A one-plume model of martian mantle convection

FOR at least the past two billion years, volcanism on Mars has been restricted to the Tharsis region1. In addition, most tectonic activity on Mars2, together with the long-wavelength topography and the non-hydrostatic gravity field3, are strongly correlated with Tharsis, implying a close connection with deep mantle processes. These observations have motivated suggestions4 that the thermal convection in the martian mantle is very different from that in the Earth's mantle, being dominated by a single large upwelling under Tharsis. Two-dimensional convection modelling has shown that the presence of an endothermic phase boundary in the lowermost mantle of a planet has a strong influence on convection, suppressing all but one or two upwellings5. Recent experiments6 indicate that such a boundary may indeed exist on Mars. Here we investigate the convective evolution of the martian mantle using a three-dimensional model which incorporates an endothermic phase transition close to the core–mantle boundary. We find that a single-plume pattern of convection gradually develops, and we show that this is consistent with the distribution of volcanism, the shape of the gravity field, and the gross tectonic stress pattern of Mars.

[1]  H. Mao,et al.  Structure and Density of FeS at High Pressure and High Temperature and the Internal Structure of Mars , 1995, Science.

[2]  Gary A. Glatzmaier,et al.  Mantle dynamics in Mars and Venus: Influence of an immobile lithosphere on three-dimensional mantle convection , 1990 .

[3]  Georges Balmino,et al.  Gravity field model of mars in spherical harmonics up to degree and order eighteen , 1982 .

[4]  M. Rabinowicz,et al.  Three-dimensional convection in spherical shells , 1986 .

[5]  D. Yuen,et al.  Layered convection induced by phase transitions , 1985 .

[6]  S. Karato.  Does partial melting reduce the creep strength of the upper mantle? , 1986, Nature.

[7]  Ulrich R. Christensen,et al.  Some effects of lateral viscosity variations on geoid and surface velocities induced by density anomalies in the mantle , 1993 .

[8]  A. Boss,et al.  Finite-amplitude models of convection in the early mantle , 1984 .

[9]  Patrice Weber,et al.  Intermittent layered convection in a model mantle with an endothermic phase change at 670 km , 1991, Nature.

[10]  Roger J. Phillips,et al.  Gravity and lithospheric stress on the terrestrial planets with reference to the Tharsis Region of Mars , 1985 .

[11]  Tilman Spohn,et al.  Thermal history of Mars and the sulfur content of its core , 1990 .

[12]  S. Weinstein.  The effects of a deep mantle endothermic phase change on the structure of thermal convection in silicate planets , 1995 .

[13]  E. Ivins,et al.  Geophysical observations pertaining to solid-state convection in the terrestrial planets , 1979 .

[14]  Roger J. Phillips,et al.  Thick shell tectonics on one-plate planets - Applications to Mars , 1982 .

[15]  David J. Stevenson,et al.  Effects of multiple phase transitions in a three-dimensional spherical model of convection in Earth's mantle , 1994 .

[16]  H. Schmeling,et al.  A mechanism for crustal thinning without lateral extension , 1990 .

[17]  D. Yuen,et al.  Phase transitions in the Martian mantle and the generation of megaplumes , 1995 .

[18]  R. Phillips,et al.  Permanent uplift in magmatic systems with application to the Tharsis Region of Mars , 1990 .