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Modelling Geochemical and Geobiologi...

Leong, James Andrew Monton.

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Modelling Geochemical and Geobiological Consequences of Low-Temperature Continental Serpentinization.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Modelling Geochemical and Geobiological Consequences of Low-Temperature Continental Serpentinization./
Author:	Leong, James Andrew Monton.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2020,
Description:	356 p.
Notes:	Source: Dissertations Abstracts International, Volume: 82-03, Section: B.
Contained By:	Dissertations Abstracts International82-03B.
Subject:	Geochemistry. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28029616
ISBN:	9798664757019

Modelling Geochemical and Geobiological Consequences of Low-Temperature Continental Serpentinization.
Leong, James Andrew Monton.

Modelling Geochemical and Geobiological Consequences of Low-Temperature Continental Serpentinization. - Ann Arbor : ProQuest Dissertations & Theses, 2020 - 356 p.

Source: Dissertations Abstracts International, Volume: 82-03, Section: B.

Thesis (Ph.D.)--Arizona State University, 2020.

This item must not be sold to any third party vendors.

The hydrous alteration of ultramafic rocks, known as serpentinization, produces some of the most reduced (H2 >1 mmolal) and alkaline (pH >11) fluids on Earth. Serpentinization can proceed even at the low-temperature conditions (<50°C) characteristic of most of Earth's continental aquifers, raising questions on the limits of life deep in the subsurface and the magnitude in the flux of reduced volatiles to the surface. In this work, I explored the compositions and consequences of fluids and volatiles found in three low-temperature serpentinizing environments: (1) active hyperalkaline springs in ophiolites, (2) modern shallow and deep peridotite aquifers, and (3) komatiitic aquifers during the Archean.Around 140 fluids were sampled from the Oman ophiolite and analyzed for their compositions. Fluid compositions can be accounted for by thermodynamic simulations of reactions accompanying incipient to advanced stages of serpentinization, as well as by simulations of mass transport processes such as fluid mixing and mineral leaching. Thermodynamic calculations were also used to predict compositions of end-member fluids representative of the shallow and deep peridotite aquifers that were ultimately used to quantify energy available to various subsurface chemolithotrophs. Calculations showed that sufficient energy and power supply can be available to support deep-seated methanogens. An additional and a more diverse energy supply can be available when surfacing deep-seated fluids mix with shallow groundwater in discharge zones of the subsurface fluid pathway. Finally, the consequence of the evolving continental composition during the Archean for the global supply of H2 generated through komatiite serpentinization was quantified. Results show that the flux of serpentinization-generated H2 could have been a significant sink for O2 during most of the Archean. This O2 sink diminished greatly towards the end of the Archean as komatiites became less common and helped set the stage for the Great Oxidation Event. Overall, this study provides a framework for exploring the origins of fluid and volatile compositions, including their redox state, that can result from various low-temperature serpentinizing environments in the present and past Earth and in other rocky bodies in the solar system.

ISBN: 9798664757019Subjects--Topical Terms:

539092
Geochemistry.
Subjects--Index Terms:

Hyperalkaline springs

Modelling Geochemical and Geobiological Consequences of Low-Temperature Continental Serpentinization.
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245 1 0 $a Modelling Geochemical and Geobiological Consequences of Low-Temperature Continental Serpentinization.
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300 $a 356 p.
500 $a Source: Dissertations Abstracts International, Volume: 82-03, Section: B.
500 $a Advisor: Shock, Everett.
502 $a Thesis (Ph.D.)--Arizona State University, 2020.
506 $a This item must not be sold to any third party vendors.
520 $a The hydrous alteration of ultramafic rocks, known as serpentinization, produces some of the most reduced (H2 >1 mmolal) and alkaline (pH >11) fluids on Earth. Serpentinization can proceed even at the low-temperature conditions (<50°C) characteristic of most of Earth's continental aquifers, raising questions on the limits of life deep in the subsurface and the magnitude in the flux of reduced volatiles to the surface. In this work, I explored the compositions and consequences of fluids and volatiles found in three low-temperature serpentinizing environments: (1) active hyperalkaline springs in ophiolites, (2) modern shallow and deep peridotite aquifers, and (3) komatiitic aquifers during the Archean.Around 140 fluids were sampled from the Oman ophiolite and analyzed for their compositions. Fluid compositions can be accounted for by thermodynamic simulations of reactions accompanying incipient to advanced stages of serpentinization, as well as by simulations of mass transport processes such as fluid mixing and mineral leaching. Thermodynamic calculations were also used to predict compositions of end-member fluids representative of the shallow and deep peridotite aquifers that were ultimately used to quantify energy available to various subsurface chemolithotrophs. Calculations showed that sufficient energy and power supply can be available to support deep-seated methanogens. An additional and a more diverse energy supply can be available when surfacing deep-seated fluids mix with shallow groundwater in discharge zones of the subsurface fluid pathway. Finally, the consequence of the evolving continental composition during the Archean for the global supply of H2 generated through komatiite serpentinization was quantified. Results show that the flux of serpentinization-generated H2 could have been a significant sink for O2 during most of the Archean. This O2 sink diminished greatly towards the end of the Archean as komatiites became less common and helped set the stage for the Great Oxidation Event. Overall, this study provides a framework for exploring the origins of fluid and volatile compositions, including their redox state, that can result from various low-temperature serpentinizing environments in the present and past Earth and in other rocky bodies in the solar system.
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650 4 $a Geobiology. $3 549918
650 4 $a Mineralogy. $3 516743
653 $a Hyperalkaline springs
653 $a Microbial energetics
653 $a Mineral alteration
653 $a Serpentinization
653 $a Thermodynamics
653 $a Water-rock interactions
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690 $a 0411
710 2 $a Arizona State University. $b Geological Sciences. $3 1678283
773 0 $t Dissertations Abstracts International $g 82-03B.
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791 $a Ph.D.
792 $a 2020
793 $a English
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28029616