Abstract
Detrital magnetic materials within cave stalagmitic formations, e.g., haematite or magnetite, carry remanence whose vector is of value in dating. Magnetometry measurements on a particular haematite-bearing sample reveal that remanence was substantially restored and/or conserved on rewarming after cooling below the Morin transition temperature. Mössbauer measurements indicate the presence of two types of haematite, distinguished primarily by particle size. The majority is small in size, partially exhibiting superparamagnetism, and does not undergo a Morin transition above liquid nitrogen temperature. Superparamagnetic goethite is the second major component. Mine haematite samples of surface location with different color and mineralogical composition have also been studied. Possible relations between the mineralogical composition of the mine samples and detrital stalagmitic magnetic material, the modifications and the origin of this mineralization are discussed. Special attention is paid to the "irreversible" Morin transition in large enough (>20 nm) haematite particles and the possible loss of natural remanent magnetization and hence of palaeomagnetic records.
| Original language | English |
|---|---|
| Journal | Hyperfine Interactions |
| Volume | 128 |
| Issue number | 4 |
| Pages (from-to) | 353-373 |
| Number of pages | 21 |
| ISSN | 0304-3843 |
| DOIs | |
| Publication status | Published - 01.12.2000 |
Funding
The authors would like to thank the Alexander von Humboldt-Foundation and the German Federal Ministry for Education, Science, Research and Technology (BMBF) for financial support. Thanks are also expressed to the University College of North Wales for assistance with magnetometry and to Dr. D. Nihtianova for assistance with electron microscopy.
