The geochemical and tectonic characteristics of the volcanic rocks in the east of Nahavand area (Sanandaj-Sirjan zone)


1 Department of Geology, Faculty of Sciences, Islamic Azad University, Khorramabad Branch, Khorramabad, Iran

2 Department of Geology, Faculty of Sciences, Lorestan University, Khorramabad, Iran

3 دانشگاه لرستان، دانشکده علوم پایه، گروه زمین شناسی


The studied area is located in east of Nahavand which is a part of Sanandaj-Sirjan zone. The petrographic and geochemical investigations show that, these rocks consist of basalt, andesite-basalt, andesite, trachy-andesite and dacite. Porphyritic, glomeroporphyritic, microlitic, hyalomicrolitic and comb textures are the common textures in the studied volcanic rocks. Two alteration zones including: argillitic and sericitic zones developed in this region. Alteration products are sericite, kaolinite, chlorite, hematite and calcite. Copper mineralization has occurred primarily in these rocks as filling voids and fractures. Malachite, covellite, magnetite, hematite and bornite are found within the veins. The geochemical data show that these rocks are related to calc-alkaline and shoshonitic magma series. Enrichment in LILE and LREE and depletion in HREE and HFSE with negative anomalies of Ti, Nb along with other evidences, such as high Th/Yb and their position on the tectonic discrimination diagrams indicate that the volcanic rocks in discussion were emplaced into the subduction zone related to an active continental margin setting. The Nahavand volcanic rocks lie in young and immature volcanic arcs or in the initial stages of volcanic arc formation. This situation is consistent with geological history of Sanandaj-Sirjan zone during the Jurassic to the Cretaceous ages.