| Abstrakt: |
The Qori metamorphic complex (QMC) is a part of the Sanandaj-Sirjan zone (SaSZ) of Iran that formed as a result of Cimmerian orogenic movements during the Toarcian (upper Early Jurassic). The complex consists mainly of meta-basites and marbles with interlayers of meta-psammitic, meta-ultramafic, and meta-pelitic rocks. Peak metamorphic mineral assemblages in meta-basites and meta-pelites comprise mostly garnet + hornblende + plagioclase + quartz ± titanite ± biotite and kyanite + garnet + biotite + plagioclase + quartz ± staurolite ± muscovite, respectively. The equilibrium assemblage olivine + orthopyroxene + clinopyroxene + amphibole + spinel + ilmenite ± chromiferrous magnetite in metaultramafic rocks formed at the peak metamorphic condition of these rocks. Geothermobarometry calculations and pseudosection modeling obtained 700-800 °C and 6-8 kbar, respectively. The majority of the minerals represent two events of crystallization, especially the spinel grains with flat and convex-concave chemical profiles for their cores and rims. The continental crust of the southern SaSZ underwent two Barrovian-type metamorphic events resulting in its preservation in the QMC meta-ultramafic rocks. The first one, ca. 187 Ma, occurred in association with crustal thickening during the initiation of Neo-Tethys oceanic lithosphere subduction beneath the Central Iran Plate (southeast Eurasia). The second one, ca. 147 Ma, occurred as a result of crustal thickening in the supra-subduction zone. Retrograde metamorphism at the end of the second metamorphism phase, as well as during outcropping towards the surface, resulted in the formation of clinochlore, serpentine, tremolite, talc, and serpentine. The results show that the peak assemblage occurred during the second metamorphic event in the upper amphibolite-lower granulite facies condition. [ABSTRACT FROM AUTHOR] |
