Geochemistry and U-series dating of Holocene and fossil marine hydrothermal manganese deposits from the Izu-Ogasawara arc |
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| Institution: | 1. Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8567, Japan;2. Geological Sciences, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968, USA;3. Faculty of Science, Kochi University, 2-5-1 Akebono-cho, Kochi 780-8520, Japan;1. Seafloor Hydrothermal Activity Laboratory of the Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;2. Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China;3. University of Chinese Academy of Sciences, Beijing 100049, China;4. Qingdao Collaborative Innovation Center of Marine Science and Technology, Qingdao 266061, China;5. Marine Biological Museum, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;1. Laboratoire de Géochimie et Métallogénie, Département Géosciences Marines, IFREMER, Z.I. Pointe du diable, BP 70, 29280 Plouzané, France;2. CNRS UMR 6538 Laboratoire Domaines Océaniques, Institut Universitaire Européen de la Mer, Université de Brest, Place Nicolas Copernic, 29280 Plouzané, France;3. Department of Geological Sciences, University of Florida, 241 Williamson Hall, Gainesville, FL 32611, USA;4. U.S. Geological Survey, 973 Denver Federal Center, Denver, CO 80225, USA;5. Department of Earth and Environmental Sciences, University of Ottawa, Advanced Research Complex, 25 Templeton St., Ottawa, Ontario K1N 6N5, Canada;1. Kochi University, B200 Monobe, Nankoku, Kochi 783-8502, Japan;2. Research Institute of Geology and Geoinformation, Geological Survey of Japan, AIST, Central 7, 1-1-1 Higashi, Tsukuba 305-8567, Japan;1. Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton Waterfront Campus, European Way, Southampton SO14 3ZH, UK;2. National Oceanography Centre, Waterfront Campus, University of Southampton, Southampton SO14 3ZH, UK;1. Saint-Petersburg State University, St. Petersburg 199034, Russia;2. Institute for Geology and Mineral Resources of the Ocean (VNIIOkeangeologia), St. Petersburg 190121, Russia;3. U.S. Geological Survey, Santa Cruz, CA 95060, USA;4. The Laboratory HERCULES, University of Evora, Évora 7000-809, Portugal;5. Estrutura de Missão para a Extensão da Plataforma Continental, Paçod''Arcos 2770-047, Portugal;6. Universidade de Évora, Instituto de Ciências da Terra, Dep. de Geociências, Évora 7000-671, Portugal;1. Geological Survey of Spain, (IGME), C/Ríos Rosas, 23, 28003 Madrid, Spain;2. Crystallography and Mineralogy Department, Complutense University of Madrid, C/Jose Antonio Novais, 2, 28040 Madrid, Spain;3. Instituto de Geociencias IGEO (CSIC, UCM), Madrid, Spain;4. Instituto Español de Oceanografía, C.O. de Málaga, Puerto Pesquero s/n, 29649 Fuengirola, Spain |
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| Abstract: | This study investigated Holocene and fossil hydrothermal manganese deposits in the Izu-Ogasawara arc. Mineralogically, these deposits comprise 10 Å and 7 Å manganate minerals, and the fossil samples showed higher 10 Å stabilities. Chemical compositions of the Holocene samples are typical of other hydrothermal manganese deposits, including low Fe/Mn ratios, low trace metals, and low rare earth elements. Although the fossil samples generally have similar chemical characteristics, they exhibit significant enrichment in Ni, Cu, Zn, Cd, Ba, REE, Tl, and Pb contents. Furthermore, the chondrite-normalized REE patterns showed more light REE enrichment trends. These chemical characteristics suggest post-depositional uptake of these metals from seawater. U-Th dating of a Holocene hydrothermal manganese deposit from the Kaikata Seamount indicated 8.8 ± 0.94 ka for the uppermost layer and downward growth beneath the seafloor with a growth rate of ca. 2 mm/kyr. This is approximately three orders of magnitude faster than that of hydrogenetic ferromanganese crusts. U-Pb age of a fossil hydrothermal manganese deposit from the Nishi-Jokyo Seamount showed 4.4 ± 1.6 Ma, which was contemporary with basaltic volcanism (5.8 ± 0.3 Ma). Hydrothermal manganese deposits contain high concentrations of high value Mn, but only small amounts of valuable minor metals; their ages constrain the periods of past hydrothermal activity and provide a vector to explore for polymetallic sulfide deposits. |
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