Magnetic Mineralogy, Changes due to Heating
Mineralogical alterations occur very often in rocks subjected to thermal treatment. Laboratory heating may cause, in many cases, not only magnetic phase transformations, but also changes in the effective magnetic grain sizes, the internal stress, and the oxidation state. The presence or absence of such alterations is crucial to the validity and success of numerous magnetic studies.
The basic assumption in paleointensity determinations in the measurement of anisotropy of thermoremanent magnetization is that the rock is not modified during the different successively applied heating treatments. For simple thermal demagnetization, the occurrence of mineralogical alteration can introduce errors in the determination of the magnetic carrier if the latter had undergone transformation a at lower temperature than its unblocking temperature. Acquisition of parasitic chemical remanent magnetization is also possible if the heating was not made in a perfectly zero magnetic field. Formation of...
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