Hybrid shallow on-axis and deep off-axis hydrothermal circulation at fast-spreading ridges.

Hasenclever, Jörg, Theissen-Krah, Sonja, Rüpke, Lars H. , Morgan, Jason P., Iyer, Karthik , Petersen, Sven and Devey, Colin W. (2014) Hybrid shallow on-axis and deep off-axis hydrothermal circulation at fast-spreading ridges. Nature, 508 (7497). pp. 508-512. DOI 10.1038/nature13174.

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Hydrothermal flow at oceanic spreading centres accounts for about ten per cent of all heat flux in the oceans and controls the thermal structure of young oceanic plates. It also influences ocean and crustal chemistry, provides a basis for chemosynthetic ecosystems, and has formed massive sulphide ore deposits throughout Earth’s history. Despite this, how and under what conditions heat is extracted, in particular from the lower crust, remains largely unclear. Here we present high-resolution, whole-crust, two- and three-dimensional simulations of hydrothermal flow beneath fast-spreading ridges that predict the existence of two interacting flow components, controlled by different physical mechanisms, that merge above the melt lens to feed ridge-centred vent sites. Shallow on-axis flow structures develop owing to the thermodynamic properties of water, whereas deeper off-axis flow is strongly shaped by crustal permeability, particularly the brittle–ductile transition. About 60 per cent of the discharging fluid mass is replenished on-axis by warm (up to 300 degrees Celsius) recharge flow surrounding the hot thermal plumes, and the remaining 40 per cent or so occurs as colder and broader recharge up to several kilometres away from the axis that feeds hot (500–700 degrees Celsius) deep-rooted off-axis flow towards the ridge. Despite its lower contribution to the total mass flux, this deep off-axis flow carries about 70 per cent of the thermal energy released at the ridge axis. This combination of two flow components explains the seismically determined thermal structure of the crust and reconciles previously incompatible models favouring either shallower on-axis or deeper off-axis hydrothermal circulation.

Document Type: Article
Additional Information: WOS:000334741600033
Keywords: geodynamics ; volcanology ; hydrothermal systems ; mid-ocean ridge ; permeability ; oceanic crust ; numerical modelling ; finite element method ; 3D
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS > Marine Mineralische Rohstoffe
Kiel University
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS
Refereed: Yes
Open Access Journal?: No
Publisher: Nature Publishing Group
Projects: Future Ocean
Date Deposited: 24 Apr 2014 06:25
Last Modified: 23 Sep 2019 19:57
URI: https://oceanrep.geomar.de/id/eprint/24352

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