CO2 Degassing Estimates from Rift Length Analysis since Pangea Fragmentation: A Key Component of the Deep Carbon Cycle?

NASA Astrophysics Data System (ADS)

Brune, S.; Williams, S.; Müller, D.

2017-12-01

The deep carbon cycle links the carbon content of crust and mantle to Earth's surface: extensional plate boundaries and arc volcanoes release CO2 to the ocean and atmosphere while subducted lithosphere carries carbon back into the mantle. The length of extensional and convergent plate boundaries therefore exerts first-order control on solid Earth CO2 degassing rates. Here we provide a global census of plate boundary length for the last 200 million years. Focusing on rift systems, we find that the most extensive rift phase during the fragmentation of Pangea occurred in the Jurassic/Early Cretaceous with more than 50.000 km of simultaneously active continental rifts. During the Late Cretaceous, in the aftermath of this pervasive rift episode, the global rift length dropped by 60% to 20,000 km. We further find that a second pronounced rift episode with global rift lengths of up to 30,000 km started in Eocene times. A close geological link between CO2 degassing and faulting has been documented in currently active rift systems worldwide. Regional-scale CO2 flux densities at rift segments in Africa, Europe, and New Zealand feature an annual average value of 200 t of CO2 per km2. Assuming that the release of CO2 scales with rift length, we show that rift-related CO2 degassing rates during the two major Mesozoic and Cenozoic rift episodes reached more than 300% of present-day values. Most importantly, the timing of enhanced CO2 degassing from continental rifts correlates with two well-known periods of elevated atmospheric CO2 in the Mesozoic and Cenozoic as evidenced by multiple independent proxy indicators. Compiling the length of other plate boundaries (mid-ocean ridges, subduction zones, continental arcs) through time, we do not reproduce such a correlation. Finally, we conduct numerical carbon cycle models that account for key feedback-mechanisms of the long-term carbon cycle. We find that only those models that feature a strong rift degassing component reproduce the timing and amplitude of the paleo-CO2 record. We therefore suggest that rift-related degassing constitutes a key component of the deep carbon cycle.

Degassing of CO2, SO2, and H2S associated with the 2009 eruption of Redoubt Volcano, Alaska

USGS Publications Warehouse

Werner, Cynthia A.; Kelly, Peter; Doukas, Michael P.; Lopez, Taryn; Pfeffer, Melissa; McGimsey, Robert G.; Neal, Christina

2013-01-01

The 2009 eruption of Redoubt Volcano, Alaska was particularly well monitored for volcanic gas emissions. We report 35 airborne measurements of CO2, SO2, and H2S emission rates that span from October 2008 to August 2010. The magmatic system degassed primarily as a closed system although minor amounts of open system degassing were observed in the 6 months prior to eruption on March 15, 2009 and over 1 year following cessation of dome extrusion. Only 14% of the total CO2 was emitted prior to eruption even though high emissions rates (between 3630 and 9020 t/d) were observed in the final 6 weeks preceding the eruption. A minor amount of the total SO2 was observed prior to eruption (4%), which was consistent with the low emission rates at that time (up to 180 t/d). The amount of the gas emitted during the explosive and dome growth period (March 15–July 1, 2009) was 59 and 66% of the total CO2and SO2, respectively. Maximum emission rates were 33,110 t/d CO2, 16,650 t/d SO2, and 1230 t/d H2S. Post-eruptive passive degassing was responsible for 27 and 30% of the total CO2 and SO2, respectively. SO2 made up on average 92% of the total sulfur degassing throughout the eruption. Magmas were vapor saturated with a C- and S-rich volatile phase, and regardless of composition, the magmas appear to be buffered by a volatile composition with a molar CO2/SO2 ratio of ~ 2.4. Primary volatile contents calculated from degassing and erupted magma volumes range from 0.9 to 2.1 wt.% CO2 and 0.27–0.56 wt.% S; whole-rock normalized values are slightly lower (0.8–1.7 wt.% CO2 and 0.22–0.47 wt.% S) and are similar to what was calculated for the 1989–90 eruption of Redoubt. Such contents argue that primary arc magmas are rich in CO2 and S. Similar trends between volumes of estimated degassed magma and observed erupted magma during the eruptive period point to primary volatile contents of 1.25 wt.% CO2 and 0.35 wt.% S. Assuming these values, up to 30% additional unerupted magma degassed in the year following final dome emplacement.

Degassing of CO2, SO2, and H2S associated with the 2009 eruption of Redoubt Volcano, Alaska

NASA Astrophysics Data System (ADS)

Werner, Cynthia; Kelly, Peter J.; Doukas, Michael; Lopez, Taryn; Pfeffer, Melissa; McGimsey, Robert; Neal, Christina

2013-06-01

The 2009 eruption of Redoubt Volcano, Alaska was particularly well monitored for volcanic gas emissions. We report 35 airborne measurements of CO2, SO2, and H2S emission rates that span from October 2008 to August 2010. The magmatic system degassed primarily as a closed system although minor amounts of open system degassing were observed in the 6 months prior to eruption on March 15, 2009 and over 1 year following cessation of dome extrusion. Only 14% of the total CO2 was emitted prior to eruption even though high emissions rates (between 3630 and 9020 t/d) were observed in the final 6 weeks preceding the eruption. A minor amount of the total SO2 was observed prior to eruption (4%), which was consistent with the low emission rates at that time (up to 180 t/d). The amount of the gas emitted during the explosive and dome growth period (March 15-July 1, 2009) was 59 and 66% of the total CO2 and SO2, respectively. Maximum emission rates were 33,110 t/d CO2, 16,650 t/d SO2, and 1230 t/d H2S. Post-eruptive passive degassing was responsible for 27 and 30% of the total CO2 and SO2, respectively. SO2 made up on average 92% of the total sulfur degassing throughout the eruption. Magmas were vapor saturated with a C- and S-rich volatile phase, and regardless of composition, the magmas appear to be buffered by a volatile composition with a molar CO2/SO2 ratio of ~ 2.4. Primary volatile contents calculated from degassing and erupted magma volumes range from 0.9 to 2.1 wt.% CO2 and 0.27-0.56 wt.% S; whole-rock normalized values are slightly lower (0.8-1.7 wt.% CO2 and 0.22-0.47 wt.% S) and are similar to what was calculated for the 1989-90 eruption of Redoubt. Such contents argue that primary arc magmas are rich in CO2 and S. Similar trends between volumes of estimated degassed magma and observed erupted magma during the eruptive period point to primary volatile contents of 1.25 wt.% CO2 and 0.35 wt.% S. Assuming these values, up to 30% additional unerupted magma degassed in the year following final dome emplacement.

Obsidian Pyroclasts: Where Do They Come From and What Can They Tell Us?

NASA Astrophysics Data System (ADS)

Watkins, J. M.; Gardner, J. E.; Befus, K.

2016-12-01

Models for how volcanic gases behave during volcanic eruptions are constructed from measurements of volatiles (δD, H2O and CO2) in melt that has been quenched to glass. Volatile measurements on obsidian pyroclasts from Mono Craters, California, have been central to the development of open- versus closed-system and equilibrium versus non-equilibrium degassing models, and these models have been applied to the interpretation of volatile data from volcanic centers worldwide. Even for the well-studied Mono Craters system, however, there are several different degassing models that are compatible with existing data, and the origin of the vesicle-poor obsidian pyroclasts (upon which the degassing models have been built) remains ambiguous. To better establish the link between the volatiles in the pyroclasts and volcanic eruption processes, we combine textural analysis with area maps of CO2 and H2O. We show that obsidian pyroclasts are heterogeneous with respect to dissolved CO2 and H2O, and that many clasts have multiple textural and chemical domains that are sutured together. The observations suggest that clasts are assembled from non-equilibrated juvenile melt and ash during repeated melt fracturing and healing, ash sintering, and shearing along conduit margins. Melt fracturing promotes gas extraction from magma, whereas healing promotes gas resorption and glass densification. Some of the clasts have bands or patches of elevated CO2 associated with cuspate vesicles, which are evidence for CO2-rich vapor fluxing through the magmatic system. Collectively, the data support a model of open-system, non-equilibrium degassing with intermittent regassing caused by increases in pressure and exposure to different vapor compositions.

Degassing behavior of Mt. Etna volcano (Italy) before and during the 2008-2009 eruption, inferred from crater plume and soil gas measurements

NASA Astrophysics Data System (ADS)

Salerno, Giuseppe; La Spina, Alessandro; Giammanco, Salvatore; Burton, Michael; Caltabiano, Tommaso; Murè, Filippo; Randazzo, Daniele; Lopez, Manuela; Bruno, Nicola; Longo, Vincenza

2010-05-01

The evolution of magmatic degassing that preceded and accompanied the 2008-2009 Mt. Etna eruption was monitored by using a combination of: i) near-daily SO2 flux measurements; ii) calculated HCl and HF fluxes, obtained combining the daily SO2 flux values with discrete FTIR measurements of SO2/HCl and SO2/HF molar ratios; iii) periodic soil CO2 flux measurements. Thanks to the differential release of magmatic gas species from an ascending magma body we were able to track the magma transfer process in the volcano plumbing system from depth (< 5 km) to the surface. Our data suggest that the intermittent paroxysmal activity that mainly affected the South-East Crater (SEC) during 2007, displayed the efficient but complex nature of Mt. Etna's plumbing system, with gas-rich magma ascending and degassing via the central conduit system prior to eruption at the peripheral SEC. Conversely, the 15 month long 2008-09 eruption event was characterized by quasi steady state magma supply. The calculated volume of magma required to produce the observed SO2 flux during the 2008-2009 eruption closely matches the volume of erupted magma. This "eruptive" steady-state would indicate an almost perfect process of magma migration and eruption at the surface, without substantial storage within the volcano plumbing system.

Are Avellino (4365 cal BP) and Pompeii twin plinian eruptions? Pre-eruptive constraints and degassing history

NASA Astrophysics Data System (ADS)

Boudon, Georges; Balcone-Boissard, Hélène; Villemant, Benoît.; Ucciani, Guillaume; Cioni, Raffaello

2010-05-01

Somma-Vesuvius activity started 35 ky ago and is characterized by numerous eruptions of variable composition and eruptive style, sometimes interrupted by long periods of unrest. The main explosive eruptions are represented by four plinian eruptions: Pomici di Base eruption (22 cal ky), Mercato (~8900 cal BP), Avellino (4365 cal BP) and Pompeii (79 AD). The 79 AD eruption embodies the most famous eruption since it's responsible of the destruction of Pompeii and Herculanum and it's the first described eruption. The Avellino eruption represents the last plinian event that preceded the Pompeii eruption. The eruptive sequence is similar to the 79 AD plinian eruption, with an opening phase preceding a main plinian fallout activity which ended by a phreatomagmatic phase. The fallout deposit displays a sharp colour contrast from white to grey pumice, corresponding to a magma composition evolution. We focus our study on the main fallout deposit that we sampled in detail in the Traianello quarry, 9 km North-North East of the crater, to investigate the degassing processes during the eruption, using volatile content and textural observations. Density and vesicularity measurements were obtained on a minimum of 100 pumice clasts sampled in 10 stratigraphic levels in the fallout deposit. On the basis of the density distribution, bulk geochemical data, point analytical measurements on glasses (melt inclusions and residual glass) and textural observations were obtained simultaneously on a minimum of 5 pumice clasts per eruptive unit. The glass composition, in particular the Na/K ratio, evolves from Na-rich phonolite for white pumices to a more K-rich phonolite for grey pumices. The pre-eruptive conditions are constrained by systematic Cl measurements in melt inclusions and matrix glass of pumice clasts. The entire magma was saturated relative to sub-critical fluids (a Cl-rich H2O vapour phase and a brine), with a Cl melt content buffered at ~6000 ppm, and a mean pre-eruptive H2O content depending of the magma composition. Most of the pumices of the different eruptive units show that H2O degassing during the eruption followed a typical closed-system evolution as expected for plinian eruption. Contrary to H2O, Cl was not efficiently degassed during the plinian phase of the eruption: the matrix glass composition remains close to the pre-eruptive content. Compared to the 79AD eruption the degassing processes showed by the whole Avellino plinian phase is more homogeneous and similar to the white pumice phase of the Pompeii eruption whereas the open-system degassing mode identified from the grey pumices of the 79AD eruption is not represented during the Avellino eruption.

Ultrafast syn-eruptive degassing and ascent trigger high-energy basic eruptions.

PubMed

Giuffrida, Marisa; Viccaro, Marco; Ottolini, Luisa

2018-01-09

Lithium gradients in plagioclase are capable of recording extremely short-lived processes associated with gas loss from magmas prior to extrusion at the surface. We present SIMS profiles of the 7 Li/ 30 Si ion ratio in plagioclase crystals from products of the paroxysmal sequence that occurred in the period 2011-2013 at Mt. Etna (Italy) in an attempt to constrain the final ascent and degassing processes leading to these powerful eruptions involving basic magma. The observed Li concentrations reflect cycles of Li addition to the melt through gas flushing, and a syn-eruptive stage of magma degassing driven by decompression that finally produce significant Li depletion from the melt. Modeling the decreases in Li concentration in plagioclase by diffusion allowed determination of magma ascent timescales that are on the order of minutes or less. Knowledge of the storage depth beneath the volcano has led to the quantification of a mean magma ascent velocity of ~43 m/s for paroxysmal eruptions at Etna. The importance of these results relies on the application of methods, recently used exclusively for closed-system volcanoes producing violent eruptions, to open-conduit systems that have generally quiet eruptive periods of activity sometimes interrupted by sudden re-awakening and the production of anomalously energetic eruptions.

Diffuse degassing at Longonot volcano, Kenya: Implications for CO2 flux in continental rifts

NASA Astrophysics Data System (ADS)

Robertson, Elspeth; Biggs, Juliet; Edmonds, Marie; Clor, Laura; Fischer, Tobias P.; Vye-Brown, Charlotte; Kianji, Gladys; Koros, Wesley; Kandie, Risper

2016-11-01

Magma movement, fault structures and hydrothermal systems influence volatile emissions at rift volcanoes. Longonot is a Quaternary caldera volcano located in the southern Kenyan Rift, where regional extension controls recent shallow magma ascent. Here we report the results of a soil carbon dioxide (CO2) survey in the vicinity of Longonot volcano, as well as fumarolic gas compositions and carbon isotope data. The total non-biogenic CO2 degassing is estimated at < 300 kg d- 1, and is largely controlled by crater faults and fractures close to the summit. Thus, recent volcanic structures, rather than regional tectonics, control fluid pathways and degassing. Fumarolic gases are characterised by a narrow range in carbon isotope ratios (δ13C), from - 4.7‰ to - 6.4‰ (vs. PDB) suggesting a magmatic origin with minor contributions from biogenic CO2. Comparison with other degassing measurements in the East African Rift shows that records of historical eruptions or unrest do not correspond directly to the magnitude of CO2 flux from volcanic centres, which may instead reflect the current size and characteristics of the subsurface magma reservoir. Interestingly, the integrated CO2 flux from faulted rift basins is reported to be an order of magnitude higher than that from any of the volcanic centres for which CO2 surveys have so far been reported.

Vapor-phase cristobalite as a durable indicator of magmatic pore structure and halogen degassing: an example from White Island volcano (New Zealand)

NASA Astrophysics Data System (ADS)

Ian Schipper, C.; Mandon, Céline; Maksimenko, Anton; Castro, Jonathan M.; Conway, Chris E.; Hauer, Peter; Kirilova, Martina; Kilgour, Geoff

2017-10-01

Vesicles in volcanic rocks are physical records of magmatic degassing; however, the interpretation of their textures is complicated by resorption, coalescence, and collapse. We discuss the textural significance of vesicle-hosted vapor-phase cristobalite (high-T, low-P SiO2 polymorph), and its utility as a complement to textural assessments of magmatic degassing, using a representative dacite bomb erupted from White Island volcano (New Zealand) in 1999. Imaging in 2D (SEM) and 3D (CT) shows the bomb to have 56% bulk porosity, almost all of which is connected ( 99%) and devoid of SiO2 phases. The remaining ( 1%) of porosity is in isolated, sub-spherical vesicles that have corroded walls and contain small (< 30 μm across) prismatic vapor-phase cristobalite crystals (98.4 ± 0.4 wt.% SiO2 with diagnostic laser Raman spectra). Halogen degassing models show vapor-phase cristobalite to be indicative of closed-system chlorine and fluorine partitioning into H2O-rich fluid in isolated pores. At White Island, this occurred during shallow (< 100s of meters) ascent and extensive ( 50%) groundmass crystallization associated with slow cooling in a volcanic plug. Pristine textures in this White Island bomb demonstrate the link between pore isolation and vapor-phase cristobalite deposition. We suggest that because these crystals have higher preservation potential than the bubbles in which they form, they can serve as durable, qualitative textural indicators of halogen degassing and pre-quench bubble morphologies in slowly cooled volcanic rocks (e.g., lava flows and domes), even where emplacement mechanisms have overprinted original bubble textures.

Investigating Degassing in Felsic and Mafic Magmas by 3-D Imaging of Vesicle Pathways

NASA Astrophysics Data System (ADS)

Polacci, M.; Baker, D. R.; Piochi, M.; Mancini, L.

2009-12-01

Volatiles are the motor of volcanic eruptions. Studies of vesiculation in erupted products can provide information on how volatiles exsolve, grow and are lost from magmas as lava and tephra fragments bear the fingerprints of such processes in vesicle and crystal textures. We summarize here the results of a series of X-ray computed microtomographic experiments that were performed on about 70 volcanic specimens of mainly basaltic and trachytic compositions. A first sample suite comprises samples collected from explosive activity at persistently degassing basaltic volcanoes, namely Stromboli (Aeolian Islands), Etna (Eastern Sicily) and Ambrym (Vanuatu Islands); a second suite consists of pumice and scoria clasts from Plinian to Subplinian to Vulcanian eruptions that occurred in the Campi Flegrei caldera (Southern Italy). The tomographic images provide us with a complete 3-D view of our sampled material through which it is possible to reconstruct the geometry of the vesicle network and explore how gas was transported in the investigated magmas. We find that basaltic scoriae exhibit two types of vesicles: large (~ mm^3), coalescing vesicles with complex, convoluted shapes and small-to-intermediate sized (<~1x10^-3 mm^3), spherical to sub-spherical, poorly connected or isolated vesicles. The former vesicles were interpreted as percolation pathways for gas to flow non-explosively to the volcano crater and thought to sustain the persistent passive gas release that characterizes these volcanoes. The fact that such vesicles were found in products erupted from active basaltic volcanoes located in different tectonic settings and characterized by different explosivity strongly suggests that basaltic systems appear to follow a common degassing pathway. However, not all explosive basaltic rocks contain large, coalescing vesicles. Pumice clasts from the much more violent, dangerous and less frequent paroxysmal explosions at Stromboli do not have this type of vesicles, demonstrating that basaltic volcanoes develop different vesicle textures and therefore degassing dynamics with increasing explosive activity. Trachytic pumices from highly explosive eruptions display a much finer structure in comparison to scoriae having sub-spherical to slightly deformed large vesicles and a large population of small spherical vesicles (1x10^-3 - <1x10^-5 mm^3). These two vesicle textures were mainly ascribed to the rapid ascent of a supersaturated magma under closed-system degassing, in comparison to the open-system conditions of basaltic magmas. Large interconnected vesicles that form micro-cracks are, however, found in some denser pyroclasts from Campi Flegrei. This suggests that gas was percolating in the conduit system before the eruption and that open-system degassing may be an effective way through which gas is lost in a moderately violent manner at the crater surface in some explosive felsic eruptions. Ultimately this study reveals that 3-D imaging of volcanic rocks is an essential tool for investigating degassing conditions in erupted magmas.

Magma degassing and eruption dynamics of the Avellino pumice Plinian eruption of Somma-Vesuvius (Italy). Comparison with the Pompeii eruption

NASA Astrophysics Data System (ADS)

Balcone-Boissard, H.; Boudon, G.; Ucciani, G.; Villemant, B.; Cioni, R.; Civetta, L.; Orsi, G.

2012-05-01

The eruptive history of Mt. Somma-Vesuvius is characterised by large explosive events: Pomici di Base eruption (22,030 ± 175 yr cal BP), Mercato (8890 ± 90 yr cal BP), Avellino (3945 ± 10 yr cal BP) and Pompeii (79 AD). Pre-eruptive conditions and sin-eruptive degassing processes of the Avellino eruption, the highest-magnitude Plinian event, have been investigated, using volatile contents (F, Cl, H2O) in melt inclusions and residual glass, and textural characteristics of pumice clasts of the 9 fallout layers sampled in detail in a representative sequence. The sequence displays an up-section sharp colour change from white to grey, corresponding to variations in both magma composition and textural characteristics. The pre-eruptive conditions have been constrained by systematic measurements of Cl content in both melt inclusions and matrix glass of pumice clasts. The pumice glass composition varies from Na-rich phonolite (white pumice) to K-rich phonolite (grey pumice). The measured Cl values constantly cluster at 5200 ± 400 ppm (buffer value), whatever the composition of the melt, suggesting that the entire magma body was saturated with sub-critical fluids. This Cl saturation constrains the pre-eruptive pressures and maximum H2O contents at 200 ± 10 MPa and 6.3 ± 0.2 wt.% H2O for the white pumice melt and 195 ± 15 MPa and 5.2 ± 0.2 wt.% H2O for the grey pumice melt. The fluid phase, mainly composed of a H2O-rich vapour phase and brine, probably accumulated at the top of the reservoir and generated an overpressure able to trigger the onset of the eruption. Magma degassing was rather homogeneous for the white and grey eruptive units, mostly occurring through closed-system processes, leading to a typical Plinian eruptive style. A steady-state withdrawal of an H2O-saturated magma may explain the establishment of a sustained Plinian column. Variation from white to grey pumice is accompanied by decrease of mean vesicularity and increase of mean microcrystallinity and permeability related to significant vesicle coalescence. Despite this, the ascending magma column still evolves under closed-system degassing, without significant gas loss through conduit walls. The Avellino eruption shows numerous similarities with the 79 AD Pompeii eruption in pre-eruptive conditions, degassing processes and eruptive style which are discussed here.

Variable mixing and degassing of mantle CO2 within continental subsurface water bodies evidenced by compared gas geochemistry and fluid-phase equilibrium modeling

NASA Astrophysics Data System (ADS)

Virgile, R.

2016-12-01

The continental degassing of mantle volatiles is known from a variety of areas characterized by Asthenosphere updoming, such as the US Basin and Range and the European Cenozoic Rift System. Mantle degassing is there usually associated to magmatic provinces where non-volcanic upwellings of cold to hot waters are frequently associated with high CO2 gas loads. The resulting aquifers, springs and mofets express variable gas compositions which are often attributed to the mixing of crustal and mantle CO2, and less often to the variable degassing states of the waters. Indeed, the compositions of water and gas in CO2, δ13C and the noble gases may justify both models. However, the implications of each model for the bulk degassing mass quantification of mantle volatiles are drastically different, and would therefore need to be confirmed or rejected on a case by case basis. We introduce here a new model for predicting fluid phase equilibrium for systems comprising CO2-CH4-H2-H2S-N2-O2-He-Ne-Ar-Kr-Xe-H2O-NaCl at shallow subsurface conditions (1-250 bars, 0-150°C). The model was applied in P-T conditions comparable to non-volcanic CO2 degassing systems, where initial fluids were defined as variable mixtures of air equilibrated water (AEW) and mantle volatiles (CO2, He, CO2/3He = 5 x109). Literature data from European non-volcanic mantle degassing systems were compiled and compared to different modeling scenarios. The distribution of the CO2/3He (from 108 to 1012) and N2/3He (from 106 to 1011) ratios in natural samples are consistent with the open system degassing of initial fluids at depths above 2000m, with variable recharges of AEW. Initial single phase fluids are composed of up to 300 mol.m-3 CO2, 7 x10-3 mol.m-3 He and N2 with typical AEW contents (0.5 mol.m-3). Most degassed systems correspond to 98% degassed initial fluids, which incorporated up to 10% of fresh AEW subsequently to degassing. Our results suggest that fluid phase fractionation effects alone are sufficient to generate the range of compositions observed in the studied natural water-gas systems, without the need to invoke a crustal CO2 end-member.

CO2 diffuse emission from maar lake: An example in Changbai volcanic field, NE China

NASA Astrophysics Data System (ADS)

Sun, Yutao; Guo, Zhengfu; Liu, Jiaqi; Du, Jianguo

2018-01-01

Numerous maars and monogenetic volcanic cones are distributed in northeast China, which are related to westward deep subduction of the Pacific Ocean lithosphere, comprising a significant part of the "Pacific Ring of Fire". It is well known that diffuse CO2 emissions from monogenetic volcanoes, including wet (e.g., maar lake) and dry degassing systems (e.g., soil diffuse emission, fault degassing, etc.), may contribute to budget of globally nature-derived greenhouse gases. However, their relationship between wet (e.g., maar lake) and concomitant dry degassing systems (e.g., soil diffuse emission, fault degassing, etc.) related to monogenetic volcanic field is poorly understood. Yuanchi maar, one of the typical monogenetic volcanic systems, is located on the eastern flank of Tianchi caldera in Changbai volcanic field of northeast China, which displays all of three forms of CO2 degassing including the maar lake, soil micro-seepage and fault degassing. Measurements of efflux of CO2 diffusion from the Yuanchi maar system (YMS) indicate that the average values of CO2 emissions from soil micro-seepage, fault degassing and water-air interface diffusion are 24.3 ± 23.3 g m- 2 d- 1, 39.2 ± 22.4 g m- 2 d- 1 and 2.4 ± 1.1 g m- 2 d- 1, respectively. The minimum output of CO2 diffuse emission from the YMS to the atmosphere is about 176.1 ± 88.3 ton/yr, of which 80.4% results from the dry degassing system. Degassing from the fault contributes to the most of CO2 emissions in all of the three forms of degassing in the YMS. Contributions of mantle, crust, air and organic CO2 to the soil gas are 0.01-0.10%, 10-20%, 32-36% and 48-54%, respectively, which are quantitatively constrained by a He-C isotope coupling calculation model. We propose that CO2 exsolves from the upper mantle melting beneath the Tianchi caldera, which migrates to the crustal magma chamber and further transports to the surface of YMS along the deep fault system. During the transportation processes, the emission of gas experiences crustal contamination, influence of magma chamber beneath the YMS, sub-surface processes and air dilution.

Carbon isotope constraints on degassing of carbon dioxide from Kilauea Volcano

USGS Publications Warehouse

Gerlach, T.M.; Taylor, B.E.

1990-01-01

We examine models for batch-equilibrium and fractional-equilibrium degassing of CO2 from magma at Kilauea Volcano. The models are based on 1. (1) the concept of two-stage degassing of CO2 from magma supplied to the summit chamber, 2. (2) C isotope data for CO2 in eruptive and noneruptive (quiescent) gases from Kilauea and 3. (3) data for the isotopic fractionation of C between CO2 and C dissolved in tholeiitic basalt melt. The results of our study indicate that 1. (1) both eruptive and noneruptive degassing of CO2 most closely approach a batch equilibrium process, 2. (2) the ??13C of parental magma supplied to the summit chamber is in the range -4.1 to-3.4??? and 3. (3) the ??13C of melt after summit chamber degassing is in the range -7 to -8???, depending upon the depth of equilibration. We also present ??13C data for CO2 in eruptive gases from the current East Rift Zone eruption. These are the first C isotope data for CO2 in high-temperature (>900??C) eruptive gases from Kilauea; they have a mean ??13C value of -7.82 ?? 0.24??? and are similar to those predicted for the melt after summit chamber degassing. The minor role played by fractional degassing of ascending magma at Kilauea means that exsolved CO2 tends to remain entrained in and coherent with its host melt during ascent from both mantle source regions and crustal magma reservoirs. This has important implications for magma dynamics at Kilauea. ?? 1990.

Volatile concentrations in variably vesicular pyroclasts from the Rotongaio ash (181 AD Taupo eruption): did shallow magma degassing trigger exceptionally violent phreatomagmatic activity?

NASA Astrophysics Data System (ADS)

Tuffen, Hugh; Houghton, Bruce F.; Dingwellp, Donald B.; Pinkerton, Harry

2010-05-01

Measurement of dissolved volatile concentrations in pyroclasts has formed the basis of our understanding of the links between magma degassing and the explosivity of silicic eruptions[1]. To date these studies have focussed exclusively on the densest pyroclastic obsidians, which comprise on a tiny proportion of the erupted products, in order to bypass the difficulty of analysing vesicular material. As a consequence, crucial information is missing about how degassing in the densest clasts relates to the behaviour of the bulk of the magma volume. To overcome this shortcoming, the volatile content of variably vesicular pyroclasts from the Rotongaio ash has been analysed using both micro-analytical (SIMS, synchrotron FTIR) and bulk techniques (TGA-MS). The Rotongaio ash was an exceptionally violent phase of phreatomagmatic activity during the 181 AD rhyolitic eruption of Taupo (New Zealand), the most powerful worldwide in the last 5000 years. The Rotongaio phase involved opening of new vents beneath Lake Taupo and the ash is characterised by a wide range of clast vesicularities (<10 to ~80 % by volume). Volatile measurement was challenging due to the high bubble number densities and small clast sizes. The mismatch between the water content of matrix glasses measured using bulk and micro-analytical techniques reflects pervasive post-eruption hydration of vesicle walls, which is most problematic at high vesicularities. Micron-scale maps of water concentration variations around vesicles in 30-50 vol % vesicular samples were acquired using SIMS. They indicate strong hydration within ~5 microns of vesicle walls, with pockets of unhydrated glass remaining in the thickest septa. Analysis of these unhydrated domains allowed robust measurement of water contents in pyroclasts ranging from ~1 to >50 vol % vesicles. Matrix glasses had largely degassed (0.19-0.49 wt % H2O, compared with an initial concentration in melt inclusions of ~3.6 wt %). The water contents measured using SIMS decreased systematically with increasing magma vesicularity. These results are fit well by a simple magma degassing model, in which a batch of magma first undergoes partial open-system degassing to a uniform water concentration of ~0.4 wt % H2O. Vesiculation then occurs with closed-system degassing, creating a negative relationship between vesicle content and the water content remaining in the melt. This model is consistent with the intrusion of a shallow cryptodome beneath Lake Taupo (depth ~100-200 metres) and prolonged stalling of magma at this shallow level. This was then followed by abrupt magma ascent and vesiculation, accompanied by interaction with the overlying lake water. Recent experiments have shown that the most violent interactions between rhyolitic magma and water may occur when the magma is highly viscous and prone to shear failure, as this creates the initial surface area for magma-water contact that results in explosive fuel-coolant interaction. The accumulation of a large volume (~1 km3) of degassed, highly-viscous rhyolitic magma directly beneath Lake Taupo may have therefore caused the exceptionally violent magma-water interaction that occurred during the Rotongaio phase. This reveals new links between magma degassing and the explosivity of eruptions when external water is involved, and illustrates the value of analysing pyroclastic material spanning a wide range of vesicularity in order to better reconstruct degassing systematics. References [1] Newman S. et al. (1988) J. Volcanol. Geotherm. Res. 35, 75-96. [2] Smith RT & Houghton BF (1995) Bull. Volcanol. 57, 432-439. [3] A. Austin-Erickson et al. (2008) J. Geophys. Res., 113, B11201.

Constraining the presence and abundance of an excess gas phase prior to the June 1991 eruption of Mt Pinatubo (Philippines) using S-isotopes

NASA Astrophysics Data System (ADS)

Bouvet de Maisonneuve, C.; Fiege, A.; Fabbro, G.; Kubo, A. I.

2016-12-01

Large explosive eruptions typically release orders of magnitude more S to the atmosphere than expected based on degassing of the erupted magma. To explain this, an excess, accumulated vapor phase is often proposed. Resolving the presence, composition, and source of such an exsolved volatile phase is essential, as it will drive eruptions towards increased explosivity. Integration of melt inclusion (MI) volatile contents (H, C, S, Cl, F) with S isotope data on melt inclusions, and sulfur-bearing minerals (anhydrite) can provide information on pre- and syn-eruptive degassing. The June 1991 eruption of Mt Pinatubo is an ideal candidate for such a study as it injected a >17 Mt of SO2 into the stratosphere, corresponding to a S excess release of a factor close to 100. The erupted magma was oxidized (QFM+3) and should therefore yield a clear isotopic trend. Volatile contents in glassy but vesicular quartz-hosted MIs were measured by SIMS and yield <3 wt% H2O and <100 ppm S but up to 1500 ppm CO2, in agreement with previous measurements. The MIs with few but large vapor bubbles (avoided during analysis) have lower H2O and CO2 contents and smaller standard deviations. The MIs with many small bubbles have higher volatile contents and standard deviations because the gas phase was not avoided during analysis. We observed scattered S contents and highly variable S isotope compositions for all MIs, which could be due to the presence of submicron S phases. Thus, we homogenized a batch of MIs under P-T-fO2 conditions that best correspond to pre-eruptive conditions. The δ34S for quartz-hosted MIs ranges from -1 to +14 ‰ and δ34S vs. S-H-C content trends are used to infer open or closed system degassing processes. In the near future, anhydrites and melt inclusions in other mineral hosts (amphibole and plagioclase) will be investigated in order to reconstruct the degassing history of the 1991 Pinatubo magma and to trace the S source.

Timing of degassing and plagioclase growth in lavas erupted from Mount St. Helens, 2004-2005, from 210Po-210Pb-226Ra disequilibria: Chapter 37 in A volcano rekindled: the renewed eruption of Mount St. Helens, 2004-2006

USGS Publications Warehouse

Reagan, Mark K.; Cooper, Kari M.; Pallister, John S.; Thornber, Carl R.; Wortel, Matthew; Sherrod, David R.; Scott, William E.; Stauffer, Peter H.

2008-01-01

Disequilibrium between 210Po, 210Pb, and 226Ra was measured on rocks and plagioclase mineral separates erupted during the first year of the ongoing eruption of Mount St. Helens. The purpose of this study was to monitor the volatile fluxing and crystal growth that occurred in the weeks, years, and decades leading up to eruption. Whole-rock samples were leached in dilute HCl to remove 210Po precipitated in open spaces. Before leaching, samples had variable initial (210Po) values, whereas after leaching, the groundmasses of nearly all juvenile samples were found to have had (210Po) ≈ 0 when they erupted. Thus, most samples degassed 210Po both before and after the magmas switched from open- to closed-system degassing. All juvenile samples have (210Pb)/(226Ra) ratios within 2 δ of equilibrium, suggesting that the magmas involved in the ongoing eruption did not have strong, persistent fluxes of 222Rn in or out of magmas during the decades and years leading to eruption. These equilibrium values also require a period of at least a century after magma generation and the last significant differentiation of the Mount St. Helens dacites. Despite this, the elevated (210Pb)/(226Ra) value measured in a plagioclase mineral separate from lava erupted in 2004 suggests that a significant proportion of this plagioclase grew within a few decades of eruption. The combined dataset suggests that for most 2004-5 lavas, the last stage of open-system degassing of the dacite magmas at Mount St. Helens is confined to the period between 1-2 years and 1-2 weeks before eruption, whereas plagioclase large enough to be included in the mineral separate grew around the time of the 1980s eruption or earlier.

Textural and geochemical constraints on eruptive style of the 79AD eruption at Vesuvius

NASA Astrophysics Data System (ADS)

Balcone-Boissard, Hélène; Boudon, Georges; Villemant, Benoît.

2010-05-01

The 79AD eruption of Vesuvius, also known as the "Pompeii eruption", is the reference for one of the explosive eruptive styles, the plinian-type eruption. The eruption involved H2O-rich phonolitic magmas and is commonly divided into three phases: an initial phreatomagmatic phase, followed by a plinian event which produced a thick pumice fallout deposit and a final phase that was dominated by numerous column-collapse events. During the plinian phase, a first white pumice fallout was produced from a high steady eruptive column, followed by a grey pumice fallout originated by an oscillatory eruptive column with several partial column collapse events. This study focuses on the pumice fallout deposits, sampled in a proximal thick section, at the Terzigno quarry, 6 km southeast of the present crater. In order to constrain the degassing processes and the eruptive dynamics, major element compositions, residual volatile contents (H2O, Cl) and textural characteristics (vesicularity and microcrystallinity) were studied. A previous study that we performed on the pre-eruptive Cl content has shown that Cl may be used as an indicator of magma saturation with Cl-rich fluids and of pre-eruptive pressures. Cl contents measured in melt inclusions show that only the white pumice and the upper part of the grey pumice magma were H2O saturated prior eruption. Large variations in residual volatile contents exist between the different eruptive units and textural features strongly differ between white and grey pumice clasts but also within the grey pumice clasts. The degassing processes were thus highly heterogeneous: the white pumice eruptive units represent a typical closed-system degassing evolution whereas the first grey pumice one, stored in the same pre-eruptive saturation conditions, follows a particular open-system degassing evolution. Here we propose a new model of the 79AD eruption where pre-eruptive conditions (H2O saturation, magma temperature and viscosity) are the critical parameters which determine the diversity of the syn-eruptive degassing processes and hence the eruptive dynamics. We suggest that the oscillatory regime that dominates the grey pumice eruptive phase is linked to the pre-eruptive water undersaturation of most part of the grey magma and to the time delays necessary for H2O exsolution.

Unraveling the dynamics of magmatic CO2 degassing at Mammoth Mountain, California

NASA Astrophysics Data System (ADS)

Peiffer, Loïc; Wanner, Christoph; Lewicki, Jennifer L.

2018-02-01

The accumulation of magmatic CO2 beneath low-permeability barriers may lead to the formation of CO2-rich gas reservoirs within volcanic systems. Such accumulation is often evidenced by high surface CO2 emissions that fluctuate over time. The temporal variability in surface degassing is believed in part to reflect a complex interplay between deep magmatic degassing and the permeability of degassing pathways. A better understanding of the dynamics of CO2 degassing is required to improve monitoring and hazards mitigation in these systems. Owing to the availability of long-term records of CO2 emissions rates and seismicity, Mammoth Mountain in California constitutes an ideal site towards such predictive understanding. Mammoth Mountain is characterized by intense soil CO2 degassing (up to ∼1000 t d-1) and tree kill areas that resulted from leakage of CO2 from a CO2-rich gas reservoir located in the upper ∼4 km. The release of CO2-rich fluids from deeper basaltic intrusions towards the reservoir induces seismicity and potentially reactivates faults connecting the reservoir to the surface. While this conceptual model is well-accepted, there is still a debate whether temporally variable surface CO2 fluxes directly reflect degassing of intrusions or variations in fault permeability. Here, we report the first large-scale numerical model of fluid and heat transport for Mammoth Mountain. We discuss processes (i) leading to the initial formation of the CO2-rich gas reservoir prior to the occurrence of high surface CO2 degassing rates and (ii) controlling current CO2 degassing at the surface. Although the modeling settings are site-specific, the key mechanisms discussed in this study are likely at play at other volcanic systems hosting CO2-rich gas reservoirs. In particular, our model results illustrate the role of convection in stripping a CO2-rich gas phase from a rising hydrothermal fluid and leading to an accumulation of a large mass of CO2 (∼107-108 t) in a shallow gas reservoir. Moreover, we show that both, short-lived (months to years) and long-lived (hundreds of years) events of magmatic fluid injection can lead to critical pressures within the reservoir and potentially trigger fault reactivation. Our sensitivity analysis suggests that observed temporal fluctuations in surface degassing are only indirectly controlled by variations in magmatic degassing and are mainly the result of temporally variable fault permeability. Finally, we suggest that long-term CO2 emission monitoring, seismic tomography and coupled thermal-hydraulic-mechanical modeling are important for CO2-related hazard mitigation.

MAGA, a new database of gas natural emissions: a collaborative web environment for collecting data.

NASA Astrophysics Data System (ADS)

Cardellini, Carlo; Chiodini, Giovanni; Frigeri, Alessandro; Bagnato, Emanuela; Frondini, Francesco; Aiuppa, Alessandro

2014-05-01

The data on volcanic and non-volcanic gas emissions available online are, as today, are incomplete and most importantly, fragmentary. Hence, there is need for common frameworks to aggregate available data, in order to characterize and quantify the phenomena at various scales. A new and detailed web database (MAGA: MApping GAs emissions) has been developed, and recently improved, to collect data on carbon degassing form volcanic and non-volcanic environments. MAGA database allows researchers to insert data interactively and dynamically into a spatially referred relational database management system, as well as to extract data. MAGA kicked-off with the database set up and with the ingestion in to the database of the data from: i) a literature survey on publications on volcanic gas fluxes including data on active craters degassing, diffuse soil degassing and fumaroles both from dormant closed-conduit volcanoes (e.g., Vulcano, Phlegrean Fields, Santorini, Nysiros, Teide, etc.) and open-vent volcanoes (e.g., Etna, Stromboli, etc.) in the Mediterranean area and Azores, and ii) the revision and update of Googas database on non-volcanic emission of the Italian territory (Chiodini et al., 2008), in the framework of the Deep Earth Carbon Degassing (DECADE) research initiative of the Deep Carbon Observatory (DCO). For each geo-located gas emission site, the database holds images and description of the site and of the emission type (e.g., diffuse emission, plume, fumarole, etc.), gas chemical-isotopic composition (when available), gas temperature and gases fluxes magnitude. Gas sampling, analysis and flux measurement methods are also reported together with references and contacts to researchers expert of each site. In this phase data can be accessed on the network from a web interface, and data-driven web service, where software clients can request data directly from the database, are planned to be implemented shortly. This way Geographical Information Systems (GIS) and Virtual Globes (e.g., Google Earth) could easily access the database, and data could be exchanged with other database. At the moment the database includes: i) more than 1000 flux data about volcanic plume degassing from Etna and Stromboli volcanoes, ii) data from ~ 30 sites of diffuse soil degassing from Napoletan volcanoes, Azores, Canary, Etna, Stromboli, and Vulcano Island, several data on fumarolic emissions (~ 7 sites) with CO2 fluxes; iii) data from ~ 270 non volcanic gas emission site in Italy. We believe MAGA data-base is an important starting point to develop a large scale, expandable data-base aimed to excite, inspire, and encourage participation among researchers. In addition, the possibility to archive location and qualitative information for gas emission/sites not yet investigated, could stimulate the scientific community for future researches and will provide an indication on the current uncertainty on deep carbon fluxes global estimates

Unraveling the dynamics of magmatic CO2 degassing at Mammoth Mountain, California

USGS Publications Warehouse

Pfeiffer, Loic; Wanner, Christoph; Lewicki, Jennifer L.

2018-01-01

The accumulation of magmatic CO2 beneath low-permeability barriers may lead to the formation of CO2-rich gas reservoirs within volcanic systems. Such accumulation is often evidenced by high surface CO2 emissions that fluctuate over time. The temporal variability in surface degassing is believed in part to reflect a complex interplay between deep magmatic degassing and the permeability of degassing pathways. A better understanding of the dynamics of CO2 degassing is required to improve monitoring and hazards mitigation in these systems. Owing to the availability of long-term records of CO2 emissions rates and seismicity, Mammoth Mountain in California constitutes an ideal site towards such predictive understanding. Mammoth Mountain is characterized by intense soil CO2 degassing (up to ∼1000 t d−1) and tree kill areas that resulted from leakage of CO2 from a CO2-rich gas reservoir located in the upper ∼4 km. The release of CO2-rich fluids from deeper basaltic intrusions towards the reservoir induces seismicity and potentially reactivates faults connecting the reservoir to the surface. While this conceptual model is well-accepted, there is still a debate whether temporally variable surface CO2 fluxes directly reflect degassing of intrusions or variations in fault permeability. Here, we report the first large-scale numerical model of fluid and heat transport for Mammoth Mountain. We discuss processes (i) leading to the initial formation of the CO2-rich gas reservoir prior to the occurrence of high surface CO2 degassing rates and (ii) controlling current CO2 degassing at the surface. Although the modeling settings are site-specific, the key mechanisms discussed in this study are likely at play at other volcanic systems hosting CO2-rich gas reservoirs. In particular, our model results illustrate the role of convection in stripping a CO2-rich gas phase from a rising hydrothermal fluid and leading to an accumulation of a large mass of CO2 (∼107–108 t) in a shallow gas reservoir. Moreover, we show that both, short-lived (months to years) and long-lived (hundreds of years) events of magmatic fluid injection can lead to critical pressures within the reservoir and potentially trigger fault reactivation. Our sensitivity analysis suggests that observed temporal fluctuations in surface degassing are only indirectly controlled by variations in magmatic degassing and are mainly the result of temporally variable fault permeability. Finally, we suggest that long-term CO2 emission monitoring, seismic tomography and coupled thermal–hydraulic–mechanical modeling are important for CO2-related hazard mitigation.

The development of a new database of gas emissions: MAGA, a collaborative web environment for collecting data

NASA Astrophysics Data System (ADS)

Cardellini, C.; Chiodini, G.; Frigeri, A.; Bagnato, E.; Aiuppa, A.; McCormick, B.

2013-12-01

The data on volcanic and non-volcanic gas emissions available online are, as today, incomplete and most importantly, fragmentary. Hence, there is need for common frameworks to aggregate available data, in order to characterize and quantify the phenomena at various spatial and temporal scales. Building on the Googas experience we are now extending its capability, particularly on the user side, by developing a new web environment for collecting and publishing data. We have started to create a new and detailed web database (MAGA: MApping GAs emissions) for the deep carbon degassing in the Mediterranean area. This project is part of the Deep Earth Carbon Degassing (DECADE) research initiative, lunched in 2012 by the Deep Carbon Observatory (DCO) to improve the global budget of endogenous carbon from volcanoes. MAGA database is planned to complement and integrate the work in progress within DECADE in developing CARD (Carbon Degassing) database. MAGA database will allow researchers to insert data interactively and dynamically into a spatially referred relational database management system, as well as to extract data. MAGA kicked-off with the database set up and a complete literature survey on publications on volcanic gas fluxes, by including data on active craters degassing, diffuse soil degassing and fumaroles both from dormant closed-conduit volcanoes (e.g., Vulcano, Phlegrean Fields, Santorini, Nysiros, Teide, etc.) and open-vent volcanoes (e.g., Etna, Stromboli, etc.) in the Mediterranean area and Azores. For each geo-located gas emission site, the database holds images and description of the site and of the emission type (e.g., diffuse emission, plume, fumarole, etc.), gas chemical-isotopic composition (when available), gas temperature and gases fluxes magnitude. Gas sampling, analysis and flux measurement methods are also reported together with references and contacts to researchers expert of the site. Data can be accessed on the network from a web interface or as a data-driven web service, where software clients can request data directly from the database. This way Geographical Information Systems (GIS) and Virtual Globes (e.g., Google Earth) can easily access the database, and data can be exchanged with other database. In details the database now includes: i) more than 1000 flux data about volcanic plume degassing from Etna (4 summit craters and bulk degassing) and Stromboli volcanoes, with time averaged CO2 fluxes of ~ 18000 and 766 t/d, respectively; ii) data from ~ 30 sites of diffuse soil degassing from Napoletan volcanoes, Azores, Canary, Etna, Stromboli, and Vulcano Island, with a wide range of CO2 fluxes (from les than 1 to 1500 t/d) and iii) several data on fumarolic emissions (~ 7 sites) with CO2 fluxes up to 1340 t/day (i.e., Stromboli). When available, time series of compositional data have been archived in the database (e.g., for Campi Flegrei fumaroles). We believe MAGA data-base is an important starting point to develop a large scale, expandable data-base aimed to excite, inspire, and encourage participation among researchers. In addition, the possibility to archive location and qualitative information for gas emission/sites not yet investigated, could stimulate the scientific community for future researches and will provide an indication on the current uncertainty on deep carbon fluxes global estimates.

DECADE web portal: toward the integration of MaGa, EarthChem and VOTW data systems to further the knowledge on Earth degassing

NASA Astrophysics Data System (ADS)

Cardellini, Carlo; Frigeri, Alessandro; Lehnert, Kerstin; Ash, Jason; McCormick, Brendan; Chiodini, Giovanni; Fischer, Tobias; Cottrell, Elizabeth

2015-04-01

The release of volatiles from the Earth's interior takes place in both volcanic and non-volcanic areas of the planet. The comprehension of such complex process and the improvement of the current estimates of global carbon emissions, will greatly benefit from the integration of geochemical, petrological and volcanological data. At present, major online data repositories relevant to studies of degassing are not linked and interoperable. In the framework of the Deep Earth Carbon Degassing (DECADE) initiative of the Deep Carbon Observatory (DCO), we are developing interoperability between three data systems that will make their data accessible via the DECADE portal: (1) the Smithsonian Institutionian's Global Volcanism Program database (VOTW) of volcanic activity data, (2) EarthChem databases for geochemical and geochronological data of rocks and melt inclusions, and (3) the MaGa database (Mapping Gas emissions) which contains compositional and flux data of gases released at volcanic and non-volcanic degassing sites. The DECADE web portal will create a powerful search engine of these databases from a single entry point and will return comprehensive multi-component datasets. A user will be able, for example, to obtain data relating to compositions of emitted gases, compositions and age of the erupted products and coincident activity, of a specific volcano. This level of capability requires a complete synergy between the databases, including availability of standard-based web services (WMS, WFS) at all data systems. Data and metadata can thus be extracted from each system without interfering with each database's local schema or being replicated to achieve integration at the DECADE web portal. The DECADE portal will enable new synoptic perspectives on the Earth degassing process allowing to explore Earth degassing related datasets over previously unexplored spatial or temporal ranges.

Asymmetrical hydrothermal system below Merapi volcano imaged by geophysical data.

NASA Astrophysics Data System (ADS)

Byrdina, Svetlana; Friedel, Sven; Budi-Santoso, Agus; Suryanto, Wiwit; Suhari, Aldjarishy; Vandemeulebrouck, Jean; Rizal, Mohhamed H.; Grandis, Hendra

2017-04-01

A high-resolution image of the hydrothermal system of Merapi volcano is obtained using electrical resistivity tomography (ERT), self-potential, and CO2 flux mappings. The ERT inversions identify two distinct low-resistivity bodies, at the base of the south flank and in the summit area, that represent likely two parts of an interconnected hydrothermal system. In the summit area, the extension of the hydrothermal system is clearly limited by the main geological structures which are actual and ancient craters. A sharp resistivity contrast at ancient crater rim Pasar-Bubar separates a conductive hydrothermal system (20 - 50 Ωm) from the resistive andesite lava flows and pyroclastic deposits (2000 - 50 000 Ωm). High diffuse CO2 degassing (with a median value of 400g m -2 d -1) is observed in a narrow vicinity of the active crater rim and close to the Pasar-Bubar. The existence of preferential fluid circulation along this ancient crater rim is also evidenced by self-potential data. The total CO2 degassing across the accessible summit area with a surface of 1.4 · 10 5 m 2 is around 20 td -1. Before the 2010 eruption, Toutain et al. (2009) estimated a higher value of the total diffuse degassing from the summit area (about 200 - 230 td -1). This drop in the diffuse degassing can be related to the decrease in the magmatic activity, to the change of the summit morphology or to a combination of these factors. On the south flank of Merapi, the resistivity model shows spectacular stratification. While surficial recent andesite lava flows are characterized by resistivity exceeding 100 000 Ωm, resistivity as low as 10 Ωm has been encountered at a depth of 200 m at the base of the south flank and was interpreted as a presence of the hydrothermal system. We suggest that a sandwich-like structure of stratified pyroclastic deposits on the flanks of Merapi screen and separate the flow of hydrothermal fluids with the degassing occurring mostly through the fractured crater rims, while the liquid water flows down to the base of the volcanic dome. Our ERT results suggest the existence of a peripheral hydrothermal system below the south and west flanks in agreement with previous electromagnetic studies. In contrast, no evidence of hydrothermal system is found below the north flank, where the resistivity values are too high to be assigned to a hydrothermal system, at least to the ERT investigation depth. A probable cause of this asymmetry could be a non-axial location of the magmatic heat source. Such non-axial location of the magmatic source relative to the edifice is suggested by the shift of the volcanic activity to the south as proposed in the geological model by Camus et al, (2000). In addition, the hypocenters of seismic events located by Budi-Santoso et al, (2013) seem to be distributed to the SW from the active crater suggesting that the magma conduits and likely, the magmatic source, are shifted to the SW with respect to the actual crater.

Constraining pre-eruptive volatile contents and degassing histories in submarine lavas

NASA Astrophysics Data System (ADS)

Jones, M.; Soule, S. A.; Liao, Y.; Le Roux, V.; Brodsky, H.; Kurz, M. D.

2017-12-01

Vesicle textures in submarine lavas have been used to calculate total (pre-eruption) volatile concentrations in mid-ocean ridge basalts (MORB), which provide constraints on upper mantle volatile contents and CO2 fluxes along the global MOR. In this study, we evaluate vesicle size distributions and volatile contents in a suite of 20 MORB samples, which span the range of typical vesicularities and bubble number densities observed in global MORB. We demonstrate that 2D imaging coupled with traditional stereological methods closely reproduces vesicle size distributions and vesicularities measured using 3D x-ray micro-computed tomography (μ-CT). We further demonstrate that x-ray μ-CT provides additional information about bubble deformation and clustering that are linked to bubble nucleation and lava emplacement dynamics. The validation of vesicularity measurements allows us to evaluate the methods for calculating total CO2 concentrations in MORB using dissolved volatile content (SIMS), vesicularity, vesicle gas density, and equations of state. We model bubble and melt contraction during lava quenching and show that the melt viscosity prevents bubbles from reaching equilibrium at the glass transition temperature. Thus, we suggest that higher temperatures should be used to calculate exsolved volatile concentrations based on observed vesicularities. Our revised method reconciles discrepancies between exsolved volatile contents measured by gas manometry and calculated from vesicularity. In addition, our revised method suggests that some previous studies may have overestimated MORB volatile concentrations by up to a factor of two, with the greatest differences in samples with the highest vesicularities (e.g., `popping rock' 2πD43). These new results have important implications for CO2/Nb of `undegassed' MORB and global ridge CO2 fluxes. Lastly, our revised method yields constant total CO2 concentrations in sample suites from individual MOR eruptions that experienced syn-eruptive degassing. These results imply closed-system degassing during magma ascent and emplacement following equilibration at the depth of melt storage in the crust.

Geophysical image of the hydrothermal system of Merapi volcano

NASA Astrophysics Data System (ADS)

Byrdina, S.; Friedel, S.; Vandemeulebrouck, J.; Budi-Santoso, A.; Suhari; Suryanto, W.; Rizal, M. H.; Winata, E.; Kusdaryanto

2017-01-01

We present an image of the hydrothermal system of Merapi volcano based on results from electrical resistivity tomography (ERT), self-potential, and CO2 flux mappings. The ERT models identify two distinct low-resistivity bodies interpreted as two parts of a probably interconnected hydrothermal system: at the base of the south flank and in the summit area. In the summit area, a sharp resistivity contrast at ancient crater rim Pasar-Bubar separates a conductive hydrothermal system (20-50 Ω m) from the resistive andesite lava flows and pyroclastic deposits (2000-50,000 Ω m). The existence of preferential fluid circulation along this ancient crater rim is also evidenced by self-potential data. The significative diffuse CO2 degassing (with a median value of 400 g m-2 d-1) is observed in a narrow vicinity of the active crater rim and close to the ancient rim of Pasar-Bubar. The total CO2 degassing across the accessible summital area with a surface of 1.4 ṡ 105 m2 is around 20 t d-1. Before the 2010 eruption, Toutain et al. (2009) estimated a higher value of the total diffuse degassing from the summit area (about 200-230 t d-1). This drop in the diffuse degassing from the summit area can be related to the decrease in the magmatic activity, to the change of the summit morphology, to the approximations used by Toutain et al. (2009), or, more likely, to a combination of these factors. On the south flank of Merapi, the resistivity model shows spectacular stratification. While surficial recent andesite lava flows are characterized by resistivity exceeding 100,000 Ω m, resistivity as low as 10 Ω m has been encountered at a depth of 200 m at the base of the south flank and was interpreted as a presence of the hydrothermal system. No evidence of the hydrothermal system is found on the basis of the north flank at the same depth. This asymmetry might be caused by the asymmetry of the heat supply source of Merapi whose activity is moving south or/and to the asymmetry in topography caused by the presence of Merbabu volcano in the north. On the basis of our results we suggest that stratified pyroclastic deposits on the south flank of Merapi screen and separate the flow of hydrothermal fluids with the gaseous part rising through the crater rims, while the liquid part is flowing downwards to the base of the edifice.

Recirculating Molten Metal Supply System And Method

DOEpatents

Kinosz, Michael J.; Meyer, Thomas N.

2003-07-01

The melter furnace includes a heating chamber (16), a pump chamber (18), a degassing chamber (20), and a filter chamber (22). The pump chamber (18) is located adjacent the heating chamber (16) and houses a molten metal pump (30). The degassing chamber (20) is located adjacent and in fluid communication with the pump chamber (18), and houses a degassing mechanism (36). The filter chamber (22) is located adjacent and in fluid communication with the degassing chamber (20). The filter chamber (22) includes a molten metal filter (38). The melter furnace (12) is used to supply molten metal to an externally located holder furnace (14), which then recirculates molten metal back to the melter furnace (12).

An experimental study of the fluid-melt partitioning of volatiles (H2O, CO2, S) during the degassing of ascending basalt

NASA Astrophysics Data System (ADS)

Le Gall, Nolwenn; Pichavant, Michel; Di Carlo, Ida; Scaillet, Bruno

2017-04-01

We performed decompression experiments to constrain the fluid-melt partitioning of volatiles (H2O, CO2, S) in ascending basalt magmas associated with violent eruptions. Experiments were conducted in an internally heated pressure vessel under oxidizing conditions (fO2: NNO+1.1) so that all sulphur occurs as sulfate (S6+) in the melt. Volatile-bearing (2.72 ± 0.02 wt% H2O, 1291 ± 85 ppm CO2, 1535 ± 369 ppm S) melts, prepared from Stromboli pumice, were synthesized at 1200°C and 200 MPa, decompressed between 150 and 25 MPa at constant rates of 39 and 78 kPa/s (or 1.5 and 3 m/s), and rapidly quenched. Run products were characterized both chemically (by IR spectroscopy and electron microprobe analysis) and texturally (by scanning electron microscopy), and then compared with Stromboli pumice products (glass inclusions, volcanic gases). In H2O-CO2-S-bearing basaltic melts, bubbles start to nucleate heterogeneously on Fe sulfides for supersaturation pressures ΔPHeN ≤ 1 MPa and to nucleate homogeneously for ΔPHoN < 50 MPa (ΔPHeN and ΔPHoN are the difference between the saturation pressure and the pressure at which heterogeneous and homogeneous bubble nucleation are observed, respectively). Bubble growth, coalescence and outgassing occur in addition to continuous bubble nucleation, which is sustained by the preservation of CO2 supersaturated melts during decompression. In addition to model the degassing behaviour of sulphur (and also of CO2 and H2O), our experiments aim to assist in the interpretation of geochemical observables. On the one hand, the volatile degassing trend recorded by Stromboli natural glasses (unsealed glass embayments) was closely experimentally simulated, with a coupled decrease of H2O and S whereas CO2 concentrations remain elevated. On the other hand, the experimental H2O/CO2 and CO2/SO2 fluid molar ratios, calculated by mass balance, both reproduced or closely approached the lower ranges of gas ratios measured at Stromboli for quiescent magma degassing and explosive activity. Compared to models that attribute a deep origin to CO2-rich fluxes and high CO2/SO2 gas ratios, our experimental observations support a model of low pressure (Pf << 25 MPa) explosive degassing of CO2-rich melts generated as a result of disequilibrium degassing to generate Strombolian paroxysms.

Monitoring diffuse volcanic degassing during volcanic unrests: the case of Campi Flegrei (Italy).

PubMed

Cardellini, C; Chiodini, G; Frondini, F; Avino, R; Bagnato, E; Caliro, S; Lelli, M; Rosiello, A

2017-07-28

In volcanoes with active hydrothermal systems, diffuse CO 2 degassing may constitute the primary mode of volcanic degassing. The monitoring of CO 2 emissions can provide important clues in understanding the evolution of volcanic activity especially at calderas where the interpretation of unrest signals is often complex. Here, we report eighteen years of CO 2 fluxes from the soil at Solfatara of Pozzuoli, located in the restless Campi Flegrei caldera. The entire dataset, one of the largest of diffuse CO 2 degassing ever produced, is made available for the scientific community. We show that, from 2003 to 2016, the area releasing deep-sourced CO 2 tripled its extent. This expansion was accompanied by an increase of the background CO 2 flux, over most of the surveyed area (1.4 km 2 ), with increased contributions from non-biogenic source. Concurrently, the amount of diffusively released CO 2 increased up to values typical of persistently degassing active volcanoes (up to 3000 t d -1 ). These variations are consistent with the increase in the flux of magmatic fluids injected into the hydrothermal system, which cause pressure increase and, in turn, condensation within the vapor plume feeding the Solfatara emission.

Comparison of diffuse CO2 degassing at Miravalles and Rincón de la Vieja volcanoes (Guanacaste Province, Costa Rica)

NASA Astrophysics Data System (ADS)

Liegler, A.; Bakkar Hindeleh, H.; Deering, C. D.; Fentress, S. E.

2015-12-01

Volcanic gas emissions are a key component for monitoring volcanic activity, magmatic input of volatiles to the atmosphere and the assessment of geothermal potential in volcanic regions. Diffuse soil degassing has been shown to represent a major part of volcanic gas emissions. However, this type of gas emission has not yet been quantified in the Guanacaste province of Costa Rica; a region of the country with several large, active or dormant volcanoes. We conducted the first study of diffuse CO2 degassing at Rincón de la Vieja and Miravalles volcanoes, both located in Guanacaste. Diffuse degassing was measured using the accumulation chamber method to quantify CO2 flux in regions where hydrothermal surface features indicate anomalous activity. The total diffuse carbon dioxide flux estimated at Miravalles in two areas, together roughly 2 km2 in size, was 135 t/day and in several areas at Rincón de la Vieja a minimum of 4 t/day. Comparatively low flux values and a very local concentration (few m2) of CO2 flux were observed at the active Rincón de la Vieja volcano, compared to the dormant Miravalles volcano, where significant soil flux was found over extended areas, not only around vents. Our assessment of the origin of these differences leads to two possibilities depending on if the surface features on the two volcanoes are fed by a common hydrothermal system or two separate ones. In the former case, the different intensity of diffuse CO2 flux could indicate a different degassing behavior and stronger concentration of gas emissions at the active vent areas at Rincon de la Vieja. In the latter case, where the hydrothermal systems are not linked, the amount of CO2 degassed through the flanks of the volcanoes could indicate that different physical and chemical conditions are governing the degassing of the two systems.

Rapid and slow: Varying magma ascent rates as a mechanism for Vulcanian explosions

NASA Astrophysics Data System (ADS)

Cassidy, Mike; Cole, Paul. D.; Hicks, Kelby E.; Varley, Nick R.; Peters, Nial; Lerner, Allan H.

2015-06-01

Vulcanian explosions are one of the most common types of volcanic activity observed at silicic volcanoes. Magma ascent rates are often invoked as being the fundamental control on their explosivity, yet this factor is poorly constrained for low magnitude end-member Vulcanian explosions, which are particularly poorly understood, partly due to the rarity of ash samples and low gas fluxes. We describe ash generated by small Vulcanian explosions at Volcán de Colima in 2013, where we document for the first time marked differences in the vesicularity, crystal characteristics (volume fraction, size and shape) and glass compositions in juvenile material from discrete events. We interpret these variations as representing differing ascent styles and speeds of magma pulses within the conduit. Heterogeneous degassing during ascent leads to fast ascending, gas-rich magma pulses together with slow ascending gas-poor magma pulses within the same conduit. This inferred heterogeneity is complemented by SO2 flux data, which show transient episodes of both open and closed system degassing, indicating efficient shallow fracture sealing mechanisms, which allows for gas overpressure to generate small Vulcanian explosions.

CO2 fluxes from diffuse degassing in Italy

NASA Astrophysics Data System (ADS)

Cardellini, C.; Chiodini, G.; Frondini, F.; Caliro, S.

2016-12-01

Central and southern Italy are affected by an intense process of CO2 Earth degassing from both active volcanoes, and tectonically active areas. Regional scale studies, based on C mass balance of groundwater of regional aquifers in not volcanically active areas, highlighted the presence of two large CO2 degassing structures that, for magnitude and the geochemical-isotopic features, were related to a regional process of mantle degassing. Quantitative estimates provided a CO2 flux of 9 Mt/y for the region (62000 km2). Besides the magnitude of the process, a strong link between the deep CO2 degassing and the seismicity of the region and a strict correlation between migration of deep CO2-rich fluids and the heat flux have been highlighted. In addition, the region is also characterised by the presence of many cold gas emissions where deeply derived CO2 is released by vents and soil diffuse degassing areas. Both direct CO2 expulsion at the surface and C-rich groundwater are different manifestations of the same process, in fact, the deeply produced gas can be dissolved by groundwater or emitted directly to the atmosphere depending on the gas flux rate, and the geological-structural and hydrogeological settings. Quantitative estimations of the CO2 fluxes are available only for a limited number ( 30) of the about 270 catalogued gas manifestations allowing an estimations of a CO2 flux of 1.4 Mt/y. Summing the two estimates the non-volcanic CO2 flux from the region results globally relevant, being from 2 to 10% of the estimated present-day global CO2 discharge from subaerial volcanoes. Large amounts of CO2 is also discharged by soil diffuse degassing in volcanic-hydrothermal systems. Specific surveys at Solfatara of Pozzuoli (Campi Flegrei Caldera) pointed out the relevance of this process. CO2 diffuse degassing at Solfatara, measured since 1998 shows a persistent CO2 flux of 1300 t/d (± 390 t/d), a flux comparable to an erupting volcano. The quantification of diffuse CO2 degassing in Italy points out the relevance of non-volcanic CO2 degassing and of soil degassing from volcanoes, suggesting that the actual underestimation of the global CO2 degassing, may arise also from the lack of specific and systematic studies of the numerous "degassing areas" of the world, that would contribute to better constrain the global CO2 budget.

DECADE Web Portal: Integrating MaGa, EarthChem and GVP Will Further Our Knowledge on Earth Degassing

NASA Astrophysics Data System (ADS)

Cardellini, C.; Frigeri, A.; Lehnert, K. A.; Ash, J.; McCormick, B.; Chiodini, G.; Fischer, T. P.; Cottrell, E.

2014-12-01

The release of gases from the Earth's interior to the exosphere takes place in both volcanic and non-volcanic areas of the planet. Fully understanding this complex process requires the integration of geochemical, petrological and volcanological data. At present, major online data repositories relevant to studies of degassing are not linked and interoperable. We are developing interoperability between three of those, which will support more powerful synoptic studies of degassing. The three data systems that will make their data accessible via the DECADE portal are: (1) the Smithsonian Institution's Global Volcanism Program database (GVP) of volcanic activity data, (2) EarthChem databases for geochemical and geochronological data of rocks and melt inclusions, and (3) the MaGa database (Mapping Gas emissions) which contains compositional and flux data of gases released at volcanic and non-volcanic degassing sites. These databases are developed and maintained by institutions or groups of experts in a specific field, and data are archived in formats specific to these databases. In the framework of the Deep Earth Carbon Degassing (DECADE) initiative of the Deep Carbon Observatory (DCO), we are developing a web portal that will create a powerful search engine of these databases from a single entry point. The portal will return comprehensive multi-component datasets, based on the search criteria selected by the user. For example, a single geographic or temporal search will return data relating to compositions of emitted gases and erupted products, the age of the erupted products, and coincident activity at the volcano. The development of this level of capability for the DECADE Portal requires complete synergy between these databases, including availability of standard-based web services (WMS, WFS) at all data systems. Data and metadata can thus be extracted from each system without interfering with each database's local schema or being replicated to achieve integration at the DECADE web portal. The DECADE portal will enable new synoptic perspectives on the Earth degassing process. Other data systems can be easily plugged in using the existing framework. Our vision is to explore Earth degassing related datasets over previously unexplored spatial or temporal ranges.

Garan performs TCS Water Loop Degassing in Columbus

NASA Image and Video Library

2011-04-08

ISS027-E-011325 (8 April 2011) --- NASA astronaut Ron Garan, Expedition 27 flight engineer, works on degassing the water loop of the running Water Pump Assembly 2 / Thermal Control System (WPA2/TCS) in the Columbus laboratory of the International Space Station.

Garan performs TCS Water Loop Degassing in Columbus

NASA Image and Video Library

2011-04-08

ISS027-E-011324 (8 April 2011) --- NASA astronaut Ron Garan, Expedition 27 flight engineer, works on degassing the water loop of the running Water Pump Assembly 2 / Thermal Control System (WPA2/TCS) in the Columbus laboratory of the International Space Station.

Elevated gas flux and trace metal degassing from the 2014-2015 fissure eruption at the Bárðarbunga volcanic system, Iceland

NASA Astrophysics Data System (ADS)

Gauthier, Pierre-Jean; Sigmarsson, Olgeir; Gouhier, Mathieu; Haddadi, Baptiste; Moune, Séverine

2016-03-01

The 2014 Bárðarbunga rifting event in Iceland resulted in a 6-month long eruption at Holuhraun. This eruption was characterized by high lava discharge rate and significant gas emission. The SO2 flux for the first 3 months was measured with satellite sensors and the petrologic method. High-resolution time series of the satellite data give 1200 kg/s that concurs with 1050 kg/s obtained from melt inclusion minus degassed lava sulfur contents scaled to the mass of magma produced. A high-purity gas sample, with elevated S/Cl due to limited chlorine degassing, reveals a similar degassing pattern of trace metals as observed at Kīlauea (Hawai'i) and Erta Ale (Ethiopia). This suggests a common degassing mechanism at mantle plume-related volcanoes. The trace metal fluxes, calculated from trace element to sulfur ratios in the gas sample and scaled to the sulfur dioxide flux, are 1-2 orders of magnitude stronger at Holuhraun than Kīlauea and Erta Ale. In contrast, volcanoes at convergent margins (Etna and Stromboli, Italy) have 1-2 orders of magnitude higher trace element fluxes, most likely caused by abundant chlorine degassing. This emphasizes the importance of metal degassing as chlorine species. Short-lived disequilibria between radon daughters, 210Pb-210Bi-210Po measured in the gas, suggest degassing of a continuously replenished magma batch beneath the eruption site. Earlier and deep degassing phase of carbon dioxide and polonium is inferred from low (210Po/210Pb) in the gas, consistent with magma transfer rate of 0.75 m/s.

Diverse long Period tremors and their implications on degassing and heating inside Aso volcano

NASA Astrophysics Data System (ADS)

Niu, Jieming; Song, Teh-Ru Alex

2017-04-01

Long-period tremors (LPTs) are frequently observed and documented in many active volcanoes around the world, Typically, LPTs are in the period range of 2-100 seconds and total duration of 300 seconds or less. In many instances, LPTs in different volcanic settings are repetitive, but time-invariant in their location, frequency content and waveform shape, suggesting a nondestructive source and providing critical insights into the fluid-dynamic processes operating inside a volcanic system. However, the diversities of LPTs in a single volcanic system are not necessarily well understood and they could potentially provide a clue on the interplay between volcanic degassing, magmatic heating and the style of upcoming eruption. To explore possible diverse LPT behavior in a volcanic system, we investigate LPTs in Aso-san, one of the most well studied and active volcanoes in the southwest Kyushu, Japan. We carry out systematic analysis of continuous seismic data (2010-2016) operated at V-net by NIED and Japan Meterogeolgical Agency (JMA) Volcanic Seismic Network, covering the interval where Aso-san experiences diverse behaviors, including long period of quiescence (2010-2013), phreatic eruption (2013-2014), Strombolian-type eruption (2014-2015) and phreatomagmatic eruption (2016). We use LPT waveforms identified in previous studies as templates and cross-correlate them against the entire dataset in the wavelet domain to construct LPTs catalog. However, LPTs with different phase, but similar frequency content and location are also retained to examine possible temporal changes in the characteristics of LPTs. Through waveform cross-correlation and stacking, we identify four types of LPTs that are located in close proximity as those identified in prior studies, but they display diverse waveform polarity and shape. We will present waveform semblance analysis and moment tensor inversion of these LPTs and discuss how their frequency, amplitude and energetics may be indicative of the state of degassing and magmatic heating inside the Aso volcano.

Intense magmatic degassing through the lake of Copahue volcano, 2013-2014

NASA Astrophysics Data System (ADS)

Tamburello, G.; Agusto, M.; Caselli, A.; Tassi, F.; Vaselli, O.; Calabrese, S.; Rouwet, D.; Capaccioni, B.; Di Napoli, R.; Cardellini, C.; Chiodini, G.; Bitetto, M.; Brusca, L.; Bellomo, S.; Aiuppa, A.

2015-09-01

Here we report on the first assessment of volatile fluxes from the hyperacid crater lake hosted within the summit crater of Copahue, a very active volcano on the Argentina-Chile border. Our observations were performed using a variety of in situ and remote sensing techniques during field campaigns in March 2013, when the crater hosted an active fumarole field, and in March 2014, when an acidic volcanic lake covered the fumarole field. In the latter campaign, we found that 566 to 1373 t d-1 of SO2 were being emitted from the lake in a plume that appeared largely invisible. This, combined with our derived bulk plume composition, was converted into flux of other volcanic species (H2O ~ 10989 t d-1, CO2 ~ 638 t d-1, HCl ~ 66 t d-1, H2 ~ 3.3 t d-1, and HBr ~ 0.05 t d-1). These levels of degassing, comparable to those seen at many open-vent degassing arc volcanoes, were surprisingly high for a volcano hosting a crater lake. Copahue's unusual degassing regime was also confirmed by the chemical composition of the plume that, although issuing from a hot (65°C) lake, preserves a close-to-magmatic signature. EQ3/6 models of gas-water-rock interaction in the lake were able to match observed compositions and demonstrated that magmatic gases emitted to the atmosphere were virtually unaffected by scrubbing of soluble (S and Cl) species. Finally, the derived large H2O flux (10,988 t d-1) suggested a mechanism in which magmatic gas stripping drove enhanced lake water evaporation, a process likely common to many degassing volcanic lakes worldwide.

Diffuse CO_{2} degassing monitoring of the oceanic active volcanic island of El Hierro, Canary Islands, Spain

NASA Astrophysics Data System (ADS)

Hernández, Pedro A.; Norrie, Janice; Withoos, Yannick; García-Merino, Marta; Melián, Gladys; Padrón, Eleazar; Barrancos, José; Padilla, Germán; Rodríguez, Fátima; Pérez, Nemesio M.

2017-04-01

Even during repose periods, volcanoes release large amounts of gases from both visible (fumaroles, solfataras, plumes) and non-visible emanations (diffuse degassing). In the last 20 years, there has been considerable interest in the study of diffuse degassing as a powerful tool in volcano monitoring programs, particularly in those volcanic areas where there are no visible volcanic-hydrothermal gas emissions. Historically, soil gas and diffuse degassing surveys in volcanic environments have focused mainly on CO2 because it is, after water vapor, the most abundant gas dissolved in magma. As CO2 travels upward by advective-diffusive transport mechanisms and manifests itself at the surface, changes in its flux pattern over time provide important information for monitoring volcanic and seismic activity. Since 1998, diffuse CO2 emission has been monitored at El Hierro Island, the smallest and south westernmost island of the Canarian archipelago with an area of 278 km2. As no visible emanations occur at the surface environment of El Hierro, diffuse degassing studies have become the most useful geochemical tool to monitor the volcanic activity in this volcanic island. The island experienced a volcano-seismic unrest that began in July 2011, characterized by the location of a large number of relatively small earthquakes (M<2.5) beneath El Hierro at depths between 8 and 15 km. On October 12, 2011, a submarine eruption was confirmed during the afternoon of October 12, 2011 by visual observations off the coast of El Hierro, about 2 km south of the small village of La Restinga in the southernmost part of the island. During the pre-eruptive and eruptive periods, the time series of the diffuse CO2 emission released by the whole island experienced two significant increases. The first started almost 2 weeks before the onset of the submarine eruption, reflecting a clear geochemical anomaly in CO2 emission, most likely due to increasing release of deep seated magmatic gases to the surface. The second one, between October 24 and November 27, 2011, before the most energetic seismic events of the volcanic-seismic unrest (Melián et al., 2014. J. Geophys. Res. Solid Earth, 119, 6976-6991). The highest CO2 degassing rate measured in the last three years (1684 t/d) was observed during a seismo-volcanic unrest. This value decreased until close to background value (˜422 t/d, Melián et al., 2014) contemporaneously with the decline of the seismic activity during the first half of 2013. The last diffuse CO2 degassing survey was carried out in the summer of 2016, showing a emission rate of 854 t/d. Discrete surveys of diffuse CO2 emission have provided important information to optimize the early warning system in the volcano monitoring programs of El Hierro and to monitor the evolution of an ongoing volcanic eruption, even though is a submarine eruption.

Water content, speciation and isotopic composition in volcanic glass: an open window on magma degassing processes or paleoclimate?

NASA Astrophysics Data System (ADS)

Martin, Erwan; Bindeman, Ilya; Balan, Etienne; Palandri, Jim; Seligman, Angela; Villemant, Benoit

2016-04-01

The content, speciation and isotopic composition of water in volcanic glass have been used for decades as recorder of magma degassing or late glass rehydration processes. Magmatic or paleoclimate information are derived depending on the primary (magmatic) or meteoric (secondary) origin of water. In this study, we attempt to discriminate residual magmatic from secondary meteoric water in volcanic glass. Using samples from different geological settings and different climatic conditions, we show that the H-isotope composition and water content measured via a TC/EA-MAT253 system in volcanic glass alone are not always sufficient to provide clear distinction between magmatic and meteoric origin. However, it is quite easy to resolve δD evolution during post-deposit rehydration by meteoric water from magma degassing when volcanic glass have a δD <-100‰ or >-50‰ and [H2O]tot >1.5-2wt.%. Water speciation inferred from near-infrared spectroscopy also provides valuable information complementary to isotopic and total water measurements. During magma degassing (typically with [H2O]tot decreasing from 6wt.% to ~0wt.% water) H2O/OH is expected to decrease from 2 to close to 0. However, our dataset shows the opposite trend with an increase of H2O/OH from 2 to ~5. We interpret it as post deposit rehydration of the volcanic glass. Overall our results show that the discrimination of the water origin is essential to discuss magma degassing processes or paleoclimatic reconstitutions. The present study of hydrous glass supports the use of H-isotopes of volcanic glass to discuss paleoclimate reconstitution in a specific region. To this purpose, the volcanic glass has to be almost fully rehydrated in order to fingerprint the isotopic composition of the rehydration water. A sharp time constrain can be obtained if the full rehydration occurs quickly after the eruption. This is most likely to occur in meters thick volcanic pyroclast deposits that undergo slow cooling rates and thus can stay at few hundreds °C for a time long enough to ensure complete chemical reaction (few to hundreds of years) after the eruption but still short on a geological scale.

Enabling two-phase microfluidic thermal transport systems using a novel thermal-flux degassing and fluid charging approach

NASA Astrophysics Data System (ADS)

Singh Dhillon, Navdeep; Pisano, Albert P.

2014-03-01

A novel two-port thermal-flux method has been proposed and demonstrated for degassing and charging two-phase microfluidic thermal transport systems with a degassed working fluid. In microscale heat pipes and loop heat pipes (mLHPs), small device volumes and large capillary forces associated with smaller feature sizes render conventional vacuum pump-based degassing methods quite impractical. Instead, we employ a thermally generated pressure differential to purge non-condensable gases from these devices before charging them with a degassed working fluid in a two-step process. Based on the results of preliminary experiments studying the effectiveness and reliability of three different high temperature-compatible device packaging approaches, an optimized compression packaging technique was developed to degas and charge a mLHP device using the thermal-flux method. An induction heating-based noninvasive hermetic sealing approach for permanently sealing the degassed and charged mLHP devices has also been proposed. To demonstrate the efficacy of this approach, induction heating experiments were performed to noninvasively seal 1 mm square silicon fill-hole samples with donut-shaped solder preforms. The results show that the minimum hole sealing induction heating time is heat flux limited and can be estimated using a lumped capacitance thermal model. However, further continued heating of the solder uncovers the hole due to surface tension-induced contact line dynamics of the molten solder. It was found that an optimum mass of the solder preform is required to ensure a wide enough induction-heating time window for successful sealing of a fill-hole.

The transition from explosive to effusive eruptive regime: The example of the 1912 Novarupta eruption, Alaska

USGS Publications Warehouse

Adams, N.K.; Houghton, Bruce F.; Fagents, S.A.; Hildreth, W.

2006-01-01

The shift from explosive to effusive silicic volcanism seen in many historical eruptions reflects a change in the style of degassing of erupted magma. This paper focuses on such a transition during the largest eruption of the twentieth century, the 1912 eruption of Novarupta. The transition is recorded in a dacite block bed, which covers an elliptical area of 4 km2 around the vent. Approximately 700 studied blocks fall into four main lithologic categories: (1) pumiceous, (2) dense, (3) flow-banded dacites, and (4) welded breccias. Textural analyses of the blocks indicate portions of the melt underwent highly variable degrees of outgassing. Vesicle populations show features characteristic of bubble coalescence and collapse. A decrease in measured vesicularity and increased evidence for bubble collapse compared with pumice from earlier Plinian episodes mark the transition from closed- to open-system degassing. Block morphology and textures strongly suggest the magma was first erupted as a relatively gas-rich lava dome/plug, but incomplete out-gassing led to explosive disruption. Heterogeneous degassing of ascending magma began in Plinian Episode III and resulted in instability during Episode IV dome growth and a (series of) Vulcanian explosion(s). Modeling of the dynamics of explosion initiation and ejecta dispersal indicates that a significant concentration in gas is required to produce the explosions responsible for the observed block field dispersal. The amount of gas available in the hot pumiceous dome material appears to have been inadequate to drive the explosion(s); therefore, external water most likely contributed to the destruction. ?? 2006 Geological Society of America.

Degassing dynamics at Mount Etna inferred from radioactive disequilibria (210Pb-210Bi-210Po) in volcanic gases

NASA Astrophysics Data System (ADS)

Terray, Luca; Gauthier, Pierre-Jean; Salerno, Giuseppe; La Spina, Alessandro; Giammanco, Salvatore; Sellitto, Pasquale; Briole, Pierre

2016-04-01

Volcanic gases are significantly enriched in the last short-half-life radionuclides of the 238U series, namely the so-called Radon daughters 210Pb, 210Bi and 210Po. Because of their contrasted volatilities, these isotopes are strongly fractionated upon degassing, which gives rise to significant radioactive disequilibria between them in the gas phase. These disequilibria carry precious information on shallow degassing processes beneath active volcanoes: they remarkably constrain the magma residence time in the degassing reservoir and the duration of gas extraction from magma to surface. On Mount Etna (Sicily), where the study of these disequilibria was initiated thirty years ago (Lambert et al., EPSL, 1985-86), no measurement of 210Pb, 210Bi and 210Po in the gases has been performed for the last twenty years. Here we present new 210Pb-210Bi-210Po radioactive disequilibria measurements in volcanic plume gases of Mount Etna. Samples were collected in the bulk diluted plume at kilometric distance from the summit area during the May 2015 eruption, then in more concentrated plumes arising from each summit crater of Etna during quiescent degassing in July 2015. We found values of (210Bi/210Pb) = 7.0 ± 0.3 and (210Po/210Pb) = 80 ± 6 during both periods. These results suggest that 210Pb, 210Bi and 210Po are not significantly fractionated during the transport of the plume from the crater rim to close-downslope sites (<1 km). None of the previous degassing models (Lambert et al., EPSL, 1985-86 ; Gauthier et al., JVGR, 2000) satisfactorily explain measured activity ratios. We propose here a new degassing model based on the previous conceptualization designed for basaltic open-conduit volcanoes, like Stromboli. This model considers extreme Radon enrichments in volcanic gases as a source of 210Pb atoms produced by radioactive decay of 222Rn within gas bubbles travelling to surface. We constrain a magma residence time of 470 ± 170 days and an extraction time of the gases of 4.9 ± 0.8 days. Along with SO2 fluxes, we also derive a volume of the degassing reservoir of 0.2-0.6 km3 in good agreement with previous estimates. Results gathered from these campaigns have intriguing implication for potential routine survey of the plume radioactivity, as part of the monitoring network of active volcanoes.

Fluid geochemistry and soil gas fluxes (CO2-CH4-H2S) at a promissory Hot Dry Rock Geothermal System: The Acoculco caldera, Mexico

NASA Astrophysics Data System (ADS)

Peiffer, L.; Bernard-Romero, R.; Mazot, A.; Taran, Y. A.; Guevara, M.; Santoyo, E.

2014-09-01

The Acoculco caldera has been recognized by the Mexican Federal Electricity Company (CFE) as a Hot Dry Rock Geothermal System (HDR) and could be a potential candidate for developing an Enhanced Geothermal System (EGS). Apart from hydrothermally altered rocks, geothermal manifestations within the Acoculco caldera are scarce. Close to ambient temperature bubbling springs and soil degassing are reported inside the caldera while a few springs discharge warm water on the periphery of the caldera. In this study, we infer the origin of fluids and we characterize for the first time the soil degassing dynamic. Chemical and isotopic (δ18O-δD) analyses of spring waters indicate a meteoric origin and the dissolution of CO2 and H2S gases, while gas chemical and isotopic compositions (N2/He, 3He/4He, 13C, 15N) reveal a magmatic contribution with both MORB- and arc-type signatures which could be explained by an extension regime created by local and regional fault systems. Gas geothermometry results are in agreement with temperature measured during well drilling (260 °C-300 °C). Absence of well-developed water reservoir at depth impedes re-equilibration of gases upon surface. A multi-gas flux survey including CO2, CH4 and H2S measurements was performed within the caldera. Using the graphical statistical analysis (GSA) approach, CO2 flux measurements were classified in two populations. Population A, representing 95% of measured fluxes is characterized by low values (mean: 18 g m- 2 day- 1) while the remaining 5% fluxes belonging to Population B are much higher (mean: 5543 g m- 2 day- 1). This low degassing rate probably reflects the low permeability of the system, a consequence of the intense hydrothermal alteration observed in the upper 800 m of volcanic rocks. An attempt to interpret the origin and transport mechanism of these fluxes is proposed by means of flux ratios as well as by numerical modeling. Measurements with CO2/CH4 and CO2/H2S flux ratios similar to mass ratios of sampled gases were considered as reflecting advective transport. A numerical model of CO2 migration in the subsoil system under fully water and gas saturated conditions was performed using the TOUGH2 code in order to reproduce semi-quantitatively field measurements. The main results show that high flux values produced by advective geothermal degassing can be very localized and that low and heterogeneous permeability conditions can induce low advective CO2 flux values. Therefore, in this case the populations discriminated by the GSA method should not be interpreted in terms of origin and/or transport mechanism but rather in terms of permeability conditions.

Halogen degassing during ascent and eruption of water-poor basaltic magma

USGS Publications Warehouse

Edmonds, M.; Gerlach, T.M.; Herd, Richard A.

2009-01-01

A study of volcanic gas composition and matrix glass volatile concentrations has allowed a model for halogen degassing to be formulated for K??lauea Volcano, Hawai'i. Volcanic gases emitted during 2004-2005 were characterised by a molar SO2/HCl of 10-64, with a mean of 33; and a molar HF/HCl of 0-5, with a mean of 1.0 (from approximately 2500 measurements). The HF/HCl ratio was more variable than the SO2/HCl ratio, and the two correlate weakly. Variations in ratio took place over rapid timescales (seconds). Matrix glasses of Pele's tears erupted in 2006 have a mean S, Cl and F content of 67, 85 and 173??ppm respectively, but are associated with a large range in S/F. A model is developed that describes the open system degassing of halogens from parental magmas, using the glass data from this study, previously published results and parameterisation of sulphur degassing from previous work. The results illustrate that halogen degassing takes place at pressures of < 1??MPa, equivalent to < ~ 35??m in the conduit. Fluid-melt partition coefficients for Cl and F are low (< 1.5); F only degasses appreciably at < 0.1??MPa above atmospheric pressure, virtually at the top of the magma column. This model reproduces the volcanic gas data and other observations of volcanic activity well and is consistent with other studies of halogen degassing from basaltic magmas. The model suggests that variation in volcanic gas halogen ratios is caused by exsolution and gas-melt separation at low pressures in the conduit. There is no evidence that either diffusive fractionation or near-vent chemical reactions involving halogens is important in the system, although these processes cannot be ruled out. The fluxes of HCl and HF from K??lauea during 2004-5 were ~ 25 and 12??t/d respectively. ?? 2008 Elsevier B.V.

Experimental investigation of nitrogen isotopic effects associated with ammonia degassing at 0-70 °C

NASA Astrophysics Data System (ADS)

Deng, Yuying; Li, Yingzhou; Li, Long

2018-04-01

Ammonia degassing is a common process in natural alkaline waters and in the atmosphere. To quantitatively assess the nitrogen cycle in these systems, the essential parameter of nitrogen isotope fractionation factors associated with ammonia degassing is required, but still not constrained yet. In this study, we carried out laboratory experiments to examine the nitrogen isotope behavior during ammonia degassing in alkaline conditions. The experiments started with ammonium sulfate solution with excess sodium hydroxide. The reaction can be described as: NH4+ + OH- (excess) → NH3·nH2O → NH3 (g)↑. Two sets of experiments, one with ammonia degassing under static conditions and the other with ammonia degassing by bubbling of N2 gas, were carried out at 2, 21, 50, and 70 °C. The results indicate that kinetic isotopic effects are dominated during efficient degassing of ammonia in the bubbling experiments, which yielded kinetic nitrogen isotope fractionation factors αNH3(g)-NH3(aq) of 0.9898 at 2 °C, 0.9918 at 21 °C, 0.9935 at 50 °C and 0.9948 at 70 °C. These values show a good relationship with temperature as 103lnαNH3(g)-NH3(aq) = 14.6 - 6.8 × 1000/T. In contrast, isotopic effects during less efficient degassing of ammonia in the static experiments are more complicated. The results do not match either kinetic isotope fractionation or equilibrium isotope fractionation but sit between these two. The most likely cause is that back dissolution of the degassed ammonia occurred in these experiments and consequently shifted kinetic isotope fractionation toward equilibrium isotope fractionation. Our experimental results highlight complicated isotopic effects may occur in natural environments, and need to be fully considered in the interpretation of field data.

Influence of water quench cooling on degassing and aroma stability of roasted coffee.

PubMed

Baggenstoss, Juerg; Poisson, Luigi; Luethi, Regina; Perren, Rainer; Escher, Felix

2007-08-08

Coffee roasting experiments with air cooling versus water quench cooling were carried out on laboratory scale with a fluidized-bed hot air roasting system (200 g batch size) and on production scale with a rotating bowl roaster (320 kg batch size). Two series of coffees with different water contents resulted, which were stored at 25 degrees C under normal atmospheric conditions. Carbon dioxide desorption was followed and stability of selected aroma compounds was tested with headspace solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) and stable isotope labeled compounds as internal standards. Degassing is faster in water-quenched coffees with higher moisture content, but pore size distribution in the different coffee samples did not correlate with degassing behavior. Bean firmness, which increases with increasing moisture content, might have an influence on degassing. Air- and water-quenched coffees exhibit similar stability of most aroma compounds despite different degassing behavior. However, evolution of dimethyl trisulfide was different in coffees with increased water content. This suggests higher thiol oxidation rates, a factor that is cited to be related to a faster loss of freshness attributes.

210Pb and 210Po Abundances in Dacites Erupted May, 2003 From Anatahan Volcano: Implications for the Time-scales of Magma Generation and Degassing

NASA Astrophysics Data System (ADS)

Reagan, M. K.; Matthew, W.; Brian, H.

2003-12-01

Six samples of dacite pumice and scoria erupted in May, 2003 and collected from a number of sites around Anathan by Tobias Fischer and David Hilton were analyzed for 210Po activities on three occasions between early June and the time of this writing. With two exceptions, all scoria and pumice samples have 210Po activities that plot on a single growth curve indicating initial (210Po)=0.15 +/-0.07 (1σ ) dpm/g and (210Pb)=1.08+/-0.20 dpm/g. More precise values for these initial activities will be presented at the meeting after further analyses are performed in November. Preliminary alpha spectrometry analyses for U and Th, and ICPMS analyses distributed by Terry Plank suggest that the average (238U) is about 0.53 dpm/g. Equilibrium (228Th)/( 232Th) ratios indicate that these samples do not have excess 228Ra. Assuming that (210Pb )< (226Ra) because of minor degassing of 210Pb (see Gauthier and Condomines, 1999, EPSL, v. 172), the degassing efficiency factor for 210Po is greater than or equal to about 0.85, which is identical to the value calculated for a basaltic andesitic lava from Arenal volcano in Costa Rica (Gill et al., 1985, GRL, v. 12). This is surprising, as the May 10 plinian eruption of Anatahan should have resulted in more closed-system degassing than a lava eruption. This and the similar 210Po values for the scoria and pumice samples suggest that the shallow-level degassing history has little impact on the efficiency of polonium degassing. The scoria and pumice samples from sample 8-1e both have significant excesses of 210Po over the calculated initial (210Pb) value for the other samples. These excesses were partially leachable, indicating that 210Po was sublimated onto these samples, and that these ejecta resided in the vent before being ejected and redeposited The high inferred (226Ra)/( 230Th) for the Anatahan dacites despite the nearly equilibrium (238U)/( 230Th) value measured for one sample contrasts with the values for these ratios in more mafic Mariana samples, which are characterized by a direct correlation between radium and uranium excesses (Turner et al., 2001, Science, v. 292). Assuming that these trends hold up after additional analysis, the most straightforward interpretation of our alpha spectrometry data is that the dacite was generated by distillation of more mafic intrusives over a period of time that is significant compared to the half-life of 230Th, and that radium was added to the dacite recently either by inmixing a Ra-enriched basalt or a crust-derived fluid.

Constraining the Sulfur Dioxide Degassing Flux from Turrialba Volcano, Costa Rica Using Unmanned Aerial System Measurements

NASA Technical Reports Server (NTRS)

Xi, Xin; Johnson, Matthew S.; Jeong, Seongeun; Fladeland, Matthew; Pieri, David; Diaz, Jorge Andres; Bland, Geoffrey L.

2016-01-01

Observed sulfur dioxide (SO2)mixing ratios onboard unmanned aerial systems (UAS) duringMarch 11-13, 2013 are used to constrain the three-day averaged SO2 degassing flux fromTurrialba volcanowithin a Bayesian inverse modeling framework. A mesoscale model coupled with Lagrangian stochastic particle backward trajectories is used to quantify the source-receptor relationships at very high spatial resolutions (i.e., b1 km). The model shows better performance in reproducing the near-surface meteorological properties and observed SO2 variations when using a first-order closure non-local planetary boundary layer (PBL) scheme. The optimized SO2 degassing fluxes vary from 0.59 +/- 0.37 to 0.83 +/- 0.33 kt d-1 depending on the PBL scheme used. These fluxes are in good agreement with ground-based gas flux measurements, and correspond to corrective scale factors of 8-12 to the posteruptive SO2 degassing rate in the AeroCom emission inventory. The maximum a posteriori solution for the SO2 flux is highly sensitive to the specification of prior and observational errors, and relatively insensitive to the SO2 loss term and temporal averaging of observations. Our results indicate relatively low degassing activity but sustained sulfur emissions from Turrialba volcano to the troposphere during March 2013. This study demonstrates the utility of low-cost small UAS platforms for volcanic gas composition and flux analysis.

Airborne detection of diffuse carbon dioxide emissions at Mammoth Mountain, California

USGS Publications Warehouse

Gerlach, T.M.; Doukas, M.P.; McGee, K.A.; Kessler, R.

1999-01-01

We report the first airborne detection of CO2 degassing from diffuse volcanic sources. Airborne measurement of diffuse CO2 degassing offers a rapid alternative for monitoring CO2 emission rates at Mammoth Mountain. CO2 concentrations, temperatures, and barometric pressures were measured at ~2,500 GPS-referenced locations during a one-hour, eleven-orbit survey of air around Mammoth Mountain at ~3 km from the summit and altitudes of 2,895-3,657 m. A volcanic CO2 anomaly 4-5 km across with CO2 levels ~1 ppm above background was revealed downwind of tree-kill areas. It contained a 1-km core with concentrations exceeding background by >3 ppm. Emission rates of ~250 t d-1 are indicated. Orographic winds may play a key role in transporting the diffusely degassed CO2 upslope to elevations where it is lofted into the regional wind system.We report the first airborne detection of CO2 degassing from diffuse volcanic sources. Airborne measurement of diffuse CO2 degassing offers a rapid alternative for monitoring CO2 emission rates at Mammoth Mountain. CO2 concentrations, temperatures, and barometric pressures were measured at approximately 2,500 GPS-referenced locations during a one-hour, eleven-orbit survey of air around Mammoth Mountain at approximately 3 km from the summit and altitudes of 2,895-3,657 m. A volcanic CO2 anomaly 4-5 km across with CO2 levels approximately 1 ppm above background was revealed downwind of tree-kill areas. It contained a 1-km core with concentrations exceeding background by >3 ppm. Emission rates of approximately 250 t d-1 are indicated. Orographic winds may play a key role in transporting the diffusely degassed CO2 upslope to elevations where it is lofted into the regional wind system.

Early and long-term mantle processing rates derived from xenon isotopes

NASA Astrophysics Data System (ADS)

Mukhopadhyay, S.; Parai, R.; Tucker, J.; Middleton, J. L.; Langmuir, C. H.

2015-12-01

Noble gases, particularly xenon (Xe), in mantle-derived basalts provide a rich portrait of mantle degassing and surface-interior volatile exchange. The combination of extinct and extant radioactive species in the I-Pu-U-Xe systems shed light on the degassing history of the early Earth throughout accretion, as well as the long-term degassing of the Earth's interior in association with plate tectonics. The ubiquitous presence of shallow-level air contamination, however, frequently obscures the mantle Xe signal. In a majority of the samples, shallow air contamination dominates the Xe budget. For example, in the gas-rich popping rock 2ΠD43, 129Xe/130Xe ratios reach 7.7±0.23 in individual step-crushes, but the bulk composition of the sample is close to air (129Xe/130Xe of 6.7). Thus, the extent of variability in mantle source Xe composition is not well-constrained. Here, we present new MORB Xe data and explore constraints placed on mantle processing rates by the Xe data. Ten step-crushes were obtained on a depleted popping glass that was sealed in ultrapure N2 after dredge retrieval from between the Kane-Atlantis Fracture Zone of the Mid Atlantic Ridge in May 2012. 9 steps yielded 129Xe/130Xe of 7.50-7.67 and one yielded 7.3. The bulk 129Xe/130Xe of the sample is 7.6, nearly identical to the estimated mantle source value of 7.7 for the sample. Hence, the sample is virtually free of shallow-level air contamination. Because sealing the sample in N2upon dredge retrieval largely eliminated air contamination, for many samples, contamination must be added after sample retrieval from the ocean bottom. Our new high-precision Xe isotopic measurements in upper mantle-derived samples provide improved constraints on the Xe isotopic composition of the mantle source. We developed a forward model of mantle volatile evolution to identify solutions that satisfy our Xe isotopic data. We find that accretion timescales of ~10±5 Myr are consistent with I-Pu-Xe constraints, and the last giant impact occurred 45-70 Myr after the start of the solar system. After the giant impact stage, the Pu-U-Xe system indicates that degassing of the planet via solid-state mantle convection and plate tectonics continued to liberate volatiles to the atmosphere and has led to between ~5-8 mantle turnovers over the age of the Earth.

MaGa, a web-based collaborative database for gas emissions: a tool to improve the knowledge on Earth degassing

NASA Astrophysics Data System (ADS)

Frigeri, A.; Cardellini, C.; Chiodini, G.; Frondini, F.; Bagnato, E.; Aiuppa, A.; Fischer, T. P.; Lehnert, K. A.

2014-12-01

The study of the main pathways of carbon flux from the deep Earth requires the analysis of a large quantity and variety of data on volcanic and non-volcanic gas emissions. Hence, there is need for common frameworks to aggregate available data and insert new observations. Since 2010 we have been developing the Mapping Gas emissions (MaGa) web-based database to collect data on carbon degassing form volcanic and non-volcanic environments. MaGa uses an Object-relational model, translating the experience of field surveyors into the database schema. The current web interface of MaGa allows users to browse the data in tabular format or by browsing an interactive web-map. Enabled users can insert information as measurement methods, instrument details as well as the actual values collected in the field. Measurements found in the literature can be inserted as well as direct field observations made by human-operated instruments. Currently the database includes fluxes and gas compositions from active craters degassing, diffuse soil degassing and fumaroles both from dormant volcanoes and open-vent volcanoes from literature survey and data about non-volcanic emission of the Italian territory. Currently, MaGa holds more than 1000 volcanic plume degassing fluxes, data from 30 sites of diffuse soil degassing from italian volcanoes, and about 60 measurements from fumarolic and non volcanic emission sites. For each gas emission site, the MaGa holds data, pictures, descriptions on gas sampling, analysis and measurement methods, together with bibliographic references and contacts to researchers having experience on each site. From 2012, MaGa developments started to be focused towards the framework of the Deep Earth Carbon Degassing research initiative of the Deep Carbon Observatory. Whithin the DECADE initiative, there are others data systems, as EarthChem and the Smithsonian Institution's Global Volcanism Program. An interoperable interaction between the DECADE data systems is being planned. MaGa is showing good potentials to improve the knowledge on Earth degassing firstly by making data more accessible and encouraging participation among researchers, and secondly by allowing to observe and explore, for the first time, a gas emission dataset with spatial and temporal extents never analyzed before.

Monitoring diffuse volcanic degassing during volcanic unrests: the case of Campi Flegrei (Italy)

NASA Astrophysics Data System (ADS)

Cardellini, Carlo; Chiodini, Giovanni; Avino, Rosario; Bagnato, Emanuela; Caliro, Stefano; Frondini, Francesco; Lelli, Matteo; Rosiello, Angelo

2017-04-01

Hydrothermal activity at Solfatara of Pozzuoli (Campi Flegrei caldera, Italy) results on a large area of hot soils, diffuse CO2 degassing and numerous fumaroles, releasing at the surface large amounts of gasses and thermal energy. Solfatara is one of the first sites of the world where the techniques for measuring and interpreting soil CO2 diffuse degassing were developed during 1990's and, more recently, it has become a sort of natural laboratory for testing new types of measurements of the CO2 fluxes from hydrothermal sites. The results of 30 diffuse CO2 flux surveys performed at Solfatara from 1998 to 2016 are presented and discussed. CO2 soil fluxes were measured over an area of about 1.2  1.2 km including the Solfatara crater and the hydrothermal site of Pisciarelli using the accumulation chamber technique. Each survey consisted in a number of CO2 flux measurements varying from 372 to 583 resulting in a total of 13158 measurements. This data set is one of the largest dataset ever made in the world on a single degassing volcanic-hydrothermal system. It is particularly relevant in the frame of volcanological sciences because it was acquired during a long period of unrest at Campi Flegrei caldera and because Solfatara release an amount of CO2 comparable to that released by medium-large volcanic plumes. Statistical and geostatistical elaborations of CO2 flux data allowed to characterise the sources of soil diffuse degassing, to define the extent of the area interested by the release of hydrothermal CO2 (Solfatara DDS) and to quantify the total amount of released CO2. During the last eighteen years relevant variations affected Solfatara degassing, and in particular the "background" CO2 emission , the extent of DDS and the total CO2 output, that may reflect variations in the subterraneous gas plume feeding the Solfatara and Pisciarelli emissions. In fact, the most relevant variations in Solfatara diffuse degassing well correlates with steam condensation and temperature increase affecting the Solfatara system resulting from repeated inputs of magmatic fluids into the hydrothermal systems as suggested by Chiodini et al., (2015; 2016; 2017) and show a long-term increase on the amount of released CO2 that accompanies the ongoing unrest of Campi Flegrei caldera.

An experimental device for characterizing degassing processes and related elastic fingerprints: Analog volcano seismo-acoustic observations.

PubMed

Spina, Laura; Morgavi, Daniele; Cannata, Andrea; Campeggi, Carlo; Perugini, Diego

2018-05-01

A challenging objective of modern volcanology is to quantitatively characterize eruptive/degassing regimes from geophysical signals (in particular seismic and infrasonic), for both research and monitoring purposes. However, the outcomes of the attempts made so far are still considered very uncertain because volcanoes remain inaccessible when deriving quantitative information on crucial parameters such as plumbing system geometry and magma viscosity. In order to improve our knowledge of volcanic systems, a novel experimental device, which is capable of mimicking volcanic degassing processes with different regimes and gas flow rates, and allowing for the investigation of the related seismo-acoustic emissions, was designed and developed. The benefits of integrating observations on real volcanoes with seismo-acoustic signals generated in laboratory are many and include (i) the possibility to fix the controlling parameters such as the geometry of the structure where the gas flows, the gas flow rate, and the fluid viscosity; (ii) the possibility of performing acoustic measurements at different azimuthal and zenithal angles around the opening of the analog conduit, hence constraining the radiation pattern of different acoustic sources; (iii) the possibility to measure micro-seismic signals in distinct points of the analog conduit; (iv) finally, thanks to the transparent structure, it is possible to directly observe the degassing pattern through the optically clear analog magma and define the degassing regime producing the seismo-acoustic radiations. The above-described device represents a step forward in the analog volcano seismo-acoustic measurements.

An experimental device for characterizing degassing processes and related elastic fingerprints: Analog volcano seismo-acoustic observations

NASA Astrophysics Data System (ADS)

Spina, Laura; Morgavi, Daniele; Cannata, Andrea; Campeggi, Carlo; Perugini, Diego

2018-05-01

A challenging objective of modern volcanology is to quantitatively characterize eruptive/degassing regimes from geophysical signals (in particular seismic and infrasonic), for both research and monitoring purposes. However, the outcomes of the attempts made so far are still considered very uncertain because volcanoes remain inaccessible when deriving quantitative information on crucial parameters such as plumbing system geometry and magma viscosity. In order to improve our knowledge of volcanic systems, a novel experimental device, which is capable of mimicking volcanic degassing processes with different regimes and gas flow rates, and allowing for the investigation of the related seismo-acoustic emissions, was designed and developed. The benefits of integrating observations on real volcanoes with seismo-acoustic signals generated in laboratory are many and include (i) the possibility to fix the controlling parameters such as the geometry of the structure where the gas flows, the gas flow rate, and the fluid viscosity; (ii) the possibility of performing acoustic measurements at different azimuthal and zenithal angles around the opening of the analog conduit, hence constraining the radiation pattern of different acoustic sources; (iii) the possibility to measure micro-seismic signals in distinct points of the analog conduit; (iv) finally, thanks to the transparent structure, it is possible to directly observe the degassing pattern through the optically clear analog magma and define the degassing regime producing the seismo-acoustic radiations. The above-described device represents a step forward in the analog volcano seismo-acoustic measurements.

Degassing of metals and metalloids from erupting seamount and mid-ocean ridge volcanoes: Observations and predictions

NASA Astrophysics Data System (ADS)

Rubin, Ken

1997-09-01

Recently, it has been reported that the element polonium degasses from mid-ocean ridge and seamount volcanoes during eruptions. Published and new observations on other volatile metal and metalloid elements can also be interpreted as indicating significant degassing of magmatic vapors during submarine eruptions. This process potentially plays an important role in the net transfer of chemical elements from erupting volcanoes to seawater in addition to that arising from sea floor hydrothermal systems. In this paper, a framework is constructed for predicting and assessing semiquantitatively the potential magnitude and chemical fingerprints in the water column of metal and metalloid degassing using (1) predictions from a summary of element volatilities during mafic subaerial volcanism worldwide and (2) limited data from submarine volcanic effusives. The latter include analyses of polonium and trace metals in near-volcano water masses sampled following a submarine eruption at Loihi seamount, Hawaii (1000 m bsl) in 1996. The element volatility predictions and observations show good agreement, considering the limited dataset. Some of the highest volatility main group and transition element enrichments in seawater over Loihi are predicted by the degassing mass transfer model I present. When expanded to cover all submarine volcanic activity, it is predicted that exit fluxes of these elements are up to 10 2-10 3 greater by degassing than by normal MOR hydrothermalism. In contrast, MOR exit fluxes of low volatility alkali and alkaline earth elements are likely 10 2-10 6 greater from hydrothermal inputs. Degassing inputs to the ocean are probably highly episodic, occurring almost entirely during eruptions; these are times of enhanced and abnormal hydrothermalism as well. Although major hydrothermal and degassing events may not be chemically recognizable in real water masses as wholly distinct entities, it is nevertheless possible to predict to what extent each process flavors the effluents of the other. Degassing at mid-ocean ridges may explain a variety of observations previously ascribed to complexities occurring during hydrothermal venting and/or fluid ascent in the buoyant hydrothermal plumes above ridges.

Stable isotope and petrologic evidence for open-system degassing during the climactic and pre-climactic eruptions of Mt. Mazama, Crater Lake, Oregon

USGS Publications Warehouse

Mandeville, C.W.; Webster, J.D.; Tappen, C.; Taylor, B.E.; Timbal, A.; Sasaki, A.; Hauri, E.; Bacon, C.R.

2009-01-01

Evaluation of the extent of volatile element recycling in convergent margin volcanism requires delineating likely source(s) of magmatic volatiles through stable isotopic characterization of sulfur, hydrogen and oxygen in erupted tephra with appropriate assessment of modification by degassing. The climactic eruption of Mt. Mazama ejected approximately 50 km3 of rhyodacitic magma into the atmosphere and resulted in formation of a 10-km diameter caldera now occupied by Crater Lake, Oregon (lat. 43??N, long. 122??W). Isotopic compositions of whole-rocks, matrix glasses and minerals from Mt. Mazama climactic, pre-climactic and postcaldera tephra were determined to identify the likely source(s) of H2O and S. Integration of stable isotopic data with petrologic data from melt inclusions has allowed for estimation of pre-eruptive dissolved volatile concentrations and placed constraints on the extent, conditions and style of degassing. Sulfur isotope analyses of climactic rhyodacitic whole rocks yield ??34S values of 2.8-14.8??? with corresponding matrix glass values of 2.4-13.2???. ??34S tends to increase with stratigraphic height through climactic eruptive units, consistent with open-system degassing. Dissolved sulfur concentrations in melt inclusions (MIs) from pre-climactic and climactic rhyodacitic pumices varies from 80 to 330 ppm, with highest concentrations in inclusions with 4.8-5.2 wt% H2O (by FTIR). Up to 50% of the initial S may have been lost through pre-eruptive degassing at depths of 4-5 km. Ion microprobe analyses of pyrrhotite in climactic rhyodacitic tephra and andesitic scoria indicate a range in ??34S from -0.4??? to 5.8??? and from -0.1??? to 3.5???, respectively. Initial ??34S values of rhyodacitic and andesitic magmas were likely near the mantle value of 0???. Hydrogen isotope (??D) and total H2O analyses of rhyodacitic obsidian (and vitrophyre) from the climactic fall deposit yielded values ??f -103 to -53??? and 0.23-1.74 wt%, respectively. Values of ??D and wt% H2O of obsidian decrease towards the top of the fall deposit. Samples with depleted ??D, and mantle ??18O values, have elevated ??34S values consistent with open-system degassing. These results imply that more mantle-derived sulfur is degassed to the Earth's atmosphere/hydrosphere through convergent margin volcanism than previously attributed. Magmatic degassing can modify initial isotopic compositions of sulfur by >14??? (to ??34S values of 14??? or more here) and hydrogen isotopic compositions by 90??? (to ??D values of -127??? in this case). ?? 2009 Elsevier Ltd.

Research on Melt Degassing Processes of High Conductivity Hard Drawn Aluminum Wire

NASA Astrophysics Data System (ADS)

Xu, Xuexia; Feng, Yanting; Wang, Qing; Li, Wenbin; Fan, Hui; Wang, Yong; Li, Guowei; Zhang, Daoqian

2018-03-01

Degassing effects of ultrasonic and vacuum processes on high conductivity hard drawn aluminum melt were studied. Results showed that the degassing efficiency improved with the increase of ultrasonic power within certain range, stabilizing at 70% with 240W. For vacuum degassing process, hydrogen content of aluminum melt decreased with the loading time and was linear with logarithm of vacuum degree. Comparison of degassing effects of ultrasonic, vacuum, vacuum-ultrasonic degassing process showed that vacuum-ultrasonic process presented optimal effect.

Magma Vesiculation and Infrasonic Activity in Open Conduit Volcanoes

NASA Astrophysics Data System (ADS)

Colo', L.; Baker, D. R.; Polacci, M.; Ripepe, M.

2007-12-01

At persistently active basaltic volcanoes such as Stromboli, Italy degassing of the magma column can occur in "passive" and "active" conditions. Passive degassing is generally understood as a continuous, non explosive release of gas mainly from the open summit vents and subordinately from the conduit's wall or from fumaroles. In passive degassing generally gas is in equilibrium with atmospheric pressure, while in active degassing the gas approaches the surface at overpressurized conditions. During active degassing (or puffing), the magma column is interested by the bursting of small gas bubbles at the magma free surface and, as a consequence, the active degassing process generates infrasonic signals. We postulated, in this study, that the rate and the amplitude of infrasonic activity is somehow linked to the rate and the volume of the overpressured gas bubbles, which are generated in the magma column. Our hypothesis is that infrasound is controlled by the quantities of gas exsolved in the magma column and then, that a relationship between infrasound and the vesiculation process should exist. In order to achieve this goal, infrasonic records and bubble size distributions of scoria samples from normal explosive activity at Stromboli processed via X ray tomography have been compared. We observed that the cumulative distribution for both data sets follow similar power laws, indicating that both processes are controlled by a scale invariant phenomenon. However the power law is not stable but changes in different scoria clasts, reflecting when gas bubble nucleation is predominant over bubbles coalescence and viceversa. The power law also changes for the infrasonic activity from time to time, suggesting that infrasound may be controlled also by a different gas exsolution within the magma column. Changes in power law distributions are the same for infrasound and scoria indicating that they are linked to the same process acting in the magmatic system. We suggest that monitoring infrasound on an active volcano could represent an alternative way to monitor the vesiculation process of an open conduit system.

Hydrogen isotope investigation of amphibole and glass in dacite magmas erupted in 1980-1986 and 2005 at Mount St. Helens, Washington

USGS Publications Warehouse

Underwood, S.J.; Feeley, T.C.; Clynne, M.A.

2013-01-01

In active, shallow, sub-volcanic magma conduits the extent of the dehydrogenation–oxidation reaction in amphibole phenocrysts is controlled by energetic processes that cause crystal lattice damage or conditions that increase hydrogen diffusivity in magmatic phases. Amphibole phenocrysts separated from dacitic volcanic rocks erupted from 1980 to 1986 and in 2005 at Mount St. Helens (MSH) were analyzed for δD, water content and Fe3+/Fe2+, and fragments of glassy groundmass were analyzed for δD and water content. Changes in amphibole δD values through time are evaluated within the context of carefully observed volcanic eruption behavior and published petrological and geochemical investigations. Driving forces for amphibole dehydrogenation include increase in magma oxygen fugacity, decrease in amphibole hydrogen fugacity, or both. The phenocryst amphibole (δD value c. –57‰ and 2 wt % H2O) in the white fallout pumice of the May 18, 1980 plinian eruptive phase is probably little modified during rapid magma ascent up an ∼7 km conduit. Younger volcanic rocks incorporate some shallowly degassed dacitic magma from earlier pulses, based on amphibole phenocryst populations that exhibit varying degrees of dehydrogenation. Pyroclastic rocks from explosive eruptions in June–October 1980 have elevated abundances of mottled amphibole phenocrysts (peaking in some pyroclastic rocks erupted on July 22, 1980), and extensive amphibole dehydrogenation is linked to crystal damage from vesiculation and pyroclastic fountain collapse that increased effective hydrogen diffusion in amphibole. Multiple amphibole δD populations in many 1980 pyroclastic rocks combined with their groundmass characteristics (e.g. mixed pumice textures) support models of shallow mixing prior to, or during, eruption as new, volatile-rich magma pulses blended with more oxidized, degassed magma. Amphibole dehydrogenation is quenched at the top surface of MSH dacite lava lobes, but the diversity in the δDamph populations in original fresh lava flow surfaces may occur from blending magma domains with different ascent histories in the sub-volcanic environment immediately before eruption. Multi-stage open-system magma degassing operated in each parcel of magma rising toward the surface, whereas the magma below ∼7 km was a relatively closed system, at least to the October 1986 eruption based on the large population of minimally dehydrogenated, rim-free amphibole in the lavas. Magma degassing and possibly H isotope exchange with low-δD fluids around the roof zone may have accompanied the ∼1·5 km upward migration of the 1980 magma body. The low-δDamph (c. –188 to –122‰) oxy-amphibole phenocrysts in lava spines extruded in May 2005 reflect dehydrogenation as ascending viscous magma degassed and crystallized, and fractures that admitted oxygen into the hot solidified lava spine interior facilitated additional iron oxidation.

Are closed landfills free of CH_{4} emissions? A case study of Arico's landfill, Tenerife, Canary Islands

NASA Astrophysics Data System (ADS)

Barrancos, José; Cook, Jenny; Phillips, Victoria; Asensio-Ramos, María; Melián, Gladys; Hernández, Pedro A.; Pérez, Nemesio M.

2016-04-01

Landfills are authentic chemical and biological reactors that introduce in the environment a wide amount of gas pollutants (CO2, CH4, volatile organic compounds, etc.) and leachates. Even after years of being closed, a significant amount of landfill gas could be released to the atmosphere through the surface in a diffuse form, also known as non-controlled emission. The study of the spatial-temporal distribution of diffuse emissions provides information of how a landfill degassing takes place. The main objective of this study was to estimate the diffuse uncontrolled emission of CH4 into the atmosphere from the closed Arico's landfill (0.3 km2) in Tenerife Island, Spain. To do so, a non-controlled biogenic gas emission survey of nearly 450 sampling sites was carried out during August 2015. Surface gas sampling and surface landfill CO2 efflux measurements were carried out at each sampling site by means of a portable non-dispersive infrared spectrophotometer (NDIR) model LICOR Li800 following the accumulation chamber method. Landfill gases, CO2 and CH4, were analyzed using a double channel VARIAN 4900 micro-GC. The CH4 efflux was computed combining CO2 efflux and CH4/CO2 ratio in the landfill's surface gas. To quantify the total CH4 emission, CH4 efflux contour map was constructed using sequential Gaussian simulation (sGs) as interpolation method. The total diffuse CH4 emission was estimated in 2.2 t d-1, with CH4 efflux values ranging from 0-922 mg m-2 d-1. This type of studies provides knowledge of how a landfill degasses and serves to public and private entities to establish effective systems for extraction of biogas. This aims not only to achieve higher levels of controlled gas release from landfills resulting in a higher level of energy production but also will contribute to minimize air pollution caused by them.

Bubble formation, vesicularity and fractionation of noble gases during MORB degassing

NASA Astrophysics Data System (ADS)

Sator, N.; Guillot, B. B.; Aubry, G.

2012-12-01

The fractionation of noble gases in oceanic basalts gives information on the source region and on the transport of volatiles up to the seafloor. For instance, the large distribution (~1-1,000) of the 4He/40Ar* ratio in mid-ocean ridge basalts (MORB), is interpreted as the signature of different degassing scenarios taking place at depth. Thus, a low value of this ratio is explained by a closed system degassing whereas a high value is assigned either to an open system degassing (where vesicles are lost in a magma chamber or at depth during magma ascent) or to a kinetic disequilibrium induced by a rapid magma ascent just prior eruption. Unfortunately, CO2 has a very low solubility in basaltic melts at pressure corresponding to the seafloor and an overwhelming majority of erupted lavas have lost their pristine volatile contents. However notable exceptions are the popping rocks characterized by a large vesicularity, a high CO2 content and a 4He/40Ar* ratio compatible with the expected U/K ratio of the upper mantle. Those samples likely have experienced a CO2 exsolution at about 35 km depth in the oceanic mantle. So, the very existence of these exceptional MORB samples suggests that CO2-rich melts could be present at a greater depth. Thus, explosive eruptions near ocean spreading centers are well documented (Hekinian et al., 2000) and are associated with volcaniclastic deposits containing highly vesicular basalts, a feature which suggests that this volcanism is driven by CO2-rich magmas (Helo et al., 2011). But how much CO2-rich are these magmas, that is the question. The objective of this study is to use molecular dynamics simulation (MD) to evaluate the vesicularity and the fractionation of noble gases in a degassing MORB melt. A previous simulation study (Guillot and Sator, 2011) has shown that the solubility of CO2 in basaltic melts increases steadily with the pressure and deviates significantly from the Henry's law at high pressures. From the CO2 solubility curve and the equations of state of the two coexisting phases, deduced from the MD simulation, we have evaluated the evolution of the vesicularity of a MORB melt at depth as function of its initial CO2 contents. An excellent agreement is obtained between our results and data on MORB samples collected at oceanic ridges. A conclusion is that CO2-rich magmas may exist at 100 km depth or more in the oceanic mantle. Moreover, we have evaluated the partitioning and the fractionation of noble gases between the CO2-saturated melt and supercritical CO2 vesicles as function of the pressure. We show that the large distribution of the 4He/40Ar* ratio reported in the literature can be explained if the magma experiences a suite of vesiculation and vesicle loss during ascent. Finally, by applying a pressure drop to a volatile bearing melt (CO2+noble gas), the MD simulation reveals the main steps of bubble formation and noble gas transfer at the nanometric scale. A key result is that the transfer of noble gases is found to be concomitant with CO2 bubble nucleation, a finding which suggests that the difference in diffusivity between He and Ar in the degassing melt has practically no effect on the 4He/40Ar* ratio measured in the vesicles. Guillot B., Sator N. (2011), GCA 75, 1829-1857 Hekinian et al. (2000), J. Volcanol. Geotherm. Res. 98, 49-77 Helo et al. (2011), Nature Geoscience 4, 260-263

Prodigious emission rates and magma degassing budget of major, trace and radioactive volatile species from Ambrym basaltic volcano, Vanuatu island Arc

NASA Astrophysics Data System (ADS)

Allard, P.; Aiuppa, A.; Bani, P.; Métrich, N.; Bertagnini, A.; Gauthier, P.-J.; Shinohara, H.; Sawyer, G.; Parello, F.; Bagnato, E.; Pelletier, B.; Garaebiti, E.

2016-08-01

Ambrym volcano, in the Vanuatu arc, is one of the most active volcanoes of the Southwest Pacific region, where persistent lava lake and/or Strombolian activity sustains voluminous gas plume emissions. Here we report on the first comprehensive budget for the discharge of major, minor, trace and radioactive volatile species from Ambrym volcano, as well as the first data for volatiles dissolved in its basaltic magma (olivine-hosted melt inclusions). In situ MultiGAS analysis of H2O, CO2, SO2 and H2S in crater rim emissions, coupled with filter-pack determination of SO2, halogens, stable and radioactive metals demonstrates a common magmatic source for volcanic gases emitted by its two main active craters, Benbow and Marum. These share a high water content ( 93 mol%), similar S/Cl, Cl/F, Br/Cl molar ratios, similar (210Po/210Pb) and (210Bi/210Pb) activity ratios, as well as comparable proportions in most trace metals. Their difference in CO2/SO2 ratio (1.0 and 5.6-3.0, respectively) is attributed to deeper gas-melt separation at Marum (Strombolian explosions) than Benbow (lava lake degassing) during our measurements in 2007. Airborne UV sensing of the SO2 plume flux (90 kg s- 1 or 7800 tons d- 1) demonstrates a prevalent degassing contribution ( 65%) of Benbow crater in that period and allows us to quantify the total volatile fluxes during medium-level eruptive activity of the volcano. Results reveal that Ambrym ranks among the most powerful volcanic gas emitters on Earth, producing between 5% and 9% of current estimates for global subaerial volcanic emissions of H2O, CO2, HCl, Cu, Cr, Cd, Au, Cs and Tl, between 10% and 17% of SO2, HF, HBr, Hg, 210Po and 210Pb, and over 30% of Ag, Se and Sn. Global flux estimates thus need to integrate its contribution and be revised accordingly. Prodigious gas emission from Ambrym does not result from an anomalous volatile enrichment nor a differential excess degassing of its feeding basalt: this latter contains relatively modest dissolved amounts of H2O (≤ 1.3 wt%), CO2 ( 0.10 wt%), S (0.075 wt%) and Cl (0.05 wt%), and its degassing under prevalent closed-system conditions well reproduces the composition of emitted volcanic gases. Instead, we show that the gas discharge is sustained by a very high basalt supply rate of 25 m3 s- 1, from a large ( 0.5 km3) magma reservoir probably emplaced at 3.8 km depth below the summit caldera according to both the H2O-CO2 content of bubble-free melt inclusions and preliminary seismic data. Radioactive disequilibria in the volcanic gases constrain that this reservoir may be entirely renewed in about 240 days. The comparatively low magma extrusion rate requires extensive convective overturn of the basaltic magma column and recycling of the unerupted (denser) degassed magma in the plumbing system, in agreement with textural features of erupted products. Finally, our results suggest that the Indian MORB-type mantle source of Ambrym basalts is modestly enriched in slab-derived water and other volatiles, in agreement with the prevalent volcanoclastic nature of subducted sediments and their lower subduction rate under the central Vanuatu arc due to its collision with the D'Entrecasteaux Ridge.

Influence of starting material on the degassing behavior of trachytic and phonolitic melts

NASA Astrophysics Data System (ADS)

Preuss, Oliver; Marxer, Holger; Nowak, Marcus

2015-04-01

The dynamic magmatic processes beneath volcanic systems, occurring during magma ascent, cannot be observed directly in nature. Simulation of magma ascent in the lab realized by continuous decompression (CD) of a volatile containing melt is essential to understand these processes that may lead to potentially catastrophic eruptions threatening millions of people in highly populated areas like Naples located between the Campi Flegrei Volcanic Field and the Monte Somma-Vesuvio strato-volcano. In this project, experimental simulations of Campanian Ignimbrite (CI) magma ascent will give insight to the mechanisms of the CI super eruption, thus providing tools for volcanic hazard assessment at the high risk Campanian Volcanic District and other comparable volcanic systems. Additionally, comparable experiments with the same conditions using the 'white pumice' composition of the catastrophic Vesuvius AD 79 (VAD79) eruption, have been conducted. So far, the experiments were performed in an internally heated argon pressure vessel coupled with a high-pressure low-flow metering valve and a piezoelectric nano-positioning system using a starting pressure of 200 MPa, H2O content of about 5 wt% and two different decompression rates (0.024 and 0.17 MPa/s) at a superliquidus temperature of 1050 ° C to ensure a crystal free melt and a homogeneous bubble nucleation. Experiments were conducted with both, glass powder and cylinders, subsequently decompressed to 75 and 100 MPa and rapidly quenched. Beside the results that e.g. decompression rate, volatile content, fluid solubility and target pressure affect the degassing behavior of the melt, the influence of the starting material on the degassing processes is significant. Analyses of BSE- and transmitted light microscopy images revealed a different degassing behavior of glass cylinder experiments compared to powders. Nitrogen has a very low solubility in hydrous silicate melts, supporting our suggestion that preexisting nitrogen rich bubbles (from trapped air between the single glass grains) in the melt lead to growth of these preexisting bubbles resulting in near equilibrium degassing where no further nucleation is needed. This results in much higher porosities of the degassed samples compared to those where pure dissolved H2O is present. The same effect was observed by repeating these experiments with a phonolitic VAD79 composition. In ongoing experiments using glass cylinders as starting material, approximately 0.4 wt% chlorine (average Campanian Ignimbrite melt inclusion data [1]) will be added as a volatile component to study the influence on the degassing behavior of hydrous CI melt. [1] Marianelli et al. (2006) Geology 34(11), 937

Power recovery system for coal liquefaction process

DOEpatents

Horton, Joel R.

1985-01-01

Method and apparatus for minimizing energy required to inject reactant such as coal-oil slurry into a reaction vessel, using high pressure effluent from the latter to displace the reactant from a containment vessel into the reaction vessel with assistance of low pressure pump. Effluent is degassed in the containment vessel, and a heel of the degassed effluent is maintained between incoming effluent and reactant in the containment vessel.

Pinatubo Lake Chemistry and Degassing 1991-2010

NASA Astrophysics Data System (ADS)

Schwandner, F. M.; Newhall, C. G.; Christenson, B. W.; Apfelbeck, C. A.; Arpa, M. C. B.; Vaquilar, R.; Bariso, E.

2016-12-01

We review the history of degassing, bathymetry and water chemistry of the crater lake of Mt. Pinatubo (Philippines) using data obtained during 1991-2001, and 2010. In late 1992, the initial small lake had a significant acid-sulfate component from a volcanic degassing through a hydrothermal system and the lake, and anhydrite dissolution. Subsequently, this component was "drowned" by rainfall (2-4 m/y), meteoric groundwater draining from the crater walls into the lake, and a few neutral chloride crater wall springs. Conductivity-Temperature-Depth (CTD) measurements in August 2000 found a strong inverted thermal gradient below 20m depth, reaching over 70°C at 50-60 m depth. By January 2001 the lake had homogenized and was much cooler (27°C at all depths), and it was again well-mixed and still cool when re-surveyed in June 2001 and November 2010. By 2010, the lake was well mixed, at neutral pH, with no significant vertical or horizontal structure. Bubbling of a predominantly carbon dioxide (CO2) gas phase persists throughout the lake's history, some from 1991-92 magma and some from degassing of the long-standing (pre-1991) hydrothermal system fed from a deeper magmatic or mantle source. Crater wall fumaroles emit boiling-point hydrothermal gases dominated by water, air, and CO2.

Modeling CO2 degassing and pH in a stream-aquifer system

USGS Publications Warehouse

Choi, J.; Hulseapple, S.M.; Conklin, M.H.; Harvey, J.W.

1998-01-01

Pinal Creek, Arizona receives an inflow of ground water with high dissolved inorganic carbon (57-75 mg/l) and low pH (5.8-6.3). There is an observed increase of in-stream pH from approximately 6.0-7.8 over the 3 km downstream of the point of groundwater inflow. We hypothesized that CO2 gas-exchange was the most important factor causing the pH increase in this stream-aquifer system. An existing transport model, for coupled ground water-surface water systems (OTIS), was modified to include carbonate equilibria and CO2 degassing, used to simulate alkalinity, total dissolved inorganic carbon (C(T)), and pH in Pinal Creek. Because of the non-linear relation between pH and C(T), the modified transport model used the numerical iteration method to solve the non-linearity. The transport model parameters were determined by the injection of two tracers, bromide and propane. The resulting simulations of alkalinity, C(T) and pH reproduced, without fitting, the overall trends in downstream concentrations. A multi-parametric sensitivity analysis (MPSA) was used to identify the relative sensitivities of the predictions to six of the physical and chemical parameters used in the transport model. MPSA results implied that C(T) and pH in stream water were controlled by the mixing of ground water with stream water and CO2 degassing. The relative importance of these two processes varied spatially depending on the hydrologic conditions, such as stream flow velocity and whether a reach gained or lost stream water caused by the interaction with the ground water. The coupled transport model with CO2 degassing and generalized sensitivity analysis presented in this study can be applied to evaluate carbon transport and pH in other coupled stream-ground water systems.An existing transport model for coupled groundwater-surface water systems was modified to include carbonate equilibria and CO2 degassing. The modified model was used to simulate alkalinity, total dissolved inorganic carbon (CT) and pH in Pinal Creek. The model used the numerical iteration method to solve the nonlinear relation between pH and CT. A multi-parametric sensitivity analysis (MPSA) was used to identify the relative sensitivities of the predictions to six of the physical and chemical parameters used in the transport model. MPSA results implied that CT and pH in the stream water were controlled by the mixing of groundwater with stream water and CO2 degassing.

Reprint of: Effects of solution degassing on solubility, crystal growth and dissolution-Case study: Salicylic acid in methanol

NASA Astrophysics Data System (ADS)

Seidel, J.; Ulrich, J.

2017-07-01

The influence of dissolved gases on the crystallization parameter solubility, MZW, growth and dissolution rates was investigated experimentally using degassed and non-degassed (air-saturated) solutions. The results of this study show that degassing has no effect on the solubility curve of the used model substance salicylic acid (SA) in methanol (MeOH). This reveals in the assumption that a thermodynamic effect of dissolved gases can be excluded. Growth rates were measured by means of a desupersaturation method and the results indicate that the growth rates of SA are not affected by degassing. The results of the dissolution rate measurements reveal a distinct decrease in dissolution rates for non-degassed solutions compared to degassed solutions, especially, at low temperature (10 °C). To explain this phenomenon the gas solubility, represented by oxygen, in MeOH in dependence on the SA concentration was estimated by means of Hansen Solubility Parameters (HSP) [1]. It was found that the oxygen solubility decreases with increasing SA content which explains the inhibition of crystal dissolution in non-degassed solution compared to degassed solution. Moreover, this kind of 'drowing-out' mechanism would not appear in growth rate measurements, where indeed no effect of degassing could be observed.

Rates of Earth degassing

NASA Technical Reports Server (NTRS)

Onions, R. K.

1994-01-01

The degassing of the Earth during accretion is constrained by Pu-U-I-Xe systematics. Degassing was much more efficient during the first 100-200 Ma than subsequently, and it was more complete for Xe than for the lighter gases. More than 90 percent of the degassed Xe escaped from the atmosphere during this period. The combination of fractional degassing of melts and rare gas escape from the atmosphere is able to explain the deficit of terrestrial Xe as a simple consequence of this early degassing history. By the time Xe was quantitatively retained in the atmosphere, the abundances of Kr and the lighter gases in the Earth's interior were similar to or higher than the present-day atmospheric abundances. Subsequent transfer of these lighter rare gases into the atmosphere requires a high rate of post-accretion degassing and melt production. Considerations of Pu-U-Xe systematics suggest that relatively rapid post-accretion degassing was continued to ca. 4.1-4.2 Ga. The present-day degassing history of the Earth is investigated through consideration of rare gas isotope abundances. Although the Earth is a highly degassed body, depleted in rare gases by many orders of magnitude relative to their solar abundances, it is at the present-day losing primordial rare gases which were trapped at the time of accretion.

Effects of solution degassing on solubility, crystal growth and dissolution-Case study: Salicylic acid in methanol

NASA Astrophysics Data System (ADS)

Seidel, J.; Ulrich, J.

2017-02-01

The influence of dissolved gases on the crystallization parameter solubility, MZW, growth and dissolution rates was investigated experimentally using degassed and non-degassed (air-saturated) solutions. The results of this study show that degassing has no effect on the solubility curve of the used model substance salicylic acid (SA) in methanol (MeOH). This reveals in the assumption that a thermodynamic effect of dissolved gases can be excluded. Growth rates were measured by means of a desupersaturation method and the results indicate that the growth rates of SA are not affected by degassing. The results of the dissolution rate measurements reveal a distinct decrease in dissolution rates for non-degassed solutions compared to degassed solutions, especially, at low temperature (10 °C). To explain this phenomenon the gas solubility, represented by oxygen, in MeOH in dependence on the SA concentration was estimated by means of Hansen Solubility Parameters (HSP) [1]. It was found that the oxygen solubility decreases with increasing SA content which explains the inhibition of crystal dissolution in non-degassed solution compared to degassed solution. Moreover, this kind of 'drowing-out' mechanism would not appear in growth rate measurements, where indeed no effect of degassing could be observed.

Travertines associated with the Alhama-Jaraba thermal waters (NE, Spain): Genesis and geochemistry

NASA Astrophysics Data System (ADS)

Asta, Maria P.; Auqué, Luis F.; Sanz, Francisco J.; Gimeno, Maria J.; Acero, Patricia; Blasco, Mónica; García-Alix, Antonio; Gómez, Javier; Delgado-Huertas, Antonio; Mandado, Juan

2017-01-01

Freshwater carbonates are interesting archives in palaeoenvironmental reconstructions. However, more studies of those systems are needed to fully understand past environments. In this work the actively-forming travertines of the Alhama-Jaraba thermal system were studied for the first time in order to evaluate the relationship between the geochemical and mineralogical composition and the environmental conditions during their formation. With that aim, a combination of petrographical, mineralogical, geochemical and stable isotope analyses were carried out. These carbonates provide a natural laboratory for the study of the effect of different variables (natural and anthropogenic) on carbonate precipitation. The results showed that there is a close relationship between the mineralogy of the solid precipitates and the formation temperature, and only the samples formed from overheated waters (40-60 °C) show significant concentrations of aragonite. Aragonite-bearing samples show higher concentrations in Sr, Ba and U while calcitic solids are enriched in Mg. These differences could be attributed to mineralogy, temperature or different precipitation rates. The geochemical evaluation of the chemistry of both the solids and their parental waters suggests that differences in the rate of CO2-degassing and, in some cases, evaporation are the primary environmental controls on isotopic compositions. In addition, the results show that, if strong evaporation and CO2-degassing are involved, calcite precipitation occurs under conditions of isotopic disequilibrium with its parental water. The results of our study are useful to interpret old depositional environments and palaeotemperatures.

Development of a prototype for dissolved CO2 rapid measurement and preliminary tests

NASA Astrophysics Data System (ADS)

Li, Meng; Guo, Jinjia; Zhang, Zhihao; Luo, Zhao; Qin, Chuan; Zheng, Ronger

2017-10-01

The measurements of dissolved CO2 in seawater is of great significance for the study of global carbon cycle. At present, the commercial sensors used for dissolved CO2 measurements are mostly equipped with permeable membranes for the purpose of gas-liquid separation, with the advantages of easy operation, low cost, etc.. However, most of these devices measure CO2 after reaching gas equilibrium, so it takes a few minutes to respond, which limited its applications in rapid measurements. In this paper, a set of prototype was developed for the rapid measurements of dissolved CO2. The system was built basing the direct absorption TDLAS. To detect the CO2 absorption line located at 4991.26 cm-1 , a fiber-coupled DFB laser operating at 2004 nm was selected as the light source. A Herriott type multi-pass cavity with an effective optical path length of 10 m and an inner volume of 90 mL was used for absorption measurements. A detection limit of 26 μatm can be obtained with this compact cavity. To realize the rapid measurements of dissolved CO2, a degasser with high degassing rate was necessary. A hollow fiber membrane with a large permeable area used in this paper can achieve degassing rate up to 2.88 kPa/min. Benefitted from the high degassing rate of the degasser and high sensitivity of the compact TDLAS system, a rapid measurement of dissolved CO2 in water can be achieved within 1s time, and the response time of the prototype when the dissolved CO2 concentration changed abruptly in actual measurement was 15 s. To evaluate the performance of the prototype, comparison measurements were carried out with a commercial mass spectrometer. The dissolved CO2 in both seawater and tap-water was measured, and the experimental results showed good consistent trends with R2 of 0.973 and 0.931. The experimental results proved the feasibility of dissolved CO2 rapid measurement. In the near future, more system evaluation experiments will be carried out and the system will be further optimized focusing on the underwater in-situ detection system.

Integrated geophysical and hydrothermal models of flank degassing and fluid flow at Masaya Volcano, Nicaragua

USGS Publications Warehouse

Sanford, Ward E.; Pearson, S.C.P.; Kiyosugi, K.; Lehto, H.L.; Saballos, J.A.; Connor, C.B.

2012-01-01

We investigate geologic controls on circulation in the shallow hydrothermal system of Masaya volcano, Nicaragua, and their relationship to surface diffuse degassing. On a local scale (~250 m), relatively impermeable normal faults dipping at ~60° control the flowpath of water vapor and other gases in the vadose zone. These shallow normal faults are identified by modeling of a NE-SW trending magnetic anomaly of up to 2300 nT that corresponds to a topographic offset. Elevated SP and CO2 to the NW of the faults and an absence of CO2 to the SE suggest that these faults are barriers to flow. TOUGH2 numerical models of fluid circulation show enhanced flow through the footwalls of the faults, and corresponding increased mass flow and temperature at the surface (diffuse degassing zones). On a larger scale, TOUGH2 modeling suggests that groundwater convection may be occurring in a 3-4 km radial fracture zone transecting the entire flank of the volcano. Hot water rising uniformly into the base of the model at 1 x 10-5 kg/m2s results in convection that focuses heat and fluid and can explain the three distinct diffuse degassing zones distributed along the fracture. Our data and models suggest that the unusually active surface degassing zones at Masaya volcano can result purely from uniform heat and fluid flux at depth that is complicated by groundwater convection and permeability variations in the upper few km. Therefore isolating the effects of subsurface geology is vital when trying to interpret diffuse degassing in light of volcanic activity.

Potential links between continental rifting, CO2 degassing and climate change through time

NASA Astrophysics Data System (ADS)

Brune, Sascha; Williams, Simon E.; Müller, R. Dietmar

2017-12-01

The concentration of CO2 in the atmosphere is a key influence on Earth's climate. Today, significant quantities of CO2 are emitted at continental rifts, suggesting that the spatial and temporal extent of rift systems may have influenced deep carbon fluxes and thus climate change throughout geological time. Here we test this hypothesis by conducting a worldwide census of continental rift lengths over the last 200 million years. We estimate tectonic CO2 release rates through time and show that along the extensive Mesozoic and Cenozoic rift systems, rift-related CO2 degassing rates reached more than 300% of present-day values. Using a numerical carbon cycle model, we find that two prominent periods of enhanced rifting 160 to 100 million years ago and after 55 million years ago coincided with greenhouse climate episodes, during which atmospheric CO2 concentrations were more than three times higher than today. We therefore propose that continental fragmentation and long-term climate change could plausibly be linked via massive CO2 degassing in rift systems.

Turmoil at Turrialba Volcano (Costa Rica): Degassing and eruptive processes inferred from high-frequency gas monitoring.

PubMed

de Moor, J Maarten; Aiuppa, A; Avard, G; Wehrmann, H; Dunbar, N; Muller, C; Tamburello, G; Giudice, G; Liuzzo, M; Moretti, R; Conde, V; Galle, B

2016-08-01

Eruptive activity at Turrialba Volcano (Costa Rica) has escalated significantly since 2014, causing airport and school closures in the capital city of San José. Whether or not new magma is involved in the current unrest seems probable but remains a matter of debate as ash deposits are dominated by hydrothermal material. Here we use high-frequency gas monitoring to track the behavior of the volcano between 2014 and 2015 and to decipher magmatic versus hydrothermal contributions to the eruptions. Pulses of deeply derived CO 2 -rich gas (CO 2 /S total  > 4.5) precede explosive activity, providing a clear precursor to eruptive periods that occurs up to 2 weeks before eruptions, which are accompanied by shallowly derived sulfur-rich magmatic gas emissions. Degassing modeling suggests that the deep magmatic reservoir is ~8-10 km deep, whereas the shallow magmatic gas source is at ~3-5 km. Two cycles of degassing and eruption are observed, each attributed to pulses of magma ascending through the deep reservoir to shallow crustal levels. The magmatic degassing signals were overprinted by a fluid contribution from the shallow hydrothermal system, modifying the gas compositions, contributing volatiles to the emissions, and reflecting complex processes of scrubbing, displacement, and volatilization. H 2 S/SO 2 varies over 2 orders of magnitude through the monitoring period and demonstrates that the first eruptive episode involved hydrothermal gases, whereas the second did not. Massive degassing (>3000 T/d SO 2 and H 2 S/SO 2  > 1) followed, suggesting boiling off of the hydrothermal system. The gas emissions show a remarkable shift to purely magmatic composition (H 2 S/SO 2  < 0.05) during the second eruptive period, reflecting the depletion of the hydrothermal system or the establishment of high-temperature conduits bypassing remnant hydrothermal reservoirs, and the transition from phreatic to phreatomagmatic eruptive activity.

Turmoil at Turrialba Volcano (Costa Rica): Degassing and eruptive processes inferred from high‐frequency gas monitoring

PubMed Central

Aiuppa, A.; Avard, G.; Wehrmann, H.; Dunbar, N.; Muller, C.; Tamburello, G.; Giudice, G.; Liuzzo, M.; Moretti, R.; Conde, V.; Galle, B.

2016-01-01

Abstract Eruptive activity at Turrialba Volcano (Costa Rica) has escalated significantly since 2014, causing airport and school closures in the capital city of San José. Whether or not new magma is involved in the current unrest seems probable but remains a matter of debate as ash deposits are dominated by hydrothermal material. Here we use high‐frequency gas monitoring to track the behavior of the volcano between 2014 and 2015 and to decipher magmatic versus hydrothermal contributions to the eruptions. Pulses of deeply derived CO2‐rich gas (CO2/Stotal > 4.5) precede explosive activity, providing a clear precursor to eruptive periods that occurs up to 2 weeks before eruptions, which are accompanied by shallowly derived sulfur‐rich magmatic gas emissions. Degassing modeling suggests that the deep magmatic reservoir is ~8–10 km deep, whereas the shallow magmatic gas source is at ~3–5 km. Two cycles of degassing and eruption are observed, each attributed to pulses of magma ascending through the deep reservoir to shallow crustal levels. The magmatic degassing signals were overprinted by a fluid contribution from the shallow hydrothermal system, modifying the gas compositions, contributing volatiles to the emissions, and reflecting complex processes of scrubbing, displacement, and volatilization. H2S/SO2 varies over 2 orders of magnitude through the monitoring period and demonstrates that the first eruptive episode involved hydrothermal gases, whereas the second did not. Massive degassing (>3000 T/d SO2 and H2S/SO2 > 1) followed, suggesting boiling off of the hydrothermal system. The gas emissions show a remarkable shift to purely magmatic composition (H2S/SO2 < 0.05) during the second eruptive period, reflecting the depletion of the hydrothermal system or the establishment of high‐temperature conduits bypassing remnant hydrothermal reservoirs, and the transition from phreatic to phreatomagmatic eruptive activity. PMID:27774371

Turmoil at Turrialba Volcano (Costa Rica): Degassing and eruptive processes inferred from high-frequency gas monitoring

NASA Astrophysics Data System (ADS)

de Moor, J. Maarten; Aiuppa, A.; Avard, G.; Wehrmann, H.; Dunbar, N.; Muller, C.; Tamburello, G.; Giudice, G.; Liuzzo, M.; Moretti, R.; Conde, V.; Galle, B.

2016-08-01

Eruptive activity at Turrialba Volcano (Costa Rica) has escalated significantly since 2014, causing airport and school closures in the capital city of San José. Whether or not new magma is involved in the current unrest seems probable but remains a matter of debate as ash deposits are dominated by hydrothermal material. Here we use high-frequency gas monitoring to track the behavior of the volcano between 2014 and 2015 and to decipher magmatic versus hydrothermal contributions to the eruptions. Pulses of deeply derived CO2-rich gas (CO2/Stotal > 4.5) precede explosive activity, providing a clear precursor to eruptive periods that occurs up to 2 weeks before eruptions, which are accompanied by shallowly derived sulfur-rich magmatic gas emissions. Degassing modeling suggests that the deep magmatic reservoir is 8-10 km deep, whereas the shallow magmatic gas source is at 3-5 km. Two cycles of degassing and eruption are observed, each attributed to pulses of magma ascending through the deep reservoir to shallow crustal levels. The magmatic degassing signals were overprinted by a fluid contribution from the shallow hydrothermal system, modifying the gas compositions, contributing volatiles to the emissions, and reflecting complex processes of scrubbing, displacement, and volatilization. H2S/SO2 varies over 2 orders of magnitude through the monitoring period and demonstrates that the first eruptive episode involved hydrothermal gases, whereas the second did not. Massive degassing (>3000 T/d SO2 and H2S/SO2 > 1) followed, suggesting boiling off of the hydrothermal system. The gas emissions show a remarkable shift to purely magmatic composition (H2S/SO2 < 0.05) during the second eruptive period, reflecting the depletion of the hydrothermal system or the establishment of high-temperature conduits bypassing remnant hydrothermal reservoirs, and the transition from phreatic to phreatomagmatic eruptive activity.

Effect of degassing temperature on specific surface area and pore volume measurements of biochar

NASA Astrophysics Data System (ADS)

Sigmund, Gabriel; Hüffer, Thorsten; Kah, Melanie; Hofmann, Thilo

2017-04-01

Specific surface area, pore volume, and pore size distribution are key biochar properties that have been related to water and nutrient cycling, microbial activity as well as sorption potential for organic compounds. Specific surface area and pore volume are commonly determined by measurement of physisorption of N2 and/or CO2. The measurement requires prior degassing of the samples, which may change the structure of the materials. Information on degassing temperature is rarely reported in literature, and recommendations differ considerably between existing guidelines for biochar characterization. Therefore, the influence of degassing temperature on N2 and CO2physisorption measurements was investigated by systematically degassing a range of materials, including four biochars, Al2O3 and carbon nanotubes at different temperatures (105 ˚ C, 150 ˚ C, 200 ˚ C, 250 ˚ C and 300 ˚ C for ≥ 14 h each). Measured specific surface area and pore volume increased with increasing degassing temperature for all biochars. Additional surface area and pore volume may have become available as components in biochars volatilized during the degassing phase. The results of our study showed that (i) degassing conditions change material properties, and influence physisorption measurements for biochar (ii) comparison between parameters derived from different degassing protocols may not be appropriate, and (iii) degassing protocols should be harmonized in the biochar community [1]. [1] Sigmund, et al. (2016), "Biochar total surface area and total pore volume determined by N2 and CO2 physisorption are strongly influenced by degassing temperature", STOTEN, doi: http://dx.doi.org/10.1016/j.scitotenv.2016.12.023.

Natural sources of greenhouse gases: carbon dioxide emissions from volcanoes

USGS Publications Warehouse

Gerlach, Terrence

1990-01-01

Volcanic degassing of carbon dioxide plays an important role in keeping the atmosphere-ocean portion of the carbon geochemical cycle in balance. The atmosphere-ocean carbon deficit requires replenishment of 6??1012 mol CO2/yr, and places an upper limit on the output of carbon dioxide from volcanoes. The CO2 output of the global mid-oceanic ridge system is ca. 0.7??1012 mol/yr, thus supplying only a fraction of the amount needed to balance the carbon deficit. The carbon dioxide flux from subaerial volcanoes is poorly known, but it appears to be at least as large as the mid-oceanic ridge flux. Much (perhaps most) of the CO2 emitted from volcanoes is degassed noneruptively. This mode of degassing may lead to impacts on the environment and biosphere that are fundamentally different in character from those envisioned in published scenarios, which are based on the assumption that CO2 degassing occurs predominantly by eruptive processes. Although the flux of carbon dioxide from volcanoes is poorly constrained at present, it is clearly two orders of magnitude lower than the anthropogenic output of CO2.

Self Sealing Magmas

NASA Astrophysics Data System (ADS)

von Aulock, Felix W.; Wadsworth, Fabian B.; Kennedy, Ben M.; Lavallee, Yan

2015-04-01

During ascent of magma, pressure decreases and bubbles form. If the volume increases more rapidly than the relaxation timescale, the magma fragments catastrophically. If a permeable network forms, the magma degasses non-violently. This process is generally assumed to be unidirectional, however, recent studies have shown how shear and compaction can drive self sealing. Here, we additionally constrain skin formation during degassing and sintering. We heated natural samples of obsidian in a dry atmosphere and monitored foaming and impermeable skin formation. We suggest a model for skin formation that is controlled by diffusional loss of water and bubble collapse at free surfaces. We heated synthetic glass beads in a hydrous atmosphere to measure the timescale of viscous sintering. The beads sinter at drastically shorter timescales as water vapour rehydrates an otherwise degassed melt, reducing viscosity and glass transition temperatures. Both processes can produce dense inhomogeneities within the timescales of magma ascent and effectively disturb permeabilities and form barriers, particularly at the margins of the conduit, where strain localisation takes place. Localised ash in failure zones (i.e. Tuffisite) then becomes associated with water vapour fluxes and alow rapid rehydration and sintering. When measuring permeabilities in laboratory and field, and when discussing shallow degassing in volcanoes, local barriers for degassing should be taken into account. Highlighting the processes that lead to the formation of such dense skins and sintered infills of cavities can help understanding the bulk permeabilities of volcanic systems.

Terrestrial Planets: Volatiles Loss & Speed of Rotation

NASA Astrophysics Data System (ADS)

Kochemasov, G. G.

There is a close relation between orbiting frequencies of terrestrial planets and intensities of their outgassing [1]. ``Sweeping'' out volatiles of their bodies is provoked and facilitated by body shaking (wave oscillations) caused by movement of celestial bodies in elliptical orbits. Non-round orbits cause inertia-gravity warpings in all spheres of the bodies producing their tectonic granulation. The higher orbiting frequency -- the smaller tectonic granula -- more thorough interior degassing. Sizes of tectonic granulas inversely proportional to orbiting frequencies are: Mars π R/2, Earth π R/4, Venus π R/6, Mercury π R/16. The atmospheric masses increase from Mars through Earth to Venus as ˜ 0. 01 : 1 : 90 (radiogenic/primordial Ar is 3000 : 300 : 1, marking degassing intensity). Mercury in this sequence should have been even more outgassed (˜ 500 times comparative to Venus, having in mind different planetary masses [2]). But now it possesses only very weak atmosphere of noble gases, Na, K -- remnants of past significant outgassing now witnessed by a great amount of small deep structurally controlled pits (craters), lobate scarps caused by strong contraction and slow rotation. The slow rotation is due to loss of angular momentum to the atmosphere now wiped out by the solar wind. The same partitioning of angular momentum occurs at Venus: slowly rotating solid body is wrapped in rapidly rotating massive atmosphere (the solid surface exposes many features of contraction due to subsidence -- vast areas of wrinkle ridges). On the contrary to slow Mercury and Venus, Earth and Mars keep their moderate rotation corresponding to their moderate and mild degassing [3]. Still further from Sun weakly outgassed gas giants rotate very rapidly. Sun itself with slowly rotating photosphere and corresponding supergranula size π R/60 is a strongly outgassed object (some think that Sun lost upto 10% of its original mass). In line with the established regularity between orbiting frequency and granula size, small solar granulas (1000-2000 km) could keep memory of the rapider rotation in the past before a strong degassing (mesogranulas indicate at some stage of mass loss) [3]. Thus, according to volatile loss in the Solar system there are bodies rotating rapidly -the outer planets, moderately -- Mars, Earth, slowly - Venus, Mercury, Sun. References: [1] Kochemasov G.G. (2003) Surprisingly rich in H2 O soils of Mars: a consequence of mild degassing // Geophys. Res. Abstr., v. 5, 02167, (CD-ROM); [2] Kochemasov G.G. (2003) // 38th Vernadsky-Brown microsymp. ``Topics in Comparative Planetology'', Abstr., Moscow, Oct.27-28, (CD-ROM); [3] Ibid.,Structures of the wave planetology and their projection onto the solar photosphere: why solar supergranules are 30000 km across. _

Correlation of cycles in Lava Lake motion and degassing at Erebus Volcano, Antarctica

NASA Astrophysics Data System (ADS)

Peters, Nial; Oppenheimer, Clive; Killingsworth, Drea Rae; Frechette, Jed; Kyle, Philip

2014-08-01

Several studies at Erebus volcano have recorded pulsatory behavior in many of the observable properties of its active lava lake. A strong correlation between the variations in surface speed of the lake and the composition of gas emitted has previously been noted. While previous studies have shown that the SO2 flux and the surface elevation exhibit pulsatory behavior with a similar period to that of the surface speed and gas composition, suggesting they are linked, a lack of overlap between the different measurements has prevented direct comparisons from being made. Using high time-resolution measurements of surface elevation, surface speed, gas composition, and SO2 flux, we demonstrate for the first time an unambiguous link between the cyclic behavior in each of these properties. We also show that the variation in gas composition may be explained by a subtle change in oxygen fugacity. The cycles are found to be in-phase with each other, with a small but consistent lag of 1-3 min between the peaks in surface elevation and surface speed. Explosive events are found to have no observable effect on the pulsatory behavior beyond the ˜5 min period required for lake refill. The close correspondences between the varying lake surface motion, gas flux and composition, and modeled oxygen fugacity suggest strong links between magma degassing, redox change, and the fluid dynamics of the shallow magmatic system.

Soil temperature and CO2 degassing, SO2 fluxes and field observations before and after the February 29, 2016 new vent inside Nyiragongo crater

NASA Astrophysics Data System (ADS)

Balagizi, Charles M.; Yalire, Mathieu M.; Ciraba, Honoré M.; Kajeje, Vicky B.; Minani, Abel S.; Kinja, Annie B.; Kasereka, Marcellin M.

2016-09-01

Nyiragongo volcano threatens ˜1.5 million inhabitants of Goma (DR Congo) and Gisenyi (Rwanda) cities and people living in the surrounding villages. In 2002, the volcano produced lava flows which invaded Goma and destroyed the economic district of the city, forced a mass exodus of the population and caused the loss of several lives. Nyiragongo volcanic activity is therefore closely followed by the inhabitants, and any news related to increased activity agitates people in the area, especially those in Goma. Here, we report a short time series of soil temperature and carbon dioxide degassing for four locations, and plume sulphur dioxide fluxes preceding and following the opening of a new vent inside the main Nyiragongo crater on February 29, 2016. The observed sudden and unexpected changes in Nyiragongo activity raised the fear of a new volcanic eruption and led to panic in Goma and the surroundings, inducing some people to leaving the city. We use the dataset and field observations before and after the opening of the new vent, in conjunction with published information about Nyiragongo's eruptive mechanism and of the volcano's plumbing system geometry (mainly the crater), to show that the new vent was fed by magma intruded from the lava lake or the upper conduit.

Monitoring fugitive CH4 and CO2 emissions from a closed landfill at Tenerife, Canary Islands

NASA Astrophysics Data System (ADS)

Asensio-Ramos, María; Tompkins, Mitchell R. K.; Turtle, Lara A. K.; García-Merino, Marta; Amonte, Cecilia; Rodrígez, Fátima; Padrón, Eleazar; Melián, Gladys V.; Padilla, Germán; Barrancos, José; Pérez, Nemesio M.

2017-04-01

Solid waste must be managed systematically to ensure environmental best practices. One of the ways to manage this huge problem is to systematic dispose waste materials in locations such as landfills. However, landfills could face possible threats to the environment such as groundwater pollution and the release of landfill gases (CH4, volatile organic compounds, etc.) to the atmosphere. These structures should be carefully filled, monitored and maintained while they are active and for up to 30 years after they are closed. Even after years of being closed, a systematically amount of landfill gas could be released to the atmosphere through its surface in a diffuse and fugitive form. During the period 1999-2016, we have studied the spatial-temporal distribution of the surface fugitive emission of CO2 and CH4 into the atmosphere in a cell in the Arico's municipal landfill (0.3 km2) at Tenerife, Canary Islands, Spain. This cell was operative until 2004, when it was filled and closed. Monitoring these diffuse landfill emissions provides information of how the closed landfill is degassing. To do so, we have performed 9 gas emission surveys during the period 1999-2016. Surface landfill CO2 efflux measurements were carried out at around 450 sampling site by means of a portable non-dispersive infrared spectrophotometer (NDIR) model LICOR Li800 following the accumulation chamber method. Landfill gases taken in the chamber were analyzed using a double channel VARIAN 4900 micro-GC. CH4 efflux measurements were computed combining CO2 efflux measurements and CH4/CO2 ratio in the landfill's surface gas. To quantify the total CH4 emission, CH4 efflux contour map was constructed using sequential Gaussian simulation (sGs) as interpolation method. In general, a decrease in the CO2 emission is observed since the cell was closed (2004) to the present. The total CO2 and CH4 diffuse emissions estimated in the 2016 survey were 4.54 ± 0.14 t d-1 and 268.65 ± 17.99 t d-1, respectively. These types of studies provide knowledge of how a landfill degasses and serves to public and private entities to establish effective systems for extraction of biogas. This aims not only to achieve higher levels of controlled gas release from landfills resulting in a higher level of energy production but also will contribute to minimize air pollution caused by them.

Mapping of the Samara city by definition of areas with hydrogen degassing using Raman spectroscopy

NASA Astrophysics Data System (ADS)

Timchenko, E. V.; Timchenko, P. E.; Zherdeva Taskina, L. A.; Тregub, N. V.; Selezneva, E. A.

2015-03-01

One of the complicating factors for environmental situation is degassing of land. The high concentrations of hydrogen near the bearing metal structures can weaken them as a result of embrittlement. Therefore, the study problems of hydrogen concentration in the soil and hydrogen influence on living organisms are relevant. However, the exit of deep hydrogen has a volley character. This problem can be solved by the plant bioobjects as the local integral indicators. The dandelion (Taráxacum) was selected as the research object. The collection of objects was produced from the degassing zone and a zone without degassing. Selection of degassing zone was driven by information that was provided by the Volga branch of the Institute of Geology and Exploration of fossil fuels of the Samara Region. Experimental studies of the hydrogen influence on the optical properties of plants were conducted using a complex of Raman spectroscopy and confocal microscopy. Laboratory and field research were conducted. Raman spectroscopy was implemented using the experimental stand that includes a radiation source, a fiber system for collect and feed of radiation and SR-303i spectrophotometer with integrated digital camera ANDOR DV-420A-OE (1024 * 256). The experimental stand allows to work in the spectral range of 180 - 1200 nm and with a registration accuracy about 0.2 nm. A detailed analysis of the structural changes in plant cells under the hydrogen influence was performed by confocal microscopy.

Mantle Degassing and Atmosphere Evolution

NASA Astrophysics Data System (ADS)

Zhang, Y.

2011-12-01

Noble gas isotopes have provided much of our understanding of Earth's early history [1-3]. Various degassing models have been developed, including degassing of the whole mantle, degassing of all gases at similar relative rate [1], solubility-controlled degassing [2], and steady-state degassing models [4]. This report will evaluate various degassing models using recent data. For example, helium outgassing flux has been lowered by more than a factor of two based on sophisticated ocean general circulation models [5], which also impacts on the estimated degassing flux of carbon. Years of measurements and progress have allowed isotopic ratios of various mantle reservoirs being pieced together [6]. For example, 129Xe/130Xe in OIB mantle is found to be lower than that in MORB mantle [7]. Missing Xe has been found to be a non-issue [8]. Nucleogenic 21Ne production rate relative radiogenic 4He has been revised [9-10], which leads to an interesting neon paradox that nucleogenic 21Ne production in the whole silicate Earth is barely enough to supply nucleogenic 21Ne in air. 40Ar/36Ar ratio in BSE seems to be much lower than any OIB samples, another interesting paradox. Although non-nucleogenic mantle neon is solar, nonradiogenic mantle argon is atmospheric [11]. For Kr and Xe, the jury is still out. When mantle degassing models are evaluated using volatile data of the MORB and OIB, solubility-controlled degassing is able to reconcile more data than other degassing models. On the other hand, the vailable data seem to indicate that atmosphere evolution is more than mantle degassing; there may be significant contribution to the atmosphere from impact degassing and other sources. Furthermore, we are now suffering from too many data so that understanding the whole picture is elusive. [1] Allegre et al. (1986/87) EPSL 81, 127-150. [2] Zhang & Zindler (1989) J. Geophys. Res. 94, 13719-13737. [3] Zhang (1998) Geochim. Cosmochim. Acta 62, 3185-3189. [4] Pocelli & Wasserburg (1995) Geochim. Cosmochim. Acta 59, 4921-4937. [5] Bianchi et al. (2010) EPSL 297, 379-386. [6] Jackson et al. (2009) EPSL 287, 519-528. [7] Graham (2002) Rev. Mineral. Geochem. 47, 247-317. [8] Zhang (2002) Earth-Sci. Rev. 59, 235-263. [9] Yatsevich and Honda (1997).

Degassing during quiescence as a trigger of magma ascent and volcanic eruptions.

PubMed

Girona, Társilo; Costa, Fidel; Schubert, Gerald

2015-12-15

Understanding the mechanisms that control the start-up of volcanic unrest is crucial to improve the forecasting of eruptions at active volcanoes. Among the most active volcanoes in the world are the so-called persistently degassing ones (e.g., Etna, Italy; Merapi, Indonesia), which emit massive amounts of gas during quiescence (several kilotonnes per day) and erupt every few months or years. The hyperactivity of these volcanoes results from frequent pressurizations of the shallow magma plumbing system, which in most cases are thought to occur by the ascent of magma from deep to shallow reservoirs. However, the driving force that causes magma ascent from depth remains unknown. Here we demonstrate that magma ascent can be triggered by the passive release of gas during quiescence, which induces the opening of pathways connecting deep and shallow magma reservoirs. This top-down mechanism for volcanic eruptions contrasts with the more common bottom-up mechanisms in which magma ascent is only driven by processes occurring at depth. A cause-effect relationship between passive degassing and magma ascent can explain the fact that repose times are typically much longer than unrest times preceding eruptions, and may account for the so frequent unrest episodes of persistently degassing volcanoes.

Spatial variability in degassing at Erebus volcano, Antarctica

NASA Astrophysics Data System (ADS)

Ilanko, Tehnuka; Oppenheimer, Clive; Kyle, Philip; Burgisser, Alain

2015-04-01

Erebus volcano on Ross Island, Antarctica, hosts an active phonolitic lava lake, along with a number of persistently degassing vents in its summit crater. Flank degassing also occurs through ice caves and towers. The longevity of the lake, and its stable convection, have been the subject of numerous studies, including Fourier transform infrared (FTIR) spectroscopy of the lava lake. Two distinct gas compositions were previously identified in the main lava lake plume (Oppenheimer et al., 2009; 2011): a persistent 'conduit' gas with a more oxidised signature, ascribed to degassing through a permeable magma conduit; and a H2O- and SO2- enriched 'lake' composition that increases and decreases cyclically due to shallow degassing of incoming magma batches. During the past decade of annual field seasons on Erebus, gas compositions have been measured through FTIR spectroscopy at multiple sites around Erebus volcano, including flank degassing through an ice cave (Warren Cave). We present measurements from four such vents, and compare their compositions to those emitted from the main lava lake. Summit degassing involves variable proportions of H2O, CO2, CO, SO2, HF, HCl, OCS. Cyclicity is evident in some summit vents, but with signatures indicative of shallower magmatic degassing than that of the lava lake. By contrast, flank degassing at Warren Cave is dominated by H2O, CO2, and CH4. The spatial variability in gas compositions within the summit crater suggests an alternative origin for 'conduit' and 'lake' degassing to previous models that assume permeability in the main conduit. Rather, the two compositions observed in main lake degassing may be a result of decoupled 'conduit' gas and pulses of magma rising through discrete fractures before combining in the lake floor or the main plume. Smaller vents around the crater thus emit isolated 'lake' or 'conduit' compositions while their combined signature is observed in the lava lake. We suggest that this separation between gas sources is enabled by a complex shallow fracture network, collapses of which also promote frequent changes to crater morphology. Flank degassing results from decoupling and ascent of CO2-rich gas through deeper fractures, and re-equilibration to lower temperatures and pressures.

Residual Gases in Crystal Growth Systems: Their Origin, Magnitude, and Dependence on the Processing Conditions

NASA Technical Reports Server (NTRS)

Palosz, W.

2003-01-01

Residual gases present in closed ampoules may affect different crystal growth processes. Their presence may affect techniques requiring low pressures and affect the crystal quality in different ways. For that reason a good understanding and control of formation of residual gases may be important for an optimum design and meaningful interpretation of crystal growth experiments. Our extensive experimental and theoretical study includes degassing of silica glass and generation of gases from various source materials. Different materials processing conditions, like outgassing under vacuum, annealing in hydrogen, resublimation, different material preparation procedures, multiple annealings, different processing times, and others were applied and their effect on the amount and composition of gas were analyzed. The experimental results were interpreted based on theoretical calculations on diffusion in silica glass and source materials and thermochemistry of the system. Procedures for a reduction of the amount of gas are also discussed.

Geochemical constraints on volatile sources and subsurface conditions at Mount Martin, Mount Mageik, and Trident Volcanoes, Katmai Volcanic Cluster, Alaska

NASA Astrophysics Data System (ADS)

Lopez, T.; Tassi, F.; Aiuppa, A.; Galle, B.; Rizzo, A. L.; Fiebig, J.; Capecchiacci, F.; Giudice, G.; Caliro, S.; Tamburello, G.

2017-11-01

We use the chemical and isotopic composition of volcanic gases and steam condensate, in situ measurements of plume composition and remote measurements of SO2 flux to constrain volatile sources and characterize subvolcanic conditions at three persistently degassing and seismically active volcanoes within the Katmai Volcanic Cluster (KVC), Alaska: Mount Martin, Mount Mageik and Trident. In situ plume measurements of gas composition were collected at all three volcanoes using MultiGAS instruments to calculate gas ratios (e.g. CO2/H2S, SO2/H2S and H2O/H2S), and remote measurements of SO2 column density were collected from Mount Martin and Mount Mageik by ultraviolet spectrometer systems to calculate SO2 fluxes. Fumaroles were directly sampled for chemical and isotopic composition from Mount Mageik and Trident. Mid Ocean Ridge Basalt (MORB)-like 3He/4He ratios ( 7.2-7.6 Rc/RA) within Mount Mageik and Trident's fumarole emissions and a moderate SO2 flux ( 75 t/d) from Mount Martin, combined with gas compositions dominated by H2O, CO2 and H2S from all three volcanoes, indicate magma degassing and active hydrothermal systems in the subsurface of these volcanoes. Mount Martin's gas emissions have the lowest CO2/H2S ratio ( 2-4) and highest SO2 flux compared to the other KVC volcanoes, indicative of shallow magma degassing. Geothermometry techniques applied to Mount Mageik and Trident's fumarolic gas compositions suggest that their hydrothermal reservoirs are located at depths of 0.2 and 4 km below the surface, respectively. Observations of an unusually reducing gas composition at Trident and organic material in the near-surface soils suggest that thermal decomposition of sediments may be influencing gas composition. When the measured gas compositions from Mount Mageik and Trident are compared with previous samples collected in the late 1990's, relatively stable magmatic-hydrothermal conditions are inferred for Mount Mageik, while gradual degassing of residual magma and contamination by shallow crustal fluids is inferred for Trident. The isotopic composition of volcanic gases emitted from Mount Mageik and Trident reflect mixing of subducted slab, mantle and crustal volatile sources, with organic sediment and carbonate being the predominant sources. Considering the close proximity of the target volcanoes in comparison with the depth to the subducted slab we speculate that Aleutian Arc volatiles are fed by a relatively homogeneous subducted fluid and that much of the apparent variability in volatile provenance can be explained by shallow crustal volatile sources and/or processes.

Degassing system from the magma reservoir of Miyakejima volcano revealed by GPS observations

NASA Astrophysics Data System (ADS)

Oikawa, J.; Nakao, S.; Matsushima, T.

2013-12-01

Miyake-jima is a volcanic island located approximately 180 km south of Tokyo. The island is an active basaltic volcano that was dormant for a 17-year period between an eruption in 1983 and June 26, 2000, when it again became active. The volcanic activity that occurred in 2000 is divided into the following four stages: the magma intrusion stage, summit subsidence stage, summit eruptive stage, and degassing stage (Nakada et al., 2001). Earthquake swarm activity began on June 26, 2000, accompanied by large-scale crustal deformation. This led to a summit eruption on July 8, 2000. Based on the pattern of hypocenter migration and the nature of crustal deformation, it was estimated that magma migrated from beneath the summit of Miyake-jima to the northwest during the magma intrusion stage. The rapid collapse of the summit took place between July 8 and the beginning of August 2000 (summit subsidence stage). Large-scale eruptions took place on August 10, 18, and 29, 2000 (explosion stage). The eruptions largely ceased after August 29, followed by the release of large amounts of gas from the summit crater (degassing stage). In this study, we examined the location of the magma reservoir during the degassing stage based on crustal deformation observed by GPS. By comparing the amounts of degassing and volume change of the magma reservoir, as determined from crustal deformation, we determined the mechanism of degassing and the nature of the magma reservoir-vent system. According to observations by the Japan Meteorological Agency, a large amount of volcanic gas began to be released from Miyake-jima in September 2000 (Kazahaya et al., 2003). Approximately 42,000 tons/day of SO2 was released during the period between September 2000 and January 2001. Analysis of GPS data during the period [Figure 1] indicates a source of crustal deformation on the south side of the summit crater wall at a depth of 5.2 km. The rate of volume change was -3.8 x 106 m3/month [Figure 2]. As the volume is equivalent to the volume occupied by the volatile components such as SO2, H2O, CO2 dissolved in the magma, it is proposed that contraction of the magma reservoir reflects degassing of its volatile components. The observations indicate that the magma reservoir is connected to the summit crater by a magma-filled vent. Convection within the vent carries volatile-rich magma upward to the crater, where volcanic gas is released by degassing. The depleted magma is then carried into the magma reservoir, which contracts due to the loss of volume originally occupied by the volcanic gas. Figure 1 shows displacements per month. Vectors show the horizontal movements. Contours and shading indicate vertical displacement. Figure 2 shows theoretical displacement assuming the Mogi model.

Getting the gas out - developing gas networks in magmatic systems

NASA Astrophysics Data System (ADS)

Cashman, Katharine; Rust, Alison; Oppenheimer, Julie; Belien, Isolde

2015-04-01

Volcanic eruption style, and explosive potential, are strongly controlled by the pre-eruptive history of the magmatic volatiles: specifically, the more efficient the gas loss prior to eruption, the lower the likelihood of primary (magmatic) explosive activity. Commonly considered gas loss mechanisms include separated flow, where individual bubbles (or bubble clouds) travel at a rate that is faster than the host magma, and permeable flow, where gas escapes through permeable (connected) pathways developed within a (relatively) static matrix. Importantly, gas loss via separated flow is episodic, while gas loss via permeable flow is likely to be continuous. Analogue experiments and numerical models on three phase (solid-liquid-gas) systems also suggest a third mechanism of gas loss that involves the opening and closing of 'pseudo fractures'. Pseudo fractures form at a critical crystallinity that is close to the maximum particle packing. Fractures form by local rearrangement of solid particles and liquid to form a through-going gas fracture; gas escape is episodic, and modulated by the available gas volume and the rate of return flow of interstitial liquid back into the fracture. In all of the gas escape scenarios described above, a fundamental control on gas behaviour is the melt viscosity, which affects the rate of individual bubble rise, the rate of bubble expansion, the rate of film thinning (required for bubble coalescence), and the rate of melt flow into gas-generated fractures. From the perspective of magma degassing, rates of gas expansion and film thinning are key to the formation of an interconnected (permeable) gas pathway. Experiments with both analogue and natural materials show that bubble coalescence is relatively slow, and, in particle-poor melts, does not necessarily create permeable gas networks. As a result, degassing efficiency is modulated by the time scales required either (1) to produce large individual bubbles or bubble clouds (in low viscosity melts) or (2) to develop sufficient porosity for full connectivity of a bubble network (in high viscosity melts). In contrast, our experiments suggest that the presence of solid particles may greatly enhance gas escape. On the one hand, the addition of solid particles increases the bulk viscosity of the mixture, which reduces the migration rate of large single bubbles. On the other hand, the strength of networks created by touching crystals inhibits bulk magma deformation and forces smaller bubbles to deform to occupy the spaces between particles, thereby increasing both the bubble shape anisotropy and, correspondingly, the probability of bubble coalescence. Gas pathways created in this way take advantage of inhomogeneities in the spatial distribution of crystals and allow large-scale gas release at relatively low vesicularities. This mechanism of gas escape is likely to be important not only in mafic arc volcanoes, where shallow conduits are likely to be highly crystalline, but also for degassing of crystal-mush-dominated magmatic systems.

What goes up might come down: Backflow in the conduits of persistently degassing volcanoes and ramifications for melt-inclusion analysis

NASA Astrophysics Data System (ADS)

Suckale, J.; Qin, Z.; Picchi, D.; Keller, T.

2017-12-01

Many active volcanoes erupt significantly less magma than they degas, implying that large quantities of magma must descend back into the plumbing system after degassing. The resulting bidirectional flow field in the volcanic conduit is fundamentally unstable. These instabilities are important to understand, because they likely control the episodicity of eruptive behavior observed at persistently degassing volcanoes. Laboratory experiments have provided invaluable insights into the flow regimes that may arise in volcanic conduits, but are not straightforward to scale up to volcanic systems. The goal of this study is to use direct numerical simulations to virtually reproduce the analogue experiments by Stevenson and Blake, 1998, compare them to simple analytical models and gain insights into the different flow regimes and interface instabilities observed in actual volcanic conduits. Direct numerical simulations provide a compelling complement to analogue experiments, because they are not constrained by the scales or flow properties achievable in a laboratory setting. By linking virtual and analogue experiments, we show that the interface between ascending and descending fluid is not usually stationary in volcanic conduits (see fig). The intuition that buoyant, volatile-rich magma moves up while heavy, degassed magma moves down is hence not generally true in bidirectional conduit flow. Instead, our results show that a potentially significant portion of the volatile-rich magma flows downwards despite its positive buoyancy - a process commonly referred to as backflow. The existence of backflow in volcanic conduits has potentially important ramifications for understanding melt-inclusion trends, because it affects exsolved and dissolved volatile components differently. Our preliminary results suggest that carbon dioxide bubbles exsolved at depth tend to decouple from the backflow and escape into the upward moving portion of the fluid, while dissolved water is recycled back to depth. The ascending magma, which is likely sampled by eruptive products, is hence enriched in carbon dioxide but deprived of water, which could be reflected in the common observation that melt inclusions from persistently degassing volcanic systems appear to be shifted to higher carbon dioxide contents for a given amount of water.

Magma ascent and lava flow emplacement rates during the 2011 Axial Seamount eruption based on CO2 degassing

NASA Astrophysics Data System (ADS)

Jones, M. R.; Soule, S. A.; Gonnermann, H. M.; Le Roux, V.; Clague, D. A.

2018-07-01

Quantitative metrics for eruption rates at mid-ocean ridges (MORs) would improve our understanding of the structure and formation of the uppermost oceanic crust and would provide a means to link volcanic processes with the conditions of the underlying magmatic system. However, these metrics remain elusive because no MOR eruptions have been directly observed. The possibility of disequilibrium degassing in mid-ocean ridge basalts (MORB), due to high eruptive depressurization rates, makes the analysis of volatile concentrations in MORB glass a promising method for evaluating eruption rates. In this study, we estimate magma ascent and lava flow emplacement rates during the 2011 eruption of Axial Seamount based on numerical modeling of diffusion-controlled bubble growth and new measurements of dissolved volatiles, vesicularity, and vesicle size distributions in erupted basalts. This dataset provides a unique view of the variability in magma ascent (∼0.02-1.2 m/s) and lava flow rates (∼0.1-0.7 m/s) during a submarine MOR eruption based on 50 samples collected from a >10 km long fissure system and three individual lava flow lobes. Samples from the 2011 eruption display an unprecedented range in dissolved CO2 concentrations, nearly spanning the full range observed on the global MOR system. The variable vesicularity and dissolved CO2 concentrations in these samples can be explained by differences in the extent of degassing, dictated by flow lengths and velocities during both vertical ascent and horizontal flow along the seafloor. Our results document, for the first time, the variability in magma ascent rates during a submarine eruption (∼0.02-1.2 m/s), which spans the global range previously proposed based on CO2 degassing. The slowest ascent rates are associated with hummocky flows while faster ascent rates produce channelized sheet flows. This study corroborates degassing-based models for eruption rates using comparisons with independent methods and documents the relationship between eruption dynamics, magma ascent rates, and the morphology of eruptive products. Globally, this approach allows interrogation of the processes that govern mid-ocean ridge eruptions and influence the formation of the oceanic crust.

Three-year decline of magmatic CO2 emissions from soils of a Mammoth Mountain tree kill: Horseshoe Lake, CA, 1995-1997

USGS Publications Warehouse

Gerlach, T.M.; Doukas, M.P.; McGee, K.A.; Kessler, R.

1998-01-01

We used the closed chamber method to measure soil CO2 efflux over a three-year period at the Horseshoe Lake tree kill (HLTK) - the largest tree kill on Mammoth Mountain in central eastern California. Efflux contour maps show a significant decline in the areas and rates of CO2 emission from 1995 to 1997. The emission rate fell from 350 t d-1 (metric tons per day) in 1995 to 130 t d-1 in 1997. The trend suggests a return to background soil CO2 efflux levels by early to mid 1999 and may reflect exhaustion of CO2 in a deep reservoir of accumulated gas and/or mechanical closure or sealing of fault conduits transmitting gas to the surface. However, emissions rose to 220 t d-1 on 23 September 1997 at the onset of a degassing event that lasted until 5 December 1997. Recent reservoir recharge and/or extension-enhanced gas flow may have caused the degassing event.

The impact of degassing on the oxidation state of basaltic magmas: A case study of Kīlauea volcano

NASA Astrophysics Data System (ADS)

Moussallam, Yves; Edmonds, Marie; Scaillet, Bruno; Peters, Nial; Gennaro, Emanuela; Sides, Issy; Oppenheimer, Clive

2016-09-01

Volcanic emissions link the oxidation state of the Earth's mantle to the composition of the atmosphere. Whether the oxidation state of an ascending magma follows a redox buffer - hence preserving mantle conditions - or deviates as a consequence of degassing remains under debate. Thus, further progress is required before erupted basalts can be used to infer the redox state of the upper mantle or the composition of their co-emitted gases to the atmosphere. Here we present the results of X-ray absorption near-edge structure (XANES) spectroscopy at the iron K-edge carried out for a series of melt inclusions and matrix glasses from ejecta associated with three eruptions of Kīlauea volcano (Hawai'i). We show that the oxidation state of these melts is strongly correlated with their volatile content, particularly in respect of water and sulfur contents. We argue that sulfur degassing has played a major role in the observed reduction of iron in the melt, while the degassing of H2O and CO2 appears to have had a negligible effect on the melt oxidation state under the conditions investigated. Using gas-melt equilibrium degassing models, we relate the oxidation state of the melt to the composition of the gases emitted at Kīlauea. Our measurements and modelling yield a lower constraint on the oxygen fugacity of the mantle source beneath Kīlauea volcano, which we infer to be near the nickel nickel-oxide (NNO) buffer. Our findings should be widely applicable to other basaltic systems and we predict that the oxidation state of the mantle underneath most hotspot volcanoes is more oxidised than that of the associated lavas. We also suggest that whether the oxidation states of a basalt (in particular MORB) reflects that of its source, is primarily determined by the extent of sulfur degassing.

Kilauea volcano: the degassing of a hot spot

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gerlach, T.M.

1986-03-01

Hot spots such as Kilauea volcano can degas by a one-stage eruptive process or a two-stage process involving eruptive and noneruptive degassing. One stage degassing occurs during sustained summit eruptions and causes a direct environmental impact. Although generally less efficient than the one-stage degassing process, two stage degassing can cause 1 to 2 orders of magnitude greater impact in just a few hours during flank eruptions. Hot spot volcanos with resupplied crustal magma chambers may be capable of maintaining an equivalent impact from CO/sub 2/ and S outgassing during both eruptive and noneruptive periods. On average, a hot spot volcanomore » such as Kilauea is a minor polluter compared to man.« less

Reconciling Gases With Glasses: Magma Degassing, Overturn and Mixing at Kilauea Volcano, Hawai`i

NASA Astrophysics Data System (ADS)

Edmonds, M.; Gerlach, T. M.

2006-12-01

Our understanding of the volatile budget at Kilauea Volcano is based on measurements of the abundance of volatile elements in volcanic glasses and gases. Observations of volcanic gases gave rise to a fundamental model describing volatile fractionation between the summit and rift zone during the current eruption [Gerlach and Graeber, 1985]. Other workers' analysis of glasses from the Puna Ridge, Kilauea Iki and Pu`u `O`o indicate that magma degassing, drain-back, mixing and assimilation are important processes at Kilauea Volcano. Volcanic gases have not illustrated these kinds of processes clearly in the past, owing to infrequent and poorly resolved data. New, detailed studies of volcanic gas emissions have refined our understanding of volatile degassing and magma budgets at Kilauea Volcano. Open Path Fourier Transform Infra-Red spectroscopy measurements carried out during 2004-2005 allow retrieval of the relative abundances of the major volatile species H2O, CO2 and SO2, which together make up >99 vol% of the magmatic vapor phase. The proportions of these gases vary over time and space and can be used to infer magma transport, ascent, degassing, overturn and mixing and gas segregation processes within the plumbing system of Kilauea Volcano. Gases from Pu`u `O`o in 2004-2005 display a range in composition. A trend relates molar C/S to the total H2O content of the gases over time and space; total H2O ranges from 60-98 mol %, while molar C/S ranges from <0.01 to >50. The range in volcanic gas composition over time and space is caused by magma degassing, overturn and mixing of partially degassed magma with fresh primary magma beneath Pu`u `O`o. Measurements of the mean rate of magma degassing (from SO2 emissions) and mean lava effusion rate (from geophysical measurements of lava tube flux) suggest that a larger volume (DRE) of magma is degassing than is being erupted, on average. This analysis suggests that magma storage in the Rift Zone might be important during eruptions as well as between them; this has important implications for volcano monitoring. Application of this new, remote and accurate technique to measure volcanic gases allows data concerning the volatile budget, both from glasses and from gases, to be reconciled and used in tandem to provide more detailed and complete models for magma migration, storage and transport at Kilauea Volcano.

Infrasonic harmonic tremor and degassing bursts from Halema'uma'u Crater, Kilauea Volcano, Hawaii

USGS Publications Warehouse

Fee, David; Garcés, Milton; Patrick, Matt; Chouet, Bernard; Dawson, Phil; Swanson, Donald A.

2010-01-01

The formation, evolution, collapse, and subsequent resurrection of a vent within Halema'uma'u Crater, Kilauea Volcano, produced energetic and varied degassing signals recorded by a nearby infrasound array between 2008 and early 2009. After 25 years of quiescence, a vent-clearing explosive burst on 19 March 2008 produced a clear, complex acoustic signal. Near-continuous harmonic infrasonic tremor followed this burst until 4 December 2008, when a period of decreased degassing occurred. The tremor spectra suggest volume oscillation and reverberation of a shallow gas-filled cavity beneath the vent. The dominant tremor peak can be sustained through Helmholtz oscillations of the cavity, while the secondary tremor peak and overtones are interpreted assuming acoustic resonance. The dominant tremor frequency matches the oscillation frequency of the gas emanating from the vent observed by video. Tremor spectra and power are also correlated with cavity geometry and dynamics, with the cavity depth estimated at ~219 m and volume ~3 x 106 m3 in November 2008. Over 21 varied degassing bursts were observed with extended burst durations and frequency content consistent with a transient release of gas exciting the cavity into resonance. Correlation of infrasound with seismicity suggests an open system connecting the atmosphere to the seismic excitation process at depth. Numerous degassing bursts produced very long period (0.03-0.1 Hz) infrasound, the first recorded at Kilauea, indicative of long-duration atmospheric accelerations. Kilauea infrasound appears controlled by the exsolution of gas from the magma, and the interaction of this gas with the conduits and cavities confining it.

U-Xe Degassing Ages of Terrestrial and Lunar Impact Zircons

NASA Astrophysics Data System (ADS)

Crow, C. A.; Crowther, S. A.; Gilmour, J. D.; Busemann, H.; Moser, D. E.; McKeegan, K. D.

2015-07-01

We present U-Xe degassing ages for individual zircons from Apollo 14 samples and the terrestrial impact structure at Vrederfort, South Africa. Preliminary results suggest the degassing ages are consistent with or younger than their 207Pb-206Pb ages.

76 FR 8773 - Superalloy Degassed Chromium From Japan

Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-15

... INTERNATIONAL TRADE COMMISSION [Investigation No. 731-TA-1090 (Review)] Superalloy Degassed Chromium From Japan AGENCY: United States International Trade Commission. ACTION: Termination of five-year... revocation of the antidumping duty order on superalloy degassed chromium from Japan would be likely to lead...

Degassing during quiescence as a trigger of magma ascent and volcanic eruptions

PubMed Central

Girona, Társilo; Costa, Fidel; Schubert, Gerald

2015-01-01

Understanding the mechanisms that control the start-up of volcanic unrest is crucial to improve the forecasting of eruptions at active volcanoes. Among the most active volcanoes in the world are the so-called persistently degassing ones (e.g., Etna, Italy; Merapi, Indonesia), which emit massive amounts of gas during quiescence (several kilotonnes per day) and erupt every few months or years. The hyperactivity of these volcanoes results from frequent pressurizations of the shallow magma plumbing system, which in most cases are thought to occur by the ascent of magma from deep to shallow reservoirs. However, the driving force that causes magma ascent from depth remains unknown. Here we demonstrate that magma ascent can be triggered by the passive release of gas during quiescence, which induces the opening of pathways connecting deep and shallow magma reservoirs. This top-down mechanism for volcanic eruptions contrasts with the more common bottom-up mechanisms in which magma ascent is only driven by processes occurring at depth. A cause-effect relationship between passive degassing and magma ascent can explain the fact that repose times are typically much longer than unrest times preceding eruptions, and may account for the so frequent unrest episodes of persistently degassing volcanoes. PMID:26666396

[Effect of different heat treatment on the bonding strength of porcelain and Co-Cr alloy].

PubMed

Liao, Juan-kun; Ye, Jian-tao; Zhu, Feng; Zhang, Cui-cui; Wen, Xiao-shan; Zhang, Yi-ping; Li, Bo-hua

2011-12-01

To investigate and compare the effect of different heat treatment on the metal- ceramic bonding strength and the interfacial microstructure of the Co-Cr alloy. Thirty specimens were made according to ISO 9693,and then divided into 3 groups (n=10) through the measurements .Group A(degassed 60s):degassed and then maintained 60s in 980 degrees centigrade Group B(degassed 60s and preoxidation 60s): degassed and maintained 60s in 980 degrees centigrade, then were maintained continuously for 60s in 980 degrees centigrade after re-gassed,Group C(degassed 120s): degassed and maintained 120s in 980 degrees centigrade. The bonding strengths of the three groups were evaluated through three point bending test. Six specimens divided into 3 group were made in the same method to observe the metal-ceramic interface through scanning electronic microscope(SEM) and energy dispersive spectrum(EDS).The bonding strength data were analyzed using ANOVA and Bonferroni's test by SPSS13.0 software package. The mean value of bonding strength was (39.03±2.70)MPa for group A, (34.43±2.36)MPa for group B, (31.65±1.49)MPa for group C, respectively. There were significant difference between every two groups (P<0.05). SEM demonstrated that the width of interfacial transition layer was 12.3-16.4μm in group A, 15.2-21.8μm in group B and 26.3-32.2μm in group C. Higher metal-ceramic bonding strength for Co-Cr alloy will be formed under the situation of degassed,and maintained 60s in 980 degrees centigrade ; while extending degassed time, prolonging the heat maintained time and preoxidation after degassing will reduce metal-ceramic bonding strength.

Petrologic constraints on the decompression history of magma prior to Vulcanian explosions at the Soufrière Hills volcano, Montserrat

NASA Astrophysics Data System (ADS)

Clarke, A. B.; Stephens, S.; Teasdale, R.; Sparks, R. S. J.; Diller, K.

2007-04-01

A series of 88 Vulcanian explosions occurred at the Soufrière Hills volcano, Montserrat, between August and October, 1997. Conduit conditions conducive to creating these and other Vulcanian explosions were explored via analysis of eruptive products and one-dimensional numerical modeling of magma ascent through a cylindrical conduit. The number densities and textures of plagioclase microlites were documented for twenty-three samples from the events. The natural samples all show very high number densities of microlites, and > 50% by number of microlites have areas < 20 μm 2. Pre-explosion conduit conditions and decompression history have been inferred from these data by comparison with experimental decompressions of similar groundmass compositions. Our comparisons suggest quench pressures < 30 MPa (origin depths < 2 km) and multiple rapid decompressions of > 13.75 MPa each during ascent from chamber to surface. Values are consistent with field studies of the same events and statistical analysis of explosion time-series data. The microlite volume number density trend with depth reveals an apparent transition from growth-dominated crystallization to nucleation-dominated crystallization at pressures of ˜ 7 MPa and lower. A concurrent sharp increase in bulk density marks the onset of significant open-system degassing, apparently due to a large increase in system permeability above ˜ 70% vesicularity. This open-system degassing results in a dense plug which eventually seals the conduit and forms conditions favorable to Vulcanian explosions. The corresponding inferred depth of overpressure at 250-700 m, near the base of the dense plug, is consistent with depth to center of pressure estimated from deformation measurements. Here we also illustrate that one-dimensional models representing ascent of a degassing, crystal-rich magma are broadly consistent with conduit profiles constructed via our petrologic analysis. The comparison between models and petrologic data suggests that the dense conduit plug forms as a result of high overpressure and open-system degassing through conduit walls.

Novel Apparatus for the Real-Time Quantification of Dissolved Gas Concentrations and Isotope Ratios

NASA Astrophysics Data System (ADS)

Gupta, M.; Leen, J.; Baer, D. S.; Owano, T. G.; Liem, J.

2013-12-01

Measurements of dissolved gases and their isotopic composition are critical in studying a variety of phenomena, including underwater greenhouse gas generation, air-surface exchange, and pollution migration. These studies typically involve obtaining water samples from streams, lakes, or ocean water and transporting them to a laboratory, where they are degased. The gases obtained are then generally measured using gas chromatography and isotope ratio mass spectrometry for concentrations and isotope ratios, respectively. This conventional, off-line methodology is time consuming, significantly limits the number of the samples that can be measured and thus severely inhibits detailed spatial and temporal mapping of gas concentrations and isotope ratios. In this work, we describe the development of a new membrane-based degassing device that interfaces directly to Los Gatos Research (cavity enhanced laser absorption or Off-Axis ICOS) gas analyzers (cavity enhanced laser absorption or Off-Axis ICOS analyzers) to create an autonomous system that can continuously and quickly measure concentrations and isotope ratios of dissolved gases in real time in the field. By accurately controlling the water flow rate through the membrane degasser, gas pressure on the outside of the membrane, and water pressure on the inside of the membrane, the system is able to generate precise and highly reproducible results. Moreover, by accurately measuring the gas flow rates in and out of the degasser, the gas-phase concentrations (ppm) could be converted into dissolved gas concentrations (nM). We will present detailed laboratory test data that quantifies the linearity, precision, and dynamic range of the system for the concentrations and isotope ratios of dissolved methane, carbon dioxide, and nitrous oxide. By interfacing the degassing device to a novel cavity-enhanced spectrometer (developed by LGR), preliminary data will also be presented for dissolved volatile organics (VOC) and other pollutants. Finally, the system was deployed shipboard, and field deployment data will also be presented.

Effects of Degassing on the Microstructure, Chemistry, and Estimated Mechanical Properties of a Cryomilled Al-Mg Alloy

NASA Astrophysics Data System (ADS)

Hofmeister, Clara; Zhou, Le; Kellogg, Frank; Giri, Anit; Cho, Kyu; Sohn, Yongho

2018-04-01

Nanostructured aluminum alloys produced through cryomilling have generated interest due to their potential to create consolidated parts with high strength and low density. Degassing prior to consolidation minimizes adsorbed and absorbed volatiles, but is accompanied by microstructural changes such as grain growth, dislocation annihilation, and formation of dispersoids. These changes can influence the mechanical behavior of consolidated components. Cryomilled AA5083 was degassed at temperatures from 473 K to 773 K (200 °C to 500 °C) with a vacuum at or below 2.7 × 10-3 Pa. Grain size in the as-cryomilled powder (ranging from 21 to 34 nm) increased with higher degassing temperature and reached a maximum size of up to 70 to 80 nm. The dislocation density of 1.11 × 1015 m-2 in as-cryomilled powder decreased to 1.56 × 1014 m-2 for powder degassed at 773 K (500 °C). The Al6(MnFeCr) dispersoid formed when powders were degassed at or above 573 K (300 °C). Oxygen and nitrogen concentrations were unaffected by degassing; however, hydrogen concentration decreased with increasing degassing temperature to a minimum of 45 ± 3.16 ppm. Evolutions in composition and microstructure in cryomilled AA5083 were correlated to the strengthening mechanisms of grain size reduction (i.e., Hall-Petch), dislocation forest, and Orowan. However, strengthening by grain size reduction was the dominant strengthening mechanism.

Cyclic thermal behavior associated to the degassing process at El Hierro submarine volcano, Canary Islands.

NASA Astrophysics Data System (ADS)

Fraile-Nuez, E.; Santana-Casiano, J. M.; González-Dávila, M.

2016-12-01

One year after the ceasing of magmatic activity in the shallow submarine volcano of the island of El Hierro, significant physical-chemical anomalies produced by the degassing process as: (i) thermal anomalies increase of +0.44 °C, (ii) pH decrease of -0.034 units, (iii) total dissolved inorganic carbon, CT increase by +43.5 µmol kg-1 and (iv) total alkalinity, AT by +12.81 µmol kg-1 were still present in the area. These evidences highlight the potential role of the shallow degassing processes as a natural ecosystem-scale experiments for the study of significant effects of global change stressors on marine environments. Additionally, thermal time series obtained from a temporal yo-yo CTD study, in isopycnal components, over one of the most active points of the submarine volcano have been analyzed in order to investigate the behavior of the system. Signal processing of the thermal time series highlights a strong cyclic temperature period of 125-150 min at 99.9% confidence, due to characteristic time-scales revealed in the periodogram. These long cycles might reflect dynamics occurring within the shallow magma supply system below the island of El Hierro.

Izu-Oshima volcano, Japan: ten years of geochemical monitoring by means of CO2 soil diffuse degassing

NASA Astrophysics Data System (ADS)

Hernandez Perez, P. A.; Mori, T.; Notsu, K.; Morita, M.; Padron, E.; Onizawa, S.; Melián, G.; Sumino, H.; Asensio-Ramos, M.; Nogami, K.; Yamane, K.; Perez, N. M.

2016-12-01

Izu-Oshima is an active volcanic island located around 100 km SSW of Tokyo. The centre of the island is occupied by a caldera complex with a diameter of 3 km. A large post-caldera cone known as Mt. Mihara is located at the south-western quadrant of the caldera. Izu-Oshima has erupted 74 times, consisting mainly in fissure eruptions, both inside and outside of the caldera. The last eruption of Izu-Oshima occurred in 1986. Since 2007, eight soil gas surveys have been carried out to investigate the spatial and temporal evolution of diffuse CO2 emission from this volcanic system and to identify those structures controlling the degassing process. Diffuse CO2 emission surveys were always carried out following the accumulation chamber method. Spatial distribution maps were constructed following the sequential Gaussian simulation (sGs) procedure. The location of the CO2 anomalies has always shown a close relationship with the structural characteristics of Miharayama, with most of the gas discharged from the rim of the summit crater. Temporal evolution of diffuse CO2 emission rate from Mt. Miharayama has shown a good temporal correlation with the main two peaks of seismic activity occur when highest CO diffuse emissions were computed, March 2007, August 2010 and July 2011, may be associated with fluid pressure fluctuations in the volcanic system due stress changes at depth. In order to strength the contribution of deep seated gases, we performed carbon isotopic analysis of soil gas samples at selected sites during 2010, 2013, 2015 and 2016 surveys. At isotopic compositions lighter than - 6‰, the soil CO2 effluxes were always low, while at heavier isotopic compositions an increasing number of points are characterized by relatively high soil CO efflux. Soil CO2 efflux peak values (xB) showed also a good correlation with the observed seismicity, with the largest value computed on June 2013. This parameter is a geochemical expression of the magnitude of the anomalous degassing, and the observed change in the trend may indicate an increase of the seismic-volcanic activity in the next future. Therefore, performing regularly soil CO2 efflux surveys seems to be an effective geochemical surveillance tool Izu-Oshima volcano in order to detect a change in the tendency of the CO2 emission rate in case of future episodes of volcanic unrest.

Shallow magmatic degassing into the hydrothermal system of Copahue, Argentina

NASA Astrophysics Data System (ADS)

Varekamp, J.; Ouimette, A.; Kreulen, R.; Delpino, D.; Bermudez, A.

2001-05-01

Copahue volcano has a crater lake and acid hot springs that discharge into the Rio Agrio river system. These fluids are very concentrated (up to 6 percent sulfate), rich in rock-forming elements (up to 2000 ppm Mg) and small spheres of native sulfur float in the crater lake. The stable isotope composition of the waters (delta 18O =-2.1 to + 3.6 per mille; delta D = -49 to -26 per mille) indicates that the hot spring waters are at their most concentrated about 70 percent volcanic brine and 30 percent glacial meltwater. The crater lake waters have similar mixing proportions but added isotope effects from intense evaporation. Further dilution of the waters in the Rio Agrio gives values closer to local meteoric waters (delta 18O = -11 per mille; delta D = -77 per mille), whereas evaporation in closed ponds led to very heavy water (up to delta 18O = +12 per mille). The delta 34S value of dissolved sulfate is +14.2 per mille, whereas the native sulfur has values of -8.2 to -10.5 per mille. The heavy sulfate probably formed when SO2 disproportionated into bisulfate and native sulfur. We measured the sulfate fluxes in the Rio Agrio, and from these flux values and the stoichiometry of the disproportionation reaction we calculated the rate of liquid sulfur storage inside the volcano (6000 m3/year). During the eruptions of 1995/2000, large amounts of that stored liquid sulfur were ejected as pyroclastic sulfur. The calculated rate of rock dissolution (from rock- forming element fluxes in the Rio Agrio) suggests that the void space generated by rock dissolution is largely filled by native sulfur. The isotopic signature of the magmatic sulfur can be reconstituted at about +7 per mille, which is a source signature with superposed effects of shallow degassing. Lead isotope and 129Iodine data from the fluids indicate that subducted components may have played a role in the Copahue magma formation. Primary glass inclusions in plagioclase and olivine have 1110-1670 ppm Cl, 90-400 ppm S and low water contents (0.4 - 1.5 percent). Matrix glasses have similar volatile concentrations as many plagioclase-hosted glass inclusions. The S/Cl ratio in the hydrothermal fluids is about 2, whereas the glass inclusions have S/Cl = 0.2, indicating the strong preferential degassing of sulfur.

A heterogeneous lunar interior for hydrogen isotopes as revealed by the lunar highlands samples

NASA Astrophysics Data System (ADS)

Hui, Hejiu; Guan, Yunbin; Chen, Yang; Peslier, Anne H.; Zhang, Youxue; Liu, Yang; Flemming, Roberta L.; Rossman, George R.; Eiler, John M.; Neal, Clive R.; Osinski, Gordon R.

2017-09-01

Knowing the amount and timing of water incorporation into the Moon has fundamental implications for our understanding of how the Earth-Moon system formed. Water has been detected in lunar samples but its abundance, distribution and origin are debated. To address these issues, we report water concentrations and hydrogen isotope ratios obtained by secondary ion mass spectrometry (SIMS) of plagioclase from ferroan anorthosites (FANs), the only available lithology thought to have crystallized directly from the lunar magma ocean (LMO). The measured water contents are consistent with previous results by Fourier transform infrared spectroscopy (FTIR). Combined with literature data, δD values of lunar igneous materials least-degassed at the time of their crystallization range from -280 to + 310 ‰, the latter value being that of FAN 60015 corrected for cosmic ray exposure. We interpret these results as hydrogen isotopes being fractionated during degassing of molecular hydrogen (H2) in the LMO, starting with the magmatic δD value of primordial water at the beginning of LMO being about - 280 ‰, evolving to about + 310 ‰ at the time of anorthite crystallization, i.e. during the formation of the primary lunar crust. The degassing of hydrogen in the LMO is consistent with those of other volatile elements. The wide range of δD values observed in lunar igneous rocks could be due to either various degrees of mixing of the different mantle end members, or from a range of mantle sources that were degassed to different degrees during magma evolution. Degassing of the LMO is a viable mechanism that resulted in a heterogeneous lunar interior for hydrogen isotopes.

Gas evolution in eruptive conduits: Combining insights from high temperature and pressure decompression experiments with steady-state flow modeling

USGS Publications Warehouse

Mangan, M.; Mastin, L.; Sisson, T.

2004-01-01

In this paper we examine the consequences of bubble nucleation mechanism on eruptive degassing of rhyolite magma. We use the results of published high temperature and pressure decompression experiments as input to a modified version of CONFLOW, the numerical model of Mastin and Ghiorso [(2000) U.S.G.S. Open-File Rep. 00-209, 53 pp.] and Mastin [(2002) Geochem. Geophys. Geosyst. 3, 10.1029/2001GC000192] for steady, two-phase flow in vertical conduits. Synthesis of the available experimental data shows that heterogeneous nucleation is triggered at ??P 120-150 MPa, and leads to disequilibrium degassing at extreme H2O supersaturation. In this latter case, nucleation is an ongoing process controlled by changing supersaturation conditions. Exponential bubble size distributions are often produced with number densities of 106-109 bubbles/cm3. Our numerical analysis adopts an end-member approach that specifically compares equilibrium degassing with delayed, disequilibrium degassing characteristic of homogeneously-nucleating systems. The disequilibrium simulations show that delaying nucleation until ??P =150 MPa restricts degassing to within ???1500 m of the surface. Fragmentation occurs at similar porosity in both the disequilibrium and equilibrium modes (???80 vol%), but at the distinct depths of ???500 m and ???2300 m, respectively. The vesiculation delay leads to higher pressures at equivalent depths in the conduit, and the mass flux and exit pressure are each higher by a factor of ???2.0. Residual water contents in the melt reaching the vent are between 0.5 and 1.0 wt%, roughly twice that of the equilibrium model. ?? 2003 Elsevier B.V. All rights reserved.

Sink- or Source-driven Phanerozoic carbon cycle?

NASA Astrophysics Data System (ADS)

Godderis, Y.; Donnadieu, Y.; Maffre, P.; Carretier, S.

2017-12-01

The Phanerozoic evolution of the atmospheric CO2 level is controlled by the fluxes entering or leaving the exospheric system. Those fluxes (including continental weathering, magmatic degassing, organic carbon burial, oxidation of sedimentary organic carbon) are intertwined, and their relative importance in driving the global carbon cycle evolution may have fluctuated through time. Deciphering the causes of the Phanerozoic climate evolution thus requires a holistic and quantitative approach. Here we focus on the role played by the paleogeographic configuration on the efficiency of the CO2 sink by continental silicate weathering, and on the impact of the magmatic degassing of CO2. We use the spatially resolved numerical model GEOCLIM (geoclimmodel.worpress.com) to compute the response of the silicate weathering and atmospheric CO2 to continental drift for 22 time slices of the Phanerozoic. Regarding the CO2 released by the magmatic activity, we reconstruct several Phanerozoic histories of this flux, based on published indexes. We calculate the CO2 evolution for each degassing scenario, and accounting for the paleogeographic setting. We show that the paleogeographic setting is a main driver of the climate from 540 Ma to about the beginning of the Jurassic. Regarding the role of the magmatic degassing, the various reconstructions do not converge towards a single signal, and thus introduce large uncertainties in the calculated CO2 level over time. Nevertheless, the continental dispersion, which prevails since the Jurassic, promotes the CO2 consumption by weathering and forces atmospheric CO2 to stay low. Warm climates of the "middle" Cretaceous and early Cenozoic require enhanced CO2 degassing by magmatic activity. In summary, the Phanerozoic climate evolution can be hardly assigned to a single process, but is the result of complex and intertwined processes.

The influence of episodic shallow magma degassing on heat and chemical transport in volcanic hydrothermal systems

USGS Publications Warehouse

Chen, Kewei; Zhan, Hongbin; Burns, Erick; Ingebritsen, Steven E.; Agrinier, Pierre

2018-01-01

Springs at La Soufrière of Guadeloupe have been monitored for nearly four decades since the phreatic eruption and associated seismic activity in 1976. We conceptualize degassing vapor/gas mixtures as square‐wave sources of chloride and heat and apply a new semianalytic solution to demonstrate that chloride and heat pulses with the same timing and duration result in good matches between measured and simulated spring temperatures and concentrations. While the concentration of chloride pulses is variable, the local boiling temperature of 96°C was assigned to all thermal pulses. Because chloride is a conservative tracer, chloride breakthrough is only affected by one‐dimensional advection and dispersion. The thermal tracer is damped and lagged relative to chloride due to conductive heat exchange with the overlying and underlying strata. Joint analysis of temperature and chloride allows estimation of the onset and duration of degassing pulses, refining the chronology of recent magmatic intrusion.

The Influence of Episodic Shallow Magma Degassing on Heat and Chemical Transport in Volcanic Hydrothermal Systems

NASA Astrophysics Data System (ADS)

Chen, Kewei; Zhan, Hongbin; Burns, Erick R.; Ingebritsen, Steven E.; Agrinier, Pierre

2018-04-01

Springs at La Soufrière of Guadeloupe have been monitored for nearly four decades since the phreatic eruption and associated seismic activity in 1976. We conceptualize degassing vapor/gas mixtures as square-wave sources of chloride and heat and apply a new semianalytic solution to demonstrate that chloride and heat pulses with the same timing and duration result in good matches between measured and simulated spring temperatures and concentrations. While the concentration of chloride pulses is variable, the local boiling temperature of 96°C was assigned to all thermal pulses. Because chloride is a conservative tracer, chloride breakthrough is only affected by one-dimensional advection and dispersion. The thermal tracer is damped and lagged relative to chloride due to conductive heat exchange with the overlying and underlying strata. Joint analysis of temperature and chloride allows estimation of the onset and duration of degassing pulses, refining the chronology of recent magmatic intrusion.

K-T Transition into Chaos.

ERIC Educational Resources Information Center

McLean, Dewey M.

1988-01-01

Discusses the destabilizing influences that affect feedback systems in the earth and trigger disorganization. Presents information that integrates mantle degassing with feed-back systems, and the Sun-Earth-Space energy flow system which is the primary source of energy that drives the Earth's biosphere. (RT)

Degassing of 3H/3He, CFCs and SF6 by denitrification: measurements and two-phase transport simulations.

PubMed

Visser, Ate; Schaap, Joris D; Broers, Hans Peter; Bierkens, Marc F P

2009-01-26

The production of N2 gas by denitrification may lead to the appearance of a gas phase below the water table prohibiting the conservative transport of tracer gases required for groundwater dating. We used a two-phase flow and transport model (STOMP) to study the reliability of 3H/3He, CFCs and SF6 as groundwater age tracers under agricultural land where denitrification causes degassing. We were able to reproduce the amount of degassing (R2=69%), as well as the 3H (R2=79%) and 3He (R2=76%) concentrations observed in a 3H/3He data set using simple 2D models. We found that the TDG correction of the 3H/3He age overestimated the control 3He/3He age by 2.1 years, due to the accumulation of 3He in the gas phase. The total uncertainty of degassed 3H/3He ages of 6 years (+/-2 sigma) is due to the correction of degassed 3He using the TDG method, but also due to the travel time in the unsaturated zone and the diffusion of bomb peak 3He. CFCs appear to be subject to significant degradation in anoxic groundwater and SF6 is highly susceptible to degassing. We conclude that 3H/3He is the most reliable method to date degassed groundwater and that two-phase flow models such as STOMP are useful tools to assist in the interpretation of degassed groundwater age tracer data.

Effect of ultrasonic waves on the freezing rates of potatoes in degassed coolant and untreated coolant.

PubMed

Yu, D Y; Liu, B L

2014-01-01

Ultrasonic waves are shown to enhance the rate of freezing. To elucidate the mechanism of immersion freezing of potatos with ultrasonic waves. Ultrasound is applied to potato samples immersed in degassed coolant and untreated coolant. Sonic waves were intermittently applied at temperature below -1 degree C. The freezing rates were measured under different experimental conditions. The use of ultrasonic waves increased the freezing rates of potatoes immersed in both degassed coolant and untreated coolant. However, the freezing rate in the degassed coolant was less than that in the untreated coolant. Heat transfer on the interface between the potato sample and sonicated degassed coolant appears to be less than that within the sample in the absence of cavitation. The interface heat transfer between the potato sample and untreated coolant is likely improved due to ultrasonic cavitation.

Syn-eruptive CO2 Degassing of Submarine Lavas Flows: Constraints on Eruption Dynamics

NASA Astrophysics Data System (ADS)

Soule, S. A.; Boulahanis, B.; Fundis, A.; Clague, D. A.; Chadwick, B.

2013-12-01

At fast- and intermediate-spreading rate mid-ocean ridges, quenched lava samples are commonly supersaturated in CO2 with concentrations similar to the pressure/depth of shallow crustal melt lenses. This supersaturation is attributed to rapid ascent and decompression rates that exceed the kinetic rates of bubble nucleation and growth. During emplacement, CO2 supersaturated lavas experience nearly isothermal and isobaric conditions over a period of hours. A recent study has demonstrated systematic decreases in CO2 with increasing transport distance (i.e. time) along a single flow pathway within the 2005-06 eruption at the East Pacific Rise (~2500 m.b.s.l.). Based on analysis of vesicle population characteristics and complementary noble gas measurements, it is proposed that diffusion of CO2 into bubbles can be used as a basis to model the gas loss from the melt and thus place constraints on the dynamics of the eruption. We suggest that submarine lava flows represent a natural experiment in degassing that isolates conditions of low to moderate supersaturation and highlights timescales of diffusion and vesiculation processes that are relevant to shallow crustal and conduit processes in subaerial basaltic volcanic systems. Here we report a new suite of volatile concentration analyses and vesicle size distributions from the 2011 eruption of Axial Volcano along the Juan de Fuca Ridge (~1500 m.b.s.l.). The lava flows from this eruption are mapped by differencing of repeat high-resolution bathymetric surveys, so that the geologic context of the samples is known. In addition, in-situ instrument records record the onset of the eruption and place constraints on timing that can be used to verify estimates of eruption dynamics derived from degassing. This sample suite provides a comprehensive view of the variability in volatile concentrations within a submarine eruption and new constraints for evaluating models of degassing and vesiculation. Initial results show systematic variability in CO2 supersaturation along eruptive fissures as well as with increasing distance along flows pathways providing constraints on threshold decompression rates required to nucleate and grow bubbles in a basaltic melt, timescales of degassing in natural systems, and the properties of consequent vesicle populations.

Columbus Thermal Control System (TCS) Degassing Operations

NASA Image and Video Library

2013-07-29

ISS036-E-026213 (29 July 2013) --- European Space Agency astronaut Luca Parmitano, Expedition 36 flight engineer, performs maintenance on the Water Pump Assembly 2 / Thermal Control System (WPA2/TCS) in the Columbus laboratory of the International Space Station.

Thermal History and Volatile Partitioning between Proto-Atmosphere and Interior of Mars Accreted in a Solar Nebula

NASA Astrophysics Data System (ADS)

Saito, Hiroaki; Kuramoto, Kiyoshi

2015-11-01

Recent precise Hf-W chronometry of Martian meteorites reveals that Mars had likely reached the half of its present mass within 3 Myr from the birth of the solar system (Dauphas and Pourmand, 2011). Hence, the accretion is considered to almost proceed within the solar nebula associated with the capture of nebula gas components. At the same time, the impact degassing may inevitably occur because impact velocity increases high enough for such degassing when a proto-planet gets larger than around lunar size. Thus, we can expect the formation of a hybrid-type proto-atmosphere that consists of nebula gas and degassed one.This study analyzes the thermal structure of this proto-atmosphere sustained by accretional heating by building a 1D radiative-convective equilibrium model. Raw materials of Mars are supposed to be volatile-rich on the basis of the geochemical systematics of Mars meteorites (Dreibus and Wanke, 1988). The composition of degassed component comprised of H2, H2O, CH4, and CO is determined by chemical equilibrium with silicate and metal under the physical condition of locally heated region generated by each impact (Kuramoto, 1997). Degassed component lies beneath the nebula gas atmosphere at altitudes below the compositional boundary height that would change depending on the amount of degassed component. The accretion time is taken to be from 1 to 6 Myr.Our model predicts that the surface temperature exceeds the liquidus temperature of rock when a proto Mars grows larger than 0.7 times of its present mass for the longest accretion time case. In this case, the magma ocean mass just after the end of accretion is 0.2 times of its present mass if heat transfer and heat sources such as short-lived radionuclides are neglected in the interior. The corresponding amount of water dissolved into the magma ocean would be around 1.8 times the present Earth ocean mass. These results suggest that the earliest Mars would be hot enough to form deep magma oceans, which promotes the core-mantle differentiation, and wet sufficient to make a deep-water ocean.

Degassing vs. eruptive styles at Mt. Etna volcano (Sicily, Italy): Volatile stocking, gas fluxing, and the shift from low-energy to highly-explosive basaltic eruptions

NASA Astrophysics Data System (ADS)

Moretti, Roberto; Métrich, Nicole; Di Renzo, Valeria; Aiuppa, Alessandro; Allard, Patrick; Arienzo, Ilenia

2017-04-01

Basaltic magmas can transport and release large amounts of volatiles into the atmosphere, especially in subduction zones, where slab-derived fluids enrich the mantle wedge. Depending on magma volatile content, basaltic volcanoes thus display a wide spectrum of eruptive styles, from common Strombolian-type activity to Plinian events. Mt. Etna in Sicily, is a typical basaltic volcano where the volatile control on such a variable activity can be investigated. Based on a melt inclusion study in products from Strombolian or lava-fountain activity to Plinian eruptions, here we show that for the same initial volatile content, different eruptive styles reflect variable degassing paths throughout the composite Etnean plumbing system. The combined influence of i) crystallization, ii) deep degassing and iii) CO2 gas fluxing can explain the evolution of H2O, CO2, S and Cl in products from such a spectrum of activity. Deep crystallization produces the CO2-rich gas fluxing the upward magma portions, which will become buoyant and easily mobilized in small gas-rich batches stored within the plumbing system. When reaching gas dominated conditions (i.e., a gas/melt mass ratio of 0.3 and CO2,gas/H2Ogas molar ratio 5 ), these will erupt effusively or mildly explosively, whilst in case of the 122 BC Plinian eruption, open-system degassing conditions took place within the plumbing system, such that continuous CO2-fluxing determined gas accumulation on top of the magmatic system. The emission of such a cap in the early eruptive phase triggered the arrival of deep H2O-rich whose fast decompression and bubble nucleation lead to the highly explosive character, enhanced by abundant microlite crystallization and consequent increase of magma effective viscosity. This could explain why open system basaltic systems like Etna may experience highly explosive or even Plinian episodes during eruptions that start with effusive to mildly explosive phases. The proposed mechanism also determines a depression of chlorine contents in CO2-fluxed (and less explosive) magmas with respect to those feeding Plinian events like 122 BC one. The opposite is seen for sulfur: low to mild-explosive fluxed magmas are S-enriched, whereas the 122 BC Plinian products are relatively S-poor, likely because of early sulfide separation accompanying magma crystallization. The proposed mechanism involving CO2 separation and fluxing may suggest a subordinate role for variable mixing of different sources having different degrees of K-enrichment. However, such a mechanism requires further experimental studies about the effects on S and Cl dissolution and does not exclude self-mixing between degassed and undegassed batches within the Etna plumbing system. Finally, our findings may represent a new interpretative tool for the geochemical and petrological monitoring of plume gas discharges and melt inclusions, and allow tracking the switch from mild-explosive to highly explosive or even Plinian events at Etna.

Failed magmatic eruptions: Late-stage cessation of magma ascent

USGS Publications Warehouse

Moran, S.C.; Newhall, C.; Roman, D.C.

2011-01-01

When a volcano becomes restless, a primary question is whether the unrest will lead to an eruption. Here we recognize four possible outcomes of a magmatic intrusion: "deep intrusion", "shallow intrusion", "sluggish/viscous magmatic eruption", and "rapid, often explosive magmatic eruption". We define "failed eruptions" as instances in which magma reaches but does not pass the "shallow intrusion" stage, i. e., when magma gets close to, but does not reach, the surface. Competing factors act to promote or hinder the eventual eruption of a magma intrusion. Fresh intrusion from depth, high magma gas content, rapid ascent rates that leave little time for enroute degassing, opening of pathways, and sudden decompression near the surface all act to promote eruption, whereas decreased magma supply from depth, slow ascent, significant enroute degassing and associated increases in viscosity, and impingement on structural barriers all act to hinder eruption. All of these factors interact in complex ways with variable results, but often cause magma to stall at some depth before reaching the surface. Although certain precursory phenomena, such as rapidly escalating seismic swarms or rates of degassing or deformation, are good indicators that an eruption is likely, such phenomena have also been observed in association with intrusions that have ultimately failed to erupt. A perpetual difficulty with quantifying the probability of eruption is a lack of data, particularly on instances of failed eruptions. This difficulty is being addressed in part through the WOVOdat database. Papers in this volume will be an additional resource for scientists grappling with the issue of whether or not an episode of unrest will lead to a magmatic eruption.

Identifying open and closed system behaviors at Tungurahua volcano (Ecuador) using SO2 and seismo-acoustic measurements

NASA Astrophysics Data System (ADS)

Hidalgo, Silvana; Battaglia, Jean; Bernard, Benjamin; Steele, Alexander; Arellano, Santiago; Galle, Bo

2014-05-01

Tungurahua is one of the most active volcanoes in Ecuador. It is located in Central Ecuador, 160 km South of Quito and 8 km South of the touristic town of Baños. Tungurahua had one eruption every century since 1500, with an activity characterized by ash fallouts and pyroclastic and lava flows. The current eruptive period of Tungurahua began in 1999 with multiple episodes of explosive activity that have threatened the local population. The monitoring network is constituted by 5 short period and 5 broadband seismic stations, 4 DOAS permanent instruments, 4 tiltmeters, 2 permanent high resolution GPS, 4 digital cameras and 10 acoustic flow monitors. The correct interpretation of the different data acquired by this network allows a better understanding of the eruptive behavior of Tungurahua in order to provide early warning to the local population. Tungurahua changed its behavior from a continuously erupting volcano, as it was until 2008, to a sporadically erupting one, showing clear quiescence phases lasting from 40 to 184 days, and intense activity phases lasting from 15 to 70 days. Activity phases are characterized by Strombolian and Vulcanian eruptive styles, producing ash fallouts and in a few occasions pyroclastic flows. In terms of hazard to the local population, one of the goals of monitoring Tungurahura is to forecast the onset and evolution of eruptive phases. In particular the occurrence of large Vulcanian explosions which occur when the conduit is closed is a major issue. Since 2010 we focused our study on the relation between SO2 gas emissions, the seismic and acoustic energies of explosions and the tremor amplitudes. The first observation of comparing these different datasets is that the correlation between seismic and SO2 degassing is not straightforward, and actually the relation reflects the conditions at the vent: open or closed. The onset of eruptive phases in open conduit conditions can be identified which leads to an effective eruption forecasting. An example of this behavior is the eruptive phase between December 2009 and March 2010 when SO2 measurements increased 4 days before the amplitude of tremor and 9 days before the occurrence of the first explosions. Conversely, if the vent is closed at the beginning of a phase and no evident seismic precursors are observed forecasting is hardly possible. During an ongoing eruptive phase, the relation between these parameters allows to identify periods when the conduit is totally open as degassing may occur almost without generating any seismicity. Therefore the forecasting of escalating open conduit activity or a partial closing of the system is possible. Such a case was observed and forecasted on December 2011. In this work, we present observational evidence of these mechanisms which are used to identify possible patterns of evolution of the activity, contributing to a more effective volcanic hazard assessment.

Residual Gases in Crystal Growth Systems

NASA Technical Reports Server (NTRS)

Palosz, W.

2003-01-01

Residual gases present in closed ampoules may affect different crystal growth processes. That seems to be particularly true under microgravity conditions where, due to weightlessness of the melt, the gases may lead to detached solidification and/or formation of voids and bubbles, as observed in the past. For that reason a good understanding and control of formation of residual gases is important for an optimum design and meaningful interpretation of crystal growth experiments. Our extensive experimental and theoretical studies of the subject, summarized in this paper, include degassing of silica glass and generation of gases from different source materials. Different materials processing conditions, like outgassing under vacuum, annealing in hydrogen, resublimation, different material preparation procedures, multiple annealings, different processing times, and others were applied and their effect on the amount and composition of gas were analyzed. The experimental results were interpreted based on theoretical calculations on diffusion in silica glass and source materials and thermochemistry of the system. Procedures for a reduction of the amount of gas are also discussed.

Geochemical exploration of a promissory Enhanced Geothermal System (EGS): the Acoculco caldera, Mexico.

NASA Astrophysics Data System (ADS)

Peiffer, Loic; Romero, Ruben Bernard; Pérez-Zarate, Daniel; Guevara, Mirna; Santoyo Gutiérrez, Edgar

2014-05-01

The Acoculco caldera (Puebla, Mexico) has been identified by the Mexican Federal Electricity Company (in Spanish 'Comisión Federal de Electricidad', CFE) as a potential Enhanced Geothermal System (EGS) candidate. Two exploration wells were drilled and promising temperatures of ~300° C have been measured at a depth of 2000 m with a geothermal gradient of 11oC/100m, which is three times higher than the baseline gradient measured within the Trans-Mexican Volcanic Belt. As usually observed in Hot Dry Rock systems, thermal manifestations in surface are scarce and consist in low-temperature bubbling springs and soil degassing. The goals of this study were to identify the origin of these fluids, to estimate the soil degassing rate and to explore new areas for a future detailed exploration and drilling activities. Water and gas samples were collected for chemical and isotopic analysis (δ18O, δD, 3He/4He, 13C, 15N) and a multi-gas (CO2, CH4, H2S) soil survey was carried out using the accumulation chamber method. Springs' compositions indicate a meteoric origin and the dissolution of CO2 and H2S-rich gases, while gas compositions reveal a MORB-type origin mixed with some arc-type contribution. Gas geothermometry results are similar to temperatures measured during well drilling (260° C-300° C). Amongst all measured CO2 fluxes, only 5% (mean: 5543 g m-2 day-1) show typical geothermal values, while the remaining fluxes are low and correspond to biogenic degassing (mean: 18 g m-2 day-1). The low degassing rate of the geothermal system is a consequence of the intense hydrothermal alteration observed in the upper 800 m of the system which acts as an impermeable caprock. Highest measured CO2 fluxes (above > 600 g m-2 day-1) have corresponding CH4/CO2 flux ratios similar to mass ratios of sampled gases, which suggest an advective fluid transport. To represent field conditions, a numerical model was also applied to simulate the migration of CO2 towards the surface through a shallow aquifer under fully saturated conditions. By changing some of the aquifer properties (i.e., depth, permeability and porosity), it was found how geothermal CO2 fluxes can show values similar to a biogenic background flux. Future field work at Acoculco will include δ13C analysis together with soil flux measurements for a better discrimination of the degassing origin, and a thinner flux measurement grid will be defined for a better detection of any possible gas flux anomaly.

H2O-CO2-S-Cl partitioning and mixing in rhyolitic melts and fluid - Implications on closed-system degassing in rhyolite

NASA Astrophysics Data System (ADS)

Ding, S.; Webster, J. D.

2017-12-01

Magmatic degassing involving multiple volatile components (C, O, H, S, Cl, etc.) is one of the key factors influencing the timing and nature of volcanic eruptions, and the chemistry of volcanic gases released to the surface. In particular, exsolution of these volatiles from silicic magma during ascent could trigger explosive volcanic eruptions, which can exert strong impacts on surface temperature, ecology and human health. However, quantitative evaluation of this process in silicic magma remains ambiguous due to the lack of experiments in such chemically complex systems. Rhyolite-fluid(s) equilibria experiments were conducted in an IHPVat 100-300 MPa and 800 ° C to determine the solubilities, fluid-melt partitioning, and mixing properties of H2O, CO2, S, and Cl in the oxygen fugacity (fO2) range of FMQ to FMQ+3. The integrated bulk fluids contain up to 94 mol% H2O, 32 mol% CO2, 1 mol% S and 1mol% Cl. Rhyolite melt dissolved 20- 770 ppm CO2 and 4-7 wt.% H2O, varying with pressure, fluid composition, and fO2. Concentrations of H2O and CO2 in melt from C-O-H-S-Cl- bearing experiments at 100 and 200 MPa, and from C-O-H only experiments are generally consistent with the predictions of existing CO2-H2O solubility models based on the C-O-H only system [1-4], while the solubilities of H2O and CO2 in melt with addition of S±Cl at 300 MPa are less than those of the C-O-H- only system. This reduction in H2O and CO2 solubilities exceeds the effects of simple dilution of the coexisting fluid owing to addition of other volatiles, and rather, reflects complex mixing relations. Rhyolite melt also dissolved 20-150 ppm S and 850-2000 ppm Cl, varying with pressure. At 300 MPa, S concentrations in the melt change with fO2. The partitioning of CO2 and S between fluid and melt varies as a function of fluid composition and fO2. Solubilities and complex mixing relationships of CO2, H2O, S and Cl revealed in our experiments can be applied to massive rhyolitic eruptions like those of the Bishop tuff, Toba tuff and Pinatubo to better understand the degassing process, to estimate fluid compositions, and thus, to evaluate the potential environmental impacts of these super eruptions. [1] Ghiorso amd Gualda, 2015, CMP; [2] Liu et al., 2005, J. Volcanol. Geotherm. Res.; [3] Newman and Lowenstern, 2002, Comput. Geosci.; [3] Tamic et al., 2001, Chem. Geol..

Conduit degassing and thermal controls on eruption styles at Mount St. Helens

NASA Astrophysics Data System (ADS)

Schneider, Andrew; Rempel, Alan W.; Cashman, Katharine V.

2012-12-01

The explosivity of silicic eruptions depends on the interplay between magma rheology, exsolution kinetics, and degassing. Magma degassing is governed by the competing effects of vertical transport within the conduit and the lateral flux of gas out of the conduit (Diller et al., 2006; Jaupart and Allegre, 1991). We combine a simplified treatment of these degassing processes with thermodynamic modeling to examine the conditions present at Mount St. Helens during the spine extruding eruption from 2004 to 2008. We find that two parameters are primarily responsible for controlling the eruptive style: the magma chamber temperature, and a dimensionless parameter that gauges the efficiency of lateral degassing. Together, these parameters determine whether and where magma can solidify at depth to form a dense solid plug that is gradually extruded as a volcanic spine. We show that the small (50 oC) decrease in magma chamber temperature between eruptive activity in the 1980s and that of 2004-2008, combined with a modest increase in degassing efficiency associated with lower volumetric flux, can explain the observed change in erupted material from viscous lava flows to solidified spines. More generally, we suggest that similar threshold behavior may explain observed abrupt transitions in effusive eruptive styles at other intermediate composition volcanoes. Finally, we extrapolate our results to suggest that the increase in degassing efficiency accompanying decreasing magma supply rates may have caused the transition from explosive to effusive activity in late 1980.

Col WPA2 Degassing

NASA Image and Video Library

2009-07-09

ISS020-E-018137 (9 July 2009) --- European Space Agency astronaut Frank De Winne, Expedition 20 flight engineer, works with the Fluid Servicing System (FSS) in the Columbus laboratory of the International Space Station.

Col WPA2 Degassing

NASA Image and Video Library

2009-07-09

ISS020-E-018135 (9 July 2009) --- European Space Agency astronaut Frank De Winne, Expedition 20 flight engineer, works with the Fluid Servicing System (FSS) in the Columbus laboratory of the International Space Station.

Using fumarolic inert gas composition to investigate magma dynamics at Campi Flegrei (Italy)

NASA Astrophysics Data System (ADS)

Chiodini, G.; Caliro, S.; Paonita, A.; Cardellini, C.

2013-12-01

Since 2000 the Campi Flegrei caldera sited in Neapolitan area (Italy), has showed signs of reactivation, marked by ground uplift, seismic activity, compositional variations of fumarolic effluents from La Solfatara, an increase of the fumarolic activity as well as of soil CO2 fluxes. Comparing long time series of geochemical signals with ground deformation and seismicity, we show that these changes are at least partially caused by repeated injections of magmatic fluid into the hydrothermal system. The frequency of these degassing episodes has increased in the last years, causing pulsed uplift episodes and swarms of low magnitude earthquakes. We focus here in the inert gas species (CO2-He-Ar-N2) of Solfatara fumaroles which displayed in the time spectacular and persistent variation trends affecting all the monitored vents. The observed variations, which include a continuous decrease of both N2/He and N2/CO2 ratios since 1985, paralleled by an increase of He/CO2, can not be explained neither with changes in processes of boiling-condensation in the local hydrothermal system nor with changes in the mixing proportions between a magmatic vapour and hydrothermal fluids. Consequently we investigated the possibility that the trends of inert gas species are governed by changes in the conditions controlling magma degassing at depth. We applied a magma degassing model, with the most recent updates for inert gas solubilities, after to have included petrologic constraints from the ranges of melt composition and reservoir pressure at Campi Flegrei. The model simulations for mafic melts (trachybasalt and shoshonite) show a surprising agreement with the measured data. Both decompressive degassing of an ascending magma and mixing between magmatic fluids exsolved at various levels along the ascent path can explain the long-time geochemical changes. Our work highlights that, in caldera systems where the presence of hydrothermal aquifers commonly masks the magmatic signature of reactive volatiles, inert gases are the preferred species to achieve information on the dynamics and structure of the magma plumbing systems.

40 CFR 61.242-3 - Standards: Compressors.

Code of Federal Regulations, 2010 CFR

2010-07-01

... barrier fluid system degassing reservoir that is routed to a process or fuel gas system or connected by a... paragraphs (a)-(c) of this section shall be equipped with a sensor that will detect failure of the seal system, barrier fluid system, or both. (e)(1) Each sensor as required in paragraph (d) of this section...

40 CFR 61.242-3 - Standards: Compressors.

Code of Federal Regulations, 2011 CFR

2011-07-01

... barrier fluid system degassing reservoir that is routed to a process or fuel gas system or connected by a... paragraphs (a)-(c) of this section shall be equipped with a sensor that will detect failure of the seal system, barrier fluid system, or both. (e)(1) Each sensor as required in paragraph (d) of this section...

Infiltration-driven metamorphism, New England, USA: Regional CO2 fluxes and implications for Devonian climate and extinctions

NASA Astrophysics Data System (ADS)

Stewart, E. M.; Ague, Jay J.

2018-05-01

We undertake thermodynamic pseudosection modeling of metacarbonate rocks in the Wepawaug Schist, Connecticut, USA, and examine the implications for CO2 outgassing from collisional orogenic belts. Two broad types of pseudosections are calculated: (1) a fully closed-system model with no fluid infiltration and (2) a fluid-buffered model including an H2O-CO2 fluid of a fixed composition. This fluid-buffered model is used to approximate a system open to infiltration by a water-bearing fluid. In all cases the fully closed-system model fails to reproduce the observed major mineral zones, mineral compositions, reaction temperatures, and fluid compositions. The fluid-infiltrated models, on the other hand, successfully reproduce these observations when the XCO2 of the fluid is in the range ∼0.05 to ∼0.15. Fluid-infiltrated models predict significant progressive CO2 loss, peaking at ∼50% decarbonation at amphibolite facies. The closed-system models dramatically underestimate the degree of decarbonation, predicting only ∼15% CO2 loss at peak conditions, and, remarkably, <1% CO2 loss below ∼600 °C. We propagate the results of fluid-infiltrated pseudosections to determine an areal CO2 flux for the Wepawaug Schist. This yields ∼1012 mol CO2 km-2 Myr-1, consistent with multiple independent estimates of the metamorphic CO2 flux, and comparable in magnitude to fluxes from mid-ocean ridges and volcanic arcs. Extrapolating to the area of the Acadian orogenic belt, we suggest that metamorphic CO2 degassing is a plausible driver of global warming, sea level rise, and, perhaps, extinction in the mid- to late-Devonian.

Reconstructing mantle volatile contents through the veil of degassing

NASA Astrophysics Data System (ADS)

Tucker, J.; Mukhopadhyay, S.; Gonnermann, H. M.

2014-12-01

The abundance of volatile elements in the mantle reveals critical information about the Earth's origin and evolution such as the chemical constituents that built the Earth and material exchange between the mantle and exosphere. However, due to magmatic degassing, volatile element abundances measured in basalts usually do not represent those in undegassed magmas and hence in the mantle source of the basalts. While estimates of average mantle concentrations of some volatile species can be obtained, such as from the 3He flux into the oceans, volatile element variability within the mantle remains poorly constrained. Here, we use CO2-He-Ne-Ar-Xe measurements in basalts and a new degassing model to reconstruct the initial volatile contents of 8 MORBs from the Mid-Atlantic Ridge and Southwest Indian Ridge that span a wide geochemical range from depleted to enriched MORBs. We first show that equilibrium degassing (e.g. Rayleigh degassing), cannot simultaneously fit the measured CO2-He-Ne-Ar-Xe compositions in MORBs and argue that kinetic fractionation between bubbles and melt lowers the dissolved ratios of light to heavy noble gas species in the melt from that expected at equilibrium. We present a degassing model (after Gonnermann and Mukhopadhyay, 2007) that explicitly accounts for diffusive fractionation between melt and bubbles. The model computes the degassed composition based on an initial volatile composition and a diffusive timescale. To reconstruct the undegassed volatile content of a sample, we find the initial composition and degassing timescale which minimize the misfit between predicted and measured degassed compositions. Initial 3He contents calculated for the 8 MORB samples vary by a factor of ~7. We observe a correlation between initial 3He and CO2 contents, indicating relatively constant CO2/3He ratios despite the geochemical diversity and variable gas content in the basalts. Importantly, the gas-rich popping rock from the North Atlantic, as well as the average mantle ratio computed from the ridge 3He flux and independently estimated CO2 content fall along the same correlation. This observation suggests that undegassed CO2 and noble gas concentrations can be reconstructed in individual samples through measurement of noble gases and CO2 in erupted basalts.

Effect of degassing on the aggregation of carbon nanotubes dispersed in water

NASA Astrophysics Data System (ADS)

Chen, C.-J.; Huang, J.-R.; Hwang, I.-S.; Choi, H. J.; Lai, P.-Y.; Chan, C. K.

2017-10-01

Dynamic light scattering (DLS) along with centrifugation and shaking tests reveal that dissolved gases can significantly affect the aggregation behavior of carbon nanotubes (CNTs) dispersed in water. The CNTs in non-degassed samples form loose, stable networks having the DLS result reminiscent of semidilute polymer solutions, whereas the CNTs in degassed samples aggregate to form Brownian colloids that sediment quickly. Interestingly, the CNTs dispersed in acetone, with or without degassing, also behave like semidilute polymers in DLS experiments. We propose a surface nanobubble-assisted mechanism to explain the observed aggregation behaviors. Our work signifies that dissolved gases may play an important role in determining hydrophobicity and biomolecular functions in aqueous environments.

Sills, aureoles and pipes in the Karoo Basin, South Africa, as triggers for Early Jurassic environmental changes

NASA Astrophysics Data System (ADS)

Svensen, Henrik H.; Planke, Sverre; Silkoset, Petter; Hammer, Øyvind; Iyer, Karthik; Schmid, Dani W.; Chevallier, Luc

2017-04-01

Most of the Large Igneous Provinces (LIPs) formed during the last 260 million years are associated with climatic change, oceanic anoxia, or extinctions in marine and terrestrial environments. Current hypotheses involve A) degassing of carbon either from oceans or shallow sea-bed reservoirs, B) carbon and sulfur degassing from flood basalts, C) degassing from sedimentary basins heavily intruded by LIPs. Here we present new data on gas generation and degassing from the Karoo LIP, based on fieldwork, borehole studies (geochemistry, petrography), and thermal modeling. Our data expand and corroborate earlier work on the sub-volcanic processes in the Karoo Basin. We show that 1) hundreds of breccia pipes are rooted in Early Jurassic sill complexes and contact aureoles within the organic-rich Ecca Group, 2) statistical analyses reveal a fractal distribution of pipes and that they are overdispersed at small scales (<50 m), but clustered at larger scales (>800 m), 3) contact aureoles show a reduction in organic matter content towards the sill contacts, reduced to zero in the nearest zones, producing more carbon gas compared to thermal model calculations, 4) we find up to 3 permil reduction in the d13C of the organic matter remaining in the aureoles, and finally 5) some pipes contain recent oil seeps. We conclude that the sill-pipe system released thermogenic gases to the Early Jurassic atmosphere and that the pipes may have acted as permanent fluid flow pathways.

In-situ measurement of sulfur isotopic ratios in zoned apatite crystals via SIMS: a new tool for interpreting dynamic sulfur behavior in magmas

NASA Astrophysics Data System (ADS)

Economos, R. C.; Boehnke, P.; Burgisser, A.

2017-12-01

Sulfur is an important element in igneous systems due to its impact on magma redox, its role in the formation of economically valuable ore deposits, and the influence of catastrophic volcanogenic sulfur degassing on global climate. The mobility and geochemical behavior of sulfur in magmas is complex due to its multi-valent (from S2- to S6+) and multi-phase (solid, immiscible liquid, gaseous, dissolved ions) nature. Sulfur behavior is closely linked with the evolution of oxygen fugacity (fO2) in magmas; the record of fO2 evolution is often difficult to extract from rock records, particularly for intrusive systems that undergo cyclical magmatic processes and crystallize to the solidus. We apply a novel method of measuring S isotopic ratios via secondary ion mass spectrometry (SIMS) in zoned apatite crystals that we interpret as a record of open-system magmatic processes. We analyzed the S concentration and isotopic variations preserved in multiple apatite crystals from single hand specimens from the Cadiz Valley Batholith, CA via electron microprobe and ion microprobe at UCLA. A single, isotopically homogeneous crystal of Durango apatite was characterized for absolute isotopic ratio for this study (UCLA-D1). Isotopic variations in single apatite crystals ranged from 0 to 3.8‰ δ34S and total variation within a single hand sample was 6.1‰ δ34S. High S concentration cores yielded high isotopic ratios while low S concentration rims yielded low isotopic ratios. We favor an explanation of a combination of magma mixing and open-system, ascent-driven degassing under moderately reduced conditions: fO2 at or below NNO +1, although the synchronous crystallization of apatite and anhydrite is also a viable scenario. These findings have implications for the coupled S and fO2 evolution of granitic plutons and suggest that in-situ apatite S isotopic measurements could be a powerful new tool for evaluating redox and S systematics in magmatic systems.

Effect of ice-quenching on the change in hardness of a Pd-Au-Zn alloy during porcelain firing simulation.

PubMed

Shin, Hye-Jeong; Kim, Min-Jung; Kim, Hyung-Il; Kwon, Yong Hoon; Seol, Hyo-Joung

2017-03-31

This study examined the effect of ice-quenching after degassing on the change in hardness of a Pd-Au-Zn alloy during porcelain firing simulations. By ice-quenching after degassing, the specimens were softened due to homogenization without the need for an additional softening heat treatment. The lowered hardness by ice-quenching after degassing was recovered greatly from the first stage of porcelain firing process by controlling the cooling rate. The increase in hardness during cooling after porcelain firing was attributed to the precipitation of the f.c.t. PdZn phase containing Au, which caused severe lattice strain in the interphase boundary between the precipitates and matrix of the f.c.c. structure. The final hardness was slightly higher in the ice-quenched specimen than in the specimen cooled at stage 0 (the most effective cooling rate for alloy hardening) after degassing. This was attributed to the more active grain interior precipitation during cooling in the ice-quenched specimen after degassing.

Volcanic gas composition changes during the gradual decrease of the gigantic degassing activity of Miyakejima volcano, Japan, 2000-2015

NASA Astrophysics Data System (ADS)

Shinohara, Hiroshi; Geshi, Nobuo; Matsushima, Nobuo; Saito, Genji; Kazahaya, Ryunosuke

2017-02-01

The composition of volcanic gases discharged from Miyakejima volcano has been monitored during the intensive degassing activity that began after the eruption in 2000. During the 15 years from 2000 to 2015, Miyakejima volcano discharged 25.5 Mt of SO2, which required degassing of 3 km3 of basaltic magma. The SO2 emission rate peaked at 50 kt/day at the end of 2000 and quickly decreased to 5 kt/day by 2003. During the early degassing period, the volcanic gas composition was constant with the CO2/SO2 = 0.8 (mol ratio), H2O/SO2 = 35, HCl/SO2 = 0.08, and SO2/H2S = 15. The SO2 emission rate decreased gradually to 0.5 kt/day by 2012, and the gas composition also changed gradually to CO2/SO2 = 1.5, H2O/SO2 = 150, HCl/SO2 = 0.15, and SO2/H2S = 6. The compositional changes are not likely caused by changes in degassing pressure or volatile heterogeneity of a magma chamber but are likely attributed to an increase of hydrothermal scrubbing caused by large decrease of the volcanic gas emission rate, suggesting a supply of gases with constant composition during the 15 years. The intensive degassing was modeled based on degassing of a convecting magma conduit. The gradual SO2 emission rate that decrease without changes in volcanic gas composition is attributed to a reduction of diameter of the convecting magma conduit.

Multi-Sensor Mapping of Diffuse Degassing of C-O-H Compounds in Terrestrial Hydrothermal Systems

NASA Astrophysics Data System (ADS)

Schwandner, F. M.; Shock, E. L.

2004-12-01

In-situ single-sensor detection and mapping of diffuse degassing phenomena in hydrothermal and volcanic areas can be used to elucidate subsurface tectonic structures, assess emission rates, and to monitor emission variability (Williams 1985; Chiodini et al. 1996, Werner et al., 2003). More than one technique has been deployed to measure several gas species simultaneously (e.g., Crenshaw et al. 1982), and correlations of one gas species (usually CO2) with physical parameters like heat flux (Brombach et al., 2001), or with one other gas species (Rn, He) have been demonstrated (Barberi & Carapezza 1994; Williams-Jones et al., 2000). Recently, correlations of multiple gas species with one another were reported (Schwandner et al., 2004), leading to the possibility of quantitative mapping of subsurface hydrothermal chemical processes by simultaneous measurement of reaction partners and products that continuously and diffusely degas. In the present study, we joined a fully-quantitative multi-sensor instrument (Draeger Multiwarn II) to a modified accumulation-chamber sensing method (Chiodini et al., 1996) and measured diffuse degassing of CH4, H2, CO2, CO, and H2S. In this approach, each batch of gas that is recirculated through the detector is simultaneously analyzed by all sensors. To test this approach we chose two magmatically influenced, hydrothermally active areas at Yellowstone National Park (USA): Sylvan Springs and the Greater Obsidian Pool Area. The area near Obsidian Pool was previously studied during a diffuse CO2 degassing campaign (Werner & Brantley, 2004). Preliminary results show that elevated reduced gas emissions appear to be most prominent near hydrothermal pools, whereas CO2-dominated degassing anomalies highlight subsurface tectonic structures. This multimodal distribution allows us to distinguish deep degassing sources (CO2 anomalies) from shallow localized hydrothermal processes (reduced gas anomalies). The results permit us to positively identify and partially map a previously-inferred active lineament in the Obsidian Pool area. In addition, reduced gas data are yielding areal ratio distributions of CO/CO2, H2/CH4, and CO/CH4, that may be indicative of reactions such as the catalytic hydrogenation of CO2 (Sabatier-Process) and of CO (Fischer-Tropsch-Process) within the shallow hydrothermal system. Barberi & Carapezza (1994). Bull. Volcanol. 56(5): 335-342. Brombach, et al. (2001). Geophys. Res. Lett. 28(1): 69-72. Crenshaw et al. (1982). Nature 300: 345-346. Chiodini et al. (1996). Bull. Volcanol. 58(1): 41-50. Schwandner et al. (2004). JGR D 109: D04301, doi:10.1029/2003JD003890. Werner & Brantley (2004) JGR B 105: 10,831-10,846. Werner et al. (2003). Earth Planet. Sci. Lett. 210: 561-577. Williams (1985). Science 229(4713): 551-553. Williams-Jones et al. (2000). Bull. Volcanol. 62: 130-142.

40 CFR 60.482-3a - Standards: Compressors.

Code of Federal Regulations, 2010 CFR

2010-07-01

... (2) Equipped with a barrier fluid system degassing reservoir that is routed to a process or fuel gas... equipped with a sensor that will detect failure of the seal system, barrier fluid system, or both. (e)(1) Each sensor as required in paragraph (d) of this section shall be checked daily or shall be equipped...

40 CFR 60.482-3a - Standards: Compressors.

Code of Federal Regulations, 2011 CFR

2011-07-01

... (2) Equipped with a barrier fluid system degassing reservoir that is routed to a process or fuel gas... equipped with a sensor that will detect failure of the seal system, barrier fluid system, or both. (e)(1) Each sensor as required in paragraph (d) of this section shall be checked daily or shall be equipped...

The ratios of carbon and non-radiogenic helium and argon isotopes in the mantle and crustal rocks

NASA Technical Reports Server (NTRS)

Lokhov, K.; Levsky, L.

1994-01-01

The studies of the relations of carbon and primary isotopes of noble gases were carried out on the natural gases and on the mantle rocks from the mantle M-type sources, which represent the degassed mantle reservoir (MORB's). These works has the aim of estimation of the values of the C/3He ratios in the deep mantle fluids to determine the flux of the mantle CO2 on the basis of known flux of primary mantle 3He. It was found, that in the natural gases the values of the C/3He ratios fall into the range from 1 times E plus 6 to 1 times E plus 15, and in the fluids of MORB's are constant near 2 times E plus 9. We have studied the mantle rocks from the relatively undergassed mantle P minus type sources: continental; Baikal Rift (Siberia), Mongolia, Catalonia (Spain), Pannonia Depression (central Europe) and ocean; Spietzbergen isl., Hawaii isl., Canarian isl. It ws found, that in mantle xenolites and the host alkaline basalts from the continental rifts and ocean islands, the values of the C/3He ratios fall into the range from E plus 11 to E plus 15 (and this result needed to be explained; the higher carbon to helium ratios is relatively undergassed mantle reservoir compared with the degassed one, requires whether hilly compatibility of helium compared with carbon, whether additional flux of 3He to the degassed mantle reservoir). From the other hand it was found that in the mantle rocks from the sources of P minus and M minus types, continental carbonatites, the values of the C/36Ar ratios are constant in the range from E plus 9 to E plus 10, the close values have the MORB's also.

The unsteady end to a powerful Plinian eruption: insights from a Vulcanian block apron from the 1912 eruption of Novarupta, Alaska

NASA Astrophysics Data System (ADS)

Isgett, S. J.; Houghton, B. F.; Burgisser, A.; Arbaret, L.

2016-12-01

Current models propose a static conduit architecture prior to Vulcanian eruptions where a dense, outgassed dome/plug overlies an orderly, texturally horizontally layered conduit. Blocks from a Vulcanian phase (Episode IV) during the 1912 eruption of Novarupta provide special insight to the state of the magma within a complex shallow conduit prior to fragmentation. Extreme conduit heterogeneity is seen in a diverse range of dacitic block types, including pumiceous, dense, flow-banded, and variably welded breccia clasts, all with a range of surface-breadcrusting. Diverse 2D and 3D textures suggest a variety of degassing states, with ranges of vesicle textures (e.g. bubble number, shape, and size) in each of the block types. The nonbreadcrusted pumice exhibit textures similar to preceding Plinian phases, reflecting bubble nucleation, growth, and coalescence followed by fragmentation. Breadcrusted rind and dense dacite textures are the result of bubble collapse with the dense dacites progressing furthest along the outgassing pathway. Residual water contents within the quenched glass are all less than 0.5 wt% and indicate that the melt came from the upper 100 m of the conduit. There is no correlation between water content and vesicularity. Overall, the evidence indicates 1) the mingling of variably degassed and outgassed melts in varying states of chemical disequilibrium over a narrow depth range close to the surface and 2) fragmentation was probably driven by the melt forming the non-breadcrusted pumices which we consider was probably newly arrived in the shallow conduit at the time of fragmentation. We therefore propose a revised, dynamic model applicable to Vulcanian explosions in the context of downscaling Plinian eruptions that involves vigorous mingling of melts that are all actively degassing and outgassing to varying degrees within the shallow conduit.

Puhimau thermal area: a window into the upper east rift zone of Kilauea Volcano, Hawaii?

USGS Publications Warehouse

McGee, K.A.; Sutton, A.J.; Elias, T.; Doukas, M.P.; Gerlach, T.M.

2006-01-01

We report the results of two soil CO2 efflux surveys by the closed chamber circulation method at the Puhimau thermal area in the upper East Rift Zone (ERZ) of Kilauea volcano, Hawaii. The surveys were undertaken in 1996 and 1998 to constrain how much CO2 might be reaching the ERZ after degassing beneath the summit caldera and whether the Puhimau thermal area might be a significant contributor to the overall CO2 budget of Kilauea. The area was revisited in 2001 to determine the effects of surface disturbance on efflux values by the collar emplacement technique utilized in the earlier surveys. Utilizing a cutoff value of 50 g m−2 d−1 for the surrounding forest background efflux, the CO2 emission rates for the anomaly at Puhimau thermal area were 27 t d−1 in 1996 and 17 t d−1 in 1998. Water vapor was removed before analysis in all cases in order to obtain CO2 values on a dry air basis and mitigate the effect of water vapor dilution on the measurements. It is clear that Puhimau thermal area is not a significant contributor to Kilauea's CO2 output and that most of Kilauea's CO2 (8500 t d−1) is degassed at the summit, leaving only magma with its remaining stored volatiles, such as SO2, for injection down the ERZ. Because of the low CO2 emission rate and the presence of a shallow water table in the upper ERZ that effectively scrubs SO2 and other acid gases, Puhimau thermal area currently does not appear to be generally well suited for observing temporal changes in degassing at Kilauea.

Improved Rare Earth Element Sorption from Simulated Geothermal Brines: Effect of Gassed versus Degassed Brines

DOE Data Explorer

Dean Stull

2016-05-24

A study exploring sorption and stripping characteristics of sorption media when simulated geothermal brines are degassed or not degassed. Experiments were done at 70°C. The brines used in this study were formulated by Tusaar. The two brines used/simulated are labeled 1M and 1CF. The data consists of a Word file explaining the results and an Excel file of the data.

Volatiles in glasses from the HSDP2 drill core

NASA Astrophysics Data System (ADS)

Seaman, Caroline; Sherman, Sarah Bean; Garcia, Michael O.; Baker, Michael B.; Balta, Brian; Stolper, Edward

2004-09-01

H2O, CO2, S, Cl, and F concentrations are reported for 556 glasses from the submarine section of the 1999 phase of HSDP drilling in Hilo, Hawaii, providing a high-resolution record of magmatic volatiles over ˜200 kyr of a Hawaiian volcano's lifetime. Glasses range from undegassed to having lost significant volatiles at near-atmospheric pressure. Nearly all hyaloclastite glasses are degassed, compatible with formation from subaerial lavas that fragmented on entering the ocean and were transported by gravity flows down the volcano flank. Most pillows are undegassed, indicating submarine eruption. The shallowest pillows and most massive lavas are degassed, suggesting formation by subaerial flows that penetrated the shoreline and flowed some distance under water. Some pillow rim glasses have H2O and S contents indicating degassing but elevated CO2 contents that correlate with depth in the core; these tend to be more fractionated and could have formed by mixing of degassed, fractionated magmas with undegassed magmas during magma chamber overturn or by resorption of rising CO2-rich bubbles by degassed magmas. Intrusive glasses are undegassed and have CO2 contents similar to adjacent pillows, indicating intrusion shallow in the volcanic edifice. Cl correlates weakly with H2O and S, suggesting loss during low-pressure degassing, although most samples appear contaminated by seawater-derived components. F behaves as an involatile incompatible element. Fractionation trends were modeled using MELTS. Degassed glasses require fractionation at p? ≈ 5-10 bars. Undegassed low-SiO2 glasses require fractionation at p? ≈ 50 bars. Undegassed and partially degassed high-SiO2 glasses can be modeled by coupled crystallization and degassing. Eruption depths of undegassed pillows can be calculated from their volatile contents assuming vapor saturation. The amount of subsidence can be determined from the difference between this depth and the sample's depth in the core. Assuming subsidence at 2.5 mm/y, the amount of subsidence suggests ages of ˜500 ka for samples from the lower 750 m of the core, consistent with radiometric ages. H2O contents of undegassed low-SiO2 HSDP2 glasses are systematically higher than those of high-SiO2 glasses, and their H2O/K2O and H2O/Ce ratios are higher than typical tholeiitic pillow rim glasses from Hawaiian volcanoes.

Consolidation processing parameters and alternative processing methods for powder metallurgy Al-Cu-Mg-X-X alloys

NASA Technical Reports Server (NTRS)

Sankaran, K. K.

1987-01-01

The effects of varying the vacuum degassing parameters on the microstructure and properties of Al-4Cu-1Mg-X-X (X-X = 1.5Li-0.2Zr or 1.5Fe-0.75Ce) alloys processed from either prealloyed (PA) or mechanically alloyed (M) powder, and consolidated by either using sealed aluminum containers or containerless vacuum hot pressing were studied. The consolidated billets were hot extruded to evaluate microstructure and properties. The MA Li-containing alloy did not include Zr, and the MA Fe- and Ce-containing alloy was made from both elemental and partially prealloyed powder. The alloys were vacuum degassed both above and below the solution heat treatment temperature. While vacuum degassing lowered the hydrogen content of these alloys, the range over which the vacuum degassing parameters were varied was not large enough to cause significant changes in degassing efficiency, and the observed variations in the mechanical properties of the heat treated alloys were attributed to varying contributions to strengthening by the sub-structure and the dispersoids. Mechanical alloying increased the strength over that of alloys of similar composition made from PA powder. The inferior properties in the transverse orientation, especially in the Li-containing alloys, suggested deficiencies in degassing. Among all of the alloys processed for this study, the Fe- and Ce-containing alloys made from MA powder possessed better combinations of strength and toughness.

Continental degassing of 4He by surficial discharge of deep groundwater

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aggarwal, Pradeep K.; Matsumoto, Takuya; Sturchio, Neil C.

2014-12-01

Radiogenic He-4 is produced by the decay of uranium and thorium in the Earths mantle and crust. From here, it is degassed to the atmosphere(1-5) and eventually escapes to space(1,5,6). Assuming that all of the He-4 produced is degassed, about 70% of the total He-4 degassed from Earth comes from the continental crust(2,-5,7). However, the outgoing flux of crustal He-4 has not been directly measured at the Earths surface(2) and the migration pathways are poorly understood(2-4,7,8). Here we present measurements of helium isotopes and the long-lived cosmogenic radio-isotope Kr-81 in the deep, continental-scale Guarani aquifer in Brazil and show thatmore » crustal He-4 reaches the atmosphere primarily by the surficial discharge of deep groundwater. We estimate that He-4 in Guarani groundwater discharge accounts for about 20% of the assumed global flux from continental crust, and that other large aquifers may account for about 33%. Old groundwater ages suggest that He-4 in the Guarani aquifer accumulates over half- to one-million-year timescales. We conclude that He-4 degassing from the continents is regulated by groundwater discharge, rather than episodic tectonic events, and suggest that the assumed steady state between crustal production and degassing of He-4, and its resulting atmospheric residence time, should be re-examined« less

Magma transfer processes at persistently active volcanoes: insights from gravity observations

NASA Astrophysics Data System (ADS)

Locke, Corinne A.; Rymer, Hazel; Cassidy, John

2003-09-01

Magma transfer processes at persistently active volcanoes are distinguished by the large magma flux required to sustain the prodigious quantities of heat and gas emitted at the surface. Although the resulting degassed magma has been conjectured to accumulate either deep within the volcanic edifice or in the upper levels of the sub-edifice system, no direct evidence for such active accumulation has been reported. Temporal gravity data are unique in being able to quantify mass changes and have been successfully used to model shallow magma movements on different temporal scales, but have not generally been applied to the investigation of postulated long-term accumulation of magma at greater spatial scales within volcanic systems. Here, we model the critical data acquisition parameters required to detect mass flux at volcanoes, we review existing data from a number of volcanoes that exemplify the measurement of shallow mass changes and present new data from Poas and Telica volcanoes. We show that if a substantial proportion of degassed magma lodges within the sub-edifice region, it would result in measurable annual to decadal gravity increases occurring over spatial scales of tens of kilometres and propose that existing microgravity data from Sakurajima and, possibly, Etna volcanoes could be interpreted in these terms. Furthermore, such repeat microgravity data could be used to determine whether the accumulation rate is in equilibrium with the rate of production of degassed magma as calculated from the surface gas flux and hence identify the build-up of gas-rich magma at depth that may be significant in terms of eruption potential. We also argue that large magma bodies, both molten and frozen, modelled beneath volcanoes from seismic and gravity data, could represent endogenous or cryptic intrusions of degassed magma based on order of magnitude calculations using present-day emission rates and typical volcano lifetimes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Polacci, M.; Baker, D.R.; Bai, L.

Volcanic degassing is directly linked to magma dynamics and controls the style of eruptive activity. To better understand how gas is transported within basaltic magma we perform a 3D investigation of vesicles preserved in scoria from the 2005 activity at Stromboli volcano (Italy). We find that clasts are characterized by the ubiquitous occurrence of one to a few large vesicles, exhibiting mostly irregular, tortuous, channel-like textures, orders of magnitude greater in volume than all the other vesicles in the sample. We compare observations on natural samples with results from numerical simulations and experimental investigations of vesicle size distributions and demonstratemore » that this type of vesicle invariably forms in magmas with vesicularities > 0.30 (and possibly > 0.10). We suggest that large vesicles represent pathways used by gas to flow non-explosively to the surface and that they indicate the development of an efficient system that sustains persistent degassing in basaltic systems.« less

Study on the Removal of Gases in RH Refining Progress through Experiments Using Vacuum Induction Furnace

NASA Astrophysics Data System (ADS)

Niu, Deliang; Liu, Qingcai; Wang, Zhu; Ren, Shan; Lan, Yuanpei; Xu, Minren

Removal of gas is the major function of RH degasser. To optimize the RH refining craft in Chongqing Iron and Steel Co. Ltd, the degassing effect of RH degasser at different degrees of vacuum was investigated using a vacuum induction furnace. In addition, the effect of processing time on the gas content dissolved in molten steel was also studied. The results showed that degree of vacuum was one of the important factors that determined the degassing efficiency in RH refining process. High vacuum degree is helpful in the removal of gas, especially in the removal of [H] dissolved in molten steel. The processing time could be reduced from 25-30 min to 15 minutes and gas content could also meet the demand of RH refining.

No effect of H2O degassing on the oxidation state of hydrous rhyolite magmas: a comparison of pre- and post-eruptive Fe2+ concentrations in six obsidian samples from the Mexican and Cascade arcs

NASA Astrophysics Data System (ADS)

Waters, L.; Lange, R. A.

2011-12-01

The extent to which degassing affects the oxidation state of arc magmas is widely debated. Several researchers have examined how degassing of mixed H-C-O-S-Cl fluids may change the Fe3+/FeT ratio of magmas, and it has been proposed that degassing may induce either oxidation or reduction depending on the initial oxidation state. A commonly proposed oxidation reaction is related to H2O degassing: H2O (melt) + 2FeO (melt) = H2 (fluid) + Fe2O3 (melt). Another mechanism by which H2O degassing can affect the iron redox state is if dissolved water affects the activity of ferrous and/or ferric iron in the melt. Although Moore et al. (1995) presented experiments showing no evidence of an affect of dissolved water on the activity of the ferric-ferrous ratio in silicate melts, other experimental results (e.g., Baker and Rutherford, 1996; Gaillard et al., 2001; 2003) indicate that there may be such an effect in rhyolite liquids. It has long been understood that rhyolites, owing to their low total iron concentrations, are more sensitive than other magma types to degassing-induced change in redox state. Therefore, a rigorous test of whether H2O degassing affects the redox state of arc magmas is best evaluated on rhyolites. In this study, a comparison is made between the pre-eruptive (pre-degassing) Fe2+ concentrations in six, phenocryst-poor (<5%), fresh, glassy obsidian samples with their post-eruptive (post-degassing) Fe2+ concentrations. Near-liquidus co-precipitation of two Fe-Ti oxides allows the pre-eruptive oxygen fugacity and temperature to be calculated in each rhyolite using the oxygen barometer and thermometer of Ghiorso and Evans (2008). Temperatures range from 793 (± 19) to 939 (± 15) °C, and ΔNNO values (log10fO2 of sample - log10fO2 of Ni-NiO buffer) range from -0.4 to +1.4. These ΔNNO values allow the ferric-ferrous ratio in the liquid to be calculated, using the experimental calibration of Kress and Carmichael (1991), which relates melt composition (not including dissolved water), oxygen fugacity and temperature to melt ferric-ferrous ratios. With temperature known, the plagioclase-liquid hygrometer of Lange et al. (2009) was applied and maximum melt water concentrations range from 4.2 to 7.5 wt%. Both the oxidation state and water concentration are known prior to eruption, at the time of phenocryst growth. After eruption, the rhyolites lost nearly all of their volatiles, as indicated by the low loss on ignition values (LOI ≤ 0.7 wt%). In order to test how much oxidation of ferrous iron occurred as a consequence of that degassing, we measured the ferrous iron concentration in the bulk samples by titration, using the Wilson (1960) method, which was successfully tested again three USGS and one Canadian Geological Survey standards. Our results indicate no detectable change within analytical error between pre- and post-eruptive FeO concentrations, with an average deviation of 0.09 wt% and a maximum deviation of 0.15 wt%. Our results show that H2O degassing has no effect on the redox state of rhyolite magmas, which requires that dissolved water has no resolvable affect on the activity ratio of the iron oxide components in melt.

40 CFR 63.163 - Standards: Pumps in light liquid service.

Code of Federal Regulations, 2011 CFR

2011-07-01

...) Equipped with a barrier fluid degassing reservoir that is routed to a process or fuel gas system or... with a sensor that will detect failure of the seal system, the barrier fluid system, or both. (4) Each... per million or greater is measured, a leak is detected. (5) Each sensor as described in paragraph (e...

Melt fracturing and healing: A mechanism for degassing and origin of silicic obsidian

USGS Publications Warehouse

Cabrera, A.; Weinberg, R.F.; Wright, H.M.N.; Zlotnik, S.; Cas, Ray A.F.

2011-01-01

We present water content transects across a healed fault in pyroclastic obsidian from Lami pumice cone, Lipari, Italy, using synchrotron Fourier transform infrared spectroscopy. Results indicate that rhyolite melt degassed through the fault surface. Transects define a trough of low water content coincident with the fault trace, surrounded on either side by high-water-content plateaus. Plateaus indicate that obsidian on either side of the fault equilibrated at different pressure-temperature (P-T) conditions before being juxtaposed. The curves into the troughs indicate disequilibrium and water loss through diffusion. If we assume constant T, melt equilibrated at pressures differing by 0.74 MPa before juxtaposition, and the fault acted as a low-P permeable path for H2O that diffused from the glass within time scales of 10 and 30 min. Assuming constant P instead, melt on either side could have equilibrated at temperatures differing by as much as 100 ??C, before being brought together. Water content on the fault trace is particularly sensitive to post-healing diffusion. Its preserved value indicates either higher temperature or lower pressure than the surroundings, indicative of shear heating and dynamic decompression. Our results reveal that water contents of obsidian on either side of the faults equilibrated under different P-T conditions and were out of equilibrium with each other when they were juxtaposed due to faulting immediately before the system was quenched. Degassing due to faulting could be linked to cyclical seismic activity and general degassing during silicic volcanic activity, and could be an efficient mechanism of producing low-water-content obsidian. ?? 2011 Geological Society of America.

Vapor segregation and loss in basaltic melts

USGS Publications Warehouse

Edmonds, M.; Gerlach, T.M.

2007-01-01

Measurements of volcanic gases at Pu'u'O??'o??, Kilauea Volcano, Hawai'i, reveal distinct degassing regimes with respect to vapor segregation and loss during effusive activity in 2004-2005. Three styles of vapor loss are distinguished by the chemical character of the emitted volcanic gases, measured by open path Fourier transform infrared spectroscopy: 1 persistent continuous gas emission, 2 gas piston events, and 3 lava spattering. Persistent continuous gas emission is associated with magma ascent and degassing beneath the crater vents, then eruption of the degassed magma from flank vents. Gas piston events are the result of static gas accumulation at depths of 400-900 m beneath Pu'u'O??'o??. A CO2-rich gas slug travels up the conduit at a few meters per second, displacing magma as it expands. Lava spattering occurs due to dynamic bubble coalescence in a column of relatively stagnant magma. The Large gas bubbles are H2O rich and are generated by open-system degassing at depths of <150 m. Static gas accumulation and dynamic bubble coalescence are both manifestations of vapor segregation in basaltic melts, but their implications differ. Accumulation and segregation of CO2-rich vapor at depth does not deplete the melt of H2O (required to drive lava fountains near to the surface) and therefore gas piston events can occur interspersed with lava fountaining activity. Lava spattering, however, efficiently strips H2O-rich vapor from magma beneath the crater vents; the magma must then erupt effusively from vents on the flank of the cone. ?? 2007 The Geological Society of America.

Vapor segregation and loss in basaltic melts

NASA Astrophysics Data System (ADS)

Edmonds, Marie; Gerlach, Terrence M.

2007-08-01

Measurements of volcanic gases at Pu'u‘Ō’ō, Kilauea Volcano, Hawai'i, reveal distinct degassing regimes with respect to vapor segregation and loss during effusive activity in 2004-2005. Three styles of vapor loss are distinguished by the chemical character of the emitted volcanic gases, measured by open path Fourier transform infrared spectroscopy: (1) persistent continuous gas emission, (2) gas piston events, and (3) lava spattering. Persistent continuous gas emission is associated with magma ascent and degassing beneath the crater vents, then eruption of the degassed magma from flank vents. Gas piston events are the result of static gas accumulation at depths of 400-900 m beneath Pu'u‘Ō’ō. A CO2-rich gas slug travels up the conduit at a few meters per second, displacing magma as it expands. Lava spattering occurs due to dynamic bubble coalescence in a column of relatively stagnant magma. The large gas bubbles are H2O rich and are generated by open-system degassing at depths of <150 m. Static gas accumulation and dynamic bubble coalescence are both manifestations of vapor segregation in basaltic melts, but their implications differ. Accumulation and segregation of CO2-rich vapor at depth does not deplete the melt of H2O (required to drive lava fountains near to the surface) and therefore gas piston events can occur interspersed with lava fountaining activity. Lava spattering, however, efficiently strips H2O-rich vapor from magma beneath the crater vents; the magma must then erupt effusively from vents on the flank of the cone.

Third prize: the impact of fluid environment manipulation on shockwave lithotripsy artificial calculi fragmentation rates.

PubMed

Méndez-Probst, Carlos E; Fernadez, Alfonso; Erdeljan, Petar; Vanjecek, Maaike; Cadieux, Peter A; Razvi, Hassan

2011-03-01

Studies have suggested that shockwave lithotripsy (SWL) stone fragmentation rates can be affected by characteristics of the fluid media surrounding the stone, although evidence to implicate the impact of urine specific gravity (SG) is limited and inconclusive. Our aim is to further explore the impact fluid media and SGs have on stone fragmentation using a variable focus lithotripter. Artificial stones were presoaked for 24 hours in urine and then shocked in various fluid media including artificial urine (SG 1.010 control, 1.020, and 1.07), human pooled urine (HPU), degassed HPU, Pentastarch, 100% and 30% contrast, degassed 30% contrast, 100% ethanol, deionized water (dH(2)O), degassed dH(2)O, 5% glucose, Ringer lactate, 0.9% saline, glycerol, whole blood, and lubricating gel. After soaking, SWL using the Modulith SLX-F2 electromagnetic lithotripter was performed. Fragments were dried and sieved using a 4-mm diameter opening grid. Fragments >4 mm were weighed and fragmentation coefficients (FCs) calculated (pre-SWL weight - post-SWL weight)/(pre-SWL weight) × 100. Fifteen stones were shocked for each fluid group. Fluid type, viscosity, and degassing all significantly impacted stone fragmentation. While the solutions' SG, per se, did not appear to affect stone fragmentation, the use of degassed 30% contrast significantly improved stone destruction over the SG 1.010 artificial urine control (95.3% vs 71.4, P < 0.01). Furthermore, degassing improved comminution rates by increasing the number of completely fragmented stones (FC = 100%). Using degassed 30% contrast, 12/15 stones were completely fragmented, compared with only 2/15 in the control group (P = 0.007). Among the whole blood, glycerol, and lubricating gel groups, only 1/15, 0/15, and 1/15 stones reached 100% FC respectively in the narrow focus, possibly because of the detrimental impact of increased viscosity. Different fluid media can significantly affect FC in vitro. Among the various fluids tested, degassed 30% contrast significantly increased the FC and total number of completely fragmented stones.

The chlorine isotope fingerprint of the lunar magma ocean

PubMed Central

Boyce, Jeremy W.; Treiman, Allan H.; Guan, Yunbin; Ma, Chi; Eiler, John M.; Gross, Juliane; Greenwood, James P.; Stolper, Edward M.

2015-01-01

The Moon contains chlorine that is isotopically unlike that of any other body yet studied in the Solar System, an observation that has been interpreted to support traditional models of the formation of a nominally hydrogen-free (“dry”) Moon. We have analyzed abundances and isotopic compositions of Cl and H in lunar mare basalts, and find little evidence that anhydrous lava outgassing was important in generating chlorine isotope anomalies, because 37Cl/35Cl ratios are not related to Cl abundance, H abundance, or D/H ratios in a manner consistent with the lava-outgassing hypothesis. Instead, 37Cl/35Cl correlates positively with Cl abundance in apatite, as well as with whole-rock Th abundances and La/Lu ratios, suggesting that the high 37Cl/35Cl in lunar basalts is inherited from urKREEP, the last dregs of the lunar magma ocean. These new data suggest that the high chlorine isotope ratios of lunar basalts result not from the degassing of their lavas but from degassing of the lunar magma ocean early in the Moon’s history. Chlorine isotope variability is therefore an indicator of planetary magma ocean degassing, an important stage in the formation of terrestrial planets. PMID:26601265

The chlorine isotope fingerprint of the lunar magma ocean.

PubMed

Boyce, Jeremy W; Treiman, Allan H; Guan, Yunbin; Ma, Chi; Eiler, John M; Gross, Juliane; Greenwood, James P; Stolper, Edward M

2015-09-01

The Moon contains chlorine that is isotopically unlike that of any other body yet studied in the Solar System, an observation that has been interpreted to support traditional models of the formation of a nominally hydrogen-free ("dry") Moon. We have analyzed abundances and isotopic compositions of Cl and H in lunar mare basalts, and find little evidence that anhydrous lava outgassing was important in generating chlorine isotope anomalies, because (37)Cl/(35)Cl ratios are not related to Cl abundance, H abundance, or D/H ratios in a manner consistent with the lava-outgassing hypothesis. Instead, (37)Cl/(35)Cl correlates positively with Cl abundance in apatite, as well as with whole-rock Th abundances and La/Lu ratios, suggesting that the high (37)Cl/(35)Cl in lunar basalts is inherited from urKREEP, the last dregs of the lunar magma ocean. These new data suggest that the high chlorine isotope ratios of lunar basalts result not from the degassing of their lavas but from degassing of the lunar magma ocean early in the Moon's history. Chlorine isotope variability is therefore an indicator of planetary magma ocean degassing, an important stage in the formation of terrestrial planets.

Monitoring very-long-period seismicity at Kilauea Volcano, Hawaii

USGS Publications Warehouse

Dawson, Phillip B.; Benítez, M. C.; Chouet, Bernard A.; Wilson, David; Okubo, Paul G.

2010-01-01

On 19 March, 2008 eruptive activity returned to the summit of Kilauea Volcano, Hawaii with the formation of a new vent within the Halemaumau pit crater. The new vent has been gradually increasing in size, and exhibiting sustained degassing and the episodic bursting of gas slugs at the surface of a lava pond ∼200 m below the floor of Halemaumau. The spectral characteristics, source location obtained by radial semblance, and Hidden Markov Model pattern recognition of the degassing burst signals are consistent with an increase in gas content in the magma transport system beginning in October, 2007. This increase plateaus between March – September 2008, and exhibits a fluctuating pattern until 31 January, 2010, suggesting that the release of gas is slowly diminishing over time.

Strong S-wave attenuation and actively degassing magma beneath Taal volcano, Philippines, inferred from source location analysis using high-frequency seismic amplitudes

NASA Astrophysics Data System (ADS)

Kumagai, H.; Lacson, R. _Jr., Jr.; Maeda, Y.; Figueroa, M. S., II; Yamashina, T.

2014-12-01

Taal volcano, Philippines, is one of the world's most dangerous volcanoes given its history of explosive eruptions and its close proximity to populated areas. A key feature of these eruptions is that the eruption vents were not limited to Main Crater but occurred on the flanks of Volcano Island. This complex eruption history and the fact that thousands of people inhabit the island, which has been declared a permanent danger zone, together imply an enormous potential for disasters. The Philippine Institute of Volcanology and Seismology (PHIVOLCS) constantly monitors Taal, and international collaborations have conducted seismic, geodetic, electromagnetic, and geochemical studies to investigate the volcano's magma system. Realtime broadband seismic, GPS, and magnetic networks were deployed in 2010 to improve monitoring capabilities and to better understand the volcano. The seismic network has recorded volcano-tectonic (VT) events beneath Volcano Island. We located these VT events based on high-frequency seismic amplitudes, and found that some events showed considerable discrepancies between the amplitude source locations and hypocenters determined by using onset arrival times. Our analysis of the source location discrepancies points to the existence of a region of strong S-wave attenuation near the ground surface beneath the east flank of Volcano Island. This region is beneath the active fumarolic area and above sources of pressure contributing inflation and deflation, and it coincides with a region of high electrical conductivity. The high-attenuation region matches that inferred from an active-seismic survey conducted at Taal in 1993. Our results, synthesized with previous results, suggest that this region represents actively degassing magma near the surface, and imply a high risk of future eruptions on the east flank of Volcano Island.

H2S in Shallow Groundwater: Hydrogeochemical Processes, Degassing Experiments and Health Impacts

NASA Astrophysics Data System (ADS)

Broers, H. P.; Weert, J. D.; Bouma, R.

2016-12-01

Hydrogen sulfide is known to be a hazardous gas even at rather low concentrations and may pose a serious health risk. Occurrences of H2S in groundwater and degassing into the atmosphere are known for volcanic or tectonic active regions, coal mining or gypsum dissolution regions. We studied the occurrence and origin of H2S in shallow groundwater and its degassing into air after pumping in a setting of shallow unconsolidated deposits in the south of the Netherlands, where the sulfate source is antropogenic. We measured H2S concentrations in water using a field photo spectrometer and the degassing into air with a Jerome 631. We analyzed for macro-ions and determined the apparent 3H/3He age to assess the origin of the sulfide in the groundwater. H2S was formed in-situ within organic-rich and carbonate free sediments and peat layers of a fluvio-glacial sediment series in groundwater that infiltrated approximately 15 years ago. Sulfate is omnipresent in Dutch shallow groundwater due to historical atmospheric inputs of SOx, sulfur inputs from intensive livestock farming and subsurface production of sulfate from pyrite oxidation following nitrate leaching from agricultural fields (Zhang et al. 2009 GCA, 2012 AppGeochem). The co-existence of H2S and sulfate in our groundwater appears to be determined by the low pH of the water (4.8-5.5) which limits the precipitation of mackinawite or amorphous FeS. Mapping the combination of observations wells with pH < 5.5, sulfate > 75 mg/L and Fe > 10 mg/l delineated large areas where H2S appeared to be present in concentration between 0.1 and 1.0 mg/L S2- in water. Degassing of groundwater with 0.7 mg S2-/L into a contained volume of air yielded concentrations > 50 ppmv within 15 minutes. Using the degassing rates observed in the experiments and assuming equilibrium degassing, we calibrated a simple model which describes the inflow of water, the degassing and the export of gas in relation to wind velocity. We used the model to evaluate scenario's of human exposure for typical private and commercial uses. The private uses are at largest risk for exposure to harmful concentrations of H2S in air, due to closer exposure distances towards the degassing water, especially under conditions of low wind speeds. Indeed, a health incident was reported at a site where groundwater was pumped into a children's water play.

Carbon dioxide degassing at the groundwater-stream-atmosphere interface: isotopic equilibration and hydrological mass balance in a sandy watershed

NASA Astrophysics Data System (ADS)

Deirmendjian, Loris; Abril, Gwenaël

2018-03-01

Streams and rivers emit significant amounts of CO2 and constitute a preferential pathway of carbon transport from terrestrial ecosystems to the atmosphere. However, the estimation of CO2 degassing based on the water-air CO2 gradient, gas transfer velocity and stream surface area is subject to large uncertainties. Furthermore, the stable isotope signature of dissolved inorganic carbon (δ13C-DIC) in streams is strongly impacted by gas exchange, which makes it a useful tracer of CO2 degassing under specific conditions. For this study, we characterized the annual transfers of dissolved inorganic carbon (DIC) along the groundwater-stream-river continuum based on DIC concentrations, stable isotope composition and measurements of stream discharges. We selected a homogeneous, forested and sandy lowland watershed as a study site, where the hydrology occurs almost exclusively through drainage of shallow groundwater (no surface runoff). We observed the first general spatial pattern of decreases in pCO2 and DIC and an increase in δ13C-DIC from groundwater to stream orders 1 and 2, which was due to the experimentally verified faster degassing of groundwater 12C-DIC compared to 13C-DIC. This downstream enrichment in 13C-DIC could be modelled by simply considering the isotopic equilibration of groundwater-derived DIC with the atmosphere during CO2 degassing. A second spatial pattern occurred between stream orders 2 and 4, consisting of an increase in the proportion of carbonate alkalinity to the DIC accompanied by the enrichment of 13C in the stream DIC, which was due to the occurrence of carbonate rock weathering downstream. We could separate the contribution of these two processes (gas exchange and carbonate weathering) in the stable isotope budget of the river network. Thereafter, we built a hydrological mass balance based on drainages and the relative contribution of groundwater in streams of increasing order. After combining with the dissolved CO2 concentrations, we quantified CO2 degassing for each stream order for the whole watershed. Approximately 75% of the total CO2 degassing from the watershed occurred in first- and second-order streams. Furthermore, from stream order 2-4, our CO2 degassing fluxes compared well with those based on stream hydraulic geometry, water pCO2, gas transfer velocity, and stream surface area. In first-order streams, however, our approach showed CO2 fluxes that were twice as large, suggesting that a fraction of degassing occurred as hotspots in the vicinity of groundwater resurgence and was missed by conventional stream sampling.

Argon-40 as a Constraint on the Volcanic Degassing History and Thermal Evolution of Mars

NASA Astrophysics Data System (ADS)

Kiefer, W. S.

2017-12-01

Models for the thermal and magmatic evolution of Mars are strongly controlled by the volcanic degassing of water from the interior. Water affects the mantle's viscosity and hence the vigor of convective flow. It also affects the mantle's solidus temperature and hence the rate of magma generation. This set of coupled feedback loops affects both the volume of crustal production and the possible production of a magnetic field via a core dynamo (e.g., Sandu and Kiefer, GRL 2012, 2011GL050225). Volcanic degassing also affects other atmospheric components. Argon-40, which is a radioactive decay product of potassium-40, can potentially serve as an additional test of thermal evolution models. As a noble gas, 40Ar is highly incompatible in mantle and crustal rocks and thus tends to degas to the atmosphere during magmatic events. 40K has a half-life of 1.25 billion years and thus 40Ar measures volcanic degassing throughout martian history. It is relatively insensitive to atmospheric loss processes during the earliest part of solar system history, and long-term loss of 40Ar from the atmosphere can be estimated from fractionation of the 38Ar/36Ar ratio relative to solar (MAVEN results indicate that 66% of 36Ar has been lost from the martian atmosphere, Jakosky et al., Science 2017). The noble gas composition of the martian atmosphere has been measured both in situ using the SAM mass spectrometer on NASA's Curiosity rover and via measurements of trapped atmospheric gases in martian meteorites. One important application of 40Ar degassing models is as a constraint on the bulk silicate composition of Mars. The most widely accepted composition model for Mars has a potassium abundance of 305-310 ppm, slightly higher than the bulk silicate Earth. However, several other models assume a bulk silicate Mars K of up to 1040 ppm. Preliminary Ar degassing modeling favors K in the lower half of this range, consistent with results from long-term and present-day magma production models. Constraints on the bulk silicate K abundance are important to understanding the thermal and magmatic history of Mars because 40K is a radioactive heat source. In addition, the expected abundances of K and Na are correlated and elevated values of Na act to lower the peridotite solidus and thus to enhance the magma production rate (Kiefer et al., Geochimica, 2015).

Ambient aging of rhenium filaments used in thermal ionization mass spectrometry: Growth of oxo-rhenium crystallites and anti-aging strategies.

PubMed

Mannion, Joseph M; Wellons, Matthew S; Shick, Charles R; Fugate, Glenn A; Powell, Brian A; Husson, Scott M

2017-01-01

Degassing is a common preparation technique for rhenium filaments used for thermal ionization mass spectrometric analysis of actinides, including plutonium. Although optimization studies regarding degassing conditions have been reported, little work has been done to characterize filament aging after degassing. In this study, the effects of filament aging after degassing were explored to determine a "shelf-life" for degassed rhenium filaments, and methods to limit filament aging were investigated. Zone-refined rhenium filaments were degassed by resistance heating under high vacuum before exposure to ambient atmosphere for up to 2 months. After degassing the nucleation and preferential growth of oxo-rhenium crystallites on the surface of polycrystalline rhenium filaments was observed by atomic force microscopy and scanning electron microscopy (SEM). Compositional analysis of the crystallites was conducted using SEM-Raman spectroscopy and SEM energy dispersive X-ray spectroscopy, and grain orientation at the metal surface was investigated by electron back-scatter diffraction mapping. Spectra collected by SEM-Raman suggest crystallites are composed primarily of perrhenic acid. The relative extent of growth and crystallite morphology were found to be grain dependent and affected by the dissolution of carbon into filaments during annealing (often referred to as carbonization or carburization). Crystallites were observed to nucleate in region specific modes and grow over time through transfer of material from the surface. Factors most likely to affect the rates of crystallite growth include rhenium substrate properties such as grain size, orientation, levels of dissolved carbon, and relative abundance of defect sites; as well as environmental factors such as length of exposure to oxygen and relative humidity. Thin (∼180 nm) hydrophobic films of poly(vinylbenzyl chloride) were found to slow the growth of oxo-rhenium crystallites on the filament surfaces and may serve as an alternative carbon source for filament carburization.

Adventive hydrothermal circulation on Stromboli volcano (Aeolian Islands, Italy) revealed by geophysical and geochemical approaches: Implications for general fluid flow models on volcanoes

NASA Astrophysics Data System (ADS)

Finizola, A.; Ricci, T.; Deiana, R.; Cabusson, S. Barde; Rossi, M.; Praticelli, N.; Giocoli, A.; Romano, G.; Delcher, E.; Suski, B.; Revil, A.; Menny, P.; Di Gangi, F.; Letort, J.; Peltier, A.; Villasante-Marcos, V.; Douillet, G.; Avard, G.; Lelli, M.

2010-09-01

On March 15th 2007 a paroxysmal explosion occurred at the Stromboli volcano. This event generated a large amount of products, mostly lithic blocks, some of which impacted the ground as far as down to 200 m a.s.l., about 1.5 km far away from the active vents. Two days after the explosion, a new vapour emission was discovered on the north-eastern flank of the volcanic edifice, at 560 m a.s.l., just above the area called "Nel Cannestrà". This new vapour emission was due to a block impact. In order to investigate the block impact area to understand the appearance of the vapour emission, we conducted on May 2008 a multidisciplinary study involving Electrical Resistivity Tomography (ERT), Ground Penetrating Radar (GPR), Self-Potential (SP), CO 2 soil diffuse degassing and soil temperature surveys. This complementary data set revealed the presence of an anomalous conductive body, probably related to a shallow hydrothermal level, at about 10-15 m depth, more or less parallel to the topography. It is the first time that such a hydrothermal fluid flow, with a temperature close to the water boiling point (76 °C) has been evidenced at Stromboli at this low elevation on the flank of the edifice. The ERT results suggest a possible link between (1) the main central hydrothermal system of Stromboli, located just above the plumbing system feeding the active vents, with a maximum of subsurface soil temperature close to 90 °C and limited by the NeoStromboli summit crater boundary and (2) the investigated area of Nel Cannestrà, at ~ 500 m a.s.l., a buried eruptive fissure active 9 ka ago. In parallel, SP and CO 2 soil diffuse degassing measurements suggest in this sector at slightly lower elevation from the block impact crater a magmatic and hydrothermal fluid rising system along the N41° regional fault. A complementary ERT profile, on May 2009, carried out from the NeoStromboli crater boundary down to the block impact crater displayed a flank fluid flow apparently connected to a deeper system. The concept of shallow hydrothermal level have been compared to similar ERT results recently obtained on Mount Etna and La Fossa cone of Vulcano. This information needs to be taken into account in general fluid flow models on volcanoes. In particular, peripheral thermal waters (as those bordering the north-eastern coast of Stromboli) could be contaminated by hydrothermal and magmatic fluids coming from regional faults but also from the summit.

The 2012 Copahue eruption: magnitude of gas fluxes and time scale of degassing

NASA Astrophysics Data System (ADS)

Varekamp, J. C.; Camfield, L.

2015-12-01

Copahue volcano (Argentina, 37.5 S, 71.5 W) erupted in 2000 and 2012 with initial phreato-magmatic blasts, violent Strombolian eruptions of several hours duration, followed by open conduit activity for days to months. The 2012 basal deposits 10 km S of Copahue are mm-sized ashes with hydrothermally altered debris, followed by up to 10cm pancake pumices, while denser cinders fell near the crater in the waning stages. The strombolian plume was ~ 6 km high and satellite images show its trajectory up to 200 km S. The pumices have finely porous rims (0.3mm vesicles) that were probably quenched by hydrothermal fluids and coarse interiors (several mm vesicles) that inflated during eruption. All the products have identical chemical composition and mineralogy, and only vary in degree of vesiculation. The 2012 products are the most mafic of the whole volcanic history of Copahue, with MgO ~ 4.5 %. The quench rim pumice glass contains 1160 ppm Cl while glass inclusions have up to 1800 ppm Cl. Water concentrations are 0.5-2.0 % (by difference with EMPA) and plagioclase hygrometry. Pre-eruptive conditions were 1080 oC and 1-2.5 kb pressure. The magmato-hydrothermal system is leaking fluids into the overlying crater lake and into a river. The hot springs have pH <1 and these fluids are up to 60% magmatic in origin. Annual river flux measurements and non-steady state modeling between 1997 and 2013 constrain the mean hydrothermal Cl flux at 1170 tonnes/month. The 2012 erupted magma mass is about 1012 gr, and from the measured total Cl loss between 2000 and 2012 and mean degassed Cl in the magma the volume of degassing magma is estimated at 1014-1015 grams. Much more magma was degassing than was erupted. Analyses of 226Ra-210Pb constrained the maximum degassing time at 8-10 years prior to the 2012 eruption. Almost all rock samples have 210Pb deficits, and so most gas escaped from the magma into the hydrothermal system. Nonetheless, the top of the magma reservoir accumulated bubbles, which caused overpressurization that led to the eruption. Calculations of bubble rise velocities help constrain the geometry of the underlying magma reservoir. The decadal eruption rhythm of Copahue is probably more determined by the time needed for bubble accumulation and associated pressure increase (about ten years) and less by new magma intrusions.

The effect of ultrasonic waves on the nucleation of pure water and degassed water.

PubMed

Yu, Deyang; Liu, Baolin; Wang, Bochun

2012-05-01

In order to clarify the mechanism of nucleation of ice induced by ultrasound, ultrasonic waves have been applied to supercooled pure water and degassed water, respectively. For each experiment, water sample is cooled at a constant cooling rate of 0.15 °C/min and the ultrasonic waves are applied from the water temperature of 0 °C until the water in a sample vessel nucleates. This nucleation temperature is measured. The use of ultrasound increased the nucleation temperature of both degassed water and pure water. However, the undercooling temperature for pure water to nucleate is less than that of degassed water. It is concluded that cavitation and fluctuations of density, energy and temperature induced by ultrasound are factors that affect the nucleation of water. Cavitation is a major factor for sonocrystallisation of ice. Crown Copyright © 2011. Published by Elsevier B.V. All rights reserved.

Electrical tree initiation in polyethylene absorbing Penning gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shimizu, N.; Tohyama, N.; Sato, H.

1996-12-31

Ac tree initiation voltage was examined in untreated LDPE, vacuum degassed LDPE and LDPE absorbing He gas (He gas was absorbed after vacuum degassing). The authors have already reported that vacuum degassed LDPE shows much higher tree initiation voltage than untreated one because of absence of oxygen. Therefore they expected that LDPE absorbing He shows the same property with vacuum degassed LDPE. However tree initiation voltage of LDPE absorbing He is as low as that of untreated LDPE. LDPE absorbing Ar gas shows the same tendency. He or Ar gas does not change so much impulse tree initiation voltage. LDPEmore » absorbing He was not well dyed with methylene blue after ac voltage application, which indicates that active oxidation does not occur. Low ac tree initiation voltage in LDPE absorbing He or Ar may be caused by Penning ionization in free volume.« less

Melt inclusion constraints on volatile systematics and degassing history of the 2014-2015 Holuhraun eruption, Iceland

NASA Astrophysics Data System (ADS)

Bali, E.; Hartley, M. E.; Halldórsson, S. A.; Gudfinnsson, G. H.; Jakobsson, S.

2018-02-01

The mass of volatiles emitted during volcanic eruptions is often estimated by comparing the volatile contents of undegassed melt inclusions, trapped in crystals at an early stage of magmatic evolution, with that of the degassed matrix glass. Here we present detailed characterisation of magmatic volatiles (H2O, CO2, S, Fl and Cl) of crystal-hosted melt and fluid inclusions from the 2014-2015 Holuhraun eruption of the Bárðarbunga volcanic system, Iceland. Based on the ratios of magmatic volatiles to similarly incompatible trace elements, the undegassed primary volatile contents of the Holuhraun parental melt are estimated at 1500-1700 ppm CO2, 0.13-0.16 wt% H2O, 60-80 ppm Cl, 130-240 ppm F and 500-800 ppm S. High-density fluid inclusions indicate onset of crystallisation at pressures ≥ 0.4 GPa ( 12 km depth) promoting deep degassing of CO2. Prior to the onset of degassing, the melt CO2 content may have reached 3000-4000 ppm, with the total magmatic CO2 budget estimated at 23-55 Mt. SO2 release commenced at 0.12 GPa ( 3.6 km depth), eventually leading to entrapment of SO2 vapour in low-density fluid inclusions. We calculate the syn-eruptive volatile release as 22.2 Mt of magmatic H2O, 5.9-7.7 Mt CO2, and 11.3 Mt of SO2 over the course of the eruption; F and Cl release were insignificant. Melt inclusion constraints on syn-eruptive volatile release are similar to estimates made during in situ field monitoring, with the exception of H2O, where field measurements may be heavily biased by the incorporation of meteoric water.

A new sulfur and carbon degassing inventory for the Southern Central American Volcanic Arc: The importance of accurate time-series datasets and possible tectonic processes responsible for temporal variations in arc-scale volatile emissions

USGS Publications Warehouse

de Moor, Maarten; Kern, Christoph; Avard, Geoffroy; Muller, Cyril; Aiuppa, Sandro; Saballos, Armando; Ibarra, Martha; LaFemina, Peter; Protti, Mario; Fischer, Tobias

2017-01-01

This work presents a new database of SO2 and CO2 fluxes from the Southern Central American Volcanic Arc (SCAVA) for the period 2015–2016. We report ∼300 SO2 flux measurements from 10 volcanoes and gas ratios from 11 volcanoes in Costa Rica and Nicaragua representing the most extensive available assessment of this ∼500 km arc segment. The SO2 flux from SCAVA is estimated at 6,240 ± 1,150 T/d, about a factor of three higher than previous estimations (1972–2013). We attribute this increase in part to our more complete assessment of the arc. Another consideration in interpreting the difference is the context of increased volcanic activity, as there were more eruptions in 2015–2016 than in any period since ∼1980. A potential explanation for increased degassing and volcanic activity is a change in crustal stress regime (from compression to extension, opening volcanic conduits) following two large (Mw > 7) earthquakes in the region in 2012. The CO2 flux from the arc is estimated at 22,500 ± 4,900 T/d, which is equal to or greater than estimates of C input into the SCAVA subduction zone. Time‐series data sets for arc degassing need to be improved in temporal and spatial coverage to robustly constrain volatile budgets and tectonic controls. Arc volatile budgets are strongly influenced by short‐lived degassing events and arc systems likely display significant short‐term variations in volatile output, calling for expansion of nascent geochemical monitoring networks to achieve spatial and temporal coverage similar to traditional geophysical networks.

A New Sulfur and Carbon Degassing Inventory for the Southern Central American Volcanic Arc: The Importance of Accurate Time-Series Data Sets and Possible Tectonic Processes Responsible for Temporal Variations in Arc-Scale Volatile Emissions

NASA Astrophysics Data System (ADS)

de Moor, J. M.; Kern, C.; Avard, G.; Muller, C.; Aiuppa, A.; Saballos, A.; Ibarra, M.; LaFemina, P.; Protti, M.; Fischer, T. P.

2017-12-01

This work presents a new database of SO2 and CO2 fluxes from the Southern Central American Volcanic Arc (SCAVA) for the period 2015-2016. We report ˜300 SO2 flux measurements from 10 volcanoes and gas ratios from 11 volcanoes in Costa Rica and Nicaragua representing the most extensive available assessment of this ˜500 km arc segment. The SO2 flux from SCAVA is estimated at 6,240 ± 1,150 T/d, about a factor of three higher than previous estimations (1972-2013). We attribute this increase in part to our more complete assessment of the arc. Another consideration in interpreting the difference is the context of increased volcanic activity, as there were more eruptions in 2015-2016 than in any period since ˜1980. A potential explanation for increased degassing and volcanic activity is a change in crustal stress regime (from compression to extension, opening volcanic conduits) following two large (Mw > 7) earthquakes in the region in 2012. The CO2 flux from the arc is estimated at 22,500 ± 4,900 T/d, which is equal to or greater than estimates of C input into the SCAVA subduction zone. Time-series data sets for arc degassing need to be improved in temporal and spatial coverage to robustly constrain volatile budgets and tectonic controls. Arc volatile budgets are strongly influenced by short-lived degassing events and arc systems likely display significant short-term variations in volatile output, calling for expansion of nascent geochemical monitoring networks to achieve spatial and temporal coverage similar to traditional geophysical networks.

The effect of regional groundwater on carbon dioxide and methane emissions from a lowland rainforest stream in Costa Rica

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oviedo-Vargas, Diana; Genereux, David P.; Dierick, Diego

In the tropical rainforest at La Selva Biological Station in Costa Rica, regional bedrock groundwater high in dissolved carbon discharges into some streams and wetlands, with the potential for multiple cascading effects on ecosystem carbon pools and fluxes. We investigated carbon dioxide (CO 2) and methane (CH 4) degassing from two streams at La Selva: the Arboleda, where ~1/3 of the streamflow is from regional groundwater, and the Taconazo, fed exclusively by local groundwater recharged within the catchment. The regional groundwater inflow to the Arboleda had no measurable effect on stream gas exchange velocity, dissolved CH 4 concentration, or CHmore » 4 emissions but significantly increased stream CO 2 concentration and degassing. CO 2 evasion from the reach of the Arboleda receiving regional groundwater (lower Arboleda) averaged 5.5 mol C m -2 d -1, ~7.5x higher than the average (0.7 mol C m -2 d -1) from the stream reaches with no regional groundwater inflow (the Taconazo and upper Arboleda). Carbon emissions from both streams were dominated by CO 2; CH 4 accounted for only 0.06-1.70% of the total (average of both streams: 5 x10 -3 mol C m -2 d -1). Annual stream degassing fluxes normalized by watershed area were 48 and 299 g C m -2 for the Taconazo and Arboleda, respectively. CO 2 degassing from the Arboleda is a significant carbon flux, similar in magnitude to the average net ecosystem exchange estimated by eddy covariance. As a result, examining the effects of catchment connections to underlying hydrogeological systems can help avoid overestimation of ecosystem respiration and advance our understanding of carbon source/sink status and overall terrestrial ecosystem carbon budgets.« less

The effect of regional groundwater on carbon dioxide and methane emissions from a lowland rainforest stream in Costa Rica

DOE PAGES

Oviedo-Vargas, Diana; Genereux, David P.; Dierick, Diego; ...

2015-12-22

In the tropical rainforest at La Selva Biological Station in Costa Rica, regional bedrock groundwater high in dissolved carbon discharges into some streams and wetlands, with the potential for multiple cascading effects on ecosystem carbon pools and fluxes. We investigated carbon dioxide (CO 2) and methane (CH 4) degassing from two streams at La Selva: the Arboleda, where ~1/3 of the streamflow is from regional groundwater, and the Taconazo, fed exclusively by local groundwater recharged within the catchment. The regional groundwater inflow to the Arboleda had no measurable effect on stream gas exchange velocity, dissolved CH 4 concentration, or CHmore » 4 emissions but significantly increased stream CO 2 concentration and degassing. CO 2 evasion from the reach of the Arboleda receiving regional groundwater (lower Arboleda) averaged 5.5 mol C m -2 d -1, ~7.5x higher than the average (0.7 mol C m -2 d -1) from the stream reaches with no regional groundwater inflow (the Taconazo and upper Arboleda). Carbon emissions from both streams were dominated by CO 2; CH 4 accounted for only 0.06-1.70% of the total (average of both streams: 5 x10 -3 mol C m -2 d -1). Annual stream degassing fluxes normalized by watershed area were 48 and 299 g C m -2 for the Taconazo and Arboleda, respectively. CO 2 degassing from the Arboleda is a significant carbon flux, similar in magnitude to the average net ecosystem exchange estimated by eddy covariance. As a result, examining the effects of catchment connections to underlying hydrogeological systems can help avoid overestimation of ecosystem respiration and advance our understanding of carbon source/sink status and overall terrestrial ecosystem carbon budgets.« less

Degassing of Cl, F, Li and Be during extrusion and crystallization of the rhyolite dome at Volcán Chaitén, Chile during 2008 and 2009

USGS Publications Warehouse

Lowenstern, Jacob B.; Bleick, Heather; Vazquez, Jorge A.; Castro, Jonathan M.; Larson, Peter B.

2012-01-01

We investigated the distribution of Cl, F, Li, and Be in pumices, obsidians, and crystallized dome rocks at Chaitén volcano in 2008–2009 in order to explore the behavior of these elements during explosive and effusive volcanic activity. Electron and ion microprobe analyses of matrix and inclusion glasses from pumice, obsidian, and microlite-rich dome rock indicate that Cl and other elements were lost primarily during crystallization of the rhyolitic dome after it had approached the surface. Glass in pumice and microlite-free obsidian has 888 ± 121 ppm Cl, whereas residual glass in evolved microlite-rich dome rock generally retains less Cl (as low as 0.7 Mt Cl, with a potential maximum of 1.8 Mt for the entire 0.8-km3 dome. Elemental variations reflect an integrated bulk distribution ratio for Cl > 1.7 (1.7 times more Cl was degassed or incorporated into crystals than remained in the melt). Because Cl is lost dominantly as the very last H2O is degassed, and Cl is minimally (if at all) partitioned into microlites, the integrated vapor/melt distribution ratio for Cl exceeds 200 (200 times more Cl in the evolved vapor than in the melt). Cl is likely lost as HCl, which is readily partitioned into magmatic vapor at low pressure. Cl loss is accelerated by the change in the composition of the residual melt due to microlite growth. Cl loss also may be affected by open-system gas fluxing. Integrated vapor-melt distribution ratios for Li, F, and Be all exceed 1,000. On degassing, an unknown fraction of these volatiles could be immediately dissolved in rainwater.

Deep magmatic degassing versus scrubbing: Elevated CO2 emissions and C/S in the lead-up to the 2009 eruption of Redoubt Volcano, Alaska

USGS Publications Warehouse

Werner, Cynthia A.; Evans, William C.; Kelly, Peter; McGimsey, Robert G.; Pfeffer, Melissa; Doukas, Michael P.; Neal, Christina

2012-01-01

We report CO2, SO2, and H2S emission rates and C/S ratios during the five months leading up to the 2009 eruption of Redoubt Volcano, Alaska. CO2emission rates up to 9018 t/d and C/S ratios ≥30 measured in the months prior to the eruption were critical for fully informed forecasting efforts. Observations of ice-melt rates, meltwater discharge, and water chemistry suggest that surface waters represented drainage from surficial, perched reservoirs of condensed magmatic steam and glacial meltwater. These fluids scrubbed only a few hundred tonnes/day of SO2, not the >2100 t/d SO2expected from degassing of magma in the mid- to upper crust (3–6.5 km), where petrologic analysis shows the final magmatic equilibration occurred. All data are consistent with upflow of a CO2-rich magmatic gas for at least 5 months prior to eruption, and minimal scrubbing of SO2by near-surface groundwater. The high C/S ratios observed could reflect bulk degassing of mid-crustal magma followed by nearly complete loss of SO2in a deep magmatic-hydrothermal system. Alternatively, high C/S ratios could be attributed to decompressional degassing of low silica andesitic magma that intruded into the mid-crust in the 5 months prior to eruption, thereby mobilizing the pre-existing high silica andesite magma or mush in this region. The latter scenario is supported by several lines of evidence, including deep long-period earthquakes (−28 to −32 km) prior to and during the eruption, and far-field deformation following the onset of eruptive activity.

Elimination of gases and contamination from water

NASA Technical Reports Server (NTRS)

Buck, A. P.

1970-01-01

Filtration system with membrane type hydrophilic and hydrophobic filters gives absolute filtration with automatic venting of freed gases, and prevents backward transmission of contamination with no bacterial growth through the filters. Filter aids in degassing industrial solutions and in removing oxygen from sea water.

Diffuse CO2 degassing at Vesuvio, Italy

NASA Astrophysics Data System (ADS)

Frondini, Francesco; Chiodini, Giovanni; Caliro, Stefano; Cardellini, Carlo; Granieri, Domenico; Ventura, Guido

2004-10-01

At Vesuvio, a significant fraction of the rising hydrothermal-volcanic fluids is subjected to a condensation and separation process producing a CO2-rich gas phase, mainly expulsed through soil diffuse degassing from well defined areas called diffuse degassing structures (DDS), and a liquid phase that flows towards the outer part of the volcanic cone. A large amount of thermal energy is associated with the steam condensation process and subsequent cooling of the liquid phase. The total amount of volcanic-hydrothermal CO2 discharged through diffuse degassing has been computed through a sequential Gaussian simulation (sGs) approach based on several hundred accumulation chamber measurements and, at the time of the survey, amounted to 151 t d-1. The steam associated with the CO2 output, computed assuming that the original H2O/CO2 ratio of hydrothermal fluids is preserved in fumarolic effluents, is 553 t d-1, and the energy produced by the steam condensation and cooling of the liquid phase is 1.47×1012 J d-1 (17 MW). The location of the CO2 and temperature anomalies show that most of the gas is discharged from the inner part of the crater and suggests that crater morphology and local stratigraphy exert strong control on CO2 degassing and subsurface steam condensation. The amounts of gas and energy released by Vesuvio are comparable to those released by other volcanic degassing areas of the world and their estimates, through periodic surveys of soil CO2 flux, can constitute a useful tool to monitor volcanic activity.

Geochemical evidence for a magmatic CO2 degassing event at Mammoth Mountain, California, September-December 1997

USGS Publications Warehouse

McGee, K.A.; Gerlach, T.M.; Kessler, R.; Doukas, M.P.

2000-01-01

Recent time series soil CO2 concentration data from monitoring stations in the vicinity of Mammoth Mountain, California, reveal strong evidence for a magmatic degassing event during the fall of 1997 lasting more than 2 months. Two sensors at Horseshoe Lake first recorded the episode on September 23, 1997, followed 10 days later by a sensor on the north flank of Mammoth Mountain. Direct degassing from shallow intruding magma seems an implausible cause of the degassing event, since the gas released at Horseshoe Lake continued to be cold and barren of other magmatic gases, except for He. We suggest that an increase in compressional strain on the area south of Mammoth Mountain driven by movement of major fault blocks in Long Valley caldera may have triggered an episode of increased degassing by squeezing additional accumulated CO2 from a shallow gas reservoir to the surface along faults and other structures where it could be detected by the CO2 monitoring network. Recharge of the gas reservoir by CO2 emanating from the deep intrusions that probably triggered deep long-period earthquakes may also have contributed to the degassing event. The nature of CO2 discharge at the soil-air interface is influenced by the porous character of High Sierra soils and by meteorological processes. Solar insolation is the primary source of energy for the Earth atmosphere and plays a significant role in most diurnal processes at the Earth surface. Data from this study suggest that external forcing due largely to local orographic winds influences the fine structure of the recorded CO2 signals.

No effect of H2O degassing on the oxidation state of magmatic liquids

NASA Astrophysics Data System (ADS)

Waters, Laura E.; Lange, Rebecca A.

2016-08-01

The underlying cause for why subduction-zone magmas are systematically more oxidized than those formed at mid-ocean spreading ridges is a topic of vigorous debate. It is either a primary feature inherited from the subduction of oxidized oceanic crust into the mantle or a secondary feature that develops because of H2O degassing and/or magma differentiation. Low total iron contents and high melt H2O contents render rhyolites sensitive to any effect of H2O degassing on ferric-ferrous ratios. Here, pre-eruptive magmatic Fe2+ concentrations, measured using Fe-Ti oxides that co-crystallized with silicate phenocrysts under hydrous conditions, are compared with Fe2+ post-eruptive concentrations in ten crystal-poor, fully-degassed obsidian samples; five are microlite free. No effect of H2O degassing on the ferric-ferrous ratio is found. In addition, Fe-Ti oxide data from this study and the literature show that arc magmas are systematically more oxidized than both basalts and hydrous silicic melts from Iceland and Yellowstone prior to extensive degassing. Nor is there any evidence that differentiation (i.e., crystal fractionation, crustal assimilation) is the cause of the higher redox state of arc magmas relative to those of Iceland/Yellowstone rhyolites. Instead, the evidence points to subduction of oxidized crust and the release of an H2O-rich fluid and/or melt with a high oxygen fugacity (fO2), which plays a role during H2O-flux melting of the mantle in creating basalts that are relatively oxidized.

Long period seismicity and very long period infrasound driven by shallow magmatic degassing at Mount Pagan, Mariana Islands

USGS Publications Warehouse

Lyons, John; Haney, Matt; Werner, Cynthia A.; Kelly, Peter; Patrick, Matthew R.; Kern, Christoph; Trusdell, Frank A.

2016-01-01

Long period (LP) seismicity and very long period infrasound (iVLP) were recorded during continuous degassing from Mount Pagan, Mariana Islands, in July 2013 to January 2014. The frequency content of the LP and iVLP events and delay times between the two arrivals were remarkably stable and indicate nearly co-located sources. Using phase-weighted stacking over similar events to dampen noise, we find that the LP source centroid is located 60 m below and 180 m west of the summit vent. The moment tensor reveals a volumetric source modeled as resonance of a subhorizontal sill intersecting a dike. We model the seismoacoustic wavefields with a coupled earth-air 3-D finite difference code. The ratios of pressure to velocity measured at the infrasound arrays are an order of magnitude larger than the synthetic ratios, so the iVLP is not the result of LP energy transmitting into the atmosphere at its epicenter. Based on crater shape and dimensions determined by structure from motion, we model the iVLP as acoustic resonance of an exponential horn. The source of the continuous plume from gas analysis is shallow magmatic degassing, which repeatedly pressurized the dike-sill portion of the conduit over the 7 months of observation. Periodic gas release caused the geologically controlled sill to partially collapse and resonate, while venting of gas at the surface triggered resonance in the crater. LP degassing only accounts for ~12% of total degassing, indicating that most degassing is relatively aseismic and that multiple active pathways exist beneath the vent.

Using dissolved gas analysis to investigate the performance of an organic carbon permeable reactive barrier for the treatment of mine drainage

USGS Publications Warehouse

Williams, R.L.; Mayer, K.U.; Amos, R.T.; Blowes, D.W.; Ptacek, C.J.; Bain, J.G.

2007-01-01

The strongly reducing nature of permeable reactive barrier (PRB) treatment materials can lead to gas production, potentially resulting in the formation of gas bubbles and ebullition. Degassing in organic C based PRB systems due to the production of gases (primarily CO2 and CH4) is investigated using the depletion of naturally occurring non-reactive gases Ar and N2, to identify, confirm, and quantify chemical and physical processes. Sampling and analysis of dissolved gases were performed at the Nickel Rim Mine Organic Carbon PRB, which was designed for the treatment of groundwater contaminated by low quality mine drainage characterized by slightly acidic pH, and elevated Fe(II) and SO4 concentrations. A simple 4-gas degassing model was used to analyze the dissolved gas data, and the results indicate that SO4 reduction is by far the dominant process of organic C consumption within the barrier. The data provided additional information to delineate rates of microbially mediated SO4 reduction and confirm the presence of slow and fast flow zones within the barrier. Degassing was incorporated into multicomponent reactive transport simulations for the barrier and the simulations were successful in reproducing observed dissolved gas trends.

A review of noble gas geochemistry in relation to early Earth history

NASA Technical Reports Server (NTRS)

Kurz, M. D.

1985-01-01

One of the most fundamental noble gas constraints on early Earth history is derived from isotopic differences in (129)Xe/(130)Xe between various terrestrial materials. The short half life (17 m.y.) of extinct (129I, parent of (129)Xe, means that these differences must have been produced within the first 100 m.y. after terrestrial accretion. The identification of large anomalies in (129)Xe/(130)Xe in mid ocean ridge basalts (MORB), with respect to atmospheric xenon, suggests that the atmosphere and upper mantle have remained separate since that time. This alone is a very strong argument for early catastrophic degassing, which would be consistent with an early fractionation resulting in core formation. However, noble gas isotopic systematics of oceanic basalts show that the mantle cannot necessarily be regarded as a homogeneous system, since there are significant variations in (3)He/(4)He, (40)Ar/(36)Ar, and (129)Xe/(130)Xe. Therefore, the early degassing cannot be considered to have acted on the whole mantle. The specific mechanisms of degassing, in particular the thickness and growth of the early crust, is an important variable in understanding present day noble gas inventories. Another constraint can be obtained from rocks that are thought to be derived from near the lithosphere asthenosphere boundary: ultramafic xenoliths.

Degassing Processes at Persistently Active Explosive Volcanoes

NASA Astrophysics Data System (ADS)

Smekens, Jean-Francois

Among volcanic gases, sulfur dioxide (SO2) is by far the most commonly measured. More than a monitoring proxy for volcanic degassing, SO 2 has the potential to alter climate patterns. Persistently active explosive volcanoes are characterized by short explosive bursts, which often occur at periodic intervals numerous times per day, spanning years to decades. SO 2 emissions at those volcanoes are poorly constrained, in large part because the current satellite monitoring techniques are unable to detect or quantify plumes of low concentration in the troposphere. Eruption plumes also often show high concentrations of ash and/or aerosols, which further inhibit the detection methods. In this work I focus on quantifying volcanic gas emissions at persistently active explosive volcanoes and their variations over short timescales (minutes to hours), in order to document their contribution to natural SO2 flux as well as investigate the physical processes that control their behavior. In order to make these measurements, I first develop and assemble a UV ground-based instrument, and validate it against an independently measured source of SO2 at a coal-burning power plant in Arizona. I establish a measurement protocol and demonstrate that the instrument measures SO 2 fluxes with < 20 % error. Using the same protocol, I establish a record of the degassing patterns at Semeru volcano (Indonesia), a volcano that has been producing cycles of repeated explosions with periods of minutes to hours for the past several decades. Semeru produces an average of 21-71 tons of SO2 per day, amounting to a yearly output of 8-26 Mt. Using the Semeru data, along with a 1-D transient numerical model of magma ascent, I test the validity of a model in which a viscous plug at the top of the conduit produces cycles of eruption and gas release. I find that it can be a valid hypothesis to explain the observed patterns of degassing at Semeru. Periodic behavior in such a system occurs for a very narrow range of conditions, for which the mass balance between magma flux and open-system gas escape repeatedly generates a viscous plug, pressurizes the magma beneath the plug, and then explosively disrupts it.

Rare gases in Samoan xenoliths

NASA Astrophysics Data System (ADS)

Poreda, R. J.; Farley, K. A.

1992-09-01

The rare gas isotopic compositions of residual harzburgite xenoliths from Savai'i (SAV locality) and an unnamed seamount south of the Samoan chain (PPT locality) provide important constraints on the rare gas evolution of the mantle and atmosphere. Despite heterogeneous trace element compositions, the rare gas characteristics of the xenoliths from each of the two localities are strikingly similar. SAV and PPT xenoliths have 3He/ 4He ratios of11.1 ± 0.5 R A and21.6 ± 1 R A, respectively; this range is comparable to the 3He/ 4He ratios in Samoan lavas and clearly demonstrates that they have trapped gases from a relatively undegassed reservoir. The neon results are not consistent with mixing between MORB and a plume source with an atmospheric signature. Rather, the neon isotopes reflect either a variably degassed mantle (with a relative order of degassing of Loihi < PPT < Reunion < SAV < MORB), or mixing between the Loihi source and MORB. The data supports the conclusions of Honda et al. that the 20Ne/ 22Ne ratio in the mantle more closely resembles the solar ratio than the atmospheric one. 40Ar/ 36Ar ratios in the least contaminated samples range from 4,000 to 12,000 with the highest values in the 22 RA PPT xenoliths. There is no evidence for atmospheric 40Ar/ 36Ar ratios in the mantle source of these samples, which indicates that the lower mantle may have 40Ar/ 36Ar ratios in excess of 5,000. Xenon isotopic anomalies in 129Xe and 136Xe are as high as 6%, or about half of the maximum MORB excess and are consistent with the less degassed nature of the Samoan mantle source. These results contradict previous suggestions that the high 3He/ 4He mantle has a near-atmospheric heavy rare gas isotopic composition.

Interactions between tectonics, silicate weathering, and climate explored with carbon cycle modeling

NASA Astrophysics Data System (ADS)

Penman, D. E.; Caves Rugenstein, J. K.; Ibarra, D. E.; Winnick, M.

2017-12-01

Earth's long-term carbon cycle is thought to benefit from a stabilizing negative feedback in the form of CO2 consumption by the chemical weathering of silicate minerals: during periods of elevated atmospheric pCO2, chemical weathering rates increase, thus consuming more atmospheric CO2 and cooling global climate, whereas during periods of low pCO2, weathering rates decrease, allowing buildup of CO2 in the atmosphere and warming. At equilibrium, CO2 consumption by silicate weathering balances volcanic CO2 degassing at a specific atmospheric pCO2 dictated by the relationship between total silicate weathering rate and pCO2: Earth's "weathering curve." We use numerical carbon cycle modeling to demonstrate that the shape and slope of the weathering curve is crucial to understanding proposed tectonic controls on pCO2 and climate. First, the shape of the weathering curve dictates the equilibrium response of the carbon cycle to changes in the rate of background volcanic/solid Earth CO2 degassing, which has been suggested to vary significantly with plate tectonic reorganizations over geologic timescales. Second, we demonstrate that if tectonic events can significantly change the weathering curve, this can act as an effective driver of pCO2 and climate on tectonic timescales by changing the atmospheric pCO2 at which silicate weathering balances a constant volcanic/solid Earth degassing rate. Finally, we review the complex interplay of environmental factors that affect modern weathering rates in the field and highlight how the resulting uncertainty surrounding the shape of Earth's weathering curve significantly hampers our ability to quantitatively predict the response of pCO2 and climate to tectonic forcing, and thus represents a substantial knowledge gap in Earth science. We conclude with strategies for closing this knowledge gap by using precise paleoclimatic reconstructions of intervals with known tectonic forcings.

Helium in the Archaean komatiites revisited: significantly high 3He/4He ratios revealed by fractional crushing gas extraction

NASA Astrophysics Data System (ADS)

Matsumoto, T.; Seta, A.; Matsuda, J.; Chen, Y.; Arai, S.

2001-12-01

In order to provide constraints on 3He/4He ratios in the Archaean mantle source, we have analysed helium isotopic compositions in 2.7Ga old Archaean komatiites from the Abitibi green stone belt, Ontario, Canada. Two spinifex-textured komatiites yielded significantly high 3He/4He ratios of about 30Ra (where Ra denotes the atmospheric 3He/4He ratio) in fractions released by sequential crushing. These results are the first confirmation of the occurrence of high 3He/4He component in Archaean komatiites after the intriguing finding by [Richard et al., Science 273 (1996) 93-95] in komatiites from a nearby locality, Alexo. We also found that the crystal structure of the komatiites was significantly enriched in a radiogenic component (4He) and that the radiogenic 4He in the crystal structure was actually degassed by a crushing gas extraction, indicating that the nominal 3He/4He ratios measured by crushing are lower limits for the 3He/4He ratio of an intrinsic component. By constraining the release behaviour of radiogenic 4He by crushing, we have estimated the initial 3He/4He ratio of an inclusion-trapped component to be 73 (+7.8/-5.5) Ra. A mantle source with such a high 3He/4He ratio at 2.7Ga would, if evolved in a closed-system, have present-day 3He/4He ratio of 46-60Ra, indicating that the komatiites from Munro had been trapped their helium from a mantle reservoir with very high 3He/4He ratio in the context of the present-day value. However, whether or not such a source can be considered as the one that is equivalent to the primitive mantle source (such that sampled at hotspots) is highly model-dependent. If a closed-system evolution model were assumed, helium in the Munro komatiites is not likely to be derived from the MORB-source-like reservoir. However, the notion that the komatiites may be derived from a depleted reservoir in terms of trace elemental and isotopic geochemistry might requires an alternative view for the evolution of 3He/4He ratio in ancient mantle reservoirs, as has been demonstrated by a recent model calculation by [Seta et al., Earth Planet. Sci. Lett. 188 (2001) 211-219] in which the 3He/4He ratios in the MORB mantle source could have been as high as those in the primitive (less-degassed) mantle source in Archaean.

Helium in the Archean komatiites revisited: significantly high 3He/ 4He ratios revealed by fractional crushing gas extraction

NASA Astrophysics Data System (ADS)

Matsumoto, Takuya; Seta, Akihiro; Matsuda, Jun-ichi; Takebe, Masamichi; Chen, Yuelong; Arai, Shoji

2002-03-01

In order to provide constraints on 3He/ 4He ratios in the Archean mantle source, we have analyzed helium isotopic compositions in 2.7 Ga old Archean komatiites from the Abitibi green stone belt, Ontario, Canada. Two spinifex-textured komatiites yielded significantly high 3He/ 4He ratios of about 30 Ra (where Ra denotes the atmospheric 3He/ 4He ratio) in fractions released by sequential crushing. These results are the first confirmation of the occurrence of high 3He/ 4He ratios in Archean komatiites after the intriguing finding by Richard et al. [Science 273 (1996) 93-95] in komatiites from a nearby locality, Alexo. We also found that the crystal structure of the komatiites was significantly enriched in a radiogenic component ( 4He) and that this 4He was actually degassed by crushing gas extraction, indicating that the nominal 3He/ 4He ratios measured by crushing are lower limits for the 3He/ 4He ratio of the intrinsic component. By constraining the release behavior of radiogenic 4He by crushing, we have estimated the initial 3He/ 4He ratio of the inclusion-trapped component to be 73.0 +7.8-5.5 Ra. A mantle source with such a high 3He/ 4He ratio at 2.7 Ga, if evolved in a closed system, would have a present-day 3He/ 4He ratio of 46-60 Ra, indicating that the komatiites from Munro have trapped their helium from a mantle reservoir with a very high 3He/ 4He ratio in the context of the present-day value. However, whether or not such a source can be considered as equivalent to the primitive mantle source (such that sampled at hotspots) is highly model-dependent. If a closed system evolution model is assumed, helium in the Munro komatiites is not likely to be derived from the mid-ocean ridge basalt (MORB) source-like reservoir. However, the notion that the komatiites may be derived from a depleted reservoir in terms of trace elemental and isotopic geochemistry might require an alternative view for the 3He/ 4He evolution in ancient mantle reservoirs, as has been demonstrated by a recent model calculation by Seta et al. [Earth Planet. Sci. Lett. 188 (2001) 211-219] in which the 3He/ 4He ratios in the MORB mantle source could have been as high as those in the primitive (less degassed) mantle source in the Archean.

Degassing history of water, sulfur, and carbon in submarine lavas from Kilauea Volcano, Hawaii

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dixon, J.E.; Stolper, E.M.; Clague, D.A.

1991-05-01

Major, minor, and dissolved volatile element concentrations were measured in tholeiitic glasses from the submarine portion (Puna Ridge) of the east rift zone of Kilauea Volcano, Hawaii. Dissolved H{sub 2}O and S concentrations display a wide range relative to nonvolatile incompatible elements at all depths. This range cannot be readily explained by fractional crystallization, degassing of H{sub 2}O and S during eruption on the seafloor, or source region heterogeneities. Dissolved CO{sub 2} concentrations, in contrast, show a positive correlation with eruption depth and typically agree within error with the solubility at that depth. The authors propose that most magmas alongmore » the Puna Ridge result from (1) mixing of a relatively volatile-rich, undegassed component with magmas that experienced low pressure (perhaps subaerial) degassing during which substantial H{sub 2}O, S, and CO{sub 2} were lost, followed by (2) fractional crystallization of olivine, clinopyroxene, and plagioclase from this mixture to generate a residual liquid; and (3) further degassing, principally of CO{sub 2} for samples erupted deeper than 1,000 m, during eruption on the seafloor. They predict that average Kilauean primary magmas with 16% MgO contain {approximately}0.47 wt % H{sub 2}0, {approximately}900 ppm S, and have {delta}D values of {approximately}{minus}30 to {minus}40%. The model predicts that submarine lavas from wholly submarine volcanoes (i.e., Loihi), for which there is no opportunity to generate the degassed end member by low pressure degassing, will be enriched in volatiles relative to those from volcanoes whose summits have breached the sea surface (i.e., Kilauea and Mauna Loa).« less

Redox variations in Mauna Kea lavas, the oxygen fugacity of the Hawaiian plume, and the role of volcanic gases in Earth’s oxygenation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brounce, Maryjo; Stolper, Edward; Eiler, John

The behavior of C, H, and S in the solid Earth depends on their oxidation states, which are related to oxygen fugacity (fO2). Volcanic degassing is a source of these elements to Earth’s surface; therefore, variations in mantle fO2 may influence the fO2 at Earth’s surface. However, degassing can impact magmatic fO2 before or during eruption, potentially obscuring relationships between the fO2 of the solid Earth and of emitted gases and their impact on surface fO2. We show that low-pressure degassing resulted in reduction of the fO2 of Mauna Kea magmas by more than an order of magnitude. The leastmore » degassed magmas from Mauna Kea are more oxidized than midocean ridge basalt (MORB) magmas, suggesting that the upper mantle sources of Hawaiian magmas have higher fO2 than MORB sources. One explanation for this difference is recycling of material from the oxidized surface to the deep mantle, which is then returned to the surface as a component of buoyant plumes. It has been proposed that a decreasing pressure of volcanic eruptions led to the oxygenation of the atmosphere. Extension of our findings via modeling of degassing trends suggests that a decrease in eruption pressure would not produce this effect. If degassing of basalts were responsible for the rise in oxygen, it requires that Archean magmas had at least two orders of magnitude lower fO2 than modern magmas. Estimates of fO2 of Archean magmas are not this low, arguing for alternative explanations for the oxygenation of the atmosphere.« less

Redox variations in Mauna Kea lavas, the oxygen fugacity of the Hawaiian plume, and the role of volcanic gases in Earth's oxygenation.

PubMed

Brounce, Maryjo; Stolper, Edward; Eiler, John

2017-08-22

The behavior of C, H, and S in the solid Earth depends on their oxidation states, which are related to oxygen fugacity ( f O 2 ). Volcanic degassing is a source of these elements to Earth's surface; therefore, variations in mantle f O 2 may influence the f O 2 at Earth's surface. However, degassing can impact magmatic f O 2 before or during eruption, potentially obscuring relationships between the f O 2 of the solid Earth and of emitted gases and their impact on surface f O 2 We show that low-pressure degassing resulted in reduction of the f O 2 of Mauna Kea magmas by more than an order of magnitude. The least degassed magmas from Mauna Kea are more oxidized than midocean ridge basalt (MORB) magmas, suggesting that the upper mantle sources of Hawaiian magmas have higher f O 2 than MORB sources. One explanation for this difference is recycling of material from the oxidized surface to the deep mantle, which is then returned to the surface as a component of buoyant plumes. It has been proposed that a decreasing pressure of volcanic eruptions led to the oxygenation of the atmosphere. Extension of our findings via modeling of degassing trends suggests that a decrease in eruption pressure would not produce this effect. If degassing of basalts were responsible for the rise in oxygen, it requires that Archean magmas had at least two orders of magnitude lower f O 2 than modern magmas. Estimates of f O 2 of Archean magmas are not this low, arguing for alternative explanations for the oxygenation of the atmosphere.

Total (fumarolic + diffuse soil) CO2 output from Furnas volcano.

PubMed

Pedone, M; Viveiros, F; Aiuppa, A; Giudice, G; Grassa, F; Gagliano, A L; Francofonte, V; Ferreira, T

Furnas volcano, in São Miguel island (Azores), being the surface expression of rising hydrothermal steam, is the site of intense carbon dioxide (CO 2 ) release by diffuse degassing and fumaroles. While the diffusive CO 2 output has long (since the early 1990s) been characterized by soil CO 2 surveys, no information is presently available on the fumarolic CO 2 output. Here, we performed (in August 2014) a study in which soil CO 2 degassing survey was combined for the first time with the measurement of the fumarolic CO 2 flux. The results were achieved by using a GasFinder 2.0 tunable diode laser. Our measurements were performed in two degassing sites at Furnas volcano (Furnas Lake and Furnas Village), with the aim of quantifying the total (fumarolic + soil diffuse) CO 2 output. We show that, within the main degassing (fumarolic) areas, the soil CO 2 flux contribution (9.2 t day -1 ) represents a minor (~15 %) fraction of the total CO 2 output (59 t day -1 ), which is dominated by the fumaroles (~50 t day -1 ). The same fumaroles contribute to ~0.25 t day -1 of H 2 S, based on a fumarole CO 2 /H 2 S ratio of 150 to 353 (measured with a portable Multi-GAS). However, we also find that the soil CO 2 contribution from a more distal wider degassing structure dominates the total Furnas volcano CO 2 budget, which we evaluate (summing up the CO 2 flux contributions for degassing soils, fumarolic emissions and springs) at ~1030 t day -1 .

Redox variations in Mauna Kea lavas, the oxygen fugacity of the Hawaiian plume, and the role of volcanic gases in Earth’s oxygenation

PubMed Central

Stolper, Edward; Eiler, John

2017-01-01

The behavior of C, H, and S in the solid Earth depends on their oxidation states, which are related to oxygen fugacity (fO2). Volcanic degassing is a source of these elements to Earth’s surface; therefore, variations in mantle fO2 may influence the fO2 at Earth’s surface. However, degassing can impact magmatic fO2 before or during eruption, potentially obscuring relationships between the fO2 of the solid Earth and of emitted gases and their impact on surface fO2. We show that low-pressure degassing resulted in reduction of the fO2 of Mauna Kea magmas by more than an order of magnitude. The least degassed magmas from Mauna Kea are more oxidized than midocean ridge basalt (MORB) magmas, suggesting that the upper mantle sources of Hawaiian magmas have higher fO2 than MORB sources. One explanation for this difference is recycling of material from the oxidized surface to the deep mantle, which is then returned to the surface as a component of buoyant plumes. It has been proposed that a decreasing pressure of volcanic eruptions led to the oxygenation of the atmosphere. Extension of our findings via modeling of degassing trends suggests that a decrease in eruption pressure would not produce this effect. If degassing of basalts were responsible for the rise in oxygen, it requires that Archean magmas had at least two orders of magnitude lower fO2 than modern magmas. Estimates of fO2 of Archean magmas are not this low, arguing for alternative explanations for the oxygenation of the atmosphere. PMID:28784788

Redox variations in Mauna Kea lavas, the oxygen fugacity of the Hawaiian plume, and the role of volcanic gases in Earth's oxygenation

NASA Astrophysics Data System (ADS)

Brounce, Maryjo; Stolper, Edward; Eiler, John

2017-08-01

The behavior of C, H, and S in the solid Earth depends on their oxidation states, which are related to oxygen fugacity (fO2). Volcanic degassing is a source of these elements to Earth’s surface; therefore, variations in mantle fO2 may influence the fO2 at Earth’s surface. However, degassing can impact magmatic fO2 before or during eruption, potentially obscuring relationships between the fO2 of the solid Earth and of emitted gases and their impact on surface fO2. We show that low-pressure degassing resulted in reduction of the fO2 of Mauna Kea magmas by more than an order of magnitude. The least degassed magmas from Mauna Kea are more oxidized than midocean ridge basalt (MORB) magmas, suggesting that the upper mantle sources of Hawaiian magmas have higher fO2 than MORB sources. One explanation for this difference is recycling of material from the oxidized surface to the deep mantle, which is then returned to the surface as a component of buoyant plumes. It has been proposed that a decreasing pressure of volcanic eruptions led to the oxygenation of the atmosphere. Extension of our findings via modeling of degassing trends suggests that a decrease in eruption pressure would not produce this effect. If degassing of basalts were responsible for the rise in oxygen, it requires that Archean magmas had at least two orders of magnitude lower fO2 than modern magmas. Estimates of fO2 of Archean magmas are not this low, arguing for alternative explanations for the oxygenation of the atmosphere.

A permanent volcanic hazard hiding in diffuse degassing areas

NASA Astrophysics Data System (ADS)

Viveiros, Fátima; Silva, Catarina; Ferreira, Teresa; Pacheco, Joana; Luís Gaspar, João

2017-04-01

Carbon dioxide (CO2) is one of the most abundant volcanic gases and it is released not only during eruptive events, but also during periods of quiescence through fumaroles, springs and soil diffuse degassing areas. In this last case, CO2 is permanently and silently released from the soils and high CO2 concentrations can be measured if the gas accumulates in depressed and non-ventilated areas (such as caves, pits), or even if it enters in buildings. From a public health perspective CO2 is considered an inert asphyxiant gas and may be lethal when present in concentrations higher than 10 vol.%. In the last 30 years several diffuse degassing areas have been identified in different volcanic systems and lethal incidents due to high CO2 concentrations were reported in volcanic environments of Italy (Alban Hills), New Zealand (Rotorua), Cameroon (Lake Nyos and Lake Cameroon), USA (Mammoth Mountain) and Portugal (Azores archipelago). In the Azores volcanic archipelago several villages are located in diffuse degassing areas, where lethal indoor CO2 concentrations (> 20 vol.%) were measured. Recent studies showed that the rate of CO2 emission may change not only during seismo-volcanic unrest, but also due to changes in the meteorological conditions (e.g. barometric pressure, rainfall, wind speed). Few works are available in the literature with permanent monitoring of indoor CO2 in diffuse degassing environments and the monitoring tests are usually applied during a short period of time. This study shows the results of four years (2012-2016) of permanent CO2 monitoring in 12 buildings placed at Caldeiras da Ribeira Grande, an area located in the north flank of Fogo Volcano (São Miguel Island, Azores archipelago), where thermal anomalies and CO2 emissions were detected. CO2 fluxes as high as 20000 g m-2 d-1 are released from the soils and temperature in some sites reaches 100°C. Spike-like and long term variations are observed in the time series recorded by a total of 52 infrared CO2 detectors installed. Results highlight that CO2 can reach hazardous concentrations (> 15 vol.%) due to meteorological changes and show the occurrence of seasonal variations. Different indoor CO2 patterns are displayed depending on the location of the buildings over thermal anomalous zone. Due to its density at standard temperature and pressure, CO2 tends to accumulate in the underground and/or in the ground floor of the buildings, however in the present study higher CO2 concentrations were also measured in the upper floors of some buildings, fact that is correlated with the presence of thermal anomaly. Results obtained based on this robust and continuous monitoring system show once again that indoor CO2 can reach frequently lethal concentrations even in periods of quiescence and that inhabitants of these buildings are exposed to a permanent and quiet hazard, which is detected only through the use of specific instruments. The existence of thermal anomaly associated with the CO2 emission is also responsible for different patterns when compared with the "cold" CO2 degassing areas.

Degassing procedure for ultrahigh vacuum

NASA Technical Reports Server (NTRS)

Moore, B. C.

1979-01-01

Calculations based on diffusion coefficients and degassing rates for stainless-steel vacuum chambers indicate that baking at lower temperatures for longer periods give lower ultimate pressures than rapid baking at high temperatures. Process could reduce pressures in chambers for particle accelerators, fusion reactors, material research, and other applications.

Remote Laser Welding of Zinc Coated Steel Sheets in an Edge Lap Configuration with Zero Gap

NASA Astrophysics Data System (ADS)

Roos, Christian; Schmidt, Michael

Remote Laser Welding (RLW) of zinc-coated steel sheets is a great challenge for the automotive industry but offers high potentials with respect to flexibility and costs. In state of the art applications, sheets are joined in overlap configuration with a preset gap for a stable zinc degassing. This paper investigates RLW of fillets without a preset gap and conditions for a stable process. The influence of process parameters on weld quality and process stability is shown. Experimental data give evidence, that the degassing of zinc through the capillary and the rear melt pool are the major degassing mechanisms. Furthermore the paper gives experimental validation of the zinc degassing in advance of the process zone to the open side of the fillet. Chemical analysis of the hot-dip galvanized zinc coating proof the iron-zinc-alloys to be the reason for a limited effectiveness of this mechanism in comparison to pure zinc as intermediate.

Facile generation of cell microarrays using vacuum degassing and coverslip sweeping.

PubMed

Wang, Min S; Luo, Zhen; Cherukuri, Sundar; Nitin, Nitin

2014-07-15

A simple method to generate cell microarrays with high-percentage well occupancy and well-defined cell confinement is presented. This method uses a synergistic combination of vacuum degassing and coverslip sweeping. The vacuum degassing step dislodges air bubbles from the microwells, which in turn enables the cells to enter the microwells, while the physical sweeping step using a glass coverslip removes the excess cells outside the microwells. This low-cost preparation method provides a simple solution to generating cell microarrays that can be performed in basic research laboratories and point-of-care settings for routine cell-based screening assays. Copyright © 2014 Elsevier Inc. All rights reserved.

Hybrid Macro-Micro Fluidics System for a Chip-Based Biosensor

DTIC Science & Technology

2002-02-18

fluids, including elements based on acoustic, centrifugal and electromagnetic forces; electroosmotic and electrophoretic effects; micro- mechanical and... mixed then degassed in a desiccator under vacuum for 30 min. The mixture was poured into the mold and allowed to stand for 5 min to self-level. The PDMS

40 CFR 98.128 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... GREENHOUSE GAS REPORTING Fluorinated Gas Production § 98.128 Definitions. Except as provided in this section... not in light liquid service; each barrier fluid system is equipped with a sensor that will detect... pressure; or (2) Equipped with a barrier fluid degassing reservoir that is routed to a process or fuel gas...

MOLA Constraints on Lava Flow Rheologies

NASA Technical Reports Server (NTRS)

Glaze, L. S.; Stofan, E. R.; Baloga, S. M.; McColley, S.; Sakimoto, S.; Mitchell, D.

2002-01-01

MOLA data allow us to distinguish the nature of a viscosity change in the presence of degassing. For a 35 km flow in Elysium we conclude that the viscosity increased exponentially at least 50 times, compared to only 10 times if no degassing occurs. Additional information is contained in the original extended abstract.

Sulfur partitioning applied to LIP magmatism - A new approach for quantifying sulfur concentration in basaltic melts

NASA Astrophysics Data System (ADS)

Marzoli, A.; Callegaro, S.; Baker, D. R.; De Min, A.; Cavazzini, G.; Martin, W.; Renne, P. R.; Svensen, H.

2017-12-01

Magmatism from Large Igneous Provinces (LIPs) has often been demonstrated synchronous with mass extinctions. Prominent examples in the Phanerozoic are the end-Permian, end-Triassic and end-Cretaceous extinctions, associated with, respectively, the Siberian Traps, the CAMP and the Deccan Traps. Despite the growing body of evidence for causal and temporal links between these events, it is not yet entirely clear how a LIP can severly affect the global environment. Degassing of volatile species such as S, C and halogen compounds directly from LIP magmas, and from contact metamorphism of volatile-rich sediments heated by the intrusions appears as the most realistic mechanism. Modeling the atmospheric response to LIP gas loads requires quantitative constraints on the degassed volatiles and emission rates, but these are challenging to obtain for magmatic systems from the geologic past. We therefore propose a new method to calculate the sulfur load of basaltic melts, by measuring sulfur content in natural minerals (clinopyroxene and plagioclase) and combining it with an experimentally determined partition coefficients (KD). We measured partitioning of sulfur between crystals and melt by ion microprobe (Nordsim, Stockholm) on experimentally produced crystals and glasses. Piston cylinder experiments were performed with conditions typical of basaltic, andesitic and dacitic melts (800 or 1000 MPa; 1000°-1350°C), to constrain KD variations as a function of melt composition, oxidation state and water content. We obtained a clinopyroxene/melt sulfur KD of 0.001 for basaltic melts, which can be applied to natural continental flood basalts. Preliminary results from thoroughly-dated lava piles from the Deccan Traps and from the Siberian Traps sills confirm that most of the basalts were at or close to sulfide saturation (ca. 2000 ppm for low fO2 melts). These results can be compared with the scenario modeled by Schmidt et al. (2016) for Deccan Traps magmatism, for which sulfur from flood basalts can only cause a biotic crisis if released in repeated and closely-spaced pulses. Combined with other studies of H, C, Cl and F partitioning, our study on sulfur allows complete assessment of the volatile cocktail contained in, and exsolved from, a basaltic melt. Schmidt A., et al. (2016). Nature Geosciences 9, 77-82.

Crustal Deformation Associated With the 2000 Eruption and Degassing Process of Miyakejima, Izu Islands, Japan

NASA Astrophysics Data System (ADS)

Nishimura, T.; Ozawa, S.; Murakami, M.; Sagiya, T.; Yarai, H.; Tada, T.; Kaidzu, M.

2001-12-01

Miyakejima is located in the northern part of the Izu Islands lying along the boundary between the Pacific plate and the Philippine Sea plate. Miyakejima volcano erupted on Miyakejima is located in the northern part of the Izu Islands which are a chain of volcanoes lying along the boundary between the Pacific plate and the Philippine Sea plate. Miyakejima volcano erupted on June 27, 2000 after the quiescence of 17 years. First eruption is a small submarine eruption 1.5km off the western coast of Miyakejima. Subsequently, several summit eruptions as tephra ejecta occurred in July and August 2000. The summit collapsed just after the first summit eruption and a caldera was formed for 40 days. Collapsed volume and erupted volume are estimated to be 0.6km3 and 0.02km3, respectively. In September 2000, the collapse caldera started emitting a large amount of volcanic gasses. A peak amount of degassing SO2 is ~70000 ton/day in the period from October to December 2000. Amount of volcanic gas is decreasing gradually and is 15000 ton/day (SO2 ) now. However, it is still larger than other active volcanoes. Permanent GPS data reveals the spatial pattern and time evolution of ground deformation. Inflation of Miyakejima was observed by continuous GPS and leveling before the 2000 eruption. The observed displacements associated with the 2000 eruption show radial pattern suggesting shrinking of the island and subsidence. This pattern continues for 14 months from July 2000. Though the rate of crustal deformation is almost constant from July to August 2000, it is decreasing exponentially with a time constant of ~150days from September 2000. We assumed a point deflation source and inverted the observed displacement to estimate parameters of the point source. Volume decrease and depth of the deflation source is 0.12km3 and 4.2km from July to August 2000. We interpret that it is the squeezing of magma from a magma chamber of Miyakejima volcano. The displacement observed in neighbor islands suggests that the squeezed magma and collapsed material of Miyakejima migrated northwestward by as much as 30km in the form of a dike intrusion. Volume decrease and depth of the deflation source is 2.9km and 0.016km3 from September 2000 to May 2001. Decreasing rate of the deflation source is an order of magnitude smaller than that of the previous period. We considered that degassing from magma mainly causes the deflation of magma chamber after September 2000. The decreasing rate estimated from crustal deformation was quantitatively consistent with that estimated from the rate of the emitting volcanic gasses (Kazahaya, personal communication). This consideration suggests that the magma does not migrate any more and that the magma chamber is in closed system. However, recent rate of the deformation is much smaller than that calculated from the degassing rate. This implies that new magma is supplied to the magma chamber from deeper region or that the depth of magma head becomes deeper in a conduit from the magma chamber to the caldera.

Caldera unrest driven by CO2-induced drying of the deep hydrothermal system.

PubMed

Moretti, R; Troise, C; Sarno, F; De Natale, G

2018-05-29

Interpreting volcanic unrest is a highly challenging and non-unique problem at calderas, since large hydrothermal systems may either hide or amplify the dynamics of buried magma(s). Here we use the exceptional ground displacement and geochemical datasets from the actively degassing Campi Flegrei caldera (Southern Italy) to show that ambiguities disappear when the thermal evolution of the deep hydrothermal system is accurately tracked. By using temperatures from the CO 2 -CH 4 exchange of 13 C and thermodynamic analysis of gas ascending in the crust, we demonstrate that after the last 1982-84 crisis the deep hydrothermal system evolved through supercritical conditions under the continuous isenthalpic inflow of hot CO 2 -rich gases released from the deep (~8 km) magma reservoir of regional size. This resulted in the drying of the base of the hot hydrothermal system, no more buffered along the liquid-vapour equilibrium, and excludes any shallow arrival of new magma, whose abundant steam degassing due to decompression would have restored liquid-vapour equilibrium. The consequent CO 2 -infiltration and progressive heating of the surrounding deforming rock volume cause the build-up of pore pressure in aquifers, and generate the striking temporal symmetry that characterizes the ongoing uplift and the post-1984 subsidence, both originated by the same but reversed deformation mechanism.

Fault Networks in the Northwestern Albuquerque Basin and Their Potential Role in Controlling Mantle CO2 Degassing and Fluid Migration from the Valles Caldera

NASA Astrophysics Data System (ADS)

Smith, J. R.; Crossey, L. J.; Karlstrom, K. E.; Fischer, T. P.; Lee, H.; McGibbon, C. J.

2015-12-01

The Rio Grande rift (RGR) has Quaternary and active volcanism and faulting that provide a field laboratory for examining links between mantle degassing and faults as fluid conduits. Diffuse and spring CO2 flux measurements were taken at 6 sites in the northwestern Albuquerque Basin (NWAB) and Valles caldera geothermal system. All sites progress to the southwest from the 1.25 Ma Valles caldera, down the rift-related Jemez fault network, to intersect with the Nacimiento fault system. Mantle CO2 and He degassing are well documented at 5 of 6 sites, with decreasing 3He/4He ratios away from the caldera. The instrument used to measure CO2 flux was an EGM-4 CO2 gas analyzer (PP systems) with an accumulation chamber. Carbonic springs at Penasco Springs (PS) and San Ysidro (SY), and the carbonate-cemented Sand Hill Fault (SHF) were targeted, all near the western border of the RGR. The SHF has no spring activity, had the smallest maximum flux of all the sites (8 g/m2d), but carbonate along the fault zone (<2 m wide) attest to past CO2 flux. The other two sites are equal distance (30-40 km) between the SHF site and Valles caldera sites. These sites have active carbonic springs that precipitate travertine mounds. Our work suggests these sites reflect intersections of the Nacimiento fault with NE trending faults that connect to the Jemez fault network. The maximum diffuse flux recorded at SY (297 g/m2d) and PS (25 g/m2d) are high, especially along the fault and near springs. At SY and PS the instruments capacity was exceeded (2,400 g/m2d) at 6 of 9 springs. Interpretations indicate a direct CO2 flux through a fault-related artesian aquifer system that is connected to magmatic gases from the caldera. Maximum diffuse flux measurements of Alamo Canyon (20,906 g/m2d), Sulphur Springs (2,400 g/m2d) and Soda Dam (1,882 g/m2d) at Valles caldera geothermal sites are comparable to Yellowstone geothermal systems. We use geospatial analysis and local geologic mapping to examine relationships of CO2 flux to structure. Travertine mounds can create impermeable barriers that modify near-surface degassing patterns, making it difficult to decipher where CO2 and fluids preferentially migrate up the damage zones in the hanging-wall or footwall. Future work will utilize grids to more accurately assess the localized affect fault zones have on CO2 flux rates.

Magma flow instability and cyclic activity at soufriere hills volcano, montserrat, british west indies

PubMed

Voight; Sparks; Miller; Stewart; Hoblitt; Clarke; Ewart; Aspinall; Baptie; Calder; Cole; Druitt; Hartford; Herd; Jackson; Lejeune; Lockhart; Loughlin; Luckett; Lynch; Norton; Robertson; Watson; Watts; Young

1999-02-19

Dome growth at the Soufriere Hills volcano (1996 to 1998) was frequently accompanied by repetitive cycles of earthquakes, ground deformation, degassing, and explosive eruptions. The cycles reflected unsteady conduit flow of volatile-charged magma resulting from gas exsolution, rheological stiffening, and pressurization. The cycles, over hours to days, initiated when degassed stiff magma retarded flow in the upper conduit. Conduit pressure built with gas exsolution, causing shallow seismicity and edifice inflation. Magma and gas were then expelled and the edifice deflated. The repeat time-scale is controlled by magma ascent rates, degassing, and microlite crystallization kinetics. Cyclic behavior allows short-term forecasting of timing, and of eruption style related to explosivity potential.

Evolution of seafloor spreading rate based on Ar-40 degassing history

NASA Astrophysics Data System (ADS)

Tajika, Eiichi; Matsui, Takafumi

1993-05-01

A new degassing model of Ar-40 coupled with thermal evolution of the mantle is constructed to constrain the temporal variation of seafloor spreading rate. In this model, we take into account the effects of elemental partition and solubility during melt generation and bubble formation, and changes in both seafloor spreading rate and melt generation depth in the mantle. It is suggested that the seafloor spreading rate would have been almost the same as that of today over the history of the earth in order to explain the present amount of Ar-40 in the atmosphere. This result may also imply the mild degassing history of volatiles from the mantle.

VOLATILECALC: A silicate melt-H2O-CO2 solution model written in Visual Basic for excel

USGS Publications Warehouse

Newman, S.; Lowenstern, J. B.

2002-01-01

We present solution models for the rhyolite-H2O-CO2 and basalt-H2O-CO2 systems at magmatic temperatures and pressures below ~ 5000 bar. The models are coded as macros written in Visual Basic for Applications, for use within MicrosoftR Excel (Office'98 and 2000). The series of macros, entitled VOLATILECALC, can calculate the following: (1) Saturation pressures for silicate melt of known dissolved H2O and CO2 concentrations and the corresponding equilibrium vapor composition; (2) open- and closed-system degassing paths (melt and vapor composition) for depressurizing rhyolitic and basaltic melts; (3) isobaric solubility curves for rhyolitic and basaltic melts; (4) isoplethic solubility curves (constant vapor composition) for rhyolitic and basaltic melts; (5) polybaric solubility curves for the two end members and (6) end member fugacities of H2O and CO2 vapors at magmatic temperatures. The basalt-H2O-CO2 macros in VOLATILECALC are capable of calculating melt-vapor solubility over a range of silicate-melt compositions by using the relationships provided by Dixon (American Mineralogist 82 (1997) 368). The output agrees well with the published solution models and experimental data for silicate melt-vapor systems for pressures below 5000 bar. ?? 2002 Elsevier Science Ltd. All rights reserved.

V OLATILEC ALC: a silicate melt-H 2O-CO 2 solution model written in Visual Basic for excel

NASA Astrophysics Data System (ADS)

Newman, Sally; Lowenstern, Jacob B.

2002-06-01

We present solution models for the rhyolite-H 2O-CO 2 and basalt-H 2O-CO 2 systems at magmatic temperatures and pressures below ˜5000 bar. The models are coded as macros written in Visual Basic for Applications, for use within Microsoft ® Excel (Office'98 and 2000). The series of macros, entitled V OLATILEC ALC, can calculate the following: (1) Saturation pressures for silicate melt of known dissolved H 2O and CO 2 concentrations and the corresponding equilibrium vapor composition; (2) open- and closed-system degassing paths (melt and vapor composition) for depressurizing rhyolitic and basaltic melts; (3) isobaric solubility curves for rhyolitic and basaltic melts; (4) isoplethic solubility curves (constant vapor composition) for rhyolitic and basaltic melts; (5) polybaric solubility curves for the two end members and (6) end member fugacities of H 2O and CO 2 vapors at magmatic temperatures. The basalt-H 2O-CO 2 macros in V OLATILEC ALC are capable of calculating melt-vapor solubility over a range of silicate-melt compositions by using the relationships provided by Dixon (American Mineralogist 82 (1997) 368). The output agrees well with the published solution models and experimental data for silicate melt-vapor systems for pressures below 5000 bar.

40 CFR 63.120 - Storage vessel provisions-procedures to determine compliance.

Code of Federal Regulations, 2012 CFR

2012-07-01

... Organic Chemical Manufacturing Industry for Process Vents, Storage Vessels, Transfer Operations, and...) each time the storage vessel is emptied and degassed, and at least once every 10 years after the... (if any) each time the storage vessel is emptied and degassed and at least once every 5 years after...

40 CFR 63.120 - Storage vessel provisions-procedures to determine compliance.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Organic Chemical Manufacturing Industry for Process Vents, Storage Vessels, Transfer Operations, and...) each time the storage vessel is emptied and degassed, and at least once every 10 years after the... (if any) each time the storage vessel is emptied and degassed and at least once every 5 years after...

40 CFR 63.120 - Storage vessel provisions-procedures to determine compliance.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Organic Chemical Manufacturing Industry for Process Vents, Storage Vessels, Transfer Operations, and...) each time the storage vessel is emptied and degassed, and at least once every 10 years after the... (if any) each time the storage vessel is emptied and degassed and at least once every 5 years after...

40 CFR 63.120 - Storage vessel provisions-procedures to determine compliance.

Code of Federal Regulations, 2011 CFR

2011-07-01

... Chemical Manufacturing Industry for Process Vents, Storage Vessels, Transfer Operations, and Wastewater... time the storage vessel is emptied and degassed, and at least once every 10 years after the compliance... (if any) each time the storage vessel is emptied and degassed and at least once every 5 years after...

40 CFR 63.695 - Inspection and monitoring requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... least once every calendar year after initial fill, and (B) Visually inspect the internal floating roof...) each time the tank is emptied and degassed and at least every 10 years. Prior to each inspection, the... emptied and degassed and at least every 5 years. Prior to each inspection, the owner or operator shall...

Effect of dynamic oxygen concentrations on the growth of Neochloris oleoabundans at sub-saturating light conditions.

PubMed

Sousa, Claudia; Valev, Dimitar; Vermuë, Marian H; Wijffels, Rene H

2013-08-01

In tubular photobioreactors micro-algae continuously experience dynamically changing oxygen and light conditions when circulating from the solar receiver to the dark degasser. These changes in oxygen concentration and light were simulated in a CSTR using sub-saturating light intensity. Elongation of the residence time in the solar receiver from 30 to 300 min was also investigated. Specific growth rates measured at constant low oxygen concentration PO2=0.21 bar were; 1.14 ± 0.06 day(-1) using continuous light 0.80 ± 0.16 day(-1) with 30 min light and 1.09 ± 0.05 day(-1) with 300 min light. The effect of dynamically changing oxygen concentrations from PO2=0.21 to 0.63 bar followed by degassing resulted in similar specific growth rates. The exposure of the algae cells to dark periods in the degasser has a bigger negative impact than the temporary exposure to accumulating oxygen concentrations in the solar receiver. This shows that considerable energy savings for degassing are possible. Copyright © 2013 Elsevier Ltd. All rights reserved.

Structural control on the CO2 release west of Mt. Epomeo resurgent block (Ischia, Italy)

NASA Astrophysics Data System (ADS)

de Vita, S.; Marotta, E.; Ventura, G.; Chiodini, G.

2003-04-01

Volcanism at Ischia started more than 150 ka B.P. and continued until the last eruption occurred in 1302 A.D. Ischia is dominated by the caldera forming eruption of Mt. Epomeo Green Tuff (55 ka), which was followed by block resurgence inside the caldera from 33 ka B.P. Resurgence influenced the volcanic activity determining the conditions for magma ascent mainly along the eastern edge of the resurgent block. The resurgent area has a poligonal shape resulting from reactivation of regional faults and by activation of faults related to volcanotectonism. The western sector is bordered by inward dipping, high angle strike-slip/reverse faults testifying a compressional stress regime in this area. These features are cut by late outward dipping normal faults due to gravitational stress. The activity of the volcanic system is testified by seismicity and thermal manifestations. Fumarolic activity concentrates along the faults that borders westward the Mt. Epomeo resurgent block, where the Green Tuff overlies fractured lavas. The structural data show that, outside the most active degassing zone, fractures show a NNW-SSE strike and dip toward Mt. Epomeo. These fractures delimit the northern sector of Mt. Epomeo and show strike and dip consistent with the inward dipping reverse faults. Inside the degassing area fractures show a NW-SE strike and dip outward Mt. Epomeo. These gravity-related faults cut the lavas where the hydrothermal circulation is active. The dip direction of the NW-SE striking fractures within the degassing zone is not consistent with that of the strike-slip/reverse faults (i.e. towards NE) but agrees well with that of the gravity-induced faults (dip direction towards SW). Inside the degassing zone, NW-SE striking faults with lengths not exceeding the hydrothermalized extension occur. This arrangement indicate that the syn-resurgence faults act as permeability barriers, whereas the youngest faults act as the main fluid pathway.

A missing element of the deep carbon cycle: CO2 degassing estimates from rift length analysis during Pangea fragmentation

NASA Astrophysics Data System (ADS)

Brune, S.; Williams, S.; Müller, D.

2016-12-01

The deep carbon cycle connects CO2 within the atmosphere and oceans to the vast CO2 reservoir in Earth's mantle: subducted lithosphere carries CO2 into the mantle, while extensional plate boundaries and arc volcanoes release it back to Earth's surface. The length of plate boundaries thereby exerts first-order control on global CO2 fluxes on geological time scales. Here we provide a worldwide census of extensional plate boundary length from the Triassic to present day, in one million year time intervals, using a novel analysis technique (Brune et al. 2016, Nature, doi:10.1038/nature18319). The most extensive rift phase during the fragmentation of Pangea occurred in the Cretaceous with extension along the South Atlantic (9700 km) and North Atlantic rifts (9100 km), within East Gondwana (8500 km), and the failed African rift systems (4900 km). The combined extent of these and several smaller rifts amounts to more than 30.000 km of simultaneously active continental rifting. It is well-accepted that volcanoes at plate boundaries release large amounts of CO2 from the Earth's interior. Recent work, however, revealed the importance of deep-cutting faults and diffuse degassing on CO2 emissions in the East African rift (Lee et al. 2016, Nature Geoscience, doi: 10.1038/ngeo2622). Upscaling these measured CO2 fluxes to all concurrently active global rift zones, we compute first-order estimates of total rift-related CO2 degassing rates for the last 240 Myr. Our results show that rift-related CO2 release rates may have reached 600 Mt/yr in the Early Cretaceous, while Cenozoic rates rarely exceeded 200 Mt/yr. By comparison, present-day estimates of CO2 release at mid-ocean ridges range between 53 and 97 Mt/yr. We suggest that rift-related degassing during supercontinental breakup played a major role in maintaining high atmospheric CO2 concentrations through Mesozoic times, which exceeded Quaternary values by 400%.

Systematic Satellite Observations of the Impact of Aerosols from Passive Volcanic Degassing on Local Cloud Properties

NASA Technical Reports Server (NTRS)

Ebmeier, S.K.; Sayer, Andrew M.; Grainger, R. G.; Mather, T. A.; Carboni, E.

2014-01-01

The impact of volcanic emissions, especially from passive degassing and minor explosions, is a source of uncertainty in estimations of aerosol indirect effects. Observations of the impact of volcanic aerosol on clouds contribute to our understanding of both present-day atmospheric properties and of the pre-industrial baseline necessary to assess aerosol radiative forcing. We present systematic measurements over several years at multiple active and inactive volcanic islands in regions of low present-day aerosol burden. The timeaveraged indirect aerosol effects within 200 kilometers downwind of island volcanoes are observed using Moderate Resolution Imaging Spectroradiometer (MODIS, 2002-2013) and Advanced Along-Track Scanning Radiometer (AATSR, 2002- 2008) data. Retrievals of aerosol and cloud properties at Kilauea (Hawaii), Yasur (Vanuatu) and Piton de la Fournaise (la Reunion) are rotated about the volcanic vent to be parallel to wind direction, so that upwind and downwind retrievals can be compared. The emissions from all three volcanoes - including those from passive degassing, Strombolian activity and minor explosions - lead to measurably increased aerosol optical depth downwind of the active vent. Average cloud droplet effective radius is lower downwind of the volcano in all cases, with the peak difference ranging from 2 - 8 micrometers at the different volcanoes in different seasons. Estimations of the difference in Top of Atmosphere upward Short Wave flux upwind and downwind of the active volcanoes from NASA's Clouds and the Earth's Radiant Energy System (CERES) suggest a downwind elevation of between 10 and 45 Watts per square meter at distances of 150 - 400 kilometers from the volcano, with much greater local (less than 80 kilometers) effects. Comparison of these observations with cloud properties at isolated islands without degassing or erupting volcanoes suggests that these patterns are not purely orographic in origin. Our observations of unpolluted, isolated marine settings may capture processes similar to those in the pre-industrial marine atmosphere.

Spatially resolved SO2 flux emissions from Mt Etna.

PubMed

D'Aleo, R; Bitetto, M; Delle Donne, D; Tamburello, G; Battaglia, A; Coltelli, M; Patanè, D; Prestifilippo, M; Sciotto, M; Aiuppa, A

2016-07-28

We report on a systematic record of SO 2 flux emissions from individual vents of Etna volcano (Sicily), which we obtained using a permanent UV camera network. Observations were carried out in summer 2014, a period encompassing two eruptive episodes of the New South East Crater (NSEC) and a fissure-fed eruption in the upper Valle del Bove. We demonstrate that our vent-resolved SO 2 flux time series allow capturing shifts in activity from one vent to another and contribute to our understanding of Etna's shallow plumbing system structure. We find that the fissure eruption contributed ~50,000 t of SO 2 or ~30% of the SO 2 emitted by the volcano during the 5 July to 10 August eruptive interval. Activity from this eruptive vent gradually vanished on 10 August, marking a switch of degassing toward the NSEC. Onset of degassing at the NSEC was a precursory to explosive paroxysmal activity on 11-15 August.

Tritium concentrations in the active Pu'u O'o crater, Kilauea volcano, Hawaii: implications for cold fusion in the Earth's interior

NASA Astrophysics Data System (ADS)

Quick, J. E.; Hinkley, T. K.; Reimer, G. M.; Hedge, C. E.

1991-11-01

The assertion that deuterium-deuterium fusion may occur at low temperature suggests a potential new source of geothermal heat. If a cold-fusion-like process occurs within the Earth, then a test for its existence would be a search for anomalous tritium in volcanic emissions. The Pu'u O'o crater is the first point at which large amounts of water are degassed from the magma that feeds the Kilauea system. The magma is probably not contaminated by meteoric-source ground water prior to degassing at Pu'u O'o, although mixing of meteoric and magmatic H 2O occurs within the crater. Tritium contents of samples from within the crater are lower than in samples taken simultaneously from the nearby upwind crater rim. These results provide no evidence in support of a cold-fusion-like process in the Earth's interior.

Tritium concentrations in the active Pu'u O'o crater, Kilauea volcano, Hawaii: implications for cold fusion in the Earth's interior

USGS Publications Warehouse

Quick, J.E.; Hinkley, T.K.; Reimer, G.M.; Hedge, C.E.

1991-01-01

The assertion that deuterium-deuterium fusion may occur at low temperature suggests a potential new source of geothermal heat. If a cold-fusion-like process occurs within the Earth, then a test for its existence would be a search for anomalous tritium in volcanic emissions. The Pu'u O'o crater is the first point at which large amounts of water are degassed from the magma that feeds the Kilauea system. The magma is probably not contaminated by meteoric-source ground water prior to degassing at Pu'u O'o, although mixing of meteoric and magmatic H2O occurs within the crater. Tritium contents of samples from within the crater are lower than in samples taken simultaneously from the nearby upwind crater rim. These results provide no evidence in support of a cold-fusion-like process in the Earth's interior. ?? 1991.

Role of air bubbles overlooked in the adsorption of perfluorooctanesulfonate on hydrophobic carbonaceous adsorbents.

PubMed

Meng, Pingping; Deng, Shubo; Lu, Xinyu; Du, Ziwen; Wang, Bin; Huang, Jun; Wang, Yujue; Yu, Gang; Xing, Baoshan

2014-12-02

Hydrophobic interaction has been considered to be responsible for adsorption of perfluorooctanesulfonate (PFOS) on the surface of hydrophobic adsorbents, but the long C-F chain in PFOS is not only hydrophobic but also oleophobic. In this study, for the first time we propose that air bubbles on the surface of hydrophobic carbonaceous adsorbents play an important role in the adsorption of PFOS. The level of adsorption of PFOS on carbon nanotubes (CNTs), graphite (GI), graphene (GE), and powdered activated carbon (PAC) decreases after vacuum degassing. Vacuum degassing time and pressure significantly affect the removal of PFOS by these adsorbents. After vacuum degassing at 0.01 atm for 36 h, the extent of removal of PFOS by the pristine CNTs and GI decreases 79% and 74%, respectively, indicating the main contribution of air bubbles to PFOS adsorption. When the degassed solution is recontacted with air during the adsorption process, the removal of PFOS recovers to the value obtained without vacuum degassing, further verifying the key role of air bubbles in PFOS adsorption. By theoretical calculation, the distribution of PFOS in air bubbles on the adsorbent surfaces is discussed, and a new schematic sorption model of PFOS on carbonaceous adsorbents in the presence of air bubbles is proposed. The accumulation of PFOS at the interface of air bubbles on the adsorbents is primarily responsible for its adsorption, providing a new mechanistic insight into the transport, fate, and removal of PFOS.

Enhance performance of micro direct methanol fuel cell by in situ CO2 removal using novel anode flow field with superhydrophobic degassing channels

NASA Astrophysics Data System (ADS)

Liang, Junsheng; Luo, Ying; Zheng, Sheng; Wang, Dazhi

2017-05-01

Capillary blocking caused by CO2 bubbles in anode flow field (AFF) is one of the bottlenecks for performance improvement of a micro direct methanol fuel cell (μDMFC). In this work, we present a novel AFF structure with nested layout of hydrophilic fuel channels and superhydrophobic degassing channels which can remove most of CO2 from AFF before it is released to the fuel channels. The new AFFs are fabricated on Ti substrates by using micro photochemical etching combined with anodization and fluorination treatments. Performance of the μDMFCs with and without superhydrophobic degassing channels in their AFF is comparatively studied. Results show that the superhydrophobic degassing channels can significantly speed up the exhaust of CO2 from the AFF. CO2 clogging is not observed in the new AFFs even when their comparison AFFs have been seriously blocked by CO2 slugs under the same operating conditions. 55% and 60% of total CO2 produced in μDMFCs with N-serpentine and N-spiral AFF can be respectively removed by the superhydrophobic degassing channels. The power densities of the μDMFCs equipped with new serpentine and spiral AFFs are respectively improved by 30% and 90% compared with those using conventional AFFs. This means that the new AFFs developed in this work can effectively prevent CO2-induced capillary blocking in the fuel channels, and finally significantly improve the performance of the μDMFCs.

On evolutionary climate tracks in deep mantle volatile cycle computed from numerical mantle convection simulations and its impact on the habitability of the Earth-like planets

NASA Astrophysics Data System (ADS)

Nakagawa, T.; Tajika, E.; Kadoya, S.

2017-12-01

Discussing an impact of evolution and dynamics in the Earth's deep interior on the surface climate change for the last few decades (see review by Ehlmann et al., 2016), the mantle volatile (particularly carbon) degassing in the mid-oceanic ridges seems to play a key role in understanding the evolutionary climate track for Earth-like planets (e.g. Kadoya and Tajika, 2015). However, since the mantle degassing occurs not only in the mid-oceanic ridges but also in the wedge mantle (island arc volcanism) and hotspots, to incorporate more accurate estimate of mantle degassing flux into the climate evolution framework, we developed a coupled model of surface climate-deep Earth evolution in numerical mantle convection simulations, including more accurate deep water and carbon cycle (e.g. Nakagawa and Spiegelman, 2017) with an energy balance theory of climate change. Modeling results suggest that the evolution of planetary climate computed from a developed model is basically consistent with an evolutionary climate track in simplified mantle degassing model (Kadoya and Tajika, 2015), but an occurrence timing of global (snowball) glaciation is strongly dependent on mantle degassing rate occurred with activities of surface plate motions. With this implication, the surface plate motion driven by deep mantle dynamics would play an important role in the planetary habitability of such as the Earth and Earth-like planets over geologic time-scale.

Review of calcium carbonate polymorph precipitation in spring systems

NASA Astrophysics Data System (ADS)

Jones, Brian

2017-05-01

Many spring deposits throughout the world are characterized by spectacular deposits of calcium carbonate that are formed of various combinations of aragonite and calcite, and in very rare cases vaterite. The factors that control the precipitation of the aragonite and calcite have been the subject of considerable debate that has been based on natural precipitates and information gained from numerous laboratory experiments. Synthesis of this information indicates that there is probably no single universal factor that controls calcite and aragonite precipitation in all springs. Instead, the reason for aragonite as opposed to calcite precipitation should be ascertained by considering the following ordered series of possibilities for each system. First, aragonite, commonly with calcite as a co-precipitate, will form from spring water that has a high CO2 content and rapid CO2 degassing, irrespective of the Mg:Ca ratio and scale of precipitation. Second, aragonite can be precipitated from waters that have low levels of CO2 degassing provided that the Mg:Ca ratio is high enough to inhibit calcite precipitation. Third, the presence of biofilms may lead to the simultaneous precipitation of aragonite and calcite (irrespective of CO2 degassing or Mg:Ca ratio) either within the different microdomains that develop in the biofilm or because of diurnal changes in various geochemical parameters associated with the biofilm. Although the precipitation of calcite and aragonite has commonly been linked directly to water temperature, there is no clear evidence for this proposition. It is possible, however, that temperature may be influencing another parameter that plays a more direct role in the precipitation of these CaCO3 polymorphs. Despite the advances that have been made, the factors that ultimately control calcite and aragonite are still open to debate because this long-standing problem has still not been fully resolved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hochstein, M.P.; Sudarman, Sayogi

There are at least 30 high temperatures systems (with inferred reservoir temperatures > 200 C) along the active Sumatra Arc that transfer heat from crustal intrusions to the surface. These systems, together with eleven active volcanoes, five degassing volcanoes and one caldera volcano (Lake Toba), are controlled by the Sumatra Fault Zone, an active mega shear zone that follows the median axis of the arc. At least half of the active and degassing volcanoes are associated with volcanic geothermal reservoirs containing magmatic gases and acid fluids. Large, low temperature resources exist in the Tertiary sedimentary basins of east Sumatra (back-arcmore » region), where anomalously higher thermal gradients (up to 8 C/100 m) have been measured. Volcanic activity was not continuous during the Cenozoic; subduction and arc volcanism probably decreased after the Eocene as a result of a clockwise rotation of Sumatra. In the Late Miocene, subduction started again, and andesitic volcanism reached a new peak of intensity in the Pliocene and has been continuous ever since. Rhyolitic volcanism, which has produced voluminous ignimbrite flows, began later (Pliocene/Pleistocene). All known rhyolitic centers associated with ignimbrite flows appear to lie along the Sumatra Fault Zone.« less

Emergence of the continents

NASA Technical Reports Server (NTRS)

Frey, H.

1978-01-01

If early degassing of the Earth produced a global ocean several km deep overlying a global sialic crust, then late heavy bombardment of that crust by basin forming impacting bodies would have produced topography such that by 4 billion years ago dry continential landmasses would stand above sea level. From extrapolation of lunar crater statistics, at least 50% of an original global crust on the earth would have been converted into basins averaging 4 km deep after isostatic adjustment. These basins formed the sink into which such a global ocean would drain. If the ocean was initially 2 km deep, then approximately 50% of the early Earth would have stood above sea level when the late heavy bombardment came to a close.

Distinct Crater and Conduit Infrasound Reveal an Open Vent Volcano Running Out of Gas

NASA Astrophysics Data System (ADS)

Lyons, J. J.; Fee, D.; Haney, M. M.; Diefenbach, A. K.; Carn, S. A.

2017-12-01

Open-vent degassing dominated activity at Mount Pagan, Mariana Islands dating back to at least 2013, when ground-based sensors were installed, to mid-2015 when degassing fell below detection limits. Gas sampling indicated shallow magma was the source, and an analysis of LP seismicity showed that repeated pressurization and venting of a shallow crack controlled degassing. Open-vent degassing also produced abundant infrasound, recorded on two 6-element arrays. Two main infrasound features are the focus of this study: 1) a 0.3 Hz iVLP and 2) a 1.7 Hz iLP. Tens of thousands of iVLPs and iLPs were recorded over the 22-month study period, and correlation and cluster analyses show little change in both waveform and frequency content, suggesting a non-destructive, repeating source. An interesting upper conduit-crater geometry was discovered in helicopter overflights of the summit crater, and to test the effects of the crater and conduit shape and size on the infrasound signals, a high-resolution (<1 meter) DEM of the crater was produced by structure-from-motion using video captured during helicopter orbits. We perform full-waveform inversion of the infrasound data using the 3D topography, and show that a synthetic monopole source induces distinct resonance in the crater and upper conduit that mostly reproduces the iVLP and iLP signals, respectively. Further investigation of the infrasound catalogue shows that while the frequency content and waveforms remained stable through time, the amplitude of the iVLP events began decreasing months prior to cessation of degassing. Initially, the iLP amplitudes remained unaffected while the iVLP amplitudes dropped, but in the final months before degassing ended iLP amplitudes also began decreasing. We interpret this pattern as a progressive decline in the gas overpressure, initially resulting in a decreased ability to trigger resonance in the large crater volume, but eventually affecting the ability of the monopole source to induce resonance in the smaller upper conduit volume. We compare the infrasound amplitudes to passive SO2 degassing of measured from the OMI sensor on NASA's Aura satellite during the study period and find a remarkable similarity in the datasets, confirming that the subtle waning of infrasound amplitudes was a harbinger of an open vent volcano running out of gas.

Problems and advances in the use of magmatic degassing during subglacial eruptions to reconstruct palaeo-ice thicknesses

NASA Astrophysics Data System (ADS)

Tuffen, Hugh; Owen, Jacqueline; Denton, Joanna S.

2010-05-01

The degassing of magmatic volatiles during eruptions beneath ice sheets and glaciers, as recorded by the dissolved volatile content quenched in volcanic rocks, could provide powerful new constraints on former ice thicknesses in volcanic areas. As volcanic rocks are readily dateable using radiometric methods, subglacial volcanoes may therefore provide crucial information on Quaternary palaeo-environmental fluctuations. The use of a degassing-based reconstruction technique would be particularly valuable when studying deposits that were erupted entirely subglacially and therefore lack other diagnostic indicators of ice thickness such as subglacial-subaerial transitions. In order for magma degassing to potentially record palaeo-ice thicknesses a number of factors need to be considered[1,2], which include whether non-equilibrium degassing may have occurred, whether samples have undergone post-eruption hydration, are strongly compositionally heterogeneous, or have moved post-quenching, whether the quenching pressure reflected loading by rock, ice or meltwater, and whether pressure may have deviated significantly from glaciostatic due to meltwater drainage. Degassing during individual eruptions may be considerably more complex than anticipated[2], making interpretation of results challenging. Examples from both rhyolitic and basaltic eruptions in Iceland and elsewhere will be used to illustrate these important factors. The analytical techniques used to measure volatile concentrations need to improve on the common practise of using infra-red spectroscopy alone to determine H2O contents in one part of a sample. Multiple analyses are required to quantify the degree of heterogeneity within samples and techniques such as manometry, ion microprobe or electron microprobe are required to analyse other species (CO2, S, F, Cl). CO2 is particularly important as only trace amounts, beneath the detection limits of commonly-used analytical techniques (30 ppm), strongly affect the solubility-pressure relationships of water in silicate melts[1]. Measurement of the initial volatile contents of magmas, as recorded in melt inclusions, is also needed to provide full insight into the degassing path from the chamber to the surface. More evidence for non-glaciostatic pressures and abrupt changes in pressure during subglacial eruptions needs to be gathered from detailed measurements of volatile concentrations and combined with geological evidence for changes in subglacial meltwater drainage. Studies of deposits with good secondary constraints on ice thickness (from direct observations of recent eruptions or other geological evidence for ancient eruptions) are also required in order to assess the reliability of using volatile degassing to reconstruct palaeo-ice thicknesses. We are beginning to gain limited understanding of the behaviour of magmatic volatiles during subglacial eruptions, and to realise their potential for palaeo-environmental reconstructions. However, there remain many substantial and fundamental gaps in our knowledge that must be addressed in future research. [1] Tuffen, H., Owen, J., Denton, J. S. (2010) Magma degassing during subglacial eruptions and its use to reconstruct palaeo-ice thicknesses. Earth Science Reviews, in press. [2] Owen, J., Tuffen, H., McGarvie, D. W., Pinkerton, H., Wilson, L. The use of magmatic water to reconstruct palaeo-ice thicknesses during subglacial rhyolitic eruptions. Poster presentation, this session.

The degassing and crystallisation behaviour of basaltic lavas

NASA Astrophysics Data System (ADS)

Applegarth, L. J.; Tuffen, H.; Pinkerton, H.; James, M. R.

2010-12-01

Degassing is a fundamental volcanic process that can play a major role in controlling eruptive styles. Volatile loss during magma ascent and decompression increases the liquidus temperature of the residual melt, resulting in undercooling that can trigger crystallisation (1,2). Late-stage crystallisation and vesiculation are significant factors in controlling the eruptive behaviour of volcanoes of intermediate composition (2), but their effects on basaltic volcanic activity have yet to be fully investigated. We present the results of experiments designed to measure the degassing and crystallisation behaviour of volcanic rocks at temperatures up to 1250°C, using thermo-gravimetric analysis coupled with differential scanning calorimetry and mass spectrometry (TGA-DSC-MS). During TGA-DSC-MS analysis, volatiles released from a sample under a controlled heating programme are identified in a mass spectrometer whilst changes to the sample weight and heat flow are simultaneously recorded. By subjecting samples of basaltic lava and bombs to two heating cycles, we have shown that the onset of degassing (mass loss) is systematically followed by crystallisation (exothermic events) on the first heating cycle. During the second cycle, when the sample has been fully degassed, no mass loss or crystallisation are recorded. Our results also highlight complexities in the processes; in some cases up to four pulses of degassing and crystallisation have been identified during a single heating cycle. Our results allow us to measure the total volatile content of samples, the onset temperatures of degassing and crystallisation and the time lag between the two processes, and the enthalpy, hence percentage, of crystallisation taking place. These results have important implications for our understanding of basaltic volcanic eruptions. During effusive basaltic eruptions, lava can travel many kilometres, threatening property and infrastructure. The final areal flow extent is partly dependent on the highly variable rheology. Cooling strongly affects rheology, but is mainly restricted to thermal boundary layers. Degassing-induced undercooling and crystallisation, however, may alter the bulk rheology (1), and may have contrasting effects. Rapid microlite growth may lead to crystal-crystal interactions, and the development of non-linear rheological properties such as a yield strength (3,4), which will impede advance. Alternatively, the latent heat of crystallisation may reduce the viscosity of the residual melt and suppress further crystal nucleation (5), tending to render the lava more mobile. As yet, the complex effects of degassing on the crystallisation, and hence rheological, behaviour of basaltic melts are not yet sufficiently well constrained for inclusion in the current generation of numerical lava flow models. An improved understanding of these processes is a critical step in improving our ability to forecast flow behaviour. 1. Sparks, R.S.J. and Pinkerton, H. (1978) Nature, 276, 385. 2. Blundy, J. and Cashman, K.V. (2001) Contrib. Mineral. Petrol. 140, 631. 3. Marsh, B.D. (1981) Contrib. Mineral. Petrol. 78, 85. 4. Bagdassarov, N. and Pinkerton, H. (2004) J. Volcanol. Geotherm. Res. 132, 115. 5. Brandeis, G., Jaupart, C., and Allegre, C.J. (1984) J. Geophys. Res. 89(B12), 10161.

Comparing eruptions of varying intensity at Kilauea via melt inclusion analysis

NASA Astrophysics Data System (ADS)

Ferguson, D. J.; Plank, T. A.; Hauri, E. H.; Houghton, B. F.; Gonnermann, H. M.; Swanson, D. A.; Blaser, A. P.

2013-12-01

Over the past 500 years explosive summit eruptions from Kilauea volcano, Hawaii, have exhibited a range of eruption magnitudes, from large basaltic sub-plinian events to Hawaiian lava fountains of various intensity. Knowledge of the factors controlling such dramatic changes in explosivity and mass discharge rate is vital for understanding the dynamics of explosive basaltic magma systems, but these remain poorly constrained. At Kilauea this information also has important implications for hazard assessment, as future eruptions may be far larger than those observed historically. To investigate the processes associated with eruptions of varying magnitudes we have analyzed the composition and dissolved volatile contents (H2O-CO2-S-Cl-F) of olivine-hosted melt inclusions, sampled from tephra deposits associated with three eruptions of different sizes: a moderate lava-fountain (1959 Episode of Kilauea Iki); an exceptionally high lava-fountain (1500 CE Keanakāko'i reticulite) and a basaltic sub-plinian eruption (1650 CE Keanakāko'i layer 6 scoria). Over this time period (~500 years) we find no major shifts in the major element composition of primary melts feeding the Kilauea magmatic system, and melt inclusions from all eruptions record similar maximum water (~0.7 wt% H2O) and CO2 (~300 ppm) contents, regardless of eruption magnitude. Co-variations between other volatile species, such as CO2 and S, do not support a role for excess volatiles (i.e. CO2) in the larger eruptions via ';gas-fluxing'. Our data therefore suggests that major shifts in eruptive magnitude are unlikely to be linked to either changes in the primary volatile content of the melts or excess gas supplied by open-system degassing of deeper melts. Rather we find evidence for significant variations in the shallow degassing behavior of magmas associated with the larger Keanakāko'i eruptions (sub-plinian and strong lava-fountaining events) compared to that from less vigorous moderate Kilauea Iki lava-fountaining events. On plots of CO2 versus H2O, Kilauea Iki MI's record volatile contents consistent with equilibrium degassing of magma rising from a depth of ~3 km. In contrast, the volatile contents of melts from the more explosive eruptions appear to be strongly affected by degassing processes at shallow depths (< 300 m), indicating variations in the ascent and storage of melts over this time-period. These changes in storage conditions may be linked to variations in the depth of the summit caldera, which was significantly greater during the older more explosive eruptive phases.

Magmatic gas scrubbing: Implications for volcano monitoring

USGS Publications Warehouse

Symonds, R.B.; Gerlach, T.M.; Reed, M.H.

2001-01-01

Despite the abundance of SO2(g) in magmatic gases, precursory increases in magmatic SO2(g) are not always observed prior to volcanic eruption, probably because many terrestrial volcanoes contain abundant groundwater or surface water that scrubs magmatic gases until a dry pathway to the atmosphere is established. To better understand scrubbing and its implications for volcano monitoring, we model thermochemically the reaction of magmatic gases with water. First, we inject a 915??C magmatic gas from Merapi volcano into 25??C air-saturated water (ASW) over a wide range of gas/water mass ratios from 0.0002 to 100 and at a total pressure of 0.1 MPa. Then we model closed-system cooling of the magmatic gas, magmatic gas-ASW mixing at 5.0 MPa, runs with varied temperature and composition of the ASW, a case with a wide range of magmatic-gas compositions, and a reaction of a magmatic gas-ASW mixture with rock. The modeling predicts gas and water compositions, and, in one case, alteration assemblages for a wide range of scrubbing conditions; these results can be compared directly with samples from degassing volcanoes. The modeling suggests that CO2(g) is the main species to monitor when scrubbing exists; another candidate is H2S(g), but it can be affected by reactions with aqueous ferrous iron. In contrast, scrubbing by water will prevent significant SO2(g) and most HCl(g) emissions until dry pathways are established, except for moderate HCl(g) degassing from pH 100 t/d (tons per day) of SO2(g) in addition to CO2(g) and H2S(g) should be taken as a criterion of magma intrusion. Finally, the modeling suggests that the interpretation of gas-ratio data requires a case-by-case evaluation since ratio changes can often be produced by several mechanisms; nevertheless, several gas ratios may provide useful indices for monitoring the drying out of gas pathways. Published by Elsevier Science B.V.

Formation of magmatic brine lenses via focussed fluid-flow beneath volcanoes

NASA Astrophysics Data System (ADS)

Afanasyev, Andrey; Blundy, Jon; Melnik, Oleg; Sparks, Steve

2018-03-01

Many active or dormant volcanoes show regions of high electrical conductivity at depths of a few kilometres beneath the edifice. We explore the possibility that these regions represent lenses of high-salinity brine separated from a single-phase magmatic fluid containing H2O and NaCl. Since chloride-bearing fluids are highly conductive and have an exceptional capacity to transport metals, these regions can be an indication of an active hydrothermal ore-formation beneath volcanoes. To investigate this possibility we have performed hydrodynamic simulations of magma degassing into permeable rock. In our models the magma source is located at 7 km depth and the fluid salinity approximates that expected for fluids released from typical arc magmas. Our model differs from previous models of a similar process because it is (a) axisymmetric and (b) includes a static high-permeability pathway that links the magma source to the surface. This pathway simulates the presence of a volcanic conduit and/or plexus of feeder dykes that are typical of most volcanic systems. The presence of the conduit leads to a number of important hydrodynamic consequences, not observed in previous models. Importantly, we show that an annular brine lens capped by crystallised halite is likely to form above an actively degassing sub-volcanic magma body and can persist for more than 250 kyr after degassing ceases. Parametric analysis shows that brine lenses are more prevalent when the fluid is released at temperatures above the wet granite solidus, when magmatic fluid salinity is high, and when the high-permeability pathway is narrow. The calculated depth, form and electrical conductivity of our modelled system shares many features with published magnetotelluric images of volcano subsurfaces. The formation and persistence of sub-volcanic brine lenses has implications for geothermal systems and hydrothermal ore formation, although these features are not explored in the presented model.

Abundance and isotope systematics of carbon in subglacial basalts, geothermal gases and fluids from Iceland's rift zones

NASA Astrophysics Data System (ADS)

Barry, P. H.; Hilton, D. R.; Fueri, E.; Halldorsson, S. A.; Fischer, T. P.; Gronvold, K.

2010-12-01

P. H. BARRY1*, D. R. HILTON1, E. FÜRI1, S.A. HALLDÓRSON1, T.P. FISCHER2, K. GRONVOLD3 1 Scripps Institution of Oceanography, UCSD, La Jolla, California 92093, USA (*Correspondence: pbarry@ucsd.edu). 2University of New Mexico, Albuquerque, NM 87131, USA. 3University of Iceland, Askja, Sturlugata 7, IS-101, Reykjavik, Iceland Carbon dioxide (CO2) is the dominant non-aqueous volatile species found in oceanic basalts and geothermal fluids and serves as the carrier gas for trace volatiles such as He and other noble gases. The aim of this study is to identify the superimposed effects of degassing and crustal contamination on the CO2 systematics of the Icelandic hotspot in order to reveal and characterize the carbon abundance and isotopic features of the underlying mantle source. Our approach involves coupling CO2 with He, utilizing the sensitivity of 3He/4He ratios to reveal mantle and crustal inputs. We report new C-isotope (δ13C) and abundance characteristics for a suite of 47 subglacial basalts and 50 geothermal gases and fluids from Iceland. CO2 contents in hyaloclastite glasses are extremely low (10-100 ppm) and likely residual following extensive degassing whereas geothermal fluids are dominated by CO2 (>90 %). C-isotopes range from -27.2 to -3.6 ‰ (vs. PDB) for basalts and from -18.8 to 2.86 ‰ (vs. PDB) for geothermal samples (mean = -4.2 ± 3.6 ‰). CO2/3He ratios range from 108 to 1012 for basalts and from 105 to 1012 for geothermal samples: In both cases, our results extend He-CO2 relationships over a much broader range than reported previously [1]. Taken together, these data suggest that several processes including mixing, degassing, and/or syn- or post-eruptive crustal contamination may act to modify CO2 source characteristics. Equilibrium degassing models are compatible with ~75 % of the basalt data, and preliminary results indicate that initial Icelandic source characteristics are ~500 ppm CO2 and δ13C ~ -5 ‰ (vs. PDB). These values are high compared to N-MORB mantle source estimates (72-134 ppm) based upon CO2/Nb ratios [2, 3]; however, they are in good agreement with those from submarine glasses on adjacent segments from the Reykjanes and Kolbeinsey ridges [4,5]. Significantly, the model-derived δ13C estimate is close to the mean Icelandic geothermal value, implying that fluids closely resemble source values, i.e. they likely represent the exsolved component. Integrating the estimated source CO2 content with magma production values of 0.079 km3/yr [6] yields a CO2 flux of ~1.2 x 1011 mol CO2 yr-1for Iceland, representing ~ 5.4 % of the total carbon ridge flux of 2.2 x 1012 mol CO2 yr-1 [7]. Thus, the average CO2 flux estimate for Iceland is ~2.2 x 108 mol CO2 yr-1km-1 strike of ridge axis, which compares to an overall ridge flux (including Iceland) of ~2.9 x 107 mol CO2 yr-1km-1. This difference highlights both heterogeneity in source volatile contents and magma production rates as important controls for determining mantle CO2 fluxes. [1] Poreda et al., 1992 [2] Saal et al., 2002. [3] Shaw et al., 2010. [4] de Leeuw, 2007 [5] Macpherson et al., 2005. [6] Thordarson et al., 2007 [7] Marty et al., 1998.

In situ dating on Mars: A new approach to the K-Ar method utilizing cosmogenic argon

NASA Astrophysics Data System (ADS)

Cassata, William S.

2014-01-01

Cosmogenic argon isotopes are produced in feldspars via nuclear reactions between cosmic rays and Ca and K atoms within the lattice. These cosmogenic isotopes can be used as proxies for K and Ca, much like nuclear reactor-derived 39Ar and 37Ar are used as proxies for K and Ca, respectively, in 40Ar/39Ar geochronology. If Ca and K are uniformly distributed, then the ratio of radiogenic 40Ar (40Ar*) to cosmogenic 38Ar or 36Ar (38Arcos or 36Arcos) is proportional to the difference between the radioisotopic and exposure ages, as well as the K/Ca ratio of the degassing phase. Thus cosmogenic, radiogenic, and trapped Ar isotopes, all of which can be measured remotely and are stable over geologic time, are sufficient to generate an isochron-like diagram from which the isotopic composition of the trapped component may be inferred. Such data also provide a means to assess the extent to which the system has remained closed with respect to 40Ar*, thereby mitigating otherwise unquantifiable uncertainties that complicate the conventional K-Ar dating method.

Annual cycle of magmatic CO2 in a tree-kill soil at Mammoth Mountain, California: implications for soil acidification

USGS Publications Warehouse

McGee, K.A.; Gerlach, T.M.

1998-01-01

Time-series sensor data reveal significant short-term and seasonal variations of magmatic CO2 in soil over a 12 month period in 1995-1996 at the largest tree-kill site on Mammoth Mountain, central-eastern California. Short-term variations leading to ground-level soil CO2 concentrations hazardous and lethal to humans were triggered by shallow faulting in the absence of increased seismicity or intrusion, consistent with tapping a reservoir of accumulated CO2, rather than direct magma degassing. Hydrologic processes closely modulated seasonal variations in CO2 concentrations, which rose to 65%-100% in soil gas under winter snowpack and plunged more than 25% in just days as the CO2 dissolved in spring snowmelt. The high efflux of CO2 through the tree-kill soils acts as an open-system CO2 buffer causing infiltration of waters with pH values commonly of < 4.2, acid loading of up to 7 keqH+.ha-1.yr-1, mobilization of toxic Al3+, and long-term decline of soil fertility.

Groundwater helium anomaly reflects strain change during the 2016 Kumamoto earthquake in Southwest Japan

NASA Astrophysics Data System (ADS)

Sano, Yuji; Takahata, Naoto; Kagoshima, Takanori; Shibata, Tomo; Onoue, Tetsuji; Zhao, Dapeng

2016-11-01

Geochemical monitoring of groundwater and soil gas emission pointed out precursor and/or coseismic anomalies of noble gases associated with earthquakes, but there was lack of plausible physico-chemical basis. A laboratory experiment of rock fracturing and noble gas emission was conducted, but there is no quantitative connection between the laboratory results and observation in field. We report here deep groundwater helium anomalies related to the 2016 Kumamoto earthquake, which is an inland crustal earthquake with a strike-slip fault and a shallow hypocenter (10 km depth) close to highly populated areas in Southwest Japan. The observed helium isotope changes, soon after the earthquake, are quantitatively coupled with volumetric strain changes estimated from a fault model, which can be explained by experimental studies of helium degassing during compressional loading of rock samples. Groundwater helium is considered as an effective strain gauge. This suggests the first quantitative linkage between geochemical and seismological observations and may open the possibility to develop a new monitoring system to detect a possible strain change prior to a hazardous earthquake in regions where conventional borehole strain meter is not available.

Combining High Resolution InSAR and infrared photogrammetry for studying dome degassing and densification mechanisms at Volcán de Colima, Mexico

NASA Astrophysics Data System (ADS)

Salzer, Jacqueline T.; Milillo, Pietro; Varley, Nick; Perissin, Daniele; Pantaleo, Michele; Walter, Thomas R.

2017-04-01

Active volcanoes often display cyclic behaviour with alternating quiescent and eruptive periods. Continuously monitoring volcanic processes such as deformation, seismicity and degassing, irrespective of their current status, is crucial for understanding the parameters governing the fluid transport within the edifice and the transitions between different regimes. However, mapping the deformation and details of fluid escape at the summit of steep sloped volcanoes and integrating these with other types of data is challenging. Here we present for the first time the near-3D surface deformation field derived from high resolution radar interferometry (InSAR) acquired by the satellite TerraSAR-X at a degassing volcano dome and interpret the results in combination with overflight infrared and topographic data. We find that the results strongly differ depending on the chosen InSAR time series method, which potentially overprints the true physical complexities of small scale, shallow deformation processes. We present a new method for accurate mapping of heterogeneities in the dome deformation, and comparison to the topography and precisely located surface temperature anomalies. The identified deformation is dominated by strong but highly localized subsidence of the summit dome. Our results highlight the competing effects of the topography, permeability and shallow volcanic structures controlling the degassing pathways. On small spatial scales compaction sufficiently reduced the dome permeability to redirect the fluid flow. High resolution InSAR monitoring of volcanic domes thus provides valuable data for constraining models of their internal structure, degassing pathways and densification processes.

Evidence of water degassing during emplacement and crystallization of 2.7 Ga komatiites from the Agnew-Wiluna greenstone belt, Western Australia

NASA Astrophysics Data System (ADS)

Fiorentini, M. L.; Beresford, S. W.; Stone, W. E.; Deloule, E.

2012-07-01

Komatiites are ancient volcanic rocks, mostly over 2.7 billion years old, which formed through >30% partial melting of the mantle. This study addresses the crucial relationship between volcanology and physical manifestation of primary magmatic water content in komatiites of the Agnew-Wiluna greenstone belt, Western Australia, and documents the degassing processes that occurred during the emplacement and crystallization of these magmas. The Agnew-Wiluna greenstone belt of Western Australia contains three co-genetic komatiite units that (1) display laterally variable volcanological features, including thick cumulates and spinifex-textured units, and (2) were emplaced as both lava flows and intrusions at various locations. Komatiite sills up to 500 m thick contain widespread occurrence of hydromagmatic amphibole in orthocumulate- and mesocumulate-textured rocks, which contain ca. 40-50 wt% MgO and <3 wt% TiO2. Conversely, komatiite flows do not contain any volatile-bearing mineral phases: ~150-m-thick flows only contain vesicles, amygdales and segregation structures, whereas <5-10-m-thick flows lack any textural and petrographic evidence of primary volatile contents. The main results of this study demonstrate that komatiites from the Agnew-Wiluna greenstone belt, irrespective of their initial water content, have degassed upon emplacement, flow and crystallization. More importantly, data show that komatiite flows most likely degassed more water than komatiite intrusions. Komatiite degassing may have indirectly influenced numerous physical and chemical parameters of the water from the primordial oceans and hence indirectly contributed to the creation of a complex zonation at the interface between water and seafloor.

Plate tectonic controls on atmospheric CO2 levels since the Triassic.

PubMed

Van Der Meer, Douwe G; Zeebe, Richard E; van Hinsbergen, Douwe J J; Sluijs, Appy; Spakman, Wim; Torsvik, Trond H

2014-03-25

Climate trends on timescales of 10s to 100s of millions of years are controlled by changes in solar luminosity, continent distribution, and atmosphere composition. Plate tectonics affect geography, but also atmosphere composition through volcanic degassing of CO2 at subduction zones and midocean ridges. So far, such degassing estimates were based on reconstructions of ocean floor production for the last 150 My and indirectly, through sea level inversion before 150 My. Here we quantitatively estimate CO2 degassing by reconstructing lithosphere subduction evolution, using recent advances in combining global plate reconstructions and present-day structure of the mantle. First, we estimate that since the Triassic (250-200 My) until the present, the total paleosubduction-zone length reached up to ∼200% of the present-day value. Comparing our subduction-zone lengths with previously reconstructed ocean-crust production rates over the past 140 My suggests average global subduction rates have been constant, ∼6 cm/y: Higher ocean-crust production is associated with longer total subduction length. We compute a strontium isotope record based on subduction-zone length, which agrees well with geological records supporting the validity of our approach: The total subduction-zone length is proportional to the summed arc and ridge volcanic CO2 production and thereby to global volcanic degassing at plate boundaries. We therefore use our degassing curve as input for the GEOCARBSULF model to estimate atmospheric CO2 levels since the Triassic. Our calculated CO2 levels for the mid Mesozoic differ from previous modeling results and are more consistent with available proxy data.

Plate tectonic controls on atmospheric CO2 levels since the Triassic

PubMed Central

Van Der Meer, Douwe G.; Zeebe, Richard E.; van Hinsbergen, Douwe J. J.; Sluijs, Appy; Spakman, Wim; Torsvik, Trond H.

2014-01-01

Climate trends on timescales of 10s to 100s of millions of years are controlled by changes in solar luminosity, continent distribution, and atmosphere composition. Plate tectonics affect geography, but also atmosphere composition through volcanic degassing of CO2 at subduction zones and midocean ridges. So far, such degassing estimates were based on reconstructions of ocean floor production for the last 150 My and indirectly, through sea level inversion before 150 My. Here we quantitatively estimate CO2 degassing by reconstructing lithosphere subduction evolution, using recent advances in combining global plate reconstructions and present-day structure of the mantle. First, we estimate that since the Triassic (250–200 My) until the present, the total paleosubduction-zone length reached up to ∼200% of the present-day value. Comparing our subduction-zone lengths with previously reconstructed ocean-crust production rates over the past 140 My suggests average global subduction rates have been constant, ∼6 cm/y: Higher ocean-crust production is associated with longer total subduction length. We compute a strontium isotope record based on subduction-zone length, which agrees well with geological records supporting the validity of our approach: The total subduction-zone length is proportional to the summed arc and ridge volcanic CO2 production and thereby to global volcanic degassing at plate boundaries. We therefore use our degassing curve as input for the GEOCARBSULF model to estimate atmospheric CO2 levels since the Triassic. Our calculated CO2 levels for the mid Mesozoic differ from previous modeling results and are more consistent with available proxy data. PMID:24616495

Smart Nanofibers Self-Assembled from Dumbbell-Shaped Rod Amphiphiles

DTIC Science & Technology

2011-09-01

using JEOL-JEM 2100. MALDI-TOF-MS was performed on a Bruker Microflex LRF20 using α-cyano-4-hydroxy cinnamic acid (CHCA) as matrix. Preparative high...and 4,4’-biphenyl diboronic acid (28.8 mg, 0.12 mmol) were dissolved in degassed THF (25 ml). Degassed 2 M aqueous Na2CO3 (25 ml) was added to the

Conditions for oceans on Earth-like planets orbiting within the habitable zone: importance of volcanic CO{sub 2} degassing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kadoya, S.; Tajika, E., E-mail: kadoya@astrobio.k.u-tokyo.ac.jp, E-mail: tajika@astrobio.k.u-tokyo.ac.jp

2014-08-01

Earth-like planets in the habitable zone (HZ) have been considered to have warm climates and liquid water on their surfaces if the carbonate-silicate geochemical cycle is working as on Earth. However, it is known that even the present Earth may be globally ice-covered when the rate of CO{sub 2} degassing via volcanism becomes low. Here we discuss the climates of Earth-like planets in which the carbonate-silicate geochemical cycle is working, with focusing particularly on insolation and the CO{sub 2} degassing rate. The climate of Earth-like planets within the HZ can be classified into three climate modes (hot, warm, and snowballmore » climate modes). We found that the conditions for the existence of liquid water should be largely restricted even when the planet is orbiting within the HZ and the carbonate-silicate geochemical cycle is working. We show that these conditions should depend strongly on the rate of CO{sub 2} degassing via volcanism. It is, therefore, suggested that thermal evolution of the planetary interiors will be a controlling factor for Earth-like planets to have liquid water on their surface.« less

Dynamics of carbon dioxide emission at Mammoth Mountain, California

USGS Publications Warehouse

Rogie, J.D.; Kerrick, Derrill M.; Sorey, M.L.; Chiodini, G.; Galloway, D.L.

2001-01-01

Mammoth Mountain, a dormant volcano in the eastern Sierra Nevada, California, has been passively degassing large quantities of cold magmatic CO2 since 1990 following a 6-month-long earthquake swarm associated with a shallow magmatic intrussion in 1989. A search for any link between gas discharge and volcanic hazard at this popular recreation area led us to initiate a detailed study of the degassing process in 1997. Our continuous monitoring results elucidate some of the physical controls that influence dynamics in flank CO2 degassing at this volcano. High coherence between variations in CO2 efflux and variations in atmospheric pressure and wind speed imply that meteorological parameters account for much, if not all of the variability in CO2 efflux rates. Our results help explain differences among previously published estimates of CO2 efflux at Mammoth Mountain and indicate that the long-term (annual) CO2 degassing rate has in fact remained constant since ~ 1997. Discounting the possibility of large meteorologically driven temporal variations in gas efflux at other volcanoes may result in spurious interpretations of transients do not reflect actual geologic processes. ?? 2001 Elsevier Science B.V. All rights reserved.

Changes in CO2 diffuse degassing induced by the passing of seismic waves

NASA Astrophysics Data System (ADS)

Gresse, M.; Vandemeulebrouck, J.; Byrdina, S.; Chiodini, G.; Bruno, P. P.

2016-06-01

Solfatara crater, located in the Campi Flegrei caldera, is a volcano with one of the highest degassing rates on Earth, more than 1500 t of CO2 released by diffusion or through vents. Here, we investigated how this gas release can be disrupted by the passage of seismic waves. We performed continuous soil CO2 flux measurements during the propagation of seismic vibrations in the range of 5 Hz to 200 Hz induced by a vibroseis truck. The CO2 flux was continuously recorded using the accumulation chamber method. The data show a temporary and drastic (up to two-fold) increase in CO2 flux exclusively during the vibrations, before returning to the initial flux values. These transient variations are interpreted as fluidization of the surficial granular layer that releases the stored gas. Similar degassing processes might occur at a larger scale during earthquakes, to cause temporary increases in the total gas outflow in volcanic or tectonic areas. Our findings are useful to better assess and monitor the potential hazard from sudden CO2 flux release during earthquakes as several cases of intoxication or death have already been related to volcanic degassing.

Shock-induced devolatization of calcium sulfate and implications for K-T extinctions

NASA Technical Reports Server (NTRS)

Chen, Guangqing; Tyburczy, James A.; Ahrens, Thomas J.

1993-01-01

Calcium sulfate devolatization during the impact at Chicxulub, Mexico and dispersal in the stratosphere of the resultant sulfuric acid aerosol have been suggested as a possible mechanism for the Cretaceous-Tertiary extinctions. In this paper, we investigated two shock-induced devolatization reactions of calcium sulfate up to 42 GPa in the laboratory: CaSO4 + SiO2 yields CaSiO3 + SO3(degassed) and CaSO4 yields CaO + SO2(degassed) + 1/2 O2(degassed). We found both to proceed to a much less extent than calculated by equilibrium thermodynamic calculations. Reaction products are found to be 10(exp -2) times those calculated for equilibrium. Consequently our estimate of the amount of sulfur oxides degassed into the atmosphere from shock devolatization of CaS04 in the Chicxulub lithographic section (6x10(exp 15)-2x10(exp 16)g in sulfur mass) is lower by a factor of 70 to 400 than previous estimates; the related environmental stress arising from the resultant global cooling of approximately 4 K and fallout of acid rain does not appear to suffice to explain the widespread K-T extinctions.

Degassing of reduced carbon from planetary basalts.

PubMed

Wetzel, Diane T; Rutherford, Malcolm J; Jacobsen, Steven D; Hauri, Erik H; Saal, Alberto E

2013-05-14

Degassing of planetary interiors through surface volcanism plays an important role in the evolution of planetary bodies and atmospheres. On Earth, carbon dioxide and water are the primary volatile species in magmas. However, little is known about the speciation and degassing of carbon in magmas formed on other planets (i.e., Moon, Mars, Mercury), where the mantle oxidation state [oxygen fugacity (fO2)] is different from that of the Earth. Using experiments on a lunar basalt composition, we confirm that carbon dissolves as carbonate at an fO2 higher than -0.55 relative to the iron wustite oxygen buffer (IW-0.55), whereas at a lower fO2, we discover that carbon is present mainly as iron pentacarbonyl and in smaller amounts as methane in the melt. The transition of carbon speciation in mantle-derived melts at fO2 less than IW-0.55 is associated with a decrease in carbon solubility by a factor of 2. Thus, the fO2 controls carbon speciation and solubility in mantle-derived melts even more than previous data indicate, and the degassing of reduced carbon from Fe-rich basalts on planetary bodies would produce methane-bearing, CO-rich early atmospheres with a strong greenhouse potential.

A model of diffuse degassing at three subduction-related volcanoes

NASA Astrophysics Data System (ADS)

Williams-Jones, Glyn; Stix, John; Heiligmann, Martin; Charland, Anne; Sherwood Lollar, Barbara; Arner, N.; Garzón, Gustavo V.; Barquero, Jorge; Fernandez, Erik

Radon, CO2 and δ13C in soil gas were measured at three active subduction-related stratovolcanoes (Arenal and Poás, Costa Rica; Galeras, Colombia). In general, Rn, CO2 and δ13C values are higher on the lower flanks of the volcanoes, except near fumaroles in the active craters. The upper flanks of these volcanoes have low Rn concentrations and light δ13C values. These observations suggest that diffuse degassing of magmatic gas on the upper flanks of these volcanoes is negligible and that more magmatic degassing occurs on the lower flanks where major faults and greater fracturing in the older lavas can channel magmatic gases to the surface. These results are in contrast to findings for Mount Etna where a broad halo of magmatic CO2 has been postulated to exist over much of the edifice. Differences in radon levels among the three volcanoes studied here may result from differences in age, the degree of fracturing and faulting, regional structures or the level of hydrothermal activity. Volcanoes, such as those studied here, act as plugs in the continental crust, focusing magmatic degassing towards crater fumaroles, faults and the fractured lower flanks.

40 CFR 60.482-2 - Standards: Pumps in light liquid service.

Code of Federal Regulations, 2011 CFR

2011-07-01

...; or (ii) Equipped with a barrier fluid degassing reservoir that is routed to a process or fuel gas... in VOC service. (3) Each barrier fluid system is equipped with a sensor that will detect failure of...) Designate the visual indications of liquids dripping as a leak. (5)(i) Each sensor as described in paragraph...

40 CFR 60.482-2 - Standards: Pumps in light liquid service.

Code of Federal Regulations, 2010 CFR

2010-07-01

...; or (ii) Equipped with a barrier fluid degassing reservoir that is routed to a process or fuel gas... in VOC service. (3) Each barrier fluid system is equipped with a sensor that will detect failure of...) Designate the visual indications of liquids dripping as a leak. (5)(i) Each sensor as described in paragraph...

Chemical Characterization of Simulated Boiling Water Reactor Coolant

DTIC Science & Technology

1990-05-01

33 Table 3. 1: BCCL Sample Block Design Calculations ........................................... 45 Table 5.1: Gas Absorption...cover gas . The cool, degassed pure water is pumped through a regenerative heat exchanger and then through an electric feedwater heater. The feedwater is...POINTS DWCMRHEAT DOWNOMER---EXCHANGER CHEMICAL GAHP INJECTIOIN PUMP SYSTEM COIVER GAS IN-CLIRE SECTION CAGN TANK RECOMBINER! ______ DEMINERALIZER (Cic

Fracture healing in a magma: An experimental approach and implications for volcanic seismicity and degassing

NASA Astrophysics Data System (ADS)

Yoshimura, Shumpei; Nakamura, Michihiko

2010-09-01

The healing of magmatic fractures is considered essential to repetitive seismicity and the closure of degassing paths during emplacement of lavas. To estimate the healing time of magmatic fractures, we performed healing experiments on rhyolitic melts at 850°-1000°C and 1.6-3.2 MPa for 0.5-94 h. Two cylindrical obsidian cores were juxtaposed on surfaces prepared by cutting the cores both with and without polishing. These were annealed in an open-system cell. The contact interface became coherent and finally disappeared. The water content across the contact initially decreased toward the interface via diffusive dehydration, but later homogenized. This change was interpreted to reflect atomic-scale closure of the interface, probably by chemical bonding. We defined this closure interval as microscopic healing time and determined this by fitting the measured profiles with a diffusion model. The microscopic healing time was strongly dependent on temperature and roughness of the interface and was, for the nonpolished interfaces, 67-74, 4.0-4.9, and 0.36-0.38 h at 850°, 900°, and 950°C, respectively, whereas for the polished examples it was 1-3 and 0.5-0.6 h at 850° and 900°C, respectively. This microscopic healing time is consistent with the period of actual seismicity and is prolonged sufficiently to permit the formation of millimeter-thick bubble-free obsidian layers along fractures in vesicular lavas through bubble resorption due to diffusive degassing.

Gas emissions from failed and actual eruptions from Cook Inlet Volcanoes, Alaska, 1989-2006

USGS Publications Warehouse

Werner, C.A.; Doukas, M.P.; Kelly, P.J.

2011-01-01

Cook Inlet volcanoes that experienced an eruption between 1989 and 2006 had mean gas emission rates that were roughly an order of magnitude higher than at volcanoes where unrest stalled. For the six events studied, mean emission rates for eruptions were ~13,000 t/d CO2 and 5200 t/d SO2, but only ~1200 t/d CO2 and 500 t/d SO2 for non-eruptive events (‘failed eruptions’). Statistical analysis suggests degassing thresholds for eruption on the order of 1500 and 1000 t/d for CO2 and SO2, respectively. Emission rates greater than 4000 and 2000 t/d for CO2 and SO2, respectively, almost exclusively resulted during eruptive events (the only exception being two measurements at Fourpeaked). While this analysis could suggest that unerupted magmas have lower pre-eruptive volatile contents, we favor the explanations that either the amount of magma feeding actual eruptions is larger than that driving failed eruptions, or that magmas from failed eruptions experience less decompression such that the majority of H2O remains dissolved and thus insufficient permeability is produced to release the trapped volatile phase (or both). In the majority of unrest and eruption sequences, increases in CO2 emission relative to SO2 emission were observed early in the sequence. With time, all events converged to a common molar value of C/S between 0.5 and 2. These geochemical trends argue for roughly similar decompression histories until shallow levels are reached beneath the edifice (i.e., from 20–35 to ~4–6 km) and perhaps roughly similar initial volatile contents in all cases. Early elevated CO2 levels that we find at these high-latitude, andesitic arc volcanoes have also been observed at mid-latitude, relatively snow-free, basaltic volcanoes such as Stromboli and Etna. Typically such patterns are attributed to injection and decompression of deep (CO2-rich) magma into a shallower chamber and open system degassing prior to eruption. Here we argue that the C/S trends probably represent tapping of vapor-saturated regions with high C/S, and then gradual degassing of remaining dissolved volatiles as the magma progresses toward the surface. At these volcanoes, however, C/S is often accentuated due to early preferential scrubbing of sulfur gases. The range of equilibrium degassing is consistent with the bulk degassing of a magma with initial CO2 and S of 0.6 and 0.2 wt.%, respectively, similar to what has been suggested for primitive Redoubt magmas.

A Model of Volcanic Outgassing for Earth's Early Atmosphere

NASA Astrophysics Data System (ADS)

Dhaliwal, J. K.; Kasting, J. F.; Zhang, Z.

2017-12-01

We build on historical paradigms of volcanic degassing [1] to account for non-linear relations among C-O-H-S volatiles, their speciation, solubility and concentrations in magmatic melts, and the resulting contribution to atmospheric volatile inventories. We focus on the build-up of greenhouse-relevant carbon species (CO2 and CH4) and molecular oxygen to better understand the environments of early life and the Great Oxygenation Event [2,3,4]. The mantle is an important reservoir of C-O-H-S volatiles [5], and melt concentrations depend on temperature, pressure and oxygen fugacity. We present a preliminary chemical model that simulates volatile concentrations released into the Earth's atmosphere at 1 bar, or pressures corresponding to the early Earth prior to 2.4 Ga. We maintain redox balance in the system using H+ [2, 6] because the melt oxidation state evolves with volatile melt concentrations [7] and affects the composition of degassed compounds. For example, low fO2 in the melt degasses CO, CH4, H2S and H2 while high fO2 yields CO2, SO2 and H2O [1,8,9]. Our calculations incorporate empirical relations from experimental petrology studies [e.g., 10, 11] to account for inter-dependencies among volatile element solubility trends. This model has implications for exploring planetary atmospheric evolution and potential greenhouse effects on Venus and Mars [12]­, and possibly exoplanets. A future direction of this work would be to link this chemical degassing model with different tectonic regimes [13] to account for degassing and ingassing, such as during subduction. References: [1] Holland, H. D. (1984) The chemical evolution of the atmosphere and oceans [2] Kasting, J. F. (2013) Chem. Geo. 362, 13-25 [3] Kasting, J.F. (1993) Sci. 259, 920-926 [4] Duncan, M.S. & Dasgupta, R. (2017) Nat. Geoscience 10, 387-392. [5] Hier-Majumder, S. & Hirschmann, M.M. (2017) G3, doi: 10.1002/2017GC006937 [6] Gaillard, F. et al. (2003) GCA 67, 2427- 2441 [7] Moussalam, Y. et al. (2014) EPSL 393, 200-209 [8] Holloway, J. R. & Blank, J. G. (1994) Rev. in Min. 30, 187-187 [9] Hirschmann, M. M. (2012) EPSL 341, 48-57 [10] Iacono-Marziano, G. et al. (2012) GCA 97, 1-23 [11] O'Neill, H. St. C. & Mavrogenes, J.A. (2002) J. of Pet. 6, 1049-1087 [12] Gaillard, F. & Scaillet, B. (2014) EPSL 403, 307-316. [13] Rozel, A.B. et al. (2017) Nature 545, 332-335.

SO2 camera measurements at Lastarria volcano and Lascar volcano in Chile

NASA Astrophysics Data System (ADS)

Lübcke, Peter; Bobrowski, Nicole; Dinger, Florian; Klein, Angelika; Kuhn, Jonas; Platt, Ulrich

2015-04-01

The SO2 camera is a remote-sensing technique that measures volcanic SO2 emissions via the strong SO2 absorption structures in the UV using scattered solar radiation as a light source. The 2D-imagery (usually recorded with a frame rate of up to 1 Hz) allows new insights into degassing processes of volcanoes. Besides the large advantage of high frequency sampling the spatial resolution allows to investigate SO2 emissions from individual fumaroles and not only the total SO2 emission flux of a volcano, which is often dominated by the volcanic plume. Here we present SO2 camera measurements that were made during the CCVG workshop in Chile in November 2014. Measurements were performed at Lastarria volcano, a 5700 m high stratovolcano and Lascar volcano, a 5600 m high stratovolcano both in northern Chile on 21 - 22 November, 2014 and on 26 - 27 November, 2014, respectively. At both volcanoes measurements were conducted from a distance of roughly 6-7 km under close to ideal conditions (low solar zenith angle, a very dry and cloudless atmosphere and an only slightly condensed plume). However, determination of absolute SO2 emission rates proves challenging as part of the volcanic plume hovered close to the ground. The volcanic plume therefore is in front of the mountain in our camera images. An SO2 camera system consisting of a UV sensitive CCD and two UV band-pass filters (centered at 315 nm and 330 nm) was used. The two band-pass filters are installed in a rotating wheel and images are taken with both filter sequentially. The instrument used a CCD with 1024 x 1024 pixels and an imaging area of 13.3 mm x 13.3 mm. In combination with the focal length of 32 mm this results in a field-of-view of 25° x 25°. The calibration of the instrument was performed with help of a DOAS instrument that is co-aligned with the SO2 camera. We will present images and SO2 emission rates from both volcanoes. At Lastarria gases are emitted from three different fumarole fields and we will attempt to investigate the degassing behavior of the individual fumaroles. Lascar volcano only had a very weak plume originating from the active central crater with maximum SO2 column densities of only up to 5 × 1017[molecules/cm2] during our measurements. These low SO2 column densities in combination with the almost ideal measurements conditions will be used to assess the detection limit of our current SO2 camera system.

Diffuse CO2 degassing monitoring of Cerro Negro volcano, Nicaragua

NASA Astrophysics Data System (ADS)

Hernández, Pedro A.; Alonso, Mar; Ibarra, Martha; Rodríguez, Wesly; Melián, Gladys V.; Saballos, Armando; Barrancos, José; Pérez, Nemesio M.; Álvarez, Julio; Martínez, William

2017-04-01

We report the results of fourteen soil CO2 efflux surveys by the closed accumulation chamber method at Cerro Negro volcano, Nicaragua. The surveys were undertaken from 1999 to 2016 to constrain the diffuse CO2 emission from this volcano and to evaluate the spatial and temporal variations of CO2 degassing rate in relation to the eruptive cycle. Cerro Negro is an active basaltic volcano belonging to the active Central American Volcanic Arc which includes a 1,100 Km long chain of 41 active volcanoes from Guatemala to Panama. Cerro Negro first erupted in 1850 and has experienced 21 eruptive eruptions with inter eruptive average periods between 7 and 9 years. Since the last eruption occurred on 5 August 1999, with erupted lava flows and ash clouds together with gas emissions, a collaborative research program between INETER and ITER/INVOLCAN has been established for monitoring diffuse CO2 emissions from this volcano. The first survey carried out at Cerro Negro was in December 1999, just 3 months after the 1999 eruption, with a total diffuse CO2 emission output estimated on 1,869 ± 197 td-1. The second survey carried out in March 2003, three years after the eruption, yielded a value of 432 ± 54 td-1. Both values that can be considered within the post-eruptive phase. The last survey performed at Cerro Negro was in November 2016, with an estimated diffuse CO2 emission of 63 ± 14 tṡd-1and soil CO2 efflux values ranging from non-detectable (˜0.5 g m-2 d-1) up to 7264 g m-2 d-1. The long-term record of diffuse CO2 emissions at Cerro Negro shows small temporal variations in CO2 emissions with a peak in 2004 (256 ± 26 td-1) followed by a peak in seismicity. Except this value, the rest of estimated values can be considered within the inter-eruptive phase, period during which a decreasing trend on the total diffuse CO2 output has been observed, with estimates between 10 and 83 tṡd-1. Regarding to the spatial distribution of diffuse CO2 values, most of relatively high CO2 efflux values were measured along the 1995 and 1999 craters together with higher soil H2S efflux and soil temperatures, and always close to the fumarolic areas, suggesting a structural control of the degassing process. The observed relationship between the long-term record of diffuse CO2 emissions and volcanic-seismic activity indicates that monitoring CO2 emission is an important geochemical tool for the volcanic surveillance at Cerro Negro.

Quantitative evaluation of the effect of H2O degassing on the oxidation state of magmas

NASA Astrophysics Data System (ADS)

Lange, R. A.; Waters, L.

2014-12-01

The extent to which degassing of the H2O component affects the oxidation state of hydrous magmas is widely debated. Several researchers have examined how degassing of mixed H-C-O-S-Cl fluids may change the Fe3+/FeT ratio of various magmas, whereas our focus is on the H2O component. There are two ways that degassing of H2O by itself may cause oxidation: (1) the reaction: H2O (melt) + 2FeO (melt) = H2 (fluid) + Fe2O3 (melt), and/or (2) if dissolved water preferentially enhances the activity of ferrous vs. ferric iron in magmatic liquids. In this study, a comparison is made between the pre-eruptive oxidation states of 14 crystal-poor, jet-black obsidian samples (obtained from two Fe-Ti oxides) and their post-eruptive values (analyzed with the Wilson 1960 titration method tested against USGS standards). The obsidians are from Medicine Lake (CA), Long Valley (CA), and the western Mexican arc; all have low FeOT (1.1-2.1 wt%), rendering their Fe2+/Fe3+ ratios highly sensitive to the possible effects of substantial H2O degassing. The Fe-Ti oxide thermometer/oxybarometer of Ghiorso and Evans, (2008) gave temperatures for the 14 samples that range for 720 to 940°C and ΔNNO values of -0.9 to +1.4. With temperature known, the plagioclase-liquid hygrometer was applied and show that ≤ 6.5 wt% H2O was dissolved in the melts prior to eruption. In addition, pre-eruptive Cl and S concentrations were constrained on the basis of apatite analyses (Webster et al., 2009) and sulfur concentrations needed for saturation with pyrrhotite (Clemente et al., 2004), respectively. Maximum pre-eruptive chlorine and sulfur contents are 6000 and 200 ppm, respectively. After eruption, the rhyolites lost nearly all of their volatiles. Our results indicate no detectable change between pre- and post-eruptive Fe2+ concentrations, with an average deviation of ± 0.1 wt % FeO. Although degassing of large concentrations of S and/or Cl may affect the oxidation state of magmas, at the pre-eruptive levels in these 14 rhyolitic magmas, no effect is detected. Therefore, it can be robustly concluded that degassing of substantial amounts of the H2O component (≤ 6.5 wt%), by itself, does not induce oxidation in erupted magmas, particularly those more iron-rich than rhyolites (e.g., arc basalts).

Degassing of H2O in a phonolitic melt: A closer look at decompression experiments

NASA Astrophysics Data System (ADS)

Marxer, Holger; Bellucci, Philipp; Nowak, Marcus

2015-05-01

Melt degassing during magma ascent is controlled by the decompression rate and can be simulated in decompression experiments. H2O-bearing phonolitic melts were decompressed at a super-liquidus T of 1323 K in an internally heated argon pressure vessel, applying continuous decompression (CD) as well as to date commonly used step-wise decompression (SD) techniques to investigate the effect of decompression method on melt degassing. The hydrous melts were decompressed from 200 MPa at nominal decompression rates of 0.0028-1.7 MPa·s- 1. At final pressure (Pfinal), the samples were quenched rapidly at isobaric conditions with ~ 150 K·s- 1. The bubbles in the quenched samples are often deformed and dented. Flow textures in the glass indicate melt transport at high viscosity. We suggest that this observation is due to bubble shrinkage during quench. This general problem was mostly overlooked in the interpretation of experimentally degassed samples to date. Bubble shrinkage due to decreasing molar volume (Vm) of the exsolved H2O in the bubbles occurs during isobaric rapid quench until the melt is too viscous too relax. The decrease of Vm(H2O) during cooling at Pfinal of the experiments results in a decrease of the bubble volume by a shrinking factor Bs: At nominal decompression rates > 0.17 MPa·s- 1 and a Pfinal of 75 MPa, the decompression method has only minor influence on melt degassing. SD and CD result in high bubble number densities of 104-105 mm- 3. Fast P drop leads to immediate supersaturation with H2O in the melt. At such high nominal decompression rates, the diffusional transport of H2O is limited and therefore bubble nucleation is the predominant degassing process. The residual H2O contents in the melts decompressed to 75 MPa increase with nominal decompression rate. After homogeneous nucleation is triggered, CD rates ≤ 0.024 MPa·s- 1 facilitate continuous reduction of the supersaturation by H2O diffusion into previously nucleated bubbles. Bubble number densities of CD samples with low nominal decompression rates are several orders of magnitude lower than for SD experiments and the bubble diameters are larger. The reproducibility of MSD experiments with low nominal decompression rates is worse than for CD runs. Commonly used SD techniques are therefore not suitable to simulate melt degassing during continuous magma ascent with low ascent rates.

Evidence of degassing-induced oxidation of relatively oxidized K-rich magmas caused by degassing of dissolved SO­42- (S6+) component in the melt to SO2 (S4+) in the gas phase

NASA Astrophysics Data System (ADS)

Pu, X.; Lange, R. A.; Moore, G. M.

2016-12-01

Near Volcán Colima in the Mexican volcanic arc, nine cones erupted minette, leucite basanite and basanite. These K-rich lavas have high post-eruptive Fe3+/FeT ratios (≤0.63) and sulfur contents (≤ 1004 ppm) (Carmichael et al., 2006). Olivine-hosted melt inclusions record ≤ 6.2wt% H2O and ≤ 6700ppm sulfur (Vigouroux et al., 2008). Here, we test whether the post-eruptive Fe3+/FeT ratios, measured by titration on fresh lavas, reflect magmatic values or a change in oxidation state during degassing. To constrain pre-eruptive fO2 (ilmenite is absent), the most Mg-rich olivine analyzed in each sample, together with a Fe-Mg KD (olivine-melt) of 0.355 (from hydrous experiments of Righter and Carmichael (1996) on a minette and the Jayasuriya et al. (2004) model to relate melt Fe2+/Fe3+ ratio to melt temperature and fO2), were used to obtain the Fe3+/FeT ratio at the onset of olivine crystallization. The resulting Fe3+/FeT ratios (0.31-0.41) and ΔNNO values (1.2-2.4) for the nine K-rich magmas are systematically lower than the post-eruptive values, which suggests that degassing induced oxidation may have occurred. In addition, the pre-eruptive Fe3+/FeT ratios and ΔNNO values are higher than those (0.19-0.31 and -0.2 to +1.2, respectively) documented for calc-alkaline basalts from Michoacán-Guanajuato Volcanic Field (MGVF) using a similar method (Pu et al., 2016). Because a similar increase between pre- and post-eruptive Fe3+/FeT ratios is not found in the MGVF samples, we infer that the increase between the pre- and post-eruptive Fe3+/FeT ratios in the K-rich samples is caused by the relatively high solubility of sulfate (S6+ in CaSO4 component) in the relatively oxidized (ΔNNO ≤ 2.4) potassic melts, which then degassed as S4+ (SO2). We deduce that oxidation caused by degassing of sulfur can only occur in melts that were already relatively oxidized, because the degassing-induced oxidation process requires an initial high concentration of sulfate in the melt phase.

Eruption Depths, Magma Storage and Magma Degassing at Sumisu Caldera, Izu-Bonin Arc: Evidence from Glasses and Melt Inclusions

NASA Astrophysics Data System (ADS)

Johnson, E. R.

2015-12-01

Island arc volcanoes can become submarine during cataclysmal caldera collapse. The passage of a volcanic vent from atmospheric to under water environment involves complex modifications of the eruption style and subsequent transport of the pyroclasts. Here, we use FTIR measurements of the volatile contents of glass and melt inclusions in the juvenile pumice clasts in the Sumisu basin and its surroundings (Izu-Bonin arc) to investigate changes in eruption depths, magma storage and degassing over time. This study is based on legacy cores from ODP 126, where numerous unconsolidated (<65 ka), extremely thick (few m to >250 m), massive to normally graded pumice lapilli-tuffs were recovered over four cores (788C, 790A, 790B and 791A). Glass and clast geochemistry indicate the submarine Sumisu caldera as the source of several of these pumice lapilli-tuffs. Glass chips and melt inclusions from these samples were analyzed using FTIR for H2O and CO2 contents. Glass chips record variable H2O contents; most chips contain 0.6-1.6 wt% H2O, corresponding to eruption depths of 320-2100 mbsl. Variations in glass H2O and pressure estimates suggest that edifice collapse occurred prior-to or during eruption of the oldest of these samples, and that the edifice may have subsequently grown over time. Sanidine-hosted melt inclusions from two units record variably degassed but H2O-rich melts (1.1-5.6 wt% H2O). The lowest H2O contents overlap with glass chips, consistent with degassing and crystallization of melts until eruption, and the highest H2O contents suggest that large amounts of degassing accompanied likely explosive eruptions. Most inclusions, from both units, contain 2-4 wt% H2O, which further indicates that the magmas crystallized at pressures of ~50-100 MPa, or depths ~400-2800 m below the seafloor. Further glass and melt inclusion analyses, including major element compositions, will elucidate changes in magma storage, degassing and evolution over time.

Quantitative degassing of gas hydrate-bearing pressure cores from Green Canyon 955, Gulf of Mexico

NASA Astrophysics Data System (ADS)

Phillips, S. C.; Holland, M. E.; Flemings, P. B.; Schultheiss, P. J.; Waite, W. F.; Petrou, E. G.; Jang, J.; Polito, P. J.; O'Connell, J.; Dong, T.; Meazell, K.

2017-12-01

We present results from 20 quantitative degassing experiments of pressure-core sections collected during Expedition UT-GOM2-1 from Green Canyon 955 in the northern Gulf of Mexico. These experiments highlight an average pore-space methane hydrate saturation, Sh, of 59% (min: 12%; max 87%) in sediments between 413 and 440 mbsf in 2032 m water depth. There is a strong lithofacies control of hydrate saturation within the reservoir, with a high saturation sandy silt facies (Sh of 65 to 87%) interbedded with a low saturation clayey silt facies (Sh of 12 to 30%). Bedding occurs on the scale of tens of centimeters. Outside of the main hydrate reservoir, methane hydrate occurs in low saturations (Sh of 0.8 to 3%). Hydrate saturations exhibit a strong correlation (R2=0.89) with the average P-wave velocity measured through the degassed sections. These preliminary hydrate saturations were calculated assuming a porosity of 40% with core filling the full internal diameter of the core liner. Gas recovered during these experiments is composed of almost entirely methane, with an average of 94 ppm ethane and detectable, but not quantifiable, propane. Degassed pressure cores were depressurized through a manifold by the stepwise release of fluid, and the volumes of produced gas and water were monitored. The core's hydrostatic pressure was measured and recorded continuously at the manifold. Pressure and temperature were also measured by data storage tags within the sample chambers. Two slow, multi-day degassing experiments were performed to estimate the in situ salinity within core sections. Based on temperature and pressure observations at the point of the initial pressure rebound due to hydrate dissociation, we estimate the salinity within these samples to be between 33 and 42 g kg-1.

Persistent explosive activity at Stromboli investigated with OP-FTIR and SO2 cameras

NASA Astrophysics Data System (ADS)

Burton, M. R.; La Spina, A.; Sawyer, G. M.; Harris, A. J.

2012-12-01

Stromboli volcano in Italy exhibits what is perhaps one of the most well-known examples of cyclic activity, in the form of its regular explosions, which send a few m3 of material 100-200 m into the air every 10-20 minutes. Recent developments in measurements of volatile release from Stromboli using a series of novel approaches have allowed this cyclic behaviour to be examined in detail. In particular, the use of an automated OP-FTIR has revealed unprecedented detail in the dynamics of degassing from individual craters at the summit of Stromboli. Furthermore, the variations in composition of explosive degassing from Stromboli demonstrate a deep source ~2 km for the gas slugs which produce explosions at this volcano, in contrast to the commonly-held view that gas coalescence at shallow depth is responsible for the behaviour. The SO2 camera has revealed fascinating new details on the dynamics of degassing at Stromboli, and has allowed direct quantification of the amount of gas released during explosions and through quiescent degassing. The remarkable observation that 99% of degassing takes place quiescently, and that the explosions, whilst apparently more significant, are in fact a secondary process compared with the mass and energy involved in background, quiet processes. The new insight that the explosions are actually only a relatively minor aspect of the activity (in terms of mass and energy) actually makes the regularity of the cyclic explosive activity still more remarkable. In this paper we present a detailed overview of the state of the art of our understanding of cyclic explosive activity at Stromboli volcano from the perspective of recent advances in geochemical monitoring of the gas emissions. We also report initial results from a multidisciplinary campaign on Stromboli which utilised both OP-FTIR and SO2 camera techniques.

Gas composition of Popocatépetl Volcano between 2007 and 2008: FTIR spectroscopic measurements of an explosive event and during quiescent degassing

NASA Astrophysics Data System (ADS)

Stremme, W.; Ortega, I.; Siebe, C.; Grutter, M.

2011-01-01

On December 1, 2007, the solar absorption infrared spectra of the Popocatépetl volcanic plume was recorded during an eruptive event and complementarily on November 17, 2008, the passive quiescent degassing was measured from the same site. A portable FTIR spectrometer with a scanning mirror for fast tracking of the sun provided the flexibility, quality, and simplicity needed for field deployment. Slant columns of the gases SO 2, HCl, HF, and SiF 4 were retrieved and strong differences could be observed when comparing gas ratios in both time periods. During the explosive eruption, the SO 2/HCl ratio was three times greater and the HF/HCl ratio was slightly smaller than during passive degassing. While the ratios among SO 2, HCl, HF, and SiF 4 describe the chemical composition of the volcanic gas mixture, the SiF 4/HF ratio provides information about the equilibrium temperatures of the stored gases which in this study were calculated at 150° and 185 °C for the explosive and quiescent degassing episodes, respectively. We conclude that cooling of lava domes in the crater precedes Vulcanian explosions as suggested by Schaaf et al (2005). Based on SO 2 flux (Grutter et al., 2008) and measurements and data from the November 2008 event, the average fluxes for HCl, HF, SiF 4, and F through quiescent degassing are estimated to be 204, 22.7, 9.8, and 31.7 tons/day, respectively. These values are similar to those reported by Love et al. (1998) more than 10 yrs ago.

Stability of unsaturated pyroclastic deposits at La Fossa flank (Vulcano Island, Italy): Do soil suction variations establish a link with crater degassing ?

NASA Astrophysics Data System (ADS)

Olivares, L.; Tommasi, P.; Madonia, P.; Moretti, R.

2012-04-01

The stability of steep ( > 40°) slopes in loose or poorly cemented pyroclastic materials mantling some of the Italian mountain areas is guaranteed by the positive effects of matrix suction on shear strength until an increase in saturation (and hence a decrease in suction) occurs. Therefore, unsaturated cohesionless or slightly-bonded pyroclastic steep deposits are relatively stable. Slope instability, initiated by wetting, can occur through different processes, such as vapor condensation and, most typically, rainfall infiltration. The main effect is the decrease in suction up to possible development of positive pore pressures. Here, we examine the peculiar case of a landslide on the flank of the pyroclastic cone of La Fossa volcanic edifice in Vulcano Island (Aeolian Archipelago, Southern Italy). Its initiation is believed to have been influenced by a sharp increase in condensed vapor produced by the degassing of the active volcano. In active volcanoes hydraulic conditions are affected not only by infiltrating rainwater but also by volcanic activity, which produces complex changes in the state variables of pore fluids (i.e. pore fluid pressure). In particular, volcanic activity can modify pore fluid pressure as far as to induce slope instability. At La Fossa crater the phenomenon was evidenced by in situ monitoring of soil suction and soil temperature. In situ observations and measurements indicate that seepage of condensed vapor is appreciable. Simple models based on the geotechnical characterization of pyroclastic materials suggest the hypothesis that variations in suction can be significant to stability of volcano slopes when these are very close to limit conditions and if material hydraulic anisotropy is considered. Noteworthy, at La Fossa at Vulcano Island steam condensation increased and variations of chemical ratios at fumaloles occurred while large slope movements developed on the NE flank of the cone during the most intense well documented volcanic unrest. The validation of this hypothesis requires further monitoring data during periods of intense unrest and more comprehensive models that account for non-isothermal multiphase pore fluid pressure and groundwater circulation, influencing the state of stress and hence stability. Our in-progress approach points toward a correlation between degassing activity of the hydrothermal-magmatic system and slope movements, that may bear significant implications for the definition of the scenarios of joint volcanic-hydrogeological hazard and for the development of monitoring techniques in the frame of volcanic surveillance. However, much more efforts are needed to establish phenomenological relationships with the budgets of volcanic steam condensation. This should include extensive field measurement of CO2 and thermal fluxes from the soil, as well as electrical measurements.

Influence of addition of degassed water on bulk nanobubbles.

PubMed

Tuziuti, Toru; Yasui, Kyuichi; Kanematsu, Wataru

2018-05-01

The effects of the addition of degassed water on bulk nanobubbles (ultrafine bubbles) of air in liquid water were investigated by measuring the volumetric concentration and size distribution at different dissolved air degree of saturation (DOS) values. The proportion of degassed water mixed with water containing bulk nanobubbles was increased to prepare samples having lower DOS values. It was found that the volumetric concentration of nanobubbles mostly decreased and the average nanobubble size became larger as the DOS was decreased. In our proposed mechanism, smaller nanobubbles are selectively dissolved into the surrounding liquid by Laplace pressure due to surface tension as the DOS is reduced. These results demonstrate that stable bulk nanobubbles are present even in water undersaturated with gas. The role of nanobubble under an ultrasound is also discussed. Copyright © 2018 Elsevier B.V. All rights reserved.

Degassing of molten alloys with the assistance of ultrasonic vibration

DOEpatents

Han, Qingyou; Xu, Hanbing; Meek, Thomas T.

2010-03-23

An apparatus and method are disclosed in which ultrasonic vibration is used to assist the degassing of molten metals or metal alloys thereby reducing gas content in the molten metals or alloys. High-intensity ultrasonic vibration is applied to a radiator that creates cavitation bubbles, induces acoustic streaming in the melt, and breaks up purge gas (e.g., argon or nitrogen) which is intentionally introduced in a small amount into the melt in order to collect the cavitation bubbles and to make the cavitation bubbles survive in the melt. The molten metal or alloy in one version of the invention is an aluminum alloy. The ultrasonic vibrations create cavitation bubbles and break up the large purge gas bubbles into small bubbles and disperse the bubbles in the molten metal or alloy more uniformly, resulting in a fast and clean degassing.

Quantifying, assessing and removing the extreme gas load from meromictic Guadiana pit lake, Southwest Spain.

PubMed

Boehrer, Bertram; Yusta, Iñaki; Magin, Katrin; Sanchez-España, Javier

2016-09-01

High gas charges in deep waters of lakes can represent a hazard to the lives of human beings and animals in the surrounding. As this danger was feared, we quantified the amount of dissolved gas in Guadiana pit lake (Las Herrerías, Huelva; southwest Spain) and documented the temporal evolution over a period of two years. Gas pressure due to dissolved gases, such as carbon dioxide, methane and nitrogen was measured. Based on these data, we assessed the risk and the associated danger of limnic eruptions from the lake and concluded that the present situation cannot be considered safe. By deploying a vertical pipe, the updraft of degassing water was tested and demonstrated: the pilot plant provided enough energy to drive a self-sustained flow. Such a system could be implemented to remove the extreme gas pressure from the deep water. Measurements of discharges could be extrapolated to indicate the size for an efficient plant for the gas removal. The construction of such a system would be technically and economically viable. A reintroduction of degassed water into the monimolimnion would be advisable. Copyright © 2016 Elsevier B.V. All rights reserved.

Prodigious degassing of a billion years of accumulated radiogenic helium at Yellowstone

USGS Publications Warehouse

Lowenstern, Jacob B.; Evans, William C.; Bergfeld, D.; Hunt, Andrew G.

2014-01-01

Helium is used as a critical tracer throughout the Earth sciences, where its relatively simple isotopic systematics is used to trace degassing from the mantle, to date groundwater and to time the rise of continents1. The hydrothermal system at Yellowstone National Park is famous for its high helium-3/helium-4 isotope ratio, commonly cited as evidence for a deep mantle source for the Yellowstone hotspot2. However, much of the helium emitted from this region is actually radiogenic helium-4 produced within the crust by α-decay of uranium and thorium. Here we show, by combining gas emission rates with chemistry and isotopic analyses, that crustal helium-4 emission rates from Yellowstone exceed (by orders of magnitude) any conceivable rate of generation within the crust. It seems that helium has accumulated for (at least) many hundreds of millions of years in Archaean (more than 2.5 billion years old) cratonic rocks beneath Yellowstone, only to be liberated over the past two million years by intense crustal metamorphism induced by the Yellowstone hotspot. Our results demonstrate the extremes in variability of crustal helium efflux on geologic timescales and imply crustal-scale open-system behaviour of helium in tectonically and magmatically active regions.

Spatially resolved SO2 flux emissions from Mt Etna

PubMed Central

Bitetto, M.; Delle Donne, D.; Tamburello, G.; Battaglia, A.; Coltelli, M.; Patanè, D.; Prestifilippo, M.; Sciotto, M.; Aiuppa, A.

2016-01-01

Abstract We report on a systematic record of SO2 flux emissions from individual vents of Etna volcano (Sicily), which we obtained using a permanent UV camera network. Observations were carried out in summer 2014, a period encompassing two eruptive episodes of the New South East Crater (NSEC) and a fissure‐fed eruption in the upper Valle del Bove. We demonstrate that our vent‐resolved SO2 flux time series allow capturing shifts in activity from one vent to another and contribute to our understanding of Etna's shallow plumbing system structure. We find that the fissure eruption contributed ~50,000 t of SO2 or ~30% of the SO2 emitted by the volcano during the 5 July to 10 August eruptive interval. Activity from this eruptive vent gradually vanished on 10 August, marking a switch of degassing toward the NSEC. Onset of degassing at the NSEC was a precursory to explosive paroxysmal activity on 11–15 August. PMID:27773952

Gas flushing through hyper-acidic crater lakes: the next steps within a reframed monitoring time window

NASA Astrophysics Data System (ADS)

Rouwet, Dmitri

2016-04-01

Tracking variations in the chemical composition, water temperature and pH of brines from peak-activity crater lakes is the most obvious way to forecast phreatic activity. Volcano monitoring intrinsically implies a time window of observation that should be synchronised with the kinetics of magmatic processes, such as degassing and magma intrusion. To decipher "how much time ago" a variation in degassing regime actually occurred before eventually being detected in a crater lake is key, and depends on the lake water residence time. The above reasoning assumes that gas is preserved as anions in the lake water (SO4, Cl, F anions), in other words, that scrubbing of acid gases is complete and irreversible. Less is true. Recent work has confirmed, by direct MultiGas measurement from evaporative plumes, that even the strongest acid in liquid medium (i.e. SO2) degasses from hyper-acidic crater lakes. The less strong acid HCl has long been recognised as being more volatile than hydrophyle in extremely acidic solutions (pH near 0), through a long-term steady increase in SO4/Cl ratios in the vigorously evaporating crater lake of Poás volcano. We now know that acidic gases flush through hyper-acidic crater lake brines, but we don't know to which extend (completely or partially?), and with which speed. The chemical composition hence only reflects a transient phase of the gas flushing through the lake. In terms of volcanic surveillance this brings the advantage that the monitoring time window is definitely shorter than defined by the water chemistry, but yet, we do not know how much shorter. Empirical experiments by Capaccioni et al. (in press) have tried to tackle this kinetic problem for HCl degassing from a "lab-lake" on the short-term (2 days). With this state of the art in mind, two new monitoring strategies can be proposed to seek for precursory signals of phreatic eruptions from crater lakes: (1) Tracking variations in gas compositions, fluxes and ratios between species in evaporative degassing plumes can be useful as monitoring tool on the short-term, but only if the underlying process of gas flushing through acidic lakes is better understood, and linked with the lake water chemistry; (2) The second method forgets about chemical kinetics, degassing models and dynamics of phreatic eruptions, and sticks to the classical principle in geology of "the past is the key for the future". How did lake chemistry parameters vary during the various stages of unrest and eruption, on a purely mathematical basis? Can we recognise patterns in the numerical values related to the changes in volcanic activity? Water chemistry only as a monitoring tool for extremely dynamic and erupting crater lake systems, is inefficient in revealing short-term precursors for single phreatic eruptions, within the current perspective of the residence time dependent monitoring time window. The monitoring rules established since decades based only on water chemistry have thus somehow become obsolete and need revision.

A Short Study of Large Rotary Forged Cylinders

DTIC Science & Technology

1979-06-01

ESR Steel Hollow ESR Steel Rotary Forge Vacuum Degassed Steel 20. ABSTRACT (Continue on reverse aide It necessary and identity by block number...treatment rging Line was used to produce steel for the Advanced ocram. Cylinders were rotary forged from cast hollow ESR ssed steel . Anomalies in the data...prompted a more detailed The results are presented. Satisfactory properties were cuum degassed steel . However, the very light forging th the very

Degassing of reduced carbon from planetary basalts

PubMed Central

Wetzel, Diane T.; Rutherford, Malcolm J.; Jacobsen, Steven D.; Hauri, Erik H.; Saal, Alberto E.

2013-01-01

Degassing of planetary interiors through surface volcanism plays an important role in the evolution of planetary bodies and atmospheres. On Earth, carbon dioxide and water are the primary volatile species in magmas. However, little is known about the speciation and degassing of carbon in magmas formed on other planets (i.e., Moon, Mars, Mercury), where the mantle oxidation state [oxygen fugacity (fO2)] is different from that of the Earth. Using experiments on a lunar basalt composition, we confirm that carbon dissolves as carbonate at an fO2 higher than -0.55 relative to the iron wustite oxygen buffer (IW-0.55), whereas at a lower fO2, we discover that carbon is present mainly as iron pentacarbonyl and in smaller amounts as methane in the melt. The transition of carbon speciation in mantle-derived melts at fO2 less than IW-0.55 is associated with a decrease in carbon solubility by a factor of 2. Thus, the fO2 controls carbon speciation and solubility in mantle-derived melts even more than previous data indicate, and the degassing of reduced carbon from Fe-rich basalts on planetary bodies would produce methane-bearing, CO-rich early atmospheres with a strong greenhouse potential. PMID:23569260

Spatial and temporal variations of diffuse CO_{2} degassing at the Tenerife North-South Rift Zone (NSRZ) volcano (Canary Islands) during the period 2002-2016

NASA Astrophysics Data System (ADS)

Rodríguez, Fátima; McCollum, John J. K.; Orland, Elijah D. M.; Barrancos, José; Padilla, Germán D.; Calvo, David; Amonte, Cecilia; Pérez, Nemesio M.

2017-04-01

Subaerial volcanic activity on Tenerife (2034 km2), the largest island of the Canary archipelago, started 14 My ago and 4 volcanic eruptions have occurred in historical times during the last 300 years. The main volcano-structural and geomorphological features of Tenerife are (i) the central volcanic complex, nowadays formed by Las Cañadas caldera, a volcanic depression measuring 16×9 km that resulted from multiple vertical collapses and partially filled by post-caldera volcanic products and (ii) the triple junction-shaped rift system, formed by numerous aligned monogenetic cones. Up to 297 mafic monogenetic cones have been recognized on Tenerife, and they represent the most common eruptive activity occurring on the island during the last 1 My (Dóniz et al., 2008). The North-South Rift Zone (NSRZ) of Tenerife comprises at least 139 cones. The main structural characteristic of the NSRZ of the island is an apparent absence of a distinct ridge, and a fan shaped distribution of monogenetic cones. Since there are currently no visible gas emissions at the NSRZ, diffuse degassing surveys have become an important geochemical tool for the surveillance of this volcanic system. Five diffuse CO2 degassing surveys have been carried out at NSRZ of Tenerife since 2002, the last one in the summer period of 2016, to evaluate the spatio-temporal variations of CO2 degassing as a volcanic surveillance tool for the NSRZ of Tenerife. At each survey, around 600 sampling sites were selected to cover homogenously the study area (325 km2) using the accumulation chamber method. The diffuse CO2 output ranged from 78 to 707 t/d in the study period, with the highest emission rate measured in 2015. The backgroung emission rate was estimated in 300 t/d. The last results the soil CO2 efflux values ranged from non-detectable up to 24.7 g m-2 d-1. The spatial distribution map, constructed following the sequential Gaussian simulation (sGs) procedure, showed the highest CO2 values as multiple isolated anomalies and did not show a clear relation with the main volcano-structural features of the area. The CO2 output released to the atmosphere in a diffuse way has been estimated at 524 t d-1, which represents a value lower than the previous one (707 t d-1 at summer of 2015) but higher than the background emission rate. These changes in the temporal series confirm the need of periodic diffuse emission surveys in the area as a powerful volcanic surveillance tool in volcanic systems where visible gas emanations are absent. References: Dóniz et al., 2008. J. Volcanol. Geotherm. Res. 173, 185.

It's the little things that matter most: The role of volatiles in volcanoes and their magmatic roots

NASA Astrophysics Data System (ADS)

Keller, T.; Suckale, J.

2017-12-01

Many volcanic eruptions are driven by volatiles - mostly H2O and CO2 - that degas from magmas rising up beneath the volcano. Gas expands during ascent, thus frequently creating lavas with upward of 50% vesicularity. That is a particularly compelling observation considering that volatiles are only present at concentrations of order 100 ppm in the mantle source. Yet, even at these small concentrations, volatiles significantly lower the peridotite solidus. That leads to the production of reactive volatile-rich melts at depth, which has important consequences for melt transport in the asthenosphere. Thus, volatiles have a pivotal role both at the beginning and the end of the magmatic storyline. A growing amount of observational evidence provides various perspectives on these systems. Volcanic products are characterised increasingly well by geochemical and petrological data. And, volcano monitoring now often provides continuous records of degassing flux and composition. What is missing to better interpret these data are coupled fluid mechanic and thermodynamic models that link melt production and reactive transport in the mantle and crust with degassing-driven volcanic activity at the surface. Such models need to describe the deformation and segregation of multiple material phases (liquids, solids, gases) and track the reactive transport of diverse chemical components (major elements, trace elements, volatiles). I will present progress towards a generalization of existing two-phase model for melt transport in the mantle, extending them to three-phase flows appropriate for magma circulation and degassing in volcanoes. What sets the two environments apart is the presence of a compressible vapor in volcanoes. Also, volcanic degassing may occur by convecting suspensions as well as porous segregation. The model framework we are developing for these processes is based on mixture theory. Uncovering the underlying physics that connects these diverse expressions of magma transport will provide an opportunity to gain deeper insights into magmatic and volcanic phenomena as related rather than separate processes. In time we may thus come to more fully understand how it is that the little things that are mantle volatiles do matter most in volcanoes and their magmatic roots.

Influence of conduit flow mechanics on magma rheology and the growth style of lava domes

NASA Astrophysics Data System (ADS)

Husain, Taha; Elsworth, Derek; Voight, Barry; Mattioli, Glen; Jansma, Pamela

2018-06-01

We develop a 2-D particle-mechanics model to explore different lava-dome growth styles. These range from endogenous lava dome growth comprising expansion of a ductile dome core to the exogenous extrusion of a degassed lava plug resulting in generation of a lava spine. We couple conduit flow dynamics with surface growth of the evolving lava dome, fuelled by an open-system magma chamber undergoing continuous replenishment. The conduit flow model accounts for the variation in rheology of ascending magma that results from degassing-induced crystallization. A period of reduced effusive flow rates promote enhanced degassing-induced crystallization. A degassed lava plug extrudes exogenously for magmas with crystal contents (ϕ) of 78 per cent, yield strength >1.62 MPa, and at flow rates of <0.5 m3 s-1, while endogenous dome growth is predicted at higher flow rates (Qout > 3 m3 s-1) for magma with lower relative yield strengths (<1 MPa). At moderately high flow rates (Qout = 4 m3 s-1), the extrusion of magma with lower crystal content (62 per cent) and low interparticulate yield strength (0.6 MPa) results in the development of endogenous shear lobes. Our simulations model the periodic extrusion history at Mount St. Helens (1980-1983). Endogenous growth initiates in the simulated lava dome with the extrusion of low yield strength magma (ϕ = 0.63 and τp = 0.76 MPa) after the crystallized viscous plug (ϕ = 0.87 and τp = 3 MPa) at the conduit exit is forced out by the high discharge rate pulse (2 < Qout < 12 m3 s-1). The size of the endogenous viscous plug and the occurrence of exogenous growth depend on magma yield strength and the magma chamber volume, which control the periodicity of the effusion. Our simulations generate dome morphologies similar to those observed at Mount St Helens, and demonstrate the degree to which domes can sag and spread during and following extrusion pulses. This process, which has been observed at Mount St. Helens and other locations, largely reflects gravitational loading of dome with a viscous core, with retardation by yield strength and talus friction.

Popping rocks from the Mid-Atlantic Ridge: Insights into mantle volatile concentrations and degassing dynamics

NASA Astrophysics Data System (ADS)

Jones, M.; Soule, S. A.; Kurz, M. D.; Wanless, V. D.; Le Roux, V.; Klein, F.; Mittelstaedt, E. L.; Curtice, J.

2016-12-01

During a 1985 cruise, the Mid-Atlantic Ridge (MAR) near 14°N yielded an unusually vesicular mid-ocean ridge (MOR) basalt that popped upon recovery from the seafloor due to the release of trapped volatiles. This `popping rock' has been inferred to be representative of primitive, undegassed magmas from the upper mantle due to its high volatile concentrations. Thus, the sample has been used to constrain CO2 flux from the MOR system, upper mantle volatile concentrations, and magma degassing dynamics. However, the lack of geologic context for the original popping rock raises questions about whether it truly reflects the volatile content of its mantle source. Here, we present results from a 2016 cruise to the MAR aimed at characterizing the geologic context of popping rocks and understanding their origins. The newly recovered samples display differences in volatile concentrations and vesicularities between popping and non-popping rocks. These differences may be related to geologic setting and eruption dynamics with potential implications for mantle volatile concentrations. Volatile concentrations in the outer quenched margin of new samples were measured by ion microprobe to elucidate degassing systematics, brine/magma interactions, and popping rock formation. The large variability in dissolved H2O (0.05-0.77 wt%) can be attributed to spatially variable brine contamination. Dissolved CO2 concentrations (153-356 ppm) are likely controlled by initial volatile concentrations and variable degrees of degassing. The subset of popping samples display low dissolved CO2 concentrations (161-178 ppm) and moderate dissolved H2O concentrations (.44-.50 wt%) and are at equilibrium with their eruption depth based on solubility calculations. X-ray microtomography reveals vesicularity in newly collected popping rocks exceeding 19%, making these samples the most highly vesicular recovered from the MAR. The total gas contents in the basaltic glasses are inferred from dissolved volatile concentrations and vesicularity. These calculations are aided by analysis of gas contents in vesicles by confocal Raman spectroscopy and vacuum crushing experiments. The preliminary results and seafloor observations allow an evaluation of the origins of popping rocks and their implications for mantle volatile concentrations.

Infrasonic Observations of Explosions and Degassing at Kilauea Summit

NASA Astrophysics Data System (ADS)

Fee, D.; Garces, M.

2008-12-01

After 25 years of quiescence, eruptive activity returned to Kilauea Caldera with an explosion in Halema'uma'u crater on March 19th 2008. The explosion is presumed to be the clearing of a clogged vent. Along with the 3/19 explosion, at least 5 more gas-driven explosions have occurred and were clearly recorded at a 4-element infrasound array 7 km away. Acoustic energy estimates for these explosions yield energies between ~ 0.2-3 × 107 J. Infrasonic VLP energy is present for some of the explosions, but not all. The relatively long explosion durations (>20 seconds) and frequency content are consistent with a transient pressure pulse followed by the reverberation of a shallow gas chamber or conduit. Persistent degassing from Halema'uma'u followed the initial explosion. The harmonic infrasonic tremor produced by the degassing is the most energetic to date at Kilauea, with the cumulative tremor acoustic energy at ~107-108 Joules/hour. The complex tremor spectra show numerous peaks, with the dominant peak between 0.3-0.6 Hz and a smaller amplitude peak around 1-3 Hz. The peak frequency of the harmonic tremor has changed over time, which could be related to a change in the gas-filled chamber dimensions or temperature. Further analysis of the tremor spectra may help constrain dimensions. Consistent with our previous observations at Kilauea from Pu'u 'O'o, Fissure D, and lava skylights, the excitation of a gas within a confined volume appears to be the acoustic (and possibly seismic) source. For the tremor, we propose a mechanism where persistent degassing excites the gas volume into resonance. The explosions signals are consistent with a slug of gas reaching the free surface and exciting the conduit as well. Correlation of the infrasound signals with seismic tremor, LP and VLP signals suggest an open system connecting the atmosphere to the seismic excitation process at depth. Results will also be presented in relation to the recent observation of a visible lava lake within the conduit.

Secular Variations of Soil CO2 Efflux at Santa Ana-Izalco-Coatepeque Volcanic Complex, El Salvador, Central America

NASA Astrophysics Data System (ADS)

Olmos, R.; Barahona, F.; Cartagena, R.; Soriano, T.; Salazar, J.; Hernandez, P.; Perez, N.; Lopez, D.

2002-12-01

The Santa Ana-Izalco-Coatepeque volcanic complex (2,365 m elevation), located 40 Km west of San Salvador, consists of the Coatepeque collapse caldera (a 6.5 x 10.5 Km elliptical depression), the Santa Ana and Izalco stratovolcanoes, as well as numerous cinder cones and explosion craters. The summit of the Santa Ana volcano contains an acid lake where hot springs, gas bubbling and intense fumarolic emissions occur. A volcanic plume, usually driven by the NE trades, may be seen rising up to 500 m from the summit crater of the Santa Ana volcano. The goal of this study is to provide a multidisciplinary approach for the volcanic surveillance by means of performing geochemical continuous monitoring of diffuse CO2 emission rate in addition to seismic monitoring. Temporal variations of soil CO2 efflux measured at Cerro Pacho dome, Coatepeque caldera, by means of the accumulation chamber method and using a CO2 efflux continuous monitoring station developed by WEST Systems (Italy). From May 2001 till May 2002, CO2 efflux ranged from 4.3 to 327 gm-2d-1, with a median value of 98 and a quartile range of 26 gm-2d-1. Two distinct diffuse CO2 degassing periods have been observed: (1) an increasing trend from May to July 2001, and (2) a stationary period from November 2001 to May 2002. The increasing-trend period may be due to the anomalous plume degassing at the Santa Ana volcano during 2001 and soon after the January and February 2001 earthquakes. Temporal variations of CO2 efllux during the second period seem to be coupled with those of barometric pressure and wind speed at different time scales, though most of the variance is contained at diurnal and semi-diurnal frequencies. These observations can help to explain the existence of a persistent behavior (Hurst exponent, H=0.934 +/- 0.0039) within the diffuse CO2 degassing phenomena. However, further observations are in progress to understand the long-term memory of diffuse CO2 degassing at the Santa Ana volcanic complex.

Understanding and forecasting phreatic eruptions driven by magmatic degassing

NASA Astrophysics Data System (ADS)

Stix, John; de Moor, J. Maarten

2018-05-01

This paper examines phreatic eruptions which are driven by inputs of magma and magmatic gas. We synthesize data from several significant phreatic systems, including two in Costa Rica (Turrialba and Poás) which are currently highly active and hazardous. We define two endmember types of phreatic eruptions, the first (type 1) in which a deeper hydrothermal system fed by magmatic gases is sealed and produces overpressure sufficient to drive explosive eruptions, and the second (type 2) where magmatic gases are supplied via open-vent degassing to a near-surface hydrothermal system, vaporizing liquid water which drives the phreatic eruptions. The surficial source of type 2 eruptions is characteristic, while the source depth of type 1 eruptions is commonly greater. Hence, type 1 eruptions tend to be more energetic than type 2 eruptions. The first type of eruption we term "phreato-vulcanian", and the second we term "phreato-surtseyan". Some systems (e.g., Ruapehu, Poás) can produce both type 1 and type 2 eruptions, and all systems can undergo sealing at various timescales. We examine a number of precursory signals which appear to be important in understanding and forecasting phreatic eruptions; these include very long period events, banded tremor, and gas ratios, in particular H2S/SO2 and CO2/SO2. We propose that if these datasets are carefully integrated during a monitoring program, it may be possible to accurately forecast phreatic eruptions.[Figure not available: see fulltext.

Relationships between CO 2, thermodynamic limits on silicate weathering, and the strength of the silicate weathering feedback

DOE PAGES

Winnick, Matthew J.; Maher, Kate

2018-01-27

Recent studies have suggested that thermodynamic limitations on chemical weathering rates exert a first-order control on riverine solute fluxes and by extension, global chemical weathering rates. As such, these limitations may play a prominent role in the regulation of carbon dioxide levels (pCO 2) over geologic timescales by constraining the maximum global weathering flux. In this study, we develop a theoretical scaling relationship between equilibrium solute concentrations and pCO 2 based on equilibrium constants and reaction stoichiometry relating primary mineral dissolution and secondary mineral precipitation. Here, we test this theoretical scaling relationship against reactive transport simulations of chemical weathering profilesmore » under open-and closed-system conditions, representing partially and fully water-saturated regolith, respectively. Under open-system conditions, equilibrium bicarbonate concentrations vary as a power-law function of pCO 2(y =kx n)where nis dependent on reaction stoichiometry and kis dependent on both reaction stoichiometry and the equilibrium constant. Under closed-system conditions, bicarbonate concentrations vary linearly with pCO 2 at low values and approach open-system scaling at high pCO 2. To describe the potential role of thermodynamic limitations in the global silicate weathering feedback, we develop a new mathematical framework to assess weathering feedback strength in terms of both (1) steady-state atmospheric pCO 2 concentrations, and (2) susceptibility to secular changes in degassing rates and transient carbon cycle perturbations, which we term 1st and 2nd order feedback strength, respectively. Finally, we discuss the implications of these results for the effects of vascular land plant evolution on feedback strength, the potential role of vegetation in controlling modern solute fluxes, and the application of these frameworks to a more complete functional description of the silicate weathering feedback. Most notably, the dependence of equilibrium solute concentrations on pCO 2 may represent a direct weathering feedback largely independent of climate and modulated by belowground organic carbon respiration.« less

Relationships between CO 2, thermodynamic limits on silicate weathering, and the strength of the silicate weathering feedback

DOE Office of Scientific and Technical Information (OSTI.GOV)

Winnick, Matthew J.; Maher, Kate

Recent studies have suggested that thermodynamic limitations on chemical weathering rates exert a first-order control on riverine solute fluxes and by extension, global chemical weathering rates. As such, these limitations may play a prominent role in the regulation of carbon dioxide levels (pCO 2) over geologic timescales by constraining the maximum global weathering flux. In this study, we develop a theoretical scaling relationship between equilibrium solute concentrations and pCO 2 based on equilibrium constants and reaction stoichiometry relating primary mineral dissolution and secondary mineral precipitation. Here, we test this theoretical scaling relationship against reactive transport simulations of chemical weathering profilesmore » under open-and closed-system conditions, representing partially and fully water-saturated regolith, respectively. Under open-system conditions, equilibrium bicarbonate concentrations vary as a power-law function of pCO 2(y =kx n)where nis dependent on reaction stoichiometry and kis dependent on both reaction stoichiometry and the equilibrium constant. Under closed-system conditions, bicarbonate concentrations vary linearly with pCO 2 at low values and approach open-system scaling at high pCO 2. To describe the potential role of thermodynamic limitations in the global silicate weathering feedback, we develop a new mathematical framework to assess weathering feedback strength in terms of both (1) steady-state atmospheric pCO 2 concentrations, and (2) susceptibility to secular changes in degassing rates and transient carbon cycle perturbations, which we term 1st and 2nd order feedback strength, respectively. Finally, we discuss the implications of these results for the effects of vascular land plant evolution on feedback strength, the potential role of vegetation in controlling modern solute fluxes, and the application of these frameworks to a more complete functional description of the silicate weathering feedback. Most notably, the dependence of equilibrium solute concentrations on pCO 2 may represent a direct weathering feedback largely independent of climate and modulated by belowground organic carbon respiration.« less

Relationships between CO2, thermodynamic limits on silicate weathering, and the strength of the silicate weathering feedback

NASA Astrophysics Data System (ADS)

Winnick, Matthew J.; Maher, Kate

2018-03-01

Recent studies have suggested that thermodynamic limitations on chemical weathering rates exert a first-order control on riverine solute fluxes and by extension, global chemical weathering rates. As such, these limitations may play a prominent role in the regulation of carbon dioxide levels (pCO2) over geologic timescales by constraining the maximum global weathering flux. In this study, we develop a theoretical scaling relationship between equilibrium solute concentrations and pCO2 based on equilibrium constants and reaction stoichiometry relating primary mineral dissolution and secondary mineral precipitation. We test this theoretical scaling relationship against reactive transport simulations of chemical weathering profiles under open- and closed-system conditions, representing partially and fully water-saturated regolith, respectively. Under open-system conditions, equilibrium bicarbonate concentrations vary as a power-law function of pCO2 (y = kxn) where n is dependent on reaction stoichiometry and k is dependent on both reaction stoichiometry and the equilibrium constant. Under closed-system conditions, bicarbonate concentrations vary linearly with pCO2 at low values and approach open-system scaling at high pCO2. To describe the potential role of thermodynamic limitations in the global silicate weathering feedback, we develop a new mathematical framework to assess weathering feedback strength in terms of both (1) steady-state atmospheric pCO2 concentrations, and (2) susceptibility to secular changes in degassing rates and transient carbon cycle perturbations, which we term 1st and 2nd order feedback strength, respectively. Finally, we discuss the implications of these results for the effects of vascular land plant evolution on feedback strength, the potential role of vegetation in controlling modern solute fluxes, and the application of these frameworks to a more complete functional description of the silicate weathering feedback. Most notably, the dependence of equilibrium solute concentrations on pCO2 may represent a direct weathering feedback largely independent of climate and modulated by belowground organic carbon respiration.

A global census of continental rift activity since 250 Ma reveals a missing element of the deep carbon cycle

NASA Astrophysics Data System (ADS)

Brune, Sascha; Williams, Simon; Müller, Dietmar

2017-04-01

The deep carbon cycle connects CO2 concentrations within the atmosphere to the vast carbon reservoir in Earth's mantle: subducted lithosphere carries carbon into the mantle, while extensional plate boundaries and arc volcanoes release it back to Earth's surface. The length of plate boundaries thereby exerts first-order control on global CO2 fluxes on geological time scales. Here we provide a global census of rift length from the Triassic to present day, combining a new plate reconstruction analysis technique with data from the geological rift record. We find that the most extensive rift phase during the fragmentation of Pangea occurred in the Jurassic/Early Cretaceous with extension along the South Atlantic (9700 km) and North Atlantic rifts (9100 km), within East Gondwana (8500 km), the failed African rift systems (4900 km), and between Australia and Antarctica (3700 km). The combined extent of these and other rift systems amounts to more than 50.000 km of simultaneously active continental rifts. During the Late Cretaceous, in the aftermath of this massive rift episode, the global rift length dropped by 60% to 20.000 km. We further show that a second pronounced rift episode starts in the Eocene with global rift lengths of up to 30.000 km. It is well-accepted that volcanoes at plate boundaries release large amounts of CO2 from the Earth's interior. Recent work, however, highlights the importance of deep-cutting faults and diffuse degassing on CO2 emissions in the East African Rift, which appear to be comparable to CO2 release rates at mid-ocean ridges worldwide. Upscaling measured CO2 fluxes from East Africa to all concurrently active global rift zones with due caution, we compute the first-order history of cumulative rift-related CO2 degassing rates for the last 250 Myr. We demonstrate that rift-related CO2 release in the Early Cretaceous may have reached 400% of present-day rates. In first-order agreement with paleo-atmospheric CO2 concentrations from proxy indicators, our degassing rates correlate with the two distinct periods of elevated atmospheric CO2 in the Mesozoic and Cenozoic. Compiling the length of other plate boundaries through time (mid-ocean ridges, subduction zones, continental arcs), we do not find such a correlation with the paleo-CO2 record, which leads us to suggest that rift-related degassing constitutes an important element of the deep carbon cycle.

New evidence of CO2 soil degassing anomalies on Piton de la Fournaise volcano and the link with volcano tectonic structures

NASA Astrophysics Data System (ADS)

Liuzzo, M.; Di Muro, A.; Giudice, G.; Michon, L.; Ferrazzini, V.; Gurrieri, S.

2015-12-01

Piton de la Fournaise (PdF) is recognized as one of the world's most active volcanoes in terms of eruptive frequency and the substantial quantity of lava produced. Yet with the sole exception of rather modest intracrateric fumarole activity, this seems to be in contrast with an apparent absence of any type of natural fluid emission during periods of quiescence. Measurement campaigns were undertaken during a long-lasting quiescent period (2012-2014) and just after a short-lived summit eruption (June 2014) in order to identify potential degassing areas in relation to the main structural features of the volcano (e.g., rift zones) with the aim of developing a broader understanding of the geometry of the plumbing and degassing system. In order to assess the possible existence of anomalous soil CO2 flux, 513 measurements were taken along transects roughly orthogonal to the known tectonic lineaments crossing PdF edifice. In addition, 53 samples of gas for C isotope analysis were taken at measurement points that showed a relatively high CO2 concentration in the soil. CO2 flux values range from 10 to 1300 g m-2 d-1 while δ13C are between -26.6 and -8‰. The results of our investigation clearly indicate that there is a strong spatial correlation between the anomalous high values of diffusive soil emissions and the main rift zones cutting the PdF massif and, moreover, that generally high soil CO2 fluxes show a δ13C signature clearly related to a magmatic origin.

Global-scale water circulation in the Earth's mantle: Implications for the mantle water budget in the early Earth

NASA Astrophysics Data System (ADS)

Nakagawa, Takashi; Spiegelman, Marc W.

2017-04-01

We investigate the influence of the mantle water content in the early Earth on that in the present mantle using numerical convection simulations that include three processes for redistribution of water: dehydration, partitioning of water into partially molten mantle, and regassing assuming an infinite water reservoir at the surface. These models suggest that the water content of the present mantle is insensitive to that of the early Earth. The initial water stored during planetary formation is regulated up to 1.2 OMs (OM = Ocean Mass; 1.4 ×1021 kg), which is reasonable for early Earth. However, the mantle water content is sensitive to the rheological dependence on the water content and can range from 1.2 to 3 OMs at the present day. To explain the evolution of mantle water content, we computed water fluxes due to subducting plates (regassing), degassing and dehydration. For weakly water dependent viscosity, the net water flux is almost balanced with those three fluxes but, for strongly water dependent viscosity, the regassing dominates the water cycle system because the surface plate activity is more vigorous. The increased convection is due to enhanced lubrication of the plates caused by a weak hydrous crust for strongly water dependent viscosity. The degassing history is insensitive to the initial water content of the early Earth as well as rheological strength. The degassing flux from Earth's surface is calculated to be approximately O (1013) kg /yr, consistent with a coupled model of climate evolution and mantle thermal evolution.

Influence of ultrasound on the electrical breakdown of transformer oil

NASA Astrophysics Data System (ADS)

Isakaev, E. Kh; Tyuftyaev, A. S.; Gadzhiev, M. Kh; Demirov, N. A.; Akimov, P. L.

2018-01-01

When the transformer oil is exposed to low power ultrasonic waves (< 2 W/cm2) at initial moment the breakdown voltage of transformer oil is reduced relative to the breakdown voltage of pure oil due to degassing and the occurrence of cavitation bubbles. With the increase of sonication time the breakdown voltage also increases, nonlinearly. The experimental data indicate the possibility of using ultrasonic waves of low power for degassing of transformer oil.

Geochemical variation of groundwater in the Abruzzi region: earthquakes related signals?

NASA Astrophysics Data System (ADS)

Cardellini, C.; Chiodini, G.; Caliro, S.; Frondini, F.; Avino, R.; Minopoli, C.; Morgantini, N.

2009-12-01

The presence of a deep and inorganic source of CO2 has been recently recognized in Italy on the basis of the deeply derived carbon dissolved in the groundwater. In particular, the regional map of CO2 Earth degassing shows that two large degassing structures affect the Tyrrhenian side of the Italian peninsula. The northern degassing structure (TRDS, Tuscan Roman degassing structure) includes Tuscany, Latium and part of Umbria regions (~30000 km2) and releases > 6.1 Mt/y of deeply derived CO2. The southern degassing structure (CDS, Campanian degassing structure) affects the Campania region (~10000 km2) and releases > 3.1 Mt/y of deeply derived CO2. The total CO2 released by TRDS and CDS (> 9.2 Mt/y) is globally significant, being ~10% of the estimated present-day total CO2 discharge from sub aerial volcanoes of the Earth. The comparison between the map of CO2 Earth degassing and of the location of the Italian earthquakes highlights that the anomalous CO2 flux suddenly disappears in the Apennine in correspondence of a narrow band where most of the seismicity concentrates. A previous conceptual model proposed that in this area, at the eastern borders of TRDS and CDS plumes, the CO2 from the mantle wedge intrudes the crust and accumulate in structural traps generating over-pressurized reservoirs. These CO2 over-pressurized levels can play a major role in triggering the Apennine earthquakes, by reducing fault strength and potentially controlling the nucleation, arrest, and recurrence of both micro and major (M>5) earthquakes. The 2009 Abruzzo earthquakes, like previous seismic crises in the Northern Apennine, occurred at the border of the TRDS, suggesting also in this case a possible role played by deeply derived fluids in the earthquake generation. In order to investigate this process, detailed hydro-geochemical campaigns started immediately after the main shock of the 6th of April 2009. The surveys include the main springs of the area which were previously studied in detail, during a campaign performed ten years ago, constituting a pre-crisis reference case. The new data includes the determination of the main dissolved ions, the dissolved gases (CO2, CH4, N2, Ar, He) and the stable isotopes of the water (H, O), CO2 (13C) and He (3He/4He). All the springs collected in 2009 show a systematic increase in the content of the deeply derived CO2 dissolved in the aquifers, respect to the 1997. The origin of this regional variation is still under investigation. A monthly sampling of the main spring has been programmed in order to differentiate the variation derived by seasonal processes from eventual signals linked to seismic processes. The first results will be presented and discussed.

Static feed water electrolysis module

NASA Technical Reports Server (NTRS)

Powell, J. D.; Schubert, F. H.; Jensen, F. C.

1974-01-01

An advanced static feed water electrolysis module (SFWEM) and associated instrumentation for generating breathable O2 was developed. The system also generates a H2 byproduct for use in an air revitalization system for O2 recovery from metabolic CO2. Special attention was given to: (1) eliminating water feed compartment degassing, (2) eliminating need for zero gravity condenser/separators, (3) increasing current density capability, and (4) providing a self contained module so that operation is independent of laboratory instrumentation and complicated startup/shutdown procedures.

Fumarole emissions at Mount St. Helens volcano, June 1980 to October 1981: Degassing of a magma-hydrothermal system

USGS Publications Warehouse

Gerlach, T.M.; Casadevall, T.J.

1986-01-01

This study is an investigation of the chemical changes in the Mount St. Helens fumarole gases up to October 1981, the sources of the fumarole gases, and the stability of gas species in the shallow magma system. These problems are investigated by calculations of element compositions, thermodynamic equilibria, and magmatic volatile-hydrothermal steam mixing models. The fumarole gases are treated as mixtures of magmatic volatiles and hydrothermal steam formed by magma degassing and boiling of local waters in a dryout zone near conduit and dome magma. The magmatic volatile fraction is significant in fumaroles with temperatures in excess of the magma cracking-temperature (??? 700??C) - i.e., the temperature below which cracking is induced by thermal stresses during cooling and solidification. Linear composition changes of the fumarole gases over time appear to be the result of a steady decline in the magmatic volatile mixing fraction, which may be due to the tapping of progressively volatile-depleted magma. The maximum proportion of hydrothermal steam in the fumaroles rose from about 25-35% in September 1980 to around 50-70% by October 1981. Fractional degassing of magmatic CO2 and sulfur also contributed to the chemical changes in the fumarole gases. The steady chemical changes indicate that replenishment of the magma system with undegassed magma was not significant between September 1980 and September 1981. Extrapolations of chemical trends suggest that fumarole gases emitted at the time of formation of the first dome in mid-June 1980 were more enriched in a magmatic volatile fraction and contained a minimum of 9% CO2. Calculations show H2S is the predominant sulfur species in Mount St. Helens magma below depths of 200 m. Rapid release of gases from magma below this depth is a plausible mechanism for producing the high H2S/SO2 observed in Mount St. Helens plumes during explosive eruptions. This study suggests that dacite-andesite volcanos may emit gases richer in CO2 during the earlier episodes of an eruptive cycle and burden the atmosphere with much more H2S than SO2 during explosive eruptions. ?? 1986.

Timescales of magma ascent and degassing and the role of crustal assimilation at Merapi volcano (2006-2010), Indonesia: Constraints from uranium-series and radiogenic isotopic compositions

NASA Astrophysics Data System (ADS)

Handley, H. K.; Reagan, M.; Gertisser, R.; Preece, K.; Berlo, K.; McGee, L. E.; Barclay, J.; Herd, R.

2018-02-01

We present new 238U-230Th-226Ra-210Pb-210Po, 87Sr/86Sr and 143Nd/144Nd isotopic data of whole-rock samples and plagioclase separates from volcanic deposits of the 2006 and 2010 eruptions at Merapi volcano, Java, Indonesia. These data are combined with available eruption monitoring, petrographic, mineralogical and Pb isotopic data to assess current theories on the cause of a recent transition from effusive dome-building (2006) to explosive (2010) activity at the volcano, as well as to further investigate the petrogenetic components involved in magma genesis and evolution. Despite the significant difference in eruption style, the 2006 and 2010 volcanic rocks show no significant difference in (238U/232Th), (230Th/232Th) and (226Ra/230Th) activity ratios, with all samples displaying U and Ra excesses. The 226Ra and 210Pb excesses observed in plagioclase separates from the 2006 and 2010 eruptions indicate that a proportion of the plagioclase grew within the decades preceding eruption. The 2006 and 2010 samples were depleted in 210Po relative to 210Pb ((210Po/210Pb)i < 1) at the time of eruption but were variably degassed (69%-100%), with the degree of 210Pb degassing strongly related to sample texture and eruption phase. In good agreement with several activity monitoring parameters, 210Po ingrowth calculations suggest that initial intrusion into the shallow magma plumbing system occurred several weeks to a few months prior to the initial 2010 eruption. The 2006 and 2010 samples show a wide range in (210Pb/226Ra) activity ratio within a single eruption at Merapi and are largely characterised by 210Pb deficits ((210Pb/226Ra) < 1). Assuming a model of complete radon degassing, the 210Pb deficits in the 2006 volcanic rocks indicate relatively longer degassing timescales of ∼2-4 years than those given by the 2010 samples of ∼0-3 years. The uranium-series and radiogenic isotopic data do not support greater crustal assimilation of carbonate material as the explanation for the more explosive behaviour of Merapi in 2010 (as has been previously suggested) and instead indicate that relatively rapid ascent of a more undegassed magma was the primary difference responsible for the transition in explosive behaviour. This interpretation is in good agreement with gas monitoring data, previous petrological studies (mineral, microlite and melt inclusion work) and maximum calculated timescale estimates using Fe-Mg compositional gradients in clinopyroxene, that also suggest more rapid movement of relatively undegassed magma in 2010 relative to 2006.

Soufrière Hills Plagioclase: Postcards From the Edge.

NASA Astrophysics Data System (ADS)

Genareau, K.; Clarke, A.; Hervig, R.

2005-12-01

Secondary Ion Mass Spectrometry (SIMS) can provide sub-micron depth resolution for analyzing products of volcanic eruptions. SIMS was used to examine the outer rims of plagioclase phenocrysts derived from both explosive and effusive eruptions of the Soufrière Hills Volcano (SHV), Montserrat. Phenocrysts were separated from the host igneous rock by crushing with a mortar and pestle and then cleaned with a Branson Sonifier. A 12.5 kV O2+ primary ion beam was used to examine the variation in ten elements (Ca, Na, Si, Al, Ti, Zr, K, Fe, Sr, Li) through a crystal depth of 5-9 microns. Plagioclase crystals separated from explosively produced pumice clasts show increasing anorthite (An) content with depth into the crystal surface, starting at ~10% An at the surface and reaching a constant composition of ~45% An at 2-4 microns depth. According to experimentally determined estimates of plagioclase growth rates for the SHV magma (Couch et al. 2003; J. Petrology 44, 1477-1502), the 2-4 microns depth over which An changes corresponds to 1-7 hours of growth. Sr also shows a general increase with depth into the crystal. K shows a rapid decrease in abundance with depth. Fe shows more complex patterns that may indicate late-stage crystallization of magnetite. Plagioclase derived from exogenous dome samples also have surface compositions of ~10% An increasing with depth to ~30% An, but rather than plateau, the values begin to decrease again at 2-5 microns depth. This fluctuating abundance of An may reveal the presence of micron-scale decompression-induced growth zones that have not been previously documented due to limitations in the spatial resolution of conventional analytical techniques. Explosive and effusive samples exhibit conflicting Li trends. The explosively derived plagioclase have elevated surface Li concentrations while the dome derived plagioclase have low surface Li concentrations. These differing trends may provide evidence of closed system vs. open system degassing as a function of eruptive style. Geochemical analyses of igneous phenocrysts using the SIMS depth-profiling technique can be used to constrain the style of magma decompression and eruption. Additional analyses are currently being performed on an expanded suite of samples in order to confirm these results and to relate crystal-edge chemistry to other parameters such as quench pressure and degree of magma degassing.

Partitioning of light lithophile elements during basalt eruptions on Earth and application to Martian shergottites

NASA Astrophysics Data System (ADS)

Edmonds, Marie

2015-02-01

An enigmatic record of light lithophile element (LLE) zoning in pyroxenes in basaltic shergottite meteorites, whereby LLE concentrations decrease dramatically from the cores to the rims, has been interpreted as being due to partitioning of LLE into a hydrous vapor during magma ascent to the surface on Mars. These trends are used as evidence that Martian basaltic melts are water-rich (McSween et al., 2001). Lithium and boron are light lithophile elements (LLE) that partition into volcanic minerals and into vapor from silicate melts, making them potential tracers of degassing processes during magma ascent to the surface of Earth and of other planets. While LLE degassing behavior is relatively well understood for silica-rich melts, where water and LLE concentrations are relatively high, very little data exists for LLE abundance, heterogeneity and degassing in basaltic melts. The lack of data hampers interpretation of the trends in the shergottite meteorites. Through a geochemical study of LLE, volatile and trace elements in olivine-hosted melt inclusions from Kilauea Volcano, Hawaii, it can be demonstrated that lithium behaves similarly to the light to middle rare Earth elements during melting, magma mixing and fractionation. Considerable heterogeneity in lithium and boron is inherited from mantle-derived primary melts, which is dominant over the fractionation and degassing signal. Lithium and boron are only very weakly volatile in basaltic melt erupted from Kilauea Volcano, with vapor-melt partition coefficients <0.1. Degassing of LLE is further inhibited at high temperatures. Pyroxene and associated melt inclusion LLE concentrations from a range of volcanoes are used to quantify lithium pyroxene-melt partition coefficients, which correlate negatively with melt H2O content, ranging from 0.13 at low water contents to <0.08 at H2O contents >4 wt%. The observed terrestrial LLE partitioning behavior is extrapolated to Martian primitive melts through modeling. The zoning observed in the shergottite pyroxenes is only consistent with degassing of LLE from a Martian melt near its liquidus temperature if the vapor-melt partition coefficient was an order of magnitude larger than observed on Earth. The range in LLE and trace elements observed in shergottite pyroxenes are instead consistent with concurrent mixing and fractionation of heterogeneous melts from the mantle.

Sulfur, chlorine, and fluorine degassing and atmospheric loading by the 1783 1784 AD Laki (Skaftár Fires) eruption in Iceland

NASA Astrophysics Data System (ADS)

Thordarson, T.; Self, S.; Óskarsson, N.; Hulsebosch, T.

1996-09-01

The 1783 1784 Laki tholeiitic basalt fissure eruption in Iceland was one of the greatest atmospheric pollution events of the past 250 years, with widespread effects in the northern hemisphere. The degassing history and volatile budget of this event are determined by measurements of pre-eruption and residual contents of sulfur, chlorine, and fluorine in the products of all phases of the eruption. In fissure eruptions such as Laki, degassing occurs in two stages: by explosive activity or lava fountaining at the vents, and from the lava as it flows away from the vents. Using the measured sulfur concentrations in glass inclusions in phenocrysts and in groundmass glasses of quenched eruption products, we calculate that the total accumulative atmospheric mass loading of sulfur dioxide was 122 Mt over a period of 8 months. This volatile release is sufficient to have generated ˜250 Mt of H2SO4 aerosols, an amount which agrees with an independent estimate of the Laki aerosol yield based on atmospheric turbidity measurements. Most of this volatile mass (˜60 wt.%) was released during the first 1.5 months of activity. The measured chlorine and fluorine concentrations in the samples indicate that the atmospheric loading of hydrochloric acid and hydrofluoric acid was ˜7.0 and 15.0 Mt, respectively. Furthermore, ˜75% of the volatile mass dissolved by the Laki magma was released at the vents and carried by eruption columns to altitudes between 6 and 13 km. The high degree of degassing at the vents is attributed to development of a separated two-phase flow in the upper magma conduit, and implies that high-discharge basaltic eruptions such as Laki are able to loft huge quantities of gas to altitudes where the resulting aerosols can reside for months or even 1 2 years. The atmospheric volatile contribution due to subsequent degassing of the Laki lava flow is only 18 wt.% of the total dissolved in the magma, and these emissions were confined to the lowest regions of the troposphere and therefore important only over Iceland. This study indicates that determination of the amount of sulfur degassed from the Laki magma batch by measurements of sulfur in the volcanic products (the petrologic method) yields a result which is sufficient to account for the mass of aerosols estimated by other methods.

Carbon degassing from the lithosphere

NASA Astrophysics Data System (ADS)

Mörner, Nils-Axel; Etiope, Giuseppe

2002-06-01

So far, the role of present-day Earth degassing in global C budget and climate effects has been focused to volcanic emissions. The non-volcanic escape of CO 2-CH 4 from the upper mantle, from carbonate bearing rocks in the crust, from hydrocarbon accumulations and from surface deposits and processes is here discussed in detail. An inventory of recent available data is presented. For the first time, a so large quantity of data is considered altogether showing clearly that the geological flux of carbon was previously significantly underestimated. Several lines of evidence show that non-volcanic C fluxes in «colder» environments are much greater than generally assumed. Local and regional data suggest that metamorphic decarbonation, hydrocarbon leakage and mud volcanoes could be significant CO 2-CH 4 sources at global scale. Moreover, extensive surface gas-geochemical observations, including soil-atmosphere flux investigations, open the possibility that ecosystems controlled by biogenic activity (soil, permafrost, seawater) can host important components of endogenous C gas (geogas), even in the absence of surface gas manifestations. This would imply the existence of a geological diffuse, background emission over large areas of our planet. New theories concerning the occurrence of pervasive geogas and lithospheric processes of C-gas production («lithospheric loss in rigidity») can be taken as novel reference and rationale for re-evaluating geological sources of CO 2 and CH 4, and an important endeavour and work prospect for the years to come. Our survey shows that it is still very hard to arrive at a meaningful estimate of the lithospheric non-volcanic degassing into the atmosphere. Orders of 10 2-10 3 Mt CO 2/year can be provisionally considered. Assuming as lower limit for a global subaerial volcanic degassing 300 Mt/year, the lithosphere may emit directly into the atmosphere at least 600 Mt CO 2/year (about 10% of the C source due to deforestation and land-use exchange), an estimate we still consider conservative. It is likely that temporal variations of lithosphere degassing, at Quaternary and secular scale, may influence the atmospheric C budget. The present-day lithosphere degassing would seem higher than the value considered to balance at Ma time-scale the CO 2 uptake due to silicate weathering.

Isotopic insights into the degassing and secondary hydration of volcanic glass from the 1980 eruptions of Mount St. Helens

NASA Astrophysics Data System (ADS)

Seligman, Angela N.; Bindeman, Ilya; Van Eaton, Alexa; Hoblitt, Richard

2018-04-01

Abstract The magmatic degassing history of newly erupted volcanic glass is recorded in its remaining volatile content. However, this history is subsequently overprinted by post-depositional (secondary) hydration, the rates and origins of which are not yet adequately constrained. Here, we present the results of a natural experiment using products of the 1980 eruptions of Mount St. Helens. We measured water concentration, δDglass, and δ18OBSG (δ18O of the bulk silicate glass) of samples collected during the dry summer months of 1980 and compared them with material resampled in 2015 from the same deposits. Samples collected from the subsurface near gas escape pipes show elevated water concentrations (near 2.0 wt%), and these are associated with lower δDglass (- 110 to - 130‰) and δ18OBSG (6.0 to 6.6‰) values than the 1980 glass (- 70 to - 100‰ and 6.8 to 6.9‰, respectively). Samples collected in 2015 from the surface to 10-cm subsurface of the 1980 summer deposits have a small increase in average water contents of 0.1-0.2 wt% but similar δ18OBSG (6.8-6.9‰) values compared to the 1980 glass values. These samples, however, show 15‰ higher δDglass values; exchange with meteoric water is expected to yield lower δDglass values. We attribute higher δDglass values in the upper portion of the 1980 deposits collected in 2015 to rehydration by higher δD waters that were degassed for several months to a year from the hot underlying deposits, which hydrated the overlying deposits with relatively high δD gases. Our data also contribute to magmatic degassing of crystal-rich volcanoes. Using the 1980 samples, our reconstructed δD-H2O trends for the dacitic Mount St. Helens deposits with rhyolitic groundmass yield a trend that overlaps with the degassing trend for crystal-poor rhyolitic eruptions studied previously elsewhere, suggesting similar behavior of volatiles upon exsolution from magma. Furthermore, our data support previous studies proposing that exsolved volatiles were trapped within a rapidly rising magma and started degassing only at shallow depths during the 1980 eruptions.

Sulfur, Chlorine, and Flourine Degassing and Atmospheric Loading by the 1783 - 1784 AD Laki (Skaftar Fires) Eruption in Iceland

NASA Technical Reports Server (NTRS)

Thordarson, T.; Self, S.; Hulsebosch, T.; Oskarsson, N.; McPhie, Jocelyn (Editor)

1996-01-01

The 1783-1784 Laki tholeiitic basalt fissure eruption in Iceland was one of the greatest atmospheric pollution events of the past 250 years, with widespread effects in the northern hemisphere. The degassing history and volatile budget of this event are determined by measurements of pre-eruption and residual contents of sulfur, chlorine, and fluorine in the products of all phases of the eruption. In fissure eruptions such as Laki, degassing occurs in two stages: by explosive activity or lava fountaining at the vents, and from the lava as it flows away from the vents. Using the measured sulfur concentrations in glass inclusions in phenocrysts and in groundmass glasses of quenched eruption products, we calculate that the total accumulative atmospheric mass loading of sulfur dioxide was 122 Mt over a period of 8 months. This volatile release is sufficient to have generated approximately 250 Mt of H2SO4 aerosols, an amount which agrees with an independent estimate of the Laki aerosol yield based on atmospheric turbidity measurements. Most of this volatile mass (approximately 60 wt.%) was released during the first 1.5 months of activity. The measured chlorine and fluorine concentrations in the samples indicate that the atmospheric loading of hydrochloric acid and hydrofluoric acid was approximately 7.0 and 15.0 Mt, respectively. Furthermore, approximately 75% of the volatile mass dissolved by the Laki magma was released at the vents and carried by eruption columns to altitudes between 6 and 13 km. The high degree of degassing at the vents is attributed to development of a separated two-phase flow in the upper magma conduit, and implies that high-discharge basaltic eruptions such as Laki are able to loft huge quantities of gas to altitudes where the resulting aerosols can reside for months, or even 1-2 years. The atmospheric volatile contribution due to subsequent degassing of the Laki lava flow is only 18 wt.% of the total dissolved in the magma, and these emissions were confined to the lowest regions of the troposhere and therefore important only over Iceland. This study indicates that determination of the amount of sulfur degassed from the Laki magma batch by measurements of sulfur in the volcanic products (the petrologic method) yields a result which is sufficient to account for the mass of aerosols estimated by other methods.

Pathophysiology of Non-Freezing Cold Injury

DTIC Science & Technology

1989-07-01

the leg. Salicylic acid was injected through the femoral vein at the end of some experiments to assay hydroxy radical (OH*). Our results demonstrated...pH 4.5); 50 J1 of 70% perchloric acid was then added to the mixtur,". The resultant mixture was degassed and filtered through a Rainin Nylon-66...consisting of a Model 510 pump and a Model 460 electrochemical detector. The hydroxylated products of salicylic acid were eluted with buffer (degassed and

Effect of thermal exposure, forming, and welding on high-temperature, dispersion-strengthened aluminum alloy: Al-8Fe-1V-2Si

NASA Technical Reports Server (NTRS)

Kennedy, J. R.; Gilman, P. S.; Zedalis, M. S.; Skinner, D. J.; Peltier, J. M.

1991-01-01

The feasibility of applying conventional hot forming and welding methods to high temperature aluminum alloy, Al-8Fe-1V-2Si (FVS812), for structural applications and the effect of thermal exposure on mechanical properties were determined. FVS812 (AA8009) sheet exhibited good hot forming and resistance welding characteristics. It was brake formed to 90 deg bends (0.5T bend radius) at temperatures greater than or equal to 390 C (730 F), indicating the feasibility of fabricating basic shapes, such as angles and zees. Hot forming of simple contoured-flanged parts was demonstrated. Resistance spot welds with good static and fatigue strength at room and elevated temperatures were readily produced. Extended vacuum degassing during billet fabrication reduced porosity in fusion and resistance welds. However, electron beam welding was not possible because of extreme degassing during welding, and gas-tungsten-arc welds were not acceptable because of severely degraded mechanical properties. The FVS812 alloy exhibited excellent high temperature strength stability after thermal exposures up to 315 C (600 F) for 1000 h. Extended billet degassing appeared to generally improve tensile ductility, fatigue strength, and notch toughness. But the effects of billet degassing and thermal exposure on properties need to be further clarified. The manufacture of zee-stiffened, riveted, and resistance-spot-welded compression panels was demonstrated.

Mechanisms of Exchange Reactions of Primary and Secondary Alkyl Iodides with Elementary Iodine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bujake, John E.; Pratt, M. W. T.; Noyes, Richard M.

1961-04-01

Several primary and secondary alkyl iodides exchange thermally with I/ sup 131/ in hexachlorobutadiene between 130 and 200 deg . If the solutions are saturated with oxygen at one atmosphere, rates of exchange fit the kinetic expression k/sub b/STARI! STAl/sub 2/!1/2. Degassed solutions always exchange faster than oxygen saturated ones, but methyl, ethyl, and n-propyl iodides show the same kinetics as with oxygen. Exchange rates of degassed isopropyl and neopentyl iodides also show contributions from a k/sub a/STARI! term. Exchange in degassed ethylene dichloride is 3 to 4 times as fast as in degassed hexachlorobutadiene. Activation energies for k/sub b/more » are usually about 27 to 31 kcal/mole. Effects of substitution on alpha carbon are illustrated by the rate sequence methyl < ethyl < i-propyl = sec-butyl. Effects of substitution on beta carbon are illustrated by the rate sequence ethyl < npropyl>> neopentyl. Since the rates of exchange of methyl, ethyl, and i-propyl iodides vary in the opposite direction from the sequence for bimolecular nucleophilic substitution, the explanation proposed suggests that for nucleophilic substitution the effect of added methyl groups on an alpha carbon is a steric hindrance to solvation by solvent dipoles rather than a steric hindrance to the group attacking the carbon atom itself.« less

Soil CO2 efflux measurement network by means of closed static chambers to monitor volcanic activity at Tenerife, Canary Islands

NASA Astrophysics Data System (ADS)

Amonte, Cecilia; García-Merino, Marta; Asensio-Ramos, María; Melián, Gladys; García-Hernández, Rubén; Pérez, Aaron; Hernández, Pedro A.; Pérez, Nemesio M.

2017-04-01

Tenerife (2304 km2) is the largest of the Canary Islands and has developed a central volcanic complex (Cañadas edifice), that started to grow about 3.5 My ago. Coeval with the construction of the Cañadas edifice, shield basaltic volcanism continued until the present along three rift zones oriented NW-SE, NE-SW and NS (hereinafter referred as NW, NE and NS respectively). Main volcanic historical activity has occurred along de NW and NE rift-zones, although summit cone of Teide volcano, in central volcanic complex, is the only area of the island where surface geothermal manifestations are visible. Uprising of deep-seated gases occurs along the aforementioned volcanic structures causing diffuse emissions at the surface environment of the rift-zones. In the last 20 years, there has been considerable interest in the study of diffuse degassing as a powerful tool in volcano monitoring programs. Diffuse degassing studies are even more important volcanic surveillance tool at those volcanic areas where visible manifestations of volcanic gases are absent. Historically, soil gas and diffuse degassing surveys in volcanic environments have focused mainly on CO2 because it is, after water vapor, the most abundant gas dissolved in magma. One of the most popular methods used to determine CO2 fluxes in soil sciences is based on the absorption of CO2 through an alkaline medium, in its solid or liquid form, followed by gravimetric, conductivity, or titration analyses. In the summer of 2016, a network of 31 closed static chambers was installed, covering the three main structural zones of Tenerife (NE, NW and NS) as well as Cañadas Caldera with volcanic surveillance porpoises. 50 cc of 0.1N KOH solution is placed inside the chamber to absorb the CO2 released from the soil. The solution is replaced weekly and the trapped CO2 is then analyzed at the laboratory by titration. The are expressed as weekly integrated CO2 efflux values. The CO2 efflux values ranged from 3.2 to 12.9 gṡm-2ṡd-1, with average values of 7.0 gṡm-2ṡd-1 for the NE rift-zone and 6.4 gṡm-2ṡd-1 for NW and NS rift-zones. The most significant CO2 efflux values were observed in the NE rift-zone, with maximum values of 12.5 gṡm-2ṡd-1. To investigate the origin of the soil CO2 at the three volcanic rifts, soil gas samples were weekly taken on the head space of the closed chambers to study the chemical composition and the isotopic composition of the CO2. Collected gas samples can be considered as CO2-enriched air, showing concentrations of CO2 in the range 370-22,448 ppmV, with average values of 2,859 ppmV, 1,396 ppmV and 1,216 ppmV for the NE, NW and NS rift-zones, respectively. The CO2isotopic composition, expressed as dxzC-CO2, indicates that most of the sampling sites exhibited CO2 composed by different mixing degrees between atmospheric and biogenic CO2 with slight inputs of deep-seated CO2, with mean values of -17.5‰ -13.6‰ and -16.4‰ for the NE, NW and NS rift-zones, respectively. The methodology presented here represents an inexpensive method that might help to detect early warning signals of future unrest episodes in Tenerife.

Aroma recovery from roasted coffee by wet grinding.

PubMed

Baggenstoss, J; Thomann, D; Perren, R; Escher, F

2010-01-01

Aroma recovery as determined by solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) was compared in coffees resulting from conventional grinding processes, and from wet grinding with cold and hot water. Freshly roasted coffee as well as old, completely degassed coffee was ground in order to estimate the relationship of internal carbon dioxide pressure in freshly roasted coffee with the aroma loss during grinding. The release of volatile aroma substances during grinding was found to be related to the internal carbon dioxide pressure, and wet grinding with cold water was shown to minimize losses of aroma compounds by trapping them in water. Due to the high solubility of roasted coffee in water, the use of wet-grinding equipment is limited to processes where grinding is followed by an extraction step. Combining grinding and extraction by the use of hot water for wet grinding resulted in considerable losses of aroma compounds because of the prolonged heat impact. Therefore, a more promising two-step process involving cold wet grinding and subsequent hot extraction in a closed system was introduced. The yield of aroma compounds in the resulting coffee was substantially higher compared to conventionally ground coffee. © 2010 Institute of Food Technologists®

In situ dating on Mars: A new approach to the K–Ar method utilizing cosmogenic argon

DOE PAGES

Cassata, William S.

2013-08-22

In this paper, cosmogenic argon isotopes are produced in feldspars via nuclear reactions between cosmic rays and Ca and K atoms within the lattice. These cosmogenic isotopes can be used as proxies for K and Ca, much like nuclear reactor-derived 39Ar and 37Ar are used as proxies for K and Ca, respectively, in 40Ar/ 39Ar geochronology. If Ca and K are uniformly distributed, then the ratio of radiogenic 40Ar ( 40Ar*) to cosmogenic 38Ar or 36Ar ( 38Ar cos or 36Ar cos) is proportional to the difference between the radioisotopic and exposure ages, as well as the K/Ca ratio ofmore » the degassing phase. Thus cosmogenic, radiogenic, and trapped Ar isotopes, all of which can be measured remotely and are stable over geologic time, are sufficient to generate an isochron-like diagram from which the isotopic composition of the trapped component may be inferred. Finally, such data also provide a means to assess the extent to which the system has remained closed with respect to 40Ar*, thereby mitigating otherwise unquantifiable uncertainties that complicate the conventional K–Ar dating method.« less

The persistent and pernicious myth of the early CO2-N2 atmospheres of terrestrial planets

NASA Astrophysics Data System (ADS)

Shaw, G. H.

2009-12-01

The accepted model for early atmospheres of terrestrial planets has settled on a CO2-N2 composition. Unfortunately, while it is largely based on a brilliant geological analysis by Rubey, there is no compelling evidence whatsoever for such a composition as the first “permanent” atmosphere for Earth or any other planet. In fact, geological discoveries of the past 50+ years reveal several problems with a CO2-N2 atmosphere, some of which Rubey recognized in his own analysis. He clearly addressed the problem of timing of degassing, concluding that early massive degassing of CO2 would produce readily observed and profound effects, which are not evident. Modeling and constraints on the timing of planetary accretion and core formation indicate massive early degassing. If early degassing emitted CO2-N2, the effects are concealed. Plate tectonic recycling is not a solution, as conditions would have persisted beyond the time of the earliest rocks, which do not show the effects. Attempts to return degassed CO2 to the mantle are not only ad hoc, but inconsistent with early thermal structure of the Earth. Second, production of prebiotic organic compounds from a CO2-N2 atmosphere has been a nagging problem. At best this has been addressed by invoking hydrogen production from the mantle to provide reducing capacity. While hydrogen may be emitted in volcanic eruptions, it is exceedingly difficult to imagine this process generating enough organics to yield high concentrations in a global ocean. The recent fashion of invoking organic synthesis at deep-sea vents suffers from the same problem: how to achieve sufficient concentrations of organics in a global ocean by abiotic synthesis when hydrothermal activity stirs the solution and carries the prebiotic products off to great dilution? Suggesting life began at deep-sea vents, and continues to carry on chemosynthesis there, begs the question. Unless you get high enough concentrations of prebiotics by abiotic processes, you simply don’t get life. Third, solutions invoking high atmospheric CO2 as the answer to the faint young sun problem encounter exactly the same problems associated with prompt degassing of CO2. Fourth, the carbon isotope record, in which early carbonaceous deposits show signs of photosynthetic fractionation of carbon are problematical if most of the primary surface and near-surface carbon was CO2. Finally, the delay in oxidation of Earth’s surface following oxygenic photosynthesis is problematical if early photosynthesizers had a vast CO2 source from early degassing. Given an abundant food supply, what prevented early cyanobacteria from rapidly oxidizing the surface? Although discovery of CO2-rich atmospheres on Venus and Mars seem to support CO2 as the primary surface carbon reservoir, these atmospheres are the result of atmospheric evolution, particularly loss of H to space. ALL of these problems disappear with early degassing of reduced gases such as CH4 and NH3. Considerations of meteoritic compositions, accretionary processes, and early atmosphere/hydrosphere chemical processing all support reduced gases as dominant in the early atmospheres of the terrestrial planets. The time has come to revert to any earlier idea of strongly reducing conditions on early terrestrial planet surfaces, followed by long-term evolutionary trends toward oxidation.

Carbon monoxide degassing from seismic fault zones in the Basin and Range province, west of Beijing, China

NASA Astrophysics Data System (ADS)

Sun, Yutao; Zhou, Xiaocheng; Zheng, Guodong; Li, Jing; Shi, Hongyu; Guo, Zhengfu; Du, Jianguo

2017-11-01

Degassing of carbon monoxide (CO), which plays a significant role in the contribution of deep carbon to the atmosphere, commonly occurs within active fault zones. CO degassing from soil to the atmosphere in the Basin and Range province, west of Beijing (BRPB), China, was investigated by in-situ field measurements in the active fault zones. The measured concentrations of CO in soil gas in the BRPB ranged from 0.29 × 10-6 to 1.1 × 10-6 with a mean value of 0.6 × 10-6, which is approximately twice as large as that in the atmosphere. Net fluxes of CO degassing ranged from -48.6 mg m-2 d-1 to 12.03 mg m-2 d-1. The diffusion of CO from soil to the atmosphere in the BRPB was estimated to be at least 7.6 × 103 ton/a, which is comparable to the corresponding result of about 1.2 × 104 ton/a for CO2. CO concentrations were spatially heterogeneous with clearly higher concentrations along the NE-SW trending in the BRPB. These elevated values of CO concentrations were also coincident with the region with low-velocity and high conductivity in deep mantle, and high Poisson's ratio in the crust, thereby suggesting that CO degassing from the soil might be linked to upwelling of the asthenospheric mantle. Other sources of CO in the soil gas are suggested to be dominated by chemical reactions between deep fluids and carbonate minerals (e.g., dolomite, limestone, and siderite) in country rocks. Biogenic processes may also contribute to the CO in soil gas. The spatial distribution patterns of CO concentrations are coincident with the stress field, suggesting that the concentrations of CO could be a potential indicator for crustal stress field and, hence is potential useful for earthquake monitoring in the BRPB.

Simultaneous pyroclastic and effusive venting at rhyolite volcanoes: the cases of Puyehue-Cordón Caulle and Chaitén

NASA Astrophysics Data System (ADS)

Castro, J. M.; Schipper, C. I.; Tuffen, H.

2012-04-01

The recent silicic eruptions at volcán Chaiten and Puyehue-Cordón Caulle (PCC) demonstrate that ash and pyroclast production characterizes not only the vigorous initial stages of these eruptions, but can continue on for months, even during the effusive phases of activity. As we observed at PCC in January, 2012 and at Chaitén in 2008-2009, pyroclastic venting taking the form of ash jetting and punctuated Vulcanian blasts (Schipper et al. this session) occurs simultaneously with lava effusion (Tuffen et al., this session) and does so from what appears to be a common vent. This close spatial and temporal correlation implies a genetic and/or causal relation between two very different eruption styles. In this paper, we explore the chemical and physical signatures of this pyroclastic-effusive bridge, and discuss mechanisms by which silicic magma degasses to produce simultaneous, but apparently disparate eruption styles. Geochemical and textural analyses are underway on a range of eruption products from PCC and Chaitén, including early air-fall pyroclastic obsidian and pumice lapilli, ballistic bombs collected within 2 km of the vents, and glassy lavas. Ballistic bombs display a variety of textures ranging from homogeneous glassy obsidian through breadcrusted and highly brecciated bombs with re-annealing textures (e.g., collapsed foams and rewelded obsidian fragments). Bombs from Chaitén contain abundant tuffisites, comprising planar to anastomising veins filled with variably welded juvenile ash. At Chaiten, ballistic bomb water contents (~0.3-1.2 wt.% H2O) and H2O/OH speciation suggest that bombs are shallowly sourced (<<1 km) in the conduit and experienced similar pre-ejection cooling paths to magma that would become obsidian lava. These preliminary observations suggest that bombs are aliquots of magma attempting to become obsidian lava but this development was arrested by the build up of overpressure in the conduit followed by explosive evacuation. The build up of pressure depends on the permeability of the ascending magma, which is likely a function of the density of fractures and vesicularity of magma bodies. Thus factors that affect permeable flow through fractures and interconnected bubble pathways, such as magma deformation, ascent rate and rheology (relating to degassing path and cooling), likely control the cycling of explosive episodes during effusive activity. We are currently exploring how rheological and dynamical parameters inferred from samples can be related back to eruption observations at PCC, including the frequency of explosions and effusion and degassing rates, in order to evaluate the role of pyroclastic venting on the production of dense degassed rhyolite magma (lava). That explosive activity has persisted at PCC for several months suggests that a balance is maintained between the overpressure driving magma supply and the cycles of mechanical failure that typify pyroclastic and effusive activity at the PCC vent.

Diffuse degassing survey at the Higashi Izu monogenetic volcano field, Japan

NASA Astrophysics Data System (ADS)

Notsu, Kenji; Pérez, Nemesio M.; Fujii, Naoyuki; Hernández, Pedro A.; Mori, Toshiya; Padrón, Eleazar; Melián, Gladys

2016-04-01

The Higashi-Izu monogenetic volcanic group, which consists of more than 60 volcanoes, overlies the polygenetic volcanoes in the eastern part of the Izu peninsula, Japan, which are distributed over the area of 350 km2. Some of the monogenetic volcanoes are located on northwest-southeast alignments, suggesting that they developed along fissures. Recent volcanic activity occurred offshore, e.g., at the Izu-Oshima volcano, which erupted in 1986 and a submarine eruption of the small new Teishi knoll off eastern Izu Peninsula in 1989 (Hasebe et al., 2001). This study was carried out to investigate the possible relationship of diffuse CO2 emission and the recent seismic activity recorded NE of Higashi Izu monogenetic volcanic field, to quantify the rate at which CO2 is diffusely degassed from the studied area including Omuroyama volcano and to identify the structures controlling the degassing process. Measurements were carried out over a three day period from 8-10 July 2013. Diffuse CO2 emission surveys were always carried out following the accumulation chamber method and spatial distribution maps were constructed following the sequential Gaussian simulation (sGs) procedure. Soil gas samples were collected at 30-40 cm depth by withdrawal into 60 cc hypodermic syringes to characterize the chemical and isotopic composition of the soil gas. At Omurayama volcano, soil CO2 efflux values ranged from non-detectable to 97.5 g m-2 d-1, while at the seismic swarm zone ranged from 1.5 to 233.2 g m-2 d-1 and at the fault zone ranged from 5.7 to 101.2 g m-2 d-1. Probability-plot technique of all CO2 efflux data showed two different populations, background with a mean of 8.7 g m-2 d-1 and peak with a mean of 92.7 g m-2 d-1. In order to strength the deep seated contribution to the soil gases at the studied are, carbon isotopic analysis were performed in the CO2 gas. Soil gases (He, CO2 and N2) showed a clear mixing trend between air composition and a rich CO2 end member, suggesting the influence of a deep magmatic reservoir on the soil degassing at the studied area. To estimate the total diffuse CO2 output released from Omurayama, the average of 100 simulations was considered, giving an average of 22 ± 2 t d-1 of diffuse CO2 released by Miharayama. Regarding to the geochemical transects along the Amagi Road and perpendicular to the fault, CO2 efflux values >9xBackground were observed close to the location of the fault. These results show possible linear positive anomalies may be caused by the presence of the active fault which has a higher porosity than surrounding soils, allowing an increased flux of CO2 to reach the surface from depth. References: Hasebe et al., 2001. Bull. Volcanol., 63, 377.

Primordial domains in the depleted upper mantle identified by noble gases in MORBs

NASA Astrophysics Data System (ADS)

Tucker, J.; Mukhopadhyay, S.; Langmuir, C. H.; Hamelin, C.; Fuentes, J.

2017-12-01

The distribution of noble gas isotopic compositions in the mantle provides important constraints on the large-scale mantle evolution, as noble gases can trace the interaction between degassed, or processed, mantle domains and undegassed, or primitive, mantle domains. Data from the radiogenic He, Ne, Ar and Xe isotopic systems have shown that plume-related lavas sample relatively undegassed mantle domains, and the recent identification of isotopic anomalies in the short-lived I-Xe and Hf-W isotopic systems in plume-related lavas further suggests that these domains may be ancient, dating back to Earth's accretion. However, little is known about the potential variability of the heavy noble gas systems and the distribution of undegassed domains in the ambient upper mantle not influenced by plumes. Here, we present new high-precision He, Ne, Ar, and Xe isotopic data for a series of MORBs from a depleted section of the subtropical north Mid-Atlantic Ridge, distant from any known plume influence. Some samples have extremely low (unradiogenic) 4He/3He, 21Ne/22Ne, 40Ar/36Ar, and 129Xe/130Xe ratios, including some of the lowest values ever determined for MORBs. Such unradiogenic compositions are reminiscent of OIBs and plume-influenced E-MORBs, suggesting the presence of a relatively undegassed or primitive reservoir in the source of these depleted MORBs. The He, Ne, and Ar isotopic systems are sensitive to the long-term degassing history, suggesting that this domain in the MORB source is ancient. The 129Xe/130Xe ratio is sensitive to degassing only during the first 100 Ma of Earth history, suggesting that some of the isotopic character of these samples has been preserved since Earth's accretion. Together, these observations suggest that primordial or undegassed material is not only sampled in plumes-related lavas, but also normal, depleted MORBs. Along with data from E-MORBs in the southern EPR (Kurz et al., 2005), southern MAR (Sarda et al., 2000), and equatorial MAR (Tucker et al., 2012), our new data suggest that primordial material may be present throughout the MORB source. Such material could either have been stored for a long term in the upper mantle, or recently mixed into the upper mantle from a deeper reservoir.

Metal-saturated sulfide assemblages in NWA 2737: Evidence for impact-related sulfur devolatilization in Martian meteorites

NASA Astrophysics Data System (ADS)

Lorand, Jean-Pierre; Barrat, Jean-Alix; Chevrier, Vincent; Sautter, Violaine; Pont, Sylvain

2012-11-01