Geochemical Characterization and Fluid History of the Tiger Zone; a Tertiary Distal Carbonate--Replacement Intrusion-Related Gold Deposit, Central Yukon

A paragenetic and geochemical study has resulted in the classification of the Tiger zone as a Tertiary-aged intrusion-related gold deposit. Gold-bearing mineralization occurs in two geochemically and temporally distinct assemblages. The first assemblage contains carbonate-replacement, arsenopyrite-hosted, lattice bound gold deposited from hot (∼400 °C), CO2-rich immiscible magmatic fluids derived from a local intrusive body at depths of ∼5 km. The second gold-bearing event contains native gold in fractures associated with bismuth, antimony, silver and tungsten, and may have precipitated from depressurization and/or mixing with cooler, meteoric waters. Mixing of components from the host-rock limestone with Precambrian sediments are demonstrated by carbon, oxygen and strontium isotopes, whereas sulfur and metals originate from a local intrusion. Post-gold monazite aged 58.1 +/- 0.9 Ma constrains the minimum age for Tiger zone mineralization. The waning of the magmatic system resulted in the influx of meteoric waters forming post-mineralization calcite veins.