Hf-Nd isotope constraints on the origin of Dehshir Ophiolite, Central Iran

摘要

The peri-Arabian ophiolite belt, from Cyprus in the west, eastward through Northwest Syria, Southeast Turkey, Northeast Iraq, Southwest Iran, and into Oman, marks a 3000km-long convergent margin that formed during a Late Cretaceous (ca 100Ma) episode of subduction initiation on the north side of Neotethys. The Zagros ophiolites of Iran are part of this belt and are divided into Outer (OB) and Inner (IB) Ophiolitic Belts. We here report the first Nd-Hf isotopic study of this ophiolite belt, focusing on the Dehshir ophiolite (a part of IB). Our results confirm the Indian mid-oceanic ridge basalt (MORB) mantle domain origin for the Dehshir mafic and felsic igneous rocks. All lavas have similar Hf isotopic compositions, but felsic dikes have significantly less-radiogenic Nd isotopic compositions compared to mafic lavas. Elevated Th/Nb and Th/Yb in felsic samples accompany nonradiogenic Nd, suggesting the involvement of sediments or continental crust.