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Conference Paper: The formation of magnetite in the early Archean oceans
Title | The formation of magnetite in the early Archean oceans |
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Authors | |
Issue Date | 2017 |
Publisher | American Geophysical Union. |
Citation | American Geophysical Union Fall Meeting, New Orleans, LA, 11-15 December 2017 How to Cite? |
Abstract | Banded iron formations are iron- and silica-rich chemical sedimentary rocks that were deposited throughout much of the Precambrian. It is generally accepted that biological oxidation of dissolved Fe(II) led to the precipitation of a ferric oxyhydroxide phase, such as ferrihydrite, in the marine photic zone. Upon burial, ferrihydrite was either transformed into hematite through dehydration or it was reduced to magnetite via biological or abiological Fe(III) reduction coupled to the oxidation of buried microbial biomass. However, it has always been intriguing as to why the oldest BIFs are characteristically magnetite-rich, while BIFs formed after the Neoarchean are dominated by hematite. Here, we propose that some magnetite in early Archean BIF could have precipitated directly from seawater through the reaction of settling ferrihydrite and hot, Fe(II)-rich hydrothermal fluids that vented directly into the photic zone. We conducted experiments that showed the reaction of Fe(II) with biogenic ferric iron mats under strict anoxic conditions led to the formation of a metastable green rust phase that within hours transformed into magnetite at relatively high temperatures. At lower temperatures magnetite does not form. Our model further posits that with the progressive cooling of the Earth’s oceans through Archean, the above reaction shut off, and magnetite was subsequently restricted to reactions associated with diagenesis and metamorphism. |
Description | Session Proposal: GP13A Advances in Biomagnetism, Magnetic Proxy Parameters, and Authigenesis and Diagenesis of Magnetic Minerals I - no. GP13A-01 |
Persistent Identifier | http://hdl.handle.net/10722/262137 |
DC Field | Value | Language |
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dc.contributor.author | Li, Y | - |
dc.date.accessioned | 2018-09-28T04:53:57Z | - |
dc.date.available | 2018-09-28T04:53:57Z | - |
dc.date.issued | 2017 | - |
dc.identifier.citation | American Geophysical Union Fall Meeting, New Orleans, LA, 11-15 December 2017 | - |
dc.identifier.uri | http://hdl.handle.net/10722/262137 | - |
dc.description | Session Proposal: GP13A Advances in Biomagnetism, Magnetic Proxy Parameters, and Authigenesis and Diagenesis of Magnetic Minerals I - no. GP13A-01 | - |
dc.description.abstract | Banded iron formations are iron- and silica-rich chemical sedimentary rocks that were deposited throughout much of the Precambrian. It is generally accepted that biological oxidation of dissolved Fe(II) led to the precipitation of a ferric oxyhydroxide phase, such as ferrihydrite, in the marine photic zone. Upon burial, ferrihydrite was either transformed into hematite through dehydration or it was reduced to magnetite via biological or abiological Fe(III) reduction coupled to the oxidation of buried microbial biomass. However, it has always been intriguing as to why the oldest BIFs are characteristically magnetite-rich, while BIFs formed after the Neoarchean are dominated by hematite. Here, we propose that some magnetite in early Archean BIF could have precipitated directly from seawater through the reaction of settling ferrihydrite and hot, Fe(II)-rich hydrothermal fluids that vented directly into the photic zone. We conducted experiments that showed the reaction of Fe(II) with biogenic ferric iron mats under strict anoxic conditions led to the formation of a metastable green rust phase that within hours transformed into magnetite at relatively high temperatures. At lower temperatures magnetite does not form. Our model further posits that with the progressive cooling of the Earth’s oceans through Archean, the above reaction shut off, and magnetite was subsequently restricted to reactions associated with diagenesis and metamorphism. | - |
dc.language | eng | - |
dc.publisher | American Geophysical Union. | - |
dc.relation.ispartof | American Geophysical Union Fall Meeting | - |
dc.rights | American Geophysical Union Fall Meeting. Copyright © American Geophysical Union. | - |
dc.title | The formation of magnetite in the early Archean oceans | - |
dc.type | Conference_Paper | - |
dc.identifier.email | Li, Y: yiliang@hku.hk | - |
dc.identifier.authority | Li, Y=rp01354 | - |
dc.identifier.hkuros | 293312 | - |
dc.publisher.place | New Orleans, LA | - |