Hydrogen incorporation in enstatite in the system MgO–SiO2–H2O–NaCl

Stalder, Roland; Kronz, Andreas; Simon, Klaus

doi:10.1007/s00410-008-0306-0

Cited by 22 publications

(11 citation statements)

References 34 publications

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“…The substitution of single cations does not seem to be the limiting factor for hydrogen uptake, since the incorporation of trivalent cations does not necessarily require charge balancing by H + ions. Other factors such as temperature (Mierdel and Keppler, 2004), pressure (Férot and Bolfan-Casanova, 2012;Rauch and Keppler, 2002), water activity (Stalder et al, 2008), and oxygen fugacity need to be considered as Table 2 Comparison of the results obtained by the BK90, BM85, TA98, and WES91 geothermometers (in°C) including geothermal gradients (in°C/km) at a pressure of 15 kbar. Uncertainties are given as 1 standard deviation of the mean.…”

Section: Water Incorporation Into Orthopyroxenementioning

confidence: 99%

Water in orthopyroxene from abyssal spinel peridotites of the East Pacific Rise (ODP Leg 147: Hess Deep)

Hesse

Gose

Stalder

et al. 2015

Lithos

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Section: Water Incorporation Into Orthopyroxenementioning

confidence: 99%

Water in orthopyroxene from abyssal spinel peridotites of the East Pacific Rise (ODP Leg 147: Hess Deep)

Hesse

Gose

Stalder

et al. 2015

Lithos

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“…Experiments have shown that the water incorporation in pyroxene also depends on P-T conditions [Rauch and Keppler, 2002;Mierdel and Keppler, 2004;Mierdel et al, 2007;F erot and Bolfan-Casanova, 2012;Zhang et al, 2013] and water activity [Stalder et al, 2008]. In addition, oxygen fugacity is also believed to control the incorporation of water in mantle peridotite NAMs [Peslier et al, 2002;Peslier, 2010;Yu et al, 2011].…”

Section: 1002/2016gc006767mentioning

confidence: 99%

Origins of water content variations in the suboceanic upper mantle: Insight from Southwest Indian Ridge abyssal peridotites

Li¹,

Soustelle

Zhang

et al. 2017

Geochem Geophys Geosyst

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To investigate the origin of heterogeneous water distribution in the suboceanic lithospheric mantle, we performed a detailed petrological and geochemical analysis of abyssal peridotites collected from two localities (53°E and 63.5°E) on the Southwest Indian Ridge. These serpentinized peridotites display primary olivine‐orthopyroxene‐clinopyroxene‐spinel assemblage and record equilibrium temperature of 1150–1200°C and around 1000°C for the 53°E and 63.5°E locations, respectively. The rocks were thus equilibrated in the spinel stability field prior to their exhumation to the seafloor. Our FTIR analyses show variable water contents in orthopyroxene ranging from 24 to 262 wt ppm H2O. Orthopyroxene in the 63.5°E peridotites is characterized by homogeneous and high water content (>200 ppm), whereas orthopyroxene in the 53°E peridotites displays a wider range of water contents (24–246 ppm). We first demonstrate that differences in equilibrium conditions (i.e., pressure and temperature) and mineral chemistry and serpentinization cannot explain the water content variations. Melting modeling show that a fractional melting in both garnet and spinel stability fields is needed to explain the MREE and HREE concentrations in clinopyroxene. Enrichment in LREE, high water contents, and high H2O/Ce, however, require a postmelting rehydration event such as metasomatism. Based on petrographic evidence and investigation of chemical heterogeneities at segment/dredge scale, we suggest that this event involves a metasomatic agent enriched in water and incompatible elements. We infer that the small‐scale heterogeneities in water and trace elements may result either from successive infiltration of various amounts of melt/fluids as described in the formation of oceanic core complex or from spatial heterogeneities of melt infiltration as observed in peridotite massifs.

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“…Another issue regarding excessive hydration of the clinopyroxene crystals is the effect of CO 2 on the activity of water. It has been shown that other volatiles such as CO 2 or halogens within a magmatic system reduce the incorporation of hydrogen in NAMs (e.g., Stalder et al 2008;Kovács et al 2012;Yang et al 2014). As such, the water contents in olivines annealed in a H 2 O + CO 2 fluid phase, for example, were about half of those treated in pure H 2 O (Yang et al 2014).…”

Section: Reconstruction Of Initial Water Contents In Clinopyroxenesmentioning

confidence: 99%

Experimental hydration of natural volcanic clinopyroxene phenocrysts under hydrothermal pressures (0.5–3 kbar)

Weis

Stalder

Skogby

2016

American Mineralogist

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Water is a key parameter in mantle rheology, magma genesis, magma evolution, and resulting eruption styles, because it controls the density and the viscosity, as well as the melting and crystallization behavior of a melt. The water content in nominally anhydrous minerals (NAMs) such as clinopyroxene recently has been used as a proxy for magmatic water contents. NAMs, however, may dehydrate during magma degassing and eruption. We performed rehydration experiments on potentially degassed clinopyroxene phenocrysts from various volcanic settings. The experiments were conducted in hydrogen gas at 1 atm or hydrothermal pressures ranging from 0.5 to 3 kbar to test the incorporation of water into natural clinopyroxene under water fugacities similar to those in a volcanic system. Our results show a dependence of the water content in the clinopyroxene crystals with pressure as the phenocrysts begin to dehydrate upon lower water fugacities in the experiments. Water loss or gain in a crystal occurs according to the relatively fast redox-reaction OH -+ Fe 2+ ↔ O 2-+ Fe 3+ + ½ H 2 , which was confirmed by Mössbauer spectroscopy. The kinetics of this redox-process are independent of pressure and thus water fugacity. Water contents in rehydrated clinopyroxene crystals can be related to magmatic water contents at various levels in a volcanic system. Our results thus show that the water content in erupted clinopyroxene phenocrysts cannot be taken for granted to be representative of magmatic water contents prior to magma degassing. The conducted experiments indicate the simultaneous dehydration of clinopyroxene along with magma ascent and degassing. Rehydration experiments under hydrothermal pressures, however, may be able to reconstruct clinopyroxene water contents at crystallization prior to dehydration.

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Hydrogen incorporation in enstatite in the system MgO–SiO2–H2O–NaCl

Cited by 22 publications

References 34 publications

Water in orthopyroxene from abyssal spinel peridotites of the East Pacific Rise (ODP Leg 147: Hess Deep)

Water in orthopyroxene from abyssal spinel peridotites of the East Pacific Rise (ODP Leg 147: Hess Deep)

Origins of water content variations in the suboceanic upper mantle: Insight from Southwest Indian Ridge abyssal peridotites

Experimental hydration of natural volcanic clinopyroxene phenocrysts under hydrothermal pressures (0.5–3 kbar)

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