3D deformation in strike-slip systems: Analogue modelling and numerical restoration

Luisa Pinto,Daniel González,César Arriagada,Matías Peña

doi:10.5027/andgeov39n2-a06

Abstract

Regional and local strike-slip systems in Chile are complex and pose interesting questions, such as the interaction between strike-slip and reverse faults, how they evolve, and the relationship between shortening, rotation and uplift. Within this context, we developed a new analytical method based on analogue and numerical modelling applied to 3D, pure and transtensional-transpressional strike-slip systems. Analogue modelling results indicate that in restraining stepovers of strike-slip fault systems, where antiformal pop-up structures are usually formed, pre-existent basement structures with a high angle to the main strike-slip fault will generate a higher rotation of blocks. However, when these structures are oriented at a high angle with respect to the main stress convergence vector, the rotation will be less and therefore a higher tendency to uplift will be produced. These results were applied to NW- and SE-striking basement faults oblique to N-S mega-thrust faults in central Chile (32o-35oS), for which we propose a simultaneous development based on the analogue model results. Moreover, we propose that strike-slip movement occurred on thrust faults in central Chile. Furthermore, we performed a numerical restoration of an analogue experiment which modeled a pure strike-slip system, and concluded that the restoration is very sensitive to shortening data as well as to rotational data. These results are extremely important for future numerical and regional analysis of strike-slip systems.

Highlights

The Chilean Andes provides a natural laboratory for investigating the nature of thick- and thin-skinned deformation along a convergent plate margin
We developed a new analytical method based on analogue and numerical modelling applied to 3D, pure and transtensional-transpressional strike-slip systems
These results were applied to NW- and SE-striking basement faults oblique to N-S mega-thrust faults in central Chile (32o-35oS), for which we propose a simultaneous development based on the analogue model results

Summary

Introduction

The Chilean Andes provides a natural laboratory for investigating the nature of thick- and thin-skinned deformation along a convergent plate margin. Because of the change in convergence velocity and obliquity angle from 10 mm/y to 100 mm/y and from 80o to 40o, respectively, that occurred in the Chilean Andes during the Early Eocene (Pardo-Casas and Molnar, 1987), deformation at some latitudes has occurred along a series of strike-slip systems with a significant partitioned deformation along their strike (Pardo-Casas and Molnar, 1987; Scheuber et al, 1994) These strike-slip systems developed in several periods of geological time, i.e., the Early Cretaceous and the Oligocene (Scheuber et al, 1994), and their structures channeled hydrothermal fluids that formed large porphyry Cu systems. These systems are associated to areas of seismic activity (e.g., Reutter et al, 1996; Scheuber and Giese, 1999; Amilibia et al, 2008)

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