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How to Stabilize Superplumes

This study explores the mechanisms behind superplumes and their unique behavior with depth, including the implications for mineralogy and geochemistry. The findings shed light on the complex nature of mantle convection and provide insights into the Earth's interior processes.

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How to Stabilize Superplumes

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  1. How to Stabilize Superplumes Eh Tan, Mike Gurnis Caltech Colorado Mantle Convection Workshop, 2005

  2. Modes of Mantle Convection Tackley 2000

  3. S20RT, Ritsema et al., 1999

  4. Master et al., 2000

  5. African superplume Ni et al. 2002 dVs = -3% dVp = -0.5% sharp, steep side 1000 km above CMB 1000 km wide in mid-mantle

  6. Dynamic Interpretation 1 Davaille et al., 1999

  7. Dynamic Interpretation 2 McNamara & Zhong, 2004

  8. Superplumes Explained? Not actually… • Lower layer is a lot hotter, but also more viscous • Probably OK, the layer might be made of weird material • Constant thermal expansion coefficient • We know thermal expansion decreases ~5x with depth • Can we make a superplume with depth-dependent thermal expansion?

  9. Dynamic Interpretation 3 Ni et al. 2002

  10. Constant Thermal Expansion

  11. Depth-Dep. Thermal Expansion

  12. Depth-dep. Thermal Expansion (cont.)

  13. Why does Drch changes with depth?

  14. Estimate on Elastic Modulus

  15. Numerical Model • 2D Cartesian ConMan • Modified for Truncated Anelastic Liquid Approximation • Chemical field is modeled by marker chain method • Different materials can have different Ks and r

  16. Algorithm

  17. Implication on Mineralogy • Lee et al. (AGU Spring Meeting, 2005) showed that pyroxenite under high pressure is 2% denser and has 5% higher Ks than PREM value. • How to get pyroxenite in the lower mantle? • subducted metasomatized oceanic crust, according to some petrologist

  18. Implication on Geochemistry

  19. Conclusions • Metastable superplumes are slightly denser and have higher bulk modulus • The physical and chemical properties of oceanic crust satisfy seismological, geodynamical, mineralogical and geochemical observations.

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