Ilıca Tipi Epitermal Altın Yatakları

Yıl 1991, Cilt: 15 Sayı: 2, 63 - 71, 15.11.1991

Vedat Oygür

Öz

Ilıca tipi altın yatakları, yer yüzeyinin birkaç yüz metre derinliğinde oluşmuş ve halen oluşmakta olan volkanik tip epitermal yatakların ayrı bir grubu olarak ele alınmaktadır. Silika sinter ve yaygın silisleşme ile hidrotermal patlama breşleri bu tipin belirgin özellikleridir. Yatak tipi için en uygun bölgesel tektonik konum kaldera kenarları boyunca veya çaprazınadır. Bununla birlikte, cevherleşme genelde ana fay zonu içerisindeki tali kırıklarda yerleşmektedir. Cevher yataklarının, volkanik kayalarla doğrudan bir ilişkisi yoktur. Mağmatik etkinlik sadece, hidrotermal dolaşımı yürütmek üzere gerekli ısıyı sağlamaktadır. Cevherin değişik litolojilerde bulunması, ana kaya bileşiminin kontrol edici bir etken olmadığını gösterir. Altın, elektrum, stibnit, realgar, gümüş sülfotuzları ve pirit başlıca cevher mineralleridir. Baz metal içeriği tipik olarak düşüktür. Adülarya, serisit ve kuvars ana gang mineralleridir ve manganez cevherleşmenin çevresinde bir hale oluşturur. Cevherleşme saçılmıştır, fakat bantlı damar dolguları da görülür. Au-As-Sb-Hg-Tl derinlikle azalırken, Ag ve baz metaller düşey jeokimyasal zonlanmada artarlar. Serisitik ve arjilik yan kaya aberasyonu geneldir. Duraylı izotop incelemeleri, hidrotermal akışkanların başlıca meteorik su kökenli olduklarını gösterir. Cevherli sıvıların tuzluluğu 0 ile 13 ağırlık % NaCl eşdeğeri arasındadır. Ortalama kloridiyon konsantrasyonu 1200 ppm, ve toplam indirgenmiş kükürt 100 ppm dir. Akışkanların pH sı nötre yakındır. Au, hatta As ve Sb tiyo-karmaşıklar (Au (HS)2) olarak taşınmıştır. Hidrostatik ve litostatik basınç düzeyleri arasında akışkanların kaynaması tiyo-karmaşıkların bozulmasına ve nabit altının çökelmesine yol açmıştır.

Anahtar Kelimeler

Ilıca Tipi altın, Epitermal, Altın

Kaynakça

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