Diagenetic, metamorphic, and hydrogeologic consequences of hydrothermal circulation in subducting crust

Heat Flow Evidence for Hydrothermal Circulation in Oceanic Crust Offshore Grays Harbor, Washington

“…Our models are consistent with the idea that hydrothermal circulation is present within the subducting oceanic crust and that this hydrothermal circulation brings heat seaward of the deformation front (Cozzens and Spinelli, 2008;Spinelli et al, 2018) Their models were constructed to estimate the thermal regime landward of the deformation front such that the thermal regime is consistent with the seismically imaged basalt-to-eclogite transition. Details of this methodology are given by Spinelli et al (2018) and solutions were parameterized in terms of aquifer permeability by relating the Rayleigh number to Nu. Models that best fit the basalt to eclogite transition have pre-subduction permeabilities between -10 and 10 -9 m 2 , consistent with permeability measurements in the FlankFlux area (Becker and Davis, 2004).…”

“…Along Line 5, qsed values are well fit by these models if the crustal aquifer has a high Nu (Figure 7b). These models suggest that to fit both Group A and B qsed values, additional heat may be introduced to the system by seaward transport of heat from the subducting crustal aquifer (Cozzens and Spinelli, 2012;Spinelli et al, 2018).…”

“…In many thermal models of subduction, the temperature of the incoming plate is parameterized in terms of a conductively cooling plate. In warm subduction zones where young oceanic crust is being subducted, such as Cascadia, ongoing hydrothermal circulation in the subducting oceanic crust can modify the crustal geotherm relative to conductive predictions prior to subduction, and can also play a substantial role in modulating temperatures along the plate interface (Spinelli and Wang, 2008;Rotman and Spinelli, 2013;Harris et al, 2017;Spinelli et al, 2018).…”

“…A wider seismogenic zone can increase the hazard of both deep and shallow earthquakes. These models were augmented by exploring how hydrothermal circulation in subducting crust could impact plate interface temperatures (Cozzens and Spinelli, 2012;Spinelli et al, 2018). These later studies found that fluid flow within the upper 600 m of the subducting oceanic crust broadens the thermally defined seismogenic zone by shifting the 350 °C isotherm on the plate boundary 30 to 50 km landward relative to models without fluid flow.…”

Coupled Evolution of Deformation, Pore Fluid Pressure, and Fluid Flow in Shallow Subduction Forearcs

“…Abundant thermal and hydrological observations suggest vigorous hydrothermal circulation in the oceanic slab at numerous margins (Davis et al, 1997; Harris et al, 2017; Spinelli et al, 2018; Spinelli & Wang, 2008). This is likely related to the presence of permeable fractures and pillow boundaries (e.g., Becker & Davis, 2004) and the high density of bending‐related normal faults near the outer rise (Ranero et al, 2003).…”