Evolution of mantle plumes and uplift of continents during the Pangea breakup

Abstract

[1]  The paper presents results derived from numerical modeling of mantle heating and reorganization of mantle flows during assemblage of two continents and subsequent breakup of the supercontinent. The simplest mantle model consisting of an extended rectangular region filled with a viscous fluid heated from below is considered. Thermal convection develops in the mantle. Due to viscosity dependence on temperature and pressure, a high viscosity lithosphere and a low viscosity asthenosphere arise in the mantle. Two continents modeled as rigid thick floating plates are then placed into the mantle. Driven by viscous coupling with mantle flows, the continents start moving and converge above the nearest descending mantle flow. The resulting supercontinent hinders the outflow of mantle heat, the subcontinental mantle starts heating, and the cold descending mantle flow gives way to a hot ascending flow. The latter assumes the shape of a plume with a spherical head and a thin tail. The resulting tensile stress breaks up the supercontinent. The Atlantic Ocean structure with a ridge and a lithosphere thickening toward continents forms between the diverging parts of the supercontinent. The calculated distribution of heat flux from the mantle has a maximum of about 200 mW m^-2 in the zone of the mid-ocean ridge and drops by about six times toward the continents, which agrees with data of observations. The Pacific Ocean structure with typical subduction zones develops on the opposite side of the continents. A high-viscosity mantle layer corresponding to continental lithosphere moves together with continents. The Atlantic Ocean structure persists for about 50-100 Myr, after which the heavy oceanic lithosphere separates from the continents and starts sinking into the mantle. Both continents are uplifted by a few hundred meters for about 50 Myr before and 50 Myr after the breakup of the supercontinent. This result is consistent with data on sea level fluctuations and can account for the duration of the Paleozoic, Mesozoic, and Cenozoic periods and for the origin of their changes.

Received 5 November 2004; accepted 5 March 2005; published 14 June 2005.

Keywords: Global geodynamics, Numerical modeling, Convection.

Index Terms: 8120 Tectonophysics: Dynamics of lithosphere and mantle: general; 8121 Tectonophysics: Dynamics: convection currents, and mantle plumes; 8149 Tectonophysics: Planetary tectonics; 8158 Tectonophysics: Plate motions: present and recent.

Citation: Trubitsyn, V. P., and A. P. Trubitsyn (2005), Evolution of mantle plumes and uplift of continents during the Pangea breakup, Russ. J. Earth Sci., 7, ES3001, doi:10.2205/2005ES000179.