The volcanoes that lie along the Earth's tectonic boundaries are fed by melt generated in the mantle. How this melt is extracted and focused to the volcanoes, however, remains an unresolved question. Here we present new theoretical results with implications for melt focusing beneath mid-ocean ridges. By modelling laboratory experiments1,2, we test a formulation for magma dynamics and provide an explanation for localized bands of high-porosity and concentrated shear deformation observed in experiments. These bands emerge and persist at 15°–25° to the plane of shear. Past theoretical work on this system predicted the emergence of melt bands3,4 but at an angle inconsistent with experiments. Our results suggest that the observed band angle results from a balance of porosity-weakening and strain-rate-weakening deformation mechanisms. Lower band angles are predicted for greater strain-rate weakening. From these lower band angles, we estimate the orientation of melt bands beneath mid-ocean ridges and show that they may enhance magma focusing toward the ridge axis.
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Zimmerman, M., Zhang, S., Kohlstedt, D. & Karato, S. Melt distribution in mantle rocks deformed in shear. Geophys. Res. Lett. 26, 1505–1508 (1999)
Holtzman, B., Groebner, N., Zimmerman, M., Ginsberg, S. & Kohlstedt, D. Stress-driven melt segregation in partially molten rocks. Geochem. Geophys. Geosyst. 4, 8607 (2003)
Stevenson, D. Spontaneous small-scale melt segregation in partial melts undergoing deformation. Geophys. Res. Lett. 16, 1067–1070 (1989)
Spiegelman, M. Linear analysis of melt band formation by simple shear. Geochem. Geophys. Geosyst. 4, 8615, doi:10.1029/2002GC000499 (2003)
McKenzie, D. The generation and compaction of partially molten rock. J. Petrol. 25, 713–765 (1984)
Scott, D. & Stevenson, D. Magma ascent by porous flow. J. Geophys. Res. 91, 9283–9296 (1986)
Fowler, A. A mathematical model of magma transport in the asthenosphere. Geophys. Astrophys. Fluid Dyn. 33, 63–96 (1985)
Bercovici, D., Ricard, Y. & Schubert, G. A two-phase model for compaction and damage 1. General theory. J. Geophys. Res. 106, 8887–8906 (2001)
Hirth, G. & Kohlstedt, D. in The Subduction Factory (ed. Eiler, J.) 83–105 (AGU Geophysical Monograph 138, American Geophysical Union, Washington DC, 2003)
Richardson, C. Melt flow in a variable viscosity matrix. Geophys. Res. Lett. 25, 1099–1102 (1998)
Hall, C. & Parmentier, E. Spontaneous melt localization in a deforming solid with viscosity variations due to water weakening. Geophys. Res. Lett. 27, 9–12 (2000)
Karato, S. & Wu, P. Rheology of the upper mantle: A synthesis. Science 260, 771–778 (1993)
Kelemen, P., Hirth, G., Shimizu, N., Spiegelman, M. & Dick, H. A review of melt migration processes in the adiabatically upwelling mantle beneath oceanic spreading ridges. Phil. Trans. R. Soc. Lond. A 355, 283–318 (1997)
Mei, S., Bai, W., Hiraga, T. & Kohlstedt, D. Influence of melt on the creep behavior of olivine-basalt aggregates under hydrous conditions. Earth Planet. Sci. Lett. 201, 491–507 (2002)
Kelemen, P., Shimizu, N. & Salters, V. Extraction of mid-ocean-ridge basalt from the upwelling mantle by focused flow of melt in dunite channels. Nature 375, 747–753 (1995)
Knepley, M., Katz, R. & Smith, B. in Numerical Solution of Partial Differential Equations on Parallel Computers (eds Bruaset, A. & Tveito, A.) 413–438 (Lecture Notes in Computational Science and Engineering Vol. 51, Springer, Berlin, 2006)
Balay, S. et al. Portable Extensible Toolkit for Scientific computation (PETSc) http://www.mcs.anl.gov/petsc (2001).
Holtzman, B., Kohlstedt, D. & Morgan, J. P. Viscous energy dissipation and strain partitioning in partially molten rocks. J. Petrol. 46, 2593–2613 (2005)
Forsyth, D. et al. Imaging the deep seismic structure beneath a mid-ocean ridge: the melt experiment. Science 280, 1215–1218 (1998)
Spiegelman, M. & McKenzie, D. Simple 2-D models for melt extraction at mid-ocean ridges and island arcs. Earth Planet. Sci. Lett. 83, 137–152 (1987)
Morgan, J. Melt migration beneath mid-ocean spreading centers. Geophys. Res. Lett. 14, 1238–1241 (1987)
Sparks, D. & Parmentier, E. Melt extraction from the mantle beneath spreading centers. Earth Planet. Sci. Lett. 105, 368–377 (1991)
Katz, R., Spiegelman, M. & Carbotte, S. Ridge migration, asthenospheric flow and the origin of magmatic segmentation in the global mid-ocean ridge system. Geophys. Res. Lett. 31, L15605, doi:10.1029/2004GL020388 (2004)
Daines, M. & Kohlstedt, D. Influence of deformation on melt topology in peridotites. J. Geophys. Res. 102, 10257–10271 (1997)
This work was supported by the Department of Energy Computational Science Graduate Fellowship Program of the Office of Science and National Nuclear Security Administration in the Department of Energy, and the NSF. We thank B. Smith, M. Knepley and the PETSc team at Argonne National Laboratory. We are also grateful to E. Coon, P. Kelemen and the solid Earth geodynamics group at LDEO for discussions. Comments by M. Jellinek helped to improve the manuscript.
Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.
This file contains Supplementary Discussion with equations. This section contains text detailing the derivation of linear analysis results presented in the text. The text also describes the methods, boundary and initial conditions and results of numerical simulations. This file also contains Supplementary Figures 1–4. These figures help to elucidate the behavior of the numerical and analytical models for different values of the non-linear parameter n. This file also contains Supplementary Movie Legend and additional references. (PDF 904 kb)
This movie shows the results of a numerical simulation as described in the text and movie caption. This simulation progresses to a shear strain of about 2.75. High porosity bands develop and shear strain is concentrated onto these bands, as shown by the black strain markers. Band reconnection and realignment may be observed in the porosity field. (MOV 2543 kb)
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Katz, R., Spiegelman, M. & Holtzman, B. The dynamics of melt and shear localization in partially molten aggregates. Nature 442, 676–679 (2006). https://doi.org/10.1038/nature05039
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