Lead-zinc sulfides were deposited during the Devonian in the locality of the Jason prospect, Yukon Territory. Massive and laminated sulfides are interbedded with clastics of the Canol Formation; galena and sphalerite, among other minerals, precipitated on the sea floor from exhalative fluids along the fault margins of a small graben. The depositional graben center consists of a thick sequence of conglomerates, sandstones, and finer clastics. These were derived from a western source, and were deposited largely by turbidity currents in channel and channel-flanking areas. Conglomerates are massive or graded, and some show faint parallel stratification. Sandstones show Bouma-interval sequences and some grooves and flutes. In contrast, the ore area has a thinner sequence which consists dominantly of sedimentary breccias, pebbly mudstones, and shales. Breccias and pebbly mudstones were deposited from debris flows and show a range of plastic mass-flow structures. Stratigraphic thinning and presence of laterally discontinuous and locally derived mass failure deposits indicate the existence of a penecontemporaneous fault zone. A few conglomerates and sandstones are interbedded with the ore horizon, and these and siltstones and shales were likely deposited from large turbidity currents. Involvement of sediments which had been deposited near the bottom of the graben in later mass failures indicates episodic fault movement during sedimentation. The fault zone appears to have positioned a sub-sea surface, geothermal system which formed metal-depositing fluids. Diamond drilling is underway to determine ore reserves. Core 78-30 shows the range of sedimentary structures and bedding styles of the ore zone.