The andesitic ignimbrites from the Lower Permian volcanic sequence in the Val di Cave and Val di Fregio area (Trento, N Italy)

The Lower Permian volcanic sequence from the Val di Cave and Val di Fregio belongs to the southern sector of the Atesina platform. Rock types include andesites and dacites and rhyodacitic ignimbrites. The andesitic ignimbrites show widespread mineralogical and geochemical modifications due to syngenetic and post-eruptive interaction between rocks and low-temperature fluids. Andesitic magmas may have evolved towards dacitic terms through fractional crystallization of an assemblage dominated by plagioclase as it is supported by the mass-balance calculations. In contrast, the calculations rule out that the dacities could be the result of mixing between andesitic and silica-rich (rhyodacitic) magmas. -from Authors