The Dead Sea Fault (DSF) is a crustal‐scale continental transform fault separating the African and the Arabian plates. Neogene to Quaternary volcanic activity is well‐spread in Northern Israel. Yet, ...the origin of the magmas that fed the eruptions is still unpinned. Our local earthquake tomography depicts velocity distributions typical of rifting settings. At 9 km depth, a prominent high Vp/Vs anomaly marks the presence of cooling melts. We propose that protracted transtension along the DSF caused crustal thinning promoting the emplacement of magmatic bodies. Crustal emplacements of magmas in Northern Israel reconcile multiple observations, including the high geothermal gradient, the prominent magnetic anomalies and the traces of mantle‐derived fluids in the springs across the Sea of Galilee. We provide a compelling evidence for rifting in segments of the DSF and identify the potential source of magmatism that fed part of the volcanic activity of the area.
Plain Language Summary
The Dead Sea Fault (DSF) is a deep‐reaching fault separating the African and the Arabian plates. Geologically recent volcanic activity is well‐spread in Northern Israel but the origin of the magmas that fed the eruptions is yet to be found. We propose that protracted extensional motion along the DSF caused crustal thinning facilitating the emplacement of magmatic bodies in the crust. Our local earthquake tomography depicts velocity distributions typical of spreading margins. At 9 km depth, a prominent anomaly marks the presence of cooling melts. Crustal emplacements of magmas in Northern Israel reconcile multiple observations that are normally not common in sedimentary environments. The occurrence of magmas at depth would release fluids that would be compatible with the seismicity that sporadically affects the region. We provide a compelling evidence for rifting in segments of the DSF and identify the potential source of magmatism that fed part of the volcanic activity of the area. Our findings hold major implications for revisiting the natural hazard assessment of the Levant region.
Key Points
Magma emplaced along the Dead Sea Fault (DSF)
Localized rifting along the segment of the DSF
Occurrence of cooling magmas may reconcile several geophysical, geological and geochemical observations in around the Sea of Galilee
Vesteris Seamount is a large Quaternary intraplate submarine volcano in the SW Greenland Sea, about 1,000 km NE of Iceland and 300 km NW of the Mohn's spreading ridge, whose mode of formation remains ...unsolved. We present geochemical data for new samples dredged from the Vesteris edifice, including major, trace elements and Sr‐Nd‐Pb‐Hf isotopes. The isotopic characteristics of the alkaline lavas, covering the basanite/tephrite to benmoreite range, indicate the involvement of depleted and enriched mantle components. The source is dominated by the depleted mantle (85%–90%) and a deep enriched component possibly supplied by the Iceland Plume (IP) (10%–15%). Additional source enrichment was due to recycled crust and sub‐continental lithospheric mantle, as suggested by Hf isotopes (0.283147 ± 0.000005) measured for the first time in Vesteris lavas and by a decoupling in Pb isotopes evidenced by relatively low‐radiogenic 207Pb/204Pb (15.510) and high‐radiogenic 208Pb/204Pb (38.554) with respect to the Northern Hemisphere Reference Line. We interpret the geochemical results using existing knowledge about the regional lithospheric and upper mantle structure. Our findings suggest that a deep (ca. 420–320 km) mantle anomaly, with seismological characteristics of the Iceland mantle plume, extends from East Greenland to the north of Jan Mayen Fracture Zone. The regional lithospheric thinning toward the Greenland Basin enabled the melting events that produced the Vesteris seamount. This lateral NNE‐directed flow lobe of the Iceland plume may have carved and transferred enriched components from the continental lithospheric margin of Greenland north of Scoresby Sund toward the Vesteris source.
Plain Language Summary
This study investigates the formation of Vesteris Seamount, the largest submarine volcano in the Greenland Sea, situated north of Iceland and the Jan Mayen Fracture Zone and east of the Greenland continental margin. Given the isolated position of Vesteris, it is challenging to define its formation mechanisms and the mantle source. This study presents geochemical data by analyzing samples dredged from Vesteris' flanks. A deep mantle component, similar to the Iceland plume, seems to contribute to the mantle source of Vesteris magmas and the regional depleted asthenosphere. However, our results also suggest a contribution of an enriched component. This could be the sub‐continental mantle lithosphere (SCLM) and a crustal component. These components could have been transported from the Northeastern Greenland Margin, North of Scoresby Sund, along with the mantle flow. Subsurface seismic tomography images indicate an NNE‐directed flow lobe from the mantle plume under Iceland. We suggest that this setting played an important role in the seamount formation and explain the isotope signatures of SCLM‐like and crustal components by deep mantle carving of the western Greenland margin.
Key Points
New volcanic rock samples are dredged from Vesteris Seamount in the SW Greenland Sea
Sample analysis shows geochemical evidence of deep mantle component and continental crust remobilization
Melting underneath Vesteris was enhanced by steep lithospheric thickness change that allowed channeling of the Iceland plume branch
Mud volcanoes are geologically important manifestations of vertical fluid flow and mud eruption in sedimentary basins worldwide. Their formation is predominantly ascribed to release of overpressure ...from clay- and organic-rich sediments, leading to impressive build-up of mud mountains in submarine and subaerial settings. Here we report on a newly born mud volcano appearing close to an active magmatic complex in a backarc sedimentary basin in Indonesia. The location of the mud volcano close to magmatic volcanoes results in a high background temperature gradient that triggers mineralogical transformations and geochemical reactions at shallow depth. The eruption of 100 °C mud and gas that started the 29th of May 2006 flooded a large area within the Sidoarjo village in Northeast Java. Thousands of people have so far been evacuated due to the mud flood hazards from the eruption. Since the initial eruption, the flow rate escalated from 5000 to 120,000 m
3/d during the first eleven weeks. Then the erupted volume started to pulsate between almost zero and 120,000 m
3/d in the period August 14 to September 10, whereas it increased dramatically following swarms of earthquakes in September, before reaching almost 180,000 m
3/d in December 2006. Sampling and observations were completed during two fieldwork campaigns on the site. The eruption of boiling water is accompanied by mud, aqueous vapour, CO
2 and CH
4. Based on geochemical and field results, we propose a mechanism where the eruptions started following the 27th of May earthquake due to fracturing and accompanied depressurization of > 100 °C pore fluids from > 1700 m depth. This resulted in the formation of a quasi-hydrothermal system with a geyser-like surface expression and with an activity influenced by the regional seismicity.
Ongoing studies conducted in northern polar regions reveal that permafrost stability plays a key role in the modern carbon cycle as it potentially stores considerable quantities of greenhouse gases. ...Rapid and recent warming of the Arctic permafrost is resulting in significant greenhouse gas emissions, both from physical and microbial processes. The potential impact of greenhouse gas release from the Antarctic region has not, to date, been investigated. In Antarctica, the McMurdo Dry Valleys comprise 10 % of the ice-free soil surface areas in Antarctica and like the northern polar regions are also warming albeit at a slower rate.
The work presented herein examines a comprehensive sample suite of soil gas (e.g., CO2, CH4 and He) concentrations and CO2 flux measurements conducted in Taylor Valley during austral summer 2019/2020. Analytical results reveal the presence of significant concentrations of CO2, CH4 and He (up to 3.44 vol%, 18,447 ppmv and 6.49 ppmv, respectively) at the base of the active layer. When compared with the few previously obtained measurements, we observe increased CO2 flux rates (estimated CO2 emissions in the study area of 21.6 km2 ≈ 15 tons day−1). We suggest that the gas source is connected with the deep brines migrating from inland (potentially from beneath the Antarctic Ice Sheet) towards the coast beneath the permafrost layer. These data provide a baseline for future investigations aimed at monitoring the changing rate of greenhouse gas emissions from Antarctic permafrost, and the potential origin of gases, as the southern polar region warms.
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•First extensive soil gas and flux survey in Antarctica•Discovered zones of multigas (CO2, CH4, He, H2) anomalies•CO2 emissions estimation in Lower Taylor Valley•Gas rising from deep brines
Acoustic imaging has revealed more than 7000 pockmarks on the seafloor above the Troll East gas field in the Norwegian North Sea. We present the first comprehensive study conducted on one of the ...World's largest pockmark fields complementing the acoustic data with extensive sampling, geochemical and petrographical studies. Specifically, we aimed at detecting possible active seepage still present over this vast area. The pockmarks are present as isolated structures, on average ~35m wide and up to 100m in size. In addition, smaller satellite pockmarks surround some of the pockmarks. In contrast to the muddy surroundings, parts of the investigated pockmarks contain laterally extensive carbonate deposits or meter sized carbonate blocks. These blocks provide shelter to abundant colonies of benthic megafauna. The carbonate blocks are comprised of micritic Mg-calcite and calcite, micritic aragonite, and botryoidal aragonite. Framboidal pyrite is also commonly present. Carbon isotopic values of the carbonates are 13C-depleted (δ13C as low as −59.7‰) and with δ18O up to 4.5‰, indicating a methanogenic origin, possibly linked to gas hydrate dissociation. Pore water extracted from shallow cores from the centre and the flanks of the pockmarks show similar Cl and SO4 profiles as the reference cores outside the pockmarks, ruling out active methane seepage. This conclusion is also supported by seafloor video observations that did not reveal any evidence of visual fluid seepage, and by the absence of microbial mats and by the fact that the carbonate blocks are exposed on the seafloor and party oxidized on the surface. We conclude that methane seepage formed this extensive gas field following to gas hydrate dissociation.
•Troll is one of the World's largest pockmark fields.•Widespread methane release is responsible for the formation of the large field as well as carbonate precipitation.•Multidisciplinary studies show that the Troll pockmark field is currently inactive.
Summary
In physiological conditions, red blood cells (RBCs) are capable of dramatic deformations when passing through the microvasculature. This extreme deformability is closely related to the RBC ...biconcave shape, to the fluidic nature of the haemoglobin and the cell membrane structure, primarily consisting of a phospholipid bilayer with an underlying two‐dimensional spectrin network. In many pathological and inflammatory conditions, the shape and the extreme deformability of erythrocytes appear to be significantly altered. These findings have stimulated intense research towards the search and validation of novel erythrocyte‐based mechanical biomarkers, useful for disease diagnosis and therapy monitoring. In this study, we investigated with Atomic Force Microscopy (AFM) the mechanical properties of erythrocytes obtained from a 68 years old cirrhotic man diagnosed with spur cell anaemia and cold agglutinated disease, before and after liver transplantation. Mechanical changes are compared with ultrastructural alterations as studied by scanning electron microscopy and discussed according to confocal fluorescence microscopy results, showing possible alterations induced by the cirrhotic environment at the level of the RBCs cytoskeletal organisation and lipidic composition. Taken together, the results here presented show that liver transplantation not only contributes to restoring the proper RBC morphology, but it also induces recovery of the physiological viscous behaviour of cells, further stressing the relevance of viscous and dissipative forces in determining the RBC biomechanical response.
The worlds >1500 mud volcanoes are normally in a dormant stage due to the short duration of eruptions. Their dormant stage activity is often characterized by vigorous seepage of water, gas, and ...petroleum. However, the source of the fluids and the fluid–rock interactions within the mud volcano conduit remain poorly understood. In order to investigate this type of activity, we have combined satellite images with fieldwork and extensive sampling of water and gas at seeping gryphons, pools and salsa lakes at the Dashgil mud volcano in Azerbaijan. We find that caldera collapse faults and E–W oriented faults determine the location of the seeps. The seeping gas is dominated by methane (94.9–99.6%), with a δ
13C (‰ V-PDB) in the −43.9 to −40.4‰ range, consistent throughout the 12 analysed seeps. Ethane and carbon dioxide occur in minor amounts. Seventeen samples of seeping water show a wide range in solute content and isotopic composition. Pools and salsa lakes have the highest salinities (up to 101,043
ppm Cl) and the lowest δ
18O (‰ V-SMOW) values (1–4‰). The mud-rich gryphons have low salinities (<18,000
ppm Cl) and are enriched in
18O (δ
18O
=
4–6‰).
The gas geochemistry suggests that the gases migrate to the surface from continuously leaking deep-seated reservoirs underneath the mud volcano, with minimal oxidation during migration. However, variations in gas wetness can be ascribed to molecular fractionation during the gas rise. In contrast, the water shows seasonal variations in isotopic composition and surface evaporation is proposed as a mechanism to explain high water salinities in salsa lakes. By contrast, gryphons have geochemical signals suggesting a deep-seated water source.
These results demonstrate that the plumbing system of dormant mud volcanoes is continuously recharged from deeper sedimentary reservoirs and that a branched system of conduits exists in the shallow subsurface. While the gas composition is consistently similar throughout the crater, the large assortment of water present reflects the type of seep (i.e. gryphons versus pools and salsa lakes) and their location within the volcano. Our data highlight the importance of a carefully planned sampling strategy when the target is water geochemistry, whereas the methane content and isotopic composition is relatively independent of the particular seep morphology.
Subtle mounds have been discovered in the source areas of Martian kilometer‐sized flows and on top of summit areas of domes. These features have been suggested to be related to subsurface sediment ...mobilization, opening questions regarding their formation mechanisms. Previous studies hypothesized that they mark the position of feeder vents through which mud was brought to the surface. Two theories have been proposed: (a) ascent of more viscous mud during the late stage of eruption and (b) expansion of mud within the conduit due to the instability of water under Martian conditions. Here, we present experiments performed inside a low‐pressure chamber designed to investigate whether the volume of mud changes when exposed to a Martian atmospheric pressure. Depending on the mud viscosity, we observe a volumetric increase of up to 30% at the Martian average pressure of ∼6 mbar. The reason is that the low pressure causes instability of the water within the mud, leading to the bubble formation that increases the volume of the mixture. This mechanism bears resemblance to the volumetric changes associated with the degassing of terrestrial lava or mud volcano eruptions caused by a rapid pressure drop. We conclude that the mounds associated with putative Martian sedimentary volcanoes might indeed be explained by volumetric changes in the mud. We also show that mud flows on Mars and elsewhere in the Solar System could behave differently to those found on Earth because mud dynamics are affected by the formation of bubbles in response to the different atmospheric pressures.
Plain Language Summary
Mars is a planet whose surface atmospheric pressure is ∼160 times weaker than that on Earth. This means that water cannot be present on the Mars surface since in these conditions, lit should boil and evaporate. At the same time, many edifices previously observed on the planet’s surface are believed to be the result of mud movement over the Martian surface. Many authors proposed that these structures are the result of a process of sedimentary volcanism during which the sediment was mobilized by liquid water. However, until now, it remained unclear how muds of various viscosities would behave under current Martian conditions. Here, we show that depending on the mud viscosity, a volumetric increase in up to 30% might occur. The reason is that the low pressure causes instability of the water within the mud, leading to the formation of bubbles that increase the volume of the mud mixture. This shows that mud flows on Mars and elsewhere in the Solar System could behave differently to those found on Earth and therefore we might encounter different shapes of edifices formed on Mars by sedimentary volcanism than on Earth.
Key Points
High viscosity muds are able to prevent the easy escape of water vapor bubbles leading to the increase in the volume of such mixtures
Depending on the thickness of the mudflow, the volumetric increase can reach up to 30% and thus change the resulting shape of the mudflow
Presence of small mounds associated with putative Martian sedimentary volcanoes might be explained by volumetric changes in the mud
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