LEAD-ISOTOPE COMPOSITIONS OF GALENA IN CARBONATE-HOSTED DEPOSITS OF WESTERN NEWFOUNDLAND - EVIDENCE FOR DIVERSE LEAD SOURCES

Carbonate-hosted zinc and lead deposits occur in two settings in the Humber Terrane of western Newfoundland: associated with dolomitized units and breccias in Cambrian and Ordovician shelf-facies carbonate rocks; and as open-space, vein, and breccia fillings associated with calcite within or near the margins of Carboniferous basins. We report 11 new lead-isotope analyses from deposits of the former type on the Great Northern Peninsula (the GNP suite) and 8 new analyses from deposits of the latter type on the Port au Port Peninsula and the northern part of the Bay St. George subbasin (BSG suite). Lead isotopes in deposits in the Bay St. George area cluster near average crustal model growth curves. Metal sources for these deposits, considered by previous workers as diagenetic in origin, are interpreted as being clastic sediments within the sedimentary basin.