Origin of Pillow Basalts in the Maden Complex (çatak-Van): Petrographic and Geochemical Approach

Abstract

The Southeastern Anatolia orogenic belt is formed by the tectonic amalgamation of units with different ages and lithologies. The Middle Eocene pillow-structured basaltic rocks and sedimentary units within this belt are generally referred to as the Maden Complex. The characterization, dating, origin, and structural position of the volcanic rocks within the Maden Complex are highly debated. This study aims to petrographically analyze samples taken from the volcanic units of the Maden Complex in the Çatak-Van region and to elucidate the formation mechanism of the basalts. As a result of petrographic examinations of the basaltic rocks, it was found that plagioclase, pyroxene, and olivine phenocrysts are present as phenocrysts in the basaltic rocks, while the groundmass is characterized by plagioclase, pyroxene, olivine ± opaque minerals. The basalts generally exhibit a hypocrystalline texture. The presence of chlorite and epidote minerals observed in the basaltic rocks indicates that these rocks have undergone low-grade metamorphism. Geochemical analyses also support the effects of low-grade metamorphism and hydrothermal alteration in the basalts. The pillow-structured basaltic rocks observed in the region exhibit subalkaline-tholeiitic and transitional characteristics. It has been determined that the pillow basalts of the Maden Complex originated from a spinel lherzolite-type mantle source representing shallow depth. Geochemically, a slight enrichment in Th, Ta, and Nb, along with a moderate enrichment in light rare earth elements (LREE) [(La/Yb)N=2.1-3.6], indicates that these rocks have received contributions from a more chemically enriched, unexhausted source. The studies conducted show that the major and trace element data of the pillow basalts observed in the region exhibit similar characteristics, suggesting that the magma forming the basalts might have been influenced by an enriched source and similar processes. © 2024, Hacettepe Universitesi Yerbilmleri. All rights reserved.