OICC Press Iranian Journal of Earth Sciences 2228-785X 17 1 2025 01 10 Geochemistry and tectnomagmatic environment of Eocene volcanic rocks in Yuzbashi Chay region, west of Qazvin (Iran) 1 13 10.57647/j.ijes.2025.1701.04 EN Saman Salehpour Department of Geology, Science and Research Branch, Islamic Azad University, Tehran, Iran https://orcid.org/0009-0005-1165-3650 Mohammad Ali Arian Department of Geology, North Tehran Branch, Islamic Azad University, Tehran, Iran https://orcid.org/0000-0001-9876-6415 Alireza Jafari Rad Department of Geology, Science and Research Branch, Islamic Azad University, Tehran, Iran https://orcid.org/0000-0002-4371-0841 Reza Zarei Sahamieh Department of Geology, Lorestan University, Khorramabad, Iran https://orcid.org/0000-0002-1030-6682 Abdollah Yazdi Department of Geology, Kahnooj Branch, Islamic Azad University, Kahnooj, Iran https://orcid.org/0000-0002-6096-4739 Journal Article 2025 01 10 The study area is 92 km northeast of Zanjan City (Iran), north of the Tehran-Tabriz freeway. The rock units outcropped in the Zanjan quadrangle​ include the Precambrian and the Quaternary from the old to the new. However, the volcanic rocks in this vast area are of Eocene age and younger. Volcanic rocks include acidic, rhyolitic, rhyodacite, andesitic lavas, along with tuff and ignimbrite. From the mineralogical perspective, these volcanic rocks have low contents of quartz, low alkaline feldspar, and abundant plagioclase and pyroxene. In addition, porphyritic, microlithic porphyry, glomeroporphyritic, and poikilitic textures are dominant in these rocks. Geochemical studies based on oxides of major and Minor elements indicate the calc-alkaline nature of these volcanic rocks. Furthermore, studying the change trends in major, trace, and rare earth elements demonstrates a connection and affiliation between different rock groups. These rocks have formed during the subduction process and probably originate from a lower crustal source.