TY - JOUR A1 - Negro, Francois A1 - Bousquet, Romain A1 - Vils, Flurin A1 - Pellet, Clara-Marine A1 - Hänggi-Schaub, Jeanette T1 - Thermal structure and metamorphic evolution of the Piemont-Ligurian metasediments in the northern Western Alps JF - Swiss journal of geosciences N2 - In the Western Alps, the Piemont-Ligurian oceanic domain records blueschist to eclogite metamorphic conditions during the Alpine orogeny. This domain is classically divided into two "zones" (Combin and Zermatt-Saas), with contrasting metamorphic evolution, and separated tectonically by the Combin fault. This study presents new metamorphic and temperature (RSCM thermometry) data obtained in Piemont-Ligurian metasediments and proposes a reevaluation of the P-T evolution of this domain. In the upper unit (or "Combin zone") temperatures are in the range of 420-530 A degrees C, with an increase of temperature from upper to lower structural levels. Petrological evidences show that these temperatures are related to the retrograde path and to deformation at greenschist metamorphic conditions. This highlights heating during exhumation of HP metamorphic rocks. In the lower unit (or "Zermatt-Saas zone"), temperatures are very homogeneous in the range of 500-540 A degrees C. This shows almost continuous downward temperature increase in the Piemont-Ligurian domain. The observed thermal structure is interpreted as the result of the upper and lower unit juxtaposition along shear zones at a temperature of similar to 500 A degrees C during the Middle Eocene. This juxtaposition probably occurred at shallow crustal levels (similar to 15-20 km) within a subduction channel. We finally propose that the Piemont-Ligurian Domain should not be viewed as two distinct "zones", but rather as a stack of several tectonic slices. KW - RSCM thermometry KW - Zermatt-Saas KW - Combin KW - Cignana KW - HP and UHP metamorphism Y1 - 2013 U6 - https://doi.org/10.1007/s00015-013-0119-7 SN - 1661-8726 VL - 106 IS - 1 SP - 63 EP - 78 PB - Springer CY - Basel ER -