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Department of Geology, University of New Brunswick, Fredericton, NB Canada, E3B 5A3ellie_macinnes{at}hotmail.com
The Minas fault system is an ENE-WSW trending transpressional boundary between the Appalachian Meguma and Avalon tectono-stratigraphic terranes of Nova Scotia, Canada. Along this boundary there is large-scale partitioning of deformation into distinct external (contractional) and internal (shear) zones. With the increase in strain from external to internal zones there is progressive localization of deformation, culminating in the discrete shear band domain. Deformation has produced materially, temporally and spatially distinct folds and faults throughout the fault system history. Ductile structures are generally composite features derived from multiple transposition of pre-existing layers. The partitioning of deformation found amongst fault rock units can in turn be associated with contrasting deformation micromechanisms. The distinctive variation in mechanical response and microstructures provides an insight into the role of localization, partitioning and distribution of deformation. Kinematic analysis has demonstrated that the Minas fault system segment examined here is a thinning deformation zone, in which strain is accommodated within progressively narrower volumes of rock. Deformation can be summarized as a broad, initially diffuse zone of triclinic transpression that has evolved, with the accumulation of finite strain, into zones of distinct structural style and variation in finite strain. It is not possible to demarcate ‘deformed shear zone’ and ‘undeformed host rocks’. Instead, the Minas fault system is described in terms of discontinuous transitions in finite strain and deformation style within a large scale movement picture.
