2025/06/09 by Arghaee, Rowshanak, Ghorbani, Mansour, Francisco Santos, José
#Alkaline magmatism #Continental rift #Crustal contamination #Northern Alborz
paper · doi:10.57647/j.ijes.2025.16895
Cretaceous volcanic rocks are extensively developed in the Alborz structural zone, located in northern Iran. The petrogenesis and evolution of the northern Alborz basalts and other volcanic rocks have been studied before, but various theories have been proposed regarding their petrogenesis and geodynamic settings. To further explore their petrogenesis, we are conducting a study featuring three different regions of the northern Alborz dominated by extensive outcrops of Cretaceous volcanic rocks. The study area consists of the southern part of Amol city, JavaherDasht village in the east of Gilan province, and south of Lahijan in NarenjLengeh village in the west of Gilan province. Petrographic examination of the studied rocks shows evidence of primary magma, indicating the presence of alkaline magma in the region. Feldspathoids such as nepheline and nosean dominate most samples, providing evidence of alkaline magmatism. All analyzed samples from these three regions fall within the alkaline series. Geochemical studies point to a rift tectonic with significant crustal contamination. In a spider diagram of incompatible elements, an increase in the Nb/La ratio indicates crustal contamination, which is generally observed in continental rifts. All samples exhibit depletion of Y, confirming intraplate magmatism within the region. Chondrite-normalized rare-earth-element (REEs) patterns show a notable enrichment in light REEs (LREEs) relative to heavy REEs (HREEs). Our study suggests a rift tectonic setting for the northern Alborz rocks with prevalent alkaline magmatism during the Cretaceous.