Petrology and Geochemistry of Bubak and Sikh- kuh Plio - Quaternary volcanic cones, West of Nehbandan, East of Lut block

Kuh-Bubak and Sikh-kuh volcanic cones are located in Southeast of South Khorasan province, north and Southwest Nehbandan city. Based on structural geology classification of Iran, these volcanos are belonging to Lut zone. These cones are composed mainly of Thrachybasalte and Thrachyandesite composition rocks and they are dominant porphyric texture. These rocks have plagioclase, pyroxene, olivine, hornblende and biotite as main minerals and quartze, sericite, epidote, zeolite and calcite is secondary minerals. Twelve fresh rock samples are selected for chemical analysis and then send to the Zrazmay Mahan laboratory were analyzed major and trace elements with XRF and ICP methods respectively. Geochemical characteristics of these rocks show that the primary magma formed these rocks have changes from Calk-alkaline to alkaline. In spider diagrams observed that LREE enrichment and HREE depletion, similar pattern can be seen in parallel and indicated their origin is the same. In addition, enrichment in LILE, and Pb, ratio elements of Nb/U and Ce/Pb indicates that they are contamination with crustal rocks. On the other hand, geochemical diagrams La/Yb versus La and Zr versus TiO2 indicating fractional crystallization process are happen in these rocks. Geochemical various diagrams show that fractionation and crustal contamination has affected on the primary magma. Nb and Ti negative anomalies and geochemical properties indicating that these volcanoes are belonging to subduction zone.