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Selected Works of Susan DeBari
Article
The missing half of the subduction factory: shipboard results from the Izu rear arc, IODP Expedition 350
International Geology Review (2017)
  • Cathy J. Busby, University of California, Davis
  • Yoshihiko Tamura, Japan Agency for Marine-Earth Science and Technology
  • Peter Blum, Texas A&M University
  • Gilles Guèrin, Lamont–Doherty Earth Observatory
  • Graham D. M. Andrews, West Virginia University
  • Abigail K. Barker, Uppsala University
  • Julien L. R. Berger, Paul Sabatier University
  • Everton M. Bongiolo, Federal University of Rio de Janeiro
  • Manuela Bordiga, Uppsala University
  • Susan M. DeBari, Western Washington University
  • James B. Gill, University of California, Santa Cruz
  • Cedric Hamelin, University of Bergen
  • Jihui Jia, Kyoto University
  • Eleanor H. John, University of the South Pacific
  • Ann-Sophie Jonas, University of Kiel
  • Martin Jutzeler, University of Tasmania
  • Myriam A. C. Kars, Kōchi University
  • Zachary A. Kita, University of Nebraska–Lincoln
  • Kevin Konrad, Oregon State University
  • Susan H. Mahony, University of Bristol
  • Michelangelo Martini, National Autonomous University of Mexico
  • Takashi Miyazaki, Japan Agency for Marine-Earth Science and Technology
  • Robert J. Musgrave, University of Sydney
  • Debora B. Nascimento, Federal University of Rio de Janeiro
  • Alexander R. L. Nichols, University of Canterbury
  • Julia M. Ribeiro, Rice University
  • Tomoki Sato, Japan Agency for Marine-Earth Science and Technology
  • Julie C. Schindlbeck, GEOMAR Helmholtz Center for Ocean Research Kiel, Kiel, Germany
  • Axel K. Schmitt, Heidelberg University
  • Susanne M. Straub, Lamont–Doherty Earth Observatory
  • Maryline J. Mleneck-Vautravers, University of Cambridge
  • Alexandra Yang Yang, Chinese Academy of Sciences
Link
Abstract
IODP Expedition 350 was the first to be drilled in the rear part of the Izu-Bonin, although several sites had been drilled in the arc axis to fore-arc region; the scientific objective was to understand the evolution of the Izu rear arc, by drilling a deep-water volcaniclastic section with a long temporal record (Site U1437). The Izu rear arc is dominated by a series of basaltic to dacitic seamount chains up to ~100-km long roughly perpendicular to the arc front. Dredge samples from these are geochemically distinct from arc front rocks, and drilling was undertaken to understand this arc asymmetry. Site U1437 lies in an ~20-km-wide basin between two rear arc seamount chains, ~90-km west of the arc front, and was drilled to 1804 m below the sea floor (mbsf) with excellent recovery. We expected to drill a volcaniclastic apron, but the section is much more mud-rich than expected (~60%), and the remaining fraction of the section is much finer-grained than predicted from its position within the Izu arc, composed half of ashes/tuffs, and half of lapilli tuffs of fine grain size (clasts <3 cm). Volcanic blocks (>6.4 cm) are only sparsely scattered through the lowermost 25% of the section, and only one igneous unit was encountered, a rhyolite peperite intrusion at ~1390 mbsf. The lowest biostratigaphic datum is at 867 mbsf (~6.5 Ma), the lowest palaeomagnetic datum is at ~1300 mbsf (~9 Ma), and the rhyolite peperite at ~1390 mbsf has yielded a U–Pb zircon concordia intercept age of (13.6 + 1.6/−1.7) Ma. Both arc front and rear arc sources contributed to the fine-grained (distal) tephras of the upper 1320 m, but the coarse-grained (proximal) volcaniclastics in the lowest 25% of the section are geochemically similar to the arc front, suggesting arc asymmetry is not recorded in rocks older than ~13 Ma.
Keywords
  • International Ocean Discovery Program,
  • Izu-Bonin-Marianas arc,
  • island arcs,
  • magmatic arcs,
  • rear arc,
  • Japanese volcanoes
Disciplines
Publication Date
October 3, 2017
DOI
10.1080/00206814.2017.1292469
Publisher Statement
Published by Taylor & Francis Group
Citation Information
Cathy J. Busby, Yoshihiko Tamura, Peter Blum, Gilles Guèrin, et al.. "The missing half of the subduction factory: shipboard results from the Izu rear arc, IODP Expedition 350" International Geology Review Vol. 59 Iss. 13 (2017) p. 1677 - 1708
Available at: http://works.bepress.com/susan-debari/5/