Petrological characterization of the Cenozoic igneous rocks of the Tafresh area, central Urumieh-Dokhtar Magmatic Arc (Iran)

We report a petrographic and whole-rock geochemical characterization of the Cenozoic volcanic rocks cropping out in the Tafresh area of the central Urumieh-Dokhtar Magmatic Arc of Iran. The investigated rocks range mainly from basaltic andesite to dacite, and are considered to be genetically linked by (mostly) closed-system evolutionary processes involving fractionation of ferromagnesian minerals and plagioclase first, then of plagioclase and lesser amphibole (plus minor clinopyroxene) and finally of plagioclase with lesser alkali feldspar and minor amphibole. These represent a typical calcalkaline series emplaced in a subduction-related setting, producing the observed LILE-enriched and HFSE-depleted geochemical signature. The basaltic andesite compositions likely derived from an unsampled hydrous primitive melt equilibrated in a spinel-bearing metasomatized peridotite source, evolving at shallow to moderate crustal depths.Additional lithotypes cropping out in the Tafresh area include much rarer strongly evolved leucocratic rocks and evolved rocks with adakitic signature. The first are thought to derive from crustal anatexis of a meta-sedimentary source, whereas the latter are interpreted as the product of the melting of a meta-mafic source rock with residual garnet and amphibole. The association of magmatic rocks pointing to all such different petrogenetic processes in a relatively limited area is strongly suggestive of emplacement in a post-collisional stage.