Petrology and geochemistry of the Paleocene-Eocene volcanic rocks from Revenj area, Southeast of Fariman (Khorasan Razavi, Iran)

The study area is located in the Southeast of Fariman and it is considered as a part of the central Iranian zone. According to field and petrographic studies the composition of volcanic rocks a range from basalt andesite-basalt andesite، trachyandesite to dacite with Paleocene-Eocene age. The dominant textures of the volcanic rocks are microlitic porphyric and glomeroporphyric and the major minerals are plagioclase، olivine، pyroxene، hornblende، alkali feldspar and quartz. Biotite، apatite، sphene and magnetite are as minor minerals. Microscopic studies reveal the presence of disequilibrium textures in plagioclases (eg. zoning and corrosion). The occurrence of xenolites indicates magma contamination. Based on geochemistry of major and minor elements، the studied rocks belong to calc-alkaline series with moderate to high potassium type and meta-aluminous nature. The geochemical behavior of major and trace elements reveals the normal trend of differentiation in the magma. According to geochemical data، garnet-lerzolite may be the principal source rock for the studied volcanic rocks which experienced 1 to 10% partial melting in a depth of around 90 to 100 km. Based on petrographic studies، some evidences of magmatic contamination can be distinguished which can be also supported by Nb and Ti negative anomalies and Pb positive anomaly on spider diagrams and Ce/Pb and Nb/U ratios. Enrichment in LILE and depletion of HFSE in the studied rocks as well as various petrologic diagrams point to magmatism in arc of an active continental margin.