A peculiar feature of the Himalaya is the occurrence of a system of low‐angle normal faults and shear zones, the South Tibetan Detachment System (STDS), at the mountain crests. The STDS was active during synconvergent tectonics. We describe the STDS‐related sheared rocks along the Dhauli Ganga valley, in the Garhwal Himalaya (NW India), where the Malari granite, reported as an undeformed igneous body crosscutting the STDS, occurs. A detailed multidisciplinary study, integrating field‐based, microstructural, petrographic, and geochronological analyses, was carried out on rocks along this valley. We demonstrate how the noncoaxial ductile portion of the STDS affected the upper part of the Greater Himalaya Sequence migmatite, which experienced peak pressure (P)‐temperature (T) conditions of 0.9–1.1 GPa and ≥750°C at ≥24 Ma. This migmatite has been reworked structurally upward leading to the formation of high‐T sillimanite‐bearing mylonites. Further upward, medium‐T shearing deformed the Malari granite and leucogranite dykes, forming medium‐T mylonites. Ductile shearing was temporally constrained, based on new in situ monazite datings and previously published Ar‐Ar geochronology, between ~20 and 15 Ma. We demonstrate that a preserved ductile to brittle spatial and temporal transition of the STDS deformation exists, with the brittle features overprinting ductile ones. Our data shed new light on the geological evolution of the STDS in the NW Himalaya with implications for the relationship and relative timing of partial melting, granite emplacement, and deformation along low‐angle normal faults.

Detailed geological field mapping, integrated with meso- and microstructural investigations, kinematic of the flow and finite strain analyses, combined with geochronology, are fundamental tools to obtain information on the temperature–deformation–timing path of crystalline rocks and shear zone. The Posada-Asinara shear zone (PASZ) in northern Sardinia (Italy) is a steeply dipping km-thick transpressive shear zone. In the study area, located in the Baronie region (NE Sardinia), the presence of mylonites within the PASZ, affecting high- and medium-grade metamorphic rocks, provides an opportunity to quantify finite strain and kinematic vorticity. The main structures of the study area are controlled by a D₂ deformation phase, linked to the PASZ activity, in which the strain is partitioned into folds and shear zone domains. Applying two independent vorticity methods, we detected an important variation in the percentage of pure shear and simple shear along the deformation gradient, that increases from south to north. We constrained, for the first time in this sector, the timing of the transpressive deformation by U–(Th)–Pb analysis on monazite. Results indicate that the shear zone has been active at ~325–300 Ma in a transpressive setting, in agreement with the ages of the other dextral transpressive shear zones in the southern Variscan belt.

Joining geological mapping, structural analysis, petrology and geochronology allowed the internal architecture of the Greater Himalayan Sequence (GHS) to be unraveled. Several top-to-the-south/SW tectonic–metamorphic discontinuities developed at the regional scale, dividing it into three main units exhumed progressively from the upper to the lower one, starting from c. 40 Ma and lasting for several million years. The activity of shear zones has been constrained and linked to the pressure–temperature–time–deformation ( P – T – t – D ) evolution of the deformed rocks by the use of petrochronology. Hanging wall and footwall rocks of the shear zones recorded maximum P – T conditions at different times. Above the Main Central Thrust, a cryptic tectonometamorphic discontinuity (the High Himalayan Discontinuity (HHD)) has been recognized in Central-Eastern Himalaya. The older shear zone, that was active at c. 41–28 Ma, triggered the earlier exhumation of the uppermost GHS and allowed the migration of melt, which was produced at peak metamorphic conditions and subsequently produced in abundance at the time of the activation of the HHD. Production of melt continued at low pressure, with nearly isobaric heating leading to the genesis and emplacement of andalusite- and cordierite-bearing granites. The timing of the activation of the shear zones from deeper to upper structural levels fits with an in-sequence shearing tectonic model for the exhumation of the GHS, further affected by out-of-sequence thrusts.