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  • 1
    Electronic Resource
    Electronic Resource
    Geothermobarometry in metasediments of the southern Grossvenediger area (Tauern Window, Austria) (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of metamorphic geology 8 (1990), S. 0 
    Details
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Metasediments in the southern Grossvenediger area (Tauern Window, Austria) were studied along a cross-section through rocks of increasing metamorphic grade from the margin of the Tauern Window in the south to the base of the Upper Schieferhülle, including the Eclogite Zone, in the north.In the southern part of the cross-section there is no evidence for a pre-late Alpine metamorphic history in the form of high-pressure relics or pseudomorphs. Mineral assemblages are characterized by the stability of tremolite + calcite, biotite + calcite and biotite + chlorite + calcite. In the northern part a more complete Alpine metamorphic evolution is preserved. Primary high-pressure assemblages are dolomite + quartz, tremolite + zoisite, zoisite + dolomite + quartz + phengite I and probably tremolite + dolomite + phengite I. Secondary, post-kinematic assemblages [tremolite + calcite, talc + calcite, phengite II + chlorite + calcite (+ quartz), biotite + chlorite + calcite, biotite + zoisite + calcite] formed as a result of the dominant late Alpine metamorphic overprint. The occurrence of biotite + zoisite + calcite is confined to the northernmost area and defines a biotite–zoisite–calcite isograd. P–T estimates based on standard thermobarometric techniques and on stability relationships of tremolite + calcite + dolomite + quartz and zoisite give consistent results. P–T conditions of the main Tertiary metamorphic overprint were 525° C, P= 7.5 ± 1 kbar in the northern part of the cross-section. The southern part was metamorphosed at lower temperatures of 430–470° C. The Si-content of phengites from this area is almost as high as that of phengites from the Eclogite Zone (Simax= 3.4 pfu). Pressures 〉 10 kbar at 420° C are suggested by phengite barometry according to Massone & Schreyer (1987). In the absence of high-pressure relics or pseudomorphs, these phengites, which lack late Alpine re-equilibration, are the only record that rocks of the southern part probably also experienced an early non-eclogitic high-pressure metamorphism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1525-1314.1990.tb00467.x
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  • 2
    Electronic Resource
    Electronic Resource
    Constraints on the duration of high-pressure metamorphism in the Tauern Window from diffusion modelling of discontinuous growth zones in eclogite garnet (2002)
    Oxford, UK : Blackwell Science Inc
    Journal of metamorphic geology 20 (2002), S. 0 
    Details
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: An eclogite sample from the Grossgockner region of the Hohe Tauern, Austria contains garnet with a pronounced compositional discontinuity between a Mn-rich core and an Fe-rich rim. This jump in composition was caused by a garnet-consuming reaction followed by growth of the garnet rim + omphacite and marks the prograde transition from epidote–amphibolite to eclogite facies metamorphism. Garnet growth ended at peak metamorphic conditions of 570 °C, 17 kbar, but intracrystalline diffusion continued until about 450 °C, 4 kbar on the retrograde path. This garnet overgrowth texture represents a natural diffusion couple and a time span of 1 Myr was calculated from the diffusion profile developing out of the original sharp compositional step. For typical crustal densities, this time corresponds to a minimum average velocity in the range 4.6–7.4 cm yr−1 (for vertical movement), which is one of the fastest exhumation rates reported. The diffusion of all divalent cations of four profiles was modelled, both analytically and numerically. Both approaches gave comparable results, but the times computed for each element were always discrepant up to a factor of 2. Variations of diffusion coefficients within 2 in analytical calculations remedied this and gave consistent upper time limits. Numerical modelling does not require the simplifications introduced in the analytical approach. On the other hand, error propagation was computationally unfeasible with this method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1525-1314.2002.00404.x
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  • 3
    Electronic Resource
    Electronic Resource
    Contrasting parageneses in mica schists of the Hohe Tauern, caused by manganese and zinc (2000)
    Springer
    Mineralogy and petrology 69 (2000), S. 197-212 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung. ¶Mangan und Zink: Ursachen unterschiedlicher Paragenesen in Glimmerschiefern der Hohen Tauern Zwei Metapelittypen mit sehr ähnlichem Chemismus, vom selben Aufschluß in den Hohen Tauern/Österreich, entwickelten zwei deutlich unterschiedliche AFM-Para-genesen. Während beide Quarz, Muskovit, Kyanit and Hämatit enthalten, führt ein Typ zusätzlich Chloritoid (Chloritoidschiefer), der andere zusätzlich Granat, Chlorit, Staurolith und Allanit (Granatschiefer). Dieses Verhalten wird durch die höheren Gehalte von Mangan und Zink in den Granatschiefern hervorgerufen (MnO ≥ 0.25%, Zn ≥ 140 ppm), welche zwei FMASH-Isogradenreaktionen auslösten, die von den chemisch reineren Chloritoidschiefern (MnO ≤ 0.03%, Zn ≤ 70 ppm) nie erreicht wurden. Granat und Staurolith entstanden als neue Phasen, die jeweils Mangan beziehungsweise Zink pufferten. Beide Glimmerschiefertypen haben sich aus einem chemisch beinahe homogenen Pelit beziehungsweise Chlorit-Pyrophyllit-Schiefer entwickelt. Tatsächlich sind Reaktionen, die bestimmten Isograden entsprechen, nur in den “verunreinigten” Glimmerschiefern abgelaufen. Die dadurch zusätzlich entstandenen Phasen ermöglichten uns außerdem erst die Berechnung der PT-Bedingungen der letzten Equilibrierung (um 540 ±25 °C and 12 ± 2 kbar). Diese Gesteine sind ein gutes Beispiel für die Bedeutung von Nebenelementen in mäßig Hochdruck-metamorphen Schiefern, im Vergleich zur bereits bekannten Wirkung dieser Elemente in mittelgradig metamorphen Glimmerschiefern.
    Notes: Summary. ¶Two compositionally similar types of metapelites from the same outcrop in the eastern Hohe Tauern/Austria (Lieserkarscharte, Silbereck Series) have evolved two distinctly different AFM parageneses. While both contain quartz, muscovite, kyanite and hematite, one type contains additional chloritoid (chloritoid schist), the other one additional garnet, chlorite, staurolite and allanite (garnet schist). This behaviour is shown to be caused by higher contents of manganese and zinc in the garnet schists (MnO ≥ 0.25%, Zn ≥ 140 ppm), which triggered two FMASH isograd reactions that were never reached by the chemically purer chloritoid schists (MnO ≤ 0.03%, Zn ≤ 70 ppm). Garnet and staurolite appeared as new phases, buffering manganese and zinc, respectively. Both types of mica schist have evolved from a single, compositionally almost homogeneous pelite or chlorite pyrophyllite schist. In fact, reactions representing specific isograds occurred only in mica schists containing impurities. They caused the growth of some extra phases which enabled us to calculate the PT-conditions of the final equilibration (around 540 ± 25 °C and 12 ± 2 kbar). These rocks are a good example of the importance of minor elements in moderately high-pressure schists as compared to the already well known effects of these elements in medium-grade metamorphic mica schists.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007100070021
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  • 4
    Electronic Resource
    Electronic Resource
    The stability of annite+quartz: reversed experimental data for the reaction 2 annite+3 quartz=2 sanidine+3 fayalite +2 H2O (1995)
    Springer
    Contributions to mineralogy and petrology 121 (1995), S. 380-387 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Reversals for the reaction 2 annite+3 quartz=2 sanidine+3 fayalite+2 H2O have been experimentally determined in cold-seal pressure vessels at pressures of 2, 3, 4 and 5 kbar, limiting annite +quartz stability towards higher temperatures. The equilibrium passes through the temperature intervals 500–540° C (2 kbar), 550–570° C (3 kbar), 570–590° C (4 kbar) and 590–610° C (5 kbar). Starting materials for most experiments were mixtures of synthetic annite +fayalite+sanidine+quartz and in some runs annite+quartz alone. Microprobe analyses of the reacted mixtures showed that the annites deviate slightly from their ideal Si/Al ratio (Si per formula unit ranges between 2.85 and 2.92, AlVI between 0.06 and 0.15). As determined by Mössbauer spectroscopy, the Fe3+ content of annite in the assemblage annite+fayalite +sanidine+quartz is around 5–7%. The experimental data were used to extract the thermodynamic standard state enthalpy and entropy of annite as follows: H 0 f, Ann =−5125.896±8.319 [kJ/mol] and S 0 Ann=432.62±8.89 [J/mol/K] (consistent with the Holland and Powell 1990 data set), and H 0 f,Ann =−5130.971±7.939 [kJ/mol] and S 0 Ann=424.02±8.39 [J/mol/K] (consistent with the TWEEQ data base, Berman 1991). The preceeding values are close to the standard state properties derived from hydrogen sensor data of the redox reaction annite=sanidine+magnetite+H 2 (Dachs 1994). The experimental half-reversal of Eugster and Wones (1962) on the annite +quartz breakdown reaction could not be reproduced experimentally (formation of annite from sanidine+fayalite+quartz at 540° C/1.035 kbar/magnetite-iron buffer) and probable reasons for this discrepancy remain unclear. The extracted thermodynamic standard state properties of annite were used to calculate annite and annite+quartz stabilities for pressures between 2 and 5 kbar.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050103
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  • 5
    Electronic Resource
    Electronic Resource
    Annite stability revised. 1. Hydrogen-sensor data for the reaction annite = sanidine + magnetite + H2 (1994)
    Springer
    Contributions to mineralogy and petrology 117 (1994), S. 229-240 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract In P - T - logfO2 space, the stability of annite (ideally KFe 3 2+ (OH)2AlSi3O10) at high fO2 (low fH2) is limited by the reaction: annite = sanidine + magnetite + H2. Using the hydrogen-sensor technique, the equilibrium fH2 of this reaction was measured between 500 and 800° C at 2.8 kbar in 50° C intervals. Microbrobe analyses of the reacted annite+sanidine+magnetite mixtures show that tetrahedral positions of annite have a lower Si/Al ratio than the ideal value of 3/1. Silicon decreases from ∼2.9 per formula unit at low temperatures to ∼2.76 at high temperatures. As determined by Mössbauer spectroscopy in three experimental runs, the Fe3+ content of annite in the equilibrium assemblage is 11%±3. A least squares fit to the hydrogensensor data gives ΔH R 0 = 50.269 ± 3.987 kJ and ΔS R 0 = 83.01 ± 4.35 J/K for equilibrium (1). The hydrogene-sensor data are consistent with temperature half brackets determined in the classical way along the nickel-nickel oxide (NNO) and quartz-fayalite-magnetite (QFM) buffers with a mixture of annite+sanidine+magnetite for control. Compared to published oxygen buffer reversals, agreement is only found at high temperature and possible reasons for that discrepancy are discussed. The resulting slope of equilibrium (1) in logfO2 − T dimensions is considerably steeper than previously determined and between 400 and 800°C only intersects with the QFM buffer curve. Based on the hydrogen-sensor data and on the thermodynamic dataset of Berman (1988, and TWEEQ data base) for sanidine, magnetite and H2, the deduced standard-state properties of annite are: H f 0 =-5127.376±5.279 kJ and S 0=422.84±5.29 J/(mol K). From the recently published unit cell refinements of annites and their Fe3+ contents, determined by Mössbauer spectroscopy (Redhammer et al. 1993), the molar volume of pure annite was constrained as 15.568±0.030 J/bar. A revised stability field for annite is presented, calculated between 400 and 800°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00310865
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  • 6
    Electronic Resource
    Electronic Resource
    Activity-composition relationship in Tschermak's substituted Fe biotites at 700°C, 2 kbar (1996)
    Springer
    Contributions to mineralogy and petrology 125 (1996), S. 85-99 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  The reaction-displacement technique was applied to the end-member reaction annite = sanidine + magnetite + H2 in order to determine the activity of the annite component (a Ann) in iron biotites with variable degrees of the Tschermak's substitution ([6]Fe + [4]Si = [6]Al + [4]Al). Based on the simplified relation a Ann = f H 2/foH2 (foH2 = hydrogen fugacity of the end-member reaction at P, T), two types of experiments were performed at 700°C / 2 kbar: Type I used Fe-Al biotites of known starting composition together with sanidine + magnetite + H2O. This assemblage was exposed to various f H 2 conditions (f H 2 〈 foH2) produced in the pressure vessel either by using different ratios of water/oil as pressure medium (f H 2 in this case was measured by the hydrogen sensor technique), or by the Ni′NiO buffer. The composition of the Fe-Al biotites changed through incorporation or release of the annite component in response to the externally imposed f H 2. By using opposite biotite starting compositions, the equilibrium composition as a function of f H2 was bracketed. For type II, f H 2 in equilibrium with a specific combination of fine-grained Fe-Al biotite (+ sanidine + magnetite + H2O) was measured internally by application of the hydrogen sensor technique. Both type I and type II experiments yield consistent results demonstrating that a fine-grained assemblage of Fe-Al biotite (+ sanidine + magnetite + H2O) is able to act as a sliding-scale buffer. The final chemical composition of the Fe-Al biotite after the experiments was determined by electron microprobe and Mössbauer spectroscopy. The [4]Al and [6]Al in the biotites are coupled according to the Tschermak's substitution. In the tetrahedral sheet 0.1 Al-atoms per formula unit are present in excess to the amount required to balance [6]Al, and all Fe-Al biotites contain 8–10% Fe3+. Therefore, they are not members of the pure annite - siderophyllite join, but have an almost constant amount (15 Mol%) of two additional Fe3+-bearing components (ferri-siderophyllite and a vacancy end-member). The volume - composition relationship obtained does not indicate excess molar volumes of mixing for the annite (Ann) - siderophyllite (Sid) binary. The data are consistent with a molar volume of annite of 15.46 ± 0.02 Jbar–1 and of 15.06 ± 0.02 Jbar–1 for siderophyllite. The experimentally determined activity - composition relation shows that biotites on the join annite - siderophyllite deviate negatively from ideality. A symmetric interaction parameter WAnnSid is sufficient to represent the data within error. This was constrained as: W AnnSid = –29 ± 4 kJmol–1. This is in contradiction to empirical interaction parameters derived from natural assemblages for this binary that predict positive deviation from ideality. Reasons for this discrepancy are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050208
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  • 7
    Electronic Resource
    Electronic Resource
    A Mössbauer and X-ray diffraction study of annites synthesized at different oxygen fugacities and crystal chemical implications (1993)
    Springer
    Physics and chemistry of minerals 20 (1993), S. 382-394 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract A refined set of Mössbauer parameters (isomer shifts, quadrupole splittings, Fe2+/Fe3+ ratios) and lattice parameters were obtained from annites synthesized hydrothermally at pressures between 3 and 5 kbars, temperatures ranging from 250 to 780° C and oxygen fugacities controlled by solid state buffers (NNO, QMF, IM, IQF). Mössbauer spectra showed Fe2+ and Fe3+ on both the M1 and the M2 site. A linear relationship between Fe3+ content and oxygen fugacity was observed. Towards low Fe3+ values this linear relationship ends at ≈10% of total iron showing that the Fe3+ content cannot be reduced further even if more reducing conditions are used. This indicates that in annite at least 10% Fe2+ are substituted by Fe3+ in order to match the larger octahedral layer to the smaller tetrahedral layer. IR spectra indicate that formation of octahedral vacancies plays an important role for charge balance through the substitution 3 Fe2+ → 2 Fe3+ + ▪(oct).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203107
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  • 8
    Electronic Resource
    Electronic Resource
    Mössbauer spectroscopic and x-ray powder diffraction studies of synthetic micas on the join annite KFe3AlSi3O10(OH)2-phlogopite KMg3AlSi3O10(OH)2 (1995)
    Springer
    Physics and chemistry of minerals 22 (1995), S. 282-294 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Micas of the composition K(Fe3−x Mg x )AlSi3 O10(OH)2 (x=0.6, 1.2, 1.8, 2.4 and 3.0, corresponding to ann80phl20, ann60phl40, ann40phl60, ann20phl80 and ann0phl100) were synthesized hydrothermally under controlled oxygen fugacity conditions. Lattice parameters a 0 and b 0 show a distinct linear decrease with increasing Mg content. With increasing ferric iron content a deviation from this linear trend is observed especially within iron rich samples. The tetrahedral rotation angle α increases smoothly from 0° in annite to 9.1° in phlogopite. Mössbauer spectra show Fe2+ and Fe3+ on the octahedral M1 and M2 sites and partially also Fe3+ on the tetrahedral site. There is a smooth increase of the quadrupole splitting on both the M1 and the M2 site going from annite to phlogopite, probably due to changes in the lattice contribution to the electric field gradient, assuming a positive correlation between quadrupole splitting and distortion. Fe3+ contents, as determined by Mössbauer spectroscopy, versus oxygen fugacity shows that, depending on the composition of the micas, minimum amounts of Fe3+ are present. For ann80phl20 this minimum amount of Fe3+ is about 8% decreasing to about 1–2% Fe3+ for ann20phl80. The molar volume of each solid solution member has been estimated from the determined relations of the molar volume versus % Fe3+ contents, extrapolated back to 0% Fe3+. Plotting these volumes as a function of Xphl shows that negative excess volume occur in the annitephlogopite join, with the maximum deviation from ideality around X phl=0.3. Margules volume parameters have been constrained as: Wv, AnnPhl=0.018±0.016 J/(bar.mol) and Wv, PhlAnn=-0.391±0.025 J(bar.mol) (three site basis).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202768
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  • 9
    Electronic Resource
    Electronic Resource
    Alpine geodynamic evolution of passive and active continental margin sequences in the Tauern Window (eastern Alps, Austria, Italy): a review (1998)
    Springer
    Geologische Rundschau 87 (1998), S. 225-242 
    Details
    ISSN: 0016-7835
    Keywords: Key words Tauern Window ; Eastern Alps ; Penninic ; Tectonostratigraphy ; Geodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Penninic oceanic sequence of the Glockner nappe and the foot-wall Penninic continental margin sequences exposed within the Tauern Window (eastern Alps) have been investigated in detail. Field data as well as structural and petrological data have been combined with data from the literature in order to constrain the geodynamic evolution of these units. Volcanic and sedimentary sequences document the evolution from a stable continent that was formed subsequent to the Variscan orogeny, to its disintegration associated with subsidence and rifting in the Triassic and Jurassic, the formation of the Glockner oceanic basin and its consumption during the Upper Cretaceous and the Paleogene. These units are incorporated into a nappe stack that was formed during the collision between a Penninic Zentralgneis block in the north and a southern Austroalpine block. The Venediger nappe and the Storz nappe are characterized by metamorphic Jurassic shelf deposits (Hochstegen group) and Cretaceous flysch sediments (Kaserer and Murtörl groups), the Eclogite Zone and the Rote Wand–Modereck nappe comprise Permian to Triassic clastic sequences (Wustkogel quartzite) and remnants of platform carbonates (Seidlwinkl group) as well as Jurassic volcanoclastic material and rift sediments (Brennkogel facies), covered by Cretaceous flyschoid sequences. Nappe stacking was contemporaneous to and postdated subduction-related (high-pressure) eclogite and blueschist facies metamorphism. Emplacement of the eclogite-bearing units of the Eclogite zone and the Glockner nappe onto Penninic continental units (Zentralgneis block) occurred subsequent to eclogite facies metamorphism. The Eclogite zone, a former extended continental margin, was subsequently overridden by a pile of basement-cover nappes (Rote Wand–Modereck nappe) along a ductile out-of-sequence thrust. Low-angle normal faults that have developed during the Jurassic extensional phase might have been inverted during nappe emplacement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005310050204
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  • 10
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    Standard-state thermodynamic properties of annite, KFe3[(OH)2AlSi3O10], based on new calorimetric measurements (2015)
    Schweizerbart
    Details
    Publication Date: 2015-08-22
    Description: The heat capacity ( C p ) of synthetic annite was measured using a Physical Properties Measurement System (PPMS) for temperatures ranging from 2 to 300 K, and by differential scanning calorimetry (DSC) for temperatures between 282 and 363 K. The sample was synthesized in a hydrothermal apparatus at 2 kbar and 800°C, with a log f O 2 of –20. It was characterized using electron microprobe analysis, Mössbauer spectroscopy, XRD, SEM, and single-crystal structural refinement methods and contained the well-established minimum possible Fe 3+ content of 10% ( i.e. , Fe 3+ /Fe tot = 0.1), representing the closest possible synthetic composition to ‘ideal’ annite. A distinct kink in the slope of C p plotted against T at around 49 K indicated a heat-capacity anomaly, which is interpreted to have been caused by a magnetic ordering phase transition. In order to compute the magnetic contribution ( C mag ) to the overall C p , the C p data between 40 and 65 K were therefore excluded from the measured C p data set and the remaining data fitted to a combination of Debye, Einstein, and Schottky functions. These functions then served as a model for estimating the vibrational part of the heat capacity ( C vib ) within the temperature range of the magnetic phase transition. Integrating the C p data with respect to temperature yields a calorimetric entropy of 411.4±2.9 J/mol·K at 298 K for ‘pure’ annite (excluding any configurational terms). The magnetic entropy amounts to only 1.5 J/mol·K, which is much less than predicted theoretically. The DSC data, combined with C p values from published literature, are represented by the following polynomial, which can be used to compute the C p of annite at temperatures above 298 K: \[ {C}_{\mathrm{p}}=728.6-5581\cdot {T}^{-0.5}-2.896\cdot {10}^{6}\cdot {T}^{-2}+2.957\cdot {10}^{8}\cdot {T}^{-3}. \] Applying the calorimetrically determined entropy of annite (and adding a configurational entropy of 11.53 J/mol·K, representing Al-avoidance) to published phase-equilibrium data on the reaction annite + quartz = sanidine + fayalite + H 2 O resulted in a standard enthalpy of formation for annite of H o f =–5132.5±2.0 kJ/mol. The published experimental data on the reaction annite = sanidine + magnetite + H 2 (hydrogen-sensor experiments and conventional oxygen-buffer brackets) were analysed using the calorimetrically derived entropy of annite. With the exception of magnetite–wüstite buffered experiments, all experimental constraints could be satisfied using the annite standard-state properties S o =422.9±2.9 J/mol·K and H o f, values ranging between 5128 and –5135 kJ/mol. A plot is presented showing contours for the Fe 3+ /Fe tot ratio of annite within the assemblage annite–sanidine–magnetite (+H 2 ) as function of log f O 2 and temperature.
    Print ISSN: 0935-1221
    Electronic ISSN: 1617-4011
    Topics: Geosciences
    Published by Schweizerbart
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