When and why the Neo-Tethyan subduction initiated along the Eurasian
margin: a case study from a Jurassic eclogite in southern Iran
Abstract
Tethyan evolution is characterized by cyclical continent-transfer from
Gondwana to the continents in the Northern Hemisphere, similar to a
“one-way” train. Subduction has been viewed as the primary driver of
transference. Therefore, it is crucial to understand the tectonic
evolution of all past subduction zones that occurred along Eurasia’s
southern margin. We studied the earliest known eclogite located at the
Neo-Tethyan suture in the Iranian segment. A prograde-E-MORB-like
eclogite reached a peak metamorphic condition of 2.2 GPa and 560°C, at
190 ± 11 Ma (1 rutile U-Pb ages), which constrains the youngest age for
subduction initiation of the Neo-Tethyan slab. Combined with regional
magmatic and structural data, the oldest age for Neo-Tethys subduction
initiation is 210–192 Ma, which is younger than the Paleo-Tethyan
closure time of 228–209 Ma. These data, used with previous numerical
modeling, supports collision-induced subduction initiation. The
collision-induced force, together with the Paleo-Tethyan subduction
driven-mantle flow, is likely to have exploited weak inherited
structures from earlier Neo-Tethyan rifting, resulting in a northward
directed subduction zone along the southern margin of Central Iran
Block.