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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MDPI AG
2022
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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 |
container_volume |
12 |
container_issue |
12 |
container_start_page |
1627 |
_version_ |
1766204195523788800 |