Depth-Dependent Permeability and Heat Output at Basalt-Hosted Hydrothermal Systems Across Mid-Ocean Ridge Spreading Rates
Type | Article | ||||||||
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Date | 2018-04 | ||||||||
Language | English | ||||||||
Author(s) | Barreyre Thibaut1, 2, Olive Jean-Arthur3, Crone Timothy J.4, Sohn Robert A.2 | ||||||||
Affiliation(s) | 1 : Univ Bergen, Dept Earth Sci, KG Jebsen Ctr Deep Sea Res, Bergen, Norway. 2 : Woods Hole Oceanog Inst, Woods Hole, MA 02543 ,USA. 3 : PSL Res Univ, Ecole Normale Super, Lab Geol, CNRS UMR 8538, Paris, France. 4 : Columbia Univ, Lamont Doherty Geol Observ, Palisades, NY 10964, USA. |
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Source | Geochemistry Geophysics Geosystems (1525-2027) (Amer Geophysical Union), 2018-04 , Vol. 19 , N. 4 , P. 1259-1281 | ||||||||
DOI | 10.1002/2017GC007152 | ||||||||
WOS© Times Cited | 17 | ||||||||
Keyword(s) | permeability, heat output, mid-ocean ridges, hydrothermal, poroelasticity | ||||||||
Abstract | The permeability of the oceanic crust exerts a primary influence on the vigor of hydrothermal circulation at mid-ocean ridges, but it is a difficult to measure parameter that varies with time, space, and geological setting. Here we develop an analytical model for the poroelastic response of hydrothermal exit-fluid velocities and temperatures to ocean tidal loading in a two-layered medium to constrain the discharge zone permeability of each layer. The top layer, corresponding to extrusive lithologies (e.g., seismic layer 2A) overlies a lower permeability layer, corresponding to intrusive lithologies (e.g., layer 2B). We apply the model to three basalt-hosted hydrothermal fields (i.e., Lucky Strike, Main Endeavour and 9 degrees 46N L-vent) for which the seismic stratigraphy is well-established, and for which robust exit-fluid temperature data are available. We find that the poroelastic response to tidal loading is primarily controlled by layer 2A permeability, which is about 3 orders of magnitude higher for the Lucky Strike site (approximate to 10(-10) m(2)) than the 9 degrees 46N L-vent site (approximate to 10(-13) m(2)). By contrast, layer 2B permeability does not exert a strong control on the poroelastic response to tidal loading, yet strongly modulates the heat output of hydrothermal discharge zones. Taking these constraints into account, we estimate a plausible range of layer 2B permeability between approximate to 10(-15) m(2) and an upper-bound value of approximate to 10(-14) (9 degrees 46N L-vent) to approximate to 10(-12) m(2) (Lucky Strike). These permeability structures reconcile the short-term response and long-term thermal output of hydrothermal sites, and provide new insights into the links between permeability and tectono-magmatic processes along the global mid-ocean ridge. |
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