The Joe Mountain area of the Yukon contains Middle Triassic to Upper Triassic volcanic, sedimentary and intrusive rocks of the Stikine Terrane. The Ladinian (~237 to 228 Ma) rocks of the Joe Mountain Formation of Stikinia are divided into four units, including: 1) a lowermost mafic-ultramafic complex (mTJM4); 2) a lower basalt-flow-dominated unit (mTJM3); 3) a volcaniclastic- and sedimentary-rockdominated unit; and 4) and uppermost unit of black pillow basalts and volcaniclastic rocks (mTJM4). In the Joe Mountain Formation there is a general increase in the abundance of volcaniclastic and sedimentary material, and a decrease in flow material, away from Joe Mountain suggesting that Joe Mountain is a volcanic centre. Hematite-magnetite iron formation was discovered in 2004 interlayered with unit mTJM3 basalts. These iron formations have anomalous metal concentrations, but more importantly, have hydrothermal geochemical signatures (e.g., high Fe/Al ratios) similar to volcanogenic massive sulphide-associated iron formations globally.
