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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Minerals
2022
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Online Access: | http://hdl.handle.net/1828/14682 https://doi.org/10.3390/min12121627 |
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ftuvicpubl:oai:dspace.library.uvic.ca:1828/14682 2023-05-15T13:51:13+02:00 Calcium carbonate hexahydrate (ikaite): History of mineral formation as recorded by stable isotopes Whiticar, Michael J. Suess, Erwin Wefer, Gerold Müller, Peter J. 2022 application/pdf http://hdl.handle.net/1828/14682 https://doi.org/10.3390/min12121627 en eng Minerals Whiticar, M. J., Suess, E., Wefer, G., & Müller, P. J. (2022). “Calcium carbonate hexahydrate (ikaite): History of mineral formation as recorded by stable isotopes.” Minerals, 12(12), 1627. https://doi.org/10.3390/min12121627 https://doi.org/10.3390/min12121627 http://hdl.handle.net/1828/14682 ikaite calcium carbonate hexahydrate glendonite Bransfield Strait diagenesis stable isotope geochemistry palaeoclimate Article 2022 ftuvicpubl https://doi.org/10.3390/min12121627 2023-01-25T00:45:29Z 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 (δ13Cikaite = -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 (δ18Oikaite = 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 2H/1H (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 interstitial ... Article in Journal/Newspaper Antarc* Antarctica Bransfield Strait University of Victoria (Canada): UVicDSpace Bransfield Strait Minerals 12 12 1627 |
institution |
Open Polar |
collection |
University of Victoria (Canada): UVicDSpace |
op_collection_id |
ftuvicpubl |
language |
English |
topic |
ikaite calcium carbonate hexahydrate glendonite Bransfield Strait diagenesis stable isotope geochemistry palaeoclimate |
spellingShingle |
ikaite calcium carbonate hexahydrate glendonite Bransfield Strait diagenesis stable isotope geochemistry palaeoclimate Whiticar, Michael J. Suess, Erwin Wefer, Gerold Müller, Peter J. 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 geochemistry palaeoclimate |
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 (δ13Cikaite = -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 (δ18Oikaite = 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 2H/1H (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 interstitial ... |
format |
Article in Journal/Newspaper |
author |
Whiticar, Michael J. Suess, Erwin Wefer, Gerold Müller, Peter J. |
author_facet |
Whiticar, Michael J. Suess, Erwin Wefer, Gerold Müller, Peter J. |
author_sort |
Whiticar, Michael J. |
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 |
Minerals |
publishDate |
2022 |
url |
http://hdl.handle.net/1828/14682 https://doi.org/10.3390/min12121627 |
geographic |
Bransfield Strait |
geographic_facet |
Bransfield Strait |
genre |
Antarc* Antarctica Bransfield Strait |
genre_facet |
Antarc* Antarctica Bransfield Strait |
op_relation |
Whiticar, M. J., Suess, E., Wefer, G., & Müller, P. J. (2022). “Calcium carbonate hexahydrate (ikaite): History of mineral formation as recorded by stable isotopes.” Minerals, 12(12), 1627. https://doi.org/10.3390/min12121627 https://doi.org/10.3390/min12121627 http://hdl.handle.net/1828/14682 |
op_doi |
https://doi.org/10.3390/min12121627 |
container_title |
Minerals |
container_volume |
12 |
container_issue |
12 |
container_start_page |
1627 |
_version_ |
1766254991305080832 |