Geochemistry of ferromanganese nodules in the soil of Okinawa Island, Japan: Paleoclimatic implications and discrimination scheme of the nodule origins
Shimajiri–Mahji refers to dark-red soil covering Ryukyu limestone that is characterized by buried ferromanganese (Fe–Mn) nodules, and it is widely distributed in Okinawa Island, southwestern Japan. The formation environment of the Fe–Mn nodules is considered closely related to the pedogenetic proces...
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| Format: | Article |
| Language: | English |
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Elsevier
2022-12-01
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| Series: | Journal of Asian Earth Sciences: X |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S2590056022000482 |
| _version_ | 1828167824331243520 |
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| author | Keishiro Azami Kazutaka Yasukawa Yasuhiro Kato |
| author_facet | Keishiro Azami Kazutaka Yasukawa Yasuhiro Kato |
| author_sort | Keishiro Azami |
| collection | DOAJ |
| description | Shimajiri–Mahji refers to dark-red soil covering Ryukyu limestone that is characterized by buried ferromanganese (Fe–Mn) nodules, and it is widely distributed in Okinawa Island, southwestern Japan. The formation environment of the Fe–Mn nodules is considered closely related to the pedogenetic process of Shimajiri–Mahji because the mineral assemblage of the nodules is similar to that of the surrounding soil. There are two competing hypotheses about the formation environment of the Fe–Mn nodules: marine or terrestrial. In this study, the chemical composition of the Fe–Mn nodules was analyzed to determine their origin. The low Ni and Cu contents and the positive Ce and negative Y anomalies of the Fe–Mn nodules are inconsistent with the geochemical features associated with formation in the deep ocean and shallow seas or lakes, respectively. In contrast, the geochemical features of the Fe–Mn nodules correspond to formation in terrestrial soil, especially in terra rossa. An elemental map of the Mn/Fe ratio and computed tomography results demonstrated that the Fe–Mn nodules have a layered structure, which indicates a temporal change in the redox potential of Shimajiri–Mahji. This may be attributed to changes in the soil moisture owing to the variable intensity of the East Asian monsoon and climate change. A new discrimination diagram based on Al/Na and Co/Rb ratios was developed for classifying the formation environments of Fe–Mn nodules, which may help improve understanding of the formation history of soils and sediments containing them. |
| first_indexed | 2024-04-12T02:23:41Z |
| format | Article |
| id | doaj.art-cd318e07902a44d6874f4a85e9f0a013 |
| institution | Directory Open Access Journal |
| issn | 2590-0560 |
| language | English |
| last_indexed | 2024-04-12T02:23:41Z |
| publishDate | 2022-12-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Journal of Asian Earth Sciences: X |
| spelling | doaj.art-cd318e07902a44d6874f4a85e9f0a0132022-12-22T03:52:04ZengElsevierJournal of Asian Earth Sciences: X2590-05602022-12-018100127Geochemistry of ferromanganese nodules in the soil of Okinawa Island, Japan: Paleoclimatic implications and discrimination scheme of the nodule originsKeishiro Azami0Kazutaka Yasukawa1Yasuhiro Kato2Department of Systems Innovation, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, JapanFrontier Research Center for Energy and Resources, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan; Department of Systems Innovation, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, JapanDepartment of Systems Innovation, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan; Ocean Resources Research Center for Next Generation, Chiba Institution of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan; Submarine Resources Research Center, Research Institute for Marine Resources Utilization, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan; Corresponding author at: Department of Systems Innovation, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.Shimajiri–Mahji refers to dark-red soil covering Ryukyu limestone that is characterized by buried ferromanganese (Fe–Mn) nodules, and it is widely distributed in Okinawa Island, southwestern Japan. The formation environment of the Fe–Mn nodules is considered closely related to the pedogenetic process of Shimajiri–Mahji because the mineral assemblage of the nodules is similar to that of the surrounding soil. There are two competing hypotheses about the formation environment of the Fe–Mn nodules: marine or terrestrial. In this study, the chemical composition of the Fe–Mn nodules was analyzed to determine their origin. The low Ni and Cu contents and the positive Ce and negative Y anomalies of the Fe–Mn nodules are inconsistent with the geochemical features associated with formation in the deep ocean and shallow seas or lakes, respectively. In contrast, the geochemical features of the Fe–Mn nodules correspond to formation in terrestrial soil, especially in terra rossa. An elemental map of the Mn/Fe ratio and computed tomography results demonstrated that the Fe–Mn nodules have a layered structure, which indicates a temporal change in the redox potential of Shimajiri–Mahji. This may be attributed to changes in the soil moisture owing to the variable intensity of the East Asian monsoon and climate change. A new discrimination diagram based on Al/Na and Co/Rb ratios was developed for classifying the formation environments of Fe–Mn nodules, which may help improve understanding of the formation history of soils and sediments containing them.http://www.sciencedirect.com/science/article/pii/S2590056022000482Ferromanganese noduleRare-earth elementComputed tomographyOkinawa IslandDiscrimination diagramPaleoclimate |
| spellingShingle | Keishiro Azami Kazutaka Yasukawa Yasuhiro Kato Geochemistry of ferromanganese nodules in the soil of Okinawa Island, Japan: Paleoclimatic implications and discrimination scheme of the nodule origins Journal of Asian Earth Sciences: X Ferromanganese nodule Rare-earth element Computed tomography Okinawa Island Discrimination diagram Paleoclimate |
| title | Geochemistry of ferromanganese nodules in the soil of Okinawa Island, Japan: Paleoclimatic implications and discrimination scheme of the nodule origins |
| title_full | Geochemistry of ferromanganese nodules in the soil of Okinawa Island, Japan: Paleoclimatic implications and discrimination scheme of the nodule origins |
| title_fullStr | Geochemistry of ferromanganese nodules in the soil of Okinawa Island, Japan: Paleoclimatic implications and discrimination scheme of the nodule origins |
| title_full_unstemmed | Geochemistry of ferromanganese nodules in the soil of Okinawa Island, Japan: Paleoclimatic implications and discrimination scheme of the nodule origins |
| title_short | Geochemistry of ferromanganese nodules in the soil of Okinawa Island, Japan: Paleoclimatic implications and discrimination scheme of the nodule origins |
| title_sort | geochemistry of ferromanganese nodules in the soil of okinawa island japan paleoclimatic implications and discrimination scheme of the nodule origins |
| topic | Ferromanganese nodule Rare-earth element Computed tomography Okinawa Island Discrimination diagram Paleoclimate |
| url | http://www.sciencedirect.com/science/article/pii/S2590056022000482 |
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