼1.09‰) and weakly depleted in δ18O (−4.94∼0.89‰), whereas the growth layers are strongly depleted both in δ13C (−16.94∼–12.57‰) and δ18O (−23.05∼–17.48‰). These values indicate that carbon in the nucleus is mainly inorganic carbon from volcanism, whereas the carbon in the growth layers is related to the leakage of deep old hydrocarbon. The fluid inclusions in the quartz from the nucleus show records of at least two periods of CO 2 -rich hydrothermal activity and an origin from deep Mesozoic strata before release by mud volcanism. Given the widespread mud volcanism, the quartz from the nucleus may come from debris carried by mud volcano eruptions; the quartz also experienced diagenesis related with micro-organisms. The growth layers are considered to be hydrogenic and affected by the leakage of mature thermogenic hydrocarbons from deep old strata. These findings provide insights into deep mature hydrocarbon sources and thermogenic activity and improve understanding of mud volcanism and deep oil and gas resources in the southeastern Dongsha waters. • The ferromanganese nodules have been discovered in eruption vent of mud volcanoes developed in northern margin of South China Sea. • The edge crusts of the ferromanganese nodules enriched in Fe2+ and Mn2+ reflecting anaerobic oxidation environment is hydrogenic. • The nucleus of the ferromanganese nodules enriched quartz with multi-stage CO 2 -rich hot fluid inclusions may carried by mud volcano eruption. • Strongly depleted δ13C and δ18O in crusts of the ferromanganese nodules related to the mature hydrocarbon rich fluid ventingof mud volcanoes. [ABSTRACT FROM AUTHOR]

Abstract: Since 2004, there have been three great interplate earthquakes (Mw > 8.0) offshore Sumatra. In addition to rupturing the megathrust, these earthquakes might also have ruptured the backthrusts that bound the Andaman Islands to the Mentawai Islands toward the forearc basins. Here we apply a combination of traveltime tomography and seismic full waveform inversion to an ultralong offset seismic reflection profile from the Mentawai forearc basin, in the region of the 2007 Mw 8.4 Bengkulu earthquake. We perform a waveform inversion of far‐offset data followed by a waveform inversion of near‐offset data using the starting model derived from the traveltime tomography. Our results show the presence of a large, low‐velocity anomaly above the backthrust. The seismic reflection image indicates that this low‐velocity anomaly lies either within highly compacted sediments from the accretionary wedge or within highly deformed sediments from the forearc basin. The porosity estimation, using the effective medium theory, suggests that a small amount of gas (from 2 to 13%) or a significant amount of fluid (from 17 to 40%) could generate this low‐velocity zone. The presence of fluids and the observation of bottom simulating reflector below a push‐up ridge might be associated with mud diapirism. The fluids could originate locally from the dewatering of the sediments from the accretionary wedge or forearc basin. The high reflectivity of the backthrust in this region might also indicate deeper fluid origin, either from underplated sediments on the subduction interface or from the serpentinized mantle wedge. [ABSTRACT FROM AUTHOR]

ᅟ: An elongated, flat-floored basin, located in the northern part of Terra Sirenum on Mars, holds numerous enigmatic mounds (100 m wide) on the surface of its floor. We investigated their geological context, spatial distribution, morphological characteristics, and morphometric parameters by analyzing a variety of current remote sensing data sets of Mars. Over 700 mounds are identified; mapping of the mounds shows the spatial density of about 21 per 100 km and appearances of several clusters, coalescence, and/or alignment. Most of the mounds have smoother surface textures in contrast to the rugged surrounding terrain. Some of the mounds display depressions on their summits, meter-sized boulders on their flanks, and distinct lobate features. We also perform high-resolution topographic analysis on 50 isolated mounds, which reveals that their heights range from 6 to 43 m with a mean of 18 m and average flank slopes of most mounds are below 10°. These characteristics are consistent with the deposition and extension of mud slurries with mud breccia and gases extruded from subsurface, almost equivalent to terrestrial mud volcanism. If so, both abundance of groundwater and abrupt increase in pore fluid pressure are necessary for triggering mud eruption. Absolute crater retention ages suggest that the floor of the basin located among middle Noachian-aged highland terrains has been resurfaced during the Late Hesperian Epoch. Because of cross-cutting relationships with the basin and the mounds superposed on the basin floor, the faults and fissures (part of Memnonia Fossae) are thought to have formed during and/or after the period of mound formation. Compressional stress fields which likely formed Memnonia Fossae and Mangala Valles, expected from the dike emplacement model of Wilson and Head (JGR 107:1-1-1-24, 2002), may have facilitated undercompaction or overpressurization of subsurface fluids, focused pore fluids beneath the basin, and opened conduits along faults for upwelling voluminous sediments and fluids. Graphical abstract: [ABSTRACT FROM AUTHOR]

This paper documents and describes through the use of 3D seismic data a prolific mud volcano province within the Eastern Mediterranean. As many as 386 mud volcanoes were mapped within the post-salt succession of the western slope of the Nile Cone, offshore Egypt, using high resolution 3D seismic data. The mud volcanoes within this field display significant geometrical variability in diameter (c. 550 m to c. 5660 m), height (c. 25 m to c. 510 m) and volume (c. 0.1 km 3 to c. 3.3 km 3 ) and lie at depths ranging from c. > 6000 m subsea to c. 3100 m at the seafloor. A close spatial relationship between mud volcanoes and base-salt depressions and regions of anomalous thinning within the immediate pre-salt succession, combined with documented core samples taken from mud volcanoes within this region present a powerful argument for a pre-salt source of mud. 3D seismic interpretation and volumetric analysis of these mud volcanoes and their source region permit the definition and quantification of their depletion zones. A conceptual model for a dynamic liquefaction and sediment withdrawal process is proposed whereby mud is fed into a central conduit as the depletion zone propagates radially and episodically outwards resulting in a the formation of a concentric depletion zones. Prolonged mud volcanism within this region over the last ∼5.3 Ma implies the potential for long lived pre-salt overpressure and continued mud volcanism following the catastrophic hydrodynamic impact of the Messinian Salinity Crisis. It is suggested that the scale of mud volcanism means that this region should be considered as among the largest mud volcano provinces in the world. [ABSTRACT FROM AUTHOR]

A northern ocean of Mars is still debated and, if it existed, it may have accompanied valley networks and/or outflow channels, which may have led to the emplacement of a large amount of water to the northern lowlands during the Noachian and/or Hesperian times. However, it is unclear how and under what conditions (submarine or subaerial) geologic features such as mounds and giant polygons formed in the northern lowlands. The densely-distributed mounds in Chryse and Acidalia Planitia, >1000 km-wide basins of the northern plains, were suggested to be ancient mud volcanoes formed in an aqueous setting, which is controversial (i.e., mud vs. igneous and submarine vs. subaerial). However, these mounds have not been quantitatively well characterized, particularly with respect to their detailed topography. Here we generated forty digital elevation models (DEMs) with resolution of up to 1 m/pixel from High Resolution Imaging Science Experiment (HiRISE) stereo image pairs, and we accurately measured the morphometric parameters of ~1300 mounds within the southern part of the Acidalia basin. Their heights and diameters resulted in good accordance with those of mud and igneous volcanoes in submarine/subaerial settings on Earth. Maximum depths of their source reservoirs vary from ~30 to ~450 m for a subaqueous setting and from ~110 to ~860 m for a subaerial setting, both of which are consistent with fluid expulsion from the ~100–4500 m-thick flood deposits (Vastitas Borealis Formation, VBF). On the basis of the morphometric values, we estimated rheological properties of materials forming the mounds and found them consistent with a mud flow origin, which does not rule out an igneous origin. The conditions of possible submarine mud or igneous volcanoes may have harbored less hazardous environments for past life on Mars than those on an ocean-free surface.

Mud extrusion is a well-known phenomenon whereby fluid-rich, fine grained sediments ascend within a lithological succession due to their buoyancy. In this study of the terrestrial mud volcanism associated to an active thrusted area in the northern Apennines, we investigated the effect of boron incorporation in illite crystalline lattice. A significant variation was recorded on the investigated mud samples with respect to both the amount of fixed boron (118–529 μg/g) and the full width at half-maximum height value (FWHM) of illite (0.29–0.62°Δ 2Θ). We attribute these variations to the interaction between boron-rich formation waters and the silty-clayey lithologies of the local sedimentary succession. The lack of any geographical correlation between the selected geochemical and mineralogical parameters is likely due to intensive thrust and fold deformation of the study area. Comparison of FWHM values with those from Dellisanti et al. (2008); Santerno succession, northern Apennine) lead us to suggest that application of FWHM as a depth indicator could be misleading within B-rich hydro-geological environments. [ABSTRACT FROM AUTHOR]