مرکز منطقه ای اطلاع رساني علوم و فناوري -

چكيده لاتين :

The Sanandaj-Sirjan zone is the metamorphic belt of the Zagros Orogen in western Iran that uplifted during continental collision between the Afro-Arabian continent and the Iranian microcontinent. ALS-bearing schists are part of the metamorphic rocks in northwestern half of the Sanandaj-Sirjan zone, and consist of metasediments including micaschist, garnet staurolite schist, garnet andalusite schist and garnet sillimanite schist with protolith of pelite inter-bedded with other detritic sediments. Five episodes of deformation were recognized in the ALS-bearing schists. First stage (D1) is not mapable in mesoscopic scale but is observed as bedding parallel continuous foliation (S1) under the optical microscope. The second stage (D2) is well characterized by isoclinal recumbent folds with axial plane foliation (S2) folded by the later generations. Numerous quartz veins and veins with pegmatite textures were folded along with the S2. The third stage (D3) is characterized by a crenulation foliation (S3) developed parallel to the axial plane of close to tight upright to overturned folds. The later (D4) is well recognized by mineral lineation and a less developed crenulation cleavage (S4) where its trend makes a distinct angle with S3. The last stage (D5) is rarely recognized cutting the previous generations. Porphyroblast growth was synchronous tosome deformation stages.At least, two main metamorphic events accompanied the deformation episodes as observed by mineral assemblages and thermo-barometry. Geo-thermo-barornetry based on mineral equilibrium and their paragenesis in these rocks indicate that physical condition during second prograde metamorphism was max 628°C temperature with 4 kb pressure.