Occurrence in Lower Carboniferous and Devonian strata in northern Tipperary. The deposits comprise lower discordant zones--deposited epigenetically along the channelways of the ascending ore solutions--and upper, late Tournaisian, stratiform, syngenetic-syndiagenetic zones of sedimentary exhalative origin. Mineralization occurs in a variety of sediments whose composition reflects the nature of the exhaled fluids and the variable physiochemical conditions in their depositional sites. As a result of periodic tectonism on the fault zone, these mineralized sediments were subjected to varying degrees of brecciation in a very unstable depositional environment. The stratiform deposits of Silvermines are synsedimentary products of the exhalation of mineralizing fluids from northwest-trending feeder zones on to a late Tournaisian sea floor of highly irregular paleotopography.--Modified journal abstract.