Gold occurrences in the upper Hyland River valley form a 50-km-long belt that is considered to be the easternmost portion of the Tombstone Gold Belt (TGB). Mineralization is thought to have a genetic association with nearby Cretaceous plutons, which were important in the formation of most mineralization in the TGB. However, an evaluation of the Hyland River occurrences indicates that evidence supporting an intrusion-related gold model is mostly lacking. Plutons and dykes do not occur in the vicinity of the gold occurrences; there are no obvious zones of hornfels; contact metamorphic minerals and skarns are mostly absent; there is no known mineral or metal zonation typical of intrusion-related systems; and aeromagnetic lows result from massive, variably altered quartz grit and conglomerate and not from unroofed `low-mag' intrusions. Mineralization consists of four types: 1) disseminated pyrite and arsenopyrite in altered grit; 2) quartz-arsenopyrite veins; 3) quartz-pyrite-galena veins; and, 4) massive arsenopyrite veins. Auriferous quartz veins have characteristics similar to orogenic gold veins, and thus potentially relate to regional metamorphism and large structural features.
