Native bismuth, tsumoite, and Pb-bearing tsumoite from the Tarn’er copper-zinc massive sulfide deposit, northern Urals

Abstract

Bismuth mineralization, including native bismuth, tsumoite (Bi1.99–2.03Te2.00), and Pb-bearing tsumoite (Bi1.56–1.88Pb0.45–0.14)2.00–2.03Te2.00, was identified in the Au-enriched disseminated ore at the Tarn’er massive sulfide deposit formed under the effect of a large diorite intrusion. Native bismuth associated with hessite forms idiomorphic inclusions in chalcopyrite. The assemblage of Pb-bearing tsumoite, hessite, and altaite occurs as angular allotriomorphic-granular inclusions in silicates or at the contact between silicate and sulfide aggregates. Tsumoite in allotriomorphic-granular aggregates with galena, hessite, and sphalerite is devoid of lead. Gold (Au0.65Ag0.35) was identified along with bismuth tellurides. The temperature of contact methamorphism (500–800°C) was estimated from the stability of andalusite, sillimanite, and cordierite. The morphology of the bismuth telluride aggregates in silicates and graphic intergrowth of tsumoite with galena suggest possible crystallization from anatectic melt. The positive correlation between Bi, Te, and Au confirms their probable joint transportation in the melt.