Phase Transitions in Iron Oxides and Sulphides and their Relations to Magnetic Properties of Rocks

Phase transitions in iron oxides and sulphides occurring during heating and with free access to oxygen and also the effect of uniaxial stresses on the temperatures and character of these transitions are investigated. The investigations are performed on Tertiary basaltic rocks, andesites from the Pieniny Mountains containing titanomagnetites, monomineral magnetites, ores and gneisses containing iron sulphides, pyrite crystals and synthetic pyrrhotite Fe₇S₈.
    Several experimental methods are used simultaneusly: thermomagnetic methods, observations of polished sections and thin plates and X-ray examinations. The author also uses a new experimental method using the phenomenon of thermally stimulated exo-electron emission (TSEE) and gives numerical test TSEE(T) curves for rocks containing titanomagnetites and iron sulphides. On the basis of the results obtained conclusions are drawn about the temperatures and character of phase transitions in the minerals mentioned above and a model of a thermal disintegration of pyrite is given. These conclusions serve in considering the problem of whether NRM i s of primary origin in Tertiary Lower Silesian basaltic rocks.

CONTENTS

Introduction, ...3
1. Experimental methods, ...10
    1.1 The TSEE method, ...11
    1.2 Thermomagnetic methods, ...16
    1.3 Mineralogical and petrographic methods, ...19
2. Results of the investigations of phase transitions in titanomagnetites, ...19
3. Results of the investigations of phase transitions in iron sulphides, ...33
    3.1 Thermomagnetic investigations, ...34
    3.2 Investigations by the TSEE method, ...43
    3.3 X-ray investigations, ...55
4. Application of the TSEE method for the study of the effect of stresses on phase transitions in titanomagnetites and iron
    sulphides, ...59
5. Discussion of paleomagnetic data on the basis of the results of investigations of magnetic minerals, ...70
    5.1 Primary origin of NRM, ...70
    5.2 Complete and partial self-reversal of the NRM direction, ...77
6. Summary and conclusions, ...82
    6.1 Titanomagnetites, ...83
    6.2 Iron sulphides, ...84
    6.3 The primary origin of NRM and self-reversal of its direction, ...86
References, ...89
Streszczenie, ...92