TY - JOUR
T1 - A magnetic approach to unravelling the paleoenvironmental significance of nanometer-sized Fe hydroxide in NW Pacific ferromanganese deposits
AU - Jiang, Xiaodong
AU - Zhao, Xiang
AU - Zhao, Xiangyu
AU - Chou, Yu Min
AU - Hein, James R.
AU - Sun, Xiaoming
AU - Zhong, Yi
AU - Ren, Jiangbo
AU - Liu, Qingsong
N1 - Publisher Copyright:
© 2021 Elsevier B.V.
PY - 2021/7/1
Y1 - 2021/7/1
N2 - 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 °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 ∼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.
AB - 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 °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 ∼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.
KW - Fe-Mn nodules and crusts
KW - amorphous Fe-hydroxides
KW - superparamagnetism
KW - temperature dependence of magnetic susceptibility
UR - http://www.scopus.com/inward/record.url?scp=85104489875&partnerID=8YFLogxK
U2 - 10.1016/j.epsl.2021.116945
DO - 10.1016/j.epsl.2021.116945
M3 - Article
SN - 0012-821X
VL - 565
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
M1 - 116945
ER -