Fracture Analysis of a Volcanogenic Massive Sulfide-Related Hydrothermal Cracking Zone, Upper Bell River Complex, Matagami, Quebec: Application of Permeability Tensor Theory

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

“…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 . Such cracks may have much higher permeabilities of up to ∼10 10 m 2 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, While the pore-pressure condition for microscopic crack/pore networks remains unrelaxed, that for the large-scale crack networks could be undrained for relatively low-frequency sonic/seismic velocities if the REV length of the large-scale cracks is less than several tens of meters.…”

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

“…The following assumptions were made when estimating paleo‐permeability using the equivalent channel model and permeability tensor theory, based on the work of previous researchers (Ioannou & Spooner, 2007). The host rock is generally intact and fluid flow occurs only along fractures.…”

“…This value is several orders of magnitude lower than the maximum model permeabilities in our calculations, including the paleo‐permeability of the HCT vein system in Hole GT3A, which corresponds to the sheeted dike complex of the Samail ophiolite. This difference indicates that the fractures become filled with minerals deposited by circulating hydrothermal fluids, which lowers the aperture ($$t$$) and alters the geometry of the fracture network ($$\tau $$), resulting in lower permeability in the present‐day oceanic crust (Fisher, 1998; Gilbert et al., 2018; Ioannou & Spooner, 2007; Nehlig et al., 1994; van Everdingen, 1995). However, our calculations show that the lower oceanic crust, as well as the upper crust, may have had markedly high permeability immediately after the formation of fractures related to the HCT and LCT vein systems.…”

“…Given these assumptions, the permeabilities modeled should be interpreted as a first‐order approximation of the maximum values for each vein system (Gilbert et al., 2018; Ioannou & Spooner, 2007). The magnitude and spatial variations of the calculated permeabilities for each vein system are then compared with permeabilities measured directly in the laboratory and within the in situ oceanic crust.…”

New insights into the genesis of volcanic-hosted massive sulfide deposits on the seafloor from numerical modeling studies

“…The latest notable additions are the inclusion of free-oriented discreet fractures (Yang and Large, 2001), a more detailed stratigraphy and permeability distinction (e.g., Barrie et al, 1999b), the role of anhydrite and quartz in seafloor hydrothermal systems (Martin and Lowell, 2000;Lowell and Yao, 2002;Lowell et al, 2003), 3-D numerical modeling by Rabinowicz et al (1998) and Fontaine et al (2001) or rock permeability tensor calculations (Ioannou and Spooner, 2007). These recent models can yield specific information and place constraints on certain features such as rock permeability or the system life span and help to explain certain features of individual deposits like the size and distribution of orebodies or the nature and depth of the heat source (Cathles et al, 1997;Barrie et al, 1999b).…”