Magnetomineralogy of the cordierite gneiss from the magnetic anomaly at Humpolec, Bohemian Moldanubicum (Czech Republic)
Abstract
Magnetic properties as well as the magnetomineralogy were investigated in rocks underlying a 7 km long aeromagnetic anomaly situated in the Moldanubian crystalline unit of the Bohemian Massif. The anomaly is caused by highly magnetic cordierite gneiss forming a stripe of NE - SW direction east of the town of Humpolec, eastern Bohemia.
Magnetic susceptibility and its anisotropy (AMS), natural remanent magnetization, field and temperature variations of susceptibility were measured. Optical study of thin sections, electron microprobe and Mossbauer studies were also used to reveal the carrier of the high susceptibility and the high NRM.
There appear to be two major generations of Fe-Ti oxides: older hematite with ilmenite exsolutions (Ti-hematite) which is the dominant remanence phase, and younger magnetite, the dominant susceptibility phase, usually associated with rutile.