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The Takab calcareous rocks of northwest Iran crop out in association with a variety of metamorphic rocks including mafic granulites, amphibolites, granitic gneisses, pelitic schists and meta-ultramafic rocks. They can be divided into marbles and calc-silicate rocks on the basis of the dominance of calcite/dolomite and silicate minerals. Dominant peak metamorphic granulite facies assemblage of calc-silicate rocks is Scp + Grt(I) + Cpx + Cal + Qtz +/- Hbl(I). The decrease of temperature and pressure during exhumation produced post-peak metamorphic assemblages. Coronal garnet (Grt II) in the calc-silicate rocks was produced by retrograde reactions consuming plagioclase and clinopyroxene, while peak metamorphic garnet (Grt I) occurs as preserved xenoblastic grains in calcite and/or plagioclase (Pl II). Regional metamorphism took place at 740 degrees C and X-CO2 similar to 0.9. Garnet-clinopyroxene-plagioclase-quartz (GADS) barometry yields a pressure of 8-9 kbar, corresponding to a depth of ca. 24-27 km. This was followed by decompression and hydration during exhumation of the crustal rocks up to the surface. Secondary phases such as garnet (II) hornblende (II), plagioclase (II), zoisite and titanite (II) constrain the temperature and pressure of post-peak metamorphism as similar to 600 degrees C and similar to 6 kbar respectively and a fluid with XCO2 as low as 0.4. Halogens were near-absent during the peak metamorphic stage. The scapolite and hornblende crystallized underpeak metamorphic conditions contain very low fluorine and chlorine, whereas relatively high fluorine (similar to 0.8 wt%) in the titanite (II) and hornblende (II) suggests a possible infiltration of F-rich fluids into the calc-silicate rocks during retrogression. It is interpreted to be related to external fluids released during crystallisation of granitoid magmas and/or leucosome patches in the adjacent migmatites.
The Kurancali ultramafic-mafic cumulate body, an allochthonous ophiolitic sliver in central Anatolia, is characterized by the presence of abundant hydrous phases (phlogopite, pargasite) besides augitic diopside, plagioclase, and accessory amounts of rutile, sphene, apatite, zircon, and calcite. Based on modes of the essential minerals, the olivine-orthopyroxene-free cumulates are grouped as clinopyroxenite, hydrous clinopyroxenite, phlogopitite, hornblendite, layered gabbro, and diorite. Petrographical, mineralogical and geochemical features of the rocks infer crystallization from a hydrous magma having high-K calcalkaline affinity with slightly alkaline character, and point to metasomatised mantle as the magma source. Our evidence implies that the metasomatising component, which modified the composition of the mantle wedge source rock in an intraoceanic subduction zone, was a H2O, alkali and carbonate-rich aluminosilicate fluid and/or melt, probably derived from a subducted slab. We suggest that the metasomatic agents in the subarc mantle led to the generation of a hydrous magma, which produced the Kurancali cumulates in an island-arc basement in a supra-subduction-zone setting during the closure of the Izmir-Ankara-Erzincan branch of the Alpine Neotethys Ocean.