Calc-alkaline magmatism of the Cǎlimani-Harghita Mts. has been interpreted by the authors as of “island-arc” type. Ni, Co, and V contents, similar in both Carpathian and circum-Pacific andesites conform with a derivation from partial melting of a subducted oceanic crust for rocks studied, and are also hypothesized for island-arc calc-alkaline series. According to plate-tectonics models, the authors suggest the presence of a Cenozoic subduction zone in the eastern Carpathians with a consuming crust of oceanic type and a Benioff plane, dipping westward. This subduction process, still active in the Carpathian area of maximum bend, also caused the Cenozoic tectogenic processes, besides young volcanism studied. In this study, the Transylvanian basin is considered as a retro-arc basin on sialic crust formed by distension and spreading, according to formation models of marginal basins.