Deformation of poly-mineralic materials and their effect on extensional processes at lithospheric scale- (From 15:15)

Most of rocks are poly-mineralic and the transition between brittle and ductile micromechanical deformation fields is specific for each mineral phase.  It is therefore normal that in poly-mineralic materials under certain conditions, certain mineral phases deform in a brittle manner while others are still in the ductile deformation domain generating semi-brittle deformation mechanisms. However, if this is true at the sample scale, it is also likely that such mechanisms can be observed between metric or pluri-metric blocks of different composition. Geological observations demonstrate indeed that semi-brittle deformation mechanisms can be observed in the field at all scales and suggest that these mechanisms play an important role in deformation processes from millimeter scale to lithospheric scale. To explore the role of these semi-brittle domains, I looked first at the deformation of bi-mineral materials at the sample scale and then at the lithospheric scale in an extensional setting using a numerical approach. This work demonstrates the importance of an explicit bi-mineralic composition assimilated to crustal and mantle heterogeneities on rifting processes. Subsequently, questions on the role of crustal inheritances during deformation processes emerged from this work. To address this question, I conducted a multidisciplinary study combining the analysis of geological and geophysical data of the Northeastern Canadian margin and numerical modeling.  Preliminary results of this study will be also presented in this presentation.