Biogenic signature and ultra microfossils in ferromanganese nodules of the Central Indian Ocean Basin |
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| Institution: | 1. Fourth Institute of Oceanography, Ministry of Natural Resources, Beihai 536000, China;2. School of Marine Sciences, Sun Yat–sen University, Guangzhou 510006, China;3. School of Earth Sciences and Engineering, Sun Yat–sen University, Guangzhou 510275, China;4. Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Guangzhou 510006, China;5. Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519000, China;6. South China Sea Institute of Planning and Environmental Research, State Oceanic Administration, Guangzhou 510300, China;7. Guangzhou Marine Geological Survey, China Geological Survey, Guangzhou 510075, China;1. CAS Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China;2. Department of Ocean Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China;3. University of Chinese Academy of Sciences, Beijing 100049, China;4. Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;5. Marine Geology Dv., Geological Survey of Spain (IGME), Madrid 28003, Spain;6. U.S. Geological Survey, 2885 Mission St., Santa Cruz, CA 95060, USA;7. Laboratory for Marine Geology, Qingdao National Oceanography Laboratory for Marine Science and Technology, Qingdao 266061, China;8. School of Marine Sciences, Sun Yat-Sen Univerisity, Guangzhou 510006, China;1. U.S. Geological Survey, PCMSC, 400 Natural Bridges Dr., Santa Cruz, CA 95060, USA;2. Sea-Floor Mineral Resources R&D Division, Metals Mining Technology Dept., JOGMEC, 2-10-1 Toranomon, Minato-ku, Tokyo 105-0001, Japan;3. Seabed Minerals Authority, Avarua, Rarotonga, Cook Islands;4. SOPAC Division of the SPC, Private Mail Bag, GPO, Suva, Fiji |
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| Abstract: | Theories related to the precipitation mechanism of the metallic elements in marine manganese nodules have remained controversial between two schools of thoughts (1) chemical oxidation (abiotic origin) and (2) deposition of the metals through microbial enzymatic processes (biogenic origin). One of the most important evidence in support of the biogenic origin is the occurrence of fossilized microbes. However, well-documented literature in this regard is either lacking or very scanty in case of Indian Ocean nodules. Using high resolution FEG-SEM we have recorded various biogenic signatures and ultra microfossils in the ferromanganese nodule samples from Central Indian Ocean Basin (CIOB) that are presented in this paper. The microfossils are mostly protozoans belonging to varieties of bacteria, diatoms and foraminifera. Some of the features recorded in this study have perhaps never been reported before from any manganese nodules. The chemical compositions of these ultra microfossils indicate a high-level of manganese precipitation in and around them in comparison to the distant surrounding areas. While clumpy microbes are enriched with nickel, the rod shaped bacteria are rich in copper. Up to 4.70 wt.% nickel and 5.31 wt.% Cu have been recorded in the fossilized microbe bodies. The high abundance of biogenic features as well as microfossils in the ferromanganese nodules and their chemical compositions support arguments in favor of a dominant role of the microorganisms in the construction of the nodules of the CIOB. |
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| Keywords: | Manganese nodule Ultra microfossils Biogenic origin Central Indian Ocean Basin |
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