Vent fluid chemistry of the Rainbow hydrothermal system (36°N, MAR): Phase equilibria and in situ pH controls on subseafloor alteration processes

Seyfried, William E.; Pester, Nicholas J.; Ding, Kan; Rough, Mikaella

doi:10.1016/j.gca.2011.01.001

Cited by 119 publications

(100 citation statements)

References 92 publications

(175 reference statements)

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“…1 and 2 are likely among the slowest for laboratory serpentinization experiments (e.g., 15,20). Although it is difficult to compare directly the laboratory H 2 production rates with rates in mid-ocean ridge systems, elevated H 2 generated primarily via serpentinization has been reported at mid-ocean ridge serpentinization localities at concentrations very similar to our reported values (3,8,12,26).…”

Section: Resultssupporting

confidence: 82%

Differentiating biotic from abiotic methane genesis in hydrothermally active planetary surfaces

Oze

Jones

Goldsmith

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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Molecular hydrogen (H 2 ) is derived from the hydrothermal alteration of olivine-rich planetary crust. Abiotic and biotic processes consume H 2 to produce methane (CH 4 ); however, the extent of either process is unknown. Here, we assess the temporal dependence and limit of abiotic CH 4 related to the presence and formation of mineral catalysts during olivine hydrolysis (i.e., serpentinization) at 200°C and 0.03 gigapascal. Results indicate that the rate of CH 4 production increases to a maximum value related to magnetite catalyzation. By identifying the dynamics of CH 4 production, we kinetically model how the H 2 to CH 4 ratio may be used to assess the origin of CH 4 in deep subsurface serpentinization systems on Earth and Mars. Based on our model and available field data, low H 2 ∕CH 4 ratios (less than approximately 40) indicate that life is likely present and active.kinetics | molecular hydrogen | Fischer-Tropsch type reactions | methanogenesis O livine hydrolysis (i.e., serpentinization) is a major pathway related to the near-surface synthesis of molecular hydrogen (H 2 ) on Earth, Mars, and, potentially, other planets and satellites (1-4). Molecular hydrogen from serpentinization can chemically reduce carbon (e.g., HCO 3 − , HCOOH, CO, CO 2 ) to form CH 4 or can be converted to CH 4 via microbial processes (i.e., methanogenesis) (1, 3, 5-12). Although CH 4 formation is thermodynamically favorable over a range of pressure (P) and temperature (T) (13, 14), CH 4 production via Fischer-Tropsch type (FTT) reactions is slow without the aid of mineral catalysts (3,9,15,16). To understand the limits of abiotic CH 4 production, it is imperative to assess the role of mineral catalysts, both those initially present in the system and those formed during the process of serpentinization.Chromite (FeCr 2 O 4 ), a primary mineral common in serpentinization systems, has been shown to enhance FTT synthesis reactions (17). Additionally, secondary minerals such as magnetite (Fe 3 O 4 ) and/or awaruite (Ni 3 Fe) are produced during olivine hydrolysis, providing increased opportunities for FTT catalysis (13,15,(18)(19)(20)(21). Here, we evaluate the rate of abiotic CH 4 production for systems catalyzed both by chromite and secondary minerals (magnetite and awaruite) in experimental systems undergoing serpentinization at 200°C and 0.03 gigapascal (GPa), conditions similar to hydrothermally altered peridotite in midocean ridge environments on Earth or at approximately 5 km depth in the Martian subsurface. By measuring H 2 and CH 4 formed during olivine hydrolysis, mineral-catalyzed CH 4 production can be differentiated from biogenic CH 4 production through a consideration of the H 2 -CH 4 kinetic balance. Experimental ProceduresSerpentinization experiments were carried out in the WaterRock Interaction Laboratory (US Geological Survey, Menlo Park, CA) using the parameters listed in

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Section: Resultssupporting

confidence: 82%

Differentiating biotic from abiotic methane genesis in hydrothermally active planetary surfaces

Oze

Jones

Goldsmith

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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“…In other ultramafic-hosted hydrothermal systems where abiogenic hydrocarbon formation has been proposed, such as Rainbow and Logatchev (Holm and Charlou, 2001;Charlou et al, 2002;Schmidt et al, 2007;Konn et al, 2009), reaction zone temperatures are considerably higher than Lost City. Maximum measured vent fluid temperatures at both of these locations are in excess of 350°C and reaction zone conditions are thought to be nearer 400°C (Allen and Seyfried, 2003;Seyfried et al, 2004;Seyfried et al, 2011). The experiments presented here suggest substantial H isotope exchange between the C 2+ alkanes and water can occur on timescales of months to years at 323°C, and even greater rates of isotope exchange are likely at the higher temperatures of these systems due to the enhanced stability of alkenes according to reaction (1) (Figure 6).…”

Section: H / 1 H Ratios and Abiogenesis In Igneous Environmentsmentioning

confidence: 72%

Hydrogen isotope exchange between n-alkanes and water under hydrothermal conditions

Reeves

Seewald

Sylva

2012

Geochimica et Cosmochimica Acta

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“…These are consistently lower than the B content of seawater and endmember hydrothermal fluids have been determined to 0.34-0.55 lg/g (31-51 lmol/kg), 2.57 lg/g (238 lmol/kg), and 3.62 lg/g (335 lmol/kg) for Lost City, Rainbow, and Logatchev, respectively (Schmidt et al 2007;Foustoukos et al 2008;Boschi et al 2008;Seyfried et al 2011Seyfried et al , 2015. Boron isotopic data for ultramafic-hosted vent fluids are not yet available, but have been estimated to þ 25 to +30‰ (Foustoukos et al 2008;Boschi et al 2008).…”

Section: Hydrothermal Vent Fluidsmentioning

confidence: 84%

Boron Isotopes in the Ocean Floor Realm and the Mantle

Marschall

2017

Advances in Isotope Geochemistry

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This chapter reviews the boron isotopic composition of the ocean floor, including pristine igneous oceanic crust such as mid-ocean ridge basalts and ocean island basalts and their implications for the B isotopic composition of the mantle. The chapter further discusses the B isotopic effects of assimilation of altered crustal materials in mantle-derived magmas. The systematics of seawater alteration on oceanic rocks are discussed, including sediments, igneous crust and serpentinization of ultramafic rocks and the respective marine hydrothermal vent fluids. The chapter concludes with a discussion of the secular evolution of the B isotopic composition of seawater.

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Vent fluid chemistry of the Rainbow hydrothermal system (36°N, MAR): Phase equilibria and in situ pH controls on subseafloor alteration processes

Cited by 119 publications

References 92 publications

Differentiating biotic from abiotic methane genesis in hydrothermally active planetary surfaces

Differentiating biotic from abiotic methane genesis in hydrothermally active planetary surfaces

Hydrogen isotope exchange between n-alkanes and water under hydrothermal conditions

Boron Isotopes in the Ocean Floor Realm and the Mantle

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