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The Expedition 366 Scientists, 2017 International Ocean Discovery Program Expedition 366 Preliminary Report Mariana Convergent Margin and South Chamorro Seamount 8 December 2016 to 7 February 2017 Patricia Fryer, Geoffrey Wheat, Trevor Williams, and the Expedition 366 Scientists Publisher’s notes Core samples and the wider set of data from the science program covered in this report are under moratorium and accessible only to Science Party members until 7 February 2018. This publication was prepared by the JOIDES Resolution Science Operator (JRSO) at Texas A&M University (TAMU) as an account of work performed under the International Ocean Discovery Program (IODP). Funding for IODP is provided by the following international partners: National Science Foundation (NSF), United States Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan European Consortium for Ocean Research Drilling (ECORD) Ministry of Science and Technology (MOST), People’s Republic of China Korea Institute of Geoscience and Mineral Resources (KIGAM) Australia-New Zealand IODP Consortium (ANZIC) Ministry of Earth Sciences (MoES), India Coordination for Improvement of Higher Education Personnel (CAPES), Brazil Portions of this work may have been published in whole or in part in other IODP documents or publications. Disclaimer Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the participating agencies, TAMU, or Texas A&M Research Foundation. Copyright Except where otherwise noted, this work is licensed under a Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/deed.en_US). Unrestricted use, distribution, and reproduction are permitted, provided the original author and source are credited. Citation Fryer, P., Wheat, G., Williams, T., and the Expedition 366 Scientists, 2017. Expedition 366 Preliminary Report: Mari- ana Convergent Margin and South Chamorro Seamount. International Ocean Discovery Program. https://doi.org/10.14379/iodp.pr.366.2017 ISSN World Wide Web: 2372-9562 November 2017 P. Fryer et al. Expedition 366 Preliminary Report Expedition 366 participants Expedition 366 scientists Patricia B. Fryer Yanhui Dong Co-Chief Scientist Core Description Hawaii Institute of Geophysics and Planetology/SOEST Key Laboratory of Submarine Geoscience University of Hawaii at Manoa Second Institute of Oceanography, State Oceanic USA Administration [email protected] China [email protected] C. Geoffrey Wheat Co-Chief Scientist Philip Eickenbusch College of Fisheries and Ocean Sciences Microbiologist University of Alaska Fairbanks Department of Environmental Systems Science USA ETH Zurich [email protected] Switzerland [email protected] Trevor Williams Expedition Project Manager/Staff Scientist Emanuelle A. Frery International Ocean Discovery Program Core Description Texas A&M University Commonwealth Scientific and Industrial Research Organisation USA Australia [email protected] [email protected] Elmar J. Albers Yuji Ichiyama Core Description Core Description Department of Geosciences Department of Earth Sciences University of Bremen Chiba University Germany Japan [email protected] [email protected] Barbara Bekins Kevin Johnson Petrophysics Specialist/ Downhole Tools Specialist Core Description Water Resources Department of Geology and Geophysics United States Geological Survey University of Hawaii at Mānoa USA USA [email protected] [email protected] Vitor Magalhaes Raymond M. Johnston Physical Properties Specialist Core Description Marine Geology and Georesources School of Geosciences Instituto Português do Mar e da Atmosfera University of South Florida, Tampa Portugal USA [email protected] [email protected] Baptiste P.R. Debret Richard T. Kevorkian Core Description Microbiologist Department of Earth Sciences Department of Microbiology University of Cambridge University of Tennessee United Kingdom USA [email protected] [email protected] Jianghong Deng Walter Kurz Core Description Igneous Petrologist/Metamorphic Petrologist School of Earth and Space Sciences Institute of Earth Sciences University of Science and Technology of China University of Graz China Austria [email protected] [email protected] IODP Proceedings 3Volume 366 P. Fryer et al. Expedition 366 Preliminary Report Simone S. Mantovanelli Roy E. Price Paleomagnetist Inorganic Geochemist Oceanographic Institute of São Paulo University School of Marine and Atmospheric Sciences Brazil State University of New York, Stony Brook [email protected] USA [email protected] Walter Menapace Petrophysics Specialist Jeffrey G. Ryan Marine Engineering Geology/Marine Geotechnics Inorganic Geochemist University of Bremen School of Geosciences Germany University of South Florida, Tampa [email protected] USA [email protected] Catriona D. Menzies Inorganic Geochemist John W. Shervais Ocean and Earth Science Igneous Petrologist National Oceanography Centre Department of Geology University of Southampton Utah State University United Kingdom USA [email protected] [email protected] Katsuyoshi Michibayashi Olivier J. Sissmann Core Description Organic Geochemist Institute of Geosciences IFP Energies Nouvelles Shizuoka University France Japan [email protected] [email protected] Shino Suzuki Craig L. Moyer Microbiologist Microbiologist Japan Agency for Marine-Earth Science and Technology Biology Department Japan Western Washington University [email protected] USA Ken Takai [email protected] Microbiologist Kelli K. Mullane Subground Animalcule Retrieval Project Microbiologist Japan Agency for Marine-Earth Science and Technology Scripps Institution of Oceanography Japan University of California, San Diego [email protected] USA Bastien Walter [email protected] Petrophysics Specialist Jung-Woo Park Ecole Nationale Superieure de Geologie Core Description Universite de Lorraine School of Earth and Environmental Sciences France Seoul National University [email protected] Republic of Korea Rui Zhang [email protected] Microbiologist State Key Laboratory of Marine Environmental Sciences Xiamen University China [email protected] Education/Outreach Officers Martin Böttcher Kristen Weiss Rabanus-Maurus-Schule Center for Ocean Solutions Fulda Stanford University Germany USA [email protected] [email protected] Siem offshore AS officials Steve Bradley Wayne Malone Master of the Drilling Vessel Offshore Installation Manager IODP Proceedings 4Volume 366 P. Fryer et al. Expedition 366 Preliminary Report JRSO shipboard personnel and technical representatives Timothy Blaisdell Rhonda Kappler Applications Developer Publications Specialist Lisa Brandt Nicolette Lawler Chemistry Laboratory X-Ray Laboratory Lisa Crowder Brittany Martinez Assistant Laboratory Officer Curatorial Specialist Aaron de Loach Aaron Mechler Core Laboratory Chemistry Laboratory Keith Dupuis Mike Meiring Underway Geophysics Laboratory Electronics Specialist Timothy Fulton William Mills Imaging Specialist Laboratory Officer Clayton Furman Beth Novak Schlumberger Logging Engineer Paleomagnetism Laboratory Randy Gjesvold Bill Rhinehart Marine Instrumentation Specialist Drilling Engineer Sandra Herrmann Patrick Riley Assistant Laboratory Officer Core Laboratory (temporary) Michael Hodge Michael Storms Marine Computer Specialist Operations Superintendent Jon Howell Johanna Suhonen Applications Developer Thin Section Laboratory (temporary) Minh Nhut Huynh Garrick Van Rensburg Marine Computer Specialist Marine Instrumentation Specialist IODP Proceedings 5Volume 366 P. Fryer et al. Expedition 366 Preliminary Report Abstract three seamounts drilled during Expedition 366, as well as those from Legs 125 and 195, include material from the underlying Pacific Geologic processes at convergent plate margins control geo- plate. A thin cover of pelagic sediment was recovered at many Expe- chemical cycling, seismicity, and deep biosphere activity in sub- dition 366 sites, and at Site U1498 we cored through serpentinite duction zones and suprasubduction zone lithosphere. International flows to the underlying pelagic sediment and volcanic ash deposits. Ocean Discovery Program (IODP) Expedition 366 was designed to Recovered serpentinites are largely uniform in major element com- address the nature of these processes in the shallow to intermediate position, with serpentinized ultramafic rocks and serpentinite muds depth of the Mariana subduction channel. Although no technology spanning a limited range in SiO2, MgO, and Fe2O3 compositions. is available to permit direct sampling of the subduction channel of However, variation in trace element composition reflects pore fluid an intraoceanic convergent margin at depths up to 18 km, the Mar- composition, which differs as a function of the temperature and iana forearc region (between the trench and the active volcanic arc) pressure of the underlying subduction channel. Dissolved gases H2, provides a means to access this zone. CH4, and C2H6 are highest at the site furthest from the trench, Active conduits, resulting from fractures in the forearc, are which also has the most active fluid discharge of the Expedition 366 prompted by along- and across-strike extension that allows slab-de- serpentinite mud volcanoes. These dissolved gases and their active rived fluids and materials to ascend to the seafloor along associated discharge from depth likely support active microbial communities,
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