Magnetic Mineral Diagenesis in a High Temperature and Deep Methanic Zone in Izu Rear Arc Marine Sediments, Northwest Pacific Ocean.

Kars, Myriam, Musgrave, Robert J., Hoshino, Tatsuhiko, Jonas, Ann-Sophie, Bauersachs, Thorsten, Inagaki, Fumio and Kodama, Kazuto (2018) Magnetic Mineral Diagenesis in a High Temperature and Deep Methanic Zone in Izu Rear Arc Marine Sediments, Northwest Pacific Ocean. Open Access Journal of Geophysical Research: Solid Earth, 123 (10). pp. 8331-8348. DOI 10.1029/2018JB015861.

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Abstract

Magnetic mineral diagenesis is an important process in sediments that is responsible for the partial or total destruction of records of Earth's magnetic field variations and also plays an important part in iron and sulfur cycling. A rock magnetic study has been carried out at International Ocean Discovery Program Expedition 350 Site U1437 in the Izu Bonin rear arc to investigate magnetic mineral diagenesis in deeply buried sediments from ~775 to ~1,002 m below sea floor (mbsf) with burial temperatures ranging from ~67 to 85 °C. Nonsteady state geochemical environments occur within an unusual deep methanic zone (below 850 mbsf) because of a release of sulfate below the shallow sulfate reduction zone. A drastic decline in magnetic susceptibility and remanence is observed at ~850 mbsf due to a decrease in ferrimagnetic iron oxide contents. Reduction of (titano)‐magnetite and pyritization occur at this inferred deep sulfate‐methane transition zone. Below ~850 mbsf, lower magnetic mineral contents coincide with further methane release. Geochemical analyses support a change in redox conditions and secondary precipitation of iron sulfides and carbonates in the methane‐rich zone. Magnetic mineral alteration is enhanced in zones where methane accumulates underneath low porosity intervals that act as seals. Although geochemical processes due to methane occurrence are likely dominant, more than one mechanism, possibly involving microbial activity, is probably responsible for the observed magnetic mineral assemblage changes.

Document Type: Article
Keywords: magnetic mineral diagenesis, methane, Izu arc, IODP Expedition 350, anaerobic oxidation of methane
Research affiliation: Kiel University > Kiel Marine Science
OceanRep > The Future Ocean - Cluster of Excellence
Kiel University
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1029/2018JB015861
ISSN: 2169-9313
Projects: Future Ocean
Date Deposited: 04 Feb 2019 09:33
Last Modified: 02 Jan 2020 12:28
URI: http://oceanrep.geomar.de/id/eprint/45647

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