ZAGROS CONVERGENCE: A SUBDUCTION-DOMINATED PROCESS?

This contribution aims at presenting a synthetic view of the geodynamic evolution of Zagros from ~150 to 0 Ma. The Zagros orogen and Central Iran preserve a unique record of the long-standing convergence history between Eurasia and Arabia across the Neotethys, from subduction/obduction processes to present-day collision. I herein combine the results obtained on several geodynamic issues, namely the location of the oceanic suture zone and the age of oceanic closure and collision, the magmatic and geochemical evolution of the Eurasian upper plate during convergence (as testified by the successive Sanandaj-Sirjan, Kermanshah and Urumieh-Dokhtar magmatic arcs), the P-T-t history of the few Zagros blueschists (and their relationship to those from nearby Makran and Oman), the convergence characteristics across the Neotethys (kinematic velocities, subduction zones, obduction mechanisms, thermomecanical modelling constraints), together with a survey of other recent results gathered over the past decade. A geotectonic scenario for the Zagros convergence is proposed, in which I have outlined three main periods/regimes:

(1) long-lasting subduction processes, with kinematic-related changes in arc magmatism (>150-35 Ma),

(2) a distinctive period of pertubation of subduction processes and upper-plate fragmentation (115-85 Ma),

(3) collision and partial slab tear at depths (~25-0 Ma).

This reconstruction underlines the key role played by subduction throughout the whole convergence history.