Flow rate perturbations in a black smoker hydrothermal vent in response to a mid‐ocean ridge earthquake swarm

Abstract

[1] Although there is indirect evidence for strong connections between tectonic processes and mid-ocean ridge hydrothermal flow, there are no direct observations of these links, primarily because measuring flow in these systems is difficult. Here we use an optical analysis technique to obtain a 44 day record of flow rate changes in a black smoker vent in the Main Endeavour field of the Juan de Fuca Ridge. We show that variations in the flow rate coincide with an earthquake swarm observed using an ocean bottom seismometer array. These observations indicate that connections between tectonics and flow are indeed strong, that hydraulic connections within this hydrothermal system are long ranging, and that enhanced tidal pumping of fluids may be initiated by earthquake activity. Because the effects of the swarm cross over an intervening vent field, we infer that the upflow zones feeding this field are narrow. Using the time lag between the swarm onset and the flow rate changes we estimate that the bulk permeability of the crust on the Endeavour segment ranges from 3.0 × 10 −13 m 2 to 6.0 × 10 −12 m 2 .

Permeability of the Lucky Strike deep-sea hydrothermal system: Constraints from the poroelastic response to ocean tidal loading

“…Our estimate is somewhat higher than the values obtained by methods that consider the entire crustal column, which is to be expected considering that permeabilities are highest in the extrusive layer. For example, permeability values of ∼10 −13 -10 −11 m 2 have been obtained by matching analytical flow models to heat flow data (Wilcock and McNabb, 1996;Lowell and Germanovich, 2004), values of 3.10 −13 -6.10 −12 m 2 have been derived by modeling flow rate perturbations generated by earthquake swarms at the JdFR Endeavour field (Crone et al, 2010), values of 3.10 −11 -2.10 −14 m 2 have been determined with drill-string packer experiments at the eastern flank of the JdFR (Becker and Fisher, 2000), and values of 10 −13.4 -10 −9.4 m 2 have been obtained by modeling crustal stresses inferred from poroelastically triggered earthquakes at the EPR 9 • 50 N field (Crone et al, 2011). All of these estimates, including ours, were derived by fitting an observable (e.g., phase lag, heat flow, earthquake migration) to a model, such that the accuracy of the parameter estimates depends largely on the model applicability and accuracy.…”

Review of flow rate estimates of the Deepwater Horizon oil spill

“…Oceanographers had experience in quantifying flow rates from deep sea hydrothermal vents at midocean ridges (4,5), but methods developed from those environments had not previously been applied to mixtures of oil, gas, and water. Thus, a variety of approaches were pursued.…”

Subsurface conditions in hydrothermal vents inferred from diffuse flow composition, and models of reaction and transport

“…While we do not know the required porosity reduction for anhydrite formation to shut off circulation, the above estimates suggest that it is unlikely that these calculated deposition rates are sufficiently fast to seal off flow channels (even with our relatively small required porosity reduction). Tectonic and magmatic events at both intermediate (Dziak et al, 2011) and fast-spreading (Fornari et al, 2012) mid-ocean ridges occur on timescales shorter than our calculated sealing times, and these events have the potential to control the extent of permeability change and its impact on subsurface flow either by mechanically breaking anhydrite barriers (Crone et al, 2010;Germanovich et al, 2011) or by producing high temperature vapor-rich fluid that can dissolve these barriers (Blounot and Dickson, 1969;Von Damm et al, 1997).…”