Chemico-viscous remanent magnetization in the oxidation of siderite and its implications in paleomagnetism

Studies have been done of the secondary chemico-viscous remanent magnetizat ion (CVRM) produced in the oxidization and decomposition of high-purity cry stal siderite specimens collected from Dalizi Deposit, Jilin Province. The CVRM intensity increases to a peak value at an annealing temperature of 490 degrees C. The direction of CVRM is always parallel to the applied field, and no self-reversal behavior has been observed in the transformation of ma ghemite to hematite.. It is suggested that the phase transition of magnetic minerals can make great contribution to secondary magnetization. Results o f successive beating at low temperature indicate that the crystal mineral s iderite is basically stable. Finally, the paleomagnetic significance of CVR M is discussed.