Carbon and mineral transformations in seafloor serpentinization systems
Carbon and mineral transformations in seafloor serpentinization systems
Date
2018-02
Authors
Grozeva, Niya G.
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DOI
10.1575/1912/10216
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Keywords
Carbon
Ocean bottom
Lithosphere
Hydrothermal vents
Microorganisms
Ocean bottom
Lithosphere
Hydrothermal vents
Microorganisms
Abstract
This thesis examines abiotic processes controlling the transformation and distribution of carbon
compounds in seafloor hydrothermal systems hosted in ultramafic rock. These processes have a
direct impact on carbon budgets in the oceanic lithosphere and on the sustenance of
microorganisms inhabiting hydrothermal vent ecosystems. Where mantle peridotite interacts
with carbon-bearing aqueous fluids in the subseafloor, dissolved inorganic carbon can precipitate
as carbonate minerals or undergo reduction by H2(aq) to form reduced carbon species. In Chapters
2 and 3, I conduct laboratory experiments to assess the relative extents of carbonate formation
and CO2 reduction during alteration of peridotite by CO2(aq)-rich fluids. Results from these
experiments reveal that formation of carbonate minerals is favorable on laboratory timescales,
even at high H2(aq) concentrations generated by serpentinization reactions. Although CO2(aq)
attains rapid metastable equilibrium with formate, formation of thermodynamically stable CH4(aq)
is kinetically limited on timescales relevant for active fluid circulation in the subseafloor. It has
been proposed that CH4 and potentially longer-chain hydrocarbons may be sourced, instead,
from fluid inclusions hosted in plutonic and mantle rocks. Chapter 4 analyzes CH4-rich fluid
inclusions in olivine-rich basement rocks from the Von Damm hydrothermal field and the
Zambales ophiolite to better understand the origin of abiotic hydrocarbons in ultramaficinfluenced
hydrothermal systems. Comparisons of hydrocarbon abundances and stable isotopic
compositions in fluid inclusions and associated vent fluids suggest that fluid inclusions may
provide a significant contribution of abiotic hydrocarbons to both submarine and continental
serpentinization systems.
Description
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy
at the
Massachusetts Institute of Technology
and the
Woods Hole Oceanographic Institution
February 2018
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Citation
Grozeva, N. G. (2018). Carbon and mineral transformations in seafloor serpentinization systems [Doctoral thesis, Massachusetts Institute of Technology and Woods Hole Oceanographic Institution]. Woods Hole Open Access Server. https://doi.org/10.1575/1912/10216