Gold composition and conditions of Southern Ak-Dag gold-sulfide-quartz ore occurrence formation (Western Tuva)

Research subject. The paper presents data on the mineralogical, geochemical and fluid inclusion features of the Southern Ak-Dag gold-sulphide-quartz ore occurrence in Western Tuva.

Methods. Mineral formation temperatures, salt composition and fluid salinity were examined using a Linkam TMS-600 cryostage and an Olympus BX 51 microscope. The chemical composition of samples was identified using a MIRA 3 LMU (Tescan Orsay Holding) scanning electron microscope equipped with INCA Energy 450+XMax 80 and INCA Wave 500 microanalysis systems; BSE photos were taken by Tescan Vega 3 and Hitachi ТМ-1000 SEM instruments.

Results. The ores under study were found to contain both high-grade and medium-grade gold with an Ag content of up to 17.05 wt %. The average gold fineness comprised 904 ‰, ranging from 830 to 928 ‰. According to fluid inclusion data, gold-sulphide-quartz veins were formed at temperatures of 280–240 °C and pressures of 0.8–1.2 kbar from aqueous fluids having a salinity of 8.6–6.4 wt % NaCl eq. The narrow range of fluid salinity at decreasing temperatures and the prevalence of high-grade gold in sulphide-quartz veins indicate a relatively high rate of mineral formation in a narrow permeable zone without any significant interaction with host rocks or mixing with meteoric waters.

Conclusions. Gold mineralization in the Southern Ak-Dag ore occurrence, which was formed within one ore substage, corresponds to the type of gold-galena-chalcopyrite with barite. The established similarity of native gold in the Southern Ak-Dag occurrence and other deposits in the Aldan-Maadyr ore cluster in terms of P-T parameters of ore formation and mineralogical and geochemical features, as well as association of the ore mineralization with beresites, indicate the possibility of discovering industrial ore deposits in the region and confirm its paragenetic relation with Devonian magmatic activity.

1. Ankusheva N.N., Kuzhuget R.V. (2013) The conditions of gold-quartz veins from Doushkunnug ore occurrence (Western Tuva) formation according to fluid inclusion data. Metallogeniya drevnikh i sovremennykh okeanov [The metallogeny of ancient and modern oceans]. Miass, IM UB RAS, 194-198. (In Russian)

2. Ankusheva N.N., Melekestseva I.Yu., Zaikov V.V., Kotlyarov V.A. (2013) The physical and chemical forming fluid parameters of Ulug-Sair gold deposit, Western Tuva. Ural’skaya mineralogicheskaya shkola [The Urals mineralogical School]. Ekaterinburg, IGG UB RAS, 21-23. (In Russian)

3. Ansdell K.M., Kyser T.K. (1992) Mesothermal gold mineralization in a Proterozoic greenstone belt; western Flin Flon Domain, Saskatchewan, Canada. Econ. Geol., 87, 1496-1524.

4. Baksheev I.A., Prokofiev V.Yu., Ustinov V.I. (1998) Conditions of formation of vein quartz of the Berezovsk gold ore field, Middle Urals, according to the data of study of fluid inclusions and isotope data. Uralskaya letnyaya mineralogicheskaya shkola [The Urals Summer Mineralogical School]. Ekaterinburg, UGGGA, 41-49. (In Russian)

5. Bodnar R.J., Vityk M.O. (1994) Interpretation of microthermometric data for H2O–NaCl fluid inclusions. Fluid inclusions in minerals: methods and applications. Pontignana-Siena, 117-130.

6. Borisenko A.S. (1982) The analysis of salt composition of fluid inclusions by means cryometry. Ispol’zovanie metodov termobarogeokhimii pri poiskakh i izuchenii rudnykh mestorozhdenii [The application of thermobarogeochemistry methods for ore deposit prospecting]. Мoscow, Nedra Publ., 37-46. (In Russian)

7. Borisenko A.S., Lebedev V.I., Obolenskii A.A., Zaikov V.V., Tyul’kin V.G. (1979) Physical and chemical conditions of Western Tuva hydrothermal deposits. Osnovnye parametry prirodnykh protsessov endogennogo rudoobrazovaniya [The main parameters of natural processes of endogenous ore formation]. V. 2. Novosibirsk, Nauka Publ., 226-235. (In Russian)

8. Klein E.L., Fuzikawa K., Koppe J.C., Dantas M.S.S. (2008) Fluids associated with the caxias mesothermal gold mineralization, São Luís Craton, northern Brazil: a fluid inclusion study. Revista Brasileira de Geociências, 30, 322-326.

9. Kuzhuget R.V. (2014) Zoloto-telluridnoe orudenenie AldanMaadyrskogo rudnogo uzla (Zapadnaya Tuva): mineralogo-geokhimicheskie osobennosti rud i usloviya ikh obrazovaniya. Diss. kand. geol.-min. nauk [Gold-telluride mineralization of the Aldan-Maadyr ore cluster (Western Tuva): mineralogical and geochemical features of ores and conditions of their formation. Cand. Geol and min. Sci.diss.] Novosibirsk, 20 p. (In Russian)

10. Kuzhuget R.V., Mongush А.А. (2013) The Aldan-Maadyr gold-bearing cluster, Western Tuva: geological and structural peculiarities and gold chemical composition. Vestn. Tomsk. Gos. Univer., 369, 188-192. (In Russian)

11. Kuzhuget R.V., Zaikov V.V., Ankusheva N.N. (2017) The mineralogical and geochemical peculiarities of Aryskan gold-quartz-veined ore occurrence in beresites (Western Tuva). Geologiya i mineral’no-syr’evye resursy Sibiri, 29(1), 98-110. (In Russian)

12. Kuzhuget R.V., Zaikov V.V., Lebedev V.I. (2014) Ulug-Sair gold-tourmaline-quartz deposit, Western Tuva. Litosfera, (2), 99-114. (In Russian)

13. Melekestseva I.Yu., Zaуkov V.V., Ankusheva N.N. (2013) The Aldan-Maadyr zone, Western Tuva, Russia: formation conditions of gold-quartz veins in listvenites, conglomerates, and beresites. “Ore genesis” International Conference. Miass, IMin UB RAS, 89-97.

14. Mongush А.А., Kuzhuget R.V., Druzhkova E.K. (2011) The peculiarities of magmatic rock compositions and Ar-Ar data of basite dykes from Aldan-Maadyr gold-bearing zone, Western Tuva. Metallogeniya drevnikh i sovremennykh okeanov [The metallogeny of ancient and modern oceans]. Miass, IMin UB RAS, 262-268. (In Russian)

15. Petrovskaya N.V. (1973) Samorodnoe zoloto [A Native Gold]. Мoscow, Nauka Publ., 348 p. (In Russian)

16. Prokofiev V.Yu. (2000) Geokhimicheskie osobennosti rudoobrazuyushchikh fluidov gidrotermal’nykh mestorozhdenii zolota razlichnykh geneticheskikh tipov [Geochemical features of ores forming fluids of hydrothermal gold deposits of various genetic types]. Novosibirsk, Nauka Publ., 192 с. (In Russian)

17. Prokofiev V.Yu., Spiridonov E.M. (2005) Composition of metamorphogenic fluids and conditions of transformation of ores from Kochkar gold deposit (Southern Urals). II Vserossiiskoe petrograficheskoe soveshchanie “Petrografiya na rubezhe XXI veka” [II All-Russian Petrographic Meeting “Petrography at the turn of the XXI century”]. V. 3. Syktyvkar, 88-90. (In Russian)

18. Redder E. (1987) Flyuidnye vklyucheniya v mineralakh [Fluid inclusions in minerals]. Мoscow, Mir Publ., 632 p. (In Russian)

19. Vasil’ev В.D., Druzhkov V.P., Krasikov A.I., Boyarko G.Yu. (1997) Audit and appraisal works for gold in Alash and Eilig-Khem districts of Western Tuva. 37 p.

20. Kyzyl. (In Russian unpubl.) Yoo B.C., Lee H.K., White N.C. (2006) Gold-Bearing Mesothermal Veins from the Gubong Mine, Cheongyang Gold District, Republic of Korea: Fluid Inclusion and Stable Isotope Studies. Econ. Geol., 101, 883-901.

21. Yoo B.C., Lee H.K., White N.C. (2010) Mineralogical, fluid inclusion, and stable isotope constraints on mechanisms of ore deposition at the Samgwang mine (Republic of Korea) – a mesothermal, vein-hosted gold-silver deposit. Mineral. Depos., 45, 161-187.

22. Zaikov V.V., Lebedev V.I., Tyulkin V.G., Grechishcheva V.N., Kuzhuget K.S. (1981) Rudnye formatsii Tuvy [Ore formations of Tuva]. Novosibirsk, Nauka Publ., 201 p. (In Russian)

23. Zaikova E.V., Zaikov V.V. (1969) The gold ores of the Western Tuva confined to the Devonian magmatism. Materialy po geologii Tuvinskoi ASSR [The Materials of Tuva SSR geology]. Kyzyl, 72-76. (In Russian)