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An Attempt to Study Natural H2 Resources across an Oceanic Ridge Penetrating a Continent: The Asal–Ghoubbet Rift (Republic of Djibouti). GEOSCIENCES 2021. [DOI: 10.3390/geosciences12010016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Dihydrogen (H2) is generated by fluid–rock interactions along mid-ocean ridges (MORs) and was not, until recently, considered as a resource. However, in the context of worldwide efforts to decarbonize the energy mix, clean hydrogen is now highly sought after, and the production of natural H2 is considered to be a powerful alternative to electrolysis. The Afar Rift System has many geological features in common with MORs and offers potential in terms of natural H2 resources. Here, we present data acquired during initial exploration in this region. H2 contents in soil and within fumaroles were measured along a 200 km section across the Asal–Ghoubbet rift and the various intervening grabens, extending from Obock to Lake Abhe. These newly acquired data have been synthesized with existing data, including those from the geothermal prospect area of the Asal–Ghoubbet rift zone. Our results demonstrate that basalt alteration with oxidation of iron-rich facies and simultaneous reduction in water is the likely the source of the hydrogen, although H2S reduction cannot be ruled out. However, H2 volumes at the surface within fumaroles were found to be low, reaching only a few percent. These values are considerably lower than those found in MORs. This discrepancy may be attributed to bias introduced by surface sampling; for example, microorganisms may be preferentially consuming H2 near the surface in this environment. However, the low H2 generation rates found in the study area could also be due to a lack of reactants, such as fayalite (i.e., owing to the presence of low-olivine basalts with predominantly magnesian olivines), or to the limited volume and slow circulation of water. In future, access to additional subsurface data acquired through the ongoing geothermal drilling campaign will bring new insight to help answer these questions.
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German CR, Casciotti KA, Dutay JC, Heimbürger LE, Jenkins WJ, Measures CI, Mills RA, Obata H, Schlitzer R, Tagliabue A, Turner DR, Whitby H. Hydrothermal impacts on trace element and isotope ocean biogeochemistry. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2016; 374:rsta.2016.0035. [PMID: 29035265 PMCID: PMC5069535 DOI: 10.1098/rsta.2016.0035] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 06/15/2016] [Indexed: 05/10/2023]
Abstract
Hydrothermal activity occurs in all ocean basins, releasing high concentrations of key trace elements and isotopes (TEIs) into the oceans. Importantly, the calculated rate of entrainment of the entire ocean volume through turbulently mixing buoyant hydrothermal plumes is so vigorous as to be comparable to that of deep-ocean thermohaline circulation. Consequently, biogeochemical processes active within deep-ocean hydrothermal plumes have long been known to have the potential to impact global-scale biogeochemical cycles. More recently, new results from GEOTRACES have revealed that plumes rich in dissolved Fe, an important micronutrient that is limiting to productivity in some areas, are widespread above mid-ocean ridges and extend out into the deep-ocean interior. While Fe is only one element among the full suite of TEIs of interest to GEOTRACES, these preliminary results are important because they illustrate how inputs from seafloor venting might impact the global biogeochemical budgets of many other TEIs. To determine the global impact of seafloor venting, however, requires two key questions to be addressed: (i) What processes are active close to vent sites that regulate the initial high-temperature hydrothermal fluxes for the full suite of TEIs that are dispersed through non-buoyant hydrothermal plumes? (ii) How do those processes vary, globally, in response to changing geologic settings at the seafloor and/or the geochemistry of the overlying ocean water? In this paper, we review key findings from recent work in this realm, highlight a series of key hypotheses arising from that research and propose a series of new GEOTRACES modelling, section and process studies that could be implemented, nationally and internationally, to address these issues.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.
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Affiliation(s)
- C R German
- Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
| | - K A Casciotti
- School of Earth, Energy and Environmental Sciences, Stanford University, Stanford, CA 94305, USA
| | - J-C Dutay
- SCE, IPSL/CEA, UVSQ, CNRS, Université Paris-Saclay, Gif sur Yvette, France
| | - L E Heimbürger
- Aix Marseille Université, CNRS/INSU, Université de Toulon, IRD, Mediterranean Institute of Oceanography (MIO) UM 110, 13288 Marseille, France
| | - W J Jenkins
- Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
| | - C I Measures
- Department of Oceanography, University of Hawaii, 1000 Pope Road, Honolulu, HI 96822, USA
| | - R A Mills
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton SO14 3ZH, UK
| | - H Obata
- Atmosphere and Ocean Research Institute, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan
| | - R Schlitzer
- Alfred Wegener Institute, Helmholtz-Center for Polar- and Marine Research, Am Alten Hafen 26, 27568 Bremerhaven, Germany
| | - A Tagliabue
- Department of Earth, Ocean and Ecological Sciences, School of Environmental Sciences, University of Liverpool, Liverpool L69 3GP, UK
| | - D R Turner
- Department of Marine Sciences, University of Gothenburg, 412 96 Gothenburg, Sweden
| | - H Whitby
- Department of Earth, Ocean and Ecological Sciences, School of Environmental Sciences, University of Liverpool, Liverpool L69 3GP, UK
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Wang W, Li Q, Liu X, Yang Y, Su W. Enhanced photocatalytic performance of ZnS for reversible amination of α-oxo acids by hydrothermal treatment. ORIGINS LIFE EVOL B 2012; 42:263-73. [PMID: 22638837 DOI: 10.1007/s11084-012-9275-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2012] [Accepted: 05/07/2012] [Indexed: 10/27/2022]
Abstract
To understand how life could have originated on early Earth, it is essential to know what biomolecules and metabolic pathways are shared by extant organisms and what organic compounds and their chemical reaction channels were likely to have been primordially available during the initial phase of the formation of prebiotic metabolism. In a previous study, we demonstrated for the first time the reversible amination of α-oxo acids on the surface of photo-illuminated ZnS. The sulfide mineral is a typical component at the periphery of submarine hydrothermal vents which has been frequently argued as a very attractive venue for the origin of life. In this work, in order to simulate more closely the precipitation environments of ZnS in the vent systems, we treated newly-precipitated ZnS with hydrothermal conditions and found that its photocatalytic power was significantly enhanced because the relative crystallinity of the treated sample was markedly increased with increasing temperature. Since the reported experimental conditions are believed to have been prevalent in shallow-water hydrothermal vents of early Earth and the reversible amination of α-oxo acids is a key metabolic pathway in all extant life forms, the results of this work provide a prototypical model of the prebiotic amino acid redox metabolism. The amino acid dehydrogenase-like chemistry on photo-irradiated ZnS surfaces may advance our understanding of the establishment of archaic non-enzymatic metabolic systems.
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Affiliation(s)
- Wei Wang
- CCMST, Academy of Fundamental and Interdisciplinary Sciences, Harbin Institute of Technology, Harbin 150080, China.
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Lowell RP, Yao Y, Germanovich LN. Anhydrite precipitation and the relationship between focused and diffuse flow in seafloor hydrothermal systems. ACTA ACUST UNITED AC 2003. [DOI: 10.1029/2002jb002371] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Robert P. Lowell
- School of Earth and Atmospheric Sciences; Georgia Institute of Technology; Atlanta Georgia USA
| | - Yufeng Yao
- School of Earth and Atmospheric Sciences; Georgia Institute of Technology; Atlanta Georgia USA
| | - Leonid N. Germanovich
- School of Civil and Environmental Engineering; Georgia Institute of Technology; Atlanta Georgia USA
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