Paleo-Tethys subduction induced slab-drag opening the Neo-Tethys: Evidence from an Iranian segment of Gondwana

Abstract

The Iranian plateau has a more straightforward relationship between the Paleo-Tethys and Neo-Tethys, than other regions in the Tethyan realm and is an ideal place to test the genetic connection of how the Paleo-Tethys affected the Neo-Tethys. Moreover, there is no consensus on how Paleo-Tethyan evolution influenced the Neo-Tethyan Wilson cycle. We studied the petrology , geochemistry , and metamorphic age of an eclogite suite at Rasht in northern Iran from the Paleo-Tethyan suture. The eclogitic protolith was a typical mid-ocean-ridge basalt and achieved its peak metamorphic condition of 2.7 GPa and 590 °C at 353 ± 8.9 Ma. Reconstructed pressure-temperature-time path of the eclogite-facies rocks suggests that the eclogitic protolith entered the trench at 356 ± 8.9 Ma. Mid-oceanic ridge rocks formed at ~380 Ma at the Rasht region and other places along the Alborz Mountain strike. A ~ 25 million years (Myr) period from the birth of oceanic crust to subduction at Rasht region implies that the mid-ocean-ridge was close to the trench. We propose that the Paleo-Tethyan mid-ocean-ridge was trench-parallelly subducted beneath the Eurasian boundary in northern Iran. This ridge-subduction propagated from east to west between 380 and 355 Ma. 47–27 Myr after ridge consumption, subduction of the remaining Paleo-Tethyan oceanic crust exerted a continuous extensional stress of ~0.1 GPa on the passive margin of Gondwana since the late Carboniferous. The drag-force eventually detached the Central Iranian Block from Gondwana, and opened the Neo-Tethyan ocean during the middle-late Permian .