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Influence of rheology on realignment of mantle convective structure with plate motion after a plate reorganization.

Hunen van, J. and Zhong, S. (2006) 'Influence of rheology on realignment of mantle convective structure with plate motion after a plate reorganization.', Geochemistry, geophysics, geosystems., 7 (8). Q08008.

Abstract

Small-scale convection (SSC) rolls below the oceanic lithosphere have the tendency to align with the large-scale shearing direction and thus with the plate motion direction relative to the deep mantle. Understanding the timescales of and processes responsible for realignment would contribute significantly to our understanding of the unresolved phenomena in the Pacific such as gravity lineations, small-scale seismic velocity variations, and intraplate volcanism that cannot be explained by hot spots. In this study we examine the evolution of those convection rolls when this relative plate motion direction is suddenly changed, as suggested by the kink in the Hawaii-Emperor seamount chain. Using three-dimensional numerical flow models, we investigate the realignment of SSC rolls after a change in plate motion direction. From the nature of the SSC, it is expected that rheological parameters dominate the characteristics of this realignment. Our results show that this is indeed the case. We find that (1) using constraints from onset timing of SSC, realignment of rolls can occur as fast as within 20 Ma, but might also take much longer, dependent on the rheology; (2) the realignment period is strongly correlated to the sum of large-scale shear stress induced by plate motion and small-scale shear stress from the SSC itself; (3) in a mantle deforming by dislocation creep, realignment occurs faster than by diffusion creep, because dislocation creep SSC is more vigorous; and (4) activation energy has little influence on the realignment time. Possible evidence for the realignment period might come from precise age determination of intraplate volcanism or azimuthal seismic anisotropy.

Item Type:Article
Keywords:Alignment, Convection rolls, Plate motion, Rheology.
Full text:PDF - Published Version (5568Kb)
Status:Peer-reviewed
Publisher Web site:http://dx.doi.org/10.1029/2005GC001209
Publisher statement:© 2006 American Geophysical Union. Hunen van, J. and Zhong, S. (2006), 'Influence of rheology on realignment of mantle convective structure with plate motion after a plate reorganization.', Geochemistry, geophysics, geosystems, 7, Q08008, 10.1029/2005GC001209. To view the published open abstract, go to http://dx.doi.org and enter the DOI.
Record Created:12 Mar 2009
Last Modified:16 Aug 2011 09:21

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