HR: 14:25h
AN: T32C-04    [PDF]
TI: Is the Wilson Cycle Caused by the Memory Effect of Water?
AU: * Regenauer-Lieb, K
EM: klaus.regenauer-lieb@csiro.au
AF: CSIRO Exploration and Mining, Bentley, Perth, WA 6102 Australia
AU: van der Lee, S
EM: suzan@tomo.ig.erdw.ethz.ch
AF: Department of Geological Sciences, Northwestern University 1847 Sheridan Road, Evanston, IL 0208-2150 United States
AU: Yuen, D A
EM: davey@krissy.geo.umn.edu.
AF: Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455 United States
AB: Did the Atlantic close and then re-open ? {\it (Nature, 211, 676-681, 1966)}. John Tuzo Wilson's cyclical event of opening and closing of ocean basins, later found to be a generally applicable, became the "Wilson cycle" {\it (Dewey, J.F., and Burke, K., Nature, v.249, p.313-316)}.Whilst the cyclical nature appears to be understood what then breaks and consumes the oceans at roughly the same location? Remnant textural anisotropy, structural damage and intra-crystalline water content are means of long-term plate memory ($>$ 500 Myrs). This explains a predetermined breaking point but can these heterogeneities lead to the formation of a lithosphere scale fault allowing the consumption and the opening of oceans? In a self-consistent theory, driven by gravity and thermal-mechanics, only a very narrow parameter range initiates the contraction master fault through feedback of thermal-mechanics and water weakening. We have shown that the water content in olivine must be above 200 ppm H/Si for subduction intiation to be possible {\it(Science 2001, 294, 578-580)}. Here, we provide a broader context and show that the same criticality exists for the ocean opening phase. We prove that water storage can be the critical ingredient for the whole history of the Wilson cycle. In a worked example we show an exploratory application, to the Atlantic-Iapetus pair. We also look at possible present day seismological observations focusing on the US-Atlantic margin.
DE: 5120 Plasticity, diffusion, and creep
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8150 Plate boundary--general (3040)
DE: 8155 Plate motions--general
DE: 8160 Rheology--general
SC: Tectonophysics [T]
MN: 2003 Fall Meeting