U–Pb age, Hf–O isotopes, and geochemistry of the Sardasht ophiolite in the NW Zagros orogen: Implications for the tectonic evolution of Neo‐Tethys. (24th September 2020) - Ao, Songjian
Abstract : Ophiolites in the Zagros orogen represent relics of the Neo‐Tethyan Ocean that existed between the Laurasia and Gondwana continents. There is much debate about the formation and evolution of the Neo‐Tethyan Ocean. Knowledge of its pre‐collisional tectonic evolution is essential in constraining the timing and process of the collision between the Eurasian and Arabian continents. We present a combined analysis of zircon LA–ICP–MS U–Pb ages and Hf–O isotopes of the Sardasht ophiolite from the NW Zagros orogen. Our new data demonstrate that the Sardasht ophiolite formed at ca. 50.6 Ma. Geochemistry of plagiogranite and diabase indicates that the Sardasht ophiolite probably originated in the mantle wedge, influenced by subduction fluids. The mafic rocks of the Sardasht ophiolite include boninites, arc basaltic rocks, and OIBs, which accreted together when the Neo‐Tethys finally closed. Finally, we argue that there was an intra‐oceanic fore‐arc extension and arc system during 50–24 Ma in the southern branch of the Neo‐Tethys in NW Zagros. Abstract : The subduction fluids added into the mantle wedge and made it partial melting to form the boninitic diabase, adakitic plagiogranite/diorite dykes at ca. 50 Ma (Fig. 9a). As the subduction continues, the Walash oceanic island arc started to eruption at 43 Ma (Fig. 9b). Then when trench retreating or slab‐rollback, the fore‐arc area extended and generated the oceanic core complexes at ca. 36 Ma and this intra‐oceanic arc and fore‐arc system developed until 24 Ma.