Topographic controls on dike injection in volcanic rift zones

Publication Type  Journal Article
Year of Publication  2006
Authors  Behn, M. D.; Buck, W. R.; Sacks, I. S.
Journal Title  Earth and Planetary Science Letters
Volume  246
Issue  3-4
Pages  188-196
Journal Date  Jun 30
ISBN Number  0012-821X
Accession Number  ISI:000239125500004
Key Words  dike intrusion; faulting; rifting; mid-ocean ridge; topographic stress; mid-atlantic-ridge; crustal thickness; magmatic accretion; gravity-anomalies; midocean ridges; iceland; fault; deformation; lithosphere; propagation
Abstract  

Dike emplacement in volcanic rift zones is often associated with the injection of "blade-like" dikes, which propagate long distances parallel to the rift, but frequently remain trapped at depth and erupt only near the tip of the dike. Over geologic time, this style of dike injection implies that a greater percentage of extension is accommodated by magma accretion at depth than near the surface. In this study, we investigate the evolution of faulting, topography and stress state in volcanic rift zones using a kinematic model for dike injection in an extending 2-D elastic-viscoplastic layer. We show that the intrusion of blade-like dikes focuses deformation at the rift axis, leading to the formation of an axial rift valley. However, flexure associated with the development of the rift topography generates compression at the base of the plate. If the magnitude of these deviatoric compressive stresses exceeds the deviatoric tensile stress associated with far-field extension, further dike injection will be inhibited. In general, this transition from tensile to compressive deviatoric stresses occurs when the rate of accretion in the lower crust is greater than 50-60% of the far-field extension rate. These results indicate that, over geologic timescales, the injection of blade-like dikes is a self-limiting process in which dike-generated faulting and topography result in an efficient feedback mechanism that controls the time-averaged distribution of magma accretion within the crust. (c) 2006 Elsevier B.V. All rights reserved.

Notes  

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URL  <Go to ISI>://000239125500004
DOI  DOI 10.1016/j.epsl.2006.04.005