Letter abstract
Nature Geoscience 1, 611 - 614 (2008)
Published online: 1 August 2008 | doi:10.1038/ngeo264
Subject Categories: Oceanography | Structural geology, tectonics and geodynamics
Large heat and fluid fluxes driven through mid-plate outcrops on ocean crust
M. Hutnak1, A. T. Fisher1, R. Harris2, C. Stein3, K. Wang4, G. Spinelli5, M. Schindler6, H. Villinger7 & E. Silver1
Hydrothermal circulation on the sea floor at mid-ocean ridge flanks extracts 
30% of heat from the oceanic lithosphere on a global basis1 and affects numerous tectonic, magmatic and biogeochemical processes2, 3, 4. However, the magnitude, mechanisms and implications of regional-scale fluid and heat flow on mid-ocean ridge flanks are poorly understood. Here we analyse swath-map, seismic and sea-floor heat-flux data to quantify the heat and fluid discharge through a few widely spaced basement outcrops on the Cocos Plate. Heat removed by conduction from a 14,500 square kilometre region of the sea floor is 60–90% lower than that predicted by lithospheric cooling models. This implies that a substantial portion of the heat is extracted by advection, which requires fluid discharge of 4–80
103 litres per second. The heat output of individual discharging outcrops is inferred to be comparable to that from black-smoker vent fields seen on mid-ocean ridges. Our analysis shows that hydrothermal circulation on mid-ocean ridge flanks through widely spaced outcrops can extract a large fraction of lithospheric heat. This circulation requires a very high crustal permeability at a regional scale. Focused flows of warm, nutrient-rich hydrothermal fluid may enhance sub-seafloor microbial habitats5, 6 and enable direct sampling of these systems.
- Department of Earth and Planetary Sciences and Institute for Geophysics and Planetary Physics, University of California Santa Cruz, Santa Cruz, California 95064, USA
- College of Ocean and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA
- Department of Earth and Environmental Sciences, University of Illinois at Chicago, Chicago, Illinois 60607, USA
- Pacific Geoscience Centre, Geological Survey of Canada, Sydney, BC, V8L 4B2, Canada
- Department of Earth and Environmental Science, New Mexico Tech, Socorro, New Mexico 87801, USA
- FB Federal Institute for Geosciences and Natural Resources (BGR), 30655 Hannover, Germany
- FB Geowissenschaften, Universität Bremen, Klagenfurter Strasse, 28359 Bremen, Germany
Correspondence to: M. Hutnak1 e-mail: mhutnak@pmc.ucsc.edu
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