Calcium Carbonate Hexahydrate (Ikaite): History of Mineral Formation as Recorded by Stable Isotopes

Calcium carbonate hexahydrate (ikaite) is a rare mineral that forms as metastable species in the organic-carbon-rich sediments of the King George Basin, Bransfield Strait, Antarctica, as a consequence of early diagenetic decomposition of organic matter under cold water (−1.4 °C) and high pressure (2...

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Published in:Minerals
Main Authors: Michael J. Whiticar, Erwin Suess, Gerold Wefer, Peter J. Müller
Format: Article in Journal/Newspaper
Language:English
Published: MDPI AG 2022
Subjects:
Online Access:https://doi.org/10.3390/min12121627
https://doaj.org/article/d37ab329d29244a78c26ffd4bc88b00b
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spelling ftdoajarticles:oai:doaj.org/article:d37ab329d29244a78c26ffd4bc88b00b 2023-05-15T13:44:38+02:00 Calcium Carbonate Hexahydrate (Ikaite): History of Mineral Formation as Recorded by Stable Isotopes Michael J. Whiticar Erwin Suess Gerold Wefer Peter J. Müller 2022-12-01T00:00:00Z https://doi.org/10.3390/min12121627 https://doaj.org/article/d37ab329d29244a78c26ffd4bc88b00b EN eng MDPI AG https://www.mdpi.com/2075-163X/12/12/1627 https://doaj.org/toc/2075-163X doi:10.3390/min12121627 2075-163X https://doaj.org/article/d37ab329d29244a78c26ffd4bc88b00b Minerals, Vol 12, Iss 1627, p 1627 (2022) ikaite calcium carbonate hexahydrate glendonite Bransfield Strait diagenesis stable isotope Mineralogy QE351-399.2 article 2022 ftdoajarticles https://doi.org/10.3390/min12121627 2022-12-30T19:30:53Z Calcium carbonate hexahydrate (ikaite) is a rare mineral that forms as metastable species in the organic-carbon-rich sediments of the King George Basin, Bransfield Strait, Antarctica, as a consequence of early diagenetic decomposition of organic matter under cold water (−1.4 °C) and high pressure (200 bar) conditions. Large crystals grow in the sediment immediately below the diagenetic transition between microbial sulfate reduction and methanogenesis at ~320 cm below sea floor (bsf). This process is reflected in the dissolved sulfate, total carbon dioxide, and methane concentrations, as well as in the carbon, hydrogen, and oxygen isotope chemistries of the interstitial fluids and dissolved gases of the host sediment. The ikaite crystal faithfully records in its zonal structure the changing carbon isotope ratio of the total dissolved carbon dioxide pool as it gradually diminishes during methanogenesis (δ 13 C ikaite = −17.5 to −21.4‰). These changes in the crystal’s host environment follow general Rayleigh carbon isotope fractionation. The oxygen isotopes of the ikaite carbonate (δ 18 O ikaite = 1.46 to 4.45‰) also show a strong zonal distribution, unrelated to temperature of formation, but perhaps controlled by the degree of recrystallization of ikaite to calcite. The crystal water of the ikaite is depleted 11‰ in 2 H/ 1 H (VSMOW) relative to the coexisting interstitial water, which is in excellent agreement with the isotope fractionation of other hydrated minerals. In addition to the in situ temperature and pressure, nucleation of the ikaite crystals in the Bransfield Basin sediments may be induced by the high alkalinity, high phosphate concentrations, and dissolved organic compounds. Intense microbial metabolism generates such compounds; of these, aspartic acid and glutamic acid may play an important role, as they do in biological and extracellular carbonate mineral precipitation. All indications are that low temperatures (such as of polar environments), high calcium carbonate supersaturation caused by ... Article in Journal/Newspaper Antarc* Antarctica Bransfield Strait Directory of Open Access Journals: DOAJ Articles Bransfield Strait Minerals 12 12 1627
institution Open Polar
collection Directory of Open Access Journals: DOAJ Articles
op_collection_id ftdoajarticles
language English
topic ikaite
calcium carbonate hexahydrate
glendonite
Bransfield Strait
diagenesis
stable isotope
Mineralogy
QE351-399.2
spellingShingle ikaite
calcium carbonate hexahydrate
glendonite
Bransfield Strait
diagenesis
stable isotope
Mineralogy
QE351-399.2
Michael J. Whiticar
Erwin Suess
Gerold Wefer
Peter J. Müller
Calcium Carbonate Hexahydrate (Ikaite): History of Mineral Formation as Recorded by Stable Isotopes
topic_facet ikaite
calcium carbonate hexahydrate
glendonite
Bransfield Strait
diagenesis
stable isotope
Mineralogy
QE351-399.2
description Calcium carbonate hexahydrate (ikaite) is a rare mineral that forms as metastable species in the organic-carbon-rich sediments of the King George Basin, Bransfield Strait, Antarctica, as a consequence of early diagenetic decomposition of organic matter under cold water (−1.4 °C) and high pressure (200 bar) conditions. Large crystals grow in the sediment immediately below the diagenetic transition between microbial sulfate reduction and methanogenesis at ~320 cm below sea floor (bsf). This process is reflected in the dissolved sulfate, total carbon dioxide, and methane concentrations, as well as in the carbon, hydrogen, and oxygen isotope chemistries of the interstitial fluids and dissolved gases of the host sediment. The ikaite crystal faithfully records in its zonal structure the changing carbon isotope ratio of the total dissolved carbon dioxide pool as it gradually diminishes during methanogenesis (δ 13 C ikaite = −17.5 to −21.4‰). These changes in the crystal’s host environment follow general Rayleigh carbon isotope fractionation. The oxygen isotopes of the ikaite carbonate (δ 18 O ikaite = 1.46 to 4.45‰) also show a strong zonal distribution, unrelated to temperature of formation, but perhaps controlled by the degree of recrystallization of ikaite to calcite. The crystal water of the ikaite is depleted 11‰ in 2 H/ 1 H (VSMOW) relative to the coexisting interstitial water, which is in excellent agreement with the isotope fractionation of other hydrated minerals. In addition to the in situ temperature and pressure, nucleation of the ikaite crystals in the Bransfield Basin sediments may be induced by the high alkalinity, high phosphate concentrations, and dissolved organic compounds. Intense microbial metabolism generates such compounds; of these, aspartic acid and glutamic acid may play an important role, as they do in biological and extracellular carbonate mineral precipitation. All indications are that low temperatures (such as of polar environments), high calcium carbonate supersaturation caused by ...
format Article in Journal/Newspaper
author Michael J. Whiticar
Erwin Suess
Gerold Wefer
Peter J. Müller
author_facet Michael J. Whiticar
Erwin Suess
Gerold Wefer
Peter J. Müller
author_sort Michael J. Whiticar
title Calcium Carbonate Hexahydrate (Ikaite): History of Mineral Formation as Recorded by Stable Isotopes
title_short Calcium Carbonate Hexahydrate (Ikaite): History of Mineral Formation as Recorded by Stable Isotopes
title_full Calcium Carbonate Hexahydrate (Ikaite): History of Mineral Formation as Recorded by Stable Isotopes
title_fullStr Calcium Carbonate Hexahydrate (Ikaite): History of Mineral Formation as Recorded by Stable Isotopes
title_full_unstemmed Calcium Carbonate Hexahydrate (Ikaite): History of Mineral Formation as Recorded by Stable Isotopes
title_sort calcium carbonate hexahydrate (ikaite): history of mineral formation as recorded by stable isotopes
publisher MDPI AG
publishDate 2022
url https://doi.org/10.3390/min12121627
https://doaj.org/article/d37ab329d29244a78c26ffd4bc88b00b
geographic Bransfield Strait
geographic_facet Bransfield Strait
genre Antarc*
Antarctica
Bransfield Strait
genre_facet Antarc*
Antarctica
Bransfield Strait
op_source Minerals, Vol 12, Iss 1627, p 1627 (2022)
op_relation https://www.mdpi.com/2075-163X/12/12/1627
https://doaj.org/toc/2075-163X
doi:10.3390/min12121627
2075-163X
https://doaj.org/article/d37ab329d29244a78c26ffd4bc88b00b
op_doi https://doi.org/10.3390/min12121627
container_title Minerals
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container_issue 12
container_start_page 1627
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