Iron and sulfide oxidation within the basaltic ocean crust; implications for chemolithoautotrophic microbial biomass production

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doi: 10.1016/S0016-7037(03)00304-1
Author(s): Bach, Wolfgang; Edwards, Katrina J.
Author Affiliation(s): Primary:
Woods Hole Oceanographic Institution, Department of Marine Chemistry and Geochemistry, Woods Hole, MA, United States
Volume Title: Geochimica et Cosmochimica Acta
Source: Geochimica et Cosmochimica Acta, 67(20), p.3871-3887. Publisher: Pergamon, Oxford, International. ISSN: 0016-7037 CODEN: GCACAK
Note: In English. Woods Hole Oceanogr. Inst., Contrib. No. 10801. 119 refs.; illus., incl. 3 tables, sketch map
Summary: Microbial processes within the ocean crust are of potential importance in controlling rates of chemical reactions and thereby affecting chemical exchange between the oceans and lithosphere. We here assess the oxidation state of altered ocean crust and estimate the magnitude of microbial biomass production that might be supported by oxidative and nonoxidative alteration. Compilations of Fe2O3, FeO, and S concentrations from DSDP/ODP drill core samples representing upper basaltic ocean crust suggest that Fe3+/ΣFe increases from 0.15±0.05 to 0.45±0.15 within the first 10-20 Myr of crustal evolution. Within the same time frame 70±25% of primary sulfides in basalt are oxidized. With an annual production of 4.0±1.8×1015 g of upper (500±200 m) crust and average initial concentrations of 8.0±1.3 wt% Fe and 0.125±0.020 wt% S, we estimate annual oxidation rates of 1.7±1.2×1012 mol Fe and 1.1±0.7×1011 mol S. We estimate that 50% of Fe oxidation may be attributed to hydrolysis, producing 4.5±3.0×1011 mol H2/yr. Thermodynamic and bioenergetic calculations were used to estimate the potential chemolithoautotrophic microbial biomass production within ridge flanks. Combined, aerobic and anaerobic Fe and S oxidation may support production of up to 48±21×1010 g cellular carbon (C). Hydrogen-consuming reactions may support production of a similar or larger microbial biomass if iron reduction, nitrate reduction, or hydrogen oxidation by O2(aq) are the prevailing metabolic reactions. If autotrophic sulfate reduction or methanogenesis prevail, the potential biomass production is 9±7×1010 g C/yr and 3±2×1010 g C/yr, respectively. Combined primary biomass production of up to ∼1×1012 g C/yr may be similar to that fueled by anaerobic oxidation of organic matter in deep-seated heterotrophic systems. These estimates suggest that water-rock reactions may support significant microbial life within ridge flank hydrothermal systems, These estimates suggest that water-rock reactions may support significant microbial life within ridge flank hydrothermal systems. Abstract Copyright (2003) Elsevier, B.V.
Year of Publication: 2003
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; Aerobic environment; Aliphatic hydrocarbons; Alkanes; Alteration; Anaerobic environment; Atlantic Ocean; Basaltic composition; Biogenic processes; Biomass; Chemical reactions; Crust; DSDP Site 504; Geochemistry; Heat flow; Hydrocarbons; Hydrothermal conditions; Iron; Iron oxides; Leg 102; Leg 111; Leg 129; Leg 137; Leg 140; Leg 144; Leg 148; Leg 168; Leg 176; Leg 185; Marine environment; Metals; Methane; Microorganisms; Mid-ocean ridges; Ocean Drilling Program; Oceanic crust; Organic compounds; Oxidation; Oxides; Pacific Ocean; Sulfides; Sulfur; Theoretical studies; Thermodynamic properties; Water-rock interaction
Coordinates: N011335 N011338 W0834348 W0834357
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N120546 N215523 E1562136 E1521919
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N011338 N011338 W0834349 W0834349
N011338 N011338 W0834349 W0834349
Record ID: 2005006545
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands