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

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dc.contributor.advisor Jeffrey S. Seewald. en_US
dc.contributor.author Reeves, Eoghan en_US
dc.contributor.other Woods Hole Oceanographic Institution. en_US
dc.date.accessioned 2010-10-29T18:30:05Z
dc.date.available 2010-10-29T18:30:05Z
dc.date.copyright 2010 en_US
dc.date.issued 2010 en_US
dc.identifier.uri http://hdl.handle.net/1721.1/59748
dc.description Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2010. en_US
dc.description Cataloged from PDF version of thesis. en_US
dc.description Includes bibliographical references. en_US
dc.description.abstract 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 (CH4) formation under hydrothermal conditions. The overall reduction of carbon dioxide (C02) to CH4, 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 (CH3SH), 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 CH3SH forms by reduction of CO2 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 backare 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. en_US
dc.description.statementofresponsibility by Eoghan Reeves. en_US
dc.format.extent 279 p. en_US
dc.language.iso eng en_US
dc.publisher Massachusetts Institute of Technology en_US
dc.rights M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. en_US
dc.rights.uri http://dspace.mit.edu/handle/1721.1/7582 en_US
dc.subject Joint Program in Oceanography/Applied Ocean Science and Engineering. en_US
dc.subject Earth, Atmospheric, and Planetary Sciences. en_US
dc.subject Woods Hole Oceanographic Institution. en_US
dc.subject.lcsh Hydrothermal circulation (Oceanography) en_US
dc.subject.lcsh Submarine geology en_US
dc.title Laboratory and field-based investigations of subsurface geochemical processes in seafloor hydrothermal systems en_US
dc.type Thesis en_US
dc.description.degree Ph.D. en_US
dc.contributor.department Joint Program in Oceanography/Applied Ocean Science and Engineering. en_US
dc.contributor.department Massachusetts Institute of Technology. Dept. of Earth, Atmospheric, and Planetary Sciences. en_US
dc.contributor.department Woods Hole Oceanographic Institution. en_US
dc.identifier.oclc 670431010 en_US


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