Correlated strontium, carbon and oxygen isotopes in carbonate gangue at the Nanisivik zinc-lead deposits, northern Baffin Island, N.W.T. Canada

Abstract

We have analysed the Sr and C isotopic composition of samples of white sparry dolomite (WSD) interbanded with sulfides, vug-filling dolomite and calcite, and host dolostones associated with lead-zinc mineralization at Nanisivik, N.W.T. Canada. Ore stage WSD and late stage carbonates are considerably more radiogenic in ⁸⁷Sr and depleted in ¹³C and ¹⁸0 than dolomite of the host rocks. Within single WSD bands there is a negative linear correlation between ⁸⁷Sr/⁸⁶Sr and δ ¹³C and a positive correlation between ⁸⁷Sr/⁸⁶Sr and δ ¹⁸0. The ore-forming fluids varied considerably in isotopic composition during sulfide precipitation as a result of mixing between exogenous radiogenic ⁸⁷Sr and Sr from the host-rock dolostones, as well as mixing between bicarbonate from in situ oxidation of hydrocarbon, with carbonate from the host rock. High ⁸⁷Sr/⁸⁶Sr ratios in the ore fluid was probably the result of the interaction and equilibration with underlying metalliferous Arctic Bay formation and possibly basement rocks during migration to the site of ore deposition. The post-ore carbonates show a weak positive correlation between ⁸⁷Sr/⁸⁶Sr and δ ¹³C and apparently formed by remobilization of gangue and host-rock carbonate.