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doi:10.2204/iodp.proc.314315316.215.2011

Data report: magnetic property studies of sediments and rocks from IODP Expedition 316¹

Xixi Zhao² and Yujin Kitamura³

Abstract

In this report, we present paleomagnetic and rock magnetic results from samples recovered during Integrated Ocean Drilling Program Expedition 316. Expedition 316 was designed to evaluate the deformation, inferred depth of detachment, structural partitioning, and fault zone physical characteristics and fluid flow of the Nankai Trough seismogenic zone in the Philippine Sea, off the east coast of southwestern Japan. Drilling was conducted at two sites in the megasplay region (Sites C0004 and C0008) and two sites within the frontal thrust region (Sites C0006 and C0007). Progressive demagnetization experiments conducted on discrete rock samples demonstrate that these rocks contain a stable natural remanent magnetization of both polarities, with unblocking temperatures slightly below the Curie temperature of magnetite. Two general types of behavior were found in the rock magnetic measurements of Expedition 316 cores. One group has a single phase of Ti-poor titanomagnetite. Several representative samples of this titanomagnetite group exhibit a Verwey transition in the vicinity of 120 K, which is in good agreement with the thermomagnetic characteristics of titanomagnetites with Curie temperatures of ~580°C that were identified. The second group is characterized by more than one Curie temperature, which suggests the presence of multiple magnetic phases. Thermomagnetic signatures indicate the inversion of titanomaghemite to a strongly magnetized magnetite and hysteresis ratios clustering toward the multidomain region (with higher H_cr/H_c ratios). The samples analyzed in this study indicate that rock samples from Expedition 316 sites have general good magnetic stability, supporting the inference that the characteristic directions of magnetization isolated from the Nankai Trough drill sites were acquired during original deposition and the stable inclinations identified from these samples are useful for tectonic studies.

¹ Zhao, X., and Kitamura, Y., 2011. Data report: magnetic property studies of sediments and rocks from IODP Expedition 316. In Kinoshita, M., Tobin, H., Ashi, J., Kimura, G., Lallemant, S., Screaton, E.J., Curewitz, D., Masago, H., Moe, K.T., and the Expedition 314/315/316 Scientists, Proc. IODP, 314/315/316: Washington, DC (Integrated Ocean Drilling Program Management International, Inc.). doi:10.2204/​iodp.proc.314315316.215.2011

² Center for the Study of Imaging and Dynamics of the Earth, Institute of Geophysics and Planetary Physics, University of California, Santa Cruz CA 95064, USA. xzhao@ucsc.edu

³ Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan.

Initial receipt: 29 October 2010
Acceptance: 28 July 2011
Publication: 2 November 2011
MS 314315316-215

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