Geology, mineralogy and geochemistry of Tavt gold deposit in Dzhida zone, northern Mongolia: implications for the evolution of intrusion and ore mineralization

Abstract

The Tavt gold deposit located in the Dzhida zone of northern Mongolia is hosted within intrusive complexes: Dzhida, Selenge and Orkhon. The Dzhida intrusive complex, a main host rock, shows three phases including gabbrodiorite, diorite, monzodiorite and granodiorite whereas the Selenge and Orkhon intrusive complexes have more felsic and subalkaline composition. The auriferous quartz veins are widespread within the host rocks. Gold grain mostly occurs as an electrum and gold inclusion is present within Cu-bearing sulfide minerals such as chalcopyrite and tennantite. Potassic and propylitic alterations occur in pre-ore stage whereas phyllic alteration is related to mineralization processes. With the presence of tennantite related to magmatic fluid, the variation of composition of phyllic altered minerals from muscovite to illite is likely to indicate a magmatic-hydrothermal origin of ore-forming fluids. The K-Ar ages of muscovite and illite in the Tavt deposit are 270.3 ± 5.0 and 277.2 ± 5.2 Ma, which is corresponding to the intrusive age of the Selenge complex from previous studies. This correspondence of the alteration ages to the intrusive ages indicates a spatial and temporal relationship between magmatic intrusion and gold mineralization. The gold mineralization in the Tavt deposit, therefore, is related to intrusion and hydrothermal activities.