Paper No. 7
Presentation Time: 10:00 AM


MALEKPOUR-ALAMDARI, Ahmadreza, Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801, AXEN, Gary, Department of Earth & Environmental Science, New Mexico Tech, 801 Leroy Place, Socorro, NM 87801, HEIZLER, Matthew, New Mexico Geochronology Research Laboratory, New Mexico Bureau of Mines & Mineral Resources, 801 Leroy Place, New Mexico Tech, Socorro, NM 87801-4796 and HASSANZADEH, Jamshid, Division of Geological and Planetary Sciences, California Institute of Technology, Mail Stop 100-23, Pasadena, CA 91125,

Collision of Eurasia and the Central Iran microcontinent and related ophiolite obduction produced two separated ophiolite and colored mélange belts in NE Iran: the NW-SE trending Sabzevar ophiolite and the NE-SW trending Kashmar-Doruneh ophiolite. Both have similar lithologic and stratigraphic characteristics. In both, the youngest volcano-sedimentary rocks are Late Cretaceous.

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.