Redox fluctuations, trace metal enrichment and phosphogenesis in the ~2.0 Ga Zaonega Formation
The ~2.0 Ga Zaonega Formation (ZF) holds one of the oldest phosphorites in the geologic record, reaching >15% P 2 O 5 . Understanding the depositional conditions that enabled sedimentary phosphorus enrichment in this unit will thus help us to interpret the significance of the temporal distributio...
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ftunivtroemsoe:oai:munin.uit.no:10037/19229 2023-05-15T14:26:08+02:00 Redox fluctuations, trace metal enrichment and phosphogenesis in the ~2.0 Ga Zaonega Formation Kipp, Michael A. Lepland, Aivo Buick, Roger 2020-03-24 https://hdl.handle.net/10037/19229 https://doi.org/10.1016/j.precamres.2020.105716 eng eng Elsevier Precambrian Research info:eu-repo/grantAgreement/RCN/SFF/223259/Norway/Centre for Arctic Gas Hydrate, Environment and Climate/CAGE/ Kipp, Lepland A, Buick. Redox fluctuations, trace metal enrichment and phosphogenesis in the ~2.0 Ga Zaonega Formation. Precambrian Research. 2020;343:105716:1-15 FRIDAID 1807066 doi:10.1016/j.precamres.2020.105716 0301-9268 1872-7433 https://hdl.handle.net/10037/19229 embargoedAccess Copyright 2020 Elsevier B.V. VDP::Mathematics and natural science: 400::Geosciences: 450::Sedimentology: 456 VDP::Matematikk og Naturvitenskap: 400::Geofag: 450::Sedimentologi: 456 Journal article Tidsskriftartikkel Peer reviewed acceptedVersion 2020 ftunivtroemsoe https://doi.org/10.1016/j.precamres.2020.105716 2021-06-25T17:57:39Z The ~2.0 Ga Zaonega Formation (ZF) holds one of the oldest phosphorites in the geologic record, reaching >15% P 2 O 5 . Understanding the depositional conditions that enabled sedimentary phosphorus enrichment in this unit will thus help us to interpret the significance of the temporal distribution of phosphorites in Earth’s early history. Here we use an array of major and trace element data to constrain the redox conditions in the water column and extent of basinal restriction during deposition of the ZF. We also present new selenium (Se) abundance and isotopic data to provide firmer constraints on fluctuations across high redox potentials, which might be critical for phosphogenesis. We find that Se isotope ratios shift over a range of ~3‰ in the ZF, with the earliest stratigraphically-resolved negative Se isotope excursion in the geologic record, implying at least temporarily suboxic waters in the basin. Furthermore, we find that redox-sensitive element (RSE) enrichments coincide with episodes of P enrichment, thereby implicating a common set of environmental controls on these processes. Together, our dataset implies deposition under a predominantly anoxic water column with periodic fluctuations to more oxidizing conditions because of connections to a large oxic reservoir containing Se oxyanions (and other RSE’s, as well as sulfate) in the open ocean. This is broadly consistent with the depositional setting of many modern and recent phosphorites, thereby tying these ancient deposits to a common depositional mechanism. In light of these data, we propose that the broader prevalence of phosphogenesis in the Paleoproterozoic Era was driven by growth of the seawater oxidant reservoir (namely sulfate), thus enabling diagenetic apatite precipitation in basins with high rates of export production, particularly by facilitating the activity of sulfide-oxidizing bacteria. This suggests that the muted authigenic P burial observed in marginal, marine siliciclastic sedimentary rocks during other intervals of the Precambrian was not merely a result of low dissolved P levels in the global deep ocean, but also was influenced by sulfate scarcity and strongly reducing bottom-water conditions. Article in Journal/Newspaper Arctic University of Tromsø: Munin Open Research Archive Precambrian Research 343 105716 |
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Open Polar |
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University of Tromsø: Munin Open Research Archive |
op_collection_id |
ftunivtroemsoe |
language |
English |
topic |
VDP::Mathematics and natural science: 400::Geosciences: 450::Sedimentology: 456 VDP::Matematikk og Naturvitenskap: 400::Geofag: 450::Sedimentologi: 456 |
spellingShingle |
VDP::Mathematics and natural science: 400::Geosciences: 450::Sedimentology: 456 VDP::Matematikk og Naturvitenskap: 400::Geofag: 450::Sedimentologi: 456 Kipp, Michael A. Lepland, Aivo Buick, Roger Redox fluctuations, trace metal enrichment and phosphogenesis in the ~2.0 Ga Zaonega Formation |
topic_facet |
VDP::Mathematics and natural science: 400::Geosciences: 450::Sedimentology: 456 VDP::Matematikk og Naturvitenskap: 400::Geofag: 450::Sedimentologi: 456 |
description |
The ~2.0 Ga Zaonega Formation (ZF) holds one of the oldest phosphorites in the geologic record, reaching >15% P 2 O 5 . Understanding the depositional conditions that enabled sedimentary phosphorus enrichment in this unit will thus help us to interpret the significance of the temporal distribution of phosphorites in Earth’s early history. Here we use an array of major and trace element data to constrain the redox conditions in the water column and extent of basinal restriction during deposition of the ZF. We also present new selenium (Se) abundance and isotopic data to provide firmer constraints on fluctuations across high redox potentials, which might be critical for phosphogenesis. We find that Se isotope ratios shift over a range of ~3‰ in the ZF, with the earliest stratigraphically-resolved negative Se isotope excursion in the geologic record, implying at least temporarily suboxic waters in the basin. Furthermore, we find that redox-sensitive element (RSE) enrichments coincide with episodes of P enrichment, thereby implicating a common set of environmental controls on these processes. Together, our dataset implies deposition under a predominantly anoxic water column with periodic fluctuations to more oxidizing conditions because of connections to a large oxic reservoir containing Se oxyanions (and other RSE’s, as well as sulfate) in the open ocean. This is broadly consistent with the depositional setting of many modern and recent phosphorites, thereby tying these ancient deposits to a common depositional mechanism. In light of these data, we propose that the broader prevalence of phosphogenesis in the Paleoproterozoic Era was driven by growth of the seawater oxidant reservoir (namely sulfate), thus enabling diagenetic apatite precipitation in basins with high rates of export production, particularly by facilitating the activity of sulfide-oxidizing bacteria. This suggests that the muted authigenic P burial observed in marginal, marine siliciclastic sedimentary rocks during other intervals of the Precambrian was not merely a result of low dissolved P levels in the global deep ocean, but also was influenced by sulfate scarcity and strongly reducing bottom-water conditions. |
format |
Article in Journal/Newspaper |
author |
Kipp, Michael A. Lepland, Aivo Buick, Roger |
author_facet |
Kipp, Michael A. Lepland, Aivo Buick, Roger |
author_sort |
Kipp, Michael A. |
title |
Redox fluctuations, trace metal enrichment and phosphogenesis in the ~2.0 Ga Zaonega Formation |
title_short |
Redox fluctuations, trace metal enrichment and phosphogenesis in the ~2.0 Ga Zaonega Formation |
title_full |
Redox fluctuations, trace metal enrichment and phosphogenesis in the ~2.0 Ga Zaonega Formation |
title_fullStr |
Redox fluctuations, trace metal enrichment and phosphogenesis in the ~2.0 Ga Zaonega Formation |
title_full_unstemmed |
Redox fluctuations, trace metal enrichment and phosphogenesis in the ~2.0 Ga Zaonega Formation |
title_sort |
redox fluctuations, trace metal enrichment and phosphogenesis in the ~2.0 ga zaonega formation |
publisher |
Elsevier |
publishDate |
2020 |
url |
https://hdl.handle.net/10037/19229 https://doi.org/10.1016/j.precamres.2020.105716 |
genre |
Arctic |
genre_facet |
Arctic |
op_relation |
Precambrian Research info:eu-repo/grantAgreement/RCN/SFF/223259/Norway/Centre for Arctic Gas Hydrate, Environment and Climate/CAGE/ Kipp, Lepland A, Buick. Redox fluctuations, trace metal enrichment and phosphogenesis in the ~2.0 Ga Zaonega Formation. Precambrian Research. 2020;343:105716:1-15 FRIDAID 1807066 doi:10.1016/j.precamres.2020.105716 0301-9268 1872-7433 https://hdl.handle.net/10037/19229 |
op_rights |
embargoedAccess Copyright 2020 Elsevier B.V. |
op_doi |
https://doi.org/10.1016/j.precamres.2020.105716 |
container_title |
Precambrian Research |
container_volume |
343 |
container_start_page |
105716 |
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1766298615861477376 |