TECTONOMAGMATIC EVOLUTION OF SHEETED PLUTONIC BODIES ALONG THE NORTH GIUDICARIE LINE (NORTHERN ITALY)

Tectonized slices of foliated quartz-diorite/quartz-gabbro rocks are e xposed along the north Giudicarie line between Dimaro and Rumo (Wester n Trentino region, north-east Italy). They show geochemical and minera logical similarities with the north-east corner of the Adamello bathol ith (Presanella pluton) and may be regarded as a northern apophysis la mella of Adamello. The intrusive bodies were emplaced within the Adria crust at a relatively shallow depth (approximately P(H2O) equal to 3 kbar) along a proto-Giudicarie line under transtensive conditions duri ng late Oligocene. Only near Rumo has contact metamorphism on the Aust roalpine basement been observed, whereas in other outcrops it has been tectonically removed by later movements along the Giudicarie line. In the Samoclevo lamella a magmatic flow texture, which developed during the emplacement of a crystal mush at shallow depth, is recorded by th e preferred alignment of plagioclase and hornblende. A solid state fol iation, outlined by quartz crystal aggregates, green hornblende and bi otite, has been observed mostly in the Rumo lamella. This indicates th at a later ductile deformation, which developed under decreasing tempe ratures, overprinted the intrusive rocks. This deformation probably re flects late Oligocene strike-slip movements along the Tonale and Giudi carie lines. Finally semi-brittle to brittle deformation overprints th e foliated igneous lamellae producing cataclasites and pseudotachylite s. Sometimes these structures are subsequently cut by prehnite and epi dote bearing veins. During this event, the intrusive lamellae were dec oupled from their contact aureole and carried over the Insubric Flysch of the southern Alps. This last tectonic phase may be correlated to t he Upper Miocene neo-Alpine transpressive event along the Giudicarie L ine.