Stratiform lead-zinc sulfides, mudflows, turbidites; Devonian sedimentation along a submarine fault scarp of extensional origin, Jason Deposit, Yukon Territory, Canada

Sedimentary strata show that metal sulphides at Jason accumulated along the margin of an extensional graben during the middle to late Devonian. Galena, sphalerite and baryte, among other minerals, represent sea-floor deposition mostly from expelled hydrothermal fluids. Stratiform mineralization is laminated to thickly bedded and massive. The metal sulphides were deposited in deep water and anoxic conditions. Abrupt stratigraphic thinning and the abundance of laterally discontinuous, locally derived mass failure deposits indicate the effect of syndepositional faults, some of which served as conduits for discharge of metalliferous fluids. The local tectonic setting during the late Devonian was extensional and apparently related to transform motion between the North America cratonic plate and an ocean plate to the west.