ErinAndrewsConf07_Gordfinal

ErinAndrewsConf07_Gordfinal - Composite Upper Mantle...

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Unformatted text preview: Composite Upper Mantle Rheology: Effects of Slab Age and Maximum Yield Strength on Detachment & & & Model Results: * Detachment at three depths: & & & & & & (1) 300 km for Models 4 and 5: warming controls weakening leading to detachment. & & & & & (2) 200 km for Model 6: the strongest but heaviest slab detaches by yielding. & & & & & (3) 150 km for Models 7-9: yielding controls detachment on a much shorter time scale than Model 6. & & * Rotation of the slab occurs for quick detachment times. 12 40 My 3 M P a 5 M P a 80 My 120 My Longitude D e p t h ( k m ) 0.2 My 3.2 My 12.6 My 18 My D e p t h ( k m ) Plate Age M a x i m u m Y i e l d S t r e n g t h Model 7 Model 4 Model 5 Model 6 Model 8 Model 9 Model Results for 600 km Deep Slab: Varying Plate Ages and Yield Strengths 18 21 24 27 300 600 900 300 600 900 Longitude 18 21 24 27 Longitude 18 21 24 27 0.4 My 4.0 My 22.3 My 26.4 My 27.9 My 0.5 My 4.2 My 31.2 My 4.1 My 4.9 My 5.0 My 5.0 My 8.2 My 5.9 My 8.2 My 6.0 My 6.1 My 2.1 My 1.7 My 1.1 My 0.2 My 0.2 My 0.2 My 1. Billen, M. I., M. Gurnis, and M. Simons, Multiscale dynamic models of the Tonga-Kermadec subduction zone, Geophys. J. Int., 153, 359388, 2003. 2. Billen, M.I., and G. Hirth, Rheologic Controls on Slab Dynamics, submitted to Geochemistry Geophysics Geosystems. 3. Ferrari, L., Slab detachment control on mafic volcanic pulse and mantle heterogeneity in central Mexico. Geology, 32(1), 77-80, 2004. 4. Gerya, T.V. et al., Thermomechanical modelling of slab detachment, Earth and Planet. Sci. Lett., 226, 101-116, 2004. 5. Goetze, C., and Brian Evans, Stress and temperature in the bending lithosphere as constrained by experimental rock mechanics, Geophys. J. R. astr. Soc., 59, 463-478, 1979. 6. Hirth, G., and D. Kohlstedt, Rheology of the upper mantle and the mantle wedge: a view from the experimentalists, in Inside the Subduction Factory, edited by J. Eiler, AGU, Washington D.C., 2003. 7. Moresi, L., and M. Gurnis, Constraints on the lateral strength of slabs from three-dimensional dynamic flow models, Earth and Planet. Sci. Lett., 138, 1528, 1996. 8. Yoshioka, S., and M. J. R. Wortel, 3D numerical modeling of detachment of subducted lithosphere, J. of Geophys. Res., 100, 20, 223-20, 244, 1995. Slab Detachment: process by which a portion of a subducted & lithospheric plate detaches. We define detachment as & occuring within an isolated zone of weakness that forms & within the slab on short time scales, as opposed to removal & of slab material by stretching and dripping into the lower & mantle after warming for times on the order of 100 Myr....
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