The development of bone-shaped structures in initially segmented layers during layer-parallel extension: numerical modelling and parameter sensitivity analysis

In orogenic zones the geometric occurrence of specific tectonic structures can often be related to contrasting rheological properties of rock materials. One of such tectonic structures is layer-perpendicular naturally fractured layers with vein infill that underwent subsequent deformation. Internal deformation by coaxial extension of these segmented layers, with host-rock material less competent than the vein material, gives rise to the development of bone-shaped structures (i.e. dogbones). In this paper, the formation of such dogbones is modelled using finite element techniques. A parameter sensitivity analysis of the model demonstrates that the degree of extension of the host-rock segments, their initial aspect ratio and the competence contrast between vein material and host-rock are the controlling parameters for the final shape of the dogbones during coaxial extension. The results, moreover, suggest that the specific geometry of the dogbones can serve to quantify competence contrasts between the host-rock and vein material during flow at geological strain rates.