A NUMERICAL EVOLUTIONARY MODEL OF INTERACTING CONTINENTS FLOATING ON A SPHERICAL EARTH
Аннотация и ключевые слова
Аннотация (русский):
Development of methods for the numerical modelling of global geodynamic processes provided a possibility to study the driving mechanism of moving continents periodically assembling to form supercontinents of the Pangea type. In our previous studies, we developed a method for the numerical solution of a system of equations governing the mass, heat and momentum transfer in a convecting viscous mantle and Euler equations describing the motion of solid continents. The convection and Euler equations are coupled through the conditions of no-slip, impermeability and continuity of temperature and heat flux at the continent surface submerged into the mantle. These studies demonstrated the capability of continents to assemble into a supercontinent and the capability of a supercontinent to break up. Based on an idealized spherical model, this work presents results of a numerical experiment with long evolution of 12 floating continents. The mantle was modelled by a spherical shell of a constant viscosity heated from below with the Rayleigh number Ra = 10 7. The continents were represented by thick rigid discs with angular dimensions of about 40o 40o. The initial state was modeled by the present mantle with a temperature distribution estimated from seismic tomography data. In this state, the distributions of the surface heat flux and mantle flow velocities are consistent with observations. The continents in the initial state are uniformly distributed over the mantle surface. The long-term evolution of the mantle-continents system, lasting a few billions of years, was calculated. A numerical experiment conducted within the framework of this idealized model showed that, for the most time, the continents are located above mantle downwellings and move together with them. If two mantle flows accidentally approach one another, a zone arises that pulls adjacent continents in along with underlying mantle flows. As a result, mantle downwellings and the related continents start joining. Our numerical experiment showed that the continents first form groups of four to five continents and a large supercontinent is then assembled from these groups. The overheated mantle under the supercontinent gives rise to new convective upwellings. As a result, the supercontinent first divides into two smaller supercontinents. Afterward, the latter also break up. One of the smaller supercontinents similar to Laurasia first breaks up into five continents, after which the second supercontinent similar to Gondwana also divides. Afterward, the continents scatter all over the mantle surface. The convergence and divergence events repeatedly occur during the evolution.

Ключевые слова:
mantle convection, floating continent, numerical simulation, evolution of the mantle-continent system.
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Список литературы

1. Allegre, Tectonophysics, v. 82, 1982., doi:https://doi.org/10.1016/0040-19518290125-1

2. Allegre, Earth Planet. Sci. Lett., v. 66, 1993., doi:https://doi.org/10.1016/0012-821X8390135-8

3. Anderson, Science, v. 213, 1981.

4. Anderson, Earth Planet. Sci. Lett., v. 57, 1982., doi:https://doi.org/10.1016/0012-821X8290169-8

5. Anderson, Theory of the Earth, 1989.

6. Becker, Earth. Planet. Sci Lett., v. 151, 1999., doi:https://doi.org/10.1016/S0012-821X9900160-0

7. Brunet, J. Geophys. Res., v. 103, 1998., doi:https://doi.org/10.1029/97JB01357

8. Bunge, J. Geophys. Res., v. 102, 1997., doi:https://doi.org/10.1029/96JB03806

9. Davies, Geophys. J. Roy. Astron. Soc., v. 49, 1974.

10. Davies, Nature, v. 290, 1979., doi:https://doi.org/10.1038/290208a0

11. Davies, J. Geophys. Res., v. 89, 1984.

12. Davies, Earth Planet. Sci. Lett., v. 136, 1995.

13. Davies, J. Geol., v. 100, 1992.

14. DePaolo, Geochem. Cosmochem. Acta, v. 44, 1980.

15. DePaolo, EOS, v. 52, 1981.

16. DePaolo, Geophys. Res. Lett., v. 3, 1976.

17. DePaolo, Geochem. Cosmochem. Acta, v. 43, 1979., doi:https://doi.org/10.1016/0016-70377990169-8

18. Dobretsov, Deep Geodynamics, 1994.

19. Ekstrom, Nature, v. 394, 1998., doi:https://doi.org/10.1038/28148

20. Forte, Nature, v. 290, 2000.

21. Grand, J. Geophys. Res., v. 92, 1987.

22. Grand, J. Geophys. Res., v. 99, 1994., doi:https://doi.org/10.1029/94JB00042

23. Grand, GSA Today, v. 7, 1997.

24. Gurnis, Nature, v. 332, 1988., doi:https://doi.org/10.1038/332695a0

25. Gurnis, Geophys. Res. Lett., v. 18, 1991.

26. Hoffmann, Earth Planet. Sci. Lett., v. 57, 1982., doi:https://doi.org/10.1016/0012-821X8290161-3

27. Jackson, Geophys. J. Intern., v. 134, 1998., doi:https://doi.org/10.1046/j.1365-246x.1998.00560.x

28. Jacobsen, J. Geophys. Res., v. 84, 1979.

29. Jacobsen, Tectonophysics, v. 75, 1981., doi:https://doi.org/10.1016/0040-19518190214-6

30. Jeanloz, Phil. Trans. Roy. Astr. Soc. L., v. A328, 1989.

31. Jordan, J. Geophys., v. 43, 1977.

32. Kaban, Seismic tomography and implications for models of the Earth's mantle, 2000.

33. Kellogg, Science, v. 263, 1999.

34. Lowman, Phys. Earth Planet. Inter., v. 88, 1995., doi:https://doi.org/10.1016/0031-92019405076-A

35. Lowman, J. Geophys. Res., v. 101, 1996., doi:https://doi.org/10.1029/96JB02568

36. Machetel, Nature, v. 350, 1991., doi:https://doi.org/10.1038/350055a0

37. McCulloch, Earth's mantle, I. Jackson, Ed., 1998.

38. Nakanuki, Earth and Planet. Sci. Lett., v. 146, 1997., doi:https://doi.org/10.1016/S0012-821X9600233-6

39. O'Nions, Nature, v. 306, 1983., doi:https://doi.org/10.1038/306429a0

40. O'Nions, J. Geophys. Res., v. 84, 1979.

41. Solheim, J. Geophys. Res., v. 99, 1994., doi:https://doi.org/10.1029/94JB00730

42. Steinbach, Geophys. Res. Lett., v. 20, 1993.

43. Tackley, J. Gephys. Res., v. 101, 1996., doi:https://doi.org/10.1029/95JB03211

44. Tackley, Science Print, v. 2888, 2000.

45. Tackle, J. Geophys. Res., v. 99, 1994., doi:https://doi.org/10.1029/94JB00853

46. Trubitsyn, Izvestiya, Physics of the Solid Earth, v. 36, 2000.

47. Trubitsyn, Izvestiya, Physics of the Solid Earth, v. 36, 2000.

48. Trubitsyn, Izvestia, Physics of the Solid Earth, v. 29, 1994.

49. Trubitsyn, Izvestia, Physics of the Solid Earth, v. 21, 1985.

50. Trubitsyn, J. Geodyn., v. 20, 1995., doi:https://doi.org/10.1016/0264-37079400029-U

51. Trubitsyn, Russian J. Earth Sci., v. 1, no. 1, 1998.

52. Trubitsyn, Russian J. Earth Sci., v. 1, no. 2, 1998.

53. Trubitsyn, Three-dimensional spherical models of mantle convection with floating continents, v. 88, 2000.

54. Trubitsyn, J. Geodyn., v. 28, 1999., doi:https://doi.org/10.1016/S0264-37079800038-6

55. Turcott, Geodynamics: Applications of Continuum Physics to Geological Problems, 1982.

56. Van der Hilst, Nature, v. 374, 1995., doi:https://doi.org/10.1038/374154a0

57. Van der Hilst, Nature, v. 353, 1991., doi:https://doi.org/10.1038/353037a0

58. Van der Hilst, Nature, v. 386, 1997., doi:https://doi.org/10.1038/386578a0

59. Zhong, J. Geophys. Res., v. 103, 1998., doi:https://doi.org/10.1029/98JB00605

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