Sulfide Dissolution and Awaruite Formation in Continental Serpentinization Environments and Its Implications to Supporting Life

Abstract

Metal and sulfide minerals in ultramafic rocks are ideal tracers for fluid-rock interaction processes. During hydrothermal alteration of ultramafic rocks-the so-called serpentinization reaction where the primary mantle minerals olivine and pyroxene are converted to serpentine, magnetite, talc, and brucite-H 2 is produced due to ferrous iron oxidation McCollom et al., 2016). Simultaneously, H 2 can react abiogenically with CO 2 or CO to produce CH 4 and higher hydrocarbons following Fischer-Tropsch Type and Sabatier reactions (e.g., Etiope et al., 2011). Associated with variations in water-rock ratios during ongoing serpentinization and rock fracturing, this imparts strong variations in fluid redox conditions, i.e., variations in fO 2 , fH 2 , and fS 2 conditions controlling the opaque mineralogy (Foustoukos et al., 2015;Frost, 1985;. Effectively, changes in fO 2 and fS 2 cause precipitation of secondary opaque phases and/ or decomposition of primary mantle sulfides (Alt & Shanks, 1998;Schwarzenbach et al., 2012). In fact, serpentinization environments are among the most reducing environments found on Earth allowing for formation and stabilization of native metals and metal alloys, for example, by desulfurization of magmatic pentlandite (e.g., Frost, 1985;Schwarzenbach, Gazel, & Caddick, 2014). Simultaneously, abiogenically produced H 2 and/or CH 4 as well as other reduced carbon species, produced as a result of the serpentinization process, together with oxidants such as sulfate or CO 2 , provide an ideal energy source for chemolithoautotrophic communities living at sites of active serpentinization (e.g.,

Initial Results From the Oman Drilling Project Multi‐Borehole Observatory: Petrogenesis and Ongoing Alteration of Mantle Peridotite in the Weathering Horizon

“…(2018), awaruite, native copper, heazlewoodite, pentlandite, and magentite are found—in various combinations—in the serpentinite matrix of samples from a range of depths, and a corresponding range of fO 2 in borehole waters logged at the same depth (Figure 28). Similar assemblages are reported in other peridotite massis (e.g., Alt et al., 2013; de Obeso & Kelemen, 2018, 2020; Schwarzenbach et al., 2012, 2016, 2021).…”

Comparative Metagenomics Highlight a Widespread Pathway Involved in Catabolism of Phosphonates in Marine and Terrestrial Serpentinizing Ecosystems

“…Consistent with this observation, sulfides are barely detectable in continental serpentinite springs and PBHF, whereas the H 2 S concentration in LCHF is more in the range (0.2 to 3 mM) of that of basalt-hosted hydrothermal vents, likely owing to its setting proximal to the Mid-Atlantic Ridge and its black smokers ( 51 , 52 ). However, recent studies demonstrated the key role of sulfur-cycling in supporting microbial life in continental serpentinite-hosted systems, while potentially driven by phyla other than Epsilonproteobacteria or Betaproteobacteria ( 53 , 54 ).…”

Preface: Special Issue on Ophiolites and Oceanic Lithosphere

“…A supportive community of researchers has grown around these topics, embodied in part by the annual Serpentine Days conferences in Europe. This overall topic is the subject of 24 of the papers in this Special Issue (Bernasconi et al., 2021; Cook, Blank, Rietze, et al., 2021; Cook, Blank, Suzuki, et al., 2021; Cooperdock et al., 2020; de Obeso et al., 2021; Ellison et al., 2021; O. Evans et al., 2020; Hong et al., 2022; Howells et al., 2022; Katayama et al., 2020; Kelemen et al., 2021; Leong et al., 2021; Malvoisin et al., 2020; Monnin et al., 2021; Nothaft, Templeton, Boyd, et al., 2021; Nothaft, Templeton, Rhim, et al., 2021; Renard, 2021; Sabuda et al., 2021; Schwarzenbach, Vogel, et al., 2021; Schwarzenbach, Vrijmoed, et al., 2021; Templeton et al., 2021; Ternieten et al., 2021a, 2021b; Yoshida et al., 2020).…”