Geometric and kinematic analysis of a transpression terrane boundary: Minas fault system, Nova Scotia, Canada
Published:January 01, 2004
E. A. Macinnes, J. C. White, 2004. "Geometric and kinematic analysis of a transpression terrane boundary: Minas fault system, Nova Scotia, Canada", Flow Processes in Faults and Shear Zones, G. I. Alsop, R. E. Holdsworth, K. J. W. McCaffrey, M. Hand
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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.
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Flow Processes in Faults and Shear Zones
Faults and their deeper level equivalents, shear zones, are localized regions of intense deformation within the Earth. They are recognized at all scales from micro to plate boundary, and are important examples of the nature of heterogeneous deformation in natural rocks. Faults and shear zones are significant as they profoundly influence the location, architecture and evolution of a broad range of geological phenomenao The topography and bathymetry of the Earth’s surface is marked by mountain belts and sedimentary basins that are controlled by faults and shear zoneso In addition, faults and shear zones control fluid migration and transport including hydrothermal and hydrocarbon systems. Once faults and shear zones are established, they are often long-lived features prone to multiple reactivation over very large time-scales. This collection of papers addresses lithospheric deformation and the rheology of shear zones, together with processes of partitioning and the unravelling of fault and shear zone histories.