Известия Томского политехнического университета: Инжиниринг георесурсов (Dec 2018)
IODINE_BEARING MINERALS OF СHLORARGYRITE–BROMARGYRITE SERIES IN OXIDIZED ORES OF THE KHAAK–SAIR AND THE TARDAN–2 GOLD–QUARTZ ORE OCCURRENCES (TUVA, RUSSIA)
Abstract
The rare abundance of natural iodine-bearing minerals of the chlorargyrite-bromargyrite series, their water solubility, comparatively small sizes, mineral forms (single micrograins, crusts, incrustations, micron-sized crystals), small hardness 1,5–2,5, instability for an electron beam impact in microprobe analysis caused insufficient knowledge of their mineralogical-geochemical features. The aim of the research is to determine genesis and mineralogical-geochemical features of iodine-bearing minerals of the chlorargyrite-bromargyrite series in oxidized ores in the Khaak-Sair and Tardan-2 gold-quartz ore occurrences case study. Methods: field studies, detailed mineralogical studies using ore mineralization in polished sections (polished microsections) using scanning electron microscopes MIRA 3 LMU (Tescan Orsay Holding) combined with Xray microanalysis systems INCA Energy 450+Xmax-80 and INCA Wave 500 (Oxford Instruments Nanoanalysis Ltd) and Vega 3 (Tescan) with EDA (Oxford Instruments X-act). Results. The authors have identified and described the hypergenic iodine-bearing minerals of the chlorargyrite-bromargyrite series in the oxidized ores of the Khaak-Sair and the Tardan-2 gold-quartz ore occurrences. It is confirmed that the iodine-bearing differences of the Khaak-Sair in the AgCl–AgBr series are represented by bromian iodian chlorargyrite (up to 8,16 wt. % I), chlorian iodian bromargyrite (up to 11,11 wt. % I), iodian chlorian bromargyrite (up to 13,94 wt. % I) and iodian bromargyrite (up to 15,45 wt. % I), on the Tardan-2 – bromian iodian chlorargyrite (up to 4,29 wt. % I), chlorian iodian bromargyrite (up to 10,16 wt. % I). The AgCl–AgBr halides in these ore occurrences are represented as their solubility decreases: AgCl→AgBr→AgI. Iodine content increases from chloride phases to more bromide phases within AgCl–AgBr series of the Khaak-Sair and the Tardan-2, because the parameters of face-centered cubic lattice gradually increase from AgCl to AgBr and the limits of AgI solid solutions in AgCl–AgBr series are very limited due to the fact that Ag iodides differ in structure from its chlorides and bromides.
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