Zircon U-Pb ages and emplacement history of the Nodoushan plutonic complex in the central Urumieh-Dokhtar magmatic belt, Central Iran: Product of Neotethyan subduction during the Paleogene

摘要

The Nodoushan plutonic complex is composed of a wide range of felsic and mafic rocks straddling several of the major orogenic zones in Iran. Diorite porphyry, diorite, granodiorite and granite intrusives belong to the central part of the Urumieh-Dokhtar magmatic belt, which is part of the Alpine-Himalayan orogenic belt. Monzogabbroic members of the complex are instead located within the bordering Sanandaj-Sirjan magmatic metamorphic zone. These plutons were emplaced into Permian and lower Cretaceous sedimentary units and Eocene calc-alkaline volcanic and subvolcanic rocks. New U-Pb zircon ages reveal that the plutonic complex was assembled incrementally over ca. 15 m.y. during three main episodes at 40.487 +/- 0.063 Ma near the Middle/Late Eocene boundary, at 30.52 +/- 0.11 Ma and 30.06 +/- 0.10 Ma in the Early Oligocene (Middle Rupelian) and at 24.994 +/- 0.037 and 24.13 +/- 0.19 Ma in the Late Oligocene (latest Chattian). The activity recorded in the Nodoushan plutonic complex represents the final stages of subduction-related magmatism prior to the eventual Miocene collision between the Arabian and Eurasian blocks.