The composite Meghri-Ordubad and Bargushat plutons and associated porphyry Cu-Mo deposits of the Zangezur-Ordubad region, southernmost Lesser Caucasus, were emplaced during a long-lasting, stationary Tertiary magmatic evolution. All magmas have a subduction-related signature. Radiogenic isotopes reveal a mantle-dominated magmatism, with the mantle component becoming more predominant with time. Trace element geochemistry indicates progressive thickening of the crust from the Eocene to the Miocene. Eocene calcalkaline, normal arc (non-adakitic) magmatic activity was related to subduction of the Neotethys beneath Eurasia, and magmatism was dominated by fluid-related enrichment. The Eocenece magmatic stage generated the first pulse of porphyry Cu-Mo deposits. During collision to post-collision evolution, magmatism evolved to shoshonitic during the Oligocene, and calc-alkaline to high-K calc-alkaline and adakitic during the Late Oligocene and Mio-Pliocene. The younger magmatic evolution involved a mantle source metasomatised by a sedimentary component. The second stage of porphyry Cu-Mo deposits is associated to the collision to postcollision Oligo-Miocene adakitic magmatism. Increasing mantle contribution with time was favoured by mantle flow through a slab window/tear opened as a consequence of progressive indentation and deformation of the Eurasian margin by the Gondwana-derived South Armenian block during final closure of the Neotethys.