Известия Томского политехнического университета: Инжиниринг георесурсов (Mar 2018)
Evolution of chemical composition of fahlores of the Ak-Sug gold-molybdenum-copper-porphyry deposit (North-East Tuva)
Abstract
The study of fahlores is one of the most effective areas of mineralogical research that allows deciphering the conditions for formation of ore deposits, which in its turn is the scientific basis for their search, exploration and rational mining. The main aim of the study was to reveal mineralogical-geochemical features and evolution of the composition of fahlores, as well as features of the ore-forming hydrothermal fluids that formed the Ak-Sug gold-molybdenum-copper-porphyry deposit. Research methods: field studies, detailed mineralogical studies with ore mineralization in polished sections (polished sections) with Olympus polishing microscope and electron microscope MIRA 3 LMU (Tescan Orsay Holding) combined with X-ray microanalysis systems INCA Energy 450+Xmax-80 and INCA Wave 500 (Oxford Instruments Nanoanalysis Ltd). Results. We revealed variations in composition of the fahlores group minerals of the Ak-Sug gold-molybdenum-copper-porphyry deposit, which are represented by the minerals of the tennantite-tetrahedrite series. The latter are developed as part of three mineral associations corresponding to three generations. For the fahlores, a latent smooth zoning is characteristic, due to an increase in the Sb content to the outer zones. Evolution of compositions of the I generation fahlores: Cu-tennantite - Fe-tennantite - Zn-tennantite, II generation: Cu-tennantite - Zn-tennantite - Zn-tennantite-tetrahedrite. Fahlores of the III generation is represented by Zn-tennantite-tetrahedrite. The presence of high-copper tennantite, Zn-tennantite, Zn-tennantite-tetrahedrite, and mineralogical features of the Ak-Sug ore deposits indicate a relatively increased oxidation potential of ore-forming hydrothermal fluids. The main factors of ore deposition were a change in the oxidation-reduction character, variations of fS2, fSe2, fTe2 and temperature decrease of ore-bearing fluid.
