Simulation of magma ascent by dykes in the mantle beneath mid-ocean ridges

Link:
Autor/in:
Erscheinungsjahr:
2004
Medientyp:
Text
Beschreibung:
  • Oceanic crust is formed at mid-ocean ridges. Whereas the melting zone extends up to several hundreds of km laterally, the extrusion area at the spreading axis is confined to a narrow belt of only 2-3 km width. The mechanism of melt focussing and extraction from the mantle beneath mid-ocean ridges is still poorly understood, despite the important role of the process for the formation of crust and plate tectonics. Using numerical simulations, we study the ascent paths of magma-filled dykes under different stress conditions. In contrast to early models, we have considered effects of stress and pressure gradients, buoyancy and enclosed finite fluid mass. The passive motion of the mantle due to the plate spreading has been modelled assuming an isothermal 2-D corner flow. An isotropic dynamic pressure is produced as well as a deviatoric stress field. While the dynamic pressure field is able to focus the fracture movement strongly towards the ridge axis, the deviatoric stress has a weak focussing effect and the apparent buoyancy counteracts the focussing of melt. Thus, we find that the simple stress field generated by a passive corner flow cannot explain convergent ascent paths, independent of the mantle rock viscosity chosen. This study concludes that an additional mechanism is necessary to explain the observed focussing of melt beneath mid-ocean spreading axes, e.g. large magma reservoirs or permeability barriers. The observed focussing might be explained without the demand for more complex flow models. © 2004 Elsevier Ltd. All rights reserved.
Lizenz:
  • info:eu-repo/semantics/closedAccess
Quellsystem:
Forschungsinformationssystem der UHH
Interne Metadaten
Quelldatensatz
oai:www.edit.fis.uni-hamburg.de:publications/331a1828-0e70-4498-9954-6eec77239c88