Yuya Akamatsu , Tatsu Kuwatani, Ryosuke Oyanagi

To quantify the alteration processes of mantle from geophysical data, an understanding of the relationship between alteration and the physical properties of mantle peridotite is essential. In this study, we employed independent component analysis (ICA) to evaluate variations in the physical properties of altered peridotites collected by the Oman Drilling Project, to understand the alteration processes of mantle peridotite in the Samail ophiolite. We analyzed multivariate physical properties (density, porosity, P-wave velocity, electrical resistivity, permeability, magnetic susceptibility, and color reflectance) that had been measured on core samples. The ICA results show that the observed variations in physical properties can be explained broadly by four independent components. Through their relationships with physical properties and comparisons with petrological and geochemical data from previous studies, we infer the four independent components to represent distinct alteration processes: the early and late stages of serpentinization, magnetite formation, and near-surface carbonation. These processes develop differently during the overall process of alteration, and they influenced each physical property in different ways. Our results demonstrate that ICA can separate the effects of multiple processes of alteration on various physical properties of the altered peridotites, which previously had been difficult to quantify.