Browsing by Author "Banwart, SA"

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    Mass balance assessment of initial weathering processes derived from oxygen cionsumption rares in waste sulfide ore
    (United States Department of The Interior Bureau of Mines, 1994-04-24) Strömberg, B; Banwart, SA; Bennett, JW; Ritchie, AIM
    A stoichiometric model for initial weathering processes in fresh waste rock has been developed for Aitik ore. Based on element mass balances, solubility equilibrium, mineralogy of unreacted waste rock, and literature data, we identified the dominant geochemical processes and determined geochemical reaction rates for weathering of pyrite, chalcopyrite, calcite, plagioclase and biotite using fluxes derived from large experimental columns filled with waste rock. The oxidation rate of reduced Fe and S was based on Oz-consumption rates that were previously determined in the columns. In the fresh waste rock, acidity production from pyrite weathering and rapid consumption of acidity by calcite dissolution dominate the proton balance. At an acidity production rate of 7.8 meq. kg-I year! of waste rock and a calcite alkalinity reservoir of 0-60 meq. kg-I, we expect the waste rock leachate to remain near-neutral pH for 0-8 years. When calcite is consumed and pH drops, dissolution of previously precipitated copper on the the order of 0-1.8 mmole copper kg-I of waste rock may temporarily increase the pollution load at the site.