THE SABZEVAR AND DORUNEH-KASHMAR OPHIOLITE BELTS (NE IRAN), DETACHED SUTURE ZONES
The angular relationship between these ophiolites is not well understood and these belts are generally considered as a single belt in geological literature. We focus on evolution of a ~100 km-long, attenuated, generally SE-tilted, mid- to upper crustal section northwest of the Kashmar-Doruneh ophiolite. The youngest, SE part of the tilted sequence includes Late Cretaceous globotruncana limestone sequence of the ophiolite. The oldest, NW part includes amphibolite-grade metamorphic rocks in the Biarjmand-Shotor Kuh area. These metamorphic rocks appear to belong to a metamorphic core complex beneath an originally NW-dipping low-angle detachment fault below younger, unmetamorphosed Cretaceous limestones. Multi Domain Diffusion modeling of K-feldspars from these metamorphic rocks reveals rapid cooling (15°C/Ma) starting ~70 Ma ago, that we attribute to exhumation along the detachment fault after ophiolite emplacement. In this model, the Doruneh-Kashmar ophiolite is dragged SE from its original place beside the Sabzevar ophiolite. This sequence is unconformably overlain by Paleogene conglomerate that contains ultramafic clasts in the SE parts. Younging of the Paleogene conglomerates from the southeast to northwest (Early Paleocene and Late Paleocene-Early Eocene respectively) supports this interpretation. Large-scale continental extension, accommodated on the detachment and other, unidentified structures, explains the angular relationship between the ophiolite belts. We interpret that the Great Kavir is the expression of this extensional belt.