Geological and geochemical characteristics of obsidian bearing rhyolite-flow Hasandağ (Tahtayayla-Aksaray) volcanites, Central Anatolia

Hasandağının kuzey doğusunda Tahtayayla bölgesi civarında riyolit ve obsidyenler gözlenir. Riyolit ve obsidyenler farklı gözeneklilik, kristallenme, renk ve akma bantlaşması bakımından farklı yapısal ve dokusal özellikler göstermektedir. Jeokimyasal olarak, riyolit ve obsidiyen yüksek silis bileşiminde ve kalkalkalin özellikte olup, oldukça düşük La/Y (1.5-2.3) ve Nb/Y değerlerine sahiptir. Bununla birlikte, kayaçlar Ba, Sr, Zr ve Ce'ca zengin ve $(La/Eu)_N$=11-14 ile zengin hafif nadir toprak element modeli gösterirler. Riyolit ve obsidyen akıntıları benzer şartlar altında oluşmuştur.

Orta Anadoluda Hasandağı Volkaniklerinden obsidiyen içeren riyolitik lavların jeolojik ve jeokimyasal karakteristikleri

Rhyolite and obsidian observed around Tahtayayla area in the northeast of the Hasandag are characterised by a wide range of surface structure and textures with varying in vesicularity, crystallinity, colour and flow layering. Geocherhically, the rhyolite and obsidian are highly siliceous in composition and they show calc-alkaline characteristics. They have significantly low La/Y (1.5-2.3) and Nb/Y ratios. However, the rocks are enriched in Ba, Sr, Zr and Ce and they show LREE enriched patterns with $(La/Eu)_N$=11-14. The rhyolite and obsidian flow were erupted under similar conditions.

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