Tectono-metamorphic evolution of the Neyriz metamorphic complex, Quri-Kor-e-Sefid area (Sanandaj-Sirjan Zone, SW Iran)
Résumé
The Neyriz region includes outcrops of metamorphic rocks that are thrust over the Neotethyan ophiolites. These rocks are affected by a major deformational event, the result of which includes a shearing polyphase foliation present in gneissic core domes, overprinted by a crenulation cleavage. These fundamental structures developed contemporaneously with a medium-pressure metamorphism which is characterized by the syn-kinematic crystallization of kyanite and the beginning of anatexis, followed by the development of retrometamorphic mineral parageneses. The major deformation phase in the area occurred during the Early-Cimmerian orogeny in the Late Triassic. Following the orogeny, the gneiss domes started to rise into the upper levels of the crust. From the geodynamic point of view, after the Mid-Permian the studied area was situated at southern passive margin of the Iranian plate; the central Iranian microcontinent at that time was separated by the Neotethys ocean from the Gondwanian supercontinent. After the Late Triassic the region became an active margin associated with an accretionary prism. The margin was finally involved in an orogenic wedge after the closure of the Neotethyan oceanic basin in the Late Mesozoic. Closure of the basin resulted in a major thrusting of the metamorphic rocks of the southern Iranian margin over the Neotethyan ophiolites.