Evidence of upgrading of gold tenor in an orogenic quartz-carbonate vein system by late magmatic-hydrothermal fluids at the Madrid Deposit, Hope Bay Greenstone Belt, Nunavut, Canada

The study suggests that gold upgrading, either involving newly introduced gold or remobilization of existing gold, can be linked to the incursion of a late magmatic-hydrothermal fluid that post-dated formation of the main orogenic-type auriferous quartz vein system. The geological setting and mineral-chemical features suggest an intrusion-related (i.e., porphyry), or intermediate-sulfidation epithermal mineralization style for the later event. This work provides another example of the importance of compositionally distinct cumulative hydrothermal events in the development of high-grade gold deposits in orogenic settings.