Shanderman eclogite (Iran): A supercontinent killer subduction.

During the amalgamation, tenure and break up of Pangea several oceans played a major tectonic role. Remnants of them now occur mostly along the margins of the Atlantic, Mediterranean, Black and Caspian seas, as well as in the Alpine-Himalayan and adjacent orogens. Of those oceans, three (Iapetus, Tornsquist and Rheic) were closed during the amalgamation of Pangea and another (Neo-Tethys) is the main witness of its break-up.

The Paleotethys is the enigmatic ocean that shared an internal position during most of Pangea’s tenure. There is no consensus about its origin, some suggest that opened during the latest stages of Pangea’s amalgamation (Devonian-Carboniferous) whereas others considert it a remnant of the mostly subducted Rheic ocean after Gondwana-Laurussia collision. The Shanderman eclogites, in NW Iran are a potential candidate to represent the Paleotethys ocean. They are metamorphosed oceanic rocks (protolith oceanic tholeiitic basalt with MORB composition). Eclogite occurs within a serpentinite matrix, accompanied by mafic rocks resembling a dismembered ophiolite. The eclogitic mafic rocks record different stages of metamorphism during subduction and exhumation.

In this contribution I will show the new petrological, geochemical and geochronological results from this eclogites to shed light on the Paleotethyan problem. The piece of oceanic crust preserved at Shanderman area (Iran) crystallized some time in the mid-Carboniferous (~330 Ma) showing the paleotethys kept expanding during the Gondwana-Laurussia collisions that amalgamated Pangea. Metamorphic ages, suggest that subdution initiated in this segment of the Paleotethys between 310 and 290Ma. We integrate this results into a tectonic reconstruction that shows a major plate reorganization within Pangea during the late Carboniferous and early Permian (320-270 Ma) that questions its role as a supercontinent.