Petrography, mineralogy and geochemistry of volcanic rocks in Gorazi area, southwest Khaf, Razavi Khorasan Province

The study area is located in northeast Iran, about 10 Km southwest of Khaf city. Geology of the area includes the Upper Eocene sedimentary (conglomerate), volcanic (basalt, andesite, dacite) and pyroclastic (ignimbrite) rocks. The basalt unit displays porphyritic, glomeroporphyry, vitric, sieve and amygdaloidal textures. The minerals are mainly plagioclase, pyroxene, hornblende and olivine. The andesite unit has porphyry, with microlitic groundmass, vitric, glomeroporphyry and sieve, textures. The minerals mainly consist of plagioclase, hornblende, and K-feldspar. The dacite unit has porphyry texture and consists of plagioclase and quartz minerals with lesser amounts of K-feldspar. Volcanic units of Gorazi have characteristic of Calc-alkalic to high-K Calc-alkalic. Enrichment of LREE relative to HREE and LILE to HFSE are important evidences that magma was formed in a magmatic belt of a subduction zone. Based on geochemical data, the volcanic rocks are originated within the enriched mantle source and, among subduction components, metasomatism related to sediments has played the most important role.