Origin of the Neoproterozoic Fulu iron formation, South China: Insights from iron isotopes and rare earth element patterns
International audience In the Neoproterozoic Era there was widespread deposition of iron formations in close association with global or near glaciations. These 'Snowball Earth' glaciations likely played a key role in iron formation distribution and deposition. However, the environmental co...
Published in: | Geochimica et Cosmochimica Acta |
---|---|
Main Authors: | , , , , , |
Other Authors: | , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
HAL CCSD
2018
|
Subjects: | |
Online Access: | https://hal-insu.archives-ouvertes.fr/insu-03589305 https://doi.org/10.1016/j.gca.2018.09.006 |
id |
ftinsu:oai:HAL:insu-03589305v1 |
---|---|
record_format |
openpolar |
spelling |
ftinsu:oai:HAL:insu-03589305v1 2023-06-18T03:43:00+02:00 Origin of the Neoproterozoic Fulu iron formation, South China: Insights from iron isotopes and rare earth element patterns Busigny, Vincent Planavsky, Noah J. Goldbaum, Elizabeth Lechte, Maxwell A. Feng, Lianjun Lyons, Timothy W. Institut de Physique du Globe de Paris (IPGP) Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS) 2018 https://hal-insu.archives-ouvertes.fr/insu-03589305 https://doi.org/10.1016/j.gca.2018.09.006 en eng HAL CCSD Elsevier info:eu-repo/semantics/altIdentifier/doi/10.1016/j.gca.2018.09.006 insu-03589305 https://hal-insu.archives-ouvertes.fr/insu-03589305 BIBCODE: 2018GeCoA.242.123B doi:10.1016/j.gca.2018.09.006 ISSN: 0016-7037 EISSN: 0016-7037 Geochimica et Cosmochimica Acta https://hal-insu.archives-ouvertes.fr/insu-03589305 Geochimica et Cosmochimica Acta, 2018, 242, pp.123-142. ⟨10.1016/j.gca.2018.09.006⟩ Iron isotopes REE Proterozoic Cryogenian Iron formation [SDU]Sciences of the Universe [physics] info:eu-repo/semantics/article Journal articles 2018 ftinsu https://doi.org/10.1016/j.gca.2018.09.006 2023-06-05T20:49:51Z International audience In the Neoproterozoic Era there was widespread deposition of iron formations in close association with global or near glaciations. These 'Snowball Earth' glaciations likely played a key role in iron formation distribution and deposition. However, the environmental conditions, Fe sources, and formation mechanisms remain debated. Here we present the rare earth element geochemistry and Fe isotope composition of the synglacial iron formation within the Neoproterozoic Fulu Formation, South China. The Fulu iron formation consists of layers of authigenic minerals (mainly hematite) and detrital components (quartz, feldspars, Fe chlorite, and minor biotite). Positive Eu anomalies in one of the Fulu localities indicate a hydrothermal influence, suggesting that Fe was mainly sourced from distal hydrothermal systems. The bulk-rock Fe isotope composition of the Fulu iron formation shows a large range, with δ 56 Fe from -0.23 to +1.78‰. Correlation between bulk-rock δ 56 Fe values and Al/Fe ratios demonstrates that δ 56 Fe variability reflects, in part, varying proportions of authigenic versus detrital components. The Fe isotope composition of authigenic hematite is calculated by a linear regression and shows δ 56 Fe between +0.83 and +2.21‰, with an average at +1.54 ± 0.50‰ (2σ, n = 41). Using a dispersion-reaction model, the high δ 56 Fe values of hematite constrain local dissolved O 2 concentrations of the ocean to less than 0.4 nmol/L, even in the shallow part of the water column. This relationship is consistent with highly reducing conditions in the Neoproterozoic oceans favored by isolation from the atmosphere by a sea ice. We attribute the extremely positive values to partial iron oxidation in waters that were cold relative to modern surface oceans. The dominant occurrence of hematite supports an abiotic precipitation pathway, given that biological activity would have introduced organic matter to the sediments and led to partial reduction of Fe(III) oxides and subsequent formation of magnetite ... Article in Journal/Newspaper Sea ice Institut national des sciences de l'Univers: HAL-INSU Geochimica et Cosmochimica Acta 242 123 142 |
institution |
Open Polar |
collection |
Institut national des sciences de l'Univers: HAL-INSU |
op_collection_id |
ftinsu |
language |
English |
topic |
Iron isotopes REE Proterozoic Cryogenian Iron formation [SDU]Sciences of the Universe [physics] |
spellingShingle |
Iron isotopes REE Proterozoic Cryogenian Iron formation [SDU]Sciences of the Universe [physics] Busigny, Vincent Planavsky, Noah J. Goldbaum, Elizabeth Lechte, Maxwell A. Feng, Lianjun Lyons, Timothy W. Origin of the Neoproterozoic Fulu iron formation, South China: Insights from iron isotopes and rare earth element patterns |
topic_facet |
Iron isotopes REE Proterozoic Cryogenian Iron formation [SDU]Sciences of the Universe [physics] |
description |
International audience In the Neoproterozoic Era there was widespread deposition of iron formations in close association with global or near glaciations. These 'Snowball Earth' glaciations likely played a key role in iron formation distribution and deposition. However, the environmental conditions, Fe sources, and formation mechanisms remain debated. Here we present the rare earth element geochemistry and Fe isotope composition of the synglacial iron formation within the Neoproterozoic Fulu Formation, South China. The Fulu iron formation consists of layers of authigenic minerals (mainly hematite) and detrital components (quartz, feldspars, Fe chlorite, and minor biotite). Positive Eu anomalies in one of the Fulu localities indicate a hydrothermal influence, suggesting that Fe was mainly sourced from distal hydrothermal systems. The bulk-rock Fe isotope composition of the Fulu iron formation shows a large range, with δ 56 Fe from -0.23 to +1.78‰. Correlation between bulk-rock δ 56 Fe values and Al/Fe ratios demonstrates that δ 56 Fe variability reflects, in part, varying proportions of authigenic versus detrital components. The Fe isotope composition of authigenic hematite is calculated by a linear regression and shows δ 56 Fe between +0.83 and +2.21‰, with an average at +1.54 ± 0.50‰ (2σ, n = 41). Using a dispersion-reaction model, the high δ 56 Fe values of hematite constrain local dissolved O 2 concentrations of the ocean to less than 0.4 nmol/L, even in the shallow part of the water column. This relationship is consistent with highly reducing conditions in the Neoproterozoic oceans favored by isolation from the atmosphere by a sea ice. We attribute the extremely positive values to partial iron oxidation in waters that were cold relative to modern surface oceans. The dominant occurrence of hematite supports an abiotic precipitation pathway, given that biological activity would have introduced organic matter to the sediments and led to partial reduction of Fe(III) oxides and subsequent formation of magnetite ... |
author2 |
Institut de Physique du Globe de Paris (IPGP) Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS) |
format |
Article in Journal/Newspaper |
author |
Busigny, Vincent Planavsky, Noah J. Goldbaum, Elizabeth Lechte, Maxwell A. Feng, Lianjun Lyons, Timothy W. |
author_facet |
Busigny, Vincent Planavsky, Noah J. Goldbaum, Elizabeth Lechte, Maxwell A. Feng, Lianjun Lyons, Timothy W. |
author_sort |
Busigny, Vincent |
title |
Origin of the Neoproterozoic Fulu iron formation, South China: Insights from iron isotopes and rare earth element patterns |
title_short |
Origin of the Neoproterozoic Fulu iron formation, South China: Insights from iron isotopes and rare earth element patterns |
title_full |
Origin of the Neoproterozoic Fulu iron formation, South China: Insights from iron isotopes and rare earth element patterns |
title_fullStr |
Origin of the Neoproterozoic Fulu iron formation, South China: Insights from iron isotopes and rare earth element patterns |
title_full_unstemmed |
Origin of the Neoproterozoic Fulu iron formation, South China: Insights from iron isotopes and rare earth element patterns |
title_sort |
origin of the neoproterozoic fulu iron formation, south china: insights from iron isotopes and rare earth element patterns |
publisher |
HAL CCSD |
publishDate |
2018 |
url |
https://hal-insu.archives-ouvertes.fr/insu-03589305 https://doi.org/10.1016/j.gca.2018.09.006 |
genre |
Sea ice |
genre_facet |
Sea ice |
op_source |
ISSN: 0016-7037 EISSN: 0016-7037 Geochimica et Cosmochimica Acta https://hal-insu.archives-ouvertes.fr/insu-03589305 Geochimica et Cosmochimica Acta, 2018, 242, pp.123-142. ⟨10.1016/j.gca.2018.09.006⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.1016/j.gca.2018.09.006 insu-03589305 https://hal-insu.archives-ouvertes.fr/insu-03589305 BIBCODE: 2018GeCoA.242.123B doi:10.1016/j.gca.2018.09.006 |
op_doi |
https://doi.org/10.1016/j.gca.2018.09.006 |
container_title |
Geochimica et Cosmochimica Acta |
container_volume |
242 |
container_start_page |
123 |
op_container_end_page |
142 |
_version_ |
1769009214705893376 |