Japan Geoscience Union Meeting 2019

Presentation information

[E] Poster

S (Solid Earth Sciences ) » S-CG Complex & General

[S-CG49] Hard-Rock Drilling Science: From Continental to Deep Sea Drilling, and Oman Project

Tue. May 28, 2019 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall8, Makuhari Messe)

convener:Katsuyoshi Michibayashi(Department of Earth and Planetary Sciences, Nagoya University), Eiichi TAKAZAWA(Department of Geology, Faculty of Science, Niigata University), Norikatsu Akizawa(Department of Ocean Floor Geoscience, Atmosphere and Ocean Research Institute, The University of Tokyo)

[SCG49-P09] X-ray CT images of oceanic lithologies obtained on Oman Drilling Project drillcores during ChikyuOman 2017 and 2018

*Katsuyoshi Michibayashi1, Peter B Kelemen2, Margurette Godard3, Eiichi TAKAZAWA4, Damon A H Teagle5, The Oman Drilling Project Science Party6 (1.Department of Earth and Planetary Sciences, Nagoya University, 2.Columbia University, 3.Université Montpellier, 4.Niigata University, 5.Southampton University, 6.ICDP)

Keywords:OmanDP, XCT, image

The Oman Drilling Project (OmanDP) has drilled >3,200 meters of the Oman ophiolite during Phases 1 and 2 in Holes GT1A, GT2A, GT3A, BT1B, CM1A, CM2B, BA1B, BA3A and BA4A. All cores have been described on board D/V Chikyu during the summers of 2017 and 2018. X-ray computed tomography (X-ray CT) images were obtained on all cores as a routine part of the IODP measurement protocol onboard D/V Chikyu.

The X-ray CT scanner (Discovery CT 750HD, GE Medical Systems) scans and reconstructs an image of a 1.4 m section in 10 minutes and produces a series of scan images, each 0.625 mm thick. The X-ray source and detector are installed inside of the gantry opposite each other. The excitation voltage and current for X-ray tube are 140 kV and 100 mA, respectively. Core samples are scanned in the gantry with a scanning rate of 20 mm/sec. The distribution of attenuation values mapped to an individual slice comprises the raw data that are used for subsequent image processing. Successive two-dimensional (2D) slices of 512 x 512 pixels yield a representation of attenuation values in three-dimensional (3D) voxels of 512 x 512 by ~1600 in length. Data generated for each core consist of core-axis-normal planes (XY planes) of X-ray attenuation values with dimensions of 512 × 512 pixels in 9 cm × 9 cm cross-section, with a resolution of 0.176 mm/pixel.

As a consequence, we have >3,200 meters length of X-ray CT images from the dyke/gabbro transition zone to the gabbroic sequence to the mantle sequence to the basal thrust of the ophiolite. All X-ray CT images have been processed to match with individual photo images of the archive halves of the cores. The data are useful for assessing sample locations and quality. X-ray CT images can be used for 3D fabric analyses even after core has been cut in half and subsampled for other analyses.