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

Yıl 2024, Cilt: 45 Sayı: 3, 227 - 246, 31.12.2024

Tijen Üner

https://doi.org/10.17824/yerbilimleri.1440128

Öz

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.

Anahtar Kelimeler

Alteration, E-MORB, Southeastern Anatolian, Pillow basalt, Enrichment

Maden Karmaşığı’ndaki (Çatak-Van) Yastık Yapılı Bazaltların Kökeni: Petrografik ve Jeokimyasal Yaklaşım

Öz

Çalışma alanı (Çatak-Van), farklı yaş ve litolojilere sahip birimlerin tektonik olarak bir arada bulunduğu, Güneydoğu Anadolu Orojenik Kuşağı içerisinde yer almaktadır. Bitlis Masifi ile tektonik olarak birlikte yer alan Maden Karmaşığı, bölgede Orta Eosen yaşlı volkanik ve sedimanter birimlerle temsil edilmektedir. Bu çalışmada, Çatak-Van bölgesinde Maden Karmaşığı volkanik birimlerinden alınan örnekler, karmaşıktaki bazaltların oluşum mekanizmasının ortaya konulması amacıyla incelenmiştir.
Alınan örnekler üzerinden yapılan petrografik incelemeler sonucunda, bazaltlarda düşük dereceli metamorfizma ve hidrotermal alterasyonun etkileri jeokimyasal çalışmalarla da desteklenmiştir. Jeokimyasal çalışmalara göre, bölgede gözlenen yastık yapılı bazaltik kayaçlar, subalkalin-toleyitik özellik sunmaktadır. Maden Karmaşığı’na ait bu yastık bazaltlar, %10’luk granat fasiyesi ve %90’lık spinel fasiyesinden gelen eriyik fraksiyonlarının karışmasından oluşmuştur. Jeokimyasal olarak, Th, Ta, Nb bakımından hafif bir zenginleşme ve hafif nadir toprak elementleri (LREE) [(La/Yb)N=2.1-3.6] bakımından da kısmen zengin birleşimde olmaları bu kayaların tüketilmiş bir kaynağa ek olarak, daha zengin bir kimyaya sahip tüketilmemiş bir kaynaktan katkı aldığını göstermektedir. Yapılan çalışmalar sonucunda, bölgede gözlenen yastık bazaltlarının ana ve iz element verileri birbirine benzer özellik sunmaktadır. yastık bazaltlarında gözlenen benzer özellikler, bölgede gözlenen bazaltları oluşturan magmanın aynı kaynaktan ve benzer süreçlerden etkilenmiş olabileceği söylenebilir.

Anahtar Kelimeler

Alterasyon, E-MORB, Güneydoğu Anadolu, Yastık bazaltlar, Zenginleşme

Kaynakça

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