Regional Variations in Lithosphere Rheology from Heat Flow Observations

  • G. Ranalli
Part of the Exploration of the Deep Continental Crust book series (EXPLORATION)

Abstract

The rheological properties of the lithosphere are related to its geothermal state, composition, and structure. Geotherms for differet tectonic provinces are a function of surface heat flow, while the composition and structure of the lithosphere are constrained by other geophysical (mainly seismic) data. It is therefore possible to estimate regional variations in lithosphere rheology from available evidence.

Lithospheric rheological profiles (strength envelopes) are estimated for different tectonic regions with characteristic geotherms, composition, and crustal thickness. The profiles yield information on the depth of the brittle/ductile transition, the rheological thickness of the lithosphere and its total strength, and the occurrence of soft ductile layers sandwiched between harder brittle layers. Large intraplate lateral changes in rheological properties are predicted. The response of a plate to tectonic stresses is affected in a significant way by these inhomogeneities.

The results have interesting geodynamic implications. Variations of total lithospheric strength generate zones of weakness in the lithosphere, where deformation is concentrated. The evolution of obduction and overthrusting in an orogenic belt can be studied if conditions at the time of deformation are sufficiently constrained by observation.

Keywords

Migration Quartz Hydration Silicate Sedimentation 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1991

Authors and Affiliations

  • G. Ranalli
    • 1
  1. 1.Department of Earth SciencesCarleton University and Ottawa/Carleton Geoscience CentreOttawaCanada

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