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Magmatic and tectonic extension at mid-ocean ridges : 1. Controls on fault characteristics

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dc.contributor.author Behn, Mark D.
dc.contributor.author Ito, Garrett T.
dc.date.accessioned 2010-04-20T19:00:53Z
dc.date.available 2010-04-20T19:00:53Z
dc.date.issued 2008-08-02
dc.identifier.citation Geochemistry Geophysics Geosystems 9 (2008): Q08O10 en_US
dc.identifier.uri http://hdl.handle.net/1912/3275
dc.description Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 9 (2008): Q08O10, doi:10.1029/2008GC001965. en_US
dc.description.abstract We use 2-D numerical models to explore the thermal and mechanical effects of magma intrusion on fault initiation and growth at slow and intermediate spreading ridges. Magma intrusion is simulated by widening a vertical column of model elements located within the lithosphere at a rate equal to a fraction, M, of the total spreading rate (i.e., M = 1 for fully magmatic spreading). Heat is added in proportion to the rate of intrusion to simulate the thermal effects of magma crystallization and the injection of hot magma into the crust. We examine a range of intrusion rates and axial thermal structures by varying M, spreading rate, and the efficiency of crustal cooling by conduction and hydrothermal circulation. Fault development proceeds in a sequential manner, with deformation focused on a single active normal fault whose location alternates between the two sides of the ridge axis. Fault spacing and heave are primarily sensitive to M and secondarily sensitive to axial lithosphere thickness and the rate that the lithosphere thickens with distance from the axis. Contrary to what is often cited in the literature, but consistent with prior results of mechanical modeling, we find that thicker axial lithosphere tends to reduce fault spacing and heave. In addition, fault spacing and heave are predicted to increase with decreasing rates of off-axis lithospheric thickening. The combination of low M, particularly when M approaches 0.5, as well as a reduced rate of off-axis lithospheric thickening produces long-lived, large-offset faults, similar to oceanic core complexes. Such long-lived faults produce a highly asymmetric axial thermal structure, with thinner lithosphere on the side with the active fault. This across-axis variation in thermal structure may tend to stabilize the active fault for longer periods of time and could concentrate hydrothermal circulation in the footwall of oceanic core complexes. en_US
dc.description.sponsorship Funding for this research was provided by NSF grants OCE-0327018 (M.D.B.), OCE-0548672 (M.D.B.), OCE- 0327051 (G.I.), and OCE-03-51234 (G.I.). en_US
dc.format.mimetype application/pdf
dc.language.iso en_US en_US
dc.publisher American Geophysical Union en_US
dc.relation.uri http://dx.doi.org/10.1029/2008GC001965
dc.subject Mid-ocean ridges en_US
dc.subject Faulting en_US
dc.subject Magmatism en_US
dc.subject Numerical modeling en_US
dc.title Magmatic and tectonic extension at mid-ocean ridges : 1. Controls on fault characteristics en_US
dc.type Article en_US
dc.identifier.doi 10.1029/2008GC001965


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