Pyrrhotite progressively oxidizes via magnetite to hematite during thermal demagnetization of porous artificial samples containing well-defined natural pyrrhotite. Rockmagnetic and X-ray diffraction determinations show that the intermediate alteration stages consist of pyrrhotite-magnetite-pyrite intergrowths. Alteration is quite differently expressed in two chemically vrtually identical pyrrhotites. ¿ American Geophysical Union 1990 |