Choi, Eun-seo and Gurnis, Michael (2008) Thermally induced brittle deformation in oceanic lithosphere and the spacing of fracture zones. Earth and Planetary Science Letters, 269 (1-2). pp. 259-270. ISSN 0012-821X http://resolver.caltech.edu/CaltechAUTHORS:20101129-085616901
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Brittle deformation of oceanic lithosphere due to thermal stress is explored with a numerical model, with an emphasis on the spacing of fracture zones. Brittle deformation is represented by localized plastic strain within a material having an elasto-visco-plastic rheology with strain softening. We show that crustal thickness, creep strength, and the rule governing plastic flow control the formation of cracks. The spacing of primary crack decreases with crustal thickness as long as it is smaller than a threshold value. Creep strength shifts the threshold such that crust with strong creep strength develops primary cracks regardless of crustal thicknesses, while only a thin crust can have primary cracks if its creep strength is low. For a thin crust, the spacing of primary cracks is inversely proportional to the creep strength, suggesting that creep strength might independently contribute to the degree of brittle deformation. Through finite versus zero dilatation in plastic strain, associated and non-associated flow rule results in nearly vertical and V-shaped cracks, respectively. Changes in the tectonic environment of a ridge system can be reflected in variation in crustal thickness, and thus related to brittle deformation. The fracture zone-free Reykjanes ridge is known to have a uniformly thick crust. The Australian-Antarctic Discordance has multiple fracture zones and thin crust. These syntheses are consistent with enhanced brittle deformation of oceanic lithosphere when the crust is thin and vice versa.
|Additional Information:||© 2008 Elsevier B.V. Received 22 June 2007; revised 24 January 2008; accepted 8 February 2008. Editor: C.P. Jaupart. Available online 29 February 2008. We thank Joann Stock, Laetitia Le Pourhiet, and Paul Asimow for fruitful discussions and Dietmar Müller for suggestions on the manuscript. We would like to thank Claude Jaupart, Louis Geli, and two other anonymous reviewers for their useful and constructive reviews. This is contribution number 9174 of the Division of Geological and Planetary Sciences and 72 of the Tectonics Observatory. Development of SNAC was partially supported by the NSF ITR program under EAR-0205653. All calculations carried out on the Caltech Geosciences Supercomputer Facility partially supported by NSF EAR-0521699. Additional support provided through the Caltech Tectonics Observatory by the Gordon and Betty Moore Foundation.|
|Group:||Caltech Tectonics Observatory|
|Subject Keywords:||oceanic lithosphere; fracture zone; thermal stress; brittle deformation|
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|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||29 Nov 2010 18:17|
|Last Modified:||26 Dec 2012 12:41|
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