Phase relations and pre-eruptive conditions at low f(O2) in Pantelleria peralkaline rhyolites

2021 ◽  
Author(s):  
Ernestina Appiah ◽  
Paola Stabile ◽  
Fabio Arzilli ◽  
Alessandro Fabbrizio ◽  
Michael Robert Carroll
Keyword(s):  
Water Pressure ◽  
Alkali Feldspar ◽  
Single Step ◽  
Volcanic System ◽  
Rhyolitic Magma ◽  
Transport Dynamics ◽  
Reducing Conditions ◽  
Magma Compositions ◽  
Magma System ◽  
Water Saturated

<p>The volcanic system of Pantelleria is an example of volcanism in a continental rift basin which over the years has attracted much researcher due to the different eruptive styles it exhibits, ranging from effusive to explosive. Investigating the cooling history as well as the magma transport dynamics of peralkaline rhyolitic magma is useful to understand the eruptive behaviour of the pantelleritic magma system.</p><p>The present work seeks to obtain information on the liquidus temperature of alkali feldspar in pantellerite from the Fastuca pumice fall unit (PAN13) under water-saturated conditions. Alkali feldspar is one of the most abundant crystalline phases in peralkaline rhyolitic melts as well as in evolved, alkali-rich magma compositions (e.g., trachyte, phonolite).</p><p>A series of water-saturated isobaric single-step cooling experiments were performed at reducing conditions (graphite filler rod, water P-medium, ~NNO-2) with final temperature range of 670 °C-880 °C and water pressure of 20-150 MPa. Phase equilibria show that clinopyroxene is the first liquidus phase always appearing by 750 °C, followed by alkali feldspar over the entire pressure and temperature (P-T) range investigated, with also the presence of aenigmatite crystallizing near the liquidus at P of 50 MPa. Providing experimental constraints on pre- and syn-eruptive magma crystallization is fundamental to better understand the eruptive dynamics of peralkaline rhyolitic magmas. This is important for volcanic hazard assessments of peralkaline rhyolitic magmatic systems.</p>

Basal processes beneath an Arctic glacier and their geomorphic imprint after a surge, Elisebreen, Svalbard

2005 ◽  
Vol 64 (2) ◽  
pp. 125-137 ◽  
Author(s):  
Poul Christoffersen ◽  
Jan A. Piotrowski ◽  
Nicolaj K. Larsen
Keyword(s):  
Flow Instability ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Water System ◽  
Water Drainage ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Glacier Ice ◽  
Water Saturated ◽  
Arctic Glacier

AbstractThe foreground of Elisebreen, a retreating valley glacier in West Svalbard, exhibits a well-preserved assemblage of subglacial landforms including ice-flow parallel ridges (flutings), ice-flow oblique ridges (crevasse-fill features), and meandering ridges (infill of basal meltwater conduits). Other landforms are thrust-block moraine, hummocky terrain, and drumlinoid hills. We argue in agreement with geomorphological models that this landform assemblage was generated by ice-flow instability, possibly a surge, which took place in the past when the ice was thicker and the bed warmer. The surge likely occurred due to elevated pore-water pressure in a thin layer of thawed and water-saturated till that separated glacier ice from a frozen substratum. Termination may have been caused by a combination of water drainage and loss of lubricating sediment. Sedimentological investigations indicate that key landforms may be formed by weak till oozing into basal cavities and crevasses, opening in response to accelerated ice flow, and into water conduits abandoned during rearrangement of the basal water system. Today, Elisebreen may no longer have surge potential due to its diminished size. The ability to identify ice-flow instability from geomorphological criteria is important in deglaciated terrain as well as in regions where ice dynamics are adapting to climate change.

scholarly journals Cross-diffusion induced patterns for a single-step enzymatic reaction

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Giovanni Giunta ◽  
Hamid Seyed-Allaei ◽  
Ulrich Gerland
Keyword(s):  
Enzymatic Reaction ◽  
Single Step ◽  
Enzymatic Reactions ◽  
Transport Models ◽  
Transport Dynamics ◽  
Cross Diffusion ◽  
Enzyme Transport ◽  
Apparent Diffusion ◽  
Enzyme Distribution ◽  
Competing Models

Abstract Several different enzymes display an apparent diffusion coefficient that increases with the concentration of their substrate. Moreover, their motion becomes directed in substrate gradients. Currently, there are several competing models for these transport dynamics. Here, we use mathematical modeling and numerical simulations to analyze whether the enzymatic reactions can generate a significant feedback from enzyme transport onto the substrate profile. We find that this feedback can generate spontaneous spatial patterns in the enzyme distribution, with just a single-step catalytic reaction. However, patterns are formed only for a subclass of transport models. For such models, nonspecific repulsive interactions between the enzyme and the substrate, or attractive interactions between the enzyme and the product, cause the enzyme to accumulate in regions of low substrate concentration. Reactions then amplify local substrate and product fluctuations, causing enzymes to further accumulate where substrate is low. Experimental analysis of this pattern formation process could discriminate between different transport models.

scholarly journals Semi-Empirical Method for evaluating Risk of Liquefaction during earthquakes a Study Case of Rhiss Dam

2020 ◽  
Vol 150 ◽  
pp. 01004
Author(s):  
Fatima Ezzahraa Latifi ◽  
Khadija Baba ◽  
Lahcen Bahi ◽  
Soukaina Touijrate ◽  
Choukri Cherradi
Keyword(s):  
Water Pressure ◽  
Empirical Method ◽  
Soil Liquefaction ◽  
The North ◽  
Fine Soil ◽  
Load Increase ◽  
Al Hoceima ◽  
Stability Of Structures ◽  
Water Saturated ◽  
Semi Empirical

Liquefaction is a hazardous and temporary phenomenon by which water saturated soil loses some or all of its resistance. The undrained conditions linked to the cyclic load increase the pores water pressure inside the soil and consequently reduce effective stress. As a result, the soil can no longer resist or hold the shear forces, and lead to enormous deformations that directly influence the stability of structures and infrastructures foundations. Since 1964, several semi-empirical methods have been invented to evaluate the liquefaction potential using the in-situ test results. This study is based on the correlation between experimental data results of Menard pressuremeter and SPT dynamic penetrometer tests. Samples used in this test come from the Rhiss dam located in the North of Morocco, 24 kilometers as the crow flies from the town of Al Hoceima and south of the foundations of a calcareous ridge. The studied area have high seismic activity and a high percentage of fine soil elements, which suggests the possibility of soil liquefaction. We present and discuss the results of applying Idriss and Boulanger, and Youd et al methods in the evaluation of liquefaction susceptibility.

scholarly journals Implications of the principle of effective stress

2020 ◽  
Author(s):  
Gerd Gudehus
Keyword(s):  
Critical Phenomena ◽  
Pore Water ◽  
Effective Stress ◽  
Critical Points ◽  
Pore Water Pressure ◽  
Numerical Models ◽  
Water Pressure ◽  
Shear Bands ◽  
Triaxial Tests ◽  
Water Saturated

AbstractWhile Terzaghi justified his principle of effective stress for water-saturated soil empirically, it can be derived by means of the neutrality of the mineral with respect to changes of the pore water pressure $$p_w$$ p w . This principle works also with dilating shear bands arising beyond critical points of saturated grain fabrics, and with patterns of shear bands as relics of critical phenomena. The shear strength of over-consolidated clay is explained without effective cohesion, which results also from swelling up to decay, while rapid shearing of water-saturated clay can lead to a cavitation of pore water. The $$p_w$$ p w -neutrality is also confirmed by triaxial tests with sandstone samples, while Biot’s relation with a reduction factor for $$p_w$$ p w is contestable. An effective stress tensor is heuristically legitimate also for soil and rock with relics of critical phenomena, particularly for critical points with a Mohr–Coulomb condition. Therein, the $$p_w$$ p w -neutrality of the solid mineral determines the interaction of solid fabric and pore water, but numerical models are questionable due to fractal features.

scholarly journals Water budget and partial melting in an Archean crustal column: example from the Dharwar Craton, India

2019 ◽  
Vol 489 (1) ◽  
pp. 115-133 ◽  
Author(s):  
Gautier Nicoli
Keyword(s):  
Partial Melting ◽  
Water Budget ◽  
Critical Parameter ◽  
Bound Water ◽  
Dharwar Craton ◽  
Bulk Rock ◽  
Near Surface ◽  
Surface Conditions ◽  
Magma Compositions ◽  
Water Saturated

AbstractThe fluid budget of a composite crustal column is a critical parameter that influences many lithospheric processes. The amount of water introduced into the middle and lower crust can be quantified using phase equilibrium modelling. The Dharwar Craton, India, displays a now-exposed continuous crustal section from near-surface conditions to c. 30 km depth. This section records the different steps of a c. 15 myr-long high-temperature metamorphic event (60°C kbar−1) responsible for the formation of syn- to post-tectonic anatectic intrusions. The global water budget is assessed using thermodynamic modelling on bulk-rock compositions of an average early Proterozoic supracrustal unit and c. 3.0 Ga felsic basement, the Peninsular gneisses. Results show the fast burial of a water-saturated supracrustal package (1.6 wt%) will release c. 50% of its mineral-bound water, triggering water-fluxed partial melting of the basement. Modelled anatectic magma compositions match the observed granitoid chemistries, and distinction can be made between water-fluxed melting and water-absent melting in the origin of syn- to post-tectonic anatectic granites. Findings from this study show the importance of crustal pile heterogeneity in controlling the nature of partial melting reactions, the composition of the magmas and the rheology of the crust.

Bonding BisGMA to Dentin—a Proof of Concept for Hydrophobic Dentin Bonding

2007 ◽  
Vol 86 (11) ◽  
pp. 1034-1039 ◽  
Author(s):  
F.R. Tay ◽  
D.H. Pashley ◽  
R.R. Kapur ◽  
M.R.O. Carrilho ◽  
Y.B. Hur ◽  
...  
Keyword(s):  
Phosphoric Acid ◽  
Clinical Application ◽  
Water Sorption ◽  
Water Pressure ◽  
Proof Of Concept ◽  
Acid Base ◽  
Leaching Potential ◽  
Water Saturated ◽  
Hybrid Layers ◽  
Hydrophobic Bonding

The use of TEGDMA as a diluent comonomer in the formulation of hydrophobic adhesives for ethanol wet-bonding is a concern, due to its leaching potential, higher water sorption, and bio-incompatibility. This study tested the hypothesis that hydrophobic bonding to acid-etched dentin may be accomplished with the use of ethanol-solvated BisGMA only. Phosphoric-acid-etched, oxalate-occluded, deep coronal dentin bonded under 20 cm water pressure with experimental BisGMA adhesives by ethanol wet-bonding exhibited tensile strengths that were not significantly different from that achieved with OptiBond FL bonded according to the manufacturer-recommended protocol, with similar acid-/base-resistant hybrid layers, resin tags, and nanoleakage distribution. Ethanol replacement of water-saturated dentin produced wider interfibrillar spaces, more extensive shrinkage of the collagen fibrils, and narrower hybrid layers. Experimental BisGMA adhesives provide the proof of concept that relatively hydrophobic resins may be coupled to acid-etched dentin by increasing its hydrophobic characteristics via ethanol replacement. They should be further optimized before clinical application.

X-Ray Computed Tomography of CO2 Behavior in Water Saturated Sandstone for Geological Storage

2010 ◽  
Author(s):  
Suguru Uemura ◽  
Ryoto Kataoka ◽  
Shohji Tsushima ◽  
Shuichiro Hirai
Keyword(s):  
Computed Tomography ◽  
Oil Recovery ◽  
Water Pressure ◽  
Co2 Storage ◽  
Packed Bed ◽  
Geological Storage ◽  
Co2 Geological Storage ◽  
X Ray ◽  
X Ray Computed ◽  
Water Saturated

The CO2 Geological storage is considered as an effective technology for reducing the emissions of CO2 into the atmosphere. CO2 storage is a technically feasible and effective method for CO2 mitigation because it is based on enhanced oil recovery technology, and storage sites hold significant potential. Currently, field tests for CO2 geological storage are proceeding in many parts of the world. However, the behavior of injected CO2 is still not completely understood. The CO2 storage potential and risk of leakage from reservoirs must be accurately estimated to realize practicable CO2 storage. For this reason, laboratory-scale experimental analysis of the behavior of CO2 injected in sandstone are an important issues. In this study, CO2 distribution and its behavior in sandstone were observed by micro-focus X-ray computed tomography (CT). The X-ray CT can fluoroscope the CO2 in the porous media and reconstruct a three-dimensional CO2 distribution image. A sample was kept under high pressure conditions in a cylindrical pressure vessel and filled with CO2 saturated water. Pressure in the vessel was kept at 7.5 MPa, which is the same condition as a saline aquifer at 750 m depth. Liquid or supercritical CO2 was injected from the end face of water saturated samples. Temperature conditions were set to 20 or 40°C according to the experimental objectives of the CO2 phase. In the experimental results, CO2 distribution in the silica-packed bed and sandstone was clearly visualized with high spatial resolution compared to its diameter. The possibility of improvement in storage technology discussed.

A Laboratory Study of Coinjection of Water and CO2 to Improve Oil Recovery and CO2 Storage: Effect of Fraction of CO2 Injected

SPE Journal ◽  
2020 ◽  
pp. 1-9
Author(s):  
Emmanuel Ajoma ◽  
Thanarat Sungkachart ◽  
Saria ◽  
Hang Yin ◽  
Furqan Le-Hussain
Keyword(s):  
Oil Recovery ◽  
Laboratory Experiments ◽  
Water Pressure ◽  
Co2 Storage ◽  
Water Injection ◽  
Molar Fraction ◽  
Co2 Injection ◽  
The Core ◽  
Carbon Dioxide Co2 ◽  
Water Saturated

Summary To determine the effect on oil recovery and carbon dioxide (CO2) storage, laboratory experiments are run with various fractions of CO2 injected (FCI): pure CO2 injection (FCI = 1), water-saturated CO2 (wsCO2) injection (FCI = 0.993), simultaneous water and gas (SWAG) (CO2) injection (FCI = 0.75), carbonated water injection (CWI) (FCI = 0.007), and water injection (FCI = 0). All experiments are performed on Bentheimer sandstone cores at 70°C and 11.7 MPa (1,700 psia). The oil phase is composed of 65% hexane and 35% decane by molar fraction. Before any fluid is injected, the core is filled with oil and irreducible water. Pressure difference across the core and production rate of gas are measured during the experiment. The collected produced fluids are analyzed in a gas chromatograph to determine their composition. Cumulative oil recovery after injection is found to be 78 to 83% for wsCO2, 78% for SWAG, 74% for pure CO2, 53% for CWI, and 35% for water. Net CO2 stored is also found to be the highest for wsCO2 (59 to 65% of the pore volume), followed by that for CO2 injection (56%) and that for SWAG (42%). These results suggest that wsCO2 injection might outperform pure CO2 injection at both oil recovery and net CO2stored.

scholarly journals A new methodology to simulate subglacial deformation of water-saturated granular material

2015 ◽  
Vol 9 (6) ◽  
pp. 2183-2200 ◽  
Author(s):  
A. Damsgaard ◽  
D. L. Egholm ◽  
J. A. Piotrowski ◽  
S. Tulaczyk ◽  
N. K. Larsen ◽  
...  
Keyword(s):  
Granular Material ◽  
Pore Water ◽  
Mechanical Response ◽  
Water Pressure ◽  
Shear Zones ◽  
Computational Experiments ◽  
Unconsolidated Sediments ◽  
Close Monitoring ◽  
Granular Bed ◽  
Water Saturated

Abstract. The dynamics of glaciers are to a large degree governed by processes operating at the ice–bed interface, and one of the primary mechanisms of glacier flow over soft unconsolidated sediments is subglacial deformation. However, it has proven difficult to constrain the mechanical response of subglacial sediment to the shear stress of an overriding glacier. In this study, we present a new methodology designed to simulate subglacial deformation using a coupled numerical model for computational experiments on grain-fluid mixtures. The granular phase is simulated on a per-grain basis by the discrete element method. The pore water is modeled as a compressible Newtonian fluid without inertia. The numerical approach allows close monitoring of the internal behavior under a range of conditions. Our computational experiments support the findings of previous studies where the rheology of a slowly deforming water-saturated granular bed in the steady state generally conforms to the rate-independent plastic rheology. Before this so-called critical state, deformation is in many cases accompanied by volumetric changes as grain rearrangement in active shear zones changes the local porosity. For previously consolidated beds porosity increases can cause local pore-pressure decline, dependent on till permeability and shear rate. We observe that the pore-water pressure reduction strengthens inter-granular contacts, which results in increased shear strength of the granular material. In contrast, weakening takes place when shear deformation causes consolidation of dilated sediments or during rapid fabric development. Both processes of strengthening and weakening depend inversely on the sediment permeability and are transient phenomena tied to the porosity changes during the early stages of shear. We find that the transient strengthening and weakening in turn influences the distribution of shear strain in the granular bed. Dilatant strengthening has the ability to distribute strain during early deformation to large depths, if sediment dilatancy causes the water pressure at the ice–bed interface to decline. Oppositely, if the ice–bed interface is hydrologically stable the strengthening process is minimal and instead causes shallow deformation. The depth of deformation in subglacial beds thus seems to be governed by not only local grain and pore-water feedbacks but also larger-scale hydrological properties at the ice base.

Geology and geochemistry of the Burnthill Granite and related W – Sn – Mo – F mineral deposits, central New Brunswick

1989 ◽  
Vol 26 (3) ◽  
pp. 499-514 ◽  
Author(s):  
H. E. MacLellan ◽  
R. P. Taylor
Keyword(s):  
New Brunswick ◽  
Brook Trout ◽  
Alkali Feldspar ◽  
Major And Trace Elements ◽  
Mineral Deposits ◽  
Average Value ◽  
Phase Saturation ◽  
High Concentrations ◽  
High Level ◽  
Water Saturated

Several significant W – Sn – Mo – F-bearing hydrothermal mineral deposits occur in the Miramichi Highlands of central New Brunswick. These deposits are spatially and temporally related to a group of five subcircular, undeformed, high-level, posttectonic granite plutons (Burnthill, Dungarvon, Rocky Brook, Sisters Brook, Trout Brook) of Middle Devonian age. The largest of the plutons is the Burnthill Granite (area = 180 km2), which comprises a texturally variable, polyphase intrusion composed of biotite monzogranites and alkali feldspar granites (International Union of Geological Sciences (IUGS) classification); apatite and zircon are the ubiquitous accessory minerals. Field and petrographic data indicate that the Burnthill Granite and two small (< 7 km2) adjacent intrusions (Buttermilk Brook and Burnthill Mine granites), located 1 km from the southeast contact of the main intrusion, are genetically related and are epizonal in character. Classic epizonal features include sharp, discordant intrusive contacts with the host metasediments; a narrow contact metamorphic aureole with local zones of intense hydrothermal alteration and mineralization; an isotropic internal fabric; evidence of multiple intrusion; and the presence of porphyries.Geochemically the pluton is composed of mildly peraluminous, high-silica granites (SiO2 > 74 wt. %), with low abundances of TiO2, MgO, CaO, P2O5, Sr, Ba, and Eu, and high concentrations of Y, Nb, Sn, Cs, Ta, W, Th, and U; high FeO/MgO ratios and Na2O + K2O contents are typical. Covariation among many of the major and trace elements within the volumetrically important phases of the Burnthill Granite can be explained by the process of fractional crystallization, and has resulted in an enrichment of those elements of economic interest (viz., Sn and W) in the more evolved granites. However, the anomalous behaviour of certain elements in these most evolved phases requires the operation of an additional process; this was most likely aqueous phase saturation followed by fluid separation, a process whose activity is corroborated by field and petrographic evidence (e.g., the development of miarolitic cavities and myrmekite). Normative Ab–Or–Q–An contents for the Burnthill Granite have a mean compostion of Ab31Or28Q38An3. This average value is almost identical to that of the piercing point assemblage in the "haplogranodiorite" system with 3 % normative anorthite, and is consistent with crystallization under water-saturated conditions at about 1 kbar (100 MPa) and 730–800 °C.Structural and petrochemical data demonstrate that the W – Sn – Mo – F-bearing mineral deposits were deposited in fracture and fault systems that developed after crystallization was completed, from hydrothermal fluids that were compositionally similar (high concentrations of F, Na, K, Sn, W) to the more evolved silicate melt phases of the Burnthill Granite. In addition to generating the wolframite–cassiterite–fluorite mineral deposits that occur in both endo- and exo-granitic settings, these fluids produced zones of intense, fracture-controlled, aluminosilicate alteration (viz., K-feldspathization, albitization, greisenization, and topaz alteration) that envelop the zones of mineralization.

Sign in / Sign up

Export Citation Format

Share Document