Luc Lavier from the University of Texas at Austin
Deviation from rigid plate tectonics: possible transient creep events in a semi-brittle Earth’s lithosphere
Monday, 20 April 2015 at 11:00 (CEST)
Kirchberg Salle Paul Feidert
In a given tectonic province and over thousands to millions of years, slip on faults is believed to be constant and approximately equal to the local tectonic rate in agreement with rigid plate tectonic theory. In this model the ductile lower crust flows in response to this steady plate motion. Moreover brittle and ductile behaviors interact only at a sharp boundary defined as the brittle ductile transition (BDT). However in the continental lithosphere brittle and ductile behavior may coexist over a large range of pressure and temperature conditions for different mineral compositions. This generates heterogeneities in the brittle and ductile crust that are often ignored in models of shear zones. We hypothesize that the interaction between brittle (elastic) and ductile (viscous) behavior may cause deviations from steady-state slip and generates transient creep events on shear zones that release many meters of creep over years to thousands of years marked by a single period of tectonic activity followed by quiescence. We also hypothesize that over millions of years such behavior fundamentally modifies strain accumulation in the Earth’s lithosphere.
Newly developed set of numerical and analytical models, analogue experiments as well as some observations that may support this hypothesis are presented. Numerical and analogue experiments of anastomosing shear zones formation demonstrate both the short and long term mechanisms of strain accumulation at the transition between brittle and ductile behavior in the lithosphere. We apply this formulation to the development of continental rifts to show how such mechanisms could influence the long-term development of tectonic provinces.
See also the recent paper http://hdl.handle.net/10993/19464