Alkaline magmatism in the post-orogenic Triassic Predazzo complex, Dolomites, NE Italy: Ages and significance

The Predazzo pluton (Predazzo–Monzoni intrusive complex, Dolomites) is a multipulse calc-alkaline–shoshonitic body, which was emplaced at 238.075 ± 0.087 Ma to 235.9 ± 1.8 Ma. On the eastern flank of the pluton, smaller-volume alkaline rocks are also found, but their relationships with the main magmatic products are not well understood. New field, petrographic, geochemical and geochronological data indicate that these alkaline rocks infilled a small volcano-tectonic trough and consist of trachytic lavas and volcanoclastic tephra (V2 unit), studded by small monzonite and syenite bodies (MS unit) in mingling-mixing relationships, yielding ages of 238.1 ± 1.8 to 230.1 ± 0.6 Ma. Phonotephrite to phonolite dykes (MF unit) crosscut the entire volcanic sequence at 215.0 ± 0.3 Ma and 203 ± 1 Ma. The alkaline cycle thus developed soon after and, possibly, during the main calc-alkaline–shoshonitic stage. Lamprophyric dykes (camptonites) were also emplaced from 234.5 ± 0.3 to 219.2 ± 0.7 Ma. Whol...