Age and petrogenesis of Na-rich felsic rocks in western Iran: Evidence for closure of the southern branch of the Neo-Tethys in the Late Cretaceous

Intermediate to felsic volcanic and granitic rocks with high Na2O concentrations (5.2–9.1wt.%) are widely distributed in the Harsin area along the Zagros thrust zone in western Iran. Most of these rocks are classified as low-potassium tholeiite, display affinity with oceanic plagiogranite and contain somewhat high Na content and low concentrations of K2O, Al2O3, Rb, Sr and Ca. Thus, we prefer to apply the term Na-rich felsic rocks to this complex. U–Pb dating yielded ages of 94.6±2.7Ma (2σ) from baddeleyite and 95.0±2.4Ma (2σ) from zircon grains, indicating that the complex crystallized in the Late Cretaceous. Based on the mineral compositions, the crystallization occurred at low pressures (mostly