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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Online Access: | https://oceanrep.geomar.de/id/eprint/57561/ https://oceanrep.geomar.de/id/eprint/57561/1/minerals-12-01627-v2.pdf https://doi.org/10.3390/min12121627 |
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ftoceanrep:oai:oceanrep.geomar.de:57561 2024-02-11T09:56:59+01:00 Calcium Carbonate Hexahydrate (Ikaite): History of Mineral Formation as Recorded by Stable Isotopes Whiticar, Michael J. Suess, Erwin Wefer, Gerold Müller, Peter J. 2022-12-17 text https://oceanrep.geomar.de/id/eprint/57561/ https://oceanrep.geomar.de/id/eprint/57561/1/minerals-12-01627-v2.pdf https://doi.org/10.3390/min12121627 en eng MDPI https://oceanrep.geomar.de/id/eprint/57561/1/minerals-12-01627-v2.pdf Whiticar, M. J., Suess, E., Wefer, G. and Müller, P. J. (2022) Calcium Carbonate Hexahydrate (Ikaite): History of Mineral Formation as Recorded by Stable Isotopes. Open Access Minerals, 12 . Art.Nr. 1627. DOI 10.3390/min12121627 <https://doi.org/10.3390/min12121627>. doi:10.3390/min12121627 cc_by_4.0 info:eu-repo/semantics/openAccess Article PeerReviewed 2022 ftoceanrep https://doi.org/10.3390/min12121627 2024-01-15T00:26:28Z 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 OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) Bransfield Strait Minerals 12 12 1627 |
institution |
Open Polar |
collection |
OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) |
op_collection_id |
ftoceanrep |
language |
English |
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. |
spellingShingle |
Whiticar, Michael J. Suess, Erwin Wefer, Gerold Müller, Peter J. Calcium Carbonate Hexahydrate (Ikaite): History of Mineral Formation as Recorded by Stable Isotopes |
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 |
MDPI |
publishDate |
2022 |
url |
https://oceanrep.geomar.de/id/eprint/57561/ https://oceanrep.geomar.de/id/eprint/57561/1/minerals-12-01627-v2.pdf 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 |
https://oceanrep.geomar.de/id/eprint/57561/1/minerals-12-01627-v2.pdf Whiticar, M. J., Suess, E., Wefer, G. and Müller, P. J. (2022) Calcium Carbonate Hexahydrate (Ikaite): History of Mineral Formation as Recorded by Stable Isotopes. Open Access Minerals, 12 . Art.Nr. 1627. DOI 10.3390/min12121627 <https://doi.org/10.3390/min12121627>. doi:10.3390/min12121627 |
op_rights |
cc_by_4.0 info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.3390/min12121627 |
container_title |
Minerals |
container_volume |
12 |
container_issue |
12 |
container_start_page |
1627 |
_version_ |
1790607566205616128 |