The Archean Sturgeon Lake Caldera Complex (SLCC) comprises a well-preserved, north-facing homoclinal sequence of greenschist facies metamorphosed intrusive, volcanic, and sedimentary strata. This piecemeal caldera complex is at least 25 km in strike length and contains nearly 3000 meters of dominantly subaqueously deposited intracaldera fill. Episodes of subaerial and subaqueous explosive felsic volcanism produced rhyodacitic to rhyolitic tuffs and lapilli tuffs. Progressing stratigraphically upward, the most voluminous are: a) the High Level Lake Tuff (~16km3); b) the Mattabi Tuff (~27km3); and c) the Middle L Tuff (~7km3). The subaerially erupted, subaerially and locally subaqueously deposited High Level Lake Tuff comprises an 80-300 meter-thick unit composed of basal, poorly sorted, massive to normal graded, quartz-phyric, locally spherulitic tuffs and lapilli tuffs (30-150m thick) that are overlain by thin-bedded tuffs (< l -5m thick). The subaqueously erupted and deposited Mattabi Tuff contains up to thirteen individual flow units, each comprising two distinct depositional facies: a) lower, quartz-phyric, poorly sorted, ungraded, massive tuffs and lapilli tuffs (20-250 meters thick); and b) upper, laminated to medium bedded, typically normal graded tuffs (1-13 meters thick). The subaqueously erupted and deposited Middle L Tuff is also characterized by two distinct lithofacies: a) lower graded, quartz-and, rarely, potassium feldspar-phyric tuffs and lapilli tuffs (5-120m thick); and b) overlying, well-sorted, laminated to thickly bedded, normal graded tuffs (< l -5m thick). These three voluminous tuff deposits host all known volcanic-hosted massive sulfide (VHMS) ore bodies in the SLCC. At Sturgeon Lake, VHMS ore deposition appears to be favored by processes associated with the generation of voluminous subaqueous explosive eruptions.