Influence of the Ringwoodite-Perovskite transition on mantle convection in spherical geometry as a function of Clapeyron slope and Rayleigh number
We investigate the influence on mantle convection of the negative Clapeyron slope ringwoodite to perovskite and ferro-periclase mantle phase transition, which is correlated with the seismic discontinuity at 660 km depth. In particular, we focus on understanding the influence of the magnitude of the...
| Main Authors: | , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2011-12-01
|
| Series: | Solid Earth |
| Online Access: | http://www.solid-earth.net/2/315/2011/se-2-315-2011.pdf |
| Summary: | We investigate the influence on mantle convection of the negative Clapeyron slope ringwoodite to perovskite and ferro-periclase mantle phase transition, which is correlated with the seismic discontinuity at 660 km depth. In particular, we focus on understanding the influence of the magnitude of the Clapeyron slope (as measured by the Phase Buoyancy parameter, <i>P</i>) and the vigour of convection (as measured by the Rayleigh number, <i>Ra</i>) on mantle convection. We have undertaken 76 simulations of isoviscous mantle convection in spherical geometry, varying <i>Ra</i> and <i>P</i>. Three domains of behaviour were found: layered convection for high <i>Ra</i> and more negative <i>P</i>, whole mantle convection for low <i>Ra</i> and less negative <i>P</i>, and transitional behaviour in an intervening domain. The boundary between the layered and transitional domain was fit by a curve <i>P = &alpha; Ra<sup>&beta;</sup></i> where <i>α</i> = −1.05, and <i>β</i> = −0.1, and the fit for the boundary between the transitional and whole mantle convection domain was <i>α</i> = −4.8, and <i>β</i> = −0.25. These two curves converge at <i>Ra</i> ≈ 2.5 × 10<sup>4</sup> (well below Earth mantle vigour) and <i>P</i> &approx; &minus;0.38. Extrapolating to high <i>Ra</i>, which is likely earlier in Earth history, this work suggests a large transitional domain. It is therefore likely that convection in the Archean would have been influenced by this phase change, with Earth being at least in the transitional domain, if not the layered domain. |
|---|---|
| ISSN: | 1869-9510 1869-9529 |