Pseudomorphic Rhythmically Banded and Oscillatory Tetrahedrite–Tennantite Aggregates in the Darasun Gold Deposit (Eastern Transbaikalia, Russia): A Result of Coupled Dissolution–Reprecipitation Reactions

Resumo

The rhythmically banded aggregates of Fe–tennantite with oscillatory zoning resulting from simultaneous variations in the concentrations of Sb and As and Zn and Fe were registered in the Darasun gold deposit (Eastern Transbaikalia). These aggregates were formed upon pseudomorphic replacement of early Zn–tetrahedrite. This process was initiated by the dissolution of Zn–tetrahedrite with the formation of an aggregate of galena, bournonite, and late tetrahedrite–tennantite. It is shown that rhythmically banded aggregates with an oscillatory zoning were formed as a result of coupled dissolution–reprecipitation reactions under the conditions that are far from the mineral–fluid chemical equilibrium and variations in the fluid composition controlled by kinetic factors.