|
Department of Earth Sciences and Ottawa-Carleton Geoscience Centre, Carleton University, Ottawa K1S 5B6, Canada
The rheology of the lithosphere is a factor of primary importance in the kinematics and dynamics of mountain belts. This paper attempts to clarify the role of rheology in orogenesis, by applying simple physical principles to the analysis of tectonic processes. The emphasis is on broad generalizations leading to order-of-magnitude estimates. Since the rheology of lithospheric materials is strongly dependent on temperature, the discussion opens with a review of continental and oceanic geotherms and an assessment of their reliability. Then the brittle (frictional) and ductile (high-temperature creep) properties of the lithosphere are considered. In the brittle field, particular attention is paid to the problem of fault reactivation, which is shown to be more likely in extensional than in compressional regimes. In the ductile field, a summary of creep parameters for the most common lithospheric materials is presented. The central concept of rheological profiles (strength envelopes), essential to the estimation of the depth variations of lithospheric rheology, is discussed with reference not only to its applicability but also to its limitations (a two-dimensional example from the Canadian Cordillera is given). Processes related to the rheological properties and layering of the lithosphere — gravitational collapse in thickened and softened crust, tectonic inversion following the detachment of a lithospheric root, lower crustal ductile flow with consequent relaxation of Moho topography — are analysed semi-quantitatively, mainly to show that they are indeed likely to be important players in geodynamics. Finally, in a brief Archaean detour, some possible important differences between present-day and Archaean oceanic lithosphere are examined, and the conclusion is reached that in all likelihood plate tectonics, although at different rates, has been the main agent of orogenesis during most of the history of the planet.
This article has been cited by other articles:
 |
|
 |
|
  S. Cloetingh, F. Beekman, P. A. Ziegler, J.-D. van Wees, and D. Sokoutis Post-rift compressional reactivation potential of passive margins and extensional basins Geological Society, London, Special Publications, 2008; 306: 27 - 70. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. V. Hodges A synthesis of the Channel Flow-Extrusion hypothesis as developed for the Himalayan-Tibetan orogenic system Geological Society, London, Special Publications, 2006; 268: 71 - 90. [Abstract] [PDF]
|
|
|
|
|
|
E. Willingshofer, D. Sokoutis, and J.-P. Burg Lithospheric-scale analogue modelling of collision zones with a pre-existing weak zone Geological Society, London, Special Publications, 2005; 243: 277 - 294. [Abstract] [PDF]
|
|
|
|
|
|
D. Praeg Diachronous Variscan late-orogenic collapse as a response to multiple detachments: a view from the internides in France to the foreland in the Irish Sea Geological Society, London, Special Publications, 2004; 223: 89 - 138. [Abstract] [PDF]
|
|
|
|
|
|
J.-P. Brun Deformation of the continental lithosphere: Insights from brittle-ductile models Geological Society, London, Special Publications, 2002; 200: 355 - 370. [Abstract] [PDF]
|
|
|
|
|
|
J. Braun and R. Shaw A thin-plate model of Palaeozoic deformation of the Australian lithosphere: implications for understanding the dynamics of intracratonic deformation Geological Society, London, Special Publications, 2001; 184: 165 - 193. [Abstract] [PDF]
|
|
