Zoned garnets in the northern Dora-Maira Massif and their contribution to a reconstruction of the regional metamorphic evolution

Abstract

Three garnet generations are recognizable in the metapelites of the Dora-Maira polymetamorphic basement, often coexisting at the single-specimen scale or as strikingly zoned single blasts. This observation offers further evidence for a pre-Alpine history of the Massif, as well as providing new information on the meso-Alpine metamorphic event and the P-T path of its northern part. This trajectory is characterized by two metamorphic peaks at the same temperature, but at different pressures, reflecting two distinct thermal gradients and geodynamic environnments. The first (eo-Alpine event) is related to type-B subduction, whereas the second (meso-Alpine event) is linked to continental collision