Fossil thermal structure of the southern Sanandaj-Sirjan zone (SW Iran): Implications for regional-scale tectonics

Abstract The Sanandaj-Sirjan Zone (SSZ) is one of the Cimmerian blocks accreted to Eurasia during the Late Triassic and the only tectonic unit of the Zagros orogen affected by Barrovian metamorphism. Both the age and absolute temperature of this metamorphic event are still poorly defined. In the present study, we use the Raman Spectrometry of Carbonaceous Material (RSCM) to estimate maximum temperatures attained in the southern SSZ, along two SW-NE cross-sections. While maximum obtained temperature for Precambrian to Jurassic rocks ranges from ∼200 to ∼600°C, all Precambrian and Early Paleozoic samples record temperatures >500°C. Results thus reveal the existence of a major temperature contrast between Precambrian to Devonian samples (showing Tmax >500°C) and Late Devonian to Cretaceous ones (Tmax