Effects of pressure and H2O content on the compositions of primary crustal melts

1996 ◽  
Vol 87 (1-2) ◽  
pp. 11-21 ◽  
Author(s):  
Alberto E. Patiño Douce
Keyword(s):  
High Pressure ◽  
Wide Spectrum ◽  
Low Pressure ◽  
Source Material ◽  
Stability Field ◽  
Dehydration Melting ◽  
Isothermal Conditions ◽  
The Stability ◽  
Melting Experiments

ABSTRACT:Melting experiments with and without added H2O on a model metagreywacke and a natural metapelite demonstrate how pressure and H2O content control the compositions of melts and residual assemblages. Several effects are observed under isothermal conditions. Firstly, the stability field of biotite shrinks with decreasing pressure and with increasing H2O content, whereas that of plagioclase shrinks with increasing pressure and H2O content. Secondly, the ferromagnesian content of melts at the source (i.e. coexisting with their residual assemblages) decreases with decreasing H2O activity. Thirdly, with increasing pressure the Ca/Mg and Ca/Fe ratios of melts decrease relative to those of coexisting garnet. As a consequence, a wide spectrum of melts and crystalline residues can be generated from the same source material. For example, H2O-starved dehydration melting of metagreywacke at low pressure (≤10 kbar) generates K-rich (granitic) melts that coexist with pyroxene- and plagioclase-rich residues, whereas melting of the same material at high pressure (≍15 kbar) and with minor H2O infiltration can generate leucocratic Na-rich and Ca-poor (trondhjemitic) melts that coexist with biotite- and garnet-rich residues. An increased H2O content stabilises orthopyroxene at the expense of garnet + biotite + plagioclase, causing melts to shift towards granodioritic or perhaps tonalitic compositions.

scholarly journals Study of silica-undersaturated magmas through the Kalsilite- Nepheline-Diopside-Silica system at 4.0 GPa and dry conditions

2018 ◽  
Vol 18 (2) ◽  
pp. 87-102
Author(s):  
Márcio Roberto Wilbert de Souza ◽  
Rommulo Vieira Conceição ◽  
Daniel Grings Cedeño ◽  
Roberto Vicente Schmitz Quinteiro
Keyword(s):  
High Pressure ◽  
Solid Solutions ◽  
Negative Correlation ◽  
Stability Field ◽  
Thermal Barrier ◽  
High Pressure And Temperature ◽  
Alkaline Magma ◽  
Magma Genesis ◽  
Dry Conditions ◽  
The Stability

This study experimentally investigates the Kalsilite-Nepheline-Diopside-Silica system at high pressure and temperature, with emphasis on silica-undersaturated volume (leucite-nepheline-diopside — Lct-Nph-Di; and kalsilite-nepheline-diopside — Kls + Nph + Di — planes), at 4.0 GPa (~120 km deep), temperatures up to 1,400ºC and dry conditions, to better understand the influence of K2O, Na2O, and CaO in alkali-rich silica-undersaturated magma genesis. In the Lct-Nph-Di plane, we determined the stability fields for kalsilite (Klsss), nepheline (Nphss) and clinopyroxene (Cpxss) solid solutions, wollastonite (Wo) and sanidine (Sa); and three piercing points: (i) pseudo-eutectic Kls + Nph + Di + liquid (Lct62Nph29Di9) at 1,000ºC; (ii) Kls + Sa + (Di + Wo) + liquid (Lct75Nph22Di2) at 1,200ºC; and (iii) pseudo-eutectic Kls + Di + Wo + liquid (Lct74Nph17Di9) at 1,000ºC. Kalsilite stability field represents a thermal barrier between ultrapotassic/potassic vs. sodic compositions. In the plane Kls-Nph-Di, we determined the stability fields for Klsss, Nphss and Cpxss and two aluminous phases in smaller proportions: spinel (Spl) and corundum (Crn). This plane has a piercing point in Kls + Nph + Di(± Spl) + liquid (Kls47Nph43Di10) at 1,100ºC. Our data showed that pressure extends K dissolution in Nph (up to 39 mol%) and Na in Kls (up to 27 mol%), and that these solid solutions, if present, determinate how much enriched in K and Na an alkaline magma will be in an alkaline-enriched metasomatic mantle. Additionally, we noted positive correlation between K2O and SiO2 concentration in experimental melts, negative correlation between CaO and SiO2, and no evident correlation between Na2O and SiO2. 

scholarly journals New insights on the GeSe x Te1−x phase diagram from theory and experiment

2019 ◽  
Vol 75 (2) ◽  
pp. 246-256 ◽  
Author(s):  
Markus Guido Herrmann ◽  
Ralf Peter Stoffel ◽  
Michael Küpers ◽  
Mohammed Ait Haddouch ◽  
Andreas Eich ◽  
...  
Keyword(s):  
Phase Diagram ◽  
High Pressure ◽  
Low Temperature ◽  
Hexagonal Phase ◽  
Structure Type ◽  
Stability Field ◽  
Temperature Behaviour ◽  
Formation Enthalpies ◽  
The Stability

The high-pressure and low-temperature behaviour of the GeSe x Te1−x system (x = 0, 0.2, 0.5, 0.75, 1) was studied using a combination of powder diffraction measurements and first-principles calculations. Compounds in the stability field of the GeTe structure type (x = 0, 0.2, 0.5) follow the high-pressure transition pathway: GeTe-I (R3m) → GeTe-II (f.c.c.) → GeTe-III (Pnma). The newly determined GeTe-III structure is isostructural to β-GeSe, a high-pressure and high-temperature polymorph of GeSe. Pressure-dependent formation enthalpies and stability regimes of the GeSe x Te1−x polymorphs were studied by DFT calculations. Hexagonal Ge4Se3Te is stable up to at least 25 GPa. Significant differences in the high-pressure and low-temperature behaviour of the GeTe-type structures and the hexagonal phase are highlighted. The role of Ge...Ge interactions is elucidated using the crystal orbital Hamilton population method. Finally, a sketch of the high-pressure phase diagram of the system is provided.

Geochronological evidence for phased volcanic activity in Fife and Caithness necks, Scotland

1981 ◽  
Vol 72 (1) ◽  
pp. 1-7 ◽  
Author(s):  
R. M. Macintyre ◽  
R. A. Cliff ◽  
N. A. Chapman
Keyword(s):  
High Pressure ◽  
Volcanic Activity ◽  
Shallow Depth ◽  
Stability Field ◽  
Early Permian ◽  
Explosive Activity ◽  
Isotopic Studies ◽  
The Stability ◽  
Considerable Depth ◽  
Geochronological Evidence

AbstractIn an attempt to establish a chronology for volcanic neck emplacement and so elucidate petrogenesis, isotopic studies have been carried out on various cumulate inclusions, blocks and megacrysts which occur chiefly in association with tuffs infilling several Scottish vents. K-Ar ages of 13 samples of low-pressure cumulate minerals (biotite, hornblende and pyroxene) from necks in East Fife indicate crystallisation at shallow depth at 314 Ma. U-Pb analyses of zircons are concordant at 318 Ma suggesting they are also members of this suite and their formation is penecontemporaneous with the Namurian volcanic activity which is welldocumented stratigraphically. By 295 Ma crystallisation of anorthoclase megacrysts had been completed, perhaps from the fractionated residuum. An eruption from considerable depth (within the stability field of garnet precipitation) then broke through to the surface bearing high-pressure megacrysts. This penetrated and disrupted the early cumulates carrying them to the surface and producing the diverse vent assemblages. K-Ar dating of basanites suggest that the Duncansby Ness neck in Caithness was emplaced around 270 Ma in the early Permian. For two Fife necks the balance of evidence favours an age of 290 Ma (Stephanian) for this final explosive activity associated with vent formation.

Enhancement of structure of interstellar diamond microcrystals by image processing

1988 ◽  
Vol 46 ◽  
pp. 836-837
Author(s):  
Michael A. O'Keefe ◽  
David Blake ◽  
Friedemann Freund ◽  
Crispin Hetherington ◽  
John Turner
Keyword(s):  
Noble Gas ◽  
Low Pressure ◽  
Stability Field ◽  
Carbonaceous Chondrites ◽  
Particle Collisions ◽  
Mechanism Of Formation ◽  
Isotopic Data ◽  
Diamond Crystals ◽  
Difference Of Opinion ◽  
The Stability

Since the discovery of 0.5-7.5 nm diamond crystals in oxidized acid residues of carbonaceous chondrites much speculation has centered on the mechanism of their origin. Indeed; there is even some difference of opinion regarding the presence of “amorphous low-atomic number phases” intimately associated with the diamond crystallites. While the diamond-containing residue from the meteorites comprises only 50-200 ppm of the total meteorite mass, theories regarding the genesis of the diamonds have far-reaching consequences since noble gas isotopic data indicate that they predate the solar system and are from an interstellar source. Lewis et al. propose that the diamonds formed under low pressure conditions by processes similar to those used in recent low-pressure CVD laboratory syntheses. Blake et al. propose a second mechanism of formation, within the stability field of diamond, due to particle-particle collisions behind supernova shock waves. At the present time, no data exist which unequivocally support one model over the other.

Ultra-high pressure aluminous titanites in carbonate-bearing eclogites at Shuanghe in Dabieshan, central China

1996 ◽  
Vol 60 (400) ◽  
pp. 461-471 ◽  
Author(s):  
D. A. Carswell ◽  
R. N. Wilson ◽  
M. Zhai
Keyword(s):  
High Pressure ◽  
Phase Equilibria ◽  
Amphibolite Facies ◽  
Central China ◽  
Stability Field ◽  
Ultra High Pressure ◽  
Metamorphic Fluids ◽  
Metamorphic Terrane ◽  
The Stability ◽  
Peak Assemblage

AbstractPetrographic features and compositions of titanites in eclogites within the ultra-high pressure metamorphic terrane in central Dabieshan are documented and phase equilibria and thermobarometric implications discussed. Carbonate-bearing eclogite pods in marble at Shuanghe contain primary metamorphic aluminous titanites, with up to 39 mol.% Ca(Al,Fe3+)FSiO4 component. These titanites formed as part of a coesite-bearing eclogite assemblage and thus provide the first direct petrographic evidence that AlFTi−1O−1 substitution extends the stability of titanite, relative to rutile plus carbonate, to pressures within the coesite stability field. However, it is emphasised that A1 and F contents of such titanites do not provide a simple thermobarometric index of P—T conditions but are constrained by the activity of fluorine, relative to CO2, in metamorphic fluids — as signalled by observations of zoning features in these titanites.These ultra-high pressure titanites show unusual breakdown features developed under more H2O-rich amphibolite-facies conditions during exhumation of these rocks. In some samples aluminous titanites have been replaced by ilmenite plus amphibole symplectites, in others by symplectitic intergrowths of secondary, lower Al and F, titanite plus plagioclase. Most other coesite-bearing eclogite samples in the central Dabieshan terrane contain peak assemblage rutile often partly replaced by grain clusters of secondary titanites with customary low Al and F contents.

Petrological evidence for crustal thickening and extension in the Serre granulite terrane (Calabria, southern Italy)

2006 ◽  
Vol 143 (2) ◽  
pp. 145-163 ◽  
Author(s):  
PASQUALE ACQUAFREDDA ◽  
ANNAMARIA FORNELLI ◽  
ANTONIO PAGLIONICO ◽  
GIUSEPPE PICCARRETA
Keyword(s):  
High Temperature ◽  
Phase Equilibria ◽  
Southern Italy ◽  
Crustal Thickening ◽  
Stability Field ◽  
Low Grade ◽  
Dehydration Melting ◽  
Prograde Metamorphism ◽  
Isothermal Decompression ◽  
The Stability

The paper presents the metamorphic trajectory recorded by metapelitic migmatites of the upper part of the Hercynian lower continental crust of the Serre (southern Calabria, Italy). The relict minerals, reaction textures and phase equilibria define a clockwise P–T path. The prograde metamorphism from temperature of about 500°C and pressure of 4–5 kbar to T<700°C and P∼8 kbar stabilized the assemblage Grt+Ky+Bt+Ms(Si/11ox=3.26–3.29) in the uppermost metapelites of the profile. Progressive heating led to H2O-fluxed and dehydration melting first of Ms, then of Bt at T<700°C in the stability field of sillimanite. This process was followed by nearly isothermal decompression producing additional melt with a transition from Grt to a Grt+Crd stability field. Further decompression caused the formation of Crd-corona around garnet. Nearly isobaric cooling led to rehydration and retrogression across the stability field of andalusite up to the stability field of kyanite. The lowermost metapelites of the studied profile have lost most of the memory of the prograde P–T path; they record decompression and cooling. High-temperature mylonites occur in which boudinage, elongation and pull-aparts characterize the porphyroclasts. The pull-aparts in the high-T mylonites are filled with low-P minerals (Crd+Spl). The Hercynian metamorphic trajectory and the microtextures are consistent with crustal thickening and subsequent extensional regime. During extension, an important tectonic denudation probably caused the isothermal decompression. Extension also occurred in post-Hercynian times as documented by pull-aparts in sillimanite porphyroclasts filled with chloritoid within a low-grade mylonite.

scholarly journals Unconventional Stoichiometries of Na–O Compounds at High Pressures

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7650
Author(s):  
Lihua Yang ◽  
Yukai Zhang ◽  
Yanli Chen ◽  
Xin Zhong ◽  
Dandan Wang ◽  
...  
Keyword(s):  
High Pressure ◽  
High Pressures ◽  
Stability Field ◽  
First Principles Calculations ◽  
One Dimensional ◽  
Theoretical Investigations ◽  
Systematic Structure ◽  
Pressure Stability ◽  
The Stability ◽  
New Compounds

It has been realized that the stoichiometries of compounds may change under high pressure, which is crucial in the discovery of novel materials. This work uses systematic structure exploration and first-principles calculations to consider the stability of different stoichiometries of Na–O compounds with respect to pressure and, thus, construct a high-pressure stability field and convex hull diagram. Four previously unknown stoichiometries (NaO5, NaO4, Na4O, and Na3O) are predicted to be thermodynamically stable. Four new phases (P2/m and Cmc21 NaO2 and Immm and C2/m NaO3) of known stoichiometries are also found. The O-rich stoichiometries show the remarkable features of all the O atoms existing as quasimolecular O2 units and being metallic. Calculations of the O–O bond lengths and Bader charges are used to explore the electronic properties and chemical bonding of the O-rich compounds. The Na-rich compounds stabilized at extreme pressures (P > 200 GPa) are electrides with strong interstitial electron localization. The C2/c phase of Na3O is found to be a zero-dimensional electride with an insulating character. The Cmca phase of Na4O is a one-dimensional metallic electride. These findings of new compounds with unusual chemistry might stimulate future experimental and theoretical investigations.

The iron-rich blueschist facies minerals: I. Deerite

1979 ◽  
Vol 43 (326) ◽  
pp. 251-259 ◽  
Author(s):  
R. Muir Wood
Keyword(s):  
High Pressure ◽  
Low Temperature ◽  
Low Pressure ◽  
Limited Range ◽  
Iron Silicate ◽  
Stability Field ◽  
Present Survey ◽  
Ideal Formula ◽  
Pressure Stability ◽  
The Ideal

SummaryThe mineral deerite is restricted in occurrence to blueschist facies meta-ironstones. From the ideal formula of Si12O40(OH)10 there are a limited range of substitutions: Ti and V for Fe3+ and Mn on the Fe2+ site. In the present survey of deerite compositions from the majority of deerite localities the maximum substitutions have been 2Ti and 3Mn in the above formula. There is an at present unexplained anomaly in the totals of a number of the analyses indicating that there may be variations away from the ideal formula towards increased hydroxyl and decreased cation contents.From differences between the mineral compatibilities of deerites from the higher-grade Franciscan exotic block blueschist localities and those from more conformable Alpine blueschists, in conjunction with previous work on the experimental stabilities of the low-pressure/low-temperature hydrous iron silicate minerals, it has been possible to map the form of the low-pressure deerite stability field involving reactions of greenalite or minnesotaite or grunerite with magnetite and quartz. Within the deerite stability field, further deerite-forming reactions involve the breakdown of riebeckite and the hydrous incompatibility of magnetite with quartz; both are very dependent on the activity of sodium. A low-pressure stability to 4 kb at 200 °C and 6 kb at 300 °C are estimated from these low-temperature breakdown reactions. This fits in well with the high-pressure deerite stability determinations of Langer et al. (1977).

scholarly journals Decompressional equilibration of the Midsund granulite from Otrøy, Western Gneiss Region, Norway

2019 ◽  
Vol 70 (6) ◽  
pp. 471-482
Author(s):  
Johanna Holmberg ◽  
Michał Bukała ◽  
Pauline Jeanneret ◽  
Iwona Klonowska ◽  
Jarosław Majka
Keyword(s):  
High Pressure ◽  
Thermodynamic Model ◽  
Thermodynamic Modelling ◽  
Ultrahigh Pressure ◽  
Stability Field ◽  
Uhp Metamorphism ◽  
Limited Evidence ◽  
Western Gneiss Region ◽  
Widespread Phenomenon ◽  
The Stability

Abstract The Western Gneiss Region (WGR) of the Scandinavian Caledonides is an archetypal terrain for high-pressure (HP) and ultrahigh-pressure (UHP) metamorphism. However, the vast majority of lithologies occurring there bear no, or only limited, evidence for HP or UHP metamorphism. The studied Midsund HP granulite occurs on the island of Otrøy, a locality known for the occurrence of the UHP eclogites and mantle-derived, garnet-bearing ultramafics. The Midsund granulite consists of plagioclase, garnet, clinopyroxene, relict phengitic mica, biotite, rutile, quartz, amphibole, ilmenite and titanite, among the most prominent phases. Applied thermodynamic modelling in the NCKFMMnASHT system resulted in a pressure–temperature (P–T) pseudosection that provides an intersection of compositional isopleths of XMg (Mg/Mg+Fe) in garnet, albite in plagioclase and XNa (Na/Na+Ca) in clinopyroxene in the stability field of melt + plagioclase + garnet + clinopyroxene + amphibole + ilmenite. The obtained thermodynamic model yields P–T conditions of 1.32–1.45 GPa and 875–970 °C. The relatively high P–T recorded by the Midsund granulite may be explained as an effect of equilibration due to exhumation from HP (presumably UHP) conditions followed by a period of stagnation under HT at lower-to-medium crustal level. The latter seems to be a more widespread phenomenon in the WGR than previously thought and may well explain commonly calculated pressure contrasts between neighboring lithologies in the WGR and other HP–UHP terranes worldwide.

Fouling Is the Beginning: Upcycling Biopolymer-Fouled Substrates for Fabricating High-Permeance Thin-Film Composite Polyamide Membranes

2020 ◽  
Author(s):  
Ruobin Dai ◽  
Hongyi Han ◽  
Tianlin Wang ◽  
Jiayi Li ◽  
Chuyang Y. Tang ◽  
...  
Keyword(s):  
Thin Film ◽  
High Pressure ◽  
End Of Life ◽  
Water Purification ◽  
Low Pressure ◽  
Polymeric Membranes ◽  
Membrane Recycling ◽  
Film Composite ◽  
Thin Film Composite ◽  
First Time

Commercial polymeric membranes are generally recognized to have low sustainability as membranes need to be replaced and abandoned after reaching the end of their life. At present, only techniques for downcycling end-of-life high-pressure membranes are available. For the first time, this study paves the way for upcycling fouled/end-of-life low-pressure membranes to fabricate new high-pressure membranes for water purification, forming a closed eco-loop of membrane recycling with significantly improved sustainability.

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