Major mineral fraction and physical properties of carbonated peridotite
(listvenite) from ICDP Oman Drilling Project Hole BT1B inferred from
X-ray CT core images
Abstract
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.