Tracing Ediacaran-Cambrian, Ordovician, Variscan and Cimmerian events from Alps towards Iran: Significance for opening and closure of Prototethys and Paleotethys oceans

The basement of the Alpine-Himalayan mountain belt between the Alps and Iran preserves evidence of multiple tectonic events within distinct microcontinental blocks. However, the distribution and tectonic significance of the Late Neoproterozoic-Early Cambrian (“Cadomian”), Ordovician (“Cenerian”), Carboniferous (“Variscan”), and Permian-Jurassic (“Cimmerian”) tectonic stages remain incompletely understood. Based on geochronological and high-pressure/low temperature datasets in context with geological observations from the Alps to Iran, we show the key stages along northern Gondwana. Ediacaran-Cambrian arc systems and associated ophiolites forming the basement of the future Alpine-Himalayan belt. The western part of the belt was affected by Ordovician arc systems, but also by rift systems creating a flare-up of felsic magmatism, whereas in the east Silurian plume systems evolved related to the opening of a branch of the Paleotethys Ocean. Late Devonian and Carboniferous high-pressure metamorphism, felsic magmatism and associated migmatites can be traced from Alps towards to the Arax fault in NW Iran, whereas in Iran bimodal magmatism evolved in the Sanandaj-Sirjan Zone in a Carboniferous rift. On the other hand, 40 Ar/ 39 Ar geochronology provides evidence for orogenic metamorphism arguing for Variscan tectonic events in Central Iran. Furthermore, in contrast to previous models, Cimmerian metamorphism affected substantial portions of the Cimmerian microcontinent and is superimposed on Variscan tectonothermal events.