Compositional controls on hydrogen generation during serpentinization of ultramafic rocks

Klein, Frieder; Bach, Wolfgang; McCollom, T. M.

doi:10.1016/j.lithos.2013.03.008

Cited by 226 publications

(229 citation statements)

References 62 publications

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“…Partial or total re-equilibration of C-H bonds in CH 4 during extraction by seawater heated to >300°C during active hydrothermal circulation would pull the δD values of CH 4 towards an equilibrium value of −130 to −110‰ (depending on the calibration), consistent with the narrow range of data from high-temperature endmember fluids (Fig. 3.5).It is worth noting that while serpentinization of olivine and orthopyroxene in oceanic peridotites generates large quantities of H 2 (Klein et al, 2009;McCollom and Bach, 2009;Klein et al, 2013), methane synthesis does not necessarily require serpentinization of peridotite. At temperatures of~400°C, oxygen fugacities at or below FMQ are sufficiently reducing for CH 4 to be stable relative to CO 2 (Figs.…”

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confidence: 69%

“…It is worth noting that while serpentinization of olivine and orthopyroxene in oceanic peridotites generates large quantities of H 2 (Klein et al, 2009;McCollom and Bach, 2009;Klein et al, 2013), methane synthesis does not necessarily require serpentinization of peridotite. At temperatures of~400°C, oxygen fugacities at or below FMQ are sufficiently reducing for CH 4 to be stable relative to CO 2 (Figs.…”

Section: Hydrogen Exchange and The Origin Of Hydrogen In Chmentioning

confidence: 99%

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The geochemistry of methane isotopologues

Wang¹

2017

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This thesis documents the origin, distribution, and fate of methane and several of its isotopic forms on Earth. Using observational, experimental, and theoretical approaches, I illustrate how the relative abundances of 12 CH 4 , 13 CH 4 , 12 CH 3 D, and 13 CH 3 D record the formation, transport, and breakdown of methane in selected settings.Chapter 2 reports precise determinations of 13 CH 3 D, a "clumped" isotopologue of methane, in samples collected from various settings representing many of the major sources and reservoirs of methane on Earth. The results show that the information encoded by the abundance of 13 CH 3 D enables differentiation of methane generated by microbial, thermogenic, and abiogenic processes. A strong correlation between clumped-and hydrogen-isotope signatures in microbial methane is identified and quantitatively linked to the availability of H 2 and the reversibility of microbially-mediated methanogenesis in the environment. Determination of 13 CH 3 D in combination with hydrogen-isotope ratios of methane and water provides a sensitive indicator of the extent of C-H bond equilibration, enables fingerprinting of methane-generating mechanisms, and in some cases, supplies direct constraints for locating the waters from which migrated gases were sourced. Chapter 3 applies this concept to constrain the origin of methane in hydrothermal fluids from sediment-poor vent fields hosted in mafic and ultramafic rocks on slow-and ultraslow-spreading mid-ocean ridges. The data support a hypogene model whereby methane forms abiotically within plutonic rocks of the oceanic crust at temperatures above ca. 300• C during respeciation of magmatic volatiles, and is subsequently extracted during active, convective hydrothermal circulation. Chapter 4 presents the results of culture experiments in which methane is oxidized in the presence of O 2 by the bacterium Methylococcus capsulatus strain Bath. The results show that the clumped isotopologue abundances of partially-oxidized methane can be predicted from knowledge of 13 C/ 12 C and D/H isotope fractionation factors alone.: Shuhei Ono, Ph.D. Acknowledgments I fear that this section will not do justice to the people I have not the space to thank individually. Alas, here goes. To those whose names are not specifically listed here, thank you too. I wish first to thank Shuhei Ono. The work this thesis represents could not have happened without his bold vision and the license to explore and question that working in his lab afforded. His unbridled optimism, breadth of scientific curiosity, personal integrity, and accessibility to his personnel are traits I one day hope to emulate. I thank him for his nonjudgmental yet appropriately measured support of many of my ideas-even those that led nowhere-, for believing in me even when I found it difficult to do so myself, and for teaching me to change pump oil, build vacuum lines, and drink Icelandic vodka.I also wish to thank my thesis committee members Jeff Seewald, Roger Summons, and John Pohlman, for their in...

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confidence: 69%

Section: Hydrogen Exchange and The Origin Of Hydrogen In Chmentioning

confidence: 99%

The geochemistry of methane isotopologues

Wang¹

2017

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“…Serpentinization went to completion in most recovered samples and produced serpentine (lizardite + chrysotile), brucite, minor chlorite, and traces of magnetite and other opaque minerals. Thermodynamic constraints and hydrothermal experiments suggest that serpentinization fluids associated with this assemblage are alkaline, depleted in dissolved inorganic carbon (ΣCO 2 = CO 2 , HCO 3 − , CO 3 2− ), SiO 2 , and Mg but enriched in dissolved Ca and H 2 compared with seawater (30,31). Accessory opaque minerals include valleriite, pentlandite, millerite, chalcopyrite, siegenite, polydymite, and pyrite, in addition to the relict Ni−Fe alloy awaruite and native Cu (26).…”

Section: Serpentinization Beneath the Iberia Abyssal Plainmentioning

confidence: 95%

Fluid mixing and the deep biosphere of a fossil Lost City-type hydrothermal system at the Iberia Margin

Klein

Humphris

Guo

et al. 2015

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

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Subseafloor mixing of reduced hydrothermal fluids with seawater is believed to provide the energy and substrates needed to support deep chemolithoautotrophic life in the hydrated oceanic mantle (i.e., serpentinite). However, geosphere-biosphere interactions in serpentinite-hosted subseafloor mixing zones remain poorly constrained. Here we examine fossil microbial communities and fluid mixing processes in the subseafloor of a Cretaceous Lost City-type hydrothermal system at the magma-poor passive Iberia Margin (Ocean Drilling Program Leg 149, Hole 897D). Brucite−calcite mineral assemblages precipitated from mixed fluids ca. 65 m below the Cretaceous paleo-seafloor at temperatures of 31.7 ± 4.3°C within steep chemical gradients between weathered, carbonate-rich serpentinite breccia and serpentinite. Mixing of oxidized seawater and strongly reducing hydrothermal fluid at moderate temperatures created conditions capable of supporting microbial activity. Dense microbial colonies are fossilized in brucite−calcite veins that are strongly enriched in organic carbon (up to 0.5 wt.% of the total carbon) but depleted in 13 C (δ 13 C TOC = −19.4‰). We detected a combination of bacterial diether lipid biomarkers, archaeol, and archaeal tetraethers analogous to those found in carbonate chimneys at the active Lost City hydrothermal field. The exposure of mantle rocks to seawater during the breakup of Pangaea fueled chemolithoautotrophic microbial communities at the Iberia Margin, possibly before the onset of seafloor spreading. Lost City-type serpentinization systems have been discovered at midocean ridges, in forearc settings of subduction zones, and at continental margins. It appears that, wherever they occur, they can support microbial life, even in deep subseafloor environments.serpentinization | microfossils | lipid biomarkers | brucite−calcite | passive margin

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“…High-temperature hydrothermal alteration on oceanic spreading ridges can produce a hot (>350°C) acidic hydrothermal fluid driven by magmatic intrusion that fuels black smokers, named after the black particles that form as the rapid temperature / pH change induces precipitation of metal sulfides at the fluid interface. In the absence of magmatic heating, reducing hydrothermal fluids can also be produced by serpentinization, a process in which seawater permeates through fractures in the Fe/Mg-silicate ocean crust and produces an alkaline, H2-and CH4-enriched, moderately hot (~100-200°C) hydrothermal fluid (Russell et al, 1989;Kelley et al, 2001Kelley et al, , 2005Bradley and Summons 2010;Klein et al, 2013;Charlou et al 2010) and even in low temperature exhalations (Neal and Stanger, 1983;Coveney et al 1987;Etiope and Sherwood-Lollar, 2013;). Both black smoker and alkaline vents can produce chimney precipitates where hydrothermal fluids feed back into the ocean, and these naturally occurring mineral precipitates are significant in that they provide a semi-permeable and semiconducting barrier between the two contrasting fluids.…”

Section: Examples Of Fuel Cell-like Systems In Biology and Geologymentioning

confidence: 99%

The Fuel Cell Model of Abiogenesis: A New Approach to Origin-of-Life Simulations

et al. 2014

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Abstract:In this paper we discuss how prebiotic geo-electrochemical systems can be modeled as a fuel cell and how laboratory simulations of the origin of life in general can benefit from this systems-led approach. As a specific example, we detail the components of what we have termed the "prebiotic fuel cell" (PFC) operating at a putative Hadean hydrothermal vent, and we present preliminary results utilizing electrochemical analysis techniques and proton exchange membrane (PEM) fuel cell components to test the properties of this and other geo-electrochemical systems. The modular nature of fuel cells makes them ideal for creating geo-electrochemical reactors to simulate hydrothermal systems on wet rocky planets and characterize the energetic properties of the seafloor / hydrothermal interface. That electrochemical techniques should be applied to simulating the origin of life follows from the recognition of the fuel cell-like properties of prebiotic chemical systems and the earliest metabolisms. Conducting this type of laboratory simulation of the emergence of bioenergetics will not only be informative in the context of the origin of life on Earth, but may help us understand whether it is possible for life to have emerged in similar environments on other worlds.2

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Compositional controls on hydrogen generation during serpentinization of ultramafic rocks

Cited by 226 publications

References 62 publications

The geochemistry of methane isotopologues

The geochemistry of methane isotopologues

Fluid mixing and the deep biosphere of a fossil Lost City-type hydrothermal system at the Iberia Margin

The Fuel Cell Model of Abiogenesis: A New Approach to Origin-of-Life Simulations

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