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...
Published in: | Minerals |
---|---|
Main Authors: | , , , |
Format: | Text |
Language: | English |
Published: |
Multidisciplinary Digital Publishing Institute
2022
|
Subjects: | |
Online Access: | https://doi.org/10.3390/min12121627 |
id |
ftmdpi:oai:mdpi.com:/2075-163X/12/12/1627/ |
---|---|
record_format |
openpolar |
spelling |
ftmdpi:oai:mdpi.com:/2075-163X/12/12/1627/ 2023-08-20T04:02:25+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 agris 2022-12-17 application/pdf https://doi.org/10.3390/min12121627 EN eng Multidisciplinary Digital Publishing Institute Crystallography and Physical Chemistry of Minerals & Nanominerals https://dx.doi.org/10.3390/min12121627 https://creativecommons.org/licenses/by/4.0/ Minerals; Volume 12; Issue 12; Pages: 1627 ikaite calcium carbonate hexahydrate glendonite Bransfield Strait diagenesis stable isotope geochemistry palaeoclimate Text 2022 ftmdpi https://doi.org/10.3390/min12121627 2023-08-01T07:50:48Z 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 ... Text Antarc* Antarctica Bransfield Strait MDPI Open Access Publishing Bransfield Strait Minerals 12 12 1627 |
institution |
Open Polar |
collection |
MDPI Open Access Publishing |
op_collection_id |
ftmdpi |
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 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 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 |
Text |
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 |
Multidisciplinary Digital Publishing Institute |
publishDate |
2022 |
url |
https://doi.org/10.3390/min12121627 |
op_coverage |
agris |
geographic |
Bransfield Strait |
geographic_facet |
Bransfield Strait |
genre |
Antarc* Antarctica Bransfield Strait |
genre_facet |
Antarc* Antarctica Bransfield Strait |
op_source |
Minerals; Volume 12; Issue 12; Pages: 1627 |
op_relation |
Crystallography and Physical Chemistry of Minerals & Nanominerals https://dx.doi.org/10.3390/min12121627 |
op_rights |
https://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.3390/min12121627 |
container_title |
Minerals |
container_volume |
12 |
container_issue |
12 |
container_start_page |
1627 |
_version_ |
1774712848654532608 |