Ore mineralization formation stages in the Mayskoe deposit (Central Chukotka)

The paper comprehensively investigates ore mineralization in the Mayskoe deposit, which involves examining structural relationships of mineral associations in mine workings, mineralogical and petrographic ore analysis, interpreting chemical and isotopic composition of sulfur sulfide. The findings identify three ore formation stages naturally associated with key geological events in North-East Russia. The first stage includes ore preparation, which corresponds to the Early Triassic sedimentary hydrothermal system when terrigenous siltstone-pelitic, less often psammitic sediments accumulated on the Carboniferous carbonate base in a passive continental margin. The stage involves lead-zinc and pyrite-arsenopyrite mineral association formation. The second stage is productive or ore-forming, pertains to the hydrothermal metasomatic system and is the most fertile for gold. During this stage, “greisen”, polymetallic, and gold-sulfide mineral associations were formed. The latter includes the bulk of refractory gold. The third stage is subvolcanic, which aligns with a hydrothermal metasomatic system, whose severe decompression resulted in forming quartz breccias with antimonite and visible gold. Sulpho-salt-polymetallic and gold-antimonite mineral associations characterize this stage, which completes the Mayskoe deposit formation. The period featured the ore co lumn in a cross-cutting position against mineral associations of the productive stage, which is notable for coarse (up to 2 mm) free gold.