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Stable Isotope Systematics of Calcite /

Olsen, Ellen K.,

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Stable Isotope Systematics of Calcite /

Record Type:	Electronic resources : Monograph/item
Title/Author:	Stable Isotope Systematics of Calcite // Ellen K Olsen.
Author:	Olsen, Ellen K.,
Description:	1 electronic resource (295 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 85-01, Section: B.
Contained By:	Dissertations Abstracts International85-01B.
Subject:	Geochemistry. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30317964
ISBN:	9798379953324

Stable Isotope Systematics of Calcite /
Olsen, Ellen K.,

Stable Isotope Systematics of Calcite /Ellen K Olsen. - 1 electronic resource (295 pages)

Source: Dissertations Abstracts International, Volume: 85-01, Section: B.

The oxygen isotopic composition of calcite is widely used in paleoclimate studies to infer the temperatures of carbonate formation across a wide range of geologic environments including hydrothermal veins, caves, lakes, surface oceans, and in marine sediments. Carbonate-based temperature reconstructions depend on empirical δ18O-T relationships that are affected by factors such as carbonate growth rate, solution composition, pH, and source(s) of dissolved inorganic carbon (DIC). We carried out calcite growth experiments over a range of pH (7.5-12.8), temperature (T = 10-25°C), ionic strength (I = 0.1-1.6; [NaCl] = 0-1.4 M) and concentration of the enzyme carbonic anhydrase ([CA] = 0-3 µM). The enzyme CA promotes isotopic equilibration of the DIC pool, which in turn, has a strong influence on the isotopic composition of the mineral. We divide the experimental results into two categories: (1) calcite grown from an equilibrated DIC pool, and (2) calcite grown from a non-equilibrated DIC pool. Results from (1) are used to determine the kinetic isotope effects (KIEs) attending the crystal growth reaction as a function of pH and ionic strength. No evidence of an ionic strength effect on oxygen isotope partitioning between calcite and DIC was found for NaCl concentrations up to 0.35 M, but in higher ionic strength solutions, NaCl was found to inhibit the efficacy of CA and prevent complete isotopic equilibration of the DIC pool, resulting in lower and more variable oxygen isotope fractionations. The oxygen isotope partitioning between calcite and water was found to systematically decrease with increasing pH. Results from (2) are used to determine the KIEs attending the CO2 hydration and hydroxylation reactions as a function of T, pH, ionic strength and [CA]. This study is the first to separately quantify the kinetic fractionation factors (KFFs) for CO2 and OH- separately during CO2 hydroxylation. The experimental results have been used to develop a generalizable model of oxygen isotope effects in the CaCO3-DIC-H2O system. The model can be used to predict the δ18O of calcites grown from variably-equilibrated DIC pools and can explain why different experimental setups have yielded different δ18O-T relationships for inorganic calcite. This dissertation includes previously published and unpublished co-authored material.

English

ISBN: 9798379953324Subjects--Topical Terms:

539092
Geochemistry.
Subjects--Index Terms:

Calcite

Stable Isotope Systematics of Calcite /
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100 1 $a Olsen, Ellen K., $e author. $0 (orcid)0009-0004-2897-5069 $3 3814472
245 1 0 $a Stable Isotope Systematics of Calcite / $c Ellen K Olsen.
264 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2023
300 $a 1 electronic resource (295 pages)
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337 $a computer $b c $2 rdamedia
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500 $a Source: Dissertations Abstracts International, Volume: 85-01, Section: B.
500 $a Advisors: Watkins, James M. Committee members: Reed, Mark H.; Wallace, Paul J.; Gavin, Daniel G.
502 $b Ph.D. $c University of Oregon $d 2023.
520 $a The oxygen isotopic composition of calcite is widely used in paleoclimate studies to infer the temperatures of carbonate formation across a wide range of geologic environments including hydrothermal veins, caves, lakes, surface oceans, and in marine sediments. Carbonate-based temperature reconstructions depend on empirical δ18O-T relationships that are affected by factors such as carbonate growth rate, solution composition, pH, and source(s) of dissolved inorganic carbon (DIC). We carried out calcite growth experiments over a range of pH (7.5-12.8), temperature (T = 10-25°C), ionic strength (I = 0.1-1.6; [NaCl] = 0-1.4 M) and concentration of the enzyme carbonic anhydrase ([CA] = 0-3 µM). The enzyme CA promotes isotopic equilibration of the DIC pool, which in turn, has a strong influence on the isotopic composition of the mineral. We divide the experimental results into two categories: (1) calcite grown from an equilibrated DIC pool, and (2) calcite grown from a non-equilibrated DIC pool. Results from (1) are used to determine the kinetic isotope effects (KIEs) attending the crystal growth reaction as a function of pH and ionic strength. No evidence of an ionic strength effect on oxygen isotope partitioning between calcite and DIC was found for NaCl concentrations up to 0.35 M, but in higher ionic strength solutions, NaCl was found to inhibit the efficacy of CA and prevent complete isotopic equilibration of the DIC pool, resulting in lower and more variable oxygen isotope fractionations. The oxygen isotope partitioning between calcite and water was found to systematically decrease with increasing pH. Results from (2) are used to determine the KIEs attending the CO2 hydration and hydroxylation reactions as a function of T, pH, ionic strength and [CA]. This study is the first to separately quantify the kinetic fractionation factors (KFFs) for CO2 and OH- separately during CO2 hydroxylation. The experimental results have been used to develop a generalizable model of oxygen isotope effects in the CaCO3-DIC-H2O system. The model can be used to predict the δ18O of calcites grown from variably-equilibrated DIC pools and can explain why different experimental setups have yielded different δ18O-T relationships for inorganic calcite. This dissertation includes previously published and unpublished co-authored material.
546 $a English
590 $a School code: 0171
650 4 $a Geochemistry. $3 539092
650 4 $a Geology. $3 516570
650 4 $a Mineralogy. $3 516743
653 $a Calcite
653 $a Carbonate
653 $a Fractionation
653 $a Geologic environments
653 $a Isotopes
653 $a Paleoclimate
690 $a 0996
690 $a 0372
690 $a 0411
710 2 $a University of Oregon. $b Department of Geological Sciences. $e degree granting institution. $3 3814473
720 1 $a Watkins, James M. $e degree supervisor.
773 0 $t Dissertations Abstracts International $g 85-01B.
790 $a 0171
791 $a Ph.D.
792 $a 2023
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30317964