Crustal Geophysics and Geochemistry Science Center

Modeling Near-Surface Processes in Mineral Systems

SubTask 5.1: Experimental Laboratory Geochemical and Microbiological Oxidation of Sulfide Minerals

Task Objectives

The objective of this task was to improve predictive capabilities for forecasting or understanding toxic element release during sulfide oxidation in the surficial environment. A concerted, multidisciplinary effort was directed at generating new geochemical and microbiological data to predict the environmental behavior of sulfide minerals. Task goals were to generate new data on:

  1. the concentration and precise location of trace elements in primary sulfides before and after reaction experiments,
  2. reaction rates of a variety of sulfide minerals, especially where bacteria are involved,
  3. low-temperature partitioning of solid-solution elements between sulfides and water
  4. reacted products and secondary phases that form during alteration experiments.

Highlights & Key Findings

We have established that both sphalerite and chalcopyrite are reactive in oxygenated water at room temperature with pH set at relatively low values (3-4).

An exciting discovery emerged from our ion microprobe analyses of sulfur isotope values in our sphalerite materials to date. We discovered a significant variation in mass fractionation with Fe content of sphalerite over the range of our standards (0-14 weight %). This discovery is critically important to investigators wishing to produce accurate sulfur isotope analyses by ion microprobe.

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