Abstract
The aim of this study is to present analog models of flanking structures and to analyze the Fábrica Nova synform, Quadrilátero Ferrífero, Minas Gerais, from a geometric point of view. We set up seven models using a linear viscous silicone and produced flanking structures with a shear velocity of 2 cm h-1. At different initial orientations with respect to the shear zone boundary, a rigid cross-cutting element with lubricated boundaries was deformed via sinistral bulk flow at a shear strain of γ = 1.28. The most interesting features of our experiments are the geometries of the different marker lines, which are heterogeneous and resulted from thickening and thinning of the silicone at the cross-cutting element terminations. To compare our analog models and the Fábrica Nova synform, we analyzed the outermost marker line of the analog models and the top surface of the Cauê Formation in the Paleoproterozoic metasediments. The best comparisons between the experiments and the natural example were obtained by our CIS90 model in terms of the flexure shape near the cross-cutting element and the cross-cutting element orientation. Thus, we suggest that the cross-cutting elements in both situations act as obstacles and consequently produce local perturbations in laminar flow.
Highlights
IntroductionWe present and discuss analog models of flanking folds. We used a simple shear rectangular box and a rigid cross-cutting element with lubricated boundaries to analyze the Fábrica Nova flanking fold thesis presented by Rossi and Endo (2015) from a geometric point of view.The term flanking structures was first used by Passchier (2001) to describe deflections on the centimeter scale (Fig. 1). Passchier (2001) showed that these structures are isolated folds that were formed in a number of different ways and commonly show shear sense opposite to the fault drag effect
In the present study, we present and discuss analog models of flanking folds
- The final geometry of flanking structures is controlled by the initial angle φ of the cutting element (CE), which influences the magnitude of the rotation angle, ω
Summary
We present and discuss analog models of flanking folds. We used a simple shear rectangular box and a rigid cross-cutting element with lubricated boundaries to analyze the Fábrica Nova flanking fold thesis presented by Rossi and Endo (2015) from a geometric point of view.The term flanking structures was first used by Passchier (2001) to describe deflections on the centimeter scale (Fig. 1). Passchier (2001) showed that these structures are isolated folds that were formed in a number of different ways and commonly show shear sense opposite to the fault drag effect. We used a simple shear rectangular box and a rigid cross-cutting element with lubricated boundaries to analyze the Fábrica Nova flanking fold thesis presented by Rossi and Endo (2015) from a geometric point of view. The term flanking structures was first used by Passchier (2001) to describe deflections on the centimeter scale (Fig. 1). Passchier (2001) showed that these structures are isolated folds that were formed in a number of different ways and commonly show shear sense opposite to the fault drag effect. Scientists agree that the flanking structures are a deflection of the passive planar fabric elements (e.g., foliation or layering) around cross-cutting objects A review of these concepts (their formation and geometric features) and the classification of flanking structures were presented by Mukherjee (2014)
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