Composition of clay minerals from mudstones in the Nankai accretionary prism, Tenryu and Shiono-misaki Canyons

Author(s): Underwood, M. B.; Guo, J.; Kawamura, K.; Ogawa, Y.; Moore, G. F.
Author Affiliation(s): Primary:
University of Missouri, Department of Geological Sciences, Columbia, MO, United States
Other:
Fukada Geological Institute, Japan
University of Tsukuba, Japan
Japan Agency for Marine-Earth Science and Technology, Japan
Volume Title: AGU 2006 fall meeting
Source: Eos, Transactions, American Geophysical Union, 87( Fall Meeting Suppl.); American Geophysical Union 2006 fall meeting, San Francisco, CA, Dec. 11-15, 2006. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0096-3941 CODEN: EOSTAJ
Note: In English. Accessed on Oct. 16, 2007
Summary: Recent submersible surveys using KAIKO and Shinkai 6500 resulted in the successful extraction of lithified rock samples from the sidewalls of Tenyru and Shiono-misaki Canyons. Both canyons are deeply incised into the accretionary prism of eastern Nankai Trough, offshore Omaezaki and Kii Peninsula, respectively. The relative heights between adjacent terrace plains and the present canyon bottoms range from 100 to 1200 m. Thus, canyon incision has exposed stratigraphic thicknesses within the accretionary prism comparable to those cored during drilling legs of the Ocean Drilling Program. Quantitative X-ray diffraction analyses show that the suite of mudstone samples contains highly variable proportions of smectite in the clay-size fraction. Percentages of smectite range from 15% to 100% (relative to illite + chlorite + quartz). Twenty-three out of the 43 specimens analyzed contain between 35% and 84% smectite. This discovery has important implications for the forthcoming IODP drilling expeditions associated with the Nankai Trough Seismogenic Zone Experiment. It seems likely that inputs to the subduction zone within the NanTroSEIZE transect area (Kii-Kumano) contain high proportions of detrital smectite, similar to what has been documented in Miocene strata along the Ashizuri transect. Smectite-rich mudstones are particularly important and commonplace within the lower Shikoku Basin facies, which is the interval through which the decollement propagates. Consequently, the subduction zone's fluid-production budgets, as well as pore pressure distributions within and beneath the plate boundary fault, are modulated by the release of interlayer water as the smectite-to-illite reaction progresses in the down-dip direction.
Year of Publication: 2006
Research Program: IODP Integrated Ocean Drilling Program
ODP Ocean Drilling Program
Key Words: 06 Petrology, Sedimentary; Accretionary wedges; Canyons; Clastic rocks; Clay mineralogy; Clay minerals; Illite; Integrated Ocean Drilling Program; Marine sediments; Mineral interlayer; Mudstone; Nankai Trough; North Pacific; Northwest Pacific; Ocean Drilling Program; Pacific Ocean; Pore pressure; Sedimentary rocks; Sediments; Sheet silicates; Shiono-misaki Canyon; Silicates; Smectite; Subduction zones; Tenryu Canyon; West Pacific
Record ID: 2009096210
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute.

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