Ebook: Methods in Rock Magnetism and Palaeomagnetism: Techniques and instrumentation

During the last 30 years the study of the magnetic properties of rocks and minerals has substantially contributed to several fields of science. Perhaps the best known and most significant advances have resulted from the study of palaeomagnetism, which led to quantitative confirmation of continental drift and polar wandering through interpretation of the direction of remanent magnetism observed in rocks of different ages from different continents. Palaeomagnetism has also, through observations of reversals of magnetiz­ ation, ancient secular variation and ancient field intensities provided data relevant to the origin of the geomagnetic field, and other investigations have contributed significantly to large-scale and local geological studies, the dating of archaeological events and artefacts and more recently to lunar and meteoritic studies. Rock and mineral magnetism has proved to be an interesting study in its own right through the complex magnetic properties and interactions observed in the iron-titanium oxide and iron sulphide minerals, as well as contributing to our understanding of remanent magnetism and magnetization processes in rocks. Simultaneous with the development of these studies has been the develop­ ment of instruments and techniques for the wide range of investigations involved.

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1 Rock magnetism and magnetic minerals.- 2 Initial magnetic susceptibility.- 3 High-field measurements.- 4 High- and low-temperature measurements.- 5 Controlled fields and field-free space.- 6 Miscellaneous techniques.- 7 A brief review of palaeomagnetism.- 8 The sampling of rocks for palaeomagnetism.- 9 Measurement of the NRM of rocks.- 10 Field and laboratory stability tests.- 11 Magnetic cleaning techniques.- 12 Presentation and treatment of data.- 13 Identification of magnetic minerals and carriers of NRM.- 14 Intensity of NRM.- Appendix 1 Conversion factors between SI and c.g.s. units.- Appendix 2 Demagnetizing factor of ellipsoids.- Appendix 3 Copper wire data.- Appendix 4 Preparation of colloidal magnetite.- Appendix 5 Correction of NRM directions to field reference systems.- Appendix 6 Measurement of the magnetic field in a coil.- Appendix 7 The off-centre measurement method with the astatic magnetometer — correction terms for cylindrical samples and the upper magnet.- Appendix 8 Detection of mains asymmetry.- References.