Late Cenozoic volcanism in the Almaludag region, Azerbaijan province, northwest Iran: Evidence for post-collisional extension

We discuss the geology, petrology, and major and trace element geochemistry of Late Cenozoic volcanic rocks in the Almaludag region in the Western Azerbaijan province, northwest Iran. Geology of this region evolved through the northward subduction of the Neotethyan oceanic lithosphere and subsequent collision of the Arabian and Eurasian plates during the Alpine-Himalayan orogeny. Two different Late Cenozoic periods of volcanic activity are recognized: Episode I produced pyroclastic deposits and trachydacitic lava (1.47 Ma, U-Pb dating) and Episode II generated mafic lava and scoria cones (including spatter/cinder). Geochemical data indicate that Episode I lavas have high-silica adakitic compositions, similar to the post-collisional and continental adakites, that formed from the partial melting of the thickened lower crust. Episode II lavas vary in composition and fall into two distinct geochemical groups. The first group includes picrobasalt-basanite and tephrite compared to the more evolved trachybasalt and basaltic trachyandesite of the second group. Both of these groups show alkaline to shoshonitic affinities.