Melt Stability and Compaction in a Partially Molten Silicate Layer Heated from Below

  • R. P. Lowell
  • G. Bergantz
Part of the NATO ASI Series book series (NSSE, volume 125)


In this paper, the possibility of convective or Rayleigh-Taylor instability in a growing layer of partially molten material, heated from below, is investigated. The relative importance of matrix compaction and thermal conduction on the dynamics of the partially molten layer is also studied by a scaling analysis of the appropriate dimensionless equations. The analysis shows that, for low viscosity melts, thermal conduction is unimportant; and melt dynamics is controlled by a combination of matrix compaction and buoyantly-driven instabilities within the melt itself. Once these instabilities occur, melt migration becomes a two- or three-dimensional process, and the chemical composition of the melt that leaves the source zone represents a mixture of melts produced at different temperature-pressure regimes in the source area. In melts with high viscosity, thermal conduction dominates the thermal regimes. Compaction and shear deformation of the matrix must both act to segregate the melt from the matrix. The melt is stable with respect to thermal or compositional convection until a large quantity of liquid has coalesced.


Rayleigh Number Bulk Composition Source Zone Local Thermodynamic Equilibrium Compositional Gradient 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    Arndt, N. T.: Ultrabasic magmas and high-degree melting of the mantle. Contrib. Mineral. Petrol., 64, 205–221, 1977.CrossRefGoogle Scholar
  2. 2.
    Waff, H. S.: Effects of the gravitational field on liquid distribution in partial melts within the upper mantle. J. Geophys. Res., 85, 1815–1825, 1980.CrossRefGoogle Scholar
  3. 3.
    Dullien, F. A. C.: Porous Media Fluid Transport and Pore Structure. Academic Press, NY, 418 p., 1979.Google Scholar
  4. 4.
    Sleep, N. H.: Segregation of magma from a mostly crystalline mush. Geol. Soc. Am. Bull., 85, 1225–1232, 1974.CrossRefGoogle Scholar
  5. 5.
    Turcotte, D. L., and J. L. Ahem: A porous flow model for magma migration in the asthenosphere. J. Geophys. Res., 83, 767–772, 1978.CrossRefGoogle Scholar
  6. 6.
    Ahem, J. L., and D. L. Turcotte: Magma migration beneath an ocean ridge. Earth Planet. Sci. Lett., 45, 115–122, 1979.CrossRefGoogle Scholar
  7. 7.
    McKenzie, D.: The generation and compaction of partially molten rock. J. Petrol., 25, 713–765, 1984.Google Scholar
  8. 8.
    Richter, F. M., and D. McKenzie: Dynamical models for melt segregation from a deformable matrix. J. Geol., 92, 729–740, 1984.CrossRefGoogle Scholar
  9. 9.
    Scott, D. R., and D. J. Stevenson: Magma solutions. Geophys. Res. Lett., 11, 1161–1164, 1984.CrossRefGoogle Scholar
  10. 10.
    Scott, D. R., and D. J. Stevenson: Magma ascent by porous flow. J. Geophys. Res., 91, 9283–9286, 1986.CrossRefGoogle Scholar
  11. 11.
    Fowler, A. C.: A mathematical model of magma transport in the asthenosphere. Geophys. Astrophys. Fluid Dynamics, 33, 63–96, 1985.CrossRefGoogle Scholar
  12. 12.
    Ribe, N. M.: The deformation and compaction of partially molten zones. Geophys. J. Roy. Astr. Soc., 83, 487–501, 1985.Google Scholar
  13. 13.
    Hills, R. N., D. E. Loper, and P. H. Roberts: Thermo-dynamically consistent model of a mushy zone. Q. J. Mech. Appl. Math, 36, 505–539, 1983.CrossRefGoogle Scholar
  14. 14.
    Ribe, N. M.: The generation and composition of partial melts in the Earth’s mantle. Earth Planet. Sci. Lett., 73, 361–376,1985.CrossRefGoogle Scholar
  15. 15.
    Lowell, R. P.: Double-diffusive convection in partially molten silicate systems: Its role during magma production and in magma chambers. J. Volcanol. Geotherm. Res., 26, 1–24, 1985.CrossRefGoogle Scholar
  16. 16.
    Roy, R. F., A. E. Beck, and Y. S. Touloukian: Thermo-physical properties of rocks. In Y. S. Touloukian, W. R. Judd, and R. F. Roy (editors), Physical Properties of Rocks and Minerals, CINDAS Data Series on Material Properties, Vol. II-2, McGraw-Hill, NY, 409–502, 1981.Google Scholar
  17. 17.
    Weill, D. F., R. Hon, and A. Navrotsky: The igneous system CaMgSi2O6-CaAl2Si2O8-NaAlSi3O8: Variations on a classic theme by Bowen. In R. Hargraves (editor), Physics of Magmatic Processes, Princeton University Press, Princeton, NJ, pp. 48–92, 1980.Google Scholar
  18. 18.
    Mo, X., I. S. E. Carmichael, M. Rivers, and J. Stebbins: The partial molar volume of Fe2O3 in multicomponent silicate liquids and the pressure dependence of the oxygen fugacity in magmas. Mineral. Mag., 45, 237–245, 1982.CrossRefGoogle Scholar
  19. 19.
    Yoder, H. S., Jr.: Albite-anorthite-quartz-water at 5 kb. Yearbook of the Geophysical Laboratory, Carnegie Inst, of Washington, 66, 477–478, 1968.Google Scholar
  20. 20.
    Carslaw, H. S., and J. C. Jaeger: Conduction of Heat in Solids, 2nd ed., 510 p., 1959.Google Scholar
  21. 21.
    Veronis, G.: On finite amplitude instability in thermo-haline convection. J. Mar. Res., 23, 1–17, 1965.Google Scholar
  22. 22.
    Turcotte, D. L., and G. Schubert: Geodynamics, John Wiley, NY, 450 p., 1982.Google Scholar
  23. 23.
    Size, W. B., and J. Covert: Petrology and structure of shear-controlled anatexis in migmatite. Geol. Soc. Am. Annual Meeting, Abstracts with Programs, 17, No. 77 719, 1985.Google Scholar

Copyright information

© Martinus Nijhoff Publishers, Dordrecht 1987

Authors and Affiliations

  • R. P. Lowell
    • 1
  • G. Bergantz
    • 2
  1. 1.School of Geophysical SciencesGeorgia Institute of TechnologyAtlantaUSA
  2. 2.Department of Geology and GeophysicsUniversity of UtahSalt Lake CityUSA

Personalised recommendations