Petrographic and geochemical charachteristic of volcanic rocks, outcropping south of Aritoprak (Ipekyolu-Van)

This thesis is to investigate the petrographic and geochemical characteristics of igneous rocks that are located in Arıtoprak village, south of Lake Van, in the southern part of Anatolia, to better understand the local geological setting. The igneous rocks in Arıtoprak village were investigated in order to obtain their mineralogy, petrography, and geochemical characteristics, and to achieve that, eleven rock samples were chosen for petrographic and geochemical analysis from various locations in the studied area. The samples include basalt, gabbro, andesite, and peridotite. Through the variation in rock types, it can be concluded that this area has been subjected to different geological activities like subduction processes and extensional tectonic environments and has a complex magmatic history. For this, we have volcanic rocks (basalt and andesite) and plutonic rocks (gabbro and peridotite). Basalt rock samples are composed mainly of plagioclase and olivine, with some veins filled with calcite; gabbro consists of medium-grained pyroxene and plagioclase with secondary minerals like amphibole, chlorite, zeolite, and sericite; and the peridotite samples with mesh texture are dominated by olivine and a minor amount of pyroxene and spinel with a few grains of plagioclase. The loss on ignition (LOI) of all samples indicates a moderate ratio of alteration, explaining that all samples have been affected by a low to moderate degree of alteration. Geochemical analysis showed the samples ranged from intermediate to ultramafic depending on Sio2 content. The abundance of plagioclase shown by the Al₂O₃ content, has the highest concentration in gabbro and basalt. LREE are enriched in volcanic rocks, including basalt and andesite, because of their incompatibility during fractional crystallization. Yttrium (Y) is low in ultramafic rock because it remains in melt and incorporates into early-forming minerals. The positive correlations between HREE with HFSE show their incompatibility and melt enrichment during differentiation. The rock samples are two types: calc-alkaline series and tholeiite series, all metaluminous type. Peridotite and gabbro represent the remains of the Neotethyan oceanic lithosphere that formed during Late Cretaceous ophiolite obduction (~90–70 Ma) along the Bitlis–Zagros suture zone. The basalt and andesite samples indicate a younger age of magmatism related to tectonic activity. These volcanic rocks date upper cretaseous and are associated with extensive calc-alkaline volcanism in eastern Anatolia.