TY - JOUR A1 - Saki, Adel A1 - Miri, Mirmohammad A1 - Oberhänsli, Roland T1 - High temperature - low pressure metamorphism during subduction of Neo-Tethys beneath the Iranian plate BT - evidence for mafic migmatite formation in the Alvand complex (western Iran) JF - Mineralogy and petrology N2 - Subduction of Neo-Tethys oceanic lithosphere beneath the Iranian plate during the Mesozoic formed several igneous bodies of ultramafic to intermediate and felsic composition. Intrusion of these magmas into a regional metamorphic sequence (the Sanandaj-Sirjan Zone) caused partial melting and formation of migmatites with meta-pelitic protoliths. The Alvand complex (west Iran) is a unique area comprising migmatites of both mafic and pelitic protoliths. In this area, the gabbroic rocks contain veins of leucosome at their contact with pyroxenite and olivine gabbro. These leucosomes are geochemically and mineralogically different from leucosomes of the meta-pelitic migmatites and clearly show properties of I-type granites. Microscopic observations and whole rock compositions of the mafic migmatite leucosomes show that migmatization occurred through partial melting of biotite, hornblende and plagioclase. Thermobarometric calculations indicate 800 degrees C and 3.7 kbar for partial melting, although phase diagram modeling demonstrates that the presence of water could decrease the solidus temperature by about 40 degrees C. Our results suggest an asthenospheric magma upwelling as the source of heat for partial melting of the gabbroic rock during subduction of Neo-Tethys oceanic crust under the western edge of the Iranian plate. The present study also reveals relationships between migmatization and formation of S- and I -type granites in the area. KW - partial melting KW - mafic migmatite KW - pelitic migmatite KW - Neo-Tethys KW - subduction KW - Gabbroic rocks Y1 - 2020 U6 - https://doi.org/10.1007/s00710-020-00721-z SN - 0930-0708 SN - 1438-1168 VL - 114 IS - 6 SP - 539 EP - 557 PB - Springer CY - Wien [u.a.] ER - TY - JOUR A1 - Saki, Adel A1 - Miri, Mirmohammad A1 - Oberhänsli, Roland T1 - Pseudosection modelling of the Precambrian meta-pelites from the Poshtuk area, NW Iran JF - Periodico di mineralogia : an international journal of mineralogy, crystallography, geochemistry, ore deposits, petrology, volcanology and applied topics on environment, archaeometry and cultural heritage / Dipartimento di Scienze della Terra, Università degli Studi di Roma la Sapienza N2 - Precambrian meta-pelites of the Poshtuk area in northwest Iran contain the prograde mineral assemblage staurolite-garnet-chloritoid-muscovite-biotite that was replaced by the assemblage garnet-staurolite-chlorite-muscovite-biotite at peak metamorphic condition. Whole-rock compositions reveal that high Fe, Al and Mn contents of their protolith rendered them prone to form these assemblages. Pseudosections calculated in KFMASH, MnKFMASH, and MnNCKFMASHO systems were used to investigate the P-T evolution of the samples. They clearly show the significant effect of MnO on the stability of the chloritoid-bearing assemblages and the formation of garnet through consumption of chlorite and chloritoid. The pseudosection in a T- aH(2)O diagram shows that the studied assemblage could be stable only at a(H2O)>0.8. X-Mg isopleths for garnet and biotite point to peak P-T conditions of about 3.75 kbar and 575 degrees C. Chloritoid stability is overstepped with such conditions. This can be attributed to thermal perturbation due to plutonism. It is concluded, metamorphism was primarily controlled by advective heat from magmatic intrusions in the Poshtuk area. The Precambrian basement complexes were extensively overprinted by the Pan-African Orogeny as well as younger magmatic and metamorphic activities associated to Alpine Orogeny during convergence of Arabian and Eurasian plate. KW - meta-pelites KW - pseudosection KW - chloritoid stability KW - Precambrain KW - Poshtuk Y1 - 2021 U6 - https://doi.org/10.13133/2239-1002/16632 SN - 0369-8963 VL - 90 IS - 3 SP - 325 EP - 340 PB - Bardi CY - Roma ER -