The early P-T evolution of a garnet-kyanite gneiss from the Variscan Ulten Zone has been defined by detailed petrographic observations leading to the detection of chlorite-epidote- and staurolite-bearing assemblages enclosed in kyanite porphyroblasts. Calculations of P-T pseudosections in the system NaCaKFeMgAlSiHO allowed us to constrain the evolution of these relics to the earliest metamorphic stages. The overall path shows a P-T increase to a peak of 11–12 kbar and 600–650°C followed by decompressional heating to 720°C and 9–10 kbar and final cooling at 7 kbar, 550–600°C. This clockwise P-T path reflects crustal thickening and subsequent thermal decay related to the continental collision of the Variscan orogeny 330–340 Ma ago. Our study demonstrates that large kyanite porphyroblasts may preserve assemblages related to prograde metamorphic stages. As a result, the detection of mineral inclusions in kyanite can complement many similar studies on mineral suites hosted in garnet and zircon.

The Takab meta-ultramafic rocks of northwestern Iran crop out in association with a variety of metamorphic rocks and they can be divided into three types on the basis of dominant mineral assemblage and degree of serpentinization: metaperidotites, talc-serpentine rocks and serpentinites. The peridotite protoliths were mainly spinel-harzburgites and -dunites. The talc-serpentine rocks formed under low-grade conditions and their dominant mineral assemblage is lizardite/chrysotile + talc + calcite/dolomite. Pseudomorphic textures after olivine and pyroxene are typical. Later, lower amphibolite-facies metamorphism produced antigorite, clinochlore and tremolite. Late alteration, assisted by local shearing, produced more antigorite and late lizardite in the metaperidotites. The mineral chemistry of the serpentine polymorphs is variable. Compositions of coexisting spinel and olivine point to an ophiolitic origin. Thermometric estimates from co-existing relict olivine, pyroxenes and spinel are in the range 1000–1200ºC; clinopyroxene barometry yields a pressure of 24± 2.7 kbar for the mantle conditions. Exhumation and hydration followed, and the stability of lizardite/chrysotile constrains the T and XCO2 to <280ºC and <0.002, respectively. Subsequent prograde regional metamorphism took place in an orogenic setting, reaching peak temperatures in the range 410–540ºC at XCO2 >0.1. A Neoproterozoic–Early Cambrian age for the Takab protoliths is suggested on the basis of correlations with the Central Iran Zone. The strips of ultramafic rock in the Takab complex can be attributed to lithospheric remnants of the Proto-Tethyan ocean which closed during the Pan-African orogeny.