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Stalder, Roland; Skogby, Henrik

doi:10.1127/0935-1221/2002/0014-1139

Cited by 62 publications

(10 citation statements)

References 10 publications

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“…, as commonly observed in natural and synthetic orthopyroxene (Bell and Rossman, 1992;Stalder and Skogby, 2002). The water contents calculated for orthopyroxene are in the range 20-370 ppm H 2 O by weight, with similar water contents in the granular and sheared xenoliths ( Figure 5).…”

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confidence: 72%

Water content of the mantle xenoliths from Kimberley and implications for explaining textural variations in cratonic roots

et al. 2011

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Water contents estimates based on infrared spectroscopy and deformation microstructures are used to constrain the origin of textural variations observed in mantle xenoliths from Kimberley, South Africa. Infrared spectra indicate water contents of 10–370 ppm (H2O by weight) in olivine, 20–370 ppm in orthopyroxene, up to 340 ppm in garnet and 30–550 ppm in clinopyroxene, although no systematic differences are detected among texturally distinct xenoliths (i.e. granular and sheared peridotites). In contrast, active slip systems in olivine, as inferred from tilt boundaries, are different between the granular and sheared peridotites; the former deformed via the [100](010) slip system, which is commonly active under hot, dry conditions, whereas the latter deformed via the [001](100) slip system, which is commonly activated in water‐rich environments. The discrepancy in water contents estimates based on infrared spectroscopy and deformation microstructures may reflect different stages of the evolution of water content: the present water contents, as analysed by infrared spectroscopy, may have been modified by the most recent events (e.g. eruption by kimberlite magma), whereas the water contents inferred from tilt boundaries may have resulted from the various deformation processes in the deep cratonic mantle. Accordingly, we suggest that the observed heterogeneity in water content within cratonic roots facilitates local deformation, and gives rise to the range of textures seen in cratonic mantle xenoliths. Copyright © 2010 John Wiley & Sons, Ltd.

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confidence: 72%

Water content of the mantle xenoliths from Kimberley and implications for explaining textural variations in cratonic roots

et al. 2011

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“…According to previous studies [24,38,39], the most likely substitution mechanism for Al incorporation in aluminous orthopyroxene is through the Tschermaks-substitution reaction: Mg 2+ + Si 4+ = 2Al 3+ . Nevertheless, hydrothermal annealing experiments have shown that most water is dissolved by the coupled substitution of Al 3+ +H + for Si 4+ and by the substitution of Al 3+ +H + for 2Mg 2+ [13,24,38,39]. Both substitutions appear to occur with roughly equal abundance; consequently, Al is distributed approximately equally among tetrahedral and octahedral sites, irrespective of water content.…”

Section: Effects Of Temperature and Al Contentmentioning

confidence: 96%

“…Previous studies indicate that the water solubility in pure MgSiO 3 enstatite increases with increasing pressure and temperature [21,22], while behavior of water solubility in Al-free ensta-tite is comparable to that in olivine [11,23]. In contrast, the incorporation of aluminum in orthopyroxene greatly increases the water solubility relative to that in the pure Al-free system [13,21,[24][25][26]. As a result, the partition coefficient of water between aluminous enstatite and olivine is very high: [13,[27][28][29][30].…”

Section: Citationmentioning

confidence: 97%

“…Therefore, aluminous enstatite could be a more important host than olivine for water in the Earth's upper mantle, and it may be related to abnormal geophysical observations at the top of the asthenosphere [1,3,7,13,16]. The solubility of water as a function of temperature and pressure has been investigated to determine the mechanism and thermodynamics of the incorporation of water in orthopyroxene [13,21,24,25,[27][28][29]. However, it is worth noting that most studies were conducted using a pure MgSiO 3 system [21,24,[27][28][29] and single crystals of orthopyroxene.…”

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confidence: 99%

“…The solubility of water as a function of temperature and pressure has been investigated to determine the mechanism and thermodynamics of the incorporation of water in orthopyroxene [13,21,24,25,[27][28][29]. However, it is worth noting that most studies were conducted using a pure MgSiO 3 system [21,24,[27][28][29] and single crystals of orthopyroxene. Except for two studies [13,25], few data on water solubility have been systematically reported for the (Mg, Fe)SiO 3 -H 2 O-Al 2 O 3 system (Al-Fe-Mg orthopyroxene) that simultaneously consider the influences of temperature and Al content.…”

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Water solubility in orthopyroxene: Dependence on temperature and Al content

Zhang

Matsuzaki

2013

Chin. Sci. Bull.

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The water solubility in Al-Fe-Mg orthopyroxene [(Mg,Fe,Al)(Si,Al)O 3 : X Fe = 0.1] was investigated as a function of temperature and Al contents. Experiments were performed at 10 kbar with temperatures ranging from 800 to 1200°C under water-saturated conditions. Water contents in the (Mg,Fe)SiO 3 -H 2 O-Al 2 O 3 system were determined using unpolarized Fourier transform infrared spectroscopy. The present results show that water solubility in Al-bearing orthopyroxene decreases systematically with temperature from approximately 1 weight % at 800°C to 568 ± 58 ppm at 1200°C and increase significantly with increasing Al 2 O 3 contents under the same annealing temperature and pressure. Combined with published results on the dependence of hydroxyl solubility on water fugacity and pressure, the present results can be described by the relationwhere A = 0.0024 ± 0.0015 ppm/bar 0.5 , 1bar H = −103.348 ± 9.768 kJ/mol, and solid V = 9.2 ± 1.1 cm 3 /mol. This equation implies that the incorporation mechanism of water in aluminous orthopyroxene involves the isolated OH groups. Based on the experimentally established solubility model used in this study, it is suggested that water solubility decreases with increasing temperature under typical upper mantle pressure. The predicted temperature dependence of water solubility is in good agreement with the previous experimental observations in Al-bearing orthopyroxene, but the opposite dependence is observed in Al-free systems. Moreover, our estimation of the water solubility in upper-mantle minerals as a function of depth for a typical oceanic geotherm might be of potential importance in interpreting the geophysical observations. orthopyroxene, water solubility, infrared spectroscopy, asthenosphere Citation:Zhang B H, Matsuzaki T, Wu X P. Water solubility in orthopyroxene: Dependence on temperature and Al content. Chin Sci Bull, 2013Bull, , 58: 38953902, doi: 10.1007 The presence of water or hydroxyl defects in nominally anhydrous minerals (NAMs) has a dramatical influence on their geophysical properties such as solidus temperature [1], electrical conductivity [2-6] and viscosity [7][8][9], as well as on mantle dynamics such as melt generation [10] and mantle convection [7]. Critical to understanding the role of water in the Earth's mantle, a key step is to estimate the distribution of water inside the mantle and the incorporation mechanism of hydrogen in mantle minerals by combining experimentally determined mineral properties with geophysical observations. Two principal approaches can provide significant constraints on the water content in the Earth's interior. One approach is water solubility experiments in mantle minerals [11][12][13], and the other infers the water content based on the electrical conductivity of the NAMs [2-6,14-19].Orthopyroxene is considered to be one of the main constituent minerals in the Earth's upper mantle and is believed to constitute approximately 20-40 vol% [20]. Previous studies indicate that the water solubility in pure MgSiO 3 enstatite increa...

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Pyroxenes as tracers of mantle water variations

2014

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The concentration and distribution of volatiles in the Earth's mantle influence properties such as melting temperature, conductivity, and viscosity. To constrain upper mantle water content, concentrations of H 2 O, P, and F were measured in olivine, orthopyroxene, and clinopyroxene in mantle peridotites by secondary ion mass spectrometry. Analyzed peridotites are xenoliths (Pali Aike, Spitsbergen, Samoa), orogenic peridotites (Josephine Peridotite), and abyssal peridotites (Gakkel Ridge, Southwest Indian Ridge, Tonga Trench). The comparison of fresh and altered peridotites demonstrates that low to moderate levels of alteration do not affect H 2 O concentrations, in agreement with mineral diffusion data. Olivines have diffusively lost water during emplacement, as demonstrated by disequilibrium between olivine and coexisting pyroxenes. In contrast, clinopyroxene and orthopyroxene preserve their high-temperature water contents, and their partitioning agrees with published experiments and other xenoliths. Hence, olivine water concentrations can be determined from pyroxene concentrations using mineral-mineral partition coefficients. Clinopyroxenes have 60-670 ppm H 2 O, while orthopyroxenes have 10-300 ppm, which gives calculated olivine concentrations of 8-34 ppm. The highest olivine water concentration translates to an effective viscosity of 6 × 1019 Pa s at 1250°C and~15 km depth, compared to a dry effective viscosity of 2.5 × 10 21 Pa s. Bulk rock water concentrations, calculated using mineral modes, are 20-220 ppm and correlate with peridotite indices of melt depletion. However, trace element melt modeling indicates that peridotites have too much water relative to their rare earth element concentrations, which may be explained by late-stage melt addition, during which only hydrogen diffuses fast enough for reequilibration.

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Cited by 62 publications

References 10 publications

Water content of the mantle xenoliths from Kimberley and implications for explaining textural variations in cratonic roots

Water content of the mantle xenoliths from Kimberley and implications for explaining textural variations in cratonic roots

Water solubility in orthopyroxene: Dependence on temperature and Al content

Pyroxenes as tracers of mantle water variations

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