MINERALOGICAL PECULIARITIES AND PT-PARAMETERS OF FORMATION OF OVUR-ONGESH GOLD-TELLURIDE ORE OCCURENCE (Southern Tuva, Russia)
R.V. Kuzhuget1, N.N. Ankusheva2, A.Sh. Shavekina3, Yu.A. Kalinin3, A.A. Redina3
1 Tuvinian Institute for Exploration of Natural Resources, Siberian Branch of the Russian Academy of Sciences, Kyzyl, Russia
2 South Urals Federal Research Center of Mineralogy and Geoecology, Ural Branch of the Russian Academy of Sciences, Miass, Russia
3 V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
Keywords: Gold-telluride ore mineralization, epithermal mineralization, quartz, fluid inclusions, stable isotopes, Tuva.
Abstract
For the Ovur-Ongesh gold-telluride mineralization, 2 ore stages were determined. In ore stage I, gold, electrum, Au-Ag tellurides (petzite Ag3AuTe2, mutmannite AgAuTe2, sylvanite AgAuTe2, kostovite AuСuTe2), uytenbogaardtite Ag3AuS2
were formed; in ore stage II – gold, electrum, calaverite, petzite, hessite, petrovskaite AuAg(S,Se)2, fichesserite Ag3AuSe2
with naumannite Ag2Se and acanthite Ag2S. Fluid inclusions data in quartz (microthermometry, Raman spectroscopy) showed that minerals of ore stage I were formed at P ~0.95–1.3 kbar from Na-K chloride fluid with salinity from 6.9 to 33.1 wt % NaCl eq. at temperatures of 372–327 °C, ore stage II – from NaCl fluid with a salinity from 6.6 up to 8.6 wt % NaCl eq. at 257–227 °C. The δ18ОH2O values of ore stage I fluid vary from +8.1 up to +6.9 ‰ (T=330 °C), ore stage II – from +4.5 up to +3.5 ‰ (T=245 °C) that suggested the fluid has magmatic origin during the early ore-forming stages, and, at later stages, the fluid was mixed with meteoric water. The wide range of fluid salinity from 33.1 up to 6.9 wt % NaCl eq. may be due to dilution of high saline magmatic fluid with by heated meteoric water. The δ³⁴S(H₂S) values of the fluid – ranging from -6.3 to -2.7 ‰ for the I ore stage and from -6.3 to +5.5 ‰ for the II one indicate that, in addition to magmatic fluid, hydrothermal fluid of a different origin participated in mineral formation. The results from mineralogical, fluid inclusion, and isotopic studies demonstrated the similarities between the Ovur-Ongesh ore occurrence and the gold-telluride mineral type associated with volcano-plutonic complexes.
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