Experimental investigation of single carbon compounds under hydrothermal conditions

Seewald, Jeffrey S.; Zolotov, M. Yu.; McCollom, T. M.

doi:10.1016/j.gca.2005.09.002

Cited by 231 publications

(255 citation statements)

References 38 publications

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“…Experimental investigations of organic synthesis under realistic hydrothermal conditions have 15 largely focused on hydrocarbon formation by mineral catalysis (FOUSTOUKOS and SEYFRIED, 2004;MCCOLLOM and SEEWALD, 2006; FU et al, 2007 HUBER and WACHTERSHAUSER, 1997; MARTIN and RUSSELL, 2006;. Chapter 3 represents the first known survey of the distribution of CH 3 SH in present day vent fluids and discusses possible origins.…”

Section: Chapter 1 Introductionmentioning

confidence: 99%

Laboratory and field-based investigations of subsurface geochemical processes in seafloor hydrothermal systems

Reeves¹

2010

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This thesis presents the results of four discrete investigations into processes governing the organic and inorganic chemical composition of seafloor hydrothermal fluids in a variety of geologic settings. Though Chapters 2 through 5 of this thesis are disparate in focus, each represents a novel investigation aimed at furthering our understanding of subsurface geochemical processes affecting hydrothermal fluid compositions. Chapters 2 and 3 concern the abiotic (nonbiological) formation of organic compounds in high temperature vent fluids, a process which has direct implications for the emergence of life in early Earth settings and sustainment of present day microbial populations in hydrothermal environments. Chapter 2 represents an experimental investigation of methane (CH 4 ) formation under hydrothermal conditions. The overall reduction of carbon dioxide (CO 2 ) to CH 4 , previously assumed to be kinetically inhibited in the absence of mineral catalysts, is shown to proceed on timescales pertinent to crustal residence times of hydrothermal fluids. In Chapter 3, the abundance of methanethiol (CH 3 SH), considered to be a crucial precursor for the emergence of primitive chemoautotrophic life, is characterized in vent fluids from ultramafic-, basalt-and sediment-hosted hydrothermal systems. Previous assumptions that CH 3 SH forms by reduction of CO 2 are not supported by the observed distribution in natural systems. Chapter 4 investigates factors regulating the hydrogen isotope composition of hydrocarbons under hydrothermal conditions. Isotopic exchange between low molecular weight n-alkanes and water is shown to be facilitated by metastable equilibrium reactions between alkanes and their corresponding alkenes, which are feasible in natural systems. In Chapter 5, the controls on vent fluid composition in a backarc hydrothermal system are investigated. A comprehensive survey of the inorganic geochemistry of fluids from sites of hydrothermal activity in the eastern Manus Basin indicates that fluids there are influenced by input of acidic magmatic solutions at depth, and subsequently modified by variable extents of seawater entrainment and mixing-related secondary acidity production. CHAPTER 1 IntroductionSeafloor hydrothermal systems associated with the generation of oceanic crust represent a dramatic expression of heat and mass transfer from the interior of the Earth. In addition to profound effects on ocean chemistry, convective circulation of seawater through volcanically active oceanic crust leads to the formation of metal sulfide deposits. In addition, seafloor hot springs are often invoked as ideal settings from which early microbial life could have emerged.Since the initial discovery of low temperature venting at the Galápagos Spreading Center in 1977 (CORLISS et al., 1979), our understanding of the composition and diversity of hydrothermal solutions has expanded greatly. During convection through oceanic crust of basaltic composition, O 2 -replete seawater reacts with crustal rock, typically producin...

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Section: Chapter 1 Introductionmentioning

confidence: 99%

Laboratory and field-based investigations of subsurface geochemical processes in seafloor hydrothermal systems

Reeves¹

2010

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“…The d 13 C of the dissolved CO 2 was À14‰ and values for methane and light hydrocarbons were as low as À49‰. Again these results show that organic products are depleted in 13 C to a degree typically ascribed to biological processes, indicating that the carbon isotopic composition may not be an effective diagnostic means to differentiate between biologic and nonbiologic sources (McCollom and Seewald 2006). …”

Section: Definitionmentioning

confidence: 91%

“…In addition to the thermal instability of sugars, HCHO does not appear to be a stable one-carbon species under hydrothermal conditions (Osada et al 2004;Seewald et al 2006).…”

Section: Hydrothermal Ventsmentioning

confidence: 99%

“…The d 13 C values of abiotic CH 4 produced from dissolved CO 2 with a mantle-like 13 C signature varied from À4 to À50‰, overlapping typical d 13 C values of thermogenic CH 4 . McCollom and Seewald (2006) produced H 2 , CO 2 , CH 4 , and light hydrocarbons (C 2 -C 5 ) by heating an aqueous solution of ▶ formic acid (HCOOH) in the presence of iron powder at 250 C and 325 bar in a hydrothermal cell. The d 13 C of the dissolved CO 2 was À14‰ and values for methane and light hydrocarbons were as low as À49‰.…”

Section: Definitionmentioning

confidence: 99%

“…HCHO could also potentially be produced in hydrothermal vents (Ferris 1994), for example, by the reduction of aqueous formate, CO or CO 2 , or by the oxidation of methanol or CH 4 , although HCHO does not appear to be a stable redox state of carbon under hydrothermal conditions. HCHO may be an intermediate in the redox equilibration of other more stable compounds (Seewald et al 2006). …”

Section: Overviewmentioning

confidence: 99%

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Decades of research have now firmly established that aqueous fluids in Earth's crust from groundwater to deep basinal brines to shallow mid-ocean ridge hydrothermal systems can contain metastable equilibria involving C-species in which methane does not participate. It now appears, however, that this situation does not extend to the upper mantle. Instead, field evidence from theoretical models, experimental diamond-anvil cell and fluid inclusion studies, and high-pressure metamorphic rocks all indicate a wide variety of aqueous C-species at high pressures. At pressures above about 2.0-3.0 GPa, methane and all other aqueous C-species with different oxidation states between -4.0 and +4.0 can coexist in variable proportions. Furthermore, the aqueous fluids can coexist with immiscible hydrocarbon fluids. As a consequence, C-species with a mixture of oxidation states in aqueous fluids and hydrocarbon fluids at high pressures in the upper mantle can influence the oxidation state of their upper mantle environment.

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Experimental investigation of single carbon compounds under hydrothermal conditions

Cited by 231 publications

References 38 publications

Laboratory and field-based investigations of subsurface geochemical processes in seafloor hydrothermal systems

Laboratory and field-based investigations of subsurface geochemical processes in seafloor hydrothermal systems

Facula, Faculae

The Changing Character of Carbon in Fluids with Pressure

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