Phase equilibria and P-T-t path of metapelitic rocks in SE-Hamedan, Sanandaj-Sirjan Zone, Iran

  • Shahryar Mahmoudi
  • Ali-Akbar Baharifar
Original Paper


In the southeast of Hamedan, in the Sanandaj-Sirjan Zone of Iran, metamorphic rocks display different metamorphic assemblages formed during dynamothermal and contact metamorphic events. The isograds in metapelitic rocks vary across the region: in the south, the sequence is chlorite – biotite – garnet – staurolite, but in the east and southeast it is chlorite – garnet – biotite – andalusite – sillimanite. Based on microstructure, peak metamorphic conditions were the same for both Al2SiO5(ALS) bearing and Al2SiO5 free assemblages: 628 °C and 4.4 kbar for the sillimanite zone and 577 °C and 4.2 kbar for the staurolite zone. Pseudosections were constructed for two representative bulk rock compositions, in the Kamari area for ALS bearing rocks and in the Aliabad-Damagh area for ALS free rocks. Comparing pseudosections with the estimated P and T shows that the appearance of ALS polymorphs was controlled by the chemical composition of the parent rocks rather than variations in P and T. The P-T paths of both ALS-bearing and ALS-free sequences are similar and both follow an anticlockwise trend but the geothermal gradient is slightly higher for ALS-bearing schists. It is concluded that different zones in the area developed at the same time, during the same deformation phases, but under different geothermal gradients. Metamorphism of the Hamedan area occurred during the convergent orogeny and subduction of the Neo-Tethys in the Jurassic and was coeval with the main magmatic phases.


Metapelites P-T path Phase equilibrium Sanandaj-Sirjan Zone Hamedan Iran 



Careful reviews by Dr. Robin Offler and Dr. Hossein Azizi and journal editor Dr. William Guenthner and Editor-in-chief Dr. Maarten A.T.M. BROEKMANS greatly helped to improve this paper.


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© Springer-Verlag GmbH Austria, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Faculty of Earth SciencesGeochemistry Department, Kharazmi UniversityTehranIran
  2. 2.Geology DepartmentPayam-e-Noor University (PNU)TehranIran

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