The Behavior of Co, Ni, Zn, Cu, Mn, and Cr in Magnetite during Alteration to Maghemite and Hematite
1980
Sidhu, P. S. | Gilkes, R. J. | Posner, A. M.
Synthetic magnetites containing small amounts of a trace element were altered to maghemites by heating in air at 220°C and to hematites by heatings at 650°C. The distributions of the trace elements in the magnitites, maghemites, and hematites were determined by a dissolution technique. Cobalt, nickel, and zinc were uniformly distributed in the magnetite grains. Chromium was concentrated near the center and Cu and Mn were concentrated near surfaces. The trace elements were retained within maghemite grains and the outer regions contained less trace element than the corresponding magnetites due to the outward migration of iron during oxidation. During alteration to hematite much of the Co, Ni, Zn, and Cu was ejected from the hematite to form a surface layer rich in these elements. Manganese and Chromium were retained by hematite grains. The behavior of the trace elements is discussed in terms of their ionic radii and their crystal field stabilization energies.
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