Reduced
intrusion-related gold deposits have become a new, low-grade, large-tonnage
exploration target during the last decade. The best recognized examples of such
deposits are recognized throughout the Tintina Gold Province of the northern North American
Cordillera. Because such examples may have many features in common with orogenic
gold deposits, such as anomalous Bi, W and Te, low salinity and
CO2-rich ore fluids, and a spatial/temporal association with igneous
rocks, confusion and controversy have now become commonplace in classification
of many gold deposits formed along convergent margins. The best discriminators
of IRGS are likely to be their:

regional location in deformed shelf sequences on the
inboard side of a series of accreted terranes and within terranes that also
contain important tin and (or) tungsten deposits;

local spatial association of gold ores with cupolas and
contact aureoles of relatively reduced, alkaline-leaning, and volatile-rich
plutons;

post-deformational timing of gold deposition;

extremely low sulfide content (commonly <1 vol %) of>
ores within igneous bodies and the outward zoning, through proximal skarns and
to distal base metal-rich veins, from the causative pluton; and

low grades (<1 g t au) of auriferous sheeted vein>
systems in pluton cupolas.