Continental crust variance between post-collisional compressional and extensional domains controlled magmatic activity at damavand volcano, Northern Iran

The Quaternary Damavand stratovolcano, with an elevation of 5670 m, is the highest mountain in Iran and is the subject of this study. The main rocks are trachyandesite and trachybasalt, and Sr-Nd isotope ratios of whole rock samples show small variations in ɛSr (+3.2 to + 6.4) and ɛNd (−1 to + 1). Overall, rock chemistry and Sr-Nd isotope ratios support a metasomatic asthenospheric mantle with minor pelagic sediments from the oceanic subducted slab and/or carbonatite melts from the deep mantle as sources. Collision of the Arabian and Eurasian plates compressed the Iranian plateau between them, resulting in compressional and extensional domains in different regions. As a result of continuous pressure from the Arabian plate, thrusting and folding in compressional domains increased crustal thickness while thinning occurred in extensional areas. These processes cause thermal gradient perturbations at the boundaries between the two, leading to the melting of the mantle and/or lower crustal mafic rocks and production of alkaline rocks. Damavand volcano is located at the junction of compressional and extensional regimes, and its activity has been influenced by the variation of crustal thickness along the Alborz Mountain in the southern Caspian Sea. Therefore, the variation of crustal thickness can be suggested as a main mechanism for the generation of magmatic activity along the entire Iranian plateau in a post-collision system.