ANDALUSITE VEINS FROM THE PISCHAHORN (GRI SONS, SWITZERLAND)

New structural and mineralogical data about the quartz-andalusite and/ or muscovite, albile veins occurring near the Pischahorn mountain (Gri sons, Switzerland) are presented. The veins are closely related to mic aschists and staurolite-micaschists within a thick paragneissic sequen ce belonging to the polymetamorphic basement of the Upper Austroalpine Silvretta nappe. The veins display a large spectrum of morphologies w hich reflect their crystallization in a dynamic context. The recogniti on of the syn- or post-D3 emplacement of the veins and the existence o f kyanite relics being replaced by andalusite in one vein leeds to a m odification of the Late Variscan Pressure-Temperature path followed by the Silvretta nappe basement.