Geology-Mineralogy and Isotope (O-D, S, Cu And Ar/Ar) Geochemistry of Sisorta High Sulfidation Epithermal Gold Deposit (Koyulhisar-Sivas)

Yıl 2016, Cilt: 59 Sayı: 1, 87 - 114, 01.01.2016

Çiğdem Şahin Demir Ali Uçurum

https://doi.org/10.25288/tjb.298300

Öz

This study presents geological and geochemical features of gold deposit located in Sisorta area near Evliya Tepe, Güzelyurt village. The investigation area covers 42 km2 land and located in 200 km NW of Sivas province in Sisorta. . δ 34S ‰ isotope values are ranging from -0,4 and ‰ ‰ 22, in Sisorta gold deposit. At the early stage of mineralization S isotope value number is light and later S isotope value shows heavy numbers. This is indicating that the S isotope was originated from magma and changed due to temperature variations in the last stages of the hydrothermal process. δ18O isotope values of gangue minerals are ranging from; ‰ 7,1 and ‰ 15,6 however, δD value is ranging from ‰ -77 to ‰ -25,3 Combining δ18O with δD from Sisorta samples, demonstrates meteoric waters were important in the formation of the alteration silicate minerals analyzed. This is common in high sulfidation silicate alteration minerals. 40Ar/ 39Ar age dating is ranging from 78,85±0,94 Ma and 76,59±2,19 Ma as a plateau age and 78,25±0,42 Ma and 75,30±0,90 Ma as isochron age in K-alunite, 80,44±0,84 in hornblende minerals from unaltered andesitic volcanic rocks. This shows that hydrothermal gold mineralization is deposited 3 Ma later than the volcanic host rock eruption. δ 65Cu ‰ values from copper-bearing minerals associated with Sisorta gold deposits are ranging from -5.502 ‰ to +3.032 ‰. The copper isotope values closest to the intrusions (deepest part of the system) do not show significant copper isotope variations (<1 per mil), in contrast the upper parts of the system show large copper isotope variations and indicate enrichment of copper due to supergene processes.

Anahtar Kelimeler

Ar/Ar Dating, High Sulphidation Epithermal Gold Deposit, Sisorta, Stable Isotopes

Sisorta (Koyulhisar-Sivas) Yüksek Sülfidasyon Epitermal Altın Yatağının Jeoloji-Mineralojisi ve İzotop (O-D, S, Cu ve Ar/Ar) Jeokimyası

Öz

Bu çalışma Evliya Tepe yakınında Güzelyurt köyü Sisorta bölgesindeki altın yatağının jeolojik ve jeokimyasal özelliklerini sunmaktadır. Çalışma alanı 42 km²’lik alanı kapsamakta ve Sivas’ın 200 km KB’da Sisorta’dadır. Sisorta altın yatağında kükürt izotop değerleri; ‰ -0,4 ile ‰ 22,0 arasında değişmektedir. Bu sonuçlarda cevherleşmenin oluşumunda etkili olan S’ün kaynağının ilk evrelerinde hafif S izotopunun etkin olduğu daha sonraki evrelerde ise ağır S izotopunun etkin olduğu gözlenmektedir. O değeri ‰ 7,1 ile ‰ 15,6 arasında değişirken, *D değeri ise ‰ -77 ile ‰ -25,3 arasındadır. Gang ve alteasyon minerallerinde yapılan oksijen ve döteryum analizlerine göre;

O ve *D izotop değerleri birlikte değerlendirildiğinde meteorik sular, silikat alterasyon minerallerinin oluşumunda önemli rol oynamıştır. Yapılan Ar/Ar yaş analizleri sonucunda K-alünit minerallerinde; plato yaşı 78,85±0,94 My ve 76,59±2,19 My, izokron yaşı 78,25±0,42 My ve 75,30±0,90 My olarak, bozunmamış andezitik volkanik kayaçlardan ayrılan hornblend mineralinde ise plato yaşı 80,44±0,84 My elde edilmiştir. Bu sonuçlar altın cevherleşmesinde etkin olan hidrotermal alterasyonun ana kayacın yerleşiminden 3 My sonra geliştiğini göstermektedir.

Sisorta altın yatağında bulunan bakır minerallerinde elde edilen ‰ Cu izotop değerleri -5.502 ile +3.032 arasında değişim göstermektedir. Intrüzyona (sistemin derin kısmı) yakın yerlerdeki bakır izotop değerleri önemli bir izotopsal değişim göstermemektedir (‰ <1), bunun tersine sistemin üst kesimlerinde bakır izotop değerleri geniş bir değişim göstermekte ve buda ikincil süreçlerle bakır zenginleşmesini işaret etmektedir.

Anahtar Kelimeler

Ar/Ar Yaşlandırma, Duraylı İzotop, Sisorta, Yüksek Sülfidasyon Epitermal Altın

Kaynakça

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