Structural evolution along the Susa Shear Zone: the role of a first-order shear zone in the exhumation of meta-ophiolite units (Western Alps)

A significant new model explains the role of the Susa Shear Zone (SSZ) in the exhumation of meta-ophiolite units within the Western Alps, revealing its function as a first-order shear zone that couples tectonometamorphic units with distinct pressure-temperature (P–T) peaks. The study identifies two key shearing events (T1 and T2) during Alpine subduction and exhumation, characterized by contrasting kinematics—'apparent reverse' Top-to-E during early exhumation and Top-to-W during late exhumation. Detailed fieldwork and structural analysis allowed the reconstruction of four main deformation phases (D1 to D4), clarifying their relative timing and geometrical relationships. This four-step geodynamic model underscores the SSZ's critical role in shaping the axial sector of the Western Alps, offering insights into the complex tectonic processes governing mountain building.

Ghignone, S., Balestro, G., Gattiglio, M., & Borghi, A. (2020). Structural evolution along the Susa Shear Zone: the role of a first-order shear zone in the exhumation of meta-ophiolite units (Western Alps). Swiss Journal of Geosciences, 113(1). https://doi.org/10.1186/s00015-020-00370-6