Active Mud Volcanoes Research Articles

Biogeochemical evidence of anaerobic methane oxidation on active submarine mud volcanoes on the continental slope of the Canadian Beaufort Sea

Abstract. In this study, we report lipid biomarker patterns and phylogenetic identities of key microbial communities mediating anaerobic oxidation of methane (AOM) in active mud volcanoes (MVs) on the continental slope of the Canadian Beaufort Sea. The carbon isotopic compositions (δ13C) of sn-2- and sn-3-hydroxyarchaeol showed the highly 13C-depleted values (−114 ‰ to −82 ‰) associated with a steep depletion in sulfate concentrations within 0.7 m of sediment depths. This suggested the presence of methanotrophic archaea involved in sulfate-dependent AOM, albeit in a small amount. The ratio of sn-2-hydroxyarchaeol to archaeol (> 1) and operational taxonomic units (OTUs) indicated that the anaerobic methanotrophic archaea (ANME) clades ANME-2c and ANME-3 were involved in AOM. Higher δ13C values of archaeol and biphytanes (BPs; -55.2±10.0 ‰ and -39.3±13.0 ‰, respectively) suggested that archaeal communities were also assimilating AOM-derived inorganic carbon. Furthermore, the distinct distribution patterns of methanotrophs in the three MVs appears to be associated with varying intensities of ascending gas fluids. Consequently, our results suggest that the niche diversification of active mud volcanoes has shaped distinct archaeal communities that play important roles in AOM in the Beaufort Sea.

Measurement of terrestrial radiation level in a neotectonic fault system in Trinidad

Present study area, which is located in the Central Range Fault (CRF) in the island of Trinidad, can provide solution to that problem as this strike-slip fault system is reported to be active in present time (during Holocene, most current geological epoch) with a movement of geodetic rate of 12 ± 3 mm/yr. Most recent work, with improved GPS time series analysis indicated that as creeping fault rather than locked fault. Moreover, the selected fault system is accompanied by mud volcanoes, which can amplify the level of radiation activity by slight but significant anomalies as described by some researchers from other areas. Furthermore, being one of the first environmental radiation study in the Caribbean Islands, this study is significant. With the aim to achieve a continuous monitoring of radiological data to assess the activity along CRF for possible earthquake forecasting, objectives of this preliminary investigation are to delineate CRFZ using radiation survey and to investigate the potential of using this survey to detect tectonic activities in this zone. As a pilot study, radiation measurements were carried out with the help of a portable Geiger Muller counter in 52 locations along the 25 km long section of CRF between Naved Dam and Pointe-a-Pierre. Radiation measurements were taken both at 1 m level above the surface and at nearly 1 m below the ground. Results from this pilot study showed that lithology was not the lone contributor to terrestrial radiation levels, as CRFZ and associated fissure plane have good control also (∼3–5 times higher than the average background level). Although present study was not able to indicate the possibility of earthquakes in recent times (as previously stated), however, elevated radiation values in the vicinity of CRF, associated fissures (possibly interconnected fractures) and active mud volcanoes indicate possible activity in the study area. However, detail and periodic radiological studies are required before concluding that CRF is a creep fault rather than a locked fault.

Recent, deep-sourced methane/mud discharge at the most active mud volcano in the western Mediterranean

Active mud volcanism in the West Alboran Basin (WAB) is closely associated with tectonically mobilized, overpressurized shales and shale-diapirism. This appears to control mud expulsion at Carmen mud volcano, a cone-shaped structure 65 m high and 1 km in basal diameter.The presence of gas-rich mud breccia, living chemosynthetic fauna, the absence of hemipelagic draping and the abrupt transition that occurs between high dissolved sulfate in the uppermost interval and low sulfate together with high methane concentrations in the lowermost sediment interval all point to a recent expulsion of mud breccia at the summit of Carmen MV.For the lowermost interval, the depletion of major elements (i.e., Ca2+ and Mg2+) and the enrichment of trace species (i.e., Li and B) in the pore water all indicate a deep fluid source. The δ18Opw (5.7‰ VSMOW) and δDpw (−10‰ VSMOW) of pore water in the lowermost interval correspond with smectite dehydration as the main pore-water freshening mechanism. Water-formation temperatures calculated with empirical geo-thermometers (K-Na, K-Mg; δ18Opw, δDpw, and dissolved B) reveal that fluids were generated at temperatures of ~140 ± 20 °C. Taking a regional geothermal gradient for the WAB of 25–27 °C/km, this points to a fluid source from ~5 ± 1 km sediment depth. This is not only consistent with the depth of overpressurized shales and megabreccia of Lower to Middle Miocene age, but it also fits nicely with the Upper/Middle-Miocene seawater value for the porewater 87Sr/86Sr derived from dissolving carbonates. The stable carbon and hydrogen isotopic composition of methane (δ13Cmethane ~ −59.4‰ VPDB and δDmethane −184‰ VSMOW) for the deepest samples of summit-core GP05PC is consistent with the mentioned deep origin.Mud breccia expulsion of overpressurized deep sedimentary units would be accompanied by rigorous degassing, leading to rapid, ‘instantaneous’ replacement of pore fluid by bottom water in the upper sediments. The absence of oxidized sediment draping, the seawater-like pore-water composition in the uppermost part of the mud breccia interval, and the abrupt methane to sulfate transition all provide evidence for a very recent mud expulsion.The distinctively kink-shaped pore-water Cl− profile in core GP05PC has been used in a numerical transport-reaction model to derive the timing for this event. This eruptive event appears to have taken place very recently, namely 12 ± 5 yrs prior to the 2012 coring, thus in the year 2000 CE.

Morphology and activity of the Helgoland Mud Volcano in the Sorokin Trough, northern Black Sea

Abstract Morphological change and activity of submarine mud volcanoes (MVs) are still poorly understood. In this study, we integrated acoustic subbottom profiles, Autonomous Underwater Vehicle (AUV) high-resolution bathymetric and backscatter data, Remotely Operated Vehicle (ROV) seafloor observations, Bottom Water Temperatures (BWT), and compositions of gas samples collected from three research expeditions, to study the morphology and activity of the Helgoland mud volcano (Helgoland MV) in the Sorokin Trough of the Black Sea. Based on the micro bathymetric and backscatter maps, we conducted a geomorphological analysis which differentiates the Helgoland MV into five regions, which are: the active center, the inner crest, the inner moat, the outer crest, and an outer moat. Special seafloor features, such as gas bubble emissions, mud breccia and mud pools, were observed in different regions by ROV observations. They indicate a heterogeneous distribution of materials and activities at the Helgoland MV. Active mud extrusion from the center was inferred from BWT elevations (up to 1.652 °C) that showed the same orientation as a major fault (NW-SE) at the location. Methane stable carbon isotopes (−58.1∼−63.6‰) and molecular compositions of light hydrocarbons (C1/C2+ = 2836, CH4 = 99.545%, C2H6 = 0.033%, C3H8 = 0.002%, CO2 = 0.417%) suggest a predominance of biogenic hydrocarbons with an admixture of thermogenic gas. Circular faults surrounding the Helgoland MV, as observed in the bathymetric and sub-bottom profiles, are speculated to be formed due to subsidence of the MV caldera and gravity driven sediment movement. A conceptual model is proposed to explain the interrelationship between the seafloor morphology and activity of the Helgoland MV. Combining multidisciplinary data, especially from the application of ROVs and AUVs, broaden the scope in which the activity and morphology of submarine mud volcanoes can be investigated.

Taphonomy of ghost shrimps (Decapoda: Axiidea: Callianassidae) associated with their burrows within a middle Miocene mud volcano complex of Persian (Arabian) Gulf, Kuwait

Shallow-marine strata of the Ghar Formation exposed along the Kuwait arch in the north of Kuwait contains fields of mud volcanoes associated with an assemblage dominated by pectinid bivalves and callianassid ghost shrimps. The depositional palaeoenvironment is interpreted to be intertidal to subtidal with the water depth not exceeding 50 m and with normal to hypersaline conditions. Based on the microfossil assemblage a middle Miocene age (early Langhian) is inferred, suggesting a longer stratigraphic span of the formation despite the previous studies treating the Ghar Formation as strictly early Miocene. Callianassid body fossils and numerous trace fossils assignable to Ophiomorpha have been identified. Ghost shrimp remains consisting of isolated cheliped elements are assigned to Neocallichirus (s.l.), which is the likely producer of Ophiomorpha burrows as documented by cheliped elements present within burrows and in the substrate around them. Stable isotopes discrimination modelling confirmed that fluids in the substrate were derived from at least two sources implying the presence of active mud volcanoes in the environment inhabited by ghost shrimps. Effusive activity of mud volcanoes further enhanced disarticulation and fragmentation of callianassid remains. The micritic matrix of ghost shrimp exoskeletons is indicated to have resulted from a mixture of local seawater with fluid of continental origin. This ghost shrimp occurrence is the first formal report of fossil decapod crustaceans from Kuwait.

Microbial Community Level Physiological Profiles of Active Mud Volcano Soils in Andaman and Nicobar Islands

The aim of this work was to determine if any differences exist in the community-level physiological profiles (CLPP) in different regions of mud volcano. The microbial functional diversity in the four soils sampled in the vicinity of a mud volcano, Baratang, Andaman and Nicobar Islands, India, was determined using Biolog EcoPlates. Comparisons of the patterns of substrate use showed differences in the community composition, reflecting the heterogeneous distribution of microorganisms in this environment. The results showed statistically significant differences among different volcanic environments both by total colony-forming unit and by average well colour development. On the basis of similarity percentage analysis, it was found that i-erythritol was the most commonly used substrate, but substrates such as dl-glycerol phosphate (end mud volcano × point mud volcano), l-asparagine (end mud volcano × dried mud volcano) and ketobutyric acid (outside mud volcano × point mud volcano) were found in only one environment. The metabolic diversity varied depending on the environments compared, indicating specific utilization of compounds’ effect. Microbial response in terms of the overall metabolic activity in outside mud volcano was higher than in other inside mud volcano soils. To the best of our knowledge, this is the first attempt to use CLPP study in volcanic environments in the Andaman and Nicobar Islands.

Slope failure and mass transport processes along the Queen Charlotte Fault Zone, western British Columbia

Abstract Multibeam echosounder (MBES) images, 3.5 kHz seismic-reflection profiles and piston cores obtained along the southern Queen Charlotte Fault Zone are used to map and date mass-wasting events at this transform margin – a seismically active boundary that separates the Pacific Plate from the North American Plate. Whereas the upper continental slope adjacent to and east (upslope) of the fault zone offshore of the Haida Gwaii is heavily gullied, few large-sized submarine landslides in this area are observed in the MBES images. However, smaller submarine seafloor slides exist locally in areas where fluid flow appears to be occurring and large seafloor slides have recently been detected at the base of the steep continental slope just above its contact with the abyssal plain on the Queen Charlotte Terrace. In addition, along the subtle slope re-entrant area offshore of the Dixon Entrance shelf bathymetric data suggest that extensive mass wasting has occurred in the vicinity of an active mud volcano venting gas. We surmise that the relative lack of submarine slides along the upper slope in close proximity to the Queen Charlotte Fault Zone may be the result of seismic strengthening (compaction and cohesion) of a sediment-starved shelf and slope through multiple seismic events.

Origin of the mud volcanoes in the south east Caspian Basin, Iran

Abstract: The Gorgan Plain (SE Caspian Basin) contains several mud volcanoes. The Gharenyaregh, Neftlijeh, Sofikam and Inche mud volcanoes are active and erupting mud and gas. Mud volcanoes occur in an area characterized by seismic activity. The Sofikam mud volcano consists of five craters that define a NE-directed (60°) linear arrangement, which coincides with a subsurface anticline of the western Kopeh Dagh fold-thrust belt. The main craters of the Inche and Neftlijeh mud volcanoes are submerged. The Gharenyaregh mud volcano is an active mud volcano whose crater is nearly 500 m in diameter. Clasts collected from the Gharenyaregh mud volcano (GMV) mainly consist of glauconite-sandstone, limestone (±ammonite), marl, and fossiliferous limestone (lumachelle) with bioclasts ranging in size from millimeters to centimeters. X-ray diffraction (XRD) analyses revealed quartz, calcite, feldspar, chlorite, illite, glauconite, halite and gypsum minerals in the clasts and soft materials of the GMV. The clasts are comparable with rock fragments originating from the underlying Kopeh Dagh related formations and the uppermost Caspian basin sediments. Regression of the South Caspian Sea shoreline from east to west (across modern-day Golestan province), seismic activity and buried folds indicate that the south east Caspian basin mud volcanoes are located in a tectonically active area and generated from deeper parts of the Gorgan Plain. Some large, conical hills with a record of historical human activity, located between the Kopeh Dagh zone and the South Caspian Sea, seem to be inactive mud volcanoes.

Does carbonate-associated sulphate record nutrition in lucinid and thyasirid bivalve shells from modern hydrocarbon seeps?

We test whether chemosymbiotic bivalves with sulphide-oxidizing bacteria record their nutritional strategy in the sulphur isotope composition of the carbonate-associated sulphate (CAS) in their shells, as a possible indicator of thiotrophic chemosymbiosis in the fossil record. The hypothesis rests on the possible incorporation of ³⁴S-depleted sulphate resulting from sulphide oxidation in sufficient quantity to affect the intrashell sulphate-sulphur isotope mass balance and hence the isotopic composition of sulphate, which is incorporated into carbonate with little or no fractionation. We analysed shell material of lucinid (Lucinoma asapheus) and thyasirid (Thyasira vulcolutre) bivalves from active mud volcanoes in the Gulf of Cadiz. Our results show that the CAS-δ³⁴S values of the bivalve shells do not reflect the variety of sulphur sources present at hydrocarbon seeps, but instead only record seawater sulphate values. Low δ³⁴S values were, however, measured in the animals’ soft tissues and shell organic matter (SOM), both displaying a strong influence of the depleted sulphide used as nutrition by the chemosynthethic bacteria. Given its potential for long-term preservation, SOM may therefore represent a more promising record of chemosymbiosis in the fossil record, while CAS from seep bivalves can be used to reconstruct local seawater sulphate.

Dynamic Triggering of Mud Volcano Eruptions During the 2016–2017 Central Italy Seismic Sequence

AbstractOn 24 August 2016 a seismic event (Mw6.0) was the first of the long Central Italy sequence (ongoing at the end of 2017) of medium‐to‐high magnitude earthquakes, with nineMw≥5 up to October 2017, and with about 74.000 seismic events registered after 1 year. The largest was theMw6.5 30 October 2016 event near Norcia. After the major seismic events, 17 mud volcanoes erupted around Monteleone di Fermo village (Marche region). Mud volcano eruptions generally occurred a few hours to a few days after the main earthquakes, suggesting a seismic triggering. We analyzed the peak ground velocities and dynamic stresses during the three largest earthquakes. We also evaluated the static stress changes in order to assess the potential influence of normal stress changes on the feeder system of the activated mud volcanoes. We find a correlation with dynamic stresses, whereas static stress changes are negligible or negative (with values reaching −0.44 bar, clamping feeder dykes). We conclude that seismic shaking (up to ~3.9 bar during Norcia earthquake) is the dominant driver for these eruptions. Finally, we evaluated the response ratio as a function of the dynamic stress. It increases exponentially with peak dynamic stress varying from <10% for peak dynamic stress >0.3 bar to >50% for peak dynamic stress >2 bar, indicating a link between earthquake shaking and mud volcano activity.

The 2011 strong fire eruption of Shikhzarli mud volcano, Azerbaijan: a case study with implications for methane flux estimation

Shikhzarli is a typical active mud volcano (MV) in Azerbaijan with extremely high percentages of fire eruptions reaching 74%. The strong eruption of Shikhzarli MV on 13 March 2011 (Shamakhi–Gobustan region, central Azerbaijan, at 40°29′12.5′′N; 49°02′03.4′′E) was accompanied by gas ignition with a straight-flow vertical gas flare. A large (60 m height) short-living (30 min) gas flare and small (1.5 m height) gas spouts with longer lifetimes (5 h) were simulated in SigmaFlow, and the model was used to evaluate methane flux and the amount of combusted methane. Geological and mineralogical data, field observations, as well as eye witness reports and photographs in mass media were used to choose the boundary conditions for the gas fire simulation. This study provides the first quantitative evaluation for methane emission during an MV catastrophic eruption. As simulation predicts, 14,000 m3 of methane was consumed for the life time (30 min) of the main 60-m high flare, which is equivalent to nine tons of cold gas at ambient conditions; the volume of erupted methane for the 5-h lifetime of a small spout (1.5 m high) was 72.6 m3 (45 kg) of cold CH4. The amount of methane emitted during a single strong flame eruption is commensurate with the annual output of permanently active individual MV vents or may be ten to hundred times as high.

AGE OF MUD BRECCIA FROM MUD VOLCANOES IN ACADEMICIAN RIDGE, LAKE BAIKAL

LakeBaikalis the only freshwater reservoir on Earth with gas-hydrate accumulations in its bottom sediments, partly due to the activity of mud volcanoes. This paper describes a group of mud volcanoes recently discovered on the slope of the Academician Ridge between the northern and central LakeBaikalbasins. Our analysis of diatom skeletons in the mud breccia sampled from the study area shows a high abundance of Cyclotella iris et var . These extinct species were also discovered in a core sample from BDP-98 borehole. Based on the biostratigraphic and seismostratigraphic correlations, the age of the mud breccia in the studied mud volcanoes ranges from the Late Miocene to the Early Pliocene (4.6 to 5.6 Ma). The correlations suggest that the material originated from a depth of less than310 m below the lake bottom.

Integrated analysis of bacterial and microeukaryotic communities from differentially active mud volcanoes in the Gulf of Cadiz.

The present study assesses the diversity and composition of sediment bacterial and microeukaryotic communities from deep-sea mud volcanoes (MVs) associated with strike-slip faults in the South-West Iberian Margin (SWIM). We used a 16S/18S rRNA gene based pyrosequencing approach to characterize and correlate the sediment bacterial and microeukaryotic communities from MVs with differing gas seep regimes and from an additional site with no apparent seeping activity. In general, our results showed significant compositional changes of bacterial and microeukaryotic communities in sampling sites with different seepage regimes. Sediment bacterial communities were enriched with Methylococcales (putative methanotrophs) but had lower abundances of Rhodospirillales, Nitrospirales and SAR202 in the more active MVs. Within microeukaryotic communities, members of the Lobosa (lobose amoebae) were enriched in more active MVs. We also showed a strong correlation between Methylococcales populations and lobose amoeba in active MVs. This study provides baseline information on the diversity and composition of bacterial and microeukaryotic communities in deep-sea MVs associated with strike-slip faults.

COBERTURA DE LOS FONDOS Y PAISAJES BENTÓNICOS ASOCIADOS A FORMACIONES DIAPÍRICAS EN LOS BANCOS DE SALMEDINA, PLATAFORMA CONTINENTAL DEL CARIBE COLOMBIANO

The submarine ecological units around an active mud volcano in the offshore banks of Salmedina, Colombian Caribbean, were determined and mapped employing geo-referenced submarine video-transects, bathymetry analysis, and interpretation of satellite imagery. Distribution, relative cover, and the most representative benthic, sessile organisms of the different ecological units are described. In the shallow zone of the banks, 60 % of the substrate was covered by algae and only 10 % by living corals. The relative cover of living corals in deeper zones increased to 33 % in semi vertical slopes and up to 55 % on the upper flats of deeper located banks. The dominant coral species overall were Siderastrea siderea and Montastraea annularis. A determining natural factor in the reef structure in the zone seems to be recent diapiric activity, with a constant mud emanation in the western sector. The Banks of Salmedina are under the influence of turbid plumes that seemingly increase sedimentation and are impacted by blast fishing as well. Although the shallowest zone of the bank shows the highest affectation, the coral community in the deeper zones still exhibit a noticeable cover of living coral, even higher than in other areas in the region with similar features. The recent diapiric activity of constant mud ejection determines the coral community structure in the western sector.

Active Mud Volcano Field Discovered off Southeast Alaska

A cruise to study landslide potential along an earthquake-prone fault found a surprising methane plume.

Ultramafic clasts from the South Chamorro serpentine mud volcano reveal a polyphase serpentinization history of the Mariana forearc mantle

Serpentine seamounts located on the outer half of the pervasively fractured Mariana forearc provide an excellent window into the forearc devolatilization processes, which can strongly influence the cycling of volatiles and trace elements in subduction zones. Serpentinized ultramafic clasts recovered from an active mud volcano in the Mariana forearc reveal microstructures, mineral assemblages and compositions that are indicative of a complex polyphase alteration history. Petrologic phase relations and oxygen isotopes suggest that ultramafic clasts were serpentinized at temperatures below 200°C. Several successive serpentinization events represented by different vein generations with distinct trace element contents can be recognized. Measured in situ Rb/Cs ratios are fairly uniform ranging between 1 and 10, which is consistent with Cs mobilization from sediments at lower temperatures and lends further credence to the low-temperature conditions proposed in models of the thermal structure in forearc settings. Late veins show lower fluid mobile element (FME) concentrations than early veins, suggesting a decreasing influence of fluid discharge from the subducting slab on the composition of the serpentinizing fluids. The continuous microfabric and mineral chemical evolution observed in the ultramafic clasts may have implications as to the origin and nature of the serpentinizing fluids. We hypothesize that opal and smectite dehydration produce quartz-saturated fluids with high FME contents and Rb/Cs between 1 and 4 that cause the early pervasive serpentinization. The partially serpentinized material may then be eroded from the basal plane of the suprasubduction mantle wedge. Serpentinization continued but the interacting fluids did not carry a pronounced sedimentary signature, either because FMEs were no longer released from the slab, or due to an en route loss of FMEs. Late chrysotile veins that document the increased access of fluids in a now fluid-dominated regime are characterized by reduced trace element contents with a slightly increased Rb/Cs ratio near 10. This lack of sediment-dominated geochemical signatures consistently displayed in all late serpentinization stages may indicate that the sediment-derived fluids have been completely reset (i.e. the FME excesses were removed) by continued water–rock reaction within the subduction channel. The final stage of buoyant rise of matrix and clasts in the conduits is characterized by brucite-dominated alteration of the clasts from the clast rim inward (independent of the intra-clast fabric relations), which corresponds to re-equilibration with alkaline, low-silica activity fluids in the rising mud.

Mud Diapirism on the Gorgan, North Iran

The several mud volcanoes have been exposed at the Gorgan area in the north Iran. The Garniarig-Tapeh is the biggest mud volcano and the investigation of its tectonic geomorphology is the main aim in this paper. Also, we have determinated tectonic and geologic setting of Naft-Lije mud volcanoes and several Salses as the exposed mud diapirs at Gorgan on the northern margin of Iran. These mud volcanoes have been formed during quaternary of as a shield shape hill or pool on the flat plain in coastal region SE Caspian Sea. There are flat area and several mud volcanoes that they have been triggered by buoyant driving mechanisms, have been appeared during dormant periods of mud volcanoes activity. This mechanism has been developed in neotectonic regime by convergent setting between The Cimmerian and Eurasian plates. Finally, the main characteristics of the Gorgan area have presented.

Geochemical and magnetic signals for the mud volcano-induced methane seepage in the core sediments of Shenhu area, northern South China Sea

The Shenhu Area of the northern South China Sea (SCS) has been regarded as a promising area for gas hydrate exploration. In this research, the petrography and stable isotopic composition of authigenic carbonates within a core of shallow sediment from Site 08CF7 in the Shenhu area have been studied. Based on the results of grain sizes, magnetic susceptibility, carbonate contents, textural characteristics, the age constrains of the core and the tectonic setting of the study area, it can be inferred that the core may represent the subsurface sediment in a mud volcano area within the gas hydrate system. Core sediments below 188 cm in the core may be associated with the in situ mud volcano activity. The authigenic carbonates (calcite, aragonite and dolomite) in fine size fraction below 188 cm indicate the mud volcano-induced methane seepage and anaerobic oxidation of methane (AOM), and their carbon source was mainly biogenic methane. In addition, the variation in magnetic susceptibility corresponds with in situ mud volcano sediments and associated methane seepage. These signals provide new methods of identifying AOM and application prospect for the exploration of seepage gas hydrates in SCS.

Warm brine lakes in craters of active mud volcanoes, Menes caldera off NW Egypt: evidence for deep-rooted thermogenic processes

The Menes caldera is a fault-controlled depression (~8 km in diameter) at ~3,000 m water depth in the western province of the Nile deep-sea fan off NW Egypt, comprising seven mud volcanoes (MVs) of which two are active. Based on multichannel and chirp seismic data, temperature profiles, and high-resolution bathymetric data collected during the 2000 Fanil, 2004 Mimes and 2007 Medeco2 expeditions, the present study investigates factors controlling MV morphology, the geometry of feeder channels, and the origin of emitted fluids. The active Cheops and Chephren MVs are 1,500 m wide with subcircular craters at their summits, about 250 m in diameter, generally a few tens of metres deep, and filled with methane-rich muddy brines with temperatures reaching 42 °C and 57 °C respectively. Deployments of CTDs and corers with attached temperature sensors tracked these warm temperatures down to almost 0.5 km depth below the brine lake surface at the Cheops MV, in a feeder channel probably only a few tens of metres wide. Thermogenic processes involve the dissolution of Messinian evaporites by warm fluids likely sourced even deeper, i.e. 1.7 and 2.6 km below the seabed at the Cheops and Chephren MVs respectively, and which ascend along listric faults. Seepage activity appears broadly persistent since the initiation of mud volcanism in the Early Pliocene, possibly accompanied by lateral migration of feeder channels.

Characteristics and developmental mechanisms of mud volcanoes on the southern margin of the Junggar Basin, NW China

AbstractMud volcanoes have provided much meaningful information about the deep Earth and the recent crustal and neotectonic movements in an area for over 200 years. However, the triggering mechanisms have puzzled geologists for a long time. This study investigated the factors controlling mud volcano activity and the triggering mechanisms of mud volcano eruptions on the southern margin of the Junggar Basin, NW China. The Baiyanggou, Aiqigou and Dushanzi mud volcanoes are all located along the Dushanzi Anticline, which belongs to the third anticline belt on the southern margin of the basin. The extensive, thick mudstone at depth provides a wealth of material for the formation of mud volcanoes. Simultaneously, the overpressure serves as the driving force for the eruption of the mud volcanoes. The torsional–compressional stress field created by the collision between the Indian and Eurasian plates not only enhanced the abnormal formational pressure in the region but also lead to the development of extensional faults in the core of the Dushanzi Anticline, which served as the conduits for the mud volcanoes. The continuous collision between the Indian and Eurasian plates and the regional torsional–compressional stress field may largely control the cyclical activity of the mud volcanoes and serve as their primary trigger mechanism. Copyright © 2014 John Wiley & Sons, Ltd.