Palaeoproterozoic magnesite: lithological and isotopic evidence for playa/sabkha environments
Magnesite forms a series of 1‐ to 15‐m‐thick beds within the ≈2·0 Ga (Palaeoproterozoic) Tulomozerskaya Formation, NW Fennoscandian Shield, Russia. Drillcore material together with natural exposures reveal that the 680‐m‐thick formation is composed of a stromatolite–dolomite–‘red bed’ sequence forme...
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crwiley:10.1046/j.1365-3091.2001.00369.x 2024-09-15T18:06:08+00:00 Palaeoproterozoic magnesite: lithological and isotopic evidence for playa/sabkha environments Melezhik, Victor A. Fallick, Anthony E. Medvedev, Pavel V. Makarikhin, Vladimir V. 2001 http://dx.doi.org/10.1046/j.1365-3091.2001.00369.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1046%2Fj.1365-3091.2001.00369.x https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-3091.2001.00369.x en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor Sedimentology volume 48, issue 2, page 379-397 ISSN 0037-0746 1365-3091 journal-article 2001 crwiley https://doi.org/10.1046/j.1365-3091.2001.00369.x 2024-07-02T04:14:04Z Magnesite forms a series of 1‐ to 15‐m‐thick beds within the ≈2·0 Ga (Palaeoproterozoic) Tulomozerskaya Formation, NW Fennoscandian Shield, Russia. Drillcore material together with natural exposures reveal that the 680‐m‐thick formation is composed of a stromatolite–dolomite–‘red bed’ sequence formed in a complex combination of shallow‐marine and non‐marine, evaporitic environments. Dolomite‐collapse breccia, stromatolitic and micritic dolostones and sparry allochemical dolostones are the principal rocks hosting the magnesite beds. All dolomite lithologies are marked by δ 13 C values from +7·1‰ to +11·6‰ (V‐PDB) and δ 18 O ranging from 17·4‰ to 26·3‰ (V‐SMOW). Magnesite occurs in different forms: finely laminated micritic; stromatolitic magnesite; and structureless micritic, crystalline and coarsely crystalline magnesite. All varieties exhibit anomalously high δ 13 C values ranging from +9·0‰ to +11·6‰ and δ 18 O values of 20·0–25·7‰. Laminated and structureless micritic magnesite forms as a secondary phase replacing dolomite during early diagenesis, and replaced dolomite before the major phase of burial. Crystalline and coarsely crystalline magnesite replacing micritic magnesite formed late in the diagenetic/metamorphic history. Magnesite apparently precipitated from sea water‐derived brine, diluted by meteoric fluids. Magnesitization was accomplished under evaporitic conditions (sabkha to playa lake environment) proposed to be similar to the Coorong or Lake Walyungup coastal playa magnesite. Magnesite and host dolostones formed in evaporative and partly restricted environments; consequently, extremely high δ 13 C values reflect a combined contribution from both global and local carbon reservoirs. A 13 C‐rich global carbon reservoir (δ 13 C at around +5‰) is related to the perturbation of the carbon cycle at 2·0 Ga, whereas the local enhancement in 13 C (up to +12‰) is associated with evaporative and restricted environments with high bioproductivity. Article in Journal/Newspaper Fennoscandian Wiley Online Library Sedimentology 48 2 379 397 |
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Wiley Online Library |
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crwiley |
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English |
description |
Magnesite forms a series of 1‐ to 15‐m‐thick beds within the ≈2·0 Ga (Palaeoproterozoic) Tulomozerskaya Formation, NW Fennoscandian Shield, Russia. Drillcore material together with natural exposures reveal that the 680‐m‐thick formation is composed of a stromatolite–dolomite–‘red bed’ sequence formed in a complex combination of shallow‐marine and non‐marine, evaporitic environments. Dolomite‐collapse breccia, stromatolitic and micritic dolostones and sparry allochemical dolostones are the principal rocks hosting the magnesite beds. All dolomite lithologies are marked by δ 13 C values from +7·1‰ to +11·6‰ (V‐PDB) and δ 18 O ranging from 17·4‰ to 26·3‰ (V‐SMOW). Magnesite occurs in different forms: finely laminated micritic; stromatolitic magnesite; and structureless micritic, crystalline and coarsely crystalline magnesite. All varieties exhibit anomalously high δ 13 C values ranging from +9·0‰ to +11·6‰ and δ 18 O values of 20·0–25·7‰. Laminated and structureless micritic magnesite forms as a secondary phase replacing dolomite during early diagenesis, and replaced dolomite before the major phase of burial. Crystalline and coarsely crystalline magnesite replacing micritic magnesite formed late in the diagenetic/metamorphic history. Magnesite apparently precipitated from sea water‐derived brine, diluted by meteoric fluids. Magnesitization was accomplished under evaporitic conditions (sabkha to playa lake environment) proposed to be similar to the Coorong or Lake Walyungup coastal playa magnesite. Magnesite and host dolostones formed in evaporative and partly restricted environments; consequently, extremely high δ 13 C values reflect a combined contribution from both global and local carbon reservoirs. A 13 C‐rich global carbon reservoir (δ 13 C at around +5‰) is related to the perturbation of the carbon cycle at 2·0 Ga, whereas the local enhancement in 13 C (up to +12‰) is associated with evaporative and restricted environments with high bioproductivity. |
format |
Article in Journal/Newspaper |
author |
Melezhik, Victor A. Fallick, Anthony E. Medvedev, Pavel V. Makarikhin, Vladimir V. |
spellingShingle |
Melezhik, Victor A. Fallick, Anthony E. Medvedev, Pavel V. Makarikhin, Vladimir V. Palaeoproterozoic magnesite: lithological and isotopic evidence for playa/sabkha environments |
author_facet |
Melezhik, Victor A. Fallick, Anthony E. Medvedev, Pavel V. Makarikhin, Vladimir V. |
author_sort |
Melezhik, Victor A. |
title |
Palaeoproterozoic magnesite: lithological and isotopic evidence for playa/sabkha environments |
title_short |
Palaeoproterozoic magnesite: lithological and isotopic evidence for playa/sabkha environments |
title_full |
Palaeoproterozoic magnesite: lithological and isotopic evidence for playa/sabkha environments |
title_fullStr |
Palaeoproterozoic magnesite: lithological and isotopic evidence for playa/sabkha environments |
title_full_unstemmed |
Palaeoproterozoic magnesite: lithological and isotopic evidence for playa/sabkha environments |
title_sort |
palaeoproterozoic magnesite: lithological and isotopic evidence for playa/sabkha environments |
publisher |
Wiley |
publishDate |
2001 |
url |
http://dx.doi.org/10.1046/j.1365-3091.2001.00369.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1046%2Fj.1365-3091.2001.00369.x https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-3091.2001.00369.x |
genre |
Fennoscandian |
genre_facet |
Fennoscandian |
op_source |
Sedimentology volume 48, issue 2, page 379-397 ISSN 0037-0746 1365-3091 |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1046/j.1365-3091.2001.00369.x |
container_title |
Sedimentology |
container_volume |
48 |
container_issue |
2 |
container_start_page |
379 |
op_container_end_page |
397 |
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1810443632707108864 |