Applications of Auger-electron spectroscopy to geochemistry
Applications of Auger-electron spectroscopy to geochemistry (in Microbeam techniques in the earth sciences, Frank C. Hawthorne (editor) and R. F. Martin (editor))
The Canadian Mineralogist (April 1995) 33, Part 2: 243-259
The composition of the uppermost 50 Aa of mineral surfaces is readily determined by Auger electron spectroscopy; analytical spot-sizes of < 1 mu m can be achieved routinely and the concentration of most elements can be quantitatively determined at levels as low as 1/4-1 wt.%. Compositional depth-profiles through air-oxidized pyrrhotite surfaces are reported, demonstrating that Fe diffuses rapidly from the bulk to the surface of pyrrhotite grains during oxidation in air. Auger results for a goethite surface, combined with EPMA, show that Al is distributed throughout the bulk of the mineral, and that Ni is concentrated at the surface (uppermost 50 Aa); sensitivity factors for Fe and O in goethite are derived from the data. The technique is a boon to experimental petrologists and geochemists in that detection of Aangstrom-thick leached veneers and authigenic overgrowths helps to circumvent the ever-present problem of slow rates of reaction.