Redox evolution and mass transfer during serpentinization: An experimental and theoretical study at 200°C, 500bar with implications for ultramafic-hosted hydrothermal systems at Mid-Ocean Ridges

Seyfried, William E.; Foustoukos, Dionysis I.; Fu, Qi

doi:10.1016/j.gca.2007.05.015

Cited by 236 publications

(234 citation statements)

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“…In the first stage, within the first few hundred hours of the experiment, the concentration of dissolved H 2 was close to the detection limit. Similar observation was reported by Seyfried et al (2007) from their experiments on peridotites. In the case of peridotite-water reaction experiment, Seyfried et al (2007) suggested that Fe substitution for Mg in serpentine and brucite limits the availability of Fe for magnetite formation.…”

Section: Resultssupporting

confidence: 91%

“…Similar observation was reported by Seyfried et al (2007) from their experiments on peridotites. In the case of peridotite-water reaction experiment, Seyfried et al (2007) suggested that Fe substitution for Mg in serpentine and brucite limits the availability of Fe for magnetite formation. This mechanism in turn prohibits a significant release of hydrogen because the reduction of water by ferrous iron in olivine and pyroxene is considered to be a primary mechanism for the simultaneous formation of magnetite and hydrogen (Bach et al, 2006).…”

Section: Resultssupporting

confidence: 91%

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H2 generation by experimental hydrothermal alteration of komatiitic glass at 300°C and 500 bars: A preliminary result from on-going experiment

et al. 2009

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Hydration of komatiite can be a source of significant amount of hydrogen in the Hadean and early Archean ocean floor. We report the first direct evidence for this process based on the results of our hydrothermal alteration experiments on the synthetic komatiitic glass at 300°C and 500 bars. Komatiitic glass was synthesized by dehydration and remelting of serpentinized Al-depleted komatiite collected from the early Archean Komati Formation, the Barberton Greenstone Belt, South Africa. Though the run is still continuing in our lab, the observed accumulation of hydrogen (2.4 mmol/kg) over 2,600 hours is truly significant and is comparable to those observed by hydration of peridotitic rocks. Our results suggest that hydrothermal alteration of komatiites may have provided the source of H 2 in the vicinity of hydrothermal vents that fueled the early evolution of living ecosystems in the Hadean and early Archean.

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Section: Resultssupporting

confidence: 91%

Section: Resultssupporting

confidence: 91%

H2 generation by experimental hydrothermal alteration of komatiitic glass at 300°C and 500 bars: A preliminary result from on-going experiment

et al. 2009

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“…For example, in the Lost City hydrothermal field on the MidAtlantic Ridge, H 2 is abundant, the pH is high, and the reactions occur at moderately low temperature. When Seyfried et al (2007) experimentally constrained hydrogen production at the low temperature of 200 C and 50 MPa, they found that changes in the concentrations of Ca, Mg, and Si in the reacted fluid agreed quantitatively with those predicted theoretically by a reaction pathway model of seawater-lherzolite interaction (fluid:rock mass ratio, 1:1) at 200 C and 50 MPa. However, the time variations of pH, dissolved chloride, and H 2 monitored during their experiment did not agree with the theoretically predicted results (Fig.…”

Section: 2supporting

confidence: 55%

“…Therefore, we synthesized komatiite glass by dehydrating and remelting serpentinized komatiite collected from the Komati Formation, Barberton Greenstone Belt, South Africa, and then reacted the synthesized komatiitic glass with an NaCl solution at 300 C and 50 MPa (Yoshizaki et al 2009). (Seyfried et al 2007). The difference between measured and predicted dissolved H 2 concentrations may reflect (in part) the lack of thermodynamic data for Fe-rich alteration minerals in the database used for the theoretical model…”

Section: 3mentioning

confidence: 99%

“…Several petrographical (Cressey 1979) and theoretical (Wetzel and Shock 2000;Sleep et al 2004) studies have examined the H 2 -generating geochemical and mineralogical reactions associated with the serpentinization of ocean-floor ultramafic rocks, and experimental investigations (Berndt et al 1996;Allen and Seyfried 2003;Seyfried et al 2007) have significantly increased our understanding of the mechanisms of H 2 production during serpentinization. In the present paper, we focus on these experimental results, because it is generally difficult to directly observe chemical processes in subseafloor environments.…”

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confidence: 99%

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Experimental Hydrogen Production in Hydrothermal and Fault Systems: Significance for Habitability of Subseafloor H2 Chemoautotroph Microbial Ecosystems

Suzuki

Shibuya

Yoshizaki

et al. 2014

Subseafloor Biosphere Linked to Hydrothermal Systems

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Hydrogen generated in hydrothermal and fault systems has recently received considerable attention as a potential energy source for hydrogen-based microbial activity such as methanogenesis. Laboratory experiments that have reproduced conditions for the serpentinization of ultramafic rocks such as peridotite and komatiite have clarified the chemical and petrological processes of H 2 production. In a frictional experimental study, we recently showed that abundant H 2 can also be generated in a simulated fault system. This result suggests that microbial ecosystems might exist in subseafloor fault systems. Here we review the experimental constraints on hydrogen production in hydrothermal and fault systems.

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Magnetic signatures of serpentinization at ophiolite complexes

Bonnemains

Carlut

Escartı́n

et al. 2016

Geochem Geophys Geosyst

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International audienceWe compare magnetic properties of 58 variably serpentinized peridotites from three ophiolite complexes (Pindos, Greece; Oman; Chenaillet, France) and the mid-Atlantic Ridge near the Kane fracture zone (MARK). The Pindos and Oman sites show low susceptibility and remanence (K < 0.02 SI; M s < 0.4 Am 2 / kg), while the Chenaillet and MARK sites show instead high susceptibility and remanence (K up to 0.15 SI; M s up to 6 Am 2 /kg), regardless of serpentinization degree. Petrographic observations confirm that Pindos and Oman samples contain serpentine with very little magnetite, while Chenaillet and MARK samples display abundant magnetite in serpentine mesh cells. Bulk rock analyses show similar amounts of ferric iron at a given serpentinization degree, suggesting that iron is oxidized during the serpentinization reaction in both cases, but that its distribution among phases differs. Microprobe analyses show iron-rich serpentine minerals (5–7 wt % FeO) in low-susceptibility samples, while iron-poor serpentine minerals (2–4 wt % FeO) occur in high susceptibility samples. The contrasted magnetic properties between the two groups of sites thus reflect different iron partitioning during serpentinization, that must be related to distinct conditions at which the serpentinization reaction takes place. We propose that magnetic properties of ophiolitic serpen-tinites can be used as a proxy to differentiate between high temperature serpentinization (>250–3008C) occurring at the axis (i.e., Chenaillet, similar to serpentinites from magmatically poor mid-ocean ridges), from lower temperature serpentinization (<200–2508C), likely occurring off axis and possibly during obduction (i.e., Pindos and Oman). At both settings, serpentinization can result in significant hydrogen release

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Redox evolution and mass transfer during serpentinization: An experimental and theoretical study at 200°C, 500bar with implications for ultramafic-hosted hydrothermal systems at Mid-Ocean Ridges

Cited by 236 publications

References 50 publications

H2 generation by experimental hydrothermal alteration of komatiitic glass at 300°C and 500 bars: A preliminary result from on-going experiment

H2 generation by experimental hydrothermal alteration of komatiitic glass at 300°C and 500 bars: A preliminary result from on-going experiment

Experimental Hydrogen Production in Hydrothermal and Fault Systems: Significance for Habitability of Subseafloor H2 Chemoautotroph Microbial Ecosystems

Magnetic signatures of serpentinization at ophiolite complexes

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