Middle Triassic evolution of the Rio Freddo volcanism, southern Alps, Italy

---Petrographic and petrochemical investigations permit: 1) to distinguish the Upper Anisian volcanism from the Lower Ladinian one; 2) to suggest an evolution within the Rio Freddo Volcanics (rhyolitic to rhyodacitic); 3) to point out different characters of the various kinds of pyroclastics. Particularly, K-contents show anomalous enrichments in the ignimbrites. A model of vapour-phase crystallization, related to a fumerolic activity and fluid circulation, is suggested. -from English summar