On a thermomagnetic criterion for the identification of the domain structure

Correct determination of paleointensity and paleotectonic and magnetostrati graphic reconstructions from ingneous rocks are possible only in the case o f validity of the Thellier laws on the pTRM independence and additivity, wh ich hold rigorously only in samples with a single-domain grain size. The Bo lshakov-Shcherbakova thermomagnetic criterion (TC) for the recognition of d omain structure is based on measurement of the pTRM tail value. However, he ating of a sample to Tc, required to remove its NRM, often changes the mine ralogy and structure of ferromagnetic grains, thereby considerably decreasi ng the practical value of TC. An alternative to heating is the NRM removal under the action of an alternating magnetic field with decreasing amplitude , i.e., the pTRM creation from the zero state (ZS). The TC efficiency is as sessed for pTRM created from various magnetic states. The ZS-derived pTRM t ail is shown to be three times smaller than its value in the standard appli cation of TC. In the paleomagnetic practice this implies that, when ZS-deri ved pTRM is used, TC can provide only rough selection of multidomain sample s.