Thermally enhanced mimetic fabric of magnetite in a biotite granite

The thermally induced growth of mimetic magnetite after biotite is here dem onstrated by the equivalence of anisotropies of magnetic susceptibility (AM S) and anhysteretic remanence (AAR) after heating of biotite single crystal s and whole rock specimens from a magnetite-free granite (Elba Island, Ital y). It is concluded that between 500 degrees and 725 degreesC magnetite nuc leates and grows within and parallel to the biotite cleavages yielding a ma gnetic fabric mimetic of the biotite fabric. At higher temperatures magneti te undergoes partial haematization, accounting for the decrease in remanenc e, susceptibility and anisotropy degree. This experiment may be used as a p roxy for fabric study of granites having composite (tourmaline + biotite) p aramagnetic fabrics in which the fabric of biotite can be selectively therm ally enhanced.