The development of small-scale convection below evolving oceanic plates

Abstract:

Seafloor of older ages shows a constancy of heat flow, and bathymetry that is different from what is expected for a half-space cooling model. These observations led to consideration of the existence of small-scale convection below the lithosphere (Parsons and McKenzie, 1978). Previous studies have characterized the detailed physics of such processes (Davaille and Jaupart, 1994; Choblet and Sotin, 2000; Solomatov and Moresi, 2000; Korenaga and Jordan, 2003 among others). However, questions remain for applications to the Earth: what is the shape of developed small-scale convection, what length-scales are involved, how does associated small-scale convection depend on the plate layout and its time-dependence.

Using 3D spherical models of mantle convection with plate-like behaviour (Tackley, 2008), we will present a study of developed small-scale convection in a context of self-organization of plates and mantle flow. Small-scale convection depends on the resistance of the lithosphere, and its development beneath large plates produce network shapes with specific length-scales and orientations (see figure). We will show the impact of the size of plates and the evolution of subduction on the small-scale convection, and characterize how the age-heat flow relationship can change with time. The potential for seismic detection of the spatiotemporal patterns of temperature heterogeneity will also be discussed.

References

Choblet, G., and C. Sotin, Phys. Earth Planet. Inter. 119, 321–336 (2000).

Davaille, A., and C. Jaupart, J. Geophys. Res. 99, 19,853–19,866 (1994).

Korenaga, J., and T. H. Jordan, J. Geophys. Res. 108, 2333, (2003).

Parsons, B., and D. McKenzie, J. Geophys. Res. 83, 4485–4496 (1978).

Solomatov, V. S., and L. N. Moresi, J. Geophys. Res. 105, 21,795–21,817 (2000).

Tackley, P. J., Phys. Earth Planet. Inter. 171, 7-18 (2008).

Figure: Age of the seafloor in Myrs and white countour of a cold temperature isotherm showing the network of small-scale convection.