Interplay between polyphase deformation and metamorphism of the NW Sanandaj-Sirjan Zone, Hamedan Area, Western Iran

Abstract

Deciphering the interplay between deformation and metamorphism represents the key to unveil the tectono-metamorphic evolution of orogens. Despite the ongoing of high-resolution techniques and the ability to extract important information from small objects or sites, the integration of meso and microstructural analysis and the blasthesis deformation relations represents the starting point for further investigation. The Hamedan region in the Sanandaj-Sirjan Zone of the Zagros orogeny, western Iran, represents a natural laboratory where is possible to observe this interplay. In particulate, this region hosts the Middle Jurassic Alvand plutonic complex intruded into low- to high-grade regional metamorphic rocks. This study identified four stages of ductile deformation (D₁–D₄) characterized by folds (F₁–F₄), foliations (S₁–S₄), and lineations (L₂–L₄). The development of pre-, syn-, and post-tectonic garnet, andalusite, staurolite, and cordierite porphyroblasts is closely associated with these deformation stages. Type 3 interference patterns among F₁, F₂, and F₃ folds suggest a predominantly coaxial nature for D₁, D₂, and D₃ deformations. Syn-tectonic emplacement of the Alvand plutonic complex during D₂ caused significant rotation of structural elements in the host rocks. Our results emphasize the important of unravel the interplay between deformation, metamorphism, to reconstruct the tectono-metamorphic history of the Hamedan region and the emplacement of the Alvand plutonic complex. The plutonism reflects the regional tectonics driven by the subduction of the Neo-Tethys Ocean beneath the Iran microplate. The findings contribute to understanding the complex tectono-metamorphic evolution of the Sanandaj-Sirjan Zone and the broader Zagros orogeny.