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Major mineral fraction and physical properties of carbonated peridotite (listvenite) from ICDP Oman Drilling Project Hole BT1B inferred from X-ray CT core images
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  • Keishi Okazaki,
  • Katsuyoshi Michibayashi,
  • Kohei Hatakeyama,
  • Natsue Abe,
  • Kevin TM Johnson,
  • Peter B Kelemen
Keishi Okazaki
Japan Agency for Marine-Earth Science and Technology

Corresponding Author:[email protected]

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Katsuyoshi Michibayashi
Nagoya University
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Kohei Hatakeyama
Hiroshima University
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Natsue Abe
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Kevin TM Johnson
National Science Foundation
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Peter B Kelemen
Columbia University
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We evaluated the mineral fractions of listvenite (completely carbonated peridotite) in Hole BT1B drilled by the ICDP Oman Drilling Project from 3D X-ray Computed Tomography (XCT) images. Total >250,000 XCT images from continuous ~200 m listvenite core samples were analyzed. Histograms of the intensity of X-ray attenuation (XCT number) of each XCT core-slice image were fitted assuming that the CT histogram is composed of magnesite, quartz, and dolomite peaks. These mineral peaks were confirmed by comparison of XCT numbers with chemical mapping data obtained using an XRF core scanner. In most core sections, XCT data indicate that listvenite matrix is composed of magnesite and quartz, consistent with discrete XRD and XRF data. Veins are composed mostly of dolomite. The mean abundance of dolomite in listvenite from BT1B is 11 vol.%, whereas that in core sections within 15 m of the basal thrust is >50 vol.%, suggesting that the basal thrust acted as a pathway for Ca- and CO fraction than that of Oman peridotite (39:60:1), indicating enrichment of Si during carbonation. P- and S-wave velocities and density of listvenite is close to that of peridotite while higher than that of serpentinites. These results suggest that limited material transfer during carbonation and hydration of the Oman Ophiolite, except for Si, Ca, CO2 and H2O, but potential as an overlooked carrier of CO2 into the deep of Earth’s interior.
Dec 2021Published in Journal of Geophysical Research: Solid Earth volume 126 issue 12. 10.1029/2021JB022719