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

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

1. Bedi, Y., 1998, Geology of the region between Mesudiye (Ordu)-Ortakent (Koyulhisar-Sivas) and the Petrographical-Geochemical analysis of the magmatic rocks, Ph.D. Thesis, Selçuk University, 193 s.
2. Braxton, D., ve Mathur, R., 2011, Exploration Applications of Copper Isotopes in the Supergene Environment: A Case Study of the Bayugo Porphyry Copper-Gold Deposit, Southern Philippines: Economic Geology, v. 106, p. 14471463.
3. Chadwick, T., 2005, Geology of Sisorta prospect, Eurasian Minerals Inc. report.
4. Chambers, L.A., 1982, Sulfur isotope study of a modern intertidal environment and the interpretation of ancient sulfides. Geochim. Cosmochim. Acta, 46, 721-728.
5. Chaussidon, M., Albarede, F., and Sheppard, S.M.F., 1989, Sulphur isotope variations in the mantle from ion microprope analyses of micro-sulphide inclusions. Earth Planet. Sci. Lett., 92, 144-156.
6. Claypool, G.E., Holser, W.T., Kaplan, I.R., Sakai, H., and Zak, I., 1980, The age curves of sulfur and oxygen isotopes in marine sulfate and their mutual interpretation. Chemical Geol., 28, 199-260.
7. Coleman, M.L., 1977, Sulpfur isotopes in petrology. J. Geol. Soc. Lond., 133, 593-608.
8. Corbett, G.J., and Leach, T.M., 1988, Southwest Pasific Rim Gold-Copper Systems: Structure, Alteration, and Mineralization: SEG Special Publication, No. 6, Chapter 3, p.31-67.

9. Craig, H., 1961, Isotopic variations in meteoric waters. Science v. 133, p, 1702-1703.
10. Garofali, K., Robinson, R., Thoennessen, M., 2012, Discovery of Chromium, Manganese, Nickel, and Copper Isotopes: Atomic Data and Nuclear Data Tables, 98, p. 356-372.
11. Graham, S., Pearson, N., Jackson, S., Griffin, W., O’Reilly, S.Y., 2004, Tracing Cu and Fe from Source to Porphyry: in Situ Determination of Cu and Fe Isotope Ratios in Sulfides from the Grasberg Cu-Au Deposit: Chemical Geology, 207,
12. Ikehata, K., ve Hirata, T., 2012, Copper Isotope Characteristics of Copper-Rich Minerals from the Horoman Peridotite Complex, Hokkaido, Northhern Japan: Economic Geology, v. 107, p.1489-1497.
13. Jebrak, M., 1997, Hydrothermal breccias in veintype ore deposits: A review of mechanisms, morphology and size distribution: Ore Geology Reviews v.12, p. 111-134.
14. Kerridge, J.F., Haymon, R.M., and Kastner M., 1983, Sulfur isotope systematics at the 21oN site, East Pasific Rise. Earth Planet. Sci. Lett., 66, 91-100.
15. Larson, B.P., Maher, K., Ramos, F.C., Chang, Z., Gaspar, M., Meinert, L.D., 2003, Copper Isotope Ratios in Magmatic and Hydrothermal Oreforming Environments: Chemical Geology, 201, p. 337-350.
16. Lawless, J.V., White, P.J., 1990, Ore-Related Breccias: A Reviesed Genetic Classification with Particular Reference to Epithermal Deposits: 12th New Zealand Geothermal Workshop, p. 197-201.
17. Li, W., Jackson, S.E., Pearson, N.J, Graham, S., 2010, Copper isotopic zonation in the Northparkes porphyry Cu-Au deposit, SE Australia: Geochimica et Cosmochimica Acta v. 74, p. 40784096.
18. Liu, S-A., Huang, J., Liu, J., Wörner, G., Yang, W., Tang, Y.C., Tang, L., Zheng, J., Li, S., 2015, Copper isotopic composition of the silicate Earth: Earth and Planetary Science Letters, v. 427, p.95103.
19. Mathur, R., Dendas, M., Titley, S., ve Phillips, A., 2010, Patterns in the Copper Isotope Composition of Minerals in Porphyry Copper Deposits in Southwestern United States, Economic Geology, 105, p. 1457-1467.
20. Mathur, R., Titley, S., Barra, F., Brantley, S., Wilson, M., Phillips, A., Munizaga, F., Maksaev, V., Vervoort, J., Hart, G., 2009a, Exploration Potential of Cu Isotope Fractionation in Porphyry Copper Deposits: Journal of Geochemical Exploration, 102, p. 1-6.
21. Mathur, R., Titley, S., Barra, F., Brantley, S., Wilson, M., Phillips, A., Munizaga, F., Maksaev, V., Vervoort, J., Hart, G., 2009b, Copper Isotope Fractionation Used to Identify Supergene Processes: Society of Economic Geologists, Special Publication 14, p. 45-49.
22. Mirnejad, H., Mathur, R., Einali, M., Dendas, M., ve Alirezaei, S., 2010, A Comparative Copper Isotope Study of Porphyry Copper Deposits in Iran: Geochemistry: Exploration, Environment, Analysis, v.10 , p. 413-418.
23. Ollier, C.D., 2007, Breccia-Filled Pipes: Distinguishing Between Volcanic And Non-Volcanic Origins: Geogr. Fis. Dinam. Quat. 30, p. 63-76.
24. Picot, P., ve Johan, Z., 1982, Atlas of Ore Minerals, Elsevier, Amsterdam, 458 pp.
25. Şahin Demir, Ç., 2015, Sisorta (Ortakent-Koyulhisar Sivas) yöresi altın yatağının jeolojik ve jeokimyasal özellikleri: Cumhuriyet Üniversitesi Fen Bilimleri Enstitüsü, doktora tezi, 270 s, yayımlanmamış.
26. Sakai H., Casadevall T.J. and Moore, J.G., 1982, Chemistry and isotope ratios of sulfur in basalts and volcanic gases at Kilauea volcano, Hawaii. Geochim. Cosmochim. Acta, 46,729-738.
27. Sakai H., Des Maris, D.J., Ueda, A., and Moore, J.G., 1984, Concentrations and isotope ratios of carbon, nitrogen and sulfur in ocean-floor basalts and volcanic gases at Kilauea volcano, Hawaii. Geochim. Cosmochim. Acta,48, 2433-2441.
28. Tamaş, C.G., Milesi, J.P., 2002, Hydrovolcanic Breccia Pipe Structures - General Features And Genetic Criteria - I. Phreatomagmatic Breccias: Studia Universitatis Babeş-Bolyai, Geologia, Xlvii, 1, p. 127-147.
29. Tamaş, C.G., Milesi, J.P., 2003, Hydrothermal Breccia Pipe Structures – General Features And Genetic Criteria – II. Phreatic Breccias: Studia Universitatis Babeş-Bolyai, Geologia, Xlviii, 1, p. 55-66.
30. Taylor, J.r., H. P., 1997, Oxygenand and Hydrogen Isotope Relationships in Hydrothermal Mineral Deposits, Geochemistry of Hydrothermal Ore Deposit, 3rd Edition ed. Barnes, H.L. John Wiley & Sons, New York, p. 229-302.
31. Uçurum A., Lechler, P.J., Arehart, G.B., Molnar, F., 2007, Platinum-Group Element, Stable Isotope, and Fluid Inclusion Investigation of the Ultramafic Rock-Hosted Gunes-Sogucak Ni-Cu-Sulfide Mineralization, Gunes Ophiolite, East-Central Turkey: International Geology Review, v.49, p.169-192.
32. Ueda, A., and Sakai, H., 1984, Sulfur isotope study of Quaternary volcanic rocks from the Japanese island arc. Geochim. Cosmochim. Acta, 48, 18371848.
33. Yetkin, E., 2009, Alteration identification by hyperspectral remote sensing in Sisorta Gold Prospect (Sivas-Turkey): unpublished PhD thesis, Middle East Technical University, 129 p.