期刊
EARTH AND PLANETARY SCIENCE LETTERS
卷 565, 期 -, 页码 -出版社
ELSEVIER
DOI: 10.1016/j.epsl.2021.116945
关键词
amorphous Fe-hydroxides; Fe-Mn nodules and crusts; temperature dependence of magnetic; susceptibility; superparamagnetism
资金
- Shenzhen Key Laboratory of Marine Archaea Geo-Omics [ZDSYS20180208184349083]
- National Key Research and Development Program of China [2016YFA0601903]
- National Natural Science Foundation of China [41874078, 42074071, U1606401]
- National Program on Global Change and Air Sea Interaction and Air Sea Interaction [GASI-GEOGE-03]
- Shenzhen Science and Technology Program [KQTD20170810111725321]
- Guangdong Basic and Applied Basic Research Foundation [2019A1515011860]
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) [GML2019ZD0210]
- Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering
- Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology [MGQNLM201803]
Ferromanganese deposits are being widely explored for their economic potential and paleoenvironmental archives. A novel approach using thermal treatment can transform nanometer-sized amorphous Fe hydroxides (AFH) into magnetic magnetite, allowing for feasible quantification in Fe-Mn deposits. Investigations in the western Pacific Ocean suggest an increase in AFH abundance at a depth of around 5000 meters, possibly due to bottom-current stratification.
Ferromanganese nodules and crusts (Fe-Mn deposits) are being widely explored for their significant economic potential and paleoenvironmentally significant archives. Fe-Mn deposits contain abundant Fe-bearing minerals including detrital minerals, biogenic Fe-bearing components, but predominantly amorphous Fe hydroxides (AFH). Particularly, the hydrogenetic Fe that is formed in bottom water should be closely related with oceanic environmental and Fe-cycling processes. However, it remains challenging to characterize and quantify the x-ray amorphous AFH component in Fe-Mn deposits. To resolve this problem, we systematically investigated thermally treated hydrogenetic Fe-Mn deposits sampled from the northwestern Pacific Ocean to unravel the AFH component. Our results show that the nanometer-sized AFHs can be transformed into strongly magnetic nanometer-sized (approximately 10-20 nm) magnetite upon heating above 500 degrees C, which can be feasibly quantified by systematic rock magnetic analyses. Using this novel approach, several Fe-Mn deposits at different water depths from the western Pacific Ocean are investigated. Our results indicate that the abundance of AFH increase at a water depth of similar to 5000 m, which can be ascribed to bottom-current stratification. The magnetic approach to indirectly quantify the AFH component in Fe-Mn deposits has a great potential in exploring oceanic paleoenvironment significance. (C) 2021 Elsevier B.V. All rights reserved.
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