Spatiotemporal characterization of smectite-to-illite diagenesis in the Nankai Trough accretionary prism revealed by samples from 3 km below seafloor

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doi: 10.1029/2018GC008015
Author(s): Hüpers, A.; Grathoff, G.; Warr, L. N.; Wemmer, K.; Spinelli, Glenn; Underwood, Michael B.
Author Affiliation(s): Primary:
University of Bremen, MARUM-Center for Marine Environmental Sciences, Bremen, Germany
University of Greifswald, Germany
New Mexico Institute of Mining and Technology, United States
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 20(2), p.933-951. Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English. 95 refs.; illus., incl. sect., 1 table, sketch map
Summary: The up-dip limit of seismogenesis in subduction zone forearcs depends on the lithological composition of the incoming sediment and its subsequent modification during compaction and diagenesis. Here we present results of a multimethodological approach to characterize the smectite-to-illite diagenesis in the accretionary prism of the Nankai Trough subduction zone offshore SW Japan. Our X-ray diffraction analysis, scanning electron microscopy, and transmission electron microscopy clay mineralogical analysis reveal that advanced states of smectite-to-illlite diagenesis occur in samples recovered from down to 3 km subseafloor at Integrated Ocean Drilling Program Site C0002, which sampled the inner accretionary prism. Our temperature- and time-dependent reaction kinetics models require elevated temperatures in the prism to explain the illitization, which is consistent with revised thermal models based on recent plate reconstructions. Biostratigraphic data suggest that the inner prism sediment was deposited during a period of slow or inactive subduction and buried in the accretionary prism after the Philippine Sea plate resumed subduction. Rapid burial in the past 6 Ma led to the formation of two authigenic smectite-illite phases consistent with a broad 1-9.3 Ma age determined by K-Ar dating. The low K+ smectite-illite reflects the long-term burial history, whereas the K+-rich smectite-illite was inherited from the younger accretion event. Our study predicts the illitization of smectite approaches completion at ∼5 km below the seafloor in the hanging wall of the plate boundary and the megasplay fault zone, respectively, which coincides with the proposed seaward extent of coseismic slip in the 1944 Mw=8.1 Tonankai earthquake along those faults. Abstract Copyright (2019). American Geophysical Union. All Rights Reserved.
Year of Publication: 2019
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; 18 Geophysics, Solid-Earth; Absolute age; Accretionary wedges; Biostratigraphy; Cenozoic; Clay minerals; Dates; Diagenesis; Earthquakes; Electron microscopy data; Expedition 316; Expedition 319; Faults; IODP Site C0002; IODP Site C0004; IODP Site C0007; IODP Site C0009; IODP Site C0011; IODP Site C0012; Illite; Integrated Ocean Drilling Program; K/Ar; Kumano Basin; NanTroSEIZE; Nankai Trough; North Pacific; Northwest Pacific; Ocean floors; Pacific Ocean; Plate tectonics; Plates; Quaternary; Sheet silicates; Shikoku Basin; Silicates; Slip rates; Smectite; TEM data; Tonankai earthquake 1944; West Pacific; X-ray diffraction data
Coordinates: N320000 N340000 E1380000 E1350000
Record ID: 2019066571
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom, Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union