Paleo‐Permeability Structure of the Crustal Section of the Samail Ophiolite Based on Automated Detection of Veins in X‐Ray CT Core Images From the Oman Drilling Project

Abstract

Water transported into an oceanic plate plays a key role in various geochemical and geophysical processes, such as global transfers of heat and elements moving with fluid (Müller & Dutkiewicz, 2018;Stein & Stein, 1994) and magmatic and seismic activities at subduction zones (Hacker, 2008;Peacock, 2001). The water is supplied mainly through fractures and faults in the oceanic crust that are formed by tectonic and thermal stresses (Faccenda, 2014;Korenaga, 2007). It is, therefore, important to characterize fractures in the interior of the crust if we are to understand fluid behavior in the oceanic lithosphere.Permeability is a measure of the ease of fluid flow in a rock, and it is an important physical property for constraining the flow rate and mechanism of fluid circulation in oceanic plates (Guéguen & Palciauskas, 1994). To

Spatial Heterogeneity of Pore Structure in the Crustal Section of the Samail Ophiolite: Implications for High VP/VS Anomalies in Subducting Oceanic Crust

“…However, natural geological systems likely contain multiple scales of porosity structures, as opposed to just microscopic pores and cracks (Bailly et al., 2019; Ringrose et al., 2008). The core samples from Hole GT3A contain numerous millimeter‐wide mineral veins, which could be interpreted as cracks that once acted as fluid pathways within the oceanic crust (Akamatsu, Katayama, et al., 2023). Such cracks may have much higher permeabilities of up to ∼10 −10 m 2 (Akamatsu, Katayama, et al., 2023; Hosono et al., 2022; Ioannou & Spooner, 2007), as permeability is strongly dependent on the crack aperture (Guéguen & Palciauskas, 1994).…”

“…The core samples from Hole GT3A contain numerous millimeter‐wide mineral veins, which could be interpreted as cracks that once acted as fluid pathways within the oceanic crust (Akamatsu, Katayama, et al., 2023). Such cracks may have much higher permeabilities of up to ∼10 −10 m 2 (Akamatsu, Katayama, et al., 2023; Hosono et al., 2022; Ioannou & Spooner, 2007), as permeability is strongly dependent on the crack aperture (Guéguen & Palciauskas, 1994). WIFF can rapidly spread within a given REV that possesses such a high permeability, even though both the scale of heterogeneity and REV of the large‐scale cracks might be a few orders of magnitude larger than those of microcracks (Bailly et al., 2019; Koike & Ichikawa, 2006).…”