Facies studies and depositional environment of Sahand volcanic complex (NW of Iran)

Sahand volcanic complex is located in the south of Tabriz and east of Urmia Lake and includes an alternation of lava, igneous materials and clastic sediments that were affected by many folds and fractures. Sahand volcano is relatively young in age (Miocene to Pliocene) and its structure is somewhat intact. Consequently, where there is a good lateral continuity, facies and volcanological studies can be carried out in the upper part of the complex. Based on these studies, it was determined that the Sahand volcanic structure can be divided into four central, near, medium and distant facies. Facies studies show that the structure of Sahand Volcano was created by several explosive phases, some of which were associated with water intrusion and there was not much time between eruptions. Characteristics, such as severe welding and discoloration of pyroclastic deposits show that these units had a high temperature at the time of formation and were formed on land. Overall, Sahand volcanic eruptions were more explosive, and thus, the number of pyroclastic deposits is much higher than lava flows. In the central, near and middle facies of Sahand, no traces of younger hydrothermal activities can be found, and only in the distant facies, there is a hot spring (Bostan Abad), the relationship of which needs further study to prove the connection of these springs with the Sahand Volcano.