Two stages of folding evolution, at a dome structure in the Almogholagh region, west Hamadan

Category Tectonic & Seismotectonic
Group GSI.IR
Location 21th symposium on geosciences
Holding Date 24 May 2008

      Almogholagh region is located in northwestern part of the Sanandaj-Sirjan zone of Zagros orogen in western Iran. This area is located 15km to the west of Hamadan. Three rock units exist, consisting of volcano-sediments (Almogholagh sequence) at the lower part, carbonate (Chenarsheikh sequence) in the middle, and schist (Hamadan schist) at the upper part. These rocks are metamorphosed in green- schist facies. Two main stages of folding are identified in this area. First stage is recognized by tight to isoclinals, recumbent folds shallowly plunging to NE or SW, with horizontal to sub-horizontal axial plane schistosity, which is predominant foliation in this area. The second stage folding produced upright open to gentle folds, co-axial to the previous folds, with steeply dipping axial surface locally developed crenellation cleavage. Type three interference patterns of two-generation folds imply progressive refolding. Doming of the Almogholagh pluton rearranged the structural parameters of the two stages of folds.