Gold mineralization in explosive breccia bodies: mineralogical characterization and genetic aspects (Sentyabrsky NE Deposit, Chukotka Region, Arctic Russia)

Abstract

The results of detailed mineralogical and microthermometric studies of gold–polymetallic ores located in tubular bodies of explosive breccias at the Sentyabrsky NE deposit (Central Chukotka region) are reported. Two stages of ore formation were detected: the early (gold–polymetallic) stage traced based on the core samples up to 250 m deep and the late (gold–silver–lead–telluride) stage was detected in the near-surface sampling pits. Early-stage ores filling the tubular body had low silver content (Au:Ag—2:1–10:1), as well as low As and Sb contents. Late-stage ores had high silver content (Au:Ag up to 1:30) and were rich in hessite. Fineness of native gold of early and late paragenesis is 755–810 and 820–860‰, respectively. Numerous spheroidal structures were investigated. It was found by studying fluid inclusions that ore formation took place in an open system during two hydrodynamic (meso-epithermal and geothermal) regimes and involved repeated dilution of mineralized hydrotherms with meteoric water and boiling of solutions.