Subaqueous Oxidation of Pyrite and Stable Isotope Geochemistry
of an Acidic Pit Lake
Principal Investigator: Dr. Chris Gammons
cgammons@mtech.edu
The processes responsible for the chemical evolution of the Berkeley
Pit lake were investigated through field and experimental studies
in this project. The primary objective was to evaluate the role
of subaqueous oxidation of pyrite by dissolved ferric iron in controlling
pH and metals concentrations in the pit lake. Other factors considered
were evapoconcentration, leaching of soluble salts from weathered
bedrock, and the influx of low pH ground water from an unknown source.
A suite of water samples was collected from three flooded mine shafts,
the Horseshoe Bend Springs, which flows into the Berkeley Pit, and
the Berkeley Pit, itself. Samples were analyzed for field parameters,
Fe(II)/Fe(III) speciation, dissolved metals, and the stable isotopes
d18Owater, dDwater, d18Osulfate, and d34Ssulfate. In the laboratory,
the rate of anaerobic oxidation of pyrite by dissolved ferric iron
was quantified experimentally. Field and laboratory studies indicate
that while subaqueous oxidation of pyrite plays an important role
in the chemistry of the Berkeley Pit, factors such as evapoconcentration
and wall-rock leaching also make significant contributions to this
complex pit lake system.
MWTP Activity IV, Project 27
Final Report
|
