Paleomagnetism of Mississippi Valley-type ores in Navan, Ireland, and Robb Lake, British Columbia, and of dolomitization in southern British Columbia, Canada

摘要

The genesis of the Mississippi Valley-type (MVT) Pb-Zn mineralization at Navan, Ireland and at Robb Lake, British Columbia, has been disputed, in part because their ages are undefined. Paleomagnetism will be used to date the mineralization and dolomitization of the Navan and Robb Lake study areas and of the dolomitization in southeastern British Columbia. The Navan orebody is hosted in Mississippian carbonates of the Navan Group. Red Beds at the base of the group are overlain by dolostones and limestones that host pale brown-yellow sphalerite with lesser amounts of galena in a dolomite and barite gangue. Host rocks of the Robb Lake mineralization are Lower and Middle Devonian platform carbonates, which contain pale to medium brown sphalerite occurring as large crystals within the white sparry dolomite that fills fractures, forms the matrix of breccias, and lines or fills open spaces. The dolomitization in southeastern British Columbia occurred in the Middle Cambrian Chancellor carbonates.