Petrophabric and Microtectonic studies of the metamorphic rocks in southeast of Fariman in order to reconstruct the metamorphism evolution

Ranjbarmoghadam, Fereshteh; Masoudi, Fariborz; Homam, Masoud; Mohajel, Mohammad

doi:10.52547/esrj.10.3.108

Petrophabric and Microtectonic studies of the metamorphic rocks in southeast of Fariman in order to reconstruct the metamorphism evolution

Document Type : علمی -پژوهشی

Authors

¹ Departement of Geology, Faculty of Earth Sciences, Shahid Beheshti Univercity, Tehran, Iran

² Departement of Geology, Sciences Faculty, Ferdousi Univercity of Mashhad, Mashhad, Iran

³ Departement of Geology, Faculty of Earth Sciences, Kharazmi Univercity, Tehran, Iran

10.52547/esrj.10.3.108

Abstract

IntroductionFariman metamorphic complex located in Northeast of Iran and indicative different metamorphism and deformation phases. This area is similar to many others Precambrian metamorphic rocks in central Iran that metamorphed in upper amphibolite facies and Sillimanite zone. In this research microfabric of andalusite schists and magmatic rocks investigated in order to constrain P-T path during metamorphic events.Materials and methodsStudied metamorphic complex contain metasandstone (metapsemites), metagraywack and metacarbonates are as interlayered with metapelitic rocks that are major part of metamorphic rocks in study area. The metamorphic volcanic rocks also are seen that named Sibac complex and are in contact with granitic and gabbroic rocks. For petrography and microfabric studies, 80 oriented samples selected from andalusite schists and igneous rocks from Sibac complex. The samples cut and thin sections prepared. Results and DiscussionMetamorphic rocks of Fariman have effected by two deformation phases, D1 and D2. D1 phase related to M1 that is a regional metamorphism event and D2 as an active deformation is related to dynamothermal metamorphism of M2. M2 reveals emplacement of nap and outcropping of lower crust and present an erosion window of neoprotrozoic rocks that are appeared as an uplift formation from central Iran basement that emplaced close to Paleozoic-Cenozoic sedimentation. The retrograde event has affected metamorphic rocks after M2. Evidences of this retrograde metamorphism are change andalusite to chlorite and muscovite or sericite and muscovite, growth of chlorite and talc in rim or on the other mineral, forming of tourmaline in rim of andalusite or in the veins. The D1 phase created schistosity S1, D2 has folded S1 and has formed S2 schistosite. Microstructure evidence, mineral paragenises and estimated Pressure and temperature show an anticlockwise P-T path that involving advective heating in result of intrusive abundant magma into lower- middle crust. The peak of Metamorphism followed by isobaric cooling. The affect of shearing motion is not equal in throughout of study area and in different rocks. Microtectonic evidences indicate a deformation in both ductile and brittle conditions with dextral component. Shear zones spatially can be observed in south and southwest of study area and has been made mylonites and phylonite type rocks.ConclusionIn Fariman area, first high T-low P metamorphism occurred, and followed by dynamothermal metamorphism with shear zones.

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