Türkiye Jeoloji Bülteni

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

Abstract: This study presents geological and geochemical features of gold deposit located in Sisorta area nearEvliya Tepe, Güzelyurt village. The investigation area covers 42 km2 land and located in 200 km NW ofSivas province in Sisorta. .δ 34S ‰ isotope values are ranging from -0,4 and ‰ ‰ 22, in Sisorta gold deposit. At the early stage ofmineralization S isotope value number is light and later S isotope value shows heavy numbers. This isindicating that the S isotope was originated from magma and changed due to temperature variations inthe last stages of the hydrothermal process.δ18O isotope values of gangue minerals are ranging from; ‰ 7,1 and ‰ 15,6 however, δD value is rangingfrom ‰ -77 to ‰ -25,3 Combining δ18O with δD from Sisorta samples, demonstrates meteoric waters wereimportant in the formation of the alteration silicate minerals analyzed. This is common in high sulfidationsilicate 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±0,42Ma and 75,30±0,90 Ma as isochron age in K-alunite, 80,44±0,84 in hornblende minerals from unalteredandesitic volcanic rocks. This shows that hydrothermal gold mineralization is deposited 3 Ma later thanthe 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) donot show significant copper isotope variations (<1 per mil), in contrast the upper parts of the system showlarge copper isotope variations and indicate enrichment of copper due to supergene processes.