 Gold quartz breccias and veins cut the McDougall Brook Microgranite and its volcanic wall-rock, while molybdenum-bismuth-tungsten and later polymetallic mineralization are related to the multiphase Mount Pleasant Granite.The numerous felsic sections are associated with episodes of fractional crystallization in a high-level, zoned magma chamber.Fractionation was continually interrupted by eruption of material from the roof zone such that seven phases of caldera growth have been recognized.