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The Golpayegan metamorphic complex is located in the Sanandaj-Sirjan Zone, Iran. This complex consists of various metamorphic rocks including schists, marbles, slates, gneisses, and amphibolites, most of them have Neoproterozoic age. The presence of structures such as sigma fabrics, boudinage, folded boudinage and interfering fold patterns indicates the occurrence of more than two deformation phases in the Golpayegan metamorphic complex. The measurement of strain intensity in the folds indicated deep immersion of structures and old Precambrian settings that had been influenced by orogenic events in the Neoproterozoic. These deformed rocks were exposed during extensional movements and, subsequently, sheared. The results based on field works shown geochemical relations and initial εNd(600 Ma) values of amphibolites in three sampling points located in Golpayegan region manifested that the protolith of the first (a') and second (b') sampling points had mantle origin (ortho-amphibolite), whilst protolith of the third (c') sampling point had sedimentary origin (para-amphibolite). Geochemically, the Golpayegan ortho-amphibolites showed sub-alkaline basalt-basaltic andesite compositions of tholeiitic affinity. The negative anomalies of Nb and Ti relative to Pb, La, and Ce in the primitive mantle-normalized spider-diagram and εNd(600 Ma) values revealed the subduction environment for ortho-amphibolites. The ortho-amphibolites exhibited the intermediate chemistry between the normal mid-ocean ridge basalt and island-arc tholeiitic basalt. Enrichment in large ion lithophile elements (LILE), light rare earth elements (LREE), and relative depletion in high field strength elements (HFSE) suggest the back-arc basin setting for the Golpayegan ortho-amphibolites. The primitive magma of the ortho-amphibolites was produced by 8–20% melting of spinel lherzolite. According to the Neoproterozoic age of the Golpayegan ortho-amphibolites and their relationship with the Golpayegan granitic gneiss (596‒578 Ma), it shows that they can be related to the Cadomian back-arc basin in the north of Peri-Gondwana at the Neoproterozoic. The high values of 87Sr/86Sr (0.708450‒0.714986) interpreted as result of seawater hydrothermal alteration. [ABSTRACT FROM AUTHOR]

The metabasites of Chadegan, including eclogite, garnet amphibolite and amphibolite, are forming a part of Sanandaj-Sirjan Zone. These rocks have formed during the subduction of the Neo-Tethys ocean crust under Iranian plate. This subduction resulted in a subduction metamorphism under high pressuremedium temperature of eclogite and amphibolites facies condition. Then the metamorphic rocks were exhumed during the continental collision between the Afro-Arabian continent and the Iranian microcontinent. In the metabasite rocks, with typical MORB composition, garnet preserved a compositional zoning occurred during metamorphism. The magnesium (XMg) gradually increases from core to rim of garnets, while the manganese (XMn) decreases towards the rim. Chondrite-normalized Rare Earth Element patterns for these garnets exhibit core-to-rim increases in Light Rare Earth Elements. The chondrite-normalized REE patterns of garnets, amphiboles and pyroxenes display positive trend from LREEs to Heavy Rare Earth Elements (especially in garnet), which suggests the role of these minerals as the major controller of HREE distribution. The geochemical features show that the studied eclogite and associated rocks have a MORB origin, and probably formed in a deep-seated subduction channel environment. The geothermometry estimation yields average pressure of ~22 kbar and temperature of 470-520°C for eclogite fomation. The thermobarometry results gave T = 650-700°C and P ≈ 10-11 kbar for amphibolite facies. [ABSTRACT FROM AUTHOR]