Despite detailed geological studies on the Late Cretaceous Sabzevar ophiolites, the non-ophiolitic, subduction-related igneous rocks of NE Iran are still enigmatic. This paper focuses on the Late Cretaceous, non-ophiolitic Sabzevar magmatic rocks, and presents both precise U–Pb ages and a tectonomagmatic scenario for the genesis of these igneous rocks. A thick sequence of Late Cretaceous acidic volcanic rocks associated with sandstones, shales and pelagic limestones dominates the northern parts of the Lut block. This sequence is intruded by a series of shallow mafic to felsic intrusions. New zircon U–Pb results on the intrusive and extrusive rocks show ages of 75–101 Ma. These ages show a pulsed magmatism in NE Iran, which lasted for c. 25 myr. The whole-rock geochemistry of the igneous rocks shows suprasubduction-zone-related geochemical signatures, represented by negative anomalies in high field strength elements and enrichment in large ion lithophile elements. The initial 87Sr/86Sr ratios and εNd(t) values of the extrusive rocks range from 0.70411 to 0.70628 and from +5.9 to +7.4 respectively, and for intrusive rocks are in the range of 0.70423–0.70579 and +5.8 to +7.2. High εNd(t) values for these rocks confirm that their melts were derived from a depleted-mantle source. Both geochemical and isotopic data indicate that the genesis of these rocks was related to the partial melting of mid-ocean ridge basalt-type slab or depleted-mantle wedge sources during the northward movement of the Sabzevar oceanic slab beneath the southern edge of Eurasia (Turan block) in Late Cretaceous time.

You do not currently have access to this article.