Publication Date:
2022-05-25
Description:
Author Posting. © Elsevier B.V., 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 246 (2006): 188-196, doi:10.1016/j.epsl.2006.04.005.
Description:
Dike emplacement in volcanic rift zones is often associated with the injection of “bladelike”
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 time-scales 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.
Description:
Funding
for this research was provided by NSF Grants OCE 04-43246, OCE 05-50147, OCE 02-42597 and OCE 04-26575, and a Carnegie Postdoctoral Fellowship to M.B.
Keywords:
Dike intrusion
;
Faulting
;
Rifting
;
Mid-ocean ridge
;
Topographic stress
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
Format:
4675408 bytes
Format:
application/pdf
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