Geochemistry and tectonomagmatic environment of Eocene volcanic rocks in the Southeastern region of Abhar, NW Iran

Abstract

Eocene volcanic are exposed in southeast of Zanjan in the Tarom magmatic zone that located in the Central Iran structural zone. The Abhar Eosen pyroclastic with andesite, trachy-andesite, dacite and rhyolite along with tuff compositions is located 120 km southeast of Zanjan. Mineralogically point of view, the studied volcanic rocks have low quartz, negligible alkaline feldspar, abundant plagioclase, and pyroxene contents. Textureally, Porphyritic, microlithic porphyritic, glomeroporphyritic, and poikilitic are predominant in these rocks. All of the studied samples display REE patterns characterized by LREE-enriched (Rb and Ba) and HREE-depleted segments typical of arc lavas which is one of the characteristics of subduction zone. The geochemical characteristics of the studied samples indicated that fractional crystallization is the primary cause of the diversity and differentiation of these rocks compared to crustal contamination. The rocks of the study area are composed of a similar origin to the OIB (mantle components) and partial melting of subcontinental lithospheric mantles. Of course, this mantle source has been modified by recycled sediments and melt released from the edge of the subducting oceanic crust.