Appendix Q

PHREEQC version 3 is a computer program written in the C and C++ programming languages that is designed to perform a wide variety of aqueous geochemical calculations. PHREEQC implements several types of aqueous models: two ion-association aqueous models (the Lawrence Livermore National Laboratory model and WATEQ4F), a Pitzer specific-ion-interaction aqueous model, and the SIT (Specific ion Interaction Theory) aqueous model.

There are about a dozen major hydrogeochemical processes that can account for the chemical composition of most natural waters. One of these is the oxidation of pyrite, a process at least as important a source of sulfate in natural waters as seawater and sea spray, gypsum dissolution, and atmospheric emissions. The natural process of pyrite oxidation is fundamental to the super-gene alteration of ore deposits, the formation of acid-sulfate soils, and the development of acidity and metal mobilization in natural waters.

This report presents the results from a simulation model designed to predict the chemistry of water that will be collected in the underground workings of the Resolution Copper Project mine.

Pit lakes are an increasingly common legacy of modem, large-scale surface mining operations. Pit lakes formed in open pit metal mines, where base and precious metals are extracted from ore deposits hosted in predominantly igneous and metamorphic silicate rocks, comprise one category of pit lakes.

The GoldSim contaminant transport module provides capabilities for simulating chemical processes such as partitioning and solubilities. While flexible and easily configurable, these simple processes do not represent complete reaction paths, hence additional chemical relationships are sometimes needed to model complex hydrochemical systems. A versatile approach for representing complex chemical processes of chemical equilibration and aqueous speciation is to rely on GoldSim’s dynamic link library (DLL) element.

Chemical composition and equilibrium trends in mine pit lakes were examined to provide guidance for the application of geochemical models in predicting future lake water quality at prospective open pit mines. Composition trends show that elevated solute levels generally occur only at the extremes of acidic and alkaline pH conditions.

In this chapter we survey and synthesize available information on the major physical-chemical properties of hydrous ferric oxide (HFO). After examining the structure and composition of HFO, we present published data for surface area, site densities, and surface acid-base properties. Our main purpose is to obtain best estimates for the surface properties of HFO and provide a sense for the consistency of the corresponding experimental data.

Rio Tinto is evaluating the Resolution Copper deposit located in Arizona. The main interest for this project is copper, with a secondary value in molybdenum. The principle objectives of this project were to:

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