Influência reológica na geração de estruturas transcorrentes: aplicação da modelagem física e PIV

Abstract

Physical modeling is a tool that has been widely applied in several fields of geology, in particular, structural geology focusing on the tectonics of sedimentary basins and mountain ranges formation, and their associated processes. In this research, analogical physical modeling was used to investigate the influence of rheology on the nucleation and evolution of secondary structures associated with transcurrent tectonics. The experimental models performed in a sandbox apparatus were monitored by conventional photographs, Laser Scanner (LS) and Particle Image Velocimetry (PIV). This latest enabled the analysis of the strain distribution within the damage zone, the structures nucleation, their relative chronological relationships and their influence on the topographic evolution of the deformed area. The experiments simulated the development of secondary structures nucleated during a progressive deformation in a dextral shear zone. The models were executed with granular analog materials of different rheological behaviors, such as quartz sand, dry clay, plaster powder and a mixture of sand and plaster powder. The physical properties of these materials were characterized by Ring Shear Tester (RST). Along with the deformational evolution of the experiments, secondary fractures (R, R’, P, Y), pullapart basin, positive and negative flowers (transpression and transtension zones, respectively) and block rotation were analyzed qualitatively. Models constituted of different pre-tectonic sequences without rheological contrasts (a single type of granular material) displayed a geometrical and evolutional diversified structural framework conditioning to the used material. Experiments with rheological stratification (pre-tectonic sequences with different granular materials) displayed a structural architecture distinct from rheological homogeneous models. Our results confirm that rheology has a significant role in the arrangement of secondary faults and their relative chronology during the transcurrent tectonics. These experimental analyses corroborate with structures (Riedel fractures, pullapart basin, and block rotation) of natural examples available in the literature.