S. MELI & B. BERTOLO
ABSTRACT
Geochemical characters of the Val Roja amphibolites (Ötztal basement, Eastern Alps). In the Ötztal Complex (Central Austroalpine, Alto Adige), several small amphibolitic bodies occur, showing different chemical affinities; the origin of the protoliths is geologically constrained in pre-Variscan times. In this paper we present new geochemical data for amphibolites and associated metaultramafites outcropping in Val Roja (upper Venosta Valley). Ortho- and para-amphibolites are distinguished on the basis of chemical variation trends; high Ti, Cr, Ni content is a further proof of the magmatic origin for a group of amphibolites. Immobile element ratios point to a subalcaline affinity for the metabasalts, and discriminant diagrams for basic rocks indicate a within plate tectonic setting. Taking into account the whole amphibolite outcrops in the Ötztal basement, it is suggested that volcanism developed mainly on continental crust.