Modelagem física da influência da herança estrutural na formação de novas estruturas: aplicação à Zona de Cisalhamento Pernambuco, NE do Brasil

Abstract

Shear zones in the crystalline basement create crustal and lithospheric heterogeneities, acting as zones of weakness that influence the location, geometry, and segmentation of more recent structures. This study investigates the impact of preexisting structures on the development of sedimentary basins and newly formed or reactivated structures during subsequent tectonic events, using the brittle deformation of the Pernambuco Shear Zone (PESZ) as a natural example. Experimental models analyzed with Particle Image Velocimetry (PIV) simulated the role of structural inheritance in forming a rift basin orthogonal to a preexisting weakness zone under different rheological conditions. The effects of preexisting structure orientation on subsequent brittle deformation were also examined. The integration of experimental and field data provided a better understanding of the brittle deformation of the PESZ. The results indicate that preexisting shear zones influence the orientation, location, and geometry of newly formed structures in orthogonal basins, even without reactivation. Rift basins associated with these structural inheritances are wider and shallower. Rheological variations also impacted the number of structures formed. In strikeslip zones, the orientation of inherited structures controlled the formation of subsidiary fractures in the Riedel system, revealing the relationship between the new stress field, the type of structures formed, and the evolutive nature (new or reactivated). This relationship affects the main fault's growth, either as a continuous or in segments, as well as the number of structures formed and the distribution of on- and off-fault deformation. The field and experimental data integration shows that inherited mylonitic fabric acted as a mechanical weakness zone, facilitating brittle reactivation. Three groups of brittle structures were identified along the PESZ: (i) dextral strike-slip reactivation at the end of the Brasiliano Cycle; (ii) sinistral reactivation in the Early Cretaceous, associated with the opening of the South Atlantic Ocean; and (iii) N-S oriented normal faults and fractures, related to the same opening process as (ii), but formed later. The experiments suggest that PESZ may act as a structural high separating the Pernambuco and Paraíba sub-basins. The results highlight the potential of analog modeling for predicting fault and fracture patterns in complex tectonic systems, demonstrating how inherited shear zones can influence the evolution of new structures.