a b s t r a c tThe study of continental subduction processes requires detailed Pressure Temperature (P-T) paths to understand the kinematic of burial and exhumation of continental units. In the French Western Alps, the Brianç onnais zone is a remnant of the continental subduction wedge. P-T conditions have been estimated in its most internal parts, but there is a lack of data in the western part, known as the "Zone houillère". This Brianç onnais Zone houillère is classically divided into two sub-units: the upper and lower Houiller units. This study focuses on both of these in the Clarée valley, north of Brianç on. In this low-grade metamorphic terrain, estimation of P-T history is complicated because there are few adapted methods and these rocks have a poor metamorphic mineralogical content, including detrital metamorphic minerals inherited from their hercynian history. Therefore, to acquire accurate P-T estimates a multi-method approach is required, involving qualitative and quantitative Raman Study of Carbonaceous Material (RSCM), chemical analysis from quantified X-ray maps and thermodynamic modelling of chlorites and K-white micas. Such multi-approach P-T estimates on a sandstone sample allow distinguishing hercynian peak metamorphic conditions of 371 ± 26 • C and 3.5 ± 1.4 kbar and alpine peak metamorphic conditions of 275 ± 23 • C and 5.9 ± 1.7 kbar. These results are consistent with our RSCM and T max estimates. Raman study conducted on organic-rich schist samples shows an eastward increase of the alpine T max in the upper Houiller unit, from 280 to 300 • C across the Brianç onnais Zone houillère. In contrast, carbonaceous material included in detrital grains of muscovite in the sandstone exhibits higher temperatures. This hercynian T max is estimated using thermodynamic modelling at 376 ± 50 • C. According to these results and previous work in more internal parts of the Brianç onnais zone, a geodynamic reconstruction is proposed, which is characterized by a diachronous evolution of the Brianç onnais zone involved in alpine continental subduction at different times. The geothermal gradient in the Brianç onnais zone changes from 8 • C/km during early continental subduction, to 40 • C/km during the collisional event at about 35-30 Ma. The intermediate gradient of 15 • C/km estimated in the Brianç onnais Zone houillère suggests that this unit was buried later, than the more internal Brianç onnais units, after 40 Ma.

The Stak massif, northern Pakistan, is a newly recognized occurrence of eclogite formed by the subduction of the northern margin of the Indian continent in the northwest Himalaya. Although this unit was extensively retrogressed during the Himalayan collision, records of the high-pressure (HP) event as well as a continuous pressure-temperature (P-T) path were assessed from a single thin section using a new multiequilibrium method. This method uses microprobe X-ray compositional maps of garnet and omphacitic pyroxene followed by calculations of ~200,000 P-T estimates using appropriate thermobarometers. The Stak eclogite underwent prograde metamorphism, increasing from 650 °C and 2.4 GPa to the peak conditions of 750 °C and 2.5 GPa, then retrogressed to 700-650 °C and 1.6-0.9 GPa under amphibolite-facies conditions. The estimated peak metamorphic conditions and P-T path are similar to those of the Kaghan and Tso Morari high-to ultrahigh-pressure (HP-UHP) massifs. We propose that these three massifs defi ne a large HP to UHP province in the northwest Himalaya, comparable to the Dabie-Sulu province in China and the Western Gneiss Region in Norway.