Abstract
SUMMARY Compared to the other volcanic rocks of the Quaternary East Eifel volcanic field (Germany), the phonolites stand out because of very low susceptibilities and intensities of natural remanent magnetization. Geomagnetic palaeointensities have been studied by means of the Thellier method for seven of these rock units. While five of them are lava flows or domes, the other two have been deposited at temperatures of about 500 C as zeolitized tuffs. Results of rock magnetic investigations indicate that the magnetic carriers are Ti-poor titanomagnetites or magnetite. Heating above 200-300 C often leads to an alteration of the magnetic carriers of the rocks. In the low-temperature range, well-defined lineari segments in the succession of the Thellier experiment data points are found for most of the lava samples as well as for the zeolitized tuffs. Because of inconsistencies of within-unit results and the presence of viscous magnetization components, the palaeointensities of only two rock units are regarded as reliable. The obtained values are about 30pT as compared to the present-day field of 48 pT.
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