Abstract 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.

Abstract The permanent GNSS station located at the Everest Pyramid Laboratory of EvK2CNR recorded its position coordinates during the earthquakes at the Gorkha (25 April 2015) and Ghorthali zones (12 May 2015) at an interval of every 30 s. The data recorded over three days prior to and after the earthquakes were analysed and the movement indicated a shifting of the GNSS station point from its original position every 30 s. From an accurate analysis of the coordinates of the station determined using GNSS Bernese software, it is possible to detect the movements of the station during the seismic events. The shifts in the GNSS point were summed to provide an integral function (PIF, Pyramid Integral Function) that can be computed for each of the three components. Comparing them with the displacement record of the GURALP broadband seismic station (IO-EVN) of the OGS (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, OGS, Trieste), located at the Pyramid, it is possible to establish a correlation, particularly with the vertical and north components; the maxima of the PIF coincide with the time of occurrence of the earthquakes.